Drenaje de la herida en la cirugía arterial del miembro inferior
Resumen
Antecedentes
Con frecuencia se utilizan drenajes en las heridas de la pierna después de una cirugía vascular a pesar de la incertidumbre con respecto a los beneficios. Los drenajes se colocan para reducir la incidencia y el tamaño de las colecciones de sangre o líquido. Por el contrario, los drenajes pueden predisponer a los pacientes a la infección y pueden prolongar la hospitalización. Los cirujanos necesitan datos consistentes con respecto a los efectos de los drenajes sobre las complicaciones después de la cirugía arterial del miembro inferior.
Objetivos
Determinar si la colocación de rutina de los drenajes de heridas da lugar a menos complicaciones después de la cirugía arterial del miembro inferior que ningún drenaje.
Métodos de búsqueda
En junio 2016, se hicieron búsquedas en: registro especializado del Grupo Cochrane de Heridas (Cochrane Wounds Group); Registro Cochrane Central de Ensayos Controlados (Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In‐Process & Other Non‐Indexed Citations); Ovid EMBASE y EBSCO CINAHL. También se realizaron búsquedas de estudios en curso en registros de ensayos clínicos. No hubo ninguna restricción en cuanto al idioma, la fecha de publicación o el ámbito de los estudios.
Criterios de selección
Se consideraron los ensayos controlados aleatorios (ECA) que evaluaran el uso de cualquier tipo de drenaje en la cirugía arterial del miembro inferior.
Obtención y análisis de los datos
Dos autores, de forma independiente, determinaron la elegibilidad de los estudios, extrajeron los datos y realizaron una evaluación del sesgo. Se hizo un esfuerzo para contactar con los autores para obtener los datos faltantes. Los métodos y los resultados de cada estudio elegible se resumieron y programaron para agrupar los datos en los metanálisis cuando se consideraron apropiados, sobre la base de la homogeneidad clínica y estadística.
Resultados principales
Se identificaron tres ensayos elegibles que incluyeron a un total de 222 participantes con 333 heridas inguinales. El drenaje por succión se comparó con ningún drenaje en todos los estudios. Dos estudios eran ensayos controlados aleatorios, de grupos paralelos, y uno fue un ensayo controlado aleatorio de cuerpo dividido. No se describieron con claridad los ámbitos de los ensayos. Se incluyeron los pacientes sometidos a procedimientos de derivación y endarterectomía, pero ninguno de los estudios aportó detalles sobre la gravedad de la enfermedad arterial subyacente.
Se consideraron todos los estudios que presentaban un alto riesgo de sesgo en tres o más dominios de la evaluación del "Riesgo de sesgo" y, en general, las pruebas fueron de muy baja calidad. Dos de cada tres estudios tuvieron una unidad de los errores de análisis (con heridas múltiples en los mismos pacientes analizadas como independientes) y no fue posible evaluar la pertinencia del análisis del tercero. El metanálisis no fue apropiado, en primer lugar debido a la heterogeneidad clínica, y en segundo lugar porque no fue posible hacer ajustes para los errores de análisis en los ensayos individuales. Un ensayo aportó datos sobre las infecciones del sitio quirúrgico (ISQ; el resultado primario de la revisión): no hubo diferencias clara entre las heridas con drenaje y las heridas sin drenaje para las ISQ (cociente de riesgos 1,33; intervalo de confianza del 95%: 0,30 a 5,94; 50 participantes con heridas inguinales bilaterales; pruebas de muy baja calidad). No fue posible evaluar ningún otro resultado de este ensayo. Los resultados de los otros dos estudios son poco fiables debido a los errores de análisis y a omisiones informantes.
Conclusiones de los autores
Los datos sobre los cuales basar la práctica en esta área son limitados y propensos a sesgos. Continúa la incertidumbre con respecto a los posibles daños y beneficios asociados con la administración de los drenajes de heridas en la cirugía arterial del miembro inferior por el reducido número de estudios y los defectos en el diseño y la realización. Se necesitan pruebas de calidad más alta para informar la toma de decisiones clínicas. Hasta lo que se sabe, no existe ningún ensayo activo sobre este tema.
PICO
Resumen en términos sencillos
Drenajes para la cirugía arterial de la pierna
Pregunta de la revisión
Un drenaje quirúrgico es una sonda utilizada para extraer sangre, pus u otros líquidos de una herida. Se examinaron las pruebas acerca de si la inserción de drenajes de heridas después de la cirugía arterial de la pierna dio lugar a menos complicaciones en comparación con la no colocación de drenajes.
