Emergency medicine for USMLE Step 2 CK

A 45-year-old man is brought in after a motor vehicle collision. He is hypotensive at 84/50 mmHg with distended neck veins and muffled heart sounds. There is no tracheal deviation and breath sounds are equal bilaterally. FAST scan shows fluid in the pericardial space. What is the most appropriate immediate intervention?

1. Aggressive crystalloid resuscitation alone A temporizing measure only. Fluid may briefly improve preload, but the obstruction is mechanical and will not resolve without drainage.
2. CT chest with contrast to define the injury He is unstable with a diagnostic FAST. Unstable patients go to intervention, not to the scanner.
3. Pericardiocentesis or emergency thoracotomy correct Correct. Beck's triad with pericardial fluid on FAST after trauma is cardiac tamponade. Relieving the pericardial pressure is the only intervention that restores cardiac output; in a trauma center, resuscitative thoracotomy may be preferred to needle drainage.
4. Needle decompression of the right chest Treats tension pneumothorax, which would give unilateral absent breath sounds and tracheal deviation, both explicitly absent.
5. Intubation and positive pressure ventilation Potentially harmful as the immediate step: positive pressure reduces venous return and can precipitate arrest in tamponade.

The point: Beck's triad plus a positive pericardial FAST is tamponade. Tension pneumothorax gives the same hypotension and distended veins but with unilateral breath sound loss. Unstable plus a diagnostic FAST means no CT.

Source: ATLS — Advanced Trauma Life Support principles American College of Surgeons (ATLS) · tier 2, specialty society or college

A 68-year-old man presents 2 hours after the sudden onset of tearing chest pain radiating to his back. Blood pressure is 186/104 mmHg in the right arm and 148/88 mmHg in the left. There is a new early diastolic murmur. Chest radiograph shows a widened mediastinum. What is the most appropriate initial pharmacologic management?

1. Intravenous beta blockade first, then a vasodilator if further blood pressure reduction is needed correct Correct. In acute aortic dissection the aim is to reduce both blood pressure and the rate of rise of pressure (dP/dt). Beta blockade lowers heart rate and contractility first; adding a vasodilator before rate control causes reflex tachycardia that increases shear stress and can extend the dissection.
2. Intravenous fluid resuscitation to maintain perfusion Wrong. He is hypertensive, and raising pressure further would extend the dissection.
3. Thrombolysis for presumed myocardial infarction Catastrophic. Dissection can occlude a coronary ostium and mimic infarction, and thrombolysing a dissection is often fatal. The blood pressure differential and the widened mediastinum are the clues.
4. Intravenous sodium nitroprusside as the first agent Wrong order. Vasodilation without prior rate control produces reflex tachycardia and a higher dP/dt, propagating the dissection.
5. Therapeutic anticoagulation with heparin Wrong. Anticoagulation does not treat dissection and increases the risk of fatal hemorrhage into the false lumen or pericardium.

The point: Aortic dissection: beta blocker before vasodilator, target systolic around 100 to 120 and heart rate below 60. Type A involving the ascending aorta is a surgical emergency; type B is usually managed medically unless complicated. Pain out of proportion, a pressure differential, and a new aortic regurgitant murmur are the triad to notice.

Source: ACC/AHA guideline for the diagnosis and management of aortic disease American College of Cardiology / AHA · tier 2, specialty society or college