From the Guidelines
Treatment of high anion gap metabolic acidosis should focus on addressing the underlying cause, and in cases of ethylene glycol poisoning, extracorporeal treatment (ECTR) is recommended if the glycolate concentration is > 12 mmol/L or anion gap > 27 mmol/L, as suggested by the EXTRIP workgroup 1.
Identifying the Underlying Cause
To effectively manage high anion gap metabolic acidosis, it is crucial to identify and treat the specific etiology. This could involve:
- Diabetic ketoacidosis: insulin therapy plus fluid resuscitation with normal saline
- Lactic acidosis: treating shock, infection, or tissue hypoperfusion
- Toxic ingestions: specific antidotes like fomepizole for methanol/ethylene glycol
- Renal failure: dialysis if severe
Role of Extracorporeal Treatment (ECTR)
In the context of ethylene glycol poisoning, ECTR is a critical component of treatment. The EXTRIP workgroup provides recommendations for the use of ECTR based on various criteria, including:
- EG concentration
- Osmol gap
- Glycolate concentration
- Anion gap
- Clinical indications such as coma, seizures, or acute kidney injury
Recommendations for ECTR
The EXTRIP workgroup recommends ECTR in the following scenarios:
- Glycolate concentration > 12 mmol/L
- Anion gap > 27 mmol/L
- EG concentration > 50 mmol/L when fomepizole or ethanol is used
- Osmol gap > 50 when fomepizole or ethanol is used
- Severe clinical features such as coma, seizures, or acute kidney injury
Modality and Cessation of ECTR
The workgroup suggests using intermittent hemodialysis as the preferred modality for ECTR, and recommends stopping ECTR when the anion gap is < 18 mmol/L or the EG concentration is < 4 mmol/L 1.
Supportive Care
Supportive care is essential in the management of high anion gap metabolic acidosis and includes:
- Careful fluid management
- Electrolyte replacement, particularly potassium
- Ventilatory support if needed for respiratory compensation
- Continuous monitoring of arterial blood gases, electrolytes, and clinical status to guide therapy
By addressing the underlying cause and following the recommendations for ECTR and supportive care, clinicians can effectively manage high anion gap metabolic acidosis and improve patient outcomes.
From the FDA Drug Label
Treatment Guidelines If ethylene glycol or methanol poisoning is left untreated, the natural progression of the poisoning leads to accumulation of toxic metabolites, including glycolic and oxalic acids (ethylene glycol intoxication) and formic acid (methanol intoxication) These metabolites can induce metabolic acidosis, nausea/vomiting, seizures, stupor, coma, calcium oxaluria, acute tubular necrosis, blindness, and death. Treatment consists of blocking the formation of toxic metabolites using inhibitors of alcohol dehydrogenase, such as fomepizole injection, and correction of metabolic abnormalities In patients with high ethylene glycol or methanol concentrations (> 50 mg/dL), significant metabolic acidosis, or renal failure, hemodialysis should be considered to remove ethylene glycol or methanol and the respective toxic metabolites of these alcohols Hemodialysis should be considered in addition to fomepizole injection in the case of renal failure, significant or worsening metabolic acidosis, or a measured ethylene glycol or methanol concentration of greater than or equal to 50 mg/dL. Laboratory Tests In addition to specific antidote treatment with fomepizole, patients intoxicated with ethylene glycol or methanol must be managed for metabolic acidosis, acute renal failure (ethylene glycol), adult respiratory distress syndrome, visual disturbances (methanol), and hypocalcemia. Fluid therapy and sodium bicarbonate administration are potential supportive therapies
Treating high anion gap metabolic acidosis due to ethylene glycol or methanol poisoning involves:
- Blocking the formation of toxic metabolites using inhibitors of alcohol dehydrogenase, such as fomepizole injection
- Correction of metabolic abnormalities
- Consideration of hemodialysis in patients with significant metabolic acidosis, renal failure, or high ethylene glycol or methanol concentrations
- Supportive therapies, including fluid therapy and sodium bicarbonate administration, to manage metabolic acidosis and other complications 2 2
From the Research
Treating High Anion Gap Metabolic Acidosis
- High anion gap metabolic acidosis can be caused by various disorders, including diabetic or alcoholic ketoacidosis, acute kidney injury, chronic kidney disease, and lactic acidosis 3
- The diagnosis of high anion gap metabolic acidosis often involves calculating the anion gap and osmolal gap, as well as considering the patient's history and physical exam 4
- In some cases, the anion gap may be normal, even in the presence of ethylene glycol poisoning, due to concurrent ethanol ingestion 5
- Treatment of high anion gap metabolic acidosis may involve the use of fomepizole and ethanol to inhibit alcohol dehydrogenase, as well as hemodialysis to remove toxic metabolites 6
Diagnostic Approach
- The anion gap is a helpful calculation that divides metabolic acidoses into two categories: high anion gap metabolic acidosis and hyperchloremic metabolic acidosis 7
- Calculating the osmolal gap can also provide important clues for diagnosis, particularly in cases of ethylene glycol or methanol poisoning 3, 6
- It is essential to consider the patient's history, physical exam, and laboratory results when diagnosing and treating high anion gap metabolic acidosis 4, 7