The application of heat or cold to an injury or area of pain is a traditional remedy. The rationale for both the use of heat (thermotherapy) and cold (cryotherapy) has developed over the years, resulting in advanced treatment options for a wide range of conditions.
Key points
- Thermotherapy and cryotherapy are typically used to treat muscle-related pain.
- Cryotherapy should be used immediately after injury, whereas thermotherapy should only be used when inflammation has reduced.
- Both treatment options should be used with caution in patients with circulatory problems or diabetes.
Thermotherapy
Thermotherapy is the application of any substance to the body that increases tissue temperature. This results in improved blood flow, tissue metabolism and connective tissue extensibility.[1]
Increased blood flow facilitates tissue healing by supplying protein, nutrients and oxygen at the site of injury.
This increase in metabolism helps the healing process by increasing both the catabolic and anabolic reactions needed to degrade and remove the metabolic by-products of tissue damage.
Skin warming has also been shown to activate the thalamus and the cerebral cortex, and some of the pain relief provided by topical heat therapy may be mediated directly by the brain.[1]
Reflect
- What thermotherapy and cryotherapy treatments are available in your pharmacy?
- Do you know when each therapy should be used and the evidence base supporting its use?
- Which patients should avoid using hot and cold treatments?
Before reading on, think about how this article may help you to do your job better.
Indications for thermotherapy
Thermotherapy is indicated for relief of a variety of painful conditions, including muscular and rheumatic pain, sciatica, fibrositis and lumbago. It can be used as a replacement or adjunct to pharmacological pain relief options. It can also be used to help healing of sports or similar injuries. Heat therapy can be superficial or deep, and provides analgesia and relaxes muscles. However, because it increases blood flow to the affected area it should only be applied to injuries once any inflammation has reduced.
The evidence for thermotherapy
A number of controlled trials have evaluated topical heat preparations in musculoskeletal pain. Most of the trials involving rubefacients have evaluated salicylates, which are key ingredients in a variety of rub and spray preparations. The quality of these trials varies with many conducted more than 10 years ago.
Topical salicylates were evaluated in a 2004 systematic review.[2]
The review included randomised, active or placebo-controlled trials in adult patients experiencing either acute (strains, sprains and sports injuries) or chronic (arthritis, musculoskeletal) pain. Clinical success was considered as a 50% reduction in pain. Outcomes at closest to seven days (but at least three days) were required for acute pain and closest to 14 days (but at least seven days) for chronic pain.
For acute pain, the review found three placebo-controlled trials with data on 182 people. Overall, at least 50% pain relief was achieved in 67% of patients using topical salicylates and 18% of those using placebo. Treatment with salicylates was significantly better than placebo, with a number needed to treat (NNT) of 2.1 (95% confidence interval 1.7 to 2.8) for at least 50% pain relief at seven days.
For chronic pain, six placebo-controlled trials had data on 492 comparisons from 403 patients. Overall, 50% pain relief was achieved in 54% of patients using topical salicylates and 36% of those using placebo. Treatment with topical salicylates was significantly better than placebo with an NNT of 5.3 (95% CI, 3.6 to10) for at least 50% pain relief at 14 days in chronic conditions compared with placebo.
In 2010, a randomised, controlled, double-blind study evaluated the efficacy of a salicylate and menthol patch in 208 patients (104 men, 104 women) aged 18–78 years with mild to moderate muscle strain compared with placebo. Pain intensity was assessed on a visual analog scale at rest and with movement for 12 hours after patch application. Patients receiving the active patch experienced greater pain relief than those patients receiving a placebo patch (mean 182.6 compared with 130.1; P=0.005). No serious adverse events were reported during the study.
Overall, controlled trials evaluating topical salicylates show these preparations can provide pain relief in both acute and chronic pain compared with placebo. However, the BNF states the evidence is not strong enough to support the use of topical rubefacients in acute or chronic musculoskeletal pain.
Source: Chassenet/Science Photo Library
Heat therapy pack used to treat lumbago
Topical treatments
Rubefacients produce local vasodilatation and create a sensation of warmth when applied to the skin and injured tissues. Analgesia is achieved by a counter-irritant mechanism that helps to mask the perception of pain.
The action of rubbing the skin increases the penetration of rubefacient into the skin. This disperses local tissue pain mediators and enhances the analgesic effect.
Two common options are nicotinates (eg, ethyl nicotinate) and salicylates. In addition to acting as counter-irritants, salicylates are hydrolysed to salicylic acid in skin tissue. This reduces the production of inflammatory prostaglandins from arachidonic acid, and therefore helps to ease swelling and pain.
Other options include turpentine oil and eucalyptus oil, both of which act as rubefacients, and capsaicin, which produces a burning sensation on the skin not accompanied by vasodilatation. Capsaicin is accepted for restricted use within NHS Scotland for the treatment of postherpetic neuralgia for patients who have not achieved adequate pain relief from, or who have not tolerated, conventional first-line treatments.
