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Drip for dogs and cats: when, how and why to use fluid therapy?

A drip for a dog

Water is a very important component of every organism.

Humans are 70% water, and so are pets - it is estimated that around 60% of an adult dog's body consists of water.

Every guardian of a dog and a cat suffering, for example, from chronic renal failure or dehydrated in hot weather, has found out about the importance of proper hydration of a pet.

It is believed that fluid therapy should also be used in most surgical interventions, as it improves the metabolism and excretion of drugs used for anesthesia.

Indications for fluid therapy also include shock, caused by blood loss, gastric torsion, but also severe cases of vomiting and diarrhea.

In such extreme situations, a pet's life is saved by appropriately selected therapy and drip, administered in the right way.

Properly replenishing water deficiencies in the body, can put a dog or cat on its feet, even in a very difficult condition.

Fluid therapy is aimed at replenishing water in the body, treating electrolyte disturbances and acid-base balance.

The main goal of fluid therapy is to restore the body's balance (i.e. replenish ions and water deficiency) as soon as possible.

Sometimes, along with fluid therapy, preparations used for parenteral nutrition are administered, but it is rarely used in veterinary medicine.

  • Water demand and water breakdown in the body
  • Types of fluids used in the drip
    • Crystalloids
    • Colloids
  • In what diseases is fluid therapy recommended?
  • Planning of fluid therapy
  • Methods of administering drips and precautions
    • Intravenous drip administration
    • Subcutaneous drip administration
    • Oral drip
  • Possible complications of fluid therapy

Water demand and water breakdown in the body

As I mentioned, an adult animal consists of 60% water, puppies and kittens - 80%.

More than 60% of the body-building water is inside the cells of the body, 40% - outside of them, of which only 10% in the blood vessels.

The intracellular and extracellular space is separated by cell membranes that are permeable to water - it moves into or out of cells, based on the osmotic pressure of the surrounding tissues.

The movement of water is a guarantee of the body's homeostasis.

Before discussing fluid therapy, calculate the patient's daily fluid requirements using a formula that takes into account the animal's body weight - in simple terms, the smaller the dog or cat's body weight, the relatively more water it needs.

And yes, a dog weighing 1 kg should take in 132 ml of water / kg of body weight, but a dog weighing 30 kg should take in 48 ml of water / kg of body weight.

It is important that this is a maintenance requirement that does not take into account possible dehydration - it is the suggested daily fluid intake.

It is estimated that dehydration at the level of:

  • about 5% - causes:
    • slight loss of skin elasticity,
    • slight drying of the mucous membranes;
  • about 8% - causes:
    • noticeable loss of skin elasticity,
    • noticeable drying of the mucous membranes,
    • a poorly palpable pulse in the peripheral vessels,
    • slight retraction of the eyeballs;
  • about 12% - causes:
    • significant loss of skin elasticity,
    • very much drying of the mucous membranes,
    • increased heart rate,
    • very poor perceptible pulse in the peripheral vessels,
    • decreased peripheral blood pressure,
    • periodic loss of consciousness.

When fluid loss occurs, the body activates two mechanisms - compensatory (manifested by vasoconstriction and mobilization of fluids from the venous bed; the effect is an increase in blood pressure without increasing fluid volume) and feedback regulation, i.e. activation of the renin-angiotensin-aldosterone system, that is, the RAA axis.

As a result of RAA axis activation, water is strongly reabsorbed in the kidneys, and the resulting urine is very concentrated.

This mechanism is aimed at centralizing the circulation, i.e. maintaining the blood supply to vital organs, until other compensatory mechanisms are activated.

Hypovolemia, i.e. a reduced amount of fluid within the blood vessels, does not have to be associated with dehydration, in the classic sense of the word.

A drop in oncotic pressure, caused by a disturbance in the amount of total protein or albumin in the circulating blood, can cause water to "escape " from the vessels to the surrounding tissues, for example, into the abdominal cavity.

The most common symptom that worries the animal's guardian is the enlarging outline of the abdominal wall and developing ascites.

The patient does not lose water physically - there is no diarrhea or vomiting, and he has not lost blood - nevertheless, he requires immediate intervention and administration of adequate fluid intake.

Attention, hypovolemia may coexist with dehydration, the two conditions are not mutually exclusive.

When planning fluid therapy, you should remember about the compensation mechanisms.

The volume of fluid administered to a patient should be carefully calculated. It should include compensation for fluid losses, compensation for electrolyte losses and coverage of the current water demand.

