What is the most appropriate initial management for a patient with a history of diabetes presenting with diabetic ketoacidosis (DKA), severe hyperglycemia, metabolic acidosis, and laboratory results showing hyperglycemia, acidosis, and low bicarbonate levels?

Initial Management of Diabetic Ketoacidosis

The most appropriate initial management is C: IV fluids and regular insulin. This patient meets diagnostic criteria for DKA (glucose >250 mg/dL, pH <7.3, bicarbonate <15 mEq/L), and the American Diabetes Association recommends beginning with aggressive isotonic saline resuscitation at 15-20 mL/kg/hour followed by continuous IV regular insulin infusion at 0.1 units/kg/hour 1, 2.

Why IV Fluids Come First

• Fluid resuscitation is the critical first step because DKA causes total body water deficits of 6-9 liters, and restoring circulatory volume improves tissue perfusion and insulin sensitivity 1, 2.

• The American College of Clinical Endocrinologists recommends isotonic saline (0.9% NaCl) at 15-20 mL/kg/hour (approximately 1-1.5 L in the average adult) during the first hour 1.

• Aggressive initial fluid replacement has been shown to be critically important for restoring tissue perfusion before insulin therapy begins 1.

Why IV Regular Insulin (Not Subcutaneous)

• For moderate-to-severe DKA with pH 7.15, continuous IV regular insulin at 0.1 units/kg/hour is the standard of care 1, 2.

• Subcutaneous rapid-acting insulin analogs are only appropriate for mild-to-moderate uncomplicated DKA in hemodynamically stable, alert patients—not for this patient with pH 7.15 (moderate DKA) 1, 3.

• The target glucose decline should be 50-75 mg/dL per hour with IV insulin 1, 2.

• If glucose does not fall by 50 mg/dL in the first hour, double the insulin infusion rate hourly until steady decline is achieved 1, 2.

Why NOT Bicarbonate (Option A)

• Bicarbonate is NOT recommended for DKA patients with pH >6.9-7.0 1, 2.

• This patient's pH of 7.15 is well above the threshold where bicarbonate might be considered 1.

• Multiple studies show no difference in resolution of acidosis or time to discharge with bicarbonate use, and it may worsen ketosis, cause hypokalemia, and increase cerebral edema risk 1, 3.

• Bicarbonate should only be considered if pH <6.9, or when pH <7.2 pre-intubation to prevent hemodynamic collapse 1, 3.

Critical Potassium Management Before Insulin

• Check potassium levels immediately—insulin therapy should NOT be started if K+ <3.3 mEq/L 1, 2.

• If K+ <3.3 mEq/L, delay insulin and aggressively replace potassium first to prevent life-threatening arrhythmias and respiratory muscle weakness 1.

• Once K+ is 3.3-5.5 mEq/L and adequate urine output is confirmed, add 20-30 mEq/L potassium to IV fluids (use 2/3 KCl and 1/3 KPO₄) 1, 2.

• Total body potassium depletion averages 3-5 mEq/kg in DKA, and insulin therapy will drive potassium intracellularly, causing rapid decline 1, 2.

Treatment Algorithm

1. Immediate assessment: Verify DKA diagnosis with blood glucose, pH, bicarbonate, and check potassium level 1, 2

2. Start IV fluids: Isotonic saline 15-20 mL/kg/hour for first hour 1, 2

3. Check potassium: If K+ <3.3 mEq/L, hold insulin and replace potassium aggressively; if K+ ≥3.3 mEq/L, proceed to insulin 1, 2

4. Start IV insulin: Continuous regular insulin infusion at 0.1 units/kg/hour 1, 2

5. Add dextrose: When glucose falls to 250 mg/dL, switch to 5% dextrose with 0.45-0.75% saline while continuing insulin to prevent hypoglycemia and ensure complete ketoacidosis resolution 1, 2

6. Monitor closely: Check glucose, electrolytes, and venous pH every 2-4 hours 1, 2

Resolution Criteria and Transition

• DKA is resolved when: glucose <200 mg/dL, serum bicarbonate ≥18 mEq/L, venous pH >7.3, and anion gap ≤12 mEq/L 1, 2.

• Critical pitfall to avoid: Administer basal insulin (intermediate or long-acting) 2-4 hours BEFORE stopping IV insulin infusion to prevent recurrence of ketoacidosis and rebound hyperglycemia 1, 2.

• Premature termination of IV insulin before complete resolution of ketosis is a common cause of DKA recurrence 1, 4.

Common Pitfalls

• Never stop IV insulin when glucose normalizes—ketoacidosis takes longer to resolve than hyperglycemia, and premature cessation causes recurrence 1, 2.

• Never use subcutaneous insulin alone for moderate-severe DKA—this patient's pH of 7.15 requires continuous IV insulin 1, 2.

• Never give bicarbonate routinely—it provides no benefit at pH 7.15 and may worsen outcomes 1, 3.

• Failure to add dextrose when glucose falls below 250 mg/dL while continuing insulin therapy leads to hypoglycemia and incomplete ketosis resolution 1.