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. 2019 May-Jun;51(3-4):232-251.
doi: 10.1080/07853890.2019.1628352. Epub 2019 Jun 17.

A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications

Jonathan Lacey  1 , Jo Corbett  2 , Lui Forni  3 , Lee Hooper  4 , Fintan Hughes  1 , Gary Minto  5   6 , Charlotte Moss  7 , Susanna Price  8 , Greg Whyte  9 , Tom Woodcock  10 , Michael Mythen  1 , Hugh Montgomery  11
Affiliations

A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications

Jonathan Lacey et al. Ann Med. 2019 May-Jun.

Abstract

Background: Dehydration appears prevalent, costly and associated with adverse outcomes. We sought to generate consensus on such key issues and elucidate need for further scientific enquiry. Materials and methods: A modified Delphi process combined expert opinion and evidence appraisal. Twelve relevant experts addressed dehydration's definition, objective markers and impact on physiology and outcome. Results: Fifteen consensus statements and seven research recommendations were generated. Key findings, evidenced in detail, were that there is no universally accepted definition for dehydration; hydration assessment is complex and requires combining physiological and laboratory variables; "dehydration" and "hypovolaemia" are incorrectly used interchangeably; abnormal hydration status includes relative and/or absolute abnormalities in body water and serum/plasma osmolality (pOsm); raised pOsm usually indicates dehydration; direct measurement of pOsm is the gold standard for determining dehydration; pOsm >300 and ≤280 mOsm/kg classifies a person as hyper or hypo-osmolar; outside extremes, signs of adult dehydration are subtle and unreliable; dehydration is common in hospitals and care homes and associated with poorer outcomes. Discussion: Dehydration poses risk to public health. Dehydration is under-recognized and poorly managed in hospital and community-based care. Further research is required to improve assessment and management of dehydration and the authors have made recommendations to focus academic endeavours. Key messages Dehydration assessment is a major clinical challenge due to a complex, varying pathophysiology, non-specific clinical presentations and the lack of international consensus on definition and diagnosis. Plasma osmolality represents a valuable, objective surrogate marker of hypertonic dehydration which is underutilized in clinical practice. Dehydration is prevalent within the healthcare setting and in the community, and appears associated with increased morbidity and mortality.

Keywords: Dehydration; body fluid compartments; body water; consensus; osmolar concentration; water–electrolyte balance.

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Conflict of interest statement

H. M. and M. M. hold a patent related to a novel means of managing fluid delivery in hospital [Patent no. EP2525767B1]. H. M. consults for Deepmind Health, which has an interest in acute kidney injury. M. M. consults for Edwards Lifesciences and Baxter. M. M. is the founding Editor of Perioperative Medicine, sits on the Editorial Boards of The British Journal of Anaesthesia and Critical Care. M. M. is the founding Editor-in-Chief of TopMedTalk. L. F. has received financial support from Baxter for research activities. J. L., J. C., L. H., F. H., G. M., C. M., S. P., G. W. and T. W. report no conflicts of interest.

Figures

Figure 1.
Figure 1.
Schematic representation of the body fluid compartments in humans and their relative sizes. The approximate absolute volumes of the compartments (in litres) are based on a 70 kg adult. TBW: total body water; ICF: intracellular fluid; ECF: extracellular fluid; ISF: interstitial fluid; IVF: intravascular fluid.
Figure 2.
Figure 2.
The homeostatic responses of the two major forms of dehydration: hypertonic (primarily osmotic-dependent response) and isotonic (primarily volume-dependent response). The osmotic response is more sensitive and acts as the principal determinant of water balance. Note that both responses can co-exist. TBW: total body water; pOsm: plasma osmolality; SNS: sympathetic nervous system; RAAS: renin–angiotensin–aldosterone system; AVP: arginine vasopressin.
Figure 3.
Figure 3.
The relationship between osmotic state and total body water (TBW). It is possible for patients to exist in any one of the nine panels. The graded colouration reflects severity of condition. Possible treatment options for different parts of each panel are written in italics, with the arrows representing intended effects of intervention to normalize physiology. IV: intravenous (Image reproduced with permission from the Perioperative Quality Initiative, POQI).
See this image and copyright information in PMC

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