EEG is better then SSEP for prognostication at 24 hours in patients cooled post cardiac arrest

Interesting study from the Netherlands in this months CCM.  Patients treated with therapeutic hypothermia for cardiac arrest (regardless of etiology or location) had continuous electroencephalogram (EEG) and daily somatosensory evoked potentials (SSEP) to see if EEG shows any benefit compared with SSEP with regards to early prognostication.  It has become difficult to clinically prognosticate as it seems likely that hypothermia delays the time to neurological recovery.  A method that reliable allowed early prognostication would allow us to provide better care to patients and families by appropriately palliating those with no chance of meaningful neurological recovery and also by carrying on with aggressive treatment for those with a good chance of recovery.
Both isoelectric EEG and absent SSEP had sensitivity of 100% for poor outcome at 24 hours.  Specificity of SSEP for 24%, while specificity of EEG was 68%.  So it appears that EEG can identify more non-survivors earlier.  Important notes of caution were that this was a relatively small (60 patient), single center study.  Also, the study wasn’t completely blinded.  Clinicians were allowed access to both EEG and SSEP data. The authors state that access was needed to EEG data so that epileptiform discharges could be treated, but obviously a flat EEG at 24 hours could have become a self-fulfilling prophecy.

Anyway, here’s the study

1. Crit Care Med. 2012 Oct;40(10):2867-75.

Continuous electroencephalography monitoring for early prediction of neurological
outcome in postanoxic patients after cardiac arrest: A prospective cohort study*.

Cloostermans MC, van Meulen FB, Eertman CJ, Hom HW, van Putten MJ.

From the Chair of Clinical Neurophysiology (MCC, FBvM, MJAMvP), MIRA institute
for Biomedical Engineering and Technical Medicine, University of Twente,
Enschede, The Netherlands; Department of Clinical Neurophysiology and Neurology
(MCC, CJE, MJAMvP), and Department of Intensive Care Medicine (HWH), Medisch
Spectrum Twente, Enschede, The Netherlands.

OBJECTIVE: : To evaluate the value of continuous electroencephalography in early 
prognostication in patients treated with hypothermia after cardiac arrest.
DESIGN: : Prospective cohort study.
SETTING: : Medical intensive care unit.
PATIENTS: : Sixty patients admitted to the intensive care unit for therapeutic
hypothermia after cardiac arrest.
MEASUREMENTS AND MAIN RESULTS: : In all patients, continuous electroencephalogram
and daily somatosensory evoked potentials were recorded during the first 5 days
of admission or until intensive care unit discharge. Neurological outcomes were
based on each patient's best achieved Cerebral Performance Category score within 
6 months. Twenty-seven of 56 patients (48%) achieved good neurological outcome
(Cerebral Performance Category score 1-2).At 12 hrs after resuscitation, 43% of
the patients with good neurological outcome showed continuous, diffuse slow
electroencephalogram rhythms, whereas this was never observed in patients with
poor outcome.The sensitivity for predicting poor neurological outcome of
low-voltage and isoelectric electroencephalogram patterns 24 hrs after
resuscitation was 40% (95% confidence interval 19%-64%) with a 100% specificity
(confidence interval 86%-100%), whereas the sensitivity and specificity of absent
somatosensory evoked potential responses during the first 24 hrs were 24%
(confidence interval 10%-44%) and 100% (confidence interval: 87%-100%),
respectively. The negative predictive value for poor outcome of low-voltage and
isoelectric electroencephalogram patterns was 68% (confidence interval 50%-81%)
compared to 55% (confidence interval 40%-60%) for bilateral somatosensory evoked 
potential absence, both with a positive predictive value of 100% (confidence
interval 63%-100% and 59%-100% respectively). Burst-suppression patterns after 24
hrs were also associated with poor neurological outcome, but not inevitably so.
CONCLUSIONS: : In patients treated with hypothermia, electroencephalogram
monitoring during the first 24 hrs after resuscitation can contribute to the
prediction of both good and poor neurological outcome. Continuous patterns within
12 hrs predicted good outcome. Isoelectric or low-voltage electroencephalograms
after 24 hrs predicted poor outcome with a sensitivity almost two times larger
than bilateral absent somatosensory evoked potential responses.

PMID: 22824933  [PubMed - in process]

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