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Geriatric Anesthesia

Geriatric Anesthesia. SC 李侑珊 石博元 VS 鄭雅蓉. Brief History. 99 y/o female with Large bedsore for 5 months s/p debridement Old right femoral fracture s/p Moore hemiarthroplasty on 1995 Osteoporosis Dementia No other systemic illness. CXR. Anesthesia record. Anesthesia record.

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Geriatric Anesthesia

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  1. Geriatric Anesthesia SC 李侑珊 石博元 VS 鄭雅蓉

  2. Brief History • 99 y/o female with • Large bedsore for 5 months s/p debridement • Old right femoral fracture s/p Moore hemiarthroplasty on 1995 • Osteoporosis • Dementia No other systemic illness

  3. CXR

  4. Anesthesia record

  5. Anesthesia record

  6. Age, Minimum Alveolar Anesthetic Concentration, and Minimum Alveolar Anesthetic Concentration-Awake Eger, Edmond I II, MD Anesth Analg. 2001 Oct;93(4):947-53

  7. Geriatric Anesthesia Age related anatomic & Physiologic Changes

  8. Cardiovascular system and Autonomic Nervous System (1) • Decline in the responsiveness of β- receptors - plasma catecholamine level unchanged - decrease in beta-adrenergic receptors density(?) - 75y/o vs. 25y/o, 20% decrease of maximal HR • Progressive replacement of supple, functional cardiac and vascular tissue (a. &v) by stiff, fibrotic material -elevated afterload - elevated systolic BP - LV hypertrophy

  9. Cardiovascular system and Autonomic Nervous System (2) • Decreased cardiac output • Decreased baroreceptor reflex These factors render the elderly patients less capable of defending their CO and BP against the usual periop challenges.

  10. Respiratory System (1) • a decline in elasticity of the bony thorax • Increased residual volume • Decreased vital capacity • Increased dead space • a loss of muscle mass with weakening of the muscles of respiration • FEV1 decreases progressively with aging • ratio of FEV to TLC of the elderly decreases. (70% vs. >80%)

  11. Respiratory system (2) • a decrease in alveolar gas exchange surface • a decrease in central nervous system responsiveness • Ventilatory response to hypercapnia and hypoxia is blunted in the elderly (1/2 of 25y/o) • Thus, we need to increase FIO2 and tidal volume (watch out for oxygen toxicity and barotrauma)

  12. Renal System • Decreased renal mass, mainly in the cortex • Decreased renal blood flow • Due to glomerulosclerosis • RPF and GFR↓ 3. Decreased tubular function • impaired fluid handling • decreased concentrating ability • decreased diluting capacity • impaired sodium handling • decreased drug excretion

  13. Liver • There is a lack of correlation between structural and functional data concerning the aging liver, as a decline in organ volume does not necessarily reflect impaired metabolic function. • Reduced hepatic drug clearance is common in the elderly

  14. Nervous System (1) Effects of aging on the nervous system include: • a general loss of neuronal substance • a decrease in the number of peripheral neurons • muscles innvervated by fewer axons, leading to possible denervation atrophy • conduction velocity is slightly affected by aging (slower)

  15. Nervous System (2) • increased sensitivity to opioid analgesics • decreased cell density, lower cerebral oxygen consumption and lower cerebral blood flow

  16. Geriatric Anesthesia Age related pharmacologic changes

  17. Pharmacokinetic and pharmacodynamic differences in the elderly (1) • Protein binding: • Circulating level of serum protein (especially albumin) decreases in quantity • Qualitative change of serum protein reduce the binding effectiveness of the available protein. • This will lead to higher free drug levels and an enhanced delivery of the drug to the brain.

  18. Pharmacokinetic and pharmacodynamic differences in the elderly (2) • Changes in body compartment • Age-related changes in body composition include a loss of skeletal muscle and an increase in percentage of body fat. • Increased availability of lipid storage sites, this will leads a gradual elution of these agents from the storage sites.

  19. Pharmacokinetic and pharmacodynamic differences in the elderly (3) • Heaptic and renal function • Hepatic and renal function are reduced about 1% per year beyond 30.

  20. Induction Agent (1) • Thiopental • Administration of IV barbiturates produces the peripheral vasodilatation with a moderate BP decrease. • With a decreased baroreceptor reflex and increased vascular wall rigidity, the drug may cause a dangerous drop in BP. • In the elderly, elimination half-life is 13-25 hrs(6-12 hrs in the young) • The thiopental dose requirement may decrease 25-75 percent.

  21. Induction Agent (2) • Methohexial • Methohexial is rapid acting and has a higher hepatic clearance rate and shorter elimination time than thiopental. • More suitable for outpatient surgery.

  22. Induction Agent (3) • Propofol • Propofol produces greater decrease in systemic BP than thiopental . • Injecting the propofol slowly with sufficient time can minimize the effect of cardiovascular depression. • Studies show patients older than 80 exhibit less post-anesthetic mental impairment with propofol than other agents. • Induction: using 1.2-1.7 mg/kg in the elderly (versus 2.0-2.5 mg/kg in younger patients)

  23. Muscle Relaxant (1) • Aging affects the neuromuscular junction in many ways: • The distance of the junction ↑ • The number of ACh vesicle ↓ • Receptors of ACh ↓ • Sensitivity of ACh receptors —

  24. Muscle Relaxant (2) • Succinylcholine • This agent is metabolized by pseudocholinesterase which is not affected by the aging process. • The response of succinylcholine is unalterd with aging.

  25. Muscle Relaxant (3) Non-depolarizing muscle relaxant • Long-acting agents: • Metocurine, pancuronium (renal)↑ • Doxacurium, pipecuronium (renal) — • Intermediate-acting agents • Vecuronium, rocuronium ↑ • Atracurium, cisatracurium (Hoffmann elimination)—

  26. Muscle Relaxant (4) • The use of the intermediate-acting agent is prudent, because even the duration of one single dose of long-acting agent may be too prolonged for the planned surgery. • Fewer dose of non-depolarizing muscle relaxant will be required.

  27. Opioids (1) • Increases in potency for alfentanil, fentanyl, and remifentanil were demonstrated in EEG studies. • A reduction in dosage in the elderly would be recommended.

  28. Opioids (2) • Fentanyl • Dose should be reduced to ½ to achieve the same effect. • Alfentanil • Same recommendation as fentanyl.

  29. Volatile agents (1) • Ventilation perfusion mismatch will decrease the rate of action. • Decreased cardiac output will make the onset of the action more rapid. • Recovery from anesthesia with a volatile agent may be prolonged because of an increased volume of distribution (increased body fat).

  30. Volatile agents (2) • The MAC of inhalational agents is reduced by 6% per decade of age over 40 years. • The lower lipid-solubility of sevoflurane and desflurane has advantage in the elderly: • More rapid control of anesthetic depth than higher lipid-solubility agents. • A faster emergence from anesthesia. (desflurane vs. isoflurane: 5.4 vs. 7 mins)

  31. Summary

  32. Anesthesia Record

  33. Thank you for your Attention

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