Effects of intra-aortic balloon counterpulsation in a model of septic shock.

Background: Fluid refractory septic shock can develop into a hypodynamic cardiovascular state in both children and adults. Despite management of these patients with empirical inotropic therapy (with or without a vasodilator), mortality remains high. Objectives: The effect of cardiovascular support using intra-aortic balloon counterpulsation was investigated in a hypodynamic, mechanically ventilated canine sepsis model in which cardiovascular and pulmonary support were titrated based on treatment protocols. Methods: Each week, three animals (n = 33, 10-12 kg) were administered intrabronchial Staphylococcus aureus challenge and then randomized to receive intra-aortic balloon counterpulsation for 68 hrs or no intra-aortic balloon counterpulsation (control). Bacterial doses were increased over the study (4-8 x 10(9) Cfu/kg) to assess the effects of intra-aortic balloon counter-pulsation during sepsis with increasing risk of death. Main Results: Compared with lower bacterial doses (4-7 x 10(9) colony-forming units/kg), control animals challenged with the highest dose (8 x 109 colony-forming units/kg) had a greater risk of death (mortality rate 86% vs. 17%), with worse lung injury ([A - a]0(2)), and renal dysfunction (creatinine).These sicker animals required higher norepinephrine infusion rates to maintain blood pressure (and higher F10(2)) and positive end-expiratory pressure levels to maintain oxygenation (p <= 0.04 for all). In animals receiving the highest bacterial dose, intra-aortic balloon counterpulsation improved survival time (23.4 +/- 10 hrs longer; p = 0.003) and lowered norepinephrine requirements (0.43 +/- 0.17 mu g/kg/min; p = 0.002) and systemic vascular resistance index (1.44 +/- 0.57 dynes/s/cm(5)/kg; p = 0.0001) compared with controls. Despite these beneficial effects, intra-aortic balloon counterpulsation was associated with an increase in blood urea nitrogen (p = 0.002) and creatinine (p = 0.12). In animals receiving lower doses of bacteria, intra-aortic balloon counterpulsation had no significant effects on survival or renal function. Conclusions. In a canine model of severe septic shock with a low cardiac index, intra-aortic balloon counterpulsation prolongs survival time and lowers vasopressor requirements. (Grit Care Med 2009; 37:7-18)