Page 434 - WSAVA2018

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25-28 September, 2018 | Singapore
The sites for intraosseous placement in birds are:
· The distal ulna
· Proximal tibiotarsal bone How Much Fluid?
Once we have assessed how dehydrated our patient is, we can calculate how much fluid is required to replace (rehydrate) the loss. We then look at how much is required to maintain normal hydration and finally if there are any ongoing losses (e.g. vomiting, diarrhoea, draining wounds etc) to take into account.
Types of fluids available will be discussed later in this section.
Rehydration
Replacement fluids are typically used for rehydration.
To calculate the amount of missing fluid (the amount that needs replacing) multiply the body weight in kg by the percentage dehydration. Remember that mathematically 5% is expressed as 5/100. This will give you the missing volume in litres. So for a 10kg animal which is 5% dehydrated: 10 X 5 / 100 = 0.5 litres (i.e. 500mls)
A quick rule-of-thumb formula to give you the result in millilitres is: percentage dehydration (just the number) X Body weight (kg) X 10 So for a 10kg animal which is 5% dehydrated: 5 X 10 X 10 = 500mls
Maintenance
The goal of maintenance fluid therapy is to replace fluid lost in normal body functions.
Maintenance fluid requirements = Insensible fluid losses + Sensible fluid losses
Insensible losses (GIT, Respiratory tract, Skin) = 20ml/kg/ day
Sensible losses (urine) = 1-2ml/kg/hour (i.e. 24-48ml/kg/ day)
Therefore, combined maintenance volume is generally estimated at 40-60ml/kg/day. Larger dogs typically have lower requirements than small dogs (due to surface area: body mass ratio).
Ongoing fluid losses
Ongoing losses refer to fluid losses over and above the maintenance requirements of a normal patient. Examples include vomiting, diarrhoea, bleeding and wound exudate.
These can be difficult to predict and so a best estimate is used.
Calculating Fluid Requirements
When calculating fluid requirements all three losses/ deficits are considered
Requirement = fluid deficit + maintenance requirements + ongoing losses
If a fluid pump is used to deliver the fluids then it has the capacity to have an hourly fluid rate set. If a gravity fed administration system is used then the fluid rate should be calculated to drops per second. Conventional administration sets generally administer 20 drops/ml. It will be printed on the packaging.
Example Calculation:
10kg dog is 8% dehydrated
Has diarrhoea – estimate it will lose 140mls of fluid via D+ in next 24hrs
Maintenance choice of rate = 50ml/kg/day Deficit + maintenance + ongoing losses
- 10 (kg) x 8 (% dehydration) ÷ 100 = 800mls (replacement amount)
- 10 x 50 (mls/kg/day) = 500mls (maintenance amount) - 140mls over 24hrs = 140mls (ongoing losses)
- 800 + 500 + 140 = 1440mls
- 1440mls ÷ 24 hrs = 60mls per hour
Calculate drops per minute
- Hourly rate (mls/hr) ÷ 60 (mins/hr) x 20 (drops/ml – giving set factor)
- 60 ÷ 60 x 20 = 20 drops per minute
- Calculate drops per second
- Minute rate ÷ 60 (secs/min) = 20 ÷ 60 = 0.33
- Convert decimal value to fraction – 0.33 = 1/3rd
- 1 drop every 3 seconds
Type of Fluid Required
The type of fluid given will depend on many factors including:
· Composition of lost fluid
· Abnormalities requiring correction
· Severity and type of fluid depletion
Considerations of choice of fluid should also include: · Tonicity
· Need for glucose
· Electrolyte balance
· Acidity
· Osmotic pressure
· Oxygen carrying capacity
Fluids can be divided into three main categories · Crystalloids
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43RD WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND 9TH FASAVA CONGRESS
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