Effect of hyperbaric oxygen preconditioning on activation of plasma protein C in a rat model of asphyxial cardiac arrest-resuscitation

Objective To investigate the effect of hyperbaric oxygen(HBO)preconditioning on activation of plasma protein C in a rat model of asphyxial cardiac arrest-resuscitation. Methods A total of 105 adult male Sprague-Dawley rats, aged 70-90 days, weighing 260-320 g, were randomly divided into 3 groups: cardiac arrest group(group CA, n=5), cardiac arrest-resuscitation group(group CA/R, n=50), and hyperbaric oxygen preconditioning group(group H, n=50). Cardiac arrest was induced by campling the endotracheal tube at the end of expiration.The animals underwent HBO preconditioning once a day for 3 consecutive days before cardiac arrest was induced in group H. The rats were placed in the HBO chamber, 10 min later the pressure was increased at a constant rate until the hyperbaric oxygen reached 2 atmosphere absolute, and maintained at this level for 45 min, after the oxygen concentration>95%, and then the pressure was decreased at a constant rate(within 20 min)until the normal pressure was reached.The rats underwent no resuscitation in group CA.Five rats were selected from CA/R and H groups at 3, 6, 12 and 24 h after restoration of spontaneous circulation, and at 30 min of cardiac arrest in group CA, and blood samples were taken from the abdominal aorta for determination of the plasma activated protein C(APC)concentrations.The time from asphyxia to cardiac arrest, time for spontaneous regular cardiac rhythm, and successful resuscitation were recorded. Results Compared with group CA, the plasma APC concentrations were significantly decreased at each time point after restoration of spontaneous circulation in CA/R and H groups(P<0.05). Compared with group CA/R, the time from asphyxia to cardiac arrest was significantly prolonged, the time for spontaneous regular cardiac rhythm was shortened, the success rate of resuscitation was increased, and the plasma APC concentrations were increased at each time point after restoration of spontaneous circulation in group H(P<0.05). Conclusion HBO preconditioning can promote activation of plasma protein C after resuscitation in a rat model of asphyxial cardiac arrest, and is helpful in improving hypercoagulation. Key words: Heart arrest; Cardiopulmonary resuscitation; Hyperbaric oxygenation; Protein C