FLUID calculated by multiplying weight in Kgs by

FLUID
THERAPY IN SMALL ANIMAL

 

Fluid
therapy is supportive. The underlying disease process that caused the fluid,
electrolyte and acid base disturbances in the patient must be diagnosed and
treated appropriately. Normal homeostatic mechanisms allow the clinician
considerable margin for error in fluid therapy, provided that the heart and
kidneys are normal (Stephen P. DiBartola and Shane Bateman; Fluid Electrolyte and Acid Base
Disorders in Small Animal Practice)

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Why
Should we Give Fluids :

•     
 Correct dehydration

•     
Correct acid-base
abnormalities d/t disease

•     
Correct
electrolyte abnormalities

•     
Deliver drugs in
a constant-rate infusion

•     
Prevent
dehydration (GI disease)

•     
Diuresis (renal
disease, toxicities)

Signs
of dehydration:

Percent
Dehydration

·      
3 sec indicate
dehydration

 

 

 

Components of Fluid Therapy:

  Fluid therapy contains
three components that should be taken into consideration.

1.   
Fluid deficit

2.   
Maintenance
requirement

3.   
On-going
losses

 

Fluid deficit: It is the deficit of plasma volume
calculated by multiplying weight in Kgs by percent dehydration which gives the
fluid deficit in litres

•     
Fluid req
(L) = Weight (Kg) X %dehydration

Maintenance requirement: The maintenance
fluid requirement is the volume needed per day to keep the animal in balance
(i.e., no net change in body water).

·       Usually
40-60 ml/kg/day

 

On-going Losses: These are losses
that are occurring during the course of treatment

It includes
losses related to vomiting, diarrhea, polyuria, large wounds or burns, drains,
peritoneal or pleural losses, panting, fever, and blood loss

 

Rate of Administration:

•     
Rate of fluid to be administered is
determined by the magnitude and rapidity of fluid loss

•     
In Normal cases (peri-operative) it is
10ml/kg/hr

•     
In case of shock – crystolloids 80-90
ml/kg/hr

                                             colloids 20ml/kg/hr

 

•     
1/4th to ½ of fluid defecit
should be administerd over a period of 2-3 hrs

•     
Reminder of the deficit + maintenance
req. + ongoing losses should be administered over a period of 24 hrs

•     
Severe ongoing losses (e.g., vomiting
and diarrhea in a patient with acute gastroenteritis) may necessitate rapid
administration to keep pace with contemporary fluid loss

•     
It usually is not necessary to replace
the hydration deficit rapidly in chronic diseases, it should be done over a
period of 24 hours

 

Monitoring While on Fluids:

•     
Weigh patient daily

•     
Auscult the lungs – presence of the
following signs indicate overhydration

–   
Crackles

–   
Wheezes

–   
Serous nasal discharge

•     
Urine production – 1-2ml/kg/min

•     
Central venous pressure

•     
Overdose:

–   
Serous nasal discharge

–   
Dyspnea, crackles

–   
Restlessness

–   
Decreased PCV, TP

–   
Increased BP

 

Administration
Routes

•     
Oral

–   
If the stomach works, use it!

–   
Safest route if tolerated

•     
Subcutaneous

–   
Works well in most animal  

–   
Sometimes need to use multiple sites

–   
Can’t add glucose, large quantity KCl,
or some drugs

•     
Intravenous

–   
Best route in dehydrated animals

–   
Possible problems:

•     
Volume overload

•     
Catheter reactions (swelling, fever)

•     
Intraosseous

 

•     
If situation is dire and no vein
accessible

•     
Into the medullary (bone marrow)
cavity of long bones

– 
Femur or Humerus are commonly used

–   
Used frequently in birds

 

Types of Fluids:

•     
Crystalloids

–   
0.9% NaCl

–   
Lactated Ringers Solution

–   
Ringers Solution

–   
5% Dextrose in water

–   
Plasmalyte, Normosol, etc

Crystalloid
Fluids

•     
Isotonic

–   
Mimic plasma electrolyte
concentrations, NS

•     
Hypertonic

–   
Osmolality higher than plasma, RL

Lactated Ringer’s
Solution

•     
Composition closely resembles ECF

–   
Contains physiological concentrations
of: sodium, chloride, potassium, and calcium

–   
Also contains lactate, which is
metabolized by the liverà
alkaline-forming

–   
Because
small animals that are sick or under anesthesia tend towards acidosis

Saline

•     
0.9% Sodium chloride = ISOTONIC

•     
Lacking in K+, Ca2+

•     
Used for hyperkalemia, hypercalcemia

•     
Used as a carrier for some drugs

Dextrose
Solutions

•     
5% dextrose is isotonic

•     
25%, 50% dextrose commonly found

•     
Used for hypoglycemia, neonates,
hyperkalemia, as part of Total Parenteral Nutrition

Colloids

Colloids are
large-molecular-weight substances that are restricted to the plasma compartment
in patients with an uncompromised intact endothelium

          Natural Colloids

•     
Blood products:

–   
Whole blood

–   
Plasma

–   
Platelet-rich plasma

–   
Packed RBC’s

 

Synthetic Colloids

•     
Dextrans, Hetastarch

•     
Used when quantity of a crystalloid is
too great to be able to infuse quickly

•     
Stays within the vasculatureà maintain
blood pressure

•     
Duration of effect is determined by
molecular size:

bigger = longer

–   
Small volumes produce immediate
increases in blood pressure

x

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