About this course:
The purpose of this course is to provide education surrounding the nuances and complexities of weaning patients from ventilatory support and the APRN’s role throughout this interdisciplinary process.
The purpose of this course is to provide education surrounding the nuances and complexities of weaning patients from ventilatory support and the APRN’s role throughout this interdisciplinary process.
By the completion of this course, the APRN will be able to:
- identify criteria for the patient requiring an advanced airway and ventilator support and describe different ventilator settings and their roles in specific goals of care for the patient
- describe the purpose of medications used for the ventilated patient, including paralytics and sedatives
- identify weaning criteria for patients and demonstrate an understanding of when it is appropriate for the care team to adjust ventilator settings
- identify and mitigate barriers to extubating patients with a complex course of intubation / advanced airway
- interpret lab values relevant to ventilator weaning and describe the steps towards successful discontinuation of mechanical ventilation
- describe the role of the APRN in the interdisciplinary process of weaning patients from mechanical ventilation
The critical care patient may face a vast array of complexities during hospitalization, including traumatic injury, surgery, organ dysfunction, lab values, sepsis, and others, any of which could contribute to the need for an advanced airway and ventilatory support. The ventilator weaning process involves adjusting ventilator settings to decrease support and allow patients to take on more work of breathing (Epstein & Walkey, 2020). The complex nature of ventilator weaning presents many challenges and comprises a significant portion of the ICU workload. Weaning is critical to improved patient outcomes, as prolonged ventilation can lead to complications such as ventilator-associated pneumonia, airway trauma, and ventilator-induced lung injury (MacIntyre, 2004). Patients who are weaned safely and effectively experience less morbidity and mortality than patients requiring prolonged mechanical ventilation. For these reasons, weaning a patient from the ventilator can and should be considered and discussed throughout their time on mechanical ventilation (Epstein & Walkey, 2020).
The following definitions are essential to understanding concepts pertaining to the critically ill and ventilated patient. These definitions cover the course of mechanical ventilation from start to finish.
- Endotracheal intubation involves inserting a breathing tube into the trachea, allowing secure airway access for mechanical ventilation (Stollings et al., 2014).
- Expiration is the process of decreasing lung volume (Lei, 2017). Expiration occurs to expel carbon dioxide (CO2) and prevent it from accumulating in the body (Hallet et al., 2020).
- Extubation is removing an endotracheal tube (ETT) to liberate a patient from ventilator dependence (Hyzy, 2020).
- Hypercapnia, or hypercarbia, is an increased CO2 level in the blood (Lei, 2017).
- Hypoxia is an oxygen (O2) deficiency in the body’s tissues (Lei, 2017).
- Inspiration is the process of increasing lung volume (Lei, 2017). Inspiration allows the body to inhale O2 that diffuses across alveolar capillaries to reach arterial blood for delivery to the body's muscles and vital organs (Hallet et al., 2020).
- Noninvasive positive pressure ventilation (NIPPV) is the forced movement of air into and out of the lungs through a face or nasal mask. NIPPV may reduce the need for endotracheal intubation (Brown, 2021).
- Oxygenation is an intervention that provides an increased O2 supply to the lungs, and therefore in the bloodstream (Mora Carpio & Mora, 2020).
- Respiration is transporting O2 from atmospheric air to the cells within tissues and transporting CO2 from the cells to the air. This is a three-part process, including gas exchange in the lungs, blood circulation, and gas exchange in the tissues and cells (Lei, 2017).
- A tracheostomy is a surgical procedure that places a breathing tube in the lower neck, allowing secure access to the lower respiratory tract (Hyzy & McSparron, 2020).
- Ventilation is the process of moving air in and out of the lungs, allowing for gas exchange (Mora Carpio & Mora, 2020)
Respiratory failure necessitating ventilator support may occur rapidly or be progressive over time, often related to a chronic illness such as emphysema or chronic obstructive pulmonary disease (COPD; Lei, 2017). APRNs should remain attentive to signs of respiratory failure in all patients. The patient’s history and baseline respiratory function should be assessed, and in patients with underlying respiratory disorders, it is crucial to evaluate respiratory status frequently (Brown, 2021). Frequent assessment allows the recognition of changes in the patient’s status that may prompt early intervention. Signs and symptoms of respiratory failure may include, but are not limited to, tachypnea, tachycardia, cyanosis, sweating, grunting, nose flaring, and decreased oxygen saturation (the amount of oxygen-saturated hemoglobin in the blood relative to total hemoglobin, as measured by pulse oximetry [SPO2] reading; Lei, 2017). In the context of respiratory distress, a hypoxic patient may present with restlessness or agitation. Worsening hypoxia symptoms may progress to confusion, somnolence, and bradycardia. The patient experiencing chronic CO2 retention may adapt to these changes over time, but acute retention is often first marked by altered mental status, confusion, and somnolence (Brown, 2021).
Intubation and Advanced Airways
The lungs play a critical role in maintaining adequate ventilation by delivering the appropriate tidal volume to maintain acceptable O2 and CO2 levels in the blood. The brain's respiratory center regulates the rate and depth of breathing to keep these components in balance. In cases of illness, the body may require support via mechanical ventilation (Hallet et al., 2020). Mechanical ventilation requires access to the patient’s airway, which can be accomplished with the insertion of a breathing tube. In the setting of acute respiratory failure, an ETT may be placed through the mouth, or sometimes the nose, into the trachea. The decision to intubate should be made when a thorough patient assessment indicates that mechanical ventilation is necessary for their safety. Calvin Brown (2021) recommends a three-question approach as outlined below:
- Is there a failure of airway maintenance or protection?
- If yes, intubate
- If no, move to the next question.
- Is there a failure of oxygenation or ventilation?
- If no, move to the next question
- If yes, evaluate the patient for NIPPV
- If not a NIPPV candidate, intubate
- If a candidate, attempt NIPPV. If unsuccessful, intubate.
- Does the anticipated clinical course require intubation?
- If yes, intubate.
- If no, continue to observe.
Regular assessments should evaluate the patient’s ability to protect their airway, manage secretions, and airway patency. Airway protection is the ability to guard against aspiration while breathing, which requires a sufficient level of consciousness (Glasgow coma scale [GCS] > 8) and cough strength. Cough strength is often evaluated informally at the bedside with or without gag reflex evaluation. However, formal assessment (i.e., spirometry testing) may benefit certain patients (e.g., those with a known neuromuscular disorder such as Parkinson's). Indications that a patient cannot protect their airway may include persistent coughing when swallowing, gurgl
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Even though well-planned algorithms and outlines are available in the decision-making process of intubation, nothing replaces patient assessment and clinical judgment. There are outlying circumstances that may not fit into the three-question algorithm where a patient is safer with a secured airway despite no apparent symptoms of respiratory distress. For example, one may anticipate fluid resuscitation in a septic patient with underlying respiratory disease and recognize that pulmonary edema could be a consequence of this treatment. The team should use clinical judgment to determine if an advanced airway’s security is preemptively indicated to avoid the possibility of potential emergency intubation in the future (Brown, 2021).
In most ICU and emergency department patients requiring advanced airways, rapid-sequence intubation (RSI) is suitable. This intubation method is utilized in patients at risk for aspiration (e.g., those who have not fasted) or at risk of losing a secure airway. If RSI becomes necessary, all necessary personnel and equipment must be present at the time of induction to ensure that the patient can be ventilated with a bag valve mask and intubated promptly (Stollings et al., 2014). An induction agent is administered to initially sedate the patient, such as propofol (Diprivan) or etomidate (Amidate; Bittner, 2019). Etomidate (Amidate) has been shown to produce rapid loss of consciousness with a relatively stable safety profile (negligible effect on heart rate or blood pressure, yet a favorable reduction in cerebral blood flow and ICP), thus making it a frequent choice in emergency, ICU, and pre-hospital situations. It is typically dosed at 0.2-0.3 mg/kg for this purpose. It is a potent steroid inhibitor, potentially causing temporary adrenal insufficiency of unknown clinical significance. It may also cause myoclonic movements, nausea, vomiting, and trismus (painful muscle spasms which limit the ability to open the jaw). Ketamine (Ketalar) dosed at 2 mg/kg may also be used for this purpose, although it is contraindicated in patients with significant coronary artery disease or non-traumatic compromise of intracranial and cerebrovascular dynamics (Flynn & Shehabi, 2012).
