LOW-OXYGEN EXTRACTION DESPITE HIGH OXYGEN DELIVERY CAUSES LOW-OXYGEN CONSUMPTION IN PATIENTS WITH BURNS RECOVERING SLOWLY FROM OPERATIVE HYPOTHERMIA

Background. Patients with burns who eventually succumbed to their inju ries tended to recover more slowly from operative hypothermia than tho se who survived. Slower recovery was associated with a lower postopera tive oxygen consumption (V over dot O-2). We have now investigated whe ther this was due to impairment of oxygen delivery or extraction. Meth ods. This study was performed in 13 adult patients with severely burns . One hundred four measurements of V over dot O-2 by indirect calorime try were made during recovery from 23 episodes of operative hypothermi a in 11 patients. Sixty-six measurements of oxygen transport variables by balloon-tipped pulmonary artery catheter were made after 17 episod es of operative hypothermia in six patients. Body temperature was moni tored in the urinary bladder. Results. The rate of temperature rise (T over dot) showed a strong positive correlation with V over dot O-2 me asured both by indirect calorimetry (r = 0.91, p < 0.001) and by ballo on-tipped pulmonary artery catheter (r = 0.83, p < 0.001). Oxygen deli very (D over dot O-2) was above normal in nearly all patients. Oxygen extraction was law in patients recovering slowly (T over dot < 1.0 deg rees C/hr) and high in those recovering quickly (T over dot greater th an or equal to 1.0 degrees C/hr). During fast recovery V over dot O-2 (373 +/- 77 ml . min(-1) . m(-2); mean +/- SD) was approximately three times normal and was independent of D over dot O-2. In contrast, a st rong linear relationship existed between V over dot O-2 and D over dot O-2 during slow recovery (r = 0.76, P < 0.001). Conclusions. Patients with burns with slow recovery from operative hypothermia exhibited im paired oxygen extraction and dependence of V over dot O-2 on D over do t O-2 over a wide range. This picture resembles that in patients with critical illness.