Transcript ELDERLY PATIENTS

1
Many elderly patients who were denied surgical treatment
in the past because of their age now routinely undergo
operative procedures as a result of improvement in
anesthetic, surgical, and medical care. Approximately 35%
of all surgical procedures are performed in elderly patients.
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NORMAL PHYSIOLOGIC CHANGES
WITH AGING
Functional and structural changes occur in most of the
organ systems with aging. The rate of aging varies in these
organ systems and is influenced by genetic factors,
environment, and diet.
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CARDIOVASCULAR SYSTEM
Aging in healthy individuals affects the peripheral
vasculature through increases in wall thickness and the
diameter and vascular stiffness of the aorta and large
arteries.
Systolic and mean arterial blood pressure increases with
widening of the pulse pressure.
7
Aortic impedance and systemic vascular resistance
increase, and there is a decrease in B-adrenergic-mediated
vasodilatation of the systemic vasculature.
8
Aging also affects the heart through increases in left
ventricular wall thickness secondary to enlargement of
cardiac myocytes. Myocardial compliance is decreased,
with a reduction in the early diastolic filling rate and
compensatory augmentation of the contribution of atrial
contraction to late left ventricular filling.
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Ventricular diastolic dysfunction, with prolonged relaxation,
should be considered in any elderly patient who has a
history of decreased exercise tolerance. Despite the
common belief that systolic cardiac function decreases with
age, it is recognized that in the absence of coexisting
cardiovascular disease, resting systolic cardiac function is
well preserved, even at very advanced ages.
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Other cardiovascular-related changes in aging include
sclerosis and calcification of the cardiac conduction system
and thickening of the aortic valve cusps. Turbulent blood
flow caused by thickening of the aortic valve cusps results
in the midsystolic ejection murmur that is commonly
present in elderly individuals.
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In addition, the incidence of aortic stenosis increases with
aging secondary to cusp calcification because of
mechanical wear and tear on the collagenous core of the
valve cusp.
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PULMONARY SYSTEM
With aging, the central airways increase in size with a
resultant increase in the anatomic and physiologic dead
spaces. Small airways decrease in diameter secondary to
loss of connective tissue support.
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However, total airway resistance is unchanged, possibly
because of opposite changes in the distal and proximal
airways. There is a progressive loss in elastic tissue and an
increase in the amount of collagen within the lung
parenchyma.
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Chest wall compliance decreases with aging. Decreased
intervertebral space and age-associated kyphoscoliosis lead
to decreased chest height and increased anteroposterior
diameter, which may alter respiratory mechanics.
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Respiratory muscle strength decreases with aging
secondary to multiple factors such as selective denervation
of skeletal muscle fibers and atrophy and degeneration of
motor nerves and muscle fibers.
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Vital capacity declines progressively with aging because of
decreases in chest wall compliance, loss of lung elastic
recoil, and decreases in respiratory muscle strength.
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Airway reflexes are more sluggish in elderly patients
secondary to diminished laryngeal and pharyngeal
responses.
The cough reflex is less efficient, and the risk for
pulmonary aspiration is increased.
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GASTROINTESTINAL SYSTEM
The swallowing and motility function of the esophagus and
the gastric emptying time are usually unchanged with
aging. Liver size decreases progressively with aging, and it
is estimated that by the age of 80 years, liver mass is
decreased by 40% with a parallel decline in hepatic blood
flow. However, the content of both microsomal and
nonmicrosomal liver enzymes is unchanged with aging.
Liver function test results are generally normal.
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RENAL SYSTEM
The kidneys lose approximately 50% of their functional
glomeruli with similar decreases in renal blood flow by 80
years of age. The decline in both renal mass and renal
blood flow occurs primarily in the cortex with
compensatory changes in the juxtamedullary region. The
glomerular filtration rate is decreased by 30% at 60 years
of age and by 50% at 80 years of age.
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In addition, elderly individuals have a decreased ability to
dilute and concentrate urine and to conserve sodium. The
decrease in renal function with aging may affect the
pharmacokinetics (prolonged elimination half-times) of
certain drugs used in anesthesia.
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The overall decline in renal functional reserve usually has
no effect on an elderly individual's ability to maintain
extracellular fluid volume and electrolyte concentrations.
