Discussion
This study showed that continuous subfascial wound administration of
ropivacaine combined to a multimodal systemic analgesia after caesarean
section is more effective than placebo.
Results showed a significant reduction in morphine consumption of 8.05
mg in the ropivacaine group. On VAS, pain at mobilisation 6 hours after
surgery was significantly reduced with ropivacaine compared to placebo.
A trend toward significance in favour of ropivacaine was observed for
pain by VAS at rest 6 hours after surgery, at rest 12 hours after
surgery and at mobilisation 48 hours after surgery. In contrast, no
significant differences were observed on VAS for pain 2 hours and 72
hours after surgery, both at rest and at mobilisation. For adverse
effects (post-operative nausea/vomiting and pruritus) and time of first
ambulation, no significant differences were observed comparing
ropivacaine to placebo continuous subfascial wound infusion.
In obstetric populations, although several studies assessed analgesic
effects of continuous anaesthetic wound infusion after caesarean
section, clear results are still lacking because of conflicting results.
(3-13) Furthermore, most of these studies showed some important
limitations and heterogenicity in their designs, regarding the local
anaesthetic agent used (ropivacaine, bupivacaine, levobupivacaine), its
mode of release (continuous infusion or PCA), the NSAID in adjunction
and the multimodal systemic analgesics used (morphine, oxycodone,
ketoprofen or diclofenac) and their mode of release (oral, intramuscular
intravenous or intrathecal).
A Cochrane Collaborative systematic review published in May 2010
concluded that morphine consumption was decreased by 1.70 mg at 24 hours
after caesarean section using anaesthetic wound infiltration compared to
placebo. (7) This modest reduction compared to the 8.05 mg reduction in
our study may be explained by selection bias. Indeed Bamigboye et al.
(2009) included next to wound infusions studies, studies of wound
infiltration with local anaesthetic or with NSAID. (7) Furthermore, in
all of the included wound infusion studies, the catheter was placed
above the fascia. (4,5,6) However, based on Rackelboom et al. (2010),
better analgesia is obtained over 48 hours when ropivacaine and
ketoprofen are infused below the fascia compared to administration above
the fascia. (8) In this study, the multi-holded catheter was placed
below the closed fascia transversalis and above the closed parietal
peritoneum, to avoid intraperitoneal leakage.
In more recent studies, Kainu et al. (2012) found no benefit of
continuous subfascial wound infusion with ropivacaine, which in their
study failed to reduce the use of PCA administered oxycodone or pain
scores compared to saline control. (10) The same conclusions were made
in another randomized trial published by Reinikainen et al. (2014) where
on the contrary ropivacaine was placed above the fascia and oxycodone
not PCA administrated, possibly explaining the lack of efficacy from
their ropivacaine infusion. (11) Conversely, Jolly et al. (2015)
concluded that after caesarean section without subarachnoid morphine,
continuous levobupivacaine compared to placebo subfascial wound
infiltration decreased PCA administered morphine consumption (6.7 mg, P
value = 0.02) and pain intensity. (12) Nevertheless, the unblinded
design of their study may have leaded to biases. Finally, Lalmand et al.
(2017) investigated the duration and effect of intrathecal analgesia and
continuous subfascial ropivacaine wound infiltration versus a control
group after caesarean delivery. The duration of postoperative analgesia
was increased with intrathecal morphine (380 minutes) and ropivacaine
wound infusion (351 minutes) compared with the control (247 minutes),
without significant difference between the morphine and catheter group.
Cumulative postoperative morphine consumption was also significantly
lower in the morphine group and catheter group compared to the control
group. (13) When comparing continuous ropivacaine wound infusion after
caesarean delivery to epidural morphine analgesia on pain evaluated by
VAS, O’Neill et al. (2012) concluded a better analgesia, a lower
incidence of side effects, less need for nursing care and shorter
duration stay using wound infusion. (9) Based on the important role in
post-operative pain of diffuse visceral nociceptive afferents in
peritoneal tissue, blockade by local anaesthetics could easily explain
the dose reduction of systemic analgesics.
Continuous subfascial wound infusion seems to be well tolerated by
patients. In this study we selected ropivacaine as local anaesthetic
because of its lower systemic toxicity and its shorter half-life
comparing to bupivacaine and levobupivacaine. The infusion rate was
chosen based on the study of Beaussier et al. showing that a constant
rate of 0.2 % ropivacaine at 10 mL/h was well tolerated and associated
with a sufficient margin of safety in colorectal surgery. (14) Liu’s et
al. meta-analysis concerning the use of continuous wound catheters
delivering local anaesthetics reported a 1% technical pump failure rate
and similar infection rates between active (0.7 %) and control groups
(1.2 %). (15) Current study observed no technical failure and no
infection issue, probably explained by the inadequate sample size for
this purpose.
The same concept can be applied to explain the fact that some of the
secondary outcomes showed a trend in favour of the ropivacaine group
without reaching the threshold of statistical significance: pain by VAS
at rest 6 hours after surgery, at rest 12 hours after surgery and at
mobilisation 48 hours after surgery. Nevertheless, a previous
assessor-blinded trial already evidenced beneficial effects of
continuous subfascial wound infusion with ropivacaine after caesarean
delivery, using pain at rest and at mobilisation on VAS as primary
outcome. (9)
The strengths of the current study include the prospective, randomized
controlled, double-blind design and the robust and rigorous
methodological approach of the study protocol. Furthermore, using
analgesic consumption on PCA device instead of VAS as primary outcome is
likely to be more objective for pain evaluation. As far as we know, no
other randomized controlled, double-blind studies were published
comparing the analgesic efficacy of continuous ropivacaine versus
placebo subfascial wound infusion after caesarean delivery using
morphine consumption on PCA as primary outcome. The limitation of this
study is the monocentric design.
In conclusion, continuous ropivacaine subfascial wound infusion trough a
multi-holded catheter can be considered as an effective method for pain
management in a multimodal analgesic approach after caesarean delivery
and this without increasing the incidence of side effects.