Effect of bilateral thoracic paravertebral block combined with general anesthesia on stress response in patients undergoing open heart surgery

AIM:To explore the effect of bilateral thoracic paravertebral block combined with general anesthesia on stress response in patients undergoing open heart surgery. METHODS: Forty patients scheduled for mitral valve replacement were randomly divided into two groups (n=20 each): bilateral thoracic paravertebral block combined with general anesthesia group (group P) and only general anesthesia group (group G). Bilateral thoracic paravertebral block and epidural insertion catheter were performed at T3,T4 interspace prior to induction of anesthesia in group P. A test dose (5 ml of 3.75 g/L ropivacacine) was injected through the catheter on two sides. After 5 min, a bolus dose of 15 ml of 3.75 g/L ropivacacine was injected. Blood samples were taken to determine serum insulin, cortisol and angiotensin II concentrations, respectively, before anesthesia, before cardiopulmonary bypass (CPB), at the end of operation and 24 h postoporatively. Clinical data including parameters of heart resuscitation, dosages of positive inotropic agent, time of mechanical ventilation, ICU stay, pulmonary complications, heart failure and death were recorded in both groups. RESULTS: Compared with those before anesthesia, levels of insulin, cortisol and angiotensin II began to rise from before CPB, peaked at the end of operation (P<0.05 and P<0.01) and declined to normal levels 24 h postoperatively in group P. No significant difference was observed in the level of insulin between groups at 24 h postoperatively. Levels of insulin, cortisol and angiotensin II in group P were significantly lower than those in group G (P<0.05) at the other time points after operation. Dosages of positive inotropic agent and time of mechanical ventilation in group P were significantly lower than those in group G (P<0.05). CONCLUSION: Bilateral thoracic paravertebral block decreases the level of stress hormone in patients undergoing open heart surgery.