What happens with a loss of 5 units of blood during surgery?

Blood loss is very common during surgery.

5 units equates to about a liter and a half (equal to approximately 3,4 pints).

While this seems like a lot, as long as the patients blood pressure and heart rate remain normal (as well as other vital signs) the surgical team would check their hemoglobin levels (the cell that carriers oxygen around the body) and if they are in deficit they merely top the patient up with more blood.

If it turns into an emergency situation they give synthetic blood (a large molecule that supports the patients intra vascular system) until human blood can be obtained.

If a persons blood pressure and other vitals are so obscure that they have to give medication, they would give a vasoconstrictor (due to the drop in blood pressure associated with blood loss [hypovolemia].