Trendelenburg versus PASG application--hemodynamic response in man

Diminished venous return is the primary determinant of reduced cardiac output in hemorrhagic hypoperfusion. In this study the hemodynamic response of two therapies commonly employed to increase venous return in hemorrhagic hypoperfusion--pneumatic antishock garment (PASG) application and Trendelenburg (TREND) positioning--were compared in normovolemic man. Five patients had PASG pressure of 20 mm Hg compared with 10 degrees Trendelenburg, eight patients had 20 and 40 mm Hg PASG application compared with 10 degrees Trendelenburg. PASG application at both 20 and 40 mm Hg resulted in a significant increase in CVP (11.1 +/- 1.9 baseline to 16.0 +/- 2.7 PASG 40; p less than 0.01) left atrial pressure (LAP) (10.1 +/- 1.3 baseline to 14.4 +/- 1.8 PASG 20; p less than 0.01) pulmonary capillary wedge pressure (PCWP) (11.6 +/- 2.0 baseline to 16.8 +/- 3.4 PASG 40; p less than 0.01) and esophageal pressure (Pes) (5.0 +/- 0.8 baseline to 8.6 +/- 0.9 PASG 40; p less than 0.01). However, transmural right and left atrial pressure (RATP, LATP) and cardiac index (CI) were unchanged. Ten degrees of Trendelenburg resulted in no increase in CVP, PCWP, RATP, or LATP, but CI (2.67 +/- 0.07 baseline to 2.82 +/- 0.1 TREND; p less than 0.01) was significantly increased. Systemic vascular resistance index (570 +/- 46 TREND vs. 668 +/- 53 PASG 40; p less than 0.01) was significantly less in Trendelenburg compared to PASG at 40 mm Hg. The data demonstrate that elevation in CVP, LAP, and PCWP following PASG application is secondary to an increase in intrathoracic pressure (as measured by Pes).(ABSTRACT TRUNCATED AT 250 WORDS)