Clinical paperPredictive power of serum NSE and OHCA score regarding 6-month neurologic outcome after out-of-hospital ventricular fibrillation and therapeutic hypothermia☆
Introduction
Therapeutic hypothermia (TH) is the only intervention that has been shown to be beneficial in randomised trials in improving outcome of patients resuscitated from out-of-hospital ventricular fibrillation (VF).1, 2 At present, TH is the only therapeutic modality of postresuscitation care that according to current resuscitation guidelines, has a high grade of evidence.3 The implementation of TH has changed clinical care after cardiac arrest remarkably, and therefore, the utility of previously validated prognostic markers and scores needs reassessment.
Early prediction of outcome is an important aspect of postresuscitation care in out-of-hospital cardiac arrest (OHCA) patients. In order to avoid unnecessary prolongation of intensive care when good functional recovery is unlikely and, on the other hand, to avoid falsely pessimistic prognosis, which could lead to unjustified withdrawal of care, the prediction of unfavourable outcome must have a high specificity. Several clinical parameters, such as initial rhythm, resuscitation delays, age of the patient, findings of neurological status at different time intervals after the arrest, and electrophysiologic tests like electroencephalography (EEG) and sensory evoked potentials (SEP) have been reported to correlate with outcome.4, 5, 6, 7, 8 General laboratory parameters like lactate and glucose concentrations at admission after resuscitation have also been shown to correlate with neurologic outcome.9, 10 Biochemical markers of brain injury like S-100B and serum neuron-specific enolase (NSE) are logical choices as prognostic markers of neurological outcome. The predictive value of NSE in OHCA patients has been shown in several trials prior to the use of hypothermia.11, 12, 13, 14 However, in a substudy of the Hypothermia after Cardiac Arrest (HACA) trial, the prognostic value of NSE was markedly decreased in patients treated with TH, rendering it almost useless in clinical practice because of the low sensitivity.15 There is an imminent need for more studies regarding the usefulness of NSE in patients treated with therapeutic hypothermia.16 Multimodal scores combining both clinical and laboratory variables have also been developed for outcome prediction. Recently, the OHCA score presented by Adrie et al. predicted outcome fairly well in a heterogenous population of OHCA patients including all initial cardiac arrest rhythms.17
To the best of our knowledge no studies are available regarding the predictive power of OHCA score and NSE levels after OHCA with VF as the initial rhythm, treated according to current guidelines including TH and glucose control.3 The aim of the present trial was to test the predictive value of clinical factors and laboratory markers in a highly homogenous cohort of patients resuscitated from out-of-hospital VF and treated with TH. Especially, we aimed to investigate the usefulness of the OHCA score at admission and NSE values 24 and 48 h after the arrest.
Section snippets
Patients
We analysed patients randomised in a previously published trial of strict versus moderate glucose control after resuscitation from VF.18 The study protocol was approved by the ethics committee of Helsinki University Central Hospital (HUCH). All postresuscitation patients in the HUCH area with witnessed out-of-hospital VF and admitted to one of two participating intensive care units (ICUs) during the study period (from November 2004 to December 2006) were screened. Patients with VF of presumed
Results
Ninety patients resuscitated from OHCA with initial rhythm of VF were enrolled to the study. Study protocol was followed for all patients during the ICU stay. Characteristics of patients at admission and during intensive care are presented in Table 1. Overall mortality at 6 months was 37%. The neurologic follow-up at 6 months was completed with all patients alive (n = 57). The outcome was assessed on a follow-up visit for 49 patients and by a phone interview for eight patients (three patients not
Discussion
The best predictor of neurologic outcome 6 months after cardiac arrest was the increase of NSE between 24 and 48 h in out-of-hospital cardiac arrest patients with ventricular fibrillation as the initial rhythm treated with therapeutic hypothermia and glucose control. The sensitivity of absolute NSE value was clearly better at 48 h than at 24 h after cardiac arrest. With a cut-off value of 6.4 μg/l increase in delta NSE, poor outcome could be predicted with a moderate sensitivity. In contrast, the
Conclusions
In patients resuscitated from OHCA with initial rhythm of VF and treated with therapeutic hypothermia and glucose control, serum NSE levels and delta NSE are moderate predictors of neurologic outcome after 48 h, but their sensitivities are only reasonable. We could not detect any reliable prognostic marker of outcome at the time of ICU admission. The previously reported OHCA score was not feasible in this homogenous patient population with VF as the initial rhythm.
Conflict of interest
There is no conflict of interest.
Acknowledgements
For funding, we would like to thank the Laerdal Foundation and the Instrumentarium Foundation, and for help in data collection, we would like to thank medical student Erkko Klemetti and our study nurses Teemu Hult, Nina Nakari, Leena Pettilä, Kirsi Ruohomäki and Pia Simon, and the ICU personnel in the Jorvi and Meilahti hospitals.
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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.2008.08.017.