Advice

Technology overview

Technology overview

This briefing describes the regulated use of the technology for the indication specified, in the setting described, and with any other specific equipment referred to. It is the responsibility of healthcare professionals to check the regulatory status of any intended use of the technology in other indications and settings. Thermogard XP can also be used for therapeutic warming to prevent perioperative hypothermia, and therapeutic cooling to manage intracranial pressure and for fever and burns. These indications are beyond the scope of this briefing.

About the technology

Thermogard XP manages a patient's core body temperature through central venous heat exchange. The system circulates temperature‑controlled saline in a closed‑loop, multi‑balloon intravascular catheter. The patient is cooled or warmed as venous blood passes over the balloons. No fluid is infused into or removed from the patient. The environmental operating temperature range for the system is 10–27°C. This briefing refers to the cooling application only.

Thermogard XP is the latest version of the intravascular temperature management system from Zoll Medical Corporation. The first generation CoolGard 2050, originally manufactured by Alsius Corporation, became commercially available in 2000 and was replaced by the CoolGard 3000 in 2002. The current Thermogard XP was introduced in 2008 and the company has stated that it has an increased cooling power output of 190 watts compared with 115 watts for CoolGard 3000. Both Thermogard XP and CoolGard 3000 have the same user interface, use the same disposable accessories and are operated in the same way.

CE marking

The CoolGard 3000 heat exchange control unit (class IIb), start‑up kit (sterile class I) and central venous heat exchange catheters (class III) were CE marked to Alsius Corporation in November 2003. An addendum for the current Thermogard XP heat exchange control unit (class IIb) was added in September 2009. The current certification for control unit, start‑up kit and catheters was awarded to Zoll Circulation in January 2014, and is valid until December 2016.

Description

The system consists of 3 main components:

  • The Thermogard XP heat exchange control unit, which is a moveable mains‑powered console (114 cm high x 43 cm wide x 76 cm deep and weighing 52 kg), consisting of a chiller and heater with a range of 0.5°C to 42°C, a 2 litre coolant well and a coolant circulating pump. It is controlled using the push buttons and rotary control knob located under the colour display, which is mounted on the integrated stand. The display shows system status, menus, messages, alarms and patient temperature trend graphs.

  • A sterile, single‑use, heparin‑coated intravascular catheter which is inserted as a central venous line and positioned in the inferior vena cava. The triple‑lumen catheters provide saline inflow and outflow connectors, in addition to standard central line ports for infusion, measuring central venous pressure and sampling. Three catheter lengths are available, branded as Cool Line (22 cm long with 2 heat exchange balloons), Icy (38 cm long with 3 heat exchange balloons) and Quattro (45 cm long with 4 heat exchange balloons). Icy and Quattro are inserted via the femoral vein, whereas the shorter Cool Line can be inserted via the subclavical or internal jugular vein access site. The intravascular catheter is inserted by a trained clinician using the Seldinger technique and connected to the primed start‑up kit via keyed Luer connectors.

  • A sterile, single‑use 'start‑up kit' connecting the catheter to the control unit. The pre‑assembled kit consists of a stainless steel heat exchange coil, an air trap to prevent air embolism in the patient, and interconnecting tubing with an inline flow indicator and a saline bag spike.

The start‑up kit coil sits in the coolant well which is filled with an equal mixture of propylene glycol and distilled water. After placing the air trap in its holder, the tubing is routed through a peristaltic pump mounted on top of the Thermogard XP control unit. The start‑up kit tubing is then primed using a standard 500 ml saline bag, which is placed inside an insulating jacket and hooked onto the integrated stand. A syringe is used to manually prime the intravascular catheter with sterile saline prior to patient insertion, which is then connected to the primed start-up kit. Therapy can be started immediately, although full cooling capacity is only reached after 20 minutes of operation.

There are 4 treatment modes:

  • 'Max power' is used to cool the patient to the target temperature as quickly as possible. This can achieve cooling rates of up to 3.5°C per hour and will maintain the patient to within 0.2°C of the target temperature.

  • 'Controlled rate' is used to programme a specific cooling or warming rate of between 0.1°C and 0.65°C per hour. The system reverts to 'max power' mode once target temperature is reached.

