Permissive hypercapnia is a well-accepted ventilator strategy for the management of acute respiratory distress syndrome as well as other causes of respiratory failure, such as the respiratory distress syndrome seen in premature infants. Multiple studies have demonstrated that both myocardial contractility and systemic vascular resistance (SVR) decrease with hypercapnic acidosis, the ultimate effect being that cardiac function is maintained or even augmented. The effects of hypercapnic acidosis on cardiac function in the preterm infant have not been elucidated. In a prospective observational study, published in the May issue of The Journal of Pediatrics, the authors analyzed paired blood gasses and echocardiograms from 29 hemodynamically stable preterm infants at 30 weeks gestation
Samples were taken within the first two weeks of life, either during the transitional period (days 1-3) or post-transitional period (days 4-14). In all, there were 103 paired blood gasses and echocardiograms from 21 subjects in the transitional period and 44 paired studies from 15 subjects in the post-transitional period. During the transitional period, pH and PaCO2 had no effect on any of the hemodynamic measures, including shortening fraction, stress-velocity index, or SVR. However, during the post-transitional period, the infants’ hemodynamics resembled those seen in adult patients. The results of the study demonstrated differences in the way the older infants responded to acidosis and hypercapnia. Read the full Concise Critical Appraisal.