OPIOIDS - CLINICAL USE AS ANESTHETIC AGENTS

Opioids (narcotic analgesics) are widely used in the practice of anesthesia for preanesthetic medication, systemic and spinal analgesia, supplementation of general anesthetic agents, and as primary anesthetics. The last use is particularly widespread for major operations, especially those involving patients with cardiovascular disease. The use of opioids in anesthetic doses is based on the absence of cardiac depression by the opioids. As with all anesthetic drugs, the opioids have limitations and side effects, but for the most part, these are easily managed on the basis of knowledge of their pharmacology. The key to their efficient use is careful titration of dose according to the individual patient's responses to the drug as well as to noxious stimulation. Although there is a very wide margin of safety, allowing administration of enormous doses intraoperatively when the patient's ventilation is supported mechanically, the disadvantage of using doses far in excess of the individual patient's need is a prolonged recovery from anesthesia with the risk of postoperative ventilatory depression. Titration of the dose can be facilitated by computer-controlled infusion pumps with the benefit that the recovery time from anesthetic doses can be appropriate for the individual patient and surgical procedure, and postoperative analgesia can be continued by patient-controlled analgesia, which is another example of computer-controlled opioid infusion. Although specific opioid antagonists are available, their use to antagonize residual anesthetic effects is potentially hazardous.