Too Hot For Comfort
A 4-month-old infant admitted to rule out sepsis was receiving maintenance intravenous (IV) fluid and IV antibiotics via a peripheral line in the left antecubital region. During shift report, nurses noted that the extremity was taut and the infant was irritable. The nurses further assessed the site and removed the IV. Prior to ending her shift, the nurse placed a warm compress on the infiltrate site and notified the resident physician.
Within the next hour, the nurse coming on shift assessed the infant further and discovered redness and a burn at the site as a result of the warm compress. The compress was removed, and the physician called a surgical consultant for further evaluation. The infant was treated with topical ointment; no surgical intervention was necessary.
This case scenario describes an incident in which a case of extravasation injury was treated with topical heat via the application of a warm compress. According to the account given, the application of the compress resulted in a cutaneous burn, which healed with conservative therapy.
Before we address the appropriate use of thermal therapies and the harm they can cause, it is important to entertain the possibility that the "burn" in this case may have been the result of extravasation of an irritating solution, rather than a result of thermal injury. To make this distinction, one should first determine whether the solution is an irritant. Commonly used agents that cause severe extravasation injuries include antineoplastic, inotropic, or osmotically active agents and certain antibiotics. Next, it is important to examine the extremity. In this case, the tautness of the extremity implied that a significant amount of fluid had been delivered to the subcutaneous and possibly muscular compartments of the arm, making it more likely that this was an extravasation injury.
Whatever the cause of this initial injury, the use of thermal therapies by nursing or allied health professions as a treatment option remains common in clinical practice. Although the evidence supporting this therapy is relatively scant, the widespread use of warm packs in a variety of clinical situations suggests that providers feel the therapy can be beneficial.(1) Below, we review a number of indications for thermal therapy, then discuss the potential harm that can result from inappropriate use of heat.
Use in Extravasation Injury and Thrombophlebitis
Hastings-Tolsma and colleagues (2) reported on the experimental effects of warm vs. cold packs in adult volunteers with intentional extravasation of fluid into the subcutaneous tissues and found improved mobilization of fluid with the warm packs. Whitney and colleagues (3) reported that local warming increases tissue perfusion and oxygen supply by overcoming local vasoconstriction and increasing blood flow to tissues. These observations provide some pathophysiologic rationale for thermal therapy, but there is limited evidence in the form of randomized controlled trials (RCTs) to support the use of topical thermal therapy in fluid extravasation or other clinical situations. Moreover, we found no systematic reviews or RCTs that supported the clinical effectiveness of thermal treatment of thrombophlebitis or acute inflammation resulting from IV therapy. Indeed, the literature on burns supports the use of cooling therapy to minimize tissue damage. The efficacy of cooling may be due to limitation of the postburn inflammatory reaction and minimization of inflammatory burn-associated edema.(4) In light of this evidence base, our practice is to cool the wound, and not apply heat, in patients with extravasation injury and thrombophlebitis.
Use to Promote Wound Healing
In contrast, the wound healing literature generally supports the use of warming therapies. Pathophysiologically, the warming of injured tissue using various devices appears to promote several actions relevant to healing. For example, studies suggest that local warming creates an environment that is conducive to biochemical and enzymatic reactions, which in turn improves local circulation and oxygen tension. Experts have postulated that local warming increases the availability of immune cells and alters inhibitory factors in the local wound environment to promote healing.(5,6) One study found significant and beneficial changes to the wound microenvironment, including improved fibroblast activity with warming (7), and a number of animal studies have shown that warming decreases bacterial counts.(8) The clinical correlation of these scientific observations is a bit uncertain. Although a systematic review (3) found that infection rates were lower and oxygen tension higher in acute and chronic wounds treated with warming therapies, this study had a number of methodological shortcomings.
