Page 31 - Journal of Special Operations Medicine - Winter 2016

Significant Pressure Loss Occurs
Under Tourniquets Within Minutes of Application

Mary R.P. Rometti, BS; Piper L. Wall, DVM, PhD; Charisse M. Buising, PhD;
Yvonne L. Gildemaster, BS; James W. Hopkins, MD; Sheryl M. Sahr, MD

ABSTRACT

Background: Pressure decreases occur after tourniquet Keywords: tourniquet; hemorrhage; first aid; emergency
application, risking arterial occlusion loss. Our hypothesis treatment
was that the decreases could be mathematically de-
scribed, allowing creation of evidence-based, tourniquet-
reassessment-time recommendations. Methods: Four Introduction
tourniquets with width (3.8cm, 3.8cm, 13.7cm, 10.4cm),
elasticity (none, none, mixed elastic/nonelastic, elastic), Effective emergency tourniquets stop blood loss by in-
and mechanical advantage differences (windlass, ratchet, terrupting extremity arterial flow. Effectiveness is lost
inflation, recoil) were applied to 57.5cm-circumference when the pressure exerted by the tourniquet becomes
10% and 20% ballistic gels for 600 seconds and a 57.5cm- less than needed for arterial occlusion. This occurs on
circumference thigh and 31.5cm-circumference arm for healthy individuals in the laboratory and also may oc-
1–3
300 seconds. Time 0 target completion-pressures were cur on injured individuals during field use. 4
262mmHg and 362mmHg. Results: Two-phase decay
equations fit the pressure-loss curves. Tourniquet type, The consequences of preventing venous return without
gel or limb composition, circumference, and completion- preventing outward arterial flow include ongoing blood
pressure affected the curves. Curves were clinically sig- loss, compartment syndrome, shock, and death. Failure
5
nificant with the nonelastic Combat Application Tourni- to achieve arterial occlusion occurs because the chosen
quet (C-A-T), nonelastic Ratcheting Medical Tourniquet tourniquet design is inadequate to the task, or because
(RMT), and mixed elastic/nonelastic blood pressure the user does not correctly apply an effective design.
cuff (BPC), and much less with the elastic Stretch Wrap Failure to maintain arterial occlusion occurs because of
And Tuck-Tourniquet (SWATT). At both completion- tourniquet movement on the limb, increases in recipi-
pressures, pressure loss was faster on 10% than 20% ent arterial pressure, decreases in limb muscle tension,
1,2
gel, and even faster and greater on the thigh. The and decreases in pressure applied by the tourniquet. 1–3
362mmHg completion-pressure had the most pressure
loss. Arm curves were different from thigh but still ap- Clinically significant decreases in tourniquet-applied
proached plateau pressure losses (maximal calculated pressure occur as quickly as 1 minute after completed
losses at infinity) in similar times. With the 362mmHg tourniquet application. Our study purpose was to
1,2
completion-pressure, thigh curve plateaus were −68mmHg characterize the pressure decreases occurring under sev-
C-A-T, −62mmHg RMT, −34mmHg BPC, and −13mmHg eral commercially available, effective emergency tourni-
SWATT. The losses would be within 5mmHg of plateau quets. Our hypothesis was that the pressure decreases
by 4.67 minutes C-A-T, 6.00 minutes RMT, 4.98 min- could be mathematically described, which should help
utes BPC, and 6.40 minutes SWATT and within 1mmHg provide evidence-based recommendations regarding re-
of plateau by 8.18 minutes C-A-T, 10.52 minutes RMT, assessing tourniquet tightness and arterial occlusion af-
10.07 minutes BPC, and 17.68 minutes SWATT. Time- ter effective tourniquet application.
sequenced images did not show visual changes during
the completion to 300 or 600 seconds pressure-drop in- Methods
terval. Conclusion: Proper initial tourniquet application
does not guarantee maintenance of arterial occlusion. All human tourniquet use was on one of the authors
Tourniquet applications should be reassessed for arterial (P.L.W.) and received institutional review board ap-
occlusion 5 or 10 minutes after application to be within proval. The Combat Application Tourniquet (C-A-T;
®
5mmHg or 1mmHg of maximal pressure loss. Elastic Composite Resources Inc.; http://combattourniquet.com/),
tourniquets have the least pressure loss. Tactical Ratcheting Medical Tourniquet (RMT; m2
™

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