Temporal Artery Thermometer versus Hemodialysis Machine Internal Blood Monitoring

In many hemodialysis units, measuring pre-dialysis body temperature is a routine part of care. The gold standard for measurement of body temperature is the temperature of central (core) blood; however, in the majority of clinical settings, it is not feasible to use core blood temperature. In most cases, temperature is measured at other sites, such as oral, axillary, tympanic, or temporal artery.

Core temperature readings can be displayed on modern hemodialysis machines equipped with an internal blood temperature monitor, yet many dialysis units record manual temperatures using peripheral thermometers. According to Meaghan Lunney, MSc, and colleagues, this practice may be unnecessary and may also be prone to error. To compare body temperature measured by hemodialysis machine thermometers with those measured by temporal artery thermometer, the researchers conducted a prospective cross-sectional study. The researchers also sought to examine the feasibility of replacing the currently used temporal artery method with dialysis machine thermometers. Results of the study were reported online in BMC Nephrology

[doi.org/10.1186s12882-018-0938-x]

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The primary outcome of interest was body temperature. Secondary outcomes were whether mean temperature varied depending on self-reported patient characteristics such as sex, age, duration of dialysis, and diabetes.

Adult patients at one of two study sites in Calgary, Alberta, Canada, with a diagnosis of end-stage renal disease and currently undergoing hemodialysis for at least 1 month were invited to participate in the study. Patients treated in Calgary hemodialysis units were dialyzed using the Fresenius 5008 machine, equipped with an internal blood monitor that measured arterial temperature to two decimal places and then transmitted to each unit’s electronic medical record system.

Ninety-four patients provided consent and were included in the analysis. More than half (59%) were male, mean age was 65 years, and median number of years since initiation of dialysis was 4. In 87 of the 94 patients (92.6%), body temperature was measured during the first 15 minutes of hemodialysis therapy.

Both the temporal artery and hemodialysis machine measurement were normally distributed. The mean temperature measured by the temporal artery thermometer was 36.7 °C compared with the mean dialysis machine temperature of 36.42 °C, a significant difference (P<.001). The mean difference between the temporal artery measurement and the dialysis machine measurement was 0.27 °C (95% confidence interval, 0.18-0.37). Three of the 94 observations were outside the limits of 95% agreement by the Bland-Altman agreement test. Using the temporal artery thermometers, two of the 94 patients (2.1%) had temperatures below 36 °C; using the dialysis machine thermometer, 12 of the 94 (12.8%) had temperatures below 36 °C.

In sensitivity analysis comparing only the first pairs of temperature measurement within the first 15 minutes of treatment (36.7 °C for temporal artery and 36.41 °C for dialysis machine), results were similar (P<.001). In the second sensitivity analysis comparing the mean of the first three measurements within the first 15 minutes of treatment (36.7 °C and 36.49 °C, respectively), results were also similar (P<.001).

Ninety-five percent of patients did not express a preference for one temperature measurement type over the other. Among the 12 nurses completing the survey, nine (75%) preferred using the dialysis machine rather than the temporal artery thermometer to measure patient temperature. Reasons given for preference for the dialysis machine were increased convenience and accuracy, reduction in workload, and reduction in perceived risk in transmitting infections between patients using the forehead thermometer.

There was no statistical difference in body temperature among the hemodialysis patients at varying times of day. Median temperatures measured by the dialysis machine were 36.24 °C during the first shift, 36.44 °C during the second shift, and 36.50 °C during the third shift (P=.53). In addition, there were no statistical differences in median body temperature by sex (36.40 °C in males, 36.44 °C in females; P=.68), age (36.49 °C in patients <65 years of age and 36.36 °C in patients ≥65 years of age; P=.15), or years on dialysis (36.43 °C if <6 years, 36.40 °C if ≥6 years; P=.72). There was a significant difference between the temperature of patients with diabetes and those without diabetes (36.33 °C vs 36.52 °C, respectively; P=.02).

The researchers cited some potential limitations to the study, including having different nurses involved in the data collections; the inability to obtain both temperature measurements during the first 15 minutes of dialysis treatment in seven of the 94 patients; the possibility that the findings are not generalizable to patients with significant access recirculation; and not including  febrile patients in the study.

“The mean body temperature of hemodialysis patients as measured by a temporal artery thermometer was 0.27 °C higher than the mean core temperature measured by the dialysis machine. As core temperature is the gold standard, using the dialysis machine to measure body temperature in hemodialysis patients rather than an external thermometer may result in slightly greater accuracy while possibly also lowering staff workload,” the researchers said.

Takeaway Points

  1. The gold standard for monitoring body temperature is measurement of core (internal) blood; however, current practice in hemodialysis centers is to use temporal artery thermometers to measure patient temperature during dialysis.
  2. Modern hemodialysis machines are equipped with an internal blood monitor that measures core body temperature. Researchers conducted a study to compare body temperature measured by dialysis machine with temperature measured by temporal artery thermometer.
  3. Temperatures measured with temporal artery thermometers were statistically and clinically higher than those measured by the dialysis machine (36.7 °C vs 36.4 °C, respectively; P<.001).