The Cardiocirculatory and Metabolic Effects of Endotoxin Challenge after Canine Resuscitated Hemorrhagic Shock

Abstract

Although adequate volume resuscitation has decreased mortality from hemorrhagic shock, recovery in many patients is complicated by sepsis. To determine whether a subject debilitated by hemorrhagic shock would exhibit greater cardiocirculatory dysfunction when challenged with sepsis, ten dogs (Group I) were hemorrhaged to a mean arterial blood pressure of 30 mm Hg. After 2 hours of hypotension, shed blood and lactated Ringer's solution (50 ml/ kg) were given, and the dogs were observed for 3 to 6 days. Ten dogs were sham hemorrhaged and served as controls (Group II). On the experimental day, all cardiovascular and hemodynamic parameters were measured in both groups of animals before endotoxin challenge. There was no significant difference in cardiac output, stroke volume, stroke work, +dP/dt max, myocardial blood flow, myocardial oxygen metabolism, or acid-base balance in the two groups. Compared to sham-hemorrhaged dogs, resuscitated shock dogs had a significantly lower mean arterial blood pressure (127 ± 7 vs. 110 ± 6 mm Hg; p < 0.05), and heart rate was significantly higher (86 ± 6 vs. 109 ± 7 beats/minute; p < 0.05). Furthermore, maximal rate of left ventricular pressure fall (—dP/dT max) was significantly lower in the animals previously hemorrhaged, suggesting a persistent defect in left ventricular relaxation. Blood glucose and insulin levels were significantly elevated in the resuscitated shocked dogs, likely due to increased circulating catecholamine concentrations and enhanced glycogenolysis. Endotoxin shock caused significant hypotension, acidosis, and impaired regional perfusion in all dogs. In addition, cardiac output, stroke volume, dP/dT, and left ventricular end-diastolic pressure fell and hyperglycemia and hyperinsulinemia occurred in all dogs after endotoxin injection. Our data indicate that endotoxin challenge impaired cardiocirculatory function and acid-base balance to a similar extent in all dogs, regardless of a previous episode of resuscitated shock.