Arterial Occlusion Effectiveness of Space Blanket‒Improvised Tourniquets for the Remote Setting

Introduction

Control of severe extremity hemorrhage by tourniquet can save lives. In remote areas or in mass casualty incidents with multiple severely bleeding victims, lack of conventional tourniquets may make it necessary to improvise tourniquets.

Methods

Occlusion of the radial artery and delayed onset of capillary refill time resulting from windlass-type tourniquets were experimentally investigated by comparing a commercial tourniquet and a space blanket‒improvised tourniquet with a carabiner as a rod. This observational study was conducted on healthy volunteers in optimal application circumstances.

Results

Operator-applied Combat Application Tourniquets were deployed more swiftly (27 s, 95% CI: 25.7–30.2 vs 94 s, 95% CI: 81.7–114.4) and achieved 100% complete radial occlusion compared with improvised tourniquets, as assessed by Doppler sonography (P<0.001). When space blanket‒improvised tourniquets were used, traces of radial perfusion persisted in 48% of the applications. In Combat Application Tourniquets, capillary refill times were significantly delayed (7 s, 95% CI: 6.0–8.2 vs 5 s, 95% CI: 3.9–6.3) compared with those when using improvised tourniquets (P=0.013).

Conclusions

Improvised tourniquets should be considered only in dire circumstances with uncontrolled extremity hemorrhage and when no commercial tourniquets are available. Complete arterial occlusion was achieved in only half of the applications using a space blanket‒improvised tourniquet when a carabiner was used as a windlass rod. The speed of application was inferior to that for Combat Application Tourniquets. Similar to Combat Action Tourniquets, the correct assembly and application of space blanket‒improvised tourniquets on upper and lower extremities have to be trained.

