Thepre-operative assessmentis an opportunity to identify co-morbidities that may lead topatient complications during theanaesthetic, surgical, or post-operative period. Patients scheduled for elective procedures will generally attend apre-operative assessment 2-4 weeks before the date of their surgery.
In this article, we shall look at the components of an effective pre-operative history, examination, and routine investigations that can be performed.
Pre-Operative History
The pre-operative history follows the same structure as typical history taking, with the addition of some anaesthetic and surgery specific topics.
History of the Presenting Complaint
Abrief historyof why the patient first attended and whatprocedurethey have subsequently been scheduled for. One should also confirm the side on which the procedure will be performed [if applicable]
There may be aspects of the disease or condition requiring surgery that are important for the anaesthetist to be aware of; for example, head and neck surgery may indicate the presence of abnormal airway anatomy.
Past Medical History
A full past medical history [PMH] is required, with the following specifically asked about:
- Cardiovascular disease, including hypertension; exercise tolerance is a useful indicator of cardiovascular fitness and, particularly for patients undergoing major surgery, can help predict their risk of post-operative complications and level of care needed post-operatively
- Screening questions may elucidate undiagnosed disease and prompt further investigation, e.g. the presence of exertional chest pain, syncopal episodes, or orthopnoea
- Respiratory disease, as adequate oxygenation and ventilation is essential in reducing the risk of acute ischaemic events in the peri-operative period
- Questions including whether the patient is able to lie flat for a prolonged period or has a chronic cough are key as these may preclude spinal anaesthesia; also screen for symptoms and signs of obstructive sleep apnoea, if the patient has any risk factors
- Renal disease, including their baseline renal function and any renal-specific medications
- Endocrine disease, specifically diabetes mellitus and thyroid disease
- Gastro-oeseophageal reflux [GORD], as the aspiration of gastric contents can potentially be fatal and the presence of GORD will likely alter anaesthetic technique
- Whilst this may be overlooked as a diagnosis or in their past medical history, particularly if patient managed with over-the-counter medicines, it is important to ask about at the pre-operative assessment
Other specific questions it may beuseful to ask themselves the following questions:
- Pregnancy as part of the pre-operative checklist on the day of surgery, for females of reproductive age a urinary pregnancy test is mandatory in the majority of hospitals
- Sickle Cell Disease could they have undiagnosed sickle cell disease, especially if their country of birth does not have routine screening for sickle cell
Past Surgical History
Has the patient had anyprevious operations? If so, what, when, and why?
If the patient is having a repeat procedure, this can significantly change both the surgical time and ease of operation, and hence influence the anaesthetic technique used
Past Anaesthetic History
Has the patienthad anaesthesia before? If so, for what operation and what type of anaesthesia? Were there any problems? Did the patient experience anypost-operative nausea and vomiting?
Drug History
Afull drug historyis required, as somemedicationsrequire stopping or altering prior to surgery. Ask about any knownallergies, both drug and non-drug allergies
Family History
Whilst most hereditary conditions relating to anaesthesia are extremely rare, such as malignant hyperthermia, it is important to ask about any known family history of problems with anaesthesia
Social History
Ensure to ask the patient aboutsmoking history, alcohol intake, and any recreational drug use
Other important social factors to make note of include:
- Language spoken and the need for an interpreter
- Living situation, as the absence of an adult at home may require an admission overnight
Pre-Operative Examination
In the pre-operative examination, two distinct examinations are performed; thegeneral examination[to identify any underlying undiagnosed pathology present] and theairway examination[to predict the difficulty of airway management e.g. intubation]. If appropriate, the area relevant to the operation can also be examined.
Perform afull general examination, looking closely for any obvious cardiovascular [in particular undiagnosed murmurs or signs of heart failure], respiratory, or abdominal signs. Ananaesthetic examination, including anairway assessment [typically using the Mallampati score],will also be performed by the anaesthetist prior to any surgery
American Society of Anaesthesiologists Grade
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 patients ASA grade directly correlates with their risk of post-operative complications and absolute mortality.
