Recent advances have led to a new mnemonic gold mark to differentiate the various causes of anion gap metabolic acidosis. In addition to high anion gap metabolic acidosis and severe ketoacidosis with low levels of glucose, our patient had an elevated serum osmolal gap, findings generally characteristic of intoxication with one of the toxic alcohols methanol, ethylene glycol, diethylene glycol, or propylene glycol 1012. Other causes include hypernatremia, certain gammopathies myeloma, and severe hypercalcemia. Metabolic acidosis is primary reduction in bicarbonate hco 3. However, the serum ag can also become abnormal in other conditions, a finding that may be of diagnostic importance 15. A recent article in ajkd by vichot and rastegar discusses the use of anion gap in metabolic acidosis. Acidbase balance and the anion gap iu school of medicine. Serum bicarbonate and dehydration severity in gastroenteritis. There are two problems in the definition of this type of metabolic acidosis which can cause confusion. Frequent causes of high anion gap metabolic acidosis hagma are lactic acidosis, ketoacidosis and impaired renal function. A high anion gap suggests metabolic acidosis ketoacidosis, lactic acidosis. Our patients anion gap and acidosis resolved, and after a few days of treatment and counseling, she was discharged in stable condition and returned home. Pdf relationship between serum anion gap and diabetes. The causes of metabolic acidosis, both high anion gap and normal anion gap varieties, are shown in box 2.
The classic mnemonic often used to remember the causes of anion gap metabolic acidosis is mudpiles d diabetic ketoacidosis. Relationship between serum anion gap and diabetes mellitus article pdf available in journal of diabetes mellitus 0504. Clinical chemistry, immunology and laboratory quality control, 2014. High anion gap metabolic acidosis hagma is a subcategory of acidosis of. Normal anion gap metabolic acidosis is also called hyperchloremic acidosis because the kidneys reabsorb chloride cl. Acidbase disorders knowledge for medical students and. It is an infrequent form of metabolic acidosis and accounts to only one to three percent of all cases. Clinically, non anion gap acidosis is associated with diarrhea, renal failure, parenteral nutrition, and ureterosigmoidostomy. The most common acidbase disorder is metabolic acidosis, especially in the inpatient setting, characterized by an increase in hydrogen ion concentration, decrease in serum bicarbonate concentration, and a compensatory reduction in pa co 2. In hyperchloraemic acidosis, the anion gap is normal in most cases. Because of fatty acid metabolism, organic acids and. Low anion gap a low anion gap is frequently caused by hypoalbuminemia. The most common causes are the accumulation of lactate, ketones, urea and. Every one gram decrease in albumin will decrease anion gap by 2.
Toxic alcohols minding the gaps emergency medicine cases. A normally high anion gap acidosis in a patient with hypoalbuminaemia may appear as a normal anion gap acidosis. The anion gap is primarily used to determine the cause of metabolic acidosis, a condition where the body is producing too much acid or not enough acid is being removed from the body. Cyclic vomiting is a disorder, which occurs at any age group. This concept is illustrated in the image to the right. Hypobicarbonatemia, or a reduced bicarbonate concentration in plasma, is a finding seen in 3 acidbase disorders.
Suspect in any patient with a non anion gap acidosis, very low serum hco3 and a urine ph that is inappropriately high above 5. In uncontrolled diabetes, there is an increase in ketoacids due to metabolism of ketones. The difference between measur able cations and anions, known as anion gap, helps to classify the severity of acidosis. Volatile acid co2 and nonvolatile acids, lactate, h2po4, h 2co3 2. The normal range fo r the serum anion gap is rela tively. Download as pptx, pdf, txt or read online from scribd. Pdf metabolic acidosis is characterized by a primary reduction in serum bicarbonate hco3. Metabolic acidosis occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body. Need to have an unexplained non anion gap metabolic acidosis i.
Bicarbonate anion gap indicates a pure non anion gap metabolic acidosis nagma. The anion gap is the difference between certain measured cations positively charged ions and the measured anions negatively charged ions in serum, plasma, or urine. Anion gap is defined as the difference between measured cations sodium and potassium and anions chloride and bicarbonate in serum. Metabolic acidoses are categorized as high or normal anion gap based on the presence or absence of unmeasured anions in serum. In one study, 50% of patients with a serum lactate level of 5 to 10 mmol per liter did not have an elevated anion gap. Anion gap is subdivided into levels depending on the symptoms and cause. Aug 25, 2014 the serum anion gap is a common tool used in clinical practice. Results from excessive accumulation of fixed acid as in ketoacidosis, lactic acidosis, late salicylate poisoning, and methanol or ethylene toxicity. The list below details some potential causes of metabolic acidosis that is associated with a high anion gap.
