Endocrine Diseases: Pituitary, Thyroid, Parathyroid, and Adrenal Glands - 2nd Edition

Educational Objectives

Summary

Endocrine Diseases: Pituitary, Thyroid, Parathyroid, and Adrenal Glands

Kathryn McGoldrick, MD, Professor and Chair of Anesthesiology, Assistant Dean for Student Affairs, New York Medical College, Westchester Medical Center, Valhalla, New York

Overview of pituitary gland: pituitary gland and hypothalamus together form central unit that regulates release of assorted hormones; anterior pituitary (adenohypophysis) — secretes prolactin, growth hormone, gonadotropins (luteinizing hormone and follicle stimulating hormone), thyroid-stimulating hormone (TSH), and adrenocorticotropic hormone (ACTH); posterior pituitary (neurohypophysis) — secretes vasopressin (antidiuretic hormone) and oxytocin; hormone release from both anterior and posterior pituitary regulated by hypothalamus

Dysfunction of anterior pituitary: hyposecretion of anterior pituitary hormones usually results from glandular compression by tumor; condition may initially present as isolated deficiency (eg, secondary amenorrhea) but usually progresses to multiglandular dysfunction; panhypopituitarism after postpartum hemorrhage (Sheehan syndrome) result of anterior pituitary necrosis; radiation therapy delivered to sella turcica (neighboring structures) and surgical hypothesectomy other causes of panhypopituitarism; panhypopituitarism requires specific hormone replacement therapy, which should be continued perioperatively; stress doses of corticosteroids necessary for patients receiving steroid replacement therapy (due to inadequate ACTH); hypersecretion of assorted anterior pituitary hormones usually caused by adenoma; galactorrhea (result of increased prolactin), Cushing disease (result of increased ACTH), gigantism, or acromegaly may occur secondary to excess growth hormone; excess secretion of TSH unusual

Dysfunction of posterior pituitary: inadequate secretion of ADH (vasopressin) or resistance of renal tubules to ADH (nephrogenic diabetes insipidus) can occur; failure to secrete appropriate amounts of ADH produces polydipsia, hypernatremia, and excessive amounts of poorly concentrated urine; ensuing hypovolemia and hypernatremia can be life threatening; diabetes insipidus typically occurs after destruction of pituitary gland by intracranial trauma (often fatal) or by infiltrating lesions or surgery; treatment of diabetes insipidus depends on severity of hormonal deficiency; anesthetic management — patients with complete diabetes insipidus receive intraoperatively intravenous (IV) infusion of aqueous ADH (100-200 mU/hour) combined with isotonic crystalloid solution; check serum sodium and plasma osmolality frequently to determine therapeutic modifications; ADH may be given intramuscularly; desmopressin acetate administered nasally has extended antidiuretic action lasting 12 to 24 hours; patients with residually functioning gland generally do not require parenteral ADH perioperatively due to large amounts of ADH secreted in response to surgical stress; if plasma osmolality >290 mOsm/L, therapeutic adjustments should be made; nonhormonal agents helpful in treatment of incomplete diabetes insipidus include chlorpropamide, 200 to 500 mg/day; chlorpropamide — stimulates release of ADH and sensitizes renal tubules to ADH; hypoglycemia may occur, restricting usefulness of drug; clofibrate — hypolipidemic agent; stimulates ADH; not effective in patients with nephrogenic diabetes insipidus; thiazide diuretics — paradoxic antidiuretic effect; causes — inappropriate and excessive secretion of ADH can occur as result of head injuries, intracranial tumors, pulmonary infections, pulmonary small cell carcinoma, and hypothyroidism; inappropriate antidiuretic hormone secretion associated with dilutional hyponatremia, reduced serum osmolality, and low urine output with high osmolality; presenting symptoms — weight gain, skeletal muscle weakness, confusion, or convulsions; diagnosis — one of exclusion, ruling out other causes of hyponatremia; prognosis — related to cause of the condition; treatment of mild to moderate inappropriate antidiuretic hormone involves restriction of fluid intake to 800 mL/day; if water intoxication severe, more aggressive treatment with IV hypertonic saline may be needed in conjunction with furosemide; if left ventricular dysfunction present, use caution; once serum sodium in safe range, substitute isotonic saline for hypertonic solution; overly rapid correction of hyponatremia can produce central pontine myelinolysis and permanent brain damage; serum sodium should not be raised by more than 12 mEq/L during 24-hour interval

