Surgery under anaesthesia for the older surgical patient

Cardiovascular

Cardiovascular disease becomes more prevalent with increasing age. The incidence of heart failure doubles every decade, and the incidence in those aged older than 80 years is approximately 10%. Heart failure can be viewed as a final common pathway for multiple cardiovascular insults.

• Structural change. The heart changes shape (more spherical), and although there is no overall change in left ventricular mass, there is relative thickening of the interventricular septum. In the absence of other diseases, systolic function is largely unchanged in healthy ageing; diastolic function is altered, however. Ventricular filling occurs later in diastole, with greater contribution of atrial filling to end-diastolic volume. These changes are compensated for at rest but become unmasked with exercise. Aerobic capacity ( V̇ o ₂ max) declines around 50% with ageing. Cardiac output decreases by around 25%, in part because of an inability to increase heart rate. The remainder of the V̇ o ₂ max decline is attributed to alterations in oxygen extraction and redistribution of blood flow with exercise. The vascular tree becomes less compliant with age, resulting in arterial systolic hypertension. Responsiveness to vasoconstrictive (α ₁ ) and vasodilatory (nitric oxide) stimuli reduces with age.

• Valvular disease. Moderate to severe mitral or aortic valvular disease affects around 13% of people older than 75 years. Echocardiography demonstrates mild calcification of the aortic valve in around 40% of people aged older than 60 years and 75% of those older than 85 years.

• Conduction and rhythm abnormalities. Atrial fibrillation (AF) is more prevalent with ageing. Around 3%–4% of 60–70 year olds have AF; 10%–17% in those aged older than 80 years. Ventricular ectopic beats are also more common, but this may not have clinical significance. Resting heart rate does not change, but peak heart rates decline by around 0.7–1.0 beats min ^–1 year ^–1 . Symptomatic sinus bradycardia is almost exclusively seen in those aged older than 60 years. Permanent pacemakers (for any indication) are most commonly inserted in older people.

Respiratory

• Lung mechanics. Elasticity of the chest wall declines with age because of loss of elastin, degeneration of joints and changes in thoracic shape. There is some decline in diaphragmatic function with age; peak inspiratory pressures are around 20% lower in those older than 65 years compared with young adults. There is enlargement of airspaces and degeneration of elastic tissue in the lung.

• Lung function. Measurements of lung function decline steadily from around 20–35 years. Forced expiratory volume in 1 second (FEV ₁ ) declines around 20–30 ml year ^–1 . Functional residual capacity (FRC) and residual volume (RV) increase with age.

• The ventilatory response to hypoxia and hypercapnia is diminished.

Neurological

• Brain volume decreases by around 0.5%–1% year ^–1 after age 60, though the decline may start earlier in adult life. These changes are not uniform across cerebral structures, and age-related changes are probably separate from pathological changes such as Alzheimer's disease.

• Ischaemic damage is common. Around 5% of people aged 60–80 years are survivors of stroke, increasing to 15% of those aged older than 80 years. Subclinical (micro) infarcts are found in around one-third of cognitively intact older people.

• The incidence of dementia increases with age. Reported rates are dependent on the degree of case ascertainment but are around 5%–10% in those aged older than 65 years; the risk may be decreasing (those born more recently may be at a lower risk).

• Mild cognitive impairment, an intermediate spectrum between normal cognition and dementia, is reported to occur in around 15%–20% of people older than 60 years.

Renal

• Glomerular filtration rate (GFR) declines on average by about 8 ml min ^–1 1.73 m ^–2 decade ^–1 after around the second to fourth decade of life. There is wide interindividual variability, in part because of association with risk factors such as diabetes, smoking, arterial hypertension and so on. Although creatinine clearance declines, so does muscle mass (and hence creatinine excretion). As a consequence, serum creatinine in the elderly may be ‘normal’ despite markedly reduced GFR.

• The balance of vasoconstriction and vasodilation, which is essential to normal renal function, is precarious in the older kidney. This may explain why even modest insults such as perioperative hypotension and hypovolaemia and the use of non-steroidal anti-inflammatory drugs (NSAIDs) may provoke acute kidney injury (AKI) in the elderly.

Haematological

• Anaemia increases with age. Around 10% of community-dwelling people aged older than 65 years are anaemic; around 50% of nursing home residents are anaemic.

• There is some evidence of hypercoagulability with increasing age.

• There is dysregulation of T-lymphocyte function affecting both cellular and humoral immune responses.

• In common with other systems there may be reduced reserve to respond to increased demands around the time of surgery.