Review Question - QID 212488

A 45-year-old man presents to the emergency department for worsening shortness of breath with exertion, mild chest pain, and lower extremity swelling. The patient reports increasing his alcohol intake and has been consuming a diet rich in salt over the past few days. Physical examination is significant for bilateral crackles in the lung bases, jugular venous distension, and pitting edema up to the knees. An electrocardiogram is unremarkable. He is admitted to the cardiac step-down unit. In the unit, he is started on his home anti-hypertensive medications, intravenous furosemide every 6 hours, and prophylactic enoxaparin. His initial labs on the day of admission are remarkable for the following:

Hemoglobin: 12 g/dL
Hematocrit: 37%
Leukocyte count: 8,500 /mm^3 with normal differential
Platelet count: 150,000 /mm^3

Serum:
Na+: 138 mEq/L
Cl-: 102 mEq/L
K+: 4.1 mEq/L
HCO3-: 25 mEq/L

On hospital day 5, routine laboratory testing is demonstrated below:

Hemoglobin: 12.5 g/dL
Hematocrit: 38%
Leukocyte count: 8,550 /mm^3 with normal differential
Platelet count: 60,000 /mm^3

Serum:
Na+: 140 mEq/L
Cl-: 100 mEq/L
K+: 3.9 mEq/L
HCO3-: 24 mEq/L

Physical examination is unremarkable for any bleeding and the patient denies any lower extremity pain. There is an erythematous and necrotic skin lesion in the left abdomen.

Which of the following best explains this patient’s current presentation?