Geriatric Anesthesia Flashcards
FRC Changes?
INCREASES
Susceptibility to stress & disease
Functional reserve can be measured for some organ systems (cardiac) but for others (hepatic/renal) more difficult to quantify.
Stochastic model
Stochastic model: random errors of protein synthesis accumulate
Cellular evidence of defects within mitochondrial DNA
Reduction in scavenging of free radicals
Non Stochastic, Biological clock or life pacemaker: neuroendocrine, immune focus
Individual rates of decline vary and decline in specific organ function varies.
Body changes with aging
Loss of lean body mass
Increased total body fat
Decreased metabolic rate
Decreased total body water
Decreased blood volume (20-30%)
T
Thermoregulation
Impair function of hypothalamus in elderly
Hypothermia last longer due to low metabolic rate
Hypothermia causes slower elimination of anesthetics and longer recovery
Shivering increases O2 consumption by 400% (hypoxia, acidosis and cardiac compromise)
Respiratory: dead space & MV
Increase in dead space requires increase in MV to maintain a normal PaCO2
Resp: compliance, elasticity, & RV
Lung compliance increases = Lungs are easier to inflate
Chest wall compliance DECREASES
Decreased Lung elasticity, promotes small airway collapse
Aged Lung is easy to inflate (high compliance) but low elasticity makes it harder to return to its original shape.
RV increases as a result
Other anatomical resp changes
Calcified joints
Flatten diaphragm
Increased AP diameter
Decreased intervertebral disc height
Decreased respiratory muscle strength
Decreased elastic recoil
WOB change?
THE WORK OF BREATHING INCREASES
Resp: hypercarbia and hypoxia
Decreased response to hypercarbia and hypoxia
Chemoreceptors
Chemoreceptors are less sensitive to changes in pH,PaCO2, and PaO2
Airway Reflexes
Decreased Protective airway reflexes
Increased aspiration risk
Airway tone and muscle strength
Decreased upper airway tone
Decreased respiratory muscle strength
Common Age related Anatomic and Physiologic Changes: Decreases
Decreased forced expiratory volume
Decreased resting arterial oxygen tension
Common age related anatomic and physiologic changes: increases
Increased residual volume and closing capacity
Increased Ventilation-perfusion mismatch
Increased alveolar-arterial gradient
Increased functional residual capacity
Lung changes with aging summary
Cardiac: compliance
Arterial and venous compliance decrease
Decreased myocardial compliance and impaired relaxation can cause diastolic dysfunction
Cardiac: arterial
Arterial = Increase SVR and afterload –> increased BP
Cardiac: venous
Venous = Changes in blood volume cause major changes in preload
Cardiac: filling pressures & atria
Heart requires higher pressures to fill and filling pressures overestimate volume
Atrial kick important to prime non-compliant ventricles
Cardiac: EF, eletrical changes
Ventricular hypertrophy reduces ventricular compliance and impairs relaxation and prolongs ejection time
Fibrosis of cardiac conduction system and loss of SA node tissue
Increased likelihood of atrial fibrillation, first degree heart block second degree HB and Sic sinus syndrome
Cardiac: BP and SV changes
Increased BP = reduced arterial compliance increases SVR
Increased pulse pressure = arterial stiffness increases systolic pressure more than diastolic pressure
Systolic function is unchanged
Diastolic function decreased = reduced compliance and increased wall stiffness impairs relaxation
Stroke volume decreases and decreased ability to increase SV reduces exercise tolerance
Cardiac: HR changes
Heart Rate decreases
Decreased responsiveness to catecholamine’s
Decreased ability to respond to hypotension, hypovolemia and hypoxia
Decreased CO, prolongs circulation time, reduced exercise tolerance and cardiac reserve
AFib
AF increases morbidity and mortality (Framingham Heart Study)
Women with AF are three times more likely to suffer stroke as women without
Men have a 2.5 times increased risk
All patients with AF are 3.5 times more likely to suffer symptoms of CHF
Cardiac Consequences
Loss of atrial synchrony
Irregular ventricular response
Impaired coronary blood flow
Loss of atrial kick in the setting of diastolic dysfunction can lead to a 20-50% decrease in cardiac output
