A patient's medical history is an important component of any pre‐operative evaluation. The history should start with current illness. This starts with the reason why the patient is having the planned procedure. It is important to include how the patient first presented with the symptoms of the condition, and any treatments that have been provided. It is important to obtain details of treatments such as previous chemotherapy or radiotherapy within the health history. A full history of current and previous medical problems should also be taken.

The history should also include a complete review of the patient's systems in order to look for undiagnosed disease or inadequately controlled chronic disease (see Chapter c02). Diseases associated with an increased risk of surgical complications include respiratory and cardiac disease, malnutrition, and diabetes mellitus (Böhmer et al. [35], Song et al. [195]). Diseases of the cardiovascular and respiratory systems are the most relevant in respect of a patient's fitness for anaesthesia and surgery (Kolh et al. [92], Kraiss et al. [93]). It is valuable to obtain information such as dates of diagnosis, severity, ongoing treatment and any history of hospitalization for the disorders. A clear record of the patient's medical history produces the foundations for a substantial plan of care. ‘This ensures the patient's surgical journey is effective, reducing the risk of suboptimal management and increasing safety with the least possible distress for the patient and their significant others’ (Walsgrove [218], p.33).

Asking the patient about illnesses that run in their family, such as hypertension, coronary artery disease, stroke, diabetes and hypercholesterolaemia, will alert the anaesthetist to any potential medical problems. A family history of adverse reactions associated with anaesthesia should also be obtained.

A history of previous major surgeries and recent anaesthetics gives the assessor a comprehensive idea of the fitness of the patient. It is vital to find out about previous anaesthetic problems, such as post‐operative nausea and vomiting. Patients with a history of bleeding complications should be carefully assessed for coagulation disorders (Gilbert‐Kawai and Montgomery [68]), and a history of adverse anaesthetic reactions (in a patient or family members) should raise concerns about susceptibility to malignant hyperthermia (Chan et al. [41]). Patients susceptible to malignant hyperthermia (a rare, life‐threatening progressive hyperthermic reaction during anaesthesia) require an anaesthesia consultation, appropriate preparation of the operating room, and adequate equipment and expertise in the event of a reaction during surgery. The Association of Anaesthetists of Great Britain and Ireland (AAGBI) ([2], [3]) offers guidance on the management of a malignant hyperthermia crisis (Figure 16.1).

The American Society of Anesthesiologists (ASA) ([15]) has developed a scale with which to classify patients on the basis of their existing co‐morbidities (Table 16.1). The scale is a well‐established scoring tool that is useful for calculating patient risk of anaesthetic complications in relation to existing conditions (Doyle and Garmon [53], Helkin et al. [77]).

A full list of the patient's current medications, including over‐the‐counter medications as well as vitamin and herbal supplements, is essential. Many medications interact with anaesthetic agents or negatively affect the patient in the intra‐ or post‐operative period. These include anticoagulants, diabetic medications, calcium channel antagonists, beta blockers and some antidepressants. If a patient is taking steroids or opiates, these require careful titration intra‐ or post‐operatively.

Generally, administration of most drugs should be continued up to and including on the morning of an operation, although some adjustments to dosage may be required (e.g. for anti‐hypertensives and insulin). Some drugs should be discontinued pre‐operatively, potentially days or weeks prior to surgery (Figure 16.2). Any monoamine oxidase inhibitors should be withdrawn 2–3 weeks before surgery because of the risk of interactions with drugs used during anaesthesia. The use of the oral contraceptive pill should be discontinued at least 4 weeks before elective surgery because of the increased risk of venous thrombosis. An assessment of any medications or herbal treatments that a patient consumes is included as part of the POA, and a decision is made on whether a further haematological work‐up is required before surgery (Tassler and Kaye [201]). Some herbal supplements may have to be discontinued prior to surgery (Abe et al. [7], Wang et al. [219]). Attributable side‐effects of herbal medicines include cardiovascular instability, electrolyte disturbance, coagulation disturbance, coagulation disorder, endocrine effects, hepatotoxicity and renal failure (Batra and Rajeev [28], Byard [40]).

The patient's allergy status should be obtained and specific details of reactions recorded in the care plan (particularly allergies to rubber products and to foods associated with latex reactions, such as bananas, avocados, kiwis, apricots and chestnuts). Medication ‘intolerance’ should also be documented to avoid severe side‐effects such as nausea and vomiting. A history of previous anaphylactic reactions should be thoroughly documented to avoid potential incidents. Patients who are allergic to latex will need to be first on the theatre list, and theatre staff will need to be alerted to avoid complications (see ‘Latex sensitivity and allergy’ below).

A social history encompasses social situations such as home life and occupation. It provides a general picture of the social practices of the patient that may affect their fitness for surgery but also influence their recovery. A patient's past and current occupational background will provide an insight into their home and financial situation, as well as potential occupational disorders such as respiratory or musculoskeletal problems.

Understanding the patient's support systems (e.g. in their family or the wider community) is important. It will provide clues to potential ‘road blocks’ for a timely discharge. If the patient is found to have little or no available support in the community, the POA practitioner will have the opportunity to initiate any necessary discharge planning or social services referrals prior to admission. This will allow the patient to avoid any potential delays in their discharge.

The social history component of the POA includes a further assessment of smoking, drug and alcohol use. Long‐term abuse of alcohol, tobacco products or drugs can result in organ damage, related medical complications, and therefore a higher incidence of perioperative morbidity and mortality. Intra‐ and post‐operative events such as delirium tremens (an acute episode of delirium) are considered medical emergencies.

Investigations are often ordered to establish baseline values, support or refute differential diagnoses, and support or monitor the management of existing disease processes. Laboratory tests should be ordered based on information obtained from both the patient history and the physical examination (Table 16.2). They should also take into account the patient's age and the complexity of the surgical procedure. NICE ([144]) offers an evidence‐based guide for the ordering and use of routine pre‐operative testing in elective surgeries. The investigations are based on ASA status (see Table 16.1), the age of the patient and their co‐morbidities.