FOR ENDOCRINE SURGERY


Hyperthyroidism





Anesthesia for Hyperthyroidism


•  Preop


• General: Euthyroid status preferred (risk of thyroid storm), check TFTs, continue antithyroid meds & β-blockers to the day of surgery


• Airway: Check for compression, tracheal deviation, & substernal thyroid mass consider awake fiberoptic intubation if airway looks challenging


• Benzodiazepines for preop sedation


•  Intraop


• General: Avoid/use sympathetic nervous system stimulants cautiously


(epinephrine, ketamine, ephedrine, phenylephrine) → severe HTN/tachycardia


• Ensure patient eye protection (pt often have exophthalmos)


• Thiopental possesses antithyroid activity in high doses


• Watch for signs of thyroid storm (hyperthermia, tachycardia, ↑ BP)


• Autoimmune thyrotoxicosis may be associated with myopathies


•  Postop


• Complications: Hormonal disturbances & airway management issues


• Thyroid storm: Life-threatening condition, can develop 6–24 hrs after surgery; caused by massive release of T3 & T4


Signs: Tachycardia, fever, confusion, vomiting, dehydration, CHF, agitation


(unlike MH, not associated withCPK, muscle rigidity or acidosis)


• Parathyroid gland damage/removal → hypocalcemia in 24–72 hrs postop


• Recurrent laryngeal n. damage → causes hoarseness if unilateral, stridor if bilateral diagnosis by fiberoptic laryngoscopy


• Neck hematoma → partial/complete upper airway obstruction


Treatment = prompt opening of neck wound & drainage



Hypothyroidism



Anesthesia for Hypothyroidism


•  Preop


• Thyroid supplements should be continued through surgery


• Delay elective surgeries in case of untreated hypothyroidism (risk of cardiovascular instability & myxedema coma)


• Subclinical hypothyroidism not associated with ↑ surgical risk


• In emergency cases: Consider pretreatment with IV thyroxine & steroids


• Pts usually obese, may have large tongue, short neck, delayed gastric emptying


•  Intraop


• Hypothyroid pts sensitive to narcotics & sedatives


• Induction: Maintain stable hemodynamics (consider ketamine or etomidate)


• Hypotension due to abnl baroreceptor fx, ↓ cardiac output, hypovolemia


• Hypothermia develops very fast & difficult to treat


• Metabolic disturbances common: ↓ Na & ↓ blood sugar


• Hypoventilation common (blunted response to hypoxia)


• Myxedema coma (severe form of decompensated hypothyroidism) can occur (see table below)


•  Postop


• Hypothermia, slow drug metabolism, & resp depression may delay extubation


• Extubation should be done in awake & normothermic pt


• Regional anesthesia & ketorolac = preferable for pain control (use opioids with caution)



PARATHYROID GLANDS


Hyperparathyroidism


Anesthesia for Hyperparathyroidism


•  ECG: Short PR & QT intervals, cardiac conduction disorders (↑ Ca levels)


•  Maintain hydration & good urine output


•  Consider using lower doses of nondepolarizing muscle relaxants in weak/somnolent pts




Hypoparathyroidism



Anesthesia for Hypoparathyroidism


•  Preop—serum & ionized Ca should be normalized, especially for pts with cardiac symptoms


•  Intraop—preexisting hypocalcemia may augment neuromuscular block


• Blood products containing citrate (as well as 5% albumin) will ↓ serum Ca level


•  Postop—hypocalcemia may cause prolonged recovery from neuromuscular blockade


Pheochromocytoma


•  May be associated with autosomal dominant multiple endocrine neoplastic synd (MEN types 2a & b)


•  Secretes epinephrine, norepinephrine, & occasionally dopamine


• Secretion may be intermittent or continuous


•  Change in tumor blood flow, direct pressure, & meds can trigger catecholamine release



Anesthesia for Pheochromocytoma


•  Preop: Goal = control BP & restore of intravascular volume


• Start α-blockade 10–14 d prior to surgery & prior to β-blockade


• If one accidentally starts β-blockade prior to α-blockade → severe HTN from unopposed α-stimulus


• Phenoxybenzamine = α-antagonist of choice (another option is prazosin)


• Starting dose = 10 mg qd or bid, then inc dose by 10–20 mg in divided doses every 2–3 d as needed to control BP (goal final dose = 20–100 mg qd)


• Propranolol 10 mg qid (should be initiated 3–4 d prior to the surgery)


• Ca-channel blockers—nicardipine 30 mg bid to supplement α- and β-blockade if BP is poorly controlled


• Hydrate all patients with pheochromocytoma—carefully in pts with signs of CHF


• Nitroprusside infusion (also phentolamine IV) for treatment of acute HTN crisis


• Metyrosine—catecholamine synthesis inhibitor, sometimes used preop


•  Intraop


• GA vs. regional—no influence on patient outcome


• Avoid desflurane, sympathetic stimulants (ketamine, ephedrine), & hypoventilation (cause nonneurogenic release of catecholamines), atracurium & morphine (histamine release)


