Clinical Anaesthesia

Carl L. Gwinnutt, Matthew Gwinnutt

• Publisher: Wiley-Blackwell
• Year: 2012
• ISBN:
  9781118329269
• Edition: 4
• Topic: Medicine
• Subtopic: Anesthesiology & Pain Management

Perfect for medical students, junior doctors, anaesthetic nurses and allied health professionals, Lecture Notes Clinical Anaesthesia provides a thorough introduction to the modern principles and practices of clinical anaesthesia.

Full-colour diagrams, photographs and key fact boxes support easy understanding of the theory of anaesthetics allowing confident transfer of information into clinical practice.

This fourth edition has been fully revised and updated to reflect recent developments within the anaesthetics specialty and is fully supported by a wide-range of self-assessments for study and revision purposes together with a range of 'tips for anaesthesia attachments' that start each chapter.

Whether you need to develop your knowledge for clinical practice, or refresh that knowledge in the run-up to examinations, Lecture Notes Clinical Anaesthesia will help foster a systematic approach to the clinical situation for all medical students and hospital doctors.

Chapter 1

Anaesthetic Assessment and Preparation for Surgery

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Tips for Anaesthesia Attachments

During your anaesthetic attachment, visit the anaesthetic preoperative assessment clinic and take the opportunity to:

• 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.

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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...