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 >>
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 >>
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 >>
What Is Metabolic Acidosis?
Metabolic acidosis happens when the chemical balance of acids and bases in your blood gets thrown off. Your body: Is making too much acid Isn't getting rid of enough acid Doesn't have enough base to offset a normal amount of acid When any of these happen, chemical reactions and processes in your body don't work right. Although severe episodes can be life-threatening, sometimes metabolic acidosis is a mild condition. You can treat it, but how depends on what's causing it. Causes of Metabolic Acidosis Different things can set up an acid-base imbalance in your blood. Ketoacidosis. When you have diabetes and don't get enough insulin and get dehydrated, your body burns fat instead of carbs as fuel, and that makes ketones. Lots of ketones in your blood turn it acidic. People who drink a lot of alcohol for a long time and don't eat enough also build up ketones. It can happen when you aren't eating at all, too. Lactic acidosis. The cells in your body make lactic acid when they don't have a lot of oxygen to use. This acid can build up, too. It might happen when you're exercising intensely. Big drops in blood pressure, heart failure, cardiac arrest, and an overwhelming infection can also cause it. Renal tubular acidosis. Healthy kidneys take acids out of your blood and get rid of them in your pee. Kidney diseases as well as some immune system and genetic disorders can damage kidneys so they leave too much acid in your blood. Hyperchloremic acidosis. Severe diarrhea, laxative abuse, and kidney problems can cause lower levels of bicarbonate, the base that helps neutralize acids in blood. Respiratory acidosis also results in blood that's too acidic. But it starts in a different way, when your body has too much carbon dioxide because of a problem with your lungs. Continue reading >>
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 >>
High Anion Gap Metabolic Acidosis
Go to: Introduction High anion gap metabolic acidosis (HAGMA) is a subcategory of acidosis of metabolic (i.e., non-respiratory) etiology. Differentiation of acidosis into a particular subtype, whether high anion gap metabolic acidosis or non-anion gap metabolic acidosis (NAGMA), aids in the determination of the etiology and hence appropriate treatment. Go to: Etiology Although there have been many broadly inclusive mnemonic devices for high anion gap metabolic acidosis, the use of "GOLD MARK" has gained popularity for its focus on causes common to the 21st century. Glycols (ethylene glycol, propylene glycol) Oxoproline (pyroglutamic acid, the toxic metabolite of excessive acetaminophen or paracetamol) L-Lactate (standard lactic acid seen in lactic acidosis) D-Lactate (exogenous lactic acid produced by gut bacteria) Methanol (this is inclusive of alcohols in general) Aspirin (salicylic acid) Ketones (diabetic, alcoholic and starvation ketosis) Of note, metformin has been omitted from this list due to a lack of evidence for metformin-induced lactic acidosis. In fact, a Cochrane review found substantial evidence that metformin was not a cause of lactic acidosis. The same could not be said of the older biguanide, phenformin, which does increase the incidence of lactic acidosis by approximately tenfold. Furthermore, the addition of massive rhabdomyolysis would be appropriate given the potentially large amounts of hydrogen ions released by muscle breakdown. Go to: Epidemiology High anion gap metabolic acidosis is one of the most common metabolic derangements seen in critical care patients. Exact numbers are not readily available. Go to: Pathophysiology The most common method of evaluation of metabolic acidosis involves the Henderson-Hasselbalch equation and the Lewis model in Continue reading >>
Treatment Of Acute Non-anion Gap Metabolic Acidosis
Treatment of acute non-anion gap metabolic acidosis Medical and Research Services VHAGLA Healthcare System, Division of Nephrology, VHAGLA Healthcare System Correspondence to: Jeffrey A. Kraut; E-mail: [email protected] Search for other works by this author on: Clinical Kidney Journal, Volume 8, Issue 1, 1 February 2015, Pages 9399, Jeffrey A. Kraut, Ira Kurtz; Treatment of acute non-anion gap metabolic acidosis, Clinical Kidney Journal, Volume 8, Issue 1, 1 February 2015, Pages 9399, Acute non-anion gap metabolic acidosis, also termed hyperchloremic acidosis, is frequently detected in seriously ill patients. The most common mechanisms leading to this acidbase disorder include loss of large quantities of base secondary to diarrhea and administration of large quantities of chloride-containing solutions in the treatment of hypovolemia and various shock states. The resultant acidic milieu can cause cellular dysfunction and contribute to poor clinical outcomes. The associated change in the chloride concentration in the distal tubule lumen might also play a role in reducing the glomerular filtration rate. Administration of base is often recommended for the treatment of acute non-anion gap acidosis. Importantly, the blood pH and/or serum bicarbonate concentration to guide the initiation of treatment has not been established for this type of metabolic acidosis; and most clinicians use guidelines derived from studies of high anion gap metabolic acidosis. Therapeutic complications resulting from base administration such as volume overload, exacerbation of hypertension and reduction in ionized calcium are likely to be as common as with high anion gap metabolic acidosis. On the other hand, exacerbation of intracellular acidosis due to the excessive generation of carbon dioxide migh 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 >>
The Anion Gap
The anion gap is a tool used to: Confirm that an acidosis is indeed metabolic Narrow down the cause of a metabolic acidosis Monitor the progress of treatment In a metabolic acidosis the anion gap is usually either ‘Normal’ or ‘High’. In rare cases it can be ‘low’, usually due to hypoalbuminaemia. An ABG machine will often give a print out of the anion gap, but it can also be useful to know how it is calculated. In blood, there are many cations and anions. However, the vast majority of the total number are potassium, sodium, chloride, or bicarbonate. The ‘anion’ gap is an artificial measure, which is calculated by subtracting the total number of anions (negatively charged ions – bicarbonate and chloride) from the total number of cations (sodium and potassium). Thus, the formula is: ([Na+]+ [K+]) –([Cl–]+ [HCO3–]) In reality, the concentration of potassium anions is negligible, and this often omitted. There are usually more measurable cations than anions, and thus a normal anion gap is value is positive. A normal value is usually 3-16, but may vary slightly depending on the technique used by the local laboratory. If the anion gap is <30, then there may not be ‘true’ high anion gap metabolic acidosis. In a healthy normal individual, the main unmeasured anions are albumin and phosphate. Almost all of the gap can be attributed to albumin. This means that in patients with hypoalbuminaemia and metabolic acidosis, there may be a normal anion gap. Be wary in severely unwell patients because they often have a low albumin. You can adjust for this in your calculation. Corrected anion gap: [AG] + (0.25 x (40-albumin)) In an unwell patient with a high anion gap metabolic acidosis (HAGMA) the anion gap is increased due: Accumulation of organic acids Inabili Continue reading >>
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 >>
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 >>
Medical Mnemonics: Causes Of Anion Gap Metabolic Acidosis – “gold Mark”
The classic mnemonic often used to remember the causes of anion gap metabolic acidosis is “MUDPILES” M – Methanol U – Uremia D – Diabetic ketoacidosis P – Propylene Glycol I – Isoniazid L – Lactic Acidosis E – Ethylene Glycol S – Salicylates More recently a new mnemonic has been suggested to update new our understanding of anion-gap generating acids. The updated mnemonic “GOLD MARK” was proposed in a 2008 article in The Lancet. G – Glycols (ethylene glycol and propylene glycol) O – Oxoproline L – L-Lactate D – D-Lactate M – Methanol A – Aspirin R – Renal Failure K – Ketoacidosis As medicine evolves, so do our Mnemonics. This is the fifth medical mnemonic in our series of Monday Mnemonics. 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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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 >>
