Other causes of anion gap metabolic acidosis are lactic acidosis, advanced renal failure, and ingestion of highdose salicylates, methanol, or ethylene glycol. The anion gap provides an estimation of the unmeasured anions in the plasma and is useful in the setting of arterial blood gas analysis. If the patient is suffering from metabolic acidosis low ph with low hco 3, the next step is to calculate the anion gap because the anion gap helps determining the etiology of the metabolic acidosis. In nonanion gap acidosis, there is a drop in bicarb acidosis but a concomitant rise in cl, making the net anion gap the same as normal serum.
Certain types of metabolic acidosis have a bigger difference or gap than others. Normal anion gap metabolic acidosis is a common but often. Sepsis is a clinical syndrome caused by the bodys immune and coagulation systems being switched on by an infection. However, in the case of complex disorders, we need to correct the calculation with some parameters to get the true ag. The urine anion gap in context american society of nephrology. High anion gap metabolic acidosis is typically caused by acid produced by the body.
Metabolic acidosis can be divided into high anion and normal anion gap. Pdf use of the ag hco3 ratio in the diagnosis of mixed acid. Potentially, the anion gap can provide valuable insights into the causes of metabolic acidosis in companion animals. Anion gap metabolic acidosis usmle how to calculate and. Always determine if there is another acidbase process occurring primary respiratory acidosis. 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. Sodium and chloride are required for anion gap calculation. Nonanion gap metabolic acidosis updated version youtube. Nov 15, 2019 a urine anion gap of more than 20 meql is seen in metabolic acidosis when the kidneys are unable to excrete ammonia such as in renal tubular acidosis. Mar 15, 2016 anion gap usmle anion gap metabolic acidosis normal anion gap metabolic acidosis. Ethylene glycol may cause renal failure with an elevated creatinine contributing to the ag metabolic acidosis, while both methanol and ethylene glycol may cause an elevated lactate. Albumin is a negatively charged protein, and thus hypoalbuminemia falsely lowers the anion gap. Unusual dlactic acid acidosis from propylene glycol metabolism in overdose.
The patient with an unexplained non gap metabolic acidosis. However, in the case of complex disorders, we need to correct the calculation with some. 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. 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. Anion gap is a calculation for classifying metabolic acidosis. Review of the diagnostic evaluation of normal anion gap metabolic. A high anion gap 12 meql during metabolic acidosis implicates a gain of an acid due to something like diabetic ketoacidosis or lactic acidosis. Anion and osmolal gaps after alcohol intoxication american. In a metabolic acidosis the anion gap is usually either normal or high.
Sepsis with shock is a lifethreatening condition that is characterised by low blood pressure despite adequate fluid replacement, and organ dysfunction or failure. After the diagnosis of metabolic acidosis, the calculation of the plasmatic anion gap ag evaluates the excess of unmeasured anions. Its kind of a confusing topic, but the central takeaway is that a direct gain or loss of cl or hco3 respectively has a non gap anion acidosis. The addition of potassium to the equation, however, adds little to the diagnostic. This analyzer should not substitute for clinical context. 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. If the urine anion gap is zero or negative but the serum ag is positive, the source is most likely gastrointestinal diarrhea or vomiting. Metabolic acidosis occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body. See approach to the adult with metabolic acidosis, section on physiologic interpretation of the serum anion gap. All software windows mac palm os linux windows 7 windows 8 windows mobile windows phone ios android windows ce windows server pocket pc blackberry tablets os2. Metabolic acidosis compensation calculation medical. Sep 17, 2019 the most important treatment of anion gap metabolic acidosis is the reversal of its cause. The most important treatment of aniongap metabolic acidosis is the reversal of its cause.
