title: The pathophysiology of fluid and electrolyte balance in the older adult surgical patient.
abstract: OBJECTIVE
  Age-related physiological changes predispose even the healthy older adult to fluid and electrolyte abnormalities which can cause morbidity and mortality. The aim of this narrative review is to highlight key aspects of age-related pathophysiological changes that affect fluid and electrolyte balance in older adults and underpin their importance in the perioperative period.
  
  
  METHODS
  The Web of Science, MEDLINE, PubMed and Google Scholar databases were searched using key terms for relevant studies published in English on fluid balance in older adults during the 15 years preceding June 2013. Randomised controlled trials and large cohort studies were sought; other studies were used when these were not available. The bibliographies of extracted papers were also searched for relevant articles.
  
  
  RESULTS
  Older adults are susceptible to dehydration and electrolyte abnormalities, with causes ranging from physical disability restricting access to fluid intake to iatrogenic causes including polypharmacy and unmonitored diuretic usage. Renal senescence, as well as physical and mental decline, increase this susceptibility. Older adults are also predisposed to water retention and related electrolyte abnormalities, exacerbated at times of physiological stress. Positive fluid balance has been shown to be an independent risk factor for morbidity and mortality in critically ill patients with acute kidney injury.
  
  
  CONCLUSIONS
  Age-related pathophysiological changes in the handling of fluid and electrolytes make older adults undergoing surgery a high-risk group and an understanding of these changes will enable better management of fluid and electrolyte therapy in the older adult.
authors.affiliation: Division of Gastrointestinal Surgery, Nottingham Digestive Diseases Centre National Institute for Health Research Biomedical Research Unit, Nottingham University Hospitals, Queen's Medical Centre, Nottingham, UK.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: El-Sharkawy
authors.affiliation: Department of Elderly Medicine, Nottingham University Hospitals, Queen's Medical Centre, Nottingham, UK.
authors.forename: Opinder
authors.initials: O
authors.lastname: Sahota
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: Ron J
authors.initials: RJ
authors.lastname: Maughan
authors.affiliation: Division of Gastrointestinal Surgery, Nottingham Digestive Diseases Centre National Institute for Health Research Biomedical Research Unit, Nottingham University Hospitals, Queen's Medical Centre, Nottingham, UK. Electronic address: Dileep.Lobo@nottingham.ac.uk.
authors.forename: Dileep N
authors.initials: DN
authors.lastname: Lobo
mesh_terms: D058186:Acute Kidney Injury / Q000628:therapy; D000368:Aged; D000375:Aging / Q000502:physiology*; D003072:Cognition Disorders / Q000209:etiology; D016638:Critical Illness / Q000628:therapy*; D003681:Dehydration / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D005440:Fluid Therapy / Q000379:methods; D006801:Humans; D007668:Kidney / Q000503:physiopathology; D059035:Perioperative Period; D012307:Risk Factors; D013894:Thirst / Q000502:physiology; D014882:Water-Electrolyte Balance / Q000502:physiology*
keywords: Clinical outcome; Dehydration; Fluid and electrolytes; Fluid overload; Older adults; Pathophysiology