After this, a neuromuscular blocking agent (NMBA), or paralytic, should be used. The two NMBAs most commonly utilized for induction purposes are succinylcholine (Anectine) and rocuronium (Zemuron). Succinylcholine (Anectine) is the only depolarizing NMBA approved for use in the US. It functions by binding to acetylcholine receptors on the motor neuron endplate, first causing depolarization followed by blocking neuromuscular transmission. For intubation, succinylcholine (Anectine) is typically dosed at 0.60-1.5 mg/kg with an ultrashort duration (half-life less than one minute, and 5-10 min to 25% recovery). It presents a higher risk for hyperkalemia in critically ill patients and is used almost exclusively for intubation purposes or for severe laryngospasm. It may also cause myalgia and bradycardia. It is contraindicated in patients with hyperkalemia, malignant hyperthermia, muscular dystrophy, pseudocholinesterase deficiency, and it is not recommended for use in children (Bittner, 2019). Additional conditions that may contraindicate the use of NMBAs include cerebral palsy, hemiplegia, peripheral nerve injury, or severe chronic botulism or tetani (Clar, 2021).
Nondepolarizing agents include benzylisoquinolinium compounds, such as cisatracurium (Nimbex), and aminosteroid compounds, such as rocuronium (Zemuron). Both function by binding to Ach receptors and preventing endplate potentials. Rocuronium (Zemuron) has both a rapid onset of action (1-2 minutes) and intermediate duration (30-80 minutes to 25% recovery; Bittner, 2019). Typical intubation dosing for rocuronium (Zemuron) is 0.45-0.90 mg/kg, cisatracurium (Nimbex) is 0.1-0.15 mg/kg (within 2 minutes of intubation), and vecuronium (Norcuron) is 0.08-0.12 mg/kg (Clar, 2021). RSI may justify a single dose of rocuronium (Zemuron) of up to 1.2 mg/kg or a single dose of cisatracurium (Nimbex) or vecuronium (Norcuron) of up to 0.2 mg/kg. The onset of cisatracurium (Nimbex) and vecuronium (Norcuron) are slightly slower, at 4-6 and 3-4 minutes, respectively. Those with severe septic shock may require higher dosing of cisatracurium (Nimbex), although this is the preferred agent in patients with renal or hepatic insufficiency. Vecuronium (Norcuron) and rocuronium (Zemuron) should be avoided in patients with hepatic or renal insufficiency if possible (Bittner, 2019).
In emergency intubations, esophageal intubation can occur up to 16% of the time. The APRN should be familiar with standards of verifying ETT placement. While auscultation of bilateral breath sounds is important, the highest standard of care for verifying ETT positioning is waveform capnography. With no waveform, it is likely that the ETT is placed in the esophagus instead of the trachea and needs to be replaced. In circumstances without wave capnography monitoring capability, a color-changing capnography device may be used. A qualified provider may even confirm placement with ultrasound until a chest x-ray can be taken for final confirmation (Adi et al., 2013).
If prolonged ventilator support is anticipated (often 10 days-3 weeks), or when ventilator weaning is unsuccessful, a tracheostomy tube may be applicable for a patient requiring ventilator support. The placement of a tracheostomy tube has been shown to reduce the work of breathing, airway resistance, peak inspiratory pressures, and intrinsic or auto-PEEP (positive end-expiratory pressure). These changes typically make weaning from mechanical ventilation easier for patients and reduce the need for sedation. When a tracheostomy is placed, the head and face are no longer encumbered by invasive equipment, immediately enhancing patient comfort. Specialized tubes also allow patients with tracheostomies more ability to communicate verbally, reducing patient anxiety. Disadvantages include the potential for cuff-site and stoma complications, increased risk for laryngeal injury, a possible increase in pulmonary infections, the potential for mediastinum infections, and a high mortality rate in the case of inadvertent decannulation before tract maturation (typically within 7 days, although maturation sutures may be used to accelerate this process). Tracheostomy procedures may be performed surgically or percutaneously, allowing the procedure to be completed at the bedside. It may be done with ultrasound guidance, bronchoscopy guidance, or dilatational. Percutaneous dilatational tracheostomies have demonstrated lower infection rates and may decrease the risk of major bleeding and mortality. Surgically placed tracheostomy tubes are easier to replace if inadvertently dislodged, as dilated stomas tend to recoil faster than surgically created tracts. Dislodged tracheostomy tubes should be replaced with the same size or smaller tube. Patients with dislodged tracheostomy tubes that cannot be replaced should be ventilated temporarily using a bag mask and may need to be orally intubated if they cannot ventilate/oxygenate independently (Hyzy & McSparron, 2020; Mitchell et al., 2012).
Monitoring and Assessment of the Critically Ill Patient
The acute care APRN is responsible for monitoring ventilated patients according to unit protocol, which typically requires frequent vital signs, including heart rate (HR) and rhythm, respiratory rate (RR), SPO2, blood pressure (BP), and temperature. Some units may require end-tidal CO2 monitoring (ETCO2), a measurement of CO2 during expiration taken from the ETT, or other advanced hemodynamic monitoring. APRNs should be familiar with expected parameters or those applicable to patient condition and adjust the vital sign-monitor alarm settings accordingly (Sowan et al., 2017).
The APRN should collaborate with the respiratory therapist to ensure applicable ventilator alarms and safety protocols are in place. “False alarms” can decrease staff responsiveness, so alarm settings should be tailored to decrease their frequency. Properly set alarm parameters reduce the risk of missing a real alarm in a life-threatening circumstance (Poncette et al., 2020). The patient’s RR, SPO2, and ETCO2 relate directly to ventilator settings and should be monitored closely. However, SPO2 may prove unreliable in a patient with poor peripheral perfusion (Brown, 2021).
Arterial Blood Gas
The interdisciplinary team may also evaluate lab values from an arterial blood gas (ABG). When interpreted correctly, an ABG is a helpful tool for assessing respiratory failure and the patient’s ventilator settings (Castro et al., 2021). They may be utilized as a component of the clinical decision-making regarding the need to intubate, as an assessment tool throughout intubation, and during ventilator weaning (Epstein, 2018). ABG values measure several components related to respiratory function. Relevant measurements, as quantified and defined by Castro and colleagues (2021), include the following:
- pH - measured acid-base balance of the blood (reference range 7.35 - 7.45)
- PaO2 - measured partial pressure of oxygen in arterial blood (reference range 75-100 mmHg)
- PaCO2 - measured partial pressure of carbon dioxide in arterial blood (reference range 35 - 45 mmHg)
- HCO3 - calculated concentration of bicarbonate in arterial blood (reference range 22-26 mEq/L)
- SaO2 - calculated oxygen saturation of arterial blood (reference range 95 - 100%)
CO2 is an acid regulated by the respiratory system, while bicarbonate (HCO3) is a base controlled by the metabolic system, primarily the kidneys. When interpreting ABG values, the APRN should first observe the pH. A pH below 7.35 is acidotic, while anything above 7.45 constitutes alkalosis (Verma & Roach, 2010). Further interpretation is required to determine if an irregularity in pH value is related to respiratory or metabolic failure or if a normal pH value is due to compensation. The APRN should evaluate the PaCO2 (acid) and HCO3 (base) values to discern the imbalance's origin. Elevated PaCO2 indicates hypoventilation or retention of CO2, while decreased levels reflect hyperventilation or excessive release of CO2. The APRN must also analyze HCO3 levels to determine if the patient’s imbalance is metabolic or respiratory in origin (Castro et al., 2021). In most cases, a low pH with a high PaCO2 indicates respiratory acidosis. However, a low pH with a low PaCO2 suggests that there is another force driving the imbalance. A metabolically driven imbalance will typically lead to a low HCO3 level (Verma & Roach, 2010).
