Scolaris Content Display Scolaris Content Display

Abdominal surgical incisions for caesarean section

Esta versión no es la más reciente

Contraer todo Desplegar todo

Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To compare, using the best available evidence, the effects of alternative methods of abdominal surgical incisions for caesarean section on maternal and/or infant health and health care resource use.

Background

Caesarean section is the commonest major operation performed on women all over the world. Essentially the operation involves exposing the uterus by entering the abdominal cavity through the abdominal wall. The peritoneum covering the uterus is opened. The uterus is then incised and the baby and the placenta delivered. Adequate haemostasis is achieved by closure of the uterine muscle followed by closure of the abdominal wall.

There are many possible ways of performing a caesarean section and operative techniques used for caesarean section vary. The techniques used may depend on many factors including the clinical situation and the preference of the operator. Some of these techniques have been evaluated through randomized trials. The protocol for a Cochrane review of the techniques used, indications for caesarean section and postoperative complications is currently being prepared.

Various abdominal incisions have been used for caesarean delivery. These include vertical (midline and paramedian) incisions and transverse incisions (Pfannensteil, Maylard, Cherney, Joel‐Cohen).

Traditionally vertical incisions were used for caesarean delivery (Myerscough 1982). Here the skin is incised in the midline between the umbilicus and the pubic symphysis. The rectus sheath and the peritoneum are incised in the midline. This area is least vascular. Vertical subumbilical midline incisions have the presumed advantage of speed of abdominal entry and less bleeding. A vertical midline incision may be extended upwards if more space is required for access. Moreover, this incision may be used if a caesarean delivery is planned under local anaesthesia (WHO 2000). The disadvantages of a vertical midline incision include the greater risk of postoperative wound dehiscence and development of incisional hernia. The scar is cosmetically worse than other incisions. In the paramedian incision, the skin incision is made to one side of the midline (usually right). The anterior rectus sheath is opened under the skin incision. The belly of the underlying rectus abdominus muscle is then retracted laterally and the posterior rectus sheath and peritoneum are opened. Because of a shutter like effect, the stress on the scar is presumed to be less. The paramedian incision is reportedly stronger (Kendall 1991) than the midline scar but has no cosmetic advantage.

The lower abdominal transverse incision is adequate for the vast majority of caesarean operations. It has the advantages of cosmetic approval and minimal risk of postoperative disruption. The risks of incisional hernia are less than those following vertical incisions. However, transverse abdominal incisions usually involve more dissection and may require more surgical skills. Blood loss following dissection may be more. Also, this incision would be difficult to make under local anaesthesia.

The traditional lower abdominal transverse incision for caesarean delivery is the incision described in 1900 by Pfannensteil. Classically, this incision is located two fingers‐breadth above the pubic symphysis. Here the skin may be entered via a low transverse incision that curves gently upward, placed in a natural fold of skin (the "smile" incision). After the skin is entered, the incision is rapidly carried through subcutaneous tissue to the fascia which is then nicked on either side of the midline. The subcutaneous tissue is incised sharply with a scalpel. Once the fascia is exposed, it is incised transversely with heavy curved Mayo scissors. In the standard technique, the upper and then the lower fascial edges are next grasped with a heavy toothed clamp, such as a Kocher, and elevated. Under continuous tension, the fascia is then separated from the underlying muscles by blunt and sharp dissection. Once the upper and lower fascia have been dissected free, and any perforating vessel sutured or electrocoagulated, the underlying rectus abdominus muscles are separated with finger dissection. If the muscles are adherent, sharp dissection is necessary to separate them. The peritoneum is then opened sharply in the midline. The initial entry is then widened sharply with fine scissors exposing intraperitoneal contents.

When exposure is limited and additional space is required, the Maylard or Cherney modification may be used. In the Maylard procedure, the rectus abdominus muscles are divided either sharply or by electrocautery to allow greater access to the abdomen. However, this may result in a good deal of tissue damage and the underlying artery may be entered (O'Grady 1995). The Maylard incision length is usually longer than the Pfannensteil incision. However, difficulty in delivery of the fetus is minimal with Pfannesteil incisions measuring at least 15 cm in length (Ayers 1987), the length of a standard Allis clamp ‐ the Allis clamp test (Finan 1991). Shorter incisions may lead to difficulty in general exposure and/or delivery of the baby's head.

