Considerations for geriatric anaesthesia

Question 1

When is an animal geriatric?

Answer 1

• Dogs > 10 years
• Cats > 12 years
• > 80% anticipated life span

Question 2

What CNS changes are seen in the geriatric patient?

Answer 2

• Progressive reduction in CNS activity
• Visual and auditory acuity reduced
• Reduced amount of neurotransmitters and receptors
• Thermoregulatory ability reduced

Question 3

How does the geriatric patient have altered drug disposition?

Answer 3

• Decreased muscle mass
• Increase adipose tissue
• Decreased albumin
• Decreased total body water
• MAC values decreased by 30%
• Hepatic elimination decreased
• Renal reserve is decreased
• Extradural injections will spread more cranially

Question 4

What cardiovascular changes are seen in the geriatric patient?

Answer 4

• Cardiac performance decreases gradually with age
• Reduced baroreceptor activity
• Increased vagal tone
• Reduced cardiac output and slower circulation time
• Cardiac output become preload dependant
• More prone to hypotension or volume overload
• Chronic valvular disease
• Autonomic responses are slower
• Exercise tolerance tests may be influenced by other disease processes

Question 5

What Respiratory changes are seen in the geriatric patient?

Answer 5

• Reduced functional residual capacity
• Increased risk of atelectasis and V/Q mismatch
• Diffusion capacity is decreased
• Chest wall compliance decreased
• Increased incidence of respiratory tract pathologies

Question 6

What Renal changes are seen in the geriatric patient?

Answer 6

• Reduced number of functional nephrons
• Reduced cardiac output → reduced renal blood flow
• Reduced renal mass
• Their ability to correct for fluid, electrolyte and acid-base derangements is less.
• More prone to fluid overload

Question 7

What Hepatic changes are seen in the geriatric patient?

Answer 7

• Reduced cardiac output → reduced liver blood flow
• Reduced hepatic function
• Reduced albumin formation
• Slower drug metabolism
• Less exothermic processes

Question 8

What Endocrinopathies changes are seen in the geriatric patient?

Answer 8

• Increased age does not increase risk of anaesthesia, but increased incidence of
  concurrent disease
• Including some endocrinopathies; canine hypothyroidism, Cushing’s disease,
  diabetes Mellitus, feline hyperthyroidism

Question 9

What can you do prior to an anaesthetic to help stabilise the patient?

Answer 9

• Stabilise as much as possible before anaesthesia.
• If anaesthesia elective, use preceding 2 weeks to improve fitness for GA
• Dieting
• Respiratory disease : Antitussives, mucolytics,bronchodilators
• Renal disease: dietry protein restriction
• Hepatic disease: low protein diets, multivitamins

Question 10

What considerations for the premed should there be?

Answer 10

• Require lower doses of sedative drugs
• Short acting drugs
• Benzodiazepines may be useful