Dr
John Loadsman
Conjoint Lecturer
Department of Anaesthetics
Royal Prince Alfred Hospital
Sydney, Australia
Two main goals:
1. Evaluation of patient's general health (+ optimisation if
necessary)
2. Anticipation of possible complications (+ planning to avoid
them)
An extreme example: two patients on a renal transplant waiting list with almost identical names; wrong patient sent to the hospital by the transplant coordinators; even the patient had no idea of the error; only discovered at the last moment when the surgeon realised there was no scar from a previous rejected transplant which the correct patient was supposed to have had. Check everything! Name, date of birth, medical record number, scheduled operation (site, side and nature). Be very alert to inconsistencies.
Check date, place and reason for previous anaesthetics. Specifically enquire (and check medical records if possible) about agents used and any adverse reactions or events, such as difficult intubation or awareness, so that these may be avoided. Be aware that side effects such as nausea and vomiting are frequently reported as allergies but a careful history should make clear the distinction. A family history of anaesthesia problems should also be obtained since some, for example atypical plasma cholinesterase and malignant hyperpyrexia, are genetically determined.
Some medications interact with anaesthetic agents. Check also for the taking of over-the-counter, alternative and illicit drugs as well as tobacco and ethanol use as these can also have serious implications. Medications may also indicate the nature of concurrent illnesses which the patient may have neglected to reveal.
Taking a history of known allergies before prescribing or administering any drug is essential. Anaesthetics are no exception. Again, be aware of the difference between an allergy and a side effect.
The teeth are vulnerable to damage during airway instrumentation. Pre-existing damage should be noted for medico-legal reasons. The presence of caps or crowns and loose or unhealthy teeth (especially in front) should be noted and the risk of damage discussed with the patient.
An anaesthetist would be foolish not to examine for features which may indicate possible difficulty with mask ventilation or intubation. These include prominent upper incisors, a protuding or receding chin, limited mouth opening, short neck, stiffness of the cervical spine, disease of the pharynx or larynx and deviation of the trachea. If nasal intubation is required, patency of the nasal passages should be checked also.
Many medical illnesses may complicate the course of anaesthesia and surgery. Some, such as cardiac or respiratory diseases, have fairly obvious implications. Rare conditions and syndromes have even the most experienced anaesthetist referring to textbooks. Concurrent disease, as well as a variety of other patient factors such as age, also guide the anaesthetist in the choice of what preoperative investigations may be required.
This can be a difficult issue to resolve and must include consideration of all the abovementioned factors, whether or not the patient is in the best possible state of health consistent with his/her organic illness, the necessity of the operation and its urgency. The final decision can only be made by careful consultation between surgeon, anaesthetist and the patient.
The most common classification is that recommended by the American
Society of Anesthesiologists (ASA):
Class I fit and healthy
Class II mild systemic illness (such as hypertension)
Class III severe systemic illness which is not incapacitating
Class IV incapacitating illness/constant threat to life
Class V moribund/not expected to live more than 24 hours
"E" added to above if operation is an emergency
Preoperative Assessment and Premedication (Chapter Organiser John
Ascah) in The Virtual Anaesthesia Textbook <www.virtual-anaesthesia-textbook.com>
Preoperative Assessment and Preparation of the Patient (Chapter 12)
in Essentials of Anesthesiology (Chung and Lam eds). W.B. Saunders
Company. [A book ideally suited to the personal library of a
medical student]
Preoperative Assessment and Premedication (Chapter 5) in Lee's
Synopsis of Anaesthesia (Atkinson, Rushman and Davies eds).
Butterworth Heinemann.
See also any of the major textbooks of anaesthesia (eg Miller or
Barash, Cullen and Stoelting). These invariably have enormous
sections (hundreds of pages!) devoted to this topic.