Diagnosing and Managing Hypernatremia


Question

Could you pl write how to differentiate if hypernatremia is from hypo or adypsia versus reset osmostat in an individual with hx of head injury in the past and if the history about thirst is limited because of mental retardation. Also pl let me know how to manage hypernatremia from reset osmostat. padmalatha berikai

Response

This is a difficult problem, and in principle it may not be possible to differentiate hypodipsia from a reset osmostat (indeed, they may be pathophysiologically the same process). Managing patients with adipsia is one of the most challenging to neuroendocrinologists, and this is especially the case with patients less mentally astute. I generally admit them for a few days and get a baseline weight and fluid intake which keeps the serum osmolality in the normal range, and then instruct their carers to keep them to this input with at least weekly weighing. If their weight departs from the determined set-point then the fluid intake can be adapted accordingly. If possible, a check on the osmolality at intervals will allow them to see if the balance is working out. This means a lot of input from the carer, but the only patients who do well long-term are those with good home input. Ashley Grossman, MD