Department of Anaesthesia, University of Toronto, Toronto Western Hospital, 399 Bathurst St., EC 2-046, Toronto, Ontario, Canada M5T 2S8*Corresponding author
This review is accompanied by Editorial II.
Abstract
Elderly patients still have the highest postoperative mortality and morbidity rate in the adult surgical population. Preoperative clinical assessment to detect patients at high risk of postoperative events, and specific intraoperative and postoperative anaesthesia management are important to minimize postoperative adverse events in the elderly.
Br J Anaesth 2001; 87: 60824
Keywords: anaesthesia; complications; age factors, surgery
Among the steadily increasing population of surgical patients aged 65 yr and older, the fastest growing sector is individuals of 85 yr or older.149 As a result, greater numbers of patients are presenting for surgery with ageing-related, pre-existing conditions that place them at greater risk of an adverse outcome, such as cardiac or pulmonary disease or diabetes mellitus.122 It is, therefore, not surprising that the elderly have the highest mortality rate in the adult surgical population.108 Postoperative adverse effects on the cardiac, pulmonary, cerebral systems, and on cognitive function are the main concerns for elderly surgical patients who are at high risk. Recently some studies have focused on elderly surgical patients regarding the incidence of postoperative complications, predictors for developing postoperative complications, preoperative assessment and screening for elderly patients at high risk, and perioperative management. In this review, we document the incidence of postoperative adverse outcomes and discuss ways of improving perioperative anaesthesia care for this vulnerable surgical population.
Anaesthesia- and surgery-related mortality
Incidence
Mortality associated with anaesthesia and surgery is defined as the death rate within 30 days of operation. Advances in anaesthetic/surgical technique and perioperative care have substantially reduced related mortality.43 108 However, overall mortality in the general population remains at 1.2%,108 compared with 2.2% in patients aged 6069 yr,108 2.9% in those 7079 yr,108 5.86.2% in patients over 80 yr,43 and 8.4% in those over 90 yr.69 Major surgery further increases elderly mortality; for example, emergency abdominal surgery results in a 9.7% mortality for patients over 80 yr,79 thoracotomy in a 17% mortality for those over 70 yr,20 and any major surgical procedure a 19.8% mortality in those over 90 yr.2
Predictive factors
The function capacity of organs reduces with ageing, resulting in decreased reserve and ability to endure stress.75 114 Advanced age is, therefore, a significant risk factor for increased mortality.43 108 114 Co-existing disease further depresses organ function and/or reserve, exacerbating risk.75 108 For example, pre-existing hypertension, diabetes mellitus, or renal failure contributes to a higher incidence of perioperative myocardial infarction (MI) (5.1%), cardiac death (5.7%)68 or ischaemia (1217.7%).30 Additional risk factors in the elderly2 43 69 108 (Table 1) include the need for emergency surgery,2 69 major surgical procedures, ASA physical status III or IV, and poor nutritional status.
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The cerebrovascular mortality was 0.05% in elderly patients who underwent incontinence surgery. Peri operatively, the period of greatest risk appears to be the postoperative period.108 It is the most physiologically stressful, with major changes in adrenergic activity, body temperature, pulmonary function, fluid balance, and perception of pain.95 These changes cause tachycardia and hypertension, increase imbalance in oxygen supply and demand, and incur cardiac ischaemia.96 109 Most of the pulmonary emboli occurred during the surgical procedure or within 7 days of surgery.127
Accordingly, to decrease perioperative risk in the elderly population requires rigorous preoperative assessment of organ function and reserve, good intraoperative control of concomitant disorders such as coronary artery disease, ischaemic heart disease, hypertension, chronic obstructive pulmonary disease (COPD) or diabetes mellitus, and vigilant postoperative monitoring and pain management. For example, patient-controlled analgesia/epidural analgesia (PCA/PCEA) can decrease postoperative myocardial ischaemia.15 124
Postoperative cardiac complications
Physiological changes, incidence rate, and predictive factors
Ageing affects cardiac function in many ways. Stiffening of large arteries increases afterload on the heart, while myocardial stiffening impairs early diastolic filling.53 114 The beta-adrenergic responsiveness of the heart decreases. Contractility does not change (despite prolongation in duration26), but the resulting increase in end-diastolic volume plays an important role in preserving maximal cardiac output during exercise. Conduction abnormalities and bradyarrhythmias are more prevalent in the elderly and hypertension is common, potentially contributing to ischaemic heart disease and sudden cardiac death. Antihypertensive treatment appears to reduce cardiovascular mortality and heart failure.148
Silent ischaemia and unrecognized MI also occur.70 153 Elderly patients at high risk for these conditions can be identified preoperatively by ambulatory electrocardiography and/or exercise or pharmacological stress testing.70 110 153
