EFFECT
OF SCARRING AND COVERING IN SUBCUTANEOUS TRANSPORT
Title.
Study of the effect of the scarring process
and covering with various substances of cutaneous incisions
made over the migration pathway of sodium pertechnetate.
Background.
Subcutaneous injection of Tc-99m in the form
of sodium pertechnetate in points of low electrical resistance
prompts the progressive and rapid longitudinal migration of
the tracer following a specific and constant pathway, both
in experiments in man and in animal. It has been shown
that this pattern of migration is not observed with 131I,
201Tl or 186Rhenium injected in these points nor when any
isotope is injected in points of normal electrical resistance.
It has been ruled
out that the migration pathway of the hypodermically injected
Tc-99m in points of lower electrical resistance might be due
to the diffusion of the isotope through lymphatic, nerve or
vascular routes. It has also been ruled out that the nature
of its migration might be explained by some known biological
function.
It is
known that longitudinal migration of the isotope is altered
by the cut in the skin covering its migration pathway or that
of the skin of the symmetrical territory of the opposite-side
extremity. A cutaneous cut before the injection, whether in
the injected extremity or in the opposite side, prevents migration.
A cut made after the isotope injection, once the migration
has begun, makes it stop-if the cut is in the opposite extremity
to that injected-or makes the pathway previously observed
disappear- if the cut is made in the injected extremity.
Nonetheless, how much time it takes after
the suture of the cuts intersecting the pathway for the longitudinal
migration to be reestablished has not been studied. Comparing
the period when the migration is reestablished with different
phases of cutaneous scarring could suggest which is the essential
cutaneous structure to permit it. Additionally, studying variations
of that period in terms of different manipulations could provide
data on the role played by the skin in the mechanism of migration.
Objectives.
- To study how long it takes to re-establish
the migration of the pertechnetate after the suture of the
skin cuts.
- To study the effect produced by
covering the cutaneous cuts with different substances: Vaseline
gel, sonogram gel, silicone gel and sheet of solid silicone.
Methodology.
72 male beagles between 18 and 36 months
old were anesthetized and later injected with 200 to 250 mCi
of Tc-99m in a point of low electrical resistance in the posterior
part of the wrist. Various kinds of experiments were made
and the cutaneous cuts that intersected the migratory pathway
of the Tc-99m were made before or after the injection of Tc-99m
and in the opposite side and same side (homolateral) extremity.
Additionally, the cuts that were not sutured were covered
with different electrical conductive agents: Vaseline gel,
sonogram gel, silicone gel and sheet of solid silicone placed
over the skin and sheet of solid silicone placed between the
edges of the wound.
Participants, along with the Foundation's
Science Department.
Departments of Nuclear Medicine of the Hospital
Clínico of Barcelona, de Morphological Sciences of
the Central University of Barcelona (Medical School), and
of Animal Surgery of the Autónomo University of Barcelona
(Veterinary School).
Funded in full by the Kovacs Foundation.
Results.
Published in the journal European Radiology
(Kovacs FM, García A, Mufraggi N, et al. Migration
pathways of hypodermically injected technetium-99m in dogs.
Eur-Radiol 2000; 10:1019-1025).
In summary they indicate that:
-
After the suture of a cut in the skin, the subcutaneous
transport of the radioactive isotope is reestablished
much before the tissues scar. There are individual variations
in the time needed for the transport to return to normal
and be identical to that observed before the cut, but
in some cases, this occurred in minutes.
-
There was no transport in the cases in which the wound
remained open, without suturing, or in those in which
the open wound was refilled with Vaseline or a sheet of
solid silicone placed between its edges.
-
Normal transport of the isotope was observed when the
open wound was filled with silicone gel or sonogram gel,
as well as when the skin was covered with a sheet of solid
silicone.
These data suggest that for the isotope to be transported,
two indispensable conditions must be met: the transmission
of ions in the subcutaneous medium must be possible, and this
medium has to be electrically isolated from the exterior.
That would suggest that under normal conditions, the participation
of the skin in the transport mechanism of the radioactive
isotope consists essentially of guaranteeing the electrical
isolation of the subcutaneous medium. The study suggests that
the transport mechanism of the radioactive isotope could be
similar to that of capillary electrophoresis that consists
of the flowing of liquid due to the electrical effect that
its walls generate when they have a negative electrical charge.
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