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Geriatric anesthesia
 

Geriatric anesthesia

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    Geriatric anesthesia Geriatric anesthesia Presentation Transcript

    •  Usually we refer to patients aged ≥65 yr as the elderly, but there is no precise definition of ‘the aged’, ‘the elderly’ or ‘advanced age’ as there is no specific clinical marker of the ‘geriatric’ patient, and ageing does not occur abruptly.  Approximately 15% of the Western population, and about 25% of surgical patients are aged ≥65 yr. Half of these will undergo surgery in the remainder of their life time.  Age itself is an independent morbidity and mortality risk factor for a long list of diseases and injuries, hospitalization, length of hospitalization, and adverse drug reactions. Aging is a progressive physiologic process characterized by : 1- decreased end-organ reserve 2- decreased functional capacity 3- increasing imbalance of homeostatic mechanisms 4- increasing incidence of pathologic processes.
    • Physiological changes Nervous system  Memory decline occurs in > 40% of individuals older than age 60 years.  There is a decrease in the volume of gray and white matter. The decrease in gray matter volume is thought to be secondary to neuronal shrinkage or neuronal loss. Such loss results in gyral atrophy and increased ventricular size.  Decreases in brain reserve are manifested by : increased sensitivity to anesthetic medications increased risk for perioperative delirium and postoperative cognitive dysfunction.  Neuraxial changes : a) reduction of the area of the epidural space, increased permeability of the dura, and decreased volume of CSF. b) The diameter and number of myelinated fibers in the dorsal and ventral nerve roots are decreased. c) decreased conduction velocity in peripheral nerves. These changes tend to make elderly individuals more sensitive to neuraxial and PNBs.  Dementia and parkinsonism Cognitive deficits are associated with poorer rehabilitation outcomes and higher surgical mortality. Parkinson's patients are at increased risk for: postoperative pharyngeal dysfunction, and risk of aspiration. autonomic instability.
    • Cardiovascular changes Heart:  decreased myocytes number, left ventricular wall thickening Aortic valve sclerosis and mitral annular calcification decreased conduction fiber density and sinus node cell number.  Functionally, these changes translate to decreased contractility, increased myocardial stiffness and ventricular filling pressures, decreased β-adrenergic sensitivity.  Ageing is associated with structural and functional changes in the coronary vasculature, which could affect myocardial perfusion with advancing age Vascular:  The large arteries dilate, their walls thicken, and smooth muscle tone increases. As a result, vascular stiffness increases with advancing age. This is related to: breakdown of elastin and collagen Alterations in nitric oxide–induced vasodilation. Functionally, these changes are observed as: elevated MAP and pulse pressure.
    • Fig 1 Cardiac adjustments to arterial stiffening during ageing. MDO2=myocardial oxygen supply. MVO2=myocardial oxygen demand.
    •  Decreased ventricular compliance and increased afterload  compensatory prolongation of myocardial contraction  decreased early diastolic filling time  making the contribution of atrial contraction to late ventricular filling more important : this explains why cardiac rhythm other than sinus is often poorly tolerated in elderly individuals.  Changes in the autonomic system with aging include: a) decrease in response to β-receptor stimulation b) increase in sympathetic nervous system activity. Decreased β-receptor responsiveness : 1) causes the increased peripheral flow demand to be met primarily by preload reserve. 2) is 2ry to: decreased receptor affinity and alterations in signal transduction. sympathetic overactivity leading to desensitization of β‐adrenoceptors  Cardiovascular diseases (IHD, CHF and arrhythmias) are superimposed on age‐associated changes.
    • Fig 2 Cardiac response to increased flow demand in the young and the elderly. The young meet the increased flow demand primarily by β‐adrenoceptor‐mediated augmentation of heart rate and contractility, thus preserving preload reserve. In contrast, the elderly employ primarily the preload reserve to augment cardiac performance, thereby losing additional cardiovascular reserve and becoming susceptible to cardiac insufficiency.
    • Respiratory System  Changes in control of respiration, lung structure, mechanics, and pulmonary blood flow place the elderly patients at increased risk for perioperative pulmonary complications.  A) Centrally: Ventilatory responses to hypoxia, hypercapnia, and mechanical stress are impaired secondary to reduced CNS activity. The respiratory depressant effects of BZD, opioids, and volatile anesthetics are exaggerated.  B) Structural changes in the lung with aging include: .. loss of elastic recoil with enlargement of the respiratory bronchioles and alveolar ducts .. tendency for early collapse of the small airways on exhalation. .. progressive loss of alveolar surface area.  The functional results of these changes are .. Increased anatomic DS .. decreased diffusing capacity .. increased closing capacity  C) Loss of height and calcification of the vertebral column and rib cage lead to a typical barrel chest appearance with diaphragmatic flattening: making the diaphragm less efficient, and its function is impaired further by a significant loss of muscle mass associated with aging.  Functionally, the chest wall becomes less compliant, and work of breathing is increased.
