The place for short-acting opioids: special emphasis on remifentanil

Pain is among the worst possible experiences for the critically ill. Therefore, nearly all intensive care patients receive some kind of pain relief, and opioids are most frequently administered. Morphine has a number of important adverse effects, including histamine release, pruritus, constipation, and, in particular, accumulation of morphine-6-glucuronide in patients with renal impairment. Hence, it is not an ideal analgesic for use in critically ill patients. Although the synthetic opioids fentanyl, alfentanil, and sufentanil have better profiles, they undergo hepatic metabolism and their continuous infusion also leads to accumulation and prolonged drug effects. Various attempts have been made to limit these adverse effects, including daily interruption of infusion of sedatives and analgesics, intermittent bolus injections rather than continuous infusions, and selection of a ventilatory support pattern that allows more spontaneous ventilation. However, these techniques at best only limit the effects of drug accumulation, but they do not solve the problem. Another type of approach is to use remifentanil in critically ill patients. Remifentanil is metabolized by unspecific blood and tissue esterases and undergoes rapid metabolism, independent of the duration of infusion or any organ insufficiency. There are data indicating that remifentanil can be used for analgesia and sedation in all kinds of adult intensive care unit patients, and that its use will result in rapid and predictable offset of effect. This may permit both a significant reduction in weaning and extubation times, and clear differentiation between over-sedation and brain dysfunction. This article provides an overview of the use of short-acting opioids in the intensive care unit, with special emphasis on remifentanil. It summarizes the currently available study data regarding remifentanil and provides recommendations for clinical use of this agent.