Effects of naloxone on hemodynamics, oxygen transport, and metabolic variables in canine endotoxin shock

The effects of naloxone (2 mg/kg body weight) on hemodynamics, oxygen transport, and some metabolic variables were studied in mongrel dogs under general anesthesia and controlled ventilation. All 19 dogs received Escherichia coli endotoxin (1.5 mg/kg) and subsequently were randomized into three groups. The first group (N = 7) served as a control group in which at 90 min after endotoxin (t 90), NaCl (0.65%, 4 ml/kg) was infused during 30 min. In the second group (N = 7) naloxone (2 mg/kg) dissolved in the same amount of fluid was administered at t 90 in 30 min. In the third group (N = 5) naloxone (2 mg/kg) was injected as a bolus in 5 ml NaCl (0.65%) at t 90, which was followed by NaCl (0.65%, 4 ml/kg) infused in 30 min. Differences in the three groups after intervention were tested statistically. After naloxone, blood pressure, cardiac output, and left ventricular stroke work increased significantly. Although oxygen availability increased, oxygen consumption and serum lactate did not change when compared with the control group. As to all other measured and calculated variables, no systematic differences were found in the three groups. In six dogs, plasma beta-endorphins were measured and were shown to rise substantially after induction of endotoxin shock. As to the hemodynamic changes, our observations confirm data from the literature. Naloxone apparently improves hemodynamics in endotoxin shock, but at least in this study fails to influence oxygen consumption and serum lactate levels.