Management of Metabolic Acidosis
Primary Management Principle
Treatment of metabolic acidosis must be directed at the underlying cause rather than routine bicarbonate administration, as sodium bicarbonate has not demonstrated mortality benefit in most acute organic acidoses and may worsen intracellular acidosis. 1, 2
Initial Assessment and Monitoring
Immediately assess serum electrolytes, particularly potassium levels, as acidosis causes transcellular potassium shift leading to hyperkalemia. 1, 2
- Measure arterial blood gas to determine pH, PaCO2, and confirm metabolic acidosis (pH <7.35, bicarbonate <22 mmol/L) 3
- Calculate the anion gap to differentiate between high anion gap (endogenous acid accumulation) and normal anion gap (bicarbonate loss) metabolic acidosis 4
- Monitor blood gases, plasma osmolarity, arterial lactate, hemodynamics, and cardiac rhythm during treatment 5
Etiology-Based Treatment Algorithm
Diabetic Ketoacidosis (DKA)
Focus treatment on insulin therapy, fluid resuscitation, and electrolyte replacement—NOT bicarbonate. 1, 2
- Continuous intravenous insulin is the standard of care for critically ill and mentally obtunded DKA patients 1
- Restoration of circulatory volume and tissue perfusion is the primary goal 1
- Bicarbonate administration has NOT been shown to improve resolution of acidosis or time to discharge in DKA 1
- Bicarbonate should only be considered if pH < 6.9 (Grade C recommendation), with 1-2 mEq/kg IV given slowly in children 1
- Successful transition from IV to subcutaneous insulin requires basal insulin administration 2-4 hours before stopping IV insulin 1
Chronic Kidney Disease (CKD)-Associated Acidosis
Treat when serum bicarbonate is consistently <18 mmol/L to prevent bone and muscle metabolism abnormalities. 1, 2
Treatment algorithm based on bicarbonate levels: 3
- Bicarbonate ≥22 mmol/L: Monitor without pharmacological intervention, check monthly 1, 3
- Bicarbonate 18-22 mmol/L: Consider oral alkali supplementation (2-4 g/day or 25-50 mEq/day sodium bicarbonate) with or without dietary intervention 1, 3
- Bicarbonate <18 mmol/L: Initiate pharmacological treatment with oral sodium bicarbonate 1, 3, 2
Target maintenance is serum bicarbonate ≥22 mmol/L at all times. 1, 3
Benefits of correction include: 1, 3
- Increased serum albumin and decreased protein degradation rates
- Reduced muscle wasting and malnutrition
- Prevention of bone demineralization and improved bone histology
- Slowed CKD progression
- Normal growth parameters in children with renal tubular acidosis
Avoid citrate alkali salts in CKD patients exposed to aluminum salts, as they increase aluminum absorption. 1
Sepsis-Related Acidosis
Prioritize fluid resuscitation and vasopressors over bicarbonate. 2
- Sodium bicarbonate should NOT be used to treat metabolic acidosis from tissue hypoperfusion in sepsis 3
- Focus on restoring tissue perfusion rather than correcting pH 3
- The effectiveness of sodium bicarbonate in septic shock is uncertain, and acidosis may have protective effects 3
Severe Malaria in Children
Volume resuscitation with 20-40 ml/kg of 0.9% saline or 4.5% human albumin solution safely corrects hemodynamic features. 1, 2
- Metabolic acidosis resolves with correction of hypovolemia and treatment of anemia by adequate blood transfusion 1
- No evidence supports sodium bicarbonate use 1
- Human albumin solution should be considered the resuscitation fluid of choice in children presenting with coma and shock 1
Lactic Acidosis
The only effective treatment for organic acidosis is cessation of acid production via improvement of tissue oxygenation. 4
- Treatment with sodium bicarbonate has failed to reduce morbidity and mortality despite improvement in acid-base parameters 4
- Bicarbonate-containing solutions are preferred over lactate in CRRT patients with lactic acidosis and/or liver failure 1
Severe Metabolic Acidosis Management
Indications for Hemodialysis
Hemodialysis is the definitive treatment for patients with severe acidosis (pH <7.20) and acute kidney injury, as it simultaneously corrects acidemia, removes uremic toxins, and manages volume status. 1
- Dialysis should NOT be delayed while attempting medical management, as acidosis is refractory to conservative measures with this degree of renal impairment 1
- Patients require ICU-level care with nephrology consultation for urgent dialysis 1
- Once stabilized, maintain serum bicarbonate ≥22 mmol/L through dialysate bicarbonate concentration adjustment 1
Cardiac Arrest
In cardiac arrest, a rapid intravenous dose of one to two 50 mL vials (44.6 to 100 mEq) may be given initially and continued at 50 mL every 5-10 minutes if necessary. 5
- The risks from acidosis exceed those of hypernatremia in cardiac arrest 5
- Monitor with arterial pH and blood gas measurements 5
Sodium Bicarbonate Administration Guidelines
Dosing for Less Urgent Metabolic Acidosis
For older children and adults, administer approximately 2-5 mEq/kg body weight over 4-8 hours, depending on severity. 5
- Initially infuse 2-5 mEq/kg over 4-8 hours to produce measurable improvement 5
- It is unwise to attempt full correction of low total CO2 during the first 24 hours, as this may be accompanied by unrecognized alkalosis due to delayed readjustment of ventilation 5
- Target total CO2 of approximately 20 mEq/L at the end of the first day 5
- Values brought to normal or above normal within the first day are very likely associated with grossly alkaline blood pH 5
Monitoring During Bicarbonate Therapy
Therapy should always be planned in a stepwise fashion, as the degree of response from a given dose is not precisely predictable. 5
- Measure arterial or venous blood gases to assess treatment response 1, 3
- Monitor for hypokalemia, as acidosis correction shifts potassium intracellularly and can cause life-threatening hypokalemia 2
- Check blood pressure, serum potassium, and fluid status regularly 3
Common Pitfalls to Avoid
Recognize that bicarbonate administration may worsen intracellular acidosis, reduce ionized calcium, and produce hyperosmolality. 1, 2
- Avoid furosemide unless hypervolemia, hyperkalemia, and/or renal acidosis are present 1, 2
- Avoid dopamine in an attempt to improve renal function 1, 2
- Avoid hypotonic fluids (glucose solutions) for fluid resuscitation 1, 2
- Do not use bicarbonate routinely in organic acidoses (lactic acidosis, ketoacidosis) unless pH <6.9-7.0 1, 3, 2
- Be cautious with sodium bicarbonate in patients with advanced heart failure with volume overload, severe uncontrolled hypertension, or significant edema 3
Special Populations
Maintenance Dialysis Patients
Maintain serum bicarbonate at or above 22 mmol/L. 1
- Monitor serum bicarbonate levels monthly 1
- Use higher dialysate bicarbonate concentrations (38 mmol/L) combined with oral supplementation if needed 3
Pediatric Patients with CKD
Pediatric clinicians may choose to treat milder acidosis (bicarbonate >18 mmol/L) more aggressively to optimize growth and bone health. 3
- Chronic metabolic acidosis can cause growth retardation in children 3
- Normalization of serum bicarbonate is important for normal growth parameters in children with renal tubular acidosis 1
Compensated Chronic Respiratory Acidosis
The elevated bicarbonate is protective and should NOT be treated directly, as it is maintaining normal pH and is physiologically appropriate. 3