Geriatric Anesthesia SC 李侑珊 石博元 VS 鄭雅蓉

Brief History 99 y/o female with No other systemic illness 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 Agent Given dose Regular dose fentanyl 1 ml 2 ml propofol 50 mg 80-90 mg rocuronium 20 mg 40 mg atropine 0.4 mg Enlon 28 mg 32-40 mg

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

Age related anatomic & Physiologic Changes Geriatric Anesthesia Age related anatomic & Physiologic Changes

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

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.

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%)

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)

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

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

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)

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

Age related pharmacologic changes Geriatric Anesthesia Age related pharmacologic changes

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.

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.

Pharmacokinetic and pharmacodynamic differences in the elderly (3) Heaptic and renal function Hepatic and renal function are reduced about 1% per year beyond 30. Elimination half-life Drug Young adult Old adult Fentanyl 250min 925min Diazepam 24hrs 72hrs midazolam 2.8hrs 4.3hrs vecuronium 16min 45min

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.

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.

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)

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 —

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.

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)—

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.

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.

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

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).

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)

Summary

Anesthesia Record Agent Given dose Regular dose fentanyl 1 ml 2 ml propofol 50 mg 80-90 mg rocuronium 20 mg 40 mg atropine 0.4 mg Enlon 28 mg 32-40 mg

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