Pre-assessment clinic



Anaesthetic pre-assessment clinic is key to providing patients with a smooth and safe elective operation.

Elective surgery refers to operations that are planned in advance to admission to hospital at a time convenient for the patient, staff and hospital. Patients undergoing elective surgery should always be pre-assessed prior to admission to hospital.

This involves pre-operative assessment clinics that review the patient and their co-morbidities with reference to the planned procedure. It may be lead by nurses, PA's, surgical juniors or anaesthetists (particularly for high-risk patients).

The goal is to ensure the patient is appropriate and prepared for surgery, potentials issues are identified and where needed pre-operative optimisation can be carried out.

General principles

Pre-op assessment clinic normally involves a history, examination and ordering of relevant investigations.

These clinics are generally nurse or PA lead and protocol driven with input from anaesthetists when required. Patients either come into the clinic to be assessed or have telephone assessment if they are fit and well having low risk surgery.

Patients who are undergoing complex, high risk surgery or who have multiple co-morbidities may be seen in specialised pre-assessment clinics where they are reviewed by several members of the multidisciplinary team. 

Pre-operative investigations

Investigations may be ordered to aid with pre-operative optimisation, guide peri-operative management and help establish risks to the patient.

Investigations are based on a number of factors. These include society, NICE and local guidance and depend on patients’ comorbidities and grade of surgery. 

The below advice is largely based on NICE guideline 45: Routine preoperative tests for elective surgery. Each individual case must be reviewed with its own merits and local guidance followed.

General advice

Pregnancy testing should be carried out on all patients with child-bearing potential on the day of surgery with consent of the patient. Each locality will have its own guidelines on pregnancy testing prior to the day of surgery.

Patients with a history of diabetes should have a recorded HbA1c within the last three months. Echocardiogram should be considered in those with heart murmur associated with cardiac symptoms or features of heart failure.

A nutritional assessment will often be offered for those undergoing intermediate to major/complex surgery.

Minor surgery

Example: excision of skin lesion. In some cases no investigation will be needed. FBCs, U&Es and ECG should be considered in elderly patients and those with significant co-morbidities. NICE advise considering the following in patients with an ASA III/IV:

  • ECG: If no result available in the past 12 months.
  • Renal function: If patient is at risk of AKI.

Intermediate surgery

Example: knee arthroscopy. In patients with ASA I blood tests and ECGs are not routinely advised. In those with an ASA II, NICE advise:

  • ECG: Consider if history of cardiovascular disease, renal impairment or diabetes. 
  • Renal function: If patient is at risk of AKI.

In those with an ASA III/IV the following is advised:

  • FBC: If history of cardiac or renal disease if no recent investigations for symptoms
  • Clotting screen: Consider if history of chronic liver disease (prudent to also check if history of other coagulopathies)
  • ECG: Routinely arrange
  • Renal function: Routinely arrange
  • Lung function: Consider if history of respiratory disease

Major complex surgery

Example: total colectomy. FBC should be checked in all patients. In those with an ASA I, renal function testing should be considered if at risk of AKI. In those with an ASA I over the age of 65 an ECG may be arranged if one is not available in the last 12 months. In those with an ASA II NICE advise:

  • FBC: Routinely arrange
  • ECG: Routinely arrange
  • Renal function: Routinely arrange

In those with an ASA III/IV NICE advise:

  • FBC: Routinely arrange
  • Clotting screen: Consider if history of chronic liver disease (prudent to also check if history of other coagulopathies)
  • ECG: Routinely arrange
  • Renal function: Routinely arrange
  • Lung function: Consider if history of respiratory disease

These patients are also more likely to have been seen in more extensive pre-assessment clinics or high-risk anaesthetic clinics.

Certain operations may dictate aggressive investigations, a patient undergoing liver transplant for example may need a coronary angiogram pre-operatively. Other major operations have a minimum set of investigations. For example patients awaiting a CABG will have an echocardiogram, carotid dopplers, lung function tests and chest x-ray at most centres (as well as a coronary angiogram of course).

Routine advice

Patients should be informed of fasting protocols during their pre-operative clinic assessment.


Advice may vary somewhat from hospital to hospital or operation to operation. Standard advice would be:

  1. No food for 6 hours prior to surgery 
  2. Clear fluids until 2 hours prior to surgery
  3. Nil by mouth from that point on

This generally translates as nothing to eat from midnight and clear fluids until 6am prior to their operation. This may be adjusted for patients listed in the afternoon.

