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Cochrane Database of Systematic Reviews Protocol - Intervention

Negative pressure wound therapy for managing the open abdomen after midline laparotomy

Authors' declarations of interest

Version published: 12 November 2014 Version history

https://doi.org/10.1002/14651858.CD011356

This is not the most recent version

view the current version 17 November 2016
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Abstract

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

To determine the effects of NPWT on primary fascial closure in patients with an open abdomen after undergoing midline laparotomy.

Background

A glossary of terms used in this protocol can be found in Appendix 1.

Description of the condition

A laparotomy is a surgical procedure involving a large incision through the abdominal wall to gain access to the abdominal cavity. Although there are several types of incisions used to enter the abdominal cavity, the midline incision (a vertical incision) is most commonly used especially in emergency laparotomies (Brown 2005). Between 2% to 18% of surgical patients in the Intensive Care Unit (ICU) have had an emergency laparotomy (Bee 2008; Garner 2001). In serious conditions following emergency laparotomy, closing the abdominal fascia (layer of fibrous tissue) may not be possible or desirable. In these cases, the abdomen is left open, a condition known as the 'open abdomen'. If the abdomen is left open after midline laparotomy, the muscles of the abdominal wall tend to retract the edges of the wound laterally. These patients are especially at risk for developing a ventral, or incisional, hernia (Brandl 2014).

There are three relatively common scenarios in which the open abdomen may occur. Firstly, in patients with severe peritonitis (inflammation of the tissue that lines the abdomen and organs) where the infection may cause such severe oedema (fluid accumulation) that closure of the abdominal fascia is not possible at the end of the laparotomy (Doyon 2001; Fortelny 2014). Secondly, in patients with (severe) abdominal trauma where damage control surgery consists of a rapid assessment and control of the bleeding, with the result that the haemostatic packing and extensive bowel oedema often prevent fascial closure (Demetriades 2014; Suliburk 2003). Finally, in patients who require a decompressive laparotomy for Abdominal Compartment Syndrome (ACS), where release of fluid into the abdomen threatens organ failure, the extent of bowel oedema often prevents fascial closure at the end of the laparotomy (Björck 2014; Keramati 2007).

It can be seen, from these scenarios, that patients with an open abdomen are severely ill and will be treated mainly in the ICU. The mortality rate of patients with an open abdomen ranges from 0% to 60% (Boele van Hensbroek 2009; Fortelny 2014). Whilst it is thought that the main cause of death in these patients is multiple organ dysfunction syndrome (Mayr 2006), the cause of death is hardly ever reported. Current evidence is insufficient to determine whether the underlying condition or the (temporary) abdominal closure technique is responsible for, or contributes to, the high mortality rate. Temporary closure of the open abdomen has gained much interest over the past decades (Quyn 2012).

Another aspect of the open abdomen is that it often involves (multiple) re‐operations, either for the underlying condition or for changing the wound dressing, and these operations increase the burden for patients as well as costs for the hospital (Kushimoto 2007).

Description of the intervention

Before the abdominal fascia can be closed properly, the open abdomen requires temporary closure. This temporary abdominal closure (TAC) has several aims: first, to protect the abdominal viscera (internal organs) and prevent further contamination; second, to prevent evisceration; third, to limit infection and allow quantification of fluid loss; and, finally, to prevent lateral retraction of the fascial edges without causing ACS. Prevention of lateral retraction may increase the chance of achieving successful primary fascial closure. Successfull primary fascial closure is full closure of the abdomen (fascia‐to‐fascia) after open abdominal treatment.

Several techniques are used to temporarily cover the open abdomen and examples of these techniques include absorbable or non‐absorbable meshes or sheets that are sutured to the fascia. The Bogota bag method consists of a sterilised intravenous fluid bag sutured to the fascia to allow the abdominal contents to expand (Tremblay 2001). Wittmann described the use of two opposing Velcro sheets (artificial burr) sutured to the lateral fasciae to allow easy re‐operations as well as re‐approximation of the fascia (Wittmann 1993). Some authors describe the use of a sterilised zipper (often sewn in a mesh or sheet) (Cuesta 1991). The last decades have also seen the development of topical negative pressure wound therapy (NPWT) techniques. NPWT can be applied using commercially available products such as the Vacuum Assisted Closure device (V.A.C.®, KCI, San Antonio, Texas) (Miller 2004), or assembled by clinicians using a vacuum pack (Garner 2001).