Blood gasses may also reflect a mixed acid/base disorder, where PaCO2 and HCO3 are altered. The origin of mixed disorders is more difficult to identify, so assessing the patient’s health history and current status is essential. For example, a patient with chronic renal failure may present with metabolic acidosis (i.e., a decreased HCO3) due to the inability to excrete acids in the urine. If they hyperventilate due to anxiety, they will blow off excessive CO2 and present with a low PaCO2. The combined low HCO3 and CO2 may result in a pH that is within normal limits due to compensation. Mixed respiratory-metabolic disorders typically cause abnormal PaCO2 or HCO3 values accompanied by a normal pH (Verma & Roach, 2010). Compensatory responses rely on the lungs and kidneys functioning properly and vary based on the severity of the pH disturbance that initiates this response. Respiratory compensation occurs significantly faster than the compensatory metabolic response from the kidneys. Initiation of the compensatory response can take from hours to days (Castro et al., 2010).
ABG interpretation can discern if the patient is experiencing type one (hypoxic) or type two (hypercapnic) respiratory failure. Both conditions will result in a PaO2 below 60 mmHg. Hypoxic respiratory failure, or lung failure, is identified by a normal or near-normal PaCO2 level. This is usually the result of a condition in which the blood is inadequately oxygenated when passing through the lungs (e.g., an arteriovenous shunt, gas diffusion impairment, or ventilation/perfusion mismatch). Hypercapnic respiratory failure results in a PaCO2 above 50 mmHg. This may be a consequence of chest trauma, respiratory fatigue, excessive airway resistance, or decreased respiratory drive (Lei, 2017).
Blood gas interpretation is particularly relevant to the ventilated patient as these lab values can inform ventilator setting adjustments. For example, respiratory acidosis implies that the patient is retaining too much CO2. Increasing the ventilator’s RR may allow the patient to “blow off” or expel the excess CO2. In contrast, if a patient’s ABG values indicate respiratory alkalosis, reducing the RR could reverse the deficiency of CO2, leading to this imbalance (Verma & Roach, 2010). ABG readings provide critical information regarding whether a patient is ready to wean to a lower ventilator setting or be extubated.
While ABGs are an informative decision-making tool throughout a patient’s hospitalization, the patient’s clinical presentation should always be considered. For example, the patient’s lab values may fall within expected limits on paper. Still, intervening must be contemplated if a patient is in apparent respiratory distress or at risk for rapid onset of respiratory failure (Brown, 2021).
Understanding Mechanical Ventilation
Natural ventilation without intervention occurs as a negative pressure system. The diaphragm pushes down during inspiration, creating pressure in the pleural cavity that pulls air into the airways and lungs. Mechanical ventilation operates utilizing positive pressure. The ventilator pushes air into the lungs to open the alveoli, promoting gas exchange and positive pressure in the pleural space (see Figure 1). The primary objectives of mechanical ventilation include relieving respiratory distress, improving pulmonary gas exchange, permitting lung or airway healing, and reversing hypoxemia or hypercapnia (Mora Carpio & Mora, 2020). Goals should include patient safety, patient comfort, and ultimately the patient’s liberation from the ventilator (Mireles-Cabodeviela et al., 2013). The American Thoracic Society and American College of Chest Physicians both advocate for the use of early mobilization with a physical therapist in mechanically ventilated patients; this prevents the associated complications of prolonged immobility and promotes liberation from mechanical ventilation (Epstein & Joyce-Brady, 2020).
The following definitions are key components to understanding the concepts of mechanical ventilation (Hallet et al., 2020; Lei, 2017; Mora Carpio & Mora, 2020):
- As a refresher, ventilation is the exchange of gas between atmospheric air and the lungs, whether by spontaneous breaths or delivered by a ventilator.
- Compliance measures pressure tolerance in the lungs and chest wall, calculated by dividing volume by change in pressure. Standard lung compliance is around 100 mL/cmH20. Decreased lung compliance is common in patients with a respiratory illness that causes lung stiffness, such as acute respiratory distress syndrome (ARDS) or pulmonary fibrosis.
- FiO2, or fraction of inspired oxygen, is the percentage of O2 in the air that is delivered to the patient.
- Flow is the speed at which the ventilator delivers breaths, reported in breaths per minute.
- Minute ventilation is a measurement of the amount of air that enters the lungs per minute - a product of RR multiplied by tidal volume.
- Oxygenation is an intervention that increases the delivery of O2 to the lungs, allowing diffusion into the bloodstream. In mechanical ventilation, this is accomplished through modifications to the FiO2 percentage or PEEP.
- Peak pressure is the pressure achieved during inspiration when that air is being pushed into the lungs. Peak pressure measures airway resistance.
- The plateau pressure is the pressure imposed on the small airways and alveoli during mechanical ventilation. An increase in plateau pressure puts the patient at risk of alveolar rupture.
- Positive end-expiratory pressure, or PEEP, is the positive pressure remaining in the lungs at the end of exhalation. PEEP keeps the alveoli open and promotes gas exchange.
- Tidal volume is the amount of air that moves in or out of the lungs with each respiratory cycle. Ventilator settings should be adjusted to deliver tidal volumes large enough to adequately ventilate the patient, but not large enough to induce traumatic lung injury. The current standard is to use tidal volumes of 6 mL/kg to protect lungs from trauma. On average, this equates to tidal volumes around 500 mL in a healthy adult male (average of 83 kg or 183 lb) and 400 mL in a healthy adult female (average of 67 kg or 147 lb).
Modes of Ventilation
Ventilator settings can be customized to the patient’s condition, and the combinations of settings are innumerable. Hyzy & Jia (2021) provide the following descriptions of ventilator settings frequently utilized in the ICU to provide baseline mechanical ventilation knowledge:
- Volume-controlled or volume-limited ventilation
- A set tidal volume is delivered to the patient with every breath.
- Airway pressure may vary with breaths, and minute volume is dictated by the RR accompanying the set tidal volume (Hyzy & Jia, 2021).
- Pressure-controlled or pressure-limited ventilation
- Tidal volumes vary from breath to breath, but peak airway pressure is constant.
- Pressure-controlled modes are associated with lower peak pressures, improved synchrony with the ventilator, and earlier extubation (Hyzy & Jia, 2021).
Within these categories, ventilator modes are further categorized as follows:
- Controlled mechanical ventilation (CMV)
- Volume controlled minute ventilation is determined by the RR and tidal volume set by the APRN. This is most appropriate for heavily sedated or paralyzed patients, as it does not require any patient work.
- CMV may also be delivered with pressure limited settings, allowing the minute ventilation to be determined by the set RR in conjunction with inspiratory pressure level (Hyzy & Jia, 2021).
- Assist control (AC)
- With a volume-controlled setting (AC/VC), the APRN sets the RR and tidal volume, but the patient may trigger additional breaths. The patient receives the same tidal volume with every breath.
- With a pressure-controlled setting (AC/PC), inspired volumes will vary, but peak inspiratory pressures are limited (Hyzy & Jia, 2021).
- Intermittent mandatory ventilation (IMV)
- The APRN sets the minimum RR and tidal volume, but the patient can increase the minute ventilation with spontaneous breaths of whatever volume the patient can generate (Hyzy & Jia, 2021).
- Synchronized intermittent mandatory ventilation (SIMV)
- The APRN sets the minimum RR and tidal volume and ventilator breaths are synchronized with the patient’s inspiratory effort.
- The RR can vary depending on the patient’s respiratory drive and initiation of breaths but will not drop below the minimum or mandatory set (Hyzy & Jia, 2021).
- Pressure support ventilation (PSV)
- The APRN sets the inspiratory pressure level, PEEP, and Fi02, but the patient controls the RR and tidal volume.
- PSV is a more “comfortable” mode that gives the patient greater control over inspiratory flow and RR while the machine’s pressure augments the patient’s spontaneous breath efforts (Hyzy & Jia, 2021).
- Levels of pressure support can be adjusted based on patient condition, and a lower level of pressure support requires the patient to work more to breathe. This makes PSV a useful setting for a patient being weaned from the ventilator since the interdisciplinary team can observe the patient's respiratory drive and endurance (Hyzy & Jia, 2021).
- Continuous positive airway pressure (CPAP)
- Continuous positive airway pressure is delivered without variation, with no RR or tidal volume set. The patient must initiate all breaths (Hyzy & Jia, 2021).
