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An Urban Experience
Continuous Intravenous Fluid Therapy
Continuous  uid therapy involves 3 components:
· Maintenance:Thisincludesallsensiblelossesincluding normal urine output, normal faeces, panting and sweating. Maintenance rate is approximately 2 mL/kg/hr.
· Ongoing losses: This includes any insensible losses including vomiting, diarrhoea, polyuria, or 3rd space loss of  uids (cavitary effusions), and wounds. Ongoing losses can be measured (e.g. using a urinary catheter, weighing incontinence sheets) or estimated visually.
An approximate rate wold be 0.5 – 1.5 x maintenance rate.
· Replacement: This is the amount of dehydration which needs to be replaced. The volume to be replaced can be calculated by:
Replacement volume (mL) = % dehydration/100 x body weight (kg) x 1000
The replacement volume is then divided by how many hours you choose to deliver the replacement volume over, which is standardly 8 – 24 hour. Patients at risk of  uid overload should have  uid delivered slowly.
Once the rate of each of the 3 components have been calculated, they are added together to determine the total rate.
Example: A 15 year old 10 kg dog with a history of diarrhoea and vomiting, presents with skin tenting and dry mucus membranes, and not in shock. We estimate this dog to be 8% dehydrated.
Maintenance = 2 mL/kg/hr = 20 mL/hr
Ongoing losses = estimated at 0.5 x maintenance = 10 mL/hr
Replacement = 8/100 x 10 x 1000 = 800 mL/hr; delivered over 24 hr = 33 mL/hr
Total = 20 + 10 + 33 = 63 mL/hr
It is always important to monitor you patients for signs
of  uid overload. What we describe as  uid overload
is interstitial oedema due to increased hydrostatic pressure (e.g. too much  uid therapy), decreased oncotic pressure (e.g. hypoalbuminaemia), or increased capillary permeability (e.g. vasodilatory shock). Patients who are prone to  uid overload include animals with cardiac or respiratory disease, hypoproteinaemia, sepsis, anuric or oliguric renal failure, geriatrics, and cats. Fluid overload
is seen as interstitial oedema on the dorsal neck, feet, elbows, hocks; chemosis of the conjunctiva; bilateral serous nasal discharge; and pulmonary oedema. In patients predisposed to  uid overload, careful  uid monitoring is imperative, which can be performed by regular body weight measurements, calculating INS (total volume of  uids administered including oral water and IV infusions) and OUTS (total volume of  uid produced by patients including urine, drains, diarrhoea); and always considering if  uid rates could be reduced.
References can be provided at request.

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