Download as pptx, pdf, txt or read online from scribd. Frequent causes of high anion gap metabolic acidosis hagma are lactic acidosis, ketoacidosis and impaired renal function. Hyperglycemia causes an osmotic diuresis with significant fluid and electrolyte loss. For discussion purpose, these causes can be conveniently divided into the following categories. 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. Understanding the acidbase disorders relies on a structured diagnostic approach, based on hendersonhasselbalchs equation. It generally is believed that in the absence of detectable blood ethanol, the combination of high anion gap metabolic acidosis and increased serum osmolal gap. This simple urine test can help differentiate the causes of a non gap metabolic acidosis hardup.
Elevated anion gap is concerning, because many causes of this are immediately lifethreatening. Metabolic acidosis endocrine and metabolic disorders. Dka is diagnosed by detection of hyperketonemia and anion gap metabolic acidosis in the presence of. This test measures the ph of your blood and the levels of oxygen and carbon dioxide. 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. Differential diagnosis of nongap metabolic acidosis. More rarely, it may be caused by ingesting methanol or overdosing on aspirin. 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.
The hospitalist calculated his bedside anion gap to be approximately 32. Reference range, interpretation, collection and panels. Both calculating anion gap for acidosis student doctor. Determining if a patients acidosis also has an elevated anion gap. Download32 is source for anion gap shareware, freeware download anion gap, acid base disorders, acid plus the abg calculator, medcalc 3000 kidney, acidosis, etc. In rare cases it can be low, usually due to hypoalbuminaemia. However, the serum ag can also become abnormal in other conditions, a finding that may be of diagnostic importance 15. We now have an abg analyzer to help with acidbase analysis as well.
The serum anions and cations are usually used, but urine measurements can also be used. So yes, even if they dont give you the ph from the abg, if you determine the patient is acidotic and has a high anion gap, its metabolic acidosis and consider the mudpiles list of causes. Congenital heart failure anion gap metabolic acidosis diabetic ketoacidosis. See more ideas about metabolic acidosis, nursing tips and nursing school tips. Anion gap used to differentiate the causes of metabolic acidosis blood gas analysis analyze blood gas measurements to determine acidosis alkalosis and metabolic vs. Therefore the urine ag is inappropriately positive in the setting of a non anion gap metabolic acidosis. Metabolic acidoses are categorized as high or normal anion gap based on the presence or absence of unmeasured anions in serum.
When the gap is higher than normal, high anion gap metabolic acidosis is revealed, whereas if the gap is low, low anion gap metabolic acidosis is. Anion gap metabolic acidosis is associated with generalized seizure. The plasma anion gap may not change in hyperchloremic metabolic acidosis. In renal tubular acidosis, the kidney is unable to excrete ammonium normally.
The degree of the gap in the serum electrolytes is calculated to determine reasons for metabolic acidosis. Clinical clerkships overview and causes of non anion gap metabolic acidosis made with help of blueberry flashback recorder. Its kind of a confusing topic, but the central takeaway is that a direct gain or loss of cl or hco3 respectively has a. This is the most clinically useful way to classify metabolic acidosis and it is used extensively when. Uremic agma traditionally, bicarbonate has been used to support the ph in efforts to stave off dialysis. Raised anion gap suggests there is an unmeasured anion responsible for a metabolic acidosis, eg lactate, ketones, urate, acid poisoning. Assessment of metabolic acidosis and the use of albumin. Jul 22, 2016 after the diagnosis of metabolic acidosis, the calculation of the plasmatic anion gap ag evaluates the excess of unmeasured anions. A denver seizure score greater than 20 appears to predict generalized seizure in the ed and may be useful in guiding a targeted evaluation for patients with unwitnessed loss of consciousness.
Between 19% and 41% of patients in intensive care units with acute metabolic acidosis and 20%55% of individuals with chronic uremic acidosis have a nongap pattern 3,4. Search results normal anion gap acidosis pubmed health. In non anion gap acidosis, there is a drop in bicarb acidosis but a concomitant rise in cl, making the net anion gap the same as normal serum. More discussion of the anion gap in the chapter on diagnosing acidbase problems here. Metabolic acidosis occurs when the body produces too much acid. It causes nausea, vomiting, and abdominal pain and can progress to cerebral edema, coma, and death. Metabolic acidosis is primary reduction in bicarbonate hco 3.
