Anaesthesia for the Elderly Patient
"The seventh age of man : second childishness and mere oblivion, sans teeth, sans eyes, sans taste, sans everything" William Shakespeare
The loss of autonomic responses is the most important anaesthetic consideration. The extremes of age have similar problems.
Ageing causes irreversible cell loss and integrated systems lose their reserves.
Age is an independent predictor of perioperative mortality and increases from 1 % in the general population to 8.4% in those aged >80 years. Mortality approaches 50% in major emergency surgery. (NCEPOD) The geriatric patient (age >65 yrs) differs from the young adult.
• Biological age does not correlate with chronological age as it depends on the individual patient and vital organ dysfunction.
• Compensatory mechanisms are inefficient due to reduced physiological reserves. • Concomitant medical diseases further limit baseline functions and accelerate loss of functional reserve in the affected organ.
• Increased medications and altered pharmocokinetics and dynamics, increase the incidence of untoward reactions to anaesthetic drugs and surgical interventions.
Common surgical procedures : Orthopaedic (see page 14. 7) Ophthalmic (see page 17.1-4) Genito-urinary (see page 12.10)
PATHOPHYSIOLOGY OF AGEING Cardiovascular system
• Reduced elasticity of vessels (lead pipe effect) leads to systolic hypertension and high pulse pressures.
• Reduced sympathetic and parasympathetic responses with reduced baroreceptor sensitivity result in reduced resting and maximal heart rates. Poor compensation for hypovolaemia, hypotension, and hypoxia Reduced response to cardiac drugs e.g. atropine, ephedrine
• Myocardial dysfunction and dysrhythmias such as atrial fibrillation, are common. Reduced cardiac contractility, conduction and reserve cause low cardiac output and hypotension at induction.
• Prolonged circulation time causes delayed onset of i.v. drugs but rapid onset of inhalational drugs.
• Iron deficiency anaemia and reduced blood volume
Respiratory function • Pa02
(reduces with age)= 100-(age/4) mmHg. Hypoxaemia is due to low compliance, airway closure when supine at 65years and increasing V /Q mismatch
• Reduced ventilatory response to hypoxia and hypercarbia • Reduced airway reflexes (cough) and tendency to silent aspiration pneumonia • Snoring and desaturation during sleep •
Inefficient muco-ciliary action and atelectasis lead to chest infections.
Renal function • Reduced renal blood flow, glomerular filtration rate and concentrating capacity, affecting the excretion of drugs and fluid balance.
• Impaired autoregulation and tolerance to water and electrolyte overload I underload Hepatic function Reduced hepatic mass, blood flow, albumin, enzyme activity, drug metabolism Metabolic and endocrine function
Basal metabolic rate reduces by 1 % per year after 30 years. Reduced endocrine production cause diabetic and hypothyroid states.
Central nervous system • Impaired communication, unreliable memory, history, hearing (35% ), vision (30%) • Reduced cerebral blood flow (CBF) and impaired autoregulation Dizziness whep looking up while seated indicates atherosclerosis and low CBF.
• Reduced cognitive, motor and sensory function, dementia, Parkinsonism • Autonomic and peripheral neuropathy • More stoic and often shows less anxiety than younger patients • Decreased requirements of anaesthetic agents
Temperature regulation Impaired thermoregulation. Shivering may cause hypoxia. Gastro intestinal Reduced motility, acidity, blood flow. Increased reflux. Malnutrition and dehydration. Skin and bones Skin is fragile, thin and bruise easily (caution during i.v. access) Osteoporosis with decreased bone mass and strength requires careful positioning. Calcified ligaments make central blockade difficult.
Kyphoscoliosis, arthritis, and immobile joints make positioning difficult. Cervical spondylosis makes intubation difficult.
Pharma co kinetics
Reduced lean body mass, body water, blood volume, protein binding Increased total body fat and distribution volume for fat soluble drugs Reduced hepatic and renal blood flow and clearance causing prolonged effects of drugs
Pharmacodynamics •
Volatile agents : reduced MAC and blood gas solubility (faster inhalational induction) Myocardial depressant effects will be exaggerated. Recovery may be prolonged due to the fat reservoir.
• Intravenous induction agents : lower dose requirement, delayed onset and difficult titration due to slow circulation
• Opioids : sensitive, slow elimination, greater respiratory depression • Benzodiazepines : dose requirement reduced. A void diazepam and midazolam. Lorazepam is more suitable.
• Muscle relaxants : atracurium is the best option. Response to drugs is therefore :
• delayed (due to slow circulation) • exaggerated (effects and side effects) • prolonged (delayed excretion) • poorly compensated for
PRE-OPERATIVE ASSESSMENT HISTORY AND EXAMINATION Special features
1. Exercise tolerance and functional ability, 6min walk, shopping (best assessment) 2. Physiological ageing and reduced vital organ function and reserves (ASA, MET) 3. Concomitant diseases : cardiac, vascular, respiratory, renal disease, diabetes mellitus require optimization to reduce mortality and morbidity.
