Cardiovascular response in canine endotoxic shock: effect of ibuprofen pretreatment

Ibuprofen pretreatment increases arterial pressure and reduces mortality in endotoxic dogs. The increase in arterial pressure may be caused by increases in arterial resistance, arterial sphincter tone, or both. Thus it is not clear if ibuprofen pretreatment prevents the hemodynamic effects of endotoxemia or merely masks such effects by producing concomitant increases in arterial resistance. Accordingly, this study was performed to determine the effects of ibuprofen pretreatment on arterial pressure-flow relations and other measures of cardiovascular function in a canine model of endotoxic shock. In 19 pentobarbital-anesthetized and splenectomized, closed-chest dogs, biventricular stroke volumes were measured with electromagnetic flow probes, and intrathoracic vascular and pleural pressures were measured with catheters. Instantaneous venous return curves (see Pinsky MR, J Appl Physiol 56:765, 1984) were generated during positive-pressure ventilation, and steady-state arterial pressure-flow relations, left ventricular function, peripheral vascular compliance, oxygen consumption/oxygen delivery ratio, and arterial blood lactate levels were measured during two sequential volume loading and removal (20 ml/kg) sequences. All but two dogs received a bolus infusion of Escherichia coli endotoxin (2 mg/kg) between the two fluid challenge runs. Eleven of the 17 endotoxic dogs also received ibuprofen (15 mg/kg) immediately before the initial fluid challenge. Ibuprofen pretreatment abolished all hemodynamic effects of endotoxin, whereas in the untreated group endotoxin caused decreases in calculated arterial outflow pressure and in peripheral vascular capacitance. Oxygen consumption remained constant despite changes in oxygen delivery in the nonendotoxic dogs and in the ibuprofen-pretreated dogs, whereas oxygen consumption covaried with oxygen delivery in the endotoxic dogs not pretreated with ibuprofen. Arterial lactate levels were higher after endotoxin infusion (2.1 +/- 0.5 to 3.1 +/- 0.6 mmol/liter; P less than 0.05 pre- to postvolume) but were not different between treatment groups. These data suggest that ibuprofen alters many, but not all, of the hemodynamic effects of endotoxin infusion in the dog.