Dialysis therapy is dependent on diffusion and convection through a large amount of water, so during that patient gets exposed to temperature changes of water directly.
Malfunction of the heating element in the dialysis machine can result in the production of excessively cool or hot dialysis solution. Use of cool dialysis solution (down to 35°C) is not dangerous unless the patient is unconscious, in which case hypothermia can occur and reduce diffusion so the treatment is less efficient. A conscious patient will complain of feeling cold and shiver. On the other hand, use of a dialysis solution heated to >42°C can lead to blood protein denaturation and haemolysis.
Accumulation of thermal energy over a prolonged period of time may eventually lead to heat stress. This with hypovolemic stress leads to cardiovascular instability.
Control of body temperature during haemodialysis has the potential to improve cardiovascular stability during haemodialysis.
In all dialysate delivery systems, dialysate is routinely kept in the range of 37°C to 38°C (98.6°F to 100.4°F). Water needs to be heated to a certain temperature before mixing with the concentrates. Temperature check and control is done during formation of dialysate and during dialysis therapy.
- During formation of dialysate
Temperature Blending Valve
Figure 1 Temperature Blending Valve
The temperature blending valve is a device that can be set to mix hot and cold water to achieve a specific water temperature.
A defective blending valve will not necessarily endanger your patients as dialysis machines have a bypass mechanism for overheated water/dialysate, but it can damage the heart of your dialysis clinic, your water treatment equipment. There is a 1.5% decrease in efficiency for every 1°F drop in temperature.
A temperature gauge is placed downstream from the temperature blending valve as a monitor. The temperature blending valve should be checked each day by measuring the temperature after the valve.
What to look for?
- Appropriate water temperature (25°C)
- Minimal temperature fluctuation (2°C).
To maintain temperature, a heater is used if water is cold. Heat exchanger can be placed before the heater to save energy. In these systems, used dialysate transfers its heat to the incoming cold water, warming it before it enters the heater. But if the water is having temperature above the set limit we will have temperature alarms. To solve this issue of avoiding excessive heating of RO water we need to cover RO plant with shade and for distribution of RO water CPVC to be used.
The temperature blending valve should be checked each day by measuring the temperature after the valve.
- During dialysis therapy
Temperature alarm
To check dialysate temperature, a separate temperature monitor is placed in the dialysate path before the dialyzer. This monitor’s limits are pre-set. Many alarm systems have a low setting, which should not be below 33°C (91°F). The high limit should be set at not higher than 41°C. If the temperature is too hot or cold, a circuit sets off audible and visible alarms. Circuits also trigger bypass to shunt dialysate to a drain.
Before each dialysis treatment, check the dialysate temperature alarm to ensure that it is working properly.
Concept of lower dialysis solution temperature
Ideally, the dialysis solution temperature should be maintained at its initial level throughout dialysis. When the dialysis solution temperature is higher than this ideal level, cutaneous vasodilation occurs that increases risk of hypotension.
Temperature set of 35.5°C– 36.0°C are better initial choices, with adjustment made up or down depending on tolerance (chills) and effectiveness (blood pressure). We can do individualizing dialysis solution temperature as per clinical symptoms. Tympanic membrane temperature is measured, and the dialysis solution temperature is set 0.5°C below this level. This system of individualized cooling has been shown to avoid the sensation of cold and chills commonly found by simply lowering dialysate temperature to a given level for all patients (Odudu, 2012). Individualized, cooled dialysate is associated with a shorter post-dialysis recovery time, better maintenance of blood pressure, reduced myocardial stunning, and less evidence of progressive ischemia-related brain white matter damage (McIntyre, 2014) but still it needs long term data.
Blood temperature control module
Function
Small arterio-venous temperature gradients in the extracorporeal circulation cause considerable flows of thermal energy between the patient and the environment.
Monitoring the temperature of the incoming and the exiting blood, as well as of the dialysis solution to maintain “isothermic” dialysis for increased hemodynamic stability. May also be used to measure access recirculation or blood flow.
Short sections of the extracorporeal circulation are inserted into arterial and venous measuring heads equipped with sensors to measure arterial and venous temperature.
Temperature and hemodiafiltration
A number of studies have found that hemodiafiltration is associated with a better tolerance to ultrafiltration and less IDH than haemodialysis. However, it appears that the beneficial effect of hemodiafiltration may have been due primarily to a lower extracorporeal circuit temperature due to the cooling effect of the replacement solution. When heat transfer from the extracorporeal circuit was kept constant, the hemodiafiltration advantage over haemodialysis with regard to blood pressure was no longer found (Kumar, 2013).
Temperature of CRRT dialysis solution/replacement fluid.
CRRT can be set up so that dialysis solution and replacement fluid are infused at room temperature. Use of room temperature fluid results in heat subtraction from the patient; in fact, the hemodynamic benefits of CRRT appear to be due largely to such thermal cooling effects. When applied over long periods, CRRT-associated heat subtraction may mask the presence of fever, thus reducing the reliability of body temperature as a marker for infection or inflammation. Current CRRT delivery systems have heating systems. Heating sometimes is associated with an appearance of bubbles in the replacement or dialysis solutions, especially with bicarbonate formulations; the clinical importance of this effect remains to be determined.
Article Courtesy – Dr. Jigar Shrimali
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