Endoscopic Endonasal Transsphenoidal Pituitary Tumor Resection

Anesthetic Considerations and Protocol for Transsphenoidal and Endoscopic Endonasal Pituitary Tumor Surgeries

Background: Pituitary Masses

Although most pituitary tumors are benign and slow growing, issues can arise when tumors secrete hormones and/or are large enough to cause compression. Compression may lead to hormone deficiencies, so be aware that patients may present with an excess or deficiency of certain hormones. Pathology from pituitary tumors, including acromegaly, adrenal insufficiency, thyroid storm, etc, can lead to significant anesthetic challenges; therefore, it is critical to know what kind of tumor and symptoms your patient has. Patients should have undergone an endocrine evaluation prior to surgery, which you must review in the chart before the case.

🧠 Functioning adenomas secrete one or more hormones of the anterior pituitary. Note: patients may over-produce some hormones and have a subsequent deficiency in other hormones.

1. Acromegaly (GH-secreting adenomas): Every anesthesiologist should have a healthy respect for acromegaly!! If a patient endorses recent tongue or jaw growth, voice changes, new snoring and/or sleep apnea, this is a red flag for a difficult mask ventilation and intubation - consider an awake fiberoptic intubation for these patients. Other s/s of acromegaly can include an increase in ring or shoe size, arthritis, carpal tunnel syndrome, excessive sweating, new-onset diabetes, and new-onset cardiovascular disease.

   1. Airway S/S: macroglossia, enlarged epiglottis, glottic and subglottic narrowing, nasal turbinate enlargement.

   2. Respiratory S/S: OSA, pulm HTN, Rt ventricular dysfunction

   3. Cardiovascular S/S: HTN, LVH, diastolic dysfunction, arrhythmias, CAD, cardiomyopathy

   4. Endocrine S/S: DM, hyperglycemia

   5. Diagnosis: Elevated IGF-1. GH secretion varies throughout the day, so IGF-1 is more reliable. If IGF-1 level is equivocal, GH can be measured after an oral glucose load, which would normally suppress GH secretion.

2. Secondary Hyperthyroidism (TSH-secreting adenomas):

   1. Endocrine labs may show elevated FT3, FT4, total T4, and TSH (TSH may be normal or “inadequately suppressed” despite high T3/4).

   2. Cardiovascular symptoms to be concerned about include palpitations, tachycardia, new afib, arrhythmias, congestive heart failure, chest pain, and HTN.

   3. Preop treatment/management: Patients should be stable (ie symptoms controlled, normal T3/4) on methimazole or propylthiouracil prior to surgery. It can take weeks to months to achieve a clinical and chemical euthryroid state. Patients may also be on propranolol or other beta blocker to manage arrhythmias. These home meds should be taken as scheduled before surgery. Inadequately treated hyperthyroidism may lead to hypovolemia (hypotension on induction) and cadiac issues intraop.

3. Cushing’s (ACTH-secreting adenomas): Endocrine workup may show elevated ACTH and cortisol. Signs/symptoms can include weight gain, HTN, uncontrolled DM. Labs: hypokalemia, hyperglycemia, metabolic alkalosis.

4. Prolactin-secreting adenomas: Less critical hormone abnormality from an anesthetic standpoint. Fertility issues may lead to discovery of tumor - remember to offer a pregnancy test to anyone who may be pregnant.

5. Diabetes Insipidus (DI): This is technically a hormone deficiency, but deserves mention. DI is lack of ADH (aka Vasopressin), which normally stimulates renal reabsorption of H2O It is caused by dysregulation or death of ADH-secreting neurons in the hypothalamus or damage to posterior pituitary. Although this is typically presents postop, we occasionally see it preoperaively, especially in patients returning with a tumor recurrence. Signs and symptoms include hypovolemic hypernatremia, excessive thirst and urination. Treatment is desmopressin. Importantly, intraoperatively, urine output should be closely monitored and replaced 1:1 with an isotonic fluid like normosol.

🧠 Non-Functioning Adenomas: do not secrete hormones, but can cause symptoms via mass effect.

🧠 Tumor Size: Microadenoma is a tumor <10 mm; macroadenoma >10mm; giant pituitary tumors are >40 mm. Look at the preop MRI with contrast to get a sense of how big the tumor is.

🧠 Symptoms From Mass Effect:

1. Visual Impairment: Suprasellar extension of a pituirary adenoma compresses optic chiasm. Oculomotor (CN3) involvement can lead to diplopia. If patients have vision loss, discuss BP goals with neurosurgery and consider a preop arterial line to maintain BP during induction.