How the intervention might work

In order to apply NPWT to the open abdomen, a perforated plastic sheet is extended laterally under the anterior abdominal wall and used to cover the exposed bowel. In the vacuum pack technique, a moist, sterile laparotomy towel is placed over the sheet and two closed suction drains are placed upon it. The entire wound (and a wide margin of surrounding skin) is covered with an adhesive drape and negative pressure is applied through the drains. 

The V.A.C.® system consists of a (polyurethane) sponge, cut to the size of the wound and placed over the perforated plastic sheet. An adhesive drape and drain are put on top of the sponge before negative pressure is applied by a separate pump that includes a container for the collection of fluids.

In both techniques, dressings are changed every two to five days and this procedure is repeated until the abdominal fascia have either been completely re‐approximated or the fascial edges cannot be approximated any further. In cases where the fascial edges cannot be approximated further, a mesh graft can be inserted in the remaining fascial defect (gap), or the wound can be left open to heal by secondary intention, or can be covered by a split‐thickness skin graft.

Why it is important to do this review

There is great variation in the management of the open abdomen that is due to cost, available resources, surgical specialty and tradition. Several authors have suggested management strategies (Kreis 2013; López‐Cano 2013). NPWT is amongst these proposed therapies, however, it is not established internationally as the preferred standard technique for management of the open abdomen. This may be partly because complications such as enteroatmospheric fistulae (a connection between the open abdomen and the atmosphere) do occur (Fortelny 2014). It is not known whether NPWT has a beneficial effect on the success of primary fascial closure in patients with an open abdomen, or whether complications such as fistulae are condition‐ or treatment‐specific.

From a patient perspective, closure of the abdominal fascia is important because it is the best way to prevent ventral hernias (these can occur in the absence of a natural abdominal wall with fascia and muscles). Ventral hernias cause considerable discomfort and are infamous for trapping and strangulating the intestine. They can be corrected at a later stage, but these are extensive and risky operations as the abdomens in question are likely to have many adhesions. Preventing the development of ventral hernias decreases these burdens and risks.

The National Institue of Clinical Excellance in the UK (NICE 2013) has produced a consultation document about negative pressure wound therapy (NPWT) for the open abdomen. In this document they conclude that current evidence on the safety and efficacy is inadequate in quality and quantity. There has been concern about the occurrence of internal fistulae associated with this procedure but there is no evidence about whether NPWT is the cause.They state that NPWT for the open abdomen should only be carried out by staff with specific training in the procedure and in accordance with the manufacturers instructions when commercial products are used. NICE encourages further research into the role of NPWT for the open abdomen.

Objectives

To determine the effects of NPWT on primary fascial closure in patients with an open abdomen after undergoing midline laparotomy.

Methods

Criteria for considering studies for this review

Types of studies

All randomised controlled trials (RCTs) comparing NPWT and other TAC techniques in patients with an open abdomen.

Types of participants

People of any age with an open abdomen after undergoing midline laparotomy.People who are undergoing abdominal wall correction months or years after having the open abdomen will be excluded on the basis that this is no primary fascial closure.

Types of interventions

Any NPWT technique compared with an alternative method of TAC or a different NPWT technique.

Types of outcome measures

Primary outcomes

  • Rate of successful primary fascial closure of the abdomen. Primary fascial closure is defined as full fascia‐to‐fascia closure after open abdominal treatment during index admission. The review authors define index admission as the admission during which the open abdominal treatment was started.

  • Time to successful primary fascial closure.

Secondary outcomes

  • In hospital all‐cause mortality.