Afib management
Preoperative patient presents with AF
Is the rhythm acute change or chronic
For chronic AF check rate control and coagulation status and proceed
New onset evaluate hemodynamic status and recommend cardiac workup rule out MI protocol and evaluate thrombus formation
Must evaluate the urgency of the procedure
Metabolic Equivalent (MET)
1 MET is equal to an oxygen consumption of 3.5ml/kg/min
Inability to achieve 4 METS is associated with increased perioperative risk of cardiac complications
Goldman Cardiac Risk Index
Goldman Cardiac Risk Index - points total & risk
ANS: SNS tone
SNS tone increased = higher norepinephrine concentration in plasma
ANS - beta receptors
Reduced beta receptor sensitivity
ANS: PNS tone
PNS tone decreased = anticholinergics may not increase HR as expected
ANS: catecholamines
Decreased response to catecholamines = decreased adrenergic receptor density, impaired beta receptor sensitivity, reduced ability to increase HR during hypotension or times of stress
MAC changes
MAC decreases 6% for each decade of life after 40, IV agent dose should be reduced by 30-40%
ANS changes re anesthesia
Reduced activity of Ach, NE, DA and GABA
Number of receptors may be reduced
Increased sensitivity to anesthesia agents
Brain mass & nerves
Decreased Brain mass, but does not reduce mental capacity
Reduced number of myelinated nerves and degeneration of nerves that remain
Postop delirium vs. cognitive dysfunction
Alzheimer’s Disease
- Chronic neurodegenerative disorder
- Most common cause of dementia and forth most common cause of disease related death in patients older than 65
- Amyloid rich senile plaques and neurofibrillary tangles are the hallmark of pathologic findings
- Changes in acetylcholine and central nicotinic receptors
- Genetic factors-Autosomal dominant mode of transmission
- Early onset < 60 non-hereditary
- Late onset > 60 hereditary
Alz Treatment
NO cure
Cholinesterase inhibitors
Tarcrine, donepezil, rivastigmine and galantamine
Poor Prognosis
Cholinesterase inhibitors reduce plasma pseudocholinesterase and increase the duration of succinylcholine and mivacurium
Parkinson’s Disease
A disorder of the extrapyramidal system and is one of the most common neurodegenerative diseases
Age is the single most consistent risk factor affecting 3% of the population older than 65 and 50% of the population older than 85
Parkinson’s disease is characterized by progressive depletion of dopaminergic neurons in the substantia nigra of the basal ganglia… **Imbalance between the inhibitory action of dopamine and the excitatory action of acetylcholine **
Parkinsons: S&S, Tx
Classic symptoms rigidity resting tremor and bradykinesia
Treatment: L-dopa or dopamine receptor agonist
Surgical deep brain stimulation and fetal mesencephalic tissue implantation
Patho of Parkinsons
Dopaminergic neurons in the basal ganglia are destroyed
Increase in cholinergic activity
Increased Ach in the basal ganglia increases GABA activity in the thalamus
Thalamic inhibition suppresses cortical motor system and motor areas in the brainstem –> over activity of the extrapyramidal system
Decreased dopamine and normal acetylcholine = a relative Ach increase –> suppression of corticospinal motor system and overactive extrapyramidal motor system
Levodopa and Carbidopa
- Given together the drugs increase the concentration of dopamine in the basal ganglia
- Levodopa is the precursor to dopamine, it is metabolized in the blood to DA and can not penetrate the CNS
- Carbidopa is the decarboxylase inhibitor that prevents the metabolism in blood so more can enter the CNS
- CV side effects: increased inotropy, tachycardia, and orthostatic hypotension
- Dyskinesia nausea and vomiting are other side effects
Selegiline
A MAO inhibitor that works by slowing the breakdown of neurotransmitters dopamine norepinephrine and serotonin in the brain
Parkinsons Anesthesia Care
- Patients are at risk for: autonomic instability, orthostatic hypotension arrhythmia and aspiration
- Medications should be administered as close to the regular schedule as possible Levodopa has a half life of 6-12 hours consider giving PO dose for longer procedures.
