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Heat and Pain

Results
Comment

How good is heat at relieving pain? Several readers have posed this question. A quick Bandolier review looked for randomised trials of heat in patients with clinical pain.

Results


Five trials were found (Table 1), of various heat therapies, in various conditions. All of them were relatively short in duration.


Table 1: Randomised trials examining heat for pain relief



Reference
Study design
Main results
B Curkovic et al. Z Rheum 1993 52: 289-291 Randomised comparison of 30 women with rheumatoid arthritis, comparing fingers with ice massage for 1-3 mins and 38ºC bath for 10 minutes.
Experimental pain measured at finger joint for an hour
Both cold and heat increased force needed for first sensation of pain immediately after the treatment, and for up to 30 minutes with cold
SF Nadler et al. Spine 2002 27: 1012-1017 Randomised, investigator blind study in 371 patients with acute low back pain comparing heat wrap with oral paracetamol (4000 mg daily) and ibuprofen (1200 mg daily) over 4 days Pain relief, muscle stiffness, and lateral trunk flexibility were significantly better with heat wrap than with paracetamol or ibuprofen. Results maintained over four days
SF Nadler et al. Archives of Physical and medical Rehabilitation 2003 84: 329-334 Randomised, investigator blind study in 191 patients with acute low back pain comparing heat wrap with oral placebo over 5 days Pain relief, muscle stiffness, and lateral trunk flexibility were significantly better with heat wrap than with placebo.
S Michlovitz et al. Archives of Physical and medical Rehabilitation 2004 85: 1409-1416 Randomised, investigator blind study in 81 patients with wrist pain of different causes, comparing heat wrap with oral placebo over 5 days Pain relief was better over three days of treatment and follow up overall, and for strains, tendoinitis and arthritis, and carpal tunnel syndrome, though analysis was on small subgroups
SA Mazzuca et al. Arthritis & Rheumatism 2004 51: 716-721 Randomised, double-blind study in 52 patients with symptomatic knee osteoarthritis, comparing heat-retaining sleeve with cotton sleeve over 4 weeks Reduction in pain in both groups, but not significantly greater with heat-retaining sleeve. Some indication that average result may obscure significant benefit for about 40% of patients



The best evidence came from three relatively large trials in acute low back pain or wrist pain, using a heat wrap device that wraps around the body or wrist and that heats to 40ºC within 30 minutes and maintains that temperature for eight hours. In back pain in two large studies there was benefit over placebo heat wrap, and over oral paracetamol and ibuprofen. In wrist pain, there was benefit over oral placebo.

One trial of a heat-retaining sleeve in knee osteoarthritis had small and nonsignificant benefit over four weeks, but had a hint that a minority patients did rather well, a result obscured by the use of average scores rather than people with good clinical results, with criteria for a good result set beforehand.

Comment


There is more evidence here than one might have thought, although it remains limited. There seems to be enough to advise patients not to avoid heat therapies. We have to bear in mind that while there appear to be few significant adverse events, we have too little information to quantify any rare but serious harm. It is comforting that medical devices are the subject of randomised trials.

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