Sodium Bicarbonate Dosing for Severe Metabolic Acidosis
For a 71-year-old female with pH 7.04 and HCO3 of 12, administer 50 mmol sodium bicarbonate diluted in 200 ml sterile water and infused at a rate of 200 ml/h. 1
Dosing Based on pH Level
- For pH 6.9-7.0 (as in this case), 50 mmol sodium bicarbonate should be diluted in 200 ml sterile water and infused at a rate of 200 ml/h 1
- No bicarbonate is necessary if pH is >7.0, but this patient's pH is 7.04, which falls within the range requiring bicarbonate therapy 1, 2
- For more severe acidosis (pH <6.9), a higher dose of 1-2 mEq/kg may be warranted 2
Administration Guidelines
- When administering sodium bicarbonate, it should be diluted to avoid excessive hypernatremia 3
- The FDA recommends that in less urgent forms of metabolic acidosis, sodium bicarbonate may be added to other intravenous fluids 3
- Bicarbonate therapy should be monitored by measuring blood gases, plasma osmolarity, arterial blood lactate, hemodynamics and cardiac rhythm 3
Monitoring During Therapy
- Monitor serum potassium closely as insulin therapy and correction of acidosis will decrease serum potassium concentration 1
- Begin potassium replacement once serum levels fall below 5.5 mEq/L, assuming adequate urine output 1
- Monitor for signs of fluid overload, especially in elderly patients who may have compromised cardiac function 4
- Monitor ionized calcium as bicarbonate therapy can decrease serum ionized calcium 5
Potential Complications to Watch For
- Overly rapid correction of acidosis can lead to paradoxical central nervous system acidosis and cerebral edema 4
- The maximum rate of reduction in serum osmolality should not exceed 3 mOsm/kg/hr to prevent cerebral edema 4
- Bicarbonate administration can cause sodium and fluid overload, especially in elderly patients 2
- Hypokalemia may develop during treatment as potassium shifts into cells with correction of acidosis 5
Special Considerations for This Patient
- At age 71, this patient may have reduced renal function, which could affect acid-base balance recovery 6
- The underlying cause of metabolic acidosis should be identified and treated simultaneously, as this is the definitive treatment 7
- If the patient has concomitant hyperkalemia, sodium bicarbonate administration can help shift potassium into cells 4
- For this patient with pH 7.04 and HCO3 of 12, bicarbonate therapy is indicated based on the American Diabetes Association guidelines 1, 2
Common Pitfalls to Avoid
- Avoid overzealous bicarbonate therapy which can lead to metabolic alkalosis 3
- Do not attempt full correction of low total CO2 content during the first 24 hours of therapy 3
- Do not mix sodium bicarbonate with vasoactive amines or calcium 5
- Avoid rapid infusion of large quantities of bicarbonate as it can produce an undesirable rise in plasma sodium concentration 3