11.4: Acid / Alka Flashcards
What is metabolic acidosis?
- Decrease in bicarb [] in plasma
- Increases [H] plasma
- Accompanied by decrease in PCO2 to maintain PH
- Known as respiratory alkalosis
What is respiratory alkalosis?
- Decrease in PCO2 to normalize PH increase in metabolic acidosis
What is total CO2 / CO2 content?
What the chemistry lab calls bicarb when they measure it
What is the henderson Equation?
H+ = 24 PCO2 / HCO3-
***Want to keep hydrogen ion constant
Various [H] and PHs
- 1 = 80
- 2 = 63
- 3 = 51
- 4 = 40
- 5 = 32
- 6 = 25
- 7 = 20
Equation of acid base homeostasis?
H + HCO3- -> H2CO3 -> H20 + PCO2 (excreted by lungs)
What are the abnormalities with respiratory alk/acidosis in?
- PCO2
- Compensatory movement in bicarb
Predicted volume of compensation in alka / acid?
1.2 decrease bicarb = decrease in PCO2
.7 increase bicarb = increase in PCO2
What is electroneutrality?
- Anions in body must match volume of cations
- Na + UC = HCO3 + Cl + UA
- UC/A: unmeasured cations and anions
What is the anion gap?
- Na+, Cl-, and HCO3- are most prevalent ions
- DIfference between Na+ and Cl- + HCO3- is “anion gap”
- Anions must equal cations so no “real” gap
- ***Usually is 10 - 12
What does increased anion gap acidosis point to?
- Overproduction of an organic acid with retention of organic anion
- Organic acids are anions
- The acid is titrating the bicarb dropping its volume
2 causes and subclasses of increased anion gap acidosis?
Increase organic acid production 1. Ketoacidosis 2. Lactic acidosis 3. Toxin ingestion Failure to excrete organic ions: 1. Renal failure
What is hyperchloremic acidosis?
- Bicarb is low, Cl- may increase to keep neutrality
Causes of Hyperchloremic acidosis?
- GI loss of bicarb: diarrhea
- Renal loss of bicarb: Renal tubular acidosis (RTA)
- Failure to excrete acid: renal failure
- Acid administration: TPN
- High doses of saline
What is type II RTA?
“Renal Tubular acidosis” proximal tubule
- Impairment in HCO 3 reabsorption in proximal
- Bicarb begins to be spilled in urine at earlier level
- Causes acidosis in body with increased Cl- resorption with Na to neutralize HCO3 that was dumped
- Patient will have low serum bicarb and high Cl
What is Type I RTA?
- Inability to excrete H in distal tubule
- H ATPase normally pumps H out to combine with bicard
- This is impaired in RTA II
2 most common causes of hyperchloremic acidosis?
- Diarrhea
2. Kidney disease
How treat metabolic acidosis?
Normal anion gap: bicarb
- Na or K / bicarb can be given as well
- Bicarb formers can be given as well
What is metabolic alkalosis?
- Increase in plasma bicarb
- Accompanied by increased PCO2 to maintain PH
Generation of metabolic alkalosis?
- Net loss of H from ECF
- Increased Bicarb to ECF
- Loss of chloride in excess of bicarb
How can H be lost?
- GI tract: vomit
- Renal: in urine
- Shift into cells
What happens to H in stomach?
- Titrate by pancreatic bicarb
- If H is lost in vomiting, net increase in bicarb
How is H lost in urine?
- Excess mineralocorticoids: ADH (tumor)
What is mineralocorticoid in humans?
Aldosterone
Why does H shift into cells?
- K moves out of cells in sever HYPOkalemia
- H moves in to replace charge
What can cause bicard gain?
- Exogenous: bicarb, lactate, citrate, acetate
2. Chloride rich fluid loss: more bicarb resorbed
How is Cl lost in GI?
- Villous adenoma: Cl secreting tumor into school
2. Failure of gut to resorb
Causes of renal chloride loss?
- Diuretics: impair resorption
- Bartter’s syndrome: defect of K2Cl in loop
- Gitelman’s syndrome: defect in NACL cotransporter in distal
How is Cl lost in skin?
CF loss of Cl in excess of bicarb in sweat
How does kidney handle bicard?
- Freely filtered
- Reabsorbed in proximal nephron
- That consumed by acid is regenerated in distal
Reason for maintenance of metabolic alkalosis?
- Chloride depletion
- If you give solely Cl- back it corrects
- Usually given as NaCl
Why does chloride correct metabolic alkalosis?
- In type B intercalated cell, Cl moves into cell allowing bicarb to be dumped in urine to correct alkalosis
Signs of metabolic alkalosis?
- Hypoventilation
- Vomiting
- Diuretics
- Cramps
- Htn.
What is low Cl in urine indicative of?
- Cl depletion
DD for metabolic alkalosis?
- Chloride responsive: low Cl in urine
- Chloride resistant: high Cl seen in urine: ADH excess state
- Extra Cl- will just be dumped in urine
How is metabolic alkalosis treated?
- Potassium administration
- Acetazolamide
- Volume repletion
- Intravenous HCl or NH4Cl
What is normal PCO2?
40
What is normal anion gap?
- 10 - 12
- If less than this when you calculate its normal anion gap
- If higher, high anion gap