2. Headaches

3. Hormonal Deficiencies (Hypopituitism):

   1. Secondary Adrenal insufficiency (ACTH deficiency): lack of ACTH production leads to hypocortisolism. Patients will likely be on exogenous steroids preop and will likely need a stress dose of steroids intraop (confirm with the surgical team).

   2. TSH deficiency: hypothyroidism

   3. GH deficiency: in adults, can cause fatigue and weight gain

   4. Gonadotropin deficiency: amenorrhea and erectile dysfunction

🧠 Pituitary apoplexy is a sudden infarct or hemorrhage into a pituitary adenoma. It can present with acute onset of symptoms including sudden headaches, vision changes, hormonal deficiencies, and altered mental status. When symptoms are severe or vision is threatened, this becomes an urgent/emergent surgery. Patients should be on stress dose corticosteroids and will likely require an intraop stress dose. Fluid status, electrolytes, and hemodynamic instability should be monitored closely. Be prepared to manage any hormone-related crises intraop. Keep in mind that patients may not be optimized prior to surgery – if you have any specific concerns, discuss with the surgeon; however, avoid delaying the case as these are usually urgent or emergent cases (delaying surgery can lead to permanent vision loss, permanent damage to the HPA axis, and even death).

Q&A about the about the surgery:

🧠    What is an endoscopic endonasal transsphenoidal approach to a pituitary tumor? To break it down simply, endoscopic means the surgeons use an endoscope (instead of microsurgery, which uses a microscope, for example). Endonasal means they go through the nose. And transsphenoidal means they pass through the sphenoid sinus. Because the pituitary sits in the sella turcica, a depression of the sphenoid bone, it is possible to access the tumor via this less invasive approach. Nose > mucosa > thick bone > sphenoid sinus > thin bone > sella/pituitary/tumor. (see images 1 & 2)

🧠    How do they repair the hole in the back of the nose? Once they have resected the tumor, the OHNS team will put back the layers they dissected through. Specifically, the layers and repair techniques can include:

• Dural repair: ex abdominal fat graft

• Sellar floor reconstruction: ex small piece of bone or cartilage

• Nasoseptal flap: ex mucosa from nasal septum

• Biological glue or sealants: used to ensure watertight seal

• Nasal Packing – often left in until after extubation

🧠 What are some common surgical complications to be aware of?

1. Bleeding: The nasal cavity is highly vascular, so bleeding is common during surgery. Although blood loss is usually not hemodynamically significant, even small amounts can significantly impair endoscopic visualization and complicate the procedure. Topical vasoconstrictors such as epinephrine and cocaine are frequently used at the start of the case to reduce mucosal bleeding. Additional measures, including tight blood pressure control and reducing PEEP, may further minimize bleeding.

Anatomically, the internal carotid artery courses near the operative field, and in some cases, tumor extension into the cavernous sinus may place it at risk. However, direct carotid injury is rare, as this region is generally avoided. In select cases, intraoperative ultrasound may be used to help localize the carotid artery.

1. CSF Leak: This occurs when the arachnoid membrane is inadvertently breached. In high-risk cases, surgeons may place a lumbar drain preemptively and intermittently request drainage of approximately 10 mL of CSF to reduce intracranial pressure and tension at the repair site.

Intraoperatively, avoidance of coughing, bucking, and straining during emergence helps minimize CSF egress. Limiting positive pressure ventilation when feasible may also reduce disruption of the surgical repair. Postoperatively, patients may present with positional headache and rhinorrhea. Management includes head-of-bed elevation and strict avoidance of activities that increase intracranial pressure (e.g., nose blowing, sneezing, Valsalva maneuvers). The surgical team should be notified promptly of any concerning symptoms.

1. Pneumocephalus and tension pneumocephalus: Small amounts of intracranial air are expected postoperatively; however, excessive intracranial air can lead to increased intracranial pressure and brain compression, which may be life-threatening.

Prevention is critical. Positive pressure ventilation should be avoided after extubation, so adequate spontaneous ventilation must be confirmed prior to endotracheal tube removal. Nasal instrumentation (e.g., nasal trumpets or nasogastric tubes) should be avoided. Postoperative use of noninvasive positive pressure ventilation (CPAP or BiPAP) is also contraindicated. These precautions should be clearly communicated to PACU staff.

1. Things in the brain that are not the brain: do not place nasal tumpets, NG tubes, or anything else up the nose in these patients. THe surgical team will suction the stomach and airway with an OG tube at the end of the surgery. Some surgeons may be willing to place a nasal trumput under direct visualization in patients at risk of obstruction. Oral airways and yankauers are safe to use, but make sure you aim caudal (down towards the toes) when placing them.

Anesthetic Management/Plan for Transsphenoidal and Endoscopic Endonasal Surgeries