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: 2.84). 06/2011; 70(3):267-71. DOI: 10.1203/PDR.0b013e3182275232
Source: PubMed

ABSTRACT 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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    ABSTRACT: The inspiratory impedance threshold device (ITD) has been shown to improve hemodynamic variables and survival outcomes during cardiopulmonary resuscitation in animals and humans. We hypothesized that use of an ITD, with a resistance of -10 cm H2O, will improve hemodynamics and short-term survival rates during hypovolemic hypotension in spontaneously breathing pigs. Female farm pigs ( approximately 26 kg) were intubated and anesthetized with propofol with the dose adjusted to permit spontaneous respirations. They were bled to 50% of calculated blood volume through an arterial catheter and then prospectively randomized to either treatment with an ITD or observation alone. Arterial and intratracheal pressures as well as arterial blood gases were measured. After 90 min the ITD was removed, normal saline was administered to all surviving animals, the anesthetic was discontinued, and animals were allowed to recover. Statistical analysis was performed with one-way repeated ANOVA and survival rates were calculated with Kaplan-Meier analysis. Treatment with the ITD resulted in lower intratracheal inspiratory pressure in the treatment group (-11+/-0.4 mmHg versus -4+/-0.7 mmHg, respectively, P<0.005). Mean arterial pressure after 30 min of treatment with the ITD was higher in the treatment group (61.1+/-5.5 mmHg versus 37.4+/-2.1 mmHg, respectively, P<0.005). All pigs in the control group died within 65 min of the initial bleed, whereas 7/8 (87%) treated with an ITD survived for >90 min (P<0.001). During the recovery phase, 6/8 (75%) in the ITD group survived for >3h and awoke without neurological deficit; one surviving animal in the ITD group never woke up. Arterial oxygenation was not compromised in the ITD group. Use of an ITD improved blood pressure and short-term survival rates in a spontaneously breathing porcine model of hypovolemic hypotension.
    Resuscitation 03/2006; 68(3):399-404. DOI:10.1016/j.resuscitation.2005.07.015 · 3.96 Impact Factor
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    ABSTRACT: An inspiratory impedance threshold device was evaluated in spontaneously breathing animals with hypotension to determine whether it could help improve systemic arterial pressures when fluid replacement was not immediately available. Prospective, randomized. Animal laboratory. Thirty-nine female farm pigs (weight, 28-33 kg). A total of 39 anesthetized spontaneously breathing pigs were treated with an impedance threshold device, with cracking pressures from 0 to -20 cm H2O. Four separate experimental protocols were performed: protocol A, in which the hemodynamics of seven pigs were examined during application of an impedance threshold device at various levels of inspiratory impedance (-5, -10, -15, and -20 cm H(2)O), both before and after a severe, controlled hemorrhage to a systolic blood pressure of 50 - 55 mm Hg; protocol B, in which nine pigs bled to systolic blood pressure of 50 -55 mm Hg were treated with an impedance threshold device set at -12 cm H2O and were compared with nine others treated with a sham device; protocol C, in which the effects of the impedance threshold device on mixed venous gases were measured in seven hemorrhaged pigs; and protocol D, in which the effects of the impedance threshold device on cardiac output in seven hemorrhaged pigs were measured. During initial studies with both normovolemic and hypovolemic pigs, sequential increases in inspiratory impedance resulted in a significant increase in systolic blood pressure, whereas diastolic left ventricular and right atrial pressures decreased significantly and proportionally to the level of impedance. When comparing the sham vs. active impedance threshold device (-12 cm H(2)O) in hypotensive pigs, systolic blood pressure (mean +/- sem) with active impedance threshold device treatment increased from 70 +/- 2 mm Hg to 105 +/- 4 mm Hg (p <.01). Pressures in the control group remained at 70 +/- 4 mm Hg (p <.01). Cardiac output increased by nearly 25% (p <.01) with the active impedance threshold device when calculated using the mixed gas equation and when determined by thermodilution. These studies demonstrate that it is feasible to use a device that creates inspiratory impedance in spontaneously breathing normotensive and hypotensive pigs to increase blood pressure and enhance cardiopulmonary circulation in the absence of immediate fluid resuscitation. Further studies are needed to evaluate the potential long-term effects and limitations of this new approach to treat hypovolemic hypotension.
    Critical Care Medicine 08/2004; 32(7):1555-62. DOI:10.1097/01.CCM.0000131207.29081.A2 · 6.15 Impact Factor
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    ABSTRACT: Hemorrhagic shock secondary to trauma is associated with poor survival. The impedance threshold device (ITD) has been shown to improve blood pressure and survival rates in an adult porcine model of hemorrhagic hypovolemia. Pediatric hemodynamics, anatomy, and physiology differ from adults. Evaluation of the ITD has not been previously assessed in a pediatric porcine model of hypovolemia induced by hemorrhage. To determine whether ITD-assisted breathing, with and without positive end-expiratory pressure, will improve key hemodynamic parameters following hypovolemia induced by hemorrhage in a pediatric porcine model. Intubated, anesthetized, hemodynamically stable, spontaneously breathing piglets were rapidly bled 40% of their calculated blood volume. Piglets' hemodynamic and intrathoracic pressures were continuously monitored during 10-min normovolemic baseline, bleed to hypotensive baseline, 10-min ITD-assisted breathing, 10 mins without ITD, 10-min ITD-assisted breathing randomized with or without positive end-expiratory pressure (3 cm H2O), 10 mins without ITD, reinfusion of shed blood, 10-min baseline following return to normovolemia. The ITD had an inspiratory cracking pressure of -7 cm H2O. Transthoracic echocardiographic parameters were measured at the end of each 10-min period. There was no significant difference in baseline assessments between groups. Systolic blood pressure, cardiac index, and stroke volume index were significantly greater during ITD-assisted breathing. There was a trend toward increased left ventricular end-diastolic dimension during ITD use. Heart rate, systemic vascular resistance index, left ventricular end-systolic dimension, and shortening fraction did not change significantly during ITD-assisted breathing. There was equivalent improvement in systolic blood pressure, cardiac index, and stroke volume index, when the ITD alone and ITD plus positive end-expiratory pressure were used. ITD-assisted breathing significantly augmented systolic blood pressure, cardiac index, and stroke volume index in this pediatric porcine model of hemorrhagic hypovolemia. These effects appear related to increased left ventricular preload and not by increased systemic vascular resistance or heart rate. These beneficial effects of ITD-assisted breathing are not changed by the addition of positive end-expiratory pressures of 3 cm H2O.
    Critical Care Medicine 10/2004; 32(9 Suppl):S398-405. DOI:10.1097/01.CCM.0000139950.39972.68 · 6.15 Impact Factor

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