High Tensile Strength Increases Multifunctional Use of Survival Blankets in Wilderness Emergencies.

INTRODUCTION: Metallic survival blankets are multifunctional medical devices frequently used to provide thermal insulation in sport and leisure activities and in emergency care. To assess further properties of survival blankets, we investigated their breaking strength under laboratory conditions. METHODS: An experimental study was performed with 2 commercially available survival blankets used by emergency medical services. Breaking strength measured with a tensile testing machine was determined consecutively with 10 tests conducted per brand. RESULTS: Breaking strength (mean±SD) of the tested brands was 3.8±0.4 kN, (range: 2.8-4.1 kN) and 4.0±0.5 kN (range: 3.2-4.6 kN). When using the windlass of a commercially available tourniquet for the longitudinally folded survival blanket, the windlass bent at a force of 0.8 kN; when using a carabiner, the force exceeded 3.6 kN before failure occurred in both blanket brands. CONCLUSIONS: Both brands of survival blankets show impressive tensile strength, indicating that they have the potential to serve as temporary pelvic binders or even as makeshift tourniquets when urgent bleeding control is needed.

Human Responses to 5 Heated Hypothermia Wrap Systems in a Cold Environment.

INTRODUCTION: We compared the effectiveness of 5 heated hypothermia wrap systems. METHODS: Physiologic and subjective responses were determined in 5 normothermic subjects (1 female) for 5 heated hypothermia wraps (with vapor barrier and chemical heat sources) during 60 min of exposure to a temperature of -22°C. The 5 systems were 1) user-assembled; 2) Doctor Down Rescue Wrap; 3) hypothermia prevention and management kit (HPMK); 4) MARSARS Hypothermia Stabilizer Bag; and 5) Wiggy's Victims Casualty Hypothermia Bag. Core and skin temperature, metabolic heat production, skin heat loss, and body net heat gain were determined. Subjective responses were also evaluated for whole body cold discomfort, overall shivering rating, overall temperature rating, and preferential ranking. RESULTS: The Doctor Down and user-assembled systems were generally more effective, with higher skin temperatures and lower metabolic heat production; they allowed less heat loss, resulting in higher net heat gain (P<0.05). HPMK had the lowest skin temperature and highest shivering heat production and scored worse than the other 4 systems for the "whole body cold discomfort" and "overall temperature" ratings (P<0.05). CONCLUSIONS: The user-assembled and Doctor Down systems were most effective, and subjects were coldest with the HPMK system. However, it is likely that any of the tested systems would be viable options for wilderness responders, and the choice would depend on considerations of cost; volume, as it relates to available space; and weight, as it relates to ability to carry or transport the system to the patient.

Chemical Heat Packs as an Intervention to Prolong Ultrasound Battery Runtime.

INTRODUCTION: Point-of-care ultrasonography is a burgeoning field of practice and study. Although point-of-care ultrasonography has started to penetrate the field of wilderness medicine, its use in cold environments is often limited by poor battery performance. In the current study, we investigated the effect of chemical foot warmers on battery runtime of handheld ultrasound machines in cold weather. METHODS: This prospective study used a balanced, crossover randomization design to compare handheld ultrasound machines exposed to cold weather with and without the application of chemical foot warmers. Time to power off, ambient temperature, air humidity, and wind speed were recorded for each trial and compared in a mixed-effects model analysis of variance. RESULTS: Ultrasound machines showed significantly decreased functional battery life with decreasing temperature (P<0.01) and increasing wind speed (P=0.01). Addition of the chemical foot warmer resulted in a statistically significant increase in handheld ultrasound machine runtime compared with controls (P<0.001). Overall machine runtime was increased by approximately 21.8 min (95% CI 16.2-27.3). CONCLUSIONS: The application of chemical foot warmers to handheld ultrasound machines exposed to cold environments prolongs usable battery life and, consequently, may allow for extended scanning time in austere and remote environments.