4. Polypharmacy and possible interactions (30% take> 3 drugs/day) 5. Level of hydration (dehydration is common) 6. Limited head extension due to cervical spondylosis Dentures, missing and loose teeth
7. Mental status (for suitability of local anaesthesia) 8. Consider possibility of medical disease as the cause of fall or trauma 9. Consider duration of bed rest (after fractures) , risk of DVT, pressure sores, pneumonia, urine infection
10. Consider need for pre-operative analgesia
INVESTIGATIONS Routine Full blood count, blood sugar, urea I creatinine, electrolytes, ECG Special
as indicated by history and examination
INTRA-OPERATIVE PERIOD Emergency surgery without optimization increases the risk significantly. Fractures however should be scheduled early (<36h) for day time surgery. Surgery in a dedicated unit with a multi-disciplinary team improves outcome. Consider day care surgery if appropriate. GENERAL ANAESTHESIA (Special problems) Premedication Anxiety and apprehension are less likely. Give lorazepam or temazepam in reduced dose.
Anti ischaemic prophylaxis with 13 blocker therapy with the aim of maintaining the heart rate < 80/min for those with increased risk of ischaemic heart disease. DVT prophylaxis (see page 1.7)
Monitoring ECG Lii and V5
, BP, Sp02 , ETC02
Peripheral nerve stimulation, temperature Venous access Fragile skin and veins need special care
Drugs Choice and dose should be tailored to the individual patient (given very slowly, and not on a mg/kg basis)
Do not • give too much • give too fast • give too frequently • expect normal responses as they will be delayed and exaggerated.
--------~~--~·-· ~· .. Induction
Slow titration as hypotension is likely because compensation is poor, and drug interactions are common.
Airway Difficult to maintain and mask ventilate due to lack of good fit especially if edentulous Difficult intubation due to cervical spondylosis, tempero-mandibular joint dysfunction, loose or deficient teeth Tendency to aspirate during anaesthesia with face mask
Positioning Needs special care due to limited mobility of joints, osteoporosis, and osteoarthritis Risk of tissue and nerve injury as there is little fat.
Maintenance Muscle relaxants allow a low dose of volatile agent. Give IPPV with 50% 0 2
, maintaining normocarbia, avoiding hypocarbia at all costs.
Fluids Poor tolerance for under or overloading Temperature Tendency to hypothermia. Use warming blankets and warm fluid infusions.
REGIONAL ANAESTIIESIA Advantages The elderly accept regional techniques better than the young adult.
Very suitable where limited block is required e.g. TURP and hip surgery Lower incidence of thromboembolism. Less post-operative cognitive defects, CNS and respiratory complications Allows immediate recognition of TIA, TURP syndrome Minimizes bleeding Post-operative pain relief to allow early mobilization Reduced incidence of post-dural puncture headache in the elderly SAB : Use a lateral approach as the ligaments maybe ossified. Use the standard dose. EDB : Lateral approach maybe easier. Reduce the volume oflocal anaesthetic.
CSE : Provides optimum conditions with excellent muscle relaxation for surgery, slow extension of block to minimize hypotension, and post-operative pain relief.
Management on the table
• A void the technique if mentally deranged or uncooperative. • Provide supplemental oxygen. • Avoid intra-operative sedation which causes airway obstruction, respiratory depression and disorientation.
• For hypotension in the first twenty minutes due to vasodilatation, use a vasoconstrictor by infusion rather than fluids, to avoid overload.
Phenylephrine or metaraminol lOmg in 500rnl of saline, titrated to BP.
• Keep a pillow under the patient's knees for comfort. • Assess blood Joss accurately and replace early (consider urinary catheter I CVP).
POST-OPERATIVE PERIOD
1. After GA, do not extubate until ventilation is adequate and the patient is conscious, but avoid bucking on the tube which may cause pulmonary oedema.
2. Continue supplemental oxygen therapy and monitoring till stable. Consider the need for oxygen therapy for the first 3 nights.
3. Keep the patient warm. 4. Keep in the semi-sitting position to improve oxygenation or lateral position if needed to avoid aspiration. Attend to pressure points.
5. Continue drug therapy as required for medical conditions. 6. Give adequate pain relief with regional techniques and nerve blocks. Caution with opiates and NSAID (limit to 3 days and ensure hydration).
7. Allow a relative at the bedside to avoid confusion and disorientation. 8. Return personal items (dentures, spectacles, hearing aids) 9. Give oral feeds as early as possible and ensure hydration (i.v. fluids may overload). 10. Early mobilization, physiotherapy, and DVT prophylaxis
POST-OPERATIVE COGNITIVE DYSFUNCTION Patient factors
: Prior mental status, infections, alcoholics, electrolyte imbalance (low Na, BS), unfamiliar surroundings (ward or ICU), pain, distended bladder
Surgical factors
: C-P bypass, joint replacement, carotid endarterectomy, aortic cross clamping due to ischaemia or embolization
Anaesthetic factors : Commoner after GA, opiate, benzodiazepine, sedative, hypoxia