The Ohio State University Veterinary Teaching Hospital has had an organized blood bank for small-animal transfusion medicine for more than 20 years. We currently process one to two units of feline blood a week and store both packed red blood cells and fresh frozen plasma.
Before 1998, cats were housed at the hospital to be on-demand donors of whole fresh blood. Because of the nature of on-demand donation, cats were not typically fasted at the time of blood collection, and the choice of chemical restraint (sedatives and anesthetics) was based primarily on time, expense, and ease of administration. During those years, intramuscular injections of ketamine hydrochloride were used with minimal complications. However, several aspects of chemical restraint with ketamine as a sole restraint agent were undesirable, such as the pain associated with administration, the extended recovery periods, and the worsening fractiousness of the cats with each subsequent donation. From 1998 to 2003, we evaluated several chemical restraint protocols for blood donor cats to improve the quality and efficiency of the blood bank, as well as the donors' quality of life.
We investigated the use of various chemical restraint protocols to facilitate quicker recovery times with minimal adverse effects, since the donors now have a scheduled time for donation, are appropriately fasted, and are to be sent home with the owners as soon as they recover. In this article, we review the advantages and disadvantages of the various methods of chemical restraint used by The Ohio State University Transfusion Medicine Service. We evaluated ketamine, midazolam hydrochloride and ketamine, medetomidine hydrochloride and atipamezole hydrochloride, acepromazine maleate and butorphanol tartrate, and sevoflurane. We chose not to evaluate propofol, another commonly used induction agent in private practice, because it has a short duration of action, it is best administered by intravenous catheter, it can induce apnea, and it has a high cost per average dose.
The subjective criteria used by the Transfusion Medicine Service staff to evaluate these restraint protocols are listed in Table 1. Table 2 presents additional information on the chemical restraint protocols we evaluated. A blood collection was considered successful if a minimum of 50 ml blood was collected.
TABLE 1: Criteria for Evaluating Chemical Restraint Protocols for Feline Blood Collection
BLOOD COLLECTION PROCEDURE
Blood donors were neutered males and spayed females between 2 and 7 years old. Twenty to 30 cats were enrolled in the donation program at any given time. The cats weighed at least 8 lb (3.6 kg) and had negative test results for feline leukemia virus, feline immunodeficiency virus, and heartworm infections. Most had type-A blood, though a limited number of type-B cats were also used in the program. Complete blood count and serum chemistry profile results and thyroid hormone concentrations for all donors were within reference ranges for our laboratory.
TABLE 2: Comparison of Chemical Restraint Protocols for Collecting Blood for Transfusion in Cats
For each collection, the cat was sedated or anesthetized, the hair over the jugular vein was clipped, and the site was scrubbed with chlorhexidine and cleaned with isopropyl alcohol. Each cat was placed on a circulating warm-water blanket, and ophthalmic lubricant was administered. A 20-ga butterfly catheter was placed in the jugular vein, and the blood was collected into a 60-ml syringe containing 8 ml acid citrate dextrose (ACD) solution. The blood was then transferred to a blood collection bag and separated into plasma and packed red blood cells. On rare occasions, the blood was used as whole fresh blood. Lactated Ringer's solution (50 ml) was administered subcutaneously to each donor immediately after donation. The cats' heart and respiratory rates and capillary refill times were monitored during donation and recovery.