The pre-operative assessment is an opportunity to identify co-morbidities that may lead to patient complications during the anaesthetic, surgical, or post-operative period. Patients scheduled for elective procedures will generally attend a pre-operative assessment 2-4 weeks before their date of surgery.
In this article, we shall look at the components of an effective pre-operative history, examination and routine investigations that can be performed.
The pre-operative history follows the same structure as typical history taking, with the addition of some anaesthetic and surgery specific topics.
Female of reproductive age – could they be pregnant?
African or Afro-Caribbean descent – could they have undiagnosed sickle cell disease?
Has the patient had any previous operations? If so, what, when, and why?
Has the patient had anaesthesia before? If so, were there any issues? Were they well post-operatively?
Has the patient experienced to any previous post-operative nausea and vomiting?
A full drug history is required, as some medications require stopping or altering prior to surgery. Ask about any known drug allergies.
An important condition to ask about is malignant hyperpyrexia* (also known as malignant hyperthermia), yet any other adverse reactions in surgery of immediate family members should also be documented.
In the pre-operative examination, two distinct examinations are performed; the general examination (to identify any underlying pathology) and the airway examination (to predict the difficulty of intubation). If appropriate, the area relevant to the operation can also be examined.
Perform a full general examination, looking closely for any obvious cardiovascular, respiratory, or abdominal signs. An anaesthetic exam, including an airway assessment, will also be performed by the anaesthetist prior to any surgery, as discussed in Appendix 1.
On all anaesthetic charts, a patient will be given an American Society of Anaesthesiologists (ASA) grade after their pre-operative assessment, which has been subjectively assessed and based on the criteria below. A patient’s ASA grade directly correlates with their risk of post-operative complications and absolute mortality.
The nature of the exact investigations required depends on a number of factors, including co-morbidities, age and the seriousness of the procedure.
Each specific hospital is likely to provide local guidelines, however it is useful to understand the tests than could be done pre-operatively and have an appreciation as to why each may be requested. NICE produce a colour traffic light table which can further guide your investigative decisions.
Most patients will get a full blood count, predominantly used to assess if there is undiagnosed anaemia or thrombocytopenia, as this requires correction pre-operatively to reduce the risk of cardiovascular events.
A G&S determines the patient’s blood group (ABO and RhD) and screens the blood for any atypical antibodies. The process takes around 40 minutes and no blood is issued. A G&S is recommended if blood loss is not anticipated, but blood may be required should there be greater blood loss than expected.
A X-match involves physically mixing the patient’s blood with the donor’s blood, in order to see if any immune reaction takes places. If it does not, the donor blood is issued and can be transfused in to the patient, otherwise alternative blood is trialled. This process also takes ~40 minutes (in addition to the 40 minutes required to G&S the blood, which must be done first). A X-match is done if blood loss is anticipated, which the surgeon should inform you of.
An ECG is often performed in individuals with a history of cardiovascular disease or for those undergoing major surgery. It can indicate any underlying cardiac pathology and provide a baseline if there are post-operative signs of cardiac ischaemia.
N.B An echocardiogram (ECHO) can be considered if the person has (1) a heart murmur (2) cardiac symptom(s) (3) signs or symptoms of heart failure.
If a patient has a chronic lung condition, spirometry may be of use in assessing current baseline and predicting post-operative pulmonary complications in these patients.
Consider pregnancy testing in women of reproductive age; carry out a pregnancy test with the woman’s consent if there is any doubt about whether she could be pregnant.
Do not routinely offer testing for sickle cell disease or sickle cell trait before surgery. If the person has any member of their family with sickle cell disease, or is Africa or Afro-Caribbean descent, strongly consider performing a sickle cell test.
All patients will have swabs taken from the nostril ± perineum ± other sites for MRSA colonisation. If this is isolated, antiseptic hair and body wash, along with topical ointment applied to the nostrils, will be given; in some hospitals, this is given for all elective patients pre-operatively, even if this means the operation is delayed.
A urinalysis is performed if any evidence or suspicion of ongoing glycosuria or urinary tract infection, yet should not be done routinely pre-operatively.
The airway examination will typically be covered during the anaesthetist’s assessment of the patient but is always good practice to assess during the preoperative assessment. Look at the face for any obvious facial abnormalities. Particularly, do they have a receding mandible (retrognathia)? This could cause difficulties during airway insertion.
Their degree of mouth opening (favourable if inter-incisor distance is above 3cm).
Their teeth, mainly do they have teeth? If so, what is their dentition like? Are any teeth loose?
Their oropharynx. Ask the patient to maximally protrude their tongue. A Mallampati classification (Fig. 2), which correlates with difficulty of intubation, can be assessed.
Lastly, assess the neck. Ask the patient to flex, extend and laterally flex the neck to see their range of movement. Then, ask the patient to maximally extend their neck and measure the distance between the thyroid cartilage and chin (the thyromental distance); if this is less than 6.5cm (~3 finger breadths), it indicates that intubation may be difficult.
How long before surgery should a patient have a pre-operative assessment?
What is the most important additional test that should be given to women of reproductive age?
What classification is used to assess a patient's airway for potential difficulty in intubation?