Lifestyle Influences On Anaesthetic Risk

Alcohol

Excessive alcohol ingestion leads to a spectrum of pathology depending on the extent and chronicity of the problem:

• Increased cellular tolerance of drugs means that higher than expected doses of anaesthetic agents will be required.

• Withdrawal symptoms in the postoperative period require aggressive treatment to prevent the patient from injuring themselves or staff members. Symptoms include: disorientation, hallucinations, tachycardia, hypertension and grand mal convulsions. Management includes thiamine, benzodiazepine sedation and beta-blockers. Mild alcohol withdrawal symptoms occurring within 6-8 h of abstinence require no specific therapy.

Potential perioperative problems include:

• cellular tolerance leading to higher anaesthetic requirements,

• chronic brain syndrome (alcoholic dementia),

• clotting abnormalities,

• increased risk of infection,

• acute withdrawal syndrome (delerium tremens),

• agitation and self-harm,

• wound disruption,

• cardiovascular instability,

• bleeding varices.

Morbid obesity

Obesity is an increasing health problem worldwide. It is defined as having 25-30% greater than ideal body weight or body mass index (BMI) >30. The BMI is defined as weight (kg) divided by height (m) squared. Morbid obesity may be defined as being 100% greater than ideal body weight or BMI > 35. Morbid obesity is associated with a significant diminution of physiological reserve and an increase in associated pathological conditions including hypertension, coronary artery disease, diabetes and oesophageal reflux. Cardiovascular performance shows impaired diastolic filling and reduced rise in ejection fraction with exercise compared with non-obese patients. These associated medical conditions pose increased difficulties during surgery and anaesthesia. Osteoarthritis, hiatus hernia and gallbladder disease are common and frequently require surgery.

Perioperative problems associated with morbid obesity

Induction

• Venous access is often difficult and a central line may be required for access.

• Accurate BP monitoring is difficult and wide BP cuffs will be required if non-invasive monitoring is used. An arterial line may provide more reliable readings in this situation.

• Difficulty in intubation.

Intraoperative problems

• Patient positioning.

• Drug dosage to ensure adequate depth of anaesthesia. Postoperative problems

• Respiratory insufficiency due to mass loading of chest wall and abdomen plus reduced vital capacity.

• The high incidence of OSA Patients with morbid obesity and OSA have a 20-25% incidence of daytime hypoxia leading to pulmonary hypertension and 50% incidence of hypercarbia.

• Increased incidence of deep vein thrombosis (DVT).

Smoking

Smoking significantly increases perioperative risk. Elevated carboxyhaemoglobin levels due to inhaled carbon monoxide persist for up to 12 h after cessation of smoking and laryngeal irritability and bronchial reactivity are enhanced by smoking. Co-existing smoking-induced pathology is common and includes:

• hypertension,

• ischaemic heart disease and peripheral vascular disease,

Patients should be advised to cease smoking prior to surgery, however, compliance is poor and no decrease in postoperative complications has been found unless smoking is stopped >8 weeks prior to surgery. Careful assessment is necessary because symptoms of the presenting illness may mask those of other cigarette-induced disease processes, with angina, intermittent claudication and exertional dyspnoea being common examples.

Non-prescription drugs and substance abuse

The large number of 'recreational' and addictive drugs have implications for anaesthesia and surgery:

• Patients using injectable agents have an increased risk of blood-borne infections, including HIV, hepatitis and bacterial endocarditis.

• Withdrawal symptoms may appear and include violent and aggressive behaviour, or delusional and hallucinatory behaviour. A high clinical index of suspicion is necessary to diagnose drug withdrawal.

• Interactions between therapeutic and non-prescription drugs may complicate management, for example, opioid resistance in narcotics abuse, hypertension and tachycardia with amphetamine use and resistance to anaesthetic agents with sedative abuse.

• Venous access may be particularly difficult, especially in the hypovolaemic chronic drug user.

• Solvent inhalation sensitises the myocardium to arrhythmias especially with inhalational anaesthetic agents.

Herbal products

Because herbal products are not considered 'drugs' by most patients, the use of these products may not be volunteered at the preoperative interview. The use of these substances is increasing worldwide with up to 22% of patients (USA) taking some form of herbal supplement. Although most appear to have no effect on the conduct of surgery or anaesthesia, several can have significant effects (Table 1.7) and should be ceased prior to surgery whenever possible. In addition, many may be taken as individually prepared preparations and hence the 'dose' consumed may vary widely.

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