Transsphenoidal Surgery

Pituitary gland hormone production may be influenced by tumor location and/or hypersecretion caused by adenoma.

Anterior Pituitary

FSH/LH

May cause male impotence or secondary amenorrhea

Prolactin

Causes galactorrhea

ACTH

Excess production causes Cushing's disease (elevated cortisol levels)

Growth Hormone

Excess causes acromegaly (influences anesthesia as hypertrophy occurs in skeletal, connective, and soft tissues

The patient may have an enlarged tongue and epiglottis, making them prone to airway obstruction and possibly difficult intubation

• Have a glide scope in the room

Hoarseness may indicate thickening of vocal cords or issues with recurrent laryngeal nerve due to stretching

Dyspnea or stridor may indicate subglottic narrowing

Do a thorough airway assessment and consider awake intubation

The patient may also present with peripheral nerve injuries, HTN, or diabetes mellitus

TSH

Rarely excess production

Posterior Pituitary

ADH/Vasopressin

ADH as multiple functions

• Maintains extracellular fluid volume and regulates plasma osmolality
• Increases BP by constricting smooth vascular muscle (careful with cardiac disease pts, can cause ischemia)
• Promotes hemostasis through an increase in von Willebrand factor and factor VIII (accelerates coagulation)

The main stimulus is plasma osmolality, but also positive pressure ventilation, stress, anxiety, hyperthermia, B-adrenergic stimulation or histamine release can cause increased secretion of ADH

Diabetes Insipidus

Failure to secrete adequate ADH

• Results in significant increase in diuresis, hypernatremia (dehydration) and hypovolemia, poorly concentrated urine

Treatment

If complete DI, administer infusion of aqueous ADH 100-200mU/hr along with isotonic infusion while monitoring serum sodium and plasma osmolality

Pt may also receive ADH IM or DDAVP intranasally, which has prolonged action of 12 - 24hrs.

Excessive ADH Production

Caused by head injuries, intracranial tumors, pulmonary infections, small cell carcinoma of the lung, and hypothyroidism (causes hypothermia, which causes coagulopathy)

• Results in dilutional hyponatremia, decreased serum osmolality, decreased urine output with increased osmolality
• Weight gain, skeletal muscle weakness (low Na), mental confusion, or convulsions

Treatment

Fluid restriction, democlocycline, which interferes with the ability of the renal tubules to concentrate urine

Oxytocin

Contraction of the uterus stimulates milk production.

Transsphenoidal Resection Procedure

Presenting symptoms

• Hormone abnormalities, vision (usually loss of side vision, N/V, possible headaches

Tumors <10 mm usually via transsphenoidal approach, whereas tumors >20 mm via bifrontal craniotomy

The approach to sella turcica and region is associated with fewer complications than craniotomy

Access transnasally involves the creation of a tunnel to the sphenoid sinus. The sphenoid's rostrum (beak-like shape) is removed, the floor of the sella is removed, the Dura is opened, and the tumor is removed using microcurettes. Fat taken from the subcutaneous tissue at the time of the facial resection, or abdomen or thigh used to fill the sphenoid and hold the graft material in place (to seal the Dura if CSF leaks)

The lateral wall of the sphenoid sinus protects part of the optic nerve and the carotid artery

Operation is performed using a microscope and/or endoscope, mainly in the midline position, to protect the carotid arteries

The floor of the sella is reconstructed as needed, and the sphenoid bone may be packed and sealed like the Sella

The endoscopic approach provides improved surgical view and access, fewer complications, and faster recovery

Position

Supine, head elevated 20-30 degrees

Ensure 2-3 fingerbreadths between chin and chest

Possible Mayfield tongs placed by the surgeon to stabilize the head for seated access and to help with surgical drainage or a three-point pin head holder

• Premedicate with opioids before placement of Mayfield
• Very painful

The surgeon then correlates the CT/MRI findings with neurological marking, and you can retape the eyes afterward

Possible throat pack to prevent aspiration of blood

All pressure points are padded, and arms are tucked

Considerations

The possible use of evoked potentials influences the choice of anesthesia

ETT is taped out of the surgeon's way, and oral RAE is used. Secure well, as shared airway with the surgeon

Vasoconstrictors to the nasal area may cause elevated BP and dysrhythmia

Painful dissection of the nasal cavity can cause elevated BP and ICP

No hyperventilation as decreased ICP can lead to retraction of the pituitary gland = making it difficult to get to the surgical field

Risk of massive bleeding from carotid arteries

F/C to monitor urine output

The risk of post-op DI usually resolves in about 10 days

Avoid hyperglycemia (keep BS < 140-180)

Preoperative considerations

Antibiotics

Per surgeon

Surgical Time

2.5-3 hrs

EBL

25-250 mL

Age Range

18-85 yr (usually 30-50yr)

Mortality

1 %

Information

Patient ID, consent, NPO, HX, allergies, airway assessment. Questions answered. Premedicate with Versed and Robinul (consider the risk of increased ICP due to hypoventilation and subsequent elevated CO₂)

Inform the patient of possible nasal packing post-op, so they will have to breathe through the mouth

Complications

Carotid artery injury (rare)

Venous air embolism

Hypopituitarism - note the need for steroid replacement (due to lack of cortisol)

Diabetes Insipidus 24-48 hrs postop

CSF leak

Epistaxis

Meningitis

SIADH

Cranial nerve injury

• Optical nerve with loss of vision

Anesthesia Considerations

Induction

GETA

May need lumbar drain if elevated ICP (tumors usually located in sella turcica and thus no elevation of ICP)

Oral RAE secured the left side of the mouth

OGT? to empty the stomach of blood post-op

Eyes taped and then protected with Tegaderm

• May wait to do final taping until the surgeon has done marking as mentioned above

Note surgical infiltration with epinephrine - monitor for dysrhythmia

Drugs to Consider

Lidocaine 1 mg/kg

Rocuronium: 5 mg pre-succinylcholine to prevent myalgias (10 mg/mL)

Propofol 1-2 mg/kg, possible infusion if doing TIVA

Succinylcholine 0.5-1.5 mg/kg (can cause elevated ICP)

Opioid

Fentanyl 1-3 mcg/kg IV

Remifentanil drip

Sufentanil - shorter duration of action and elimination half-life than fentanyl (high protein binding, low volume of distribution, tighter bound to receptors. Excreted via liver, little by renal)

Rule of thumb: Sufentanil is 10 times as potent as fentanyl

Maintenance

Consider modified hypotension to minimize bleeding along with the elevated head

O₂/Isoflurane <1 MAC (must prevent vasodilation)

Fentanyl 1-10 mcg/kg or sufentanil 1-2 mcg/kg

Atracurium or vecuronium

Zofran 4 mg IV

Emergence

Reversal with neostigmine and glycopyrrolate or sugammadex

Lidocaine IV and via ETT to prevent any coughing

If coughing and not ready to extubate, give a little propofol IV

Extubate deep if possible. The patient must have spontaneous ventilation, been suctioned, and then emerge on a mask (this can also be difficult depending on the nasal status)

Remove tracheal packing if applicable