KeywordsIntroductionControl of severe extremity hemorrhage by tourniquets (TQs) in patients with peripheral vascular injuries can prevent trauma deaths.Teixeira P.G.R. Brown C.V.R. Emigh B. Long M. Foreman M. Eastridge B. et al.Civilian prehospital tourniquet use is associated with improved survival in patients with peripheral vascular injury.,Martinson J. Park H. Butler Jr., F.K. Hammesfahr R. DuBose J.J. Scalea T.M. Tourniquets USA: a review of the current literature for commercially available alternative tourniquets for use in the prehospital civilian environment. Commercial TQs have been found to effectively control extremity hemorrhage.Kragh Jr., J.F. Dubick M.A. Bleeding control with limb tourniquet use in the wilderness setting: review of science.Schroll R. Smith A. McSwain Jr., N.E. Myers J. Rocchi K. Inaba K. et al.A multi-institutional analysis of prehospital tourniquet use.Scerbo M.H. Mumm J.P. Gates K. Love J.D. Wade C.E. Holcomb J.B. et al.Safety and appropriateness of tourniquets in 105 civilians. Application of a TQ demands adequate tightness, proper placement technique, and correct positioning in order to exert sufficient vascular compression to control bleeding by completely stopping the blood flow in an extremity.Kragh Jr., J.F. Dubick M.A. Bleeding control with limb tourniquet use in the wilderness setting: review of science.,Scerbo M.H. Mumm J.P. Gates K. Love J.D. Wade C.E. Holcomb J.B. et al.Safety and appropriateness of tourniquets in 105 civilians.,Sanak T. Brzozowski R. Dabrowski M. Kozak M. Dabrowska A. Sip M. et al.Evaluation of tourniquet application in a simulated tactical environment. An improperly tightened TQ that occludes only the venous return can even increase blood loss.Cremonini C. Nee N. Demarest M. Piccinini A. Minneti M. Canamar C.P. et al.Evaluation of the efficacy of commercial and noncommercial tourniquets for extremity hemorrhage control in a perfused cadaver model. Obstruction of only venous outflow increases the likelihood of developing compartment syndrome. Pain from both compression and ischemia is common with TQs, but the rate of lasting complications has been reported to be low.Rohrich C. Plackett T.P. Scholz B.M. Hetzler M.R. Proficiency in improvised tourniquets for extremities: a review. Potential complications include nerve palsy, compartment syndrome, venous thromboembolic events, and postischemic reperfusion damage.Scerbo M.H. Mumm J.P. Gates K. Love J.D. Wade C.E. Holcomb J.B. et al.Safety and appropriateness of tourniquets in 105 civilians. There are multiple commercially available TQs designed for bleeding control, such as windlass-type, elastic-type, ratchet-type, and pneumatic-type TQs.Martinson J. Park H. Butler Jr., F.K. Hammesfahr R. DuBose J.J. Scalea T.M. Tourniquets USA: a review of the current literature for commercially available alternative tourniquets for use in the prehospital civilian environment.,Schroll R. Smith A. McSwain Jr., N.E. Myers J. Rocchi K. Inaba K. et al.A multi-institutional analysis of prehospital tourniquet use. Originally adopted by the military, the windlass-type Combat Application Tourniquet (CAT) is now frequently used by first responders and emergency medical services.Martinson J. Park H. Butler Jr., F.K. Hammesfahr R. DuBose J.J. Scalea T.M. Tourniquets USA: a review of the current literature for commercially available alternative tourniquets for use in the prehospital civilian environment.,Schroll R. Smith A. McSwain Jr., N.E. Myers J. Rocchi K. Inaba K. et al.A multi-institutional analysis of prehospital tourniquet use.,Cremonini C. Nee N. Demarest M. Piccinini A. Minneti M. Canamar C.P. et al.Evaluation of the efficacy of commercial and noncommercial tourniquets for extremity hemorrhage control in a perfused cadaver model.,Rohrich C. Plackett T.P. Scholz B.M. Hetzler M.R. Proficiency in improvised tourniquets for extremities: a review.In an emergency setting where commercial devices are not available and prolonged direct pressure is not practicable, an improvised TQ (I-TQ) may be an effective bridge to definitive care.Cremonini C. Nee N. Demarest M. Piccinini A. Minneti M. Canamar C.P. et al.Evaluation of the efficacy of commercial and noncommercial tourniquets for extremity hemorrhage control in a perfused cadaver model.,Rohrich C. Plackett T.P. Scholz B.M. Hetzler M.R. Proficiency in improvised tourniquets for extremities: a review. Early hemorrhage control is crucial.Jacobs L.M. Rotondo M. McSwain N. Wade D.S. Fabbri W.P. Eastman A. et al.Joint committee to create a national policy to enhance survivability from mass casualty shooting events: Hartford consensus II. This particularly applies to severe hemorrhage in the wilderness setting under extreme environmental conditions when mountaineers have to rigorously stop bleeding until professional rescuers arrive on the scene.Kragh Jr., J.F. Dubick M.A. Bleeding control with limb tourniquet use in the wilderness setting: review of science. For mass casualty incidents with multiple severely bleeding victims, even rescue personnel can quickly run out of commercial TQs.Cornelissen M.P. Brandwijk A. Schoonmade L. Giannakopoulos G. van Oostendorp S. Geeraedts Jr., L. The safety and efficacy of improvised tourniquets in life-threatening hemorrhage: a systematic review., When applied properly, I-TQs were reported to reliably stop severe extremity hemorrhage in prehospital emergency care.Cremonini C. Nee N. Demarest M. Piccinini A. Minneti M. Canamar C.P. et al.Evaluation of the efficacy of commercial and noncommercial tourniquets for extremity hemorrhage control in a perfused cadaver model.,Cornelissen M.P. Brandwijk A. Schoonmade L. Giannakopoulos G. van Oostendorp S. Geeraedts Jr., L. The safety and efficacy of improvised tourniquets in life-threatening hemorrhage: a systematic review. Although the cloth and wooden dowel design achieved 42 to 100% success, an effective and safe I-TQ design has not yet been found.Cornelissen M.P. Brandwijk A. Schoonmade L. Giannakopoulos G. van Oostendorp S. Geeraedts Jr., L. The safety and efficacy of improvised tourniquets in life-threatening hemorrhage: a systematic review. To lay rescuers keeping an eye out for materials suitable for building an I-TQ, a space blanket (SB) may appear adequate at first glance. SBs are generally available as common components of the first aid equipment used in Europe in prehospital emergency medicine and outdoor sports as part of hypothermia prevention.Henriksson O. Lundgren P.J. Kuklane K. Holmér I. Giesbrecht G.G. Naredi P. et al.Protection against cold in prehospital care: wet clothing removal or addition of a vapor barrier.

