Acidosis & alkalosis: Difference between revisions
Kingrajinix (talk | contribs) |
Kingrajinix (talk | contribs) |
||
| Line 17: | Line 17: | ||
===Normal anion gap=== | ===Normal anion gap=== | ||
Essentially, what happens is that bicarbonate is lost or H<sup>+</sup> ions are ingested (though Cl<sup>-</sup> is retained). This decreases blood pH. It's usually caused by [[diarrhoea]] but other causes include: renal tubular acidosis (failure of the kidneys to transport H<sup>+</sup> ions into urine); drugs, particularly acetazolamide; [[Addison's disease]]; [[pancreatic]] [[fistulae]]; and ammonium chloride ingestion. | Essentially, what happens is that bicarbonate is lost or H<sup>+</sup> ions are ingested (though Cl<sup>-</sup> is retained). This decreases blood pH. It's usually caused by '''[[diarrhoea]]''' but other causes include: renal tubular acidosis (failure of the kidneys to transport H<sup>+</sup> ions into urine); drugs, particularly acetazolamide; [[Addison's disease]]; [[pancreatic]] [[fistulae]]; and ammonium chloride ingestion. | ||
===Metabolic alkalosis=== | ===Metabolic alkalosis=== | ||
===Respiratory acidosis=== | ===Respiratory acidosis=== | ||
===Respiratory alkalosis=== | ===Respiratory alkalosis=== | ||
Revision as of 12:39, 22 September 2009
Here is a glossary of these terms, which is useful for understanding some of the blood buffer systems. There are basically four abnormalities with regards to the acid-base balance in blood. You should ask yourself three questions:
- Is the pH high or low? - low pH= acidosis and high pH = alkalosis.
- Is CO2 abnormal? - if 'yes':
- Is this in keeping with the pH change? - i.e. when pH↑, CO2↓ OR pH↓, CO2↑. These changes point to a respiratory acidosis/alkalosis. If the change is not there, then it is a compensatory change.
- Is the HCO3- abnormal? - if 'yes'
- Is this change in keeping with the pH change? - i.e. (opposite to CO2 changes) when pH↑, HCO3-↑ OR pH↓ HCO3-↓ then the change is metabolic. Otherwise, the change is again a compensatory change.
- Is this change in keeping with the pH change? - i.e. (opposite to CO2 changes) when pH↑, HCO3-↑ OR pH↓ HCO3-↓ then the change is metabolic. Otherwise, the change is again a compensatory change.
"Compensatory" means that there is a change to the body's acid-base balance but the buffer systems the body has in place are attempting to deal with it. At the end of asking these questions you should end with one of five options. They are the titles the following titles
Metabolic acidosis
Unfortunately, life as ever, is not so simple. There are two types of metabolic acidosis - with or without an anion gap. Essentially, this is the difference in concentrations between cations (+ve ions) and anions (-ve ions). You calculate it using the following formula
Na+ - (Cl- + HCO3-) = 8-12mEq/l (that's the number of charges)
We then split metabolic acidosis into:
High anion gap
This caused when there is an increase of non-measured acids. That is lactic acid (due to shock, infection or hypoxia), urate i.e. uric acid (in [[renal failure), ketoacidosis (diabetes, alcohol) and with drugs or toxins (salicylates, biguanides like metformin, ethylene glycol and methanol which are found in antifreeze)
Normal anion gap
Essentially, what happens is that bicarbonate is lost or H+ ions are ingested (though Cl- is retained). This decreases blood pH. It's usually caused by diarrhoea but other causes include: renal tubular acidosis (failure of the kidneys to transport H+ ions into urine); drugs, particularly acetazolamide; Addison's disease; pancreatic fistulae; and ammonium chloride ingestion.