An arteriovenous (AV) graft is a surgically created access point that allows patients with kidney failure to receive hemodialysis treatments. This access facilitates the continuous, high-volume flow of blood required for the filtering machine. Maintaining the graft’s functionality is a daily responsibility, and its health is assessed by specific physical sensations that confirm its proper working state.
What is an Arteriovenous Graft?
An AV graft is a vascular access created by a surgeon connecting an artery to a vein using a piece of synthetic tubing. This tube, typically made of polytetrafluoroethylene (PTFE), is placed just beneath the skin, often in the forearm or upper arm. The connection channels high-pressure blood from the artery through the synthetic conduit and into the vein.
This procedure is performed when a patient’s native veins are too small or weak to mature into an arteriovenous fistula. The graft provides a reliable, high-flow pathway that can withstand the repeated needle insertions required during dialysis sessions. Unlike a fistula, which takes several months to mature, a graft can usually be used for dialysis within two to four weeks after placement.
The Expected Sounds and Sensations: Bruit and Thrill
A functioning AV graft must exhibit a thrill and a bruit, which confirm successful blood flow. Their presence is the primary indicator of the graft’s patency. These sensations result from the arterial blood’s high-pressure, rapid flow being diverted into the lower-pressure venous system through the narrow surgical connection.
The thrill is a palpable vibration or buzzing sensation felt when gently touching the skin over the graft. This feeling is created by the turbulent flow of blood rushing through the synthetic tube, often described as a continuous purring. The bruit is the auditory equivalent of the thrill; it is a whooshing or continuous roaring sound heard when a stethoscope is placed over the graft site. Both the thrill and the bruit should be strongest near the connection point, gradually diminishing in strength along the length of the graft.
Daily Monitoring: Recognizing Warning Signs
Patients must monitor their AV graft daily, as any change in the thrill or bruit can signal a complication. The most important warning sign is the complete loss of the thrill and bruit, which suggests the graft has clotted off (thrombosis) and is blocked. The absence of these sensations requires immediate contact with the dialysis team or physician, as prompt intervention is necessary to restore flow and save the access.
A noticeable change in the character of the sensations is also concerning and should be reported without delay. For instance, if the thrill becomes weaker, or if the bruit changes from a low-pitched hum to a higher-pitched sound, it may indicate a narrowing of the blood vessel, known as stenosis.
Other physical signs that warrant immediate medical attention include swelling of the arm, redness or warmth over the graft, or a cold sensation in the hand or fingers. A cold sensation can be a sign of reduced blood supply to the limb. Consistent self-assessment and rapid reporting of these changes are the best defense against graft failure.