• Prepare nitroprusside & phenylephrine infusions in advance


• A-line before induction, ± central line (assessment of intravascular volume), ± PA line


Gentle induction—intubation may cause massive release of catecholamines


• Tumor manipulation—may cause massive catecholamine release → HTN crisis


• Suprarenal vein ligation → acute drop in blood catecholamine level → cause hypotension (treat with fluid administration and direct sympathomimetics)


• Catecholamine-resistant vasoplegia: Can also use vasopressin to reverse


• Refractory tachycardia: Treat with esmolol (25–300 mcg/kg/min)


•  Postop


• Maintain normal BP; in about 50% pts BP will remain elevated


• Bilateral adrenalectomy → steroid support may be necessary


DIABETES




Anesthesia for Diabetes


•  Preoperative


• Check type, duration, and severity of diabetes—the more severe, poorly controlled and longstanding is the disease, the higher is the risk of long-term complications


• Check current therapy for type and dose (diet, oral hypoglycemic drug or insulin)


• Morning blood sugar and HbA1c assay help to assess status of diabetic control. Creatinine level and electrolytes may reflect degree of nephropathy


• Check for the presence of coronary artery disease, HTN, cerebrovascular disease and peripheral vascular disease, check EKG for presence of rhythm disturbances and prior MIs


• Consider Na bicitrate and metoclopramide in pts with GERD and gastroparesis


• Severe peripheral neuropathy may preclude use of regional anesthesia


• Long-acting insulins should be stopped and substituted by protamine and lente insulins


• Long-acting sulfonylurea drugs such as chlorpropamide should be stopped and substituted by short-acting agents. Metformin stopped if concern for intraop metabolic acidosis. Type-2-diabetic patients with marked hyperglycemia on oral treatment should be switched to insulin before operation


•  Emergency surgery


• Stabilize metabolic control/volume status as much as possible (delay surgery if possible)


• Maximize glucose, electrolyte, acid–base status—insulin & glucose infusions


• Saline infusion if volume is depleted (depending on renal function & cardiac status)


• K+ infusion if renal function is normal & serum K+ normal or low


• Bicarbonate infusion only in pts with severe acidosis


•  Intraoperative management


• Monitoring blood sugar = mandatory for all insulin dependent pts & poorly controlled pts


• Pts on NPH (neutral protamine Hagedorn) or PZI (protamine zinc insulin)


• ↑ risk for anaphylactic protamine reactions (2° to prior sensitization)


• Insulin requirements in diabetics vary during surgery; must individualize





•  Postop


• Treat N/V in pts with gastroparesis with metoclopramide as pts have increased risk of infection, MI, hyper/hypoglycemia, CV, and renal dysfunction


•  Diabetic emergencies


Diabetic ketoacidosis: Usually triggered by trauma or infection in Type I DM


• Nausea, vomiting, dehydration, polyuria, polydipsia, somnolence → coma


• Hyperglycemia, wide anion gap metabolic acidosis, ketones in blood & urine, ↓ K+


• Management: Place A-line, consider intubation for severe CNS depression


• Start insulin infusion (10 U IV, then 5–10 U/hr)


• Normal saline at 5–10 ml/kg/hr (fluid deficit of 3–8 L not uncommon) add 5% glucose when blood sugar <250 mg/dL


• Replenish K (0.3–0.5 meq/kg/hr)


• Bicarbonate not usually required


Hyperosmolar, hyperglycemic, nonketotic coma (usually type II DM)


• Severe dehydration & associated with acute hyperglycemia (>600 mg/dL)


• Treatment: Correct hypovolemia & hyperglycemia


Fluid resuscitation with 0.45% saline


Give 10 U regular insulin IV stat → insulin drip (see protocol above)


Hypoglycemia—result of stress, missed meal, exercise, alcohol consumption


• Hypoglycemia is much more dangerous in unconscious pt than hyperglycemia (safer to err on the side of hyperglycemia)


• Symptoms: Diaphoresis, tachy, impaired cognition, confusion, loc & seizures


• Treatment: 50% IV glucose, initial dose 25 mL


ADRENAL INSUFFICIENCY



Anesthesia for Adrenal Insufficiency


•  Preop—administer stress dose of corticosteroid (usually 100 mg hydrocortisone IV)


•  Intraop


• Risk of poor fluid loading tolerance, hypoglycemia, ↑ K+, dysrhythmias


• Unexplained hypotension (that is unresponsive to fluids & vasopressors)


→ Treat with glucocorticoid


• Avoid etomidate (suppresses adrenal function)


•  Postop


• Provide adequate corticosteroid supplementation


Excess of Corticosteroids (Cushing’s Syndrome)


•  Causes


• 1°—Adrenal adenoma/hyperplasia


• 2°—ACTH-secreting pituitary microadenoma (Cushing’s dz), ACTH-secreting tumors, exogenous steroid usage


