Acid Base balance E videos

Question 1

with this equation, define what metabolic and respiratory acidosis is

H = PCO2/HCO3-

Answer 1

1. acidosis: low pH high H ion concentration

Respiratory: Low H with HIGH CO2 (primarily), increased bicarbonate can be seen due to renal compensation

Metabolic: Low H with LOW BICARBONATE, reduced PCO2 seen due to respiratory compensation

NB lots of metabolic acidosis cause

Question 2

Normal ranges of:
pH, upper and lower limit
HCO3 levels to maintain normal pH

Answer 2

pH range: 7.35-7.45
Upper: 8.0
Lower: 6.8

Hco3 level: 24-26mmol/L

Question 3

clinical parameters to differentiate metabolic acidosis (x2)

Answer 3

1. Base excess

2. Anion gap

Question 4

define base excess and the normal range. explain what they mean

Answer 4

the concentration of strong acid or base needed to return pH to normal level, under NORMAL body temperature AND CO2 level

normal range -/+ 3mEq/L

base excess: positive value. indicates metabolic alkalosis (too much base)

base deficit: negative value: indicates metabolic acidosis because less HCO3- to buffer

Question 5

what is the anion gap and the reference value.

name and explain the 3 types of AG situation

Answer 5

definition: [Na+K]-[Cl+HCO3], normal value: 12mmol/L
USED TO DIFFERENTIATE causes of METABOLIC acidosis

normal ion gap metabolic acidosis:
MA: reduced HCO3- level
normal gap because:
1. equal amount of +ve loss ie diarrhoea Na loss too
2.Cl- retension to balance = ‘apparent’ no difference (hypercloraemia)
ie: renal tubular acidosis, azetazolamide drug use

increased AG metabolic acidosis
MA: reduced HCO3-
Raised gap: increased anion from different sources, uses up buffer system = reduced HCO3- = increase gap

sources: lactic acid, ketone bodies, salicylic acid (aspirin)

Question 6

what does base deficit with normal AG implicate

Answer 6

base deficit: metabolic acidosis

normal AG: hypercloraemia, equal Na loss see above

Question 7

what are the 3 main chemical buffer system

Answer 7

chemical buffer system is the most efficient:

1. protein buffer - haemoglobin
2. bicarbonate buffer system: main one in extracellular fluid and blood
3. phosphate buffer system: HPO4 2-

Question 8

2 other buffer system

Answer 8

respiratory - quick

renal - slow, takes days: increase or decrease H/Hco3 reabsorption/ excretion

Question 9

transporters to correct:

CELLULAR acidosis/ alkalosis

Answer 9

cellular acidosis: Na/H exchanger: H out, Na in

cellular alkalosis:HCO3-/Cl- exchanger: cl shift

Question 10

explain hyperkalaemia seen in metabolic acidosis

Answer 10

1. acidosis: increase H gradient, increased H INTO cells
   2.Na/H activity reduced:
   3.intracellular NA decrease = inhibit activity of Na/K ATPase
   = less K move into cell
   HYPERKALAEMIA

diabetic KB careful as sudden hypokalaemia dangerous