Feasibility of Perioperative Stellate Ganglion Blocks in Cardiac Surgery

Atrial Fibrillation

stellate ganglion block, cardiac surgery

Based upon Northern New England Cardiovascular Study Group data, the rate of post operative atrial fibrillation (POAF) requiring treatment following coronary artery bypass grafting (CABG) at Maine Medical Center (MMC) is currently 30%. Nationally, POAF occurs in up to 40% of patients post CABG, 50% of patients after valve surgery, 64% of patients post mitral valve and CABG and 49% after aortic valve replacement. Atrial fibrillation worsens a patient's hemodynamic status and increases the risk of congestive heart failure (CHF), embolic events and longer ICU stays leading to increased patient morbidity and strain on financial resources. In the U.S., POAF carries a higher risk of stroke (37% OR 2.0 in-hospital mortality (OR = 1.7), worsened survival (74% versus 87%), and an additional 4.9 days and $10,000-$11,500 in hospital stay costs. Atrial fibrillation requires both an initiation trigger and favorable environment for maintenance and the sympathetic and parasympathetic nervous systems play important roles in this regard. Unfortunately, the precise mechanisms of POAF are still being investigated. This postoperative complication has persisted in spite of efforts to mitigate it pharmacologically with beta blockers and amiodarone, an experience shared by most other cardiac surgery centers. The stellate ganglion is formed by the fusion of the inferior cervical sympathetic ganglion and first thoracic sympathetic ganglion. By modulating the sympathetic component of the autonomic nervous system, stellate ganglion stimulation has been shown to facilitate induction of atrial fibrillation while ablation may reduce or prevent episodes. Human studies have further supported this model. Preliminary studies of perioperative stellate ganglion block (SGB) in cardiac surgery suggest that this technique may reduce or prevent episodes of POAF requiring treatment. The investigator's ultimate goal is to determine whether SGB reduces the incidence of POAF in specific cardiac surgery populations at MMC. First, however, the investigator proposes to test the hypothesis that SGB, performed perioperatively by cardiac anesthesiologists in a population of patients undergoing cardiac surgery, is both safe and clinically feasible.

Patients at MMC undergoing transapical transcatheter aortic valve replacement (TA TAVR) routinely receive a paravertebral block for analgesia. This has the added benefit of providing a unilateral sympathectomy which may be analogous to a stellate ganglion block, albeit via a different technique. In a recent retrospective chart review, TA TAVR block patients showed a decreased rate of new onset POAF. Furthermore, when studying whether pre-emptive stellate ganglion block increases the patency of radial artery grafts in coronary bypass surgery, researchers found a statistically significant decrease (p = 0.048) in atrial fibrillation and the use of anti-arrhythmic agents. Unfortunately, this was a secondary outcome in a small patient population and, while suggestive, the study was not sufficiently powered to draw a definitive conclusion. Importantly, however, they reported no complications related to the block in the fifty patients who received an intervention. Lastly, an additional study demonstrated the safety and feasibility of stellate ganglion mapping and ablation during CABG while also suggesting a clinically significant effect on POAF, but used a permanent, technically complex and time intensive procedure. The investigator's hypothesis is that perioperative SGB in cardiac surgery is clinically efficient and efficacious. To address this, the investigator will: 1. Recruit 49 patients to undergo perioperative SGB during prior to cardiac surgery (CABG, CABG/Aortic Valve Replacement, Aortic Valve Replacement). 2. Monitor the safety of SGB using post procedure surface ultrasound of the neck and active solicitation on Post-op Day (POD) 0 and 1 for identified complications, in addition to routine clinical monitoring. 3. Assess clinical feasibility of SGB by measuring procedural efficacy and efficiency: 1. Efficacy will be measured using post procedure hand temperature; success is indicated by an increase greater than 1 degree Celsius. 2. Efficiency will be measured as the time to complete the block and the time added to the standard anesthesia induction sequence, as a proportion of total time in the operating room. Significance: If the investigator is able to demonstrate that perioperative SGB in cardiac surgery is safe and clinically feasible, the next step will be to design a study to investigate the effect of SGB on POAF incidence (and thereby its attendant morbidity, mortality and costs) in this clinical population.

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