A connection of a patient's vascular system to an extracorporeal blood treatment machine is monitored to ensure the patient's safety during a procedure. The procedure may be hemodialysis, apheresis, plasmapheresis, a coronary by-pass operation, or other procedure. To ensure safe electrical connection, a contact and a return are connected via a conductive connection into the extracorporeal blood circuit. A current is then generated between the contact and the return and is monitored by a non-contact sensor near an access site of the patient. If the current or other quantity related to the current changes significantly, a signal is sent to the machine or a controller to notify a caregiver or a medical professional. The signal may also be sent to immediately stop a blood pump or other component of the machine.
