Fluid Therapy Flashcards
Two phases of IV fluid therapy
- Replacement (accounting for losses)
2. Maintenance (no significant losses)
When should IV fluid therapy be given
- Dehydration
- Hypovolemia
- Electrolyte disorders
- Renal function impairment
- Parenteral nutrition
- Certain GI disorders
- Extensive burns
- Shock (except cardiogenic)
The golden rules of fluid therapy
- Fluids should be considered as therapeutic drugs
2. Fluids should be carefully chosen to treat a specific disorder or for a specific reason
If there is a fluid loss, what questions should you ask?
- Where is the fluid loss?
- How much is lost?
- What is the change in fluid content? (helps to determine what kind of fluids to give)
Subjective fluid replacement indications
- Prolonged skin tent
- Sunken eyes (fat pad behind eyes loses fluid)
- Tacky MM
- Neurologically inappropriate (dull, confused)
- Pulse quality
Objective fluid replacement indications
- Hemoglobin
- Hematocrit
- Heart rate
- Blood pressure
- Respiratory rate
- Serum albumin
- BUN
- Creatinine
Fluid replacement
Estimate fluid deficit (sometimes difficult with animals that usually deal with dehydration; ex: camelids)
Measuring dehydration
=Fluid deficit
% dehydration x body weight (kg) = fluid deficit (L)
Maintenance rates
Variable (depending on species), but rule of thumb (all include insensible losses):
- Adult LA: 60 mL/kg/day
- Neonate LA: 100 mL/kg/day
- SA: 60-90 mL/kg/day
- -Cats/small dogs: closer to 90 mL/kg/day
- -Large dogs: closer to 60 mL/kg/day
Rate of fluid replacement
- Depends on a variety of factors:
- -Patient status (shock?, mild v. severe dehydration)
- -Patient co-morbidities (ex: heart failure or CKD)
- -Fluid type (colloids v. crystalloids)
- -Fluid additives (KCl, dextrose, antibiotics)
- Monitor patient closely - large boluses may lead to edema
- -Auscultate for crackles
- -Vital signs at least hourly (monitor for fluid overload)
- -Monitor for urination (may need to quantify)
- -Evaluate patient’s clinical status
Maintenance fluids
- Still risk of edema if overzealous with treatment
- Use a fluid pump when possible
- Gravity flow = increased risk of too much or too little fluids (monitor fluid bag level frequently)
- Correct percentage and speed will promote urination (decreases risk of iatrogenic toxicity) and should not affect blood protein concentration too much
Fluid types
- Isotonic fluid
- Hypotonic fluid
- Hypertonic fluid
Isotonic fluids
=Tonicity is similar to that of plasma (0.9% saline, lactated ringer’s, plasmalite, etc.)
-Used to restore fluid deficit, correct electrolyte imbalance, and for maintenance
Hypotonic fluids
- Used when there is sodium and water retention (congestive heart failure, hepatic disease), or when severe hypernatremia (free water deficit)
- Ex: 0.5% saline, 2.5-5% dextrose
Hypertonic fluids
- Used to draw fluid from interstitial compartment into the vascular compartment (do NOT use if interstitial dehydration is present)
- Short-term effect (~20 minutes)
- Infuse along with crystalloid solution to prevent interstitial dehydration
- Ex: 3-7% saline (give over a few minutes)
Dehydration
- Priority: maintain blood volume and blood pressure (tissues donate fluid to circulation)
- When dehydrated, fluid moves from the interstitium, then from inside the cells, then from the vessel
Hypovolemia
=Decreased blood volume
-Secondary to severe dehydration
Replacement solutions contain more sodium and less potassium than the patient loses. What are the risks when given for maintenance?
Hypernatremia
Is excess sodium a problem
Yes, pulls water in (retention)
–Can eventually affect the brain (water follows sodium)
When could hypokalemia occur?
- Vomiting
- When giving a diuretic
- Insulin (drives K into the cell)
How can these risks be prevented?
Monitoring fluids given (how much, what kind, check calculations)
Crystalloid fluid
=Crystals or salts dissolved in solution
Colloid fluid
=Contains negatively charged high molecular weight particles that are osmotically active (i.e. draw sodium around their core structure, thus leading to water retention where they are located)
- Only used to correct intravascular fluid deficits; always used along with crystalloid fluids to restore intravascular and interstitial fluid volumes
- Decrease calculated crystalloid requirements by 25-50% to prevent fluid overload
- Monitor for signs of intravascular fluid overload
Examples of colloids
- Artificial colloids
- Natural colloids
Artificial colloids
Examples:
- Hetastarch (used commonly to increase blood pressure)
- Dextran 40
- Dextran 70
- Etc.
Natural colloids
- Whole blood (for loss of blood)
- Packed red blood cells (for anemia)
- Plasma (for clotting factors, antiproteinase activity in case of inflammation - needs hetastarch to maintain colloid oncotic pressure)
- Concentrated human albumin (for severe hypoalbuminemia - pretreat with antihistamine, ex: diphenhydramine)
Examples of uses of fluids
- To replace interstitial fluid loss
- -Isotonic crystalloid solution in case of dehydration and shock
- Colloid solutions possible if no interstitial dehydration
- In case of decompensated or terminal shock, a hypertonic saline may by helpful as it uses small volumes of fluid that can be rapidly administered, but total fluid loss still needs to be compensated after initial fluid replacement
