Effect of Stellate Ganglion Block on Internal Mammary Artery Dynamics

The aim of this study is to compare the diameter of Left internal mammary artery and its blood flow by using the pulsatility index before and after the left stellate ganglion block in patients undergoing coronary artery bypass grafting.

The internal mammary artery (IMA) is the preferred graft for myocardial revascularization because of its superiority over venous grafts owing to long term patency, lower mortality rates and improved post-operative outcomes. However, conduit spasm is a recognized complication of coronary artery bypass surgery mainly affecting the arterial conduits, a major concern that can lead to acute myocardial ischemia and may contribute to reduce graft patency. Topical application or systemic administration of many pharmacological agents has been shown to reverse or prevent graft spasm, but side effects are reported with the use of these agents. Various vasodilators that have been tried included various organic nitrates, calcium channel blockers, sodium nitroprusside (SNP) and papaverine. Over the last few years, there were some studies, which investigated the effect of regional anesthesia techniques such as thoracic epidural anesthesia (TEA) and stellate ganglion block (SGB) for sympatholysis and studied its effects on internal mammary artery diameter . The stellate ganglion block with local anesthetics have been widely used to provide pain relief to treat vascular spastic disorders of upper limbs, chronic pain conditions and treatment of refractory angina. The stellate ganglion block has also been used for increasing radial artery (RA) blood flow and preventing RA spasm by sympathetic blockade in coronary artery bypass surgery. In our study, two groups will be compared regarding the internal mammary artery diameter and its blood flow using the pulsatility index before and after stellate ganglion block.

patients will be positioned with head in midline position and mild extension of the neck. Cricoid cartilage will be identified by midline palpation of the neck and a 12 mega hertz ultrasound probe will be used. The airway will be identified by the shadow of the cricoid cartilage at the level of C6 vertebrae. The probe will be moved laterally to identify internal jugular vein, carotid artery and thyroid. Depth of ultrasound field will be adjusted to include the transverse process of the C6 vertebra. Following complete aseptic precautions, an echogenic insulated needle 5 cm long will be inserted under ultrasound guidance and directed toward the transverse process of the C6 vertebra. After the needle tip will make contact with the transverse process, it will be withdrawn 2 mm and 8 ml of 0.25% bupivacaine will be injected.

diameter will be measured before, 10 min, and 20 min after the block at the level of 2nd, 3rd, 4th and 5th rib by the ultrasound.

Baseline, every 5 minutes after the block for 20 minutes, immediately before measuring internal mammary artery blood flow, at 10 minutes post aortic cross clamp, during rewarming, and at every 10-minute till ICU transferal up to 1 day

Baseline, every 5 minutes after the block for 20 minutes, immediately before measuring internal mammary artery blood flow, at 10 minutes post aortic cross clamp, during rewarming, and at every 10-minute till ICU transferal up to 1 day

Baseline, every 5 minutes after the block for 20 minutes, immediately before measuring internal mammary artery blood flow, at 10 minutes post aortic cross clamp, during rewarming, and at every 10-minute till ICU transferal up to 1 day

Baseline, every 5 minutes after the block for 20 minutes, immediately before measuring internal mammary artery blood flow, at 10 minutes post aortic cross clamp, during rewarming, and at every 10-minute till ICU transferal up to 1 day

Inclusion Criteria: Age: 18 to 65 years. Patients who will be slated to undergo elective coronary artery bypass graft surgery under Cardiopulmonary bypass in the Department of Cardiothoracic Surgery. Exclusion Criteria: Patient not willing to participate in the study. Age more than 65 years. Ejection fraction < 45%. History of strokes / Transient ischaemic attacks and vertebro basilar insufficiency History of Glaucoma. History of allergy to local anaesthetic drugs. Emergency coronary artery bypass graft or reoperations. Pre-existing contralateral phrenic nerve palsy. Patients with existing coagulopathy.