Temperature-related differences in mean expired pump and arterial carbon dioxide in patients undergoing cardiopulmonary bypass.
OBJECTIVE
To investigate the relationship between arterial carbon dioxide (PaCO(2)) and mean expired pump CO(2) during cardiopulmonary bypass (PeCPBCO(2)) in patients undergoing cardiac surgery with CPB during steady state, cooling, and rewarming phases of CPB.


METHODS
Consenting patients, prospective study.


METHODS
University-affiliated hospital.


METHODS
Twenty-nine patients.


METHODS
Patients aged 22 to 81 years were enrolled. An alpha-stat acid-base regimen was performed during CPB. The PeCPBCO(2) was measured by an infrared multigas analyzer with the sampling line connected to the scavenging port of the oxygenator. Values for PaCPBCO(2) from the arterial outflow to the patient and PeCPBCO(2) during CPB at various oxygenator arterial temperatures were collected and compared. Data were analyzed by analysis of variance with 1-way repeated measures and post hoc pair-wise Tukey testing when appropriate. The differences between PaCPBCO(2) and PeCPBCO(2) were linearly regressed against temperature. A p value <0.05 was considered significant.


RESULTS
Three to 5 data sets during CPB were collected from each patient. The mean gradient between PaCPBCO(2) and PeCPBCO(2) was positive 12.4 +/- 10.0 mmHg during the cooling phase and negative 9.3 +/- 9.9 mmHg during the rewarming phase, respectively. On regression of the data, the difference between PaCPBCO(2) and PeCPBCO(2) shows a good correlation with the change in temperature (r(2) = 0.79). The arterial CO(2) +/- x mmHg can be predicted by the formula PaCPBCO(2) = (-2.17x + 69.2) + PeCPBCO(2), where x is temperature in degrees C.


CONCLUSIONS
Monitoring the mean expired CO(2) value from the CPB oxygenator exhaust scavenging port with a capnography monitor provides a continuous and noninvasive data source to aid in sweep flow CPB circuit management during CPB.
Peng
Yong G
YG
Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL 32610, USA. ypeng@anest.ufl.edu
Morey
Timothy E
TE
Clark
Dale
D
Forthofer
Matthew D
MD
Gravenstein
Nikolaus
N
Janelle
Gregory M
GM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001784:Blood Gas Analysis; D001831:Body Temperature / Q000502:physiology*; D019296:Capnography / Q000379:methods; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism*; D002315:Cardiopulmonary Bypass / Q000379:methods*; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D011446:Prospective Studies; D017694:Rewarming / Q000379:methods
D002245:Carbon Dioxide