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Boards: Patient Populations > Geriatrics > Flashcards

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
Q

Neuroplasticity

A

slower, less complete vs younger individuals

26
Q

What generally remains intact with CNS?

A

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
Q

Neuraxial Changes

A

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
Q

Summary: Nervous System Changes

A

-Overall brain volume decreases
-Changes in NT amts
-R number/ sensitivity may change
-Structural changes: alterations in neuraxial ax

29
Q

ANS Effects

A

–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
Q

Cognition

A

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
Q

Serotonin Syndrome MOA

A

excess stimulation of serotoninergic R in NS  mentation changes, autonomic dysfunction, NM abnormalities
 Dx: hx of ingestion of serotonergic drug

32
Q

Clinical Signs of Serotonin Syndrome

A

–Autonomic hyperactivity: diarrhea, mydriasis, tachycardia
–NM signs: hyperreflexia, myoclonus, tremors, rigidity, altered mentation
–Systemic hypo/hypertension, PH, vomiting, anorexia, hyperthermia, restlessness, ataxia, sz

33
Q

SSRIs - examples

A

sertraline, fluoxetine, citalopram (Celaxa)
* MOA: decrease ability of platelets to take up serotonin, safer

34
Q

MAOi Inhibitors - examples

A

selegiline (canine cognitive dysfunction, hyperadrenocorticism), tranylcypromine
* Hypertension, tachycardia secondary to catecholamine release

35
Q

Serotonin releasing agents - examples

A

amphetamines in ADHD meds – Adderall, Ritalin

36
Q

TCAs - examples

A

trazodone, mirtazapine, amitriptyline, tramadol
* MOA: block reuptake of serotonin, NE in presynaptic terminals
* Narrow safety margin

37
Q

Treatment of SS

A
  • 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
Q

Drugs Assoc with Serotonin Syndrome

A

Antidepressants: trazodone, mirtazapine, amitriptyline, seleginine, fluoxetine, citalopram (Celexa), sertraline

GI: ondansetron, metoclopramide

Opioids: buprenorphine, methadone, meperidine, tapentadol, tramadol

Anticonvulsants: valproic acid

39
Q

Hepatic Function Tests

A

glucose, BUN, albumin, cholesterol, bile acids

40
Q

Hepatic Metabolism Depends on:

A

 Enzyme function – preserved
* Overall hepatic mass reduced, functional reduction in enzyme function
 HBF: decreased – prolonged plasma clearance

41
Q

Main Hepatic Change assoc with age

A

Decreased liver mass –> decreases hepatic clearance

Microsomal, non-microsomal activity maintained

42
Q

Overall Effect on Liver function

A

–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
Q

Renal Effects

A

-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
Q

Main Renal Effects

A

o Effect: less able to tolerate hypovolemia AND hypervolemia, hemorrhage, electrolyte and acid-base disturbances

45
Q

Renal Mass Loss

A

o Primary loss of cortical kidney mass, functional nephron units
 50% reduction in functional nephrons

46
Q

Renal BF Changes

A

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
Q

Urine Concentration Changes

A

o Decreased response to ADH, impaired ability to conserve Na/concentrate urine
 RAAS less responsive
 Overvigorous fluids: fluid overload, HR, pulmonary edema

48
Q

Changes in Body Composition

A

decrease in SkM
increase in body fat as total percentage of body weight
Loss of intracellular water

49
Q

Intracellular Water Loss

A

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
Q

Increased Adipose Tissue

A

increase in fraction of single dose of lipid-soluble drug redistributed to adipose tissue – delayed elimination

51
Q

Reduced Albumin

A

reduced protein binding
 Structural changes in serum protein that occur with aging may decrease binding to available protein

52
Q

Old Dog Lungs

A
  • Old Dog Lungs, hypoventilation may prolong equilibrium of inhalant with brain – slower changes
53
Q

increase in Body Fat

A
  • Greater Vd with prolonged clinical effect of lipophilic drugs
54
Q

Decrease in Total Body Water

A
  • Smaller central compartment, increased serum concentrations after boluses of hydrophilic drugs
55
Q

Opioids

A

Increased brain sensitivity, consider dose reduction

56
Q

Propofol

A

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
Q

Ketamine

A

prolonged effect in patients with failing hepatic, renal systems

58
Q

Maintenance

A

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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