Electrocardiographic changes during cesarean section: a review.

Recently, various authors have noticed and studied the phenomenon of ST segment depression during cesarean section. We have undertaken a review of the various postulated etiologies including venous air emboli, hormonal influences, autonomic nervous system influences tachycardia, postural influences, hypokalemia, hyperventilation, and myocardial ischemia. It appears that ST segment depression during cesarean section is almost certainly a multifactorial phenomenon. There is evidence that some myocardial dysfunction occurs during these episodes. Additionally, the hormonal milieu, tachycardia, and the postural component probably contribute to the phenomenon. Venous air emboli, hypokalemia, and hyperventilation probably have a minimal role. The sympatholysis produced by regional anesthesia is of unclear significance. It is important to note the apparent lack of morbidity associated with these changes.