Acromegaly: produced by excessive growth hormone secretion in adults, usually caused by benign macroadenoma in pituitary; prevalence — 40/1 million people, occurring with equal frequency in men and women; common associated conditions augmenting perioperative risk — airway abnormalities, cardiovascular dysfunction, hypertension, respiratory impairment (particularly obstructive sleep apnea), and endocrine abnormalities (including hyperglycemia); characterized by overgrowth of soft tissues, bone, and cartilage, which manifests with prominent nose, jaw, hands, fingers, feet, and toes; excess growth hormone before puberty leads to gigantism, accounting for <5% of all acromegalies; primary therapy — surgery; transsphenoidal microsurgery more common than transcranial approach and associated with less morbidity; pituitary radiation reserved for persistent postsurgical disease or when surgery contraindicated; airway difficulties — tongue and epiglottis enlarged, increasing vulnerability to upper airway obstruction; difficult intubation ≤30%; hoarseness may be indicative of vocal cord thickening or paralysis of recurrent laryngeal nerve as result of stretching; subglottic narrowing may manifest as dyspnea or stridor; awake fiberoptic intubation may be prudent; hemodynamic parameters — optimize preoperatively; if panhypopituitarism present from mass effect, hydrocortisone may be required; monitor serum glucose intraoperatively and treat as indicated; anticipate airway obstruction on both induction and emergence; in obstructive sleep apnea, exercise caution with narcotics; postoperative complications — transient diabetes insipidus and anterior pituitary insufficiency (manifesting as low levels of ACTH, TSH, and gonadotropin) develops in approximately 20% of patients; hormone replacement therapy with tapered cortisol therapy may be required; other postoperative complications include meningitis, sinusitis, hematoma, cranial nerve palsy (typically involving cranial nerves 3, 4, or 6), nasal septal perforation, and visual disturbances

Diseases of thyroid gland: active uptake in concentration of iodide in thyroid gland triggers production of thyroid hormone; after organification, monoiodothyronine or diiodothyronine couple enzymatically with thyroid peroxidase to form T3 or T4, which then attach to thyroglobulin and are stored as colloids in the gland; thyroid tropin (TSH) produced by anterior pituitary and secretion regulated by thyroid tropin-releasing hormone in hypothalamus; TSH responsible for uptake of iodine and proteolytic release of thyroid hormones; as thyroid function diminishes, thyroid tropin concentrations increase; thyroid gland secretes thyroxin (T4) and triiodothyronine (T3) that serve as major regulators of cellular metabolic activity; hormones regulate synthesis and activity of variety of proteins and essential for normal cardiac, pulmonary, and neurologic function; most effects exerted by more potent and less protein-bound T3; thyroid hormone vital to array of functions; anesthesiology concerned with cardiovascular manifestations of thyroid disease (affect tissue responses to sympathetic stimulation and myocardial contractility)