There are deviations from the above informed by developing science and guidance. Many departments are moving towards patients having small amounts of water each hour right until their operation to reduce dehydration.

Furthermore a number of 'enhanced recovery pathways' now feature carbohydrate drinks, taken up to two hours prior to surgery to improve peri-operative nutrition and recovery.

Oestrogen containing medications

NICE advise considering stopping oestrogen containing hormone replacement therapy (HRT) 4 weeks prior to elective surgery to reduce the risk of venous thromboembolism.

In certain settings the COCs need to be stopped pre-operatively to reduce the risk of venous thromboembolism. NICE CKS advise COC should be stopped 4 weeks prior to:

  • Major surgery (including any operation lasting longer than 30 minutes)
  • Any operation on the legs
  • Any procedure involving prolonged immobilisation of legs

Alternative contraceptive methods should be offered to the patient if cessation of the COC is required.

Modifiable risk factors

Patients should be given smoking cessation advice and can be referred to smoking cessation services from pre-assessment clinic. The advantages to stopping smoking are vast including reduced complication rates (both surgical and anaesthetic), improved wound healing, reduced rates of post-operative infections and generally improved health and wellbeing. 

Obesity is associated with longer operative times, increased complication rates and longer hospital stay. As such where appropriate and time permitting weight loss may be advised and facilitated. Where relevant, a reduction in alcohol consumption should be advised.


Being safe to drive depends on the surgical procedure and the anaesthetic provided. This information should be given to patients at pre-assessment as it will allow them to make appropriate plans. From a general anaesthetic point of view the recommended time to abstain from driving is between 1 to 4 days depending on which drugs are used.

Patients who have regional anaesthesia will not be safe to drive until they have regained full neurological function. Different operations are associated with varying length of time until driving is considered safe.

Day-case surgery

Many surgical procedures can be done as day cases, with the patient going home the same day following their operation.

This is a growing field with more complex procedures and patients with more co-morbidities being included. It takes meticulous planning, use of day case pathways and appropriate patient selection in order to be successful.

The patient needs to be fit enough to be able to go home after the operation as well as having an operation where it is safe to go home soon afterwards. They should be educated on the process from the point of booking.

There are social considerations with day-case patients needing a responsible adult to take them home and stay with them for 24 hours after surgery. In addition they need access to basic facilities such as a toilet and telephone and also be close to a hospital that can treat potential complications. 

Common conditions

There are several common conditions that need to be considered and optimised in patients undergoing elective surgery.

There are many conditions that should be considered and optimised pre-operatively. Below we discuss some important co-morbidities that may need to be managed - this is by no means exhaustive!


If a patient’s diabetes is poorly controlled they will be referred to their GP or diabetes team for optimisation of this. A HbA1c < 69mmol/mol within 3 months of surgery is the aim in the elective setting. However if an operation is more urgent a clinical decision of risk versus benefit needs to be made with the patient.

Where possible patients with diabetes are put first on the list to prevent prolonged starvation, hypoglycaemic or hyperglycaemic episodes and limit interruptions to their management regimen.

Changes to insulin and oral hypoglycaemics depend on the drug and timing of surgery and so are made on an individual patient basis. When the process is managed well variable rate insulin infusions are rarely required and usually reserved for patients who have prolonged peri-operative starvation or poorly controlled diabetes. 


If a patient has new high blood pressure recordings in pre-assessment clinic the diagnosis of hypertension should still be made in primary care with use of home monitoring if appropriate. Spurious high readings and white coat syndrome need to be excluded. 

From an anaesthetic viewpoint aim is for patients to have a systolic blood pressure < 160/100mmHg in everyday life. Patients with established hypertension should be investigated pre-operatively as per national and local guidance.

ACE-inhibitors are usually omitted on the day of surgery to reduce severe hypotension associated with concomitant general anaesthesia, regional anaesthesia and operative blood loss. Most other antihypertensives can be continued in stable patients having elective surgery. 


Patients who are undergoing surgical procedures with a risk of >500ml blood loss should be screened for anaemia. Other indications for a FBC can be seen in the investigations section above. Ideally this is done around 4-6 weeks prior to surgery so that if anaemia is identified its cause can be investigated (which may include upper and lower GI endoscopy) and treated.

Iron deficiency is a common cause of anaemia and oral iron supplementation is usually effective after 2-3 weeks of therapy; if there is not sufficient time or oral iron has been ineffective, IV iron can be given. Generally for elective operating a haemoglobin level > 130g/dL for men and women is the aim and surgery may be delayed to allow time to reach these targets. However it is not always possible to get to these targets, as anaemia is often multi-factorial in aetiology and may not respond to iron, vitamin B12 or folate.

