Clinical paperDiffusion and perfusion MRI of the brain in comatose patients treated with mild hypothermia after cardiac arrest: A prospective observational study☆
Introduction
Despite recent advances in cardiopulmonary resuscitation, the outcome after cardiac arrest (CA) is poor. The 1-year survival rate with favourable neurological outcome after out-of-hospital CA is reported to be 4%.1 Among resuscitated CA patients treated in an ICU, approximately 50% regain consciousness, whereas the other 50% remain comatose before they die.2 About 30% of the survivors suffer permanent brain damage,3 due to lack of blood flow and oxygen delivery to the brain.4 Treatment with induced hypothermia (32–34 °C during 12–24 h) after CA is believed to significantly improve the neurological outcome and mortality in patients with primary CA who remain comatose after return of spontaneous circulation.5, 6, 7, 8 A reduction in core body temperature limits neuronal cell injury and improves recovery by several mechanisms.9 Persistent coma with a Glasgow Coma Scale (GCS) of 3 or 4 at 72 h after CA predicts a poor outcome and so does myoclonus status epilepticus,10 and pathological somatosensory-evoked potentials,11 but additional prognostic tests are needed. Magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) is sensitive to the microscopic motion of water in biologic tissues,12 and is more sensitive than conventional MRI for the detection of hyperacute cerebral ischaemia.13 Perfusion MRI (pMRI) depicts nutritive delivery of arterial blood to tissue. Cerebral reperfusion injury may occur when cerebral blood flow is restored after CA and resuscitation.7, 14 Previous MRI studies on comatose survivors of cardiac resuscitation have only included patients without induced hypothermia.15 Our hypothesis was that DWI and pMRI could be helpful tools for the evaluation of ischaemic brain damage in resuscitated comatose patients treated with hypothermia after CA.
Section snippets
Patient population
A prospective observational study of CA patients treated with mild hypothermia was performed in our university hospital 2003–2006. MRI of the brain with diffusion and perfusion imaging was conducted in patients remaining unconscious after regaining normal body temperature. Informed consent was obtained from the next of kin before enrolment, or retrospectively from the patient. Eligible criteria for induced hypothermia were comatose patients after in- or out-of-hospital CA with a GCS score less
Patient population
The 82 resuscitated CA patients treated with induced hypothermia at our university hospital from September 2003 to March 2006 are described in Fig. 2. Twenty patients, 11 men and 9 women, mean age 57.8 years (range 14–81) matched the inclusion criteria. The majority of the patients (85%) had suffered an out-of-hospital CA. Twelve patients (60%) had an initial ventricular fibrillation (VF), whereas asystole and pulseless electric activity (PEA) were seen in six patients (30%) and two patients
Discussion
This is the first study reporting the diffusion and perfusion MRI findings in patients treated with mild hypothermia after CA. Our data suggest that diffusion and perfusion measurements are useful tools for grading ischaemic brain damage after CA in patients treated with mild hypothermia. Among the patients who died within the first month, the diffusion lesions were more pronounced both in size and number that they were in the patients who recovered. Regarding perfusion, seven out of the eight
Conclusion
The observed differences between the deceased and recovering patients regarding location, incidence, and size of the diffusion lesions and the perfusion abnormalities suggest that DWI and pMRI could be helpful tools for the evaluation of ischaemic brain damage in resuscitated comatose patients treated with hypothermia after CA.
Conflict of interest
There was no conflict of interest related to this study.
Acknowledgements
This study was generously supported by the Knut and Alice Wallenberg Foundation, grant number 1998.0182 and by the Swedish Research Council (project no. 2007-6079). Study sponsors had no involvement in the study design, in the collection, analysis and interpretation of data; in the writing of the manuscript; and in the decision to submit the manuscript for publication.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2009.01.004.
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Present address: Department of Radiology, Aalborg Hospital/Århus University Hospital, Aalborg, Denmark.