  • 'Fever' is a cooling‑only mode to maintain normothermia when the patient's temperature rises above the target temperature. High and low patient temperature safety alarms can be set.

  • 'Warming' warms the patient when their temperature falls below the target temperature.

After setting the target patient temperature between 31°C and 38°C and selecting the treatment mode, therapy is started by changing the Thermogard XP from standby to run mode. The pump then circulates the temperature‑controlled saline through the closed‑loop start‑up kit and intravascular catheter. The catheter balloons act as a heat exchange surface between the circulating saline and the patient's bloodstream.

As cooled blood circulates throughout the body, patient temperature is monitored by 1 or 2 temperature probes connected via an interface cable. A Foley catheter‑type temperature probe placed in the bladder is recommended as the primary sensing probe. A secondary probe can be placed in the rectum or oesophagus to act as a back‑up in the event of the primary sensor's failure. If this back‑up is not used, the patient must be monitored by a separate temperature monitor. Coolant temperature is automatically adjusted to achieve and maintain operator‑selected target patient temperature. Patient temperature trend graphs can be viewed at any point during therapy.

An optional interface accessory mounts to the rear panel of the main display, allowing the patient temperature (as measured using the primary probe) to be simultaneously displayed on an external patient monitor.

After treatment, patient temperature and system activity data must be either deleted or downloaded via the control unit serial interface to a PC installed with TempTrend software (supplied as standard) for viewing, before use on the next patient.

Setting and intended use

The Thermogard XP would be used in hospital settings including the operating theatre, recovery room and intensive care unit on critically ill adult patients with central line venous access. The system would be used by anaesthetists, theatre nurses and intensive care unit staff trained in central venous catheterisation who have appropriate training in using the system.

Current NHS options

The adult advanced life support chapter of the Resuscitation Council UK Guidelines 2010 states that therapeutic hypothermia can be used in post‑resuscitation care, including in comatose survivors of cardiac arrest associated with both shockable and non‑shockable rhythms, although there is less evidence to support its use after cardiac arrest from non‑shockable rhythms. NICE interventional procedures guidance on therapeutic hypothermia following cardiac arrest states that the evidence for the safety and efficacy of the procedure is adequate to support its use with normal arrangements for clinical governance, audit and consent.

The standard application of therapeutic hypothermia in current NHS practice is divided into 3 phases: induction, maintenance and rewarming.

External or internal cooling techniques can be used to induce cooling. Methods to induce or maintain hypothermia include the infusion of 4°C 0.9% sodium chloride or Hartmann's solution, simple ice packs or wet towels, cooling blankets or pads, water or air circulating blankets, water‑circulating gel‑coated pads, intravascular heat exchangers and cardiopulmonary bypass (Resuscitation Council UK 2010).

In the maintenance phase, the main goal is to avoid temperature fluctuations. This is best achieved with external or internal cooling devices that include continuous temperature feedback to achieve a set target temperature (Resuscitation Council UK 2010).

After cardiac arrest, comatose patients who have a return of spontaneous circulation can be cooled to a core temperature of 32–34°C to improve neurological outcomes. The patient's body is maintained at this temperature for 12–24 hours from the start of cooling and is monitored using a bladder temperature probe. In addition to cooling, patients generally also have standard critical care interventions, intravenous sedation and muscle relaxants (to prevent shivering). The guidance also recognises that prevention of rebound pyrexia is important for up to 72 hours from rewarming (Nielsen 2013).

NICE is not aware of any other CE‑marked devices that have a similar mode of action to the Thermogard XP intravascular temperature management system.

Costs and use of the technology

Thermogard XP consists of 3 main components and a number of consumables, accessories and options. The UK supplier of the Thermogard XP, Delta Surgical, has provided the following list prices (excluding VAT):

  • Thermogard XP heat exchange control unit: £21,500. Delta Surgical Limited may also provide Thermogard XP units free of charge in the UK, dependent upon committed volumes of consumable orders.

