Acid-Base balance

Question 1

what is normal range for pH

Answer 1

7.35-7.45

Question 2

what is normal range for CO2

Answer 2

4.7-6

Question 3

what is normal range for bicarbonate

Answer 3

22-30

Question 4

what is the systematic way to determine acid-base balance?

Answer 4

1) assess pH
2) evaluate pCO2
3) evaluate bicarbonate
4) determine compensation (partial/complete)

Question 5

how does one compensate for metabolic acidosis?

Answer 5

hyperventilation (to get rid of CO2)

Question 6

what is the anion gap

Answer 6

cations - anions
= (Na + K) - (HCO3 + Cl-)
=(sodium + potassium) - (bicarb + chloride)
= concentration of unmeasured anions in blood (almost entirely contributed by albumin)

Question 7

what is the normal range for anion gap

Answer 7

14-18 mmol/L

Question 8

high anion gap metabolic acidosis causes?

Answer 8

GOLD MARK

G= glycols (ethylene glycol = antifreeze, propyly glycol)
O = oxoproline (chornic paracetamol use)
L = L-lactate (sepsis)
D = D-lactate (short bowel syndrome)
M = methanol
A = aspirin overdose (initially causes respiratory alkalosis due to hyperventilation but in severe/moderate metabolic acidosis)
R= renal failure (uraemia)
K = ketoacidosis (DKA, alcoholic, starvation)

Question 9

what are causes of a normal anion gap metabolic acidosis?

Answer 9

here bicarbonate is lost and replaced with chloride leading to normal anion gap

ABCD

A = addisons disease
B = bicarbonate loss (diarrhoea, laxative abuse, renal tubular acidosis)
C = chloride gain (sodium chloride 0.9% infusion)
D = drugs (acetazolamide)

Question 10

why during metabolic alkalosis with hypokalameia in bulimia nervosa is the urine paradoxically acidic?

Answer 10

-shift of H+ out of cells to buffer the increase blood pH
-to maintain electrical neutrality, K+ moves into cells, so low extracellular potassium (hypokalemia)
-in DCT, there is exchange of K+ for H+ - where H+ is secreted into urine. since high K+ in cells, this causes more H+ to be released into urine, causing acidic urine

Question 11

when can lactate be falsely elevated

Answer 11

when using Hartmanns solution (contains lactate)

Question 12

what are causes of a metabolic alkalosis?

Answer 12

(loss of H+, loss of K+, ingestion of bicarboante)

-vomiting (H+ loss)
-loop diuretics (K+ loss)
-hypokalameia
-Conns syndrome (K+ loss)
-antacids
-burns
-milk-alkali syndrome (excess intake of alkali)

Question 13

what are causes of respiratory acidosis?

Answer 13

Hypoventilation
-type 2 resp failure
-acute/chronic lung disease (COPD)
-opioids
-sedatives
-neuromuscular weakness
(normal/high PaCO2 is worrying)

Question 14

what are causes of respiratory alkalosis?

Answer 14

hyperventilation
-stroke, SAH, meningitis, asthma, anxiety, PE, pregnnacy, altitude (hypoxaemia), salicylates (early brainstem rxn)

(think of brain things stimulating resp centers in brainstem & pregnancy (with associated PE)