The Effects of Naloxone on Central Hemodynamics and Myocardial Metabolism in Experimental Propoxyphene‐Induced Circulatory Shock

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Abstract
The courses of the hemodynamic and cardiometabolic effects of naloxine were evaluated in propoxyphene-induced shock in eight pentobarbital-anesthetized pigs. Circulatory shock was induced by an infusion of propoxyphene chloride 15 mg .cntdot. min-1 i.v. At shock, i.e. MAP < 60 mmHg and/or CI < 2.0 1 .cntdot. min-1 .cntdot. n-2, naloxone was administered at 0.75, 1.5 and 3.0 mg .cntdot. kg-1 with an interval between increments of 8 min. The propoxyphene infusion of 15 mg .cntdot. min-1 was continued throughout the study. Following the injection of naloxone 0.75 mg .cntdot. kg-1, increases were observed (% of baseline value) in MAP (41%), i.e. deficit to baseline 59%, HR (66%), CI (76%) and SVI (108%), whereas MPAP and MPAOP were unchanged, dP/dt increased (34%). In the coronary circulation naloxone initiated the following changes: CSF increased (69%) as did MVo2 (48%) with unchanged MO2-extraction, but CVR decreased further (36%). The maximum effects of naloxone were registered 2-3 min after 0.75 mg kg-1. Following 1.5 and 3.0 mg .cntdot. kg-1, no changes in hemodynamics were observed other than those caused by progressing propoxyphene intoxication.