Use in Patients with Pain
A Cochrane review of the use of warming therapy in rheumatoid arthritis (RA) found no objective improvements but also found no adverse reactions and that patients preferred thermotherapy over no therapy.(9) This preference demonstrates that thermal therapy does help relieve pain in both RA and various painful musculoskeletal conditions. For example, another trial assessing the efficacy of local heat application in relieving pain found that acute low back pain was relieved by active warming.(10)
The Safety of Thermal Therapy
In summary, thermal therapy probably relieves pain in certain musculoskeletal conditions, and there is pathophysiologic rationale, at least, to believe that it may help some patients with wound healing. While the Cochrane review (9) concluded that thermal therapy causes no adverse events, this case clearly demonstrates that this treatment does carry risks.
In this case, a contact burn was noted at the IV site as a result of the application of the warm compress for a prolonged period of time. Burn injury (including scalds) caused by medical therapies usually results from prolonged exposure and/or poor thermoregulatory control of the device; the risk is particularly high in vulnerable populations-especially children, the elderly, and those with insensate skin, chronic medical conditions (such as diabetes mellitus and peripheral vascular disease), and altered mental status.(11)
Even in those without risk factors for burn injury, temperatures greater than 140°F will cause thermal burn within 4 seconds.(12) A typical hot water tap produces water at a temperature of about 120°F, while a hot cup of coffee may have a temperature of up to 180°F. In other words, thermal therapy has a relatively narrow therapeutic window-the difference between a "therapeutic temperature" (keeping in mind the limited evidence of efficacy in any clinical condition) and a potentially toxic one is relatively small. Of note, wet heat (scald) travels much more rapidly into tissue, and is thus much more dangerous, than dry heat (flame). A surface temperature of more than 156°F by wet heat produces immediate tissue death as well as vessel clotting, while a significantly higher temperature would be required with dry heat.
If heating devices are to be used, then the temperature of the device should be accurately measured and kept below 140°F. This effectively precludes the use of hot water bottles (unless the water temperature can be accurately measured) and of packs heated in microwave ovens but whose temperature may be unknown.
Other strategies to increase the safety of heat application include:
- Placing the heating device on top of, not underneath, the patient, if possible.
- Assessing skin integrity frequently and adjusting the therapy interval according to the patient's skin tolerance.
- Restricting use of the heating device to no longer than 15 to 20 minutes.
It should be noted that areas with decreased blood flow are also more prone to tissue damage, due to decreased ability to conduct heat away from the area. A common example of this is when Plaster of Paris (which becomes quite hot as it "sets") is applied to limbs that are ischemic due to tourniquet application intraoperatively.
Patient education and instruction regarding use of a heating device are important parts of any therapy. Nursing and allied health staff should not apply an unregulated heating device directly onto a patient's skin unless a protective cover that cocoons the device and prevents its having direct contact with the skin is provided. Vigilant monitoring of the patient's skin for marked redness, swelling, pain, and edema should also be instituted; if seen, the heating device should be removed immediately.
This clinical scenario was fortunately associated with no significant burn injury. However, every burn surgeon has seen iatrogenic burn injury as the result of “therapeutic” application of local warming devices. It is time that the use of unregulated local heat therapy disappeared from the therapeutic armamentarium. Further investigation into the therapeutic efficacy of this modality, and the best practices for applying heat safely in a variety of conditions, is warranted.
- Although heat therapy is common, little evidence supports its effectiveness.
- Thermal therapy may relieve pain for certain musculoskeletal conditions and may help in wound healing.
- If heat therapy is used, the device must be kept at a temperature below 140°F and must be used for no longer than 15 to 20 minutes.
- The patient's skin should be vigilantly monitored and heat removed immediately if there is evidence of injury, such as severe redness, swelling, pain, or edema.
Heather Cleland, MBBS Director, Victorian Adult Burns Service The Alfred Hospital Melbourne, Australia
Jason Wasiak, BN, MPH Senior Research Fellow, Victorian Adult Burns Service The Alfred Hospital Melbourne, Australia
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