PRE-OPERATIVE EVALUATION AND PREPARATION (PRIOR

TO PROCEDURE UNDER GENERAL ANESTHESIA)

AishahAwatifHaziq

Introduction Anaesthesia = absence of all sensation Analgesia = absence of pain General anaesthesia = a state where all

sensation is lost and the patient is rendered unconscious by drugs.

GA should be performed by qualified anasthetists in a hospital setting with access to appropriate medical support.

Assessment of risk Patient should be made as fit as

possible for the operation. The anticipated benefit should outweigh

the anesthetic and surgical risks involved.

Overall mortality rate ≈ 1 in 100 000 Surgical mortality ≈ 1 in 1000

Factors contribute to this mortality:Poor preoperative assessmentInadequate supervision and monitoring in

the intraoperative periodInadequate postoperative care

Aims of Pre-operative evaluation and preparation To provide diagnostic & prognostic information. To ensure the patient understands the nature, aim,

and expected outcome of surgery. To relieve anxiety and pain. Ensure that the right patient gets the right surgery. Get informed consent. Assess/balance risks of anaesthesia ans

maximize fitness. Check anaesthesia/analgesia type with

anesthesia.

Preoperative assessment and premedication

History Past medical history:

AsthmaDiabetesTuberculosisSeizuresChronic organ dysfunctionHIV infectionDrug allergyDVTPost-operative nausea and vomiting

Drug history Drug interactions

Anticoagulant might be contraindicated to spinal, epidural or other regional techniques

Anticonvulsants might increase the requirements for anasthetic agents, enflurane should be avoided as it might precipitate seizures

Beta-blockers – negative ionotropic effect – hypotension

Corticosteroids – extra cover might be needed

Diuretics – might have hypokalaemiaInsulin – careful monitoring of plasma

glucoseAntibiotics: tetracycline and neomycin may ↑

neuromuscular blockade.

Social history Ceasing smoking 12h before surgery

can improve the oxygen carrying capacity of the blood.

Excessive alcohol – hepatic and cardiac damage

Family history Hereditary traits:

Haemophilia PorphyriaCholinesterase abnormalities – prolongation

of muscle relaxants such as suxamethonium

Physical examination Assess cardiorespiratory system, exercise

tolerance, existing illness, drugs, and allergies. Is the neck unstable (eg; arthritis complicating

intubation?) Assess past history of; MI, diabetes, asthma,

hypertension, rheumatic fever, epilepsy, jaundice.

Assess any specific risk, eg is the patient pregnant? Is the neck/jaw immobile and teeth stable (intubation risk)?

Has there been previous anaesthesia? Were there any complications (eg

nausea, DVT)? Is DVT/PE prophylaxis needed?

Per-op investigation of elective patients

Indications of preoperative investigations

Full blood countanaemiafemales post menarchecardiopulmonary diseasepossible haematological pathology, e.g.haemoglobinopathieslikelihood of significant intraoperative blood losshistory of anticoagulantschronic diseases such as rheumatoid disease

Clotting screenliver diseaseanticoagulant drugs or a history of bleeding orbruisingkidney diseasemajor surgery

Urea and electrolyte concentrationsmajor surgery >40 yearskidney diseasediabetes mellitisdigoxin, diuretics, corticosteroids, lithiumhistory of diarrhoea and vomiting

Liver function tests: these will be carried out when thereis any suspicion of liver disease

ECG>40 years asymptomatic male or >50 years

asymptomatic femalehistory of myocardial infarction or other heart or

vascular disease<40 years with risk factors e.g. hyperlipidaemia,

diabetes mellitus, smoking, obesity, hypertension and cardiac medication

Chest radiographybreathlessness on mild exertionsuspected malignancy, tuberculosis or chest infectionthoracic surgery

American Society of Anesthesiologists (ASA) classification

Class I Normally healthy

Class II Mild systemic disease

Class III Severe systemic disease that limits activity but is not incapacitating

Class IV Incapacitating systemic disease which poses a constant threat to life

Class V Moribund: not expected to survive 24h even with operation

Pre-op therapy Pt with respiratory disease –

physiotherapy or bronchodilator therapy

Infective endocarditis – prophylactic antibiotic

Hypertension – adjustment of drug therapy to obtain optimal control (diastolic pressure below 110 mmHg)

Postponement of surgery Pt with acute upper resp tract infection Cardiac/endocrine diseases that are not

yet under optimal control Elective surgery should not be undertaken

unless:Pt has fasted for 6h for solid food, Infant

formula or other milk4h for breast milk2h for clear non-particulate and non-

carbonated fluids

Pre-medication benzodiazepines – anxiolysis, anterograde

amnesia Anticholinergic drug – reduce excessive

secretions in the airway Antiemetic Antihistamine Metoclopramide - enhance gastric emptying Sodium citrate, H2 blockers, proton pump

inhibitor – reduce gastric acidity

Preparation for anesthesia Fast patient.

Nil by mouth ≥ 2h pre-op for clear fluid and ≥ 6h for solids

Is there any bowel or skin preparation needed, or prophylactic antibiotic?

Start DVT prophylaxis as indicated, eg: graduated compression stockings + heparin 5000U sc 2h pre-op, then every 8-12h sc for 7d or until ambulant.

Write up the pre-meds; book any pre-, intra-, or post-operative x-rays or frozen sections. Book post-op physiotherapy.

If needed, catheterize and insert Ryle’s tube before induction. These can reduce organ bulk, making it easier to operate in the abdomen.