Animals maintain a normal fluid balance in the body by drinking and taking in fluids in their foods to offset the fluids lost in urine, feces and from the respiratory tract when panting. When fluid balance is severely disrupted, dehydration and shock may occur. Supplemental fluids may be needed if fluid intake decreases, losses increase, or both occur. Eating and drinking less lowers the intake of fluids. Increased losses can also occur through vomiting, diarrhea, panting, kidney diseases, bleeding or surface burns.
Fluid therapy involves fluids or supplemental body electrolytes, such as sodium and potassium, to be given by intravenous methods. Intravenous fluids are given through the needle or through catheter inserted into a vein. IV catheters are most commonly inserted into the veins of the front legs. Large amounts of IV fluids can be administered quickly, making this an ideal route when the need for fluids is urgent. A variety of fluids and electrolyte mixtures, as well as many medications, can be given intravenously.
Crystalloid solutions have about the same consistency as the watery part of blood and can contain varying amounts of electrolytes. Glucose and other medications may be added to crystalloid fluids. Colloid solutions contain substances that are similar to normal blood proteins. Colloids are used primarily when blood proteins are low, to keep water from leaving the bloodstream. Colloid solutions can be irritating, so they are usually administered IV in a large vein. Fluids may be administered continuously or intermittently, through open drip lines or through an IV pump that strictly controls the rate and amount to be given. For IV fluid therapy, the hair on the skin is clipped at the site of catheter insertion, and the skin is cleaned with an antiseptic solution until all dirt and debris are removed. After the catheter is inserted and a cap or plug is applied, it is bandaged to the skin.
Complications are uncommon but can include infection and temporary bleeding where the needle is inserted. Most infections arise from bacterial contamination of the fluid or entry site. Complication of IV administration includes premature removal of the catheter, bleeding from the catheter port or insertion site, irritation to the vein, and loss of catheter into the bloodstream which is thankfully extremely rare. Overdosage of fluids can aggravate existing heart disease and lead to accumulation of fluid in the lungs and abdomen. If you feel your dog may be dehydrated, your veterinarian can ascertain if this is true, and recommend intravenous fluids for your pet.
Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.