Anesthesia for Geriatrics
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theories describing aging mechanisms
- protein damage- collagen becomes stiffer, elastin is replaced with collagen, CV system has more rx
- mitochondiral deterioration- body runs out of energy b/c mitochondria are less effective due to oxidative stress, leads to decline in organ function
functional reserve of organ function
- difference between the basal (min) and max organ system function
- safety margin to meet additional demands (increase CO, incr CO2 elim) of trauma and disease
How does organ system functional reserve change with aging?
- functional reserve decreases as we age (begins at age 40, sharp decrease after age 70)
- decreases in functional reserve may not become apparent until the body is stressed (illness, surgery, polypharmacy)
How does body composition change with aging? (Ie muscle, fat, metabolism, metabolically active areas, CO) What effect does this have?
- Atrophy of metabolically active areas (kidney, brain, liver)
- Loss of lean muscle
- Increased adipose mass
- Prolonged drug effects
- Decreased metabolism and heat prod
- Decreased resting CO
How does the neuro system change with aging? What effect does this have?
- Loss of neuronal tissue mass
- Reduced central NT activity
- Decreased anesthetic req
- Impaired autonomic homeostasis
How does the CV system change with aging? What effect does this have?
- Decreased elasticity
- Decreased beta adrenergic responsiveness
- Decreased cardiac and arterial compliance
- Decreased max HR and CO
How does the pulmonary system change with aging? What effect does this have?
- Increased intrathoracic stiffness
- Decreased lung recoil
- Reduced alveolar surface area
- Reduced VC
- Increased WOB
- Impaired efficiency of gas exchange
How do the renal and hepatic systems change with aging? What effect does this have?
- Decreased perfusion and vascularity
- Loss of tissue mass
- Decreased drug clearance
- Inability to withstand salt or water loads
How do the blood and immune systems change with aging? What effect does this have?
- Decreased immune competence
- Loss of hematopoietic reserve
How does TBW composition change with aging? What about adipose tissue?
- Decrease TBW
- Incr adipose tissue
Hepatic enzyme activity is ____. Hepatic blood flow is ____. Drugs dependent on biotransformation in the liver have ____ clearance.
How should renal function be assess in a geri pt?
- Look at creatinine clearance
- Serum creatinine is NOT accurate due to decreased skeletal muscle mass
How does the concentrating ability of the kidneys change with aging?
- Decreased ability to conserve water or eliminate excess Na+
T or F, the collecting ducts have increased sensitivity to ADH?
F, decreased sensitivity, ADH levels are increased
Most common lyte abn
- Hyponatremia < 135
- mild- moderate < 125
- severe < 120
Differentiate btw chronic and acute hyponatremia
- Chronic- well tolerated and asymptomatic
- Acute- dangerous, presents as CNS disorder, N/V, sz, muscle cramps
- increased rx to insulin, esp in skeletal muscle
- decreased aldosterone secretion
-SA node cells
- -decreased # myocytes
- -increased thickness LV wall
- -decreased density of conduction fibers
- -decreased # SA node cells
Effects of age related heart changes
- incr stiffness
- decr contractility
- decr beta responsiveness
T or F, the heart has less of a response to endogenous and exogenous catecholamines
-elastin and collagen
-MAP and pulse pressure
- loss of elastin and increase in collagen causes decr arterial compliance
- decreased compliance
- increased MAP and pulse pressure
Which is more common diastolic or systolic HTN
systolic due to increased periph vascular rx due loss of elastin and increase in collagen
- increased SNS activity
- decreased response to beta adrenergic activity due to decreased receptor activity and decreased signaling
Changes to alpha adrenergic responsiveness
Net effect of decr beta VD receptor responsiveness and unchanged alpha VC responsiveness
Why is end diastolic volume so important?
- Need enough EDV to get length tension relationship for optimum contractility (Starling Law)
- LV is stiff, so this can be difficult
Why can AF be detrimental?
- EDV is important for optimum CO
- but filling is impaired due to stiff LV
- thus need atrial kick to aid ventricular filling and maintain CO
How are plasma levels of NE affected?
By age 80, ___% of elderly have some degree of CAD and ___ % have angina.
T or F, DM facilitates the atherosclerosis of coronary arteries
- assoc autonomic neuropathy
- VD of coronary arteries is impaired
Why is upper airway obstruction risk increased
Loss of collagen, elastin, and pharyngeal muscle support
T or F, aspiration risk is incr?
What are the effects of the anatomic changes to the respiratory system?
- Increased anatomic dead space
- Decreasing perfusing capacity
- Increased CC
- Impaired gas exchange
T or F, chest wall compliance is increased?
F, decreased due to kyphosis, vertebral collapse, and costochondral calcifications
Increase or decrease in the following with aging?
Max insp and exp force
At what age does CC exceed FRC?
~ 60 yo
T or F, HPV is unchanged with aging?
F, it's impaired
What occurs when CC > FRC?
