Efficacy of intravenous tissue plasminogen activator in frostbite patients and presentation of a treatment protocol for frostbite patients

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2024 Update

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for the prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the guidelines published in 2019.

American Burn Association Clinical Practice Guidelines on the Treatment of Severe Frostbite

This Clinical Practice Guideline addresses severe frostbite treatment. We defined severe frostbite as atmospheric cooling that results in a perfusion deficit to the extremities. We limited our review to adults and excluded cold contact or rapid freeze injuries that resulted in isolated devitalized tissue. After developing population, intervention, comparator, outcomes (PICO) questions, a comprehensive literature search was conducted with the help of a professional medical librarian. Available literature was reviewed and systematically evaluated. Recommendations based on the available scientific evidence were formulated through consensus of a multidisciplinary committee. We conditionally recommend the use of rapid rewarming in a 38 to 42°C water bath and the use of thrombolytics for fewer amputations and/or a more distal level of amputation. We conditionally recommend the use of "early" administration of thrombolytics (≤12 hours from rewarming) compared to "later" administration of thrombolytics for fewer amputations and/or a more distal level of amputation. No recommendation could be formed on the use of vascular imaging studies to determine the use of and/or the time to initiate thrombolytic therapy. No recommendation could be formed on the use of intravenous thrombolytics compared to the use of intra-arterial thrombolytics on fewer amputations and/or a more distal level of amputation. No recommendation could be formed on the use of iloprost resulting in fewer amputations and/or more distal levels of amputation. No recommendation could be formed on the use of diagnostic imaging modalities for surgical planning on fewer amputations, a more distal level of amputation, or earlier timing of amputation.

Update on Cold-Induced Injuries

Cold-induced injuries are a major challenge for burn surgeons, leading to significant sequelae for the patients including amputations, long-term disability, and death. Rapid assessment and diagnosis are essential for optimal outcomes. Various therapies have emerged to improve outcomes. Topical, oral, and intravenous agents have shown to minimize the impact of cold-induced injuries. Thrombolytics have shown the greatest promise in improving tissue perfusion outcomes in cold-induced injuries. This article provides an update on the evidence-based assessment and management of cold-induced injuries, as well as reviews outcomes and future directions of this challenging pathology.

Frostbite in the Pediatric Population: A Comprehensive Review and a Prospective Canadian Survey

INTRODUCTION

Frostbite in the pediatric population, where skeletal maturity has not been achieved, can have important repercussions on subsequent growth. Yet, the optimal management of frostbite injuries in children remains vague. This review aims to summarize the current evidence for frostbite management in children and understand Canadian practice trends on this topic.

METHODS

A review using Medline, Scopus, Web of Science, and gray literature was performed to identify relevant literature on the clinical manifestations, diagnostic methods, and treatment options in pediatric frostbite. An online survey was sent to plastic surgeons through the Canadian Society of Plastic Surgeons (CSPS) mailing list to further identify national practices and trends for pediatric frostbite management.

RESULTS

A total of 109 articles were reviewed. No article provided a specific algorithm for pediatric frostbite, with existing recommendations suggesting the use of adult guidelines for treating children. Our survey yielded 9 responses and highlighted the rarity of pediatric frostbite cases, with no responder treating more than 10 cases per year. Most (55.6%) do not use a pediatric-specific treatment algorithm, whereas 30% apply adult guidelines. A conservative approach focusing on rewarming (55.6%), limb elevation (50%), and tetanus status verification (66.7%) was predominant. Imaging and surgical interventions seem to be reserved for severe cases.

CONCLUSIONS

The current literature for pediatric frostbite management lacks specificity. Canadian practices vary, with a trend toward a conservative approach. The limited evidence and rarity of experience highlight the need for further research, ideally in a collaborative multicentric manner, to create a consensus for pediatric frostbite care.

Frostbite treatment: a systematic review with meta-analyses

INTRODUCTION

Our objective was to perform a systematic review of the outcomes of various frostbite treatments to determine which treatments are effective. We also planned to perform meta-analyses of the outcomes of individual treatments for which suitable data were available.

MAIN BODY

We performed a systematic review and meta-analyses in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. We searched PubMed, Cochrane Trials, and EMBase to identify primary references from January 1, 1900, to June 18, 2022. After eliminating duplicates, we screened abstracts to identify eligible studies containing information on treatment and outcomes of Grade 2 to 4 frostbite. We performed meta-analyses of groups of articles that provided sufficient data. We registered our review in the prospective registry of systematic reviews PROSPERO (Nr. 293,693). We identified 4,835 potentially relevant studies. We excluded 4,610 studies after abstract screening. We evaluated the full text of the remaining 225 studies, excluding 154. Ultimately, we included 71 articles with 978 cases of frostbite originating from 1 randomized controlled trial, 20 cohort studies and 51 case reports. We found wide variations in classifications of treatments and outcomes. The two meta-analyses we performed both found that patients treated with thrombolytics within 24 h had better outcomes than patients treated with other modalities. The one randomized controlled trial found that the prostacyclin analog iloprost was beneficial in severe frostbite if administered within 48 h.

