Abstract 2001: The Impact of Witness to Cardiac Arrest in Therapeutic Mild Hypothermia of Comatose Survivors after Cardiac Arrest
Background - In 2002, 2 randomized studies showed a neurological benefit of therapeutic mild hypothermia in comatose survivors after out-of-hospital cardiac arrest. But it is still unclear for what kind of patient therapeutic mild hypothermia is more beneficial. In many institutions, witness to cardiac arrest is necessary condition of induction of hypothermia. This study was undertaken to investigate the impact of witness to cardiac arrest on prognosis in induced mild hypothermia patients after cardiac arrest.
Methods - Between September 2003 and April 2007, 50 consecutive patients underwent therapeutic mild hypothermia after cardiac arrest whose durations of collapse to return of spontaneous circulation (ROSC) were less than 15 minutes. There were 35 (70%) witnessed cardiac arrest patients (WCA) and 15 (30%) un-witnessed cardiac arrest patients (UWCA). The time of un-witnessed patient’s collapse were estimated that the mean of suspected earliest and latest time. Duration of collapse to start of cardiopulmonary resuscitation in WCA was significantly shorter than that of UWCA (5.5±5.9 VS 13.7±7.8 minutes; P<0.01). There were no significant difference in duration of collapse to ROSC between WCA and UWCA (33±21 VS 37±23 minutes; P=0.56). Neurological outcome was assessed by cerebral performance categories at hospital discharge. The 365-day mortality curves were constructed by Kaplan-Meier method.
Results - There were no significant difference neurological outcome at hospital discharge (46% VS 27%; P=0.20) and 365-day survival curves between WCA and UWCA (50% VS 33%; P=0.30). Multivariate analysis showed presence of witness to cardiac arrest was not an independent predictor of neurological outcome at hospital discharge (odds ratio 1.83, 95% confidence interval 0.80 to 4.75; P=0.17) and 365-day mortality (odds ratio 0.86, 95% confidence interval 0.58 to 1.30; P=0.45).
Conclusions - In therapeutic mild hypothermia patients, there were no significant difference between WCA and UWCA. It was suggested that therapeutic mild hypothermia in UWCA is as effective as that in WCA. Presence of witness to cardiac arrest may not be necessary for the inclusion criteria of induction of hypothermia for comatose survivors after cardiac arrest.