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Overview :
Cotterill used changes in limb circumference to estimate the
amount of hemorrhage into soft tissue.
Site selection: An injured limb is compared to the uninjured
limb on the opposite side.
Method:
(1) A bony
reference point is identified in each limb.
(2) The
circumference of both limbs are taken at 2 cm intervals from that point. Some
measuring tapes have a width of about 2 cm.
(3) The
volume of each segment is calculated as a cylinder. If the 2 end circumferences
difference (unlikely to be much over 2 cm) then either the average of the 2
measurements can be taken or else the circumference midway along the segment can
be used.
(4) The
volumes for all the segments on each side are summated.
(5) The
volume difference between the 2 limbs indicates the amount of soft tissue
swelling, which in trauma is usually whole blood.
circumference in cm =
= 2 * π * (radius in cm)
radius in cm =
= (circumference in cm) / (2 * π)
volume for cylinder in cubic centimeters =
= π * ((radius in cm)^2) * (length in cm) =
= 2 * π * (((circumference in cm) / (2 * π))^2) =
= ((circumference in cm)^2) / (2 * π)
Interpretation:
• Following
fracture of a limb significant hemorrhage can occur into the soft tissue. A
fracture of the femur can result of a blood loss of 2.5 liters or more into the
thigh. The changes can be subtle and may be easily missed by those unfamiliar
with trauma.
Limitations:
• Injury of
both limbs with swelling limits the ability to detect changes from normal.
However, if measurements were taken before significant swelling occurred, then
these measurements can serve as baseline.
•
Shortening of one limb relative to another due to fracture affects the
measurements.
• Edema or
other causes of swelling other than bleeding can affect the accuracy of the
estimate, but in the early period after trauma bleeding tends to predominate
(Clarke, page 630).
• This does
not detect hemorrhage into the abdomen, pelvis, thorax or retroperitoneum.
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