A black eschar is seen running circularly around the upper right arm. What is the most likely diagnosis?

A 25-year-old man who works in a pizza shop presents 3 days after burning his right upper extremity. He was putting his right arm into the oven to grab his favorite slice and subsequently developed a circumferential burn that encompassed his entire upper forearm. Today he presents with significant pain distal to the burn and a pins and needles sensation in his right hand. Physical Exam: • 0 of 5 strength on extension of the right hand • Decreased radial pulses noted by palpation and barely audible by Doppler • Skin distal to the burn is tense and swollen. • There is congestion of the digits with increased capillary refill time. • A black eschar is seen running circularly around the upper right arm. What is the most likely diagnosis?

a. Cellulitis
b. Upper extremity deep venous thrombosis (DVT)
c. Rhabdomyolysis
d. Acute compartment syndrome
e. Arterial embolism

Answer d. Acute compartment syndrome The 6 Ps of compartment syndrome are pain out of proportion to what is expected based on the physical examination findings, paresthesia, pallor, paralysis, pulselessness, and poikilothermia. The underlying etiology of compartment syndrome is rising pressures in the muscle compartment. This is because the fascia layer does not stretch, and thus any swelling, bleeding, or accumulation of fluid can cause significant impairment. Cellulitis would present with pain and fever, but there is never neurologic compromise or lack of pulses. An upper extremity DVT would present with painful swelling, and arterial embolism presents as painful swelling in the setting of a patient with atrial fibrillation. Rhabdomyolysis presents with muscle pain and elevated creatinine kinase levels.
The first P sign of compartment syndrome to occur is paresthesia.
Four compartments of the hand: • Superficial volar (flexor) • Deep volar • Dorsal (extensor) compartment • Compartment containing the mobile wad of Henry
The five compartments of the lower leg: • Anterior • Lateral • Superficial posterior • Deep posterior • Tibialis posterior