Lecture 11 - Acid Base II Flashcards
Compensation for metabolic acidosis/alkalosis?
decrease/increase pCO2 to counter decreased/increased HCO3-
Compensation for respiratory acidosis/alkalosis?
increase/decrease HCO3 to counter increased/decreased pCO2 (higher degree for chronic than acute)
Base excess definition?
amount of acid or base needed to restore pH 7.4
The anion gap?
(Na + K) - (Cl + bicarb) = normal range of 14-18; useful for metabolic acidosis only
Causes of acidosis with increased anion gap?
Ketoacidosis, Uraemia, Lactic acidosis, Toxins (KULT)
Delta ratio?
increase in AG/decrease in HCO3 - determines if mixed acid/base disorder is present: <1 concurrent normal AG acidosis, 1-2 pure AG acidosis, 2+ concurrent metabolic alkalosis
Causes of normal anion gap acidosis?
non renal causes most common: diarrhoea, GI uteral connections, ileostomy
Renal tubular acidosis?
defects in acid secretion; urine pH higher than 5.5, but ammonium levels normal
Why is normal AG acidosis patients hyperchloremic?
when bicarb is low, extra Cl need be reabsorbed to maintain electroneutrality w sodium reabsorption
Linkage betwen potassium and acidosis?
acidosis = hyperkalemia, alkalosis = hypokalemia; exceptions being diarrhoea (bicarbonate & K+ loss) and renal tubular acidoses (associated w hypokalemia)
Chloride responsive alkalosis?
bicarbonate reabsorption increases to preserve Na balance, cannot be corrected until Cl is replaced, caused by vomiting or diuretics
When is it okay to use venous blood for blood gas analysis?
patient has reasonable perfusion, pO2 is not needed, severe circulatory failure is not present
Artefacts of blood sampling?
air in syringe causes abnormally high pO2 indicating respiratory alkalosis, delayed separation of plasma from RBC causes abnormal lactic acid reading indication metabolic high AG acidosis
