Advice
The technology
The technology
The Bair Hugger temperature monitoring system (3M UK) is a non-invasive device that can accurately and continuously measure the patient's core body temperature before, during and after surgery (known collectively as the perioperative phase). The system consists of a single-use zero-heat flux sensor and a reusable sensor cable, control unit and power supply. An optional monitor cable is also available for connection to other patient monitoring systems. The sensor is placed on the patient's forehead and is held in place by an adhesive backing. It is connected to the control unit through the sensor cable. If needed, it can be disconnected and reconnected to a different sensor cable and control unit each time the patient is moved to a different location. The system was marketed as SpotOn until 2016.
The control unit shows the patient's current temperature and a graphical display of up to 2 hours of previous temperature data. The current temperature can also be displayed on a patient vital signs monitor if connected by the optional cable.
The single-use sensor consists of a thermal insulator next to the skin that is covered by a flex circuit containing a heating element. The temperature of the sensor is regulated by the Bair Hugger temperature monitoring system in the control unit. The thermal insulator is designed to prevent heat loss to the environment. This establishes an isothermal pathway under the sensor, bringing the core temperature to the skin surface and enabling the temperature to be recorded and monitored. The sensor takes several minutes to reach this temperature balance.
The control unit, sensor and mains cables are cleaned after each use. The control unit needs verification every 12 months, or in accordance with the NHS trust's own maintenance protocol. A calibration verification stick is needed for this.
Innovations
Because it is not invasive, the Bair Hugger temperature monitoring system can directly monitor core temperature in both awake and anaesthetised patients throughout the perioperative phase. Typically, invasive core temperature monitoring systems can only be used with heavily sedated or anaesthetised patients, with minimally invasive technologies used on conscious patients pre- and post-operatively.
Minimally invasive methods only provide indirect estimates of core temperature and are monitored and recorded at set intervals, for example every 15 or 30 minutes. The continuous temperature display and 2-hour temperature recording by the Bair Hugger temperature monitoring system allow changes in temperature to be detected immediately so that any appropriate management can be considered. The company claims that by using a single sensor that stays on the patient, any variability in measurement between different healthcare professionals or monitoring devices is avoided.
Current NHS pathway
People having surgery under regional or general anaesthesia are at risk of developing hypothermia. Hypothermia can occur before, during and after surgery. Inadvertent perioperative hypothermia occurs frequently but is preventable and can be treated.
As an aid to prevention and detection of hypothermia, the patient's temperature is monitored during the perioperative phase. According to NICE's guideline on hypothermia, the temperature should be monitored and recorded in the hour before surgery, before the anaesthesia is induced and then every 30 minutes until the end of surgery. The temperature should then be monitored and documented on admission to the recovery room and then every 15 minutes. Once on the ward, the temperature should be recorded every 4 hours.
During surgery a direct estimate of core temperature can be monitored accurately through invasive methods such as oesophageal, nasopharyngeal, rectal or pulmonary artery catheters. Other direct estimates of core temperature include zero-heat flux sensors (such as Bair Hugger), and oral or axilla measures which can be used in the perioperative phase. In the pre- and post-surgery periods temperature is usually measured at intervals with minimally invasive methods such as oral thermometers, although tympanic thermometers (indirect measures) may also be used. NICE's guideline on hypothermia recommends that adjustments may need to be made to indirect minimally invasive recorded temperature to obtain the core temperature, and that indirect estimates of core temperature should not be used during surgery. In 2010, the national patient safety agency (now NHS Improvement) released guidance stating that the method used for taking the temperature should be clearly identified and recorded.
NICE is not aware of any CE-marked devices that appear to fulfil a similar function as the Bair Hugger temperature monitoring system.
Population, setting and intended user
The Bair Hugger temperature monitoring system is intended for use during perioperative care by anaesthetists, recovery room nurses and ward nurses in a secondary care setting. It is used by the same clinical staff who currently monitor a patient's temperature in the perioperative setting.
It can be used for children and adults having planned and emergency surgery. NICE's guideline on hypothermia states that hypothermia (core body temperature below 36°C) can occur in people having surgery and can lead to a poor outcome including infection. The risk of hypothermia is greater with longer, more invasive surgery, in older people and in those with other illnesses (Hart et al. 2011; Baquero et al. 2015).
Minimal extra training is needed to use the Bair Hugger temperature monitoring system; this training is provided by the company in person and at no additional cost.
Costs
Table 1 Device costs excluding VAT
|
Description |
Cost |
Additional information |
|
Single-use sensor |
£7.46 each £186.50 for box of 25 |
Supplied in boxes of 25, 1 sensor is used per patient operation. |
|
Control unit |
£250.00 |
Includes sensor cable, power pack and 2 monitor cables (if not compatible, additional monitor cables are available at £60 each). Offered at no extra charge if at least 2 boxes of consumables are bought per unit per year. |
|
Calibration verification stick |
£65.00 |
One needed to calibrate the control unit every 12 months. |
Costs of standard care
Electronic thermometers for oral or axilla use (costing around £116 to £276 depending on functionality) are re-useable, minimally invasive devices that are commonly used to directly estimate core temperature. They are normally used with single-use covers, which cost between £0.27 and £0.54 for each temperature measurement taken. Tympanic thermometers (indirect estimate) cost around £18 to £30 per device.
Disposable invasive devices (direct estimates of core temperature) include nasopharyngeal temperature probes, oesophageal probes and rectal probes, which cost between £2 and £7. Re-useable rectal or oesophageal probes cost between £103 and £160.
Resource consequences
The Bair Hugger temperature monitoring system is currently used by 3 NHS trusts.
If adopted, Bair Hugger would replace existing methods of measuring temperature perioperatively. Significant changes to current facilities or infrastructure are unlikely to be needed.
By accurately and continuously monitoring core temperature, there is the potential to reduce rates of hypothermia which could result in savings through a reduction in associated complications and hospital stay.