Chp. 69: Aging Patients Flashcards
Biological aging
The progressive accumulation of changes with time associated with or responsible for the ever-increasing susceptibility to disease and death
Geriatric
Statement of health status and not a specific age
What are the life stages of dogs?
Puppy (up to 6-9 months), Young adult (up to 3-4 years), Mature adult (up until last 25% of lifespan), Senior (last 25% of lifespan), End of life (terminal stage depending on pathologies)
What are the life stages of cats?
Kitten (birth to 1 year), young adult (1-6 years), mature adult (7-10 years), senior (>10 years), end of life (variable)
Describe the age-related changes to the CV system.
Reduced cardiac reserve, blood volume, blood pressure, and CO
Reduced ability to compensate for CV changes
Describe the impact of age-related CV changes on anesthesia.
Slower onset of IV general anesthesia with increased risk of overdose
Inotropic and BP support may be needed
Describe the age-related changes to the respiratory system.
Loss of lung elasticity and decrease in chest wall compliance
Increase in FRC with closing capacity increasing at a comparatively faster rate
Increased V/Q mismatching
Describe the impact of age-related respiratory changes on anesthesia.
Risk of hypoxemia and hypercapnia, respiratory support may be required
Describe the age-related changes to the neurologic system.
Reduction in brain mass and decreased neurotransmitters
Reduced cerebral blood flow
Altered central thermoregulation
Describe the impact of age-related neurologic changes on anesthesia.
Decreased anesthetic requirement, increased risk of hypothermia
Describe the age-related changes to the renal system.
Decreased renal function secondary to a reduction in GFR, RBF, and renal mass
Describe the impact of age-related renal changes on anesthesia.
Less tolerant of fluid losses, allow water consumption until premedication
Describe the age-related changes to the hepatic system.
Reduced hepatic mass and perfusion
Describe the age-related changes to the immune system.
Immunosenescence
What does decreased cardiac reserve look like in aging animals?
CO decreased by 30%, maximum HR and oxygen consumption in response to exercise is reduced, ventricular contraction is reduced, myocardial stiffness is increased
What is the implication of a decrease in CO for anesthesia in aging patients?
Increase in injection site to brain circulation time, so drugs should be given slowly to avoid an overdose
How should a rightward shift in autoregulation due to chronic hypertension be addressed?
Maintain BP within 30% of presenting BP to ensure perfusion to vital organs
What is the consequence of closing capacity increasing faster than FRC in aging animals?
At normal tidal volume, areas of low or zero ventilation to perfusion ratios may exist
Why are aging animals at higher risk of aspiration pneumonia?
Decreased pharyngeal muscle tone and less effective upper airway reflexes
Emergence delirium
Restlessness in the immediate postoperative period and can occur in any age group, is usually short lived, and can be managed with sedation with no long-term effects
Postoperative delirium
“Short-term and transient” issue and is characterized by changes in consciousness and cognition, disorientation, anxiety, and fear, which may fluctuate
Appears 2-7 days following anesthesia
Post-operative cognitive dysfunction
Longer-term changes in cognition after surgery, usually self-limiting
What is the impact of sarcopenia in aging animals undergoing anesthesia?
Decreases ability of older patients to generate heat, leaving them vulnerable to hypothermia
May maintain higher plasma concentrations of drugs for longer periods due to loss of muscle “sink”
Why is the central compartment and central volume of distribution decreased in aging patients?
Total body water, plasma, and intracellular volume are reduced
What are potential consequences of shivering?
Hypoxemia, lactic acidosis, and catecholamine release
Frailty
Multidimensional syndrome characterized by decreased physiologic reserve, diminished resistance to stressors, a state of vulnerability, or a “deficit of homeostatic capabilities”
What is the relationship between age and anesthetic risk?
Increased risk of anesthetic-related death with increasing age INDEPENDENT of patient physical status
Describe use of propofol in aging animals.
Blood levels of propofol are higher despite lower dosage and clearance is slower
Describe use of ketamine in aging animals.
High therapeutic index, anesthetic-sparing, antinociceptive, and antihyperalgesic
Mitigates post anesthetic hypothermia
How much does MAC decrease for each 1C fall in temperature?
4-5%
Postoperative residual curarization (PORC)
Predisposes to hypoxemia and upper airway obstruction in elderly patients
Due to altered pharmacokinetics
Why are aging patients more sensitive to inhalational agents?
Age-related changes in brain, including changes in receptor numbers or functions
Change in NMDA receptor binding to glutamate (decreased)