Antecedentes
Los pacientes con obstrucciones severas de las arterias de las piernas a menudo necesitan tratamiento de las mismas. Estas obstrucciones pueden ser tratadas con una cirugía, y existen varios tipos diferentes de intervenciones. La derivación arterial es una operación en que se elude la obstrucción utilizando un trozo de vena o un tubo sintético para que la sangre puede circular alrededor de la obstrucción. Una endarterectomía es una operación en que el cirujano elimina el material graso que está causando la obstrucción; de este modo, mejora el flujo de sangre. A veces después de la cirugía arterial de la pierna, los cirujanos colocan tubos de drenaje en las heridas. Se piensa que estos drenajes pueden ayudar a reducir la infección, prevenir la acumulación de sangre u otros líquidos en la herida y evitar otras complicaciones después de la intervención. No están probados estos beneficios, y nadie puede asegurar que los drenajes sean verdaderamente útiles. Es posible que los drenajes pudieran causar daño al permitir la infección en una herida, provocar el sangrado y prolongar el tiempo de estancia en el hospital. Se desconoce si los cirujanos deben usar los drenajes en todas las heridas todo el tiempo, o sólo en los casos en que piensan que se necesita un drenaje.
Características de los estudios
En junio de 2016, se buscaron ensayos controlados aleatorios (ECA) que incluyeran el uso de drenajes después de la cirugía arterial de la pierna. Se identificaron tres ensayos elegibles con 333 heridas en 222 pacientes, principalmente ancianos mayores de 65 años, que habían sido sometidos a cirugía arterial de la pierna. Se incluyeron pacientes hombres y mujeres, y todas las heridas se localizaban en la zona inguinal, como parte de las intervenciones de derivación y endarterectomía para mejorar el flujo sanguíneo.
Resultados clave
Los estudios incorporaron a un número reducido de pacientes y no se describieron claramente. Los tres estudios tenían graves defectos de diseño y realización. Los resultados de los estudios individuales no aportan información fidedigna debido a los defectos en el diseño de estudio. No está claro si los drenajes de la herida son beneficiosos o perjudiciales porque no se encontró información útil. Ninguno de los estudios aportó información sobre si los drenajes acortaron o prolongaron el número de días que los pacientes tuvieron que pasar en el hospital. Ninguno de los estudios aportó la información acerca de cómo los drenajes afectan la calidad de vida de los pacientes.
Calidad de la evidencia
En términos generales, se encontró que la calidad de las pruebas acerca de los efectos de los drenajes después de una cirugía en una arteria de la pierna fue muy baja, y no se pudo precisar si los drenajes tienen efectos beneficiosos o perjudiciales para los pacientes. Se necesita investigación de mejor calidad si los pacientes y los profesionales de la salud consideran que se trata de un tema importante.
Este resumen en términos sencillos se actualizó el 8 junio de 2016.
Authors' conclusions
Summary of findings
| Wound drainage compared with no drainage for lower limb arterial surgery | ||||||
| Patient or population: lower limb arterial surgery | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect | № of participants1 | Quality of the evidence | Comments | |
| Risk with no drainage | Risk with drainage | |||||
| Incidence of any surgical site infection | Study population | RR 1.33 | 50 | very low2 | ||
| 60 per 1000 | 80 per 1000 | |||||
| Incidence of wound dehiscence | No meaningful data were available | |||||
| Incidence of reoperation for wound or graft‐related complications | No meaningful data were available | |||||
| Changes in health‐related quality of life | Not reported | |||||
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1The unit of randomisation and analysis was the wound 2Downgraded one level due to a limitations in design and implementation (methodological flaws and lack of clarity) and two levels due to serious imprecision (small sample size). | ||||||
Background
Description of the condition
Peripheral arterial occlusive disease (PAOD), also known as peripheral vascular disease (PVD), refers to narrowing or blockage of the blood vessels that bring blood from the heart to distant parts of the body. PVD can occur in any blood vessel, but it most commonly affects the lower limbs. The blood supply to the leg may be restricted due to partial blockages caused by the presence of an embolus (a substance formed from either a blood clot, air, fat or tumour tissue that is carried by the bloodstream) or a thrombus (blood clot attached to the wall of the artery), or by a condition known as atherosclerosis. In atherosclerosis an abnormal mass of fat, fibrous tissue and inflammatory cells (atheroma) within the artery combines with narrowing and hardening of the vessels (arteriosclerosis) to restrict blood flow. Blood flow blockages due to emboli or thrombi tend to be sudden in onset, whereas those blockages caused by atherosclerosis tend to occur gradually. PVD is usually caused by atherosclerosis, although rare causes also exist. These rare causes include blockages caused by recurrent small emboli or arteritis (inflammation of the artery). People with PVD present with signs and symptoms that vary according to the severity of the arterial blockage and the subsequent reduction in arterial blood supply (ischaemia). Symptoms range from none, to intermittent claudication (leg pain when walking that is relieved by rest), to pain at rest, ulceration (development of open wounds) or gangrene (tissue death). Data from the National Health and Nutrition Examination Survey in the USA, reported the prevalence of PVD in the general population as being 12% to 14%, with prevalence increasing to 20% in those over 75 years of age. Amongst those affected, 70% to 80% are asymptomatic, and only a minority require revascularisation (a surgical procedure to restore blood supply) (Ostchega 2007; Selvin 2007; Shammas 2007). The incidence of symptomatic PVD increases with age, from about 3 per 1000 per year for men aged 40 to 55 years, to about 10 per 1000 per year for men aged over 75 years (Shammas 2007).