    •    Residual Volume increases by 5- 10% per decade. Vital capacity decreases. Closing capacity increases with age. The change in the relationship between FRC and CC cause an increased ventilation-perfusion mismatch (increased Shunt) and represent the most important mechanism for the increase in alveolar-arterial oxygen gradient. formula P(A–a)O2 = 3 + (0.21 x patient's age)    In younger individuals, CC is below FRC. At 44 years of age, CC equals FRC in the supine position, At 66 years of age, CC equals FRC in the upright position.  Increased closing capacity and depletion of muscle mass causes a progressive decrease in FEV1 by 6% to 8% per decade.  Hypoxic pulmonary vasoconstriction is blunted and may cause difficulty with one-lung ventilation.  Pneumonia may be presented by uncharacteristic features such as confusion, lethargy, and deterioration of general condition.
    • Renal and Hepatic changes with age Renal  mass may decrease 30% by age 80 years with a decrease in functioning glomeruli.  RBF decreases about 10% per decade.  There is a progressive decline in creatinine clearance with age, yet with “normal” aging, S.Cr. remains relatively unchanged : because muscle mass also decreases with aging, so, S. Cr. is a poor predictor of renal function in elderly patients.  Functional changes in the kidneys with aging include alterations in electrolyte handling and the ability to concentrate and dilute urine.  Renal capacity to conserve sodium is decreased. This, paired with a decreased thirst response, may place an elderly patient at risk for dehydration and sodium depletion. Liver  volume decreases approximately 20% to 40% with aging.  Hepatic blood flow decreases about 10% per decade.  There is a variable decrease in the liver's intrinsic capacity to metabolize drugs.
    • Other problems  Polypharmacy  The number of medications used is directly proportional to the likelihood of having an adverse drug reaction with an incidence of 5 - 35% in patients older than age 65.  Malnutrition  The prevalence of malnutrition ranges from 15% to 26% among hospitalized elderly patients. Surgical patients who are malnourished have increased morbidity and mortality and increased length of stay.  Dehydration  Dehydration accounts for approximately 6.7% of admissions (in USA) and is often associated with hypernatremia and accompanied by infection, e.g. pneumonia and UTI.  Immobility  Bed rest leads to ventricular atrophy, hypovolemia, and orthostatic intolerance. Prolonged bed rest causes decreases in muscle mass, which may influence pulmonary function.
    •  Depression  Depression is estimated to occur in 10% of the community-dwelling population older than age 65 years. The presence of Depression may influence the occurrence of delirium and length of stay, and have a significant impact on postoperative quality of life.  Antidepressants should be continued during the perioperative period as discontinuing antidepressants may increase symptoms of depression and confusion.  Hypothermia  Advancing age predisposes the patient to perioperative hypothermia. Contributing factors include frail constitution, reduced metabolic rate, reduced subcutaneous fat layer, major and long operations, and impaired thermoregulation  unintentional hypothermia has been associated with myocardial ischemia, angina, and hypoxemia during the early postoperative period.
    • Pharmacological changes  Factors that affect the pharmacologic responses of elderly patients include changes in (1) plasma protein binding, (3) drug metabolism, (2) body content, (4) pharmacodynamics.  The main plasma binding protein for acidic drugs is albumin and for basic drugs is α1-acid glycoprotein.  The level of albumin decreases with age, whereas α1-acid glycoprotein levels increase.  The effect of alterations in plasma binding protein on drug effect depend on which protein the drug is bound to, and the resulting change in fraction of unbound drug.  Changes in body composition with aging reflect a decrease in lean body mass, an increase in body fat, and a decrease in total body water.  A decrease in TBW could lead to a smaller central compartment and increased serum concentrations after bolus administration of a drug. In addition, the increase in body fat might result in a greater volume of distribution and prolonged effect of a given medication.  Depending on the degradation pathway, decreases in liver and kidney reserve can affect a drug's pharmacokinetics profile.  Slow circulation: IV vs. Inhalation anesthetics : onset & effect
    • Preoperative Evaluation Common diseases of elderly patients may have a major impact on anesthetic management and require special care and diagnosis. Cardiovascular disease and diabetes are particularly prominent in this population. Laboratory and diagnostic studies, history, physical examination, and determination of functional capacity should attempt to evaluate the patient's physiologic reserve. Laboratory testing should be guided by the patient's history, physical examination, and proposed surgical procedure, and should not be based on age alone. The decision to operate should not be based on age alone, but should reflect an assessment of the risk-to-benefit ratio of individual cases.
