Blood tests before and after surgery

Dear Ask The Doctor: Dear sir/madam I recently underwent two procedures and for my check up on the first procedure they said the hematology tests results were clear. I had presumed they had taken a sample and sent for testing during my procedure is that common practice. My question being that was in january and had the second procedure since then and am due a third in june and today I've been scheduled to take another blood test by a new doctor. Is there a reason any specific reason for this and are samples taken from patients during operations normally?

Dear Sean: You have not stated the procedures which you have done or the test that were done so I am only able to make general statements.There may be a need to run various test during a surgical procedure depending on what happens during the operation. This does not happen in all surgeries. Blood tests are normally done prior to surgery and after surgery as a means of assessing patients.