The most common cardiac complications associated with surgery in elderly patients are MI and myocardial ischaemia. Infarction usually occurs during the first 3 days after surgery, particularly on the first postoperative day. Most postoperative MIs are silent and have non-Q wave characteristics.109 129 Postoperative pain control combined with residual anaesthetic effects is responsible for the silent nature of an MI, making them difficult to detect and their precise onset difficult to determine.7 10 86 109 129 Monitoring for specific ECG changes (ST elevation and Q wave) accompanied by elevated CK, CK-MB isoenzyme and troponin T and I levels enables diagnosis. These data also permit identification of an MI as definite, probable or possible.10 30 Measurement of troponin T and I is replacing the use of CK, CK-MB levels to detect minor and early cardiac cell damage because of the greater sensitivity and specificity of these markers, especially in patients undergoing non-cardiac surgery with skeletal muscle injury, and those with chronic renal disease.3 Combined with measurement of myoglobin levels or detection of prolonged STT change, troponin levels can be an accurate indicator allowing early detection of high risk of postoperative MI.3 The specificity of cardiac troponin I for detection of MI (99%) was significantly different from that of MB creatine kinase (81%) (P<0.005).3
Patients at high risk of myocardial ischaemia should be monitored intraoperatively and for 3 days postoperatively for ST segment depression, a specific marker of ischaemic morbidity.72 As with MI, troponin levels are a more sensitive and earlier indicator of myocardial ischaemia than CK levels or STT wave change,10 and should be measured in patients who are at high risk or demonstrate ECG or haemodynamic evidence of cardiovascular dysfunction.10
Perioperative management
The principles underlying perioperative anaesthetic management of elderly surgical patients are provided in Table 4.
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Twelve-lead ECG is a screening test for all elderly patients. Left ventricular hypertrophy or ST segment depression less than 0.5 mm are independent factors associated with adverse cardiac events during major vascular surgery.86 Clinically stable elderly patients undergoing low or intermediate risk surgical procedures usually require no further preoperative testing other than 12-lead ECG.153 Ambulatory ECG can be used to identify patients with arrhythmias and silent ischaemic episodes,47 but the use of these data to predict perioperative cardiac events remains controversial.29 70
The use of advanced cardiac tests to evaluate risk should be considered primarily when anaesthetic and surgical management are likely to depend on test results. For example, conduction abnormalities and supraventricular and ventricular arrhythmias are not uncommon in elderly patients,62 and the underlying cardiac disease must be investigated before surgical treatment. In patients with second-degree (Mobiz II) or third-degree (complete) atrioventricular block, insertion of a temporary or permanent pacemaker will be necessary before elective surgery.47 Patients with cardiac murmurs should be referred for echocardiographic examination before elective surgery to detect aortic stenosis or regurgitation or mitral stenosis, common conditions in the elderly population.47 Symptomatic or severe aortic stenosis must be treated by aortic valve replacement before non-cardiac major surgery.47 Patients with aortic regurgitation should receive some form of preoperative prophylaxis for endocarditis.47 Preoperative dobutamine stress echocardiography (DTS) or radianuclide ventriculography (RVG) screening for vascular surgical patients at high risk is unnecessary.68 126
Clinically unstable elderly patients with ischaemic heart disease or severe coronary artery stenosis placing them at high risk of perioperative MI should be referred for angiography and prophylactic coronary revascularization126 before undergoing high risk surgery. Indications for coronary angiography are defined by the ACC/AHA.47
Exercise stress testing provides an objective measure of functional capacity and information about preoperative myocardial ischaemia or cardiac arrhythmias. It is recommended by the ACC/AHA as the first non-invasive test for ambulatory patients.47 For patients at intermediate risk scheduled for elective high risk surgical procedures such as major vascular surgery, the decision to perform exercise stress testing depends on the patients functional status, and the risk associated with the specific procedure. Patients aged 65 yr or older who are able to perform at least 2 min of supine bicycle exercise, raising the heart rate above 99 beats min1, are at low risk for perioperative cardiac complications.60 For elderly patients who cannot undergo exercise stress testing because of a bedridden condition, claudication or lower extremity pain,110 dipyridamole thallium scintigraphy, or dopamine stress echocardiography can provide the essential information.110 Intermediate-risk patients undergoing surgery with evidence of cardiac ischaemia will require postoperative intensive care and intensive monitoring. Detection of severe cardiac ischaemia mandates cancellation of surgery or performance of a less invasive elective procedure.
Anaesthetic management
Perioperative anaesthetic management varies according to the needs of the patient and of the surgical procedure. In elderly patients, the overall goals are to provide an appropriate operative environment, preserve myocardial and haemodynamic function, control for the effects of pre-existing disease on surgery, and avoid adverse perioperative events such as myocardial ischaemia or infarction.
