anesthetic challenges for the geriatric patient Flashcards
define the term geriatrics
refers to the study of the elderly
*many accept > 65 y/o as elderly
define octogenarian
person > or = 80 y/o
define nonagenarian
person > or = 90 y/o
define centenarian
person > or = 100 y/o
define supercentenarian
person > or = 110 y/o
what are the most frequent conditions in the elderly population?
- 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
what are some theories of aging?
- 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
what does increased intracellular free-radicals (ROS) lead to?
- damage to membranes, proteins, and genetic integrity
- > decreased antioxidant and scavenging capacity
- > oxidative stress
- > further increase in ROS
what else does damage to membranes, proteins, and genetic integrity d/t increased ROS lead to?
- decreased bioenergetics capacity
- > loss of tissue and organ functional reserve
- > increased susceptibility to disease, infection, and injury
- > increased probability of death
what does organ functional capacity determine?
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
what can influence alterations in a person’s functional capacity?
- physical and mental activity levels
- co-morbid conditions
- social habits
- diet
- genetic background
describe functional reserve
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
describe body composition of the elderly
- 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
describe changes in metabolism and thermoregulation in the elderly
- 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
describe changes in carbohydrate metabolism
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
describe CV effects of aging
- 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
how is CO best increased in the elderly?
- increasing LVEDV
* dependent on atrial kick to increase SV
what attributes to HTN and widening pulse pressure in elderly?
- 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
describe pulmonary effects of aging
- 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
what does the loss of elastic tissue recoil in the lungs lead to ?
- 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
describe closing capacity
- volume small airways collapse
- small airways cannot be kept open by elastic forces
- closing volumes > volume of lung at rest end-exhalation
what contributes to pulmonary gas exchange insufficiency?
- 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
how does age effect PaO2?
PaO2 = 100 - (0.4 {age in yrs.} mmHg)
what further complicates the elderly’s decreased response to hypoxia and hypercarbia?
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
describe hepatic effects of aging
- 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
describe renal effects of aging
- 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
what is significant about serum creatinine levels in elderly?
- may be normal
* don’t assume renal function is normal
what is the cause of less efficient renal reabsorption by the kidneys?
- decreased aldosterone leads to decreased Na+ conservation
- this leads to dehydration and hyponatremia
describe CNS effects of aging
- 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
what contributes to increased risk of post op delirium in the elderly?
- decreased cholinergic activity
- anticholinergic use
describe drug use in the elderly
-increased incidence of drug interactions d/t poly pharmacy
describe drug elimination in the elderly
- 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
describe the effect of the elderly’s body composition on drugs
- 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
what are pulmonary implications in elderly for anesthesia?
- 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
what are CV implications in elderly for anesthesia?
- 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
what are additional concerns with elderly and anesthesia?
- hypothermia with reduced BMR
- duration of epidural anesthesia is shorter
- duration of subarachnoid block is longer
what are implications for paralytic use?
- 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
what are general drug implications for elderly and anesthesia?
- 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
what are implications for anesthetic drugs and adjuncts?
- 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
