Transcutaneous oxygen tension measurements during hemorrhagic hypoperfusion using trendelenburg and the pneumatic antishock garment

Abstract

Transcutaneous oxygen tension (PtCO2) was observed during hemorrhagic hypoperfusion using four therapeutic modalities: pneumatic antishock garment (PASG), 20 degrees Trendelenburg positioning, combined PASG-Trendelenburg, and whole blood infusion. Anesthetized mongrel dogs were mechanically ventilated. A heated transcutaneous oxygen sensor was applied to the skin overlying the sternum. Animals were bled over 10 min of 25% of their calculated blood volume. A therapeutic intervention was applied at the onset of hemorrhage (PASG, Trendelenburg, PASG-Trendelenburg or control). All animals were observed for 20 min, then during a 10-min shed blood reinfusion period, and for 20 min thereafter. PtCO2 was measured continuously and the following were measured serially: cardiac output, mean arterial pressure (MAP), mixed venous oxygen tension (MvO2), and arterial oxygen tension (PaO2). Cardiac index (CI) and the oxygen extraction ratio were calculated. PtCO2 decreased immediately after hemorrhage in all animals. Control values remained consistently below values for active interventions during this time. All groups regained baseline levels of PtCO2 after reinfusion of shed blood volume. PaO2 remained nearly constant during all experiments. MAP and CI fell in all groups following hemorrhage but did so less precipitously in the PASG group. The PASG and PASG-Trendelenburg groups showed the greatest increase in CI during reinfusion. These results suggest that when PtCO2 is relied upon as an indicator of adequacy of resuscitation during moderate hemorrhagic shock, that cutaneous perfusion may be improved by the PASG or Trendelenburg position, and that perfusion is most effectively restored by blood infusion.