Fundamentals of Feline Fluid Therapy - Feline Focus Article

Question 1

What percentage of an adult cat’s body weight is made up of total body water?

Answer 1

Approximately 60%.

Question 2

How is total body water divided within the body?

Answer 2

It is divided into intracellular fluid (ICF) and extracellular fluid (ECF).

Question 3

What percentage of total body water is intracellular fluid (ICF)?

Answer 3

Approximately 66% of total body water, or 40% of body weight.

Question 4

What percentage of total body water is extracellular fluid (ECF)?

Answer 4

Approximately 33% of total body water, or 20% of body weight.

Question 5

What are the subdivisions of extracellular fluid (ECF)?

Answer 5

Interstitial fluid, plasma, and transcellular fluid.

Question 6

What percentage of body weight does interstitial fluid account for?

Answer 6

15% of body weight or 24% of total body water.

Question 7

What percentage of body weight does plasma account for?

Answer 7

4% of body weight or 8–10% of total body water.

Question 8

What is transcellular fluid, and how much of the body weight does it constitute?

Answer 8

Transcellular fluid includes synovial fluid, bile, cerebrospinal fluid, and small volumes of fluid lining body cavities. It accounts for 1% of body weight or 2% of total body water.

Question 9

Why is it important to understand fluid distribution when planning fluid therapy?

Answer 9

Because fluid is dynamic and moves between compartments, understanding distribution helps ensure the selection of an appropriate fluid type and route for therapy.

Question 10

From where must fluid losses in the body come?

Answer 10

From one or more of the fluid compartments: intracellular, interstitial, plasma, or transcellular fluid.

Question 11

What are the first steps in providing fluid therapy?

Answer 11

Determining if fluid losses are present, how severe those losses are, and where those losses have originated from.

Question 12

How can fluid losses be assessed?

Answer 12

By reviewing the patient’s clinical history and performing a thorough clinical examination.

Question 13

What are hypotonic fluid losses?

Answer 13

Fluid losses where the fluid has a lower concentration than plasma, such as when there is primary water depletion (e.g., not drinking, polyuria from chronic kidney disease, diabetes mellitus, or diabetes insipidus).

Question 14

What is the consequence of hypotonic fluid losses?

Answer 14

Water moves from the intracellular space to equilibrate fluid levels, resulting in dehydration.

Question 15

What are isotonic fluid losses?

Answer 15

Fluid losses where the fluid has the same concentration as plasma, such as with haemorrhage or ECF losses via vomiting and diarrhea.

Question 16

What happens during isotonic fluid losses?

Answer 16

There is no movement of fluid to compensate for losses, leading to intravascular volume reductions and hypovolemia.

Question 17

What are hypertonic fluid losses?

Answer 17

Fluid losses where the fluid has a higher concentration than plasma, such as with third-space losses (e.g., pleural effusion or ascites).

Question 18

What is the consequence of hypertonic fluid losses?

Answer 18

The ECF becomes less concentrated than the ICF, causing water to move into cells, worsening hypovolemia due to further intravascular volume reduction.

Question 19

What is the difference between dehydration and hypovolemia?

Answer 19

Dehydration is fluid loss from intracellular and interstitial compartments, while hypovolemia is fluid loss from the intravascular space.

Question 20

What are the clinical signs of perfusion deficits in hypovolemia?

Answer 20

Changes in heart rate, pulse quality, respiratory rate, mucous membrane color, capillary refill time, mentation, and the temperature and color of extremities (forward perfusion parameters).

Question 21

What are the clinical signs of hydration deficits in dehydration?

Answer 21

Changes in skin turgor, moistness of mucous membranes, and globe position.

Question 22

How can the severity of dehydration be used in treatment?

Answer 22

It can be used to estimate the patient’s percentage dehydration, which helps calculate replacement fluid volumes.

Question 23

Can severe dehydration affect perfusion parameters?

Answer 23

Yes, severe dehydration can cause changes to forward perfusion parameters.

Question 24

What are the main types of fluid therapy used in practice?

Answer 24

Crystalloids and colloids (including blood products).

Question 25

What are crystalloids?

Answer 25

Solutions that can easily leave the intravascular space and move into other fluid compartments, used to treat dehydration, electrolyte abnormalities, and correct free water deficits.

Question 26

How are crystalloids categorized?

Answer 26

Free water, replacement solutions, maintenance solutions, and hypertonic solutions.

Question 27

What are free water solutions?

Answer 27

Hypotonic fluids such as 5% dextrose in sterile water, 4% dextrose in 0.18% saline, and 0.45% saline, which replenish the interstitial and intracellular fluid compartments but are not suitable for intravascular volume replenishment.

