A 20-year-old diabetic patient presents with DKA, ABG shows metabolic acidosis, and he has Kussmaul respiration. What is the most important immediate therapy?

Correct option is B

DKA is caused by absolute insulin deficiency → ketosis + acidosis. IV insulin is the cornerstone of management along with fluids and electrolytes.
Explanation of options: (a) ✘ Bicarbonate is rarely needed, reserved for pH < 6.9. (b) ✔ Correct; insulin corrects hyperglycemia and stops ketogenesis. (c) ✘ Mannitol used in cerebral edema, not routine DKA management. (d) ✘ OHAs ineffective in absolute insulin deficiency.