| Background & Objective It is well documented that CABG surgery causes ischemia reperfusion injury, and leads to the brain and myocardial tissue dysfunction. Animal experiments have shown that preconditioning with hyperbaric oxygen can induce central nervous system and myocardial tissue ischemic tolerance. However, there is few of human studies has reported whether this modality has a protective effect in clinical trials. We evaluated safety, feasibility, and beneficial effect of repeated hyperbaric oxygen preconditioning as an adjunctive therapy for brain and myocardial protection in the clinical trial of CABG surgery.Methods Forty-nine patients were prospectively randomly divided into two groups, group A (control group, n=25) or group B (preconditioning group, n=24) before coronary artery bypass graft surgery. Group A included 15 patients undergoing on-pump surgery and 10 patients undergoing off-pump surgery. Group B included 14 patients undergoing on-pump surgery and 10 patients undergoing off-pump surgery, respectively. The patients in group B were intermittently exposed to hyperbaric oxygen for 120 minutes at 2.0 ATA, once daily for consecutive 5 d before surgery. Neuropsychometric testing was performed 6 d before and 1 week after surgery and haemodynamic measurements was recorded by using a PA catheter. Serum biochemical markers included S100B, NSE, cTnI and CAT were determined at different time points.To on-pump surgery, blood samples were taken from radial artery pressure line at 12 time points: before induction of anesthesia, 5 min after opened thorax, before CPB, after the onset of CPB, 5 min and 1 h after cross-clamp removal, arrival in ICU, 6, 12, 24, 48, 72 h after surgery, and to off-pump surgery, blood samples were taken at 10 time points: before induction of anesthesia, 5 min after opened thorax, 5 min after pericardiotomy, after closed thorax, arrival in ICU, 6, 12, 24, 48, 72 h after surgery, respectively. Inotrope score after surgery, hours of mechanical ventilation in the ICU, the length of stay in the ICU and the length of post-operative stay in the hospital were recorded.Results Age, body mass index, diabetes, hypertension, smoking, coronary disease severity, left ventricular function, operation time, bypass time, myocardial ischemia time and number of grafts were comparable in the two groups. The inotrope score after surgery, extubation time and postoperative hospital time were similar in the two groups. However, the POCD in group A was higher than its in group B (P<0.05), and the length of stay in ICU in group A was significantly shorter (P<0.05) than its in group B. The levels of serum CAT activity at 24 hours after surgery were higher significantly than time point of pre-induction in both groups (P<0.01), and the levels of serum CAT activity in group B were higher than its in group A at 24 hours after surgery(P<0.05).To the patients with on-pump surgery (included 15 control patients and 14 preconditioning patients, respectively), S100B release was significantly lower in the preconditioning group, especially at 1 hour after removal and arrival to ICU (P<0.01), and NSE was reduced during the period from 6 hours after surgery to 24 hours after surgery (P<0.05). Serum cTnI release was less in preconditioning group during the time point from 1 hour after removal to 48 hours after surgery (P<0.05). In group B, the levels of serum CAT activity at 24 h after surgery were higher than that of pre-induction in both groups(P<0.01), and were significantly elevated at time point of 24 h after surgery compared with group A (P<0.01). More important, the ICU time was significantly shorter in group B (P<0.05) and inotrope score during the period from 24 h after surgery to 36 h after surgery was less in group B (P<0.05).To the patients with off-pump surgery (included 10 control patients and 10 preconditioning patients, respectively), the haemodynamic measurements, inotrope score, ventilation time, ICU time and postoperative hospital time were similar in both groups (P>0.05), and the release of biochemical markers including S100B, NSE, cTnI were similar in both groups. However, the levels of CAT activity at time point of 24 h after surgery have no significant difference between the two groups (P>0.05).Conclusions A modality of repeated preconditioning with hyperbaric oxygen is feasible and well tolerated in patients undergoing CABG surgery. Repeated hyperbaric oxygen preconditioning could reduce POCD and shorten ICU stay. Hyperbaric oxygen preconditioning also can reduce the release of serum S100B, NSE and cTnI and inotropic drug use in on-pump CABG surgery, and seems that have a limitative protective effect to patients undergoing off-pump surgery. Finally, the protective effects of hyperbaric oxygen preconditioning in CABG surgery is manifest through the ability of anti-oxidative injury by this modality. However, further multicenter randomized trials are needed to clinically evaluate this form of preconditioning modality.
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