Discussion
This Australian study of 342 microvascular free flap head and neck
reconstructions investigated whether operative time is associated with
post-operative complications and length of stay. In this patient cohort,
lengthier operative times, particularly those longer than 9 hours
duration, were associated with adverse outcomes including surgical
complications, any complication, return to theatre and length of stay
after adjusting for the effect of potential confounders such as
comorbidity, patient age, tumor site, reconstruction type, and use of
tracheostomy.
In our analysis, the adjusted effect of one hour of additional operative
time was a 13% increase in the odds of developing a surgical
complication (p=0.002), a 20% increase in the odds of returning to
theatre (p<0.001), and one extra day of hospital stay
(p<0.001). This equated to more than double the odds of a
surgical complication for operations > 9 hours duration
compared to ≤ 9 hours duration (p=0.005). These findings are not unique
and are supported by several studies from other countries showing that
prolonged operative time is an independent risk factor for
post-operative complications.8,10,11 In fact, Serleti
et al. identified a similar cut-off (≥10 hours) as being associated with
complications such as flap failure, thromboembolism, bleeding, and
hematoma.13 Eskander et al. found that each hour was
associated with a 21% increase in the odds of a complication and a 24%
increase in the odds of wound-healing problems.1However, other studies have shown dramatic variations in the critical
time (cut-off) associated with adverse outcomes, ranging from 480
minutes to 920 minutes, highlighting the importance of institutional
factors and the need for individual units to publish their own
results.8,11
Unfortunately, our cohort was not large enough to analyze whether
operative time predicted free flap failure. However, two national
database studies have shown that this is the case, including Ishimaru et
al.14 who analyzed 2846 patients from the Japanese
national database and Sanati-Mehrizy et al.15 who
analyzed 2013 patients from the American College National Surgical
Quality Improvement Program database. The association between operative
time and surgical morbidity is robust across multiple specialties. This
is well demonstrated in a meta-analysis by Cheng et al. that found a
statistical association in 80% of the 66 studies they
included.16 Whilst the critical time-threshold varied
between studies (e.g. 2, 4, 6 hours), it is remarkable that pooled
adjusted risk of complications consistently doubled in all specialties,
and each additional hour was associated with a 21% increase in
complication rate (p < 0.001), similar to our results.
Determining the true independent effect of operative time is almost
impossible because it is dependent on multiple confounding factors,
including case complexity, surgeon experience and technique,
institutional factors such as operating room staff and protocols, prior
treatment (surgery or radiotherapy), and intraoperative problems, which
inevitably lengthen the operation and increase the likelihood of
postoperative complications. Some of these factors cannot be modulated,
however, head and neck microvascular reconstructions are typically long
operations, where many components can be made more efficient. These
include anaesthetic preparation time, surgical planning, equipment
preparation, team communication and multi-tasking, and concurrent flap
harvest with tumour ablation, as well as innovations in harvest and
anastomotic techniques, such as advanced sealing technology and venous
coupler use.8,11,12,17 In our institution we routinely
performing concurrent flap harvest where possible and is likely to have
the greatest impact on the duration of surgery. Several approaches make
this option viable in a greater proportion of cases. Firstly, the ALT is
the most common soft tissue flap in this cohort. This flap has the
advantage of being able to harvest a larger portion of tissue than that
anticipated to be necessary without substantially increasing the donor
site morbidity. Secondly, we frequently use virtual surgical planning
for osseous flap reconstruction. This allows the defect to be defined
prior to surgery and has been shown in several studies to reduce
operative time.18,19 Finally, we perform operative
tracheostomies at the end of the operation and avoid elective
tracheostomy use when it is felt safe to do so by both the ablative and
reconstructive surgeon. Tracheostomy not only lengthens the procedure
but was associated with double the odds of a complication in this series
(Figure 1). Chaukar et al. found that both tracheostomy and longer
operative time were independent predictors of wound complications after
head and neck surgery, suggesting contamination of the wound with
tracheal secretions as a likely mechanism.20
A prolonged operative time often indicates longer free flap ischemic
time and tissue damage due to anoxic injuries. Moreover, the risk of
reperfusion injury and the incidence of no flow phenomenon increase with
longer ischemic time.21,22 Alternatively, increased
operative time could be a proxy for procedure complexity, associated
anaesthesia risks, or intraoperative complications.23Designing a study to control for these metrics is challenging as there
are no validated measures of procedure complexity in head and neck
oncology or reconstruction.