Question 28

What are replacement solutions?

Answer 28

Balanced, isotonic crystalloids like lactated Ringer’s (Hartmann’s) solution and 0.9% saline, used to replenish both the extracellular fluid and intracellular fluid compartments, correct hypovolemia, and dehydration.

Question 29

What happens to replacement solutions when used to replenish the intravascular space?

Answer 29

They equilibrate with the surrounding interstitial fluid, leaving only 25% of the fluid volume within the vascular space after an hour.

Question 30

What are maintenance solutions?

Answer 30

Balanced, isotonic solutions like Plasmalyte-M with higher potassium and lower sodium concentrations than replacement fluids, used after fluid deficits and electrolyte derangements are corrected.

Question 31

What are hypertonic solutions?

Answer 31

Fluids like 7.2% saline that have a higher osmolarity than plasma, creating an osmotic gradient that pulls water from the interstitial space into the circulation.

Question 32

Why should hypertonic solutions not be used in dehydrated patients?

Answer 32

Because they draw water from the interstitial space, potentially worsening dehydration.

Question 33

What are colloids?

Answer 33

Large molecules that increase the colloidal pressure of plasma, holding fluid within the intravascular space and increasing intravascular volume.

Question 34

What are synthetic colloids?

Answer 34

Colloids like gelatins and hydroxyethyl starches, with gelatins having a shorter duration of effect and hydroxyethyl starches being administered as a bolus in cats.

Question 35

What are natural colloids?

Answer 35

Blood products such as whole blood, plasma, packed red blood cells, and albumin.

Question 36

What is a key consideration when using replacement fluids long-term?

Answer 36

They have relatively low levels of potassium, potentially leading to hypokalemia, especially in patients with concurrent anorexia.

Question 37

What is a key point about the use of synthetic colloids?

Answer 37

Their use is controversial due to reports of acute kidney injury associated with their use in both human and veterinary medicine.

Question 38

What type of fluid administration is required for patients with perfusion deficits or hypovolemia?

Answer 38

Urgent, rapid volume resuscitation with larger fluid boluses given over shorter periods of time (15–60 minutes) with regular monitoring of forward perfusion parameters.

Question 39

How is the hydration deficit in cats calculated?

Answer 39

Body weight (kg) x % dehydration/100 = volume to correct (in liters) or Body weight x % dehydration x 10 = volume to correct (in ml).

Question 40

Over what time period are hydration deficits typically corrected?

Answer 40

24–48 hours, depending on the severity of dehydration and the individual patient or disease process.

Question 41

What should be done after correcting a hydration deficit?

Answer 41

Fluid rates should be re-assessed and adjusted to meet the patient’s maintenance fluid requirements.

Question 42

How are maintenance fluid requirements in cats calculated?

Answer 42

Body weight (kg)^0.75 x 80 = volume required per day (in ml).

Question 43

How can ongoing fluid losses be estimated in a cat?

Answer 43

By weighing litter trays or bedding to quantify urinary losses, or by recording fluid volumes retrieved from vomiting, diarrhea, and thoracic, abdominal, or wound drains.

Question 44

Why is monitoring fluid therapy in cats important?

Answer 44

To assess whether the fluid plan is effective, to identify under or over-hydration, and to adapt the fluid therapy plan based on the patient’s clinical signs and response to treatment.

Question 45

What parameters should be regularly monitored during fluid therapy?

Answer 45

Hydration, forward perfusion parameters, regular body weight, urine output, packed cell volume, and total solids.

Question 46

How can urine output be monitored in cats during fluid therapy?

Answer 46

Through placement of an indwelling urinary catheter or by weighing bedding and litter trays.

Question 47

What indicates successful fluid therapy in cats?

Answer 47

Correction of haemoconcentration and normalization of packed cell volume and total solids.

Question 48

What is the best way to monitor a cat’s volume status during fluid therapy?

Answer 48

By measuring and comparing fluid volumes being administered with those being lost at regular intervals.

Question 49

What are the signs of volume overload in cats?

Answer 49

Edema of the limbs and/or face, tachypnea, clear nasal discharge, chemosis (conjunctival edema), and crackles on thoracic auscultation.

Question 50

What should be done if signs of volume overload are detected in a cat?

Answer 50

Fluids should be stopped immediately, and the veterinary surgeon should be notified.

Question 51

Why are cats particularly at risk of developing volume overload?

Answer 51

Due to their small size and the increased risk in cats with concurrent cardiac or renal disease, or when large volumes of fluid are administered.