ABGs ☺️ Flashcards
What are the normal ranges for
- pH
- PO2, PCO2, HCO3
- lactate, base excess
- SaO2
pH - 7.35-7.45 PO2 - 10-13 SaO2 - 98% PCO2 - 4.7-6.0 HCO3 - 22-26 Base excess - -2-+2 Lactate - U2
Describe how to interpret the ABG
- Look at the patient
- Hypoxemic? - SaO2 under 10
- pH => acidemic or alkalemic? Mixed or fully compensated? Partial compensation?
- Resp PCO2 derangement?
5 Metabolic HCO3 derangement?
What are common causes of resp acidosis
-hypoventilation
Lung issues
- acute/chronic lung diseases
- airway obstruction
Drug issues
-sedatives: BZ, opiates
NM issues
- NM disease: Guillain Barre, Myasthenia Gravis,
- obesity hypoventilation syndrome
How does respiratory acidosis present?
Management?
Respiratory distress, shallow breaths
CO2 narcosis: Headache , restless, confusion, drowsy
High HR
O2 if needed
Assess and manage cause
Ventilation may be needed
Common causes of respiratory alkalosis
Hyperventilation
Lung issues
- PE, PT
- high altitude
- asthma/COPD exacerbation
CNS (direct stimulation of resp centres)
-stroke, SAH, encephalitis
Drugs
-salicylates
Psych
-anxiety
Other
-pregnancy
How does resp alkalosis present?
-management
Numbness, light headed
Nervous
Hyperventilation
Muscle cramps, tingling
LOC, death
Management
- manage underlying cause
- O2 if sats are low
- ventilation may be needed
Common causes of metabolic acidosis
-normal anion gap
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
How to calculate the anion gap
(Na + K) - (Cl + HCO) = 8-12
Common causes of metabolic acidosis
-increased anion gap
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
Presentation of metabolic acidosis
Management
Nausea, vomiting, SOB/Kussmaul
Headache, confusion
Monitor ECG, SaO2
Assess for cause
Be prepared to ventilate
Common causes of metabolic alkalosis
HCO3 26+
Loss of acid
Hyperaldosteronism
Antacids
Loop diuretics
Vomiting
Presentation of metabolic alkalosis
Management
Hypoventilation due to inhibition of resp center in medulla
Confusion
SaO2, ECG monitoring
Assess cause
Be prepared to ventilate
Examples of mixed acidosis and alkalosis
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