Pseudomonas fluorescens contamination of a feline packed red blood cell unit and studies of canine units

Background: While screening programs have reduced the risk of infectious disease transmission by donors in human and veterinary blood banking, bacterial contamination of blood products has emerged as a major complication in human medicine. Objectives: To describe a Pseudomonas fluorescens (Pf)‐contaminated feline packed RBC (pRBC) unit and experimentally investigate Pf‐contaminated canine pRBCs. Methods: Canine pRBCs were inoculated with Pf‐rich pRBCs from the sentinel feline unit and stored at 4°C or 20°C for 72 hours. Aliquots from the pRBCs were serially evaluated by microscopy, culture, and a eubacterial 16S rRNA real‐time PCR assay. Results: One Pf‐contaminated feline unit turned black after 22 days of storage and was removed from the blood bank; a source was not found, and no other contaminated units were identified. Canine pRBCs spiked with 5 or 25 μL of the sentinel unit became culture‐ and/or 16S PCR‐positive at ≥8 hours at 20°C and 48 hours at 4°C and developed a color change at ≥24 hours. Sensitivity studies indicated that without incubation, inoculation of ≥100 μL Pf‐rich pRBCs was necessary for a positive 16S PCR test result. Conclusions: P. fluorescens grows in stored pRBCs slowly at 4°C and rapidly at 20°C. Screening of blood products for color change, estimating bacterial concentration with microscopy, and 16S PCR testing are simple and fast ways to detect bacteria in stored blood. Aseptic collection, temperature‐controlled storage, and regular visual monitoring of stored units is recommended. Discolored units should not be transfused, but examined for bacterial contamination or other blood product quality problems.     

A prospective, randomized comparison of Oxyglobin (HB-200) and packed red blood cell transfusion for canine babesiosis

Objective – To establish the efficacy of Oxyglobin (HB-200) in canine babesiosis and compare it to standard therapy, packed red blood cell transfusion (pRBCT) with respect to improvements in specific parameters of blood gas, acid-base, blood pressure, and subjective evaluations.
Design – Prospective, randomized, clinical trial.
Setting – Onderstepoort Veterinary Academic Hospital.
Animals – Twelve dogs (8–25 kg) naturally infected with Babesia rossi and a hematocrit of 0.1–0.2 L/L (10–20%).
Interventions – Treatment groups were randomized to receive either 20 mL/kg of Oxyglobin or pRBCT over 4 hours via a central venous catheter. Transfusions were followed by lactated Ringer's solution infusion. Rectal temperature, femoral arterial and mixed venous blood sampling, oscillometric blood pressure, and subjective assessment of patient status (habitus), and appetite were performed at time points 0, 1, 4, 8, 24, 48, and 72 hours.
Main Results – Dogs presented with a hypoalbuminemic alkalosis; hyperchloremic, dilutional acidosis; normotensive tachycardia; pyrexia; depression; and anorexia. Both treatments produced similar results, with the exception of significant differences in pH (4 h); PCO₂ (4 h); hemoglobin (8 h, 24 h); mean arterial pressure (48 h); albumin (4 h, 8 h); habitus (8 h, 48 h); and appetite (24 h). Arterial O₂ content was higher for pRBCT than Oxyglobin at 72 hours, but central venous PO₂ did not differ between groups or over time and was consistently subnormal.
Conclusions – Oxyglobin provides similar overall improvements to pRBCT in dogs with anemia from babesiosis, with respect to blood gas, acid-base and blood pressure, although patients receiving packed cells tended to have more rapid normalization of habitus and appetite.     

