Anion Gap: Reference Range, Interpretation, Collection And Panels
The anion gap is the difference between primary measured cations (sodium Na+ and potassium K+) and the primary measured anions (chloride Cl- and bicarbonate HCO3-) in serum. This test is most commonly performed in patients who present with altered mental status, unknown exposures, acute renal failure, and acute illnesses. [ 1 ] See the Anion Gap calculator. The reference range of the anion gap is 3-11 mEq/L The normal value for the serum anion gap is 8-16 mEq/L. However, there are always unmeasurable anions, so an anion gap of less than 11 mEq/L using any of the equations listed in Description is considered normal. For the urine anion gap, the most prominently unmeasured anion is ammonia. Healthy subjects typically have a gap of 0 to slightly normal (< 10 mEq/L). A urine anion gap of more than 20 mEq/L is seen in metabolic acidosis when the kidneys are unable to excrete ammonia (such as in renal tubular acidosis). If the urine anion gap is zero or negative but the serum AG is positive, the source is most likely gastrointestinal (diarrhea or vomiting). [ 2 ] The anion gap (see the Anion Gap calculator) can be defined as low, normal, or high. Laboratory error always needs to be ruled out first if the clinical picture does not correlate with the findings. Thus, if the results are questionable, re-assessing the electrolytes is the encouraged first step. Certain errors in collection can interfere with the ions of measured electrolytes that are used to calculate the anion gap. This can include timing, dilution, renal disease, and small sample size. For example, delays in processing the collected sample results in continued leukocyte cellular metabolism, which then causes an increase in bicarbonate levels. [ 3 ] If the anion gap is found to be high, other tests such as urine Continue reading >>
Anion Gap (blood) - Health Encyclopedia - University Of Rochester Medical Center
If you may have swallowed a poison, such as wood alcohol, salicylate (in aspirin), and ethylene glycol (in antifreeze), your provider may test your blood for it. If your provider thinks you have ketoacidosis, you might need a urine dipstick test for ketone compounds. Ketoacidosis is a health emergency. Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider. Results are given in milliequivalents per liter (mEq/L). Normal results are 3 to 10mEq/L, although the normal level may vary from lab to lab. If your results are higher, it may mean that you have metabolic acidosis. Hypoalbuminemia means you haveless albumin protein than normal. If you have this condition, your expected normal result must be lower. The test requires a blood sample, which is drawn through a needle from a vein in your arm. Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore. Being dehydrated or retaining water in your body can affect your results. Antibiotics such as penicillin can also affect your results. You don't need to prepare for this test. But be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use. Continue reading >>
Review Of The Diagnostic Evaluation Of Normal Anion Gap Metabolic Acidosis
Acid-Base, Electrolyte and Fluid Alterations: Review Review of the Diagnostic Evaluation of Normal Anion Gap Metabolic Acidosis I have read the Karger Terms and Conditions and agree. I have read the Karger Terms and Conditions and agree. Buy a Karger Article Bundle (KAB) and profit from a discount! If you would like to redeem your KAB credit, please log in . Save over 20% compared to the individual article price. Buy Cloud Access for unlimited viewing via different devices Access to all articles of the subscribed year(s) guaranteed for 5 years Unlimited re-access via Subscriber Login or MyKarger Unrestricted printing, no saving restrictions for personal use * The final prices may differ from the prices shown due to specifics of VAT rules. For additional information: Background: Normal anion gap metabolic acidosis is a common but often misdiagnosed clinical condition associated with diarrhea and renal tubular acidosis (RTA). Early identification of RTA remains challenging for inexperienced physicians, and diagnosis and treatment are often delayed. Summary: The presence of RTA should be considered in any patient with a high chloride level when the CL-/Na+ ratio is above 0.79, if the patient does not have diarrhea. In patients with significant hyperkalemia one should evaluate for RTA type 4, especially in diabetic patients, with a relatively conserved renal function. A still growing list of medications can produce RTA. Key Messages: This review highlights practical aspects concerning normal anion gap metabolic acidosis. Berend K, de Vries AP, Gans RO: Physiological approach to assessment of acid-base disturbances. N Engl J Med 2015;372:195. Kraut JA, Madias NE: Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol 2007;2:162-174. Roberts WL Continue reading >>