Sedative and analgesic medications are almost universally administered to patients undergoing invasive mechanical ventilation (Shehabi et al., 2013). These medications provide patient comfort and prevent agitation, which can lead to catastrophic consequences in a disoriented ICU patient, such as self-extubation or removal of invasive catheters (e.g., central lines or Foley catheters; Reade & Finfer, 2014).
Selecting the ideal sedative and analgesic should take a patient’s condition into account and be adjusted and reevaluated in response to changes in clinical status. Multiple sedatives and pain medications can be used in combination and titrated to patient-specific goals. While etomidate (Amidate) is frequently used as an induction sedative, it is not used continuously. The most used continuous sedatives include:
- Propofol (Diprivan) can be used for light or deep sedation, depending on the dose administered. It is used frequently due to its short half-life and quick reversal with short-term use. It should be given through a large-bore IV if given peripherally (Tietze & Fuchs, 2021).
- A known risk of prolonged propofol (Diprivan) infusion is propofol infusion syndrome (PRIS). PRIS is characterized by hyperkalemia, metabolic acidosis, renal and cardiac failure, and high mortality risk. For this reason, propofol (Diprivan) should be administered for the shortest duration possible (Shehabi et al., 2013). Routine monitoring of triglycerides, lactate, creatinine kinase, and myoglobin may assist with identifying PRIS (Tietze & Fuchs, 2021).
- Propofol (Diprivan) may cause hypotension, which can be profound with significant doses. Blood pressure should be monitored diligently, especially when infusion rates are changed (Morelli et al., 2019). Other adverse effects include bradycardia, respiratory depression, decreased myocardial contractility, and injection site pain (Tietze & Fuchs, 2021).
- Propofol (Diprivan) is typically dosed at 5-50 mcg/kg/minute. It can be titrated every 5-10 minutes, adjusting in 5-10 mcg/kg/minute increments. Dosing should not be weight-based in patients with obesity, and the maximum dosage is typically 70 mcg/kg/minute, but PRIS risk is increased with doses in this range. Onset is 1-2 minutes, and the duration is 3-10 minutes (Tietze & Fuchs, 2021).
- Benzodiazepines, commonly midazolam (Versed), lorazepam (Ativan), or alprazolam (Xanax), have significant historical use and are among the most used sedatives in critical care settings worldwide. However, benzodiazepines for continuous sedation were commonplace before ICU sedation guidelines were widespread, and the push for sedation weaning was not as typical.
- Benzodiazepines are known for unpredictable accumulation, especially when given in higher doses to achieve deep sedation. The consequence of this accumulation is prolonged sedation, even after the infusion has been discontinued. Prolonged use typically leads to tolerance or the need for a higher dose to achieve the same clinical effect (Tietze & Fuchs, 2021).
- Midazolam (Versed) is a potent amnestic associated with loss of airway reflexes, respiratory depression, and apnea (Barends et al., 2016). It may lead to delirium (Tietze & Fuchs, 2021).
- Loading doses of midazolam (Versed) range from 0.01-0.05 mg/kg (0.5-4 mg), and multiple loading doses may be required. Maintenance dosing is typically 0.02-0.1 mg/kg/hour (2-8 mg/hour) with intermittent dosing as needed. Benzodiazepine dosing should not be weight-based in patients with obesity. Onset is typically 2-5 minutes, and duration is 30 minutes. It is hepatically metabolized and may have a prolonged half-life in critically ill patients with renal or hepatic impairment. It may interact with many azole antifungals or antiretrovirals and other medications metabolized by CYP3A4 (Tietze & Fuchs, 2021).
- Lorazepam (Ativan) has a slower onset, making titration somewhat delayed and a bit more challenging. Common side effects include respiratory depression, delirium, and oversedation. The staff should be observant for IV-line precipitate, with an in-line filter in use when available (Tietze & Fuchs, 2021).
- Loading doses of lorazepam (Ativan) range from 0.02-0.04 mg/kg (1-2 mg), and multiple loading doses might be required. After this, it can be dosed intermittently 0.02-0.06 mg/kg (1-4 mg) every 2-6 hours (preferred) or 0.01-0.1 mg/kg/hour (0.5-10 mg/hour) via continuous infusion. Benzodiazepine dosing should not be weight-based in patients with obesity. Onset is typically in 15-20 minutes, while the duration may be as long as 6-8 hours. Propylene glycol solvent can accumulate with prolonged use or higher dosing, leading to metabolic acidosis. Lorazepam (Ativan) does not interact with medications metabolized by CYP3A4 (Tietze & Fuchs, 2021).
- Dexmedetomidine (Precedex) is generally used for light to moderate sedation and in patients experiencing agitation and ICU delirium. Dexmedetomidine (Precedex) has been found to prevent and resolve ICU delirium (Reade et al., 2016). It is a central sympatholytic (i.e., alpha2 agonist) with moderate anxiolytic and analgesic properties (Tietze & Fuchs, 2021).
- Patients receiving dexmedetomidine (Precedex) are more arousable than patients receiving other sedating agents, allowing successful maintenance of light to moderate sedation. This improves the patient’s ability to communicate and interact with the care team, even intubated (Shehabi et al., 2013).
- A study by Reade and colleagues (2016) found that patients treated with dexmedetomidine (Precedex), as compared to midazolam (Versed), developed delirium less often and were liberated from mechanical ventilation sooner.
- Dexmedetomidine (Precedex) produces an analgesic effect and less respiratory depression. Continuous infusions can even be used on non-intubated patients (Reade & Finfer, 2014).
- When administering a dexmedetomidine (Precedex) infusion, there is a risk of bradycardia, in some cases an extreme reduction in HR below 40 bpm. The infusion should be adjusted accordingly if the patient becomes bradycardic (Morelli et al., 2019). It can also lead to significant alterations in BP, nausea, and atrial fibrillation (Tietze & Fuchs, 2021).
- Dexmedetomidine (Precedex) loading doses are optional and rarely used due to the risk of cardiovascular instability; if used, they should be given over 10 minutes and dosed at 1 mcg/kg. Maintenance dosing is typically 0.2 mcg/kg/hour initially and can be titrated up every 30 minutes to a maximum of 1.5 mcg/kg/hour. The onset is typically 15 minutes but can be 5-10 minutes when a loading dose is used, with a duration of 1-2 hours. These doses should be reduced in renal or hepatic impairment and tapered carefully to avoid withdrawal symptoms (Tietze & Fuchs, 2021).
Analgesia addresses the pain of ICU patients and is often given alone or in conjunction with sedative medications. Untreated pain can lead to agitation, higher energy expenditure, and irregularities in the immune response. It also increases the risk of post-traumatic stress disorder if prolonged (Reade & Finfer, 2014). When managing patients unable to communicate verbally, a non-verbal pain scale may be utilized per unit/facility policy to discern the level of pain the patient may be experiencing (Azevedo-Santos & DeSantana, 2018).
- Fentanyl (Sublimaze) is the analgesic agent most frequently used in the ICU for routine pain management, procedural analgesia, and ICU sedation.
- Fentanyl (Sublimaze) is a short-acting opiate less sedating than morphine (Duramorph, Infumorph). It can, however, produce somnolence and sedation in high doses, especially in patients with renal failure (Shehabi et al., 2013). It typically causes less hypotension than other analgesic agents. It is lipophilic, accumulates in adipose tissue with prolonged use, and can cause chest wall rigidity at higher doses (Tietze & Fuchs, 2021).
- Fentanyl (Sublimaze) potentiates the effects of sedatives if administered concurrently and should be titrated in conjunction with the accompanying sedative to the patient-specific goal (Shehabi et al., 2013).
- Fentanyl (Sublimaze) loading doses are typically 1-2 mcg/kg (25-100 mcg). Maintenance dosing can be 0.35-0.5 mcg/kg (25-50 mcg) every 30-60 minutes or 0.7-3 mcg/kg/hour (50-200 mcg/hour) via continuous infusion with as needed bolus administration. Dosing should not be weight-based in patients with obesity, and the maximum dose should be 10 mcg/kg/hour (700 mcg/hour). The onset of fentanyl (Sublimaze) is 1-2 minutes, and its duration is 30-60 minutes. It is metabolized hepatically (Tietze & Fuchs, 2021).
