Geriatric Physiology

Question 1

Age related changes in renal physiology

Answer 1

Decreased renal mass
- Cortical > medulla

Decreased renal blood flow
- 10%/decade

Reduced max and min urine osmolality

Reduced Sodium conservation
–> hyponatraemia with dehydration

Question 2

Age related changes in lower urinary tract

Answer 2

Reduced bladder volume

Increased detrusor hyperactivity –> URGE INCONTINENCE

Decreased urethral outflow resistance in females and increased urethral outflow resistance in males

Increased nocturnal polyuria - reduced ADH

Question 3

Age related changes in adrenal function

Answer 3

Basal renin levels decreased 30-50%

Basal aldosterone levels decreased 30-50%
–> increased risk of hyperkalaemia

Question 4

Age related changes to the liver

Answer 4

Reduced volume, weight and blood flow

Reduced blood flow interferes with drug clearance

Normal aging does not change LFTs or Albumin

Question 5

Age related changes to the heart

Answer 5

Cardiac output does not change

Decreased maximal HR

Decreased arterial compliance and valve mobility –> increased systolic BP

Question 6

Age related changes to the lungs

Answer 6

Structural changes and 20% reduction in surface area

Fall in FEV1 and FVC

Increased residual volume

Blunting of response to declining PaO2 and increasing PaCO2

Question 7

Age related changes to immune function

Answer 7

Decreased antibody response

Auto-antibodies more common

Impaired T cell response

Question 8

Age related changes to endocrinology

Answer 8

Increased insulin resistance –> increased insulin secretion

Rise in FSH and LH

Increased PTH –> increased bone resorption

Question 9

Pharmacokinetics

Answer 9

Absorption remains similar

Reduced first pass metabolism with reduced hepatic blood flow

Reduced muscle mass and increased fat mass

• -> lipid soluble drugs have increased VoD and half life
• -> water soluble drugs have reduced VoD and higher concentrations

Reduced hepatic clearance

Reduced renal clearance