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 × 109 cfu/kg) to assess the effects of intra-aortic balloon counterpulsation during sepsis with increasing risk of death.
Main Results: Compared with lower bacterial doses (4–7 × 109 colony-forming units/kg), control animals challenged with the highest dose (8 × 109 colony-forming units/kg) had a greater risk of death (mortality rate 86% vs. 17%), with worse lung injury ([A − a]o2), and renal dysfunction (creatinine). These sicker animals required higher norepinephrine infusion rates to maintain blood pressure (and higher Fio2) 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 μg/kg/min; p = 0.002) and systemic vascular resistance index (1.44 ± 0.57 dynes/s/cm5/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.