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Anaesthesia for the elderly 

Anaesthesia for the elderly
Chapter:
Anaesthesia for the elderly
Source:
Oxford Handbook of Anaesthesia (4 ed.)
Author(s):

Stu White

and Jeffrey Handel

DOI:
10.1093/med/9780198719410.003.0032

General considerations

‘Elderly’ arbitrarily refers to patients >65yr, who are the most rapidly expanding demographic of the surgical population. Age-related physiological and cognitive decline, co-morbidity, and frailty contribute to the higher risk of perioperative morbidity and mortality among older patients. Polypharmacy is common.

Ageing is associated with progressive deterioration of function in all systems, the effect of which may be compounded by organ-specific co-morbidity.

Cardiovascular

  • Significant CVS disease is present in 50–65% of patients.

  • Myocardial fibrosis and ventricular wall thickening occur, reducing ventricular compliance. Small changes in filling may have major effects upon cardiac output and BP.

  • AF is common and reduces stroke volume through loss of the atrial component of ventricular filling.

  • Maximal cardiac output with exercise decreases by ~1% per year from the 5th decade.

  • Reduced arterial compliance causes systolic hypertension and widened pulse pressure.

  • Reduced autonomic responsiveness impairs CVS responses to hypotension. The hypotensive effect of anaesthetic agents is likely to be more pronounced.

  • Capillary permeability is increased, leading to a greater risk of pulmonary oedema.

Respiratory

  • Ventilatory responses to hypoxia and hypercapnia decline. Post-operative apnoea is commoner. Ventilatory reserve declines.

  • O2 consumption and CO2 production fall by 10–15% by the 7th decade. Patients are able to tolerate a longer period of apnoea following preoxygenation, and minute volume requirement is reduced.

  • Loss of elastic recoil increases pulmonary compliance, but chest wall compliance falls due to degenerative changes in joints. Therefore, total thoracic compliance may fall.

  • Loss of septa increases the alveolar dead space. Closing volume increases to exceed the FRC in the upright posture at 66yr, resulting in venous admixture. Thus, normal PaO2 falls steadily [(13.3 − age/30) kPa, or (100 − age/4) mmHg].

  • Airway protective reflexes decline, increasing the risk of post-operative pulmonary aspiration.

  • In edentulous patients, maintenance of a patent airway and face mask seal may be difficult. Leaving false teeth in situ may help.

Renal

  • Renal mass and number of glomeruli fall progressively (by 30% in the 8th decade), resulting in reduced GFR. Creatinine clearance falls comparably, although serum creatinine may not rise because of decreased production from a reduced muscle mass (see Anaesthesia for the elderly p. [link]).

  • Tubular function deteriorates, leading to reduced renin–aldosterone response, ADH sensitivity, and concentrating ability. As a result, all renal homeostatic functions deteriorate, so that elderly patients are more susceptible to fluid overload and hypovolaemia. Hypo- and hypernatraemia are more likely to occur.

  • Reduced clearance of renally excreted drugs necessitates dose adjustment. Particular care must be taken with potentially nephrotoxic drugs such as aminoglycosides.

Hepatic

  • Hepatic mass and blood flow fall by up to 40% by the 9th decade. Although cellular function is relatively well preserved in healthy patients, the reduction in size reduces clearance and prolongs the effect of drugs that are metabolized and excreted by the liver. These include opioids, propofol, benzodiazepines, and NDMRs.

Central nervous system

  • Brain size and neuronal mass decrease. The average brain weight falls by 18% between the ages of 30 and 80yr. Dementia affects 10% of patients over 65yr of age, and 20% over 80yr. However, it is important to distinguish between dementia and reversible confusional states due to hypoxia, sepsis, pain, metabolic derangement, and depression. The hospital environment may precipitate anxiety and confusion.

  • The elderly have lower requirements for opioid analgesics and sedatives and are more susceptible to depression of the conscious level and respiration. This is likely to be due to a pharmacodynamic, as well as a pharmacokinetic, effect. Pain threshold may be increased.

  • Post-operative delirium (POD) and cognitive dysfunction (POCD) are common in the elderly, occurring in >10% of patients. Disturbances of cerebral perfusion and cellular oxygenation are likely to be contributory factors. Potentially reversible risk factors for POD include severe pain, infection, malnutrition, electrolyte imbalance, dehydration, environmental disturbances, and substance withdrawal (alcohol, medication).

  • The thirst response to reduced ECF volume and increased plasma osmolality is reduced in the elderly, increasing susceptibility to fluid depletion.

