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Principles II > anesthetic challenges for the geriatric patient > Flashcards

anesthetic challenges for the geriatric patient Flashcards

1
Q

define the term geriatrics

A

refers to the study of the elderly

*many accept > 65 y/o as elderly

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2
Q

define octogenarian

A

person > or = 80 y/o

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3
Q

define nonagenarian

A

person > or = 90 y/o

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4
Q

define centenarian

A

person > or = 100 y/o

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5
Q

define supercentenarian

A

person > or = 110 y/o

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6
Q

what are the most frequent conditions in the elderly population?

A
  • HTN
  • diagnosed arthritis (d/t yrs. of wear and tear on joints)
  • all types of heart disease (CAD, myopathies, valve, etc.)
  • any cancer (risk increases with age)
  • DM (obesity; decreased pancreas efficiency)
  • sinusitis
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7
Q

what are some theories of aging?

A
  • Free radicals (ROS) stress cell mitochondria and its enzymatic machinery of oxidative phosphorylation
  • defective mitochondrial DNA impairs bioenergetics efficiency
  • reduced cellular ability to scavenge by-products of aerobic metabolism
  • progressive degenerative changes affect both structure and function of organism
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8
Q

what does increased intracellular free-radicals (ROS) lead to?

A
  • damage to membranes, proteins, and genetic integrity
  • > decreased antioxidant and scavenging capacity
  • > oxidative stress
  • > further increase in ROS
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9
Q

what else does damage to membranes, proteins, and genetic integrity d/t increased ROS lead to?

A
  • decreased bioenergetics capacity
  • > loss of tissue and organ functional reserve
  • > increased susceptibility to disease, infection, and injury
  • > increased probability of death
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10
Q

what does organ functional capacity determine?

A

whether a person is considered physiologically old or young

  • young person with declining organ function can be considered physiologically old & vice versa
  • chronological age is the person’s actual number of years
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11
Q

what can influence alterations in a person’s functional capacity?

A
  • physical and mental activity levels
  • co-morbid conditions
  • social habits
  • diet
  • genetic background
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12
Q

describe functional reserve

A

the difference between basal and maximal organ capacity

  • aging is associated with reduced functional reserve (maximal organ capacity declines with age; basal doesn’t change much)
  • endurance: “safety margin” allows individual to meet increased organ demands brought on by stress, disease, increased CO and CO2 production and excretion needs, poly-pharmacy and surgery
    ex: basal HR 60, when running max 170; pt. with CHF max may be less than 120, leading to quicker ischemia
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13
Q

describe body composition of the elderly

A
  • gender specific
  • atrophy of brain, liver, and kidney
  • decreased lean tissue mass (LTM)
  • increased body fat
  • decreased bone density in women
  • decreased weight (men > women)
  • total body water (TBW) decreases 10-20% d/t reduced LTM and skeletal muscle mass
  • decreased intracellular water
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14
Q

describe changes in metabolism and thermoregulation in the elderly

A
  • decreased LTM contributes to decline in basal metabolic rate (BMR)
  • decreased heat production d/t reduced LTM: core temp reduced 2x more; direct relationship b/w re-warming time required w/ age; decreased SNS activity, thermoregulatory response
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15
Q

describe changes in carbohydrate metabolism

A

altered carbohydrate metabolic response

  • decreased LTM limits storage of carbs
  • reduced sensitivity of pancreatic islet cells to glucose
  • increased insulin resistance d/t more fat
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16
Q

describe CV effects of aging

A
  • ventricles and atria are thicker and stiffer
  • decreased CO d/t decreased metabolic demands and decreased HR
  • increased vagal tone (“physiological bradycardia”)
  • decreased beta adrenergic sensitivity (decreased response to beta blockers)
  • dependent on atrial kick for ventricular filling (CO increased by LVEDV not by HR)
  • decreased venous return with PPV or decreased SV with bleeding
  • HTN, widening pulse pressure
17
Q

how is CO best increased in the elderly?

A
  • increasing LVEDV

* dependent on atrial kick to increase SV

18
Q

what attributes to HTN and widening pulse pressure in elderly?

A
  • aorta and larger vessels lose compliance and ability to store hydraulic energy
  • greater afterload which impedes stroke volume ejection
  • LV wall tension increase and LV mass increase
19
Q

describe pulmonary effects of aging

A
  • loss of elastic tissue recoil non-uniformly
  • increased closing capacity (vol. small airways collapse)
  • costo-chondral and thoracic joint stiffening further contributes to a reduction in lung compliance
  • reduced alveolar surface area (15% less gas exchange)
  • pulmonary gas exchange inefficiency
  • decreased response to hypoxia and hypercarbia
20
Q

what does the loss of elastic tissue recoil in the lungs lead to ?

A
  • increased functional reserve capacity (FRC)
  • increased residual volume (RV)
  • FRC = ERV + RV
  • elderly lungs expand but cant recoil to push all of volume back out
21
Q

describe closing capacity

A
  • volume small airways collapse
  • small airways cannot be kept open by elastic forces
  • closing volumes > volume of lung at rest end-exhalation
22
Q

what contributes to pulmonary gas exchange insufficiency?

A
  • ventilation perfusion mismatches: blood flow continues but not all being ventilated d/t decreased gas exchange; begins to mix with ventilated blood
  • progressively worsening venous admixture
23
Q

how does age effect PaO2?

A

PaO2 = 100 - (0.4 {age in yrs.} mmHg)

24
Q

what further complicates the elderly’s decreased response to hypoxia and hypercarbia?