Patients with chronic kidney disease and anaemia can be referred to specialist tertiary clinics to see if they would benefit from EPO. Blood transfusion should not be required in the elective setting as patients should be able to be optimised by the previously described methods.

Obstructive Sleep Apnoea

Patients at risk should be screened for OSA using scores such as:

  • STOP-BANG score
  • Epworth Sleepiness scale

Depending on the scores patients may need to be referred for formal investigation for OSA and potentially have CPAP treatment initiated. This should be implemented pre-operatively and is a reason to delay purely elective surgery that can otherwise wait.  

Anticoagulants & antiplatelets

Patients require clear plans for their anticoagulants & antiplatelets to prevent cancellations and allow for safe surgery.

The management of anticoagulation and antiplatelets during the peri-operative period is complex. Both local and national guidelines exist. The below information is primarily based upon British Society of Haematology Guidelines: Perioperative Management of Anticoagulation and Antiplatelet Therapy. Complex or uncertain cases should be discussed with haematology / cardiology.


It is generally wise to refer to local guidance and expertise when considering peri-operative use of anticoagulants. There is a balance of risk between surgical bleeding and complications of this if the drugs are continued versus the risk of complications of thrombosis if the drugs are stopped.

  • Warfarin: Warfarin has a half-life of around 36 hours. It is usually stopped 5-7 days prior to surgery and INR is checked on the day of surgery to ensure it is within normal range (normally ≤ 1.4). If patients are significant risk of thrombosis they are given bridging therapy usually in the form of LMWH either at prophylactic or treatment doses depending of the degree of VTE risk.
  • DOACs (e.g. rivaroxaban): Different DOACs have different half-lives that are somewhat dependent on renal function. They are usually stopped pre-operatively at a point in time determined by the exact DOAC, patients’ renal function and operative/anaesthetic risk of bleeding, typically being held for 1-3 days pre-operatively. Like for patients on warfarin bridging therapy with LMWH may be used depending on thrombosis risk.
  • LMWH: Prophylactic doses are safe 12 hours pre-procedure, treatment doses are safe 24-48 hours pre-procedure.


As with anticoagulants one should refer to local guidance and expertise when considering peri-operative use of antiplatelets. Ultimately like anticoagulants there is a balance of risk between surgical blood loss and the risk thrombosis/ischaemic events if these drugs are stopped.

  • Aspirin monotherapy for primary prevention: This is generally safe to stop 7 days prior to the procedure. In some settings it may be continued.
  • Aspirin monotherapy for secondary prevention: This is generally thought to be safer to continue with the risk of cardiac events outweighing the risk of bleeding events except for certain operations where there is the risk of bleeding into closed space and the consequences of this would be catastrophic (e.g. intracranial surgery, spinal surgery, posterior eye chamber surgery).
  • Dual antiplatelet therapy with recent ACS or coronary stent: In low risk cases (from a bleeding viewpoint) these may be continued. Other elective cases should be deferred. Where deferral is not possible discussion should be had with haematology, cardiology, anaesthetics and the operating team. Generally aspirin should be continued whilst the other agent is stopped. If clopidogrel or ticagrelor its stopped 5 days prior, if prasugrel its stopped 7 days prior.

High risk anaesthetic clinic

High-risk anaesthetic clinics are run by anaesthetists with a special interest in peri-operative medicine for patients at greater peri- or post-operative risk.

There are a number of reasons (or combination of reasons) a patient may be referred to the high-risk clinic, these include:

  • Type of procedure
  • Co-morbidities / fitness
  • History of anaesthetic problems
  • Medications

The clinic allows for a thorough review of the patient and more in depth assessment of investigations (e.g. ECHO, exercise/stress tests, lung function tests) in order to provide an individualised risk of mortality and morbidity associated with the surgical procedure and anaesthetic for each patient.

It allows assessment of fitness for an anaesthetic and for peri- and post-operative planning e.g. use of high dependency and intensive care beds. It also enables an open discussion of benefits versus risk with the patient and thus a process of shared decision making.

Further reading

  1. NICE Guideline 45: Routine preoperative tests for elective surgery, 2016
  2. NICE Guideline 180: Perioperative care in adults, 2020
  3. British Society of Haematology Guidelines: Perioperative Management of Anticoagulation and Antiplatelet Therapy, 2016
  4. Association of Anaesthetists: International consensus statement on the peri‐operative management of anaemia and iron deficiency, 2017

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