Transphenoidal resection of pituitary tumor

Transphenoidal resection of pituitary tumor

Anesthesia type	General
Airway	ETT
Lines and access	PIV x 2 Arterial line
Monitors	Standard ASA 5-lead EKG Core temp UOP ± EEG
Primary anesthetic considerations
Preoperative	Characterize baseline neurologic deficits (i.e., visual field defects) Characterize type of adenoma (secreting vs non-secreting) and which type of hormone secreted
Intraoperative	Avoidance of hypertension as it can worsen visual of endoscopic surgical field due to bleeding Avoid turbulent emergence; avoid positive pressure mask ventilation on extubation
Postoperative	PONV prophylaxis Iatrogenic diabetes insipidus (monitor intraop and post-op urinary output)
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A transphenoidal resection of pituitary tumor is a neurosurgical procedure performed through an intranasal exposure to remove tissue from the sella turica.

Overview

• Most pituitary tumors are benign adenomas
  • Only 0.1-0.2% malignant carcinomas
• Approximately 35% are invasive into adjacent bony and/or vascular structures
• Approximately 75% of tumors are functional (hormone-secreting)
• Mass effect of tumor can lead to decreased secretion of one or more pituitary hormones and other neurologic deficiencies

Indications

• Resection of pituitary tumor

Surgical procedure

• Performed via a transphenoidal approach through the nares

Preoperative management

Patient evaluation

System	Considerations
Airway	ACTH or GH secreting tumors may lead to airway abnormalities GH: macroglossia, enlarged epiglottis, RLN palsy, subglottic stenosis, enlarged nasal turbinates
Neurologic	Baseline neuro exam GH prone to peripheral neuropathies.
Cardiovascular	Hyperthyroid patients may have ECG abnormalities GH pts may have HTN, LVH, diastolic dysfunction, arrhythmias, CAD
Renal	Preoperative diabetes insipidus
Endocrine	Identify and treat (if needed) pituitary hormone abnormalities (see below)

Tumor anatomy

• Classified based upon size/structural invasion
  • Stage I: Microadenoma (<1 cm)
  • Stage II: Macroadenoma (≥1 cm)
  • Stage III: Macroadenoma with invasion
  • Stage IV: Destruction of the sella
• Mass effect can directly compress neurologic structures
  • Visual field defects (classically bitemporal hemianopsia)
  • Eye movement deficits (CN III more common than CN VI)
  • Elevated ICP rare (secondary to obstructive hydrocephalus)
• Invasion into adjacent structures
  • Bone
    • Skull base
    • Sphenoid
  • Vascular
    • Cavernous sinus
    • Carotid artery
• Tumor can be hemorrhagic and/or necrotic

Endocrine abnormalities

• Pituitary tumors can be classified as functional (hormone-secreting) or nonfunctional (not hormone-secreting)
  • Prolactin > GH > ACTH > LH/FSH > TSH
• Endocrine deficiencies from mass effect
  • GH > LH/FSH > TSH > ACTH > Prolactin
  • Panhypopituitarism possible
  • Posterior pituitary deficiencies less common (ADH, oxytocin)

Labs and studies

• Brain MRI
  • Review imaging to evaluate structural invasion
    • Invasion into cavernous sinus and/or enveloping carotid artery higher risk for bleeding

Patient preparation and premedication

• Versed
• Consider aprepitant 40 mg PO for PONV prophylaxis

Intraoperative management

Monitoring and access

• PIV x 2 (20g for drips, 18g+ for bolus)
• Arterial line

• If patient is hemodynamically stable, consider placing art line after the 180 spin as surgical team can prep simultaneously. It also reduces the chance of inadvertent line dislodgment while spinning.

Induction and airway management

• Standard induction
  • Propofol
  • Short acting opioid vs beta blocker
    • Can even use remifentanil bolus as induction agent, but consider risk of chest rigidity on induction
  • Rocuronium
    • Induction dose should be sufficient for the entire case as you are also running a remifentanil gtt, which should blunt movement
• ETT with straight connector
  • Consider mastisol and tegaderm reinforcement of the ETT as you will not have access to the airway.
  • GH: glottic opening may be very distal, traditional ETT may not be long enough, consider MLT 6.0mm

Positioning

• 180 - place all leads and wiring on one side of the body prior to induction to facilitate an easier spin
• Supine
• Arms tucked
  • Additional IV access site options: saphenous veins

Maintenance and surgical considerations

• Propofol gtt (if TIVA, start at 100-150 mcg/kg/min and consider EEG monitoring/Sedline/BISl; titrate to effect)
• Remifentanil gtt (start with 0.1mcg/kg/min and titrate normal hemodynamic parameters)
• ± Volatile (can use 0.5 MAC of Sevoflurane requiring less propofol; useful for longer cases when propofol begins to accumulate)
• No steroids unless specifically asked; may interfere with AM cortisol measurement the next day
• Pinning of the head using Mayfield pins by neurosurgery will cause a pain/sympathetic surge. Prepare to bolus 1-2 mcg/kg of remi 2-3 minutes prior to pinning; coordinate with surgeons.
• ENT will inject lidocaine with epinephrine, watch for inadvertent IV injection or mucosal absorption→ transient tachycardia, hypertension
• Combined ENT/Neurosurgery case - ENT for exposure, neurosurgery for tumor resection
• As with many ENT cases in the nasopharynx, can be very stimulating, hence the suggested remifentanil gtt. However, once the stimulation is over, it is typically not very painful so do not overdo it with long-acting opioids.
• Consider short-to-intermediate acting BB (i.e, esmolol, labetalol) for HTN/stimulation not controlled by remifentanil bolus/gtt. HTN will worsen bleeding during ENT portion.
• Surgeons will ask for Valsalva during the case.
• Note down when throat pack is placed in and taken out during case.
• Foley: yes, for duration of case and to monitor iatrogenic DI caused by the tumor resection

Emergence

• Pass OGT to ENT at end of case prior to extubation to suction out any blood that may have dripped down the esophagus and into the stomach.
• Paralytic reversal (if used).
• Spin back to neutral (particularly, if solo).
• Smooth awake extubation (i.e., remifentanil wake-up: decrease gtt to 0.03-0.05 mcg/kg/min for extubation). Patients may not spontaneously breath initially even if all volatile/propofol if out of the system, but if gently encouraged, will open their eyes and follow commands.
• Avoid positive pressure masking after extubation.

Potential Modalities of Neuromonitoring

Surgical Approach	Potential IONM Modalities	Common Pathologies
Transsphenoidal to sella	None	Adenoma, Rathke's cleft cyst
Transsphenoidal, transplanum, transtuberculum to suprasellar region	EEG, SSEPs, MEPs	Meningioma, craniopharyngioma, giant piutitary adenomas
Transsphenoidal to orbital apex	EEG, SSEPs, MEPs, EMG (CN III, IV, VI)	Hemangioma, meningioma, neoplasm

Postoperative management

Disposition

• PACU

Pain management

• Tylenol IV
• Fentanyl (be judicious) as surgeons will likely want a good neuro exam post-op.

Potential complications

• Iatrogenic diabetes insipidus if vasopressin secreting cells are affected.
  • Important to monitor intraop and post-op urinary output.

Procedure variants

	Variant 1	Variant 2
Unique considerations
Position
Surgical time
EBL
Postoperative disposition
Pain management
Potential complications