Endocrine Flashcards
1
Q
- Type 1 diabetes mellitus
A. Is characterized by a relative lack of insulin plus resistance to endogenous insulin
B. Always requires insulin
C. Affects 95% of patients with diabetes
D. Can be controlled with diet, weight loss, and oral hypoglycemic agents
A
- B.
○ Type 1 diabetes mellitus results from the autoimmune destruction of insulin-producing β cells of the pancreas and thus these patients always need insulin to prevent hyperglycemic ketoacidosis and other complications.
○ Most patients carrying the diagnoses of diabetes (95%) have type 2 diabetes, which is characterized by a relative lack of insulin plus resistance to endogenous insulin.
○ Type 2 diabetes can be controlled with diet and weight loss, and oral agents,though these patients may also require insulin.
2
Q
- Preoperative assessment of patients with diabetes mellitus should include
A. An assessment of functional status B. 24-Hour creatinine clearance
C. Pulmonary function testing
D. Cancellation of the surgical case if HbA 1c >10%
A
- A.
○ Complications of diabetes result largely from microangiopathy and macroangiopathy.
○ Diabetes is a well-recognized risk factor for coronary artery disease (CAD).
○ Cardiac autonomic neuropathy may mask angina pectoris and obscure the presence of CAD.
○ Hence, a careful assessment of functional status and any symptoms such as increasing dyspnea on exertion and fatigue may be indicative of significant CAD.
○ While diabetes is a leading cause of renalfailure, there is no evidence that a preoperative evaluation with a 24-hour creatinine clearance is helpful.
○ While the risk of complications of diabetes increases with increasing HbA 1c levels, and there is evidence that higher HbA 1c levels are associated with adverse outcomes following a variety of surgical procedures, there is insufficient evidence to recommend an upper limit of HbA 1c prior to elective surgery.
○ The risks associated with poor glycemic control should be balanced against the necessity for surgery.
3
Q
- Preferred anesthetic agent in a patient with hyperthyroidism includes
A. Desflurane
B. Ketamine
C. Sevoflurane
D. Meperidine
A
- C.
○ In patients with hyperthyroidism, the goal of anesthesia is to avoid an increase in heart rate or sympathetic activation.
○ Ketamine, desflurane, and meperidine cause sympathetic stimulation and tachycardia. ○ Conversely, anesthetics and techniques that reduce or blunt sympathetic activity are preferred. ○ Sevoflurane for anesthesia, and fentanyl and its congeners for analgesia would be favored.
○ Regional anesthesia, when practical, might also be efficacious in avoiding sympathetic activation.
4
Q
- Multiple endocrine neoplasia (MEN) I syndrome includes
A. Pheochromocytoma, medullary thyroid carcinoma, parathyroid hyperplasia
B. Pancreas tumors, medullary thyroid carcinoma, pituitary adenoma
C. Pheochromocytoma, medullary thyroid carcinoma, mucosal neuromas
D. Pancreas tumors, pituitary adenoma, parathyroid hyperplasia
A
- D.
○ MEN I syndrome includes the triad of tumors of the pancreas, pituitary, and parathyroid glands and is inherited as an autosomal-dominant trait.
○ Medullary thyroid carcinomas are a component of the MEN II endocrine syndromes, of which there are several subtypes.
5
Q
- Laboratory findings in primary hypothyroidism are
A. Low TSH, elevated T3, elevated T4
B. Low TSH, low T3, low T4
C. Normal TSH, low T3, low T4
D. Elevated TSH, low T3, low T4
A
6
Q
- Obese patients may experience rapid oxygen desaturation during induction of general anesthesia because of
A. A decrease in lung compliance
B. A reduction in functional residual capacity (FRC)
C. A history of obstructive sleep apnea
D. Restrictive lung disease
A
- B.
○ Obesity is associated with obstructive sleep apnea, decreased pulmonary compliance, and lung volumes suggestive of restrictive lung disease.
○ Total pulmonary compliance decreases due to a decrease in both chest-wall compliance and lung compliance.
○ Chest-wall compliance decreases because of excessive adipose tissue over the thorax, while lung compliance decreases because of the increased abdominal mass, which pushes the diaphragm cephalad causing an increase in pulmonary blood volume.
○ The FRC of the lung is the volume of air present in the lungs at the end of passive expiration and reflects a balance between the elastic recoil of the lungs and the pleural pressure.
○ With obesity, there is a shift in this balance due to adipose tissue in the chest wall and abdomen, resulting in a decreased FRC.
○ The FRC is the reservoir of oxygen during the apneic state associated with the induction of general anesthesia. Thus, the reduction of FRC associated with obesity results in greater oxygen desaturation during the induction of general anesthesia.
7
Q
- A 39-year-old woman with a history of headaches, hypertension, palpitations, and nephrolithiasis is undergoing a parathyroidectomy for parathyroid adenoma. During induction, she develops severe hypertension and tachycardia. The most likely diagnosis for these signs is
A. Adrenal insufficiency
B. Carcinoid syndrome
C. Thyroid storm
D. Pheochromocytoma
A
- D.
