Isotonic Dehydration

How to Cite This Chapter: Mathew A, Kokot F, Franek E, Drabczyk R. Isotonic Dehydration. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. Accessed March 03, 2021.
Last Updated: June 14, 2018
Last Reviewed: May 17, 2019
Chapter Information

Definition, Etiology, PathogenesisTop

Isotonic dehydration is loss of water with preserved normal effective osmolality of body fluids.

Causes include loss of isotonic fluids via the gastrointestinal tract, kidneys, or skin (burns); loss of blood; or as a result of fluid sequestration in the “third space” (eg, the peritoneum).

Clinical FeaturesTop

Manifestations include features of hypovolemia (decreased blood pressure and central venous pressure, tachycardia), features of central nervous system ischemia, oliguria (prerenal acute kidney injury), dry mucous membranes, dry skin, and reduced skin turgor. In case of extremely severe dehydration, the patient develops hypovolemic shock.


Diagnosis is based on a positive history of current or prior loss of body fluids as well as the presence of clinical features of dehydration and hypovolemia, and in some cases prerenal azotemia (see Acute Kidney Injury). Differential diagnosis includes all conditions associated with hypotension, such as cardiovascular or central nervous system diseases, poisonings, or other disorders.


1. Volume resuscitation using balanced crystalloid fluids, unless there are specific indications for blood or plasma, to compensate for the prior and current volume loss.Evidence 1Strong recommendation (benefits clearly outweigh downsides; right action for all or almost all patients). High Quality of Evidence (high confidence that we know true effects of the intervention). Self WH, Semler MW, Wanderer JP, et al; SALT-ED Investigators. Balanced Crystalloids versus Saline in Noncritically Ill Adults. N Engl J Med. 2018 Mar 1;378(9):819-828. doi: 10.1056/NEJMoa1711586. Epub 2018 Feb 27. PubMed PMID: 29485926; PubMed Central PMCID: PMC5846618.

2. Intensive treatment of causes of dehydration.

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