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Metabolic Acidosis; Gap Positive
Metabolic acidosis is defined by low serum pH (less than 7.35-7.45) and low serum bicarbonate. It occurs by one of three major mechanisms: 1. Increased endogenous acid (i.e., lactic acidosis, diabetic ketoacidosis). 2. Decreased renal acid excretion (i.e., renal failure). In determining the underlying etiology for a metabolic acidosis, the serum anion gap must be calculated by subtracting the major measured anions (chloride and bicarbonate) from the major measured cation (sodium). If the result is greater than 12 meq/L (which is the normal value for most laboratories), the acidosis is said to be an anion gap acidosis. The expected anion gap should is lower in hypoalbuminemia and should be corrected - for each decrease of 1gm/dl in albumin, the normal anion gap should be decreased by approximately 2.5 meq/L. A. What is the differential diagnosis for this problem? Anion gap acidosis can be the result from: 1. A fall in unmeasured cations (as seen in hypomagnesemia or hypocalcemia). The most common reasons for a rise in anions are ingestions, lactic acidosis, ketoacidosis and renal failure. Ingestions of multiple different toxins can result in unmeasured anions causing a metabolic gap acidosis. Most commonly salicylate and the alcohols (methanol and ethylene glycol) can lead to severe acidosis. The inhalant toluene may also be a culprit. Lactic acidosis is the most common cause of an elevated anion gap acidosis in hospitalized patients, occurring with decreased perfusion causing relative tissue ischemia. This leads to increased lactic acid production and impaired renal excretion with resultant acid accumulation (Type A lactic acidosis). Type B lactic acidosis occurs in patients without overt tissue and can be seen in diabetics on metformin, patients with hematologic and s Continue reading >>
Normal Anion Gap Acidosis
Terry W. Hensle, Erica H. Lambert, in Pediatric Urology , 2010 Nonanion gap acidosis occurs in situations in which HCO3 is lost from the kidney or the gastrointestinal tract or both. When this occurs, Cl (along with Na+) is reabsorbed to replace the HCO3; this leads to the hyperchloremia, which leaves the anion gap in normal range.10 Diarrhea causes a hyperchloremic, hypokalemic metabolic acidosis. Treatment depends on the severity of the acidosis incurred. In mild to moderate acidosis (pH >7.2), fluid and electrolyte replacement is often all that is required. Once adequate renal perfusion is restored, excess H+ can be excreted efficiently, restoring the pH to normal. In severe acidosis (pH <7.2), the addition of intravenous bicarbonate may be needed to correct the metabolic deficit. Before bicarbonate is administered, a serum potassium level should be obtained. The addition of bicarbonate can worsen hypokalemia, leading to neuromuscular complications. Hyperchloremic acidosis also occurs with renal insufficiency and renal tubular acidosis.9,20 Katherine Ahn Jin, in Comprehensive Pediatric Hospital Medicine , 2007 As in any condition, the first priority in management is stabilizing the ABCs, as necessary. Management of metabolic acidosis is directed toward treating the underlying cause. In general, treating the causes of anion gap acidosis can regenerate bicarbonate within hours; however, nonanion gap acidosis can take days to resolve and may require exogenous bicarbonate therapy. Insulin, hydration, and electrolyte repletion will correct the acidosis in diabetic ketoacidosis. In addition to treating the underlying condition, lactic acidosis can be resolved by increasing tissue oxygenation using crystalloid, blood products, afterload reduction, inotropic agents (e.g., d Continue reading >>
