Review Question - QID 109453

A 57-year-old man presents to the emergency department for shortness of breath. He was riding the train home from a business conference when his symptoms began. The patient has a medical history of obesity, diabetes, diabetic nephropathy, hypertension, and a 40-pack-year smoking history. His current medications include atorvastatin, lisinopril, insulin, metformin, and nicotine gum. His temperature is 99.5°F (37.5°C), blood pressure is 130/87 mmHg, pulse is 120/min, respirations are 15/min, and oxygen saturation is 93% on room air. An ECG is ordered as seen in Figure A. A chest radiograph is ordered as seen in Figure B. Laboratory values are ordered as seen below:

Serum:
Na+: 137 mEq/L
Cl-: 105 mEq/L
K+: 4.1 mEq/L
HCO3-: 24 mEq/L
BUN: 22 mg/dL
Glucose: 129 mg/dL
Creatinine: 1.2 mg/dL
Ca2+: 10.1 mg/dL
AST: 11 U/L
ALT: 12 U/L

On physical exam, the patient appears to be in distress. His cardiac exam is notable for tachycardia. Pulmonary exam reveals bilateral air movement without any wheezes or crackles. The patient's right lower extremity appears mildly inflamed, and palpation of the calf elicits pain. Which of the following is the most appropriate next step in management?