Effect of Stellate Ganglion Block on Internal Mammary Artery Dynamics

Effect of Stellate Ganglion Block on Internal Mammary Artery Dynamics

This study aims to assess the effect of a stellate ganglion block on the flow and diameter of the internal mammary artery using the pulsatility index and transient time flowmetry(TTFM) 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 IMA blood flow and diameter. The IMA pulsatility index and diameter will be measured before and after the stellate ganglion block during both the preoperative and intraoperative periods in both groups. Transit-time flowmetry (TTFM) will be used intraoperatively to assess IMA flow. Additionally, topical nitroglycerin will be applied intraoperatively in both groups, regardless of whether they received the stellate ganglion block.

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.
• Allergy to nitroglycerin.