CONCLUSIONS

Iloprost and thrombolysis may be beneficial for treating frostbite. The effectiveness of other commonly used treatments has not been validated. More prospective data from clinical trials or an international registry may help to inform optimal treatment.

Management of multiple frostbite casualties at a burn center: San Antonio, Texas, 12-20 February 2021

BACKGROUND

Frostbite is an insidious disease that normally affects people of cold climates. Winter Storm Uri, which occurred from February 12-20, 2021, created unique metrological conditions for Texas. It caused prolonged sub-freezing temperatures and led to rolling blackouts, affecting 2.8 million Texans including 300,000 people in San Antonio. We report 13 frostbite patients admitted to one burn center during this event.

OBJECTIVE

We aimed to determine the at-risk population for frostbite, to categorize their injury severity, and to describe their treatment. A secondary aim was to describe the rehabilitation management of these patients.

METHODS

This is a single-center retrospective study. Each patient's injuries were assessed by a topographical grading system. Comparisons were made among those who were admitted to the intensive care unit (ICU), admitted to the progressive care unit (PCU), and treated as outpatients.

RESULTS

Thirteen patients were identified. Ten (76.9 %) considered themselves homeless, and 9 (69.2 %) were directly exposed to the elements. The median delay between time of injury and presentation to a medical facility was 3 days (IQR 1-6). Only 3 patients presented to a medical facility within 24 h. Six (46 %) sustained grade 2 injuries, 2 (15 %) sustained grade 3 injuries, and 5 (38%) sustained grade 4 injuries. Only one patient met criteria to receive tissue plasminogen activator (tPA), which was discontinued due to hematochezia. Patients admitted to the ICU, when compared to patients admitted to the ward, had a longer length of stay (median 73 days v. 12 days, p = 0.0215), and required more amputations at below-the-knee or higher levels (3 v. 0, p-value 0.0442).

CONCLUSION

In a region unaccustomed and perhaps unprepared to deal with winter storms, the population is particularly vulnerable to frostbite. Lack of awareness of frostbite injuries likely led to the delay in the presentation of patients, which prevented the timely use of tPA. Increasing public awareness may increase readiness.

Thrombolytic Salvage of the Frostbitten Upper Extremity: A Systematic Review

BACKGROUND

Vascular thrombosis secondary to frostbite can lead to ischemic tissue damage in severe cases. Threatened extremities may be salvaged with thrombolytics to restore perfusion; however, current data are limited to single institution case series. The authors performed a systematic review to determine the efficacy of thrombolytic therapy in treating upper extremity frostbite.

METHODS

PubMed, EBSCO, and Google Scholar were queried using the keywords "thrombolytics," "frostbite," "fibrinolytics," and "tPA." Exclusion criteria were failure to delineate anatomic parts injured, failure to report number of limbs salvaged, animal studies, and non-English language publications. Thrombolytic therapy was defined as intraarterial (IA) or intravenous (IV) administration of tissue plasminogen activator (tPA), alteplase, urokinase, streptokinase, or any tPA derivative.

RESULTS

A total of 42 studies were identified, with 13 satisfying inclusion criteria. Eight studies reported catheter-directed IA thrombolysis, four reported systemic IV administration, and 1 reported both methods. A total of 157 patients received thrombolytics. In all, 73 upper extremity digits were treated by IA route and 136 digits were treated by IV route. Overall upper extremity digit salvage rate was 59%. There was a significantly higher salvage rate in digits treated by the IA route compared to the IV route.

CONCLUSIONS

Thrombolytics, particularly when administered by the intra-arterial route, are emerging as a promising treatment of severe frostbite of the upper extremity, increasing digit salvage rates.

