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Blunt vs sharp expansion of the uterine incision at cesarean delivery has been investigated as a technique primarily to reduce intraoperative blood loss. The objective of this systematic review was to compare the effects of either intervention on maternal outcomes.
A systematic review with metaanalyses that used the DerSimonian and Laird random effects model was performed. The Cochrane Central Register of Controlled Trials (The Cochrane Library 2012, Issue 4), MEDLINE (1948–Apr 2012), EMBASE (1947–Apr 2012), and the reference lists/citation history of articles were searched. Only randomized controlled trials were included.
Four trials (1731 patients) were evaluated. Data from one recently completed trial (535 patients) were not yet available. Metaanalyses revealed a trend towards reduced maternal blood loss with blunt expansion of the uterine incision that was statistically significant when measured by surgeon's estimation of volume lost, but not by comparison of pre- and postoperative hematocrit and hemoglobin levels or a requirement for blood transfusion. There was a trend towards fewer unintended extensions in the blunt group and no difference in the incidence of endometritis.
Blunt dissection of the uterine incision at cesarean delivery appears to be superior to sharp dissection in minimizing maternal blood loss. However, this conclusion could change when data from a new unpublished large trial are available.
It generally is accepted that a greater amount of blood loss is likely in an operative, compared with vaginal, delivery. As obstetric hemorrhage remains a leading cause of maternal morbidity and death, techniques such as manual placental extraction, in situ uterine repair in the place of exteriorization, and blunt traction in the cephalocaudad, rather than transverse, direction for uterine incision have been proposed to minimize intraoperative blood loss during cesarean delivery.
Previously, proponents of either the blunt or sharp method would defer to training protocols, personal experience, or theoretic reasoning to explain their choice of technique. To date, a small number of studies specifically have examined the impact of the hysterotomy expansion technique on maternal blood loss during cesarean delivery. The main suggested advantage of the blunt approach includes decreased trauma to the vasculature with less bleeding and ooze from the dissected myometrial edge.
However, there are concerns about reduced control of length and direction of the uterine incision that potentially could cause damage of lateral uterine and parametrial blood vessels and increased risk of unintended extensions that could contribute further to hemorrhage.
The aim of this review was to compare the impacts of sharp vs blunt hysterotomy on the primary outcome of maternal blood loss and the secondary outcomes of unintended extension, incidence of postoperative endometritis, injury to the neonate, postoperative pain, and operative time/time to delivery.
Materials and Methods
The Cochrane and Preferred Reporting Items for Systematic Review and Metaanalyses (PRISMA) guidelines were followed for the performance and reporting of this systematic review.
All prospective randomized controlled trials (RCTs) that compared blunt vs sharp expansion of the initial uterine incision at transverse lower segment cesarean delivery were considered. Quasirandomized trials and studies that assessed vertical lower-segment or classic upper-segment uterine incisions were excluded. Ongoing or recently completed trials with no data yet available were noted for future analyses. Our primary outcome was maternal blood loss. Our secondary outcomes were incidence of extension, endometritis, neonatal morbidity, postoperative pain, and time to delivery.
A literature search of the Cochrane Central Register of Controlled Trials (The Cochrane Library 2012, Issue 4), Medline (via Ovid; 1948–April 2012), and Embase (via Ovid) (1947–April 2012) was performed in week 4, April 2012. The prospective search protocol for each database is given in Table 1. No language restrictions were used. All titles were assessed; where the abstract suggested a potentially eligible study, the full text was retrieved. Scopus was used to cross-reference the references and citation history of full-text articles. A search for ongoing or recently completed trials was performed in week 4, April 2012, with the Australia/New Zealand, United Kingdom, and United States Clinical Trials registries (www.anzctr.org.au, www.controlled-trials.com, www.clinicaltrials.gov, respectively). Studies were evaluated critically for design and risk of bias, according to criteria set out in the Cochrane handbook for systematic reviews of interventions.
Data were extracted onto a standardized collection form by 2 independently working authors (L.X., A.C.) and entered into RevMan (version 5.1, 2011; The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). Data were analyzed with the use of a random-effects metaanalysis (DerSimonian and Laird model) with risk ratio as the pooled estimate for dichotomous data and mean difference for continuous data. Mantel-Haenszel and inverse variance methods were used, respectively. Analysis was performed on an intention-to-treat basis. Substantial statistical heterogeneity was considered to be present when there was inconsistency between trials in the direction or magnitude of effects. This was assessed visually from the forest plots or when the I2 statistic was >50%, respectively. Statistical significance was defined as a probability value < .05.
