The Association between Dyscarbia and Outcome in Out-of-hospital Cardiac Arrest Survivors Treated with Therapeutic Hypothermia

ABSTRACT

PURPOSE: There is a lack of clinical evidence in terms of the association between carbon dioxide tension and outcomes in cardiac arrest survivors treated with therapeutic hypothermia (TH). We investigated the association of time-weighted mean carbon dioxide tension (TWMCO2) and outcomes in out-of-hospital cardiac arrest (OHCA) survivors treated with TH. METHODS: This was a retrospective cohort study including 177 OHCA survivors. The patients were divided into three groups according to the values of TWMCO2 (normocarbia, 35~45 mmHg; hypocarbia, 45 mmHg). The primary outcome was in-hospital mortality and the secondary outcome was neurologic outcome at discharge. We assessed neurologic outcome at hospital discharge using the Cerebral Performance Categories (CPC). Neurologic outcome was dichotomized as either good neurologic outcome (CPC1 and CPC2) or poor neurologic outcome (CPC 3 to 5). The odds ratio with 95% confidence interval (CI) was estimated. RESULTS: The median value of PaCO2 was 38.2 (33.9-43.3) mmHg. Among a total of 1,239 PaCO2 values, normocarbia, hypocarbia, and hypercarbia were 618 (49.8%), 380 (30.7%), and 241 (19.5%), respectively. Results of univariate logistic regression analysis showed that hypocarbia had a significantly high odds ratio for in-hospital mortality (2.474 (95% CI, 1.129-5.424), p=0.024) compared with normocarbia. Results of multivariate logistic regression analysis showed that hypocarbia (2.926; 95% CI, 1.212-7.066; p=0.017) and hypercarbia (4.673; 95% CI, 1.348-16.205; p=0.015) had a significantly high odds ratio for in-hospital mortality compared with normocarbia. CONCLUSION: In OHCA survivors treated with TH, dyscarbia (hypocarbia and hypercarbia) was frequent and dyscarbia showed an association with in-hospital mortality.