Thrombolytic Use in Management of Frostbite Injuries: Eight Year Retrospective Review at a Single Institution

Frostbite injuries are uncommon, understudied, and lack standardized treatment protocols. Although thrombolytics are commonly used, their efficacy remains controversial. Herein, we report the results of a retrospective review of frostbite treatment practices at a single institution. The impact of thrombolytics on outcomes was evaluated. Medical records of frostbite patients admitted between January 2010 and April 2018 were reviewed. Demographics, injury details, treatment, and outcomes were collected. Descriptive statistics were obtained. A case-control analysis comparing patients who received tissue plasminogen activator (tPA) with those who did not was performed. A total of 102 patients were included. The mean age was 43 ± 17.7; 82.4% were male. About 13% of patients were presented with first-degree, 54% with second-degree, 29% with third-degree, and 5% with fourth-degree frostbite. Toes (69%), fingers (53%), and feet (43%) were most commonly affected. Thirteen patients had angiograms. Twelve patients received tPA: three systemic tPA and nine catheter-directed tPA. Overall, 32 patients (31%) required surgery and 27 (26.5%) patients required amputation with an average of 6.5 digits amputated. Digit salvage rate based on angiography was 84.7%. Length of stay (P = .046), number of operations (P = .037), and need for surgery (P = .030) were significantly lower for patients who received thrombolytics. Two patients had bleeding complications but did not require intervention or interruption of therapy. Despite its small sample size, our study suggests benefits from thrombolytic therapy. Prospective, well designed, and multi-institutional studies are warranted to establish evidence-based treatment guidelines for the management of frostbite injuries.

Management of severe frostbite with iloprost, alteplase and heparin: a Yukon case series

BACKGROUND

We identified the need to modernize frostbite management in our northern centre and implemented a treatment protocol in 2015. Our aim was to describe the clinical course of patients presenting to the hospital since the implementation of the protocol.

METHODS

This was a retrospective case series from Whitehorse General Hospital, Whitehorse, Yukon Territory, Canada. We reviewed the charts of patients who presented to the hospital with grade 2-4 frostbite and were treated as per our protocol between Feb. 9, 2015, and Feb. 8, 2020. Patients with grade 2-4 frostbite received iloprost; in addition, those with grade 4 frostbite received alteplase and heparin. We determined the number of digits affected and salvaged, and the time from presentation to the emergency department to treatment initiation. We also examined patients' demographic characteristics, predisposing events, frostbite severity and adverse drug reactions.

RESULTS

In 22 patients treated for grade 2-4 frostbite, 142 digits were affected: 59 with grade 2 frostbite, 25 with grade 3 frostbite and 58 with grade 4 frostbite; of the 142, 113 (79.6%) were salvaged. All 29 digits amputated had grade 4 frostbite. The mean time from presentation to iloprost initiation was reduced from 32.9 hours in 2015 to 3.0 hours in 2020. Sports (10 cases [45%]) and alcohol use (6 [27%]) were the most common precipitating events, with alcohol use tending to result in more severe injury (grade 4 in 5 of 6 cases). Adverse reactions with iloprost (e.g., headache) were common but mild. Adverse reactions with alteplase (e.g., bleeding) were less common but of greater clinical significance.

INTERPRETATION

Over the study period, our protocol contributed to improvement in frostbite care at our institution, resulting in a digit salvage rate comparable to other published results. Our 5-year experience shows that advanced medical care of frostbite can be achieved, even at a rural centre.

Remote delivery of thrombolytics prior to transfer to a regional burn center for tissue salvage in frostbite: A single center experience of 199 patients

While much has been published on efficacy and safety of systemic thrombolytics in the treatment of acute frostbite, there has been limited investigation into administration outside a tertiary care setting. Here, we present a single-center experience with remote initiation of intravenous tissue plasminogen activator (tPA) at referring hospitals prior to transfer to a regional burn center. A modified Hennepin Quantification Score based on tissue involvement was used to determine eligibility for tPA and to quantify severity of amputation. This is a retrospective review of patients with acute frostbite of the digits admitted to a single verified burn center over a five-year period. Of 199 patient admissions, 40 received tPA remotely pre-transfer, 32 received tPA on admission to our institution, and 127 patients did not qualify for tPA therapy according to the protocol. Comparing patients who required any amputation (n=99, 49.7%) to those who did not, patients who received remote tPA had lower odds of any amputation compared to both those receiving tPA at our institution (OR 0.19, 95% CI 0.05 - 0.65, p=0.01) and the group receiving no tPA (OR 0.14, 95% CI 0.05 - 0.40, p<0.001) after controlling for confounders. Only one patient receiving pre-transfer tPA according to protocol (2.3%) had a significant bleeding event requiring transfusion. These results support the protocolized use of thrombolytic therapy for frostbite prior to transfer to a tertiary center.

Research progress in the pathogenic mechanisms and imaging of severe frostbite

PURPOSE

This article reviews the pathological mechanisms and progress of imaging of severe frostbite to assist in the search for targets for clinical diagnosis and treatment of severe frostbite. This review also aims to provide strong evidence for clinical diagnosis and treatment of deep frostbite.

