desalination

Q: What is "desalination"?

Answer: Desalination is a phenomenon when a volume expansion occurs due to a large infusion of isotonic fluid. Simultaneously, if the antidiuretic hormone (ADH) level is high, it increases sodium excretion in the urine, leading to acute serum hyponatremia. This is common post-operatively due to surgery-induced syndrome of inappropriate antidiuretic hormone (SIADH). 

To make things worse, a clinician unaware of this underlying pathology may administer further isotonic saline to counter hypotension and set up a vicious cycle of worsening acute hyponatremia.

#electrolytes

Reference:

Steele A, Gowrishankar M, Abrahamson S, et al. Postoperative hyponatremia despite near-isotonic saline infusion: a phenomenon of desalination. Ann Intern Med 1997; 126:20.