Erythroderma Generalized Exfoliative Dermatitis

A 58-year-old Indian male presents with acute onset diffuse erythema and fine scaling involving >90% of his body surface area, as shown by the structure marked **A** in the diagram. He reports fever, tachycardia, and severe pruritus. His past medical history includes poorly controlled psoriasis for which he had recently discontinued oral methotrexate due to financial constraints. On examination, he has peripheral edema, alopecia, and nail dystrophy. Which of the following is the MOST LIKELY systemic complication requiring immediate management in this patient?