In this experimental study, we aimed to investigate whether rescuers can apply an SB as an I-TQ to provide adequate vascular occlusion of the upper extremity. We compared the quality of radial occlusion achieved with an SB to that of a conventional CAT in a controlled environment.

MethodsAn experimental trial concerning rescuer application of an I-TQ compared with a commercial TQ was conducted with uninjured test subjects in the training rooms of Innsbruck Medical University Hospital. The target group of this study focused on mountaineers performing bystander hemorrhage control in the wilderness setting. All voluntary participants were recruited from Mountain Rescue Tyrol (MRT) Group Innsbruck. After announcing the study on social media, 25 eligible volunteers responded, 23 (17 male, 6 female) of whom participated (inclusion rate: 92%). Written informed consent was obtained from all subjects prior to the study investigation. Inclusion criteria were volunteers >18 and Figure 1). The study was approved by the institutional ethics committee (EK No.: 1039/2020) and registered (BASG No.: 13370800/15451670) with the Austrian Federal Office for Safety in Public Health Services (https://www.basg.gv.at). After approval and registration, the measurements were made under stationary conditions on a single day in October 2020. Data were collected on a work chart and transferred to electronic files for data processing. Reporting followed the CONSORT 2010 checklist of what information to include when reporting a randomized trial and the extension to randomized pilot and feasibility trials.Schulz K.F. Altman D.G. Moher D. CONSORT Group
CONSORT 2010 statement: updated guidelines for reporting parallel group randomized trials.,Eldridge S.M. Chan C.L. Campbell M.J. Bond C.M. Hopewell S. Thabane L. et al.CONSORT 2010 statement: extension to randomised pilot and feasibility trials.Figure thumbnail gr1

Figure 1Trial design of the arterial occlusion effectiveness of a space blanket (SB)‒improvised tourniquet compared with the Combat Application Tourniquet (CAT).

Subjects were distributed randomly in a crossover trial to 2 study arms and allocated CAT and SB applications. All participants received the same 2 treatments in alternate order. Random assignment of upper limbs was achieved by rolling 2 dice (simple randomization) and predetermining even numbers for the right and uneven numbers for the left upper limb.An overview of randomization techniques: an unbiased assessment of outcome in clinical research. Sequence of participation depended on the sequence of arrival of participants.Focusing on bystander first aid in the out-of-hospital setting, the primary endpoint was assessment of the efficacy of bleeding control by the investigators using 2 assessment devices. The secondary endpoint was the operator’s assessment of practicability, and the tertiary endpoint was his ease of handling. Outcomes were recorded immediately after each application. Data were previously evaluated as part of an academic thesis.

Banyai L. An overview of tourniquets. Can they be replaced by survival blanket makeshift tourniquets? [Eine Übersicht über Tourniquets. Können sie durch behelfsmäßig verwendete Rettungsdecken ersetzt werden?]. Thesis in German language. Innsbruck, Austria: Medical University of Innsbruck; 2020.

Application of test Devices

This study was conducted by a single operator (M.I.; mountain rescuer) to avoid interoperator bias. The operator was experienced in applying commercial TQs during first aid training but was not familiar with I-TQs. All TQs and I-TQs were applied 2-handed by the operator to the upper extremity of a supine participant on the investigation table. The proximal edge of each device was located within 5 cm of the armpit, a distance that was measured and marked on the skin prior to investigation.

