Page 16 - JSOM Spring 2021

FIGURE 2 Tourniquet pressure trace. (Figure 4C) and loss of the only laying, first position audible
pulse (Figure 4D). Resumption of the leg straight position was
accompanied by a return of rhythmically pulsatile traces for
all but one application plus the appearance of rhythmically
pulsatile traces in some additional applications (Figure 4B).
The single initially present audible pulse did not become audi-
ble again, but nine other tourniquet applications had audible
pulses become present with return to the leg straight position.

For sitting arm positions, the only change in incidence of
rhythmically pulsatile traces that could not be attributed to
time-related pressure decreases occurred as a loss of rhyth-
mically pulsatile trace in one recipient going from a second
position of arm bent to a third position of arm straight (arm
circumferences of 43.3 to 42.9cm). The only change in inci-
dence of audible pulses that could not be attributed to time-
related pressure decreases occurred as losses of audible pulses
in two applications to one recipient going from a second po-
sition of arm straight to a third position of arm bent (arm
circumferences of 33.8 to 34.0cm). The remainder of the arm
application changes in incidence of rhythmically pulsatile pres-
sure traces and audible pulses could potentially be attributed
solely to time-related pressure decreases (Figure 4E and F).
The example tourniquet pressure trace is from a thigh application
with the recipient laying supine with the involved leg starting in the Discomfort
bent position. The y-axis shows tourniquet pressure, and the x-axis Coinciding with increasing thigh tourniquet pressures, all re-
shows time.
cipients indicated considerable increase in discomfort going
from sitting with their knee bent to sitting with their knee
Pressure Traces and Audible Pulses straight, especially when the knee bent position was the first
As expected with decreasing tourniquet pressure over time, position. Additionally, the extent of knee extension in the sit-
the number of tourniquet applications with rhythmically pul- ting knee straight position was generally visibly slightly less
satile pressure traces and with audible pulses increased from in the tourniquet applications that started with the knee bent 8
the first position to the last position. However, the changes in than those that started with the knee straight. Neither of these
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incidence of rhythmically pulsatile pressure traces and audible items were planned pieces of data collection.
pulses were not unidirectional over time (Figure 4). Depending
on the limb position sequence, the second position could have Discussion
either an increase or a decrease in the incidence of rhythmi-
cally pulsatile pressure traces and audible pulses. The key finding is that passive limb position changes can cause
significant changes in tourniquet pressure. When the resulting
For the sitting leg positions, the single knee bent starting posi- tourniquet pressure change is a decrease, a tourniquet appli-
tion trace interval with a rhythmically pulsatile pressure trace cation that was initially arterially occlusive can allow resump-
lost that pattern going from a knee bent starting position to tion of arterial flow, and arterial flow without venous return
a knee straight second position (Figure 4A) and did the same is associated with venous congestion, venous distention, re-
regarding an audible pulse (Figure 4B). Changing position the bleeding, expanding hematomas, compartment syndrome, and
other direction, seven of the sitting knee straight starting posi- death. Therefore, tourniquet adequacy should be reassessed
1
tion intervals without rhythmically pulsatile pressure traces or after any patient limb position change.
audible pulses had rhythmically pulsatile pressure traces and
audible pulses develop after going to a knee bent second po- For a tourniquet pressure change to occur with a nonelastic
sition (Figure 4A and B). With the return to knee straight for strap–based tourniquet, a change involving either the tour-
the third limb position, five of those seven lost their audible niquet or the underlying limb tissue must occur. Tourniquet
pulses but only one of those seven lost the rhythmically pulsa- changes that could result in a decrease in tourniquet pressure
tile pressure trace pattern (one application that did not have a would be strap tearing, strap stretching, strap slippage back-
rhythmically pulsatile pressure trace pattern in either the first wards through the redirect buckle, deformation of the redirect
or the second interval developed such in the third interval for buckle, or deformation of some aspect of the tightening system.
no net pressure trace number change between the second and Tourniquet changes that could result in an increase in tourni-
third interval). quet pressure would be additional use of the tightening system.
Limb tissue changes that could result in a decrease in tourni-
For laying leg positions, going from a leg bent starting position quet pressure would be those that increase tissue compliance
to a leg straight second position was accompanied by an in- or decrease tissue volume: a decrease in muscle tension under
crease in the presence of rhythmically pulsatile pressure traces the tourniquet, a decrease in the quantity of water contained
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(Figure 4C) and audible pulses (Figure 4D), several of which in the tissue under the tourniquet (physiology and physics),
went away with a return to the leg bent position. For laying leg changes in muscle diameters that have a net result of a decrease
positions that started straight, going to a leg bent second posi- in tissue volume under the tourniquet (physics), or a change
tion was accompanied by a loss of rhythmically pulsatile traces in cytoskeletal bonds allowing for a decrease in tissue volume

14 | JSOM Volume 21, Edition 1 / Spring 2021