METHODS

The review was based on the summary and analysis of the existing literature, and explored the pathological mechanism of deep frostbite and the advantages and disadvantages of imaging diagnostic methods.

RESULTS

According to the depth of tissue involvement, frostbite is divided into 4 levels. Severe frostbite includes Grade 3 and Grade 4 frostbite. Clinical performance evaluation and imaging diagnostic research have always been the mainstream of severe frostbite diagnosis. Imaging methods focus on vascular patency and tissue vitality. This article introduces angiography, SETCT/CT and MRA, and we summarize the advantages and disadvantages of these imaging methods. We recommend corresponding imaging modalities according to the state of frostbite patients.

CONCLUSIONS

Imaging examination, especially angiography and bone scans, provide useful information for determining the diagnosis and prognosis of severe frostbite. In order to obtain a good clinical prognosis, clinicians should first perform SPECT/CT. MRA does not burden the patient's body, but the balance between cost and benefit must be considered. Angiography provides a good feedback on the changes in blood vessel status before and after treatment, which is helpful for discovering the response of limbs to treatment.

Using Intra-arterial tPA for Severe Frostbite Cases. An Observational Comparative Retrospective Study

Frostbite causes tissue damage through five major mechanisms, out of which two are amenable to treatment. The first-line treatment is rapid rewarming therapy using water at 40°C to 42°C, which addresses the formation of ice crystals in the intra and extra cellular compartments. The second mechanism is progressive tissue ischemia after rewarming and is only accessible to a second-line therapy represented by thrombolysis. This study aimed to determine the efficacy of thrombolysis. This is a single-center retrospective cohort study, where it was aimed to evaluate two groups of patients. A total of 18 patients were included in this study. Mean times between injury to thrombolytic therapy and admission to thrombolytic therapy was 26.04 hours (SD 13.6) and 9.65 hours (SD 9.89), respectively. All patients suffered injuries ranging from second-degree deep to third degree. The rate of patients having complete, partial, and no angiographic responses were 55.6%, 11.1%, and 33.3%, respectively. The main outcome of interest showed that 11 (61.1%) patients in total had amputations at different levels. Results showed that in the intervention group, five (55.6%) of the patients had amputations compared with six (66.7%) from the control group (P = .6) at comparable levels of amputation. The literature supports that the use of intra-arterial tissue plasminogen activator might be beneficial for severe cases of frostbites; however, it lacks of studies of major significance and results are often controversial. Our study has not shown statistically significant results on amputation levels and cannot support the hypothesis of efficacy of thrombolytic therapy.

Protocoled thrombolytic therapy for frostbite improves phalangeal salvage rates

Background

Frostbite is a cold injury that has the potential to cause considerable morbidity and long-term disability. Despite the complexity of these patients, diagnostic and treatment practices lack standardization. Thrombolytic therapy has emerged as a promising treatment modality, demonstrating impressive digit salvage rates. We review our experience with thrombolytic therapy for severe upper extremity frostbite.

Methods

Retrospective data on all frostbite patients evaluated at our institution from December 2017 to March 2018 was collected. A subgroup of patients with severe frostbite treated with intra-arterial thrombolytic therapy (IATT) were analysed.

Results

Of the 17 frostbite patients treated at our institution, 14 (82%) were male and the median age was 31 (range: 19–73). Substance misuse was involved in a majority of the cases (58.8%). Five (29.4%) patients with severe frostbite met inclusion criteria for IATT and the remaining patients were treated conservatively. Angiography demonstrated a 74.5% improvement in perfusion after tissue plasminogen activator thrombolysis. When comparing phalanges at risk on initial angiography to phalanges undergoing amputation, the phalangeal salvage rate was 83.3% and the digit salvage rate was 80%. Complications associated with IATT included groin hematoma, pseudoaneurysm and retroperitoneal hematoma.

Conclusions

Thrombolytic therapy has the potential to greatly improve limb salvage and functional recovery after severe frostbite when treated at an institution that can offer comprehensive, protocoled thrombolytic therapy. A multi-center prospective study is warranted to elucidate the optimal treatment strategy in severe frostbite.

Guidelines for Thrombolytic Therapy for Frostbite

The data are insufficient to support standardized treatment of all patients with frostbite with thrombolytic therapy. The following guidelines, however, should be applied to all patients with cyanosis persisting proximal to the distal phalanx (Grade 3 or 4 frostbite injury) and demonstrated loss of perfusion at or proximal to the middle phalanx immediately after rewarming.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2019 Update

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the guidelines published in 2014.

