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This column is designed to provide the latest research findings in patient care in a format that is easy to understand and integrate into clinical practice. The information is drawn from individual protocols in the various Protocols for Practice series available from AACN, which cover research-based practice protocols in detail.
Asynchrony with the ventilator ("bucking the vent") is a common indication for starting treatment with sedative, analgesic, and neuromuscular blocking agents. These agents depress respiratory effort to reduce patients’ discomfort and facilitate oxygenation, particularly when complex ventilatory modes are being used. However, many patients who require mechanical ventilation need short-term sedation and/or analgesia for reasons that are less obvious in noncommunicating patients than in patients who can communicate: to relieve anxiety produced by the intensive care unit (ICU) environment, underlying illness, or invasive diagnostic or therapeutic procedures (eg, presence of an endotracheal tube, tracheal suctioning). It is well known that inadequate control of pain or anxiety can stimulate various stress responses, resulting in tachycardia, increased myocardial oxygen consumption, reduced lung volumes, immuno-suppression, hypercoagulability, and, ultimately, increased morbidity and mortality.1
Careful review of a patient’s medical history may reveal further indications for early intervention with sedatives. Patients with a history of substance abuse or anxiety disorder treated with sedatives may require rapid reinstitution of these agents to avoid the development of withdrawal.2
Neuromuscular blocking agents may be considered when use of the maximal dosage of sedative and analgesic agents has not achieved the desired goal of compliance with the ventilator.3 This situation occurs most often in patients with persistent, severe hypoxemia related to respiratory disease, extremely agitated patients, and patients who require complex ventilator modes for whom respiratory effort must be controlled.
Q: What factors must be considered when selecting a specific agent?
Heightened awareness of the level of anxiety and pain experienced by critically ill patients, and of the inadequacy of currently used treatment strategies, has stimulated debate about the optimal method for sedating patients who require mechanical ventilation. In order to be most effective, treatment should be selected primarily on the basis of the patient’s signs and symptoms, the presence of underlying disease, and the patient’s medication history.4,5 If a nurse perceives that a patient is experiencing pain (eyes tearing, tachycardia, sweating), analgesic therapy is warranted. However, pain or discomfort may not be apparent, and patients’ inability to communicate their immediate needs effectively compounds the problem. Therefore, sedation may be empirically initiated simply to dull the patient’s ICU experience, that is, the pain and anxiety produced by invasive life-supporting and monitoring devices. Additionally, opioid analgesics are useful in blunting cough or diaphragmatic movements that may interfere with the effective provision of mechanical ventilation. Often, combined therapy with an opioid analgesic and a benzodiazepine is used to provide synergistic sedation or respiratory depression. The amnestic qualities of the benzodiazepines (eg, midazolam, lorazepam) may be particularly useful during an unpleasant procedure. Patients who have delirium or persistent agitation despite maximal sedation may benefit from a trial of haloperidol. Haloperidol can be safely combined with other sedatives (eg, benzodiazepines, opioids) and may eventually allow the dose of these agents to be reduced, thereby lowering the associated risk of adverse effects. Pertinent clinical information on sedatives, analgesics, and neuromuscular blockers frequently used in the ICU are summarized in Tables 1
and 2. Cost is an additional factor to be considered when selecting drugs to be routinely used in the ICU. In general, the oldest agents—diazepam, morphine, and pancuronium—are the least expensive, but costs must be determined within individual institutions to be most pertinent to the decision-making process.
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Finally, a history of long-term use of sedatives or analgesics should not be overlooked, because early intervention with substitutive treatment may be required to avoid the development of withdrawal.
Q: How should drug therapy be monitored?
It is imperative that therapeutic end points be established to guide adjustments in drug dosage and to enhance the continuity of patients’ care. Random titration based solely on a sedation or pain scale places patients at risk for oversedation or undersedation and increases the frustration level for caregivers. Keeping the predetermined treatment goals in mind, caregivers should evaluate the patient’s levels of sedation, agitation, and pain each time that vital signs are assessed. Such an evaluation allows the effectiveness of treatment to be determined and enables potential treatment-related complications to be recognized and prevented. Periodic tapering of the dose is recommended, as the patient’s condition allows, to determine the lowest effective dose and to avoid drug accumulation and a prolonged sedative effect.
In patients receiving continuous treatment with neuromuscular blockers, monitoring the patient’s level of discomfort is more difficult. Autonomic instability alone may not always signal the need to increase the dosage and provide boluses of sedatives as needed. Therefore, neuromuscular blockade must be periodically reversed to ensure that the sedation and analgesia being provided are adequate.
Similarly, neuromuscular blockade must be carefully monitored according to the desired clinical end point, namely, tolerance and compliance with the ventilator mode used to achieve adequate oxygenation. Neuromuscular blockade can be assessed by observing the patient’s respiratory effort via airway pressure waveforms or pulmonary compliance measurements.7 In addition, peripheral nerve stimulation via the train-of-four (TOF) method is widely used to assess the degree of paralysis and to avoid excessive neuromuscular blockade. Peripheral nerve stimulation should be done at baseline with the patient adequately sedated to determine the level of stimulation required during therapeutic paralysis. Failure to do so may significantly reduce the accuracy of subsequent TOF monitoring. The timing of TOF monitoring depends on the clinical situation and the method of administration of neuromuscular blockers. If intermittent boluses are used, TOF monitoring can be done at the time of peak effect (to assess the dose) and just before the next scheduled dose (to assess the frequency). During continuous infusions, TOFmonitoring may be required as often as every 2 to 3 hours, depending on the patient’s condition and its relationship to the goals of treatment.
Q: What are the complications of these drug therapies and how can they be avoided?
The major complication associated with sedative and analgesic therapies in the ICU is oversedation, which can prolong the need for mechanical ventilation and the length of the ICU stay. Avoiding this situation may be difficult, particularly if large doses are administered by continuous intravenous infusion for prolonged periods. However, as tolerated, doses should be tapered periodically so that the lowest effective dose is administered and excessive accumulation is avoided. If doses cannot be tapered, intermittent doses of long-acting agents (eg, diazepam, lorazepam) may be tried, and such agents have the advantage of allowing reassessment before each scheduled dose. Intermittent dosing may also be desirable in patients who cannot tolerate large fluid volumes associated with continuous infusions. Alternatively, interrupting sedative infusions once daily has been recommended to facilitate assessments of neurological function and current sedative needs, and such interruptions may result in improved outcomes for patients.8 Despite its potential appeal, this approach should not be used in patients at risk for drug withdrawal.
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This article is based on the protocol Sedation and Neuromuscular Blockade in Patients With Acute Respiratory Failure by Jill M. Luer (product #170725: $11, AACN members; $14, nonmembers). It was taken from the Care of the Mechanically Ventilated Patient series (set of 7, product #170720; $52, AACN members; $64, nonmembers) of AACN’s Protocols for Practice. Protocols can be obtained from AACN, 101 Columbia, Aliso Viejo, CA 92656-1491, (800) 899-AACN, (949) 362-2000.
References
This article has been cited by other articles:
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  N. Ballard, L. Robley, D. Barrett, D. Fraser, and I. Mendoza Patients' Recollections of Therapeutic Paralysis in the Intensive Care Unit Am. J. Crit. Care., January 1, 2006; 15(1): 86 - 94. [Abstract] [Full Text] [PDF]
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