The CAT (Gen 7, Rock Hill, SC) was selected as a commercial TQ as used by MRT and Helicopter Emergency Medical Services (HEMS) in Austria. CAT-7 was one of the nonpneumatic TQs recommended in 2019 for tactical combat casualty care when evaluating the following criteria: arterial occlusion, TQ pressure, simplicity of application, TQ specifications, retention mechanism, complications, safety, usage reports, user preferences, and logistics.Montgomery H.R. Hammesfahr R. Fisher A.D. Cain J.S. Greydanus D.J. Butler Jr., F.K. et al.2019 Recommended limb tourniquets in tactical combat casualty care. The device was applied by inserting the patient’s arm into the prearranged loop and pulling the end of the self-adhering band tight and securing it back on itself. Then, the operator turned the windlass rod until loss of distal radial pulse was achieved. Finally, the twisted rod was locked in place with the clip and secured with the windlass strap.One brand of SB (Rescue Blanket; Leina-Werke GmbH, Windeck, Germany)—used by MRT and HEMS in Austria—served as I-TQs. Blankets were selected for their general disposability and their confirmed high tear resistance.Isser M. Kranebitter H. Fink H. Wiedermann F.J. Lederer W. High tensile strength increases multifunctional use of survival blankets in wilderness emergencies. The blankets, composed of a polyethylene terephthalate sheet coated with a thin aluminum layer, were 160 × 210 cm in size. In the original packaging, the blankets were laid in 23 layers (22 foldings) of 6.9 cm width; in an unpacked and vertically aligned position, the segment fanned out to 7.8 cm in width.The SB was routed twice around the upper arm using the single segment longitudinally unfolded. Then, the 2 ends of the SB were joined using a half-square knot (Figure 2a). Another half-square knot was made on top, and a carabiner (passO-SC, Skylotec GmbH, Neuwied, Germany) was inserted between the 2 knots (Figure 2b). This helped protect the skin from direct constriction and doubled the width on the opposite side of the torque. Torque was applied by twisting the carabiner until the radial pulse was eliminated. Then, the twisted carabiner was locked into position with one end of the SB and secured to the other end on the opposite side with another 2 to 3 knots (Figure 2c).Figure thumbnail gr2

Figure 2Application of a space blanket‒improvised tourniquet to the left upper arm with the participant supine using a carabiner as a provisional windlass rod. a, A blanket was routed around the upper arm twice, then the 2 ends were joined with a half-square knot. b, A second half-square knot was tied above the first; then, a carabiner was inserted between the knots and turned to apply torque until radial pulse elimination. c. Finally, the twisted carabiner was locked into position with one end of the SB and secured to the other end on the opposite side with another 2 to 3 knots.

Investigations and Measurements

To diminish interobserver bias, measurements were made by Investigator 1 (T.S., cardiac surgeon), assigned to objective assessment using Doppler sonography, and by Investigator 2 (H.S., anesthetist) for assessment of capillary refill times and for recording subjective assessments made by the operator and participants using a questionnaire.

Vascular compression was verified using a portable Doppler sonography device (Huntleigh Dopplex D900, Huntleigh Healthcare Ltd, Diagnostic Products Division, Cardiff, Wales, UK) using a 10-MHz probe. In addition, pressure under the TQs was measured using a slightly inflated neonate blood pressure cuff connected via a rubber tube to a manometer (roid I, boso, CE 0124, Bosch + Sohn GmbH u. Co KG, Jungingen, Germany) for blood pressure measurement. Participants underwent 3 sonographic examinations (the first examination immediately before applying the TQ, the second examination 2 min after obstructing circulation, and the third examination after removing the TQ).

Objective assessment of efficacy was based on results obtained from radial blood flow with Doppler sonography by Investigator 1, 2 min after vascular compression (no flow: missing signal; low flow: trace signal; regular flow: full signal). Capillary refill time was assessed 1 min after vascular compression by Investigator 2. Maintenance of TQ pressure and associated ischemia was restricted to 2 min.

Subjective assessment of efficacy by Investigator 2 was based on results of a capillary refill under the nail of the index finger. Refill time was defined as the time taken for the capillary bed to regain its color after short pressure has been applied to cause blanching.Pickard A. Karlen W. Ansermino J.M. Capillary refill time: Is it still a useful clinical sign?. The operator’s subjective assessment of practicability and efficacy and ease of handling were categorized by Investigator 2 on a 5-item Likert-type scale using scores between 0 and 10 (1–2=very good, 3–4=good, 5–6=satisfactory, 7–8=moderate, 9–10=inadequate) and a hardcopy questionnaire. At 1 min after application of either the SB or the CAT, participants were asked to define the maximum intensity of pain using numerical rating scores between 0 and 10 (0=none, 5=medium, 10=most severe). In addition, Investigator 2 recorded participant feedback regarding paresthesia and quality and intensity of pain. Application time defined the interval from the beginning of device application until elimination of palpated pulse after having secured either the windlass rod or the carabiner. Sufficient vascular occlusion pressure was assumed when no radial pulse was detected and confirmed by Doppler sonography. Occluding time, the time taken to stop perfusion, was defined as the interval from beginning of twisting the commercial windlass rod or the carabiner until elimination of the pulse.Statistical Analysis

