Tips for Anaesthesia Attachments- take a history and examine patients with particular attention to concurrent diseases that may impact on the conduct of anaesthesia;
- identify any risk factors for anaesthesia caused by any intercurrent disease processes;
- decide what further investigations are required;
- assess patients’ airways and identify any potential difficulties with tracheal intubation;
- discuss an anaesthetic plan with an anaesthetist;
- witness consent being obtained for both general and regional anaesthesia;
- observe patients having echocardiography and cardiopulmonary exercise testing.
The nature of anaesthetists’ training and experience makes them uniquely qualified to assess the inherent risks of anaesthetising each individual patient. Ideally, every patient should be seen by an anaesthetist prior to surgery to identify, manage, and minimize these risks. Traditionally, this occurred when the patient was admitted, usually the day before an elective surgical procedure. However, if at this time the patient was found to have any significant comorbidity, surgery was often postponed, but with insufficient time to admit a different patient, leading to wasted operating time. Increasingly, in attempts to improve efficiency, patients are admitted on the day of their planned surgical procedure. This further reduces the opportunity for an adequate anaesthetic assessment, limits the investigations that can be done and virtually prevents optimization of any comorbidities. This has led to significant changes in the preoperative management of patients undergoing elective surgery, including the introduction of clinics specifically for anaesthetic assessment. A variety of models of ‘preoperative’ or ‘anaesthetic assessment’ clinic exist; the following is intended to outline their principle functions. Those who require greater detail are advised to consult the document produced by the Association of Anaesthetists of Great Britain and Ireland (AAGBI), Pre-operative Assessment and Patient Preparation. The Role of the Anaesthetist (see useful information section).
The Preoperative Assessment Clinic
Stage 1
Although not all patients need to be seen by an anaesthetist in a preoperative assessment clinic, all patients do need to be assessed by an appropriately trained individual. This role is frequently undertaken by nurses who may take a history, examine the patient, and order investigations (see below) according to the local protocol. The primary aim is to identify those patients at low risk of complications during anaesthesia and surgery. This includes patients who:
- have no coexisting medical problems;
- have a coexisting medical problem that is well controlled and does not impair daily activities, such as hypertension;
- do not require any, or require only baseline investigations (Table 1.1);
- have no history of, or predicted, anaesthetic difficulties;
- require surgery for which complications are minimal.
Table 1.1 Baseline investigations in patients with no evidence of concurrent disease (ASA I)
Having fulfilled these criteria, patients can then be listed for surgery. At this stage the patient will usually be given preliminary information about anaesthesia, often in the form of an explanatory leaflet. On admission patients will be seen by a member of the surgical team to ensure that there have not been any significant changes since attending the clinic, reaffirm consent and mark the surgical site if appropriate. The anaesthetist will:
- confirm the findings at the preoperative assessment;
- check the results of any baseline investigations;
- explain the options for anaesthesia appropriate for the procedure;
- obtain consent for anaesthesia;
- have the ultimate responsibility for deciding whether it is safe to proceed.
Stage 2
Clearly not all patients are as described above. Common reasons are:
- coexisting medical problems that impair activities of daily living;
- the discovery of previously undiagnosed medical problems, such as diabetes or hypertension;
- medical conditions that are less than optimally managed, such as angina, chronic obstructive pulmonary disease (COPD);
- abnormal baseline investigations.
These patients will need to be sent for further investigations – for example, an ECG, pulmonary function tests, echocardiography, or will be referred to the appropriate specialist for advice or management before being re-assessed. The findings of further investigations dictate whether or not the patient needs to be seen by an anaesthetist.
Stage 3
Patients that will need to be seen by an anaesthetist in the preoperative clinic are those who:
- have concurrent disease that impairs activities of daily living (ASA 3, see below);
- are known to have had previous anaesthetic difficulties, such as difficult intubation, allergies to drugs;
- are predicted to have the potential for difficulties, for example morbid obesity or a family history of prolonged apnoea after anaesthesia;
- are to undergo complex surgery with or without planned admission to the intensive care unit (ICU) postoperatively.
The consultation will allow the anaesthetist to:
- make a full assessment of the patient’s medical condition;
- evaluate the results of any investigations or advice from other specialists;
- request any additional investigations;
- review any previous anaesthetics given;
- decide on the most appropriate anaesthetic technique, for example general or regional anaesthesia;
- begin the consent process, explaining and documenting:
the anaesthetic options available and the potential side-effects;
the risks associated with anaesthesia;- discuss plans for postoperative care.