Clinical Aspects Of The Anion Gap
The anion gap (AG) is a calculated parameter derived from measured serum/plasma electrolyte concentrations. The clinical value of this calculated parameter is the main focus of this article. Both increased and reduced anion gap have clinical significance, but the deviation from normal that has most clinical significance is increased anion gap associated with metabolic acidosis. This reflects the main clinical utility of the anion gap, which is to help in elucidating disturbances of acid-base balance. The article begins with a discussion of the concept of the anion gap, how it is calculated and issues surrounding the anion gap reference interval. CONCEPT OF THE ANION GAP - ITS DEFINITION AND CALCULATION Blood plasma is an aqueous (water) solution containing a plethora of chemical species including some that have a net electrical charge, the result of dissociation of salts and acids in the aqueous medium. Those that have a net positive charge are called cations and those with a net negative charge are called anions; collectively these electrically charged species are called ions. The law of electrochemical neutrality demands that, in common with all solutions, blood serum/plasma is electrochemically neutral so that the sum of the concentration of cations always equals the sum of the concentration of anions [1]. This immutable law is reflected in FIGURE 1, a graphic display of the concentration of the major ions normally present in plasma/serum. It is clear from this that quantitatively the most significant cation in plasma is sodium (Na+), and the most significant anions are chloride (Cl-) and bicarbonate HCO3-. The concentration of these three plasma constituents (sodium, chloride and bicarbonate) along with the cation potassium (K+) are routinely measured in the clinica Continue reading >>
Anion Gap
OVERVIEW Anion Gap = Na+ – (Cl- + HCO3-) The Anion Gap (AG) is a derived variable primarily used for the evaluation of metabolic acidosis to determine the presence of unmeasured anions The normal anion gap depends on serum phosphate and serum albumin concentrations An elevated anion gap strongly suggests the presence of a metabolic acidosis The normal anion gap varies with different assays, but is typically 4 to 12mmol/L (if measured by ion selective electrode; 8 to 16 if measured by older technique of flame photometry) If AG > 30 mmol/L then metabolic acidosis invariably present If AG 20-29mmol/L then 1/3 will not have a metabolic acidosis K can be added to Na+, but in practice offers little advantage ALBUMIN AND PHOSPHATE the normal anion gap depends on serum phosphate and serum albumin the normal AG = 0.2 x [albumin] (g/L) + 1.5 x [phosphate] (mmol/L) albumin is the major unmeasured anion and contributes almost the whole of the value of the anion gap. every 1g/L decrease in albumin will decrease anion gap by 0.25 mmoles a normally high anion gap acidosis in a patient with hypoalbuminaemia may appear as a normal anion gap acidosis. this is particularly relevant in ICU patients where lower albumin levels are common HIGH ANION GAP METABOLIC ACIDOSIS (HAGMA) HAGMA results from accumulation of organic acids or impaired H+ excretion Causes (LTKR) Lactate Toxins Ketones Renal Causes (CATMUDPILES) CO, CN Alcoholic ketoacidosis and starvation ketoacidosis Toluene Metformin, Methanol Uremia DKA Pyroglutamic acidosis, paracetamol, phenformin, propylene glycol, paraladehyde Iron, Isoniazid Lactic acidosis Ethylene glycol Salicylates Effects of albumin Anion gap may be underesitmated in hypoalbuminaemia, because if albumin decreased by 1g/L then the anion gap decreases by 0.25 Continue reading >>
Anion Gap - An Overview | Sciencedirect Topics