In the Cherney procedure, the lower fascia is reflected exposing the tendinous attachment of the rectus abdominus muscle bodies to the fascia of the pubis (O'Grady 1995). The muscle is severed as low as possible and the proximal and distal ends suture ligated. One or both muscle attachments may be divided as required.

The Mouchel incision is similar to the Maylard incision. This transverse incision runs at the upper limit of the pubic hair and is thus lower than the Maylard incision. The muscles are divided above the openings of the inguinal canals (Mouchel 1981).

In the Pelosi technique (Wood 1999) for caesarean delivery, the skin is cut in a low transverse fashion with a knife. The subcutaneous tissues and fascia are incised with electrocautery. The upper aspect of the fascial incision is elevated and the median raphe is dissected cephalad 2 to 3 cm using electrocautery. The rectus muscles are separated bluntly with fingers to identify the underlying peritoneum which is then entered by inserting the index finger inwards and upwards or sharply as required. The peritoneum and muscles are stretched to the full extent of the skin. In this technique, no bladder flap is created before hysterotomy. After delivery of the baby, the obstetrician awaits spontaneous placental expulsion before closing the hysterotomy in one layer. The fascia is closed and the skin edges are approximated with staples. The Pelosi technique was reported to be associated with decreased operative time, decreased blood loss, improved patient outcome and decreased overall cost (Wood 1999).

Joel‐Cohen 1977 described a transverse skin which was subsequently adapted for caesarean sections. This modified incision is placed about 3 cm below the line joining the anterior superior iliac spines. This incision is higher than the traditional Pfannenstiel incision. Sharp dissection is minimized. After the skin is cut, the subcutaneous tissue and the rectus sheath are opened a few centimeters only in the midline. The rectus sheath incision may be extended laterally by blunt finger dissection (Wallin 1999) or by pushing laterally with slightly opened scissor tips, deep to the subcutaneous tissues (Holmgren 1999). The rectus muscles are separated by finger traction. If exceptional speed is required in the transverse entry, the fascia may be incised in the midline and both the fascia and subcutaneous tissue are rapidly divided by blunt finger dissection (Joel‐Cohen 1977). Stark used this incision for caesarean delivery along with single layer closure of the exteriorized uterus and non‐closure of peritoneum. This package of surgical techniques for caesarean section used at the Misgav‐Ladach hospital, Jerusalem, has been popularized by Stark and others (Holmgren 1999). The reported advantages include shorter operating time (Franchi 1998; Darj 1999; Wallin 1999; Mathai 2002), less use of suture material (Bjorklund 2000), less intra‐operative blood loss (Darj 1999; Wallin 1999; Bjorklund 2000), less postoperative pain (Darj 1999; Mathai 2002) and less wound infection (Franchi 1998) in the group undergoing caesarean by these techniques.

Objectives

To compare, using the best available evidence, the effects of alternative methods of abdominal surgical incisions for caesarean section on maternal and/or infant health and health care resource use.

Methods

Criteria for considering studies for this review

Types of studies

All published, unpublished and ongoing randomised controlled trials comparing different abdominal incisions for caesarean section. Quasi‐randomized trials (e.g., those randomized by date of birth or hospital number) will be excluded from the analysis. Studies reported only in abstract form will be included in the 'studies awaiting assessment' category and will be included in analyses when published as full reports.

Types of participants

Women undergoing caesarean section.

Types of interventions

Abdominal incisions for caesarean section performed according to a pre‐specified technique.

Types of outcome measures

Outcome measures for the woman
(1) Postoperative febrile morbidity as defined by trial authors;
(2) postoperative analgesia as defined by trial authors;
(3) blood loss as defined by the trial authors;
(4) maternal death or serious disability (e.g., admission to intensive care unit);
(5) blood transfusion;
(6) wound infection as defined by trial authors;
(7) wound complications (e.g., haematoma, infection, breakdown, operative procedures carried out on wound);
(8) postoperative pain (as measured by visual analogue scale or additional analgesia);
(9) breastfeeding (at discharge or as defined by trial authors);
(10) voiding problems as defined by trial authors;
(11) duration of surgery as defined by trial authors;
(12) postoperative anaemia as defined by trial authors;
(13) thromboembolism;
(14) need for re‐laparotomy.

