anion gap


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gap

 [gap]
an opening or hiatus.
anion gap the concentration of plasma anions not routinely measured by laboratory screening, accounting for the difference between the routinely measured anions and cations and equal to the plasma sodium − (chloride + bicarbonate); used in the evaluation of acid-base disorders.
auscultatory gap a period in which Korotkoff sounds disappear during auscultation of a patient' s blood pressure.

an·i·on gap

the difference between the sum of the measured cations and anions in the plasma or serum calculated as follows: ([Na+ + [K+]) - ([Cl-] + [HCO3-]) = < 20 mmol/L. Elevated values may occur in diabetic or lactic acidosis and in various types of poisoning; normal or low values occur in bicarbonate-losing metabolic acidoses.

anion gap

the difference between the concentrations of serum or plasma cations and anions, determined by measuring the concentrations of sodium cations and chloride and bicarbonate anions. It is helpful in the diagnosis and treatment of acidosis, and it is estimated by subtracting the sum of chloride and bicarbonate concentrations in the plasma from that of sodium. It is normally about 8 to 14 mEq/L and represents the negative charges contributed to plasma by unmeasured ions or ions other than those of chloride and bicarbonate, mainly phosphate, sulfate, organic acids, and plasma proteins. Anions other than chloride and bicarbonate normally constitute about 12 mEq/L of the total anion concentration in plasma. Acidosis can develop with or without an associated anion increase. An increase in the anion gap often suggests diabetic ketoacidosis, drug poisoning, renal failure, or lactic acidosis and usually warrants further laboratory tests.

anion gap

A mathematic approximation of the difference between unmeasured anions (PO4–, SO4–, proteins and organic acids) and unmeasured cations (Ca2+, Mg2+), with the former usually exceeding the latter. The anion gap is the difference between the sum of the most abundant measured serum anions (Cl­– and HCO3–) and serum cations (Na+, K+). Urinary AG is calculated as (Na+) + (K+) – (Cl–); it is a crude index of the levels of urinary ammonium and used to evaluate hyperchloremic metabolic acidosis.
 
Specimen
Serum, heparinised plasma.
 
Ref range
8–16 mEq/L.

Increased anion gap
Renal failure due to defective renal tubular acidification, with an increase in phosphate and sulfate; starvation-related ketoacidosis due to an accumulation of acetoacetate and beta-hydroxybutyrate, or alcohol abuse; in disorders of amino acid metabolism and hyperglycaemic nonketotic coma due to various organic acids; in lactic acidosis, overdoses or poisoning (e.g., salicylates, methanol ethylene glycol antifreeze or paraldehyde).

Decreased anion gap
Hypermagnesaemia; GI loss of bicarbonate; in nephrotic syndrome due to a loss of albumin, which is anionic at a physiologic pH; after lithium ingestion; and in myeloma and Waldenström’s macroglobinaemia, due to an increase in cationic proteins.

anion gap

Lab medicine A mathematic approximation of the difference between unmeasured anions–PO4–, SO4–, proteins and organic acids, and unmeasured cations-Ca2+, Mg2+, which normally exceed unmeasured cations; the AG is the difference between the sum of the most abundant measured serum anions–Cl– and HCO3– and serum cations–Na+ and K+; urinary AG is calculated as Na+ + K+ – Cl– and is a crude index of the levels of urinary ammonium and used to evaluate hyperchloremic metabolic acidosis Ref range 8-16 mEq/L; AG is ↑ in renal failure due to defective renal tubular acidification with an ↑ in phosphate and sulfate, starvation-related DKA due to an accumulation of acetoacetate and β-hydroxybutyrate or alcohol abuse, in disorders of amino acid metabolism and hyperglycemic nonketotic coma due to various organic acids, in lactic acidosis, overdose or poisoning—eg salicylates, methanol ethylene glycol antifreeze or paraldehyde; AG is ↓ in hypermagnesemia, GI loss of bicarbonate, in nephrotic syndrome due to a loss of albumin which is anionic at a physiological pH, after lithium ingestion, and multiple myeloma and Waldenström's macroglobinemia, due to an ↑ in cationic proteins

an·i·on gap

(an'ī-on gap)
The arithmetic difference between the concentrations of routinely measured cations (Na+ + K+) and of routinely measured anions (Cl- + HCO3-) in plasma or serum; unmeasured anions (phosphate, sulfate, protein, other organic ions) account for the gap, which is increased in metabolic acidosis due to diabetic ketosis, renal failure, or extraneous substances (methanol, salicylate).

anion gap

method used to evaluate a patient's acid-base status; based on the observation that the sum of blood cations (sodium, potassium, chloride and bicarbonate ions) usually exceeds the sum of the anions (sulfates, phosphates, proteinates, organic acid ions); the difference between the two is the anion gap. Significant departure from the normal level of difference indicates acid-base disturbance.
References in periodicals archive ?
The typical biochemical findings in patients with alcoholic ketoacidosis (AKA) include increased anion gap metabolic acidosis, increased serum ketones, a low or normal plasma glucose concentration, an increased plasma lactate concentration, and normal or increased values for blood urea nitrogen and serum creatinine.
Determination of the anion gap (AG) is one of the initial, and very important, steps in the differential diagnosis of acidbase disorders.
An unexplained normal anion gap metabolic acidosis and the response to the bicarbonate therapy confirms the diagnosis.
Close attention was paid to bicarbonate levels in light of the potential for the development of anion gap acidosis, a previously described potential side effect of sodium thiosulfate.
85 Hematocrit 40% 34-47 Urine ketones positive (+++) Negative Arterial blood gas analysis Anion GAP -30 Arterial pH 6.
The Anion Gap is calculated as [Na+] - [CI-] - [HC[O.
2] (23-33 mmol/L) 23 26 23 25 23 Anion gap (7-16 mmol/L) 23.
2) Many hospitals are unable to perform EG and MTH measurements in a timely fashion; which in this case, a combination of a metabolic acidosis associated with a high anion gap and osmolar gap is considered the hallmark of toxic alcohol intoxication.
The acid-base and electrolytic parameters in blood were normal, except for mild, non-significant increases in anion gap and lactate values in the first two days of treatment (Table 1).
Es una investigacion prospectiva, descriptiva, de corte transversal, cuya finalidad fue realizar un estudio de la funcion tubular renal, a traves de la prueba de sobrecarga con bicarbonato de sodio al 5%, a ninos desnutridos graves con acidosis metabolica hipercloremica y anion gap urinario positivo, hospitalizados en el departamento de Pediatria de la Ciudad Hospitalaria Enrique Tejera, en Valencia, Venezuela, durante el lapso de realizacion del estudio (febrero de 2002-febrero de 2004).
d) measure serum electrolytes to monitor for anion gap metabolic acidosis