Pharmacodynamics of pentamorphone during coronary artery bypass grafting in humans

Pentamorphone is a new, highly potent opioid reported to have minimal cardiovascular effects in humans and a high therapeutic index in animals. Pentamorphone was injected intravenously (IV) as the sole anesthetic in 10 patients with left ventricular ejection fractions greater than 0.35 who were undergoing elective coronary artery bypass grafting (CABG). After premedication with lorazepam, 40 micrograms/kg, and establishment of hemodynamic monitoring, pentamorphone was infused at a rate of 2 micrograms/kg/min until unconsciousness occurred (5.1 +/- 1.6 micrograms/kg). Anesthetic induction was accompanied by an average 30% decrease in systolic, diastolic, and mean arterial pressure (MAP), a 19% decrease in heart rate (HR), but no change in cardiac output (CO) or pulmonary artery occlusion pressure. Five patients had a MAP less than 60 mm Hg after induction. Following incision, blood pressure, pulmonary artery occlusion pressure, and CO were unchanged from baseline but HR remained significantly lower. Despite additional pentamorphone (total dose 9.6 +/- 1.8 micrograms/kg), 6 patients required thiopental and/or enflurane to control hypertension intraoperatively. When pentamorphone is used as the sole IV anesthetic in lorazepam-premedicated patients with normal or mildly impaired ventricular function, there is a high incidence of hypotension during induction, and poor control of hemodynamic responses to stimulation. Pentamorphone, 10 micrograms/kg, does not seem to offer any significant advantage over opioids currently used for anesthesia in patients undergoing CABG.