Hyperthyroidism: when tissues exposed to excessive amounts of thyroid hormone, hyperthyroidism ensues; causes — Grave disease most common (autoimmune condition characterized by diffuse multinodular glandular enlargement, ophthalmopathy, dermopathy, and finger clubbing), thyroid adenoma (second most common), and thyroiditis (frequently follows respiratory infection and may respond to treatment with anti-inflammatory agents alone); Hashimoto thyroiditis is chronic autoimmune disease that typically produces hypothyroidism, but may produce hyperthyroidism; etiologies — pregnancy, trophoblastic tumors, radioactive iodine therapy, thyroid carcinoma, and TSH-secreting pituitary adenomas; iatrogenic hyperthyroidism can occur after thyroid replacement therapy and administration of angiographic contrast media or amiodarone; signs and symptoms — weight loss, skeletal muscle weakness and stiffness, diarrhea, warm and moist skin, heat intolerance, and nervousness; cardiovascular manifestations — increased left ventricular contractility and ejection fraction, increased systolic blood pressure, decreased diastolic blood pressure, tachycardia, hypercalcemia, mild anemia, and thrombocytopenia; agranulocytosis can occur secondary to therapy with propylthiouracil (PTU) or methimazole; elderly patients may have heart failure, atrial fibrillation, or other cardiac dysrhythmias; older patients occasionally present with apathetic hyperthyroidism characterized by depression and withdrawal without typical systemic signs or symptoms seen in younger patients; treatment and anesthetic considerations — render patient euthyroid prior to surgery, reducing risk for thyroid storm and perioperative cardiovascular perturbations ≤90%; mainstays of therapy include thiourea derivatives (PTU and methimazole), which inhibit organification of iodide and synthesis of thyroid hormone; PTU decreases peripheral conversion of T4 to T3; regulation to euthyroid state typically requires at least 2 months; inorganic iodide useful, bearing in mind that antithyroid drugs should be started before iodine treatment (due to possibility of exacerbating thyrotoxicosis); beta-adrenergic antagonists effective in blunting signs of excessive sympathetic activity and should be initiated unless specifically contraindicated; risk mitigation in emergency surgery — administer beta-adrenergic blockade to attain heart rate <90 beats/minute; beta-blockade will not prevent thyroid storm; glucocorticoids (eg, dexamethasone) 8 to 12 mg/day used to manage severe thyrotoxicosis by reducing thyroid hormone secretion and peripheral conversion of T4 to T3; iopanoic acid useful for emergency preparation

Thyroid storm: life-threatening exacerbation of hyperthyroidism, typically occurs in undiagnosed or undertreated hyperthyroidism as a result of stress of surgery or nonthyroid illness; signs and symptoms — hyperthermia, tachycardia, dysrhythmias, myocardial ischemia, congestive heart failure, agitation, and confusion; differential diagnosis — pheochromocytoma, light anesthesia, and malignant hyperthermia; treatment — large doses of PTU (200-400 mg via nasogastric tube every 6 hours), IV hydrocortisone (50-100 mg every 6 hours), propranolol (every 4-6 hours), esmolol infusion, sodium iodide (250 mg IV every 6 hours); restore intravascular volume with liberal amounts of IV fluids; monitor hemodynamics with arterial catheter and pulmonary artery catheter (helpful in patients with notable left ventricular dysfunction); administer digoxin for heart failure (particularly in atrial fibrillation with rapid ventricular response); use cooling blankets; meperidine may be helpful to prevent shivering; remove precipitating event; indications for thyroidectomy — failed medical therapy, cancer, symptomatic goiter; anesthesia — usually general endotracheal anesthesia, although laryngeal mask airway may be used (allowing for real-time visualization of vocal cord function with spontaneous respiration); bilateral superficial cervical plexus block used for limited thyroidectomy; intubation — often difficult; large goiters may warrant securing airway while patient awake; large retrosternal goiters can act like anterior mediastinal mass, causing airway obstruction after induction of general anesthesia; review computed tomography or magnetic resonance imaging results prior to selecting anesthetic plan; thyroidectomy performed with open or axilla approach; monitoring -— with minimally invasive surgery, monitor pneumothorax with end-tidal CO2 and portal ultrasound; monitor recurrent laryngeal nerve function intraoperatively using nerve simulator or nerve integrity monitor endotracheal tube (muscle relaxants and topical analgesia interfere with signals); complications after thyroidectomy — recurrent laryngeal nerve damage, tracheal compression as result of tracheomalacia or hematoma, and hypoparathyroidism as result of inadvertent removal of parathyroid glands; symptoms of hypocalcemia — develop 24 to 96 hours after surgery; laryngeal stridor progressing to laryngospasm may be earliest sign of hypocalcemic tetany; IV administration of calcium chloride or calcium gluconate indicated; check magnesium levels and correct if needed; bilateral recurrent laryngeal nerve damage (rare and characterized by aphonia) warrants immediate reintubation; unilateral recurrent laryngeal nerve injury (more common) often transient and characterized by hoarseness and paralyzed vocal cord; postoperative extubation of trachea should be performed under optimal conditions (bilateral laryngeal nerve injury or collapse of tracheal rings mandates emergency reintubation); evaluate vocal cord function after extubation by laryngoscopy or by asking patient to pronounce “E”; surreptitious bleeding can occur; examine wound prior to discharge from postanesthesia care unit; airway obstruction occasionally ensues secondary to bleeding and hematoma must be expeditiously evacuated; thyroid storm unlikely after 3 days postoperatively