Similarly, serum creatinine remains relatively stable
because of a parallel decrease in overall skeletal muscle
mass
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CENTRAL NERVOUS SYSTEM
Aging is associated with a progressive loss of neural tissue
and a parallel reduction in cerebral blood flow and cerebral
oxygen consumption. On average, 30% of total brain mass
is lost by 80 years of age. In addition, the number of
neuroreceptors generally declines with aging in various
regions of the central nervous system.
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Levels of dopamine in the neostriatum and substantia nigra
are also decreased. These structural changes are not
necessarily associated with a decline in cognitive function.
However, the incidence of postoperative delirium and
cognitive dysfunction is higher in elderly individuals.
Patients with a history of cognitive impairment are at even
higher risk for further impairment postoperatively.
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PHARMACOKINETIC AND PHARMACODYNAMIC
CHANGES
The pharmacokinetics of drugs is influenced by changes in
plasma protein binding, the percentage of body content
that is fat or skeletal muscle (lean mass), circulating blood
volume, and metabolism and excretion of drugs.
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PROTEIN BINDING
With aging, protein binding sites are reduced secondary to
both quantitative (decreased level of circulating protein)
and qualitative changes. In addition, elderly individuals
frequently take multiple medications that might interfere
with the binding of drugs to protein active sites . These
changes may increase the level of free, unbound drug in
plasma with a resulting enhanced pharmacologic effect.
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LEAN AND FAT BODY MASS
Older individuals have decreased skeletal muscle mass and
an increased percentage of body fat. These changes result
in an increased ability to store lipid-soluble drugs, which
may lead to a more gradual and prolonged release of the
drugs used during anesthesia from lipid storage sites and,
consequently, an increased elimination time and prolonged
effect.
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CIRCULATINGBLOOD VOLUME
Circulating blood volume generally decreases with aging
and results in a higher than expected initial plasma drug
concentration for the same amount of drug administered.
Gradual declines in hepatic and renal function may lead to
decreased metabolism and prolonged elimination of drugs
and their metabolites and thus may contribute to a more
gradual decline in plasma drug concentrations and a
prolonged effect of anesthetic drugs.
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BASAL METABOLIC RATE
The basal metabolic rate declines with aging, and elderly
surgical patients may have difficulty maintaining
normothermia during general anesthesia. The development
of hypothermia may lead to slower metabolism and
excretion of drugs in elderly patients. Furthermore,
hypothermia may lead to shivering, which will increase the
basal metabolic rate and oxygen consumption and result in
arterial hypoxemia or myocardial ischemia, or both.
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ENDOCRINE CHANGES
Endocrine changes occur with aging. The response of
arginine vasopressin (formerly known as antidiuretic
hormone) to hypovolemia and hypotension is reduced, but
it remains sensitive to changes in serum osmolarity. The
renal tubules are less sensitive to this hormone and atrial
natriuretic peptide
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During hyperglycemia, insulin release is impaired. However,
because of increased peripheral tissue resistance and
decreased clearance, plasma insulin levels are elevated,
which results in an enlarging fat depot.
.
32
Serum levels of renin and aldosterone decline, and the
response of both hormones to sodium restriction and
postural changes is blunted, with a decreased ability to
conserve sodium and excrete potassium
33
In contrast, adrenocorticotropic hormone, cortisol,
catecholamine production by the adrenal medulla, and
thyroid-stimulating hormone and thyroxine levels are
unchanged with aging.
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PR-EOPERATIVE EVALUATION AND ANESTHETIC
CONSIDERATIONS
The prevalence of coexisting diseases increases with aging
In older individuals undergoing surgery, the most common
coexisting diseases are systemic hypertension, diabetes
mellitus, cardiovascular disease, pulmonary disease,
neurologic disease, and renal disease.
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Optimizing the patient's medical condition before surgery is
essential because baseline health status is an important
predictor of postoperative complications. However, for
elderly patients, delaying surgery to optimize a medical
condition must be weighed against the risk of delaying
surgery because emergency surgical treatment is
associated with higher morbidity and mortality.
37
Furthermore, delaying certain surgical procedures, such as
cancer surgery, may substantially alter the patient's
prognosis. In this regard, communication among the
anesthesiologist, surgeon, and primary care physician is
critical to developing an optimal plan regarding the timing
of each elderly patient's surgery.
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LABORATORY TESTING
Data suggest that routine laboratory testing should not be
performed simply on the basis of age alone but, rather, it
should be based on a thorough preoperative evaluation to
determine coexisting medical conditions and on the type of
planned surgical procedures.This approach is likely to be
more cost-effective than routine testing in all elderly
patients.
