Timing of distant flap pedicle division using xenon 133 clearance

Clearance of intradermally injected xenon 133 was used to measure blood flow in distant flaps in humans with the donor pedicle temporarily clamped just prior to division. All 18 flaps with a blood flow of 0.5 ml per 100 gm of tissue per minute or more survived completely after separation. Of 7 with lesser flow, 3 underwent marginal necrosis adjacent to the line of division and 4 survived entirely. The false-negative result (complete flap survival in 4 patients) was artifactual due to isotope injection too close to the clamp, reflecting increased local tissue tension caused by the clamp rather than low blood flow in the flap. Xenon 133 washout does permit quantitative evaluation of blood flow, and since it is a clean isotope, it appears superior to sodium 24 and technetium 99m, which have been used in a similar manner. The test is proposed as an adjunct to clinical judgment in timing pedicle division.