Opioid analgesics in anesthesia: with special reference to their use in cardiovascular anesthesia

In this article, an attempt has been made to review the use of receptor stimulating pure agonist opioids in anesthesia, especially in patients with cardiovascular disease. Particular emphasis has been placed on the use of opioids in high doses to produce anesthesia, techniques that recently have become popular in cardiovascular anesthesia. A major benefit of opioid anesthesia is the cardiovascular stability obtained during induction and throughout operation, even in patients with severely impaired cardiac function. There is a considerable body of evidence to support this claim when fentanyl is used. Anesthetic doses of morphine are associated with a higher incidence of cardiovascular disturbances and other problems, and, therefore, more attention to detail is required in order to achieve adequate anesthesia and hemodynamic stability. Although other opioids have been used as sole or principal agents in anesthesia for cardiovascular surgery, none have gained widespread acceptance. Meperidine, for example, which is widely used in lower (nonanesthetic) doses as a supplement to nitrous oxide in cardiac and noncardiac surgery, has proved unsuitable because of severe hemodynamic disturbances when high doses are given. However, initial reports concerning two of the newer agonist opioids, sufentanil and alfentanil, suggest that they may prove to be suitable alternatives and perhaps provide advantages over morphine and fentanyl in patients with or without cardiovascular disease. Although cardiovascular stability usually can be assured in the chronically sick cardiac patient with opioid anesthesia, this is not always so with the healthier patient, particularly those presenting for coronary artery surgery. A frequently occurring problem in these patients is hypertension during or after sternotomy, which can result in myocardial ischemia and infarction. The incidence of severe hypertension (increases in systolic blood pressure greater than 20% of control values) can be reduced drastically by increasing the dose of opioid, e.g., up to 140 micrograms/kg of fentanyl. However, despite such large doses, some patients will continue to need treatment with vasodilators, inhalation anesthetics, or other supplements at certain periods during cardiovascular operations. The use of very large doses of opioids also will prolong postoperative respiratory depression. High doses of opioids can reduce or prevent the hormonal and metabolic responses to the stress of surgery. However, even very large doses of fentanyl or its newer analogues do not prevent marked increases in plasma catecholamine concentrations in response to cardiopulmonary bypass.(ABSTRACT TRUNCATED AT 400 WORDS)