Free Essay Sample about Hemodialysis
Hemodialysis is a common treatment for patients with kidney failure. A machine is used to send blood through a dialyzer. A surgically created vein is used to remove and return blood during hemodialysis. The blood travels through a tube to the dialyzer that filters out wastes and then returns the filtered blood back to the body. An AV fistula is a connection of an artery to a vein. An AV fistula causes extra pressure and blood to flow into the vein. An AV graft is a tube that connects an artery to a vein. An AV fistula is preferred due to fewer complications than an AV graft. The upper extremities are the most common for dialysis access. AV access will usually have a thrill because of the turbulent flow of the graft or vein. Changes in the thrill can indicate complications with the graft.
Ultrasound is used to assess the fistula. Ultrasound imaging of the inflow and outflow with volume flow measurements gives an indication of fistula failure or success. “The calculation of volume flow holds promise to become the most significant predictor of access dysfunction both in fistulas and grafts (Wiese, 2004). Evaluation of the fistula should include evaluation of the inflow artery proximal to the fistula or graft, inflow artery distal to the fistula or graft, anastomotic sites (fistula has one site, graft has two sites), puncture sites, proximal, mid, and distal outflow vein or graft, and axillary and subclavian veins (Teodorescu, 2012). It is normal to see low-resistance outflow to the arterial bed with diastolic flow throughout instead of triphasic waveforms that are seen in peripheral arterial beds. Pulsatile flow with high resistance or low PSV may indicate access failure.
The high stress of an AV fistula causes arterial and venous dilation. As the vein is exposed to the high pressure it starts to arterialize into a mature AV fistula. The blood flow through the fistula should be about 600 ml/min. This is so that it can sustain a standard pump rate during dialysis. Successful fistulas should be large, superficial and have high flow. “Decreased flow through the graft leading to thrombosis if the most frequent reason for graft failure and is caused by inadequate arterial inflow or venous outflow obstruction. Increased diastolic arterial flow, arterial pulsatility in the vein, and enlargement of the downstream vein due to increased volume of flow are all factors that allow us to establish a diagnosis.
Ultrasound is a great diagnostic tool for detection of AVF complications. It is able to detect AVF blood flow and possible causes of access problems. Duplex ultrasound demonstrates in a normal AVF low resistance flow in the feeding artery, turbulence and high-velocity flow at the anastomosis or fistula, thickened walls, and high-velocity flow in the dilated draining of the AVF. The detection of failure or mature fistulas is clinically significant and can be monitored through ultrasound to ensure successful dialysis.