Metabolic acidosis endocrine and metabolic disorders. Symptoms that i believe were from acidosis were very sore muscles, my eyes burned and felt dry, my throat burned and felt dry, good old fatigue, and im not sure what else. Raised anion gap suggests there is an unmeasured anion responsible for a metabolic acidosis, eg lactate, ketones, urate, acid poisoning. The anion that replaces the titrated bicarbonate is chloride and because this is accounted for in the anion gap formula, the anion gap is normal. Nonaniongap metabolic acidosis nagma emcrit project. The anion of the acid is an unmeasured anion ua and will thus increase the anion gap. Acid levels that are higher or lower than normal can tip your doctor off to a health problem and help them find the right treatment for you.
Metabolic acidosis can be divided into high anion and normal anion gap varieties, which can be present alone or. Metabolic acidosis associated with a normal anion gap can occur from the loss of bicarbonate and the retention of the chloride ion hyperchloremic metabolic acidosis. Oct 15, 2015 the decrease in serum bicarbonate concentration is usually absent until glomerular filtration rate decreases to anion gap can be readily calculated from routine laboratory data, and although it has its widest application in the diagnosis of various forms of metabolic acidosis, 1, 2 it may sometimes. Clinically, a highaniongap metabolic acidosis may reflect.
Anion gap acidosis associated with acetaminophen annals of. Case one a 63yearold caucasian woman was admitted to the icu with a nineday history of lethargy, breathlessness and confusion. Metabolic acidosis and approach linkedin slideshare. Acidosis with an increased anion gap has been found more often in infants with prolonged diarrhoea and underlying malnutrition,2 but this study excluded these children. When the anion gap is raised, an additional anion must be present. Albumin is the major unmeasured anion and contributes almost the whole of the value of the anion gap. Metabolic acidosis is commonly separated into high anion gap and non anion gap acidoses, representing a condition of either reduced acid excretion. Jul 24, 2019 subsequently, a urine sample was sent for organic acid analysis, which revealed a large elevation of pyroglutamate 5oxoproline, thus confirming the diagnosis. Cvs is a repetitive nausea and vomiting, which lasts more than one hour and in between the patient is free. Metabolic acidosis is a common acidbase disorder that can occur acutely lasting minutes to several days or chronically lasting weeks to.
Similar findings were also observed in a further five patients with high anion gap acidosis of unknown origin with increases in isocitrate 0. The anion gap ag is visually shown to be the difference between the unmeasured anions ua and the unmeasured cations uc. The anion gap can be readily calculated from routine laboratory data, and although it has its widest application in the diagnosis of various forms of metabolic acidosis,1, 2 it may sometimes provi. Apr 16, 2016 using the anion gap to distinguish between basic causes of metabolic acidosis. Diagnosis is made by arterial blood gas interpretation. Metabolic acidosis occurs when the body produces too much acid. It is generally accepted that conditions with a normal anion gap are due to bicarbonate loss, for example, renal tubular acidosis or excess gut losses. The normal anion gap depends on serum phosphate and serum albumin concentrations. The acidosis showed up on bloodwork as an anion gap that was above range mine hit 20 at the high end. Determining if a patients acidosis also has an elevated anion gap. A normal anion gap does not rule out lactic acidosis. A low anion gap is usually caused by hypoalbuminemia, a decrease in albumin in the. Nov 07, 2000 anion gap acidosis associated with acetaminophen. Mar 23, 2010 metabolic acidosis is a common acidbase disorder that can occur acutely lasting minutes to several days or chronically lasting weeks to years.
