Hyperchloraemic metabolic acidosis tends to be associated with acute infective diarrhoea. The more fluid andĪnions lost, the more marked the problem. Significant increase in stool water loss above its normal value of 100 to 200 mls/day. Development of a significant acid-base disturbance requires a Metabolic acidosis or a metabolic alkalosis. external drainage of pancreatic or biliary secretions (eg fistulas).Some typical at risk clinical situations are: Excessive loss of these fluids can result in a normal anion gap metabolic acidosis. Secretions into the large and small bowel are mostly alkaline with a bicarbonate level higher than In someĬases though some factors may be involved or there may be some doubt as to which cause is the most significant. In most cases, this will be obvious from the history. In general then the diagnosis of a normal anion gap acidosis is just to look for evidence of one of only two mechanisms:Ī key question is to distinguish GIT causes from renal causes. Situation can be diagnosed easily on history. A gain of acid can occur with certain infusions but this This may occur by either GIT or renal mechanisms. Renal tubular acidosis is discussed in the next section.Ī review of these causes shows that the predominant mechanism is loss of base (bicarbonate or bicarbonate precursors) and Some of the causes are listed in the Table in Section 5.2 and some of these areĭiscussed below. To the combination of small errors in the measurement of the component electrolytes.
This could result in a situation where the anion gap is only elevated slightly or still within the normal range due The situation may also be due to the wide normal range of the anion gap. This movement of the acidĪnion intracellularly is one mechanism responsible for a hyperchloraemic component in some types of high anionģ.
Suggests that the lactate is being taken up by some cells in exchange for chloride. So if we find a hyperchloraemic component this clearly This should therefore be a ‘pure’ lactic acidosis initially without any respiratoryĬompensation or evidence of other acid-base problem. This is an interesting situationīecause the lactic acidosis is due solely to muscular over-production, occurs rapidly & can be severe BUT itĪlso resolves rapidly. Group of patients may present with a hyperchloraemic component to their acidosis. Has been found that when lactic acidosis occurs in association with grand mal seizures then as many as 30% of this In lactic acidosis, the movement of lactate intracellularly in exchange for chloride occurs via an antiport. Another possibility is intracellular movement of acid anions in exchange for chloride Should be considered in patients with hyperchloraemic acidosis if the cause of the acidosis is otherwise not apparent.Īdministration of IV saline solution may replace lost acid anion with chloride so that treatment may result in theĪcidosis converting to a hyperchloraemic type.Ģ. In lactic acidosis, the clinical disorder can be severe but the lactate may not be grossly high (eg lactate of 6mmol/l)Īnd the change in the anion gap may still leave it in the reference range. One possibility is the increase in anions may be too low to push the anion gap out of the reference range. Patient with a metabolic acidosis you naturally tend to concentrate on looking for a renal or GIT cause. Once you note the presence of an anion gap within the reference range in a Now this can be misleading to you when youĪre trying to diagnose the disorder.
The anion gap may still be within the reference range in lactic acidosis. In a disorder that typically causes a high anion gap disorder there may sometimes be a normal anion gap! However, you should be aware that in some cases of normalĪnion-gap acidosis, there will not be a hyperchloraemia if there is a significant hyponatraemia. This could be considered a ' relative hyperchloraemia'. Hyponatraemia is present the plasma may be normal despite the presence of a normal anion gap acidosis. These terms are used here as though they were synonymous. Consider the following: What is the difference between a "hyperchloraemic acidosis" and a "normal anion gap acidosis"? There are TWO problems in the definition of this type of metabolic acidosis which can causeĬonfusion. The anion that replaces the titratedīicarbonate is chloride and because this is accounted for in the anion gap formula, the anion gap is normal. In hyperchloraemic acidosis, the anion-gap is normal (in most cases). Next 8.4.1 Is this the same as normal anion gap acidosis? Acid-Base Physiology 8.4 Hyperchloraemic Metabolic Acidosis
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