Intrathoracic Pressure Regulation Improves 24-Hour Survival in a Pediatric Porcine Model of Hemorrhagic Shock

Department of Emergency Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Pediatric Research (Impact Factor: 2.31). 06/2011; 70(3):267-71. DOI: 10.1203/PDR.0b013e3182275232
Source: PubMed


Hemorrhagic shock is a common cause of mortality and morbidity in the pediatric population. Intrathoracic pressure regulation (IPR) lowers intrathoracic pressure, thereby decreasing intracranial pressure and increasing venous return, cardiac output, and cerebral perfusion without the need for immediate fluid resuscitation. We hypothesized that IPR would improve hemodynamics and 24-h survival in a pediatric porcine model of hemorrhagic shock. Twenty piglets were subjected to a 50% total blood volume hemorrhage over 15 min and then randomized to treatment with either IPR or no treatment. After 60 min, survivors were autotransfused, weaned from the ventilator, and assessed and autopsied at 24 h. Mean arterial pressures (MAPs), cardiac index (CI), and arterial blood gases were recorded. MAP (mm Hg) was significantly higher in the IPR group (60.8 ± 3.7) versus controls (41.2 ± 4.6, p < 0.01). Mean CI (L/min/m²) was significantly higher with IPR (3.9 ± 0.24) versus controls (2.5 ± 0.39, p < 0.01). IPR survival rates were significantly improved with IPR [9/9 (IPR) versus 5/11 (controls); p < 0.02]. In this piglet model of hemorrhagic shock, IPR treatment safely and significantly improved MAP, CI, and 24-h survival rates.

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Available from: Anja Metzger, Dec 12, 2013
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    ABSTRACT: Intrathoracic pressure regulation (IPR) has been used to treat hypotension and states of hypoperfusion by providing positive pressure ventilation during inspiration followed by augmentation of negative intrathoracic pressure during expiration. This therapy augments cardiac output and lowers intracranial pressure, thereby providing greater circulation to the heart and brain. The effects of IPR on microcirculation remain unknown. Using a hemorrhagic model, hemodynamics and sublingual microcirculation were evaluated after a 55% blood loss over a 30 min timeframe in 10 female farm pigs (30 kg) previously anesthetized with isoflurane. After hemorrhage the mean arterial pressure was 27 ± 4 mm Hg. Blood cell velocity, the key indicator of microcirculation, was significantly reduced after the bleed from 1033 ± 175 μm/s pre-bleed to 147 ± 60 μm/s (p < 0.0001). Application of an IPR device reduced airway pressure during expiration to -9 mm Hg after each positive pressure breath (10 mL/kg, 10 breaths/min) and resulted in a rapid increase in systemic hemodynamics and microcirculation. During IPR treatment, average mean arterial pressure increased by 59% to 43 ± 6 mm Hg (p = 0.002) and blood cell velocity increased by 344% to 506 ± 99 μm/s (p = 0.001). In this animal model, we observed that microcirculation and systemic blood pressures are correlated and may be significantly improved by using IPR therapy.
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