General and regional anaesthesia (epidural or spinal) result in comparable short- and long-term cardiac morbidity and mortality in the elderly following peripheral vascular surgery, total hip arthroplasty, or transurethral prostate resection.32 40 45 48 Thoracic epidural anaesthesia in vascular surgery, coronary artery bypass grafting, and abdominal surgical procedure appears to provide greater benefit than the other techniques: it attenuates the perioperative stress response, improves myocardial oxygenation, reduces the release of troponin T, and effectively controls refractory unstable angina pectoris as a result of sympatholysis.77 89 104 Some studies also report that epidural anaesthesia decreases blood loss during total hip arthroplasty, prevents intraoperative hypertension in patients with intraoperative ischaemia, and results in a lower incidence of reoperation for inadequate tissue perfusion during vascular surgery.32 40 120 Perioperative infusion of bupivacaine and fentanyl significantly reduced the amount of perioperative myocardial ischaemia in elderly patients with traumatic hip fracture.124 Local anaesthesia caused fewer ischaemic episodes than general anaesthesia in high risk elderly patients who underwent cataract surgery.61 A recent systemic review on 141 trials including 9559 patients reported that overall mortality and the number of MI were reduced by one-third in patients who were allocated to neuraxial block.120 These advantages strongly support the use of regional anaesthesia and analgesia for elderly patients undergoing surgery.61 73 120 124
Maintaining intraoperative and postoperative haemodynamic stability is crucial to ensuring a balance between myocardial oxygen delivery and oxygen demand in the elderly.48 It is prudent to maintain perioperative heart rate and arterial pressure within 20% of the normal awake value and the haematocrit should be maintained above 30%.131 Hypertensive patients are prone to wide fluctuations in these parameters during surgery, especially at the induction of anaesthesia and tracheal extubation, because of decreased intravascular fluid volume and baroreflex sensitivity.107 Hypertension detected on admission to hospital is not uncommon in elderly patients, and elevated systolic arterial pressure (treated or untreated) and untreated mild hypertension on admission are reported to increase the incidence of silent cardiac ischaemia.70 For example, patients over 70 yr with hypertension and diabetes mellitus undergoing surgery who have intraoperative increases in arterial pressure of more than 20 mm Hg lasting 15 min or more have a higher incidence of postoperative ischaemic cardiac complications than their counterparts.30 These patients also are likely to display an exaggerated pressor response to tracheal intubation and to require vasodilators to control intraoperative hypertensive episodes.16
Antihypertensive therapy should be continued on the day of surgery, with the exception of drugs such as reserpine. Clonidine or a beta-blocking drug should be given preoperatively to patients with mild or moderate hypertension or admission systolic hypertension107. In patients over 50 yr old with essential hypertension undergoing intestinal or orthopaedic surgery, perioperative administration of clonidine 6 mg kg1 orally 120 min before anaesthesia and 3 mg kg1 i.v. over the final hour of surgery appears to reduce sympathetic output, increase sensitivity to phenylephrine, and improve circulatory stability.107 In contrast, perioperative discontinuation of long-term clonidine or beta-blocker therapy can cause rebound hypertension,47 so should be carefully evaluated. Severe hypertension (e.g. diastolic arterial pressure 110 mm Hg) should be well controlled before elective surgery after 2 weeks effective antihypertensive therapy.51
Long-term beta-blocker therapy is not popular for elderly hypertensive patients with MI because of its limited effectiveness in the presence of diabetes, asthma or heart failure, and unacceptable side effects such as bradycardia, hypotension, cardio-inhibitory and vasopressor carotid sinus syndromes, depression, fatigue, and reduced libido.83 Perioperatively, the primary side effects of beta-blocker administration are hypotension, bradycardia, and bronchospasm,145 conditions easily detected by routine perioperative monitoring. Moreover, short-term perioperative use of beta-blocking drugs does not appear to have a harmful effect: in one study of beta-blocker vs placebo, the incidence of systemic arterial pressure greater than 8090 mm Hg and/or heart rate greater than 40 beats min1 was rare and did not differ between the two groups.145 Therefore, assuming no contraindications, prophylactic beta-blocker therapy may be useful in avoiding adverse cardiac outcome in elderly hypertensive patients undergoing major surgery at intermediate or high risk of a negative outcome.47 Further randomized controlled trials in elderly patients need to be carried out.