In hyperchloraemic acidosis, the anion gap is normal in most cases. This pattern can originate from a number of pathophysiologic mechanisms. A nonanion gap pattern is commonly found in patients with both acute and chronic metabolic acidosis. The anion gap calculator evaluates states of metabolic acidosis. Please define the anion gap and its utility in diagnosis and how it relates to osmolality. Alcoholic ketoacidosis is a common cause of presentation to the emergency department with high anion gap metabolic acidosis. In inorganic acidosis, the anion is chloride and the anion gap does not change. Consider your goldmark differential diagnosis of ag metabolic acidosis download pdf of goldmark mnemonic. Clinical clerkships overview and causes of nonanion gap metabolic acidosis made with help of blueberry flashback recorder. In organic acidosis, the anion gap increases because bicarbonate decreases, chloride remains constant, and the unmeasured anion lactate, ketone, phosphate. Metabolic acidosis is generally associated with either a normal anion gap. 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 aniongap metabolic acidosis. Although most commonly used in the differential diagnosis of acidbase disorders, it also has been used to assess quality control in the chemical laboratory and to diagnose paraproteinemias 4,5 and intoxications with lithium, bromide, or iodide.
Decreased excretion of endogenous acids and their anions is the cause of the increased anion gap metabolic acidosis that is frequently a feature of renal failure. Pin by ravini gunawardana on medical pearls metabolic. Detects urine acidosis for evaluation of non gap metabolic acidosis. Metabolic acidosis endocrine and metabolic disorders msd.
A difference of greater than 12 meql along with a lowered bicarbonate level anion gap metabolic acidosis and is a defining feature of dka. Clinical aspects of the anion gap acute care testing. In this setting, the acidosis is said to be a high anion gap or anion gap metabolic acidosis. That means he had 20 anions floating around in his blood. There are two problems in the definition of this type of metabolic acidosis which can cause confusion. Serum osmolality in patients with this condition can be increased, primarily because of the presence of ethanol. However, in order to use this information to improve diagnosis and treatment, it is important to consider several other factors about the patient. A difference of greater than 12 meql along with a lowered bicarbonate level 12 meql during metabolic acidosis implicates a gain of an acid due to something like diabetic ketoacidosis or lactic acidosis. The diagnosis of nagma may be made in one of two ways red arrows abovepatient has normal anion gap with metabolic acidosis bicarbonate download pdf of goldmark mnemonic.
This concept is represented by the following equation. As acidosis develops, bicarbonate levels decrease and are replaced by the anionic component of the acid. Unlike, for example, non aniongap metabolic acidosis where most causes are not life threats. In the previous chapter, we presented various causes of high anion gap ag metabolic acidosis. In summary, in the setting of a non anion gap metabolic acidosis, a negative urine ag suggests diarrhea bicarbonate loss and a positive urine ag suggests an rta. The serum or plasma anion gap is an entity that is calculated from the electrolytes that are obtained in the chemical laboratory. Metabolic acidosis calculator download app metabolic acidosis is a process which if unchecked leads to acidemia, i. Nonaniongap metabolic acidosis nagma emcrit project. Sample question on calculating metabolic acidosis anion gap. The anion gap can be used to help identify the cause of metabolic acidosis. While the analyzer can often help with analysis, the history of the patient is critical for accurate interpretation. Toxic alcohols minding the gaps emergency medicine cases. A urine anion gap of more than 20 meql is seen in metabolic acidosis when the kidneys are unable to excrete ammonia such as in renal tubular acidosis.
1327 182 168 1244 37 1250 845 737 1483 1161 1070 657 526 930 1088 983 55 1078 22 1480 1156 693 1403 1567 399 21 801 36 1203 352 1306 1372 309 208 1440 536 1376