The clinical utility of an index of global oxygenation for guiding  red blood cell transfusion in cardiac surgery.
BACKGROUND
This observational study explored the potential utility of oxygen extraction ratio (O2ER) as an adjunct to the hemoglobin (Hb) concentration for guiding red blood cell (RBC) transfusion decisions after cardiac surgery with cardiopulmonary bypass (CPB).


METHODS
Hb and O2ER measures were obtained before as well as 15 and 120 minutes after RBC transfusion episodes (defined as 1-2 RBC units given in succession after CPB, within 24 hr. of surgery). Changes related to RBC transfusions among patients with normal (30%) and elevated(>30%) pretransfusion O2ERs were analyzed.


RESULTS
Of the 176 patients enrolled, 74 received RBC transfusions. Of these, 50 had data available for 62 transfusion episodes. Pretransfusion episode O2ER values were elevated in 27 cases and normal in 35(56%) cases. Among those who received transfusion for low Hb concentration, 43 percent (27/62) had normal pretransfusion O2ER values. While the posttransfusion O2ER values did not change in patients with normal pretransfusion O2ER values, they did decrease inpatients with elevated pretransfusion O2ER values (% change [+/-SD] at 15 and 120 min after transfusion was -5.2 +/- 7.8 and -3.8 +/- 8.0%, respectively; p < 0.05).


CONCLUSIONS
If a normal O2ER in anemic patients with no evidence of organ dysfunction indicates adequate tissue oxygen delivery, then our findings suggest that incorporating O2ER into the transfusion decision will substantially reduce post-cardiac surgery RBC transfusions by allowing us to safely avoid transfusing this group of patients. Future studies are needed to assess the validity of this conclusion.
Orlov
David
D
Faculty of Medicine, Department of Anesthesia, Toronto General Hospital, Toronto, Ontario, Canada.
O'Farrell
Rachel
R
McCluskey
Stuart A
SA
Carroll
Jo
J
Poonawala
Humara
H
Hozhabri
Siroos
S
Karkouti
Keyvan
K
D000328:Adult; D000368:Aged; D000740:Anemia / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects / Q000534:rehabilitation; D017707:Erythrocyte Transfusion / Q000379:methods*; D005260:Female; D006305:Health Status Indicators; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D011237:Predictive Value of Tests; D013903:Thoracic Surgery / Q000379:methods; D055815:Young Adult
D006454:Hemoglobins