  • Adverse events:

    • fistulae (both enteroenteric, enterocutaneous and enteroatmospheric (if in the middle of the open abdomen));

    • abscesses (intra‐abdominal and abdominal wall);

    • new abdominal infections during open abdominal treatment;

    • technical complications (e.g. failure to maintain negative pressure).

  • Number of dressing changes.

  • Cost of treatment.

  • Length of stay in ICU.

  • Scores to estimate the severity of the underlying condition, such as the Abdominal Trauma Index (Borlase 1990), Abdominal Abbreviated Injury Score (AIS) and Injury Severity Score (ISS) (Baker 1974) in trauma patients, and the Acute Physiology and Chronic Health Evaluation (APACHE) II score (Knaus 1985), and the Sequential Organ Failure Assessment (SOFA) score in all patients (Vincent 1996). The authors will record these scores whenever mentioned in studies.

The review authors will consider all trials that include data on secondary outcomes, but do not include data on primary outcomes, as eligible for inclusion in this review.

Search methods for identification of studies

Electronic searches

The review authors will search the following databases:

  • Cochrane Wounds Group Specialised Register;

  • The Cochrane Central Register of Controlled Trials (CENTRAL The Cochrane Library) (latest issue);

  • Health Technology Assessment Database (HTA) (latest issue);

  • Ovid MEDLINE (1950 to date);

  • Ovid EMBASE (1980 to date); and

  • EBSCO CINAHL (1982 to date).

The review authors will search the Cochrane Central Register of Controlled Trials (CENTRAL) using the following exploded MeSH headings and keywords:

#1    MeSH descriptor Negative‐Pressure Wound Therapy explode all trees
#2    MeSH descriptor Suction explode all trees
#3    MeSH descriptor Vacuum explode all trees
#4    ("negative pressure" or negative‐pressure or TNP):ti,ab,kw
#5    (sub‐atmospheric or subatmospheric):ti,ab,kw
#6    ((seal* NEXT surface*) or (seal* NEXT aspirat*)):ti,ab,kw
#7    (wound NEAR/3 suction*):ti,ab,kw
#8    (wound NEAR/3 drainage):ti,ab,kw
#9    ((foam NEXT suction) or (suction NEXT dressing*)):ti,ab,kw
#10    ((vacuum NEXT therapy) or (vacuum NEXT dressing*) or (vacuum NEXT seal*) or (vacuum NEXT assist*) or (vacuum NEAR closure) or (vacuum NEXT compression) or (vacuum NEXT pack*) or (vacuum NEXT drainage) or VAC):ti,ab,kw
#11    (#1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10)
#12    MeSH descriptor Abdomen explode all trees with qualifier: SU
#13    MeSH descriptor Laparotomy explode all trees
#14    MeSH descriptor Abdominal Injuries explode all trees
#15    MeSH descriptor Abdominal Cavity explode all trees
#16    MeSH descriptor Abdominal Wall explode all trees
#17    ("open abdomen" or "open abdominal" or "abdominal closure"):ti,ab,kw
#18    (#12 OR #13 OR #14 OR #15 OR #16 OR #17)
#19    (#11 AND #18)

The authors will adapt this strategy to search Ovid MEDLINE, Ovid EMBASE and EBSCO CINAHL. The authors will combine the Ovid MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity‐ and precision‐maximising version (2008 revision) (Lefebvre 2011). The authors will combine the EMBASE and CINAHL searches with the trial filters developed by the Scottish Intercollegiate Guidelines Network (SIGN 2009).

We will also search the following clinical trials registries.

Searching other resources

The review authors will search references of all selected articles, primary studies and review articles for further potentially eligible studies. The ProQuest database for PhD Theses will be searched for studies on the open abdomen and temporary closure techniques. The authors will search the proceedings and abstracts of:

  • The Pan‐American Trauma Society Annual Congress;

  • The European Society for Trauma and Emergency Medicine Annual Congress;

  • The American Association for the Surgery of Trauma Annual Meeting;

  • The Surgical Infection Society Annual Meeting;

  • The Surgical Infection Society Europe Annual Meeting;

  • The European Society of Intensive Care Medicine Annual Congress;

  • The Society of Critical Care Medicine Annual Congress; and

  • The Intensive Care Society Annual State of the Art Meeting.

