Felis ISSN 2398-2950

Fluid therapy: overview

Contributor(s): John Dodam, Daniel H Lewis, Claire Waters, Simon Cook

Introduction

Goals

  • Understanding the indications and benefits of fluid therapy, in addition to risks.
  • Establishing blood components that are lost of lacking.
  • Appreciating and recalling the different fluids available.
  • Recognizing different delivery routes.
  • Formulating a fluid therapy plan.

Physiology

  • Total body water is approximately two thirds of body weight, of which two-thirds is intracellular fluid (ICF) and one-third is extracellular fluid (ECF).
  • ECF is comprised of interstitial fluid, CSF, synovial fluid, etc (75%) and plasma (25%).
  • Circulating blood volume in the cat is approximately 60 ml/kg.
  • In health, the vascular space is separated from the interstitial space by the vascular endothelium and glycocalyx. Combined, these are permeable to water and small solutes, but impermeable to plasma proteins. The plasma proteins exert an oncotic pressure to maintain water within the vascular space but an intact glycocalyx is the most important factor.
  • The interstitium is separated from the intracellular space by cell membranes. These are freely permeable to water but selectively permeable to solutes.
  • Sodium is the most abundant ion of the ECF. Therefore it is known as the osmotic skeleton, 'holding' water in whatever fluid space it is in.

Establishing the deficit

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Types of fluid

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Fluid administration

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Specific conditions requiring fluid therapy

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Semler M (2016) Saline is not the first choice for crystalloid resuscitation fluids. Crit Care Med 44(8), 1541-1544 PubMed.
  • Young P (2016) Saline is the solution for crystalloid resuscitation. Crit Care Med 44(8), 1538-1540 PubMed.
  • Myburgh J A & Mythen M G (2013) Resuscitation fluids. New Engl J Med 369(25), 2462-2463 PubMed.

Other sources of information

  • Liu D T & Silverstein D (2014) Crystalloids, colloids, and haemoglobin-based oxygen-carrying solutions. In: Small Animal Critical Care Medicine, 2nd Edition. Ed. Silverstein and Hopper. 2
  • Rudloff E (2014) Assessment of hydration. In: Small Animal Critical Care Medicine, 2nd Edition. Ed. Silverstein and Hopper. 
  • Hopper K, Silverstein D & Bateman S (2012) Shock syndromes. In: Fluid, Electrolyte, and Acid-base Disorders in Small Animal Practice, 4th Edition. Ed. Dibartola. 


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