Perioperative management of the patient with pheochromocytoma

The KEY: Communication between surgeon, anesthesiologist, and internist.

Background:
Pheochromocytoma is an uncommon neuroendocrine tumor of the chromaffin cell.
The most common sign of the tumor is hypertension, which can be paroxysmal.
The tumor’s intermittent catecholamine surges can cause a variety of symptoms,including headache, chest pain, palpitations, diaphoresis, dyspnea, anxiety,and dizziness.

Surgical excision can prevent the life-threatening complications of hypertensive crises, stroke, arrhythmias, and myocardial infarction.Before 1961,surgical mortality ranged from 24–45%. With appropriate medical preparation and an experienced anesthesiologist and surgical team, survival of excision of a pheochromocytoma is 93.3–100%

Preoperative preparation
Catecholamine excess causes --vasoconstriction that leads to both hypertension and hypovolemia.
Pheochromocytoma patients can die intraoperatively from--severe hypertensive crisis or hypotension that leads to cardiovascular collapse.

When tumor veins are ligated during surgery, the sudden drop in circulating catecholamines can lead to vasodilatation. The catecholamine output of the contralateral adrenal may be suppressed from previous catecholamine excess. In the hypovolemic patient, this can lead to hypotension, shock, and death.

Alpha adrenergic blockade is the cornerstone of preoperative preparation
-it treats both hypertension and vasoconstriction
-improves circulating plasma volume prior to surgery.

Phenoxybenzamine[Non selective, non competitive]-start 2 weeks prior to Sx 5-10 mg BID, step up to control BP~140/90 with max. 300 mg per day. Caution Postural hypotension, nasal stuffiness, reflex tachycardia.

Selective Alfa 1 blockers[Prazosin SR 2-20 mg BD ,doxazosin 1-16 mg OD]- do not block NA re uptake- less reflex tachycardia and orthostatic hypotension so better tolerated.

Liberalization of salt in the diet along with alpha blockade should expand plasma volume.

Beta blockade: Propanolol/Atenolol/metoprolol few days after Alfa Blockade[once reflex tachycardia noted] but few days before srgery.[if not contraindicated by heart failure or asthma]. Beta-blockers may also prevent perioperative arrhythmias and cardiac complications.

As calcium ion transport is essential for release of catecholamines from chromaffin cells, calcium channel blockers are used for control of blood pressure and preoperative preparation at some centers Less periop fluid requirement and post op hypotension in one French study.

Metyrosin [(alpha-methyl-p-tyrosine)Tyrosin hydroxylase inhibitor] reserved for refractory cases at doses of 1–4 mg per day -Very Toxic no longer used

Preoperative evaluation of myocardial function MUST.[left ventricular hypertrophy and dysfunction, but chronic catecholamine excess induced cardiomyopathy.]

Pre op Target:
24 BP monitoring, all readings <160/90, HR <100/min, Postural drop in BP with compensatory tachy as sign of adequate alfa blockade. Intraoperative Management:
-Avoid Histamine release causing agents during induction eg. Morphine
-Adrenaline followed by noradrenaline infusion for fluid refractory hypotension [CVP~10-15mmHg].
-Terlipressin 1 mg followed by vasopressin infused can be used.
-Na.nitroprusside infusion better then Phentolamine boluses [due to shorter duration of action] for hypertensive episodes.
-IV Nicardipine and Magnesium can be used to control hypertensive spikes.
-Betablockers for tachyarrhythmia.

Postoperative Management
-12-24 hours HDU/ICU care must.
-patient may remain hypertensive up to 2 weeks after excision.
-urinary catecholamines should be checked to ensure no additional tumor remains.
-hypoglycemia may develop and persist into the postoperative period once the tumor is removed[Catecholamine withdrawal + Beta blockade induced limit to compensation and unawareness]. Glucose should be included in perioperative fluids, and blood sugars should be monitored frequently intraoperatively and postoperatively.
-patients who undergo bilateral adrenalectomy [some with unilateral surgery as well] will need steroid[Hydrocortisone + Fludrocaortisone] replacement.

If catecholamines are normal, the patient may be one of about 25% of pheochromocytoma patients whose hypertension persists after surgical excision caused by other concomitant disease, such as essential or renal hypertension.

Thanks to Dr Anuj Clerk for contributing this wonderful article.