Fluid Therapy

Question 1

Two phases of IV fluid therapy

Answer 1

1. Replacement (accounting for losses)

2. Maintenance (no significant losses)

Question 2

When should IV fluid therapy be given

Answer 2

• Dehydration
• Hypovolemia
• Electrolyte disorders
• Renal function impairment
• Parenteral nutrition
• Certain GI disorders
• Extensive burns
• Shock (except cardiogenic)

Question 3

The golden rules of fluid therapy

Answer 3

1. Fluids should be considered as therapeutic drugs

2. Fluids should be carefully chosen to treat a specific disorder or for a specific reason

Question 4

If there is a fluid loss, what questions should you ask?

Answer 4

1. Where is the fluid loss?
2. How much is lost?
3. What is the change in fluid content? (helps to determine what kind of fluids to give)

Question 5

Subjective fluid replacement indications

Answer 5

• Prolonged skin tent
• Sunken eyes (fat pad behind eyes loses fluid)
• Tacky MM
• Neurologically inappropriate (dull, confused)
• Pulse quality

Question 6

Objective fluid replacement indications

Answer 6

• Hemoglobin
• Hematocrit
• Heart rate
• Blood pressure
• Respiratory rate
• Serum albumin
• BUN
• Creatinine

Question 7

Fluid replacement

Answer 7

Estimate fluid deficit (sometimes difficult with animals that usually deal with dehydration; ex: camelids)

Question 8

Measuring dehydration

Answer 8

=Fluid deficit

% dehydration x body weight (kg) = fluid deficit (L)

Question 9

Maintenance rates

Answer 9

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

Question 10

Rate of fluid replacement

Answer 10

• 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

Question 11

Maintenance fluids

Answer 11

• 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

Question 12

Fluid types

Answer 12

• Isotonic fluid
• Hypotonic fluid
• Hypertonic fluid

Question 13

Isotonic fluids

Answer 13

=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

Question 14

Hypotonic fluids

Answer 14

• 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

Question 15

Hypertonic fluids

Answer 15

• 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)

Question 16

Dehydration

Answer 16

• 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

Question 17

Hypovolemia

Answer 17

=Decreased blood volume

-Secondary to severe dehydration

Question 18

Replacement solutions contain more sodium and less potassium than the patient loses. What are the risks when given for maintenance?

Answer 18

Hypernatremia

Question 19

Is excess sodium a problem

Answer 19

Yes, pulls water in (retention)

–Can eventually affect the brain (water follows sodium)

Question 20

When could hypokalemia occur?

Answer 20

• Vomiting
• When giving a diuretic
• Insulin (drives K into the cell)

Question 21

How can these risks be prevented?

Answer 21

Monitoring fluids given (how much, what kind, check calculations)

Question 22

Crystalloid fluid

Answer 22

=Crystals or salts dissolved in solution

Question 23

Colloid fluid

Answer 23

=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

Question 24

Examples of colloids

Answer 24

• Artificial colloids

- Natural colloids

Question 25

Artificial colloids

Answer 25

Examples:

• Hetastarch (used commonly to increase blood pressure)
• Dextran 40
• Dextran 70
• Etc.

Question 26

Natural colloids

Answer 26

• 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)

Question 27

Examples of uses of fluids

Answer 27

• 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