Lower limb arterial surgery is performed to restore blood flow to legs that are affected by acute or chronic ischaemia when non‐operative treatment has been unsuccessful (Grace 1996). Surgical procedures to restore blood supply to the leg involve removing or bypassing the blockage. A thrombus or embolus can be removed by a thrombectomy or embolectomy procedure. If the blockage is caused by the slow build up of atheroma to a critical level, an endarterectomy may be performed. This is an operation in which a short deposit of atheroma is removed, thus improving blood flow. If removing the blockage is not a suitable option, the blockage may be bypassed using a graft. Grafts can be made of synthetic material or can be autologous (i.e. a portion of the patient's own vein). In some cases peripheral angioplasty ‐ a technique in which narrowed or obstructed arteries are widened mechanically ‐ is used in conjunction with surgical treatment. In this procedure, a collapsed balloon, known as a balloon catheter, is passed with X‐ray guidance into the artery along a guide wire to the site of the obstruction. The balloon is inflated to open up the blood vessel for improved flow, then the balloon is deflated and withdrawn (Grace 1996). Arterial surgical procedures are often complicated by infections, groin haematomas (localised collection of blood outside blood vessels, within the tissue), lymphoceles (collection of lymphatic fluid that can result from damage to lymph vessels during surgery), or seromas (a pocket of clear serous fluid that develops after surgery) (Karthikesalingam 2008; Youssef 2005). Any of these complications can cause failure of the operation, and therefore they should be avoided if possible (Karthikesalingam 2008; Youssef 2005).
Description of the intervention
Drains remove blood, lymph, serum and other fluids that can accumulate in the wound bed after an operation. If allowed to collect, these fluids can form haematomas, seromas and lymphoceles that can put pressure on the surgical site and adjacent organs, vessels, and nerves. This increased pressure can cause additional pain and reduce the delivery of blood to the micro vessels (reducing perfusion) which may impair healing. Accumulated fluid may also increase the risk of infection. The practice of placing drains routinely to safeguard against complications in surgical wound management following lower limb arterial surgery remains widespread (Grobmyer 2002). Some units employ a selective policy of using drains if there have been concerns over haemostasis (stopping bleeding) intraoperatively, while others use drains routinely (Karthikesalingam 2008). Drains can rely on pressure and gravity to help drainage (passive drainage), or can be helped by a suction mechanism (active drainage). Fluids can be removed from a wound using either open or closed systems. An open drain depends on gravity to remove fluid from a wound site into a wound dressing placed over the end of the drain; examples include corrugated, Penrose and Yeates drains. A closed drainage system consists of a tube left in the wound that drains fluids from the body into a closed container. Closed drains may be assisted by suction or a vacuum, as in the Redon or Jackson‐Pratt drains. The type of drain that a surgeon chooses to use in a given operation depends upon the location of the operative site and the amount of fluid drainage expected. In certain procedures the use of drains has been shown to be of no benefit, and it has been suggested they may cause harm to the patient (for instance providing a portal for invasion by bacteria) (Barie 2002). Open drains may be associated with an increased risk of infection because they provide a portal for bacteria and the potential for drained fluid to come into contact with the incision site. Debate regarding the use of drains following lower limb arterial surgery is ongoing and this review aims to clarify the benefits and harms of this intervention in this group of patients.
How the intervention might work
The potential benefits of drainage are many, and include prevention of fluid accumulation, reduction of infection and earlier identification of bleeding (Youssef 2005). Conversely, drains may actually cause infection and may prolong hospital stay (Karthikesalingam 2008).
Why it is important to do this review
Although use of wound drains appears logical, some studies in various different types of surgery, suggest that routine drainage is not beneficial to patients (Charoenkwan 2014; Clifton 2008; Diener 2011; Gurusamy 2007a; Gurusamy 2007b; Gurusamy 2013a; Gurusamy 2013b; Hellums 2007; Karliczek 2006; Parker 2007; Samraj 2007; Wang 2015; Zhang 2011). It is unclear whether routine placement of surgical drains is of benefit in lower limb arterial surgery. Currently, there are no formal guidelines for usage of drains following arterial surgery. A systematic review on this topic was published in 2008 (Karthikesalingam 2008), and concluded there was no clear evidence that closed‐suction drainage reduced complications following lower limb revascularisation. The review included data from just four small trials which, combined with an absence of information on data extraction and validity assessment, limited the reliability of the findings. Our Cochrane review aimed to provide a definitive appraisal of the evidence on drainage in lower limb arterial surgery. We aimed to provide vascular surgeons with robust data, from a thorough evaluation of the literature, upon which to base their drain‐usage policy. In addition we hoped that this review might provide policy makers with the evidence to support or limit this practice.
