In an adult or adolescent with diabetic ketoacidosis, what are the recommended fluid resuscitation rates, potassium replacement strategy, and intravenous regular insulin dosing and transition protocol?

Management of Fluids and Insulin in Diabetic Ketoacidosis

Begin with isotonic saline at 15–20 mL/kg/hour for the first hour, confirm serum potassium ≥3.3 mEq/L before starting continuous IV regular insulin at 0.1 units/kg/hour, and administer basal subcutaneous insulin 2–4 hours before stopping the IV infusion to prevent recurrent ketoacidosis. 1

Initial Fluid Resuscitation

• Administer isotonic saline (0.9% NaCl) at 15–20 mL/kg/hour (approximately 1–1.5 L in an average adult) during the first hour to restore intravascular volume and renal perfusion. 1, 2
• The typical total body water deficit in DKA is 6–9 liters, which should be replaced over 24 hours. 1
• After the first hour, calculate corrected serum sodium by adding 1.6 mEq/L for each 100 mg/dL glucose above 100 mg/dL. 1
  • If corrected sodium is normal or elevated, switch to 0.45% NaCl at 4–14 mL/kg/hour. 1
  • If corrected sodium is low, continue 0.9% NaCl at 4–14 mL/kg/hour. 1
• When plasma glucose falls to 250 mg/dL, change IV fluids to 5% dextrose with 0.45–0.75% NaCl while maintaining the insulin infusion to prevent hypoglycemia and ensure complete ketoacidosis resolution. 1, 2

Potassium Replacement Strategy

Total body potassium depletion is universal in DKA (averaging 3–5 mEq/kg), even when initial serum levels appear normal or elevated. 1

Potassium-Based Algorithm for Insulin Initiation

• If serum K⁺ <3.3 mEq/L: Hold insulin completely and aggressively replace potassium at 20–40 mEq/hour until K⁺ ≥3.3 mEq/L to prevent life-threatening arrhythmias, cardiac arrest, and respiratory muscle weakness. 1, 2
• If K⁺ 3.3–5.5 mEq/L: Start insulin therapy and add 20–30 mEq potassium per liter of IV fluid (approximately 2/3 KCl and 1/3 KPO₄) once adequate urine output is confirmed. 1, 2
• If K⁺ >5.5 mEq/L: Start insulin immediately without potassium supplementation initially, but monitor every 2–4 hours as levels will fall rapidly; add potassium once K⁺ drops below 5.5 mEq/L. 1
• Target serum potassium of 4–5 mEq/L throughout treatment. 1

Intravenous Regular Insulin Protocol

Preparation and Initiation

• Confirm serum potassium ≥3.3 mEq/L before initiating insulin—this is an absolute contraindication with Class A evidence. 1, 2
• Prepare insulin solution by adding 100 units regular insulin to 100 mL normal saline (1 unit/mL concentration). 3
• Prime the infusion tubing with 20 mL of the prepared solution before connecting to the patient. 3
• Administer an IV bolus of 0.1 units/kg regular insulin, followed immediately by continuous infusion at 0.1 units/kg/hour (approximately 5–7 units/hour in an average adult). 3, 1, 2

Titration and Monitoring

• Target a glucose decline of 50–75 mg/dL per hour. 3, 1
• If plasma glucose does not fall by ≥50 mg/dL in the first hour despite adequate hydration, double the insulin infusion rate every hour until a steady decline is achieved. 3, 1
• When serum glucose reaches 250 mg/dL, decrease the insulin infusion rate to 0.05–0.1 units/kg/hour and add dextrose to IV fluids—never stop insulin when glucose falls. 3, 1
• Monitor blood glucose every 1–2 hours initially, then every 2–4 hours once stable. 3, 1

Laboratory Monitoring

• Draw blood every 2–4 hours for serum electrolytes (especially potassium), glucose, BUN, creatinine, osmolality, and venous pH until metabolically stable. 1, 2
• Direct measurement of β-hydroxybutyrate in blood is the preferred method for monitoring ketone clearance; nitroprusside-based tests miss the predominant ketone body and should not be used. 3, 1

Criteria for DKA Resolution

Continue insulin infusion until ALL of the following criteria are met, regardless of glucose level: 3, 1

• Glucose <200 mg/dL
• Serum bicarbonate ≥18 mEq/L
• Venous pH >7.3
• Anion gap ≤12 mEq/L

Ketonemia resolves more slowly than hyperglycemia, so insulin must not be stopped prematurely. 3

Transition to Subcutaneous Insulin

• Administer basal insulin (glargine or detemir) subcutaneously 2–4 hours BEFORE stopping the IV insulin infusion to prevent recurrence of ketoacidosis and rebound hyperglycemia. 3, 1, 2
• Continue the IV insulin infusion for 1–2 hours after the subcutaneous basal dose to ensure adequate absorption. 1
• Use approximately 50% of the total 24-hour IV insulin dose as the single daily basal insulin dose. 1
• Divide the remaining 50% equally among three meals as rapid-acting prandial insulin. 1
• When the patient can tolerate oral intake, initiate a multiple-dose schedule using a combination of short/rapid-acting and intermediate/long-acting insulin. 3, 1

Alternative Approach for Mild-Moderate Uncomplicated DKA

• For hemodynamically stable, alert patients with mild-moderate DKA, subcutaneous rapid-acting insulin analogs at 0.15 units/kg every 2–3 hours combined with aggressive fluid management are equally effective, safer, and more cost-effective than IV insulin. 1
• This approach requires adequate fluid replacement, frequent point-of-care glucose monitoring, and treatment of concurrent infections. 1
• Continuous IV insulin remains the standard of care for moderate-to-severe DKA or critically ill/mentally obtunded patients. 1

Critical Pitfalls to Avoid

• Never start insulin when serum potassium is <3.3 mEq/L—this can cause fatal cardiac arrhythmias and is the most critical error. 1, 2
• Never stop IV insulin without prior administration of subcutaneous basal insulin 2–4 hours earlier—this is the most common cause of recurrent DKA. 1, 2
• Never hold insulin when glucose falls to 250 mg/dL—instead add dextrose to IV fluids while maintaining insulin infusion to clear ketones. 3, 1
• Inadequate potassium monitoring and replacement is a leading cause of mortality in DKA—check levels every 2–4 hours. 1
• Correcting serum osmolality faster than 3 mOsm/kg/hour increases the risk of cerebral edema, particularly in children. 1

Bicarbonate Administration

• Bicarbonate is NOT recommended for DKA patients with pH >6.9–7.0, as multiple studies show no difference in resolution time or outcomes, and it may worsen ketosis, cause hypokalemia, and increase cerebral edema risk. 1
• Consider 100 mEq sodium bicarbonate in 400 mL sterile water at 200 mL/hour only if pH <6.9. 1

Identification and Treatment of Precipitating Causes

• Infection is the most frequent precipitating factor—obtain bacterial cultures (blood, urine, throat) when suspected and administer appropriate antibiotics. 1, 2
• Other common precipitants include myocardial infarction, cerebrovascular accident, pancreatitis, insulin omission, SGLT2 inhibitor use, and glucocorticoid therapy. 1
• SGLT2 inhibitors must be discontinued immediately and not restarted until 3–4 days after metabolic stability is achieved. 1