Effect of stellate ganglion block versus intraluminal application of verapamil-nitroglycerine solution on internal mammary artery graft blood flow rate in patients undergoing on-pump coronary artery bypass grafting

Background
Left internal mammary artery (IMA) graft is the most promising arterial conduit for coronary artery bypass grafting. Stellate ganglion block (SGB) induces sympathetic blockade and is used to prevent or control spasm of the internal mammary artery. The purpose of this study was to investigate the effect of left SGB on left IMA blood flow rate.
Patients and methods
A total of 170 patients aged between 65 and 70 years, with American Association of Anesthesiologists physical status II and III, and scheduled for elective coronary artery bypass grafting, were randomly allocated to either a SGB group or a verapamil-nitroglycerine group. In the SGB group, the patients received SGB using 8 ml of bupivacaine 0.25%. In the verapamil-nitroglycerine group, the patients received intraluminal injection of the harvested IMA graft with a solution, containing verapamil 5 mg, nitroglycerine 2.5 mg, heparin 500 U, 8.4% NAHCO 0.2 ml, and ringer solution 40 ml, throughout its whole length using a small syringe, and with a low dose of intravenous nicardipine infusion started after harvesting (5 mg nicardipine in 100 ml saline at a rate of 0.5 mg or 10 ml/h). IMA blood flow rate (primary outcome), abnormal ECG changes, ICU length of stay, intra-aortic balloon usage, pre–postoperative pulse rate and blood pressure, incidence of atrial fibrillation, radio-femoral arterial pressure difference, pre–postoperative ejection fraction, need for re-exploration, and mortality rate were observed.
Results
This prospective study showed a significant increase of IMA blood flow rate (<0.001) and nonsignificant decrease in mortality rate in the SGB group compared with the verapamil-nifedipine group. There was no significant difference between the two groups regarding ICU length of stay, re-exploration, intra-aortic balloon usage, preoperative and postoperative mean pulse rate, preoperative and postoperative mean blood pressure, and preoperative and postoperative ejection fractions between study groups. The incidence of atrial fibrillation (=0.030) and abnormal ECG changes (=0.043) was significantly lower in SGB group. Radio-femoral pressure difference was significantly lower in SGB group at 20 and 40 min after cardiopulmonary bypass.
Conclusion
The results of this study showed that SGB prevents IMA spasm, increases its blood flow rate, and decreases incidence of atrial fibrillations compared with intraluminal injection of verapamil and nitroglycerine combined with intravenous nicardipine.