ABGs ☺️

Question 1

What are the normal ranges for

• pH
• PO2, PCO2, HCO3
• lactate, base excess
• SaO2

Answer 1

pH - 7.35-7.45
PO2 - 10-13
SaO2 - 98%
PCO2 - 4.7-6.0
HCO3 - 22-26
Base excess - -2-+2
Lactate - U2

Question 2

Describe how to interpret the ABG

Answer 2

1. Look at the patient
2. Hypoxemic? - SaO2 under 10
3. pH => acidemic or alkalemic? Mixed or fully compensated? Partial compensation?
4. Resp PCO2 derangement?
   5 Metabolic HCO3 derangement?

Question 3

What are common causes of resp acidosis

-hypoventilation

Answer 3

Lung issues

• acute/chronic lung diseases
• airway obstruction

Drug issues
-sedatives: BZ, opiates

NM issues

• NM disease: Guillain Barre, Myasthenia Gravis,
• obesity hypoventilation syndrome

Question 4

How does respiratory acidosis present?

Management?

Answer 4

Respiratory distress, shallow breaths
CO2 narcosis: Headache , restless, confusion, drowsy
High HR

O2 if needed
Assess and manage cause
Ventilation may be needed

Question 5

Common causes of respiratory alkalosis

Hyperventilation

Answer 5

Lung issues

• PE, PT
• high altitude
• asthma/COPD exacerbation

CNS (direct stimulation of resp centres)
-stroke, SAH, encephalitis

Drugs
-salicylates

Psych
-anxiety

Other
-pregnancy

Question 6

How does resp alkalosis present?

-management

Answer 6

Numbness, light headed
Nervous
Hyperventilation

Muscle cramps, tingling
LOC, death

Management

• manage underlying cause
• O2 if sats are low
• ventilation may be needed

Question 7

Common causes of metabolic acidosis

-normal anion gap

Answer 7

Normal anion gap - 8-12 due to
HCO3 U22

Hyperalimentation - associated with high Cl
Addisons - high K => high Cl
Renal tubular acidosis - loss of HCO3
Diarrhoea - loss of HCO3
Acetazolamide - diuretic/CAinh => loss of HCO3
Spirinolactone - high K => high Cl
Saline infusion - high Cl

Question 8

How to calculate the anion gap

Answer 8

(Na + K) - (Cl + HCO) = 8-12

Question 9

Common causes of metabolic acidosis

-increased anion gap

Answer 9

12+ due to increased H that has to be buffered by HCO3
U22

Methanol (antifreeze)
Uraemia - decreased H excretion
DKA (diabetic, alcohol, malnutrition)
Propylene glycol (antifreeze)
Iron tablets
Lactic acidosis
Ethylene glycol (antifreeze)
Salicylate

Question 10

Presentation of metabolic acidosis

Management

Answer 10

Nausea, vomiting, SOB/Kussmaul
Headache, confusion

Monitor ECG, SaO2
Assess for cause
Be prepared to ventilate

Question 11

Common causes of metabolic alkalosis

Answer 11

HCO3 26+
Loss of acid

Hyperaldosteronism
Antacids
Loop diuretics
Vomiting

Question 12

Presentation of metabolic alkalosis

Management

Answer 12

Hypoventilation due to inhibition of resp center in medulla
Confusion

SaO2, ECG monitoring
Assess cause
Be prepared to ventilate

Question 13

Examples of mixed acidosis and alkalosis

Answer 13

Mixed resp and met acidosis

• cardiac arrest
• multi organ failure

Mixed resp and met alkalosis

• cirrhosis+diuretics
• hyperemrsis gravidarum
• excess ventilation in COPD

Resp alk, met acid
-salicylate poisoning