Page 432 - WSAVA2018
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 25-28 September, 2018 | Singapore
J. Hatcher1, C. Harvery Stevenson1, M. Oleary1 1Provet AIRC, Provet AIRC, Brisbane, Australia
Jo Hatcher Cert IV VN, TAE, Dip VN, AVN
Brisbane, Australia
Body water
The water content of the adult body is, on average, 60% by weight. However, the water content can vary with age and nutritional status. For example, the water content
of an older animal may be as little as 50-55% whilst the water body content of young animals may be as high as 70-80%.
The body water content is also affected by the proportion of fat to lean tissue within the body. Fatty tissue contains much smaller amounts of water
than other organs and tissue. This is an important consideration (to avoid overhydration) when devising a fluid therapy plan for the obese patient; the plan should be based on the patient’s ideal weight not current weight.
Distribution of Body Water
· Intracellular fluid
body water is located inside the cells of tissues, this is called intracellular fluid
· Extracellular fluid ECF The remaining one third of the total body water is located outside the cells. This is further divided into:
· Intravascular fluid The water contained within the blood vessels
· Interstitial fluid The water present in the spac- es between the cells (also bone, cartilage and dense tissue)
· Transcellular fluids Specialised fluids, e.g. cerebrospinal fluid, gastrointestinal secretions. However, this is only a very small amount of the extracellular fluid.
Water Balance
We need to be able to match the amount of water being lost by the body to the amount of water being taken in to the body to enable water balance. The normal water balance in a healthy dog or cat is generally calculated at 50ml per kg bodyweight per day. However, this ranges from 40-60ml/kg/day (24hrs).
This calculation is devised from the amount (on average) that a dog or cat will lose due to sensible and insensible losses. A sensible loss refers to fluid loss that an
observer can readily detect with their senses (e.g. can see it coming out)
Abnormal fluid loss
Causes of abnormal fluid loss include:
  Source of fluid loss
 Sensible / Insensible
 Respiration / sweating
 Insensible loss
 Urinary loss (normal range)
 Sensible loss
 Faecal loss (normal range)
  Sensible loss
  Total fluid loss
  ICF Two thirds of the total
Goals of fluid therapy
The goals are to replace lost fluid and electrolytes and to maintain a state of normal fluid and electrolyte balance in the presence of inadequate intake and ongoing losses.
When formulating a fluid therapy plan, the following five
questions should be considered.
· indicated? Consider the clinical indications, laborato- ry data and patient presentation that signify that fluid therapy is indicated
· much fluid should be given? Consider rehydration, maintenance and ongoing losses.
· · · · · · · · · · · ·
Blood loss
Evaporation (increased panting etc) Disease
· rate should fluid be given? The rate is very much dependent upon patient presentation and amount of fluid that can be administered to rehydrate without fluid overload occurring. Sometimes a deficit will
be replaced over 24 hours while in other cases a portion of the deficit will be replaced rapidly then the remainder of the deficit at a slower rate. The daily rate is calculated and then the hourly rate to ensure correct administration
· route should fluid be given? This has been previous- ly discussed. In this section we are concentrating on intravenous fluid administration
· type of fluid should be given? Several types of intravenous fluids are available. Choice of fluid de- pends on the nature of the deficit of electrolytes and disease factors.
Assessing Dehydration
Each patient should be individually assessed for the level of dehydration they are suffering from and an appropriate fluid therapy plan devised. There are several clinical and laboratory methods of assessing dehydration. These include:
Patient history
A thorough history assists in correct assessment of the

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