Magnetic resonance imaging in comatose adults resuscitated after out-of-hospital cardiac arrest: a posthoc study of the targeted therapeutic mild hypercapnia after resuscitated cardiac arrest trial

Background
Neuroimaging with magnetic resonance imaging (MRI) may assist clinicians in evaluating brain injury and optimising care in comatose adults resuscitated after out-of-hospital cardiac arrest (OHCA). However, contemporary international data on its use are lacking.

Aim
The primary aim was to compare the patient characteristics, early postresuscitation care, and neurological outcomes of patients according to MRI use.

Methods
We performed a posthoc analysis of the Targeted Therapeutic Mild Hypercapnia after Resuscitated Cardiac Arrest (TAME) trial, a multinational randomised trial comparing targeted mild hypercapnia or normocapnia in comatose adults after OHCA.

Results
After exclusions, 1639 patients enrolled in the TAME trial were analysed. Of these, 149 (9%) had an MRI. Compared to non-MRI patients, MRI patients were younger (58.9 versus 61.7 years, p: 0.02), had a longer median time from OHCA to return of spontaneous circulation (30 versus 25 min, p < 0.0001), and had a higher average arterial lactate level (8.78 versus 6.74 mmol/L, p < 0.0001) on admission to hospital. MRI patients were more likely to receive additional advanced diagnostic assessments during intensive care unit admission (p < 0.0001). At 6 months, 23 of 140 patients (16.4%) in the MRI group had a favourable neurological outcome, compared with 659 of 1399 patients (47.1%) in the no-MRI group (p < 0.001). On multivariable modelling, country of enrolment was the dominating predictor in the likelihood of an MRI being performed.

Conclusions
In the TAME trial, 9% of patients had an MRI during their intensive care unit admission. Among these patients, only 16% had a favourable neurological outcome at 6 months.