The literature search returned 495 articles (Figure 1). From these, 4 RCTs (1731 patients) that reported data appropriate for the clinical question (Tables 2)
All patients undergoing primary or repeat transverse lower segment cesarean delivery
Women declining participation, emergency surgery, use of vertical lower segment or classical upper segment uterine incision
Uterine incision extended by fingers or control extended with scissors; 20 units oxytocin in 1000 mL Ringer's lactate rapid infusion after placental delivery; operator: 2nd- to 4th-year residents with assistance of attending staff
Severe medical and surgical disorders; blood disorder/anemia; known thromboembolic disorder; multiple gestation; fetal macrosomia; polyhydramnios; emergency surgery for placental abruption; placenta previa, and severe preeclampsia
Uterine incision extended by fingers or control extended with scissors; manual delivery of placenta, 10 units oxytocin in 500 mL normal saline solution >10 minutes; all patients underwent general anesthesia; operator: 2nd-year resident under supervision
Xu. Blunt vs sharp hysterotomy at cesarean delivery. Am J Obstet Gynecol 2013.
Hysterotomy in the blunt expansion groups was performed after an initial 1-2cm incision was made through the uterine wall and then extended by insertion of the surgeon's index fingers laterally and cephalad. In the sharp expansion groups, the extension was achieved by cutting with bandage scissors laterally and cephalad.
There were some differences in study design between the trials. Of the studies that specified cesarean technique, 1 study used the Pfannenstiel incision
Women who underwent lower-segment cesarean delivery were included in these trials; however, there were differing additional enrolment criteria. Three studies excluded women who underwent emergency surgery.
One study had an unclear risk of selection bias because the authors did not specify the method of randomization; however, there were no statistically significant differences between the experimental and control groups in all recorded characteristics.
compared immediate preoperative hematocrit level with that 48 hours after the operation. A statistically significant reduction in hematocrit drop was found favoring the blunt group (P = .003). Consistent with this, the incidence of women who experienced a >10% decrease in hematocrit level was also significantly smaller in the blunt, rather than the sharp, group (P = .03; author calculated with χ2 test).
compared immediate preoperative hematocrit level with that 24-48 hours after the operation and found no difference in the average reduction in hematocrit level between the 2 groups (P = .58). The incidence of >10% reduction in hematocrit level was also comparable (P > .05).
measured hematocrit level immediately before the operation and 24 hours after the operation. A decreased drop in pre- to post-operative hematocrit level in the blunt group that was detected when the data were compared with the sharp group was significant (P < .05).
Combined results from the 3 trials revealed a trend that favored blunt hysterotomy for reduced drop in hematocrit level after the operation (Figure 3) ; however, this did not reach statistical significance (mean difference [MD], −0.86%; 95% CI, −2.04 to 0.32; 3 trials; 1445 patients). There was substantial statistical heterogeneity across studies (I2 = 91%).
Mean drop in hemoglobin
Three studies recorded change in pre- and postoperative hemoglobin levels.
found no difference in mean hemoglobin level decrease when they compared the hemoglobin level that was measured at admission and the 24 hours postoperative measurement in the 2 groups (P = .08; author calculated with unpaired t test).
found a significantly smaller mean hemoglobin level difference when they compared the values measured before and 24 hours after surgery in the blunt group (P < .05).
Pooled results showed a trend toward a reduced drop in hemoglobin level that favored the blunt dissection group (Figure 4), although this was not statistically significant (MD, 7.41 g/L; 95% CI, −20.53 to 5.72; 3 trials; 786 patients). There was substantial heterogeneity across studies (I2 = 98%).
Requirement for blood transfusion
Three studies reported on the number of patients who required blood transfusion after surgery.
specified a hematocrit level of <24% and hemodynamic instability as criteria for transfusion. A significantly smaller number of women in the blunt group than in the sharp group required transfusion (P = .03; author calculated with Fisher exact test).
described a hematocrit level of <24% and a change of ≥10% in hematocrit level from admission to the postpartum period as indication for transfusion. There was no difference detected in requirement for transfusion between the 2 groups (P > .05).
Combined data suggested a strong trend towards decreased incidence of blood transfusion in patients who underwent blunt dissection, although this did not reach significance (relative risk, 0.31; 95% CI, 0.08–1.19; 3 trials; 1445 patients). There was low statistical heterogeneity (I2 = 0%; Figure 5).
Blood loss by estimated volume
Two studies examined blood loss by estimated volume.
measured volume by the estimation of the surgeon and attending staff based on the blood in the suction apparatus, plastic steridrapes, lap pads, and sponges. A significantly greater volume of intraoperative hemorrhage was recorded in the sharp compared with blunt group (P = .001).
measured volume by evaluating blood in the suction apparatus and weight difference of pre- and postoperative lap pads and sponges. They found that the volume of blood lost was significantly larger in the sharp compared with blunt group (P < .05).
Metaanalysis of composite data revealed a reduced estimated volume of blood loss that favored the blunt group that was statistically significant (MD, −55.00 mL; 95% CI, −79.48 to −30.52; 2 trials; 1145 patients) with substantial heterogeneity between studies (I2 = 51%; Figure 6).
