NYACP Board Review Question of the Week
Every other Tuesday, NYACP members are sent a Board Review Question from ACP's MKSAP 18 to test professional knowledge and help prepare for the exam. Participant totals and answer percentages are distributed on the first Thursday of the month in IM Connected, the Chapter's eNewsletter, and are also published on this page.
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May 7, 2024
MKSAP 18 Nephrology, Question 27
Stem:
An 18-year-old woman is brought to the emergency department by friends. She is confused and febrile. Her friends state that she took 3,4-methylenedioxymethamphetamine (ecstasy) at a party and was previously well. There is no other medical history.
On physical examination, the patient is confused and oriented to her name only. Temperature is 38.9 °C (102.0 °F), blood pressure is 148/94 mm Hg, pulse rate is 108/min, respiration rate is 20/min, and oxygen saturation is 96% breathing 2 L/min oxygen by nasal cannula. The remainder of the examination is unremarkable.
Laboratory studies:
Blood urea nitrogen 11 mg/dL (3.9 mmol/L)
Creatinine 0.8 mg/dL (70.7 µmol/L)
Electrolytes
Sodium 118 mEq/L (118 mmol/L)
Potassium 3.5 mEq/L (3.5 mmol/L)
Chloride 88 mEq/L (88 mmol/L)
Bicarbonate 21 mEq/L (21 mmol/L)
Glucose 88 mg/dL (4.9 mmol/L)
Urine osmolality 405 mOsm/kg H2O
Which of the following is the most appropriate initial treatment?
A. 0.9% sodium chloride, 100 mL/h
B. 100-mL bolus of 3% saline
C. Fluid restriction
D. Oral urea
E. Tolvaptan
Responses Received from Members (922 member responses):
The Correct Answer is: B. 100-mL bolus of 3% saline
Educational Objective
Treat acute hyponatremia in a symptomatic patient with hypertonic saline.
Critique
The most appropriate initial treatment is a 100-mL bolus of 3% saline. The hyponatremia in this young woman who presents confused and febrile is most likely due to ingestion of 3,4-methylenedioxymethamphetamine (ecstasy). Ecstasy is associated with hyponatremia both because it stimulates the release of antidiuretic hormone and because users often drink large quantities of water. When treating hyponatremia, the rate of correction of serum sodium concentration must be carefully considered to avoid the osmotic demyelination syndrome. Brain cells adapt to chronic hyponatremia by reducing intracellular concentration of organic osmolytes, such as myoinositol, to cope with hypotonicity. Acute hyponatremia is associated with an increase in brain water and cerebral edema and should be treated rapidly. Because the brain has not adapted to the hypotonic environment by the release of organic osmolytes, the risk of rapid correction and development of osmotic demyelination is absent. Treatment is with a bolus of 3% saline, and a 100-mL bolus should raise the serum sodium level by 2 to 3 mEq/L (2-3 mmol/L). If symptoms persist, this can be repeated one to two times.
In patients with neurologic symptoms, fluid restriction by itself is not an appropriate treatment. The immediate goal is to reduce brain swelling rapidly by the acutely raising the serum sodium level. Even in cases of chronic hyponatremia, the serum sodium can be increased acutely by 2 to 3 mEq/L (2-3 mmol/L) as long as the total change in the serum sodium is <10 mEq/L (10 mmol/L) in a 24-hour period. Except in cases of hypovolemic hyponatremia, the use of 0.9% sodium chloride is not recommended. In patients who are not volume depleted and have syndrome of inappropriate antidiuretic hormone secretion with a fixed urine osmolality, the infused saline can be excreted in the urine in a smaller volume, and thus the serum sodium can actually fall.
Both oral urea and tolvaptan are appropriate treatments for chronic hyponatremia, but they do not raise the serum sodium rapidly enough to reverse neurologic abnormalities and are therefore inappropriate for treatment of acute hyponatremia in this symptomatic patient.
