Anaesthesia in the Elderly

Quick Answer

Geriatric anaesthesia (age >65-70) requires understanding of age-related physiological changes and pharmacokinetic/pharmacodynamic alterations. Cardiovascular: Reduced compliance, diastolic dysfunction, fixed stroke volume (HR-dependent CO), impaired baroreceptor reflex, coronary disease common. Respiratory: Reduced FRC, chest wall stiffness, V/Q mismatch, reduced O₂ reserve, blunted ventilatory response to CO₂. CNS: Reduced brain volume, increased sensitivity to anaesthetics, risk of delirium and POCD. Pharmacokinetics: Reduced muscle mass (↓Vd for water-soluble drugs), increased fat (↑Vd for lipophilic drugs), reduced hepatic/renal clearance. Pharmacodynamics: Enhanced sensitivity to most anaesthetics (50% dose reduction often needed). Key principles: Multimodal analgesia (minimize opioids), regional techniques preferred, TIVA (reduce delirium vs volatile), avoid benzodiazepines (delirium), active warming (impaired thermoregulation), DVT prophylaxis, early mobilization, delirium prevention (orientation, sleep hygiene, glasses/hearing aids, avoid restraints). [1-10]

Physiological Changes with Aging

Cardiovascular System

Structural Changes:

• Vascular stiffening: Reduced compliance (systolic hypertension, widened pulse pressure)
• Left ventricular hypertrophy: Concentric remodeling, diastolic dysfunction
• Valvular calcification: Aortic stenosis, mitral annular calcification
• Conduction system: Fibrosis, sick sinus syndrome, AV block

Functional Changes:

• Stroke volume: Fixed (cannot compensate by increasing SV)
• Cardiac output: Heart rate dependent
• Baroreceptor function: Impaired (pronounced hypotension with position changes, blunted response to haemorrhage)
• β-adrenergic responsiveness: Reduced (impaired response to stress, exercise)
• Coronary flow reserve: Reduced

Clinical Implications:

• Hypotension poorly tolerated: Risk of ischemia, infarction
• Tachycardia: May precipitate ischemia (reduced diastolic filling)
• Bradycardia: Reduced CO
• Positioning: Slow changes (prevent orthostatic hypotension)
• Fluid management: Precise (risk overload with diastolic dysfunction, risk underfill with fixed SV)

Respiratory System

Structural Changes:

• Chest wall: Kyphosis, calcified costal cartilages (↓compliance)
• Lungs: Loss of elastic recoil, emphysematous changes
• Closing volume: Increases, encroaches on tidal volume
• FRC: Reduced

Functional Changes:

• Vital capacity: Reduced
• FEV₁/FVC: FEV₁ declines (↓airway elastic recoil)
• V/Q mismatch: Increased (basal atelectasis, reduced hypoxic vasoconstriction)
• PaO₂: Decreases (70-80 mmHg age 70+ acceptable)
• O₂ reserve: Reduced (rapid desaturation with apnoea)
• Ventilatory response: Blunted to hypoxia and hypercapnia
• Airway reflexes: Reduced (aspiration risk)
• Cough: Weaker (muscle weakness, reduced sensitivity)

Clinical Implications:

• Rapid desaturation: Pre-oxygenation essential
• Prolonged apnoea tolerance: Poor
• Atelectasis: Common postoperatively
• Pneumonia risk: Higher
• Extubation: Ensure fully awake, gag reflex present
• Postoperative oxygen: Often needed longer

Central Nervous System

Structural Changes:

• Brain atrophy: 10-15% loss by age 80 (increased intracranial compliance)
• Neuronal loss: Variable by region
• White matter changes: Leukoaraiosis, reduced connectivity

Functional Changes:

• Neurotransmitters: Reduced (dopamine, acetylcholine, GABA)
• Cognitive reserve: Reduced
• Sleep architecture: Altered (fragile, easily disrupted)
• Sensory: Vision, hearing impairment

Clinical Implications:

• Increased anaesthetic sensitivity: ↓MAC (8% per decade after 40), ↓propofol dose
• Delirium risk: Highest risk population (15-50% postoperative)
• POCD risk: Reduced cognitive function weeks-months postoperatively
• Recovery: Slower emergence, longer PACU stay

Pharmacokinetic Changes

Distribution:

