Parathyroidectomy: Intraoperative Monitoring

Most commonly, a patient presenting for parathyroidectomy will have hypercalcemia, which is ideally controlled and medically managed prior to surgery. Radioactive scanning, ultrasound, and other imaging pre-operatively also allows the surgeon to locate and dissect appropriately to remove only those gland(s) which are pathologic. Several modalities of monitoring are important for a parathyroidectomy:

• Standard ASA monitoring – including SpO₂, HR, NIBP, temperature, capnography.
• Electrolyte monitoring – the gold standard of monitoring successful surgery is a >50% drop in the PTH level. This is feasible due to the relative short half-life of parathyroid hormone (3-5 minutes) which allows for serial assessment during the surgery by the anesthesiologist
• Each surgeon or hospital will have its own protocol for testing; most commonly, at least 4 levels are tested (pre-incision, pre-gland removal, 5 minutes post-removal, 10 minutes post-removal)
• Because of the need for frequent labwork, placement of a large bore peripheral IV or an arterial line is needed
• Neuromonitoring – due to the course of the recurrent laryngeal nerves posterior to the thyroid/parathyroid glands, the use of intraoperative neuromonitoring is frequently (but not always) employed. This is accomplished with a NIMS tube, which aligns with the vocal cords during intubation and will alert the surgery team if/when their dissection stimulates those nerves (and therefore the cords).
• This is commonly employed during re-operation for a failed parathyroidectomy, or when imaging confirms close proximity of the pathologic gland to a recurrent laryngeal nerve
• When neuromonitoring is employed, long-acting muscle relaxant should be avoided. If a non-depolarizing muscle relaxant is used, proper use of a twitch monitor prior to incision is recommended to aid in reversal.