Pre-operative Assessment

Learning Objectives

By the end of this lecture, you should be able to:

• Define pre-operative assessment
  
  

• Understand its importance
  
  

• Take a proper pre-operative history
  
  

• Perform a relevant examination with airway assessment
  
  

• Understand the Mallampati and Wilson airway assessment systems
  
  

What is Pre-operative Assessment?

Pre-operative assessment is the process of evaluating a patient’s readiness for anaesthesia and surgery. It involves reviewing their current medical status, planned surgical procedure, and formulating an anaesthetic plan.

Aims of Pre-operative Assessment

1. Reduce risk associated with anaesthesia and surgery
   
   

2. Reduce morbidity
   
   

3. Reduce mortality
   
   

Key Purposes

• Identify and optimise comorbid conditions (e.g. hypertension, diabetes)
  
  

• Coordinate specialist consultations if needed
  
  

• Decide if surgery needs to be postponed to stabilise a patient
  
  

• Plan the appropriate anaesthetic technique and post-operative care level (e.g. ICU, HDU)
  
  

Where is Pre-operative Assessment Done?

• Pre-assessment clinics
  
  

• Hospital wards
  
  

• Rural health facilities
  
  

• Anaesthetic room (not ideal)
  
  

• Community/home settings
  
  

NCEPOD Reports

(National Confidential Enquiry into Perioperative Deaths – UK system)

Identified issues leading to harm:

• Inadequate pre-op assessment
  
  

• Poor resuscitation
  
  

• Wrong anaesthetic technique
  
  

• Poor monitoring
  
  

• Lack of supervision
  
  

• Poor post-operative care
  
  

Good pre-op assessment and anaesthetic planning improve outcomes significantly.

ASA Classification (American Society of Anaesthesiologists)

Used to classify patient fitness before surgery.

ASA Grade

Description

Mortality per 10,000

Mortality %

ASA I

Healthy

6–8

0.06–0.08%

ASA II

Mild disease

27–40

0.27–0.4%

ASA III

Severe disease with functional limitation

180–430

1.8–4.3%

ASA IV

Severe disease, constant threat to life

780–2300

7.8–23%

ASA V

Moribund patient

940–5100

9.4–51%

ASA VI

Brain-dead for organ harvest

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Pre-operative History

1. Past Anaesthesia History
   
   

   • Severe: anaphylaxis, malignant hyperthermia, suxamethonium apnoea, difficult airway
     
     

   • Mild: sore throat, nausea/vomiting, dental injury
     
     

2. Family History
   
   

   • Malignant hyperthermia, suxamethonium apnoea
     
     

3. Medical History (Systems Review)
   
   

System

Conditions

Respiratory

Asthma, COPD, URTI/LRTI

Cardiovascular

Hypertension, IHD, heart failure, arrhythmias, valvular disease

GIT

GERD, hiatus hernia

CNS

Stroke, epilepsy, neuromuscular disease

Endocrine

Diabetes, thyroid disorders

Others

HIV, TB, Hepatitis, Sickle cell, bleeding disorders

4. 
   Drugs/Allergies
   
   

   • Medication list
     
     

   • Atopy/allergies (drug, latex, antiseptic)
     
     

5. Social History
   
   

   • Smoking, alcohol, recreational drug use
     
     

6. Other
   
   

   • Loose teeth, crowns, dentures (can be aspirated)
     
     

   • Blood refusal (Jehovah’s Witnesses)
     
     

   • Patient concerns
     
     

Examination Focus

General Systems:

• Cardiovascular
  
  

  • Anaemia, cyanosis, JVP, oedema, murmur, blood pressure
    
    

• Respiratory
  
  

  • Respiratory effort, auscultation, tracheal deviation, air entry
    
    

• CNS
  
  

  • Especially important if regional techniques are planned
    
    

Veins:

• Is IV access likely to be difficult?
  
  

Spine:

• For neuraxial blocks – check spinal curvature, previous surgeries
  
  

Airway Assessment

1. Inspection
   
   

   • Obvious deformities
     
     

   • Scars, masses, short neck
     
     

   • Poor dentition, loose teeth, facial structure
     
     

2. Palpation
   
   

   • Thyroid swelling, masses, trachea
     
     

3. Movement
   
   

   • Ask patient to extend neck (“look at ceiling”)
     
     

   • Open mouth and protrude tongue
     
     

4. Measurements
   
   

   • Thyromental distance: <6.5 cm = difficult intubation
     
     

   • Sterno-mental distance: <12 cm = difficult intubation
     
     

Mallampati Classification

Class

What is seen

I

Soft palate, fauces, uvula, pillars

II

Soft palate, fauces, uvula (not pillars)

III

Soft palate, base of uvula

IV

Only hard palate visible

Class III or IV predicts difficult intubation

Wilson’s Difficult Intubation Score

Variables (scored 0 = none, 1 = moderate, 2 = severe):

• Obesity
  
  

• Limited neck movement
  
  

• Limited jaw movement
  
  

• Receding mandible
  
  

• Prominent upper incisors
  
  

Score >2 = high risk of difficult intubation

Other Predictors of Difficult Airway

• Mouth opening <2 finger breadths
  
  

• Thyromental distance <6.5 cm
  
  

• Sterno-mental distance <12 cm
  
  

• Radiological signs:
  
  

  • Decreased occiput-C1 gap
    
    

  • Decreased C1–C2 spine gap

ASA Classification (American Society of Anaesthesiologists) 

Medical History (Systems Review)