Thrombolytic Salvage of Threatened Frostbitten Extremities and Digits: A Systematic Review

Frostbite is a cold injury that results in soft tissue loss and can lead to amputation. Vascular thrombosis following injury causes ischemic tissue damage. Despite understanding the pathology, its treatment has remained largely unchanged for over 30 years. Threatened extremities may be salvaged with thrombolytics to restore perfusion. The authors performed a systematic review to determine whether thrombolytic therapy is effective and to identify patients who may benefit from this treatment. The Pubmed, EBSCO, and Google Scholar databases were queried using the key words “thrombolytics,” “frostbite,” “fibrinolytics,” and “tPA.” Studies written after 1990 in English met inclusion criteria. Exclusion criteria were failure to delineate anatomic parts injured, failure to report number of limbs salvaged, animal studies, and non-English language publications. Thrombolytic therapy was defined as administration of tPA, alteplase, urokinase, or streptokinase. Forty-two studies were identified and 17 included. Included were 1 randomized trial, 10 retrospective studies, 2 case series, and 4 case reports. One thousand eight hundred and forty-four limbs and digits in 325 patients were studied and 216 patients treated with thrombolytics and 346 amputations performed. The most common means of thrombolysis was intra-arterial tPA. The most common duration of therapy was 48 hours. Limb salvage rates ranged from 0% to 100% with a weighted average of 78.7%. Thrombolytics are a safe and effective treatment of severe frostbite. They represent the first significant advancement in frostbite treatment by preventing otherwise inevitable amputations warranting both greater utilization and further research to clarify the ideal thrombolytic protocol.

Urban Frostbite: Strategies for Limb Salvage

Under ideal circumstances, severely frostbitten extremities are rapidly rewarmed and treated with thrombolytic therapy within 6 to 24 hours. In an “inner city,” urban environment, most patients who suffer frostbite injuries present in a delayed fashion, sustain repeated injuries further complicated by psychological issues or intoxication, and are rarely ideal candidates for thrombolytic therapy within the prescribed timeframe. We describe our experience with the treatment of urban frostbite injuries. A retrospective review of patients with cold injuries sustained between November 2013 and March 2014 treated at a verified burn center in an urban setting was performed. Fifty-three patients were treated (42 males, 11 females). Average patient age was 41.8 years (range 2–84 years). No patients met criteria for thrombolytic therapy due to multiple freeze-thaw cycles or presentation greater than 24 hours after rewarming. Deep frostbite was seen in 10 patients. Of these patients, nine underwent debridement, resulting in partial limb amputations at levels guided by Tri-phasic technetium (Tc-99m) bone scans. Wound closure and limb-length salvage was then achieved by: free flap coverage (n = 2), local flaps (n = 8), split-thickness skin grafting (n = 22), and secondary intention healing (n = 6). While tissue plasminogen activator has been successful in reducing the need for digital amputation following frostbite injuries, in our experience, this treatment modality is not applicable to the urban patient population who often present late and after cycles of reinjury. Therefore, our approach focused on salvaging limb length with durable coverage, as the injuries were unable to be reversed.

The Use of tPA in the Treatment of Frostbite: A Systematic Review

BACKGROUND

The use of tissue plasminogen activator (tPA) for the treatment of frostbite has been reported and advocated, but its efficacy has not been well established. We conducted a systematic review to guide physicians on the role of tPA in the treatment of frostbite. Our hypothesis was that the use of tPA improves clinical outcomes, as measured by amputation rate.

METHODS

We searched MEDLINE (PubMed) and EMBASE for primary research articles on the use of tPA for the treatment of extremity frostbite. Information related to study design, outcomes, and complications was extracted. A total of 204 citations were screened, and then 35 abstracts and 24 reports were reviewed. Fifteen studies met the standard for final review.

RESULTS

One randomized, prospective study; 3 cohort studies; 8 case series; and 3 case reports were found. A total of 208 patients were treated. Differences in protocols, inclusion criteria, and outcomes measures prevented combining the study results. In all the studies, the authors reported that the use of tPA was or may have been useful in reducing amputation rates or increasing tissue salvage. Complication rates ranged from 0% to 100%, with a combined rate of 13%. The quality of the evidence was low.

CONCLUSIONS

Due to the low scientific quality of the studies, the efficacy of tPA in reducing amputation rates cannot currently be established. Randomized, prospective trials or well-controlled cohort studies are needed to better assess the role of tPA. Consideration should be given to limiting its use to research protocols.

