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

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. 12 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-recognised 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.