- Morphine (Duramorph, Infumorph) is an opiate administered for pain management in critical care patients and especially for palliation in terminal patients.
- Morphine (Duramorph, Infumorph) is longer acting than fentanyl (Sublimaze) and has known adverse effects, including hypotension, respiratory depression, and bradycardia. It may also cause myocardial depression and reduce preload (Tietze & Fuchs, 2021).
- Morphine (Duramorph, Infumorph) remains commonly used due to familiarity and availability. In addition to relieving pain, morphine (Duramorph, Infumorph) is also sedating (Shehabi et al., 2013).
- Loading doses of morphine (Duramorph, Infumorph) are typically 2-10 mg, while maintenance dosing is either 2-4 mg every 1-2 hours or a continuous infusion of 2-30 mg/hour. The onset is typically within 5-10 minutes, while the duration of effect is 4-5 hours. It is not metabolized via the CYP3A4 route like fentanyl (Sublimaze) and hydromorphone (Dilaudid). Despite this, dose adjustments are suggested in renal or hepatic impairment (Tietze & Fuchs, 2021).
Neuromuscular blocking agents (NMBAs, sometimes referred to as paralytics) paralyze skeletal muscle by blocking nerve impulse transmission. These medications are not to be utilized as initial management for agitation, undesired movement, or ventilator dyssynchrony (the timing of mechanical breaths is not in agreement with the patient’s inspiratory attempts). These medications do not have analgesic or sedative properties, are not recommended first-line agents for undesired movement, and should only be utilized when the former mechanisms (e.g., sedation, analgesia) have failed. NMBAs should never be administered to a patient who does not have an advanced airway (e.g., intubated), as respiratory muscles will be paralyzed (Bittner, 2019). As discussed previously, NMBAs are also used for intubation following an induction sedative agent (Stollings et al., 2014). Additional circumstances in which NMBAs may be necessary include:
- severe ventilator dyssynchrony unresolved with sedative or analgesic medications
- may avert lung overinflation and injury by preventing the patient from “stacking” breaths on top of the ventilator’s programmed respirations.
- reduces oxygen consumption by the respiratory muscles and puts the work of breathing on the ventilator instead of the patient (Bittner, 2019).
- severe shivering related to therapeutic hypothermia secondary to cardiac arrest
- hypothermia prolongs the therapeutic duration of all nondepolarizing agents (Bittner, 2019)
- protocols should be developed to guide the administration of NMBAs during therapeutic hypothermia (Renew et al., 2020)
- preventing unwanted muscle movement when it may cause danger to the patient, such as when it contributes to elevated intracranial pressure or coughing that could dislodge a clot in the context of hemoptysis (Bittner, 2019)
Common intermediate-acting NMBAs include cisatracurium (Nimbex), vecuronium (Norcuron), and rocuronium (Zemuron; Bittner, 2019). These medications may be given in bolus or continuous IV doses, but continuous infusions are generally preferred over bolus dosing. Weight-based dosing should be based on the patient’s ideal or adjusted body weight rather than their actual weight (Renew et al., 2020). Cisatracurium (Nimbex) is the preferred agent for continuous infusion because its metabolism is unrelated to hepatic or renal function. Atracurium is also a feasible option in patients with hepatic or renal insufficiency but should be avoided in hemodynamically unstable patients due to the potential for histamine release (Bittner, 2019). A maintenance infusion of cisatracurium (Nimbex) is typically 1-3 mcg/kg/minute (Clar, 2021; Bittner, 2019). Patients with severe sepsis/septic shock may have a delayed or diminished response to standard cisatracurium (Nimbex) dosing regimens, but there are no specific contraindications to its use (Bittner, 2019). Neuromuscular blockade can be maintained using boluses of rocuronium (Zemuron) of 0.10-0.15 mg/kg (5-12 mcg/kg/min; Bittner, 2019; Clar, 2021). Patients may report pain on injection, and prolonged use (in the ICU) may lead to an extended half-life. Maintenance dosing of vecuronium (Norcuron) is 0.1 mg/kg (1-2 mcg/kg/min), but it is not typically used for prolonged periods in the ICU setting due to the risk of myopathy. Both rocuronium (Zemuron) and vecuronium (Norcuron) can be reversed with sugammadex (Bridion; Bittner, 2019).
Titration of a continuous infusion of NBMA can be monitored with peripheral nerve stimulation (PNS), usually ulnar or facial, and measuring twitches of the impacted muscle. As the neuromuscular blockade progresses, fewer twitches will be produced with PNS (Renew, 2020). PNS should only be used in combination with clinical assessments and should not be used as a sole indicator of medication dosing or effectiveness. This combination can be used in patients undergoing therapeutic hypothermia (Renew et al., 2020). An alternative monitoring option is the Bispectral Index (BIS). A BIS monitor utilizes electrodes to analyze EEG data and interpret a score from 0 – 100, zero indicating no brain activity and 100 representing full awareness. NMBAs may be titrated to BIS score to determine whether a patient is adequately sedated. Tachycardia, tachypnea, and hypertension are potential indicators of patient awareness or agitation, but these are not validated measures and should not be used as the sole assessment tool (Tasaka et al., 2016).
Continuous NMBA infusion should be avoided in status asthmaticus (Renew et al., 2020). Patients receiving NMBAs are also at elevated risk of multiple complications related to the complete cessation of muscle movement. When NMBAs are utilized for an extended period, the risk of muscle atrophy, foot drop, DVT, and pressure injury increases. Therapeutic range of motion should be performed every 4 hours, patients should be turned every 2 hours, and prophylactic anticoagulation medications should be ordered according to current industry guidelines (Blauvelt et al., 2019). Regularly scheduled eye care with lubrication drops/gel and eyelid closure was a strong recommendation for all patients on continuous neuromuscular blockade, and a target blood glucose of less than 180 mg/dL was a weak recommendation (Renew et al., 2020).
Patients receiving NMBAs may experience complications related to specific comorbidities. Blauvelt and colleagues (2019) outline the following considerations for interdisciplinary teams when patients are being administered NMBAs:
- Patients with a history of coronary artery disease are at increased risk of myocardial infarction due to vagolytic actions (reduced impulses from the vagus nerve, increased HR and CO) of some NMBAs, especially pancuronium (Pavulon).
- Patients with hepatic or renal failure are at greater risk of prolonged effects of NMBAs since they are eliminated through the liver and kidneys, except atracurium and cisatracurium (Nimbex).
- Rapid infusion of NMBAs may lead to a profound histamine release, causing hypotension, flushing, bronchospasm, and increased salivation, especially atracurium and to a lesser degree cisatracurium (Nimbex) at very high doses.
Evidence regarding sedative and analgesic medications in the ICU demonstrates that proper titration using goal-directed therapy can optimize patient comfort and avoid complications such as reintubation or prolonged mechanical ventilation rather than prioritizing which drug is administered. When sedatives are administered, goal-directed delivery is critical to prompt ventilator weaning. When interdisciplinary teams agree upon a targeted sedation level, the patient’s risk for complications and recovery obstacles decreases (Wesley et al., 2003). Goal-directed sedation is often driven by using a validated sedation scale.
An interdisciplinary approach with sedation goals ensures that all care team members are on the same page, improving recovery times. Providing specific goals dictating titration of sedative medications can be beneficial in the ICU. It has been proven that the use of lighter sedation results in sooner liberation from the ventilator and discharge from the ICU (Reade & Finfer, 2014). When sedative-analgesic protocols are in place and sedation-minimizing strategies employed, sedative and opioid doses are reduced overall. In addition, trials comparing continuous sedation with daily interruption of sedation demonstrated that patients receiving a daily interruption of sedative medications spent less time in the ICU and mechanically ventilated (Olsen et al., 2020). Protocolized sedation interruptions instead of assessment-driven sedation reduce the harmful effects of excessive sedation (Azevedo-Santos & DeSantana, 2018).
By verifying the Richmond Agitation-Sedation Scale’s validity, Wesley and colleagues (2003) determined that objective and goal-directed sedation therapy in ICU patients is the recommended standard to avoid oversedation and promote early extubation. They also reinforced that interdisciplinary agreement for target levels of sedation allows the swiftest course of recovery. Sedation scales allow the staff to assess the patient and determine an objective measurement of sedation level to guide titration of medications according to the patient's conditions and goal-directed therapy (Sessler et al., 2002).
