Oxygen consumption in hemodialysis patients undergoing cardiopulmonary bypass

Cardiopulmonary bypass (CPB) can be successfully performed in patients on hemodialysis. However, ischemic complications occur more often in these patients. This could partly be because of shunting through the arteriovenous (AV) fistula during CPB, resulting in reduced peripheral flow and oxygen (O2) delivery. Inadequate oxygen delivery during CPB should be reflected in a lower oxygen consumption (VO2) compared with patients without an AV fistula.

To test the hypothesis, the authors analyzed VO2 in three groups of patients retrospectively. Group 1 included 14 patients with end-stage renal failure (creatinine level 9.1 +/- 0.3 mg/dL, urea level 126 +/- 8 mg/dL) requiring hemodialysis through an AV fistula. Group 2 included 13 patients with compensated renal insufficiency (creatinine level 3.1 +/- 0.4 mg/dL, urea level 106 +/- 10 mg/dL) without an AV fistula. Group 3 included 14 patients with normal renal function (creatinine level 1.0 +/- 0.1 mg/dL, urea level 44 +/- 4 mg/dL).

An operating room of a university hospital.

Patients undergoing cardiac surgery requiring CPB.

VO2 was calculated from the recorded hemodynamic and blood gas data using standard formulae. Data were analyzed using a two-way analysis of variance with a repeated measurement on one factor. Before undergoing CPB, VO2 was similar in all three groups. VO2 decreased in all three groups during hypothermic CPB (standard flow rate 2.2 L/min/m2, standard temperature 29 degrees C) and returned to prebypass levels during rewarming. There was no difference in VO2 among the three groups during hypothermic CPB or during rewarming. Only base excess decreased more in group 1 patients compared with the other groups (p < 0.001).

During hypothermic CPB at a flow rate of 2.2 L/min/m2, shunting through an AV fistula is unlikely to lead to decreased VO2 in dialysis patients.