SUBCUTANEOUS OXYGEN-TENSION - A USEFUL ADJUNCT IN ASSESSMENT OF PERFUSION STATUS

Objectives: Using a new fluorescence-quenching optode which, unlike ea rlier oximeters, neither consumes oxygen nor generates heat, we sought to determine the effects of hemorrhage and resuscitation on subcutane ous Po-2. Additionally, we compared the effects of resuscitation with diaspirin crosslinked hemoglobin, an oxygen-carrying solution, on subc utaneous Po-2 to that of traditional resuscitative fluids. We also com pared mean arterial pressure and central venous oxygen saturation, ind irect indices of perfusion, to subcutaneous Po-2, a direct index of pe rfusion. Design: Prospective trial, randomized for selection of treatm ent regimen. Setting: Shock-trauma laboratory of a medical university. Subjects: Male Sprague-Dawley rats, weighing 260 to 380 g. Interventi ons: Rats were bled 22 mL/kg and resuscitated, 1 min later, with eithe r 66 mL/kg of lactated Ringer's solution, 22 mL/kg of human serum albu min, 22 mL/kg of blood, or 22 mL/kg of diaspirin crosslinked hemoglobi n. A fifth group of animals was not resuscitated after hemorrhage. Sub cutaneous Po-2 and mean arterial pressure were monitored continuously throughout the experiment, while central venous oxygen saturation was measured intermittently. Measurements and Main Results: Subcutaneous P o-2 decreased in response to hemorrhage and, although it did increase after resuscitation with each fluid, no treatment was able to restore subcutaneous Po-2 to baseline within 2 hrs postresuscitation. Subcutan eous Po-2 continued to decrease after hemorrhage in the unresuscitated animals. In contrast, mean arterial pressure was restored to baseline values in only blood- and diaspirin crosslinked hemoglobin-treated an imals, although this effect was lost within 30 mins in the blood-treat ed group. Only blood restored the central venous oxygen saturation to baseline values in the early postresuscitation period. Conclusions: Th e fluorescence-quenching optode consistently followed changes in subcu taneous Po-2 during hemorrhage and after resuscitation. Diaspirin cros slinked hemoglobin performed as well as blood in restoring peripheral perfusion, as measured by subcutaneous Po-2, while both of these fluid s were superior to either lactated Ringer's solution or albumin. Both whole blood and diaspirin crosslinked hemoglobin restored mean arteria l pressure to baseline, although the effect of the latter was of a lon ger duration. The presser effect of the crosslinked hemoglobin did not affect peripheral perfusion, as reflected by the values for subcutane ous Po-2. Subcutaneous Po-2 is a useful adjunct in assessment of the a dequacy of peripheral perfusion and may help redefine targets for resu scitation.