Successful Field Rewarming of a Patient with Apparent Moderate Hypothermia Using a Hypothermia Wrap and a Chemical Heat Blanket.

Hypothermia is a common problem encountered by search and rescue teams. Although mildly hypothermic patients can be rewarmed in the field and can then self-evacuate, the Wilderness Medical Society hypothermia guidelines suggest that a moderately hypothermic patient in the wilderness requires warming in a medical facility. The hypothermia prevention and management kit, developed by the US military, consists of a chemical heat blanket (CHB) and a heat-reflective shell. We present a case in which a hypothermia wrap and the CHB from a hypothermia prevention and management kit were used successfully to rewarm a patient with apparent moderate hypothermia in the field. We are unaware of previous reports of successful field rewarming of a patient with moderate hypothermia. We believe the use of the CHB in conjunction with a hypothermia wrap made field rewarming possible. We recommend that a CHB, along with the components of a hypothermia wrap, be carried by search and rescue teams when a hypothermic patient might be encountered. Although there were no documented core temperatures, we believe this case is consistent with the hypothesis that if a hypothermic patient who is found lying down and shivering is allowed to stand or walk before insulation is applied and before there has been an additional period of 30 min during which the patient continues to shiver, there may be increased afterdrop with deleterious results.

An Experience of Improvised Laryngoscopy.

Airway management in the wilderness runs the gamut from basic airway support to endotracheal intubation. Fortunately, direct laryngoscopy is a seldom called upon skill in expedition medicine. However, the medical skills required during a mission or expedition are never truly known in advance. Improvisation during evolving medical events is a mainstay of expedition medicine education and practice. It is unlikely, given constraints of weight and size of expedition medical kits, that a conventional laryngoscope would find its way into a standard "go bag." Faced with the real but rare event of needing to intubate a patient in an austere environment, how can improvisation be used? Multiple ideas for improvised laryngoscopes can be found in the wilderness medicine literature, but which, if any, of these devices have true clinical utility? To this end, participants of a recent Wilderness Medical Society preconference in medical elements of light search and rescue were given the opportunity to devise and construct their own improvised laryngoscopes and attempt intubation of a training mannequin. Participants with varying degrees of intubating experience improvised effective laryngoscopes from provided materials and successfully intubated an airway mannequin.

Development of a portable blood salvage and autotransfusion technology to enhance survivability of personnel requiring major medical interventions in austere or military environments.

INTRODUCTION: Uncontrolled haemorrhage is the leading cause of death on the battlefield, and two-thirds of these deaths result from non-compressible haemorrhage. Blood salvage and autotransfusion represent an alternative to conventional blood transfusion techniques for austere environments, potentially providing blood to the casualty at point of injury. The aim of this paper is to describe the design, development and initial proof-of-concept testing of a portable blood salvage and autotransfusion technology to enhance survivability of personnel requiring major medical interventions in austere or military environments. METHOD: A manually operable, dual-headed pump was developed that removes blood from site of injury to a collection reservoir (upper pump) and back to casualty (lower pump). Theoretical flow rate calculations determined pump configuration and a three-dimensionally printed peristaltic pump was manufactured. Flow rates were tested with fresh bovine blood under laboratory conditions representative of the predicted clinical environment. RESULTS: Mathematical modelling suggested flow rates of 3.6 L/min and 0.57 L/min for upper and lower pumps. Using fresh bovine blood, flow rates produced were 2.67 L/min and 0.43 L/min. To mimic expected battlefield conditions, upper suction pump flow rate was calculated using a blood/air mixture. CONCLUSION: The authors believe that this technology can potentially enhance survivability for casualties in austere and deployed military settings through autotransfusion and cell concentration. It reduces negative effects of blood donation on the conventional donor pool, and potentially negates the logistical constraints associated with allogenic transfusions.

Remote Damage Control Resuscitation in Austere Environments.