Incidence of extension
Three studies evaluated the incidence of unintended extension.
defined extension as any defect of >2 cm outside the original incision. The 2 groups were similar in incidence and length of extensions (P = .61). There were no cases of injury to the cervix, vagina, or broad ligament.
defined extension as any defect that was found beyond the original incision. A significantly decreased risk of any extension in the blunt, compared with sharp, group was detected (P < .0001; author calculated with χ2 test). However, there was no difference in the number of broad ligament and cervical lacerations (P = .06 and P = .14, respectively).
recorded no significant differences in the number of extensions between the 2 groups (P > .05). There were no extensions into the broad ligament or cervix.
Pooled data from 3 studies showed a strong trend toward a reduced incidence of unintended extension in the blunt, compared with sharp, group, which was not significant (relative risk, 0.57; 95% CI, 0.28–1.17; 3 trials; 1431 patients), but with considerable heterogeneity between studies (I2 = 74%; Figure 7).
defined endometritis as leukocytosis with high-grade fever (>38.5°C) that lasted >6 hours that occurred >24 hours after delivery. The incidence of endometritis was similar in the 2 groups (P > .99).
There was no significant difference in the number of women who experienced endometritis after the operation across these trials (relative risk, 0.92; 95% CI, 0.75–1.13; 3 trials; 1531 patients). Heterogeneity was low (I2 = 0%; Figure 8).
No studies reported on the incidence of intraoperative injury to the neonate.
No studies compared differences in maternal postoperative pain.
found no differences in the time from the start of surgery to the delivery of the neonate between the sharp (mean, 11.7 min) and blunt groups (11.5 min; P = .72; author calculated with unpaired t test).
found that there was no difference in total operating time when they compared the sharp (mean, 30.7 min) and blunt (mean, 27.9 min) hysterotomy (P > .05).
The effect of sharp vs blunt hysterotomy on maternal blood loss, injury to local structures, and occurrence of endometritis were evaluated in this review. As far as the authors are aware, this is the most comprehensive attempt to review the literature systematically in relation to this clinical question.
Five randomized controlled trials were identified, of which data from 4 relatively heterogeneous studies were available for metaanalysis (1731 patients).
It was found that the estimated volume of blood loss was significantly less in the blunt than the sharp dissection group. Trends that favored blunt dissection for reduced blood loss (measured through laboratory values and maternal requirement for transfusion) and unintended extensions were also detected; however, these did not reach statistical significance. The incidence of endometritis occurred equally after either procedure.
From collated evidence in the current literature, it appears that blunt dissection of the hysterotomy at cesarean delivery is superior to sharp dissection. Three of 4 proxy measures of blood loss favored the use of blunt dissection without reaching statistical significance. The fourth measure (blood loss by estimation of volume) was significantly reduced with the use of blunt dissection. However, volume estimation methods that were used in the studies were partly subjective and did not account for amniotic or other fluids that had also accumulated in the suction apparatus and absorptive material. This measure therefore is subject to a degree of inaccuracy and detection bias because of the lack of assessor blinding.
With further data from the recently completed Turkish RCT (535 women) (unpublished data) and future studies, the true significance of this trend could be better elucidated.
The strength of any systematic review lies in the quality of the studies that are examined. We used a sensitive prospective search strategy with no language limitations, extensive cross-referencing, and a search for recently completed or ongoing trials.
Critical evaluation of the RCTs that were included in this review determined a low overall risk of bias with good internal validity. Results across studies for some outcomes were able to be synthesized convincingly for quantitative metaanalysis; however, there was notable statistical heterogeneity across studies in other outcomes. The small number of studies that were involved prohibited further investigation with sensitivity analysis. The differences between study findings likely stem from a variation in patient selection, surgical techniques, and diverse peripartum management (eg, use of oxytocin postplacental delivery).
It has been suggested in the literature that blunt dissection of the uterus may contribute to a faster operative time and time to delivery of the infant.
With only one of the studies examining this outcome, there were limited data found that related to the effects of hysterotomy technique on the speed of execution. There are some data from a nonrandomized, retrospective study that compared mean operative times that could not be included in this review.
This outcome has not been evaluated in any studies to date. It would be valuable to explore these aspects in future research.
The results of this systematic review revealed blunt dissection of the uterine incision at lower-segment cesarean delivery is associated with a significant reduction in blood loss when compared with sharp dissection. Blood loss by estimation of volume was significantly lower with the use of blunt dissection. Laboratory-based outcomes of drop in hemoglobin/hematocrit level and maternal requirement for blood transfusion supported this finding but did not reach statistical significance. The addition of data from a new unpublished large trial could further clarify the clinical differences between the 2 techniques.
Rates of caesarean section: analysis of global, regional and national estimates.
Cite this article as: Xu LL, Chau AMT, Zuschmann A. Blunt vs sharp uterine expansion at lower segment cesarean section delivery: a systematic review with metaanalysis. Am J Obstet Gynecol 2013;208:62.e1-8.