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.
(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)
• 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.
• 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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Specialty: Clinical Laboratory, Surgery, general, Anesthesiology, Emergency Medicine, Critical Care