Pharmacology

  • TBW is reduced, while fat percentage is increased. The volume of distribution of water-soluble drugs is reduced, reducing dose requirements, while that of lipid-soluble drugs is increased which may prolong clearance. The initial volume of distribution falls because of reduced cardiac output. This reduces the dose requirement and is particularly relevant for induction agents. Arm–brain circulation time is prolonged, increasing the time taken for induction agents to take effect.

  • Reduced plasma albumin concentration decreases the dose requirement of drugs, such as barbiturate induction agents, which are bound to albumin.

  • MAC of inhaled agents decreases steadily with age (6% reduction per decade) and is reduced by around 40% by the age of 80yr (see Anaesthesia for the elderly p. [link]). This may be related to a reduction in neuronal mass. Reductions in blood/gas partition coefficient and cardiac output in the elderly result in shorter onset time.

  • The risk of GI bleeding due to NSAIDs is increased. These agents may also contribute to the development of ARF in the presence of impaired renal perfusion. ACE inhibitors exacerbate this risk. Fluid retention due to NSAIDs may precipitate heart failure in susceptible patients.

Thermoregulation

  • Temperature regulation is impaired, increasing the risk of hypothermia.

  • Post-operative shivering increases skeletal muscle O2 consumption, while vasoconstriction increases myocardial work and O2 demand.

Endocrine

  • Glucose loading is increasingly poorly tolerated in elderly patients. The incidence of diabetes rises and may reach 25% in patients above 80yr of age.

Nutrition

  • Nutritional status is frequently poor in the elderly, under-recognized by clinicians, and compounded by a lack of appetite resulting from surgery, pain, and nausea.

  • Perioperative complications and length of hospital stay may be reduced by nutritional supplementation prior to major surgery.

Haematology and the immune system

  • Hypercoagulability and DVT become commoner with advancing age.

  • Disorders causing anaemia are commoner, and the response of the marrow to anaemia is impaired.

  • Immune responses are reduced in the elderly, putting them at increased risk of infection. This is due to reduced bone marrow and splenic mass with loss of the thymus.

Anaesthetic management of the elderly

Perioperative mortality increases with age, ASA status, and the type and urgency of surgery. The 30-day mortality after hip fracture surgery is ~8% in the UK (see also Anaesthesia for the elderly p. [link]), and after emergency laparotomy ~10% aged 50, rising by ~5% per decade. Outcome is improved by thorough multidisciplinary preoperative assessment, choice of an anaesthetic technique appropriate to the patient’s condition, and meticulous perioperative care aimed at minimizing physiological disturbance.

Preoperative assessment and management

  • A systematic review is vital. In patients who have sustained a fracture, an underlying medical cause for a fall should be sought.

  • Day surgery is particularly appropriate for fit patients undergoing minor surgery, as the disorientation associated with a change of environment is minimized.

  • The level of physical activity that can be sustained is a useful indicator of CVS and respiratory fitness but is often limited by joint disease.

  • The mental state should be evaluated. The abbreviated mental test or mini-mental state examination may be useful in differentiating dementia from acute confusional states.

  • Consideration should be given to pre-optimization of medical conditions. This may require cross-specialty involvement and high dependency care. The benefits from delaying surgery, while this takes place, should be balanced against the risks, particularly in non-elective surgery. In patients with lower limb fractures, delay in mobilization may increase the risk of pressure sores, DVT, and pneumonia.

  • With the exception of oral hypoglycaemics, regular medications should be continued until the time of surgery. Alcohol should not be withheld the day before surgery, and nicotine patches may be helpful in smokers. Sedative premedications should generally be avoided, particularly benzodiazepines, centrally acting anticholinergics, and pethidine. Antacid prophylaxis should be considered. Maintaining β‎-blockade may reduce the risk of MI.

Perioperative management

  • The type of anaesthesia appears less important than the care with which it is given with regard to the patient’s physiological condition. However, regional anaesthesia may reduce bleeding, risk of DVT, respiratory infection, and cognitive dysfunction (particularly if given without/with minimal sedation). MAC or minimum inhibitory concentration (MIC) if using TIVA, should be age-adjusted.

  • Careful monitoring is necessary to detect hypotension during GA induction and shortly after spinal anaesthesia administration. Consideration should be given to invasive BP and depth of anaesthesia monitoring. Prolonged arm–brain circulation time delays the onset of IV induction agents; flush the drugs with saline, and remain patient to avoid an inadvertent overdose.

  • Temperature should be measured, and hypothermia prevented using fluid warmers, active body-warming devices, and elevation of ambient temperature.

  • Prolonged surgery and periods of hypotension increase the risk of pressure sores. Care should be taken to reduce pressure with soft padding. During long procedures, it is advisable to relieve pressure and massage vulnerable areas intermittently.

Post-operative management

  • High dependency facilities should be considered if this is likely to reduce morbidity or mortality significantly or if an identifiable organ support is required.