Use of Intra-arterial Thrombolytic Therapy for Acute Treatment of Frostbite in 62 Patients with Review of Thrombolytic Therapy in Frostbite

Amputations are common after severe frostbite injuries, often mediated by postinjury arterial thrombosis. Since 1994, the authors have performed angiography to identify perfusion deficits in severely frostbitten digits and treated these lesions with intraarterial infusion of thrombolytic agents, usually combined with papaverine to reduce vasospasm. A retrospective review was performed of patients admitted to the regional burn center with frostbite injury from 1994 to 2007. Patients with severe frostbite, without contraindications to thrombolytic therapy, underwent diagnostic angiography of the affected extremities. Limbs with perfusion defects received intraarterial thrombolytic therapy according to protocol and the response was documented. Delayed amputation was performed for mummified digits. Angiogram results and amputation rates were tabulated. In this 14-year review, 114 patients were admitted for frostbite injuries. There was a male predominance (84%) and the mean age was 40.4 years. Of this group, 69 patients with severe frostbite underwent angiography; 66 were treated with intraarterial thrombolytic therapy. Four treated were excluded due to incomplete data. In the remaining 62 patients, angiography identified 472 digits with frostbite injury and impaired arterial perfusion. At the termination of thrombolytic infusion, a completion angiogram was performed. Partial or complete amputations were performed on only four of 198 digits (2.0%) with distal vascular blush, and in 71 of 75 digits (94.7%) with no improvement. Amputations occurred in 73 of 199 digits (36.7%) with partially restored flow. Overall complete digit salvage rate was 68.6%. Angiography after severe frostbite is a sensitive method to detect impaired arterial blood flow and permits catheter-directed treatment with thrombolytic agents. Improved perfusion after such treatment decreases late amputations following frostbite injury.

Cold Injuries

New treatments of frostbite have led to unprecedented salvage of extremities including fingers and toes. Success is predicated on prompt institution of time-sensitive protocols initiated soon after rewarming, particularly the use of thombolytics. Unfortunately, in the urban setting, most patients are not candidates for these treatment modalities. Triple-phase bone scans have allowed for early determination of devitalized parts that need amputation. Reconstructive surgical techniques are typically used to salvage limb length in these devastating injuries.

The use of intravenous tPA for the treatment of severe frostbite

OBJECTIVE

tPA and anticoagulation for treatment of severe frostbite have been reported suggesting differences in imaging techniques, route of tPA administration and management of patients after tPA infusion. This is a report of our results following a protocol of Tc-99m scanning, intravenous tPA administration, followed by either systemic anticoagulation or antiplatelet therapy.

METHODS

Patients admitted to our burn center between February 13, 2015 and February 13, 2016 for frostbite who met inclusion criteria were treated with Tc-99m scan and intravenous tPA followed by systemic anticoagulation or antiplatelet therapy. Inclusion criteria included rewarming had not started more than 24h prior to the scan and no contraindications to the use of tPA.

RESULTS

Fifteen patients met inclusion criteria and 12 were treated according to the protocol. Nine received scans with 2 showing normal perfusion. Seven displayed perfusion defects and received intravenous tPA. Five recovered fully after tPA. Two who showed improved but abnormal scans after tPA experienced bleeding complications necessitating stopping heparin/Coumadin. Those two went on to partial amputation of digits.

CONCLUSION

The use of intra-arterial or intravenous tPA along with angiography or Tc-99m scanning followed by systemic anticoagulation or antiplatelet therapy may be beneficial to patients suffering frostbite.

A New Proposal for Management of Severe Frostbite in the Austere Environment

Despite advances in outdoor clothing and medical management of frostbite, individuals still experience catastrophic amputations. This is a particular risk for those in austere environments, due to resource limitations and delayed definitive treatment. The emerging best therapies for severe frostbite are thrombolytics and iloprost. However, they must be started within 24 hours after rewarming for recombinant tissue plasminogen activator (rt-PA) and within 48 hours for iloprost. Evacuation of individuals experiencing frostbite from remote environments within 24 to 48 hours is often impossible. To date, use of these agents has been confined to hospitals, thus depriving most individuals in the austere environment of the best treatment. We propose that thrombolytics and iloprost be considered for field treatment to maximize chances for recovery and reduce amputations. Given the small but potentially serious risk of complications, rt-PA should only be used for grade 4 frostbite where amputation is inevitable, and within 24 hours of rewarming. Prostacyclin has less risk and can be used for grades 2 to 4 frostbite within 48 hours of rewarming. Until more field experience is reported with these agents, their use should probably be restricted to experienced physicians. Other modalities, such as local nerve blocks and improving oxygenation at high altitude may also be considered. We submit that it remains possible to improve frostbite outcomes despite delayed evacuation using resource-limited treatment strategies. We present 2 cases of frostbite treated with rt-PA at K2 basecamp to illustrate feasibility and important considerations.