Types of fluids used in the drip

Types of drips

In the case of fluid therapy, the proper selection of fluids is very important.

The choice of the infusion solution should be influenced by the patient's condition, laboratory findings and the reason for dehydration.

A different type of therapy is recommended for patients who are in shock and another for those who have had diarrhea for several days.

The selected fluid should also take into account the level of ions in the animal's body - before using fluid therapy, it is worth taking an ionogram so as not to disturb the body's electrolyte balance.


Crystalloids are aqueous solutions of:

  • mineral salts,
  • organic acid salts,
  • low molecular weight carbohydrates.

They are cheap, quite accessible.

They usually do not cause any allergic reactions.

They quickly replenish the plasma volume, but for a short time - they enter the extravascular space quite quickly.

Crystalloids are administered when:

  • the patient has a deficiency of electrolytes that should be replaced as soon as possible,
  • when the volume of lost fluid is small or a short therapy is planned,
  • when there is no suspicion of a change in the amount of protein and albumin,
  • when the patient's diuresis should be increased,
  • when renal failure is suspected in combination with metabolic acidosis,
  • when the patient is not consuming water or food.


Colloids are aqueous macromolecular solutions.

The colloids are:

  • HES (Hydroxyethyl Starch),
  • gelatin solutions,
  • dextran,
  • albumin.

Colloids remain in the plasma much longer, and they replenish its volume for a longer time.

Colloids are given when:

  • it is difficult to administer enough fluid to cover the deficiencies in the body - for example in patients after heavy blood loss, massive hemorrhages,
  • tissue perfusion should be increased and oxygen supplied to them,
  • it is not advisable to administer large volumes of fluids - for example, in patients with cardiac problems,
  • it is necessary to raise the oncotic pressure in patients with decreased levels of total protein or albumin in the blood,
  • it is necessary to act longer than with crystalloids.

Colloids can be administered in conjunction with crystalloids, of course modifying the volume administered.

When planning fluid therapy, you should also consider where the fluids should go.

Plasma substitutes and most colloids remain in the intravascular space.

Crystalline solutions, such as lactated Ringer's solution, NaCl solutions are directed to the interstitial and intravascular space.

The glucose solution is located in all spaces:

  • interstitial,
  • intravascular,
  • intracellular.

In what diseases is fluid therapy recommended?

When the drip is given?

Fluid therapy is recommended most often when it comes to dehydration of the body.

A classic example is a dog or cat that has been vomiting and has had diarrhea for several days.

How to tell if your pet is dehydrated?

The simplest test is to assess the elasticity of the skin fold on the back of the pet - if the fold of skin caught on the neck does not return to its place immediately, but for some time "stands ", it means that the dog or cat is dehydrated.

Depending on the degree of dehydration, other symptoms may also occur, such as:

  • oliguria,
  • retraction of the eyeballs.

Another condition for which fluid therapy is worthwhile is kidney failure.

In this case, the fluid supply must be carefully planned to prevent overhydration of the animal and not overburden the kidneys.

It is necessary to use fluid therapy in the case of diabetes mellitus and adrenal crisis - then there are serious disturbances in the electrolyte balance and metabolic acidosis.

Fluid therapy is very important in patients who are unable to eat, do not feel thirsty in hot weather, or suffer from polyuria.

Such animals become dehydrated very quickly, and there is also a loss of potassium.

It is advisable to administer fluids in cases of surgical interventions.

It is an important part of perioperative care, especially if blood is lost during the procedure.

Administering fluids after or during the procedure has many benefits, in addition to compensating for blood loss, including:

  • supports the functioning of the blood system,
  • allows for pressure equalization,
  • reduces the negative effects of anesthetics,
  • hydrates the patient.

Planning of fluid therapy

When administering the drip, special attention should be paid to the behavior of the animal.

If the drip drips have been recommended by a veterinarian who takes care of the animal on a daily basis, when administering it at home, the animal should be checked for consciousness, whether it starts to drift on its feet or fall asleep.

It is worth checking the mucous membranes - whether they are becoming too pale or moist.

The number and speed of breathing is very important - stop fluid therapy when the animal begins to breathe quickly and restlessly.

In hospital conditions, the time of capillary filling, peripheral blood pressure, skin tension, presence or absence of pulmonary murmurs are additionally checked.

The patient's weight is regularly monitored and the daily amount of produced (excreted) urine is monitored.