Objectives
To determine whether routine placement of wound drains after lower limb arterial surgery results in fewer complications compared with not using drains.
Methods
Criteria for considering studies for this review
Types of studies
We considered randomized controlled trials (RCTs) that evaluated the use of any type of drain in lower limb arterial surgery. Cross‐over trials were deemed ineligible due to the short‐term nature of the intervention under investigation. Quasi‐randomised controlled trials were also ineligible. Cluster trials were eligible for inclusion and, if encountered, we planned to undertake a sensitivity analysis to evaluate the effect of the cluster trial(s) on the final results. A study follow‐up period of one year or less was applied for the purpose of the review to allow for the reporting of longer‐term outcomes such as reoperation.
Types of participants
We considered trials that recruited people undergoing elective or emergency lower limb arterial surgery (bypass with synthetic or autologous graft; endarterectomy with or without angioplasty; embolectomy; thrombectomy) eligible for inclusion.
Types of interventions
We aimed to compare the effects of placement of any surgical drain following lower limb arterial surgery with routine closure and no surgical drain. We planned to include trials that compared different types of drains (e.g. closed versus open drains; suction versus non‐suction drains) as separate subgroups within the review. There was no restriction regarding the location of wounds.
Types of outcome measures
Primary outcomes
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Incidence of any surgical site infection (superficial or deep, or both); incidence of all types of surgical site infection (if type not specified). Surgical site infection: as defined by the Centers for Disease Prevention and Control (CDC) (Mangram 1999), is an infection that occurs within 30 days after surgery in the part of the body where the surgery took place. Surgical site infections can be superficial, involving the skin only, or they can be deep, involving tissues under the skin, organs, or implanted material (Mangram 1999).
Secondary outcomes
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Incidence of wound dehiscence: defined as rupture of the wound suture line after surgery.
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Incidence of fluid collections: defined as a collection of either serous or lymphatic fluid within the tissue (seroma and lymphocoele respectively).
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Incidence of haematoma formation: defined as a localised collection of blood outside the blood vessels, within the tissue.
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Incidence of graft occlusion: defined as a blockage of the bypass graft that limits blood flow.
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Incidence of reoperation for wound or graft‐related complications.
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Length of hospital stay.
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Change in health‐related quality of life between pre‐operative baseline and within 30 days post‐operatively. Data generated using validated generic instruments (e.g. EQ‐5D, SF‐36, SF‐12 or SF‐6D) or validated wound‐specific instruments would have been used.
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Mortality (all cause).
Definitions of outcome in individual eligible studies were extracted from study reports and included in the review.
Search methods for identification of studies
Electronic searches
The following electronic databases were searched to identify reports of relevant randomized clinical trials:
• The Cochrane Wounds Specialised Register (8 June 2016);
• The Cochrane Central Register of Controlled Trials (CENTRAL; the Cochrane Library, 2016 Issue 6);
• Ovid MEDLINE (1946 to 8 June 2016);
• Ovid MEDLINE (In‐Process & Other Non‐Indexed Citations; 8 June 2016);
• Ovid EMBASE (1974 to 8 June 2016);
• EBSCO CINAHL (1982 to 8 June 2016).
Our search strategies are outlined in Appendix 1. Firstly, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) and then we adapted this strategy to search Ovid MEDLINE, Ovid EMBASE and EBSCO CINAHL (Appendix 1). We combined the Ovid MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomized trials in MEDLINE: sensitivity‐ and precision‐maximising version (2008 revision) (Lefebvre 2011).We combined the EMBASE search with the Ovid EMBASE filter developed by the UK Cochrane Centre (Lefebvre 2011). We combined the CINAHL search with the trial filter developed by the Scottish Intercollegiate Guidelines Network (SIGN 2015). We did not restrict studies with respect to language or date of publication or study setting.
We also searched the following online clinical trial registries on 11 June 2016:
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ClinicalTrials.gov (www.clinicaltrials.gov);
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The EU Clinical Trials Register (www.clinicaltrialsregister.eu);
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Current Controlled Trials Register (www.controlled‐trials.com);
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The World Health Organization International Trial Registry Platform (www.who.int/ictrp/en).
A detailed description of our search of online clinical trial registries can be found in Appendix 1.
Searching other resources
We attempted to contact trialists to obtain unpublished data and information as required. We also searched the reference lists of other systematic reviews and the reference lists of included trial reports.
Data collection and analysis
Selection of studies
Independently, two review authors (DH and MCM) assessed the titles and abstracts of papers retrieved by the searches and reviewed their relevance. After this initial assessment, we obtained full texts of those trials thought to be potentially relevant. Independently, two review authors (DH and MCM) checked the full papers for eligibility, with disagreements resolved by discussion and, where required, referral to a third author (SRW). We recorded our reasons for exclusions.
