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The ideal crystalloid – what is ‘balanced’?

Morgan, Thomas J.

Current Opinion in Critical Care: August 2013 - Volume 19 - Issue 4 - p 299–307
doi: 10.1097/MCC.0b013e3283632d46
INTRAVENOUS FLUIDS: Edited by John Myburgh

Purpose of review This review explores the contemporary definition of the term ‘balanced crystalloid’ and outlines optimal design features and their underlying rationale.

Recent findings Crystalloid interstitial expansion is unavoidable, but also occurs with colloids when there is endothelial glycocalyx dysfunction. Reduced chloride exposure may lessen kidney dysfunction and injury with a possible mortality benefit. Exact balance from an acid–base perspective is achieved with a crystalloid strong ion difference of 24 mEq/l. This can be done simply by replacing 24 mEq/l of chloride in 0.9% sodium chloride with bicarbonate or organic anion bicarbonate substitutes. Potassium, calcium and magnesium additives are probably unnecessary. Large volumes of mildly hypotonic crystalloids such as lactated Ringer's solution reduce extracellular tonicity in volunteers and increase intracranial pressure in nonbrain-injured experimental animals. A total cation concentration of 154 mmol/l with accompanying anions provides isotonicity. Of the commercial crystalloids, Ringer's acetate solution is close to balanced from both acid–base and tonicity perspectives, and there is little current evidence of acetate toxicity in the context of volume loading, in contrast to renal replacement.

Summary The case for balanced crystalloids is growing but unproven. A large randomized controlled trial of balanced crystalloids versus 0.9% sodium chloride is the next step.

Mater Medical Research Institute and University of Queensland, Mater Health Services, Stanley Street, South Brisbane, Brisbane, Queensland, Australia

Correspondence to Dr T.J. Morgan, Intensive Care Unit, Mater Adult Hospital, Mater Health Services, Raymond Terrace, South Brisbane, Queensland 4101, Australia. Tel: +61 7 3163 8111; fax: +61 7 3163 1503; e-mail:

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