Risk of myocardial ischaemia and mortality can be reduced in patients at high risk of coronary artery disease by administration of atenolol.145 In two recent prospective randomized studies, atenolol was given intravenously before induction of anaesthesia and every 12 h postoperatively until patients could tolerate oral administration, which continued until postoperative day 7 or the day of discharge, whichever came first. This regimen resulted in a 50% lower incidence of myocardial ischaemia during the first postoperative 48 h, a 40% lower incidence during the first postoperative week, and reduced risk for death at 2 yr.145
Risk of perioperative myocardial ischaemia increases in the presence of tachycardia. One study has reported that intraoperative tachycardia resulted in postoperative reinfarction in 14% of patients with previous MI.129 Continuous perioperative infusion of esmolol appears to be effective in controlling heart rate below the ischaemic threshold, thereby reducing the incidence of postoperative myocardial ischaemia in patients with significant preoperative cardiac ischaemia who are undergoing vascular surgery.115
Nitroglycerin also reduces the incidence of myocardial ischaemia.44 Perioperative use is recommended for patients previously taking nitroglycerin to control ischaemic signs or symptoms or those who develop symptoms of ischaemia postoperatively.47 Further study is needed to define the use of nitroglycerin in elderly patients who have hypertension with bradycardia.
That intraoperative hypotension is a risk factor for postoperative myocardial ischaemia remains controversial.10 Preoperative hypertensive patients appear more likely to develop intraoperative hypotension than non-hypertensive patients. In one study, intraoperative hypotension (30% decrease from pre-induction arterial pressure) resulted in perioperative reinfarction in 20% of patients with previous MI.129 Another study of patients undergoing non-cardiac surgery with hypertension and diabetes mellitus reported ischaemic cardiac complications in 19% of patients who had intraoperative decreases in MAP greater than 20 mm Hg lasting 60 min or more. Decreases greater than 20 mm Hg lasting 559 min increased the incidence of postoperative ischaemic cardiac complications.30 A third study of the incidence of postoperative myocardial infarction in patients with ischaemic heart disease undergoing non-cardiac surgery found no significant difference in intraoperative hypotensive episodes between patients with and without MI.10 One current study reported that deliberate hypotension to MAP of 4555 mm Hg induced by epidural anaesthesia was safe for elderly patients over 70 or 5069 yr with co-existing cardiac disease, hypertension, or diabetes mellitus who underwent total hip replacement. Patients were given supplemental oxygen, continuous haemodynamic monitoring, and sufficient i.v. infusion to avoid hypovolaemia. The postoperative cardiovascular complication rate was 6% and postoperative delirium was 9% in this patient group.152
However, it seems prudent to maintain arterial pressure within 20% of the awake value. Efforts should be made to avoid intraoperative hypotension or to shorten the duration of hypotension when it occurs.
Postoperative respiratory complications in elderly patients
Physiological changes, incidence rate, and predictive factors
COPD, pneumonia, and sleep apnoea are common in the elderly. Closing capacity increases with age,24 and forced expiratory volume in 1 s (FEV1) declines 810% each decade because of decreased compliance of the pulmonary system and of muscle power.82 Arterial blood oxygen tension decreases progressively with age-induced ventilation/perfusion mismatch, diffusion block, and anatomial shunt.132
Postoperatively, pulmonary complications occur in 2.110.2% of elderly patients108 and include pneumonia, hypoxaemia, hypoventilation, and atelectasis, all of which prolong intensive care unit stay and increase elderly mortality. Clinical predictors of adverse pulmonary outcome include the site of surgery, duration and type of anaesthesia, COPD, asthma, preoperative hypersecretion of mucus, and chest deformation.80 81 100 144 The most significant of these is the site of surgery.81 144 Obesity and older age are no longer considered risk factors.130 Chronic smoking within 1 month preoperatively increases risk approximately sixfold.18
The most important preoperative assessment instruments remain a detailed history, clinical examination, and evaluation of functional status.81 The presence of dyspnoea, smoking, coughing, and wheezing should be addressed in the history.130 Pulmonary function tests such as the ability to climb several flights of stairs can offer as much predictive value as spirometric assessment of pulmonary function.150 For example, the results can be used to determine whether to cancel a proposed surgery or perform a less invasive procedure conferring less risk, such as laparoscopy, to decrease the likelihood of adverse outcome.130 Preoperative spirometry is useful in identifying patients at risk for adverse outcome following thoracic or upper abdominal surgery.130 Emergency, thoracic, and abdominal surgery have the highest pulmonary complication rates.81 144
