acid-base metabolism

Question 1

what are the 3 most important buffers for h+ ions?

where do these buffering systems work?

Answer 1

1. Bicarbonate HCO3- (kidney)

phosphate HPO4-,

haemoglobin Hb- (red blood cells)

protein, bone

Question 2

where is bicarbonate found?

Answer 2

ECF

Glomerular filtrate

Question 3

which transport system used to take bicarbonate out into urine?

Answer 3

Na+/H+ system

Question 4

where is bicarbonate reabsorbed?

Answer 4

PCT: proximal convoluted tubule

Question 5

how does thee ABG analyser produce bicarbonate levels from blood samples?

Answer 5

the analyser does NOT directly measure bicarbonate, it calculates it using the an equation including:

co2, h+ concentration and a coefficient

Question 6

what is the primary abnormality in metabolic acidosis?

Answer 6

increased H+

decreased HCO3-

Question 7

what is the primary abnormality in (acute) respiratory acidosis and alkalosis?

Answer 7

Acidosis:
high pCO2
this causes the equation equilibrium to shift left
causes increased h+
pc02 and hco3- stay elevated post compensation
NOTE: hco3 only rises by 2-4

Alkalosis:
Low pCO2
causes low h+
pc02 and hco3- stay low post compensation

Question 8

NOTE: in exams, drawing the arrows on those diagrams has come up as questions before

Answer 8

review it .

really good cases here too

Question 9

what are the causes of respiratory alkalosis?

Answer 9

Hyperventilation:

• asthma/panic attack
• artficial ventilation
• stimulation of resp centre

Question 10

what are the principles to figure out acid base status really easily:

Answer 10

pH: tells you if its acidosis/alkalosis

pCO2: tells if respiratory distrubance present. prim/secondary

• low: alkalosis
• high: acidosis

HCO3-: reflects metabolic disturbance but can be otherwise

- low: acidosis
- high: alkalosis

Question 11

list some causes of metabolic alkalosis?

Answer 11

Hypokalaemia

Pyloric stenosis: lost in vomit = Hcl loss, K+ loss
- (RAS system)

ingestion of bicarbonate

Question 12

what are esome causes of respiratory acidosis?

Answer 12

decreased ventilation/ breathing

impaired gas exchange

poor lung perfusion

Question 13

list somee causes of metabolic ACIDosis with high anion gap

Answer 13

Main ones to remember are:
DKA
Lactic acidosis
Salicylate poisoning - aspirin

Mnemonic; MUDPILES

or KULT

• Ketoacidosis (DKA, alcoholic, starvation)
• Uraemia (renal failure)
• Lactic Acidosis
• Toxins (ethylene glycol, methanol, paraldehyde, salicylate)