Influence of transfusion technique on survival of autologous red blood cells in the dog

Objective – To determine the effect of 3 differing transfusion techniques on survival of autologous canine RBCs. Design – Prospective, blinded study. Setting – University Teaching Hospital. Animals – Nine healthy dogs. Interventions – Three distinct preparations of RBCs, each representing ～1% of red cell mass, were generated for each dog by biotinylation of RBCs at varying biotin densities. Labeled cells were transfused using 3 techniques (gravity, volumetric pump, syringe pump). Serial determinations of red cell survival were carried out by flow‐cytometric analysis of RBCs collected at 7‐day intervals for 49 days. In vitro analysis of the effect of transfusion methods on RBC integrity and osmotic fragility were carried out in 7/9 dogs. Measurements and Main Results – RBCs administered via volumetric and syringe pumps exhibited a marked decrease in short‐term probability of survival compared with RBCs delivered by gravity flow. At 24 hours, only 4/8 and 1/7 dogs had surviving cell populations delivered by volumetric and syringe pump, respectively, compared with 8/8 dogs which had surviving cell populations delivered by gravity flow. Circulating half‐life of cells surviving at 24 hours after delivery by volumetric pump was not significantly different to that delivered by gravity flow. No significant effect on in vitro RBC integrity or osmotic fragility was detected in relation to transfusion technique. Conclusions – Delivery of autologous canine RBCs via mechanical delivery systems was associated with a high risk for early loss of transfused cells.     

Controversies related to red blood cell transfusion in critically ill patients

Objective – To review the evolution of and controversies associated with allogenic blood transfusion in critically ill patients. Data sources – Veterinary and human literature review. Human Data Synthesis – RBC transfusion practices for ICU patients have come under scrutiny in the last 2 decades. Human trials have demonstrated relative tolerance to severe, euvolemic anemia and a significant outcome advantage following implementation of more restricted transfusion therapy. Investigators question the ability of RBCs stored longer than 2 weeks to improve tissue oxygenation, and theorize that both age and proinflammatory or immunomodulating effects of transfused cells may limit efficacy and contribute to increased patient morbidity and mortality. Also controversial is the ability of pre‐ and post‐storage leukoreduction of RBCs to mitigate adverse transfusion‐related events. Veterinary Data Synthesis – While there are several studies evaluating the transfusion trigger, the RBC storage lesion and transfusion‐related immunomodulation in experimental animal models, there is little research pertaining to clinical veterinary patients. Conclusions – RBC transfusion is unequivocally indicated for treatment of anemic hypoxia. However, critical hemoglobin or Hct below which all critically ill patients require transfusion has not been established and there are inherent risks associated with allogenic blood transfusion. Clinical trials designed to evaluate the effects of RBC age and leukoreduction on veterinary patient outcome are warranted. Implementation of evidence‐based transfusion guidelines and consideration of alternatives to allogenic blood transfusion are advisable.     

The effect of water intake prior to blood sampling on packed cell volume in sheep

The effect of water intake prior to blood sampling on subsequent packed cell volume (PCV) was investigated in ewe lambs (8 months of age) of the Dohne Merino, Merino and Letelle flocks at Grootfontein Agricultural Development Institute. On the afternoon of the day before the experiment was conducted, a blood sample for a baseline PCV value (R) was taken from each animal. The following day, 15 ewes of each breed (n = 45) were dosed with 1 litre of water and another 15 of each (n = 45) were used as a control. Blood samples for PCV were taken concurrently for both the control and water treatment groups before the dose (0), and at 15, 30 and 60 minutes after dosing. PCV were subsequently determined with the microcapillary centrifuge technique. Baseline PCV of Letelle ewes was higher (32.4 +/- 0.6) than that of the Dohne Merino (29.7 +/- 0.6) and Merino (28.7 +/- 0.6) ewes. Furthermore, recovery rate at 30 minutes after treatment also differed among breeds. Although there were significant differences between the control and water treatment groups at R and 0 minutes, which were probably due to inherent animal differences, there were no significant differences between PCV of the 2 groups during the remainder of the experimental period. Overall it can be concluded that water intake before blood sampling for the determination of PCV has no significant effect on haematocrit. Differences among breeds were more pronounced than those between treatment groups.