○ While inadequate anesthesia and thyroid storm may result in intraoperative hypertension and tachycardia, the most likely diagnosis is pheochromocytoma.
○ Pheochromocytoma is a catecholamine-secreting tumor and is part of the multiple endocrine neoplasia (MEN) type II syndrome, which consists of pheochromocytoma, medullary thyroid carcinoma, and parathyroid adenoma. Symptoms associated with pheochromocytoma include paroxysmal headache, hypertension, diaphoresis, and palpitations.
8
Q
- Phenoxybenzamine is a
A. Selective α 1 -receptor antagonist and a nonselective β-adrenergic receptor antagonist
B. Reversible α 1 -receptor antagonist
C. Irreversible, nonselective α-adrenergic receptor antagonist
D. Selective α 2 -receptor agonist
A
- C.
○ Phenoxybenzamine is an irreversible, nonselective α-adrenergic receptor antagonist used preoperatively for adrenergic blockade in patients with pheochromocytomas.
○ It blocks both the postsynaptic α 1 and presynaptic α 2 receptors in the nervous system, thereby reducing sympathetic activity.
○ Clinical signs of the optimal dose of phenoxybenzamine are a stuffy nose and slight dizziness due to postural hypotension.
○ Doxazosin is a reversible, selective α 1 -receptor antagonist that is an alternative to phenoxybenzamine for treatment of pheochromocytoma.
○ In patients with pheochromocytoma, α-blockade is always started prior to β-blockade.
○ Starting β-blockade first will lead to unopposed α stimulation causing further increase in the blood pressure.
9
Q
- A 40-year-old woman with a history of Graves disease is in the recovery room after undergoing a CT scan under general anesthesia. While in
the recovery room, her blood pressure drops to 80/55 mm Hg, her heart rate increases to 140 bpm, and she becomes agitated and complains of difficulty breathing and feeling hot. The most likely diagnosis for these signs is
A. Thyroid storm
B. Carcinoid syndrome
C. Malignant hyperthermia
D. Pheochromocytoma
A
- A.
○ Thyroid storm is characterized by fever, tachycardia, altered mental status, and hypertension, presenting most often in the postanesthesia care unit or in the immediate postoperative period (24 hours).
○ Hypertension may be followed by congestive heart failure that is associated with hypotension and shock. ○ Thyroid storm is a state of severe hypermetabolism induced by excessive release of thyroid hormones.
○ It can be precipitated by surgery, stress, infection, and drugs including chemotherapeutic agents, anticholinergic, and adrenergic drugs such as pseudoephedrine, amiodarone, and iodinated contrast media.
○ Unlike malignant hyperthermia, it is not associated with muscle rigidity, an elevated creatinine kinase, or acidosis.
10
Q
- Treatment of thyroid storm includes
A. Dantrolene
B. Phenoxybenzamine
C. Octreotide
D. Propylthiouracil
A
- D.
○ Thyroid storm is a medical emergency and if untreated, often fatal.
○ Supportive treatment includes cooling, hydration, and β-blockers to control heart rate.
○ Propranolol has the additional benefit of inhibiting the peripheral conversion of T4–T3.
○ Propylthiouracil and methimazole inhibit the synthesis of T4 by blocking the organification of tyrosine residues.
○ Iodide blocks the release of preformed thyroid hormones, but it should be given only after the loading dose of antithyroid medication to prevent the utilization of iodine in the synthesis of new thyroid hormones.
○ Administration of cortisol is also recommended to prevent complications from potential coexisting adrenal insufficiency.
11
Q
- During a postoperative check on a 53-year-old patient who underwent a total thyroidectomy earlier in the day, you notice that he is stridorous and is complaining of muscle cramps. The best treatment for these symptoms is
A. Administration of calcium gluconate
B. Opening the neck wound
C. Reintubation for airway protection
D. Administration of sodium bicarbonate
A
- A.
○ Hypoparathyroidism resulting from the unintentional removal of the parathyroid glands is a potential complication of thyroidectomy.
○ Low blood calcium levels interfere with normal muscle contraction and nerve conduction, and can result in muscle cramps, weakness, tetany, laryngospasm, and stridor.
○ Treatment consists of normalizing the serum calcium level with intravenous calcium.
○ While a neck hematoma can cause airway compromise due to compression, it is unlikely to cause muscle cramps.
○ Stridor due to bilateral vocal cord paralysis is evident immediately on extubation and would require reintubation to establish a patent airway.
○ Sodium bicarbonate would cause a metabolic alkalosis and potentially worsen symptoms of hypocalcemia by decreasing ionized calcium levels.