The anion gap (AG) is the difference between the sum of the commonly measured cations and the sum of the commonly measured anions in serum, calculated as follows:AG=([Na+]+[K+])([Cl]+[HCO3]). Larry R. Engelking, in Textbook of Veterinary Physiological Chemistry (Third Edition) , 2015 The plasma anion gap is normally accounted for by proteins and other organic acids in the anionic form, phosphates, and sulfate. Hypoproteinemia causes a decrease in the anion gap. Normochloremic metabolic acidosis is usually associated with an increase in the anion gap. The plasma anion gap may not change in hyperchloremic metabolic acidosis. The urinary anion gap can be used to estimate the urine NH4+ concentration. The urinary anion gap, which is usually positive, may be negative in diarrheal disease. The urinary anion gap may not provide meaningful information when the urinary bicarbonate concentration in increased, or when ketone bodies appear in urine. Non-hypoproteinemic metabolic alkalosis is associated with an increase in the anion gap. In Clinical Veterinary Advisor: The Horse , 2012 Because total cations equal total anions in the blood, the anion gap indirectly represents the difference between unmeasured anions and unmeasured cations (UA UC). In health, major unmeasured anions include albumin, phosphates, sulfates, and small organic acids; unmeasured cations include calcium, magnesium, and gamma globulins. The latter are rarely ever increased enough to decrease the anion gap. Lactic acidosis (lactate), uremic acids, ketoacids (acetoacetate, -hydroxybutyrate), and ethylene glycol and propylene glycol metabolites Next Diagnostic Step to Consider if Levels High Measure lactate concentrations, evaluate renal function (blood urea nitrogen [BUN], creatinine, and electrolytes with con Continue reading >>
Serum Anion Gap In Conditions Other Than Metabolic Acidosis
INTRODUCTION Determination of the serum anion gap (AG) is primarily used in the differential diagnosis of metabolic acidosis [1-4]. (See "Approach to the adult with metabolic acidosis", section on 'Physiologic interpretation of the serum anion gap'.) However, the serum AG can also become abnormal in other conditions, a finding that may be of diagnostic importance [1-5]. CALCULATION OF THE ANION GAP AND NORMAL VALUES The serum anion gap (AG) is calculated from the following formula: Serum AG = Measured cations - measured anions Since Na is the primary measured cation and Cl and HCO3 are the primary measured anions (calculator 1): Continue reading >>
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Approach To The Adult With Metabolic Acidosis
INTRODUCTION On a typical Western diet, approximately 15,000 mmol of carbon dioxide (which can generate carbonic acid as it combines with water) and 50 to 100 mEq of nonvolatile acid (mostly sulfuric acid derived from the metabolism of sulfur-containing amino acids) are produced each day. Acid-base balance is maintained by pulmonary and renal excretion of carbon dioxide and nonvolatile acid, respectively. Renal excretion of acid involves the combination of hydrogen ions with urinary titratable acids, particularly phosphate (HPO42- + H+ —> H2PO4-), and ammonia to form ammonium (NH3 + H+ —> NH4+) [1]. The latter is the primary adaptive response since ammonia production from the metabolism of glutamine can be appropriately increased in response to an acid load [2]. Acid-base balance is usually assessed in terms of the bicarbonate-carbon dioxide buffer system: Dissolved CO2 + H2O <—> H2CO3 <—> HCO3- + H+ The ratio between these reactants can be expressed by the Henderson-Hasselbalch equation. By convention, the pKa of 6.10 is used when the dominator is the concentration of dissolved CO2, and this is proportional to the pCO2 (the actual concentration of the acid H2CO3 is very low): TI AU Garibotto G, Sofia A, Robaudo C, Saffioti S, Sala MR, Verzola D, Vettore M, Russo R, Procopio V, Deferrari G, Tessari P To evaluate the effects of chronic metabolic acidosis on protein dynamics and amino acid oxidation in the human kidney, a combination of organ isotopic ((14)C-leucine) and mass-balance techniques in 11 subjects with normal renal function undergoing venous catheterizations was used. Five of 11 studies were performed in the presence of metabolic acidosis. In subjects with normal acid-base balance, kidney protein degradation was 35% to 130% higher than protein synthesi Continue reading >>
Metabolic Acidosis