ASA GradeDefinitionAbsolute Mortality [%]INormal healthy patient0.1IIMild systemic disease0.2IIISevere systemic disease1.8IVSevere systemic illness that is a constant threat to life7.8VMoribund,who is not expected to survive without the operation9.4ESuffix added if an emergency operation-Pre-Operative Investigations
The nature of theexact investigationsrequireddepends on a number of factors, including co-morbidities, age, and the nature of the procedure.
The urgency of the surgery will also dictate which conditions need further investigation and management prior to surgery. For example, elective surgery is often delayed for poorly controlled blood glucose levels in diabetic patients, to allow time for optimisation
Each specifichospitalis likely to providelocal guidelines, howeverit is useful to understand the tests than could be done pre-operatively and have an appreciation as to why eachmay be requested. NICE produce acolour traffic light tablewhich can further guide your investigative decisions.
Blood Tests
- Full Blood Count [FBC]
- Most patients will get afull blood count, predominantly used to assess for anyanaemia or thrombocytopenia, as this may require correction pre-operatively to reduce the risk of cardiovascular events or allow for preparation of blood products
- Urea & Electrolytes [U&Es]
- To assess the baseline renal function, which help inform fluid management and drug decisions, both for anaesthesia and post-operative analgesia [e.g. morphine is generally avoided in those with CKD]
- Liver Function Tests [LFTs]
- Important in the assessingliver metabolism and synthesising function, useful for peri-operativemanagement; if there is suspicion of liver impairment, LFTs may help direct medication choice and dosing
- Condition-specific blood tests
- There are several conditions or diseases that may require specific bloods, such as HbA1C or thyroid function tests[TFTs]
- Clotting Screen
- Any indication ofderanged coagulation, such as iatrogenic causes [e.g. warfarin], inherited coagulopathies [e.g. haemophilia A/B], or liver impairment, will need identifying and correcting or managing appropriately in the peri-operative period
- Group and Save [G&S] +/- cross-matching
Group and Save versus Cross-Match
Group and Save [G&S] and Cross-Match [X-match] are two tests that are slightly different in their aims:
- A G&S determines the patients 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 cross-match involves physically mixing the patients blood with the donors 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], and should be done pre-emptively if blood loss is anticipated
Cardiac Investigations
An ECG is often performedin individualswith ahistory of cardiovascular diseaseor for thoseundergoing major surgery. It can indicateany underlying cardiac pathology and provide a baseline for comparison if there are post-operative concerns for cardiac ischaemia.
An echocardiogram [ECHO] provides very useful information for the anaesthetist as it helps to risk stratify and tailor the intra-operative care of the patient. It may be considered if the person has [1] a heart murmur [2] ECG changes [3] signs or symptoms of heart failure.
For patients with untreated ischaemic heart disease, or symptoms of angina, myocardial perfusion scans are often performed to look for inducible ischaemia.
Respiratory Investigations
If a patient has a chronic lung condition e.g. COPD,spirometrymay be of use in assessing current baseline and predicting post-operative pulmonary complications in these patients. Patients may also be referred for spirometry if there are symptoms and signs of undiagnosed pulmonary disease.
Plain film chest radiographs[CXR] are less commonly performed routinely pre-operatively and should be used only when necessary
Other Tests
Urinalysis
Especially for urological procedures, a urinalysis must be performed to assess if there is any evidence or suspicion of ongoing urinary tract infection
MRSA Swabs
All patients will have swabs taken from the nostril and perineum for MRSA colonisation. If this is isolated, decontamination hair and body wash, along with topical ointment applied to the nostrils, will be given.
Cardiopulmonary Exercise Testing
High-risk patients undergoing major surgery may be referred for cardiopulmonary exercise testing [CPET]. This usually involves a graded intensity period on a stationary bicycle whilst wearing a mask, as well as ECG monitoring. It provides useful information, such as the VO2max and anaerobic threshold, which can be used to risk-stratify patients for post-operative complications and need for higher level care environments