These patients will also be seen by their anaesthetist on admission, who will confirm that there have not been any significant changes since they were seen in the clinic, answer any further questions that the patient may have about anaesthesia, and obtain informed consent.
The ultimate aim of this process is to ensure that once patients are admitted for surgery, their intended procedures are not cancelled as a result of them being deemed ‘unfit’ or because their medical conditions have not been adequately investigated. Clearly the time between the patient being seen in the assessment clinic and the date of admission for surgery cannot be excessive; 4–6 weeks is usually acceptable.
The Anaesthetic Assessment
The anaesthetic assessment consists of taking a history from, and examining, each patient, followed by any appropriate investigations. When performed by non-anaesthetic staff, a protocol is often used to ensure all the relevant areas are covered. This section concentrates on features of particular relevance to the anaesthetist.
Present and Past Medical History
For the anaesthetist, the patient’s medical history relating to the cardiovascular and respiratory systems are relatively more important.
Cardiovascular System
Enquire specifically about symptoms of:
- ischaemic heart disease;
- heart failure;
- hypertension;
- valvular heart disease;
- conduction defects, arrhythmias;
- peripheral vascular disease, previous deep venous thrombosis (DVT) or pulmonary embolus (PE).
Patients with a proven history of myocardial infarction (MI) are at a greater risk of further infarction perioperatively. The risk of reinfarction falls as the time elapsed since the original event increases. The time when the risk falls to an acceptable level, or to that of a patient with no previous history of MI, varies between patients. For a patient with an uncomplicated MI and a normal exercise tolerance test (ETT) elective surgery may only need to be delayed by 6–8 weeks. Patients should be asked about frequency, severity, and predictability of angina attacks. Frequently occurring or unpredictable attacks suggests unstable angina. This should prompt further investigation and optimization of anti-anginal therapy prior to proceeding with anaesthesia. The American Heart Association has produced guidance for perioperative cardiovascular evaluation (see useful information section).
Heart failure is one of the most important predictors of perioperative complications, mainly as an increased risk of perioperative cardiac morbidity and mortality. Its severity is best described using a recognized scale, such as the New York Heart Association classification (NYHA) (Table 1.2).
Table 1.2 New York Heart Association (NYHA) classification of cardiac function compared to Specific Activity Scale
| NYHA functional classification | Specific Activity Scale classification | |
| Class I: | Cardiac disease without limitation of physical activityNo fatigue, palpitations, dyspnoea or angina | Can perform activities requiring ≥7 METsJog/walk at 5 mph, ski, play squash or basketball, shovel soil |
| Class II: | Cardiac disease resulting in slight limitation of physical activity | Can perform activities requiring ≥5 but < 7 METs |
| Asymptomatic at rest, ordinary physical activity causes fatigue, palpitations, dyspnoea or angina | Walk at 4 mph on level ground, garden, rake, weed, have sexual intercourse without stopping | |
| Class III: | Cardiac disease causing marked limitation of physical activity | Can perform activities requiring ≥2 but < 5 METs |
| Asymptomatic at rest, less than ordinary activity causes fatigue, palpitations, dyspnoea or angina | Perform most household chores, play golf, push the lawnmower, shower | |
| Class IV: | Cardiac disease limiting any physical activitySymptoms of heart failure or angina at rest, increased with any physical activity | Patients cannot perform activities requiring ≥2 METs |
| Cannot dress without stopping because of symptoms; cannot perform any class III activities | ||
Untreated or poorly controlled hypertension may lead to exaggerated cardiovascular responses during anaesthesia. Both hypertension and hypotension can be precipitated, which increase the risk of myocardial and cerebral ischaemia. The severity of hypertension will determine the action required:
- Mild (SBP 140–159 mmHg, DBP 90–99 mmHg): No evidence that delaying surgery for treatment affects outcome.
- Moderate (SBP 160–179 mmHg, DBP 100–109 mmHg): Consider review of treatment. If unchanged, requires close monitoring to avoid swings during anaesthesia and surgery.
- Severe (SBP > 180 mmHg, DBP > 109 mmHg): With a blood pressure this high, elective surgery should be postponed due to the significant risk of myocardial ischaemia, arrhythmias and intracerebral haemorrhage. In an emergency, it will require acute control in conjunction with invasive monitoring.