Data extraction and management
Independently, two review authors (DH and MCM) extracted and summarised details of the eligible trials and entered the details into a review‐specific spreadsheet template, after which both data extractions were compared for agreement. We resolved disagreements by discussion. We attempted to contact trial authors to obtain potentially relevant missing data. We included trials published as duplicate reports (parallel publications) once, using all associated trial reports to extract the maximum amount of trial information, but ensuring that the trial data were not duplicated in the review. We extracted the following information in addition to the specific outcomes already listed.
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Trial authors
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Year of publication
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Country in which trial was undertaken
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Setting of care
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Participant characteristics (selection criteria and baseline characteristics)
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Trial design (e.g. pragmatic RCT, cluster RCT)
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Overall sample size and methods used to estimate statistical power
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Unit of investigation
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Number of participants allocated per group
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Intervention regimens and comparators (characteristics of drains used, duration of drainage, co‐interventions such as antibiotics)
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Outcomes (assessment methods and data per group)
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Withdrawal (numbers per group and reasons)
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Risk of bias criteria.
Assessment of risk of bias in included studies
Independently, two review authors (DH and MCM) applied the Cochrane tool for assessing risk of bias to each included study (Higgins 2011). This tool addresses six specific domains: sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting, and other issues. The criteria used to define levels of bias as high risk, low risk or unclear risk of bias are detailed in Appendix 2.
We used a 'Risk of bias’ summary figure to present our assessment of risk of bias. This presents all of the judgements in a cross‐tabulation of trials. This display of internal validity indicates the weight the reader may give the results of each trial.
Measures of treatment effect
For dichotomous variables, we planned to calculate risk ratios (RR) with 95% confidence intervals (CI). For continuous variables, we planned to calculate the mean difference (MD) with 95% CIs.
Unit of analysis issues
Lower limb revascularisation procedures often result in clustered data with multiple wounds per patient. At the time of writing our protocol, we thought that some trials might use the number of wounds as the group denominator, rather than the number of participants randomized into the group. A possible unit of analysis issue arises if individual participants with multiple wounds are randomized, the allocated treatment used on the multiple wounds per participant (or on a subset of participants) and then the results presented by wound and not person. Where studies contained some or all clustered data, we reported this alongside whether the data had been incorrectly analyzed as independent. We recorded this as part of the 'Risk of bias' assessment under the incomplete outcome data subheading. We also recorded when the wound was used as the unit of randomisation and allocation, and whether the correct paired analysis had been carried out in participants with multiple wounds. We prespecified that our main analysis would be limited to trials that reported outcomes using participants rather than wounds as the unit of analysis. We did not plan to undertake further calculation to adjust for clustering.
Dealing with missing data
We contacted primary trial authors to obtain relevant missing data. Where missing data remained unavailable, we used information that was available from the trial report (i.e. complete case data).
Assessment of heterogeneity
We planned to consider clinical and statistical heterogeneity. Statistical pooling was only considered for groups of RCTs with similar participant, intervention and outcome characteristics in order to minimise the effect of clinical heterogeneity on meta‐analyses. We planned to use the Chi2 test (P value < 0.1) and I2 and H2 values with 95% confidence intervals to test for the presence of significant statistical heterogeneity between effect sizes of included studies. We planned to interpret the I2 statistic values as follows:
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0% to 40%: might not be important;
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30% to 60%: might represent moderate heterogeneity;
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50% to 90%: might represent substantial heterogeneity;
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75% to 100%: represents considerable heterogeneity.
Where there was evidence of substantial or considerable statistical heterogeneity, we planned to explore the reasons for this.
Assessment of reporting biases
We planned to construct funnel plots to estimate publication bias if at least ten studies could be included in a meta‐analysis.
Data synthesis
We provide a narrative overview of all included RCTs, with results grouped according to the type of drain used (open or closed) and the comparator characteristics. We considered clinical and statistical heterogeneity and we planned to pool data only when trials were similar.
We planned to compare any drain versus no drain for the main analysis and we planned comparisons between different types of drains as secondary analyses. We planned to use random‐effects models rather than fixed‐effect because fixed‐effect under‐perform in the presence of any heterogeneity and random‐effects models are more conservative (Brockwell 2001). We planned to present results with 95% confidence intervals (CI). Estimates for dichotomous outcomes (e.g. wound infection ‐ yes or no) were to be reported as a pooled risk ratio (RR) (Deeks 2011), and we planned to present continuous data (e.g. length of hospital stay) as pooled mean difference (MD). We planned to use the standardised mean difference (SMD) for pooling continuous data when RCTs used a variety of instruments to assess a common underlying concept (e.g. change in health‐related quality of life).
'Summary of findings' tables
We planned to include a 'Summary of findings' table, presenting key information relating to the quality of evidence, the size of the effects of the interventions examined, the sum of the available data for the main outcomes (Schünemann 2011a) and a grading of the quality of evidence using the GRADE assessment (Grading of Recommendations Assessment, Development and Evaluation) approach (Schünemann 2011b). The GRADE approach defines the strength of a body of evidence as the extent to which one can be confident that an estimate of effect or association is close to the true value. GRADE involves consideration of within‐trial risk of bias (methodological quality), directness of evidence, heterogeneity, precision of effect estimates and risk of publication bias (Schünemann 2011b). We planned to present the following outcomes in our 'Summary of findings’ table:
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wound infection;
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wound dehiscence;
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reoperation for wound or graft‐related complications;
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changes in health‐related quality of life.
