To The Editor:
In the article "Comparison of Enoxaparin and Warfarin for the
Prevention of Venous Thromboembolic Disease After Total Hip Arthroplasty"
(81-A: 932-940, July 1999), by Colwell et al., no mention or comment
is made of the most serious potential complication of enoxaparin use:
spinal or epidural hematoma. In Table VII of their study, eighty-one
patients had minor bleeding episodes at nonoperative sites and four had
major bleeding episodes at nonoperative sites. The article states
that enoxaparin therapy was started within twenty-four hours postoperatively,
after hemostasis had been determined by the investigator.
In our own practice, we have had one patient who required emergency
spinal decompression for a spinal hematoma after an epidural, and
we have heard through the grapevine of two other patients in our
geographical area who were started on enoxaparin postoperatively
who had spinal bleeds.
The Physicians' Desk Reference3 warns that, "when epidural/spinal
anaesthesia or spinal puncture is employed, patients anticoagulated
or scheduled to be anticoagulated with low molecular weight heparins
or heparinoids for prevention of thromboembolic complications are
at risk of developing an epidural or spinal hematoma which can result
in long-term or permanent paralysis." This risk is increased by use
of indwelling catheters. Horlocker and Wedel1 recommended
that, in postoperative patients beginning on enoxaparin, the indwelling
catheter should be removed prior to the initiation of thromboprophylaxis
and the first dose should be given two hours after the catheter
is removed.
This article does not address what kind of anesthesia the patients
reported on had. Certainly, one can assume that, in the age-group
undergoing a total hip replacement, epidural anesthesia, spinal
anesthesia, or epidural Duramorph (morphine sulfate) were probably
prevalently used. If the authors could comment on the kind of anesthesia
used in their patients and on the occurrence of spinal and epidural
bleeds with use of their protocol, it would be of service to us
all. If the great majority of these patients had general anesthesia,
then the authors have done us all a great disservice by not commenting
on that.
Christopher J. Zielinski, M.D.
Virginia Orthopaedic Center
P.O. Box 5005
Culpeper, Virginia 22701
C. W. Colwell, Jr., D. K. Collis, R. Paulson, J. W. McCutchen,
G. T. Bigler, S. Lutz, and M. E. Hardwick reply:
We appreciate the letter of Dr. Zielinski with respect to the
combined use of spinal or epidural anesthesia and the use of oral
anticoagulation or low-molecular-weight heparins. In all of the
previous controlled prospective studies of low-molecular-weight
heparins, use of continuous epidurals has been prohibited because
of the potential risk of epidural bleeds. Once enoxaparin was released,
surgeons used this drug in combination with epidural anesthesia,
resulting in a number of serious complications as reported by Horlocker
and Wedel1 in their article on
neuroaxial anesthesia and anticoagulation. Since none of the original
studies included epidural anesthesia, there had not been a previous
warning in the Physicians' Desk Reference2, but, following the recommendations
of the American Society of Regional Anesthesia, that precaution
was added with regard to low-molecular-weight heparins as it had
been added to the Coumadin (warfarin) handout.
We did not collect data on each type of anesthesia used in this
particular study, and therefore we cannot comment on the absolute
numbers of epidurals or spinals, but we reviewed each of the major
bleeds. There were no major bleeds, in either the low-molecular-weight
heparin group or the Coumadin group, that were related to the spinal
cord. Since minor bleeds were not absolutely defined, there would
have been no way, in this study, to have been absolutely certain
that some of the minor bleeds originated in and about the spinal
cord, but we do know that no residual was noted in the 3000+ patient
cohort. With new data that are unpublished at this time, once-a-day dosing
with another type of low-molecular-weight heparin might well be
used with continuous epidural and/or spinal anesthesia. Until the time
of adequate peer review, our own personal recommendations remain
those of the American Society of Regional Anesthesia, published
as a consensus conference manuscript. The journal Chest, in
conjunction with the American College of Chest Physicians, is planning
an updated review on the subject, to be published sometime this year.
We thank Dr. Zielinski for his excellent question and hope that
the upcoming data might shed additional light upon this specific
issue.
Clifford W. Colwell, Jr., M.D.
Dennis K. Collis, M.D.
Rolf Paulson, M.D.
John W. McCutchen, M.D.
Gregory T. Bigler, M.D.
Susan Lutz, R.N.
Mary E. Hardwick, M.S.N.
Corresponding author: Clifford W. Colwell, Jr., M.D.
Scripps Clinic
10666 North Torrey Pines Road
La Jolla, California 92037