Respiratory System
Enquire specifically about symptoms of:
- COPD.
- asthma;
- infection;
- restrictive lung disease.
Patients with pre-existing lung disease are at increased risk of postoperative chest infections, particularly if they are also obese, or undergoing upper abdominal or thoracic surgery. If an acute upper respiratory tract infection is present, anaesthesia and surgery should be postponed unless it is for a life-threatening condition.
Assessment of Exercise Tolerance
Exercise capacity has long been recognized as a good predictor of postoperative morbidity and mortality. This is because surgery provokes similar physiological responses to exercising, namely an increase in tissue oxygen demand necessitating an increase in cardiac output and oxygen delivery. An indication of cardiac and respiratory reserves can be obtained by asking the patient about their ability to perform everyday physical activities before having to stop because of symptoms of chest pain, shortness of breath, etc. For example:
- Could you run for a bus?
- How far can you walk uphill?
- How far can you walk on the flat?
- Are you able to do the shopping?
- How many stairs can you climb before stopping?
- Are you able to do housework?
- Are you able to care for yourself?
The problem with such questions is that they are very subjective, dependent on the patient’s motivation and patients often tend to overestimate their abilities!
The assessment can be made more objective by reference to The Specific Activity Scale (Table 1.2). Common physical activities are graded in terms of their metabolic equivalents of activity or ‘METs’, with 1 MET being the energy (or more accurately oxygen) used at rest. The more strenuous the activity, the greater the number of METs used. This is not specific for each patient but serves as a useful guide, and once again relies on the patient’s assessment of their activity.
Other Important Considerations
- Indigestion, heartburn and reflux: possibility of a hiatus hernia. If exacerbated on bending forward or lying flat, this increases the risk of regurgitation and aspiration.
- Rheumatoid disease: limited movement of joints makes positioning for surgery difficult. Cervical spine and temporo-mandibular joint involvement may complicate airway management. There is often a chronic anaemia.
- Diabetes: an increased incidence of ischaemic heart disease, renal dysfunction, and autonomic and peripheral neuropathy. There is also an increased risk of perioperative complications, particularly disruption of glycaemic control, hypotension and infections.
- Neuromuscular disorders: poor respiratory function (forced vital capacity (FVC) < 1 L) predisposes to chest infection and increases the chance of needing ventilatory support postoperatively. Poor bulbar function predisposes to aspiration. Care is needed when using muscle relaxants. Consider regional anaesthesia.
- Chronic renal failure: anaemia and electrolyte abnormalities. Altered drug excretion restricts the choice of anaesthetic drugs. Surgery and dialysis treatments need to be coordinated.
- Jaundice (associated with liver dysfunction): coagulopathy. Altered drug metabolism and excretion. Care is needed especially with use of opioids.
Previous Anaesthetics and Operations
These have usually occurred in hospitals or occasionally, in the past, dental surgeries. Enquire about any perioperative problems, such as nausea, vomiting, dreams, awareness, jaundice. Ask if any information was given postoperatively, for example difficulty with intubation or delayed recovery. Whenever possible, check the records of previous anaesthetics to rule out or clarify problems such as difficulties with intubation, allergy to drugs given, or adverse reactions (such as malignant hyperpyrexia, see below). Some patients may have been issued with a ‘Medic Alert’ type bracelet or similar device giving details or a contact number. Details of previous surgical procedures may reveal potential anaesthetic problems, for example cardiac, pulmonary or cervical spine surgery.
Family History
All patients should be asked whether any family members have experienced problems with anaesthesia; for example, a history of prolonged apnoea suggests pseudocholinesterase deficiency (see Chapter 2), and an unexplained death suggests malignant hyperpyrexia (see Chapter 6). Elective surgery should be postponed if any conditions are identified while the patient is investigated appropriately. In the emergency situation, anaesthesia must be adjusted accordingly, for example by avoiding triggering drugs in a patient with a potential or actual family history of malignant hyperpyrexia.
Drug History and Allergies
Identify all medications, both prescribed and over the counter (OTC), including complementary and alternative medicines. Patients will often forget to mention the oral contraceptive pill (OCP) and hormone replacement therapy (HRT) unless specifically asked. On the whole, the numbers of medications patients take rises with age. Many commonly prescribed drugs such as angiotensin converting enzyme inhibitors (ACE-I) can have important effects during anaesthesia. These can be identified by consulting a current British National Formulary (BNF), or the BNF website. Allergies to drugs, latex, topical preparations (e.g. iodine), adhesive dressings and foodstuffs should be noted.
