Advances in veterinary medicine are often adopted from human medicine but made appropriate for the size and species of our patients. One increasingly common treatment making an impact in veterinary medicine is dialysis. I had the chance to work with a few dialysis patients this summer under the guidance of veterinary critical care specialists.
Common indications for dialysis include drug or toxin ingestion, leptospirosis, acute or chronic kidney injury, hyperkalemia, or fluid overload. The most memorable case I had the chance to assist with was a patient who presented for lethargy, dehydration, anorexia, and oliguria. He was put on fluids to alleviate the dehydration but ended up becoming fluid overloaded. It was later discovered he had acute kidney injury. The goal of dialysis is to remove small molecules in the blood such as blood urea nitrogen, creatinine, phosphorus, drugs, or toxins. In the case of this patient, the goal was to first remove the excess fluid off of him, and secondarily bring his creatinine and BUN values down while he was unable to concentrate his own urine. He started off getting one, six-hour treatment for three days, then moved to every other day to every two days. He ended up doing great!
How it Works
The dialysis machine itself works like a giant, man-made kidney. Like the kidney, the dialysis machine functions by means of diffusion. A double lumen jugular catheter is surgically placed in the patient. This catheter has two lines that it connects to on the dialysis machine during treatment. The first is the access line, equivalent to the afferent tubule of the kidney, and the other is the return line, equivalent to the efferent tubule. Blood moves out of the patient by means of a jugular catheter’s access line, moves through the machine where it is filtered and returns back to the patient through the return line. The solutes being dialyzed out of the body move from the blood, where they are in higher concentrations, through tons of tiny straws surrounded by dialysate fluid within the dialysis membrane, to this dialysate of lower concentrations of solutes. In the kidney metaphor, the dialysis membrane is comparable to the filtering abilities of the nephrons, and this dialysate with the unwanted solutes is equivalent to urine. Patients remain awake or lightly sedated for the treatment.
As more is learned with an increasing number of cases managed by dialysis as it becomes a more common tool in the veterinary ICU, outcomes improve. Prognosis overall depends on the etiology of the disease, but about a 65% survival rate after discharge is seen. Overall, it is a safe way to manage patients when indicated, and as we continue to learn more it can be a great tool for our patients.