Anaes · Applied cardiovascular & respiratory physiology
Applied physiology of the elderly
Also known as Geriatric physiology · Ageing and anaesthesia · Frailty · Elderly pharmacology · MAC reduction in elderly · Postoperative cognitive dysfunction
Ageing changes every organ system, reducing physiological reserve and increasing the sensitivity to anaesthetic drugs, and the elderly patient is the fastest-growing surgical demographic. The framework rests on five exam-critical ideas: the cardiovascular system loses vessel elasticity (raising systolic BP, lowering diastolic, widening pulse pressure) and beta-receptor sensitivity, reducing cardiac reserve; the respiratory system loses chest wall compliance and hypoxic ventilatory drive, worsening V/Q mismatch and increasing postoperative pulmonary complications; the renal and hepatic systems decline (reduced GFR, reduced drug clearance), prolonging drug action; the central nervous system loses mass and sensitivity (MAC falls 30 to 50 percent from age 20 to 80, and the elderly are at high risk of postoperative delirium and cognitive dysfunction); and pharmacokinetics change (more body fat increases Vd for lipophilic drugs, less albumin raises free drug fraction, and slower clearance prolongs every drug) — so the elderly need less drug, given more slowly, with careful monitoring. Built on the elderly intrathecal morphine study (Bursik 2026), the geriatric pulmonary complications study (Han 2026), the frailty outcomes study (Cho 2026), the age-vs-risk study (Girnyi 2026), the frailty cardiac risk study (Chatziperi 2026), and the EEG sedation study (Popovici 2026).
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Red flags
- MAC falls about 6 percent per decade after age 40, so an 80-year-old needs about 30 to 50 percent less volatile agent than a 20-year-old — over-sedation and delayed emergence are the commonest errors.
- The elderly patient has reduced beta-receptor sensitivity and reduced baroreflex sensitivity, so they tolerate hypovolaemia and vasodilation poorly — induction hypotension is common and dangerous.
- Postoperative delirium and postoperative cognitive dysfunction (POCD) are common in the elderly after major surgery and are associated with longer hospital stay, higher mortality and cognitive decline — the anaesthetic technique (depth, drugs, inflammation) may contribute.
- Frailty (a reduced physiological reserve across multiple systems, assessed by tools like the Clinical Frailty Scale) is a stronger predictor of postoperative outcomes than chronological age — a frail 70-year-old is at higher risk than a fit 85-year-old.
- The elderly have less albumin (more free drug for the same total concentration) and slower clearance (especially Phase I oxidation), so every anaesthetic drug lasts longer — titrate carefully and expect delayed emergence.
Meet the patient
An 85-year-old with a fractured neck of femur comes to your list. You reach for the propofol dose you learned at thirty — two milligrams per kilogram — and her blood pressure collapses on induction. The stiff left ventricle could not compensate, the beta-receptors did not answer, and the baroreflex was blunted. She is the topic in one patient: less reserve everywhere, more sensitivity to every drug.[1]
Hold the one idea: age is not a disease — loss of reserve is. Every system change below is a loss of buffer, and the anaesthetic technique that survives an elderly list is slower, smaller, warmer and more monitored.[1]
References6ShowHide
- [1]Buršík D, Romanová T, Lečbychová K, et al. Low-Dose Morphine Intrathecal Analgesia in Elderly Patients with Hip Fracture Undergoing Single Spinal Anesthesia: A Randomized Controlled Trial Local Reg Anesth, 2026.PMID 42152855
- [2]Han X, et al. Prediction of Postoperative Pulmonary Complications in Geriatric Patients with Hip Fracture Using Lung Ultrasonography Score and Diaphragmatic Mobility Clin Interv Aging, 2026.PMID 42078008
- [3]Cho J, et al. A High Frailty Burden is a Strong Predictor of Adverse Postoperative Outcomes in Geriatric Lumbar Spine Surgery: A Retrospective Cohort Study Global Spine J, 2026.PMID 42359918
- [4]Girnyi S, et al. Does Chronological Age Adequately Stratify Perioperative Risk? A Prospective Multicenter Cohort Study Using Frailty and Handgrip Strength J Clin Med, 2026.PMID 42279048
- [5]Chatziperi A, et al. Frailty Status and Preoperative Cardiac Risk Stratification in Older Adults Undergoing Noncardiac Surgery: A Multicenter Prospective Cohort Study J Am Heart Assoc, 2026.PMID 42261947
- [6]Popovici SE, et al. EEG-Derived Entropy Monitoring During Propofol Sedation for ERCP: Sedation Profiles, Age-Related Effects, and Implications for Procedure-Specific Target Ranges Medicina (Kaunas), 2026.PMID 42356061