ADRENALECTOMY IN THE ELDERLY: EMPHASIS ON PHEOCHROMOCYTOMA

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1 ADRENALECTOMY IN THE ELDERLY: EMPHASIS ON PHEOCHROMOCYTOMA David S. Pertsemlidis, Assistant Clinical Professor and Demetrius Pertsemlidis, Clinical Professor Department of Surgery, Mount Sinai School of Medicine New York University, New York, USA INTRODUCTION Geriatrics or medical gerontology is the study of patients 65 years or older. This arbitrary definition was derived from the traditional chronologic landmark, when retirement from work, reliance on pension and life style changes occur in North America. Unlike the abundant reporting of non-adrenal surgery outcome in the elderly, the results of adrenalectomy have been limited to anecdotal or small-sample reports in the English literature. In this report, the emphasis on pheochromocytoma was dictated by the larger proportion of elderly patients with this syndrome, in comparison to adrenocortical tumors. Pheochromocytoma is a neuroendocrine tumor, embryologically derived from the neural crest and located principally in the abdomen. Extra-abdominal tumors, mainly in the mediastinum and rarely in the neck, comprise approximately 2% of all pheochromocytomas. Until the early 1950s, about two thirds of all pheochromocytomas were discovered at autopsy. Surgery for pheochromocytoma has now attained a level of safety and efficacy that permits resection of benign or malignant tumors with minimal morbidity and rare mortality. HISTORICAL LANDMARKS The isolation of two catecholamine metabolites in the urine, vanillylmandelic acid (VMA) by Armstrong in 1956 and metanephrines by Axelrod in 1957, were landmarks in biochemical diagnosis. Gitlow and coworkers from our institution contributed immensely to the perfection of biochemical diagnostic methods and their correlation with the clinical syndrome of pheochromocytoma. Recent work done at the National Institutes of Health by Lenders et al and Eisenhofer and colleagues have added new diagnostic dimensions. Clinical associations with other entities ultimately led to genetic linkage of pheochromocytoma to multiple endocrine neoplasia Type 2 (MEN 2), neurocutaneous syndromes, especially von Hippel-Lindau disease (VHL) and neurofibromatosis Type 1 (NF 1), and the familial paraganglioma syndrome. PREVALENCE AND DISTRIBUTION The prevalence is less than 0.5% in hypertensive adults, but higher in hypertensive adolescents and children. In von Hippel-Lindau disease, pheochromocytoma occurs in 20% of such patients. Close to 40% of patients with MEN 2 harbor a pheochromocytoma. Pheochromocytoma is neither gender nor race specific and can occur at any age. In geriatric age, pheochromocytoma is almost always sporadic and unilateral adrenal. In inherited syndromes involving the adrenal medulla or cortex, the phenotypic expression occurs at much younger age and is often bilateral adrenal or in extra-adrenal location.

2 CLINICAL MANIFESTATIONS Pheochromocytoma is a capricious neoplasm with non-specific phenotypic manifestations and can therefore be difficult to diagnose clinically. Hypertension may be constant, rather than paroxysmal, in one third to one half of patients. Excess cathecholamines affect a plurality of target organs, thus inducing a wide spectrum of symptoms which are often inseparable from those of a variety of common illnesses. Some unusual clinical features are transient ischemic attacks, stroke, grand mal seizures, cardiomyopathy, gastrointestinal crises, and diabetes mellitus or insipidus. Paroxysmal events are usually precipitated by physical or emotional stress, which induces a flux of catecholamines from the expanded storage in the neurosecretory granules of the sympathetic neurons and adrenal medulla. Offspring of parents harboring germline mutations of the autosomal dominant RET proto-oncogene mapped to chromosome 10 (10q11.2) the von Hippel-Lindau tumor suppressor gene mapped to chromosome 3 (3p25-26) or the neurofibromatosis Type 1 (NF 1) gene mapped to chromosome 17 (17q11.2) are at high risk for developing pheochromocytoma and other components of the neoplastic syndromes. BIOCHEMICAL DIAGNOSIS The biochemical diagnosis of pheochromocytoma is based on the presence of elevated catecholamines and especially their metabolites in the plasma (normetanephrine and metanephrine) and in the urine (metanephrines and vanillylmandelic acid) in the absence of stress. In adults, elevation of urinary homovanillic acid strongly implies likelihood of malignancy. Physiologically higher concentrations of catecholamines and their metabolites in the plasma and urine are found in children and adolescents. There is no evidence that geriatric age influences the diagnostic values of catecholamines and their metabolites All medications should be screened, and those known to falsely elevate or suppress the catecholamines or their metabolite concentrations in the plasma or urine should be stopped for at least one week. Phenoxybenzamine, tricyclic antidepressants, labetalol, acetaminophen, alpha-methyl-dopa, monoamino oxidase (MAO) inhibitors, amphetamine, cocaine and calcium antagonists may interfere with assays of the parent catecholamines and metanephrines in the plasma and urine. Dietary caffeic acid, a catechol ingredient in natural and decaffeinated coffee, and its metabolite dihydrocaffeic acid interfere with assays of plasma catecholamines. LOCALIZATION THROUGH IMAGING Ultrasound examination may be limited by the interposition of gastric and colonic gas. Computed tomography has permitted localization of tumors as small as 5 mm with a sensitivity and specificity of 88 and 95%. The introduction of magnetic resonance imaging (MRII) has offered the additional feature of specificity through enhancement of signals on the T2-weighted images. Scintigraphy with meta-iodobenzylguanidine (MIBG), an analogue of norepinephrine, labeled with iodine-123 (I-123) or iodine-131 (I- 131), and indium-111-labeled octreotide, a somatostatin analogue, permits not only anatomical localization but also determination of function with the highest sensitivity and specificity.

