Introduction:
High anion gap metabolic acidosis (HAGMA) is a subtype of acidosis known as metabolic etiology acidosis. The condition's causes depend on the particular subtype, whether it is high anion gap metabolic acidosis or non-anion gap metabolic acidosis (NAGMA). The causes of metabolic acidosis are L-lactate, Oxoproline, glycols, Aspirin, D-lactate, methanol, ketones, and renal failures. Critical care patients notice the condition as one of the most common metabolic derangements. The symptoms of the high anion gap metabolic acidosis are generally non-specific. However, screening according to the symptoms expressed by acidosis can help diagnose the condition. The primary treatment of high anion acidosis includes correcting the underlying cause. Further, the treatment depends on the severity of the acidosis.
What Are the Causes of High Anion Gap Metabolic Acidosis?
The leading causes of high anion gap metabolic acidosis are GOLD MARK. The conditions which can lead to high anion gap metabolic acidosis are:
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Glycols: These include ethylene glycol and propylene glycol.
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Oxoproline Acidosis: pyroglutamic acid and the toxic metabolite of excessive Acetaminophen or Paracetamol.
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L-lactate: It is the standard lactic acid that is observed in cases of lactic acidosis.
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D-lactate: It is the exogenous lactic acid that is secreted by gut bacteria.
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Methanol: Alcohol is included with methanol is the cause of high anion gap acidosis.
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Aspirin is a blood-thinning agent that prevents coagulation and blockage in the blood vessels. One of the side effects of Aspirin consumption is high anion gap metabolic acidosis (HAGMA).
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Renal Failure: This is due to uremic acidosis, which may lead to HAGMA.
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Ketones: This may lead to diabetes, starvation, and alcoholic acidosis.
Metformin was earlier in the list and then got removed as there was insufficient evidence for metformin-induced lactic acidosis. A study review stated that Metformin did not cause lactic acidosis; however, the older ones, namely Biguanide and Phenformin, were observed to increase the incidences of lactic acidosis.
What Are the Symptoms Seen in High Anion Gap Metabolic Acidosis?
The symptoms reported in HAGMA (high anion gap metabolic acidosis) are not specific but depend on the underlying causes.
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Toxic ingestion or over ingestion of drugs like Aspirin or Acetaminophen may lead to acidosis.
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Polyuria: Excessive urination.
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Polydipsia: Feeling of extreme thirst even after drinking water.
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Polyphagia: Consumption of excessive amounts of food.
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Physical examination is also non-specific for the cases of metabolic acidosis. Kussmaul respirations can be noticed in patients with acidosis. It means deep, slow breaths instead of shallow rapid breathing.
How to Diagnose High Anion Gap Metabolic Acidosis?
As the symptoms are nonspecific in cases of high anion gap metabolic acidosis, it is crucial to recognize the essential chemistry value of the changes and the signs the patient shows.
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The most common method for investigating and evaluating high ion gap metabolic acidosis is the Henderson-Hasselbalch equation and the Lewis model interpretation of biological acidosis. It helps to evaluate the plasma concentration of the hydrogen ions.
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Another method in diagnosing metabolic acidosis is Strong Ion Difference (SID) which helps to describe acid-base abnormalities regarding the variations in the intense ions (sodium and chloride).
The equation to calculate the anion gap is: AG=Na - (Cl +HCO3)
Calculated osmolarity is: Osm = (2 x Na) + (BUN / 2.8) + (Blood Glucose / 18) + (EtOH / 3.7)
Osmolar Gap: OG = (Measured Osm) - (Calculated Osm).
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The largest single source of unmeasured anions in a healthy population group is albumin. Therefore, evaluating albumin is critical in diagnosing high anion gap metabolic acidosis.
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The evaluation depends on the underlying causes, such as a history of methanol, Aspirin, salicylic acid consumption, or excessive concentration of chemicals such as ketones and creatinine in the body.
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Some of the additional tests include venous or arterial blood gas, complete blood count, and urinalysis. In addition, it is also advised to undergo the evaluation of concomitant respiratory or metabolic disturbances.
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Electrocardiograms can help detect the changes caused by the abnormal electrolytes and help look for any iron ingestion or renal stones.
What Is the Treatment for High Anion Gap Metabolic Acidosis?
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The primary treatment for the high anion gap metabolic acidosis is correcting the underlying causes.
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In mild to moderate acidosis cases, the treatment can be limited to supportive measures, including intravenous fluids and respiratory support.
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In cases of severe acidosis, alkalization therapy is done. The pH in cases of severe acidosis should be less than 7.1.
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In cases of diabetic ketoacidosis, the pH is even less than 6.9, and the alkalizing agent is sodium bicarbonate. Sodium and potassium citrate can also be used as an alternative option.
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In cases of recalcitrant and severe acidosis, it is advised to treat with alcohol dehydrogenase inhibitors and prepare the patient for emergency hemodialysis. The alcohol dehydrogenase inhibitors used are Fomepizole and Ethanol. Fomepizole inhibits the conversion of alcohols onto toxic metabolites by the technique of competitive inhibition of alcohol dehydrogenase. However, Fomepizole cannot be used as a universal treatment of choice for metabolic acidosis; the drug is frequently in short supply and very expensive.
Which Conditions Are Similar to High Anion Gap Metabolic Acidosis?
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Diabetic Ketoacidosis: A severe condition of diabetes where the body produces a higher concentration of ketones. The symptoms are similar to high anion gap metabolic acidosis.
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Uraemia: Accumulation of toxins in the blood is known as uremia. This condition generally arises when the kidney cannot filter the toxins from the blood.
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Methanol.
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Salicylates.
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Lactate.
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Propylene glycol.
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Ethyl alcohol.
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Isoniazid.
Conclusion:
High anion gap metabolic acidosis is a condition caused due to toxicity in the body due to substances such as Aspirin. The disease has no symptoms but varies according to the underlying causes. Treating the condition by restoring the body's pH level is essential as it may cause several other diseases and conditions. The treatment of the disease involves the regulation of anions levels in the body.
