What is the most appropriate initial treatment for the acid-base imbalance in a 20-year-old underweight woman with dyspnea, anion gap metabolic acidosis, impaired renal function, hyperkalemia, hyponatremia, and diabetic ketoacidosis, alongside IV fluids?

Initial Treatment for Diabetic Ketoacidosis: Insulin Therapy

The most appropriate initial treatment for this patient's acid-base imbalance is continuous intravenous regular insulin infusion at 0.1 units/kg/hour, alongside aggressive fluid resuscitation with isotonic saline. 1, 2, 3

Clinical Presentation Analysis

This 20-year-old woman presents with classic diabetic ketoacidosis (DKA):

• Severe metabolic acidosis: pH 7.0, bicarbonate 12 mEq/L 2, 4
• Marked hyperglycemia: glucose 380 mg/dL with positive ketones 2, 4
• High anion gap: calculated at 29 (using Na - [Cl + HCO3]) 2, 4
• Acute kidney injury: BUN 35, creatinine 1.8 2
• Hyperkalemia: potassium 5.7 mEq/L (though total body potassium is depleted) 2, 3

This represents moderate-to-severe DKA based on pH 7.0 and bicarbonate 12 mEq/L. 2, 4

Immediate Treatment Protocol

1. Insulin Therapy (Primary Treatment for Acid-Base Imbalance)

Start continuous IV regular insulin infusion at 0.1 units/kg/hour without an initial bolus. 1, 2, 3 This is the definitive treatment to:

• Stop ketone production 3
• Clear existing ketoacids from circulation 2, 3
• Correct the metabolic acidosis 1, 2

Critical point: The American Diabetes Association emphasizes that insulin therapy is essential to resolve ketoacidosis—it cannot be corrected by fluids alone. 1, 2, 3

2. Fluid Resuscitation (Concurrent with Insulin)

Administer isotonic (0.9%) saline at 15-20 mL/kg/hour for the first hour to restore circulatory volume and tissue perfusion. 2, 3 This patient likely has a 6-9 liter total body water deficit. 2

3. Critical Potassium Management Consideration

Despite the elevated serum potassium of 5.7 mEq/L, DO NOT delay insulin therapy in this patient. 2 However, you must:

• Monitor potassium closely as insulin will drive it intracellularly, potentially causing life-threatening hypokalemia 2, 3
• Begin potassium replacement (20-30 mEq/L in IV fluids) once serum potassium falls below 5.5 mEq/L and adequate urine output is confirmed 1, 2, 3
• If potassium were <3.3 mEq/L, you would need to delay insulin and aggressively replace potassium first 2—but this is not the case here

What NOT to Do: Common Pitfalls

Bicarbonate Therapy is NOT Indicated

Do not administer bicarbonate for this patient's acidosis. 2, 3 The American Diabetes Association states that bicarbonate therapy:

• Provides no benefit in DKA resolution 3
• Should only be considered if pH <6.9 2, 3
• This patient's pH of 7.0 does not meet criteria for bicarbonate 2, 5

The acidosis will resolve with insulin therapy, which stops ketone production and allows metabolism of existing ketoacids. 2, 3

Never Stop Insulin When Glucose Normalizes

Continue insulin infusion even after glucose falls below 200 mg/dL. 2, 3 When glucose reaches 200-250 mg/dL:

• Add dextrose 5-10% to IV fluids 2, 3
• Continue insulin at the same rate to clear ketones 2, 3
• Ketoacidosis takes longer to resolve than hyperglycemia 2, 3

Stopping insulin prematurely when glucose normalizes is the most common error leading to persistent or recurrent ketoacidosis. 3

Monitoring Requirements

Check the following every 2-4 hours during treatment: 2, 3

• Blood glucose
• Serum electrolytes (especially potassium)
• Venous pH and anion gap
• BUN and creatinine
• Beta-hydroxybutyrate (preferred over urine ketones) 2, 4

Venous pH is sufficient for monitoring—repeated arterial blood gases are unnecessary after initial diagnosis. 2, 4

Resolution Criteria

DKA is resolved when ALL of the following are met: 2, 4, 3

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

Transition Planning

Before stopping IV insulin, administer basal subcutaneous insulin 2-4 hours in advance to prevent rebound hyperglycemia and recurrent ketoacidosis. 1, 2, 3 Once acidosis resolves, metformin can be initiated while continuing subcutaneous insulin therapy. 1, 2