In my experiment, I needed to collect blood, BAL fluid, and lungs. I administered ketamine/xylazine anesthesia, followed by cervical dislocation, then performed cardiac puncture for blood collection, and finally collected BAL fluid. However, I noticed that my BAL samples are contaminated with red blood cells.

Previously, when I collected BAL without performing cardiac puncture, the samples were clear. But now, with heart puncture, RBC contamination is evident.

Can anyone explain why this is happening or suggest how I can reduce this contamination?