Hemorrhage is the leading cause of preventable military and civilian trauma death. Damage control resuscitation with concomitant mechanical hemorrhage control has become the preferred in-hospital treatment of hemorrhagic shock. In particular, plasma-based resuscitation with decreased volumes of crystalloids and artificial colloids as part of damage control resuscitation has improved outcomes in the military and civilian sectors. However, translation of these principles and techniques to the prehospital, remote, and austere environments, known as remote damage control resuscitation, is challenging given the resource limitations in these settings. Rapid administration of tranexamic acid and reconstituted freeze-dried (lyophilized) plasma as early as the point of injury are feasible and likely beneficial, but comparative studies in the literature are lacking. Whole blood is likely the best fluid therapy for traumatic hemorrhagic shock, but logistical hurdles need to be addressed. Rapid control of external hemorrhage with hemostatic dressings and extremity tourniquets are proven therapies, but control of noncompressible hemorrhage (ie, torso hemorrhage) remains a significant challenge.

Bleeding Control With Limb Tourniquet Use in the Wilderness Setting: Review of Science.

The purpose of this review is to summarize tourniquet science for possible translation to wilderness settings. Much combat casualty data has been studied since 2005, and use of tourniquets in the military has changed from a last resort to first aid. The US Government has made use of tourniquets a health policy aimed to improve public access to bleeding control items. International authorities believe that education in first aid should be universal, as all can and should learn first aid. The safety record of tourniquet use is mixed, but users are reliably safe if trained well. Well-designed tourniquets can reliably attain bleeding control, may mitigate risk of shock progression, and may improve survival rates, but conclusive proof of a survival benefit remains unclear in civilian settings. Even a war setting has a bias toward survivorship by sampling mostly survivors in hospitals. Improvised tourniquets are less reliable than well-designed tourniquets but may be better than none. The tourniquet model used most often in 2016 by the US military is the Combat Application Tourniquet (C-A-T), and civilians use an array of various models, including C-A-T. Evidence on tourniquet use to date indicates that most uses are safe and effective in civilian settings. Future directions for study relevant to the wilderness setting include consideration of research priorities, study of the burdens of injury or capability gaps in caregiving for various wilderness settings, determination of the skill needs of outdoor enthusiasts and wilderness caregivers, and survey of wilderness medicine stewards regarding bleeding control.

Pressures of Wilderness Improvised Wound Irrigation Techniques: How Do They Compare?

OBJECTIVE: Compare the pressures measured by improvised irrigation techniques to a commercial device and to prior reports. METHODS: Devices tested included a commercial 500-mL compressible plastic bottle with splash guard, a 10-mL syringe, a 10-mL syringe with a 14-ga angiocatheter (with needle removed), a 50-mL Sawyer syringe, a plastic bag punctured with a 14-ga needle, a plastic bottle with cap punctured by a 14-ga needle, a plastic bottle with sports top, and a bladder-style hydration system. Each device was leveled on a support, manually compressed, and aimed toward a piece of glass. A high-speed camera placed behind the glass recorded the height of the stream upon impact at its highest and lowest point. Measurements were recorded 5 times for each device. Pressures in pounds per square inch (psi) were calculated. RESULTS: The syringe and angiocatheter pressures measured the highest pressures (16-49 psi). The 50-mL syringe (7-11 psi), 14-ga punctured water bottle (7-25 psi), and water bottle with sports top (3-7 psi) all measured at or above the commercial device (4-5 psi). Only the bladder-style hydration system (1-2 psi) and plastic bag with 14-ga needle puncture (2-3 psi) did not reach pressures generated by the commercial device. CONCLUSIONS: Pressures are consistent with those previously reported. All systems using compressible water bottles and all syringe-based systems provided pressures at or exceeding a commercial wound irrigation device. A 14-ga punctured plastic bag and bladder-style hydration pack failed to generate similar irrigation pressures.

Improvising a Posterior Nasal Pack with Equipment in a Basic First Aid Kit.

