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.
From the Department of Critical Care Medicine (SBS, PCM, KJD, JF, PQE, SMB, RLD, CN, MAS), Clinical Center, National Institutes of Health, Bethesda, MD; Department of Surgery (PCM, KJD), The Children’s Hospital of Philadelphia, Philadelphia, PA; and Cardiology Branch (MAS), National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD.
Supported, in part, by the National Institutes of Health intramural program.
Datascope Corporation provided funding ($19,378) designated to support a 6-month lease of the ultrasound machine used for this animal study. In addition to the funds for the ultrasound, Datascope loaned the Critical Care Medicine Department three intra-aortic balloon counterpulsation devices (system 98XT) and supplied 26 sterile intra-aortic balloons. This funding represents <5% of the cost of the study. Datascope Corporation, as part of the agreement with the National Institutes of Health, did not participate in the collection or analysis of the data or the manuscript.
The authors have not disclosed any potential conflicts of interest.
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