Hypothermia In Porcine Model Research Articles

Short period of mild hypothermia improves resuscitation outcome in a porcine model of prolonged ventricular fibrillation

Objective To investigate the resuscitation outcome after a short period of mild hypothermia in porcine model of prolonged ventricular fibrillation (VF). Methods Fourteen male healthy domestic swine weighting 34 to 36 kg were used. VF was induced electrically and maintained untreated for 11 mins, followed by manual cardiopulmonary resuscitation (CPR) procedure. Two investigators initiated chest compression and bag-valve mask ventilation in pattern of 2 min rotation. A biphasic wave of 120 J electric defibrillation (ED) was attempted 6 mins after CPR. If there was no return of spontaneous circulation (ROSC), CPR was restored and ED was delivered when necessarily. Resuscitation was considered unsuccessful if absence of ROSC for 12 mins. However, if ROSC occurred, animals were randomly(random number) diveded into normothermia (NT) group and hypothermia treatment (CH) group. Animals in CH group were immediately cooled by using intravenous infusion of ice-cold saline and surface cooling. Core temperature was reduced to 32-34 degrees centigrade within 120 mins and maintained at this level for 2 h. Active rewarming was completed within 2 h until baseline body temperature was reached. Data of hemodynamic variables, blood-gas analysis and blood lactate before VF of two groups were recorded. Meawhile, cardiac output (CO), heart rate and Tc after ROSC were recorded. Neurological defect scores (NDS) were evaluated every 24 h until 96 h after ROSC. Variables were compared using either Fisher test or repeated measures analysis of variance, followed by Bonferroni for multiple comparisons. A two-sided P value<0.05 was regarded statistically significant. Results There was no significant difference in body weight, mean arterial pressure, CO, pH, pressure of end-tidal carbon dioxide (ETCO2) and lactate between groups before VF. In the period of CPR, there were also no significant difference in total resuscitation time, first shock success rate, ROSC rate, shock ROSC rate, total number of shock and doses of epinephrine. However, animals in CH group survived longer time than that in NT groups [（96.00±0.00)h vs (49.71±43.65)h,P=0.031]. Meanwhile, the survival rate of 96 h was significantly higher in CH than that in NT (P<0.05). For neurological function, there was a obviously better NDS in CH group than that in NT group within ROSC 96 h (P<0.05). Conclusion Even a short duration of 2 hour mild hypothermia could improve resuscitation outcome in porcine model of 11 minute VF. Key words: Cardiopulmonary resuscitation; Mild hypothermia; Short duration; Resuscitation outcome

Ischemic post-conditioning and nitric oxide inhalation failed to demonstrate protective effect in comparison with mild hypothermia in porcine model of cardiac arrest

Ischemic post-conditioning and nitric oxide inhalation failed to demonstrate protective effect in comparison with mild hypothermia in porcine model of cardiac arrest

Epidural cooling for selective brain hypothermia in porcine model

Hypothermia has been shown to be neuroprotective in many animal models and several human trials of brain ischemic and trauma. However systemic hypothermia may result in fatal complications. This study was undertaken to test epidural cooling as a new method of inducing selective brain hypothermia. Six adult swine (mean mass, 33.8+/-3.6 kg) were studied. Anesthesia was maintained with pentobarbital sodium (25 mg kg-1, i.v.) and pancuronium bromide (0.5 mg kg-1 h-1, i.v.). Five probes were placed in the rectum, deep brain, brain surface, epidural space, and room air for temperature monitoring respectively. Epidural cooling was performed using cold-saline (4 degrees C) perfusion into the epidural space through a flexible double-lumen catheter. The dripping speed of cold saline was controlled to maintain the target temperature. The changes of the epidural space pressure, complete blood counts, basic metabolic panels, tests for fibrinolysis and coagulation status were monitored to assess hypothermia-induced changes. Following the epidural cooling perfused with cold-saline (4 degrees C) at mean dripping speed of 720 ml per hour, the local brain surface temperature could decrease rapidly to 17.3-21.6 degrees C within one minute, and deep brain temperature decreased to 27.2-29.7 degrees C within 5 minutes. The target temperatures were easily controlled by the dripping speed of cold saline (from mild to deep hypothermia). The rectal temperature was maintained at normal range within 6 perfusion hours. No arrhythmia was observed, and all hematological variables were within the normal range for swine. No increased intracranial pressure was induced by the cooling method. The data demonstrate that epidural space cooling was technically feasible and useful for selective brain hypothermia, and the target temperatures are easily controlled. The induction of hypothermia was rapid and maintained for a long period of time, whereas the body temperature was maintained within the normal range and without hemodynamic instability.