• Body composition:
  • ↓Muscle mass 30-40%
  • ↑Body fat (relative)
  • ↓Total body water
• Water-soluble drugs: ↓Vd (higher initial concentration)
  • Example: Neuromuscular blockers (rocuronium), need 20-30% less
• Lipophilic drugs: ↑Vd (prolonged effect)
  • Example: Benzodiazepines, amiodarone

Protein binding:

• Albumin: Often reduced (↓protein binding, ↑free drug)
• α1-acid glycoprotein: May increase

Metabolism:

• Hepatic mass: Reduced 20-40%
• Hepatic blood flow: Reduced
• CYP450 activity: Reduced 20-30%
• Phase II reactions: Glucuronidation better preserved
• Result: Prolonged effect of hepatically metabolized drugs

Elimination:

• Renal mass: Reduced (GFR declines ~1 mL/min/year after 40)
• GFR: Reduced despite normal creatinine (less muscle mass)
• Creatinine clearance: Calculate (Cockcroft-Gault) or measure
• Result: Drug accumulation (morphine-6-glucuronide, renally cleared drugs)

Pharmacodynamic Changes

Increased Sensitivity:

• General anaesthetics: MAC reduced 6-8% per decade
• Benzodiazepines: Enhanced CNS effects
• Opioids: Increased respiratory depression, sedation
• Anticholinergics: Delirium risk

Mechanisms:

• ↑Sensitivity of CNS receptors
• Reduced cognitive reserve
• Altered pharmacokinetics
• Polypharmacy interactions

Anaesthetic Management

Preoperative Assessment

Comprehensive Geriatric Assessment (CGA):

• Medical: Comorbidities, medications, organ function
• Functional: ADLs, mobility, frailty
• Cognitive: Baseline cognition (MMSE/MoCA), delirium risk
• Social: Support system, discharge planning

Specific Assessments:

• Frailty score: (Fried criteria - weight loss, weakness, exhaustion, slowness, low activity)
  • Frail = higher complication risk
• Cognition: Document baseline (delirium detection requires knowing normal)
• Falls risk: History, osteoporosis, vitamin D
• Polypharmacy: Review all medications
• Nutrition: Albumin, weight loss

Investigations:

• Standard: As indicated
• Additional:
  • ECG: Atrial fibrillation common
  • Echo: If cardiac disease
  • CXR: If respiratory symptoms
  • Hb: Anemia common
  • Renal: Cr + eGFR
  • Glucose: Diabetes common

Medication Management:

• Continue: Cardiac (beta-blockers, antihypertensives), statins, asthma, Parkinson's
• Stop:
  • ACEi/ARBs (risk hypotension)
  • Diuretics (morning of surgery)
  • Metformin (lactic acidosis risk if renal compromise)
  • Anticoagulants (as per bleeding risk)
• Insulin: Reduce morning dose

Premedication

Avoid:

• Benzodiazepines: Delirium risk (especially long-acting)
• Anticholinergics: Glycopyrrolate acceptable, avoid atropine if possible
• Heavy sedation: Respiratory depression, delirium

If needed:

• Anxiolysis: Low-dose midazolam 0.5-1 mg IV only if essential
• Pain: Paracetamol, consider nerve block
• Nausea prophylaxis: Dexamethasone, ondansetron

Induction

Agents:

• Propofol: Reduce dose 20-30%, risk hypotension (give slowly)
• Etomidate: Hemodynamically stable, good choice if cardiovascular concern
• Ketamine: Useful if hypotension risk (hemodynamically supportive)
• Thiopental: Rarely used

Technique:

• Slow induction: Reduces hypotension
• Reduced doses: All induction agents
• Airway: Higher aspiration risk (RSI often indicated)
• Position: Careful (baroreceptor impairment)

Maintenance

Technique:

• TIVA (propofol): Preferred over volatile
  • Reduced delirium vs sevoflurane/isoflurane (evidence mixed but trending toward benefit)
  • Faster emergence
  • Less PONV
• Balanced: If used, low-dose volatile (<0.5 MAC)
• Opioids: Reduced doses, short-acting preferred (fentanyl, remifentanil)
  • Avoid morphine (active metabolites accumulate)
  • Use tramadol cautiously (seizure risk)

Monitoring:

