Pituitary Tumor Surgery (Transsphenoidal Approach) – Anesthetic Considerations


🔹 Introduction

Pituitary adenomas are the most common tumors of the sellar region and are often approached surgically via the transsphenoidal route (TSA). This minimally invasive technique allows direct access through the nasal cavity and sphenoid sinus to the sella turcica, minimizing brain retraction and preserving neurological function.


🔹 Anatomy Refresher

  • Pituitary gland lies in the sella turcica, bordered:
    • Superiorly: optic chiasm
    • Laterally: cavernous sinuses (contains CN III, IV, V1, V2, VI, ICA)
    • Inferiorly: sphenoid sinus
  • Blood supply: superior and inferior hypophyseal arteries (branches of ICA)
  • Hormonal control: hypothalamic–pituitary axis


🔹 Indications for Surgery

Indication

Notes

Functioning adenomas

Hormone-secreting tumors (e.g., prolactinoma, GH, ACTH)

Non-functioning adenomas

Causing mass effect, visual loss

Pituitary apoplexy

Acute hemorrhage/infarction → surgical decompression

Cushing’s disease

ACTH-producing adenomas

Acromegaly

GH-producing tumors



🔹 Surgical Approaches

Approach

Description

Microscopic TSA

Traditional method using microscope

Endoscopic TSA

Minimally invasive, better visualization

Transcranial

Rare, for large/complex tumors with suprasellar extension



🔹 Preoperative Assessment

🔸 Endocrine Evaluation

Hormone Excess

Associated Features

ACTH (Cushing’s)

Obesity, HTN, DM, electrolyte disturbances

GH (Acromegaly)

Difficult airway, hypertension, OSA

Prolactin

Galactorrhea, infertility

TSH

Thyrotoxicosis

ACTH/TSH deficiency

Risk of adrenal/thyroid crisis perioperatively


Perioperative steroid coverage is essential in ACTH deficiency.

🔸 Airway Evaluation

  • Acromegaly patients: macroglossia, prognathism, glottic narrowing
  • Previous nasal surgery or trauma may complicate nasal intubation
  • Consider awake fiberoptic intubation in difficult cases

🔸 Visual Assessment

  • Visual field defects (classically bitemporal hemianopia) due to optic chiasm compression


🔹 Anesthetic Goals

  • Maintain hemodynamic stability
  • Smooth emergence to prevent bleeding or CSF leak
  • Protect endocrine and visual function
  • Ensure bloodless surgical field (often shared with ENT/neurosurgeon)
  • Prevent and manage air embolism, DI, CSF leak


🔹 Intraoperative Management

🔸 Monitoring

Monitor

Role

Standard ASA monitors

ECG, NIBP, SpO₂, EtCO₂

Invasive arterial line

For large tumors, Cushing’s, acromegaly

Central line

Rarely needed unless hemodynamic instability

Capnography with nasal intubation

To confirm ventilation

Blood glucose monitoring

Especially in Cushing’s or DM patients

Urine output

For DI detection (esp. in prolonged surgeries)


🔸 Induction

  • IV induction with propofol + short-acting opioid (fentanyl/remifentanil)
  • Consider lidocaine to blunt response
  • Non-depolarizing muscle relaxants (e.g., rocuronium)

🔸 Maintenance

Agent

Consideration

TIVA (Propofol + Remifentanil)

Preferred for rapid, smooth emergence

Volatile agents

Sevoflurane or desflurane acceptable

Avoid N₂O

Risk of pneumocephalus, PONV

Controlled hypotension

MAP ~60–70 mmHg for bloodless field (if safe)


🔸 Airway

  • Nasal RAE or flexometallic ETT preferred
  • Lubricate and gently dilate nasal passage
  • ENT surgeon may assist in nasal intubation


🔹 Shared Airway Considerations

  • Coordinate with ENT/neurosurgeon
  • Use cuffed nasal ETT placed contralateral to surgical side
  • Risk of:
    • ETT dislodgement
    • Obstruction due to blood/mucus therefore do oral packing
    • Contamination of airway


🔹 Intraoperative Complications

Complication

Cause/Management

Hemorrhage

ICA injury; control BP, rapid volume replacement

CSF Leak

During sellar floor breach; surgeon seals with fat graft

Venous Air Embolism (VAE)

Head-up position, exposed veins—look for EtCO₂ drop, mill wheel murmur

DI (Diabetes Insipidus)

Pituitary stalk manipulation → dilute polyuria; monitor UO, Na⁺, give desmopressin if needed

SIADH

Hyponatremia in later postop period



🔹 Emergence and Recovery

  • Smooth, hemodynamically stable extubation to avoid bleeding
  • Avoid coughing or straining
  • Observe for:
    • Epistaxis
    • CSF rhinorrhea
    • Airway obstruction from nasal packing

Elevate head post-op to reduce ICP & bleeding risk.


🔹 Postoperative Concerns

Problem

Management

Electrolyte imbalance (Na⁺)

Monitor serum Na⁺, treat DI or SIADH

Visual deterioration

Immediate imaging to rule out hematoma

Endocrine deficiencies

Assess pituitary function, replace hormones

CSF rhinorrhea

Risk of meningitis—may need surgical repair

Nasal obstruction

Suction carefully, humidified O₂

PONV

Prophylactic antiemetics to avoid ICP rise



🔍 Viva & Exam Points

  • Why avoid N₂O? → Pneumocephalus risk, worsens air embolism
  • Key hormone to assess peri-op? → Cortisol (ACTH axis)
  • DI vs SIADH? → DI = ↑UO, ↑Na⁺; SIADH = ↓UO, ↓Na⁺
  • Most common visual field defect in pituitary tumors? → Bitemporal hemianopia
  • Why nasal ETT? → Leaves oral cavity free for surgery
  • What is pituitary apoplexy? → Hemorrhage into tumor → acute vision loss, headache → emergency decompression


📚 References

  • Miller’s Anesthesia, 9th ed. – Neuroanesthesia section
  • Cottrell and Young’s Neuroanesthesia
  • BJA Education: Transsphenoidal Surgery
  • StatPearls: Pituitary Tumor Surgery
  • WFSA Tutorials