ABSTRACT
The purpose of this study was to assess the efficacy of clonidine in achieving perioperative hemodynamic stability in patients undergoing coronary artery bypass grafting performed under high-dose alfentanil anesthesia. Twenty-four patients with left ventricular ejection fraction greater than 0.5 were prospectively studied in a double-blind manner; those requiring emergency procedures were excluded. They were randomized to receive either oral clonidine or placebo together with their premedication. Induction of anesthesia was achieved with 10 mg of alfentanil infused over 5 minutes followed by a continuous infusion of 60 mg/h during 1 hour, or until sternotomy, and then 30 mg/h until the end of surgery. Hemodynamic responses to noxious stimuli were treated with additional alfentanil boluses and isoflurane when these were unsuccessful. Intraoperative hemodynamic profile analyses showed a continuous increase in systemic vascular resistance and mean arterial pressure in the clonidine group from the time of skin incision until the onset of bypass, whereas the cardiac output profiles remained similar in the two groups. The number of additional alfentanil boluses was similar. Isoflurane requirements (1/11 v 4/13) were not significantly different, but only a few patients required this therapy. The postbypass hemodynamic profiles were similar. Severe hemodynamic impairment occurred in the clonidine group during warming in the postoperative period: this group showed a drop in systemic vascular resistance index (1276 +/- 347 v 1757 +/- 415 dyn.sec.cm-5.m2) that could not be compensated for by an increase in cardiac output despite normal filling pressures, causing hypotension (66 +/- 10 v 79 +/- 16 mmHg). This hemodynamic status led to greater requirements for vasoactive agents and inotropics in this group.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Alfentanil/administration & dosage , Anesthesia, Intravenous , Clonidine/therapeutic use , Coronary Artery Bypass , Preanesthetic Medication , Blood Pressure/drug effects , Cardiac Output/drug effects , Clonidine/administration & dosage , Dobutamine/therapeutic use , Double-Blind Method , Female , Heart Rate/drug effects , Hemodynamics/drug effects , Humans , Hypotension/drug therapy , Male , Middle Aged , Monitoring, Intraoperative , Placebos , Postoperative Care , Pulmonary Wedge Pressure/drug effects , Time Factors , Vascular Resistance/drug effectsABSTRACT
It has been suggested that high plasma levels of alfentanil are required in order to control hemodynamic responses to noxious stimuli in patients undergoing myocardial revascularization. The present study was designed to determine the hemodynamic profile in 10 patients and the time course of alfentanil plasma concentrations and pharmacokinetics (7 patients) during and following coronary artery surgery using alfentanil administration based on an overdosage principle. Premedication consisted of lorazepam, 0.07 mg/kg, given 2 hours before surgery. Ten milligrams of alfentanil was given over 5 minutes for anesthesia induction, followed by an infusion of 60 mg/h until sternotomy and 30 mg/h up to skin closure. Additional 5-mg boluses were given prior to noxious intraoperative events. Hemodynamic measurements were performed prior to cardiopulmonary bypass. Blood was sampled simultaneously prebypass and then during the postbypass period for determination of alfentanil plasma levels. The very high alfentanil plasma concentrations achieved provided satisfactory intraoperative conditions in most, but not all, patients. Recovery time was short, despite the large amounts of narcotic used. It is concluded that very high doses of alfentanil associated with lorazepam premedication resulted in hemodynamic stability and markedly elevated narcotic plasma concentrations in most patients. Such plasma levels seem to provide satisfactory anesthetic conditions.
