Intraoperative Monitoring in Endocrine Surgery

Intro to IOM in Endocrine Surgery - Surgical Spyglass

• Definition: Real-time physiological assessment of nerve and gland function during endocrine surgery. Acts as a "Surgical Spyglass", offering crucial intraoperative insights.
• Primary Goals:
  • Early identification of critical structures (e.g., recurrent laryngeal nerve (RLN), parathyroid glands).
  • Continuous assessment of their functional integrity.
  • Guide precise surgical dissection.
  • Minimize risk of iatrogenic injury.
• Key Benefits:
  • Reduced rates of permanent complications (e.g., vocal cord palsy, hypoparathyroidism).
  • Improved preservation of endocrine function.

⭐ IOM, especially for RLN, is crucial in thyroid surgery to prevent voice changes and assess nerve integrity before closure.

IOM in Thyroid & Parathyroid Surgery - Neck Check Tech

• Nerve Integrity Monitoring (NIM): Safeguards RLN & EBSLN during surgery.
  • EMG-based: Stimulates nerve, records vocal cord (thyroarytenoid) muscle response.
  • Types: Intermittent (probe) vs. Continuous (vagus/RLN electrode).
  • Signal: Amplitude (µV), Latency (ms).
  • ⚠️ Loss of Signal (LOS): Amplitude < 100 µV or >50% drop from baseline.
  • Aids nerve ID, predicts function, guides safe dissection.
  • 📌 Nerves In Mind for RLN/EBSLN.
• Parathyroid Gland ID & Viability: Key to prevent post-op hypocalcemia.
  • Autofluorescence (NIRAF):
    • Parathyroids uniquely fluoresce (e.g., at approx. 820-830 nm) with NIR light (e.g., approx. 785 nm excitation).
    • Helps distinguish from thyroid, fat, lymph nodes.
    • 📌 Parathyroids Are Fluorescent.
  • ICG Angiography: IV dye assesses parathyroid vascularity, predicting gland viability.
• Intraoperative PTH (ioPTH): For primary hyperparathyroidism (PHPT).
  • Rapid PTH assay: Baseline, pre-excision, post-excision (5, 10, 20 min) samples.
  • Confirms complete removal of hyperfunctioning parathyroid tissue.

  ⭐ Miami Criterion: >50% PTH drop from highest baseline/pre-excision at 10 min post-final gland excision predicts PHPT cure.

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IOM for Adrenal & Pancreatic Tumors - Hormone Hunt How-To

• Adrenal Tumors:
  • Pheochromocytoma/PGL:
    • Monitor: Arterial BP (A-line), CVP.
    • Goal: Manage hypertensive crisis (tumor handling) & hypotension (post-vein ligation).
    • Consider: Glucose (post-resection hypoglycemia).
  • Conn's (Aldosteronoma):
    • Monitor: Serum K⁺, BP.
    • Goal: Confirm resection (↓Aldo, K⁺ normalization post-op).
  • Cushing's (Cortisol Adenoma):
    • Monitor: BP, glucose.
    • Goal: Expect ↓cortisol post-op (guides steroid replacement).
• Pancreatic NETs (PNETs):
  • Insulinoma:
    • Monitor: Frequent intraoperative glucose (IOGM) q 5-15 min.
    • Goal: Glucose ↑ by >25-50 mg/dL or to euglycemia within 30-60 min post-resection.
    • 📌 "Sweet Success for Insulinoma = Sugar Soars!"
    • No rise? Suspect residual/multicentric disease.

    ⭐ Rapid fall in intraoperative insulin levels (if assay available) is a more direct indicator of successful insulinoma resection.

  • Gastrinoma:
    • Goal: Confirm resection by ↓gastrin (usually post-op).
    • Consider: Intraop secretin test (if available).

Advanced Techniques & Limitations - Future Focus Finds

• Advanced:
  • AI in IOM interpretation, Ultrafast PTH assays.
  • NIR autofluorescence (parathyroid ID).
  • ML for risk prediction.
• Limitations:
  • Cost, access, data complexity.
  • Standardization needs.
• Future Focus:
  • Non-invasive sensors, multi-analyte platforms.
  • Personalized IOM strategies.

  ⭐ Continuous intraoperative PTH (C-PTH) monitoring is crucial for assessing complete resection in primary hyperparathyroidism, aiming for a >50% drop from baseline.

High‑Yield Points - ⚡ Biggest Takeaways

• IOPTH in parathyroidectomy: >50% drop from baseline indicates successful resection.
• RLN monitoring: Standard for thyroid & parathyroid surgery; prevents vocal cord palsy.
• Insulinoma resection: Requires intraoperative glucose monitoring (CGM or frequent BG).
• Pheochromocytoma surgery: Prioritizes hemodynamic stability over intraop catecholamine levels.
• Frozen section: Crucial for confirming malignancy & identifying parathyroid tissue.
• Methylene blue: Aids parathyroid identification; may interfere with IOPTH assays.
• Intraoperative cortisol: Guides resection in Cushing's & cortisol-producing adrenal tumors.