- Drugs may exacerbate Parkinson symptoms: phenothiazines (promethazine), butyrophenones (haloperidol and droperidol), and metoclopramide should be avoided
- Anticholinergics may be used to treat acute exacerbations
- Diphenhydramine has anticholinergic properties
- Hypotension should be treated with IVF and direct acting agents
- Alfentanil may cause an acute dystonic reaction
- Ketamine is controversial due to effects on SNS
- No contraindications to NMBD
- Monitor for postoperative respiratory failure
Deep Brain Stimulation
May hold levodopa and allow symptoms to worsen which facilitates electrode placement
Stereotactic guided burr holes to insert electrodes into the:
Sub-thalamic nucleus, Globus palidus, Ventralis intermedius
During electrode placement the patient must be awake
GABA agonist are avoided
Sitting position VAE risk
Risk of intracranial hemorrhage keep SBP 140mmHg
Seizures can be treated with small doses of propofol or benzodiazepine
Renal: BF, mass, creatinine clearance
- No change in serum creatinine even though GFR decreases with age muscle mass also decreases
- Renal blood flow decreases 10% per decade
- Renal mass decreases, loss of functioning glomeruli and loss of nephrons cortex»_space;> medulla
- Decreased creatinine clearance The most sensitive indicator of renal function and drug clearance in the elderly
Renal: acid load, aldosterone, ADH
Decreased response to acid load due to the reduced capacity of the renal tubules to secrete ammonium
Decreased aldosterone and impaired ability to conserve sodium risk of dehydration
Decreased ADH, and elderly have a reduced response to ADH
Hepatic changes: mass, BF, function
No change in hepatocellular function normal enzyme function
Decreased hepatic mass less total enzyme produced
Decreased hepatic blood flow less drug or toxin delivered to liver per unit time
Decreased perioperative hepatic function as a result of decreased blood flow and decreased liver mass
Hepatic: albumin, alpha 1 acid glycoprotein, pseudocholinesterase
Decreased albumin production decreased reservoir for acidic drugs
Increased alpha 1-acid glycoprotein production increased reservoir for basic drugs
Both are not significant in clinical anesthesia
Reduced pseudocholinesterase production –> prolonged duration of succinylcholine and ester local anesthetics men > women
Hepatic: phase I & II, 1st pass
Reduced phase I reactions –> oxidation, reduction and hydrolysis
No change in Phase II reactions –> conjugation and acetylation
Reduced first pass metabolism due to reduced hepatic mass and liver blood flow
Preop Eval
Testing should be directed by the type of surgical procedure , known coexisting conditions or findings on physical exam
ECG, baseline hematocrit and hemoglobin
Most important for postoperative functional recovery is the patients preoperative functional status
Cardiac testing should be reserved for patient who cannot achieve 4 METs with additional risk factors for ischemic heart disease
Malnutrition is an independent risk factor for 30 day and 1 year mortality
Neuraxial
Increased Sensitivity of nerves to local anesthetics
Decrease number of myelinated nerves, diameter of myelinated nerves and conduction velocity
Increased sensitivity to intrathecal anesthetics
Decreased CSF volume –> greater spread of LA –> reduce dose
Increased sensitivity to epidural anesthetics
Decreased epidural space volume –> greater spread of LA –> reduce dose
Dura is more permeable to LA –> reduce dose
Neuraxial: anatomic changes
Difficult placement of neuraxial block
Anatomic changes:
Less space between posterior spinous processes
Decreased intervertebral disc height
Narrow intervertebral foramen
Calcification
Because of reduced myocardial sensitivity to catecholamine’s there is a higher risk of false negative to epi test dose
Pharmacology: circ time, iv induction, surface area, body fat
Increased circulation time –> reduced CO prolongs the time of drug delivery from the site of administration to the site of action
Slower IV Induction, faster inhalation induction
Increased Surface area to body mass ratio –> reduced lean body mass
Increased total body fat –> Increased Vd of lipophilic drugs and a larger reservoir may prolong their elimination
Lean body mass changes
Decreased lean body mass –> less muscle mass
Decreases in:
- basal metabolic rate
- total body water
- blood volume and plasma volume
Smaller Vd for hydrophilic drugs higher than expected plasma concentration for a given dose
Inhalational Anesthetics
Reduced anesthetic requirement
MAC is decreased by 6% for every decade after the age of 40
Recovery from inhaled anesthetic is delayed due to increased fat content and decreased pulmonary gas exchange
Propofol
Elderly require less drug to produce unconsciousness (Decrease bolus and infusion by 50%)
Midazolam
Dose required to produce sedation decreases with increasing age minimize dose (Avoid; decrease dose by 75%)
Opioids
The dose needed to produce pharmacological effect decreases with age. (Decrease bolus by 50%)
Enhanced sensitivity to opioids mostly due to pharmacodynamics changes
Neuromuscular Blocking Drugs
Slightly slower onset of action due to decreased muscle blood flow
Dose requirement for most water soluble non-depolarizing agents is reduced since total body water is decreased
Prolonged elimination half life of drugs that are eliminated by hepatic or renal excretion
Elimination of cisatracurium is unaffected, onset is delayed
Geriatric summary
Aging is associated with progressive loss of functional reserve, the extent and onset of these changes vary between individuals
CV-less elastic large arteries, increased afterload, concentric hypertrophy of the left ventricle, increased myocardial O2 demand, diastolic dysfunction-impaired passive filling, atrial distention and fibrosis-AF, down regulation of beta adrenergic receptors
Respiratory summary
Respiratory: restrictive pulmonary changes-thoracic stiffness, increased work of breathing and decreased maximum minute ventilation closing capacity surpassed FRC by 65, decreased ventilatory response to hypoxia and hypercarbia
CNS summary
CNS: cerebral atrophy decreased blood flow, decreased synthesis of neurotransmitters
Renal summary
Renal: decreased GFR, renal blood flow, and renal mass
Hepatic summary
Hepatic: decreased liver mass, blood flow and hepatic reserve, decreased protein synthesis including albumin
Summary neuro
Serious post op complication POCD increases postoperative mortality
