Trendelenburg versus PASG Application in Moderate Hemorrhagic Hypoperfusion
In hemorrhagic hypoperfusion one of the therapeutic goals of pneumatic antishock garment (PASG) application is to increase cardiac output, presumably by augmenting venous return from below the diaphragm, an effect expected to be similar to Trendelenburg positioning. The purpose of this study was to compare the hemodynamic response of these two common therapeutic interventions in hemorrhagic hypoperfusion. Five anesthetized dogs were bled over 10 minutes 24% of measured blood volume on two separate days. At the beginning of hemorrhage, they randomly received either PASG application or Trendelenburg positioning. PASG pressures of 30 ± 5 mm Hg were applied to produce an inferior vena cava pressure of 10–15 mm Hg. Such PASG pressure had been shown previously to not diminish cardiac output from PASG application. Mean arterial pressure was maintained throughout the experiment with both therapies. With PASG application, cardiac index was depressed and systemic vascular resistance was elevated at 10, 20, and 30 minutes following hemorrhage. In contrast, Trendelenburg therapy maintained cardiac index and produced no significant increase in systemic vascular resistance index. Thus Trendelenburg therapy preserved mean arterial pressure primarily by maintaining cardiac output, probably by increasing venous return, whereas PASG application preserved mean arterial pressure primarily by increasing systemic vascular resistance. For treatment of moderate hemorrhagic hypoperfusion, Trendelenburg positioning may be superior therapy to PASG application.