The Triaging and Treatment of Cold-Induced Injuries

BACKGROUND

In Central Europe, cold-induced injuries are much less common than burns. In a burn center in western Germany, the mean ratio of these two types of injury over the past 10 years was 1 to 35. Because cold-induced injuries are so rare, physicians often do not know how to deal with them.

METHODS

This article is based on a review of publications (up to December 2014) retrieved by a selective search in PubMed using the terms "freezing," "frostbite injury," "non-freezing cold injury," and "frostbite review," as well as on the authors' clinical experience.

RESULTS

Freezing and cold-induced trauma are part of the treatment spectrum in burn centers. The treatment of cold-induced injuries is not standardized and is based largely on case reports and observations of use. distinction is drawn between non-freezing injuries, in which there is a slow temperature drop in tissue without freezing, and freezing injuries in which ice crystals form in tissue. In all cases of cold-induced injury, the patient should be slowly warmed to 22°-27°C to prevent reperfusion injury. Freezing injuries are treated with warming of the body's core temperature and with the bathing of the affected body parts in warm water with added antiseptic agents. Any large or open vesicles that are already apparent should be debrided. To inhibit prostaglandin-mediated thrombosis, ibuprofen is given (12 mg/kg body weight b.i.d.).

CONCLUSION

The treatment of cold-induced injuries is based on their type, severity, and timing. The recommendations above are grade C recommendations. The current approach to reperfusion has yielded promising initial results and should be further investigated in prospective studies.

A retrospective cohort study examining treatments and operative interventions for frostbite in a tertiary care hospital

BACKGROUND

Frostbite is a common yet challenging injury to both diagnose and treat. McCauley's frostbite treatment protocol consists of 12 treatments that might well represent the standard of care. However, its effectiveness in preventing operative intervention has yet to be examined. Our objectives were to characterize frostbite injuries in Eastern Ontario, identify risk factors for deep injuries, and assess the protocol's efficacy in preventing operative outcomes.

METHODS

This cohort study examined patients with frostbite over ten years at a tertiary care hospital. Demographics and predisposing factors were recorded. Frostbite severity was categorized into superficial or deep. Treatments were recorded, including adherence to protocol and operative outcome.

RESULTS

Of the 265 frostbite patients identified, deep frostbite accounted for 56 (21.1%, 95% CI: 16.2-26.1%), of whom 20 (35.7%) had an operative outcome. Amputation occurred in 16 (28.6%) of deep injuries and debridement in 5 (8.9%). Risk factors for deep frostbite were older age (p =0.002), smoking (p <0.001), male sex (p =0.056) and alcohol abuse (p =0.056). None of the patients with deep frostbite had all 12 treatments performed. Adherence to protocol ranged from 0.0% to 48.2% per treatment. The rate of operative intervention was 7.7% in patients with deep frostbite who did not have any McCauley's frostbite treatments and ranged from 0.0% to 100.0% per treatment in those who did receive treatments.

CONCLUSIONS

The frostbite protocol was not regularly followed and therefore its efficacy in preventing operative intervention could not be determined. Further, none of the individual treatments in the protocol were associated with preventing operative intervention. We recommend that future research focus on identifying effective individual treatments.

Frostbite: Spectrum of Imaging Findings and Guidelines for Management

Frostbite is a localized cold thermal injury that results from tissue freezing. Frostbite injuries can have a substantial effect on long-term limb function and mobility if not promptly evaluated and treated. Imaging plays a critical role in initial evaluation of frostbite injuries and in monitoring response to treatment. A multimodality approach involving radiography, digital subtraction angiography (DSA), and/or multiphase bone scintigraphy with hybrid single photon emission computed tomography (SPECT)/computed tomography (CT) is often necessary for optimal guidance of frostbite care. Radiographs serve as an initial survey of the affected limb and may demonstrate characteristic findings, depending on the time course and severity of injury. DSA is used to evaluate perfusion of affected soft tissues and identify potential targets for therapeutic intervention. Angiography-directed thrombolysis plays an essential role in tissue preservation and salvage in deep frostbite injuries. Multiphase bone scintigraphy with technetium 99m-labeled diphosphonate provides valuable information regarding the status of tissue viability after initial treatment. The addition of SPECT/CT to multiphase bone scintigraphy enables precise anatomic localization of the level and depth of tissue necrosis before its appearance at physical examination and can help uncover subtle findings that may remain occult at scintigraphy alone. Multiphase bone scintigraphy with SPECT/CT is the modality of choice for prognostication and planning of definitive surgical care of affected limbs. Appropriate use of imaging to direct frostbite care can help limit the effects that these injuries have on limb function and mobility. ^©RSNA, 2016.