Key Points
Treatment of acute symptomatic hyponatremia includes a 100-mL bolus of 3% saline to increase the serum sodium level by 2 to 3 mEq/L (2-3 mmol/L).
Bibliography
Sterns RH. Disorders of plasma sodium–causes, consequences, and correction. N Engl J Med. 2015;372:55-
65. PMID: 25551526
Copyright 2018, American College of Physicians.
April 23, 2024
MKSAP 18 Cardiovascular Medicine, Question 24
Stem:
A 72-year-old man is evaluated for exertional left calf and foot pain. Three weeks ago, the patient developed an ulcer on the medial aspect of the left great toe. His medical history is significant for coronary artery disease, type 2 diabetes mellitus, hypertension, and hyperlipidemia. Medications are low-dose aspirin, lisinopril, metoprolol, metformin, and atorvastatin.
On physical examination, blood pressure is 155/84 mm; other vital signs are normal. There are no palpable pulses in the left leg. Right femoral, popliteal, and pedal pulses are faint. Ankle-brachial index testing:
Right systolic brachial pressure 155 mm Hg
Left systolic brachial pressure 145 mm Hg
Left posterior tibialis pressure 255 mm Hg
Left dorsalis pedis pressure 255 mm Hg
Which of the following is the most appropriate diagnostic test to perform next?
A. Exercise ankle-brachial index
B. Lower extremity CT angiography
C. Toe-brachial index
D. Venous duplex ultrasonography
Responses Received from Members (852 Responses):
The Correct Answer is: C. Toe-brachial index
Educational Objective
Diagnose peripheral artery disease in a patient with noncompressible arteries.
Critique
The most appropriate diagnostic test to perform next in this patient is a toe-brachial index. The diagnostic tool that is most frequently used to identify peripheral artery disease (PAD) is the ankle-brachial index (ABI). To calculate the ABI, the higher ankle pressure in each leg is divided by the higher brachial pressure. An ABI of 0.90 or lower establishes a diagnosis of PAD, whereas an ABI greater than 1.40 indicates the presence of calcified, noncompressible arteries in the lower extremities and is considered uninterpretable. In patients with an ABI greater than 1.40, an appropriate next step is to measure toe pressure or calculate a toe-brachial index (systolic great toe pressure divided by systolic brachial pressure). A great toe systolic pressure below 40 mm Hg or a toe-brachial index below 0.70 is consistent with PAD. Because this patient has a left ABI of 1.65, a toe- brachial index is indicated.
Exercise ABI testing is useful when patients have a borderline ABI (0.91-1.00) or normal ABI (1.00-1.40) and a high likelihood of PAD. The American Heart Association has proposed a postexercise ankle pressure decrease of more than 30 mm Hg or a postexercise ABI decrease of more than 20% as a diagnostic criterion for PAD. Other organizations have proposed a postexercise ABI of less than 0.90 and/or a 30–mm Hg drop in ankle pressure after exercise. This patient's resting ABI value is greater than 1.40; therefore, exercise ABI is not indicated to diagnose PAD.
CT angiography and magnetic resonance angiography are often reserved for planning endovascular or surgical revascularization rather than for diagnosis of PAD.
In patients with venous leg ulcers, venous duplex ultrasonography is indicated to evaluate for chronic venous insufficiency and deep vein thrombosis (acute or chronic). The location of the ulceration and the lack of other findings consistent with venous disease make that diagnosis unlikely, and venous duplex ultrasonography is therefore unnecessary.
Key Points
In patients with an ankle-brachial index greater than 1.40, a toe-brachial index may be used to diagnose peripheral artery disease.
Bibliography
Aboyans V, Criqui MH, Abraham P, Allison MA, Creager MA, Diehm C, et al; American Heart Association Council on Peripheral Vascular Disease. Measurement and interpretation of the ankle-brachial index: a scientific statement from the American Heart Association. Circulation. 2012;126:2890-909. PMID: 23159553 doi:10.1161/CIR.0b013e318276fbcb
Copyright 2018, American College of Physicians.