By: 9 March 2015
Warming up nicely – Geratherm UniqueTemp

Warming up nicely – Geratherm UniqueTempA report of the trial of the Geratherm UniqueTemp patient warming system in and by the staff of the operating theatres at Homerton University Hospital, London

The Homerton Hospital in London required an alternative to the existing forced air system which was felt to be noisy, bulky and expensive. The Geratherm UniqueTemp device was postulated as an alternative, and was trailed in the theatre environment.

It has been known for some time that effectively warming a patient can reduce surgical site infections (SSIs) [1–4]. More effective patient warming means that fewer immediate post-operative interventions should be needed and that recovery beds are freed up more quickly as patients are already normothermic at the end of the operation.

Case report

Anaesthetists were asked to evaluate the Geratherm UniqueTemp patient warming system. The main objectives of the trial were to assess the device’s effectiveness in warming the patient as measured by an increase in the monitored patient core temperature; to assess the device for ease of use; and to assess its ease of decontamination.

Over a three-week period, 19 assessment forms were completed by different anaesthetists. Other theatre staff, anaesthetic and otherwise, were familiarised with the warming system in active use, which included placement and connection of the blankets on the patient, operation of the controller and post-operative blanket inspection and decontamination as per the AAGBI guidelines.


This was a subjective trial and so the marks given were the observer’s subjective comparison with forced air warming and other previously used warming systems. A natural human bias towards the familiar and aversion to the unfamiliar should be taken into account.

Observers were asked to award a score ranging from zero (poor) to 5 (excellent) for both ease of use and effectiveness (measured in terms of increase in patient core temperature).

Patient temperature

All scores given were collated and subject to analysis. The average scores for these characteristics were 4.2 out of 5 for ease of use and 3.9 out of 5 for effectiveness.

Where no score was allocated, as happened in two instances, it was not included in the mean score, although scores of zero were included. Such scoring was thought to demonstrate the ‘natural human bias towards the familiar’ and many people’s inertia to change.

An increase in the monitored temperature was seen in all instances in which this was monitored (14 out of 19 cases) except for one, although no reduction in temperature was noted in this case, where the temperature stayed the same and the patient still recovered from the average 1ºC drop in core temperature common at the onset of anaesthesia. The best recorded performance was an increase of over 1ºC in one hour.

In several instances greater patient coverage could have been achieved by using the blanket and, in one documented case, the controller was initially set to 38ºC rather than 42ºC at the start by accident. Efficient thermodynamic transfer requires a temperature gradient and the rate of heat transfer is directly proportional to this gradient – despite the initial error, an increase in patient temperature was still seen.

On one form, the effectiveness was marked as zero even though an increase in temperature was observed. If this anomalous marking is discounted, the average score for effectiveness rises to 4.2 out of 5.

It is anticipated that the average score for effectiveness would increase with familiarity of use.

Ease of use

Overall, the Geratherm UniqueTemp patient warming system was described as being easy to use and drape. The device did not affect the surgical field and was generally welcomed as advantageous. The many safety features and intuitive control unit were positively commented upon.

Infection control

Geratherm systems are designed to be used many times. As such, the blankets come under a specific AAGBI guideline (low risk item, same as operating tables [5]). The blankets are designed to actively repel contamination. The smooth polyurethane coating used is exclusive to Geratherm and coats 100% of the outside of the blanket making it impermeable to fluids while allowing patients’ skin to breathe. It is designed to be washed and wiped clean and can be easily disinfected. A decontamination efficacy study has been carried out by the team at HIRL, based in Queen Elizabeth Hospital Birmingham, and this is freely available from Geratherm.

It should additionally be noted that there was no visible contamination of any blanket in any of the procedures carried out in the trial. This is because they are placed remote to the surgical site without affecting surgical access and are then covered and protected by surgical drapes. In the extremely rare instance of a blanket being soiled with blood or other body fluids, the same wipe-down method is proven to work (see HIRL report). It is assumed that theatre staff wipe down the theatre tables between cases and cleaning the blankets normally adds another three minutes to the cleaning process.

NovDec_Articles_Geratherm_UniqueTemp_72dpi_photoCarbon footprint

In normal operation the Geratherm UniqueTemp blankets are kept permanently switched on so that there is no warm-up time. This does not have a significant bearing on carbon footprint or electricity costs since, once the blanket is at temperature, the draw of electrical power is only as large as the loss of heat to the environment or the patient – unlike forced air warming, the Geratherm UniqueTemp does not have to work at full-capacity all the time because it relies on conduction for heat transfer. Its maximum power output is 400W compared with, generally, 2500W for forced air warming. A study of forced air warming versus resistive heating [6] proves what everyone intuitively knows, that more heat is transferred by a conductive blanket than by forced warmed air. Using this study as a basis, forced air warming only transfers to the patient an estimated 8% of the energy required to run the blower, whereas the Geratherm UniqueTemp delivers over 90%. Our experience at Homerton University Hospital suggests that patients no longer require further warming in recovery when it is used intra-operatively. This leads to significantly less electricity being used and hence a smaller CO2 footprint.


Homerton Hospital wanted an alternative to forced air warming for patients undergoing surgery.

They were previously using a forced air warming system but found it to be noisy, bulky when inflated, and ineffective at warming patients. Following the trial outlined above, the hospital purchased the Geratherm UniqueTemp patient warming system.

The hospital is delighted with the system, which was paid for within 14 months from the savings made by not having to use forced air warming blankets. It now saves an estimated £35,000 a year in consumable costs and is expected to for years to come, while every patient can be warmed without worrying about the cost.

Additional savings from lower electricity consumption, less clinical waste and warmer patients at the end of surgery are evident. Furthermore, storage space required for single-use forced air blankets is completely freed-up.

Since the Geratherm UniqueTemp was put into use, no patient has had to be warmed in recovery.


  1. Kurz, A., Sessler, D.I. & Lenhardt, R. (1996) Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. N. Engl. J. Med. 334, 1209–1215
  2. Danelli, G., Berti, M., Perotti, V., et al. (2002) Temperature control and recovery of bowel function after laparoscopic or laparotomic colorectal surgery in patients receiving combined epidural/general anesthesia and postoperative epidural analgesia. Anesthesia & Analgesia 95, 467–471
  3. Fossum, S., Hays, J. & Henson, M. (2001) A comparison study on the effects of prewarming patients in the outpatient surgery setting. J. PeriAnesthesia Nursing 16(3), 187–194
  4. NICE (2008) Inadvertent perioperative hypothermia: The management of inadvertent perioperative hypothermia in adults. NICE Guideline 65. (accessed 8 December 2014)
  5. AAGBI (2008) AAGBI Safety Guideline: Infection Control in Anaesthesia. (accessed 8 December 2014)
  6. Perl, T., Flöther, L., Weyland, W., et al. (2008) Comparison of forced-air warming and resistive heating. Minerva Anestesiol. 74(12), 687–690