    • Risk Assessment The preoperative assessment of perioperative cardiovascular risk relies on the evaluation of a) clinical markers, Major : unstable coronary syndromes, decompensated congestive heart failure, significant arrhythmias, severe valvular disease Intermediate : mild angina pectoris, previous myocardial infarction (>30 days old), compensated or previous congestive heart failure, DM Minor : advanced age, abnormal ECG, rhythm other than sinus, low functional capacity, history of stroke, uncontrolled systemic hypertension b) functional capacity (1 - >10 METs) 4 METs : can you climb a flight of stairs or walk up a hill or walk on level ground at 4 mph ?? c) surgery‐specific risk. High : emergent major operations; aortic and other major vascular; peripheral vascular; anticipated prolonged surgical procedures associated with large fluid shifts and/or blood loss intermediate : carotid endarterectomy; head and neck; intraperitoneal and intrathoracic; orthopaedic; prostate low : endoscopic procedures; superficial procedures; cataract; breast
    • Anesthetic Management  Airway management : mask ventilation and laryngoscopy may be challenging especially in edentulous or debilitated patients.  Monitoring positioning equipments (e.g. warming device) ….etc.     Older patients may come to the OR with depleted volume because of : NPO orders, reduced thirst, age‐related decline in renal capacity to conserve water and salt, disease‐associated fluid and electrolyte losses, inadequate intravenous fluid substitution and more frequent use of diuretics. Because of decreased left ventricular compliance and limited β‐adrenoceptor responsiveness, the elderly, particularly those with hypertension, must be expected to be more sensitive to fluid overload.  Careful volume assessment. (Volume Dependant yet volume intolerant)  preoxygenation  More frequent and severe hypotension on induction of anaesthesia must be anticipated in the elderly because of the effects of the anaesthetics which occur on top of age‐related impaired cardiovascular compensatory mechanisms, so, more judicious use and selection of agents, and slow titration of reduced doses during induction and maintenance of anaesthesia, are required with advancing age
    •  Inhaled Anesthetics  The (MAC) decreases approximately 6% per decade for most inhaled anesthetics. Changes in ion channels, synaptic activity, or receptor sensitivity may account for these changes in pharmacodynamics.  Intravenous Anesthetics and Benzodiazepines  There is no change in brain sensitivity to thiopental with age, yet, the dose of thiopental required decreases with age, due to an age-related decrease in the initial distribution volume of the drug resulting in higher serum drug levels.  Likewise, in the case of etomidate, decreased clearance and initial Vd, rather than altered brain responsiveness, account for the decrease in etomidate dose. The brain becomes more sensitive to the effects of propofol with age. In addition, clearance of propofol is reduced.  The dose requirement of midazolam to produce sedation is decreased approximately 75% due to increased brain sensitivity and decreased drug clearance.
    •  Opiates  Morphine clearance is decreased in elderly patients. Patients with renal insufficiency may have impaired elimination of morphine glucuronides, and this may account for some of the enhanced analgesia from a given dose of morphine.  Sufentanil, alfentanil, and fentanyl are approximately twice as potent in elderly patients. These findings are primarily related to an increase in brain sensitivity to opioids with age, rather than alterations in pharmacokinetics.  There is an increase in brain sensitivity to remifentanil with age. Remifentanil is approximately twice as potent in elderly patients, and one half the bolus dose is required. The volume of the central compartment, V1, and clearance decrease with age, and approximately one third the infusion rate is required in elderly patients.
    •  Muscle Relaxants  Generally, age does not significantly affect the pharmacodynamics of muscle relaxants. Duration of action may be prolonged, however, if the drug depends on liver or renal metabolism.  Neuraxial Anesthesia and Peripheral Nerve Blocks  Age has no effect on duration of motor blockade with bupivacaine spinal anesthesia. The time of onset is decreased, however, and spread is more extensive with hyperbaric bupivacaine solution. In Epidural anesthesia, time of onset is shorter, and extent of block is greater.  Reduced plasma clearance of local anesthetics observed in elderly patients can become a factor during repeated dosing and continuous infusion techniques prompting a reduction in top-up doses and infusion rates.
