Discussion
Our result demonstrates that the incidence of adhesion at the secondary
CS is minimal or nonexistent and use of adhesion barrier did not reduce
skin-to-delivery time and the likelihood of intraoperative or
postoperative complications at the secondary CS. However, use of
adhesion barrier films at the primary CS associated with a higher
incidence of postcesarean fever which potentially means increased risk
of SSI.
Existing similar study [23]reported adhesion rates of 18% vs. 17%
in use and nonuse of HA-CMC and 20% vs. 83% in use and nonuse of ORC,
respectively, at the repeat CS [19]. Our data reported minimal
adhesion rates which are obviously lower than existing data [23]. We
believe that is reliable because we minimize the effect of confounding
factors such as history of pelvic inflammatory disease, endometriosis,
and open abdominal or laparoscopic pelvic surgery before the primary and
the secondary operations. Second, operations were performed by three
physicians with profound experience and had minimal blood loss during
operation. Third, all CS were operated with the same techniques that
reduce adhesion (e.g., rectus muscle approximation, closure of the
bladder flap and peritoneum) [3, 4, 26-30]. There were also many
proposed mechanisms to explain why adhesion formation following CS was
less than laparotomyin nonpregnant woman: (a) greater tissue perfusion
in pregnancy is associated with less tissue hypoxia; (b) the lower
segment incision is covered by the bladder which is constantly being
filled and emptied during the healing process and this movement disrupts
fibrinous formation between the uterus and the bladder and between the
lower segment and the anterior abdominal wall; (c) one single incision
in the lower segment at CS is less than myomectomy which associated with
more tissue handling; (d) less hematoma developed in the low transverse
incision at CS; (e) rapid change inuterine size in the postoperative
period disrupts adhesion formation. In fact, evidence in the literature
suggests that the consequences of postoperative adhesion such as bowel
obstruction, urinary tract injury, infertility, ectopic pregnancy, and
chronic pain may be less following CS compared with gynecological
surgery [31].
Reported studies of the HA-CMC barrier found no differences in the
incidence of adhesion, skin-to-delivery time, and total operative time
which were consistent with our result except for higher rates of
postcesarean fever after the primary CS [22-24]. However, only one
of them mentioned about postoperative complications and most CS were
elective in this study [22]. To date, cases of chemical peritonitis
(inflammation) associated with adhesion barrier following emergency CS
have been reported in Japan [32, 33]. The mechanisms leading to
chemical inflammation associated with adhesion barrier have not been
clear but the hyaluronan-based membrane has been observed to be
associated with an increased adhesion in an animal model of bacterial
peritonitis [34, 35]. These studies implied postcesarean peritonitis
in patients who received the adhesion barrier films was associated with
wound classification which reflects the degree of contamination of the
wound during operation. A recent study showed the percentage of class
III and class IV in emergency CS was 22.3% and the metritis rates of
patients who received the HA-CMC barrier with contaminated or
dirty/infected wound was much higher than cases using 4% Icodextrin
solution (32.0% vs. 10.3%, p =0.048) [36]. It was mentioned
that contaminated or dirty/infected wound with placement of
anti-adhesion films may form occlusive barrier that prevents omentum to
absorb the microabscess and serve as a culture medium to nourish
bacteria.
Our concern is that patients who used adhesion barrier at the primary CS
had significantly higher rates of postcesarean fever and therefore it is
an independent risk factor of postcesarean fever. So we performed
interaction term analysis to examine the impact of SSI risk factors
[37] and use of adhesion barrier on postcesarean fever. And we found
the strongest risk factor for postcesarean fever is the use of
anti-adhesion film during emergency CS (p=0.041) as well as in cases
where women have labor before operation (p=0.054). We think that it is
because at least half of the primary CS in our study were conducted in
emergency or having labor before operation. Most of them (e.g.,
prolonged labor, fetal distress) had long duration of labor or membrane
rupture and they also received more digital vaginal examinations before
operation. Thus, a contaminated wound with anti-adhesion films means
more chances of having SSI.
Based from our data, the incidence of adhesion at the secondary CS is
minimal or nonexistent and use of adhesion barriers at primary CS don’t
significantly reduce adhesion, shorten the time needed for neonate
delivery, and improve surgical outcome at repeat CS. Furthermore, use of
adhesion barrier films during emergency cases and when a woman has labor
before operation is associated with a significantly higher risk of
postcesarean fever which potentially means increased risk of SSI. Unlike
our study, analysis of SSI risk factors and use of adhesion barrier has
not been available previously. Collectively, our study adds new
information regarding impact of adhesion barrier on postcesarean fever.
There was only one phase IV prospective trial that has reported the
effectiveness of HA-CMC at the repeat CS but there is no prospective
trial for safety of use in specific condition such asemergency operation
or labor before operation. There is also no prospective trial reporting
the effectiveness and safety of ORC. Prospective studies comparing the
effectiveness and safety of all adhesion barriers extensively used in
primary CS can help in evaluating the cost-effectiveness of these
products and developing evidence-based decision-making.