Can you tell me what is the temperature of the dialysate used on your facility?
We have the machines set to 37 C
thank you

alex,

Our "standard" is 37.5 but it can be adjusted for patient comfort from 35.5 - 39.0. We have one facility where the medical director has ordered 36.0 for everyone, the reasoning is it tends to help support BP's.

Chuck

Alex2,

Manufactures recommend RO membrane optimum fluid flow temperatures at (37°C). This temperature is the industry standard for dialysate. However, hypothermal dialysate flows (old school), lessons client crashes. But, does this effect clearances? Maybe someone can provide this info?

Our temps. are dictated by our physicians. Some docs. use the lower temps. to help prevent hypotensive events. Others will say if the patient feels cold raise the dialysate temps. In a nutshell we have temps. ranging from 35.0C to 36.5C.

The manufacturer of the RO membranes we use recommends an optimum temperature of 25C/77F for feed water. Dialysate temperatures are an entirely different animal with an apparently wide range. 39C seems high to me, that's 102.2F! Granted, I'm not an MD, but that seems a little toasty to me.

one of our docs likes 35, the rest 37.

our machines have a range of 34.5 to 39.0 if less than 34.5 low temp alarm greater than 39.0 high temp alarm. On average the temp is set to 37

Rob

I too would like to hear some nephrologist input on the dialysate temperature issue. However, since RO feed temperature was brought up in the discussion I felt compelled to comment.

The product water flow of an RO membrane is strongly dependent upon water temperature. So any output rating must specify an accompanying temperature. Long ago 25o Celsius was arbitrarily adopted by the industry as the temperature to use when stating output.

The cellulosic membranes used in early years of dialysis suffered hydrolysis damage much more as the water temperature increased. They would have a longer life with 50o F water than with 70o F water. However for a given application the colder water would require more membrane area. So perhaps something like 77o F would have been an economic optimum.

The TFC membranes used today don’t suffer from hydrolysis attack and water temperature per se is not an important factor in membrane life. Membrane costs have fallen and it is generally not economic to heat the feedwater and use an RO of smaller rating to meet output requirements.

Dialysis is one of the few RO applications wherein feedwater heating is normally used. Since the available tap water is almost always cooler than body temperature, it makes some sense to do some of the heating on the RO feedwater rather than all in the dialysis machine. It is easier to dissolve bicarb in warmer water also. However typically ½ of the energy supplied to heat the RO feed water goes to drain with the reject water. This otherwise waste of energy is mitigated since it is usually much more expensive to heat up the dialysate with electricity than the feed water with natural gas.

Bacterial growth is slower in colder water.

Still, there is no inherent optimum RO water temperature

I am not sure how or why this discussion has bounced back and forth from Dialysis machine and RO unit water temperature, but I do have some input.

Dialysate temperature:
The warmer the dialysate (>39ºC) the greater the chances of cause hemolysis (crushing or implosion of the red blood cells) in the patient. Most dialysis machines have an alarm set point of 39ºC to prevent the temperature from every getting close to the point where hemolysis will occur at 40ºC. Also, the high the temperature of the dialysate the more energy in transferred to the patient across the membrane of the dialyzer (it acts like a radiator). This causes the issues with patients crashing or vascular restriction (increased BP). The majority of clinic/MD use 37ºC (normal body temperature) as set point for dialysate temperature, but allow some adjustment for either patient comfort or decrease the energy transfer in problematic patients. Fresenius has a BTM (Blood Temperature Module) available for the 2008 H&K that monitors both the arterial and venous temperatures in the blood lines. This allows control of the dialysate temperature to maintain the patient’s temperature or zero the energy transfer… in other words, if the pt temp at the arterial line (from the pt) was 36.7ºC, the BTM module would control the dialysis machine dialysate temp to maintain the venous temp at the venous line (returning to the pt) at 36.7ºC.

Water Temperature for RO membranes:
The colder the water the less product water will be produced by the RO membranes due to constriction (shrinkage) of the membrane. This will mean a higher quality of water out of the membrane due to the pore size being decreased also. You will have less water produced, but you will get a lower conductivity reading in the permeate.

The warmer the water… you get just the opposite. More water will be produced at a lesser quality (higher conductivity).

The recommended temperature of the feed water is and should be 77ºF (25ºC) because this is the controlled room temperature in which the membranes are produced. The nominal pore size is created at this temperature and will be the correct size when the water entering the membrane is at or near this temperature also…. Or in other words… the membrane is made at this temp and will work exactly as it designed too at this temp.

I hope this helps answer your question.

Generally, they run at 37. I've seen very few variations from this. Remember that diffusion works better at a higher temperature. I know we're only talking about a degree or two, but in this business, every little bit counts. Additionally, how does one figure that raising the temperature on the machine will make the patient feel warmer? I've never felt warmer when I was running a fever. I've always felt colder. If you can explain it, I would love to hear it.

sorry, i know this feed water discussion is off topic of the original question, but i have a question about feed water temp.

i was under the impression that the cooler the feed water temp, the greater change in viscosity of the water, not the pore size. so cooler water=thicker, does not create as much product water at a constant pressure.
also, that membranes will always allow a small percentage of salts to "seep" through regardless of the temp.
so if less product water is produced, with the same amount of salt "seepage", then the product water conductivity will increase. and the reverse would happen with warmer water=more product water with the same amount of salt, the product water conductivity would decrease.
is this correct? or have i been drinking viscosity kool-aid?
thanks again for anyones input

Fellow Technicians,

Pardon me for throwing this forum off it's axis. My concern is regarding the hypothermal dialysis therapy, As stated by Woodruff, cold water = membrane constriction. How does this effect clearances? Has anyone come across any long term studies regarding this?

I only ask, because this therapy has been around as of the early 90's and possibly longer than that. My concerns are, Is it safe? and, client mortality.

AAMI RD5 says "Under normal operating conditions, the system shall maintain the temperature of the dialysate between 33 °C and 40 °C and within ± 1 °C of its set point value." RD5 also says "No single fault of the temperature control and monitor system shall allow dialysis when the dialysate temperature is above 42 °C. An alarm condition shall interrupt delivery of dialysate to the hemodialyzer, activate audible and visual alarms, and stop the blood flow in the extracorporeal circuit." Also "Thermal hemolysis requires blood temperatures of > 45.6 °C."

As for the temperature of the RO water, it must be low enough for the heater in the dialysis machine to work properly. I would not recommend supplying 37C water to a dialysis machine. And, the heater may not be able to increase the water temperature to 37C if it is supplied below 10C. The dialysis machine manufacturers have specifications on the incoming water temperature. Check the specs for your machine. The amount of water produced by an RO membrane and the quality of the water produced by an RO membrane is temperature dependent. So that everyone can compare apples to apples, the specifications for an RO membrane are based on 77F (25C) water. Many RO systems have an upper limit around 100F. Above 100F, you could damage the RO membrane or other components in the RO.