12
Q
- Patients with obstructive sleep apnea (OSA)
A. Are at increased risk of left-heart failure
B. Have the same perioperative complication rate as patients without OSA
C. May have an increased likelihood of difficult intubation
D. Rarely require continuous positive airway pressure (CPAP) after bariatric surgery
A
- C.Patients with OSA may have an increased likelihood of difficult intubation, since the upper airway abnormalities associated with OSA (increased neck circumference, large tongue, decreased cross-sectional area of the upper airway) may also predispose to difficult intubation. Hypercapnia associated with severe OSA can lead to right-heart failure. OSA is associated with increased perioperative complications including cardiac arrhythmias, hypertension, myocardial ischemia, respiratory failure, and stroke. Supine positioning and sedative agents make the upper airway even more prone to obstruction. Thus, patients with OSA may require CPAP in the immediate postoperative period.
13
Q
- A 39-year-old patient with a BMI of 45 kg/m 2 is scheduled for a Roux-en-Y gastric bypass. She has a history ofhypertension. Your perioperative concerns include
A. Preparation for a rapid sequence induction, since she is at increased risk for aspiration of gastric contents
B. Placing her in the reverse Trendelenburg position to reduce atelectasis in dependent areas of the lung and move the chest and breast tissue caudally to allow easier access to the mouth for endotracheal intubation
C. Need to dose water-soluble drugs (e.g., neuromuscular-blocking agents) to actual body weight
D. More frequent administration of lipid-soluble drugs will be needed
A
- B.Preoperative preparation is essential for caring for the obese patient. Perioperative concerns include difficult intravenous access, possible need for arterial blood pressure monitoring, positioning, difficult endotracheal intubation, and appropriate dosing of medications. Nondiabetic obese patients are not at increased risk of aspiration of gastric contents, as they may have smaller gastric fluid volumes at higher pH than do lean nondiabetic patients. However, obesity may increase the risk of a difficult laryngeal intubation, especially in males and patients with a higher Mallampati score. Placement of the patient in the reverse Trendelenburg position during intubation is advantageous because it reduces atelectasis, increases time to oxygen desaturation after preoxygenation, and moves the chest and abdominal tissue caudally to allow easier access to the mouth for endotracheal intubation. Obese patients have a smaller volume of distribution for water-soluble drugs. Thus, dosing of these drugs should be based on ideal body weight to avoid overdosing. Larger fat stores provide an increased volume of distribution for lipid-soluble drugs. For lipid-soluble drugs, while a loading dose should be based on actual body weight, clearance will be slower because of the larger volume of distribution, and thus, maintenance doses should be administered less frequently. 14. D.Refeeding syndrome can
14
Q
- During the preoperative evaluation of a critically ill patient with ischemic bowel scheduled for a second look laparotomy and possible abdominal closure, you notice multiple electrolyte abnormalities including hypophosphatemia, hypokalemia, and hypomagnesemia. A possible cause for these electrolyte abnormalities is
A. Renal failure
B. Hypoventilation
C. Hypoparathyroidism
D. Refeeding syndrome
A
- D.Refeeding syndrome can occur in malnourished patients who are acutely fed (either enterally or parenterally). It is caused by increased adenosine triphosphate production and metabolic rate. Hypophosphatemia is the hallmark biochemical feature of refeeding syndrome. Other metabolic and electrolyte disturbances may include abnormal sodium and fluid balance; hypokalemia; hypomagnesemia; thiamine deficiency; and changes in glucose, protein, and fat metabolism. Refeeding syndrome can be avoided by slowly increasing the nutritional intake toward caloric goals.
15
Q
- You are evaluating a 55-year-old patient with type 2 diabetes mellitus for a total knee replacement. His diabetes is controlled on a regimen of Glucophage (metformin), NPH insulin twice a day, and insulin sliding scale. Perioperative instructions for glucose management should include
A. Give half of the NPH dose if morning blood glucose level is at least 150 mg/dL
B. Give regular insulin dose according to morning blood glucose level
C. Holding metformin for 48 hours preoperatively to avoid risk of fatal lactic acidosis
D. Starting insulin infusion with target glucose range of 81 to 108 mg/dL
A
- A.The primary goal of intraoperative blood sugar management is to avoid hypoglycemia. The most common perioperative management regimen consists of giving the patient a fraction (usually half) of the morning intermediate-acting insulin dose. If hypoglycemia is a concern, an infusion of dextrose may be started. Short-acting insulin preparations are held because of an increased risk of hypoglycemia and their short duration of action. Metformin has a duration of action of 6 to 24 hours (up to 48 hours with the extended release formulation). While it was previously recommended that metformin be discontinued 48 hours preoperatively to avoid risk of fatal lactic acidosis, more recent data suggest that this risk is low. The optimal level of glucose control in the perioperative setting remains controversial. The American Association of Clinical Endocrinologists (AACE) and the American Diabetes Association (ADA) recommend keeping blood glucose between 140 and 180 mg/dL in critically ill patients. For noncritically ill patients treated with insulin, premeal glucose targets should generally be <140 mg/dL and random blood glucose values should be <180 mg/dL. The NICE-SUGAR trial in critically ill patients showed an increased mortality and increased incidence of severe hypoglycemia in patients randomized to intensive glucose control (target glucose range 81–108 mg/dL).
