DPD: Preoperative assessment of the surgical patient

Question 1

Why perform a preoperative assessment?

Answer 1

Identify + modify risks associated with: airway, anaesthetic, surgery, post operative
May require further special tests/ interventions pre-op
Make decisions on medication E.g. Aspirin/ Metformin
Give advice on fasting
Make decisions on post-op care E.g. ICU/ HDU

Question 2

When is a pre-op assessment performed?

Answer 2

2-4 weeks before surgery:
Long enough to arrange Ix
Soon enough to avoid interim medical problems

Question 3

What important additional information must be gleaned in addition to a normal patient history?

Answer 3

Previous surgeries/ anaesthetics
Any problems e.g. airway/ intubation problems, reaction to drugs, N+V
Smoking/ ETOH
FHx of problems with anaesthetics e.g. malignant hyperpyrexia

Question 4

Describe the ASA grading system of patients

Answer 4

I: Healthy patient, uncompromised
II: Mild systemic disease e.g. hypothyroidism, well controlled HTN or DM
III: Moderate systemic disease e.g. ESKD requiring dialysis, uncontrolled HTN or DM
IV: Severe systemic disease, constant threat to life

Question 5

What is involved in an airway assessment pre-operatively?

Answer 5

Assess neck extension/ flexion: pain/ difficulty/ danger?
Mouth opening: how far can you open your mouth?
Mallampati score
Jaw protrusion: can they stick their bottom teeth infront of their top teeth? (needed for laryngoscope + tube insertion)

Question 6

What drugs may need to be sustained, swapped or stopped before surgery?

Answer 6

Blood thinners: anticoagulants/ antiplatelets
Diabetes drugs: metformin, insulin
Antihypertensives

Question 7

Why is a nil by mouth policy in place? What are the guidelines for fasting before surgery?

Answer 7

Reduce aspiration risk
NBM: 2 hours, Except for 30mls water with tablets
Clear fluids: 2 hours before
Solid food: 6 hours before

Question 8

What special consideration must be planned for certain diabetic patients?

Answer 8

IV Insulin infusion

Question 9

What does POSSUM use? Why is it useful?

Answer 9

Patient physiological parameters + operative variables
Calculates mortality + morbidity risk
Informs risk discussion, extra requirements in + post surgery

Question 10

How do you optimise and control a diabetic for surgery?

Answer 10

Measure glycosylated Hb

In IDDM: insulin sliding scale

Question 11

How do you optimise and control a patient with HTN for surgery?

Answer 11

Measure BP

Stay within 20% of normal BP

Question 12

How do you optimise and control a patient with IHD for surgery?

Answer 12

ECG/ symptoms

BP + HR control

Question 13

How do you optimise and control a patient on anticoagulants for surgery?

Answer 13

Reason for anticoagulants?
AF: stop
Heart valve: continue

Question 14

Which 3 factors influence whether a surgery can be a day surgery?

Answer 14

Social: consent, carer, home setup
Medical: fitness, stable chronic
Surgical: complication risks, controllable post-op symptoms, mobility

Question 15

In which patients should you perform further pre-op investigations?

Answer 15

Blood anomalies: anaemia, renal dysfunction

Question 16

What must be included in prescription of opioids? e.g. morphine

Answer 16

Dose
Form
Strength (where appropriate)
Total quantity or dosage units of the preparation in words + figures
For instalment prescriptions, specify the instalment amount + instalment interval

Question 17

What are the 2 types of spontaneous ventilation?

Answer 17

Unassisted: pressure gradient generated only by respiratory muscles
Assisted: ventilator acts as a pressure generator in series with the respiratory muscles + work is shared by the muscles + the machine

Question 18

What is natural spontaneous ventilation?

Answer 18

Respiratory apparatus pulls rib cage open, creating a negative inspiratory pressure.
Leads to lung expansion + the pulling of air into the alveoli allowing gas exchange.

Question 19

What is positive pressure ventilation?

Answer 19

Compressed air enters at the alveolar level for gas exchange.

Question 20

What is the main difference between spontaneous ventilation and mechanical ventilation?

Answer 20

Spontaneous: air pulled into the lungs
Mechanical: air pushed into the lungs

Question 21

What is a Guedel (oropharyngeal) airway? Why is it used?

Answer 21

Airway adjunct
Prevents tongue covering epiglottis in patients with reduced GCS
O2 mask or bag mask ventilation can be applied over the top if needed

Question 22

What is a bag-mask-valve? What do they do? Who are they used in?

Answer 22

Self-inflating resuscitation device
Provide positive pressure ventilation to patients not breathing.
Used in apnoeic patients

Question 23

What is an endotracheal tube? What are the indications for use?

Answer 23

Tube forms a definitive airway, attached to bag/ machine
Inadequate ventilation/oxygenation
Maintain a patient’s airway in surgery

Question 24

What is an Igel/ supraglottic device? When is it used?

Answer 24

Tube which sits over top of larynx
Provides some aspiration protection but doesn’t fully secure the airway
Airway protection during surgery
Cardiac arrest

Question 25

How much O2 is delivered by nasal cannulae? When are they used?

Answer 25

24-30% O2
1-4 L/min
Non-acute situations
Mild hypoxia

Question 26

How much O2 is delivered by Hudson facemasks? When are they used?

Answer 26

30-40% O2
5-10 L/min
Rarely used

Question 27

How much O2 is delivered by a Venturi mask? When are they used?

Answer 27

24-60% O2
Fixed flow rate (different colours)- so can adjust flow rate
COPD

Question 28

How much O2 is delivered by non-rebreather masks? When are they used?

Answer 28

60-90% O2
15 L/min
Acutely unwell + apnoeic patients

Question 29

What is CPAP? When is it used?

Answer 29

High positive pressure of O2 all the time (to splint airways open)
Used in Type 1 respiratory failure e.g. pulmonary oedema/ OSA

Question 30

What is BiPAP?

Answer 30

High positive pressure on inspiration + lower positive pressure on expiration
Used in type 2 respiratory failure e.g. COPD exacerbation (hypoxic + hypercapnic)