• R B Hirschl, K F Heiss, R E Cilley, K A Hultquist, J Housner, and R H Bartlett.
• Department of Surgery, University of Michigan Medical Center, Ann Arbor 48109-0331.
• Surgery. 1992 Jul 1; 112 (1): 37-44.

AbstractSystemic oxygen delivery (DO2) is normally four to five times higher than oxygen consumption (VO2), and VO2 is independent of DO2. If DO2 is decreased to less than twice VO2, a state of anaerobic metabolism and supply dependency occurs. Some authors have reported that this biphasic relationship is altered in the adult respiratory distress syndrome or sepsis to a condition of continuous supply dependency. If that were true, it would affect both our understanding and management of metabolism during sepsis. Therefore we measured VO2 and DO2 in a dog peritonitis model. DO2 was regulated with controlled pericardial tamponade. During sepsis VO2 increased 28% from a mean baseline of 5.6 to 7.3 cc O2/kg/min (p less than 0.005). As progressive cardiac tamponade was applied during sepsis, the DO2/VO2 ratio fell. When the DO2/VO2 ratio was greater than 2.4, VO2 remained independent of DO2. At DO2/VO2 ratios less than 2.4, VO2 was dependent on the level of DO2, and it diminished rapidly as DO2 decreased. Oxygen saturation in mixed venous blood (SvO2) consistently reflected the DO2/VO2 ratio in a fashion similar to that in normal dogs. A ratio of DO2/VO2 of 2.4 corresponded with an SvO2 of 42% +/- 12%, which was identified as a statistically significant critical SvO2 that marked onset of VO2 supply dependence. In this dog septic model, VO2 is independent of DO2 when DO2 is adequate. A state of continuous supply dependency does not exist. SvO2 reflects the status of the DO2/VO2 relationship in the septic state.

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