The most used sedation scales are the RASS and the Riker Sedation-Agitation Score (SAS), both equally effective in their guidance of patient sedation level (Reade & Finfer, 2014). The RASS values range across 10 variables from +4 to -5, with specific assessment guidelines for the evaluator scoring the patient. The expanded scale designates values for patients’ response to physical versus verbal response and assists the clinical team in titrating medications appropriately (Wesley et al., 2003).
Sessler and colleagues (2002) designed the RASS and presented the scoring criteria as follows:
- 4 - Combative
- Overtly combative or violent; immediate danger to staff
- 3 - Very Agitated
- Pulls on or removes tube(s) or catheter(s) or has aggressive behavior
- 2 - Agitated
- Frequent non-purposeful movement or patient-ventilator dyssynchrony
- 1 - Restless
- Anxious or apprehensive but movements not aggressive or vigorous
- 0 - Alert and Calm
- -1 - Drowsy
- Not fully alert, but has sustained (more than 10 seconds) awakening, with eye contact, to voice
- -2 - Light Sedation
- Briefly (less than 10 seconds) awakens with eye contact to voice
- -3 – Moderate Sedation
- Any movement (but no eye contact) to voice
- -4 – Deep Sedation
- No response to voice, but any movement to physical stimulation
- -5 – Unarousable
- No response to voice or physical stimulation (Sessler et al., 2002)
The Riker SAS offers 7 scoring points at which to categorize the patient’s level of sedation. The SAS scoring criteria are outlined by Riker and colleagues (1999) as follows:
- 7 - Dangerous Agitation
- Pulling at ETT, trying to remove catheters, climbing over bedrail, striking at staff, thrashing side-to-side
- 6 – Very Agitated
- Requiring restraint and frequent verbal reminding of limits, biting ETT
- 5 – Agitated
- Anxious or physically agitated, calms to verbal instructions
- 4 – Calm and Cooperative
- Calm, easily arousable, follows commands
- 3 – Sedated
- Difficult to arouse but awakens to verbal stimuli or gentle shaking, follows simple commands but drifts off again
- 2 – Very Sedated
- Arouses to physical stimuli but does not communicate or follow commands, may move spontaneously
- 1 – Unarousable
- Minimal or no response to noxious stimuli, does not communicate or follow commands (Riker et al., 1999)
These scales help quantify the patient’s sedation level, allowing for clear directives in managing ICU sedation and sedative medication titration. Evidence shows that for most patients in the ICU that are mechanically ventilated, an acceptable target score is 3 to 4 on the Riker SAS and -2 to 0 on the RASS (Reade & Finfer, 2014).
Many institutional protocols will also dictate a scheduled sedation interruption barring any contraindications. During the sedative interruption, or while patients are minimally sedated, they should be able to follow simple commands such as squeezing the examiner’s hand or sticking out their tongue (Olsen et al., 2020). Some patients, however, may have indications for continuous deep sedation (e.g., those with status epilepticus, elevated intracranial pressure, or the use of NMBAs). In such patients, underlying medical conditions must improve before sedation can be weaned or interrupted, allowing ventilator weaning to progress (Reade & Finfer, 2014).
Patients’ sedation levels should be assessed continuously, and sedative medications titrated to a score agreed upon by the interdisciplinary team (Reade & Finfer, 2014). Oversedation will likely prolong mechanical ventilation and produce poorer patient outcomes through the weaning process (Shehabi et al., 2013).
The Process of Weaning
Weaning is the process of reducing ventilator support, allowing patients to increase their work of breathing as they move towards independent ventilation (Epstein, 2018). Weaning assesses the patient’s ability to assume an increased proportion of their ventilation to determine if mechanical ventilation can be discontinued with positive outcomes. Weaning, like sedation, should also be approached with protocols, often driven by nursing and respiratory therapy staff. This entails daily assessment of readiness to wean and a weaning trial if the patient passes a readiness assessment. Weaning protocols are shown to reduce the duration of mechanical ventilation by up to 26% and reduce ICU length of stay. Some facilities utilize computer-driven automated protocols, but most will apply manual protocols, meaning that healthcare staff will alter ventilator settings as the patient is weaned. Manual protocols can be tailored to the patient, providing an advantage of patient-centered care (Epstein & Walkey, 2020).
The early stages of weaning typically involve a gradual reduction in ventilator support, reducing individual settings such as PEEP and FiO2 on the ventilator, and checking patient tolerance. Vital signs and ABG values should be monitored per unit protocol to assess the patient's response to the changes in ventilator settings (Epstein, 2018). As a patient stabilizes, tolerates lower ventilator support, and passes readiness testing criteria, a spontaneous breathing trial (SBT) may be initiated to wean the patient from the ventilator more aggressively. Spontaneous breathing trials may be carried out daily until a patient successfully demonstrates that they can independently support the work of breathing (Epstein & Walkey, 2020). These trials are critical to timely weaning from the ventilator, as studies show that a clinician may not recognize when a patient is capable of taking on the work of breathing nearly two-thirds of the time with clinical judgment alone (MacIntyre, 2004).
Before a patient can be weaned to less aggressive ventilator settings, it is crucial to determine that the patient is clinically ready to begin this process. Readiness testing evaluates if the patient is clinically suitable for decreased ventilator support; this should be completed by the patient’s interdisciplinary care team to determine that weaning is appropriate (Epstein, 2018). Premature weaning can lead to cardiovascular dysfunction, psychological distress, or respiratory muscle fatigue. To determine that a patient is ready to wean, Epstein (2018) and Walkey (2020) describe the following criteria that should be met based on the evidence-based guidelines published by the American College of Chest Physicians, American College of Critical Care Medicine, and American Association for Respiratory Care in 2001:
- the cause of respiratory failure has improved or resolved
- the ABGs reflect sufficient oxygenation (i.e., a PaO2/FiO2 of at least 150 [or 120 in patients with a history of chronic hypoxemia] or Sp)2 > 90%) on an FiO2 of 40% or less and PEEP of 5 or less on the ventilator.
- the ABG values indicate a pH above 7.25
- the vital signs reflect that the patient is hemodynamically stable, with minimal or no use of vasopressors
- the patient proves that they can initiate inspiratory effort, whether during sedation interruption or while lightly sedated
Ideally, the patient should be arousable and able to follow simple commands. Additional criteria included in readiness testing include a hemoglobin level of at least 7 mg/dL and a core temperature of less than 39°C (Epstein, 2018; Epstein & Walkey, 2020).
Spontaneous Breathing Trials (SBTs)
Studies analyzing SBTs compared to gradual weaning show conflicting data on which strategy produces a lessened mechanical ventilation time, making contrasting recommendations. However, research consistently suggests that SBTs are successful, efficient, and safe in most patients, making them an ideal method for ventilator weaning. A recent international study involving 1,868 adults mechanically ventilated for longer than 24 hours in six geographic regions globally found significant variation in weaning practices. Within this trial, direct extubation was related to a lower mortality rate and shorter duration of ventilation and ICU admission when compared with those undergoing a spontaneous breathing trial (SBT). However, the authors admit that this may be due to greater illness severity among those undergoing SBT. Findings indicate the need to further study optimal weaning practices worldwide (Burns et al., 2021; Epstein & Walkey, 2020).
When an SBT is initiated, the patient is switched from full respiratory support modes (consider the section on modes of ventilation - full support may be set volumes, RRs, or pressure support) to modes where the patient has more control of their ventilation, such as low-level PSV, automatic tube compensation, or CPAP. The use of PSV mitigates the increased work related to the presence of the ETT and is especially vital in those with an ETT size 7 or smaller. While the specifics vary by institution/clinician, generally, this can be achieved with inspiratory pressure augmentation of 5-8 cm H2O, a PEEP of 5 cm H2O, and an FiO2 of 40% or lower. These are consistent with the most recent national practice guidelines. Ventilatory support prevents the fatigue that may cause the patient to fail the SBT, and several clinical trials have shown that utilizing the PSV mode is associated with higher success rates (i.e., extubation) when compared to other methods. Ideally, this should be done while the patient is awake and receiving little to no sedative medication (Epstein & Walkey, 2020; Oullette et al., 2017).
