Test 3: Wk13: 2 Acid Base Imbalance 1 - Puri Flashcards
henderson hasselbach equation
pH = pH + log (HCO3- / 0.03PCO2)
hyperventilation or hypoventilation during acidosis
hyperventilation to remove excess CO2
hyperventilation or hypoventilation during alkalosis
hypoventilation to retain CO2
— is the main way to achieve net acid excretion
Ammonia
Ammonia requires
Glutamate
acidosis in the kidney does what to glutamine
increases it
Acidosis Respiratory or Metabolic stimulates Renal
resorption of HCO3 and excretion of protons
renal HCO3 is increased due to
increased activity of NHE in the PT
Extracellular Buffer System
CO2 ⇆ H2CO3 ⇆ H+ ⇆ HCO3-
Intracellular Buffer System
Uses non-bicarbonate buffers
Phosphate, Proteins, Bone
Metabolic Acidosis is characterized by — Arterial pH and — Serum HCO3
Low pH
Low Serum HCO3
Normal Arterial pH and range
- 4
7. 35 - 7.45
Normal Serum HCO3- concentration and range
24 meq/L
22-28 meq/L
4 causes of increased acid generation
Lactic Acidosis
Ketoacidosis
Ingestions
2 causes for loss of HCO3-
Diarrhea
PT Acidosis - inability to reabsorbed filters HCO3
2 causes of diminished renal acid secretion
Renal Failure
Distal renal tubular acidosis - inability to excrete daily acid load
Type 1 RTA Pathology
↓ H excretion in the
collecting ducts
Type 1 RTA Cause
Defect in the H-ATPase
Type 1 RTA Urine pH
> 5.3
Type 1 RTA Plasma K
↓
Type 2 RTA Pathology
↓ HCO3 reabsorption in
the proximal tubule
Type 2 RTA Cause
Reduced NHE activity,
possibly due to ↓
carbonic anhydrase
Type 2 RTA Urine pH
<5.3
Type 2 RTA Plasma K
↓
Type 4 RTA Pathology
↓ H excretion in the
collecting ducts
Type 4 RTA Cause
Hypoaldosteronism
Type 4 RTA Urine pH
<5.3
Type 4 RTA Plasma K
↑
Winters rule for Compensation in metabolic acidosis
Expected pCO2 = 1.5 x [HCO3] + 8 +/- 2
PCO2 appropriately low
well compensated primary metabolic acidosis
PCO2 higher than predicted
superimposed respiratory acidosis
PCO2 lower than predicted
superimposed primary respiratory alkalosis
HCO3 <25
Primary Metabolic Acidosis
HCO3 > 40
Primary Respiratory Acidosis
Metabolic acidosis depletes
body stores of K
Normal anion gap
12
Normochloremic Acidosis
Wide anion gap Mudpiles
2 most important causes of wide anion gap
Ethylene Glycol
Salicylate Poisoning
Anion Gap =
measured Cation - Measured anion
6 Causes of Hyperchloremic Acidosis
- Fistula
- Type 2 RTA
- Type 1 RTA
- Type 4 RTA
- Diarrhea
- NaCl or NH4Cl infusion
why does Cl increase in hyperchloremic acidosis
volume loss causes the kidneys to try and retain NaCl. Kidneys absorb more Cl to maintain electronegativity
Respiratory Acidosis is also called
hypercapnia
how long does renal compensation take
48 hours
4 for 10 rule
expected HCO3 in chronic respiratory acidosis will increase by 4mmol/L for every 10mmhg above pCO2 about 40mmHg
if HCO3 rises more suspect
metabolic alkalosis with respiratory acidosis
if HCO3 does not increase suspect
renal insufficiency or metabolic acidosis with respiratory acidosis
PaCO2 < 40
Metabolic Acidosis
PaCO2 > 40
Respiratory Acidosis
Metabolic Alkalosis of renal origin is associated with Volume depletion caused by
Diuretics - Loops and HCTZ
Barters Syndrome - defective NKCC2
Metabolic Alkalosis of Non-renal origin with extracellular volume depletion causes
GI fluid Loss
metabolic Alkalosis of renal origin with volume expansion and hypertension causes
Hyperaldosteronism or Liddle Syndrome
Renal Artery Stenosis
metabolic alkalosis is almost always
hypochloremic
Buffering in metabolic alkalosis causes
hypokalemia
Respiratory Compensation in metabolic alkalosis
Expected pCO2 = 40 + (.6 x deltaHCO3)
Respiratory Alkalosis main cause
hyperventilation
5 for 10 rule
at completion of compensation serum HCO3 decreased
5 mEq/L per 10mmHg decrease in PCO2 due to increased HCO3 reabsorption
if HCO3 drops more suspect
metabolic acidosis with respiratory alkalosis
if HCO3 does not decrease suspect
renal insufficiency or metabolic alkalosis with respiratory alkalosis
