Management of CO2 in Diabetic Ketoacidosis (DKA)
Bicarbonate therapy should only be considered in DKA patients with severe acidosis (pH <6.9), while most DKA patients with pH ≥7.0 do not require bicarbonate therapy as insulin administration alone will resolve the acidosis by blocking lipolysis. 1
Assessment of Acidosis Severity
The severity of DKA is classified according to the following parameters:
| Parameter | Mild | Moderate | Severe |
|---|---|---|---|
| Arterial pH | 7.25-7.30 | 7.00-7.24 | <7.00 |
| Serum bicarbonate (mEq/L) | 15-18 | 10-14 | <10 |
| Mental status | Alert | Alert/drowsy | Stupor/coma |
Bicarbonate Therapy Protocol
- For adults with pH <6.9: Administer 100 mmol sodium bicarbonate in 400 ml sterile water given at 200 ml/h 1
- For adults with pH 6.9-7.0: Administer 50 mmol sodium bicarbonate in 200 ml sterile water given at 200 ml/h 1
- For pH >7.0: Bicarbonate therapy is not recommended as insulin therapy alone will correct the metabolic acidosis 1
Monitoring Acid-Base Status
During DKA treatment, blood should be drawn every 2-4 hours for determination of:
Venous pH (which is usually 0.03 units lower than arterial pH) and anion gap can be followed to monitor resolution of acidosis 2
Generally, repeat arterial blood gases are unnecessary 2
Insulin Therapy to Correct Acidosis
Insulin therapy is the primary treatment for correcting acidosis in DKA by:
- Stopping ketone production
- Allowing metabolism of existing ketones
- Gradually normalizing bicarbonate levels
The recommended insulin protocol:
- For moderate to severe DKA: Initial IV bolus of 0.15 U/kg regular insulin followed by continuous infusion at 0.1 U/kg/hour 1
- For mild DKA: Subcutaneous or intramuscular regular insulin can be used, with an initial dose of 0.4-0.6 U/kg and subsequent dose of 0.1 U/kg/hour 1
Fluid Management Impact on Acid-Base Status
- Initial fluid resuscitation with normal saline (0.9% NaCl) is recommended at 1-1.5 L during the first hour 1
- Be aware that large volume administration of normal saline can lead to hyperchloremic metabolic acidosis due to the high chloride content (154 mEq/L) 1
- When glucose levels reach 250 mg/dl, switch to 5% dextrose with 0.45-0.75% saline solution to prevent hypoglycemia while continuing insulin therapy to clear ketones 1
Potassium Management
- Insulin therapy stimulates potassium movement into cells, which can lead to hypokalemia 3
- Hypokalemia can worsen acidosis by impairing renal acid excretion
- Maintain potassium levels between 4.0-5.0 mEq/L 1
- Add 20-40 mEq/L of potassium to IV fluids when diuresis is confirmed and serum potassium is <5.0 mEq/L 1
- Delay insulin therapy if initial potassium is <3.3 mEq/L to avoid arrhythmias, cardiac arrest, and respiratory muscle weakness 1
Resolution Criteria for DKA
DKA is considered resolved when:
- Glucose <200 mg/dL
- Serum bicarbonate ≥18 mEq/L
- Venous pH ≥7.3
- Anion gap has normalized 1
Monitoring Ketone Resolution
- Direct measurement of β-hydroxybutyrate in blood is the preferred method for monitoring ketosis resolution 1
- The nitroprusside method only measures acetoacetic acid and acetone, not β-hydroxybutyrate (the strongest and most prevalent acid in DKA) 2
- During therapy, β-hydroxybutyrate is converted to acetoacetic acid, which may lead to the false impression that ketosis has worsened if using the nitroprusside method 2
Special Considerations
- Cerebral edema risk: Rapid correction of acidosis may contribute to cerebral edema, particularly in pediatric patients 1
- Pregnant patients: Require specialized management of acidosis due to physiological respiratory alkalosis of pregnancy 1
- Elderly patients: May require more careful monitoring during fluid resuscitation and bicarbonate therapy 1
By following these guidelines, CO2 (bicarbonate) levels will gradually normalize as insulin therapy stops ketone production and allows metabolism of existing ketones, with bicarbonate therapy reserved only for cases of severe acidosis.