OSCE facts

Question 1

Calculate A-a gradient

Answer 1

PAO2 - PaO2
FiO2 (Patm - Pwv) - PaCO2 / 0.8
FiO2 (713) - PaCO2 x 1.25
150 - PaCO2 x 1.25

Normal < age/4 + 4

Question 2

Urea : creatinine ration

Answer 2

Urea mmol/L : creatinine mmol/L
Creat in micromol/L divide by 1000

Pre-renal > 100:1
Post/normal 40-100:1
Renal < 40:1

Question 3

Warfarin reversal

Answer 3

INR > 1.5 critical bleeding 
Stop warfarin 
IV vitamin K 10 mg 
Prothrombin complex concentrate 50 IU/kg 
FFP 300 mls

Question 4

Rivaroxaban / Apixaban reversal

Answer 4

TXA 1g
Prothrombin complex concentrate 50 IU/kg
Andexanet if available

Question 5

Dabigatran reversal

Answer 5

Idarucizumab 5g

TXA 1g

Question 6

Physiological pregnancy changes - A & B

Answer 6

A: 
- tissue oedema / hyperaemia 
- breast tissue & laryngoscope tissue 
- reduced LOS tone, aspiration 
B: 
- raised diaphragm, pneumothorax 
- high O2 consumption, rapid hypoxia 
- MV and TV increase, resp alkalosis
- reduced FRC, rapid hypoxia

Question 7

Physiological changes in pregnancy - Circulation

Answer 7

Low BP in 2nd trimester
HR increases 10-15 bpm
Supine hypotension, IVC compression, left tilt
Raised BV by 40%, late sigs of blood loss
Raised CO, 6L / min
Uterine blood flow 600 mls/min

Question 8

Nexus criteria

Answer 8

Normal alertness 
No intoxication 
No painful distracting injury 
No focal neurological deficit 
No midline tenderness 

Alt: canadian C-spine rule.

Question 9

VT vs SVT

Answer 9

NW axis
Very broad (>160 msec)
AV dissociation
Capture / fusion beats
Positive or negative concordance precordial leads
RSR’, taller left r wave ear
Brugada sign (onset R to nadir S) > 100 msec
Josephsons sign: notching / slurring near nadir of S
Initial R wave in aVR (Vereckei)

Age > 35, structural or ischaemic heart disease, IHD, FHx SCD.