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A3492 - Neostigmine as the Cause of Cardiac Arrest After Elective Total Knee Arthroplasty (TKA) in a Healthy Man
Author Block: L. Yung1, Z. Khan2, M. Bachan3; 1Internal medicine department, Icahn School of Medicine at Mount Sinai (Bronx), Bronx, NY, United States, 2St Vincent Catholic Medcal Cntrs, South Richmond Hill, NY, United States, 3Winchester Med Ctr, Winchester, VA, United States.
Introduction: A TKA is an orthopedic surgical procedure where the weight bearing surfaces of the knee joint is replaced to relieve pain and disability. It can be done under general or regional anesthetic. Anesthesia is generally safe, but it can cause side effects with life threatening complications. Case presentation: A 70 year old man with a baseline heart rate in the 50s to 60s, benign prostatic hypertrophy, rosacea and left knee degenerative join disease had elective left TKA. During the procedure he received cefazolin 2 gm IV (intravenous), midazolam 8mg (milligrams), bupavacaine PF 0.5% 33 ml (milliliter) for spinal and peripheral nerve block and neostigmine 10 mg IA (intra-articular). He had no complications intra-op or while he was in the recovery room. In the surgical intensive care unit (SICU) he became hypotensive, bradycardic and asystolic. Advanced cardiac life support (ACLS) was performed and he regained spontaneous circulation. He required dopamine and IV fluid to maintain blood pressure and heart rate for one day. On POD #2 he had another bradycardic event which again responded to dopamine. His pre-op EKG showed sinus rhythm without heart blocks and cardiac echo showed normal ejection fraction without any abnormalities. Discussion: Neostigmine was the most likely cause of the bradycardia and hypotension. It is parasympathetic compound that acts as a reversible acetylcholinesterase inhibitor which is used to improve muscle tone in people with myasthenia gravis and is given to reverse the residual neuromuscular block during or after surgery. It stimulates both nicotinic and muscarinic receptors indirectly and blocks the acetylcholine esterase active site to prevent acetylcholine breakdown. With the maximum dose of 5 mg (0.07mg/kg), a train-of-four twitch ratio of 90% can be achieved within 10 to 20 minutes of administration. Its elimination half-life is from 24 to 113 minutes (1.8 hours). Some of the side effects are bradycardia and hypotension especially in IV use. Thus it is usually given along with atropine or glycopyrrolate. It is usually safe to be administered intra-articular space. However, the injected neostigmine may have acted as a depot in the intra-articular space and seep into the bloodstream to cause the asystole in this otherwise healthy individual. Conclusion: Although the side effects of neostigmine are rare, especially when administered via the intra-articular route, it can cause severe bradycardia and asystole. Physicians should be aware of this symptom when using neostigimine intra-articular to patients who has baseline bradycardia or heart blocks.