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

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).
References in periodicals archive ?
* Low serum bicarbonate values inversely correlate with increasing anion gap (18)
The high anion gap and low TC[O.sub.2] are likely explained by lactic acidosis.
In our patient, lactate levels alone could not account for the entirety of the anion gap. His initial serum glucose level was low excluding diabetic ketoacidosis as a cause of the anion-gap metabolic acidosis.
Patients with salicylate toxicity typically present with tinnitus, gastrointestinal complications (nausea, vomiting, bleeding, and liver toxicity), hyperthermia (via uncoupling of oxidative phosphorylation), pulmonary edema, and a mixed acid-base disorder (high anion gap metabolic acidosis and respiratory alkalosis via stimulation of respiratory center in the brainstem) [54, 55].
Initial pH, base deficit, lactate, anion gap, strong ion difference, and strong ion gap predict outcome from major vascular injury.
Melamed, "The serum anion gap is altered in early kidney disease and associates with mortality," Kidney International, vol.
However, data showed that treatment with an ethanolic extract of MO caused a decrease in bicarbonate (P < 0.0001), and more than twofold increase in anion gap (P < 0.0001); metformin treatment also decreased bicarbonate (P < 0.0001) and resulted in a threefold increase in anion gap (P < 0.0001).
We also collected additional variables: admission "at night" (between 19:00 and 07:00); admission on weekend (from 19:00 on Friday to 07:00 on Monday); presence of a systemic inflammatory response syndrome (SIRS) [25] during the ED stay; anion gap (calculated as [[Na.sup.+] + [K.sup.+]] - [[Cl.sup.-] + alkaline reserve]) when blood ionogram was available.
In addition, renal function tests were assessed including sodium, potassium, chloride, carbon dioxide, anion gap, urea, and creatinine.
The ion contents of Na, K, Ca, P, Cl and anion gap (AG) in the serum were determined by the electrolyte analyzer (XD-687, Shanghai Xunda Co.