answer to the saudi medical council question examination

Acid Base

Questions
1. What is the decision tree in acid base disorders?
2. Sampling: where are the following sampled
a. Osmolarity
b. pH, pCO2, and calculated standard bicarbonate
3. How is the acid base balance controlled in the
a. Lungs
b. Kidneys
c. How can pH be expressed to reflect this
4. What is the anion gap?
a. Give the formula, and the normal range
b. Increased anion gap acidosis would present when?
c. Normal anion gap acidosis would present when?
d. Decreased anion gap would present when?
5. How would the following present, clinically, and the primary change
a. Metabolic acidosis
b. Metabolic alkalosis
i. Hypokalemia
c. Respiratory acidosis
i. Acute:
ii. Chronic:
d. Respiratory alkalosis
i. Acute:
ii. Chronic:

Answers
1. Decision tree in acid base disorders

2. Sampling: where are the following sampled
a. Venous blood: Osmolarity, HCO3+,Na+, K+, Cl-
b. Arterial blood: pH, pCO2, and calculated standard bicarbonate
3. Acid base balance control
a. Lungs
i. Blow off CO2
b. Kidneys
i. Na+ + HCO3- reabsorbed for H+
ii. Acid phosphate excretion
iii. NH4 excretion
c. pH=
4. Anion gap: estimate unmeasured anions
a. positive ? negative = normal anion gap
i. Na+ ? (Cl- + HCO3-)= 12-18 mEq/L (other anions)
b. ? anion gap acidosis:
i. Normal chloride, low/normal HCO3-
1. Other metabolic acid: MUDPILES
a. Methanol & other Alcohols
b. Uremic
c. Diabetic Ketoacidosis
d. Paraldehyde, Phenformin
e. Isoniazid
f. Lactate
g. Ethylene glycol
h. Salicylate
i. Sulfates, phosphates, fixed acids
c. Normal anion gap acidosis
i. Hyperchloremic acidosis
1. Diarrhea
2. Renal tubular acidosis
a. Early renal failure
3. Hyperalimentation
d. ? anion gap: <6 mEq/L
i. Cationic myeloma proteins
ii. Hyperlipidemia with decreased plasma H2O & electrolytes
5. How would the following present, clinically, and the primary change
a. Metabolic acidosis ?HCO3-
i. Kussmaul breathing: respiratory compensation
ii. Hyperkalemia
1. Decreased consciousness
b. Metabolic alkalosis ?HCO3-
i. Hypokalemia
1. Paresthesia
2. Tetany
3. Weakness
c. Respiratory acidosis ?pCO2
i. Acute:
1. Air hunger
2. Disorientation
ii. Chronic:
1. Hypoventilation
2. Hypoxemia
3. Cyanosis
d. Respiratory alkalosis ?pCO2
i. Acute:
1. Hyperventilation
a. Paresthesia
b. Light headedness
ii. Chronic:
1. Hyperventilaton
2. Latent tetany