Hypothyroidism: common condition, especially in adult women resulting from inadequate circulating levels of T4, T3, or both; primary failure of thyroid gland indicates reduced production of thyroid hormone despite adequate TSH production; accounts for approximately 95% of cases of thyroid dysfunction; diagnosis — challenging due to slow and progressive nature of condition; causes — autoimmune thyroiditis (most common), previous treatment for hyperthyroidism (radioiodine therapy, PTU, and methimazole), and external neck irradiation; secondary causes due to pituitary or hypothalamic disease and associated with other pituitary deficiencies; signs and symptoms — diffuse reduction in metabolic activity producing lethargy, slow mental functioning, slow movements, and cold intolerance; cardiovascular manifestations include bradycardia, reduced myocardial contractility and cardiac output, and increased peripheral vascular resistance; low voltage on electrocardiogram (ECG) reflective of accumulation of pericardial fluid; angina unusual, but may occur when thyroid hormone treatment started; heart failure unusual except in coexisting heart disease; ventilatory responsiveness to hypoxia and hypercapnia depressed and potentiated by sedatives, opioids, and general anesthesia; postoperative ventilator failure rarely encountered except in coexisting pulmonary disease, obesity, or myxedema coma; goiter may be present; macroglossia occasionally encountered; other abnormalities — anemia, coagulopathy, sleep apnea, hypothermia, impaired renal free water clearance with hyponatremia, and reduced gastrointestinal motility; stress response may be attenuated in chronic or severe disease and adrenal depression may occur; treatment — hormone replacement therapy; maintenance outpatient therapy for adults typically consists of oral thyroxone 0.1 to 0.2 mg/day; although controversial, evidence supports restoration to euthyroid state prior to elective surgery; no compelling reason to postpone elective surgery in mild or moderate hypothyroidism; thyroid replacement therapy indicated for severe hypothyroidism, myxedema coma, and pregnant patients with hypothyroidism; untreated hypothyroidism in pregnancy associated with increased incidence of spontaneous abortion and serious mental and physical abnormalities in the baby; anesthesia management — virtually all intravenous and volatile agents; little effect of hypothyroidism on minimum alveolar concentration for inhaled anesthetics; regional anesthesia reasonable provided intravascular volume adequate; maintain normal body temperature; monitor for hypotension, congestive heart failure, and hypothermia

Myxedema coma: extremely severe form of thyroiditis; life-threatening medical emergency with mortality rate ≤50%; characterized by stupor, coma, hypoventilation, hypotension, hypothermia, and hyponatremia; requires expeditious and aggressive therapy; only life-saving surgery should occur in this setting; treatment — IV thyroid replacement with loading dose of T4 (typically sodium levothyroxine, 200-300 μg IV over 5 to 10 minutes followed by maintenance dose of 50 to 200 μg/day IV); T3 may be used for more rapid onset (0.15-0.3 μg/kg every 6 hours); replacement therapy may trigger myocardial ischemia; administer stress doses of hydrocortisone (typically 100 mg IV, then 25 mg IV every 6 hours); improvements in heart rate, blood pressure, and body temperature may occur within 24 hours