  • Fluid balance, vital signs, serum electrolytes, and haematology must be carefully monitored and treated appropriately. Patients with CVS disease may need to have an Hb of >9–10g/dL.

  • Reversible factors should be sought if the patient exhibits delirium.

  • Pain is common but undertreated in elderly surgical patients, particularly if cognitively impaired. Regular paracetamol prescription and regional analgesia should always be considered and are preferable to opioids and NSAIDs.

  • Anaesthetists should facilitate post-operative patient ‘re-enablement’ through age-appropriate anaesthesia, fluid therapy, thermoregulation, analgesia, and communication.

Post-operative cognitive dysfunction

POCD is the persistent impairment of cognitive function (e.g. memory loss and concentration) after surgery, without a clear precipitating event or CNS pathology, and is distinct from POD and dementia. The severity is variable but may have a significant impact upon the quality of life and independence. The cause is likely to be multifactorial and may relate to inflammatory reactions, altered hormonal homeostasis, and/or direct anaesthetic agent toxicity. POCD is commoner after major surgery, cardiac surgery, and emergency surgery. There are no generally agreed criteria for the assessment of POCD. The incidence of POCD is similar after general and regional (with sedation) anaesthesia. The 1-week and 1-year incidence of POCD may be reduced, using focused anaesthesia intervention (treatment of hypoxaemia and hypotension), guided by the depth of anaesthesia and cerebral saturation monitoring.

When not to operate

Heroic curative surgery may not be appropriate if the chance of benefiting the patient is felt to be very low. Decisions regarding futility of surgery are difficult and should be multidisciplinary and taken at consultant level, with the involvement of the patient and their family. Palliative procedures to improve the quality of life should be considered if the patient is adequately prepared. These decisions must be carefully documented.

Key points

  • Older patients must be assumed to have the mental capacity to make decisions about their treatment.

  • Access to surgical or critical care should not be rationed on the basis of age. Patients must be involved in discussions about the utility/futility of surgery and/or resuscitation.

  • Avoid sedative premedications, and use regional analgesic techniques, where possible, to minimize the requirement for opioids.

  • Monitor the temperature, and use active warming devices to prevent hypothermia.

  • Always consider invasive BP and depth of anaesthesia monitoring.

  • Drug/MAC requirements are reduced. Use opioids and NSAIDs with caution, particularly if there is co-morbid renal disease.

  • Take care with positioning, and intermittently relieve pressure during long procedures to reduce the risk of pressure sores.

  • Reversible factors should be sought if the patient exhibits delirium (pain, hypoxaemia, distended bladder, myocardial/cerebral ischaemia, electrolyte disorder, drugs).

  • Facilitate early mobilization, and consider thromboprophylaxis if mobilization will not be rapid.

Further reading

American College of Surgeons (2012). ACS NSQIP®/AGS best practice guidelines: optimal preoperative assessment of the geriatric surgical patient. Anaesthesia for the elderly http://site.acsnsqip.org/wp-content/uploads/2011/12/ACS-NSQIP-AGS-Geriatric-2012-Guidelines.pdf.

Association of Anaesthetists of Great Britain and Ireland, Griffiths R, Alper J, Beckingsale A, et al. Management of proximal femoral fractures 2011: Association of Anaesthetists of Great Britain and Ireland. Anaesthesia, 67, 85–98.Find this resource:

Ballard C, Jones E, Gauge N, et al. (2012). Optimized anaesthesia to reduce post operative cognitive decline (POCD) in older patients undergoing elective surgery, a randomized controlled trial. PLoS One, 7, e37410.Find this resource:

Corcoran TB, Hillyard S (2011). Cardiopulmonary aspects of anaesthesia for the elderly. Best Pract Res Clin Anaesthesiol, 25, 329–54.Find this resource:

Dodds C, Kumar C, Veering B (2014). Oxford textbook of anaesthesia for the elderly patient. Oxford: Oxford University Press.Find this resource:

Griffiths R, Beech F, Brown A, et al.; Association of Anaesthetists of Great Britain and Ireland. Peri-operative care of the elderly 2014: Association of Anaesthetists of Great Britain and Ireland. Anaesthesia, 69, 81–98.Find this resource:

Schofield P (2014). The assessment and management of peri-operative pain in older people. Anaesthesia, 69, 54–60.Find this resource:

Stoneham M, Murray D, Foss N (2014). Emergency surgery: the big three—abdominal aortic aneurysm, laparotomy and hip fracture. Anaesthesia, 69, 70–80.Find this resource:

Strom C, Rasmussen LS, Sieber FE (2014). Should general anaesthesia be avoided in the elderly? Anaesthesia, 69, 35–44.Find this resource:

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