The Elderly

The Elderly and Critical Care

OVERVIEW

• Ageing is the process of growing old, and may result in frailty

• There is no standard definition for elderly (? age>65y, ?regional life expectancy differs (ie. Africa vs West))

• The precise mechanisms underlying ageing are poorly understood

• Increased life expectancy means more elderly patients presenting for medical care/surgical procedures

• Critically ill elderly patients have increased risk of morbidity and mortality, at least part of this risk is due to coexistent frailty rather than age per se and age alone has poor discriminatory ability when predicting outcome

PHYSIOLOGICAL CHANGES OF AGEING

CARDIOVASCULAR

• myocardial fibrosis

• ventricular wall stiffening (diastolic dysfunction)

• increased SVR -> systolic hypertension -> LVH + conductance disturbances

• widened pulse pressure

• autonomic responsiveness declines -> increased risk of hypotension

• capillary permeability increased

RESPIRATORY

• overall, progressive loss of function and increased risk of aspiration

• decreased sensitivity of respiratory center -> ventilatory response to hypercapnia and hypoxia declines (increased risk of respiratory failure)

• loss of alveolar gas exchange surface

• Decreased O2 consumption

• Decreased CO2 production

• increased pulmonary compliance from loss of elastic recoil, loss of chest wall compliance from joint disease (total compliance decreased)

• decreased FVC and FEV1

• closing volume increases to exceed FRC in the upright posture @ ~66y -> increase in venous admixture

• normal PaO2 = (100-age/4)mmHg (increasing A-a gradient with age)

• decreased responsiveness of airway protective reflexes -> increased risk of aspiration

CENTRAL NERVOUS SYSTEM

• brain size and neuronal mass/density decreases

• decrease in noradrenaline and dopamine synthesis

• decline in slow wave sleep (patient sleep more but have difficulty falling asleep)

• progressive decrease in sympathetic and parasympathetic responsiveness

• pain threshold may be increased

• Postoperative Cognitive Dysfunction (POCD) is common

• thirst response reduced -> susceptible to fluid depletion

RENAL

• renal mass and glomeruli fall progressively -> reduced GFR

• deterioration in tubular function, renin-AG-ALD responsive, ADH sensitivity and concentrating ability -> susceptibility to hypovolaemia, overload and electrolyte abnormalities

• decreased renal clearance of drugs

HEPATIC

• cellular function well preserved

• blood flow falls over time

• decreased hepatic clearance of drugs

THERMOREGULATION

• impaired thermoregulation -> increased risk of hypothermia

• ability to shiver decreased (decreased muscle mass)

• shivering and vasoconstriction dramatically increases myocardial work and O2 demand

ENDOCRINE

• tendency to hyperglycemia and risk of DM

• reduced basal metabolic rate

NUTRITION

• frequently poor

• risk of overfeeding in ICU

HAEMATOLOGY/IMMUNE SYSTEM

• hypercoagulability and DVT increased with age and comorbidity

• marrow response to anemia impaired

• immune responses are impaired (reduced bone marrow, thymus and splenic mass)

PHARMACODYNAMICS AND PHARMACOKINETICS

• duration of action of drugs may be prolonged as Vd reduced, reduced hepatic and renal clearance

• increased sensitivity to CNS depressants

• prone to polypharmacy and increased drug interactions as a result

• drug errors due to cognitive decline (overdose or non-compliance) and involvement of multiple doctors

PATHOLOGICAL CHANGES ASSOCIATED WITH AGEING

OVERVIEW

• increased risk of acquired disease

• falls

• increased risk of cancers

• subject to polypharmacy and associated risks

CARDIOVASCULAR

• increased incidence of cardiovascular disease (e.g. CAD, hypertension, dysrhythmias, CHF and valve disorders)

• ventricular wall stiffening (diastolic dysfunction)

• AF (25% life time risk) -> decreased stroke volume, risks with anticoagulation

• pacemakers and AICD

• capillary permeability increased

• less responsive to sympathetic stimulation -> require higher doses of inotropes

• beta-blockers reduce MI but increase mortality and stroke rates

RESPIRATORY

• longstanding smokers -> COPD

• increased obesity and inactivity

• OSA

RENAL

• increased risk of renal failure

• prostate hypertrophy

• chronic UTIs

CENTRAL NERVOUS SYSTEM

• dementia: 10% over 65y and 20% over 85y

• increased strokes

• memory impairment

• increased risk of Parkinson’s Disease, depression and other psychiatric illnesses

• decreased vision

• orthostatic hypotension

• gait disturbances

• syncope

• predisposed to delirium

• more sensitive to sedatives and analgesics

• Postoperative Cognitive Dysfunction (POCD) is common

ENDOCRINE

• increased glucose tolerance

• increased thyroid disorders

ADMISSION OF THE ELDERLY TO ICU

Some elderly patients benefit from ICU care, others do not, this depends on:

• their acute illness

• therapies provided (e.g. with-holding certain invasive therapies may lead to a self-fulfilling prophecy)

• coexistent frailty

• their values

ELDICUS Study

• age is independently associated with increased mortality in critical illness, likely reflecting decreased physiological reserve

• elderly patients are more likely to be refused ICU admission than younger patients

• differences between mortalities of accepted vs. rejected patients are greater for older patients, than younger patients

The proportion of patients aged >80 years admitted to intensive care in Australia and New Zealand is rapidly increasing, with an overall 80% survival to hospital discharge

GOALS OF CARE

Heyland and colleagues

• multicenter prospective cohort study

• involved 535 families of ICU patients aged >80 years admitted to ICU for >24h

• Found an incongruity between family values and preferences for end-of-life care and actual care received

• Family members reported that the “patient be comfortable and suffer as little as possible” was their most important value and “the belief that life should be preserved at all costs” was their least important value considered in making treatment decisions

• Only 57.3% of family members reported that a doctor had talked to them about treatment options for the patient

• Authors suggest that deficiencies in communication and decision-making may be associated with prolonged use of life-sustaining treatments in very elderly critically ill patients, many of whom ultimately die

PROGNOSIS

Elderly patients typically have worse longterm outcomes from critical illness compared to younger patients.

• One-quarter of patients aged 80 years or older admitted to ICU in Canada survived and returned to baseline levels of physical function at one year; mortality was 44% at 1 year

• 97% of elderly patients (over 85 years) treated in the ICU for “circulatory failure” die within 12 months of the life-threatening episode, despite 37% survival to ICU discharge

Frailty is associated with old age, but is not an inevitable consequence of being elderly. Frailty is an independent predictor of worse prognosis. Routine assessment of frailty status may aid in prognostication and informed decision-making for elderly critically ill patients.

Ref: Life in the Fastlane