Diabetic Ketoacidosis (DKA), Alcohol ic ketoacidosis or starvation ketosis Paraldehyde, Phenformin (neither used in U.S. now) Propofol Infusion Syndrome has been proposed as a replacement in mnemonic Salicylate s (do not miss Chronic Salicylate Poisoning ) IV. Causes: Metabolic Acidosis and Normal Anion Gap (Hyperchloremia) Renal Tubular Acidosis (proximal or distal) V. Causes: Metabolic Acidosis and Elevated Osmolal Gap PaCO2 drops 1.2 mmHg per 1 meq/L bicarbonate fall Calculated PaCO2 = 1.5 x HCO3 + 8 (+/- 2) Useful in High Anion Gap Metabolic Acidosis Measured PaCO2 discrepancy: respiratory disorder Investigate normal Anion Gap Metabolic Acidosis Elevated in normal Anion Gap Metabolic Acidosis VII. Labs: Consider in Metabolic Acidosis with Increased Anion Gap Basic chemistry panel as above ( Serum Glucose , Blood Urea Nitrogen ) Rutecki (Dec 1997) Consultant, p. 3067-74 Images: Related links to external sites (from Bing) These images are a random sampling from a Bing search on the term "Metabolic Acidosis." Click on the image (or right click) to open the source website in a new browser window. Search Bing for all related images Related Studies (from Trip Database) Open in New Window A condition in which the blood is too acidic. It may be caused by severe illness or sepsis (bacteria in the bloodstream). Increased acidity in the blood secondary to acid base imbalance. Causes include diabetes, kidney failure and shock. ACIDOSIS METABOLIC, metabolic acidosis, metabolic acidosis (diagnosis), Acidosis metabolic, Metabolic acidosis NOS, Metabolic Acidoses, Acidosis, Metabolic, Acidoses, Metabolic, Metabolic Acidosis, acidosis metabolic, metabolic acidosis disorder, Acidosis, Metabolic acidosis (disorder), acidosis; metabolic, metabolic; acidosis, Metabolic acidosis, NOS, M Continue reading >>
Tales Of The Anion Gap, Part Ii: Metabolic Acidosis
Tales of the Anion Gap, Part II: Metabolic Acidosis Normal acid-base balance in human beings is generally achieved by the pulmonary excretion of CO2 and the renal excretion of inorganic acids related to protein metabolism. This balance may be roughly summarized with the Henderson-Hasselbalch equation: pH=6.10 + log((HCO3-) / (0.03 X pCO2)) with a normal pH of 7.35-7.45 Acidemia refers to a metabolic condition in which, simply, the pH is low; this may be due to metabolic acidosis, respiratory acidosis, or a combination of both. Metabolic Acidosis refers to a pathologic condition in which a low pH is accompanied by a significant diminution of the serum HCO3- (versus what is normal for the patient) Metabolic acidosis is caused by or associated with the following (these may occur in combination): Increased acid production: eg. various poisonings, ketoacidosis, lactic acidosis Bicarbonate loss eg. diarrhea, Type II (proximal) renal tubular acidosis, urinary diversion Reduced renal excretion of inorganic acids eg. chronic renal failure, Type I (distal renal tubular acidosis) Hyperchloremic acidosis related to dilution of serum bicarbonate by receiving large amounts of non-balanced IV fluids (eg, normal saline) How should a patient with suspected metabolic acidosis be evaluated? The patients blood electrolytes, pH and pCO2 should be measured. A venous blood gas (rather than arterial) is generally adequate for determination of the pCO2 and pH. Most patients with a metabolic acidosis will attempt to neutralize their pH by hyperventilation, that is, by reducing their pCO2. This adaptation may occur within a few minutes and be essentially complete within hours. A variety of charts and normograms are used to evaluate the adequacy of this compensation, but the experienced clinician Continue reading >>
Test Your Knowledge: Anion Gap In Metabolicacidosis
Test Your Knowledge: Anion Gap in MetabolicAcidosis Posted on August 25, 2014 by AJKDblog in Test Your Knowledge // 0 Comments The serum anion gap is a common tool used in clinical practice. Recent advances have led to a new mnemonic GOLD MARK to differentiate the various causes of anion gap metabolic acidosis. A recent article in AJKD by Vichot and Rastegar discusses the use of anion gap in metabolic acidosis. The following questions will test your knowledge on this very important topic in nephrology. Post prepared by Dr. Helbert Rondon, eAJKD Contributor. To avoid formatting issues, we recommend using the PDF version of the questions & answers. The serum anion gap can be calculated by which of the following? Concentration of measured anions minus concentration of measured cations Concentration of serum albumin plus concentration of serum organic acids Concentration of unmeasured anions minus concentration of unmeasured cations Correct! The serum anion gap can be calculated by the difference between the concentration of measured cations (Na+) and measured anions (Cl- and HCO3-). Potassium