Practice Competent Novice

Intravenous fluid therapy in adult inpatients

BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.g7620 (Published 06 January 2015) Cite this as: BMJ 2015;350:g7620
  1. Paul Frost, consultant in intensive care medicine; clinical senior lecturer12
  1. 1Critical Care Directorate, University Hospital of Wales, Cardiff CF14 4XW, UK
  2. 2Institute of Medical Education, School of Medicine, Cardiff University, Cardiff CF14 4XN
  1. Correspondence to: P Frost Frostp2{at}cf.ac.uk
  • Accepted 12 November 2014

The bottom line

  • Fluid balance can usually be determined by history (intake, losses, current illness, and treatment) and examination (skin, neurological, cardiorespiratory, and abdominal) supported by tests (urea and electrolytes, creatinine, lactate, and haematocrit)

  • The prescription of intravenous fluids can be made simpler by junior doctors routinely considering the 5Rs: Resuscitation, Routine maintenance, Redistribution, Replacement, and Reassessment

  • Senior clinical review and occasionally invasive haemodynamic monitoring may be needed for patients with complex fluid balance problems, such as those secondary to renal, liver, and cardiac impairment

Intravenous fluid management is a common medical task, and safe unambiguous fluid prescribing is a required training outcome for junior doctors.1 Despite this, errors in intravenous fluid management are common and have been attributed to inadequate training and knowledge.2 Poor fluid management can result in serious morbidity, such as pulmonary oedema and dangerous hyponatraemia as a result of excessive fluids and acute kidney injury as a result of under resuscitation.2 3

How best to do it

There is a lack of high quality evidence, such as that from randomised controlled trials, to guide intravenous fluid management.4 Safe intravenous fluid prescribing requires the integration of relevant clinical skills, such as the assessment of fluid balance, with an understanding of fluid physiology under normal and pathological conditions and the properties of commonly available intravenous fluids.

Normal fluid balance

Water constitutes about 60% of the total body weight in men and 55% in women (women have a slightly higher fat content). Although water is non-uniformly distributed throughout the body, it can be conceptualised as occupying the intracellular and extracellular fluid compartments (fig 1). Extracellular fluid mainly comprises plasma and interstitial fluid, which are separated by the capillary membrane.

Fig 1 Body fluid compartment volumes and theoretical distribution of intravenous fluids in healthy people

Water movement between the plasma and interstitial spaces

The capillary endothelium is lined by …

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