Frostbite of the hand

Frostbite is damage caused by the freezing of tissue owing to exposure to extreme cold. Clinically, it is often difficult to identify the severity of frostbite injury. There may be a wide discrepancy between the extent of damage to the skin versus that to the deeper structures. The initial clinical impression is usually worse than actual tissue damage. In addition to physical examination, diagnostic imaging, especially triple-phase bone scan, has been proposed to help differentiate between superficial and deep damage. Principles of treatment involve rapid rewarming to thaw the tissues and halt direct cellular damage, methods to minimize progressive dermal ischemia, and active wound care to promote timely healing. Pharmacological adjuncts, such as fibrinolytics, have been proposed to minimize tissue damage. Surgical therapy is postponed until there is clear demarcation between healthy and necrotic tissue.

Frostbite: a practical approach to hospital management

Frostbite presentation to hospital is relatively infrequent, and the optimal management of the more severely injured patient requires a multidisciplinary integration of specialist care. Clinicians with an interest in wilderness medicine/freezing cold injury have the awareness of specific potential interventions but may lack the skill or experience to implement the knowledge. The on-call specialist clinician (vascular, general surgery, orthopaedic, plastic surgeon or interventional radiologist), who is likely to receive these patients, may have the skill and knowledge to administer potentially limb-saving intervention but may be unaware of the available treatment options for frostbite. Over the last 10 years, frostbite management has improved with clear guidelines and management protocols available for both the medically trained and winter sports enthusiasts. Many specialist surgeons are unaware that patients with severe frostbite injuries presenting within 24 h of the injury may be good candidates for treatment with either TPA or iloprost. In this review, we aim to give a brief overview of field frostbite care and a practical guide to the hospital management of frostbite with a stepwise approach to thrombolysis and prostacyclin administration for clinicians.

Recognition and treatment of freezing and nonfreezing cold injuries

This article reviews recent medical literature to provide an overview of the recognition and treatment of the two broad categories of cold injuries, freezing and nonfreezing. Frostbite, a freezing cold injury, is treated traditionally with rapid rewarming followed by tissue care and surgical debridement of necrotic tissue. Recently, newer therapies aimed at prevention of tissue necrosis have shown improved outcomes compared with more traditional therapies. These newer treatment regimens for frostbite include the use of various drugs such as ibuprofen, aspirin, warfarin, tissue plasminogen activator, and prostacyclin. The use of Tc bone scans, magnetic resonance imaging arthrogram, or angiography may have prognostic value for early determination of the extent of tissue loss. The more common nonfreezing cold injuries, though less severe than frostbite, may lead to short- and long-term complications requiring treatment and are discussed also.

Tissue plasminogen activator prevents mortality from sulfur mustard analog-induced airway obstruction

Sulfur mustard (SM) inhalation causes the rare but life-threatening disorder of plastic bronchitis, characterized by bronchial cast formation, resulting in severe airway obstruction that can lead to respiratory failure and death. Mortality in those requiring intubation is greater than 80%. To date, no antidote exists for SM toxicity. In addition, therapies for plastic bronchitis are solely anecdotal, due to lack of systematic research available to assess drug efficacy in improving mortality and/or morbidity. Adult rats exposed to SM analog were treated with intratracheal tissue plasminogen activator (tPA) (0.15-0.7 mg/kg, 5.5 and 6.5 h), compared with controls (no treatment, isoflurane, and placebo). Respiratory distress and pulse oximetry were assessed (for 12 or 48 h), and arterial blood gases were obtained at study termination (12 h). Microdissection of fixed lungs was done to assess airway obstruction by casts. Optimal intratracheal tPA treatment (0.7 mg/kg) completely eliminated mortality (0% at 48 h), and greatly improved morbidity in this nearly uniformly fatal disease model (90-100% mortality at 48 h). tPA normalized plastic bronchitis-associated hypoxemia, hypercarbia, and lactic acidosis, and improved respiratory distress (i.e., clinical scores) while decreasing airway fibrin casts. Intratracheal tPA diminished airway-obstructive fibrin-containing casts while improving clinical respiratory distress, pulmonary gas exchange, tissue oxygenation, and oxygen utilization in our model of severe chemically induced plastic bronchitis. Most importantly, mortality, which was associated with hypoxemia and clinical respiratory distress, was eliminated.