Subgroup analysis and investigation of heterogeneity
We planned to undertake a subgroup analysis evaluating the effect of drains specifically in revision surgery (surgery requiring reopening of a healed wound). We also planned a subgroup analysis to compare different types of drains.
Sensitivity analysis
Treatment effects may differ between cluster‐randomised and individual‐randomised trials. In some instances, large positive or negative treatment effects in cluster‐randomised trials may outweigh the results of individual‐randomised trials. To account for this, we planned to perform a sensitivity analysis to evaluate the impact of cluster trials on the pooled treatment effect estimates. We planned to conduct a further sensitivity analysis to include those studies that adhered to the strict CDC definition of wound infection within 30 days of surgery (Mangram 1999). We planned to undertake a third sensitivity analysis to evaluate the influence of the risk of bias on effect sizes; we planned to assess the influence of removing studies classed as being at high and unclear risk of bias from meta‐analyses. We planned to only include studies that were assessed as having a low risk of bias in all key domains. Clarification of the definitions in these contexts is provided in Appendix 2. As mentioned earlier, we specified that the main analysis would be limited to trials that used participants as the unit of analysis. We planned an additional sensitivity analysis that would include studies that used wounds as the unit of analysis.
Results
Description of studies
See: Characteristics of included studies.
Results of the search
The results of the search are summarised in the flow diagram (Figure 1).The search yielded 148 citations and one citation was found from other sources. We deemed 146 citations to be ineligible on the basis of examination of their titles and abstracts.
Study flow diagram.
We included three studies in this review (Dunlop 1990; Healy 1989; Youssef 2005). Some of the data relating to Youssef 2005 were also published in a conference abstract (Dawson 1994).
Included studies
Three randomized controlled trials were eligible for inclusion in this review, involving a total of 222 people with 333 wounds (Dunlop 1990; Healy 1989; Youssef 2005). All of the wounds were groin wounds for femoral artery access. Two studies were conducted in the UK (Dunlop 1990; Youssef 2005), and one was conducted in the USA (Healy 1989). One of the trials took place in two centres (Healy 1989), and the other two trials were probably single‐centre trials (Dunlop 1990; Youssef 2005), although this was not specified. The dates of conduct of all three trials were not specified. One trial used a split‐body design and included patients who underwent bilateral groin incisions with one of the wounds in each patient being randomly allocated to drainage and the other to non‐drainage (Healy 1989). The other two trials used parallel group designs (Dunlop 1990; Youssef 2005). Dunlop 1990 randomized wounds to drainage or non‐drainage and in cases of bilateral procedures only one wound was randomized and included. However, 127 wounds in 99 patients were finally included; thus some participants must have been included in the study more than once, although this was not explicitly stated in the report. Youssef 2005 also randomized wounds to drainage or non‐drainage, but in cases with bilateral groin incisions one of the groins was randomly allocated to drainage and the other to no drainage. Both men and women were included in the studies. Youssef 2005 involved patients with a median age of 72 years, while the drainage and non‐drainage groups of Dunlop 1990 had mean ages of 66 and 68 years respectively. The age profile of patients in Healy 1989 was not reported. Trial reports lacked details about other patient characteristics including comorbidities. None of the trials provided details on indications for surgery, or the severity of patients' arterial disease. The trials included bypass and endarterectomy operations and, in all three, drainage was achieved with closed suction systems only.
Excluded studies
There were no excluded studies.
Risk of bias in included studies
See Figure 2.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Allocation
No study provided details on how the random sequence was generated. One study, Youssef 2005, reported that sealed envelopes were used, but no details were provided on who had access to the envelopes, whether they were sequentially opened or whether they were opaque. The other two studies (Dunlop 1990; Healy 1989) did not provide sufficient detail to judge allocation concealment.
Blinding
Participants were not blinded in any of the studies. Healy 1989 did not provide details on who assessed outcomes or how outcomes were assessed, and there was no mention of blinded outcome assessment. Dunlop 1990 reported that outcomes were assessed by a blinded independent observer more than 48 hours postoperatively when drains would have been removed. Outcome assessors in Youssef 2005 were not blinded.
Incomplete outcome data
No study reported any attrition.
All studies were at high risk of bias due to unit of analysis issues. Healy 1989 used a split‐body design, but it was not clear whether an appropriate paired analysis was used. Dunlop 1990 randomized one wound in each patient, but some patients were included twice because 127 wounds were reported in 99 patients. The extra 28 wounds were likely to relate to revision procedures or further primary procedures. The statistical tests used did not account for repeated measurements of the same wound from the same patient. Youssef 2005 sometimes included two groin wounds simultaneously, with one groin receiving drainage and the other being a control, but a paired analysis was not used for this group. In these three different situations, outcomes from one wound in a particular patient would not be independent of outcomes in other wounds in the patient. There was no adjustment for this in the trial analyses.
