The use of fluids are a very important part of veterinary medicine. There are many types of fluids that we use the assist pets suffering from illnesses and undergoing surgery.
Why are there different types of fluids?
The most common fluids used in veterinary medicine include:
- Saline (0.9% Sodium Chloride)
- Lactated Ringers (or Hartmann’s Solution)
- Dextran 70
- Glucose Solutions
- Whole Blood Transfusions
- Plasma Transfusions
We all know that our body is made up mostly of water, and it serves a lot of very important functions in our body. You may notice that the list above are all liquids that contain an additive (e.g. Salt is contained in saline solutions). This because our body is more than just water and cells, it is a complex combination of electrolytes, proteins, enzymes and cells. When a patient is placed on fluid therapy it is important to determine what is the best fluid type. This is often determined by a blood test. For example, if your pet is deficient in potassium (an electrolyte), then a fluid high in potassium is normally given to assist correction; if your pet is anaemic, then a solution containing red blood cells (whole blood or packed red cells) is usually given.
Why are fluids given?
Generally speaking fluids are given for a several different reasons
- Support blood pressure: This is especially important for surgery. If blood pressure drops excessively then there may not be enough blood pumping through arteries to provide nutrients and oxygen to organs.
- Rehydration: if a pet is dehydrated then the body has trouble getting blood and nutrients around the body, as well as getting toxins out. When we are sick we often stop drinking and it can be difficult and dangerous to force a pet to consume water. When a pet is severely dehydrated we also need to be careful not to rehydrate too quickly.
- Maintain the body: The body has a natural requirement for water to keep it functioning and healing. If the body does not receive its needed water then your pet can quickly become dehydrated. If a pet is vomiting, then drinking fluids can make their condition worse.
- Flush out toxins: When toxin are either ingested, absorbed or produced by the body we need to clear them out of the system as quickly as possible to prevent long term effects.
- Correct abnormalities: If a blood test has revealed electrolytes, blood cell or protein levels are not normal, than it is important to correct these for the body to function effectively and prevent further damage
- Nutrition: if a pet is not able to eat for an extended period of time glucose or nutrition support can be delivered directly into circulation.
How are fluids given?
The most common methods of fluid therapy are:
- Oral: simply giving water, electrolytes or liquefied food by mouth
- Intravenous: a catheter is placed into a vein and fluids are delivered directly into circulation
- Subcutaneous: fluids are injected under the skin and slowly absorbed over a few hours. Unlike humans, dogs and cats have quite loose skin meaning this method can be very useful if fluids are needed to be given at home or regularly.
- Intraperitoneal: fluids are infused into the abdomen (belly) around the organs and absorbed
- Intraosseous: fluids are infused into a bone. This method is mostly used in very young patients, birds or reptiles.
Your veterinarian will advise on what is the most appropriate method of delivering fluids to your pet.
Why does my pet need to be hospitalised for intravenous fluids?
Because intravenous fluids go directly into the circulation it is important that they are given slowly. If too much fluids are given or if imbalances are corrected too quickly then serious damage can occur – for example fluid can leak out of the veins and into the lungs causing a “drowning”. Because intravenous fluids are about slowly correcting abnormalities or flushing out toxins, they need to be given over an extended period of time. Short periods of fluids (such as 1-2 hours) are only of benefit in situations such as surgery.