Antidiuretic Hormone Response in the Elderly
In the elderly, there is increased antidiuretic hormone response, which is the correct answer (B).
Physiological Changes in Elderly Affecting ADH Response
- Aging is associated with altered water homeostasis, with elderly individuals demonstrating increased antidiuretic hormone (ADH) response compared to younger adults 1
- This increased ADH response occurs despite decreased total body water and more vulnerable water homeostasis in older adults 1
- The enhanced ADH response contributes to the elderly's predisposition to develop hyponatremia, which is more common in this population 1, 2
Mechanisms Behind Increased ADH Response
- Age-related decreases in left ventricular compliance and glomerular filtration rate contribute to altered fluid regulation in elderly patients 3
- Baroreceptor sensitivity decreases with age, leading to impaired volume regulation and potentially inappropriate ADH secretion 3
- Elderly patients have blunted thirst perception, which can lead to compensatory increases in ADH secretion to maintain fluid balance 1
Clinical Implications of Increased ADH Response
- Increased ADH response in the elderly contributes to their higher risk of developing hyponatremia, especially when taking certain medications 2
- Elderly patients are more susceptible to adverse effects of medications affecting water balance due to this altered ADH response 3
- The increased ADH response can lead to inappropriate water retention, particularly in conditions like heart failure which are common in elderly patients 4
Other Age-Related Changes in Fluid Balance
- There is NOT decreased insensible water loss in the elderly (option A is incorrect) 1
- There is NOT increased volume of distribution of water-soluble medications in the elderly (option C is incorrect) - in fact, elderly patients have decreased total body water, which would decrease the volume of distribution for water-soluble drugs 3
- There is NOT decreased volume of distribution of lipid-soluble medications (option D is incorrect) - elderly patients typically have increased body fat percentage, which would increase, not decrease, the volume of distribution for lipid-soluble medications 3
Clinical Considerations
- When prescribing medications for elderly patients, clinicians should account for the increased ADH response and its potential impact on fluid balance 3
- Elderly patients require careful monitoring for hyponatremia, especially when taking medications that can affect ADH secretion or action 1, 2
- Initial doses and subsequent dose titration of medications affecting fluid balance should be more gradual in elderly patients due to their altered ADH response 3