Fluid balance

Reviewed and revised 15 August 2015

OVERVIEW

  • Daily fluid balance is the daily sum of all intakes and outputs, and the cumulative fluid balance is the sum total of fluid accumulation over a set period of time.
  • The harmful effects of positive fluid balance and the importance of deresuscitation of discussed in Deresuscitation and positive fluid balance

METHODS OF ASSESSING FLUID STATUS

Cumulative fluid balance chart

  • this is what is typically referred to when assessing ‘fluid balance’, rather than fluid status
  • consists of a 24 hour chart showing measurements of fluid inputs and fluid outputs, usually on an hourly basis, with cumulative totals
  • measurements are typically recorded and made by the bedside nurse

Other methods for assessing fluid status, all of which have drawbacks, include:

  • clinical assessment of fluid overload (e.g. body weight, peripheral edema and gas exchange parameters)
  • haemodynamic parameters of hypovolemia (e.g. hypotension, tachycardia, poor capillary refill and altered mental status)
  • filling pressure (central venous pressure)
  • haemodynamic monitors (e.g. EVLW on PiCCO)
  • radiological techniques (e.g. “wet looking” CXR)
  • bio-electric impedance tomography

Also see the CCC entry on Fluid Responsiveness for static and dynamic methods

PROS AND CONS OF FLUID BALANCE CHART MONITORING

Pros

  • potentially useful biomarker of critical illness
  • positive fluid balance is associated with worse morbidity and mortality in ICU patients
  • fluid balance charts are:
    • widely available
    • intuitive (“a balance sheet of ins and outs”)
    • simple
    • does not require technology (e.g. scale beds, bio-electric impedance tomography)
  • other techniques lack accuracy (e.g. clinical assessment, CVP measurement, radiological investigations) due to poor correlation with global fluid status and inter-observer variability)

Cons

  • inaccurate
    • does not account for insensible losses
    • measurement and documentation errors are common
    • losses from bowel motions and urinary catheter overflow may not be accounted for
    • other techniques may be more accurate (e.g. body weight, bioelectric impedence tomography)
  • needs to be assessed in context of patient’s presentation and condition (e.g. initial volume status – dehydrated versus fluid overloaded?)
  • lack of evidence supporting a benefit to patients from iatrogenic correction of fluid balance (e.g. versus simple resolution of patient’s condition)

EVIDENCE

  • multiple studies have found that positive fluid balance is associated with worse morbidity and mortality in ICU patients (see Deresuscitation and positive fluid balance)
  • up to a third of cumulative fluid balance charts in ICU patients are inaccurate, with errors ranging from from -3606 mL to +2020 mL (Perren et al, 2011)

References and Links

LITFL

Journal articles

  • Bouchard J, Mehta RL. Fluid balance issues in the critically ill patient. Contrib Nephrol. 2010;164:69-78. [pubmed]
  • Gonzalez F, Vincent F. The fluid balance in the critically ill patients: what are we talking about? Minerva Anestesiol. 2011;77:(8)766-7. [pubmed]
  • Mehta RL, Clark WC, Schetz M. Techniques for assessing and achieving fluid balance in acute renal failure. Curr Opin Crit Care. 2002;8:(6)535-43. [pubmed]
  • Perren A, Markmann M, Merlani G, Marone C, Merlani P. Fluid balance in critically ill patients. Should we really rely on it? Minerva Anestesiol. 2011;77:(8)802-11. [pubmed]

CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health, a Clinical Adjunct Associate Professor at Monash University, and the Chair of the Australian and New Zealand Intensive Care Society (ANZICS) Education Committee. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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