•  Clinical features: Moon facies, buffalo hump, central obesity, hirsutism, skin atrophy, osteoporosis, easy bruising, diabetes, proximal myopathy, aseptic hip necrosis, mental status changes, pancreatitis, polyuria/polydipsia


Anesthesia for Cushing’s Syndrome


•  Preop: Risk of hypokalemia & glucose intolerance (check both)


• Cushingoid pts may have HTN, CHF, fragile skin, osteoporosis


• Use stress dose steroids in case of iatrogenic Cushing’s syndrome


•  Intraop


• Obese (potentially difficult airway/IV access), often HTN


• Special attention to positioning (skin breaks down easily)


• High-dose opioids may cause resp depression & difficulty with extubation


•  Postop course


• Poor ventilatory performance (↓ FRC), poor mobilization, pressure sores, ↑ infections


Hyperaldosteronism (Conn’s Syndrome)


•  Causes


• 1°—(Conn’s syndrome) excess secretion of aldosterone by an adrenal adenoma (60%), bilateral adrenal hyperplasia (30%), carcinoma (rare)


• 2°—high plasma levels of renin & aldosterone (due to CHF/liver cirrhosis)


•  Clinical features


• Malignant HTN (centrally mediated or aldosterone-induced)


• ↓ K+ often severe & may be exacerbated by diuretics → weakness & tetany


• HTN pts often hypovolemic (hypovolemia & ↓ K+ indicate severe total K+ deficit)


• Metabolic alkalosis from H+ loss


Anesthesia for Conn’s Syndrome


•  Preop: Correct ↑ BP, metabolic alkalosis, hypokalemia


• Spironolactone (up to 400 mg qd) may control HTN & moderate hypovolemia/ ↓ K+


•  Intraop: If CHF, uncontrolled HTN, hypovolemia present → place A-line


• Surgical manipulation of adrenal may release catecholamines → CV instability


• Give corticosteroid & mineralocorticoids in cases of bilateral adrenalectomy


•  Postop: Goal = maintain normal BP, electrolyte balance


• Continue corticosteroid & mineralocorticoids in cases of bilateral adrenalectomy


POSTERIOR PITUITARY GLAND


•  Posterior pituitary releases oxytocin & antidiuretic hormone (ADH, vasopressin)


•  ADH stimulates kidneys to conserve water


• Low ADH → diabetes insipidus


• High ADH → syndrome of inappropriate antidiuretic hormone (SIADH) secretion


Diabetes Insipidus (DI)


•  Causes: Central DI—insufficient ADH by pituitary (damage from head injuries, genetic disorders, infections, vascular dz, tumors)


• Nephrogenic DI—lack of kidney response to ADH (from drugs, chronic kidney dz)


•  Clinical features: Thirst, polyuria (up to 20 L/d), low BP, & dehydration


•  Diagnosis: Urine specific gravity of ≤1.005, urine osmolality <200 mOsm/kg, random plasma osmolality > 287 mOsm/kg


•  Treatment: SQ/nasal/PO vasopressin analogues (desmopressin), chlorpropamide, carbamazepine, thiazide diuretics


•  Anesthetic management


Preop—restore intravascular volume, nasal desmopressin 10 mcg bid–tid


Intraop


• Total lack of ADH: 100 mU vasopressin before surgery followed by infusion (100–200 mU/hr titrated to urine output)


• Partial ADH deficiency: No vasopressin (unless plasma osmolality >290)


Postop—continue desmopressin & monitor electrolyte balance


Syndrome of Inappropriate Antidiuretic Hormone (SIADH) Secretion



•  Clinical features: ↓ Na superimposed upon symptoms of underlying pathology


• ↓ Na due to a dilutional effect, not Na depletion (may be no clinical symptoms)


• Symptoms: May include nausea, weakness, anorexia; Na <110 mmol/L → coma


•  Diagnosis: Must distinguish SIADH from other causes (such as dilutional hyponatremia) (causes of dilutionalNa: Excess infusion of dextrose/saline drips/use of diuretics)


• Diagnosis confirmed by serum Na <130 mmol/L, plasma osmolality <270 mOsm/L, urinary Na >20 mEq/L & elevated urine osmolality


•  Treatment: Address underlying problem


• Release of ADH (from hypophysis or tumor) cannot be suppressed by medical therapy


• Symptomatic relief: Water intake restriction to 500–1000 mL per 24 hrs


(plasma & urine osmolality should be measured regularly)


• Fluid restriction may not be appropriate in SAH—may promote vasospasm


• Demeclocycline: When fluid restriction is difficult


•  Anesthetic management


• Correct hyponatremia, monitor volume status by CVP or PA catheter


• Monitor electrolytes (urine osmolarity, plasma osmolarity, serum Na) (including immediately after surgery)


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Aug 28, 2016 | Posted by in ANESTHESIA | Comments Off on FOR ENDOCRINE SURGERY

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