[Pharmacology in elderly patients].
The increasing population of elderly patients has special anesthesia care needs. In order to meet those, the pharmacological aspects of aging must be defined. A drug entering the body will generate a blood concentration, then be distributed to the tissues, inducing a pharmacological response. The determinants of blood concentration are absorption when the drug is not administered intravenously, distribution and elimination. Absorption is scarcely affected by ageing. On the contrary, the reduction of the lean mass as well as modifications of the plasma protein concentrations of binding deeply modify distribution. The main organ of drug metabolism is liver. Liver size and hepatic blood flow are reduced in elderly patients. Ageing induces heterogeneous modifications of metabolic pathways. Phase I reactions (oxidation, reduction and hydrolysis) are often slowed down, while phase II reactions (acetylation and conjugation) remain unaffected. Glomerular filtration rate is also reduced in elderly patients. Nevertheless plasma creatinine concentration remains close to the values observed in young healthy patients because of the reduction of the lean mass. The pharmacological response can be affected by the physiological modifications observed with ageing: metabolic rate is reduced, which diminishes the amount of drug necessary to achieve anesthesia. Cardiac index is very often reduced, but the major fact is a very large variability of cardiovascular function and an important reduction of functional reserve. Vascular compliance is diminished, and peroperative arterial pressure can be unstable. Respiratory function is also altered: vital capacity is reduced and hypoxemia frequently observed. Airway protective reflexes are impaired, enhancing the risk of inhalation particularly during recovery.
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Département d'Anesthésie et de Réanimation Chirurgicale, Hôpital Bichat, Paris.
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism* / Q000502:physiology; D000777:Anesthetics / Q000493:pharmacokinetics / Q000494:pharmacology*; D001481:Basal Metabolism; D005919:Glomerular Filtration Rate; D006439:Hemodynamics; D006801:Humans; D008099:Liver / Q000378:metabolism; D012119:Respiration; D014018:Tissue Distribution
D000777:Anesthetics
Pharmacologie du sujet âgé.