Acid Base

Question 1

Acid base homeostasis

Answer 1

CO2 + H20 H2CO3 HCO3- + H+

Henderson equation
[H+] = 24 (pCO2)/[HCO3-]

HCO3- gets REAB in the proximal tubule
H+ gets secreted in the collecting duct

Carbonic anhydrase catalyzes these events

You want your pH to be 7.4
CO2 is your acid (higher than 40 is acidosis, lower is alkalosis)
HCO3- is your base (Lower than 24 is acidosis, higher is alkalosis)

Question 2

Simple acid base disturbance

Answer 2

Primary respiratory acute or chronic)- Acidosis (pCO2> 40 mmHg), Alkalosis (pCO2 < 40 mmHg)

Primary metabolic (+/- Anion Gap): Acidosis (HCO3- <24 mmol/L), Alkalosis (HCO3- > 24 mmol/L)

Mixed acid-base disturbance (combo of 2 or 3 from above)

Question 3

systematic approach

Answer 3

ph, then determine disorder (metabolic or respiratroy), calculate expected compensation, calculate anion gap, review change in HCO3- and change in AGAP

Question 4

Why compensate

Answer 4

Metabolic compensation for respiratory disorder
Respiratory compensation for metabolic disorder

Attempts to bring back pH back to 7.4
Normal pH ideal for enzymes

If not compensated likely another disorder also present

Question 5

Compensation for metabolic disorder

Answer 5

Metabolic Acidosis:
pCO2= 1.5 x [HCO3-] + 8
pCO2 = last 2 digits of pH

Metabolic Alkalosis
pCO2 = 15 + [HCO3-] (maximum pCO2 is 55 mmHg)

pCO2 compensates in same direction as bicarb

Question 6

Compensation for respiratory disorder

Answer 6

Respiratory Acidosis (Pa CO2> 40)
Acute: bicarb up 1 mmol/L per 10 mmHg up PaCO2
Chronic: bicarb up 4 mmol/L per 10 mmHg up PaCO2

Respiratory Alkalosis (PaCO2<40)
Acute bicarb down 2 mmol/L per 10 mmHg down PaCO2
Chronic: bicarb down 4 mmol/ L per 10 mmHg down PaCO2

Question 7

Why is primary metabolic disturbances compensation calculated for

Answer 7

Compensation is calculated to determine if a secondary disorder is present

Question 8

Elevated anion Gap metabolic acidosis

Answer 8

MUDPILES
Methanol intoxication
Uremia (renal faiulure)
Diabetic Ketoacidosis
Paraldehyde
Isoniazid
Lactic Acid
Ethylene glycol intoxication
Salicylate intoxication

Question 9

Anion Gap equation

Answer 9

24 mEq NaHCO3
104 mEq NaCl
12 mEq NaAG

Anion Gap= Na+ - (Cl- + HCO3-)

12= 140 - (104+24)

Normal Anion gap is 12