[TechnicalVault]

Depends what the indication is, for some kinds of trauma the evidence is that transfusions are what will keep the patient alive, e.g. you're dumping pints on the table and it's likely to be contaminated, you can't salvage and reinfuse. However, for pre-planned surgery the evidence suggests avoiding blood loss where you can is the best practice. Studies have also shown that pre-deposit autologous blood donation before surgery is of uncertain benefit so it tends to be contra-indicated in the UK at least.

Before we understood the risks we used to do transfusions a lot more frequently than we do now and this led to a generation of anaesthetists who would basically treat with blood transfusion at the slightest sign of low blood count. More recent studies have suggested that a lower blood count can be tolerated than was previously realised and that you can often get away with guaranteed pathogen free (and much cheaper) volume expanders. There has also been developments in cell salvage to reinfuse suctioned blood and methods to avoid blood loss in the first place.

Medical practice has also changed to reflect this and the changed evidence base, especially given the relative costs (hospital managers love to save money). Hip and knee replacement surgery used to use blood routinely and were almost always done under general anaesthetic, but given we now want to get patients out within a day or two post surgery we do the surgery under spinal block and minimise blood loss as much as we can.

tldr; We still need transfusions for some things but we should be using them less than we do.