Posterior epistaxis is a serious condition that can be difficult to treat in a wilderness setting. The initial standard of care involves packing the affected nostril with a 7 to 9 cm nasal pack to tamponade the bleed. These packs are often unavailable outside of the emergency or operating room. This study set out to determine whether a posterior nasal pack could be constructed from the supplies present in a basic first aid kit in order to control massive nasal hemorrhage in a wilderness setting. A basic first aid kit was utilized to construct a posterior nasal pack that was inserted into an anatomical model and visibly compared with the Rapid Rhino (Posterior, 7.5 cm; Smith & Nephew, Austin, TX) nasal packing. The shape, size, and anatomical areas of compression (ie, into nasopharynx and posterior aspect of inferior turbinate) of this pack was similar to the commercially available posterior nasal pack. Placement in an anatomical model appears to provide similar compression as the commercially available posterior pack. This technique may provide short-term hemorrhage control in cases of serious posterior nasal hemorrhage where standard treatment options are not available.

Comparison of Distal Limb Warming With Fluidotherapy and Warm Water Immersion for Mild Hypothermia Rewarming.

OBJECTIVE: The purpose of the study was to determine the effectiveness of Fluidotherapy rewarming through the distal extremities for mildly hypothermic, vigorously shivering subjects. Fluidotherapy is a dry heat modality in which cellulose particles are suspended by warm air circulation. METHODS: Seven subjects (2 female) were cooled on 3 occasions in 8˚C water for 60 minutes, or to a core temperature of 35°C. They were then dried and rewarmed in a seated position by 1) shivering only; 2) Fluidotherapy applied to the distal extremities (46 ± 1°C, mean ± SD); or 3) water immersion of the distal extremities (44 ± 1°C). The order of rewarming followed a balanced design. Esophageal temperature, skin temperature, heart rate, oxygen consumption, and heat flux were measured. RESULTS: The warm water produced the highest rewarming rate, 6.1°C·h(-1), 95% CI: 5.3-6.9, compared with Fluidotherapy, 2.2°C·h(-1), 95% CI: 1.4-3.0, and shivering only, 2.0°C·h(-1), 95% CI: 1.2-2.8. The Fluidotherapy and warm water conditions increased skin temperature and inhibited shivering heat production, thus reducing metabolic heat production (166 ± 42 W and 181 ± 45 W, respectively), compared with shivering only (322 ± 142 W). Warm water provided a significantly higher net heat gain (398.0 ± 52 W) than shivering only (288.4 ± 115 W). CONCLUSIONS: Fluidotherapy was not as effective as warm water for rewarming mildly hypothermic subjects. Although Fluidotherapy is more portable and technically simpler, it provides a lower rate of rewarming that is similar to shivering only. It does help decrease shivering heat production, lowering energy expenditure and cardiac work, and could be considered in a hospital setting, if convenient.

Which Improvised Tourniquet Windlasses Work Well and Which Ones Won't?

OBJECTIVE: Improvised tourniquets in first aid are recommended when no scientifically designed tourniquet is available. Windlasses for mechanical advantage can be a stick or pencil and can be used singly or multiply in tightening a tourniquet band, but currently there is an absence of empiric knowledge of how well such windlasses work. The purpose of the present study was to determine the performance of improvised tourniquets in their use by the type and number of windlasses to improve tourniquet practice. METHODS: A simulated Leg Tourniquet Trainer was used as a manikin thigh to test the effectiveness of improvised tourniquets of a band-and-windlass design. Two users made 20 tests each with 3 types of windlasses. Tests started with 1 representative of a given type (eg, 1 pencil), then continued with increasing numbers of each windlass type until the user reached 100% effectiveness as determined by cessation of simulated blood flow. Windlass types included chopsticks, pencils, and craft sticks. RESULTS: Effectiveness percentages in stopping bleeding were associated inversely with breakage percentages. Pulse stoppage percentages were associated inversely with breakage. The windlass turn numbers, time to stop bleeding, the number of windlasses, and the under-tourniquet pressure were associated inversely with breakage. The windlass type was associated with breakage; at 2 windlasses, only chopsticks were without breakage. Of those windlass types that broke, 20.7% were chopsticks, 26.1% were pencils, and 53.2% were craft sticks. CONCLUSIONS: A pair of chopsticks as an improvised tourniquet windlass worked better than pencils or craft sticks.