Hyperparathyroidism: normal total serum calcium concentration 8.8 to 10.4 mg/dL; maintenance of serum calcium concentration subject to tight hormonal control by parathyroid hormone (PTH) and vitamin D; PTH — maintains extracellular calcium concentration through direct effects on bone resorption and renal calcium resorption at distal tubule and indirectly through effects on synthesis of 1,25-dihydroxyvitamin D; renal effects include phosphaturia and bicarbonaturia and enhanced calcium and magnesium resorption; secretion primarily regulated by serum ionized calcium concentration; negative feedback mechanism maintains calcium levels in normal range; release of PTH affected by phosphate, magnesium, and catecholamine levels; causes of primary hyperparathyroidism — benign parathyroid adenoma (90%), hyperplasia (9%), and parathyroid carcinoma (1%); may be part of multiple endocrine neoplastic syndrome; diagnosis — most patients hypercalcemic (nephrolithiasis, polyuria, polydipsia) and asymptomatic when diagnosed; clinically notable bone disease (10%-15%), fatigability, generalized muscle weakness, epigastric discomfort, peptic ulceration, constipation, depression, memory loss, confusion, psychosis, hypertension; ECG changes include shorter QT interval and prolongation of PR segment and QR complex, resulting in heart block or bundle branch block; bradycardia also occurs; hypercalcemia — can occur secondary to ectopic production of PTH or PTH-like substances from lung, genitourinary or gastrointestinal tracts, breast, and lymphoproliferative malignancies; tumors may produce hypercalcemia through direct bone resorption or production of osteoclast-activating factor; secondary hyperparathyroidism — occurs as result of conditions that cause hypocalcemia or hyperphosphatemia (eg, chronic renal disease, gastrointestinal malabsorption disorders); tertiary hyperparathyroidism — development of hypercalcemia with prolonged secondary hyperparathyroidism that triggers adenomatous changes in parathyroid gland and unregulated PTH production; treatment — surgery for symptomatic disease; controversy surrounds optimal management of asymptomatic patient; preoperative preparation — correct intravascular volume and electrolyte abnormalities; expand intravascular volume with normal saline to lower serum calcium concentration and establish sodium diuresis with furosemide; correct hypophosphatemia; other agents to lower serum calcium — bisphosphonates, mithramycin, and calcitonin; hemodialysis may be used when agents ineffective or contraindicated; anesthetic management — no evidence to support particular drug or technique; exercise caution with muscle paralysis; increased requirement for nondepolarizing muscle relaxants; careful positioning of patient with osteopenia essential to prevent pathologic bone fractures; general anesthesia common; bilateral cervical plexus block often used for minimally invasive parathyroidectomy; postoperative complications — recurrent laryngeal nerve injury, bleeding, and transient or complete hypoparathyroidism; unilateral recurrent laryngeal nerve injury usually requires no intervention; bilateral recurrent laryngeal nerve injury requires immediate reintubation; monitor serum calcium, magnesium, and phosphate levels postoperatively until stable

Hypoparathyroidism: occurs when underproduction of PTH or end-organ resistance results in hypocalcemia (calcium <8 mg/dL); causes — inadvertent removal of parathyroid glands during thyroid or parathyroid surgery (most common); other causes include radioactive iodine therapy for thyroid disease, granulomatous disease, amyloidosis, malignancy, severe hypomagnesemia (magnesium <0.8 mEq/L), or renal insufficiency; clinical features — neuronal irritability, skeletal muscle spasms or cramps, tetany seizures, fatigue, depression, and paresthesias; latent tetany may be shown by eliciting Chvostek sign or Trousseau sign; cardiovascular manifestations of hypocalcemia — congestive heart failure, hypotension, relative insensitivity to beta-adrenergic agonists, and prolonged QT interval; treatment — electrolyte replacement (specifically correction of magnesium deficit), removal of serum phosphate through diet and phosphate-binding resins (eg, aluminum hydroxide), infusion of normal saline to facilitate excretion of phosphate, calcium supplements, and vitamin D analogs; in severe cases, administer calcium gluconate IV (10-20 mL 10% solution) followed by infusion of elemental calcium (1-2 mg/kg/hour)

