Rapid and repeated blood sampling in the conscious laboratory rat: a new technique.

A method for obtaining repeated blood samples from conscious rats by translumbar vena cava puncture is presented. Studies performed at laparotomy enabled us to select a 5/8-in., 25-gauge needle as the ideal instrument for aspirating blood. The awake rat is held prone by an assistant and the needle inserted at the level of the first lumbar vertebra in the coronal plane at an angle of 45 degrees from the vertical. We performed the procedure 350 times in 30 rats (100-300 g) at weekly intervals for 8 wk. Each time, we have obtained 2 ml of blood. The time required for obtaining 30 samples is 15-20 min. There have been no complications and only three deaths (mortality rate, 0.9% per puncture); in all three instances the rats jerked free, lacerating the vena cava. The procedure has been performed in guinea pigs and hamsters, with equal ease, without morbidity or mortality. This new technique permits rapid, atraumatic, repeated samplings from awake animals with no morbidity and minimal mortality.