Association between Post-Resuscitation Partial Pressure of Arterial Carbon Dioxide and Neurological Outcome in Patients with Post-Cardiac Arrest Syndrome
Background—Partial pressure of arterial CO2 (PaCO2) is a regulator of cerebral blood flow after brain injury. Recent guidelines for management of cardiac arrest recommend maintaining PaCO2 40-45mmHg after successful resuscitation; however, there is paucity of data on the prevalence of PaCO2 derangements during the post-cardiac arrest period, and association with outcome.
Methods and Results—We analyzed a prospectively compiled and maintained cardiac arrest registry at a single academic medical center. Inclusion criteria: age ≥18, non-trauma arrest, and comatose after return of spontaneous circulation (ROSC). We analyzed arterial blood gas data during 0-24 hours after ROSC and determined whether patients had exposure to hypocapnia and/or hypercapnia (defined as PaCO2 ≤30mmHg and PaCO2 ≥50mmHg, respectively, based on previous literature). The primary outcome was poor neurological function at hospital discharge, defined as Cerebral Performance Category ≥3. We used multivariable logistic regression, with multiple sensitivity analyses, adjusted for factors known to predict poor outcome, to determine if post-ROSC hypocapnia and/or hypercapnia were independent predictors of poor neurological function. Of 193 patients, 52 (27%) had hypocapnia only, 63 (33%) had hypercapnia only, 18 (9%) had both hypocapnia and hypercapnia exposure, and 60 (31%) had no exposure; 74% of patients had poor neurological outcome. Hypocapnia and hypercapnia were independently associated with poor neurological function, odds ratio 2.43 (95% CI 1.04-5.65) and 2.20 (95% CI 1.03-4.71) respectively.
Conclusions—Hypocapnia and hypercapnia were common after cardiac arrest and independently associated with poor neurological outcome. These data suggest PaCO2 derangements could be potentially harmful for post-cardiac arrest patients.
- anoxic brain injury
- cardiac arrest
- heart arrest
- cardiopulmonary resuscitation
- brain ischemia
- Received November 26, 2012.
- Revision received April 11, 2013.
- Accepted April 14, 2013.