Analgesic and sedative drugs are necessary in the intensive care unit (ICU) to reduce pain and discomfort after surgery, trauma, and therapeutic interventions. Self-reports from physicians treated in the ICU describe endotracheal suction as an extremely painful and frightening intervention. Other common bedside procedures, such as intravascular cannulation, wound dressings, and nursing routines, are also painful.
Sedation is necessary in the majority of patients to enable them to tolerate intermittent positive-pressure ventilation. Adequate sedation also reduces the risk of self-extubation, which is a potentially fatal event, particularly in patients with a compromised airway. Critically ill patients with marginal tissue oxygen supply benefit from sedation because of a lower sympathetic activation which reduces oxygen consumption and improves the relationship between oxygen supply and consumption. Although there are no randomized studies in adult critical care other than investigations of surrogate endpoints for outcome, sedation for adult critically ill patients may give a better outcome in terms of mortality and morbidity as well as relief from unnecessary suffering.
However, excessive administration of sedative drugs induces hypotension and reduces respiratory drive. Modern respiratory therapy is based on a synergy between the patient and the machine, and maintenance of respiratory drive will reduce ventilator time and the risk of ventilator-associated complications. Prolonged weaning from respiratory support increases length of ICU stay and costs. The hypotension induced by sedative drugs may compromise tissue perfusion (e.g. cerebral perfusion pressure) or, if the hypotension is corrected, vasoactive drugs may increase the risk of arrhythmias and vasospasm. In addition, oversedation interferes with observation of neurological status and serious central nervous system complications, such as intracerebral hemorrhage or cerebral edema, may occur undetected.
Adaptation of sedation agent dosage to the need of the individual patient is important, as both under- and oversedation are harmful to the patient. The dosage of commonly used sedative drugs to achieve a desired level of sedation varies widely from patient to patient because of large variations in metabolism and pharmacodynamics. A valid method for monitoring sedation is needed to tailor sedation to the individual patient. Also, standardized methods for estimating sedation are often missing in research, so that comparisons between different study populations are obscured.
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