A novel use of neostigmine reversal for intraoperative neural monitoring during thyroid surgery

Oh et al.1 have reported successful use of neostigmine to create a rocuronium-induced neuromuscular block in patients receiving intraoperative neural monitoring (IONM) during thyroid surgery. Once rocuronium(0.6 mg/kg)-supported intubation was achieved, neostigmine (2 mg)-glycopyrrolate (0.4 mg) was used effectively to reverse the neuromuscular block allowing adequate IONM signaling without interference to surgical relaxation. Although their pilot study showed promising results, several issues need to be considered. First, it is clear that neostigmine can be a precipitous, cost-effective method of reversing of rocuronium-induced neuromuscular block and can be used with less bucking and intraoperational movement than sugammadex. Neostigmine is a broad-spectrum agent capable of reversing all non-depolarizing neuromuscular blocking agents (NMBAs) to facilitate extubation at the end of surgery.2 However, the most appropriate time and suitable dose to administer neostigmine to facilitate IONM during surgery has not been established. When sugammadex is used to facilitate IONM for surgery, less dose (0.5 or 1.0 mg/kg) is required compared to extubation after surgery (2.0 or 4.0 mg/kg).3, 4 A similar titration of neostigmine might be also effective as a fixed dose of 2 mg in Oh's report. It may deserve further investigation. Second, anticholinergics (e.g., atropine or glycopyrrolate) are often routinely co- administered with neostigmine to prevent cardiovascular side effects.2 A dosage of neostigmine (2 mg)-glycopyrrolate (0.4 mg) at extubation could possibly present a higher risk of drug adverse cardiovascular events compared to sugammadex. Our team routinely uses neostigmine (1 mg) alone to partially reverse NMB and facilitate high-quality V1 signals. We have not found a need for anticholinergics to prevent bradycardia. Thus, instead of using a combination neostigmine and glycopyrrolate to reverse NMB, a titrated dose of neostigmine might equally effective and used with less cardiovascular risk. Third, rocuronium may be restricted in patients with severe liver disease, renal failure, dehydration, and hypersensitivity.5 Conversely, cisatracurium could be suitable for most surgical patients because of unique Hoffman elimination with cardiovascular stability. It is not known whether neostigmine can be as effective in patients with cisatracurium as rocuronium. In conclusion, the use of neostigmine-glycopyrrolate reversal in patients receiving IONM may be effective and promising, but the risks and benefits of this method need to be considered. While neostigmine is used with less intraoperative movement and lower prescription cost than sugammadex during thyroid surgery, anesthesiologists may want to remain mindful of its possible adverse effects especially when using it in combination with anticholinergics. The authors declare no conflict of interest.