Incidence of Hypocapnia, Hypercapnia, and Acidosis and the Associated Risk of Adverse Events in Preterm Neonates

• Published in: Respiratory care Vol. 63; no. 8; pp. 943 - 949
• Main Authors: Brown, Melissa K, Poeltler, Deborah M, Hassen, Kasim O, Lazarus, Danielle V, Brown, Vanessa K, Stout, Jeremiah J, Rich, Wade D, Katheria, Anup C
• Format: Journal Article
• Language: English
• Published: United States Daedalus Enterprises, Inc 01-08-2018
• Subjects: Acidosis; Blood gas analysis; Clinical trials; Health aspects; Hypercapnia; Hypocalcemia; Premature infants; carbon dioxide; premature; hypocapnia; intraventricular hemorrhage; very low birthweight infant; hypercapnia; mortality; blood gas analysis; bronchopulmonary dysplasia; ventilator-induced lung injury
• ISSN: 0020-1324; 1943-3654
• DOI: 10.4187/respcare.05801

Permissive hypercapnia is a lung-protection strategy. We sought to review our current clinical practice for the range of permissive hypercapnia and identify the relationship between P
and pH and adverse outcomes.
A secondary analysis of a delayed cord-clamping clinical trial was performed on all arterial blood gas tests in the first 72 h in infants < 32 weeks gestational age. All arterial blood gas values were categorized into a clinical range to determine the percent likelihood of occurring in the total sample. The univariate and multivariate relationships of severe adverse events and the time-weighted P
, fluctuation of P
, maximal and minimal P
, base excess, and pH were assessed.
147 infants with birthweight of 1,206 ± 395 g and gestational age of 28 ± 2 weeks were included. Of the 1,316 total samples, < 2% had hypocapnia (P
<30 mm Hg), 47% were normocapnic (P
35-45 mm Hg), 26.5% had mild hypercapnia (P
45-55 mm Hg), 13% had moderate hypercapnia (P
55-65 mm Hg), and 6.5% had severe hypercapnia (P
≥ 65 mm Hg). There were no adverse events associated with hypocapnia. Subjects with death/severe intraventricular hemorrhage had a higher mean P
of 52.3 versus 44.7 (odds ratio [OR] 1.16, 95% CI 1.04-1.29,
= .006), higher variability of P
with a standard deviation of 12.6 versus 7.8 (OR 1.15, 95% CI 1.03-1.27,
= .01), and a lower minimum pH of 7.03 versus 7.23 (OR 0, 95% CI 0-0.06,
= .003). There was no significant difference in any variables in subjects who developed other adverse events.
The routine targeting of higher than normal P
goals may lead to a low incidence of hypocapnia and associated adverse events. Hypercapnia is common, and moderate hypercapnia may increase the risk of neurologic injury and provide little pulmonary benefit.