Hypocarbia and adverse outcome in neonatal hypoxic-ischemic encephalopathy

J Pediatr. 2011 May;158(5):752-758.e1. doi: 10.1016/j.jpeds.2010.10.019. Epub 2010 Dec 10.


Objective: To evaluate the association between early hypocarbia and 18- to 22-month outcome among neonates with hypoxic-ischemic encephalopathy.

Study design: Data from the National Institute of Child Health and Human Development Neonatal Research Network randomized, controlled trial of whole-body hypothermia for neonatal hypoxic-ischemic encephalopathy were used for this secondary observational study. Infants (n = 204) had multiple blood gases recorded from birth to 12 hours of study intervention (hypothermia versus intensive care alone). The relationship between hypocarbia and outcome (death/disability at 18 to 22 months) was evaluated by unadjusted and adjusted analyses examining minimum PCO(2) and cumulative exposure to PCO(2) <35 mm Hg. The relationship between cumulative PCO(2) <35 mm Hg (calculated as the difference between 35 mm Hg and the sampled PCO(2) multiplied by the duration of time spent <35 mm Hg) and outcome was evaluated by level of exposure (none-high) using a multiple logistic regression analysis with adjustments for pH, level of encephalopathy, treatment group (± hypothermia), and time to spontaneous respiration and ventilator days; results were expressed as odds ratios and 95% confidence intervals. Alternative models of CO(2) concentration were explored to account for fluctuations in CO(2).

Results: Both minimum PCO(2) and cumulative PCO(2) <35 mm Hg were associated with poor outcome (P < .05). Moreover, death/disability increased with greater cumulative exposure to PCO(2) <35 mm Hg.

Conclusions: Hypocarbia is associated with poor outcome after hypoxic-ischemic encephalopathy.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Carbon Dioxide / blood*
  • Female
  • Humans
  • Hypocapnia / etiology*
  • Hypocapnia / mortality
  • Hypocapnia / therapy
  • Hypothermia, Induced / methods*
  • Hypoxia-Ischemia, Brain / complications*
  • Hypoxia-Ischemia, Brain / mortality
  • Hypoxia-Ischemia, Brain / therapy
  • Infant, Newborn
  • Male
  • Survival Rate
  • Treatment Outcome
  • United States / epidemiology


  • Carbon Dioxide