Initial arterial carbon dioxide tension is associated with neurological outcome after resuscitation from cardiac arrest.

STUDY OBJECTIVES: To determine the relationships between partial pressure of arterial carbon dioxide (PaCO2 ), prescribed minute ventilation (MV), and neurologic outcome in patients resuscitated from cardiac arrest.

METHODS: This was a retrospective cohort study utilizing a multicenter database of adult patients with return of spontaneous circulation (ROSC) after cardiac arrest. The primary outcome was neurologic status at hospital discharge, defined by Cerebral Performance Category (CPC) score: CPC 1-2 was favorable, CPC 3-5 was poor. We compared rates of initial normocarbia (PaCO2 31-49mmHg) and mean sequential PaCO2 measurements obtained over the first 24h. We also assessed the influence of MV on the PaCO2 at initial, 6, 12, 18, and 24h after cardiac arrest using univariate linear regression.

RESULTS: One hundred and fourteen patients from 3 institutions met inclusion criteria. Overall, 46/114 (40.4%, 95% CI: 31.4-49.4%) patients survived to hospital discharge, and 33/114 (28.9%, 20.6-37.2%) had CPC 1-2 at the time of discharge. A total of 38.9% (95% CI: 29.9-47.9%) of patients had initial normocarbia; 43.2% (28.6-57.8%) of these patients were discharged with CPC 1-2, compared with 20.3% (10.8-29.8%) of dyscarbic patients. By 6h, neurologic outcomes were not significantly associated with PaCO2 . Prescribed MV was not associated with PaCO2 at any time point with the exception of a weak correlation at hour 18.

CONCLUSION: Initial normocarbia was associated with favorable neurological outcome in patients resuscitated from cardiac arrest. This relationship was not seen at subsequent time points. There was no significant association between prescribed MV and PaCO2 or neurologic outcome.