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| Journal of the New Zealand Medical Association,
02-July-2002, Vol 115 No 1157
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Peri-operative use of oestrogen containing medications and
deep vein thrombosis - a national survey
David W Ardern, Denis R Atkinson, Anna J Fenton.
Hormone replacement therapy (HRT) and combined oral
contraceptives (COCs) are believed to increase the risk of developing deep vein
thrombosis (DVT) and pulmonary embolism among users. Public advice given by the
New Zealand Ministry of Health states that the odds of having a blood clot
increase by 3 - 4 times for those on second generation pills and 6 - 8 times for
those on third generation pills.1 For women
taking hormone replacement therapy there is now good evidence to suggest that
the risk of developing venous thromboembolism (VTE) is increased by 2 - 4
times.2-6
Surgery is associated with factors which promote DVT. It
would be reasonable to expect, therefore, that the combination of an oestrogen
containing medication and surgery could lead to significantly increased risk and
avoidable post-operative complications. Evidence to support this assumption,
however, is lacking and the risks associated with discontinuing medication are
uncertain. The advice given by pharmaceutical companies is generally to
discontinue a COC four weeks prior to surgery.7
Some also suggest withholding the medication for two weeks post-operatively. The
advice given by manufacturers for HRT is to consider temporary discontinuation
peri-operatively.7 In May 2001, the New Zealand
Guidelines Group released recommendations to discontinue HRT for at least 30
days prior to elective surgery and for 90 days following
surgery.8
Major orthopaedic surgery is known to be associated with a
relatively high incidence of DVT. Studies using surveillance methods have
reported that in the absence of prophylaxis the incidence of DVT following major
hip or knee surgery is approximately 50%.9-11 A
recent survey showed the prevalence of HRT use in New Zealand women aged between
45 - 64 years to be 20%.12 Almost half of the
women surveyed had started it to prevent osteoporosis. Last year there were over
400 000 prescriptions written for COC pills within New Zealand. The presence of
guidelines for their use peri-operatively is therefore of importance in
orthopaedic surgery. This is especially so given the high level of media and
public interest in this general area and the potential medico-legal
implications. This is a survey of orthopaedic surgeons but the issue is relevant
to all clinicians who may advise women about the use of medications in the
peri-operative period.
MethodsA postal questionnaire was sent
to all practicing orthopaedic surgeons within New Zealand. A follow-up letter
was sent to non-responders after six weeks. Those surveyed were asked to
indicate if they would stop such medications peri-operatively for major
orthopaedic surgery either routinely, only in patients considered to be high
risk, or would not discontinue. Neither the specific surgical procedures
classified as “major orthopaedic surgery”, nor the specific risk
factors that would create a “high risk patient” were listed in the
questionnaire. These were left up to the interpretation of the individual
responding to the survey. Such specific lists are not found in the relevant
guidelines for clinical practice in this area. Surgeons were then asked to
record how long prior to, and following surgery they would discontinue the
medication.
ResultsResponse.
There were 118 responses suitable for analysis out of the 148 surveyed (80%).
Not all surgeons answered every question.
Discontinuing HRT
peri-operatively (Table 1). 24% of the responding surgeons indicated that
they would routinely advise discontinuing HRT peri-operatively. 25% would only
do so in patients whom they considered to be at high risk, and 51% would not
advise discontinuing HRT.
Table 1. When would medication be stopped prior to
major orthopaedic surgery?
*Proportion of surgeons.
†High risk patients as perceived by the
surgeon.
Discontinuing the COC pill
peri-operatively (Table 1). 44% of surgeons would routinely advise women
to discontinue their contraceptive pill peri-operatively. A further 23% would
only advise this in patients who they considered to be at high risk, and 33%
would not advise discontinuing the pill.
Clinical practice compared
with guidelines (Tables 2, 3). Less than 3% (3/113) of responding
surgeons indicated that they would advise withholding HRT for at least 30 days
prior to surgery and for 90 days following surgery as suggested by the New
Zealand Guidelines Group. 25% (28/113) would advise women to discontinue their
contraceptive pill for at least 30 days prior to surgery as suggested by most
pharmaceutical companies.
Table 2. Peri-operative use of hormone replacement
therapy in relation to guidelines*.
*NZGG recommendations are to discontinue HRT for 30
days prior to surgery and 90 days following surgery.
Table 3. Peri-operative use of oral contraceptives in
relation to guidelines*.
*Most manufacturers advise discontinuing COC’s
for at least 30 days prior to surgery
+/- withholding for 14 days following surgery. DiscussionAs 80% of practising orthopaedic
surgeons within New Zealand completed the questionnaire the results are likely
to reflect current practice.
