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Geriatrics Flashcards

1
Q

What defines an animal as geriatric?

A

Animals at 75-80% of life span

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2
Q

Increased anesthetic risk with increasing age is seen in which species?

A

Horses, cats, dogs

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3
Q

Why are older patients potentially higher risk?

A

Reductions in functional reserve = decreased capacity for adaptation, predisposition to failure of homeostasis, reduced ability to respond external stress

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4
Q

Two Main Aging Theories

A
  1. Biologic Clock Theory
  2. Error Theory
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5
Q

Biologic Clock Theory

A

 Pre-programmed genetic decline
 From conception: unknown but genetically predetermined number of cellular divisions

Subtheories = endocrine theory, programed longevity, immunologic theory

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6
Q

Error Theory

A

 Environmental damage to processes lead to impaired function, progressive decline
 DNA damage, increased error frequency lead to aging

Subtheories = wear and tear theory, rate of living theory, cross linking theory, free radical theory, somatic DNA damage theory

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7
Q

Main CV Changes with Aging

A
  • Decreased contractility
    -Increased myocardial stiffness, ventricular filling pressures
    -More dependent on atrial kick, NSF, SV to maintain normal CO
    -Decreased beta adrenergic sensitivity
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8
Q

Fibrosis of endocardium, valves

A

decreased compliance, valve incompetence

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9
Q

Myocardial Fiber Atrophy

A

 Decreased myocyte number
 Decreased pump function, CO
 +/- HR changes if PM cells involved

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10
Q

Chrontropic Response to Stress

A

Maximal chronotropic response to stress decreases, despite increased circulating NE
–Receptor attrition, reduced affinity for agonist molecules
–Increase CO by increasing SV in assoc with end-diastolic volume
–Rely more on preload, not as tolerant of volume depletion in perianesthetic period

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11
Q

CV Changes in Horses

A

Valvular dz = most common
Aortic Insufficiency: 82% of valvular abnormalities, greatest incidence 15-20yo
 May not see signs until later in life – ex PDA, VSD
Conditions may be masked at rest, require stress or exercise to show arrhythmias
Age not a factor in response to dobutamine therapy
 CESEF: horses >14yo increased risk of anesthesia morbidity/mortality

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12
Q

Vasculature Changes

A

Geriatric arteries become longer, wider, thicker, stiffer

Increased MAP, increased pulse pressure

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13
Q

MOA Vasculature Changes

A

Breakdown of elastin in proximal thoracic aorta, proximal branches of great vessels
* Progressive central aortic dilatation
* Increased thickness of arterial wall
* Increased vascular stiffness

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14
Q

Pulmonary Structural Changes

A

–Loss of elastic recoil, increased compliance of lungs
* Elastic recoil: reorganization of collagen, elastin in lung parenchyma
–Altered surfactant production
–Enlargement of bronchioles, alveolar ducts – air trapping, hyperinflation, VQ mismatch
–Increased tracheal, laryngeal diameter

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15
Q

Effect of the Pulmonary Structural Changes

A

increased VD, decreased diffusing capacity (DL), increased closing capacity = impaired GE

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16
Q

Changes in Lung Capacities

A

Decreased VC, TLC, maximum breathing capacity DT reduction in IC, diaphragmatic muscle mass
* Thorax: more rigid, less compliant
Ratio of residual volume/FRC to TLC increases

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17
Q

Total Lung Capacity

A

maximum vol of air lungs can accommodate

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18
Q

Functional Residual Capacity

A

vol of air left in lungs at end of passive exhalation

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19
Q

Closing Capacity

A

vol at which smallest airways collapse, residual vol + closing vol
* Increases with age –> higher incidence of shunt, lower arterial oxygenation

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20
Q

Residual Volume

A

air left behind after maximal, forceful expiration

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21
Q

Main Changes with Respiratory Effects of Agining

A

-Loss of elastic components
-Increased CC –> VQ mismatching, impaired GE, hypoxemia/hypercapnia more likely
-M weakness: increased WOB
-Depth control may be harder with SpV

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22
Q

Sequelae of pulmonary changes

A

 Higher A-a gradient
 Impaired effectiveness of preoxygenation
 HPV blunted
 Increased PVR, PAP – secondary to decreases in cross-sectional area of pulmonary capillary bed

More likely to have issues with oxygenation, hypoxemia/hypercapnia under ax

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23
Q

Nervous System Changes - brain volume

A

–Overall decrease in vol DT decreased in both grey, white matter

–Gray matter loss: secondary to neuronal shrinkage vs neuronal loss
–15% loss WM with aging
–Regions affected in selective, differential manners – not homogenous throughout
–Overall effect: gyral atropy, increased ventricular size

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24
Q

Neurotransmitters

A

significant regional reductions in dopamine, ACh, NE, serotonin, tyrosine
 Glutamate levels are not affected.
 Reduced R affinity for NT

