Assessment of five formulae to predict post-transfusion packed cell volume in cats

Abstract

This retrospective study aimed to identify the most accurate formula for estimating the increase in packed cell volume (PCV) after whole blood transfusion of cats, as several formulae have been reported but not validated. Forty cats, of varying breeds and gender, were included from two referral institutions after database searches over a 13 year period. Five formulae were used to calculate an estimated post-transfusion PCV based on the re-working of formulae for determining the volume of donor blood to be transfused; three formulae were derived from those previously reported in the feline literature and two from human paediatric medicine, where a similar mean blood volume has been described. Cats were subdivided into two groups, the first consisting of 17 cats with non-regenerative anaemia and the second consisting of 23 cats with ongoing losses such as haemolysis and haemorrhage; it was hypothesised that formulae could be more accurate for group 1 cats, whereas formulae applied to group 2 cats could have overestimated the post-transfusion PCV. Bland-Altman analysis was performed for all cats to compare the actual increase in PCV with the calculated increase for the five formulae. Formula 1 (PCV % increase = volume of blood transfused in ml/2 × bodyweight in kg) performed best overall and is easy to calculate; however, no single formula was highly accurate at predicting the PCV increase after whole blood transfusion in cats and, owing to the wide confidence intervals, these formulae should be applied judiciously in the clinical setting.

Exploration of risk factors for non‐survival and for transfusion‐associated complications in cats receiving red cell transfusions: 450 cases (2009 to 2017)

“…No individual formula was highly accurate at predicting the post‐transfusion PCV in anaemic cats (Reed et al . ). The inaccuracy described previously could lead to underestimate or overestimate up to 8% the post‐transfusion PCV, leading to increased risk for volume overload or increased patient morbidity (Reed et al .…”

“…) and cats (Reed et al . ) have described the inaccuracies of some. No individual formula was highly accurate at predicting the post‐transfusion PCV in anaemic cats (Reed et al .…”

“…This could suggest that more conservative transfusion strategies are appropriate in cats. Although several formulae have been used in veterinary practice to estimate posttransfusion PCV, previous studies in dogs (Short et al 2012) and cats (Reed et al 2014) have described the inaccuracies of some. No individual formula was highly accurate at predicting the post-transfusion PCV in anaemic cats (Reed et al 2014).…”

“…Blood volume required to meet the target PCV was based on the following formulae: PCV rise desired (%) multiplied by bodyweight (kg) plus 2, or [(desired PCV − patient PCV)/donor PCV] multiplied by 100 plus bodyweight (kg) (Griot‐Wenk & Giger , Reed et al . ). A test dose was given to each patient, physical examination parameters were recorded before and 15 minutes after the transfusion began.…”

“…The volume of WB and pRBC product transfused was determined by the primary clinician based on clinical signs and the target PCV deemed appropriate by the clinician for the individual cat. Blood volume required to meet the target PCV was based on the following formulae: PCV rise desired (%) multiplied by bodyweight (kg) plus 2, or [(desired PCV − patient PCV)/donor PCV] multiplied by 100 plus bodyweight (kg) (Griot-Wenk & Giger 1995, Reed et al 2014. A test dose was given to each patient, physical examination parameters were recorded before and 15 minutes after the transfusion began.…”