Functional predictors include increased residual volume, and decreased FEV1 and single-breath transfer factor for carbon monoxide (TL, CO, SB).13 A decrease in the ratio of FEV1 tovital capacity (FEV1/VC) and in PaO2 are risk factors in patients undergoing vascular surgery.144 For patients with COPD undergoing bilateral volume reduction surgery, the inability to walk at least 200 m in 6 min before or after pulmonary rehabilitation or a resting room air PaCO2 45 mm Hg result in increased postoperative mortality and prolonged hospital stay (>21 days).134 Aspiration as a result of significant impariment of protective laryngeal reflexes function can also cause severe postoperative pulmonary deterioration in elderly patients.105
Perioperative management
Preoperative preparation
Patients at high risk of pulmonary complications require some preparation for surgery to minimize risk (Table 4). An algorithm exists for preoperative pulmonary assessment of patients undergoing upper abdominal or thoracic surgery (Fig. 2).80 Patients who smoke cigarettes should quit at least 8 weeks before surgery to minimize high airway reactivity and risk of bronchospastic obstruction of the airway, mucus trapping, and regional atelectasis.18 130 High risk elderly patients should be trained in forced cough and lung expansion techniques before surgery, as well as in how to cooperate with the ventilator to avoid discomfort during postoperative ventilation. Patients with COPD should receive preventive therapy with mucolytic and bronchodilating agents.64 Prophylactic ventilation, however, is ineffective in avoiding pulmonary complications in high risk elderly patients undergoing major, elective abdominal aortic reconstruction.128 Perioperative chest physical therapy can decrease the incidence of postoperative pulmonary complications,28 but pulmonary infection should be well controlled before surgery.64
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Postoperatively, the residual effects of anaesthetic agents, prolonged effects of neuromuscular blocking drugs, and post-surgical pain can contribute to pulmonary complications. Postoperative hypoxaemia is common,100 as is respiratory depression, which a survey of 198 103 anaesthetics has cited as the most common cause of postoperative death and coma attributable to anaesthesia.135 Almost all patients surveys received opioid analgesics and neuromuscular blocking drugs for which antagonists were not administered.135 Similarly, risk of a critical event appears to increase with the combined use of opioid premedication, intraoperative fentanyl greater than 2.0 µg kg1 h1, and neuromuscular blocking drugs.43 Risk also increases in the presence of residual pancuronium-induced block.17 Applying these data to elderly patients, it is important to remember that: (1) the perioperative opioid requirement for the elderly is lower than that of younger patients,50 (2) short-, or intermediate-acting neuromuscular blocking drugs are to be used, and (3) antagonists should be given to reverse residual neuromuscular blocking drugs effects. In addition, supplemental oxygen should be given by facemask during awaking from anaesthesia, transfer to the post-anaesthesia care unit, and for several days postoperatively to prevent late nocturnal hypoxaemia.121
Fluid replacement
Perioperative fluid replacement must be managed carefully in elderly patients to prevent the development of postoperative pulmonary oedema as a result of age-related prolonged extracellular water (ECW) expansion. Compared with 5 days for young patients with sepsis, elderly septic patients require 10 days to excrete overexpanded ECW.31 The elderly also require more prolonged inotropic and ventilatory support.31 Renal function deteriorates with age with reduction in renal plasma flow, glomerular filtration rate, and altered renal tubular function. The renal ability to balance sodium and water is impaired in elderly patients as a result of low plasma renin activity, urinary and blood aldosterone levels, and decreased response to ADH.131 Urine output monitoring and pulmonary artery catheterization are more valuable to guide fluid therapy in elderly patients than in young patients131. Fluid replacement should be controlled within normal maintenance levels, and vasoconstrictors, inotropic drugs, and small colloid infusions should be used to manage hypotensive episodes in elderly patients with emphysema or those undergoing lobectomy, pneumonectomy, and lung volume reduction procedures.38 In the presence of cardiac or renal disease, i.v. fluids should be cautiously administered in elderly patients undergoing TURP. To prevent the TURP syndrome, plasma sodium levels must be monitored closely during this procedure. Another method is to regularly measure breath ethanol by irrigating with an ethanol containing glycine solution.
Postoperative cerebrovascular complications
Physiological changes, incidence rate, and predictive factors
Ageing is accompanied by a progressive loss of neurones in the brain and a decline in grey-matter tissue.156 In addition, neurotransmitter molecules and receptors for dopamine and catecholamines are reduced in number. Vision, hearing, taste, and touch/sensation are compromised.147 The threshold for pain increases, but this does not alter the need for perioperative analgesia in the elderly because the perceived severity of pain is strongly influenced by intense emotional and psychological factors.67 Cognitive function declines progressively,78 and co-existing disease accelerates this process. The autonomic reflex responses for maintaining homeostasis,37 thermoregulation,27 laryngeal reflex activity, and overall baroreflex responsiveness are significantly impaired.111 Regional cerebral blood flow (rCBF) in the parietal, temporo-parietal, and temporal cortex decreases, particularly in the presence of carotid atherosclerosis35.
