The RAMER Reviews: Mild Hypercapnia or Normocapnia after Out-of-Hospital Cardiac Arrest
Written by: Jessie Chen, DO: Edited by: Timothy Khowong, MD, MSEd
Background:
In those who have been resuscitated after an out-of-hospital cardiac arrest, cerebral hypoxia is thought to be the leading cause of death. Given that hypercapnia is thought to increase cerebral perfusion, this study sought to determine whether targeted hypercapnia would provide better neurological outcomes compared to targeted normocapnia.
The Study:
This was an international, investigator-initiated, open-label randomized trial that spanned across 63 ICUs and 17 countries. There were 1700 patients enrolled in the study. These patients were randomized into two groups, mild hypercapnia (35 - 45 mm Hg) and normocapnia (50-55 mm Hg). The outcomes measured evaluated for neurological outcome. Primary outcomes of favorable neurological outcome were measured via the GOS-E score and secondary outcomes of death or poor functional outcome with the modified Rankin Score.
The patients selected were >18 year old patients that had an out-of-hospital cardiac arrest and obtained ROSC for > 20 minutes from cardiac etiology or unknown cause. The respective groups were set to achieve a certain PaCO2 goal for 24 hours. At 96 hours, a blinded clinician performed a protocolized neurological assessment. Then at 6 months, these patients were assessed with the scoring tools listed above to assess for neurological outcome and poor functional outcomes.
The results showed that at 6 months, 43.5% (332/764) in the mild hypercapnia group had favorable outcome vs. 44.6 (350/784) in normocapnia group and 53.4 %(407/762) had poor functional outcome in the normocapnia vs. 51.3% (400/779) in normocapnia group. The results were not statistically significant having a p-value of 0.76 and inadvertently showing that normocapnia may be favorable.
Conclusion:
In this international, investigator-initiated, open-label randomized study, it was found that mild hypercapnia did not lead to better neurological outcomes at 6 months. Though, this study had a large sample size