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ELECTROCARDIOGRAM
Elderly patients with a history of coronary artery disease
may benefit from a preoperative 12-lead electrocardiogram
(ECG) to determine the presence and location of any
previous myocardial infarction, left ventricular hypertrophy,
conduction abnormalities, and ST-T wave changes
indicative of ischemia. If an abnormality is present,
comparison with a previous ECG is needed to determine
the timing of the occurrence.
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However, in elderly patients, abnormalities on the
preoperative ECG are common and of limited value in
predicting postoperative cardiac complications in no cardiac
surgery. The low specificity of the preoperative ECG in
predicting postoperative cardiac complications also
suggests that a normal ECG does not rule out occult
cardiac disease.
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CHEST RADIOGRAPH
In patients undergoing high-risk surgery, a chest
radiograph may be useful in providing noninvasive
information regarding ventricular function (cardiomegaly
may indicate an ejection fraction <40%). The pulmonary
vasculature should also be examined to rule out
preoperative congestive heart failure. However, the costeffectiveness of routine preoperative chest radiographs in
elderly patients undergoing surgery has not been defined.
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BLOOD PRESSURE CONTROL
Systemic hypertension (systolic blood pressure ≥ 180 mm
Hg, diastolic blood pressure ≥1l0 mm Hg) increases the
risk for cardiac and cerebrovascular disease. Adverse
intraoperative events in hypertensive patients include
perioperative myocardial ischemia, cardiac dysrhythmias,
and cardiovascular lability.
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Although data are limited,there is little evidence of
increased perioperative cardiac risk if systolic blood
pressure is less than 180 mm Hg or diastolic blood
pressure is Jess than 110 mm Hg.
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If systemic blood pressure is consistently elevated,
optimization with appropriate antihypertensive drugs
preoperatively is often recommended for elective surgery.
45
In patients scheduled for urgent or emergency surgery
with a preinduction systolic blood pressure higher than 180
mm Hg or diastolic blood pressure higher than 110 mm
Hg, induction of anesthesia may proceed carefully, often
with invasive monitoring. In these patients, administration
of a small dose of an anxiolytic drug before induction of
anesthesia may result in more gradual lowering of systemic
blood pressure.
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In elderly patients with uncontrolled systemic hypertension
who are about to undergo emergency surgery, the use of
continuous invasive blood pressure monitoring and
postoperative surveillance in the intensive care unit may be
indicated.
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PROTECTION FROM PERIOPERATIVE MYOCARDIAL
ISCHEMIA
Postoperative myocardial ischemia is the strongest clinical
predictor of adverse postoperative cardiac events in
highrisk surgical patients, with most ischemic events
occurring within the first 24 hours after surgery.
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Therefore, reducing the number and duration of
perioperative ischemic events by improving the myocardial
oxygen supplydemand balance during surgery may
potentially improve postoperative cardiac outcomes.
Reduction of myocardial metabolic oxygen demand can be
achieved by perioperative administration of B-blockers to
decrease myocardial contractility and heart rate.
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Elderly patients (≥65 years of age) who have one or more
risk factors (systemic hypertension, current smoking,
hypercholesterolemia, diabetes mellitus) may benefit from
prophylactic perioperative B-blockade as evidenced by
decreased circulating levels of troponin. However, in elderly
patients at low risk for ischemic heart disease, this
prophylactic therapy may be potentially costly and
unnecessary.
50
Because sympathetic nervous system tone is increased
with aging, administration of B-blockers during the peri
operative period may result in hypotension, especially in
the presence of relative hypovolemia secondary to
preoperative fasting. Furthermore, autonomic control of
hemodynamics in the elderly may be compromised as a
result of the decrease in baroreceptor reflex activity with
aging.
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PHYSICAL EXAMINATION
Elderly individuals are more likely to be edentulous, and
although removal of dentures preoperatively may facilitate
direct laryngoscopy and tracheal intubation, positive
pressure ventilation by facemask may be difficult. Range of
neck motion should be evaluated because older individuals
may have limitations as a result of degenerative spine
disease.
52
Auscultation of the carotid arteries over the neck bilaterally
is helpful to rule out carotid artery disease but requires
confirmation by carotid ultrasound if loud carotid bruits are
present. Auscultation of the heart may reveal additional
heart sounds such as S3 or S4' which are commonly
associated with decreased left ventricular compliance. A
midsystolic ejection murmur is often present in elderly
patients secondary to thickening of the aortic cusps or
calcification, or both.
