Suggested Investigations based on complexity of surgery and ASA classification.
ASA Classification used in this guide:
| ASA 1 | A normal healthy patient | 
| ASA 2 | A patient with mild systemic disease | 
| ASA 3 | A patient with severe systemic disease | 
| ASA 4 | A patient with severe systemic disease that is a constant threat to life | 
If Minor Surgery:
| ASA 1 | ASA2 | ASA3 or ASA4 | |
| Full blood count | Not routinely | Not routinely | Not routinely | 
| Haemostasis | Not routinely | Not routinely | Not routinely | 
| Kidney Function | Not routinely | Not routinely | Consider in people at risk of AKI | 
| ECG | Not routinely | Not routinely | Consider if no ECG results available from past 12 months | 
| Lung function/arterial blood gas | Not routinely | Not routinely | Not routinely | 
If Intermediate Surgery:
| ASA 1 | ASA2 | ASA3 or ASA4 | |
| Full blood count | Not routinely | Not routinely | Consider for people with cardiovascular or renal disease if any symptoms not recently investigated | 
| Haemostasis | Not routinely | Not routinely | Consider in people with chronic liver disease 
 | 
| Kidney Function | Not routinely | Consider in people at risk of AKI | Yes | 
| ECG | Not routinely | Consider for people with cardiovascular, renal or diabetes comorbidities | Yes | 
| Lung function/arterial blood gas | Not routinely | Not routinely | Consider seeking advice from a senior anaesthetist as soon as possible after assessment for people who are ASA grade 3 or 4 due to known or suspected respiratory disease | 
If Major/Complex Surgery:
| ASA 1 | ASA2 | ASA3 or ASA4 | |
| Full blood count | Yes | Yes | Yes | 
| Haemostasis | Not routinely | Not routinely | Consider in people with chronic liver disease 
 | 
| Kidney Function | Consider in people at risk of AKI | Yes | Yes | 
| ECG | Consider for people aged over 65 if no ECG results available from past 12 months | Yes | Yes | 
| Lung function/arterial blood gas | Not Routinely | Not Routinely | Consider seeking advice from a senior anaesthetist as soon as possible after assessment for people who are ASA grade 3 or 4 due to known or suspected respiratory disease | 
Notes:
| Surgery Grades | Examples | 
| Minor | 
 
 | 
| Intermediate | 
 | 
| Major or Complex | 
 | 
Reference:
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