Stroke is defined as a focal neurological deficit having a sudden onset and persisting for longer than 24 h. Risk factors for stroke in elderly patients include hypertension, atherosclerosis, physical inactivity, compromised cerebral vessel wall integrity, co-existing cerebrovascular and/or ischaemic heart disease, carotid occlusion, peripheral vascular disease, diabetes mellitus, and intraoperative haemodynamic instability (Table 8).154 The most prevalent of these is hypertension, control of which can safely and effectively decrease elderly cerebrovascular morbidity and mortality.14 Most published stroke rates reflect outcome of vascular or coronary artery bypass graft surgery. One recent study of elderly women undergoing surgery to treat incontinence reported a 0.3% cerebrovascular accident rate.133 The highest incidence of ischaemic stroke appears to be associated with previous cerebrovascular disease, COPD and previous vascular disease (PVD), which confer a thirteenfold, ninefold, and eightfold increase in risk, respectively.88
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Carotid endarterectomy may be indicated to prevent stroke in elderly patients who have transient ischaemia or asymptomatic stenosis greater than 60% of the diameter of the internal carotid artery.12 Although carotid endarterectomy has a higher incidence of stroke than any other non-cardiac surgical procedure,12 133 elderly patients appear to be able to tolerate carotid endarterectomy without increased risk of postoperative stroke and death.12 Regional anaesthesia may be preferred for carotid endarterectomy because it permits reliable cerebral monitoring without the use of electroencephalography and results in fewer postoperative complications.52 However, general anaesthesia facilitates control of arterial blood pressure, ventilation, and oxygenation. In addition, transcranial Doppler monitoring can be used during general anaesthesia to assess cerebral perfusion, detect intraoperative emboli, and prevent stroke.58 Cerebral protection during carotid endarterectomy is achieved with the use of hypothermia, barbiturate drugs, and induced hypertension. Perioperative control of systemic arterial pressure also is important because both hypertension and hypotension predispose to neurological morbidity.154
Postoperative delirium
Incidence rate and predictive factors
Postoperative delirium is characterized by incoherent thought and speech, disorientation, impaired memory, and attention. The reported incidence of this effect varies from 5.1 to 61.3%,34 39 65 a wide range likely because of differences in diagnostic criteria, study populations, and methods of observation. Elderly patients usually manifest delirium following a lucid interval of 1 postoperative day or more, a condition known as interval delirium.34 Symptoms are often worse at night. Alternatively, the condition can be silent and unnoticed, or misdiagnosed as depression.138 However, the effects of elderly postoperative delirium are evident in increased morbidity, delayed functional recovery, and prolonged hospital stay. Fortunately, the postoperative cognitive dysfunction is a reversible condition in the majority of elderly surgical patients. Only 1% has persistent cognitive dysfunction at 12 yr after the surgery.1
Preoperative risk factors predisposing to delirium include ageing, lack of education, re-operation, polypharmacy and drug interaction, alcohol and sedative-hypnotic withdrawal, endocrine and metabolic compromise, impaired vision and hearing, sleep deficiency, anxiety, depression, and dementia.39 76 101 106 Bilateral total knee arthroplasty is associated with a significantly higher incidence of acute delirium than unilateral total knee arthroplasty in patients over 80 yr.92 Mollers study101 on 1218 patients over 60 yr who underwent major surgical procedures demonstrated that increasing age and duration of anaesthesia, little education, a second operation, postoperative infections and respiratory complications were risk factors for early postoperative cognitive dysfunction. Only age is a risk factor for late postoperative cognitive dysfunction. Hypoxaemia and hypotension do not appear to be predictors.101 Intraoperative risk factors include hypoperfusion and microemboli of air or blood cells during cardiac surgery, fat embolism during orthopaedic surgery, severe bilateral loss of vision in ophthalmological patients, and major intraoperative blood loss (haematocrit <30%).98 106 However, in Mollers study, there was no relation between cognitive dysfunction and blood loss (the amount of blood loss was not reported).101 Postoperative room change to a quiet, dark and isolated environment also may contribute.137
Recent studies did not show that anticholinergic drugs, barbiturate premedication or benzodiazepines are implicated in the development of postoperative delirium.101 116 151 Preoperative psychoactive agents seemed to be a modifiable risk factor for postoperative delirium.39 There appears to be no difference in the effects of general, epidural, or spinal anaesthesia on the incidence of postoperative delirium following total knee arthroplasty or TURP procedures.101 119 151 However, cognitive function appears to be better preserved in elderly patients who undergo TURP with regional anaesthesia without intraoperative sedation.33 Postoperative patient-controlled epidural analgesia can improve mental status in elderly patients.97 The use of auditory evoked potentials and the bispectral index to monitor hypnotic status and detect awakening during general anaesthesia can help anaesthetists to adjust the delivery of anaesthetic agents as needed to maintain surgical anaesthesia.46 57 One recent randomized double-blinded study in elderly hip or knee replacement surgery in our hospital confirmed that bispectral index monitoring, in particular, may decrease anaesthetic requirement during general anaesthesia and facilitate more rapid recovery.155 However, this study failed to show any difference between cognitive function with or without bispectral index monitoring.155
Perioperative management
The principles of prevention are listed in Table 9. Preoperative assessment of the patients physical and mental status and documentation of chronic medications are important to recognize and reduce the risk associated with pre-existing sensory or perceptual deficits. A multicomponent intervention strategy aimed at six risk factorscognitive impairment, sleep deprivation, immobility, visual or hearing impairment, and dehydrationmay be effective in preventing postoperative delirium.74
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Nurses should be well trained in detecting the earliest signs of delirium. Where possible, ambulatory surgery should be encouraged because of its short surgical duration and permitting elderly patients to recover in their familiar home environment. Herniorrhaphy and ophthalmological procedures in elderly patients are being performed in ambulatory surgical units under local and monitored anaesthesia care regimens.51 The increasing use of laparoscopy will allow more elderly surgical patients to return home on the day of surgery.