is usually not considered as one of the measured cations because of its small and relatively fixed contribution. However, the serum anion gap can also be expressed as the concentration of unmeasured anions minus the concentration of unmeasured cations. The unmeasured anions are composed mainly of proteins (e.g., albumin) with minor additions from organic (e.g., lactate) and inorganic (e.g., sulfate and phosphate) acids. The unmeasured cations are largely represented by potassium, calcium, and magnesium. What reference values should be used when deciding whether a patient has an abnormal serum anion gap? Correct! The reference range for serum anion gap was classically established by t Continue reading >>
Metabolic Acidosis - Endocrine And Metabolic Disorders - Merck Manuals Professional Edition
(Video) Overview of Acid-Base Maps and Compensatory Mechanisms By James L. Lewis, III, MD, Attending Physician, Brookwood Baptist Health and Saint Vincent’s Ascension Health, Birmingham Metabolic acidosis is primary reduction in bicarbonate (HCO3−), typically with compensatory reduction in carbon dioxide partial pressure (Pco2); pH may be markedly low or slightly subnormal. Metabolic acidoses are categorized as high or normal anion gap based on the presence or absence of unmeasured anions in serum. Causes include accumulation of ketones and lactic acid, renal failure, and drug or toxin ingestion (high anion gap) and GI or renal HCO3− loss (normal anion gap). Symptoms and signs in severe cases include nausea and vomiting, lethargy, and hyperpnea. Diagnosis is clinical and with ABG and serum electrolyte measurement. The cause is treated; IV sodium bicarbonate may be indicated when pH is very low. Metabolic acidosis is acid accumulation due to Increased acid production or acid ingestion Acidemia (arterial pH < 7.35) results when acid load overwhelms respiratory compensation. Causes are classified by their effect on the anion gap (see The Anion Gap and see Table: Causes of Metabolic Acidosis ). Lactic acidosis (due to physiologic processes) Lactic acidosis (due to exogenous toxins) Toluene (initially high gap; subsequent excretion of metabolites normalizes gap) HIV nucleoside reverse transcriptase inhibitors Biguanides (rare except with acute kidney injury) Normal anion gap (hyperchloremic acidosis) Renal tubular acidosis, types 1, 2, and 4 The most common causes of a high anion gap metabolic acidosis are Ketoacidosis is a common complication of type 1 diabetes mellitus (see diabetic ketoacidosis ), but it also occurs with chronic alcoholism (see alcoholic ketoacidos Continue reading >>
High Anion Gap Metabolic Acidosis
When acidosis is present on blood tests, the first step in determining the cause is determining the anion gap. If the anion gap is high (>12 mEq/L), there are several potential causes. 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 patient's serum). An anion gap is usually considered to be high if it is over 12 mEq/L. High anion gap metabolic acidosis is caused generally by acid produced by the body,. More rarely, high anion gap metabolic acidosis may be caused by ingesting methanol or overdosing on aspirin.[1][2] The Delta Ratio is a formula that can be used to assess elevated anion gap metabolic acidosis and to evaluate whether mixed acid base disorder (metabolic acidosis) is present. The list of agents that cause high anion gap metabolic acidosis is similar to but broader than the list of agents that cause a serum osmolal gap. Causes[edit] Causes include: The newest mnemonic was proposed in The Lancet reflecting current causes of anion gap metabolic acidosis:[3] G — glycols (ethylene glycol & propylene glycol) O — oxoproline, a metabolite of paracetamol L — L-lactate, the chemical responsible for lactic acidosis D — D-lactate M — methanol A — aspirin R — renal failure K — ketoacidosis, ketones generated from starvation, alcohol, and diabetic ketoacidosis The mnemonic MUDPILES is commonly used to remember the causes of increased anion gap metabolic acidosis.[4][5] M — Methanol U — Uremia (chronic kidney failure) D — Diabetic ketoacidosis P — Paracetamol, Propylene glycol (used as an inactive stabilizer in many medications; historically, the "P" also stood for Paraldehyde, though this substance is not commonly used today) I — Infectio Continue reading >>