Selective reporting
No protocols were available for evaluation; thus it is unclear whether outcomes were prespecified. Youssef 2005 did not describe the incidence of wound infections according to treatment allocation, although they collected data on wound infections. Dunlop 1990 did not report the incidence of wound infections, although incidence of wound erythema and discharge were reported, which suggests that the authors may have had data on infections. Healy 1989 was the only study deemed to be at low risk of reporting bias because all outcomes mentioned in the methods section were reported.
Other potential sources of bias
No study provided data regarding the numbers of revision procedures that were performed. This is a potential source of bias, as revision procedures are associated with worse outcomes.
Effects of interventions
See: Summary of findings for the main comparison
We prespecified that our main analysis would be limited to trials that reported outcomes using participants as the unit of investigation. It was not clear whether Healy 1989 used the appropriate paired analysis, but nonetheless the report yielded enough data to calculate risk ratios for individual outcomes at participant level using the technique described in Hirji 2011. No participant‐level data were available from Dunlop 1990 and Youssef 2005. Unfortunately, despite efforts to contact authors, it was not possible to obtain any additional data beyond what was published in the reports of the three trials.
We planned to undertake a sensitivity analysis involving trials that used wounds as the unit of investigation. Dunlop 1990 and Youssef 2005 yielded no meaningful data because they failed to adjust their analyses for the situations where participants had more than one wound, and we could not access data beyond the reports. In any case, we did not consider that we could pool outcome data from the trials because there were many reporting inadequacies, and we were not sure that studies were sufficiently similar. Even if the trials were comparable, complete data sets from each trial would have been needed to amend the errors in analysis that are highlighted above.
The remainder of this section presents the available data for each outcome in the review. The results from Dunlop 1990 and Youssef 2005 are unreliable, and Healy 1989 has major limitations, although it was still possible to generate a RR for one outcome from the Healy 1989 trial. It was not possible to perform our prespecified sensitivity analyses or secondary analyses.
Incidence of any surgical site infection
One trial provided data on the incidence of any surgical site infection in drained versus non‐drained wounds (Healy 1989). There was no clear difference in the incidence of infections (4/50 in drained wounds versus 3/50 in non‐drained wounds: RR 1.33 (95% CI 0.30 to 5.94) (analyzed using the technique described in Hirji 2011). Notably, the definition for what constituted a wound infection was not described in the trial report. Dunlop 1990 did not report explicitly on wound infection rates, rather, the trialists reported on numbers of wounds that developed erythema and discharge, which were 49/65 and 11/65, respectively, in the drainage group and 48/62 and 12/62, respectively, in the no drainage group. Finally, Youssef 2005 did not report on the incidence of wound infection according to treatment allocation.
GRADE assessment: very low quality evidence. We downgraded the evidence by one level due to limitations in design and implementation (methodological flaws and lack of clarity) and by two levels due to imprecision (sample size of 50 participants).
Incidence of wound dehiscence
Only one trial provided data on the incidence of wound dehiscence (Youssef 2005): 0/49 wounds in the drainage group and in 1/57 in the no‐drainage group dehisced. No meaningful analysis was possible due to the unit of analysis issues that we mentioned earlier. Data were unclearly reported regarding this outcome in Healy 1989, and not reported in Dunlop 1990.
GRADE assessment: no meaningful data were available.
Incidence of fluid collections
Healy 1989 and Dunlop 1990 provided data on the incidence of fluid collections. No collections were noted in Healy 1989, and therefore it was not possible to determine risk ratios. Dunlop 1990 reported that lymph cysts were found in 5/65 wounds in the drainage group versus 6/48 in the no drainage group. In this trial lymph cysts were diagnosed when a wound swelling was found from which clear fluid could be aspirated. Notably, Youssef 2005 reported that ultrasound‐detected fluid collections were found in 7/49 in the drainage group versus 14/57 in the no drainage group. However, the nature of these fluid collections was not evaluated, and in the trial report these collections were labelled as haematomas. Overall, no meaningful analysis was possible.
Incidence of haematoma formation
Two trials reported on the incidence of wound haematomas. Healy 1989 reported that no wound haematomas occurred in either treatment group (50 wounds in each group), and so it was not possible to determine risk ratios. Youssef 2005 reported that 7/49 wounds developed an ultrasound‐detected collection (which were labelled as haematomas) in the drainage group versus 14/57 in the no drainage group. Overall, no meaningful analysis was possible.
Incidence of graft occlusion
None of the trials provided data on graft occlusion rates according to the treatment groups.