3 PERIOPERATIVE MANAGEMENT Once the diagnosis of pheochromocytoma is established by biochemical parameters, alpha-adrenergic blockade should be initiated. Only after this blockade has established normotension can beta-adrenergic inhibitions be used to treat compensatory tachycardia. Phenoxybenzamine, a long-acting, nonselective oral α-blocker, is the drug of choice for outpatient management. An initial dose of 10 mg twice daily is used with progressive increases until normotension is achieved and paroxysmal symptoms are eliminated or minimized. Usually mg/day, divided in 3 or 4 doses, are sufficient. Prazocin, a selective α-receptor inhibitor with shorter duration of action than phenoxybenzamine, can be used at doses of 1-2 mg 3 times daily. IN-HOSPITAL PREOPERATIVE PREPARATION The short-acting α-blocker phentolamine, alone or combined with the b-receptor antagonist esmolol, permits easy minute-to-minute titration of the doses needed to attain normotension and cardiac eurhythmia. The short half-life and virtual absence of toxicity renders these two medications highly desirable. Continuous intravenous infusion of phentolamine should be started at 10 mg/hour with incremental rates every 5-10 minutes until normotension is achieved. Usually, an average infusion rate of 35 mg/hr is sufficient, but the requirements may range from 10 to 100 mg/hr. The solutions should be freshly prepared and contain 1.0 mg/ml of phentolamine in glucose/water. The concentration for intraoperative use should be two-to threefold higher to rapidly control intraoperative hypertensive events. Continuous intravenous infusion of esmolol is started after the development of sinus tachycardia from adequate α-receptor blockade. The esmolol solution should contain 10 mg/ml of esmolol in glucose/water. The average infusion rate is 150 mg/hr. Nitroprusside, a potent vasodilator and smooth muscle relaxant, should always be available in the perioperative setting for limited use during episodes when adrenergic blockade proves ineffective. Peripheral arterial and central venous catheters are necessary for monitoring of the respective pressures. INTRAOPERATIVE MANAGEMENT Surgery should not commence until adrenergic steady state is attained. Anesthetic induction and endotracheal intubation should be performed under optimal pharmacological protection. Infusion of phentolamine and esmolol should be adjusted, when needed, to control hypertensive or arrhythmic events during unavoidable tumor manipulation in the course of mobilization and resection of the tumor. SURGICAL APPROACHES The open transperitoneal anterior approach offers excellent exposure for complete exploration, easier control of bleeding, and resection of large invasive tumors or multiple extra-adrenal pheochromocytomas. Minimally invasive techniques offer quick recovery, less adhesion formation, and superior cosmetic results. The concern that the pressure of pneumoperitoneum may induce flux of catecholamines by the tumor has been dispelled by clinical observations and assays of plasma catecholamines during minimally invasive adrenalectomy for pheochromocytoma.

4 Complete removal of the tumor is followed by a fall of systolic arterial pressure to less than 90 mm Hg. This hypotension can be corrected within minutes by stopping the shortacting α-receptor blocker (phentolamine) and rapidly infusing 2-3 L of crystalloid. Infusion of norepinephrine to restore normotension should be avoided, as it prolongs undesirable vasoconstriction. EXTRA-ADRENAL PHEOCHROMOCYTOMA The term functioning paraganglioma is synonymous with extra-adrenal pheochromocytoma. These tumors originate from the system of paraganglia, which extends from the base of the skull to the pelvis and includes the jugulotympanic, vagal, carotid body, laryngeal, aortico-pulmonary, and viscero-autonomic regions. The incidence of extra-adrenal tumors is 15-22% of all pheochromocytomas. Multicentricity is high, ranging between 15 and 24% overall, and is higher in children. Extra-adrenal pheochromocytomas are the most aggressive of the adult sympatho-adrenal tumors, should be considered malignant, and approached accordingly, whether in the abdomen, chest, or neck. One half of all malignant pheochromocytomas arise from extraadrenal sites. SUMMARY Thirty geriatric out of 198 patients with pheochromocytoma were almost exclusively sporadic, had mostly benign unilateral adrenal tumors resected in the pre-laparoscopic era. The operative blood loss, need of blood transfusions, hospital stay and convalescence were greater and longer, respectively, than in patients younger than 65. Fourteen geriatric out of 98 patients with adrenocortical tumors (Cushing s adenoma 2, aldosteronoma 3, estrogen secreting 1, nonfunctioning adenomas and carcinomas 8) precluded meaningful statistic comparison. References 1) Pertsemlidis DS, Pertsemlidis D Pheochromocytoma: Diagnosis and treatment In: Schwartz AE, Pertsemlidis D, Gagner M, eds. Endocrine Surgery, New York-Basel, 2004: ) Pertsemlidis D, Gitlow SE, Siegel W, et al. Pheochromocytoma: 1) Specificity of laboratory diagnostic tests. 2) Safeguards during operative removal Ann Surg 1969; 169: ) Pertsemlidis D Laparoscopic versus open adrenalectomy in pheochromocytoma In: Bouch HP, Koeckerling F, Bourchard R, Schug-Pass, eds. Bologna: Monduzzi Editore 2000: ) Pertsemlidis D Minimal access versus open adrenalectomy Surg Endosc 1995;9:

5 5) Gabrielson G, Guffin A, Kaplan J, Pertsemlidis D, Iberti T Continuous intravenous infusions of phentolamine and esmolol for preoperative and intraoperative adrenergic blockade in patients with pheochromocytoma J Cardiothoracic Anesthesia 1987;6:554 6) Inabnet WB, Caragliano P, Pertsemlidis D Pheochromocytoma: Inherited associations, bilaterality and cortex preservation Surgery 2000;128: