Advanced | Endocrine and Anesthesia Flashcards

Question

Dr. Rataban is doing her pre-operative rounds on a patient. Her patient is a known hyperthyroid and is scheduled for a lobectomy. Which of the following hyperthyroid-associated conditions would make her cautious in the dosing of muscle relaxants intraoperatively? A. Multiple sclerosis B. Myasthenia gravis C. ALS D. Neuroleptic Malignant Syndrome

Answer 1

B. Myasthenia gravis The incidence of myasthenia gravis is increased in hyperthyroid patients; thus, the initial dose of muscle relaxant should be reduced, and a twitch monitor should be used to titrate subsequent doses.

Answer 2

A. 0.05 to 0.1 mg/d After bilateral adrenalectomy, most patients require 0.05 to 0.1 mg/d of fludrocortisone (9-α-fluorohydrocortisone) starting around day 5 to provide mineralocorticoid activity. Slightly higher doses may be needed if prednisone is used for glucocorticoid maintenance because it has little intrinsic mineralocorticoid activity.

Answer 3

A. Volume, electrolyte, and glucose replacement A reduction of temperature can be achieved with acetaminophen, cold lavage of body cavities, cooling blankets, ice packs, and reduction of ambient temperature. Aspirin should not be used as an antipyretic. It displaces thyroid hormones from binding proteins, thereby raising free hormone levels. Inotropes, diuretics, and supplemental oxygen may be needed for acute congestive heart failure. Magnesium can be used to reduce the severity and incidence of cardiac arrhythmias. Iodide can be used to inhibit thyroid hormone synthesis. However, iodide therapy should be delayed aft er beginning antithyroid drug therapy. Antithyroid drugs reduce the secretion and production of thyroid hormones and prevent iodide binding in the thyroid within the hour. Catecholamines contribute to the symptoms of thyrotoxicosis. Beta blockers are effective in attenuating the manifestations of excessive sympathetic activity. Beta blockers alone do not inhibit hormone synthesis, but specifically propranolol does impair the peripheral conversion of T 4 to T 3 over 1 to 2 weeks. Any beta blocker may be used, but preoperatively propranolol (in doses titrated to effect) plus potassium iodide (two to five drops every 8 hours) is frequently used before surgery to decrease cardiovascular symptoms and reduce circulating concentrations of thyroid hormones. Preoperative preparation usually requires 7 to 14 days. Rate control may improve congestive heart failure due to poorly controlled paroxysmal atrial fibrillation. Impaired left ventricular function secondary to hyperthyroidism may not be corrected with the use of beta blockers. If a hyperthyroid patient with clinically apparent disease requires emergency surgery, beta blockers should be titrated to achieve a heart rate of less than 90 beats per minute. Beta blockers do not prevent thyroid storm. If beta blockers are contraindicated, other sympatholytic drugs may be useful (reserpine [depletes catecholamine stores] or guanethidine [inhibits catecholamine release]). There are no signs of hematoma formation. Therefore, surgical decompression is not the correct choice.

Answer 4

C. Propranolol 1–2 mg slow IV push Thyroid storm may be precipitated in stressed hyperthyroid patients. Recent surgery and infection are two common causes. A major side effect of antithyroid drugs is leukopenia, but the white count is normal in this case. Mental status changes, hyperpyrexia, tachycardia, and diarrhea are the most typical manifestations; however, patients may present with lethargy, coma, and muscle weakness without the usual hyperdynamic symptoms (apathetic thyrotoxicosis) or unremitting atrial fibrillation and CHF. Thyroid storm is a clinical diagnosis. IV fluids for dehydration and supplemental oxygen should be given. Dexamethasone blocks peripheral conversion of T4 to T3. Propylthiouracil blocks the synthesis of thyroid hormone. Iodine is given 1 hour after antithyroid medication to inhibit thyroid hormone release. Propranolol blocks the sympathetic manifestations and blocks the peripheral conversion of T4 to T3. The mortality of untreated thyroid storm is virtually 100%. Aspirin should be avoided, as it can displace thyroid hormone from its binding sites and worsen the thyroid storm.

Answer 5

E. Phrenic nerve injury The following are some of the most common complications of thyroidectomy * Recurrent laryngeal nerve (RLN) damage, tracheal compression, hypoparathyroidism, pneumothorax ## Footnote Tracheal compression may occur secondary to hematoma or tracheomalacia, and pneumothorax can occur during resection of substernal goiters.

Answer 6

Within 24 to 72 hrs ## Footnote Symptoms can include laryngeal stridor and laryngospasm.

Answer 7

Intravenous (IV) administration of calcium chloride or calcium gluconate ## Footnote Magnesium levels should also be monitored and corrected if low.

Answer 8

True Unilateral is more often encountered in the setting of thyroidectomy. This usually present as hoarseness as opposed to 'stridor' or 'aphonia' which is a manifestation of bilateral injury to the RLN. ## Footnote Unilateral injury is often transient.

Answer 9

B. Dexamethasone

Answer 10

A. Cortisone

Answer 11

D. Short QT intervals - FALSE Hypocalcemia = Prolonged qT interval The clinical signs of hypocalcemia include clumsiness, convulsions, laryngeal stridor, depression, muscle stiffness, paresthesias, parkinsonism, tetany, Chvostek sign, dry and scaly skin, brittle nails, coarse hair, low serum concentrations of calcium, prolonged QT intervals, soft tissue calcifications, and Trousseau sign. Hypocalcemia*** DELAYS VENTRICULAR REPOLARIZATION***, hence increasing the QTc interval. Heart failure may occur with hypocalcemia but is rare. Patients with hypocalcemia may have seizures, often indistinguishable from epilepsy in the absence of hypocalcemia.

Answer 12

C. Low sodium, high potassium, low glucose The usual laboratory findings in patients with primary adrenal insufficiency include hyponatremia, hyperkalemia, hypoglycemia, and azotemia. Hyponatremia is present in 88% of cases and is usually mild to moderate; severe hyponatremia (<120 mEq/L) is rare. Hyperkalemia is present in 64% of cases, usually mild; the potassium level rarely exceeds 7 mEq/L. Two-thirds of patients with adrenal failure have hypoglycemia and the glucose levels less than 45 mg/dL; the pathophysiology is decreased gluconeogenesis and increased peripheral glucose use secondary to lipolysis.

Answer 13

D. Hypocalcemia The Key is TIMING: 2 days.:) Hoarseness and severe stridor presenting 24-96h after total thyroidectomy would most likely be consistent with decreased calcium Barash | 9th edit

Answer 14

A. Hyponatremia Myxedema coma represents a severe form of hypothyroidism characterized by stupor or coma, hypoventilation, hypothermia, hypotension, and hyponatremia. This is a medical emergency with a high mortality rate (25% to 50%) and, as such, requires aggressive therapy

Answer 15

C. Loading dose of IV T3 is also used but it has slower onset compared to IV T4 - INACCURATE statement. IV thyroid replacement is initiated as soon as the clinical diagnosis is made. An IV loading dose of T4 (sodium levothyroxine, 200 to 300 mcg) is given initially and followed by a maintenance dose of T4, 50 to 200 mcg/d intravenously. Alternatively, T3 may be used because it has a more RAPID ONSET. IV T3 has a more rapid onset than IV T4(sodium levothyroxine). * Loading dose of Thyroid replacement therapy (sodium levothyroxine) is 200 to 300 mcg)

Answer 16

D. Hyperkalemia and hypermagnesemia is expected after correction of calcium elevation - INACCURATE statement Hypokalemia and hypomagnesemia is seen in patients who have underwent emergency correction of hypercalcemia. Glucocorticoids are usually of no benefit in the treatment of primary hypercalcemia. Finally, hemodialysis or peritoneal dialysis can be used to lower the serum Ca2+ level when alternative regimen are ineffective or contraindicated. There is no evidence that a specific anesthetic drug or technique has advantages over another. A thorough knowledge of the clinical manifestations attributable to hypercalcemia is of the greatest value in choosing an anesthetic technique. Special monitoring is usually not required. There is an increased requirement for vecuronium, and probably all nondepolarizing muscle relaxants during onset of neuromuscular blockade

Answer 17

B. Thiazide Although diuresis play an important role in the management of hypercalcemia, Thiazides should be strongly avoided because it may ENHANCE renal tubular reabsorption of Ca. On the other hand, furosemide, a loop diuretic is commonly used as the diuretic drug of choice. Furosemide INHIBITS Na and Ca reabsorption

Answer 18

D. Hyperkalemia Cushing syndrome, caused by either overproduction of cortisol by the adrenal cortex or exogenous glucocorticoid therapy, is a syndrome characterized by truncal obesity, hypertension, hyperglycemia, increased intravascular fluid volume, hypokalemia, fatigability, abdominal striae, osteoporosis, and muscle weakness

Answer 19

C. Regional anesthesia during surgery of the lower abdomen and extremities is not effective in postponing the elevation in cortisol levels. - INACCURATE statement. Regional anesthesia is effective in postponing the elevation of cortisol. All the other statements are accurate. Barash | 9th edit

Answer 20

B. Administer 50 mg hydrocortisone IV prior to induction and 25 mg q8h for 24–36 hrs For surgeries associated with moderate stress, such as joint replacement, a common regimen involves patients taking their usual morning steroid dose, then supplementing with hydrocortisone 50 mg IV at induction, followed by hydrocortisone 25 mg IV every 8 hours for six doses, along with resumption of usual home regimen on the second postoperative day. For major surgeries (e.g., coronary artery bypass graft), patients are instructed to take their usual morning steroid dose, then supplemented with hydrocortisone 100 mg IV at induction, followed by hydrocortisone 50 mg every 8 hours for at least six doses.

Answer 21

A. 10 - 14 days Although the optimal period of preoperative treatment has not been established, most clinicians recommend beginning α-blockade therapy at least 10 to 14 days before the proposed surgery; however, periods as short as 3 to 5 days have been used.

Answer 22

FALSE β-Blockers should NOT be given until adequate α-blockade is ensured to avoid the possibility of unopposed α- mediated vasoconstriction.

Answer 23

A. α-Methyltyrosine - It is an inhibitor of catecholamine biosynthesis

Answer 24

A. IV Nitroprusside

Answer 25

C. Administer isotonic crystalloid until the MAP is 60, and proceed to surgery regardless of serum glucose