UC Davis

Background

Infants with hypoxic-ischemic encephalopathy are often treated with therapeutic hypothermia and high-frequency ventilation. Fluctuations in P_aCO2 during therapeutic hypothermia are associated with poor neurodevelopmental outcomes. Transcutaneous CO₂ monitors offer a noninvasive estimate of P_aCO2 represented by transcutaneously measured partial pressure of carbon dioxide (P_tcCO2 ). We aimed to assess the precision between P_tcCO2 and P_aCO2 values in neonates undergoing therapeutic hypothermia.

Methods

This was a retrospective chart review of 10 neonates who underwent therapeutic hypothermia requiring respiratory support over 2 y. A range of 2-27 simultaneous P_tcCO2 and P_aCO2 pairs of measurements per neonate were analyzed via linear mixed models and a Bland-Altman plot for multiple observations per neonate.

Results

A linear mixed-effect model demonstrated that P_tcCO2 and P_aCO2 (controlling for sex) were similar. The 95% CI of the mean difference ranged from -2.3 to 5.7 mm Hg (P = .41). However, precision was poor as the P_tcCO2 ranged from > 18 mm Hg to < 13 mm Hg than P_aCO2 values for 95% of observations.

Conclusions

The neonates' P_tcCO2 was as much as 18 mm Hg higher to 13 mm Hg lower than the P_aCO2 95% of the time. Transcutaneous CO₂ monitoring may not be a good trending tool, nor is it appropriate for estimating P_aCO2 in patients undergoing therapeutic hypothermia.