CENTRAL AND MIXED VENOUS-BLOOD OXYGEN CORRELATE WELL DURING ACUTE NORMOVOLEMIC HEMODILUTION IN ANESTHETIZED PIGS

Background: Central venous oxygen saturation (ScvO2) and oxygen tensio n (p(cv)O(2)), obtained from the superior vena cava, correlate well wi th mixed venous (pulmonary arterial) oxygen saturation (SvO2) and tens ion (p(v)O(2)) when the hematocrit is normal. The present study was un dertaken to assess whether extreme hemodilution affects this relation. Methods: We compared mixed and central venous blood during graded art erial desaturation (inspired fraction of oxygen (FIO2) between 1.0 and 0.10) in 10 hemodiluted pigs, and in 10 pigs with normal hematocrit ( control), during fentanyl-ketamine-pancuronium anesthesia and mechanic al ventilation. Results: Arterial oxygen saturation decreased from 100 % at FIO2 = 1.0 to 44 +/- 12% at FIO2 = 0.10 (meant +/- SD). Venous ox ygen saturation ranged from 3.5% to 97.3%. The regression coefficient between SvO2 and ScvO2 was 0.97 (R-2 = 0.93, bias -2.4 +/- 5.8%) in th e hemodiluted and 0.99 (R-2 = 0.97, bias -3.0 +/- 5.0%) in the control group. Venous oxygen tension values ranged from 0.5 kPa to 9.5 kPa, a nd the regression coefficient for oxygen tension was 0.94 (R-2 = 0.89, bias -0.20 +/- 0.47 kPa) in the hemodiluted and 0.99 (R-2 = 0.97, bia s -0.43 +/- 0.48 kPa) in the control group. The regression coefficient for pH was 0.95 in the hemodiluted and 0.98 in the control animals. C onclusion: The findings indicate that also during hemodilution monitor ing of central venous blood oxygen may be as useful as monitoring of m ixed venous blood oxygen. (C) Acta Anaesthesiologica Scandinavica 42 ( 1998).