We have a physician who orders small needles (16/17g). We have high preblood pump arterial pressures. I've been reading that this decreases the actual flow rate. I'd like to suggest that we use a bigger arterial needle (14/15g) and continue to use the smaller venous needles. Any problems with this?

Rebecca,
I have worked in units that used a larger arterial needle and smaller venous needle and it did work. You might see more elevated venous pressures from the better inflow from the arterial and the same amount of blood being fourced back into the smaller venous needle. I would use the same neelde size for both arterial and venous. Why will the MD not let you use larger needles?

In these cases I always recommend that you let your pre pump pressure be your guide. If the pre-pump pressure is greater than -200 mmHg. it's time to move to a larger gauge needle, at least for the arterial cannulation. I have heard of clinics using two different size needles for cannulating newly created accesses, but most will move to using the same size needles once the access is matured.

To support you in getting your physician to agree to move to larger gauge needles make sure he is aware of the following :
DOQI recommends that pre pump arterial pressure not exceed -200 mmHg. Negative pressures in excess of this will compromise delivered blood flow resulting in less than prescribed therapy for the patient.

Negative pressure > - 250 mmHg. causes sub-clincal hemolysis ( ANNA Core Curriculum).

Also the presence of excessive negative pressure in the extracorporeal circuit may result in the creation of micro-bubbles that may contribute to clotting within the system
reducing the effective surface area of the dialyzer, further compromising the delivered therapy dose. Micro-bubbles can result in clotted venous drip chambers as well. Also the risk of these micro-bubbles getting passed the air detector needs to be considered...it's possible.

Excessive negative pressure can cause damage to the patient's AV access.

There are several published articles and chapters in nephrology/dialysis books that discuss the importance of monitoring pre-pump arterial pressure to help maximize the delivered dose of dialysis and to minimize complications associated with excessive negative pressure in the extracorporeal circuit. One of these articles was written by our Vascular Access Moderator, Ms. Deborah Brouwer RN, CNN titled "Cannulation Camp".

Debbie, can you suggest some other reference articles for our friend Rebecca to share with her physician ?



[This message has been edited by Patt Peterson (edited 06-23-99).]