Longer term outcomes for the woman
(1) Long‐term wound complications e.g., numbness, keloid formation, incisional hernia;
(2) future fertility problems;
(3) complications in future pregnancies (e.g., placenta praevia, uterine rupture);
(4) complications at future surgery (e.g., adhesion formation);
(5) satisfaction with the wound as defined by trial authors.

Outcome measures for the infant
(1) Neonatal death;
(2) birth trauma as defined by the trial authors;
(3) time taken from anaesthesia to delivery;
(4) five minute Apgar score less than seven;
(5) cord blood pH less than 7.20;
(6) admission to special care baby unit;
(7) encephalopathy.

Health service use
(1) Length of postoperative hospital stay for mother or baby;
(2) readmission to hospital of mother and/or baby.

Only outcomes with available data will appear in the analysis table. Outcome data that are not prespecified by the reviewers, but which are reported by the authors will be labelled as such in the analysis but not used for the conclusions.

Search methods for identification of studies

This review will draw on the search strategy developed for the Cochrane Pregnancy and Childbirth Group as a whole. The Group's trials register is maintained by the Trials Search Co‐ordinator and contains trials identified from:
1. quarterly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
2. monthly searches of MEDLINE;
3. handsearches of 30 journals and the proceedings of major conferences;
4. weekly current awareness search of a further 37 journals

Details of the search strategies for CENTRAL and MEDLINE, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the 'Search strategies for identification of studies' section within the editorial information about the Cochrane Pregnancy and Childbirth Group.

Trials identified through the searching activities described above are given a code (or codes) depending on the topic. The codes are linked to review topics. The Trials Search Co‐ordinator searches the register for each review using these codes rather than keywords.

Data collection and analysis

Trials under consideration will be evaluated for methodological quality and appropriateness for inclusion according to the pre‐stated selection criteria by both authors, without consideration of their results. Individual outcome data will be included in the analysis if they meet the pre‐stated criteria in 'Types of outcome measures'. Included trial data will be processed as described in the Cochrane Reviewers' Handbook (Clarke 2003).

Trials that meet the eligibility criteria will be assessed for quality using the following criteria:

1. Generation of random allocation sequence: adequate, inadequate, unclear.
2. Allocation concealment: A = adequate; B = unclear; C = no information.
3. Blinding of participants: yes, no, inadequate, no information.
4. Blinding of caregivers: yes, no, inadequate, no information.
5. Blinding of outcome assessment: yes, no, inadequate or no information.
6. Completeness of follow‐up data (including any differential loss of participants for each group): A = less than 3% of participants excluded; B = 3 to 9.9% of participants excluded; C = 10 to 19.9% excluded; D = 20% or more excluded; E = Unclear.
7. Analysis of participants in randomised groups.

If the publication does not report analysis of participants in their randomised groups, the reviewers will attempt to restore them to the correct group. If there is insufficient information in the report to allow this, the authors will be contacted and further data requested.

Data will be extracted from the sources onto data extraction forms by both authors. Differences of opinion will be settled by consensus or referral to the primary editor. Data from different trials will be combined if they are sufficiently similar for this to be reasonable in the judgement of the reviewers. Data will be entered onto Review Manager (RevMan 2000), checked for accuracy, and analyzed as above using the RevMan software. Meta‐analyses will be performed using relative risks as the measure of effect size for binary outcomes and weighted mean differences for continuous outcome measures. If trials used different ways of measuring the same continuous outcome (e.g., pain), standardised mean differences will be used.

Fixed effects meta‐analysis will be used for combining study data if the trials are judged to be sufficiently similar. Heterogeneity will be investigated by calculating the I2 statistic (Higgins 2002), and if this indicates a high level of heterogeneity among the trials included in an analysis, a random effects meta‐analysis will be preferred for an overall summary. Where high levels of heterogeneity are found they will be explored by the pre‐specified sub‐group analyses and by sensitivity analyses excluding the trials most susceptible to bias based on the quality assessment: those with inadequate allocation concealment (B or C); high levels of post randomisation losses or exclusions (D); or unblinded outcome assessment, or blinding of outcome assessment uncertain.

Subgroup analyses will include :
(1) Primary versus repeat versus mixed/undefined caesarean section
(2) Prelabour versus intrapartum versus mixed/undefined caesarean section
(3) Preterm versus term versus mixed/undefined caesarean section
(4) General versus regional versus mixed/undefined anaesthesia

Investigation of heterogeneity will use the methods of Deeks 2001 to assess differences between the subgroups.