Geriatric Anesthesia Flashcards
What are the basic age-related physiologic changes?
Basal function is relatively unchanged BUT (1) functional reserve and (2) ability to compensate are reduced.
Describe age-related changes to the cardiovascular system.
- decreased compliance of the heart and arteries –> increased afterload; LVH (remodeling); diastolic dysfunction
- more prone to AF (SV depends more on atrial preload)
- down-regulation of beta receptor activity –> decreased response to acute stress
Describe age-related changes to the pulmonary system.
- thoracic wall stiffens –> restrictive changes
- increased work of breathing, decreased MV
- closing capacity > FRC –> higher risk of atelectasis
- centrally-mediated decrease in ventilatory response to hypoxia & hypercapnia
- decreased cough reflex, ciliary clearance & compromised swallowing –> higher risk of aspiration & pneumonia
- long-term exposure to other factors (e.g. genetic, environmental, social, etc.)
Why are elderly at higher risk for aspiration & pneumonia?
Decreased cough reflex
Decreased ciliary clearance
Compromised swallowing
What is the effect of aging on renal function?
Progressive decrease in GFR d/t decrease renal blood flow
Serum creatinine decreases or remains normal because muscle mass also decreases with GFR
What is the impact of decreased GFR?
Impaired fluid and Na, and acid homeostasis
Prolonged drug clearance
What are the changes in body composition?
Increase total body fat
Decrease muscle mass
Decrease total body water
Decrease BMR
What are the pharmacologic effects?
Higher Vd for lipid-soluble: longer effect, elimination
Lower Vd for water-soluble: higher plasma concentrations
Lower MAC (~6% per decade after 40)
Lower ED50
*more sensitive to anesthetic drugs
*more exaggerated hemodynamic effects to drugs i.e. hypotension-induced propofol
Considerations for doing neuraxial anesthesia.
decreased CSF volume: faster onset & longer duration –> lower dose (SAB & EA)
exaggerated lumbar lordosis & thoracic kyphosis: more cephalad spread and pooling in the thoracic segments –> higher block
lower incidence of PDPH
What can anesthesiologists do to limit POCD?
Limit the use of drugs already associated with delirium in the elderly e.g. long-acting opioids, BZD, anticholinergics
‘Physiologic beta-blockade’
Age-related changes in the ANS
Reduced chronotropic & inotropic response to beta-adrenergic agonists
Lower ‘maximum HR’ in response to stress
Lower ‘baroreceptor reflex-mediated tachycardia’ in response to hypotension
At risk for orthostatic hypotension
Describe changes in cardiac output.
Non-compliant ventricle increases afterload –> LVH (remodeling) –> diastolic dysfunction –> CO becomes dependent on the atrium
Increase in CO is mediated by an increase in SV, not HR (physiologic beta-blockade)
Cardiac output lowers with age
Which EKG readings would warrant further investigation?
LBBB
AV nodal delay/blocks
AF
Q waves or ischemic changes
Which EKG readings are associated with aging?
As long as isolated/asymptomatic:
sick sinus
PVC
RBBB
Effect of nondepolarizing muscle blockers in the elderly
- decreased Vd and clearance
- same dose for paralysis (ED95) but duration is longer
