Reusable devices to apply cold sensation in the assessment of regional anaesthesia

Why change is needed

Cold sprays (also known as vapo-coolants) are volatile liquids that evaporate from the patient’s skin to cause cooling via the latent heat of vaporisation. Two vapo-coolants are used in clinical practice: pentafluoropropane with tetrafluoroethane, and ethyl chloride, and both evaporate to form greenhouse gases. Global warming potential (GWP) is one way of estimating the climate impacts of a greenhouse gas against that of carbon dioxide (CO₂), which has a GWP of 1, over a certain period (eg, GWP₁₀₀ is over 100 years). One manufacturer of pentafluoropropane with tetrafluoroethane states that it has a GWP₁₀₀ of 1411.2 Ethyl chloride (the most commonly used cold spray) has a GWP of less than CO₂.3 In addition to generating greenhouse gas emissions at the point of use, cold sprays create waste via the disposal of their metal or glass containers (fig 1) and have climate impacts through their production and transport.4

It can be difficult to assess precisely the sensory blockade produced by a cold spray, as the spray can disperse across multiple dermatomes,1 and cold sprays are expensive (approximately £25 per container).

Ice is an obvious source of cold, but ice machines have been removed from many hospitals because of concerns about infection control.5 Reusable devices for cold sensation (fig 1, right), comprising a metal body on a plastic handle, are cooled in a refrigerator before use. They offer financial and environmental advantages over vapo-coolant sprays.

Evidence for the solution

Reusable cold sensation devices must remain cold for long enough to reliably assess the block. A bench study found that one brand of device maintains a temperature of below 10°C for six minutes in simulated use.6 A clinical study compared ethyl chloride with this device for assessing spinal anaesthesia in orthopaedic and obstetric patients and concluded that the reusable cold sensation devices were non-inferior for this purpose.7

Three studies have assessed financial or environmental impacts of reusable cold sensation devices. A single centre feasibility study assessed the cost of introducing them in obstetric operating theatres; ethyl chloride purchasing fell from 62 to 35 cans per month, with a projected annual saving of £6480. Researchers calculated a reduction in annual “carbon footprint” of 10 272 kg CO₂ after accounting for manufacture and transport of the devices.8 Another hospital sought to promote the use of reusable cold sensation devices as the default method for assessing regional blocks in the post-anaesthetic recovery unit and reduced the use of ethyl chloride from six to 0.8 cans per week. The hospital compared the carbon equivalent impact of cleaning the devices (using detergent wipes) with the savings from using less ethyl chloride, and estimated an annual saving of 4613 kg CO₂, equivalent to approximately 22 500 miles driven in an average UK car.9 Another institution reached a financial “break even” after one month of using reusable devices compared with ethyl chloride.10 In general, implementation of reusable cold sensation devices is reported to have proceeded smoothly, although authors note the need for staff training and familiarisation, and the potential requirement for additional refrigerators for storage where these are not already available.89

What you can do

Implementing reusable cold sensation devices requires a budget for procurement, appropriately located refrigerators, agreed cleaning and storage procedures, and buy-in from the multidisciplinary team (eg, anaesthetists, recovery staff, pain nurses, and midwives). Careful consideration should be given to the settings where reusable cold sensation devices are used, as they may not be the ideal modality for assessment of all regional anaesthesia. For example, recent guidance from the Obstetric Anaesthetists Association recommends light touch as the primary approach for the assessment of spinal anaesthesia before caesarean section.1011

Practical points to consider

• The financial case for reusable cold sensation devices should be straightforward given the high cost of vapo-coolant sprays. However, equipment and pharmaceutical budgets are often separate, so it is useful to establish at an early stage where the funds will come from.

• Refrigerators in clinical areas are typically for pharmaceutical use, so it may be necessary to obtain permission to use them for the purpose of chilling and storing cold sensation devices. Engage with colleagues from infection control to agree procedures for cleaning and storage. Detergent wipes are often used to clean devices after use.910

• Barriers to implementation can be overcome by agreeing a standard procedure for use. One hospital describes the value of trialling reusable cold sensation devices before widespread introduction; this process could be used to inform practice recommendations.910

• Complete removal of vapo-coolant sprays may not be possible in settings without refrigerators, and for indications such as cryo-analgesia.

In practice, we advise colleagues to place the metal body of the reusable cold sensation device on the patient’s skin intermittently in the relevant dermatomes or cutaneous nerve areas and asking the patient what they can feel.^1.We recommend that devices are kept in the refrigerator until after a motor block has been observed, to prevent them from warming up before use.10 Key messages for patients are presented in box 1.

Box 1

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Key points for patients

• Regional anaesthesia is injection of a local anaesthetic medication around the nerves that supply a specific part of the body. This can be used for pain relief, or to enable an operation, with or without sedation or general anaesthesia.

• The anaesthetist and other members of the healthcare team will check how well the regional anaesthetic is working, often by testing if the patient can feel a cold sensation.

• Cold sprays are often used to create the cold sensation, but these have several disadvantages: they can be non-specific, are expensive, contain greenhouse gases, and generate a lot of waste.

• Reusable cold sensation devices comprise a metal body on a plastic handle; they are stored in a refrigerator before use. They are cheaper and more sustainable than using cold sprays. CoolSticks (one brand of device) have been introduced in many hospitals in the UK.

• Sometimes alternative methods are used to check regional anaesthesia, for example, the Obstetric Anaesthetists Association recommends that spinal anaesthesia for caesarean section should be checked by “light touch,” eg, using cotton wool.

RETURN TO TEXT

Notes on delivering regional anaesthesia

• Regional anaesthetic techniques can have different aims including analgesia (removing or reducing nociceptive sensory input) and anaesthesia (removing all sensation). Immobility is often desirable in the context of surgery.

• The nerves that transmit pain are more readily blocked than those that transmit touch and motor signals. This relates to the physical qualities of the nerve fibres, with smaller diameter A-delta (1-5 μm) and C fibres (<1.5 μm), which transmit pain, being more amenable to the action of local anaesthetic than A-beta (5-12 μm) and A-alpha fibres (12-20 μm), which transmit motor and touch sensation, respectively.

• Checks should be made to evaluate the blockade of touch and pain transmission; however, using a painful stimulus to assess a block is seen by many as unethical because the block might not be working, and because defining the extent of a block involves finding the “edges” where the block doesn’t work. For these reasons, a surrogate sensation is used which is transmitted in the same nerve fibres: like pain, cold temperature sensation is transmitted in A-delta and C fibres.

• As touch is less easily blocked than pain, it is sometimes advised that touch should be the primary mode of sensory testing when anaesthesia is desired; the guidance for caesarean section prioritises this. However, when analgesia is required—such as with a labour epidural—low concentrations of local anaesthesia are used with the intention of blocking only pain sensation, while leaving touch and movement intact. In this circumstance, testing touch is not suitable, so the sensation of cold is used instead.

Education into practice

• How many containers of cold spray does your organisation procure per month, and at what cost?

• What practices do your colleagues currently use to assess regional anaesthesia?

• Which colleagues should be involved in creating a standard operating procedure for storage, cleaning, and use of reusable cold sensation devices?

• How would you measure the environmental, financial, and care quality impacts of switching to reusable cold sensation devices?

How patients were involved in the creation of this article

We showed a draft of this paper to members of the Patient, Carer and Public Involvement and Engagement (PCPIE) group of the Royal College of Anaesthetists Centre for Research and Improvement. We made the content of the article easier to read based on their feedback, and one member of the group drafted the “key points for patients.”