Flashcards in 11.4: Acid / Alka Deck (38):
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
7.1 = 80
7.2 = 63
7.3 = 51
7.4 = 40
7.5 = 32
7.6 = 25
7.7 = 20
Equation of acid base homeostasis?
H + HCO3- -> H2CO3 -> H20 + PCO2 (excreted by lungs)
What are the abnormalities with respiratory alk/acidosis in?
- 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
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?
1. GI loss of bicarb: diarrhea
2. Renal loss of bicarb: Renal tubular acidosis (RTA)
3. Failure to excrete acid: renal failure
4. Acid administration: TPN
5. 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?
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?
1. Net loss of H from ECF
2. Increased Bicarb to ECF
3. Loss of chloride in excess of bicarb
How can H be lost?
1. GI tract: vomit
2. Renal: in urine
3. 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?
1. Excess mineralocorticoids: ADH (tumor)
What is mineralocorticoid in humans?
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?
1. Exogenous: bicarb, lactate, citrate, acetate
2. Chloride rich fluid loss: more bicarb resorbed
How is Cl lost in GI?
1. Villous adenoma: Cl secreting tumor into school
2. Failure of gut to resorb
Causes of renal chloride loss?
1. Diuretics: impair resorption
2. Bartter's syndrome: defect of K2Cl in loop
3. 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?
What is low Cl in urine indicative of?
- Cl depletion
DD for metabolic alkalosis?
1. Chloride responsive: low Cl in urine
2. 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
• Volume repletion
• Intravenous HCl or NH4Cl
What is normal PCO2?