The animal is either over-anesthetized or has lost too much blood during the course of the surgical procedure. Adjust the anesthesia concentration and/or dosage, or choose a more appropriate anesthetic agent.
Minimize blood loss during surgery by careful dissection. Also, try tying off severed vessels with sutures, or use electrocautery to keep blood loss to a minimum. Do not use electrocautery while the catheter is inside the animal. This has the potential to damage the catheter and could render it inoperable.
If you require further technical assistance with this or any other issue, please contact ADInstruments Technical Support.