oxygen tension, measurement of; oxygen tension, transcutaneous measurement
Transcutaneous Oxygen Tension Measurements During Graded Hemorrhage and Reinfusion
Measurement of transcutaneous oxygen tension (PtC02) has been suggested as a useful monitoring tool in the hypovolemic patient. Our study was undertaken to evaluate changes in PtCO 2 that occur during graded hemorrhage and reinfusion,, and to compare PtCO 2 values to standard cardiorespiratory and biochemical parameters during hypovolemia. Seven mongrel dogs were bled 50% of their estimated blood volume (44 mL/kg) over one hour. This was followed by a one-hour monitoring period, a 30minute reinfusion period, and an additional one-hour monitoring period. Pulmonary capillary wedge pressure (PCWP), central venous pressure (CVP), cardiac output (CO), mean arterial pressure (MAP), mixed venous oxygen tension (My02), arterial blood gases, and PtCO 2 were measured serially throughout the study period. Cardiac index (CI), peripheral vascular resistance (PVR), 02 consumption, delivery, and percentage of extraction were calculated for each sampling period. A statistically significant fall in CL MvO 2 and PCWP occurred following the first 10% of blood loss; PtCO 2 and MAP fell significantly after 20% hemorrhage; CVP fell after 30% hemorrhage. PtCO 2 rose significantly after the first 10% of reinfusion, and it continued to rise during the entire reinfusion period, as did MvO 2, CO, MAP, CVP, and PCWP. In contrast to the other measured variables, the elevations in PtC02, and MvO 2 were more pronounced early in the reinfusion period. During postreinfusion monitoring, PtCO 2, MvO 2, CO, and PCWP fell significantly despite maintenance of prehemorrhage MAP and CVP. Overall PtCO 2 correlated well with MvO 2 and the 02 extraction ratio, and to a lesser extent with CL MAP, and 02 delivery. We conclude that PtCO 2 changes predictably in response to graded hemorrhage and reinfusion, and it correlates well with other measures used to assess severity of hemorrhage and adequacy of resuscitation.