  • Intravascular catheters (single use):

    • Cool Line £318.27

    • Icy £509.85

    • Quattro £637.94

  • Start‑up kit (model CG‑500D, single use): £235.87

  • Foley temperature probe (single use) £10.00

  • Temperature probe interface cable: £89.00

  • Propylene glycol coolant (1 gallon): £30.00

  • Coolant well lid: £150.00

  • Hospital monitor interface accessory option: £1759

  • The optional secondary temperature probe would need to be supplied by the hospital at a cost of £1.54.

The Thermogard XP has an anticipated lifespan of approximately 10 years and comes with a 12‑month warranty. The maximum continuous operating time is 7 days for the single use start‑up kit. The Icy and Quattro catheters may be left in place for up to 4 days, whereas the Cool Line catheter may be used for up to 7 days. These components must be replaced if longer treatment is needed.

Depending on which catheter is used, the cost per patient treatment for single‑use components ranges from £574.14 to £893.81 (excluding VAT).

Delta Surgical provides on‑site training covering all aspects of the Thermogard XP system. Training is provided free of charge as part of the installation and includes indication‑specific sessions, training aids and manuals. Training following system updates and refresher training is provided as part of ongoing support at no additional cost.

The Zoll Service Centre offers 3 maintenance contract options:

  • on‑demand for repairs and corrective maintenance

  • annual preventative maintenance, which includes call out, labour, parts and all specified cleaning, checks and tests (including software and hardware upgrades)

  • annual full protection, which combines the 2 other options and includes the use of a loan system if needed.

In addition, Delta Surgical provides a free‑of‑charge, biennial mini‑service package across the lifespan of the system. This includes a coolant and filter change, flow rate test, and anonymised patient treatment data and event log download and analysis.

Likely place in therapy

The Thermogard XP system is used in a hospital setting for the induction, maintenance and rewarming phases of therapeutic hypothermia after cardiac arrest, in patients with ROSC. The system would replace current standard methods with little change to the overall care pathway.

Specialist commentator comments

One specialist commentator noted that a practical advantage of Thermogard XP is that it needs the least additional work from nursing staff compared with other cooling methods and cannot cause thermal injury to the skin of a patient. It does, however, carry the risks associated with central venous access devices, although because this patient group is likely to need such central access this is not necessarily an additional risk. The system has been in routine use for just over 1 year in their patient pathway following non‑traumatic cardiac arrest with no adverse effects and an audit demonstrated effective targeted temperature management in this patient group.

A second specialist commentator stated that the problem of rebound pyrexia is clinically significant and the extended normothermia period is one explanation of the overall good outcomes reported in a large, high quality randomised controlled trial comparing various temperature management devices following ROSC (Nielsen et al. 2013). Rebound pyrexia can be difficult to prevent with surface cooling devices alone. The improved power of the Thermogard XP compared with the CoolGard 3000 suggests it will be more effective in preventing rebound pyrexia.

Regarding the optimum target temperature for therapeutic hypothermia, 3 specialist commentators concurred with the findings of Nielsen (2013), with 1 stating that this is currently the best quality evidence to inform the rationale and practice for cooling following out‑of‑hospital cardiac arrest. Another specialist commentator advised that maintaining normothermia will have fewer side effects than hypothermia and therefore, despite Nielsen (2013) being a single study, many intensive care units in the UK have adopted a normothermic approach. They also indicated that this has obvious financial implications since it is easier to achieve with cheaper equipment.

One specialist commentator noted that the forthcoming International Liaison Committee on Resuscitation and subsequent revised UK Resuscitation Council guidelines, both due in 2015, will reflect such new evidence, including a move to targeted temperature management at 36°C.

Equality considerations

NICE is committed to promoting equality and eliminating unlawful discrimination. In producing guidance, NICE aims to comply fully with all legal obligations to:

  • promote race and disability equality and equality of opportunity between men and women

  • eliminate unlawful discrimination on grounds of race, disability, age, sex, gender reassignment, pregnancy and maternity (including women post‑delivery), sexual orientation, and religion or belief (these are protected characteristics under the Equality Act 2010).

The Thermogard XP system is indicated for use with adults only. Age is a protected characteristic under the 2010 Equality Act.