Ebrahim Hassani , Rasoul Farasatkish , Evaz Heydarpour , Mohammadzia Totoonchi , Alireza Mahoori ,
Volume 67, Issue 9 (6 2009)
Abstract
Background: Measuring end tidal carbon dioxide (ETCo2) is one of the methods used for estimating arterial carbon dioxide (PaCo2) during general anesthesia. ETCo2 measurements maybe obviate the need for repeating arterial puncture for determination of arterial PaCo2. This study performed to determine the accuracy of ETCo2 levels as a measure of PaCo2 levels in patients undergoing coronary artery bypass graft and also to evaluate variation of the gradient between PaCo2 and ETCo2, peri- cardiopulmonary bypass operation. Methods: In a prospective, cross-sectional study, a total of 40 patients with age 57±11 (35-73) years old undergoing coronary artery bypass graft were enrolled. ETCo2 levels (mmHg) were recorded using side stream capnography at the time of arterial blood gas sampling, before (T0) and after (T1) cardiopulmonary bypass. Results: Mean P(a-ET)Co2 at T0 was 4.3±4.4mmHg, with the mean PaCo2, 33±6mmHg and mean ETCo2, 29±5mmHg and these values at T1 were 4.5±4.1mmHg, 33±5mmHg and 29±2mmHg respectively. There was no variation of the mean gradient (PaCo2-PETCo2) during, before and after cardiopulmonary bypass (p>0.870). Significant correlation was found between ETCo2 and PaCo2 at T0 and T1 (r=0.754 and 0.685respectively and p=0.001). Conclusion: Capnography is a non- invasive and a safe technique for determining arterial PCo2 and for measurements of ETCo2 that correlate well with PaCo2 values in healthy patients undergoing coronary artery bypass graft. ETCo2 measurements maybe sufficient measures of PaCo2 in selected patients and obviate the need for repeatingarterial blood gas determination. Further study is warranted.
