A chronic arterial cannula for blood sampling in conscious, unrestrained rats

We require repeated blood samples for at least 10 days from conscious, unrestrained rats in our studies investigating the inflammatory response to intra-abdominal infection. Furthermore, we require a means by which other experimental devices (implanted concurrently) can be kept out of reach of the animals for the duration of the study. Under these conditions, previously reported postoperative restraint and cannulation techniques did not allow cannula patency for longer than a few days. We designed a cannula that is constructed from microbore tubing, attached to a modified wing-ed infusion catheter, and sutured over the scapulae of the animal. Our device features a curved, perforated tip to allow its easy insertion into the thoracic aorta via the left carotid artery, and it provides an attachment site for a small, lightweight backpack. This cannula has a small dead-space and accommodates repeated arterial blood sampling for at least 10 days without leading to bacteremia or significant alterations in hematological or immune parameters. With minor modifications, this cannula has potential application in the chronic cannulation of other vessels and ducts in other small animals.