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Anaesthesia for the elderly

Anaesthesia for the elderly
Fiona Kelly
Anaesthesia and surgery in the elderly population are associated with increased morbidity and mortality. Specific factors to consider include:
  • Degenerative disease of all types is commoner in geriatric patients. History may be unreliable and hospital notes occasionally formidable.
  • Cardiovascular: ischaemic heart disease is common, with reduced ventricular compliance, contractility, and reduced cardiac output. Blood flow to the kidneys and brain may be reduced, with impaired autoregulation. Atherosclerosis may be widespread, resulting in a less compliant arterial tree and systemic hypertension. The physiological response to cardiovascular disturbance may be blunted, due to reduced baroreceptor sensitivity and impaired autonomic function. Atrial fibrillation is common.
  • Respiratory: pulmonary elasticity, lung and chest wall compliance, TLC, FVC, FEV1, VC, and inspiratory reserve are all reduced, with an increase in residual volume. Although FRC is unchanged, closing capacity falls progressively with age, leading to airway collapse, VQ mismatch, and hypoxaemia. Atelectasis, pulmonary embolism, and chest infection are all more common in elderly patients, the latter in part due to ineffective mucociliary activity. PAO2 and PAO2 decrease with age (PAO2 = 13.3 – age/30 kPa, or PAO2 = 100 – age/ 4 mmHg).
  • Renal system: glomerular filtration is reduced. Muscle bulk decreases with age resulting in reduced creatinine production, hence even a modest rise in serum creatinine may represent significant renal impairment. Tubular function is also impaired, with reduced renal concentrating ability and reduced free water clearance. Fluid balance is more critical, as responses to both fluid loading and dehydration are impaired.
  • Pharmacology: pharmacokinetics are altered, with reduced hepatic and renal blood flow and a reduction in total body water. Pharmacodynamics may also be altered, with increased sensitivity to many agents, especially CNS depressants. MAC decreases steadily with age (4–5% per decade after 40 years—for example, the MAC of isoflurane is approximately 0.92 at 80 years of age). Plasma proteins are often reduced, resulting in reduced protein binding of drugs and metabolites, thereby increasing free drug levels and possible toxic effects.
  • Nervous system: in addition to autonomic dysfunction, cerebrovascular disease is common, and hearing, vision, and memory may be impaired. Confusion is more likely, both pre- and postoperatively.
  • Nutrition: malnutrition is common in the elderly, and is associated with increased morbidity and mortality. Trials of nutritional supplementation show reduced length of hospital stay and reduced minor postoperative complications, but without a decrease in mortality. Consider oral protein supplementation, nocturnal nasogastric feeding, or even TPN in those with significant malnutrition.
Preoperative considerations
  • Full and thorough assessment—significant cardiac, respiratory, and renal disease may have been previously undetected. An ECG is required for all patients. Note cognitive function and the level of social support.

  • In patients who have sustained a fracture, actively seek an underlying medical cause for a fall, e.g. arrhythmias, myocardial infarction, transient ischaemic attack, CVE, pulmonary embolus, GI bleed.
  • Assessment of exercise tolerance and functional ability is important. This may be misleading, however, as patients tend to live within their functional reserve.
  • Dehydration is common. Many patients do not drink adequately when confined to bed. Consider prescribing preoperative IV fluids.
Perioperative considerations
  • Arm-brain circulation time is increased, and dose requirements for induction agents are drastically reduced. Titrate drugs slowly against effect, and inject into a running IV infusion.
  • Use fluid warmers/body warming devices whenever possible. Elderly patients have a reduced basal metabolic rate and are susceptible to heat loss as a result of impaired thermoregulation.
  • Regional anaesthesia may have some advantages over general anaesthesia, including fewer thromboembolic complications, confusion, and respiratory upset postoperatively. However, hypotension is more commonly seen in elderly patients undergoing spinal/epidural anaesthesia due to impaired autonomic function and reduced compliance of the arterial tree. General anaesthesia may be best for those who require precise control of their blood pressure. Regional anaesthesia for hip fractures may reduce mortality at 1 month, but regional and general anaesthesia appear to produce comparable results for longer-term mortality.
  • Careful perioperative fluid balance. Consider measuring the CVP when large fluid shifts are expected. Patients are more often ‘underfilled’ than ‘overloaded’. Regular review is essential following major surgery.
Postoperative considerations
  • Prescribe postoperative oxygen therapy following abdominal or thoracic surgery, in the presence of cardiovascular or respiratory disease, in situations when there has been significant blood loss, and when opioid analgesia has been prescribed. Nasal cannulae are often better tolerated.
  • Postoperative analgesia: consider prescribing a regular simple analgesic such as paracetamol, and use NSAIDs with caution (the complications of NSAID use are more prevalent in the elderly). Intramuscular and subcutaneous opioids may be unreliably absorbed due to variable tissue perfusion, and an elderly confused patient may have difficulty using a PCA. Regional techniques or an IV opioid infusion (with appropriate supervision) may be the most appropriate method of pain relief.
  • Early and frequent physiotherapy and mobilization are extremely important.
Further reading
Dickson RE, Patey RE (1999). Perioperative management of the elderly trauma patient. Hospital Medicine, 60, 425–9.

Parker MJ, Urwin SC, Handoll HHG, Griffiths R (2000). General versus spinal/ epidural anaesthesia for surgery for hip fractures in adults (Cochrane Review). The Cochrane Library, issue 3.

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