Combination of hyperoxygenation and targeted temperature management improves functional outcomes of post cardiac arrest syndrome irrespective of causes of arrest in rats

Abstract

Background The high mortality rates of patients who are resuscitated from cardiac arrest (CA) are attributed to post cardiac arrest syndrome (PCAS). This study evaluated the effect of hyperoxygenation and targeted temperature management (TTM) on PCAS in rats with different causes of CA. Methods and Results One hundred and sixty-eight Sprague-Dawley rats were equally divided into asphyxial and dysrhythmic groups. Animals were further randomized into four subgroups immediately after resuscitation: 1) Normoxia-normothermia (NO-NT): ventilated with 21% oxygen under normothermia; 2) Hyperoxia-normothermia (HO-NT): ventilated with 100% oxygen for 3 h under normothermia; 3) Normoxia-hypothermia (NO-HT): ventilated with 21% oxygen for 3 h under hypothermia; 4) Hyperoxia-hypothermia (HO-HT): ventilated with 100% oxygen for 3 h under hypothermia. Post resuscitation cardiac dysfunction, neurological recovery, and pathological analysis were assessed. For asphyxial CA, HO-NT and HO-HT (68.8% and 75.0%) had significantly higher survival than NO-NT and NO-HT (31.3% and 31.3%). For dysrhythmic CA, NO-HT and HO-HT (81.3% and 87.5%) had significantly higher survival than NO-NT and HO-NT (44.0% and 50.0%). When all of the rats were considered, the survival rate was much higher in HO-HT (81.3%). Compared with NO-NT (57.7 ± 14.9% and 40.3 ± 7.8%), the collagen volume fraction and the proportion of fluoro-jade B-positive area in HO-HT (14.0 ± 5.7% and 28.0 ± 13.3%) were significantly reduced. Conclusions The beneficial effects of hyperoxygenation and TTM are dependent on the cause of arrest: hyperoxygenation benefits asphyxial whereas TTM benefits dysrhythmic CA. The combination of hyperoxygenation and TTM could effectively improve the functional outcome of PCAS regardless of the cause of CA.