Interventions for frostbite injuries

Long-Term Sequelae of Frostbite-A Scoping Review

Frostbite is tissue damage caused by freezing temperatures and constitutes an important cause of morbidity in cold climate zones and high altitude. The direct effects of sub-zero temperatures lead to tissue freezing, electrolyte shifts and pH alterations, microvascular damage, and eventually to cell death. Upon rewarming, inflammatory reperfusion injury and thrombosis may lead to further tissue damage. Several studies and various case reports show that many patients suffer from long-term sequelae such as vasomotor disturbances (associated with susceptibility to refreezing), and neuropathic and nociceptive pain, as well as damage to skeletal structures. There are still many uncertainties regarding the pathophysiology of these sequelae. It has been shown that the transient receptor potential channel (TRP) family plays a role in cold allodynia. Botulinum Toxin type A (BTX-A) injections have been reported to be beneficial in vasomotor and neuropathic disturbances secondary to frostbite. Epidural sympathetic block has been used for short-term treatment of frostbite induced chronic pain. Furthermore, amitriptyline, gabapentinoids, and duloxetine may have some benefits. Frostbite arthritis clinically resembles regular osteoarthritis. In children there is a risk of epiphyseal cartilage damage leading to bone deformities. Despite some promising therapeutic concepts, the scarcity of data on frostbite long-term sequelae in the literature indicates the need of more in-depth studies of this pathology in all its aspects.

Interventions for frostbite injuries

BACKGROUND

Frostbite is a thermal injury caused when tissue is exposed to sub-zero temperatures (in degrees Celsius) long enough for ice crystals to form in the affected tissue. Depending on the degree of tissue damage, thrombosis, ischaemia, necrosis (tissue death), gangrene and ultimately amputation may occur. Several interventions for frostbite injuries have been proposed, such as hyperbaric oxygen therapy, sympathectomy (nerve block), thrombolytic (blood-thinning) therapy and vasodilating agents such as iloprost, reserpine, pentoxifylline and buflomedil, but the benefits and harms of these interventions are unclear.

OBJECTIVES

To assess the benefits and harms of the different management options for frostbite injuries.

SEARCH METHODS

On 25 February 2020, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, Ovid MEDLINE(R), Ovid MEDLINE(R) In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily and Ovid OLDMEDLINE(R), Embase (OvidSP), ISI Web of Science: Science Citation Index Expanded (SCI-EXPANDED), Conference Proceedings Citation Index-Science (CPCI-S), as well as trials registers. Shortly before publication, we searched Clinicaltrials.gov, the World Health Organization (WHO) International Clinical Trials Registry Platform, OpenGrey and GreyLit (9 November 2020) again. We investigated references from relevant articles, and corresponded with a trial author.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared any medical intervention, e.g. pharmacological therapy, topical treatments or rewarming techniques, for frostbite injuries to another treatment, placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data. We used Review Manager 5 for statistical analysis of dichotomous data with risk ratio (RR) with 95% confidence intervals (CIs). We used the Cochrane 'Risk of bias' tool to assess bias in the included trial. We assessed incidence of amputations, rates of serious and non-serious adverse events, acute pain, chronic pain, ability to perform activities of daily living, quality of life, withdrawal rate from medical therapy due to adverse events, occupational effects and mortality. We used GRADE to assess the quality of the evidence.

MAIN RESULTS

We included one, open-label randomised trial involving 47 participants with severe frostbite injuries. We judged this trial to be at high risk of bias for performance bias, and uncertain risk for attrition bias; all other risk of bias domains we judged as low. All participants underwent rapid rewarming, received 250 mg of aspirin and 400 mg intravascular (IV) buflomedil (since withdrawn from practice), and were then randomised to one of three treatment groups for the following eight days. Group 1 received additional IV buflomedil 400 mg for one hour per day. Group 2 received the prostacyclin, iloprost, 0.5 ng to 2 ng/kg/min IV for six hours per day. Group 3 received IV iloprost 2 ng/kg/min for six hours per day plus fibrinolysis with 100 mg recombinant tissue plasminogen activator (rtPA) for the first day only. The results suggest that iloprost and iloprost plus rtPA may reduce the rate of amputations in people with severe frostbite compared to buflomedil alone, RR 0.05 (95% CI 0.00 to 0.78; P = 0.03; very low-quality evidence) and RR 0.31 (95% CI 0.10 to 0.94; P = 0.04; very low-quality evidence), respectively. Iloprost may be as effective as iloprost plus rtPA at reducing the amputation rate, RR 0.14 (95% CI 0.01 to 2.56; P = 0.19; very low-quality evidence). There were no reported deaths or withdrawals due to adverse events in any of the groups; we assessed evidence for both outcomes as being of very low quality. Adverse events (including flushing, nausea, palpitations and vomiting) were common, but not reported separately by comparator arm (very low-quality evidence). The included study did not measure the outcomes of acute pain, chronic pain, ability to perform activities of daily living, quality of life or occupational effects.

AUTHORS' CONCLUSIONS

There is a paucity of evidence regarding interventions for frostbite injuries. Very low-quality evidence from a single small trial indicates that iloprost, and iloprost plus rtPA, in combination with buflomedil may reduce the need for amputation in people with severe frostbite compared to buflomedil alone. However, buflomedil has been withdrawn from use. High quality randomised trials are needed to establish firm evidence for the treatment of frostbite injuries.