A

anesthetic-induced hypoxic-pulmonary vasoconstriction (HPV) depression

  • this mechanism helps by vasoconstriction to areas that are hypoxic to reduce blood flow to those areas and promote blood flow to areas with oxygenation
  • anesthetics “numb” this mechanism
25
Q

describe hepatic effects of aging

A
  • reduced hepatic blood flow and portal perfusion
  • organ function decreases by 1%/yr. after age 30
  • liver mass decreases about 40% by age 80
  • reduced nitrogen handling abilities
  • reduced hepatic biotransformation and protein synthesis (decreased 1st pass metabolism)
  • both increase free drug
  • decreased CP450 enzymatic process
26
Q

describe renal effects of aging

A
  • decreased renal blood flow and renal mass
  • decreased GFR, creatinine clearance
  • unable to tolerate hypotension or decreased CO effects on metabolism
  • renal Na+ handling less efficient
  • susceptible to fluid overload if too much IVF or infused too rapidly
27
Q

what is significant about serum creatinine levels in elderly?

A
  • may be normal

* don’t assume renal function is normal

28
Q

what is the cause of less efficient renal reabsorption by the kidneys?

A
  • decreased aldosterone leads to decreased Na+ conservation

- this leads to dehydration and hyponatremia

29
Q

describe CNS effects of aging

A
  • diminished reflexes
  • decreased NT synthesis and loss of neurons
  • decreased receptor density
  • 30% brain mass can be lost by year 80
  • diminished NT conduction
  • DA depleted
  • reduction in cerebral blood flow
  • reduced O2 consumption by neuronal tissue
  • decreased cholinergic function
  • increased incidence of post op delirium
  • decreased sympathetic nervous system activity (HTN not d/t SNS but stiffer vessels)
  • decreased thermoregulatory control mechanisms
30
Q

what contributes to increased risk of post op delirium in the elderly?

A
  • decreased cholinergic activity

- anticholinergic use

31
Q

describe drug use in the elderly

A

-increased incidence of drug interactions d/t poly pharmacy

32
Q

describe drug elimination in the elderly

A
  • reduced renal excretion, hepatic biodegradation
  • loop diuretics and Ca+ channel blockers potentiate NMB agents
  • midazolam is slow to eliminate (reduce dose)
  • decreased protein binding (decreased albumin) means higher concentration of the drug in the free form causing an increased drug effect
33
Q

describe the effect of the elderly’s body composition on drugs

A
  • decreased Vd for water soluble drugs and decreased protein binding = increased concentrations/response; slower elimination
  • decreased blood volume = increase in plasma drug concentrations so decrease dose
  • increased body fat and Vd of lipid soluble drugs along with decreased muscle mass require larger dose initially, but have delayed elimination as well
34
Q

what are pulmonary implications in elderly for anesthesia?

A
  • may need an increase in FiO2 d/t declining PaO2
  • ensure adequate tidal volumes since at greater risk for atelectasis
  • aspiration risks are higher d/t protective reflexes diminished
  • delayed gastric emptying = full stomach
  • mask seal and ventilation more challenging d/t more edentulous
  • harder to re-establish spontaneous respiration d/t response to hypercarbia is diminished
35
Q

what are CV implications in elderly for anesthesia?

A
  • maintain sinus rhythm (atrial kick) to optimize preload
  • watch for an increase in dysrhythmias as nodal cells and conduction tissue are reduced (a fib, a flutter, PVCs, etc)
  • dramatic drop in BP with anesthetic drugs as baroreceptor sensitivity is decreased
  • compensatory CV responses to hypovolemia, hypoxia, and hypotension are diminished
  • greater risk for intra-op myocardial ischemia and infarct as CAD is more advanced, workload is greater d/t > afterload
36
Q

what are additional concerns with elderly and anesthesia?

A
  • hypothermia with reduced BMR
  • duration of epidural anesthesia is shorter
  • duration of subarachnoid block is longer
37
Q

what are implications for paralytic use?

A
  • NMB dosing remains unchanged in elderly (reduced lean muscle mass offset by increased cholinoreceptors)
  • duration of blockade prolonged d/t declines in hepatic and renal clearance
  • re-dose cautiously bc less LTM, increased elimination times and potentiation d/t Ca+ blockers and loop diuretics
  • organ independent metabolized/eliminated NMBs may be more effectively predictable in elimination (keep pH and temp normal): atracurium; cisatracurium
38
Q

what are general drug implications for elderly and anesthesia?

A
  • exaggerated responses warrant decrease in dosages
  • base anesthetic plan on assessment of organ function
  • expect hypotension as fluid volume and SNS activity is reduced
  • expect slower induction as circulation time is increased (don’t be inpatient and push more!)
  • inhalation agent uptake time is faster
  • no difference b/w GA and RA on POCD
39
Q

what are implications for anesthetic drugs and adjuncts?

A
  • careful with pre-op anxiolytics (renal elimination dec.)
  • consider H2 antagonist pre op as aspiration risks are greater (give Pepcid)
  • limit glucose containing IV fluids (cant handle or store glucose as well)
  • opioids depend on renal elimination
  • fentanyl considered best with renal insufficiency (quick offset)
  • run less volatile agent as anesthetic requirements fall linearly with age
  • MAC reduced around 4% per decade after age 40
  • very sensitive to anticholinergic drugs causing increased side effects

Principles II (18 decks)

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