Introduction: Blood transfusions are performed frequently in veterinary patients experiencing decompensated anaemia. Increased left atrial and ventricular dimensions have been reported in severely anaemic cats, suspected due to activation of neurohormonal compensatory responses to maintain haemodynamic stability. The clinical significance of these changes is unknown. The effect of blood transfusion on cardiac dimensions in naturally occurring anaemia has not been reported.

Methods: Dogs and cats with naturally occurring anemia of any cause were included. They received an echocardiogram and had packed cell volume (PCV) and total solids (TS) performed before and within 24 hours following packed red blood cell transfusion. Signalment, body weight, disease process, transfusion duration and volume, and treatment with steroids or intravenous fluids were recorded.

Sample size calculation predicted 20 dogs and cats were required for significance. Nonparametric statistics were performed and a post hoc Bonferroni correction amongst echocardiographic variables set significance at (p<0.006).

Results: Twenty-three cats and 27 dogs were enrolled with 10 exclusions due to poor patient compliance, failure to perform post-transfusion echocardiogram, or because blood transfusion was not required. PCV significantly increased in both cats and dogs following transfusion (p=0.001), and heart rate decreased significantly in dogs following transfusion (p<0.001). In cats, fractional shortening (FS%) significantly decreased (median 57.1, range 36.0–84.7, pretransfusion; and median 41.6, range 28.1–69.6, post-transfusion; p=0.002) and left ventricular internal diameter in systole (LVIDs) significantly increased (median 6.5, range 2.7–9.8, pretransfusion; and median 7.9, range 5.3–11.1, post-transfusion; p=0.001).

In dogs, FS% significantly decreased (median 41.57, range 24.12–62.97, pre-transfusion; and median 32.94, range 12.5–51.47, post-transfusion; p=0.006), and left ventricular internal diameter in diastole (LVIDd) (median 31.7, range 21.3–45.6 , pre-transfusion; and median 34.0, range 24.7–51.30 , post-transfusion; p=0.006) and LVIDs (median 18.4, range 11.7–34.6 pretransfusion; and median 34.4, range 14.9–44.3, post-transfusion; p<0.001) were significantly increased, as were Bodyweight-normalised values for left ventricular dimensions.

Conclusions: Blood transfusion appears well tolerated in haemodynamically compromised patients with naturally occurring anaemia of all causes.