caring for sick animals, all veterinarians eventually find themselves
faced with a patient that has anemia of such severity as to require a
Access to blood products has improved in the past few years.
Veterinary blood banks can supply canine, feline, and even ferret
blood within 24 hours via overnight mail.
For animals that need blood more immediately, however,
veterinarians have to be more resourceful.
Canine blood is usually obtained from another donor dog, often a
young, healthy large-breed dog owned by a member of the veterinary staff,
such as a technician, receptionist, or doctor.
Sometimes, the client of a dog requiring a transfusion offers the
services of one of their other dogs in an attempt to provide the
life-saving blood that their sick dog requires.
Obtaining feline blood can be more of a challenge, as the demand
for feline blood products is much greater than the supply.
Some veterinary clinics utilize a so-called “hospital cat”.
This invariably turns out to be a cat that was either abandoned by
a client or left on the doorstep of the hospital. Rather than being
surrendered to a local shelter, these cats, through their sweet
dispositions, manage to win over the hearts of the hospital staff,
becoming adopted mascots of sorts.
They live a life of relative luxury at the hospital, entertaining
clients and staff alike.
Occasionally, they get called into duty, donating blood to a
desperately ill patient in time of need. Unfortunately, most cats can
donate only small volumes of blood (35 to 50 milliliters) every four weeks
human medicine, there has been an increased demand for blood and blood
demand has been driven by the need to support procedures with heavy
transfusion requirements, such as total hip replacement, organ
transplantation, and coronary bypass surgery.
The need for blood for sophisticated procedures, coupled with the
risk of viral transmission via transfusion, has led to a quest for a blood
substitute in human medicine.
This endeavor has been beneficial for veterinary medicine.
In 1998, the Food and Drug Administration approved the use of
by Biopure Corporation, Cambridge, Massachusetts, Oxyglobin is the first
“blood substitute” approved for use in the dog.
is an iron-containing molecule found in red blood cells that is
responsible for binding oxygen.
Oxyglobin is a purified hemoglobin solution.
It has the ability to deliver oxygen from the lungs to the tissues.
Because Oxyglobin does not contain red blood cells, white blood
cells, platelets, or clotting factors, the term “blood substitute” is
somewhat of a misnomer.
The preferred term is “hemoglobin based oxygen carrier”, often
abbreviated as HBOC.
with any therapeutic product, there are both advantages and disadvantages
to its use. Advantages
include the fact that blood-typing and cross-matching is not required
Adverse transfusion reactions occur because the red blood cells of
the donor are incompatible with those of the recipient.
Oxyglobin contains hemoglobin only; red blood cells and membranes
are removed during ultrapurification, eliminating the need for typing and
cross-matching and eradicating the occurrence of adverse transfusion
advantage is the long shelf life: Oxyglobin can be stored for 36 months
has some disadvantages that veterinarians and clients need to be aware of.
When administered, Oxyglobin expands the total blood volume, and
close monitoring is necessary to prevent development of pulmonary edema
(fluid in the lungs) and pleural effusion (fluid in the chest cavity),
both signs of fluid overload.
The distinct purple color of Oxyglobin will temporarily impart an
unusual color to the gums and the urine.
Some blood parameters may be affected after administration of
Oxyglobin, temporarily affecting our ability to use these parameters as a
diagnostic or monitoring tool.
Despite these shortcomings, Oxyglobin has become a useful product
in canine transfusion medicine.
a veterinarian, I was certainly thrilled when news of the availability of
this product was announced.
As a cat specialist, however, the first thing I focused on was the
labeling: Oxyglobin is approved for use in dogs only.
Despite the label, when faced with a cat that is imminent danger of
dying from severe anemia and with compatible cat blood not readily
available, my colleagues and I have found ourselves cautiously reaching
for the Oxyglobin.
As with any off-label usage, we inform our clients that the product
is not approved for use in cats, warn them of the potential risks and
benefits as best we can, and obtain their written consent before
no reason to suspect that Oxyglobin would work differently in cats
compared to dogs, but with limited experience using the product in cats, I
still find myself asking the basic questions: is Oxyglobin useful
in cats? Is
it effective? Is
a recent article in the Journal of the American Veterinary Medical
Association, the answer to these questions is a qualified “yes”.
The article, entitled “Use of a Hemoglobin-based Oxygen Carrier
Solution in Cats”, details the results of a review of the medical
records of 72 cats that received Oxyglobin.
Ninety-seven percent of the cats receiving the Oxyglobin were
anemic and most often received it because compatible blood wasn’t
of 43 cats that were monitored very closely showed improvement in at least
one evaluation parameter, such as increased body temperature, blood
hemoglobin concentration, blood pressure, appetite and activity.
A significant number of cats, however, showed adverse events
following administration of Oxyglobin, including discoloration of mucous
membranes and urine, vomiting, pleural effusion, and pulmonary edema.
Overall, 49 cats, all severely ill, died or were euthanized,
however, 23 cats survived and were discharged to their owners.
The authors concluded that administration of a hemoglobin-based
oxygen carrier solution may provide temporary support to anemic cats,
however, they remain somewhat reluctant to recommend routine usage in cats
pending further investigation of some of the complications that may be
associated with its use, such as pulmonary edema and pleural effusion.
exciting possibility that is currently being investigated is the use of
Oxyglobin in non-anemic patients with other disorders requiring increased
oxygen delivery to tissues, for example, restoring oxygen supply to
tissues that have suffered oxygen deprivation.
This may have application for cats with aortic thromboembolism, a
devastating complication that sometimes develops
in cats with hypertrophic cardiomyopathy, a disease of the heart
still have much to learn about the clinical use of hemoglobin-based oxygen
in which HBOCs are compared to blood are difficult to interpret because
HBOCs do not have many of the properties of blood and cannot be considered
to be equivalent to transfusion with red blood cells.
It would be like comparing apples and oranges.
It would be even more difficult to perform studies comparing HBOCs
to no transfusion at all, as it would be ethically questionable to deny a
pet a transfusion when medically necessary.
We can, however, continue to make observations regarding which
species might benefit from these products, and which diseases and
conditions might improve with their use.
Hopefully, HBOCs will allow us to treat a myriad of diseases for
which current therapy is limited.