NM-315
Profound Prolongation of Neuromuscular Blockade from Single Dose Gentamicin
Chu M, Tariq S
University of Texas Health Science Center at Houston, Houston, TX, United states
Introduction:
Antibiotics from the aminoglycoside, tetracylins, and polymixins families are known to prolong the effects of paralytic agents, however, the extent of the prolongation is unknown. We present the case of a patient who received gentamycin prophylaxis for an appendectomy and had a significantly prolonged neuromuscular blockade after receiving a standard dose of rocuronium. We aim to highlight this synergistic effect so when using these antibiotics, a careful consideration should be given to the timing and the dose of neuromuscular blocking agents.
Case:
A 16-year-old, 52-kg, otherwise healthy, female presented with acute appendicitis and was scheduled for a laparoscopic appendectomy. She was allergic to PCN and the reaction was documented as angioedema. A modified rapid sequence induction was performed using fentanyl, lidocaine, propofol and rocuronium 1mg/kg and she was intubated with ease. Due to her PCN allergy and per hospital protocol, she was given gentamicin 2.5mg/kg and flagyl 500mg IV prior to incision. The case proceeded uneventfully and surgery lasted 1.5 hours. Rocuronium was not re-dosed since the initial induction dose. At the end of the case, she had no discernible twitches on TOF. We used 2 different twitch monitors and checked all of the sites for a response (ulnar, facial, posterior tibial). After another 30 minutes (2 hours since initial dose), she finally recovered 1 very weak twitch and after another 15 minutes 2 twitches were appreciated. She was reversed with neostigmine 0.07mg/kg and glycopyrrolate 0.014mg/kg and was extubated successfully when fully awake with a five second head lift. She encountered no issues in the PACU.
Discussion:
Gentamicin potentiates the effect of neuromuscular blocking agents as it possesses intrinsic neuromuscular blocking activity. The mechanism appears to be inhibition of acetylcholine release1. This effect is not reversed by neostigmine but is reversible with calcium administration, leading to the hypothesis that gentamicin exerts its effect by acting as a calcium channel blocker and reducing ach release from nerve terminal thereby depressing neuromuscular conduction. Gentamicin has the greatest neuromuscular blocking effect of all of the antibiotics. As succinylcholine is not routinely used in pediatric patients, rocuronium is often used for paralysis and for modified RSI. Prolonged blockade is a concern when rocuronium is used with antibiotics from these classes leading to an unpredictable timeline toward twitch recovery. Unfortunately, the FDA has not approved Suggamadex for pediatric use. Schultz et al study showed that with a 1.2mg/kg dose of Rocuronium, the average recovery time for the first response (T1) in TOF is 26.1 mins2. Anecdotally, our time until first twitch was approximately 120 minutes, leading to a 400% increase in duration of action. Our experience highlights the synergistic interactions between Rocuronium and Gentamicin and has implications in pediatric anesthesia as both drugs are commonly given together in pediatric surgical cases and can be an issue if the case is short in duration.
References:
1. Lee, Ji Hyeon, et al. J Anesthesiol. 2013
2. Schultz, P. Acta Anesthesiol Scand. 2001
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