During a weaning trial, patient vital signs should be monitored, including RR and tidal volume. Alert patients should be asked about the presence of dyspnea or chest pain, and all patients should be observed for indications of respiratory distress and mental status changes. Telemetry monitors should be followed closely for ST changes, prompting electrocardiography to further assess cardiac ischemia (Epstein and Walkey, 2020). Criteria for a successful SBT is described by Epstein and Walkey (2020) as the following:
- The patient should breathe for 30-120 minutes with little to no ventilator support.
- The patient should not breathe faster than 35 breaths/minute for more than 5 minutes.
- The patient’s oxygen saturation should not fall below 90% (or PaO2 50 mmHg)
- The patient’s HR should not increase >140 bpm or sustain an increase > 20% from baseline.
- The patient’s systolic BP should remain between 90 - 180 mmHg.
- The patient should not demonstrate a change in mental status (somnolence, delirium, or agitation), increased anxiety, diaphoresis, or indications of severe discomfort.
- The patient’s HR should not fall below 50 bpm.
- The patient should not show signs of respiratory distress (e.g., accessory muscle use, thoracoabdominal paradox [the inward/upward movement of the abdomen during inspiration, asynchronous with the chest rise, indicative of absent or abnormal diaphragmatic motion).
- The patient’s PaCO2 should not increase > 10 mmHg, and their pH should not decrease >0.1 from the pre-weaning baseline.
Epstein and Walkey (2020) point out that for patients who have been mechanically ventilated for longer than 10 days, extended SBTs of up to 2 hours are recommended. Some studies have demonstrated that patients with severe underlying respiratory illness could take over 2 hours to fail an SBT. Blood gas analysis may be completed after an SBT, especially in those patients at increased risk of hypercapnia (e.g., history of COPD; Epstein & Walkey, 2020). The patient’s posture during the SBT should be individualized and according to their comfort. Patients with diaphragmatic paralysis typically prefer to be seated upright. Those with intercostal muscle weakness due to a lower cervical cord lesion may choose to be supine, while patients with COPD are more variable. The patient’s airway should be suctioned entirely before each SBT to ensure no excess secretions are present. Short-acting inhaled bronchodilators (e.g., beta-adrenergic or anticholinergic agents) may be given before an SBT to reduce airway obstruction unrelated to the artificial airway (Epstein & Joyce-Brady, 2020). Muscle fatigue typically occurs early in the SBT, requiring particularly close monitoring in the initial few minutes, so a decision can be made regarding whether or not the SBT should continue (MacIntyre, 2004). If a patient completes a successful SBT, extubation will be considered (Ouellette et al., 2017).
Patients who do not meet one or more of the SBT criteria may need to be placed back on ventilator support and repeat an SBT at a later time (Ouellette, 2017). Patients who fail an SBT should resume their prior ventilator settings allowing another 24 hours to recover from any fatigue before re-attempting another SBT (Epstein & Walkey, 2020). If a patient fails their SBT, it should prompt the team to evaluate the patient’s clinical picture to find possible causes, such as fluid status, pain control, bronchodilation requirement, or other potential reasons for continued respiratory distress. The ability to identify and treat a root cause of SBT failure may promote the patient’s chances of passing in the future (Ouellette et al., 2017).
Although less common, alternatives to SBT are used infrequently. Pressure support weaning is performed by establishing a PEEP of 4-5 cm H2O and pressure support of 12-18 cm H2O, targeting 25 spontaneous respirations per minute. When able, the PSV is then reduced by 2-4 cm H2O twice daily. The final goal is for the patient to tolerate 5-8 cm H2O of pressure support for at least 2 hours. Protocols describing more rapid reduction schedules have also been described. While PSV weaning protocols have been shown to reduce ventilation duration compared to weaning at the discretion of the attending clinician, the data comparing PSV weaning to daily SBT are conflicting (Epstein & Walkey, 2020).
Intermittent mandatory ventilation weaning utilizes the IMV settings described above to establish a minimum RR and tidal volume while allowing the patient to generate spontaneous breaths at will. These weaning protocols typically include starting the patient with an IMV of 8-12 and reducing the rate by 2-4 breaths/minute twice a day. The goal is for the patient to tolerate a rate of 4-5 breaths/minute (or less) for 2 hours or more. While IMV weaning protocols appear to reduce ventilation duration compared to weaning at the discretion of the attending clinician in clinical trials, they are not superior to daily SBTs, and could be inferior (Epstein & Walkey, 2020). Finally, the use of noninvasive ventilation immediately following extubation has been proposed in patients who fulfill the initial readiness testing criteria but fail their SBT. This strategy has been used predominantly in patients with a history of COPD or chronic hypercapnic respiratory failure or those at high risk of extubation failure (Epstein & Walkey, 2020).
Barriers to Weaning
Some patients may struggle to complete an SBT for various reasons, which can be simple (e.g., oversedation) or complex (e.g., the long-term effects of chronic illness). Root causes must be identified, treated, and reassessed. Interdisciplinary teams should be in the habit of monitoring for pH overcorrection, pleural effusions, heart failure, pulmonary edema, cardiac ischemia, and patient stress related to breathing through the narrowed diameter of an ETT. Some patients struggle to breathe spontaneously with several failed trials; those who fail their first two SBTs are considered difficult to wean. If the process requires more than three attempts and more than a week, this is termed prolonged weaning. If a patient cannot pass an SBT after 7-14 days, placement of a tracheostomy should be considered (Epstein & Joyce-Brady, 2020; Epstein & Walkey, 2020).
Moving Towards Extubation
Once a patient demonstrates success in an SBT, careful consideration must be made to ensure that the patient is ready for extubation. Before removing an ETT, the APRN should evaluate the patient’s ability to protect their airway and ensure airway patency once the advanced airway is removed. If the patient has a weak cough, excessive secretions, or poor mentation, the patient may be prone to aspiration once extubated. The inability to clear secretions due to an ineffective cough increases the risk that the patient will not tolerate extubation; this risk increases to 100% when a weak cough is combined with increased sputum volume and decreased level of consciousness. Obesity may also inhibit a patient’s ability to protect their airway (Hyzy, 2020). When assessing a patient’s readiness for extubation, the APRN should consider the following:
- Assessment of secretions should be completed. If a patient requires frequent suctioning (more than every 2-3 hours), has copious secretions (the volume can be measured using the suction canister), or if the secretions are excessively thick or dry, the medical team should consider delaying extubation (Epstein & Joyce-Brady, 2020, Hyzy, 2020).
- The patient should be assessed for a productive cough and the ability to clear secretions. If the patient can cough secretions through the ETT, they are more likely to clear secretions when extubated (Epstein & Joyce-Brady, 2020). The cough can be assessed informally during deep ETT suctioning, using spirometry, or using an index card test (an index card is held 1-2 cm from the loose end of the ETT while the patient is instructed to cough 3-4 times). A patient who cannot moisten the index card is three times more likely to struggle with extubation than a patient who can (Hyzy, 2020).
- The patient’s mental status directly impacts their ability to protect their airway. Studies show that patients with a GCS of 8 or above are more likely to be extubated successfully. The inability to perform simple commands is also associated with unsuccessful extubation (Epstein & Joyce-Bracy, 2020; Hyzy, 2020).
Airway patency is paramount in the success of extubation. Airway patency should be assessed to identify patients who may be at risk for post-extubation stridor. Patients who had traumatic intubation, a large ETT (> 8 mm in men, 7 mm in women, a small ratio of patient height to ETT diameter, or > 45% ratio of ETT to laryngeal diameter on advanced imaging), prolonged intubation (this varies from > 36 hours to > 6 days), or advanced age (over 80 years) are at the highest risk. Other risk factors include an elevated APACHE II score, a GCS < 8, female sex, a history of asthma, excessive tube mobility (i.e., insufficient fixation), deficient sedation, and the presence of aspiration. This can be assessed using a “cuff leak” test, in which the cuff around the ETT is deflated. If air does not pass (leak) around the ETT when the cuff is deflated, the patient is at higher risk for post-extubation stridor due to the reduced area between the ETT and the larynx. A cuff leak test is performed by auscultating for an air leak with a stethoscope placed over the superior trachea. Cuff leaks can also be assessed during volume-cycled ventilation by comparing the inspired and expired tidal volume to establish the cuff leak volume. In this case, a cuff leak volume of at least 110 mL or 25% of the delivered tidal volume is encouraging, while smaller volumes indicate increased risk for stridor postextubation (Epstein & Joyce-Brady, 2020; Hyzy, 2020).
