A promising emerging treatment (hypercapnia) for comatose adult cardiac arrest patients has been found to yield similar results to current treatment, in a new study published the New England Journal of Medicine (NEJM).
Out-of-hospital cardiac arrests (OHCAR) cause significant mortality and morbidity, and the study is one the largest trials ever conducted on cardiac arrest patients admitted to intensive care units (ICU).

The TAME (Targeted therapeutic mild hypercapnia after resuscitated cardiac arrest) study showed that maintaining a slightly elevated CO2 level (hypercapnia) for the first 24 hours after a cardiac arrest patient has been resuscitated did not improve neurological outcomes, functional outcomes or quality of life at six months after the event, and did not impact six-month mortality. Conversely, it did not lead to worse outcomes, either.

Co-lead author, Prof Alistair Nichol, professor of critical care medicine at UCD School of Medicine, consultant at St Vincent’s University Hospital and director of the Irish Critical Care-Clinical Trials Network, leads the TAME study in Ireland, funded by the Health Research Board.

Prof Nichol’s doctoral thesis (with Prof Paul McLoughlin, professor of physiology at UCD School of Medicine in 2007) demonstrated the potential anti-inflammatory effect of hypercapnia and suggested the treatment could be used as a therapeutic intervention in critically ill patients in ICU. Subsequent observational studies in cardiac arrest patients showed that while many doctors follow guidelines and keep the CO2 level normal, it is common to have hypercapnia.

These studies further suggested hypercapnia was associated with improved outcomes and there are many physiological reasons why this might be so, including increasing blood flow and the previously demonstrated anti-inflammatory effects.

The TAME researchers also conducted an earlier smaller trial in ICU patients that suggested that hypercapnia improved outcomes, but recognised the need for a large trial to confirm this finding.

Reference: Glenn Eastwood et al. Mild Hypercapnia or Normocapnia after Out-of-Hospital Cardiac Arrest. N Engl J Med 2023; 389:45-57 doi: 10.1056/NEJMoa2214552