From the Guidelines
The treatment of metabolic acidosis should prioritize addressing the underlying cause, with a focus on fluid replacement, insulin therapy for diabetic ketoacidosis, and careful consideration of bicarbonate use, as its effectiveness is debated and generally not recommended in diabetic ketoacidosis, as shown in recent studies 1.
Key Considerations
- Identify and treat the primary condition causing the acidosis, whether it's diabetic ketoacidosis, lactic acidosis, renal failure, or toxic ingestion.
- For diabetic ketoacidosis, provide IV fluids (normal saline at 15-20 mL/kg/hr initially), insulin (0.1 units/kg/hr), and potassium replacement, with the goal of gradual normalization of pH and electrolyte balance.
- The use of bicarbonate in patients with diabetic ketoacidosis has been shown to make no significant difference in the resolution of acidosis or time to discharge, and its use is generally not recommended 1.
Management Approach
- In critically ill and mentally obtunded patients with diabetic ketoacidosis or hyperosmolar hyperglycemia, continuous intravenous insulin is the standard of care.
- Successful transition from intravenous to subcutaneous insulin requires administration of basal insulin 2–4 h before the intravenous insulin is stopped to prevent recurrence of ketoacidosis and rebound hyperglycemia 1.
- For lactic acidosis, focus on improving tissue perfusion with fluids and vasopressors if necessary, and in cases of renal failure, initiate dialysis when conventional therapy fails.
Monitoring and Adjustment
- Maintain adequate ventilation to prevent respiratory compensation failure.
- Monitor electrolytes closely, especially potassium, which may drop during treatment.
- Reassess acid-base status regularly with arterial blood gases to guide the adjustment of treatment.
- The goal is to gradually normalize pH rather than correct it rapidly, as overcorrection can lead to metabolic alkalosis and other complications.
From the FDA Drug Label
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 a rate of 50 mL (44. 6 to 50 mEq) every 5 to 10 minutes if necessary (as indicated by arterial pH and blood gas monitoring) to reverse the acidosis. In less urgent forms of metabolic acidosis, Sodium Bicarbonate Injection, USP may be added to other intravenous fluids The amount of bicarbonate to be given to older children and adults over a four-to-eight-hour period is approximately 2 to 5 mEq/kg of body weight - depending upon the severity of the acidosis as judged by the lowering of total CO2 content, blood pH and clinical condition of the patient Bicarbonate therapy should always be planned in a stepwise fashion since the degree of response from a given dose is not precisely predictable Initially an infusion of 2 to 5 mEq/kg body weight over a period of 4 to 8 hours will produce a measurable improvement in the abnormal acid-base status of the blood.
The algorithm to treat metabolic acidosis involves:
- Initial dose: 1-2 vials (44.6-100 mEq) in cardiac arrest, or 2-5 mEq/kg body weight over 4-8 hours in less urgent cases 2
- Monitoring: arterial pH, blood gas, and clinical condition to guide further therapy
- Stepwise approach: adjust dose and frequency based on clinical response, aiming for a measurable improvement in acid-base status without overcorrection
- Caution: avoid full correction of low total CO2 content during the first 24 hours to prevent unrecognized alkalosis 2
From the Research
Treatment of Metabolic Acidosis
The treatment of metabolic acidosis is a complex process that involves addressing the underlying cause of the condition.
- The use of sodium bicarbonate to treat metabolic acidosis is controversial, as it may not reduce morbidity or mortality, and can even exacerbate intracellular acidosis 3, 4, 5.
- In some cases, the administration of base, such as tris(hydroxymethyl)aminomethane (THAM), may be beneficial in improving acidosis without producing intracellular acidosis 5.
- Selective sodium-hydrogen exchanger 1 (NHE1) inhibitors have also been shown to improve hemodynamics and reduce mortality in animal studies of acute lactic acidosis 5.
- The calculation of the serum anion gap can aid in the diagnosis and treatment of metabolic acidosis, by classifying the disorder into categories of normal (hyperchloremic) anion gap or elevated anion gap 4, 6.
Approach to Metabolic Acidosis
The approach to metabolic acidosis in the emergency department should focus on treating the underlying condition, rather than just the acid-base disorder itself.
- A good understanding of normal acid-base regulation in the body, as well as the most common derangements, can prepare the emergency physician for this common disorder 7.
- The treatment of metabolic acidosis should be individualized, taking into account the underlying cause of the condition, as well as the patient's overall clinical status 3, 4, 5, 6.
Algorithm for Treatment
The algorithm for treating metabolic acidosis involves the following steps: