Effect Of Naloxone On The Resuscitation Of Asphyxial Cardiac Arrest In Rats

ObjectiveThe purpose of this study was to investigate the effects of different doses of naloxone on hemodynamic variables, hippocampal EAAClmRNA expression, β -endorphin(β - EP ) plasma levels, NDS (neurological deficit scores ) and ROSC (return of spontaneous circulation ) time in a rat model of asphyxial cardiac arrest , and to assess their effect on cardiopulmonary resuscitation (CPR).Methods32 male Wistar rats (220 - 280g) were randomly divided into four groups : sham operation group ( S group , n = 8 );after the endotracheal tube had been clamped, cardiac arrest was present in other 24 rats and remained untreated for 8 minutes. Rats were randomly assigned to receive a slow, intra - aortic infusion of oxygenated blood ( withdrawn either from the same rat before asphyxia) along with a resuscitation cocktail containing heparin(50 U/100 g) , sodium bicarbonate (0.1 mEq/100 g) , and either epinephrine(A group,5 g/100 g, n =8);or epinephrine/ low -naloxone combination(N₁ group,5 μg/100 g/0.4mg/kg , n= 8);epinephrine/ high -naloxone combination(N₂ group,5 μg/100 g/1mg/ kg , n = 8). Anesthesia was used in all surgical interventions. Body temperature was maintained between36. 5 — 37. 5℃, Before surgery, measurement of heart rate, and electroencephalography. Ventilation was performed with a press- controlled ventilator with 100% O₂ at 42 breaths per minute. Left femoral arterial and right femoral venous were cannulated and attached to pressure trans-ducers that were aligned at the level of the right atrium;mean arterial pressure tracings were recorded. The animals were collected arterial and measured (3 - endorphin( (3 - EP ) plasma levels on 180min after ROSG , and then , were killed and taked off hippocampus to observe the EAAClmRNA expression with RT - PCR . Neurological recovery was assessed with NDS.Results1. Effect of naloxone on the hemodynamic variables.There were not significantly different on the MAP among the groups (P >0. 05). Only the heart rates of Ntand N2 group were significantly higher 5min after ROSC versus A group( P < 0. 05 ) .2. Effect of naloxone on the hippocampal EAAClmRNA expression. Compared with S ,hippocampal EAAClmRNA expression of A group weresignificantly higher ( P < 0. 05 ). There were no statistically significant differences in EAAClmRNA expression among the S , N,and N2 group.3. NDS ( neurological deficit scores ) and ROSC ( return of spontaneous circulation )timeThe interval from beginning of resuscitation to ROSC in N2 group was significantly shorter versus other groups , NDS in N2 group was significantly lower than others . (P<0.05).4. (3 - endorphin( (3 - EP ) plasma levelsCompared with S group , |3 - endorphin( p - EP ) plasma levels of A , N, and N2group were significantly higher(P <0.01) , Compared with A group , Ni (P < 0. 05 ) and N2(P<0.01) group were significantly higher. There were not significantly different betwee Njand N2(P>0.05)ConclusionHigh - dose naloxone not only inhibited expression of hippocampal EAAClmRNA and effect of p - endorphin( (3 - EP ) ,but also decressed NDS(neurological deficit scores ) and ROSC (return of spontaneous circulation ) time. Low — dose naloxone inhibited expression of hippocampal EAAClmRNA and effect of p - endorphin ( (3 - EP ) , but no significantly different on NDS (neurological deficit scores ) and ROSC (return of spontaneous circulation ) time. High - dose naloxone may be have other mechanisms during cardiopulmo-nary resuscitation (CPR) of asphyxial cardiac arrest.