In a subjective assessment of efficacy, the estimated sample size was 14 participants to achieve a power of 80% and a level of significance of 5% (2-sided) to detect a true difference in means of 3 points between I-TQ applications and TQ applications. The quotient mean divided by standard deviation equals effect size=1.5. There was no supporting evidence from previous literature for this assumption. Descriptive statistics were applied using the statistical package for the social sciences from International Business Machines Corporation (IBM SPSS Statistics Standard 26, Armonk, NY) to determine measures of central tendency (median) and measures of dispersion (range, SD, variance, minimum and maximum). The null hypothesis to be tested was that there is no difference between SB and TQ regarding the efficacy of bleeding control. The alternative hypotheses were that there are differences between SB and TQ regarding practicability and ease of handling.

A nonparametric test (Wilcoxon Mann-Whitney U test) was used for comparison of ordinal data after Kruskal-Wallis analysis of variance. The association between sonographic findings (objective) and radial pulse taken by the operator (subjective) was expected to be statistically significant when using the χ2 test of independence.

Results

The median age of the 23 participants was 40 (range 20–55) y. There were no losses or exclusions after randomization. A total of 46 applications to the right and the left upper arm were performed with 2 randomly assigned devices. Prior to the investigations, median systolic blood pressure was 133 (range 100–150) mm Hg, median diastolic blood pressure was 72 (range 50–80) mm Hg, and median pulse rate was 68 (range: 50–100) beats·min‒1. Baseline values and upper arm circumference were comparable between the 2 groups.

Median application time and median choking time were shorter for the CAT (27 s, 95% CI: 25.7–30.2 vs 94 s, 95% CI: 81.7–114.4; PTable 1). Most delays in SB application resulted from the time needed to secure the carabiner in position to maintain the constricting force. For the CAT, securing the windlass rod in position took a few seconds. Three windlass rod turns were sufficient in most applications.

Table 1Survey results regarding application time, occlusion time, pain intensity under the device and paresthesia in the upper arm, and efficacy according to sonographic results from radial Doppler (Investigator 1) and capillary refill time 1 min after vascular compression (Investigator 2) with the Combat Application Tourniquet (CAT) and with space blankets (SBs) serving as improvised tourniquets.

Peak pressure under the TQs during adjustment of the SB and the CAT in 8 measurements exceeded 300 mm Hg for both devices. Peak occlusion pressure after 1 min exceeded 300 mm Hg for the CAT and 180 mm Hg for the SB. Complete radial compression 2 min after application of the device was confirmed by the absence of flow in Doppler sonography in 23 (100%) CAT applications and in 12 (52%) SB applications (P=0.005). Persistent low flow (traces) was detected in 11 (48%) SB applications. Accordingly, the delay of capillary refill time after 1 min differed between the 2 groups (5 s, 95% CI: 3.9–6.3 vs 7 s, 95% CI: 6.0–8.2; P=0.013) (Table 1). When Investigator 1 performed the second sonographic evaluation 2 min after SB application, he observed that as little as an additional quarter to half turn of the carabiner would have been sufficient to achieve arterial occlusion in 4 of the 11 applications with persistent low flow perfusion.Subjective assessment of practicability, ease of handling, and efficacy scored better marks for the CAT than for the SB (Table 2). Pain intensity 1 min after application was significantly lower for the SB and was more frequently observed as pinching, whereas pain intensity from CAT application was higher and more frequently defined as having a cutting quality (Table 1). No severe adverse reactions were observed during the study. Scratches, superficial abrasions, and small skin bruises were observed with both devices. All participants regained normal radial artery perfusion at device removal.