• Standard +:
  • Arterial line (if long case, hemodynamic lability)
  • BIS (prevents under/overdose)
  • Temperature (active warming essential)
• Neuromuscular: Quantitative monitoring (TOF) - prolonged effect common

Fluid Management:

• Goal-directed: SVV, PPV if available
• Restrictive: Evidence supports less fluid (reduce complications)
• Careful: Risk overload (diastolic dysfunction) and under-resuscitation (fixed SV)

Temperature:

• Impaired thermoregulation: Reduced shivering threshold, vasoconstriction
• Hypothermia risk: High (20-30% without active warming)
• Active warming: Forced air essential
• Target: >36°C

Regional Techniques

Preferred when appropriate:

• Benefits: Reduced systemic drug load, better analgesia, less delirium, faster mobilization
• Considerations:
  • Positioning challenges (arthritis, contractures)
  • Anticoagulation (falls common)
  • Postoperative confusion (reduce opioid needs)

Specific blocks:

• Spinal/epidural: Excellent for lower limb, abdominal
• Peripheral: Upper/lower limb surgery
• Caution: Falls risk if lower limb motor block

Emergence

Goals:

• Smooth: Reduce coughing (BP spikes)
• Rapid orientation: Reduce delirium
• Adequate analgesia: Multimodal
• Full reversal: Neuromuscular blockade

Technique:

• Reversal: Sugammadex (rocuronium) faster than neostigmine
• Opioids: Titrate carefully (respiratory depression)
• Extubation: Awake, following commands (airway reflexes impaired)
• Oxygen: Postoperatively (V/Q mismatch)

Postoperative Care

Delirium Prevention and Management

Prevention (Evidence-Based):

1. Orientation: Clocks, calendars, windows, frequent reorientation
2. Sleep hygiene: Non-pharmacological sleep protocol (warm drink, relaxation, reduce noise at night)
3. Sensory aids: Glasses, hearing aids (ensure in use)
4. Hydration: Adequate fluids
5. Mobilization: Early ambulation
6. Avoid:
   • Restraints (increase delirium)
   • Benzodiazepines
   • Anticholinergics
   • Unnecessary lines/tubes
7. Analgesia: Adequate (pain causes delirium, oversedation causes delirium - balance)

Assessment:

• CAM (Confusion Assessment Method): Screening tool
• RASS: Richmond Agitation-Sedation Scale
• Document: Type (hyperactive, hypoactive, mixed), fluctuation, severity

Treatment:

• Non-pharmacological first: All prevention measures
• Pharmacological (if distress/aggression):
  • Haloperidol 0.5-1 mg PO/IV (monitor QT)
  • Quetiapine 12.5-25 mg (less EPS, sedating)
  • Avoid benzodiazepines (unless alcohol/benzo withdrawal)
• Search for cause: Infection, hypoxia, pain, urinary retention, constipation, medications

Pain Management

Multimodal Strategy:

• Paracetamol: 1 g q6h (hepatically safe in appropriate doses)
• NSAIDs: Cautious use (renal, GI, cardiovascular risk) - celecoxib safer
• Gabapentinoids: Pregabalin 75 mg (reduce opioid needs)
• Regional: Continued if catheter
• Opioids:
  • Lowest effective dose
  • Short-acting (oxycodone, avoid morphine)
  • Monitor sedation
• Avoid: Meperidine (pethidine) - neurotoxic metabolite (norpethidine)

Other Postoperative Issues

Cognitive Dysfunction (POCD):

• Definition: Cognitive decline measurable weeks-months postoperatively
• Risk factors: Age, low education, prior cognitive impairment, complexity of surgery
• Prevention: Regional anesthesia may reduce (evidence mixed)
• Outcome: Usually resolves over months

Falls:

• Prevention: Walking aids, assistance, bed alarms
• Bone protection: If on long-term steroids, osteoporosis treatment

Urinary Retention:

• Common: Anticholinergics, opioids, immobility
• Management: Bladder scan, catheter if >400-500 mL

Constipation:

• Prevention: Early mobilization, fluids, fiber, laxatives prophylactically if on opioids

DVT Prophylaxis:

• Essential: Age >60 major risk factor
• Mechanical: SCDs
• Pharmacological: LMWH (unless contraindicated)
• Early mobilization

Nutrition:

• Early feeding: As soon as safe
• Supplements: If malnourished preoperatively

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Patients

Elderly Health Disparities:

• Earlier onset: Chronic disease at younger ages ("50 is the new 70")
• Life expectancy: 10-15 years lower
• Comorbidity: Higher rates diabetes, renal disease, cardiovascular disease

Cultural Considerations:

• Family involvement: Extended family in decision-making
• Communication: Interpreter if needed, clear explanations
• Pain expression: May be stoic - ensure adequate analgesia
• Delirium: May present differently in different cultural contexts
• Discharge planning: Return to remote communities - ensure support

Māori Health Considerations

Health Equity:

• Life expectancy disparities
• Earlier onset chronic disease

Cultural Safety:

• Whānau involvement: Critical for elderly Māori
• Karakia: Spiritual support if requested
• Communication: Respectful, clear
• Discharge: Coordination with primary care and whānau

ANZCA Final Exam Focus

Key Concepts

Physiological Changes:

• Cardiovascular: Stiff vessels, diastolic dysfunction, fixed SV, impaired baroreceptors
• Respiratory: Reduced FRC, atelectasis, rapid desaturation, blunted responses
• CNS: Brain atrophy, reduced cognitive reserve, increased drug sensitivity
• Pharmacokinetics: Reduced muscle, increased fat, reduced hepatic/renal function
• Pharmacodynamics: Enhanced sensitivity (↓MAC, ↓drug doses)

Management Principles:

• Reduced drug doses (induction, maintenance, analgesia)
• TIVA preferred (reduces delirium vs volatile)
• Regional techniques (reduce systemic drugs)
• Multimodal analgesia (minimize opioids)
• Active warming
• Delirium prevention (orientation, sleep, sensory aids, avoid restraints)
• Falls prevention

Common Exam Questions

"Why are elderly patients more sensitive to anaesthetics?"

• Pharmacokinetic changes: Reduced Vd for water-soluble drugs (higher plasma concentration), increased Vd for lipophilic drugs (prolonged effect), reduced clearance
• Pharmacodynamic changes: Increased receptor sensitivity, reduced cognitive reserve
• CNS changes: Brain atrophy, reduced neurotransmitters
• Combined effect: Need 20-50% dose reduction

"How would you prevent postoperative delirium in an elderly patient?"

• Preoperative: Document cognitive baseline, optimize medical conditions, review medications
• Intraoperative: TIVA (may reduce delirium), regional techniques, minimize anticholinergics/benzodiazepines, maintain normothermia, adequate analgesia
• Postoperative: Orientation protocols, sleep hygiene, glasses/hearing aids, early mobilization, adequate hydration, avoid restraints, treat pain adequately (but avoid oversedation)

"What are the risks of general anaesthesia in the elderly?"

• Cardiovascular: Hypotension, arrhythmias, myocardial ischemia
• Respiratory: Atelectasis, pneumonia, respiratory failure
• Neurological: Delirium, POCD, stroke
• Other: DVT, falls, urinary retention, constipation, functional decline

"How does the MAC change with age?"

• Decreases approximately 6-8% per decade after age 40
• 80-year-old has ~30-40% lower MAC than 40-year-old
• Due to CNS changes, not pharmacokinetic

References

1. ANZCA. PS55. Recommendations on Monitoring During Anaesthesia. 2020.
2. Sieber FE et al. Postoperative delirium in the elderly. Anesthesiology. 2018;128(4):738-750.
3. Deiner S et al. Anesthesia for the elderly. In: Miller RD (ed). Miller's Anesthesia. 9th ed. Elsevier; 2020:2809-2830.
4. Mohanty S et al. Optimal perioperative management of the geriatric patient. Mayo Clin Proc. 2016;91(4):566-572.
5. Aldecoa C et al. European Society of Anaesthesiology evidence-based guideline on postoperative delirium. Eur J Anaesthesiol. 2017;34(4):192-214.
6. Inouye SK et al. The Hospital Elder Life Program: A multicomponent targeted intervention. N Engl J Med. 1999;340(9):669-676.
7. Hughes CG et al. American Geriatrics Society abstracted clinical practice guideline. J Am Geriatr Soc. 2015;63(1):142-150.
8. ATSI Health. Older Aboriginal and Torres Strait Islander people. Australian Institute of Health and Welfare; 2020.