Metabolic Acidosis
Evaluation
1 . Measurement of the arterial pH and pCO2.& serum HCO3- 2. Determining whether respiratory compensation is appropriate 3. Assessment of the serum anion gap to help identify the cause of acidosis (corrected for albumin concentration) 4. calculation of the delta anion gap/delta HCO3 ratio in patients who have an elevated anion gap
Diminished renal acid excretion
1 .Reduced acid excretion that occurs in conjunction with a reduction in glomerular filtration rate 2. Distal (type 1) RTA and type 4 RTA,
Basics
Dissolved CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+ Acid-base balance is maintained by pulmonary and renal excretion of carbon dioxide and nonvolatile acid, respectively.
Metabolic acidosis with res. acidosis
Here metabolic acidosis is defined as a serum bicarbonate concentration that is lower than the expected compensation for the degree of chronic hypercapnia
Classification
High anion gap Normal anion gap must, by definition, manifest hyperchloremia so also named as hyperchloremic metabolic acidosis
Increased acid generation
Lactic acidosis, Ketoacidosis - DKA, fasting, excess alcohol intake. Ingestions or infusions - Methanol, ethylene glycol, diethylene glycol, or propylene glycol, Aspirin poisoning, Chronic acetaminophen ingestion, especially in malnourished women, D-lactic acid, generated from carbohydrates by gastrointestinal bacteria
Loss of bicarbonate
Severe diarrhea, when urine is exposed to gastrointestinal mucosa (ureteral implantation into the sigmoid colon or the creation of replacement urinary bladder using a short loop of ileum )Proximal RTA II.ketoacid anions are lost into the urine before they can be metabolized, they represent lost potential bicarbonate.
Dilution acidosis
When extraordinarily large volume of alkali-free isotonic fluid is infused
Acidemia
is defined as a low arterial pH (<7.35), which can result from a metabolic acidosis, respiratory acidosis, or both
Metabolic acidosis
pH in a patient with metabolic acidosis may be low, high, or normal
Diagnosis
serum pH is reduced and the serum bicarbonate concentration is abnormally low often defined as <22 mEq/L,
simple metabolic acidosis
the serum pH and bicarbonate concentration will both be reduced
Mechanism
three major mechanisms. 1. Increased acid generation. 2. Loss of bicarbonate 3. Diminished renal acid excretion
