Page 13 - JSOM Spring 2021

Limb Position Change Affects Tourniquet Pressure

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Piper Wall, DVM, PhD *; Charisse Buising, PhD ;
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Emma Hingtgen, BS ; Alex White ; JaNiese Jensen 5
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ABSTRACT
Background: Limb position changes are likely during trans- Introduction
port from injury location to definitive care. This study in-
vestigated passive limb position change effects on tourniquet Well-designed emergency-use limb tourniquets are lifesaving
pressure and occlusion. Methods: Triplicate buddy-applied first aid devices when they are successfully used to stop severe
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OMNA Marine Tourniquet applications to Doppler-based bleeding. Any injuries severe enough to require a tourni-
®
occlusion were done to sitting and laying supine mid-thigh quet also require patient transportation to definitive medical
(n=5) and sitting mid-arm (n=3). Tourniqueted limb positions care. During transportation from the site of injury to defin-
were bent/straight/bent and straight/bent/straight (randomized itive medical care, opportunities exist for changes in posi-
first position order, 5 seconds/position, pressure every 0.1 sec- tion of limbs with tourniquets. Changes in the positions of
ond, two-way repeated measures ANOVA). Results: Sitting limbs, even when passive, involve changes in the lengths and
thigh occlusion pressures leg bent were higher than straight diameters of muscles. Changes in the diameters of muscles
(median, minimum–maximum; 328, 307–403mmHg versus underneath tourniquets have the potential to change the pres-
312, 295–387mmHg, p = .013). In each recipient, the pressure sure under the tourniquet. Decreases in tourniquet pressure
change for each position change for each limb had p < .003. risk loss of arterial occlusion and consequent resumption of
In each recipient, when sitting, leg bent to straight increased bleeding.
pressure (326, 276–415mmHg to 371, 308–427mmHg
bent first and 275, 233–354mmHg to 311, 241–353mmHg The purpose of this proof-of-concept study was to look at the
straight first), and straight to bent decreased pressure (371, effect of limb position changes on tourniquet pressure and
308–427mmHg to 301, 262–388mmHg bent first and 312, on tourniquet-induced arterial occlusion. The hypothesis was
265–395mmHg to 275, 233–354mmHg straight first). When that limb position changes would affect tourniquet pressure
laying, position changes from leg bent first resulted in pres- and the associated arterial occlusion.
sure changes in each recipient but not in the same directions in
each recipient. From laying leg straight first, in each recipient Methods
changing to bent increased the pressure (295, 210–366mmHg
to 328, 255–376mmHg) and to straight decreased the pres- The Drake University Institutional Review Board approved this
sure (328, 255–376 mmHg to 259, 210–333 mmHg). Sitting prospective study done in Fall 2020 (expedited 2020–21008).
arm bent occlusion pressures were lower than straight (230,
228–252mmHg versus 256, 250–287mmHg, p = .026). Arm The tourniquet used was an OMNA Marine Tourniquet (Gen-
position changes resulted in pressure changes in each recipient eration 2, Lot UDI: + B123 OMTOMNA005A, OMNA Inc.,
but not in the same directions in each recipient. Changes in www.omnainc.com) that had been donated by OMNA Inc.
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pressure trace character (presence or absence of rhythmically for a previous study. OMNA Marine Tourniquets are non-
pulsatile traces) and Doppler-based occlusion were consistent elastic, 95cm-long, and have a 5.1cm-wide hook-and-loop
with limb position–induced changes in tourniquet pressure strap; non–self-securing, round, simple redirect buckle; and
(each p ≤ .001 leg, p = .071 arm traces, and p = .188 arm oc- self-securing ratcheting buckle on a toothed ladder tightening
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clusion). Conclusions: Passive limb position changes can cause system. The OMNA Marine Tourniquet was chosen for use
significant changes in tourniquet pressure. Therefore, tourni- in this study for the following reasons: (1) Like the majority
quet adequacy should be reassessed after any limb position of commercial emergency-use limb tourniquets, it is a nonelas-
change. tic, strap-based tourniquet. (2) It is a design that can achieve
arterial occlusion. (3) It does not have sharp edges, corners,
or exposed hook-and-loop material directed into the recipi-
Keywords: tourniquet; hemorrhage; first aid; emergency ent’s limb. (4) The ratcheting tightening system design has a
treatment
desirable resolution of stepwise pressure increases for ceasing
tightening just past the threshold of arterial occlusion. (5) The

*Correspondence to: Surgery Education Department, UnityPoint Health Iowa Methodist Medical Center, 1415 Woodland Ave, Suite 140, Des
Moines, IA 50309; or piperwall@q.com
1 Dr Wall is a researcher in the Surgery Education Department, UnityPoint Health Iowa Methodist Medical Center, Des Moines, IA. Dr Buising
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is a professor of biology and the director of the Biochemistry, Cell and Molecular Biology Program, Drake University, Des Moines, IA. Ms
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Hingtgen was a researcher at Drake University. Mr White and Ms Jensen are undergraduate researchers at Drake University.
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