Speech, consciousness, perception, orientation, coherence, memory, and motor activity can be assessed preoperatively to determine baseline cognitive status and postoperatively to measure change in function using the Mini Mental State Examination (MMSE) (Table 10), which is reliable, easy to conduct, and useful for serial testing in fluctuating conditions.54 MMSE should be administered to patients at high risk of postoperative delirium.
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If delirium progresses to coma, standard treatment for control of the airway, breathing, and circulation should be instituted. After recovery from an acute episode, a psychiatric or psychosocial referral may aid early functional rehabilitation. Nursing assistance at home will help to rehabilitate patients who are discharged early from hospital. Physiotherapy and occupational therapy also may be important adjuncts to rehabilitation.106
Postoperative hypothermia
Perioperative hypothermia is prevalent in both young and elderly surgical patients, but more frequent, pronounced and prolonged in the elderly who have compromised ability to regain normal thermoregulatory control quickly.142 In the early postoperative period, mild hypothermia can elevate norepinephrine concentrations and increase peripheral vasoconstriction and arterial blood pressure, thereby contributing to cardiovascular ischaemia and arrhythmia.55 Mild hypothermia may also increase blood loss during total hip replacement procedures125 and the risk of wound infection,66 decrease drug metabolism, and prolong hospitalization.87
Anaesthetics and ambient temperature contribute to hypothermia.36 As drug metabolism is impaired87 and anaesthetic-induced inhibition of thermoregulatory response is more severe than in younger patients,84 use of the lowest possible effective dosage/concentration of anaesthetic agent in the elderly is important. Whether anaesthesia is general or regional appears to have no effect on the production of perioperative hypothermia.19
Maintaining normothermia can reduce the risk of adverse outcome. It has been shown to decrease cardiac morbidity by 55%, and a perioperative core temperature of 36.7 (0.1) vs 35.4 (0.1)°C reportedly reduces cardiac morbidity during the early postoperative period.56 Elderly patients should, therefore, be maintained at normal core body temperature. Intraoperative techniques for maintaining core temperature include the use of warmed cotton blankets, a warmed water mattress, warmed i.v. fluid, heated and humidified inspired gases, and forced air warming. The latter is both effective and safe.85 The only exception to this recommendation for normothermic control is neurosurgery, where mild hypothermia (34°C) is of benefit because it decreases cerebral metabolism and prevents cerebral ischaemia.136 Temperature must be returned to normal as soon as possible.
Postoperatively, shivering is not common in elderly patients. However, when it occurs, it increases metabolic rate by 2038%.23 Factors contributing to postoperative shivering include intraoperative hypothermia (infusion of cold fluids, inhalation of cold and dry anaesthetic gases, exposure of internal organs, duration of surgery, and age and sex), decreased sympathetic activity, adrenal suppression, uninhibited spinal reflexes, and postoperative pain.23 102 Although no relationship has been demonstrated between axillary temperature and the occurrence of shivering,23 postoperative shivering can be treated by skin-surface warming, radiant heat application, or pharmacological approaches.102 The drugs useful for controlling shivering include methylphenidate, orphenadrine, magnesium sulphate, the opiates (fentanyl, morphine and meperidine), naloxone, clonidine, nefopam, and ketanserin. Meperidine and clonidine are effective for managing both postoperative shivering and postoperative pain.102
Postoperative pain management
Postoperative pain increases the risk of adverse outcome in elderly patients by contributing to cardiac ischaemia, tachycardia, hypertension, and hypoxaemia. Effective analgesia can reduce the incidence of myocardial ischaemia and pulmonary complications, accelerate recovery, promote early mobilization, shorten hospital stay, and decrease medical care costs.11 21 120 124 139 Early mobilization which enhances recovery, prevents DVT and decreases morbidity and mortality in elderly patients, can be achieved by epidural anaesthesia or balanced analgesia.120 123 However, postoperative pain control often is inadequate in the elderly, because of concerns about drug overdose, adverse response, or risk of opioid addiction. Control is made more difficult by the fact that the expression and perception of pain are affected by changes in the patients mental status.50
Current postoperative analgesic techniques include: sustained-release morphine63; non-steroidal anti-inflammatory drugs (NSAIDs); PCA/PCEA;9 local anaesthetic techniques (neuroaxial,9 intra-articular,117 nerve block118); and non-pharmacological management (transcutaneous acupoint electrical stimulation).146 However, few studies of these techniques focus on the analgesic requirements of the elderly. PCA and PCEA are recommended because they permit use of relatively low doses of opioids and result in fewer complications than intramuscular opioids.49 Epidural analgesia has been recommended after thoracic, abdominal, and major vascular surgical procedures.38 130 However, the PCA/PCEA technique can be used only in patients who can participate in self-medication, which excludes those with cognitive dysfunction. For patients with dysfunction, pain management must rely on the physicians judgment and measures of vital signs such as arterial pressure, heart rate, respiratory rate, restlessness, and sweating, which are, unfortunately, non-specific for pain control.