Adrenal disease

Disease of adrenal cortex: cortex synthesizes and secretes hormones (glucocorticoids, mineralocorticoids, and androgens); consequences of adrenal cortical hyperfunction or hypofunction occur as result of cortisol or aldosterone excess or deficiency; most potent endogenous glucocorticoid (hydrocortisone) produced by inner parts of adrenal cortex; cortisol production regulated by ACTH (corticotropin); secretion of ACTH and corticotropin-releasing factor governed predominantly by glucocorticoid stress in sleep-awake cycle; cortisol — affects intermediate carbohydrate, protein, fatty acid metabolism, and maintenance and regulation of immune and circulatory function; glucocorticoids — promote gluconeogenesis, increase blood glucose, and facilitate hepatic glycogen synthesis; net effect on protein metabolism augmented degradation of muscle and negative nitrogen balance, although catabolic effect of glucocorticoids partially blocked by insulin; other actions include anti-inflammatory effects, antagonism of leukocyte migration inhibition factor, facilitation of free water clearance, maintenance of blood pressure, induction of liver enzymes, and stimulation of hematopoiesis and appetite; contain some weak mineralocorticoid properties

Cushing syndrome: caused by overproduction of cortisol by adrenal cortex or exogenous glucocorticoid therapy; Cushing disease most common form of endogenous Cushing syndrome caused by pituitary tumor that secretes excessive amounts of ACTH and produces bilateral adrenal hyperplasia; nonendocrine tumors of lung, kidneys, or pancreas can produce Cushing syndrome via ectopic ACTH production (associated with hypokalemic alkalosis); 20% to 25% of patients have typically unilateral adrenal tumor (malignant approximately 50% of the time); characteristics — truncal obesity, hypertension, hyperglycemia (usually without overt diabetes mellitus), abdominal striae, hypokalemia, fatigability, muscle weakness, and osteoporosis; emotional lability can be profound and frank psychosis may occur; laboratory diagnosis — based on elevated plasma and urinary cortisol levels, urinary 17-hydroxycorticosteroids, and plasma ACTH; simultaneous measurement of plasma ACTH and cortisol can establish whether disease primary pituitary or adrenal disease; dexamethasone suppression tests in pituitary adenoma often show negative feedback control (unlike with adrenal tumor); anesthetic management — treat hypertension and hyperglycemia; normalize intravascular fluid volume and electrolyte concentrations; diurese with spironolactone to mobilize fluid and normalize potassium concentration; no specific agent or technique recommended; neuromuscular blockers should be used conservatively (particularly with muscular weakness); carefully position patients with osteopenia; monitoring — invasiveness based on patient reserve, site, and extent of surgery; administer glucocorticoid replacement therapy at dose equal to full replacement of adrenal output during periods of extreme stress (regardless of unilateral or bilateral adrenalectomy); management options — administer hydrocortisone IV 200 to 300 mg/70 kg in 3 divided doses on day of surgery; adjust dose upward for protracted and extensive surgical procedures; reduce total dose of hydrocortisone approximately 50% per day until daily maintenance dose of 20 to 30 mg/day steroids achieved; most patients require 0.05 to 0.1 mg/day fludrocortisone after bilateral adrenalectomy until approximately day 5 (higher doses may be needed if prednisone used); in unilateral adrenalectomy, normalization of function may occur in contralateral gland over time, hence treatment plans must be individualized; in unresectable tumors, medical therapy with steroid inhibitors (eg, metyrapone) may be needed