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A laterally displaced point of maximal impulse together
with increased heart size on the chest radiograph suggests
cardiomegaly. Auscultation of the lungs is performed to
evaluate the presence of rales or wheezes, which may be
associated with congestive heart failure or lung disease (or
both). Examination of the extremities should be performed
to rule out the presence of peripheral edema, which may
be indicative of congestive heart failure
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MANAGEMENT OF PREOPERATIVE MEDICATION
Elderly patients are typically taking multiple prescription
and over-the-counter medications . In general, all
antihypertensive and cardiac medications should be
continued until surgery, with the exception of diuretics,
which are preferably withheld on the day of surgery
because the patient will be fasting before surgery.
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For those taking aspirin or warfarin for treatment of
cerebral vascular or coronary artery disease, atrial
fibrillation, or deep vein thrombosis, the risks associated
with discontinuing anticoagulation should be weighed
against the benefits of reduced bleeding from
discontinuation of such drugs. Warfarin is typically withheld
(often four doses) to allow normalization of the
international normalized ratio.
.
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In case of emergency surgery, fresh frozen plasma or
vitamin K can be administered to reverse warfarin's effects
For patients at high risk for thromboembolism, such as
those with a prosthetic heart valve, a history of pulmonary
embolism, or a recent history of deep vein thrombosis, a
transition using low-molecular-weight heparin or
intravenous heparin is indicated when oral anticoagulation
is discontinued. Antibiotic prophylaxis is indicated for
patients with valvular heart disease and mitral valve
prolapse.
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INTRAOPERATIVEMANAGEMENT
No single anesthetic drug or technique has been
demonstrated to be superior for elderly surgical patients .
However, familiarity with the pharmacokinetics of
anesthetic drugs and how age-related changes may affect
drug dosing is important.
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INHALED ANESTHETICS
The minimum alveolar concentration (MAC) for various
inhaled anesthetics is reduced by approximately 6% per
year after the age of 40 years.
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Recovery from the depressant effects of volatile
anesthetics may be more prolonged because of an
increased volume of distribution secondary to increased
body fat and decreased pulmonary gas exchange.
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INTRAVENOUS ANESTHETICS AND NEUROMUSCULAR
BLOCKING DRUGS
Dose requirements for barbiturates, opioids, and
benzodiazepines are likely to be decreased in elderly
patients.
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OPIOIDS
The elimination half-time of fentanyl is longer in elderly
patients than younger patients because of the larger volume
of distribution. As a result, depression of ventilation and
prolonged analgesia may ensue with the same dose administered
to younger patients. Decreased hepatic clearance may
contribute to prolonged opioid effects, especially when high
does of these drugs are administered to elderly patients.
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PROPOFOL
Propofol is highly lipid soluble and produces rapid loss of
consciousness when administered intravenously. A
decreased induction dose or slow titration is recommended
for elderly patients. A decrease in age-related clearance of
propofol may result in reduced anesthetic requirements
with aging.
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Propofol, because of its negative inotropic and vasodilatory
effects, may give rise to exaggerated decreases in systemic
blood pressure when used for induction of anesthesia in
elderly patients. Despite these characteristics, propofolmay
be superior to thiopental for recovery of mental function.
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ETOMIDATE
Etomidate produces rapid loss of consciousness and has
been frequently chosen for induction of anesthesia in
elderly patients with cardiovascular instability. The initial
volume of distribution of etomidate is decreased such that
an 80-year-old patient requires less than half the dose of
etomidate to produce the same magnitude of depression
on the electroencephalogram as in younger patients.
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MIDAZOLAM
Midazolam has increased potency and decreased clearance
in elderly individuals. Context-sensitive half-times are
prolonged. Accordingly, doses of midazolam should be
decreased and a longer duration of action is expected.
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NEUROMUSCULAR BLOCKING DRUGS
Despite age-related changes in the neuromuscular
junction, the effects of depolarizing and nondepolarizing
neuromuscular blocking drugs are not altered in elderly
patients. Rather, the altered pharmacokinetics of these
drugs in older individuals is secondary to decreases in renal
and hepatic function and the altered volume of distribution
that accompanies aging.
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Clearance is decreased for nondepolarizing neuromuscular
blocking drugs (vecuronium, rocuronium) that are
dependent on either the kidneys or the liver for elimination
from plasma.
