The practice now....(Part 2)

After receiving the the attending Nephrologist/Physician permission to proceed with the first cannulation, identity the most experienced treatment practitioner whom has the best success rate of first time cannulation of new AVF to undertake the task.

The use of some form of restrain or tourniquet to sufficiently and uniformly engorged the intended vessel to be cannulated but NEVER over do it as we do not want unnecessary infiltration (swelling) to occur if something was to go wrong.

If the patient has a catheter in placed, then cannulate the arterial needle only and use the catheter as the "return". With only the AVF needle in place, if an infiltration occurs the resultant hematoma will be minimised.

Secondly, monitoring of the pre-pump arterial pressure can be done to correctly determine if the AVF has a good arterial flow. An pre-pump arterial pressure of (-) 250mmhg at a blood pump speed of 200ml/min via a 17G needle is good. A higher (-) pressure reading indicates the AVF supply flow to be insufficient and not good.

Next check the flow direction of the AVF; identify the incision or the anastomosis site of the AVF. Then palpate the AVF, find the access midpoint and compress lightly with a finger. The vessel with the arterial inflow will be engorged and pulsating with the flow, whereas the vessel for the outflow will diminished or not pulsating.

Another method is to auscultate; again use a finger to compress gently the AVF access midpoint, then with the aid of a stethoscope auscultate for the vessel of the arterial inflow and you can hear the pulsating flow of the arterial blood. As for the outflow vessel, you will hear a diminised blood flow with no pulsation.

Next compare the proposed AVF needle with the intended vessel to be cannulated with and without the vessel being constrained. Ensure the size of the AVF needle is appropriate for the intended vessel. Below is the guideline for size of AVF needles and the blood flow it can support:

       17G needle = 200-250ml/min
       16G needle = 250-350ml/min
       15G needle = 350-450ml/min
       14G needle = >450ml/min


Monitor the pre-pump arterial pressure, it should not be excessively higher of  more than (-) 250mmgh as this will indicate the AVF cannot support the blood pump speed.

Never underestimate the need to inform and explain to the patient the procedure and what to expect.

The AVF needle placement; the arterial AVF needle is cannulated either against the arterial inflow or along the blood outflow. The arterial AVF needle placement should be at least 1.5 inch from the anastomosis site. The arterial and venous AVF needle should be at least 1.5 inch apart.The venous AVF needle placement is always along the blood outflow.

Always try to locate an area where the vessels intended are straight and not torturous as this will lead to infiltrations and complications. Other no go areas are aneurysm and thinned-out areas....

to be contd......