The evidence for cryotherapy
Continuous cryotherapy has been shown to have a protective effect on injured tissue. An animal study showed that with primary injury to muscle, secondary hypoxic injury to the surrounding tissue was slowed with five hours of continuous cryotherapy.[4]
Depending on the method used, cold therapies may have different effects. In a study involving high-intensity exercise, cold application improved pain symptoms but had no effect on muscle recovery.[5]
Cold water immersion has been shown to improve muscle contractile properties and soreness after collision-based exercise.6[6]
One study found that ice massage cools the muscle faster than an ice pack.[7]
In another study, both ice pack and cold whirlpool treatment for 20 minutes decreased calf muscle temperature at the same rate.[8]
These findings suggest that ice pack and ice massage therapy are appropriate when a quick recovery is required, whereas cold whirlpool therapy is most appropriate when long-term tissue cooling is required.
One randomised study found that both ice water treatment and intermittent compression were more effective than intermittent cool pack therapy for foot and ankle injuries.[9]
A recent systematic review concluded that, from the limited evidence available to date, ice may hasten return to participation.[10]
Complications of heat therapy
Thermotherapy should be used with caution for patients with diabetes, peripheral vascular disease, multiple sclerosis and rheumatoid arthritis because it may increase disease progression. It should also be used with caution for patients with burns, skin ulceration and areas of inflamed skin.
All topical products should be kept away from the eyes, mouth and mucous membranes and should not be applied to broken skin. Hands should be washed after use. Topical heat products should not be used on young children, whose skin is more sensitive than adults and in whom adverse reactions are more likely.
The skin should be protected when using thermotherapy for high-risk patients, and application times should be restricted for therapies involving high-intensity heat (>45 degrees C) methods such as electric heating pads.[1]
Ultrasonic heat therapy should not be used for patients with joint prostheses. It may cause overheating, cracking and melting of the prosthetic joint because the prosthesis absorbs more energy than than the overlying soft tissue.[1]
| How thermotherapy and cryotherapy compare | |
|---|---|
| Thermotherapy | Cryotherapy |
| Increases circulation, bringing more blood to the area. This provides more oxygen and nutrients, giving muscles more energy | Reduces blood flow to injured area to help prevent bleeding and swelling |
| Warms connective tissue (muscles, tendons, ligaments) allowing them to stretch and move more easily which helps prevent injury | Helps alleviate the pain of delayed-onset muscle soreness (DOMS), which happens 24–48 hours after exercise |
| Provides pain relief | Provides pain relief |
| Used as part of pre-game warm up routine | Used as soon as possible after injury |
| Once injuries have recovered, used to help remodel tissue and promote faster healing | Used after exercise to assist with a cool down routine |
| Not used in acute injury | Used for up to two to three days after injury. It can be used up to 10 days (if there is still heat or swelling continue to use cooling) |
| Not uses after activity, especially if activity has caused pain, swelling or heat | Always remember PRICE – protection, rest, ice, compression, elevation |
| Never used where there may inflammation (it will increase blood flow) | Not used before or during sport |
Cryotherapy
Cold analgesia or cryotherapy is the local or general use of low temperatures in medical therapy, or the removal of heat from a body part to relieve pain. The cold causes vasoconstriction, which results in decreased tissue blood flow, and reduces tissue metabolism, oxygen utilisation, inflammation and muscle spasm.[1] Common methods include topical cooling gels and freeze sprays. Other forms of cryotherapy include ice packs, ice massages and cold whirlpools.
Cryotherapy induces effects locally at the site of application and in the spinal cord. Topical cold treatment decreases the temperature of the skin and the underlying tissues to a depth of about 2–4cm, decreasing the activation threshold of pain receptors and the conduction velocity of pain nerve signals.[1] This results in a local anaesthetic effect and a reduction in pain.
Practice points
Reading is only one way to undertake CPD and the regulator will expect to see various approaches in a pharmacist’s CPD portfolio.
- Cryotherapy is used in the removal of warts. Find out more about this treatment and where it is available in your local area.
- Get involved in your community by providing pharmacy services at a local sporting event. Where would thermotherapy and cryotherapy fit into your practice?
- Watch cryogenic chamber therapy in action – a number of videos are available on YouTube.
Consider making this activity one of your nine CPD entries this year.
Uses of cryotherapy
Cold analgesia is indicated for the relief of pain following injury to muscles and joints (eg, strains and sprains), and for the treatment of such injuries; unlike thermotherapy, it should be used immediately after injury and as part of the “PRICE” technique:
- Protect the area from further injury
- Rest the injured part
- Ice (apply cold therapy to injured body part)
- Compress the injury area
- Elevate the injured body part
Cryotherapy is particularly valuable during the early stages of injuries where tissues are stretched and blood vessels are torn or damaged.
