Metabolic acidosis

Question 1

The ddx of metabolic acidosis is based on what?

Answer 1

whether it is non-anion gap or anion gap

• since met acidosis is due to either:
  1. loss in HCO3- (non-anion gap) or
  2. addition of acid (anion gap)

*note that the addition of acid consumes and lowers HCO3-

Question 2

Normal and elevated values of anion gap

Answer 2

9 +/- 3

elevated usually considered > 18

Question 3

Renal tubular acidosis (RTA)

Answer 3

Non-anion gap metabolic acidosis from loss of HCO3-

Question 4

3 major forms of renal tubular acidosis (RTA)

Answer 4

1. proximal
2. distal
3. hyperkalemic

Question 5

ammonia production is inhibited by ______

Answer 5

hyperkalemia. This can prevent the excretion of titratable acid that can bind free H+ and result in renal tubular acidosis (RTA)

Question 6

How can urine pH be used to determine if renal acid excretion (new HCO3- generation) is appropriate?

Answer 6

normal: 5.3), this suggests that RTA is present (not fxning)

- If urine pH is acidic (

Question 7

How can urine anion gap be used to determine if renal acid excretion (new NH4+ generation) is appropriate?

Answer 7

if metabolic acidosis is present, NH4+ production should increase. This is indirectly measured via urine anion gap since [Cl-] goes up when NH4+ goes up.

• (-) urine anion gap = ammonia production is occuring, meaning that the nonanion gap metabolic acidosis = GI loss
• (+) urine anion gap = renal ammonia production is impaired and RTA is present

Urine anion gap = Urine [Na+] + Urine [K+] - [Cl-]

Question 8

causes of anion gap metabolic acidosis

Answer 8

M: methanol
U: uremia
D: DKA
P: prop glycol
I: infxn
L: lactic acid
E: ethylene glycol
S: sialic acids (aspirin)

Question 9

metabolic acidosis equation

Answer 9

(40-CO2) = 1 to 1.5 x (24 - HCO3-)

Question 10

In acute and chronic conditions the pH wil change how much for every PCO2 change?

Answer 10

acute: pH change 0.08 for every 10 mmhg change in PCO2
chronic: pH change 0.03

Question 11

How do you calculate for compensation for respiratory acidosis?

Answer 11

acidosis: two ways
1. ΔpH/Δ CO2
- 0.008 = acute
- o.oo3 = chronic
in between = mixed
2. HCO3-: CO2 ratio
- ↑1 HCO3-: ↑ 10 CO2 = acute
- ↑ 4 HCO3-: ↑ 10 CO2 = chronic

Question 12

how to tell if respiratory system is compensating correctly when a metabolic disturbance is present?

Answer 12

Δ HCO
Δ CO2

ΔCO2 should be 1-1.5 x Δ HCO3