# Diabetic Ketoacidosis: Fluid, Insulin, and Potassium

## Introduction

Diabetic ketoacidosis (DKA) is a life-threatening metabolic emergency characterized by the triad of hyperglycemia, anion gap metabolic acidosis, and ketonemia. It occurs most commonly in type 1 diabetes but can also present in type 2 diabetes during physiologic stress. The emergency physician must rapidly identify DKA, initiate aggressive fluid resuscitation, carefully manage insulin therapy, and meticulously monitor potassium to prevent iatrogenic complications.

## Pathophysiology

The underlying mechanism involves insulin deficiency (absolute or relative) combined with counterregulatory hormone excess from glucagon, cortisol, catecholamines, and growth hormone. Hepatic gluconeogenesis and glycogenolysis produce hyperglycemia. Lipolysis releases free fatty acids, which undergo hepatic beta-oxidation to produce ketone bodies (beta-hydroxybutyrate, acetoacetate, and acetone). These ketoacids consume bicarbonate buffer, producing an anion gap metabolic acidosis. Osmotic diuresis from glycosuria causes profound dehydration, with an average fluid deficit of 5 to 9 liters in adults. Total body potassium depletion averaging 3 to 5 mEq/kg occurs despite potentially normal or elevated serum potassium at presentation.

## Diagnostic Criteria

DKA is diagnosed by a blood glucose above 250 mg/dL (though euglycemic DKA can occur with SGLT2 inhibitor use, pregnancy, or reduced oral intake), arterial pH below 7.30 or venous pH below 7.25, serum bicarbonate below 18 mEq/L, anion gap above 12 (calculated as sodium minus the sum of chloride and bicarbonate), and positive serum or urine ketones (with beta-hydroxybutyrate above 3 mmol/L preferred over urine ketones).

### Severity Classification

| Severity | pH | Bicarbonate (mEq/L) | Mental Status | Anion Gap |
|----------|-----|--------------------|----|-----------|
| Mild | 7.25–7.30 | 15–18 | Alert | > 12 |
| Moderate | 7.00–7.24 | 10–14 | Drowsy | > 12 |
| Severe | < 7.00 | < 10 | Obtunded/coma | > 12 |

Mild DKA is characterized by pH of 7.25 to 7.30, bicarbonate of 15 to 18, and an alert mental status. Moderate DKA has a pH of 7.00 to 7.24, bicarbonate of 10 to 14, and drowsiness. Severe DKA presents with pH below 7.00, bicarbonate below 10, and obtundation or coma.

## Precipitating Factors -- The 5 I's

The most common precipitant is infection, including pneumonia, UTI, and soft tissue infections. Insulin noncompliance or pump failure is another frequent cause. Infarction (myocardial, cerebrovascular, mesenteric), intoxication (alcohol, cocaine, SGLT2 inhibitors), and initial presentation of new-onset diabetes round out the common triggers.

<image>Pathophysiology diagram of DKA showing the cascade from insulin deficiency to counterregulatory hormone release, hepatic gluconeogenesis, lipolysis, ketogenesis, and the resulting metabolic derangements including hyperglycemia, acidosis, and osmotic diuresis</image>

## Fluid Resuscitation

### Initial Fluid Strategy

Volume resuscitation with isotonic crystalloid (normal saline or lactated Ringer's) is the first priority. The initial bolus is 1 to 2 liters of 0.9 percent NaCl over the first hour (15 to 20 mL/kg). Subsequent fluids at 250 to 500 mL per hour are guided by hemodynamic status, urine output, and clinical reassessment. Balanced crystalloids such as lactated Ringer's may reduce the hyperchloremic metabolic acidosis that complicates normal saline-based resuscitation, though definitive evidence for clinical superiority in DKA is still emerging.

### Fluid Transition

When glucose falls to 250 mg/dL, fluids should be switched to D5 half-normal saline to prevent hypoglycemia while continuing insulin to clear ketones. This is a critical step, as premature insulin discontinuation due to normalized glucose prolongs ketosis. Average total fluid replacement is 5 to 9 liters over 24 to 48 hours.

## Insulin Therapy

### Standard Protocol

Insulin must not be started until potassium is confirmed at 3.5 mEq/L or above, as insulin drives potassium intracellularly and can precipitate life-threatening hypokalemia. The standard approach is continuous IV insulin infusion at 0.1 units/kg per hour (no bolus is needed per current evidence), with an alternative rate of 0.14 units/kg per hour without bolus. The target glucose decline is 50 to 70 mg/dL per hour. If glucose does not fall by 50 to 70 mg/dL in the first hour, the infusion rate should be doubled.