The morphine requirement for PCA for elderly patients can be calculated using the following formula:94 average first 24 h postoperative morphine requirement (mg)=100 age. The initial bolus and subsequent incremental doses should be low to safeguard elderly patients. Oxygen saturation should be monitored90 to avoid analgesia-induced hypoxaemia, which is common. To minimize the risk of an opioid-related adverse effect, a balanced analgesic technique combining opioids, non-opioids, and local anaesthetic agents should be used.118 The combination of opioids and local anaesthetics such as bupivacaine or ropivacaine for PCEA can produce satisfactory analgesia without episodes of either respiratory depression or sustained hypotension.21 42 Epidural ropivacaine at 0.10.2% can provide adequate pain control with less motor block than a higher concentration of bupivacaine 0.175% would induce.9 22
Choosing a less invasive surgical procedure, when possible, can decrease postoperative pain in elderly patients. Laparoscopic procedures appear to be an effective alternative. For example, laparoscopic cholecystectomy is safe, and results in minimal pain, a short hospital stay, and quick recovery compared with open cholecystectomy in elderly patients.91 Laparoscopic herniorrhaphy, nephrectomy and nephroureterectomy for tumour removal, paraoesophageal hernia repair, and laparoscopy-assisted colon resection for carcinoma also are possible in elderly patients.99 141 143
Malnutrition
Malnutrition is not unusual in the elderly. A survey of nutrition status in patients over 70 yr indicates that 7% have a lower haemoglobin value, and that 11.4% of elderly men and 16.9% of elderly women have albumin levels less than 35 g litre1.93 Severe protein malnutrition also may be present.112
The risk factors for malnutrition in the elderly include social isolation, limited financial resources, poor dentition, alcohol consumption, weight loss, depression, diarrhoea, constipation or any other chronic medical disease,103 and polypharmacy.93 Adverse effects of malnutrition include delayed wound healing, greater risk of sepsis, wound infection, and increased mortality.103 112 140 Preoperative assessment of nutrition status is, therefore, important for elderly patients. Global assessment should include dietary history and physical and laboratory evaluation. Simplified tools such as the Nutritional Risk Assessment Scale and the Mini Nutritional Assessment should be applied.103 When malnutrition is detected, intervention in the form of a nutritional supplement is indicated, and related underlying diseases such as anaemia should be treated before the elective surgical procedures.
Obesity is another type of malnutrition in elderly patients who are at increased risk of diabetes mellitus and cardiovascular disease. Anaesthetists should pay more attention in obese patients to: the compromised airway; the risk of decreased intrathoracic volume; and intraoperative head and arm position by the use of padding pillows beneath the head to maintain the cervical spine in the plane of the long axis of the thoracic spine.
Conclusion
Perioperative morbidity and mortality in elderly patients will continue to be an important problem. Preoperative clinical assessment to recognize patients at intermediate or high risk of postoperative events by careful history taking, physical examination, and function capacity assessment is important to guide anaesthesia management and to decrease cost by reducing the number of preoperative cardiac or pulmonary tests. Specific intraoperative and postoperative anaesthesia management in terms of maintenance of haemodynamic stabilization and normothermia, effective postoperative pain control, and prevention of hypoxaemia, will minimize postoperative adverse events in the elderly. To summarize the recommendations for clinical management of the elderly.
1. Preoperative assessment to determine the elderly patients at high risk of postoperative adverse outcome.
2. Preoperative testing (invasive or non-invasive) only when test results are likely to change the proposed surgery or intervention, or to indicate the need for high risk invasive monitoring such as pulmonary artery catheterization.
3. Effective perioperative control of co-existing disease.
4. Maintenance of stable perioperative haemodynamics for all elderly patients using vasopressor or vasodilator drugs, or beta-adrenoceptor block, or a combination of appropriate therapies.
5. Where possible, use of a less invasive surgical procedure, for example laparoscopy on an ambulatory basis.
6. Intensive perioperative monitoring of high risk patients.
7. Prevention of hypoxaemia, hypothermia, and delirium.
8. Effective postoperative pain control.
Incorporating each of these elements into decision making for perioperative management of elderly patients can only benefit outcome in this rapidly growing and increasingly vulnerable surgical population.
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