Mixed venous oxygen desaturation during early mobilization after coronary artery bypass surgery.
BACKGROUND
Early postoperative mobilization induces a marked reduction in mixed venous oxygen saturation (S(v)O(2)) after aortic valve replacement. We investigated whether a similar desaturation occurs among coronary artery bypass grafting (CABG) patients, and if the desaturation was related to the preoperative ejection fraction (EF).


METHODS
Thirty-one CABG patients with a wide range in EF were included in an open observational study. We recorded hemodynamic and oxygenation variables during mobilization on postoperative day 1 and day 2 using a pulmonary artery catheter.


RESULTS
Patients with an EF ranging from 24 to 87% were mobilized without clinical problems. S(v)O(2) at rest was 65.4 +/- 4.9% (mean +/- SD) on day 1 and 64.3 +/- 5.8% on day 2 (NS). During mobilization, cardiac index and oxygen delivery were reduced while oxygen consumption was increased (P-values: 0.000, 0.007 and 0.000, respectively). Consequently, oxygen extraction increased, resulting in a marked reduction in S(v)O(2)-42.9 +/- 8.3% on day 1 and 47.4 +/- 8.5% on day 2 (P = 0.025 between days). Several pre-, intra- and postoperative factors were tested as possible predictors for S(v)O(2) during mobilization. No factor contributed substantially.


CONCLUSIONS
Patients with CABG exhibit a marked desaturation during early postoperative mobilization. Preoperative ejection fraction did not affect S(v)O(2) during exercise. The clinical consequences and underlying mechanism require further investigation.
Kirkeby-Garstad
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I
Department of Anesthesia and Intensive Care, St Olav Hospital, University Hospital of Trondheim, Trondheim, Norway. Idar.Kirkeby-Garstad@medisin.ntnu.no
Sellevold
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OF
Stenseth
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R
Skogvoll
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E
D000368:Aged; D000369:Aged, 80 and over; D000762:Anesthesia Recovery Period; D000792:Angiography; D001021:Aortic Valve / Q000601:surgery; D001026:Coronary Artery Bypass; D004434:Early Ambulation; D005260:Female; D019918:Heart Valve Prosthesis Implantation; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology
D010100:Oxygen