### Transition to Subcutaneous Insulin

The transition occurs when pH is above 7.30, bicarbonate is above 15, the anion gap has closed, and the patient is tolerating oral intake. IV and subcutaneous insulin should overlap by 1 to 2 hours before discontinuing the drip to prevent rebound hyperglycemia and ketosis. Long-acting insulin (glargine) should be given at least 2 hours before stopping the infusion.

<image>Timeline infographic showing the parallel management tracks in DKA: fluid resuscitation (top), insulin infusion (middle), and potassium replacement (bottom) with key decision points and glucose/potassium thresholds marked at each stage</image>

## Potassium Management

### The Central Paradox

Patients are profoundly total-body potassium depleted but may present with normal or elevated serum potassium. This occurs because insulin deficiency keeps potassium extracellular, acidosis drives hydrogen-potassium exchange across cell membranes, and hyperosmolarity causes solvent drag pulling potassium out of cells.

### Replacement Protocol

If potassium is below 3.5 mEq/L, insulin must be held and potassium repleted aggressively (20 to 40 mEq per hour via central line) until potassium reaches 3.5 before starting insulin. If potassium is between 3.5 and 5.0 mEq/L, 20 to 40 mEq of KCl should be added to each liter of IV fluid, with rechecking every 1 to 2 hours. If potassium is above 5.0 mEq/L, supplementation should be withheld and potassium rechecked in 2 hours, with anticipation of a rapid decline once insulin is initiated. Monitoring potassium every 1 to 2 hours during the first 4 to 6 hours is non-negotiable.

## Bicarbonate Therapy

Routine bicarbonate is not recommended, as most patients correct acidosis with fluids and insulin alone. Bicarbonate should be considered only if pH is below 6.9, indicating life-threatening acidosis with cardiovascular compromise. The dose is 100 mEq of sodium bicarbonate in 400 mL of sterile water with 20 mEq KCl, infused over 2 hours. Risks of bicarbonate include paradoxical CNS acidosis, hypokalemia, rebound alkalosis, and delayed ketone clearance.

## Cerebral Edema

Cerebral edema is primarily a pediatric concern (occurring in 0.5 to 1 percent of pediatric DKA cases) but can occur in young adults. Risk factors include new-onset diabetes, younger age, severe acidosis, rapid glucose correction, and excessive early fluid administration. Warning signs include headache, altered mental status, bradycardia, hypertension, and pupillary changes. Treatment consists of immediate hypertonic saline (3 percent NaCl, 5 mL/kg) or mannitol (0.5 to 1 g/kg), reducing the IV fluid rate, and elevating the head of bed.

## Monitoring and Disposition

Blood glucose should be checked hourly at the point of care. A basic metabolic panel (sodium, potassium, chloride, bicarbonate, BUN, creatinine) and venous blood gas should be obtained every 1 to 2 hours. Beta-hydroxybutyrate (if available) and anion gap calculation should be performed every 2 to 4 hours. ICU admission criteria include severe DKA (pH below 7.0), altered mental status, hemodynamic instability, significant comorbidities, and pediatric patients.

<image>Monitoring checklist flowchart for DKA management showing hourly glucose checks, Q1-2hr electrolyte panels, potassium replacement decision tree, and criteria for transitioning from IV insulin to subcutaneous regimen</image>

## Clinical Pearls

Never start insulin until potassium is confirmed at 3.5 mEq/L or above -- hypokalemia, not hyperglycemia, kills in DKA. The goal of insulin is to clear ketones, not just lower glucose; insulin should be continued even when glucose normalizes by adding dextrose to IV fluids. Euglycemic DKA (glucose below 250) is increasingly common with SGLT2 inhibitors, so ketones and pH should be checked in any diabetic patient with acidosis regardless of glucose level. Potassium monitoring every 1 to 2 hours is mandatory during active DKA management, as a rapid fall should be anticipated once insulin is running. Subcutaneous and IV insulin should overlap by 1 to 2 hours before stopping the drip to prevent rebound ketoacidosis.

## References

1. Kitabchi AE, et al. "Hyperglycemic Crises in Adult Patients With Diabetes." *Diabetes Care*. 2009;32(7):1335-1343.
2. Dhatariya KK, et al. "Diabetic Ketoacidosis." *Nature Reviews Disease Primers*. 2020;6(1):40.
3. Long B, Koyfman A. "Emergency Medicine Myths: Fluids, Insulin, and Potassium in Diabetic Ketoacidosis." *Journal of Emergency Medicine*. 2017;53(4):e77-e80.
4. Tintinalli JE, et al. *Tintinalli's Emergency Medicine: A Comprehensive Study Guide*. 9th ed. McGraw-Hill; 2020. Chapter 224.