Hypodipsia of the elderly

Specialty: Geriatrics.

• abolition of thirst
• senile hypodipsia
• adipsia due to aging
• decreased water reflex

Why it occurs

• Anatomical and physiological dysfunction of hypothalamic osmoreceptors associated with intrinsic aging
• Advanced cognitive impairment with the patient's inability to perceive, process or communicate the need to drink fluids
• Cortical sequelae of previous strokes affecting the insula and anterior cingulate gyrus
• Chronic use of loop diuretics or neuroleptic drugs that alter the central perception of body volume status
• Decreased sensitivity of high and low pressure baroreceptors that reduces the neural response to hypovolemia

Initial workup

Measurement of plasma osmolality (frequently elevated above 295 mOsm/kg) and urinary osmolality; serum sodium determination (search for hypernatremia), potassium, blood urea nitrogen (BUN) and creatinine (analyzing the BUN/creatinine ratio greater than 20); urinary density; recording and strict 24-hour fluid balance by nursing or caregivers; assessment of baseline cognitive status using Lobo's MEC test.

Standard management

• 0.9% saline solution — administered via subcutaneous hypodermoclysis technique at a rate of 50-100 ml/hour as a safe and well-tolerated alternative at home for moderate rehydration
• 0.45% hypotonic saline solution — slow intravenous route for the correction of severe hypernatremia, meticulously calculating the free water deficit to avoid a decrease in sodium greater than 10 mEq/L in 24 hours, preventing cerebral edema
• Use of commercial food thickeners in patients who associate neurogenic or mechanical dysphagia to enable safe oral hydration.