Peripheral circulation during sufentanyl and morphine anesthesia

Sufentanyl is a newly developed potent, short-acting fentanyl-like morphinomimetic. No independent studies of the peripheral circulation during sufentanyl anesthesia are available. In the present study we compared the effects of sufentanyl and morphine on the peripheral perfusion in dogs. The effects of total beta-blockade during sufentanyl and morphine anesthesia were also evaluated. We elected to record skeletal muscle surface pH (m-pH) continuously as an index of the microcirculation and cellular fractions. Arterial and mixed venous blood gases and acid-base status were measured to determine the respiratory component of changes in m-pH. Hematocrits, plasma electrolytes and plasma proteins were analyzed in order to permit calculations of fluid-shifts between the blood and the interstitial fluid. Sufentanyl (0.01 mg/kg) had no adverse effects on the peripheral perfusion. Morphine (4 mg/kg) caused a severe and rapid fall in m-pH from 7.29 to 7.11 during the 30-min experimental period. At the same time, calculated blood volume decreased by 20%. This hypovolemic deterioration of the circulation was probably caused by a histamine-mediated increase in capillary pressure with filtration of plasma from the circulation to the interstitial fluid. Calculated systemic vascular resistance was not correlated to the quality of the peripheral perfusion. Propranolol administered during sufentanyl and morphine anesthesia did not influence the peripheral perfusion. On the basis of the present study we recommend human studies on sufentanyl, and discourage the use of high-dose morphine anesthesia.