Koren O. PLoS One. 2020 Jan 7;15(1):e0226956.
Cardiac arrest is a sudden loss of cardiac function as an effect of ventricular fibrillation, asystole, or pulseless electrical activity. An ischemic heart disease is the most common cause of cardiac arrest. Therapeutic Hypothermia (TH) is the only interference therapy that has been studied so far in randomized trials. In the early 1950s, TH was used in various patients who had cardiac arrest, following initial reports of clinical advantages, both in terms of survival and neurological effects. The American Cardiology Association, the European Cardiology Association, and the the International Liaison Committee on Resuscitation (ILCOR), in 2015 recommended the use of TH for comatose patients who acquired spontaneous circulation after cardiac arrest because of shockable rhythm (class II, LOE A). Various studies supported the use of TH, while others failed to prove a direct link among treatment and outcomes. Due to the failure in proving a substantial advantage for survival or neurological effects, Koren O, et al. conducted a retrospective cohort examine effectiveness of TH in both neurological and survival aspects in subgroup patients.
Patients hospitalized following out-of-hospital cardiac arrest (OHCA) between January 2000 to August 2018 were enrolled in the study. According to the therapeutic approach, these patients were categorised into two groups: Patients who were treated with TH (TH-Group) and patients who were not treated (Non-TH Group). The primary endpoint of the study was the rate of survival of patients during hospitalization and up to one year after discharge. The secondary endpoint was categorised, targeting on various points, the first being the rate of major adverse cardiovascular events (MACE), involving acute myocardial infarction, congestive heart failure, arrhythmia, cardiac arrest, and sepsis within 30 days and up to one year following discharge. An additional secondary endpoint was the neurological status as per the cerebral performance category scale (CPC) score during hospitalization, after 30 days, and up to one year following discharge. Out of 238 patients were hospitalized in the ICCU because of OHCA only 92 patients meet the inclusion criteria (n=57 patients in the TH-group and n=35 patients in the Non-TH group).
The most common first-documented rhythm seen in patients treated with hypothermia was ventricular fibrillation whereas in the non-treated group was asystole and PEA (68.4% and 58.8%, p < .001,respectively). The incidence of MACE, incorporating myocardial infarction, heart failure, arrhythmias, cardiac arrest, and sepsis, up to one year after discharge did not vary among the study groups. No significant difference was noted in mortality rates throughout hospitalization and up to one year after discharge among the two study groups. Patients who survived OHCA showed an high mortality rate of about 50% during hospitalization. An additional mortality risk of approximately 12% was seen in during the first year after discharge. Sepsis was seen in 51% of patients treated with hypothermia compared to 40% of untreated patients (p < .04). Pathogens were detected in 65.5% of patients of TH group as compared to 35.7% of patients in the Non-TH group. After discharge, TH group patients had a larger average CPC scale as compared to the Non-TH group (3.58±1.65 vs. 2.63±1.71, p < .05). No significant change was observed, in average neurological effects after 1 year. Post-hoc analysis signifies that selective patients showed greater survival rate benefited more after TH. Patients admitted because of ventricular fibrillation exhibited a higher survival rate following therapeutic treatment in spite of their age, while patients, even though patients who were younger than 65 years, admitted because of non-shockable rhythm, such as asystole, experienced a modest advantage. Patients older than 65 years who were admitted because of asystole may be at risk of harm from hypothermic treatment (Figure 1).
Figure 1: 1-year survival rate among subgroup (K-M graph)
Thus, it was concluded that TH showed a significant risk of mortality and morbidity. All patients and in all cases of OHCS may be not accept the use of TH. Post-hoc analysis recommend that proper patient selection showed a significant effect on 1-year mortality based on initial introduced arrhythmia and age of the patient.
ILCOR: International Liaison Committee on Resuscitation; CPC: Cerebral performance category scale; PEA: Pulseless electrical activity; LOE: Level of Evidence.