Table 2Survey results regarding ease of handling and practicability (operator) and efficacy (Investigator 2) in 23 measurements when using the Combat Application Tourniquet (CAT) and in 23 measurements when using a space blanket (SB) as an improvised tourniquet

DiscussionThis experimental study compared differences in arterial occlusion between CAT and SB application. The aluminum-coated SB is used for hypothermia prevention in prehospital emergency medicine.Henriksson O. Lundgren P.J. Kuklane K. Holmér I. Giesbrecht G.G. Naredi P. et al.Protection against cold in prehospital care: wet clothing removal or addition of a vapor barrier.,Bennett B.L. Giesbrect G. Zafren K. Christensen R. Littlejohn L.F. Drew B. et al.Management of hypothermia in tactical combat casualty care: TCCC guideline proposed change 20-01 (June 2020). Although the tool cannot actively rewarm a hypothermia victim, it can at least slow down heat loss from thermoradiation and thermoconvection.Kranebitter H. Wallner B. Klinger A. Isser M. Wiedermann F.J. Lederer W. Rescue blankets – transmission and reflectivity of electromagnetic radiation. In this study, an SB applied as an I-TQ proved to be tear resistant and achieved adequate vascular occlusion pressure for hemorrhage control in half of the cases. However, the difficulty, as presumably for most I-TQs, was the provisional windlass rod and its fixation. Rohrich et alRohrich C. Plackett T.P. Scholz B.M. Hetzler M.R. Proficiency in improvised tourniquets for extremities: a review. reported that a properly constructed I-TQ can be highly effective when 3 components are provided: a strap, a rod, and a securing mechanism. As our study was tailored to mountain rescue missions, a carabiner was used as a provisional windlass rod. It was secured in position, with the 2 ends of the blanket variously arranged and joined with additional knots. A single half-square knot to join the 2 ends of the SB and insertion of the carabiner underneath would have been adequate. We presume that a small stick or a pair of scissors might have provided more efficient torque and could have been more easily secured in position than a carabiner. Kragh et alKragh Jr., J.F. Wallum T.E. Aden 3rd, J.K. Dubick M.A. Baer D.G. Which improvised tourniquet windlasses work well and which ones won't?. investigated 3 types of provisional windlass rods and found that a pair of chopsticks worked better than pencils or craft sticks. Cremonini et alCremonini C. Nee N. Demarest M. Piccinini A. Minneti M. Canamar C.P. et al.Evaluation of the efficacy of commercial and noncommercial tourniquets for extremity hemorrhage control in a perfused cadaver model. observed in an experimental study that a standard leather belt was the fastest to place and was able to effectively stop the bleeding when continuous pressure was maintained. An improvised triangle bandage in windlass design was as effective as the commercial devices and was the easiest to apply.Wood et al Wood J.N. Krippendorf B.S. Blakeney C.A. Kummer T. Hooke A.W. Mullan A.F. et al.Precise limb tourniquet arterial occlusion pressure determination using real-time ultrasonography and a capacitive-based force sensor. observed in volunteers that loss of distal radial pulse does not indicate a lack of arterial flow distal to upper extremity TQ. On average, an additional one-quarter windlass turn was required to eliminate distal flow. In our study, persistent low flow perfusion was detected in 48% of SB applications. As little as an additional one-quarter to one-half rotation would have been sufficient to completely stop circulation in 4 out of 11 applications. It remains a matter of debate whether the decline in blood pressure can increase the success rate in hypovolemic individuals. Then again, pain may have increased the observed failure rate in normovolemic volunteers. However, neither anticipated pain nor skin lesions from TQ application cast doubt on the importance of hemorrhage control by vascular occlusion.The Hartford consensus proposed hemorrhage control for approaching mass shooting events, which led to implementation of the nationwide hemorrhage control training course “Stop the Bleed” from the American College of Surgeons Committee on Trauma.Jacobs L.M. Rotondo M. McSwain N. Wade D.S. Fabbri W.P. Eastman A. et al.Joint committee to create a national policy to enhance survivability from mass casualty shooting events: Hartford consensus II.,McCarty J.C. Hashmi Z.G. Herrera-Escobar J.P. de Jager E. Chaudhary M.A. Lipsitz S.R. et al.Effectiveness of the American College of Surgeons bleeding control basic training among laypeople applying different tourniquet types: a randomized clinical trial. This campaign focuses on laypersons to perform hemorrhage control for extremity injuries. However, the principles for correct TQ application are not fully translatable to different commercial or I-TQ types.McCarty J.C. Hashmi Z.G. Herrera-Escobar J.P. de Jager E. Chaudhary M.A.

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