Incidence of reoperation for wound or graft‐related complications
Two studies reported on the incidence of reoperation for wound or graft‐related complications. Healy 1989 reported that 2/50 grafts had to be removed due to infection in the drainage group and no grafts had to be removed in the no drainage group. It was not possible to calculate RR because one group had no events. Data on other types of reoperation were not reported. Youssef 2005 reported that one graft in the no drainage group became infected requiring revision surgery with subsequent amputation, and that no graft in the drainage group required reoperation. Overall, no meaningful analysis was possible.
GRADE assessment: no meaningful data were available.
Length of hospital stay
No trial provided data on length of hospital stay.
Change in health‐related quality of life
No trial provided data on change in health‐related quality of life.
Mortality
No trial provided data on mortality according to treatment allocation. Healy 1989 reported that one patient died after a graft infection in a drained wound but this was a split‐body trial.
Discussion
Summary of main results
This review includes three eligible trials involving 333 wounds in 222 patients. All of the wounds were groin incisions for femoral artery access as part of revascularisation procedures and the procedures comprised both bypasses and endarterectomies. None of the trials reported adequately on baseline characteristics of the patients or on the indications for surgery. All trials used closed suction drainage systems. Individual studies reported on surgical site infections, wound dehiscence, fluid collections, wound haematomas and incidence of reoperation for wound or graft‐related complications. Importantly, there were major errors in analysis in two of the studies (Dunlop 1990; Youssef 2005), and a lack of clarity about the analysis in the third study (Healy 1989): each study included some participants who had multiple wounds without describing analyses that would take this into account. Wound outcomes should not be considered independent when a single patient has multiple wounds. Unfortunately, we were not able to obtain any data beyond the three published reports and, as a result, we could not adjust for these errors in this review. Consequently, we found few meaningful data in the studies. We advise against making any interpretations from the individual study results.
All studies were considered to be of very low quality due to limitations in design and implementation, so, as GRADE puts it, "further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate".
Overall completeness and applicability of evidence
The chief factors that limit the completeness and applicability of evidence are limitations in design and implementation, and the indirectness of the studies. The trials had major methodological flaws, and wounds were the unit of analysis rather than participants. From the perspective of decision makers, it is much more desirable to have effect size estimates for patients rather than wounds.
We highlight that all of the studies focused on groin wounds and that no data were available on wounds in other parts of the leg. It is possible that wounds in other locations would have a reduced tendency to develop lymph leakage. A further concern is that none of the included studies provided data on patients' characteristics and the severity and nature of their arterial disease. A prespecified aim of our review was to evaluate the utility of drains specifically in revision procedures; no study provided data on outcomes following revision surgery. We also aimed to compare different types of drain (such as suction or non‐suction drains) but we found no such data.
Overall, we think that there is a lack of completeness and applicability of the evidence and that, therefore, it is not possible to make any generalisations based upon the studies contained in this review.
Quality of the evidence
We could only generate a risk ratio for one outcome (incidence of any surgical site infection) from one trial (Healy 1989). The GRADE assessment for this outcome determined that the quality of evidence was very low (downgraded for risk of bias and twice for imprecision). We could not assess inconsistency or publication bias due to insufficient number of studies. Risk of bias was denoted as unclear or high for most domains in the 'Risk of bias' assessment tool. This results from flawed or unclear methodology and reporting in the three trials. Despite efforts to contact authors, we found no additional information. Our bias assessment tables and Figure 2 outline our concerns regarding the methodology of the included trials.
Potential biases in the review process
Our search strategy was extensive, but nonetheless it is possible that potentially relevant studies were missed. We minimised bias in the review process by adhering to our strict predefined methodology. Independently, two authors determined study eligibility and extracted the data. Assessment of bias was also carried out independently and discrepancies were resolved by discussion.
Agreements and disagreements with other studies or reviews
One previous review has been performed on the topic (Karthikesalingam 2008). This review involved four studies, but the authors erroneously duplicated data from the cohort of patients in Youssef 2005 by including data that were obtained in abstract form (Dawson 1994). Their primary outcomes were wound infection, seroma/lymphocoele formation and haematoma formation, and they chose to pool all available data for each outcome, yielding no significant results. They concluded that drains were associated with no benefits and therefore should be not be used routinely. We found no meaningful data and therefore we disagree with that conclusion.
Study flow diagram.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
| Wound drainage compared with no drainage for lower limb arterial surgery | ||||||
| Patient or population: lower limb arterial surgery | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect | № of participants1 | Quality of the evidence | Comments | |
| Risk with no drainage | Risk with drainage | |||||
| Incidence of any surgical site infection | Study population | RR 1.33 | 50 | very low2 | ||
| 60 per 1000 | 80 per 1000 | |||||
| Incidence of wound dehiscence | No meaningful data were available | |||||
| Incidence of reoperation for wound or graft‐related complications | No meaningful data were available | |||||
| Changes in health‐related quality of life | Not reported | |||||
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1The unit of randomisation and analysis was the wound 2Downgraded one level due to a limitations in design and implementation (methodological flaws and lack of clarity) and two levels due to serious imprecision (small sample size). | ||||||
