Hemodialysis for Companion Animals

There are a variety of methods of treating kidney failure in dogs and cats, ranging from standard medical management to dialysis.
 

What is Dialysis?

Dialysis is a method of treating kidney failure. Natural waste products build up in the body and the kidneys are supposed to excrete many of these toxins in the urine. When the kidneys fail, the toxin levels build up. Dialysis helps to remove these toxins.

 
There are two forms of dialysis available:
  1. Hemodialysis, which removes toxins directly from the blood stream.
  2. Peritoneal dialysis, which removes toxins from the body by way of fluid placed in the belly.
 
Dialysis works on the principle of diffusion. Toxins move from an area of high concentration (the sick patient's body) to an area of low toxin concentration (the fluid supplied in the dialysis process).
 

How does this differ from fluid therapy?

When the kidneys are failing, they cannot remove as many toxin particles in each pass of the blood through the kidneys, but they still remove some of the toxins. One way to improve the kidney's ability to remove toxins is to increase the volume of fluid in the blood.
 
Fluids given orally or by injection under the skin get absorbed into the bloodstream. Fluids can also be given directly into the veins (intravenous fluids). The fluid mixes in with the blood and the heart pumps it through the body, including the kidneys.
 
Dialysis does not depend on the kidneys to remove toxins. It provides a whole different way of removing the toxins from the body by performing the function of the kidney outside the body.
 

Who would benefit from dialysis?

Hemodialysis is available for both dogs and cats.

It can be used for acute or chronic kidney failure, although these provide two very different situations.

Most hemodialysis is for acute kidney failure. These are patients who have some chance for kidney repair, and thus may need dialysis only long enough to support them until the kidneys have healed.

In some circumstances, pets with chronic kidney failure are started on hemodialysis. In this setting, it is intended to be a regular treatment for the rest of the patient's life.

 
It can also be used for certain types ot toxicosis. Antifreeze poisoning (ethylene glycol) is the most common poison treated with hemodialysis.
 
Click image to enlarge

Hemodialysis

Hemodialysis involves removing toxins directly from the bloodstream. Thus, we must have a way to get the blood from the bloodstream to the machine and then return the cleansed blood back to the patient.

Hemodialysis requires having a catheter or needle placed in a blood vessel.

Hemodialysis requires a special hemodialysis machine, and there are few places equipped to do hemodialysis on animals.

Hemodialysis is more effective per unit time than peritoneal dialysis.

 

When should hemodialysis be started?

Because there is considerable risk and cost associated with hemodialysis, it is reserved until standard therapy (intravenous fluids, medications, etc.) have proven ineffective.
 
Patients with immediately life-threatening complications of kidney failure, like high potassium levels or fluid in the lungs, may benefit from immediate dialysis.
 
Patients who have eaten a poison that can be removed with dialysis (like antifreeze) should be dialyzed as soon as possible (hopefully within six hours) for maximum benefit.
 

What happens when hemodialysis is started?

 

Access to the bloodstream

Because hemodialysis involves cleansing the blood, access to the bloodstream is necessary. In animals, this is done with a catheter.

The catheter is a two-sided catheter made especially for hemodialysis. In most cases, it has to be placed surgically, under general anesthesia.

 
Once the catheter is placed, it is intended to remain in the patient for the duration of treatment, which may be up to a month or more.
 
In some high-risk settings, a different type of catheter can be placed with only sedation. The catheter will only last for a few treatments.
 

Treatment schedule - Getting started

When a patient is first started on hemodialysis, they must introduced gradually, to give them time to adapt.
 
The first treatment is usually short, around one-and-a-half to two hours.
 
The second treatment usually occurs the next day and is a little longer, around three hours.
 
The third treatment, usually on the third day, can be four to five hours. This schedule is adapted to the individual patient's needs.
 

Treatment Schedule - Standard treatments

Once the patient is adapted to treatment, the treatments occur three days a week (Sunday, Tuesday, and Thursday at The AMC).
 
The treatment time itself is four hours for cats, five hours for dogs. In addition to the treatment time, it usually takes about an hour to prepare the patient before treatment and an hour afterwards to finish up.
 

Care in the hospital

Dialysis replaces many of the functions of the kidneys, but it cannot replace them all.
 
Dialysis patients in the initial stages of treatment will need to stay in the hospital between treatments for ongoing medical care.
 
This includes fluid treatments, antibiotics, anti-ulcer medications and many other medications. Because these animals are frequently vomiting, they need to get their medications by injection.
 
In this stage, they need constant monitoring of things like blood pressure, urine production, blood counts, etc.
 

Home Care

Once the patient is more stable, and can take medications by mouth or by feeding tube (which is frequently needed during the recovery stage), they may be able to go home between treatments. The patient would then return on the three days a week treatment schedule.

The pet goes home with the dialysis catheter still in place. The catheter is covered by a bandage around the neck. It needs no care at home other than to keep the bandage clean and dry.

 

How long will my pet need dialysis?

When dialysis is used for acute kidney failure, it is continued until the kidneys get better or it becomes clear that the kidneys are never going to heal.
 
Most of the time, whatever kidney repair is going to happen will occurr four weeks.
 
Occasionally the kidneys will heal sooner and half the time (50% of patients), they don't heal at all.
 
With chronic kidney failure, the kidneys are permanently damaged. Dialysis is continued three times a week for the rest of the patient's life.
 

Will this make my pet live longer?

Complete kidney shutdown will cause an animal to die within four days. However, it takes up to four weeks for the kidney to heal from acute injuries. Dialysis is intended to support the patient during that healing time.
 
Not all pets with acute kidney failure can recover, even with dialysis. About half of these patients die, despite all of our efforts.
 
However, about half of these patients live and they were not expected to do so without dialysis to support them. They may recover completely with no lasting effects, or they may end up with chronic kidney failure and need special diets and medications to help support them.
 
Pets with chronic kidney failure on life-long dialysis may live a year longer than they would have without dialysis, although not all patients will live this long.
 
 

How will my pet feel about dialysis?

Most animals take well to dialysis. They clearly feel better at the end of a treatment and will ask for food or want to go out and play, which are things they couldn't be coaxed to do before the treatment.
 
During the treatment, they sit on a cushioned table with a blanket and a technician by their side to comfort them.
 
Animals don't seem to have the same degree of tiredness after dialysis that many people experience.
 

Are there any risks?

Any major medical or surgical treatment carries risks, and this is true for dialysis also. Some of the risks are due to the procedure and some are due to the kidney failure itself. The staff is trained to recognize potential problems, so immediate treatment or preventive measures can be used.

How much does it cost?

Hemodialysis is an intensive treatment that requires sophisticated equipment and specially trained staff. The average estimate for the care of a hemodialysis patient is $10,000-$15,000 for the first 3-4 weeks.

 

How do I get my pet evaluated for hemodialysis at AMC?

If your pet has kidney failure, and you are interested in pursuing hemodialysis, you can make an appointment with a member of the Hemodialysis team by calling the AMC appointment desk (212) 838-8100. Our email address is hemodialysis@amcny.org
 
You can also have your veterinarian call a member of the team to discuss your pet's case.
 
If your pet needs emergency dialysis after regular hours, bring him directly to The AMC for evaluation. There is a doctor on duty 24 hours a day. If emergency dialysis is indicated based on the emergency doctor's evaluation, a member of the dialysis team will be contacted.