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The duration of action of atracurium and cisatracurium is not
prolonged because these drugs are eliminated by Hofmann
degradation, which is independent of renal and hepatic
clearance mechanisms. Monitoring of neuromuscular function
and recovery is important in elderly patients because
incomplete recovery of neuromuscular function may lead to
a higher incidence of postoperative pulmonary complications.
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REGIONAL ANESTHESIA
Cardiovascular responses to either spinal or epidural
anesthesia may be exaggerated in older individuals. The
decrease in cardiac output is thought to primarily be due to
a decrease in stroke volume. Treatment of the resultant
hypotension typically consists of the administration of
crystalloid solutions or vasopressors such as
phenylephrine.
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Surgical procedures that are amenable to regional
anesthesia include transurethral resection of the prostate,
orthopedic procedures such as hip or knee replacement,
inguinal herniorrhaphy, and minor gynecologic
procedures.Technical difficulties in performing regional
anesthesia probably reflect age-related decreases in the
intervertebral spaces and scoliosis. A thorough examination
of the targeted spinal segment must be performed before
initiating regional anesthesia.
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INTRAOPERATIVE MONITORING
Because of the prevalence of coexisting disease involving
the cardiac and pulmonary systems, consideration should
be given to using invasive monitoring such as arterial and
central venous catheterization in elderly patients
undergoing major surgical procedures, which are likely to
be prolonged and include large body fluid shifts.
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POSTOPERATIVE PAIN THERAPY
The concept that pain perception decreases with aging and
that elderly individuals have a low tolerance of opioids is
unsubstantiated. Elderly individuals are commonly afflicted
with osteoarthritic disease that results in chronic pain,
which may influence requirements for postoperative pain
medications. In addition, because elderly surgical patients
have an increased likelihood of postoperative delirium or
cognitive dysfunction, or both, assessment of the adequacy
of postoperative pain control may be difficult.
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STRATEGIES TO IMPROVE PERIOPERATIVE MANAGEMENT
AND POSTOPERATIVE OUTCOME
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DECREASING CARDIOVASCULAR COMPLICATIONS
Cardiovascular complications (cardiac dysrhythmias,
myocardial ischemia, congestive heart failure)may
influence postoperative outcomes in elderly patients.
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Perioperative planning includes (I) identifying elderly
patients who are at higher risk for postoperative
cardiovascular complications, (2) optimizing preoperative
medical therapies, (3) modifying known risk factors
preoperatively (pharmacologic therapy), and (4) planning
of postoperative care (pain control, admission to intensive
care units).
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ASSESSMENT OF CARDIAC FUNCTION
Congestive heart failure is a common problem in the
elderly population. It is estimated that congestive heart
failure will develop in 10% of persons 80 years and older
and will lead to increased mortality within 2 years. Because
clinical signs or a history of congestive heart failure is
associated with postoperative cardiac complications,
special attention should be directed to preoperative
optimization of heart function in elderly surgical patients.
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DIAGNOSIS OF CONGESTIVE HEART FAILURE
Clinical diagnosis of congestive heart failure can be
particularly challenging in elderly patients because of the
lack of typical symptoms and physical findings .when
present, symptoms of congestive heart failure are often
nonspecific and frequently misdiagnosed as symptoms of
concomitant disease (chronic pulmonary disease) or
interpreted as changes associated with aging.
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symptoms may include dyspnea, cough, edema, or fatigue.
Preoperatively, noninvasive approaches to diagnosing
diastolic dysfunction include Doppler echocardiography and
radionuclide ventriculography.
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Perioperative goals in elderly patients with diastolic
dysfunction include
(I) maintenance of normal sinus rhythm and a slow heart
rate
(2) control of systemic blood pressure
(3) optimization of blood volume
(4) Detection and treatment of myocardial ischemia
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The use of invasive monitoring such as central venous
pressure or pulmonary artery catheterization may be
indicated in managing patients with a history of congestive
heart failure secondary to diastolic dysfunction. Treatment
of diastolic congestive heart failure may include
pharmacologic interventions.
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PHARMACOLOGIC MANAGEMENT OF DIASTOLIC
DYSFUNCTION
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IMPACT OF ANESTHETIC TECHNIQUE ON CARDIOVASCULAR
COMPLICATIONS
The view that regional anesthesia is better than general
anesthesia in reducing adverse cardiac outcomes has not
been consistently demonstrated. 'There is no difference in
30-day mortality in patients undergoing major abdominal
surgery with epidural or spinal anesthesia versus general
anesthesia.