This survey has demonstrated widespread variability of
practice and significant differences from the relevant guidelines. This is
especially so for the peri-operative use of HRT where only 3% of orthopaedic
surgeons appear to be practicing in accordance with recently released
guidelines. It would seem that surgeons are largely unaware of the new HRT
guidelines released by the New Zealand Guidelines Group
(NZGG).8 It is also noted that these guidelines
differ substantially from recommendations made by the pharmaceutical companies
and authorities elsewhere (Table 4). Evidence for such recommendations is
generally lacking and they tend to be based upon knowledge of the theoretical
risks and resulting opinion. The recently published HERS
study 6 has been cited as the only significant
study to date to assess the effect of surgery on risk of
VTE.8 This randomised controlled trial was
designed to provide information on the outcome on subsequent cardiac events in
postmenopausal women. It included older women with a mean age of 67 years, and
all had established coronary artery disease (CAD). The findings suggest
significantly increased risk of VTE among HRT users following lower-extremity
fractures and for 90 days following surgery. Trial investigators thus
recommended that participants discontinue HRT during periods of high risk such
as surgery, immobilisation or severe illness and restart their medication when
they return to normal mobility.13 The increased
risk in this group has however been extrapolated to include all women in the
recommendations to stop HRT for 30 days prior and for 90 days following surgery
made by the NZGG.8
Table 4. Recommendations for peri-operative use of
oestrogen containing medications.
BNF=British National
formulary22, ACOG=American College of
Obstetricians and Gynaecologists,23 RCOG=Royal
College of Obstetricians and
Gynaecologists,21,20 ICS=International
Consensus Statement.19
The most obvious effects of discontinuing HRT for a period
of time peri-operatively are likely to be a recurrence of unpleasant menopausal
symptoms. The risks of precipitating more serious harm however, remain unknown.
The authors of the HERS study concluded that although starting HRT for secondary
prevention of CAD was not recommended given the favourable pattern of CAD events
after several years of therapy, it could be appropriate to continue treatment in
women already taking HRT.14 In view of this it
would be wise to seek advice from the patient’s cardiologist before
necessarily discontinuing HRT. Furthermore, it has been observed that the
elevated risks of VTE appear to be greatest in the first year or two of HRT
use.3,5,6 These observations might be due to a
selective effect of HRT on women with a pre-existing risk for
thrombosis.6 As yet, however, there is no
certainty about this and the risks of temporarily discontinuing HRT for a
substantial period of time before re-starting it are not clearly
defined.
We believe that the apparent lack of adherence to the new
HRT guidelines is likely to be contributed to by both a lack of awareness of
their existence and a lack of confidence in their validity. The feasibility of
being able to advise patients to discontinue their medication for a full month
prior to surgery under presently-used hospital booking arrangements is also
questionable.
Most pharmaceutical companies recommend stopping the oral
contraceptive pill for four weeks prior to surgery, but this is not universally
advocated by specialist groups (Table 4). This survey demonstrates that although
44% of orthopaedic surgeons routinely advised women to stop the pill prior to
major surgery, only 25% advised women in accordance with the recommendations
made by pharmaceutical companies. One reason for this variance is likely to be
the perceived risks of unwanted pregnancy compared with the potentially small
increased risks of not stopping the pill prior to major surgery. A policy of
routinely stopping the contraceptive pill prior to surgery could well result in
unwanted pregnancy.15 Pregnancy carries a much
greater risk of VTE than does oral contraceptive use. In addition, the
possibility of subsequent termination, with its associated physical and
psychological risks, needs to be considered.
As with HRT there are relatively few data to quantify the
increased risk posed by the use of oestrogen containing oral contraceptives
around the time of major surgery. One large prospective study suggested that the
risk of post-operative VTE was around two times but this was not statistically
significant.16 Pro-thrombotic changes in
haematological variables observed with oestrogen administration tend to return
to baseline within one to two menstrual cycles after stopping
treatment.17,18 Such observations have been
used in the formation of recommendations by oral contraceptive
manufacturers.
The use of anticoagulants has been advocated in women who
have additional risk factors present and do not stop their contraceptive
pill19,20, or hormone replacement
therapy.19,21 In practice this is likely to
include most patients taking HRT.19,21
Anticoagulant use in preference to withdrawing medication may also help explain
the findings of this survey. This was not specifically enquired about in the
survey.
Clearly the scientific data are confusing. Despite this we
feel it is important for surgeons to make patients aware of the risks of using
oestrogen-containing drugs. This is particularly so for patients undergoing
elective surgery in the lower limbs. This should form part of the normal consent
process and it should involve the prescriber and the patient. We also draw
attention to the potential that guidelines have for creating unnecessary
medico-legal risk in an increasingly hostile environment.
Author Information:
David W Ardern, Orthopaedic Registrar; Denis R Atkinson, Orthopaedic
Surgeon, Hawke’s Bay Hospital, Hastings; Anna J Fenton, Endocrinologist,
Christchurch.
Acknowledgements.
This research was funded by a grant from the Hawke’s Bay Medical Research
Foundation.
Correspondence. Dr
David Ardern, Department of Orthopaedics, Middlemore Hospital, Private Bag
93-311, Otahuhu, Auckland. email: dw.sl.ardern@xtra.co.nz.
References:
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