Adrenal insufficiency: manifestation of adrenal disease; causes — Addison disease (predominant cause) due to autoimmune destruction of gland, primary failure of adrenal gland, low levels of ACTH, infections, sepsis, hemorrhage, and metastatic cancer; secondary adrenal insufficiency — failure to secrete adequate amounts of ACTH; chronic steroid therapy may cause hypothalamic pituitary adrenal suppression and acute adrenal insufficiency during perioperative stress but not typically frank adrenal insufficiency; relative adrenal insufficiency — commonly found in critically ill surgical patients with hypotension requiring vasopressors; symptoms of idiopathic Addison disease — muscle weakness, chronic fatigue, anorexia, weight loss, hypotension, nausea, vomiting, and diarrhea; diffuse hyperpigmentation secondary to compensatory increases in ACTH and beta-lipotropin common; adrenal insufficiency secondary to pituitary disease not associated with mineralocorticoid deficiency or cutaneous hyperpigmentation; diagnosis — established with ACTH stimulation test; plasma cortisol levels measured before IV administration of 250 μg synthetic ACTH and 30 and 60 minutes after; response limited; treatment — adequate replacement therapy; replacement doses adjusted based on clinical symptoms or occurrence of intercurrent illnesses; mineralocorticoid coverage consists of 0.05 to 0.1 mg/day fludrocortisone; dose reduction should occur if severe hypokalemia, hypertension, or congestive heart failure develop; patients with secondary adrenal insufficiency encouraged to follow liberal salt diet and given glucocorticoid substitution; aldosterone replacement usually unnecessary; acute adrenal insufficiency requires immediate fluid, electrolyte, and steroid replacement; initial therapy consists of rapid IV infusion of isotonic crystalloid solution, 100 mg hydrocortisone IV bolus over several minutes; continue steroid replacement during first 24 hours, with 100 mg IV hydrocortisone every 8 hours; replace glucose as needed; taper steroid dose once stability achieved; if patient unstable after adequate fluid resuscitation, inotropic support may be needed

Mineralocorticoid excess: manifestation of disease of adrenal cortex; aldosterone increases renal tubular exchange of sodium for potassium and hydrogen ions; hypersecretion leads to hypertension, hypokalemic alkalosis, skeletal muscle weakness, and fatigue; high incidence of diastolic hypertension as result of increased renal sodium resorption and expanded extracellular fluid volume; in primary hypoaldosteronism (Conn syndrome), patients typically do not have edema; secondary aldosteronism results from increased renin production; measurement of plasma renin levels useful in differentiating primary from secondary aldosteronism; preoperative preparation for primary aldosteronism — restore intravascular volume and electrolyte concentrations to normal; restrict dietary sodium; administer spironolactone (aldosterone antagonist) to control hypertension; diuretic slowly increases potassium in doses 25 to 100 mg every 8 hours; slowly replace potassium where possible to facilitate equilibration; mineralocorticoid insufficiency — commonly seen in patients with mild renal failure and chronic diabetes mellitus; failure to increase aldosterone production in response to salt restriction or volume contraction; signs and symptoms — hypotension, hyperkalemia, and metabolic acidosis disproportionate to degree of renal impairment; treat isolated hypoaldosteronism with oral fludrocortisone 0.05 to 0.1 mg/day (higher doses required in low renin levels)