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DECREASING PERIOPERATIVE PULMONARY
COMPLICATIONS
Advanced age is not considered to be an independent risk factor for perioperative
pulmonary dysfunction. In contrast, other factors that have been shown to be
associated with postoperative pulmonary complications include
(I)
Emergency surgery,
(2) anatomic site of surgery (upper abdominal and thoracic procedures),
(3) duration of anesthesia,
(4) general anesthesia,
(5) hypercapnia,
(6) history of smoking,
(7) obesity,
(8) preexisting pulmonary disease (chronic obstructive pulmonary disease [COPD]
and asthma).
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CIGARETTE SMOKING
Cessation of cigarette smoking and the use of oxygen
therapy may improve outcomes in patients with COPD.
Preoperative cessation of smoking immediately before
surgery serves only to decrease carboxyhemoglobin levels
(half-time of about 6 hours). Prolonged cessation of
smoking (8 weeks) is necessary to result in a decrease in
postoperative pulmonary complications because of the
period necessary for improvement in mucociliary action
and a decrease in mucus secretion.
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ASTHMA
Asthma is often underdiagnosed and not optimally treated
in elderly individuals. There is a tendency to label elderly
patients with symptoms of airflow obstruction as having
COPD. Differentiation between asthma and COPD is
important because the therapeutic strategies may be
different. A postbronchodilator increase in forced exhaled
volume in 1 second (FEV,) of200 mL or 15% is considered
a sign of reversibility of airflow obstruction and suggests a
diagnosis of asthma rather than COPD.
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TREATMENT
Administration of B-agonists is relatively safe in elderly
patients, although systemic absorption of inhaled Bagonists may result in tachycardia, systemic hypertension,
and skeletal muscle tremors. Patients with asthma may be
receiving corticosteroid therapy, which may result in
adverse effects such as osteoporosis, psychiatric
disturbances, and exacerbation of chronic conditions such
as systemic hypertension and diabetes mellitus.
87
Patients being treated with corticosteroids should receive
supplemental corticosteroid before induction of anesthesia.
Medication such as B- blockers may exacerbate asthma.
The use of selective B-blockers such as metoprolol or
atenolol is preferable for the treatment of systemic
hypertension or congestive heart failure.
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INTRAOPERATIVE MANAGEMENT
INITIATION OF POSTOPERATIVE PAIN MANAGEMENT
Epidural analgesia with local anesthetics and opioids
provides considerable benefit in terms of pulmonary
outcomes after surgery, including (1) a decrease in the
incidence of atelectasis, pulmonary infections, and
complications; (2) better postoperative pain relief than with
parenteral opioids; (3) shorter time to tracheal extubation;
and (4) less time in the intensive care unit.
89
INTERVENTIONS TO IMPROVE POSTOPERATIVE
PULMONARY FUNCTION
Certain intraoperative strategies may improve pulmonary
function. Measures such as adding positive end-expiratory
pressure (5 to 10 cm H20) can increase FRC and restore
the closing capacity-to-FRC ratio.
90
The use of higher inspired oxygen concentrations (FI02)
may provide (I) a better proinflammatory and antimicrobial
response of alveolar macrophages than that associated
with 30% oxygen, (2) a lower incidence of postoperative
nausea and vomiting, and (3) a reduced incidence of
surgical wound infections.
A high FI02 does not influence postoperative pulmonary
mechanical dysfunction or alter the incidence of
postoperative complications such as pulmonary atelectasis.
91
REDUCING POSTOPERATIVE DELIRIUM
Delirium, an acute disorder of attention and cognition,
occurs in 14% to 50% of hospitalized medical patients
especially elderly patients) and is accompanied by a
mortality rate ranging from 10% to 65%. In general,
delirium is the manifestation or symptom of an underlying
medical illness for which multiple causes exist.
92
Earlier studies suggested an association between general
anesthesia and a higher incidence of cognitive dysfunction
relative to epidural anesthesia. However, recent studies
have concluded that there was no relationship between
anesthetic technique and the magnitude or pattern of
postoperative cognitive dysfunction. Intraoperative
hypotension does not appear to influence the occurrence
of postoperative cognitive dysfunction.
93
Until more definitive clinical studies become available,
minimizing the number of medications used, avoiding
arterial hypoxemia and extremes of hypocapnia or
hypercapnia, and providing adequate postoperative pain
control appear to be the best approach to minimizing the
occurrence of postoperative delirium in elderly surgical
patients.
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