The Incidence and Severity of Hypocarbia in Neonates Undergoing General Anesthesia

BACKGROUND: Extended periods of hypocarbia in preterm infants may be associated with intraventricular hemorrhage, periventricular leukomalacia, and bronchopulmonary dysplasia. To evaluate the current anesthetic practice in preterm neonates, we retrospectively reviewed the intraoperative course with regard to P_aCO2 and ventilation during non-cardiac surgical procedures in infants <60 weeks postmenstrual age.

METHODS: This was a single-center, retrospective study during non-cardiac surgical procedures in neonates. Hyperventilation was defined as a P_aCO2 ≤ 35 mm Hg, significant hyperventilation as a P_aCO2 ≤ 30 mm Hg, and extreme hyperventilation as a P_aCO2 ≤ 25 mm Hg.

RESULTS: The study cohort included 112 neonates, with a median postnatal age of 40 weeks, median gestational age of 38 weeks, and median weight of 5 kg. Thirty-seven subjects (33%) had at least one arterial blood gas value that demonstrated hyperventilation. Thirteen (12%) were noted to have significant hyperventilation (P_aCO2 ≤ 30 mm Hg) and 2 had extreme hyperventilation (P_aCO2 ≤ 25 mm Hg).

CONCLUSIONS: The incidence of at least one arterial blood gas that demonstrated inadvertent hyperventilation in neonates was high during intraoperative care. These data may provide the baseline for future studies that address more rigorous monitoring and control of P_aCO2 during intraoperative care. Although the duration of the anesthetic care and surgical procedure is brief compared with the neonatal ICU length of stay because there is no demonstrated benefit of hypocapnia and, in fact, well-documented harm associated with hyperventilation in neonates, care should be directed at limiting inadvertent hyperventilation.