In patients without risk factors for stridor, a cuff leak test is probably not necessary. In at-risk patients, failing the cuff leak test should indicate the need to delay extubation due to the potential for laryngeal edema. A short course of glucocorticoid may be administered before extubation to help reduce the swelling. 20 mg of methylprednisolone (Medrol) may be given every 4 hours for a total of 4 doses, or a single 40 mg dose may be administered approximately 4 hours before extubation (Hyzy, 2020).
Extubation should be carried out only when there is adequate staffing and resources available to address the possibility of reintubation, which is most often during the day. Nighttime extubations (after 7 pm) are rare. Those with a prior history of challenging intubation are assumed to be at high risk for difficulty while reintubating as well, and this should be considered when ensuring that staff and supplies are present if needed. Other factors to consider when timing extubation is the fatigue and availability of experts required to assist in the case of a problematic reintubation (Hyzy, 2020). While protocols will differ between institutions, the following are general guidelines for extubation (Epstein and Joyce-Brady, 2020; Hyzy, 2020):
- Tube feeds, if applicable, should be paused for at least an hour before extubation. Some facilities may measure residual volumes or aspirate gastric contents before extubation.
- Suction equipment (both oral and ETT) should be ready at the bedside to suction properly before extubation and manage oral secretions after the patient is extubated.
- A stethoscope should be present at the bedside to assess for post-extubation stridor.
- Suitable (i.e., according to the patient’s condition) supplemental oxygen equipment should be ready at the bedside, such as a low-flow and high-flow nasal cannula, a face mask, or noninvasive ventilation equipment.
- Vital signs, including HR, RR, BP, and SpO2, should be monitored closely during and after extubation.
- The patient should be sitting up as much as possible to promote airway clearance.
Other required equipment includes scissors (to cut/remove securement devices/tape) and a 10cc syringe. Prior to extubation, the ETT and the patient’s mouth should both be suctioned to ensure no secretions have pooled above the ETT cuff. To extubate, the ETT securement device is released by one team member while the ETT is held in place by another. The 10cc syringe is attached for cuff deflation. The patient is instructed to cough or exhale, during which the cuff is quickly deflated, and the ETT is removed in a smooth, swift motion. Any orogastric tubes can be removed simultaneously with the ETT. Oral secretions should be suctioned to avoid aspiration. The nurse and providers should immediately auscultate for post-intubation stridor. A patient who develops stridor may have upper airway edema and may need to be reintubated (typically with a smaller ETT) and often given a short course of glucocorticoids as described above. Patients at low risk for reintubation should be extubated with a regular nasal cannula at the bedside and weaned from this as tolerated (Epstein & Joyce-Brady, 2020; Hyzy, 2020).
Individualized plans for patients ensure that interventions are tailored to the patient’s needs. Patient assessment is key in post-extubation care. When developing a plan of care for the patient following extubation, the interdisciplinary team should consider the O2 and PEEP requirements as well as respiratory drive while the patient was ventilated. Many patients tolerate eating within a few hours of extubation, especially those intubated for a week or less. Those who were intubated for longer than 2 weeks or those with confounding factors that increase their risk of aspiration (e.g., neuromuscular condition, decreased level of consciousness, critical care myopathy) may need to wait 12-24 hours before eating. A swallow evaluation completed by a speech and language pathologist is a more conservative option for allowing an at-risk patient to resume eating safely while minimizing the risk of aspiration. Patients may be considered for discharge from the ICU after 12 - 24 hours (Hyzy, 2020).
Some patients will assume work of breathing appropriately after extubation but require additional O2 support. Risk factors for post-extubation respiratory failure include previously failed SBTs/extubations, a weak cough or absent cuff leak, a need for frequent suctioning (every 1-2 hours), GCS< 8 or other altered mental status (e.g., delirium), a positive fluid balance in the 24 hours prior to extubation, age over 65 with a chronic cardiac or respiratory disease (e.g., heart failure, COPD), pneumonia as the primary indication for mechanical ventilation, pulmonary hypertension, interstitial lung disease or multiple comorbidities. Following extubation, respiratory distress is typically related to poor secretion clearance, laryngeal edema, heart failure, bronchospasm, or aspiration. Respiratory failure following extubation typically presents with decreasing SpO2, increasing RR, stridor, and other indications of respiratory distress (e.g., accessory muscle use). A humidified high-flow nasal cannula (HFNC) provides O2 and PEEP support and has been shown to improve airway clearance and prevent reintubation in these patients. In combination with vigilant monitoring, preemptive NIPPV or HFNC are feasible options for extubated patients at increased risk for post-extubation respiratory failure. NIPPV is not used routinely for all patients following extubation but may be especially beneficial in those prone to hypercapnic respiratory failure (e.g., COPD) and those with heart failure. If a patient is stable but appears to be showing signs of respiratory distress following extubation, blood gas analysis and a chest x-ray may be considered to help determine the underlying etiology for the dysfunction (Epstein & Joyce-Brady, 2020; Hyzy, 2020).
Unplanned extubations are not frequent, occurring in only 3-12 % of intubated patients. The risk increases in patients with poorly secured ETTs, who are orally intubated (versus nasally), are agitated, less-sedated, or physically restrained. The patient should be assessed promptly, and a low threshold set for immediate reintubation at the first indication of respiratory failure. Approximately half of the patients with unplanned extubations require reintubation within 12 hours (Hyzy, 2020).
In patients reintubated due to stridor, the cuff leak test should be repeated after a short course of glucocorticoids as previously described. If the patient passes this test, bedside extubation can be re-attempted. If the patient does not pass this secondary cuff leak test, an alternative is to extubate the patient over an airway exchange catheter (e.g., a Cook catheter), allowing for a quick and easy reintubation, if necessary (Hyzy, 2020).
If patients become tachypneic or show any signs or symptoms of respiratory distress following extubation while on NIPPV, reintubation may be necessary. The underlying cause of respiratory failure should be identified to avoid future difficulty with subsequent extubation attempts. These are most often cardiac or respiratory but may be psychological (anxiety, depression, delirium), ventilator, or nutrition-related. The assessment should include a clinical exam (to identify laryngeal edema, heart failure), laboratory studies (i.e., complete blood count, electrolyte/metabolic panel, blood gas analysis), electrocardiography (to identify arrhythmias, heart failure, myocardial ischemia), and a chest x-ray (to determine aspiration, heart failure, pleural effusion). The ventilator circuit should be evaluated (assessing for auto-PEEP, overventilation), as well as the patient’s current sedative/analgesic medications. Mechanical ventilation should be continued for an additional 1-2 days before attempting to extubate again while the underlying cause is addressed (e.g., diuretics to manage heart failure, sedative medication adjustments to optimize the level of consciousness along with any mood disorder symptoms). A patient who fails more than one extubation trial generally requires a tracheostomy for extended weaning protocols (Epstein & Joyce-Brady, 2020; Hyzy, 2020). As mentioned earlier, tracheostomy placement enhances patient comfort, reduces the need for sedation, and facilitates weaning (Hyzy & McSparron, 2020).
Long-term acute care (LTAC) facilities focus solely on rehabilitation and ventilator weaning in challenging patients. Patients who may benefit from a transfer to such a facility include those with difficulty weaning previously, no ongoing acute illness, no dyspnea or hypoxemia during ventilation, a stable airway (e.g., tracheostomy), and a reliable route for daily nutrition in place (e.g., enteral feeding tube). These programs incorporate many of the tenets of rehabilitation nursing with respiratory care, integrating the family, caregivers, and exercise to accomplish specified and focused weaning goals (Epstein & Joyce-Brady, 2020). In cases of a reversible disease process, a patient should not be considered permanently ventilator-dependent until weaning attempts have been unsuccessful for 3 months (MacIntyre, 2004).
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