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