The authors will contact manufacturers of NPWT techniques and experts in the field in order to identify unpublished research and trials that are ongoing.

Data collection and analysis

Selection of studies

The review authors will conduct the selection of studies in two stages. Firstly, independently, two review authors will screen the titles and abstracts for eligibility. The authors will obtain full‐text articles of potentially eligible titles and abstracts. Articles that are not published in English, German or Dutch will be translated. Secondly, independently, two review authors will assess the full text of potentially eligible trials. The review authors who assess the relevance of studies will know the authors, institutions, journal of publication and results when they apply the eligibility criteria. Disagreement between the review authors will be resolved by a third review author. No language criteria will be applied.

Data extraction and management

Two review authors will extract data independently. They will discuss and check the data for accuracy; any disagreements will be resolved by a third review author. We will use a standardised form to extract the characteristics of the study, in accordance with procedures outlined in the Cochrane Handbook for Systematic Reviews of Interventions. This form will include details of the methodology (risk of bias criteria).study duration, participants (setting; health status; age; sex; country), interventions, and outcomes (outcomes and time‐points measured or reported) for each study.

Assessment of risk of bias in included studies

Independently, two review authors will assess each included study using the Cochrane Collaboration tool for assessment of risk of bias (Higgins 2011). This tool addresses six specific domains, namely sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting and other issues (e.g. extreme baseline imbalance) (see Appendix 2 for details of the criteria on which the judgement will be based). Blinding and completeness of outcome data will be assessed for each outcome separately. The authors will complete a 'Risk of bias' table for each eligible study. Any disagreement amongst the review authors will be resolved by discussion to achieve a consensus.

The authors will present their assessment of risk of bias using a 'Risk of bias' summary figure, which presents all of the judgements in a cross‐tabulation of study by entry. This display of internal validity indicates the weight the reader may give the results of each study and the strength of the evidence for each review outcome.

Measures of treatment effect

The risk ratio (RR) with 95% confidence intervals (CI) will be presented for dichotomous variables. The authors will present mean difference (MD) with 95% CI for continuous variables. The time to successful primary fascial closure will be analysed as time‐to‐event data (hazard ratios).The primary treatment effect is defined as the successful primary fascial closure rate after temporary abdominal closure. This is the number of patients with successful primary fascial closure during index admission divided by the number of patients per treatment (technique) group. .

Assessment of heterogeneity

Firstly, we will consider clinical and methodological heterogeneity: that is the degree to which the included studies vary in terms of participant, intervention, outcome and characteristics such as length of follow‐up. This assessment of clinical and methodological heterogeneity will be supplemented by information regarding statistical heterogeneity ‐ assessed using the Chi² test (a significance level of P < 0.10 will be considered to indicate statistically significant heterogeneity) in conjunction with I² measure (Higgins 2003). I² examines the percentage of total variation across RCTs that is due to heterogeneity rather than chance (Higgins 2003). In general I² values of 25%, or less, may mean a low level of heterogeneity and values of more than 75%, or more, indicate very high heterogeneity (Higgins 2003).

Data synthesis

The review authors will enter data into Review Manager (RevMan) 5.3 for analysis (RevMan 2012). Decisions about pooling data from similar studies will depend on our assessment of heterogeneity (Higgins 2003). The review authors will use a fixed‐effect model if the I2 statistic is 25% or less, and a random‐effects model if the I2 statistic is between 25% and 75%. No pooling will be performed if the I2 statistic is 75% or over. Summary estimates of treatment effect (with 95% CI) will be calculated for every comparison where data are pooled. The authors will consider clinical heterogeneity in relation to underlying condition and disease severity as indicated by validated scores. Data that are not suitable for analysis (narrative) will be described and not analysed. However, since these may be important, the authors will include these data separately in the review.

Subgroup analysis and investigation of heterogeneity

No subgroup analyses are planned