Social History
- Smoking: ascertain the amount of tobacco smoked. This is usually calculated as the number of pack years; number of packs smoked each day multiplied by the number of years smoked. This gives an idea of the total amount smoked and allows comparison between individuals. In the long term smoking causes chronic lung disease and carcinoma but it also has a number of other important effects relevant to the perioperative period. It produces carbon monoxide, which combines with haemoglobin and reduces oxygen carriage and nicotine, which stimulates the sympathetic nervous system causing tachycardia, hypertension, and coronary artery narrowing. Cilliary function is impaired, increasing the risk of postoperative chest infections. Stopping smoking before anaesthesia reduces the risk of perioperative complications – the further in advance, the better. As a guide, stopping for eight weeks improves the airways; for two weeks reduces airway irritability and for as little as 24 hours before anaesthesia decreases carboxyhaemoglobin levels. Help and advice should be available at the preoperative assessment clinic.
- Alcohol: this is measured as units consumed per week; > 50 units/week causes induction of liver enzymes and tolerance to anaesthetic drugs. The risk of alcohol withdrawal syndrome postoperatively must be considered.
- Drugs: ask specifically about the use of drugs for recreational purposes, including type, frequency and route of administration. This group of patients is at risk of infection with hepatitis B and human immunodeficiency virus (HIV). There can be difficulty with venous access following intravenous drug abuse due to widespread thrombosis of veins. Withdrawal syndromes can occur postoperatively.
- Pregnancy: the date of the last menstrual period should be noted in all women of childbearing age. The anaesthetist may be the only person in theatre able to give this information if X-rays are required. Anaesthesia increases the risk of inducing a spontaneous abortion in early pregnancy. There is an increased risk of regurgitation and aspiration in late pregnancy. Elective surgery is best postponed until after delivery.
The Examination
This concentrates on the cardiovascular and respiratory systems; the remaining systems are examined if problems relevant to anaesthesia have been identified in the history. At the end of the examination, the patient’s airway is assessed to try and identify any potential problems. If a regional anaesthetic is planned, the appropriate anatomy (for example, lumbar spine for central neural block) is examined.
Cardiovascular System
Examine specifically for signs of:
- arrhythmias;
- heart failure;
- hypertension;
- valvular heart disease;
- peripheral vascular disease.
Don’t forget to inspect the peripheral veins to identify any potential problems with IV access.
Respiratory System
Examine specifically for signs of:
- respiratory failure;
- impaired ventilation;
- collapse, consolidation, pleural effusion;
- additional or absent breath sounds.
Nervous System
Chronic disease of the peripheral and central nervous systems should be identified and any evidence of peripheral neuropathy, motor or sensory, recorded to ensure that any abnormalities postoperatively are not attributed to injury intraoperatively. It must be remembered that some disorders will affect the cardiovascular and respiratory systems, for example dystrophia myotonica and multiple sclerosis.
Musculoskeletal System
Note any restriction of movement and deformity if a patient has connective tissue disorders. Patients suffering from chronic rheumatoid disease frequently have a reduced muscle mass, peripheral neuropathies and pulmonary involvement. Particular attention should be paid to the patient’s cervical spine and temporomandibular joints (see below).
The Airway
The airway of all patients must be assessed, in order to try to predict those patients who may be difficult to intubate.
Observe the patient’s anatomy looking specifically for:
- limitation of mouth opening;
- a receding mandible;
- position, number and health of teeth;
- size of the tongue;
- soft tissue swelling at the front of the neck;
- deviation of the larynx or trachea;
- limitations in flexion and extension of the cervical spine.
Finding any of these suggests that intubation may be more difficult. However, it must be remembered that all of these are subjective.
Some simple bedside tests can also be performed:
- Mallampati criteria: the patient, sitting upright, is asked to open their mouth and maximally protrude their tongue. The view of the pharyngeal structures is noted and graded I–IV (Fig. 1.1). Grades III and IV suggest difficult intubation.
- Thyromental distance: with the head fully extended on the neck, the distance between the bony point of the chin and the prominence of the thyroid cartilage is measured (Fig. 1.2
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