25
Neuroplasticity
slower, less complete vs younger individuals
26
What generally remains intact with CNS?
of cerebral electrical activity, cerebral metabolic rate, CBF remains intact  Humans: overall CBF decreases 10-20% DT decreased cerebral metabolic rate, mass  Maintenance of CBF autoregulation
27
Neuraxial Changes
**increased sensitivity to neuraxial, PNBs**  Reduction in epidural space area  Increased dural permeability  Decreased CSF volume * **LJ: increased CSF vol to maintain normal ICP**  Decrease in diameter, number of myelinated fibers in dorsal, ventral nerve roots
28
Summary: Nervous System Changes
-Overall brain volume decreases -Changes in NT amts -R number/ sensitivity may change -Structural changes: alterations in neuraxial ax
29
ANS Effects
--**Decrease in response to beta R stimulation – decreased R affinity, alterations in signal transduction** --**Decreased maximum HR, peak ejection fraction under stress**  Increased peripheral flow needs must be met by **preload** reserve
30
Cognition
o Canine Cognitive Dysfunction (CCD): affects upwards of 60% of dogs >11yo  Altered dz presentations?  Increased delirium upon recovery? o Postoperative cognitive dysfunction (POCD) o Can be difficult to determine pain, location o Visual, auditory impairments – increased anxiety at vet
31
Serotonin Syndrome MOA
excess stimulation of serotoninergic R in NS  mentation changes, autonomic dysfunction, NM abnormalities  Dx: hx of ingestion of serotonergic drug
32
Clinical Signs of Serotonin Syndrome
--Autonomic hyperactivity: diarrhea, mydriasis, tachycardia --NM signs: hyperreflexia, myoclonus, tremors, rigidity, altered mentation --Systemic hypo/hypertension, PH, vomiting, anorexia, hyperthermia, restlessness, ataxia, sz
33
SSRIs - examples
sertraline, fluoxetine, citalopram (Celaxa) * MOA: decrease ability of platelets to take up serotonin, safer
34
MAOi Inhibitors - examples
selegiline (canine cognitive dysfunction, hyperadrenocorticism), tranylcypromine * Hypertension, tachycardia secondary to catecholamine release
35
Serotonin releasing agents - examples
amphetamines in ADHD meds – Adderall, Ritalin
36
TCAs - examples
trazodone, mirtazapine, amitriptyline, tramadol * MOA: block reuptake of serotonin, NE in presynaptic terminals * Narrow safety margin
37
Treatment of SS
* TCAs: enterohepatic recirculation, admin activated charcoal Q6hr * Avoid decontamination in animals with severe CS DT aspiration risk * Supportive care: antinausea meds, methocarbamol for neuro signs, diazepam, cooling measures if hyperthermic * Severe cases: NMBA/CMV * Lipid emulsion: described in humans, not proven to be effective in vet med
38
Drugs Assoc with Serotonin Syndrome
Antidepressants: trazodone, mirtazapine, amitriptyline, seleginine, fluoxetine, citalopram (Celexa), sertraline GI: ondansetron, metoclopramide Opioids: buprenorphine, methadone, meperidine, tapentadol, tramadol Anticonvulsants: valproic acid
39
Hepatic Function Tests
glucose, BUN, albumin, cholesterol, bile acids
40
Hepatic Metabolism Depends on:
 Enzyme function – preserved * Overall hepatic mass reduced, functional reduction in enzyme function  HBF: decreased – prolonged plasma clearance
41
Main Hepatic Change assoc with age
Decreased liver mass --> decreases hepatic clearance Microsomal, non-microsomal activity maintained
42
Overall Effect on Liver function
--Reduction in overall mass impairs overall function --Metabolism of lipid soluble drugs, particularly anesthetics, decreased --Combined with decreased GFR/renal excretory capacity, reduction in hepatic clearance of drugs = increased half life, duration of effective drugs that depend on these routes of elimination
43
Renal Effects
-Nephron loss, may not see biochemical changes until >75% -Decreased RBF, GFR -Difficulty regulating Na, fluid volume – prone to dehydration, increased risk fluid overload
44
Main Renal Effects
o Effect: less able to tolerate hypovolemia AND hypervolemia, hemorrhage, electrolyte and acid-base disturbances
45
Renal Mass Loss
o Primary loss of cortical kidney mass, functional nephron units  50% reduction in functional nephrons
46
Renal BF Changes
Decreased RBF (primarily renal cortex), GFR (decreased plasma vol) Longer DOA for drugs metabolized/excreted by kidney eg ketamine in cats * Greater elimination half time
47
Urine Concentration Changes
o Decreased response to ADH, impaired ability to conserve Na/concentrate urine  RAAS less responsive  Overvigorous fluids: fluid overload, HR, pulmonary edema
48
Changes in Body Composition
decrease in SkM increase in body fat as total percentage of body weight Loss of intracellular water
49
Intracellular Water Loss
Loss of total body water due to decreased intracellular water, reduction in plasma volume Effect: IV injection into contracted Vd = increased initial plasma concentration, why geriatrics seem to require lower doses of injectables
50
Increased Adipose Tissue
increase in fraction of single dose of lipid-soluble drug redistributed to adipose tissue – delayed elimination
51
Reduced Albumin
reduced protein binding  Structural changes in serum protein that occur with aging may decrease binding to available protein
52
Old Dog Lungs
* Old Dog Lungs, hypoventilation may prolong equilibrium of inhalant with brain – slower changes
53
increase in Body Fat
* Greater Vd with prolonged clinical effect of lipophilic drugs
54
Decrease in Total Body Water
* Smaller central compartment, increased serum concentrations after boluses of hydrophilic drugs
55
Opioids
Increased brain sensitivity, consider dose reduction
56
Propofol
increased sensitivity in brain, decreased clearance, slow onset (decreased CO?) Dose of propofol required to induce dogs >8.5yo lower than young dogs, eliminated more slowly
57
Ketamine
prolonged effect in patients with failing hepatic, renal systems
58
Maintenance
**LINEAR MAC REDUCTION WITH AGE**  Humans: MAC peaks at 6mo, decreases 6% every decade o Alterations in ion channels, synaptic activity, R sensitivity

Boards: Patient Populations (3 decks)

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