Loss of blood from tissues can lead to cell death, which stimulates the release of histamine and increases vasodilatation and capillary permeability.
Cold analgesia causes local vasoconstriction and therefore helps to reduce clot formation, tissue bleeding, inflammation and swelling.
It can also be used in cases of muscle spasm, delayed-onset muscle soreness (DOMS) and as an adjunct in chronic pain and inflammation.
Topical cryotherapy options
Topical cooling preparations include gels containing menthol and freeze sprays. Menthol is a naturally occurring cyclic terpene alcohol of plant origin that has been used since antiquity for medicinal purposes. It has both cooling and counter-irritant properties. A randomised trial in 16 subjects found that a topical menthol-based analgesic decreased perceived discomfort in DOMS to a greater extent than ice.[3]
Freeze sprays contain volatile propellants, such as pentane and butane, which evaporate at low temperatures and cool the skin. This causes a loss of sensation until the nerve endings warm up.
Complications of cryotherapy
Caution should be exercised when applying cryotherapy in the vicinity of superficial nerves, especially if cold is combined with compression, as it may cause nerve damage.
As cryotherapy causes vasoconstriction, it should be used with caution in patients with circulatory insufficiency, cold allergy and advanced diabetes. Reported side effects with intensely cooling methods such as ice include bradycardia, Raynaud’s phenomenon, cold urticaria, frostbite and slowed wound healing caused by a slowed metabolism.
All topical cooling products should be kept away from the eyes, mouth and mucous membranes, and should not be applied to broken skin. Hands should be washed after use. They should not be used on young children.
Cryosurgery
Cryosurgery is the application of extreme cold to destroy abnormal or diseased tissue in conditions such as warts and moles, plantar fasciitis and small skin cancers.
Several internal disorders are also treated with cryosurgery, including: liver cancer; prostate cancer; lung cancer; oral cancers; cervical disorders; and haemorrhoids.
Generally, all tumours that can be reached by the cryoprobes used during an operation are treatable. This method of treatment is effective but only appropriate for use against localised disease and solid tumours larger than 1cm. Tiny, diffuse metastases that often coincide with cancers are usually not affected by cryotherapy.
Future research
Thermotherapy and cryotherapy have come a long way in recent years and are finding new uses. Cryotherapy is increasingly being trialled in the treatment of various forms of cancer, including prostate cancer and early stage skin cancers, and is used to prevent brain damage in newborn babies with asphyxia.
Cryogenic chamber therapy is a relatively new method of cryotherapy in which the patient is placed in a cryogenic chamber for up to three minutes (which is comparable to ice swimming). Patients report that the experience is invigorating (possibly because of a release of endorphins), and improves a variety of conditions such as psychological stress and insomnia as well as muscle and joint pain.
Thermotherapy is also being trialled in patients with cancer using microwave ablation, ultrasound or a cocktail of nanoparticles and antibodies targeted at a tumour and heated by the use of a magnetic field. Further research on clinical outcomes with these therapies should provide clarification on these promising findings.
References
[1] Nadler SF, Weingand K, Kruse RJ. The physiologic basis and clinical applications of cryotherapy and thermotherapy for the pain practitioner. Pain Phys. 2004;7:395-9.
[2] Mason L, Moore RA, Edwards JE et al. Systematic review of efficacy of topical rubefacients containing salicylates for the treatment of acute and chronic pain. BMJ. 2004;328:995.
[3] Johar P, Grover V, Topp R et al. A comparison of topical menthol to ice on pain, evoked tetanic and voluntary force during delayed onset muscle soreness. Int J Sport Phys Ther. 2012;7:314-22.
[4] Merrick MA, Rankin JM, Andres FA et al. A preliminary examination of cryotherapy and secondary injury in skeletal muscle. Med Sci Sport Exercise. 1999;31:1516-21.
[5] Pointon M, Duffield R, Cannon J et al. Cold application for neuromuscular recovery following intense lower-body exercise. Eur J Appl Physiol. 2011;111:2977-86.
[6] Pointon M, Duffield R. Cold water immersion recovery after simulated collision sport exercise. Med Sci Sport Exercise. 2012;44(2):206-16.
[7] Zemke JE, Andersen JC, Guion WK et al. Intramuscular temperature responses in the human leg to two forms of cryotherapy: ice massage and ice bag. J Orthop Sport Phys Ther. 1998;27(4):301-7.
[8] Myrer JW, Measom G, Fellingham GW. Temperature changes in the human leg during and after two methods of cryotherapy. J Athl Training 1998;33(1):25-9.
[9] Stockle U, Hoffmann R, Schutz M et al. Fastest reduction of posttraumatic edema: continuous cryotherapy or intermittent impulse compression? Foot Ankle Int. 1997;18:432-8.
[10] Collins NC. Is ice right? Does cryotherapy improve outcome for acute soft tissue injury? EMJ. 2008;25:65-8.
