Risk Factors for Intraoperative Hypocapnia in Pediatric Neurosurgical Patients: A Retrospective Cohort Study

Hypocapnia has been associated with an increased risk and adverse outcomes in the injured brain. This study aimed to identify risk factors of intraoperative hypocapnia in pediatric neurosurgical patients when tidal volumes and respiratory rates were determined based on their weight and age, respectively.

Electronic medical records of pediatric patients (≤18 years) who underwent neurosurgery from December 2014 to January 2016 were retrospectively reviewed. Minute ventilation was fixed according to each patient's weight and age. Hypocapnia was defined as arterial partial pressure of carbon dioxide <35 mm Hg from intraoperative arterial blood gas analysis. Patients were divided into hypocapnia and nonhypocapnia groups. Risk factors for intraoperative hypocapnia were found using univariable and multivariable logistic regression analyses.

Of the 333 pediatric patients analyzed, 101 (30%) and 232 (70%) were included in the hypocapnia and nonhypocapnia groups, respectively. There was no difference in the minute ventilation between the two groups. The hypocapnia group had more patients taking valproate (8.9 vs. 2.2%; p = 0.008; OR, 4.441; 95% CI, 1.449-13.61) and carbonic anhydrase inhibitors (7.9 vs. 2.2%; p = 0.018; OR, 3.905; 95% CI, 1.245-12.25). An operation for hydrocephalus was more commonly performed in the hypocapnia group (26.7 vs. 15.9%; p = 0.017; OR, 1.923; 95% CI, 1.094-3.379). In the multivariable regression analysis, valproate (OR, 3.939; 95% CI, 1.250-12.41; p = 0.019), carbonic anhydrase inhibitor (OR, 3.345; 95% CI, 1.029-10.88; p = 0.045), and operation for hydrocephalus (OR, 1.838; 95% CI, 1.032-3.272; p = 0.039) were independent risk factors for intraoperative hypocapnia.

Pediatric patients taking valproate and carbonic anhydrase inhibitors and who were scheduled for surgery of hydrocephalus were at risk of developing intraoperative hypocapnia during neurosurgery, a finding warning the surgeon that a conventional ventilatory strategy would endanger these patients.