[Monitoring of cardiac rhythm changes during surgical operations with total cardiopulmonary bypass with haemodilution and hypothermia in infants and small children (author's transl)].

Surgical corrections of some serious cardiovascular anomalies in infants and small children were attempted within the last 2 years; 12 severely ill infants and children below the age of 3 years were operated. All, but one, were below 10 kg of body weight, and in all of them there was a considerable weight deficit, more than 30%. The risk of operation was undertaken because of the ineffectiveness of medical treatment and very bad prognosis. The following cardiovascular lesions were operated: large aortopulmonary septal defects, localized just above the valvular rings in 2 patients with severe pulmonary hypertension, with very good effect in both; tetralogy of Fallot - in 2 babies, in one with good effect; congenital mitral obstruction with pulmonary hypertension in one case, with good effect; total anomalous pulmonary venous return of supracardiac type in one child, decreased 1 week following operation; type 1 complete transposition of great arteries in one baby, deceased one day following operation; large ventricular septal defects, with systemic or nearly systemic pulmonary hypertension in 5 children, in one with long-term good effect. A modification of the Barrat-Boyes, Neutze and Simpson method, based upon a combination of surface and core cooling was applied. Thoracotomy was performed after surface cooling to 34-32 centigrades, and then a single venous cannula was inserted into the right atrium and an arterial cannula -- into the aorta. Deep cooling was obtained during perfusion, using a heat exchanger. The duration of cooling perfusion was, on an average, 20 min., and the patients were cooled to a temperature of 23-21 centigrades. The corrections were performed on relaxed and bloodless heart, during the circulatory arrest lasting for 20-65 min. (40 min. on an average). Following repair the patients were rewarmed to temperatures of 36-37 centigrades by warming perfusion lasting on the average 40 min., including assisted circulation, until a haemodynamically sufficient cardiac output was present. Silicated ACD-blood, diluted to a hematocrit value of 28-30 Vol. % by a polyelectrolyte buffered solution was used for priming and perfusion. During all the procedures any pH and HCO3 deviations were balanced currently. At the time of cooling perfusion, when the patient's rectal temperature fell down to 30-25 centigrades, the heart started to fibrillate. At temperatures above 26 degrees C ventricular fibrillation was sometimes preceded by sinus bradycardia, or sinoatrial block/arrest, with an AV nodal rhythm and gradually increasing intraventricular conduction slowing. In some cases high degree AV block appeared. At temperatures of 25-23 centigrades - slow fibrillation appeared, followed usually by a complete cardiac arrest.