List reasons for impaired gas exchange
- Decreased diffusion (loss of functional alveolar SA, increased alveolar membrane thickness)
- Impaired V/Q matching
- Increased A-a gradient
Ventilatory responses to hypercapnea ___ by __% and ventilatory response to hypoxia ___.
- Decreases, 50%
- esp at night
GA reduces FRC by ___%
as much as 15
MAC ___ by __% per decade after the age of 40.
Why might an elderly pt seen pre-op (DOS) have an increased sensitivity to barbs? How should be adjust the dose?
- Pt hypovolemic (NPO), drug gets concentrated in a smaller central compartment, larger reserve due to increased adipose
- 20% less
SE of barbs in the elderly
- Dose dept hypotension
- Decreased CO by decreasing preload and contractility
What the drug does to the body, the drug's pharm effect
What the body does to the drug, absorption, metab, elim, etc
Propofol dose adjustments for elderly
- decrease by 20-60%
- dose based on lean body mass
- smaller central Vd and decreased clearance
T or F, elderly pts are more likely to have reps depression and hypotension 2/2 propofol
Etomidate dose adjustment for elderly
- Decrease dose by 25-50%
- Decreased clearance in elderly
Pd and Pk changes of benzos in the elderly
- Pd- increased sensitivity
- Pk- decreased clearance
Risks associated with IV diazepam in the elderly
- increased risk of thrombophlebitis and thrombosis
- effect of active metabolites will be more profound
What sedative hypnotics have active metabolites?
- thiopental (only signif with long inf at high doses)
Which opioids have active metabolites?
T or F, elderly its are equally sensitive to opioids as younger pts
F, more sensitive
Why might uptake and elim of volatiles be prolonged in elderly pts?
- V/Q mismatch
- Alteration in CO (slowed circa time)
- myocardial depressant effect is increased
- no compensatory increase in HR
T or F, elderly pts require a decreased initial dose of NMBs?
F, initial dose is unchanged
How is the onset time of NMBs changed in the elderly pt?
Increased onset time 2/2 decreased CO and decreased muscle blood flow
How is the metabolism and clearance of NMBs altered in elderly pts?
- Prolonged 2/2 decreased hepatic blood flow and decreased GFR
- Most NMBs are eliminated by either liver or kidney
- Less of an issue with cis-atro or atrocurium (ester hydrolysis / Hoffman elim)
Is the priming technique appropriate for an elderly pt?
Not contraindicated but pts are at increased risk for aspiration and desat
T or F, the onset to complete twitch suppression at the adductor policis is slowed in the elderly?
Is brain sensitivity to the following drugs increased or decreased: volatiles, prop, midaz, morphine, sufent, remi?
In general, anesthetic agent drug doses need to be decreased in the elderly pt, T or F?
T or F, regional anesthesia is preferred over GA in the elderly?
- F, no benefit
- Positive outcomes are r/t degree of HD control, not choice of anesthetic technique
- CNS complications are minimized only if minimal sedation is used
Elderly pts are more likely to experience hypotension from a spinal, T or F?
T, more profound sympathectomy
Factors determining surgical risk in the elderly
- ASA status
- elective vs. urgent
- type of surgery
How can we evaluate functional reserve pre-op?
Exercise tolerance, goal > 4 mets
factors contributing to peri-op M+M in the elderly
- decr organ system functional reserve
- effects of age related disease and its tx
- impaired autonomic homeostasis
- need for medical intervention and invasive procedures
- emergency surgery
T or F, the sensitivity of the cerebral cortex to respiratory depressants increases with age?
T or F, no increased risk of corneal abrasion and post-op shivering in elderly pt?
- F, increased risk
- corneal abrasion due to decreased lacrimation
- shivering- altered thermoreg and decr heat production
Major CV complications
MI, myocardial ischemia, arrhythmias, HTN, hypotension
What types of non-CV surgeries are associated with the highest CV risk?
Surgeries involving thorax, blood vessels, head and neck, and abdomen
Most peri-op infarcts occur __ days post-op
Why should tachycardia be avoided?
Risk factor for myocardial ischemia and infarct due to increased myocardial O2 consumption and decreased O2 supply
Risk factors for cognitive dysfunction in the elderly
- Pre-op depression
- Surgery type
- Anesthetic technique
- Intra-op sedation
- Lyte disturbances
- Peri-op meds
T or F, GA is associated with more post-op cognitive dysfunction than regional?
F, regional is only associated with decreased cognitive dysfunction if no sedation is used
Why are elderly pts at increased risk for hypothermia?
- impaired thermoreg
- decreased subdermal tissue
- decreased muscle mass so less heat production
- impaired VC and HTN
Why are elderly pts at increased risk for hypoxia?
- Atelectasis and PNA are common
- V/Q mismatch
- High aspiration risk
- Increased incidence of sleep apnea
- Supplemental O2 is essential
Predictors of post-op pulmonary complications in elderly pts undergoing non cardiac surgery
- Post-op NGT
- Pre-op productive cough
- Long anesthetic (GA)
- ETOH use
- Chronic steroid use
- Impaired LOC / CVA
- TEE (increased aspiration risk)
Other risk factors
- chronic pain
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