    • Anesthetic Technique . It is recommended to use shorter acting anesthetics, opioids, and muscle relaxants in caring for elderly patients. When comparing inhaled anesthetics, there does not seem to be a significant difference in recovery profile of cognitive function. Desflurane is associated with the most rapid emergence.  Studies have shown that elderly patients can safely receive controlled hypotensive epidural anesthesia (MAP range 45 to 55 mm Hg) during orthopedic procedures without increased risk.  Controversy surrounds the question of whether better outcomes are obtained when invasive hemodynamic monitoring is used to optimize hemodynamics and fluid therapy.
    • Regional versus General Anesthesia  Specific effects of regional anesthesia may provide some benefit. First, regional anesthesia affects the coagulation system by preventing postoperative inhibition of fibrinolysis. Regional anesthesia may decrease the incidence of DVT after total hip arthroplasty. In lower extremity revascularization, regional anesthesia is associated with a decreased incidence of postoperative graft thrombosis compared with GA. Second, the hemodynamic effects of regional anesthesia may be associated with decreased blood loss in pelvic and lower extremity surgery. Third, regional anesthesia does not require instrumentation of the airway and may allow patients to maintain their own airway and level of pulmonary function.  Use of regional anesthesia does not seem to decrease the incidence of postoperative cognitive dysfunction compared with general anesthesia.
    • Postoperative Considerations  The incidence of common postoperative morbidities is 17% for atelectasis, 12% for acute bronchitis, 10% for pneumonia, 6% for heart failure or myocardial infarction (or both), 7% for delirium, and 1% for new focal neurologic signs.  Elderly patients may be at higher risk for aspiration secondary to the progressive decrease in laryngopharyngeal sensory discrimination.  In addition, dysfunctional swallowing predisposes elderly patients to aspiration. Swallowing dysfunction after cardiac surgery is closely associated with the use of TEE and carries with it a 90% rate of pulmonary aspiration and pneumonia.  Pulmonary complications are the third leading cause of postoperative morbidity in elderly patients undergoing noncardiac surgery.
    • Delirium    The incidence of postoperative delirium in elderly patients varies widely depending on the type of surgery. incidence : 10% after major elective surgery, but higher after cardiac surgery. Delirium is a syndrome characterized by acute onset of variable and fluctuating changes in level of consciousness accompanied by a range of other mental symptoms. “The essential feature of a delirium is a disturbance in consciousness that is accompanied by a change in cognition that cannot be better accounted for by a preexisting or evolving dementia”.  Risk and precipitating factors for delirium : include : cognitive impairment or depression, sleep deprivation, immobility, polypharmacy, pain, ICU admission, visual impairment, hearing impairment, and dehydration  Anesthetic interventions include: .. correction of metabolic and electrolyte disorders .. perioperative continuation of pharmacologic therapy for neuropsychiatric disorders. .. avoiding triggering agents: drugs (e.g., anticholinergics) or inadequately controlled pain.  Delirium has been associated with greater intraoperative blood loss, postop. blood transfusions, and postop. HCT less than 30%.
    • Postoperative Cognitive Dysfunction  Short-term changes involve multiple cognitive domains, such as attention, memory, and psychomotor speed.  Cardiac surgery is associated with a higher incidence of cognitive decline compared to major non-cardiac surgery.  Predictors of early postoperative cognitive decline include: age, low educational level, preoperative cognitive impairment, depression, and surgical procedure.  Short-term cognitive dysfunction may be attributed to: microemboli (especially with cardiac surgery), hypoperfusion, systemic inflammatory response (CPB), anesthesia, depression, and genetic factors.  Postoperative cognitive decline after major non-cardiac surgery is reversible in most cases, but may persist in approximately 1% of patients.  long-term cognitive changes may be related to underlying cerebrovascular disease risk factors, such as blood pressure, cholesterol, and DM.
    • Treatment of Acute Postoperative Pain  Experimental and clinical studies provide support for the notion of an age-related decrease in pain perception.  Evaluation of pain, in a severely cognitively impaired individual, is difficult even for a geriatrician  The combination of pain assessment and drug dose adjustment provides challenges in the management of postoperative pain in elderly patients.  Several general principles should be kept in mind when managing frail elderly patients. First, it is important to try to incorporate multiple modalities of analgesia, such as intravenous PCA and regional nerve blocks. Second, the use of site-specific analgesia is a helpful adjunct: local nerve blocks for UL surgeries and neuraxial analgesia or intercostal nerve block for thoracotomy. Third, whenever possible, use of narcotic sparing drugs : NSAIDs and paracetamol, should be used : keeping in mind, however, the alterations in dose requirements that occur with age.
    •  Chronological age is a poor predictor of physiologic age Geriatric Anesthesiology Charles H. McLeskey
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