ABG

Question 1

Relative hypoxaemia

Answer 1

When supplementary O2 is high to keep PaO2 within normal limits

PaO2 to FiO2 ratio
If <40 then deemed hypoxic

Appprox 1mmol H+/kg/day produced

Question 2

Respiratory acidosis

Answer 2

Retention of CO2
Kidney takes 48 hours to respond

Causes:
Head or spinal injury
Drug overdose
Chest wall deformity or injury
Myopathy or peripheral neuropathy
Pulmonary disease
Massive embolus

Question 3

Metabolic acidosis

Answer 3

Inability of kidney to extreme non-volatile hydrogen (or sudden increases in non-volatile load in sepsis for example)

Resp minute volume increased

Causes
Impaired tissue perfusion
Renal failure
Hepatic failure

Question 4

Respiratory alkalosis

Answer 4

Minute ventilation too high than normal required to maintain PaCO2 appropriate for H+ of 40nmol

Fever, hepatic disease, aspirin toxicity or CNS dysfunction cause this

Question 5

Metabolic alkalosis

Answer 5

Increased bicarbonate by abnormal retention or administration of bicarbonate
Can also result from loss of non-volatile acid from body (GOO, chronic aspiration)

Base excess is what is needed to return blood to normal pH under standard conditions