Hemodialysis Information for Veterinarians
Hemodialysis enables the removal of metabolic solute and fluid waste from the bloodstream of an animal or human by allowing those wastes to diffuse out of the blood across many semi-permeable, biocompatible membranes. The dialysis machine pumps blood from the patient through a dialyzer (artificial kidney) outside the body and then pumps the purified blood back to the patient; these processes happen simultaneously and continuously throughout a (usually) 3-6 hour treatment session.
Adialysis candidate may beany patient with acute uremia or oligoanuria unresponsive to medical management. In addition to treating severe azotemia, dialysis can correct severe hyperkalemia, acidemia and volume overload during the course of a treatment. Usuallythree treatments given on consecutive days are required to safely treat a severely azotemic animal, in order to avoid sudden, extreme osmotic shifts, and to permit the brain to adapt to osmotic changes. Common reasons for dialysis referral in veterinarymedicine include ethylene glycol ingestion, leptospirosis (dogs), ureteral obstruction (cats), pyelonephritis, conditioning for transplantation, acute renal failure from systemic disease (e.g., pancreatitis) and acute uremia of unknown cause. We especially encourage referral of acute (within 12 hours of ingestion) ethylene glycol ingestion. In many of these patients, dialysis can quickly and thoroughly remove ethylene glycol and its nephrotoxic metabolites from the bloodstream beforerenal damage occurs, at a comparable cost to hospitalization and 4-MP therapy.
Dialysis is an outstanding intervention in many acute poisonings. Some drugs such as aspirin, acetaminophen and many prescription medications will diffuse through the dialyzer membrane and thus can be removed directly from the bloodstream. We can also remove many non-dialyzable substances via an adsorption process called hemoperfusion. For hemoperfusion techniques, a canister of adsorbent charcoal or polystyrene beads is added in circuit with the dialyzer.
Please call us early in the course of patient management. We encourage consultation as soon as you suspect a patient might benefit from extracorporeal therapy; delay in instituting therapy for a pet with acute renal failure can jeopardize a successful outcome. We’re always happy to discuss cases, whether or not they are eventually referred.
Spare the jugulars! Successful dialysis treatment requires high blood flow rates (5-50 ml/minute for a
cat, 25-350 ml/minute for a dog), which necessitates placement of a very large-gauge jugular catheter. We therefore ask that you avoid jugular venipuncture and jugular catheters whenever possible in a potential referral to help ensure a routine, percutaneous catheter placement avoiding a more complicated, surgical placement with general anesthesia.
We feel strongly about talking to clients personally before they arrive for a dialysis appointment.
Hemodialysis is intensive and can be quite expensive. We want to ensure that clients understand the financial and emotional commitment involved with dialysis, as well as the potential benefits and limitations of therapyfor a particular pet’s illness.
Please complete and fax a referral summary form prior to patient arrival, if at all possible! This helps tremendously with efficiency and client service. If you need summary forms, we’ll be glad to send them to you.