Hemodynamic Changes during Mechanical Ventilation in Infants and Small Children after Open Heart Surgery

Abstract

The study was undertaken to clarify the hemodynamic effects of intermittent positive pressure ventilation (IPPV) and intermittent mandatory ventilation (IMV) with variation of the positive end-expiratory pressure (PEEP) from 5 to 15 mbar. The cardiac index (CI) was measured with thermodilation techniques in 30 infants who underwent open-heart surgery with extracorporeal circulation for various congenital heart lesions. The age of the patients varied from 6 to 28 months and body weight from 4 to 15 kg. During IPPV the changing of PEEP levels up to 5 mbar did not have any effect on Cl. Further increase in the PEEP to 10 and 15 mbar caused a significant decrease in Cl (from 2.6 to 2.0 l.min-1.m-2, p less than 0.05). The oxygen consumption (VO2) did not change significantly (135 ml.min-1.m-2 to 128 l.min-1.m-2, p greater than 0.5). A positive end-expiratory pressure exceeding 5 mbar caused a decrease of intrapulmonary veno-arterial blood shunting (QS/QT) from 12.3 to 7.1%; p less than 0.01), while PEEP at the level of 5 mbar did not affect this parameter. The alveolo-arterial oxygen gradient (AsDO2) also decreased from 182 to 135 torr (p less than 0.01) when PEEP was 10 and 15 mbar.(ABSTRACT TRUNCATED AT 250 WORDS)