Novel approach to the diagnosis of fractures in an austere environment using a stethoscope and a cellular phone.

BACKGROUND: Fracture diagnosis in the austere environment where radiographic tests are not available can be a challenge. In the past, a diagnostic technique has been described using a tuning fork and stethoscope to assess decreased sound conduction in the fractured extremity. In this study, we evaluate the use of a cellular phone's vibrate function and a stethoscope to limit equipment carried by expeditionary practitioners. OBJECTIVE: The purpose of this study was to evaluate the accuracy of fracture diagnosis using a cellular phone and stethoscope. METHODS: This is a pilot study to assess the usefulness of the above technique before clinical implementation. In 3 cadavers, we created fractures of the humerus and femur. Twenty-seven emergency medicine residents and an attending physician performed the diagnostic technique. RESULTS: Overall, the use of the cellular phone and stethoscope resulted in a sensitivity of 73% (95% confidence interval [CI]: 0.64 to 0.81) and a specificity of 83% (95% CI: 0.77 to 0.88), with a positive predicted value of 68% (95% CI: 0.59 to 0.77) and a negative predicted value of 86% (95% CI: 0.81 to 0.90). Positive likelihood ratio was 4.3, and negative likelihood ratio was 0.32. CONCLUSIONS: The use of a cellular phone and stethoscope may be a useful tool for the diagnosis of fractures in the austere environment. However, further study is needed to validate these findings in the clinical environment.

Dental extractions using improvised equipment.

Extracting a tooth is the final treatment for multiple dental problems. Persons who are not dentists, however, have little experience with tooth extractions. When a remote setting makes it impossible to send a patient for optimal dental treatment, the clinician may need to extract teeth, sometimes using improvised equipment. The following cases of two patients with three carious, painful molars describe such a situation. The non-dental clinicians had to improvise not only appropriate dental tools, but also personal protective equipment, a functional suction machine, medications for a dental block, a dental chair, and dental consent forms and follow-up instructions in the patients' language. In these cases, they also communicated with their patients through a translator. To prepare to do tooth extractions in remote settings, clinicians should learn and practice dental blocks and review extraction techniques before they deploy. If they must do an extraction, clinicians should use the closest approximation available to the appropriate dental tools. When done correctly, a dental extraction can take some time and should not be rushed.

Portable ultrasound for remote environments, Part I: Feasibility of field deployment.

BACKGROUND: In field medical operations, rapid diagnosis and triage of seriously injured patients is critical. With significant bulk and cost constraints placed on all equipment, it is important that any medical devices deployed in the field demonstrate high utility, durability, and ease of use. When medical ultrasound was first used in patient care, machine cost, bulk, and steep learning curves prevented use outside of the radiology department. Now, lightweight portable ultrasound is widely employed at the bedside by emergency physicians. The techniques and equipment have recently been extrapolated out of the hospital setting in a wide variety of environments in an effort to increase diagnostic accuracy in the field. OBJECTIVES: In this review, deployment of lightweight portable ultrasound in the field (by emergency medical services, military operations, disaster relief, medical missions, and expeditions to austere environments) is examined. The feasibility of field deployment and experiences of clinicians using ultrasound in a host of environments are detailed. In addition, special technological considerations such as telemedicine and machine characteristics are reviewed. CONCLUSIONS: The use of lightweight portable ultrasound shows great promise in augmenting clinical assessment for field medical operations. Although the feasibility of the technology has been demonstrated in certain medical and trauma applications, further research is needed to determine the utility of ultrasound use for medical illness in the field.