Pheochromocytoma: potentially lethal catecholamine-secreting tumor arising from chromaffin tissue, origin of which is embryonic neural crest; may develop wherever chromaffin cells located (including adrenal medulla), in paraaortic organs of Zuckerkandl, and other places such as bladder; paragangliomas — tumors of chromaffin-negative glomus cells, which originate from neural crest; paragangliomas nonsecreting but some secrete catecholamines and act similarly to pheochromocytomas; causes — de novo, familial, or in conjunction with multiple endocrine neoplasia (2a or 2b); may develop as part of neuroectodermal syndromes (von Hippel-Lindau disease, tuberous sclerosis, and Sturge-Weber syndrome); in pheochromocytomas, following features found in approximately 10%: malignancy, extraadrenal location, bilateral location, occurrence in children, and familial occurrence; familial pheochromocytomas likely to be bilateral (50%) (10% of nonfamilial cases); familial pheochromocytomas likely found in multiple sites when diagnosed; classic presentation — headache, diaphoresis, palpitations, anxiety, and increases in blood pressure; on secretion, ratio of norepinephrine to epinephrine production 85:15 (inverse of normal adrenal gland); in predominantly norepinephrine-secreting pheochromocytoma, alpha-adrenergic effects predominate, causing systolic and diastolic hypertension and reflex bradycardia; in primarily epinephrine-secreting tumor, beta-adrenergic effects predominate, causing systolic hypertension, diastolic hypotension, and tachycardia; associated cardiomyopathy may develop (hypertrophic cardiomyopathy most common); dilated cardiomyopathy and apical ballooning syndrome reported; monitoring — ECG abnormalities frequently occur, including ST segment and T-wave changes, QT prolongation, abnormal R-wave progression, and premature ventricular contractions; echocardiography useful in determining presence and type of cardiomyopathy and to detect intracardiac pheochromocytomas; diagnosis — biochemical testing for excess catecholamines; imaging studies to identify tumor; in high-risk patients, measurement of plasma metanephrines most sensitive test; in low-risk patients, measurement of metanephrine and catecholamines in 24-hour urine sample useful; perioperative care — CT scanning nearly 100% sensitivity for adrenal pheochromocytomas; magnetic resonance imaging superior for localization of extraadrenal, juxtacardiac, and juxtavascular tumors and is imaging modality of choice in pregnancy; preoperative alpha-blockade considered necessary to minimize extreme hypertension; administer phenoxybenzamine orally to attenuate effect of released catecholamines (salt and fluid mitigate effect of orthostatic hypotension); reflex tachycardia can occur; phenoxybenzamine titrated in outpatient setting at initial dose 10 mg orally twice a day and increased in 10-mg increments daily until stabilization of arterial blood pressure and improvement of symptoms; 10 to 14 days of therapy required to produce adequate alpha-blockade (defined by absence of blood pressure >160/90, presence of orthostatic hypotension, and ECG improvement); normalization of ECG may be unrealistic, particularly with cardiomyopathy; beta-blockade often used in conjunction with alpha-blockers preoperatively, especially with arrhythmias; beta-blockers contraindicated in absence of alpha-blockade; exercise caution in patients with catecholamine-induced cardiomyopathy; calcium channel antagonists may be helpful for patients with pheochromocytoma who are normotensive but have paroxysmal hypertension; may prevent catecholamine-induced coronary vasospasm; methylprednisolone often added preoperatively to combination therapy with phenoxybenzamine or other alpha-blocker and beta-blocker; surgical resection — technically challenging; in familial pheochromocytoma, open anterior or transabdominal approach often due to frequency of bilateral tumors; in bilateral adrenalectomy, begin corticosteroid supplementation; large malignant pheochromocytomas may require thoracoabdominal approach; laparoscopic adrenalectomy used in less complex cases; anesthetic management — preoperative anxiolysis important for humanistic and hemodynamic reasons; administer midazolam and/or fentanyl and local anesthesia; place arterial catheter and prepare antihypertensive agents prior to induction of anesthesia; avoid ketamine and desflurane (due to sympathomimetic properties) and analgesics that release histamine; insert central venous catheter after induction to facilitate infusion of vasoactive agents; catecholamines and associated hypertension often triggered by tumor manipulation, necessitating prompt and effective treatment; hypotension likely after tumor removal; administer liberal fluids and pressor agents (norepinephrine, phenylephrine, or dopamine); exercise caution with insulin (hyperglycemia occurs in approximately 60% of those with pheochromocytoma); rebound hypoglycemia may occur after tumor removal; postoperative management — 50% of patients remain hypertensive for several days due to elevated catecholamine stores and adrenergic nerve endings; persistent hypertension may suggest volume overload, presence of residual catecholamine-secreting tumor, accidental ligation of renal artery, or manifestation of preexisting essential hypertension; measure plasma metanephrines at 6 weeks and 6 months to confirm absence of residual tumor

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