High anion gap metabolic acidosis statpearls ncbi bookshelf. The diagnosis of nagma may be made in one of two ways red arrows abovepatient has normal anion gap with metabolic acidosis bicarbonate anion gap metabolic acidosis, but the decrease in bicarbonate is much greater than the elevation in anion gap indicating the combination of an anion gap metabolic acidosis plus a non anion gap metabolic acidosis. The following questions will test your knowledge on this. Diagnosis of metabolic acidbase disorders emcrit project. Comparison of normal anion gap acidoses finding type 1 rta type 2 rta type 4 rta gi bicarbonate normal anion gap acidosis yes yes yes yes loss minimum urine ph 5. These conditions can be categorized as acidoses or alkaloses and have a respiratory or metabolic origin, depending on the cause of the imbalance. More recently a new mnemonic has been suggested to update new our understanding of aniongap generating. The most common application of the anion gap is classifying cases of metabolic acidosis, states of lower than. Anion gap acidoses have a very different differential diagnosis than nongap acidoses. Use of sodium concentration and anion gap to improve correlation.
If the anion gap is normal, and all of the change has occurred in the chloride bicarbonate proportions, then the numerator will be low and the denominator will be high so a normal anion gap acidosis produces a delta ratio acidosis from. The anion gap is affected by changes in unmeasured ions. As bicarbonate and chloride anions are used to calculate the anion gap, there is a subsequent decrease in the gap. Rationale although most clinical data are prospective, they are scarce and observational. A work up to investigate the cause of high anion gap metabolic acidosis was pursued. Unusual dlactic acid acidosis from propylene glycol metabolism in overdose. Guidelines for the management of metabolic acidosis by dr. See approach to the adult with metabolic acidosis, section on physiologic interpretation of the serum anion gap.
Acidosis is therefore most likely to be due to bicarbonate losses in diarrhoeic stools,3 4 the estimation of which is difficult and was not carried out in this study. Quantitative displacement of acidbase equilibrium in metabolic acidosis. Albumin is a negatively charged protein and its loss from the serum results in the retention of other negatively charged ions such as chloride and bicarbonate. Acidosis is defined as an arterial ph below the normal range acidosis is a manifestation of an underlying. Engelking, in textbook of veterinary physiological chemistry third edition, 2015. Although such categorization is useful, some disorders, such as. Our patients metabolic acidosis mainly normal anion gap acidosis from gut losses adequate replacement needed mainly in tpn, as gi absorption. In the acidbase literature, a nomenclature has evolved that confused many experienced clinicians. Hypoalbuminemia is the most common cause of a low anion gap. Methanol is commonly found in windshieldwiper fluid and deicing.
Hypobicarbonatemia due to chronic respiratory alkalosis is often misdiagnosed as a metabolic acidosis and mistreated with the administration of alkali therapy. A low anion gap includes a measurement of less than three meql. We now have an abg analyzer to help with acidbase analysis as well. Clinical aspects of the anion gap acute care testing. This utility of the anion gap is based on the notion that in cases of pure increased anion gap, metabolic acidosis lactic acidosis, diabetic ketoacidosis, etc. Review of the diagnostic evaluation of normal anion gap metabolic. The toxic alcohols are methanol and ethylene glycol, which can both cause a scary anion gap metabolic acidosis in the first group and ethanol and isopropyl alcohol which arent quite as scary and generally dont cause a big anion gap metabolic acidosis in the second group. Most relevant is the lack of insulin leading to lipolysis release of free. Dec 16, 2019 the anion gap is primarily used to determine the cause of metabolic acidosis, a condition where the body is producing too much acid or not enough acid is being removed from the body. If the anion gap is 30 meql, then metabolic acidosis is present regardless of other findings. Anion gap definition of anion gap by the free dictionary.
Albumin is a negatively charged protein, and thus hypoalbuminemia falsely lowers the anion gap. To access free multiple choice questions on this topic, click here. Blood ph is described by the hendersonhasselbalch equation 3. High anion gap metabolic acidosis is a form of metabolic acidosis characterized by a high anion gap a medical value based on the concentrations of ions in a patients serum. This is commonly in the form of lactate or ketones, acetoacetate and 3hydroxynbutyrate. Paracetamol use and high anion gap metabolic acidosis. See more ideas about anion gap, gap and metabolic acidosis. I say that the patient has a primary metabolic acidosis with a concurrent respiratory acidosis, because the patient has an elevated anion gap metabolic acidosis, and using winters formula, the pco2 should be 24. The anion gap test tells you how much acid is in your blood. Her aspartate transaminase ast was within normal limits at 52 ul and her alanine transaminase alt was very slightly elevated at 69 ul. Diagnosing metabolic acidosis in the critically ill. Raised levels of acid bind to bicarbonate to form carbon dioxide through the hendersonhasselbalch equation resulting in metabolic acidosis.
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