If an anesthetized patient is undergoing fluid therapy, the saturation, i.e. the level of peripheral blood saturation with oxygen, is also checked.

In the event of instability of any of the parameters listed, the therapy is interrupted or modified to suit the current needs of the patient.

Methods of IV administration and precautions

Means of administration

First of all, any therapy should be consulted with a veterinarian.

I tried to present above that there is no one universal drip that will help with every disease and will miraculously cure the animal of all diseases. You can't give liquids just like that.

It is a therapy that should be carefully planned, based on the animal's health status, laboratory results and its conditions.

The patient should be regularly monitored during fluid therapy, and the therapy should be modified depending on changes in the patient's health condition and well-being.

Do not give fluids at home unless directed by your doctor.

Fluids can be administered intravenously, intraperitoneally, subcutaneously and orally - these are the four most common methods of administration.

In the case of very young animals, newborns, there is a possibility intraosseous administration of fluids, however, this is only done in veterinary clinics or hospitals.

Intravenous drip administration

Intravenous therapy ensures that most of the fluid is used up by the animal's body.

Thanks to this method, the amount of fluids administered can be carefully planned.

If the clinic where the animal is being treated has an infusion pump, the rate of fluid administration can also be planned.

This is very important in the case of renal failure where fluid administration is important, but by slow infusion into a vein.

This method of administering fluids requires a cannula.

Not every pet can wear it, not everyone is patient enough to withstand two or more days with a cannula.

Usually intravenous fluid therapy is performed in a hospital setting, as I mentioned, the speed of the fluid pumped into the body is important for this method.

The drip should necessarily be warmed to the body temperature of the animal, so that the body does not cool down.

Subcutaneous drip administration

Subcutaneous drip administration is much simpler.

It can be carried out at home, by an animal carer previously trained in a veterinary clinic.

The advantage of choosing this method is the speed of administration - even a large volume of fluid can be injected under the skin quite quickly.

The most important disadvantage, however, is the use of the fluid administered in this way by the body - it is much smaller and slower than in the case of intravenous administration, to achieve a similar effect you need a larger volume of fluid.

This method should not be used in the event of shock or the need for a quick fluid replacement.

In order to administer the fluid subcutaneously, you do not need to use a cannula, all you need is an injection needle and an infusion tube attached to the infusion bottle.

The depth of puncture is very important - too shallow puncture may result in intradermal drip administration, too deep may result in intramuscular or intraperitoneal injection.

With the correct administration of the subcutaneous drip, after a few moments you can observe the formation of a soft and shifting structure under the skin - this is the collection of infusion fluid, it should be absorbed within a few hours into the blood vessels of the skin and subcutaneous tissue.

Oral drip

Fluids can also be administered orally.

This method is suitable for patients who have an esophageal or gastric tube in place.

Birds are also hydrated in this way.

Intraperitoneal fluid therapy is not used very often in dogs and cats.

It is sometimes recommended as a form of dialysis.

Much more often it is used in the case of reptiles - snakes, lizards and turtles, or very small mammals - mice, rats.

It is important that the fluid fed in this way is warm.

Possible complications of fluid therapy

The major complication of inappropriate fluid therapy is fluid overload.

It consists in too much given fluids, most often with an inappropriate composition, which the body cannot cope with.

The first symptom is an increase in the number of breaths, an increase in heart rate.

In extreme cases, swelling may occur - internal organs (for example the lungs) and peripheral parts of the animal's body. Excess fluid may also be deposited in the peritoneal space and in the pleura.

Administering a fluid with the wrong composition, without taking into account the current state of ions in the body of a dehydrated animal, is also very dangerous.

Always be mindful of the patient's condition and the underlying medical condition that led to dehydration. Inappropriate selection of fluids can aggravate the pet's poor condition, cause even greater ion deficiencies or cause neurological disorders.

A common mistake in administering subcutaneous drips is improperly performed puncture.

As I mentioned above, if the injection needle is inserted too shallow, the fluid is administered intradermally - it is very unpleasant and painful for the animal.

It is very easy to insert the needle too deep, especially in young and small animals, and thus administer the fluid intraperitoneally or into the fascia or muscle area.

Inadequate preparation of the injection site, lack of disinfection of the skin before inserting the needle, may result in the formation of abscesses or inflammation in this area.

Too much fluid administered subcutaneously may cause necrosis of a given area of ​​the skin.

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