Pheochromocytoma, a rare condition caused by a tumor in the adrenal medulla affecting the chromaffin cells, results in an excess production of catecholamines (epinephrine and norepinephrine) and metanephrines. The most immediate effect of this condition is severe hypertension, but other symptoms (such as headache, palpitations, and excessive generalized sweating) can also appear.
If left untreated, pheochromocytoma may lead to hypertensive encephalopathy, cardiomyopathy, diabetes mellitus, and even death – therefore adequate treatment should be pursued as soon as the correct diagnosis is established. Surgery is the primary and the only valid approach, but a premedication step has to be undertaken prior to the procedure.
Medical Preparation for Surgery
If the patient is not adequately prepared, surgical resection of pheochromocytoma is associated with high mortality rates. The most important issue is adequate control of blood pressure in order to avoid potential hypertensive crisis when the tumor is being handled during the surgery, maintain stable blood pressure during surgery, but also to minimize any adverse effects of anesthesia.
Usually the pretreatment begins with α-blockers. Once suitable α-blockade is achieved, β-blockers are used to control the heart rate. Phenoxybenzamine, a non-selective α-blocker, is a drug of choice (other drugs that can be used include doxazosin or prazosin). It is administrated 7 to 10 days before surgery.
β -blockers can be used only post α-blockade, otherwise they cause unopposed stimulating activity of catecholamines on α-receptors, leading to life-threatening hypertensive crisis. About 10 mg of propranolol four times a day is usually used for β-blockade, which is later translated to long-acting daily dose.
There is also an option of using calcium channel blockers alone instead of α- and β-blockers. This is an option in low-risk patients who have the additional benefit of not interfering with plasma metanephrine assays. By using these drugs, hypotension or orthostatic hypotension can be prevented in the normotensive period.
With appropriate preoperative α-blockade, anesthesia should not be more hazardous than in patients with a non-functioning adrenal tumor; nevertheless, in certain patients dramatic changes in blood pressure and heart rate may occur, which requires immediate administration of pressor or vasodilator agents.
Surgical Approach
The most commonly used procedure for a majority of pheochromocytomas is laparoscopic adrenalectomy (either by transperitoneal or retroperitoneal approach), regardless of whether the disease is familial or sporadic. Preoperative biopsy is not indicated, as it is deemed potentially hazardous for the patient.
In patients with large tumors or when underlying malignancy is suspected based upon the clinical or radiographic presentation, laparotomy should be considered. If there is a need for bilateral procedure, the use of posterior retroperitoneoscopic surgery does not alter the patient position during the operation, which results in a shorter operating period.
Immediately after the surgery, low blood pressure is common and it can be effectively managed with the help of intravenous fluids, as the vascular bed is basically paralyzed by medications used preoperatively. Accordingly, volume replacement can be ample during initial 24-36 hours.
Long-Term Prognosis
Removal of the adrenal tumor usually cures high blood pressure, although up to 30 percent of patients can be hypertensive even after the surgery. There is a general consensus that biochemical testing needs to be repeated 14 days after the surgery to probe for any remaining disease.
During long-term follow-up approximately 17% of tumor reappear (and half of them with signs of malignancy). Even though follow-up is particularly important for patients harboring mutations of disease-causing genes, no method is currently at our disposal to rule out potential for recurrence or malignancy; hence periodic long-term follow-up is recommended for all cases of pheochromocytoma.
Further Reading