Anaerobic metabolism during cardiopulmonary bypass: predictive value of carbon dioxide derived parameters.
BACKGROUND
Hyperlactatemia during cardiopulmonary bypass (CPB) is a common event and is associated to a high morbidity and mortality after cardiac operations. The present study is aimed to identify the possible predictors of hyperlactatemia during CPB among a series of oxygen and carbon dioxide derived parameters measured during CPB.


METHODS
This is a prospective observational study on 54 patients undergoing cardiac surgery with CPB. Hyperlactatemia was defined as an arterial lactate concentration higher than 3 mMol/L. Serial blood lactate assays have been performed during CPB, and their association to a number of oxygen and carbon dioxide derived parameters was explored.


RESULTS
Arterial blood lactate concentration was positively correlated to the CPB duration, the carbon dioxide elimination, and the respiratory quotient, and negatively correlated to the presence of the aortic cross-clamping, the body surface area, the ratio between the oxygen delivery and the carbon dioxide production, and the arterial oxygen saturation. Predictors of hyperlactatemia during CPB are a carbon dioxide production higher than 60 mL.min(-1).m(-2), a respiratory quotient higher than 0.9, and a ratio between oxygen delivery and carbon dioxide production lower than 5.


CONCLUSIONS
Carbon dioxide derived parameters are representative of hyperlactatemia during CPB, as a result of the carbon dioxide produced under anaerobic conditions through the buffering of protons by the bicarbonate system. The carbon dioxide elimination rate measured at the exhaled site of the oxygenator may be used for an indirect assessment of the metabolic state of the patient.
Ranucci
Marco
M
Department of Cardiothoracic Anesthesia, Policlinico San Donato, Milan, Italy. cardioanestesia@virgilio.it
Isgrò
Giuseppe
G
Romitti
Federica
F
Mele
Sara
S
Biagioli
Bonizella
B
Giomarelli
Pierpaolo
P
D000368:Aged; D000693:Anaerobiosis; D019540:Area Under Curve; D002245:Carbon Dioxide / Q000097:blood*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D001026:Coronary Artery Bypass; D005260:Female; D006349:Heart Valve Diseases / Q000601:surgery; D006801:Humans; D007773:Lactates / Q000097:blood*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D010313:Partial Pressure; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve
D007773:Lactates; D002245:Carbon Dioxide; D010100:Oxygen