It has been shown clearly that hyperventilation causes vasospastic angina. However, leftward shiftment of the Hb-O2 dissociation curve leading to a difficulty in release of oxygen from the hemoglobin has not been ever been studied as a provocative factor. In this study we studied the effect of passive hyperventilation on coronary sinus lactate and oxygen content in patients undergoing coronary artery bypass surgery.

Material and Method:

15 patients undergoing elective coronary bypass operation were entered to the study. Coronary sinus catheter was placed by the surgeon before cardiopulmonary bypass for sampling. Arterial and coronary sinus blood samples were obtained before hyperventilation. 5 minutes after the initiation of hyperventilation second blood samples (PCO2 =19.6mmHg, P50vv =20.7mmHg) were obtained. Student t test was used for statistical analysis .

Results:

Arterial blood pH value increased from 7.42±0.06 to 7.60±0.06 (p<0.001). Coronary sinus oxygen content decreased from 8.0± 1.9ml/dL to 6.9±2.2 ml/dL after hyperventilation (p<0.002). Coronary sinus lactate level increased from 0.9±0.38 mmol to 1.45±0.60 mmol (p<0.006).

Conclusion:

The incidence of coronary artery spasm due to hyperventilation is approximately 25%. In our study group this incidence was found to be 80% which is significantly higher. This finding suggests that there seems to be additional factors other than vasospasm aggrevating coronary ischemia with hyperventilation such as impairment of the release of oxygen to the tissue.