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Terapia con presión negativa para heridas en las quemaduras de espesor parcial

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Resumen

Antecedentes

Una herida por quemadura es una lesión compleja y cambiante, con consecuencias locales y sistémicas. Los tratamientos de las quemaduras incluyen una variedad de apósitos, así como nuevas estrategias, como la terapia con presión negativa para heridas (TPNH), que mediante una fuerza de succión que drena el exceso de líquido de la quemadura, trata de promover el proceso de cicatrización de la herida y reducir la progresión de la misma.

Objetivos

Evaluar la efectividad de la TPNH en pacientes con quemaduras de espesor parcial.

Métodos de búsqueda

Se hicieron búsquedas en el Registro Especializado del Grupo Cochrane de Heridas (Cochrane Wounds Group) ( búsqueda 04 septiembre 2014); Registro Cochrane Central de Ensayos Controlados (Cochrane Central Register of Controlled Trials, CENTRAL) (la Cochrane Library 2014, número 8).

Criterios de selección

Todos los ensayos controlados aleatorizados (ECA) y ensayos clínicos controlados (ECC) que evaluaran la seguridad y la eficacia de la TPNH para las quemaduras de espesor parcial.

Obtención y análisis de los datos

Dos autores de la revisión, de forma independiente, utilizaron formularios estandarizados y extrajeron los datos. Se evaluó el riesgo de sesgo de cada ensayo y las diferencias se resolvieron mediante debate.

Resultados principales

Un ECA, que era un informe provisional, cumplió los criterios de inclusión. Se realizó una síntesis narrativa de los resultados, ya que la falta de datos y el informe deficiente impidió realizar un análisis estadístico formal. El riesgo de sesgo del ensayo fue alto.

Conclusiones de los autores

No se dispuso de evidencia suficiente para poder establecer conclusiones sobre el uso de la TPNH para el tratamiento de las heridas de quemaduras de espesor parcial.

PICO

Population
Intervention
Comparison
Outcome

El uso y la enseñanza del modelo PICO están muy extendidos en el ámbito de la atención sanitaria basada en la evidencia para formular preguntas y estrategias de búsqueda y para caracterizar estudios o metanálisis clínicos. PICO son las siglas en inglés de cuatro posibles componentes de una pregunta de investigación: paciente, población o problema; intervención; comparación; desenlace (outcome).

Para saber más sobre el uso del modelo PICO, puede consultar el Manual Cochrane.

Resumen en términos sencillos

Terapia con presión negativa para heridas (TPNH) para el tratamiento de quemaduras de espesor parcial

La terapia con presión negativa para heridas (TPNH) es la aplicación de presión negativa (vacío) en una herida con el objetivo de tratarla y promover la cicatrización. Los nombres alternativos para la TPNH incluyen terapia de presión negativa tópica (TPNT), cierre asistido por vacío (VAC) y succión cerrada de heridas superficiales. En el caso de las quemaduras, la TPNH se utiliza para ayudar a drenar el exceso de líquido y aumentar el flujo sanguíneo localizado. Se ha indicado que la acción de la TPNH puede dar lugar a que la quemadura reciba un mayor suministro de oxígeno y nutrición que podría promover la cicatrización. Sólo se ha podido identificar un ensayo clínico que trató de analizar si la TPNH es eficaz para tratar las quemaduras de espesor parcial, y sus resultados aún no se han publicado completamente. Por consiguiente, no se dispone de evidencia de ensayos y no se ha podido determinar si la TPNH es eficaz para el tratamiento de las quemaduras de espesor parcial. Hay que investigar mucho más en esta área para determinar si la TPNH es útil.

Authors' conclusions

Implications for practice

No data from completed RCTs on NPWT for partial‐thickness burn injury are available, which means that conclusions cannot be drawn on the merits ‐ or otherwise ‐ of this treatment.

Implications for research

This systematic review highlights the need for good quality research into the safety and effectiveness of NPWT in partial‐thickness burns. Suggestions adapted from Ubbink 2008 indicate that future research needs include:

  1. Well‐designed, adequately‐powered, multi‐centred RCTs to evaluate the contribution of NPWT in the treatment of partial thickness burns.

  2. RCTs of NPWT in which the comparison intervention represents current standard practice for partial‐thickness burns based on the best available evidence.

  3. RCTs to evaluate the effects of NPWT on healing times, cost, quality of life, pain and comfort, and to determine whether there is an optimum NPWT regime for partial‐thickness burns.

  4. Economic evaluations to determine whether the costs of NPWT justify its potential benefits in those with burn injury.

Background

Description of the condition

Burn injuries are a considerable source of morbidity and mortality. Every year in the USA alone, approximately two million people are burned, up to 80,000 are hospitalised as a result of burns and more than 6500 people die from their injuries (Brigham 1996). A skin burn is defined as damage to the skin caused by heat or caustic chemicals. Heat causes the most immediate and obvious injury. Excessive heat causes rapid protein denaturation and cell damage, and thus initiates a complex and evolving injury, with both local and systemic (whole body) consequences ‐ the latter manifesting once the burn area is greater than 20% of the body surface area (BSA) (Sheridan 2002).

Locally, the burn wound tends to extend during the acute (first) phase of the injury as a result of microvascular changes, profound activation of white cells and platelets, and the development of oedema (build up of fluid). Many small vessels are coagulated by the application of heat, while others will thrombose (block) later and develop tissue dehydration (Boykin 1980). The systemic response to burning is characterised by interstitial oedema in distant organs, i.e. the swelling of any organ or tissue due to accumulation of excess lymph fluid (between cells), and is secondary to a combination of wound‐released mediators and hypoproteinaemia (abnormally small amounts of protein in the circulating blood plasma) (Demling 1979; Youn 1992).

Burn wounds are often classified by depth: superficial (first‐degree burn), partial‐thickness (second‐degree burn) or full‐thickness (third‐degree burn). Often, the depth of injury is diagnosed by the anatomic thickness of the skin involved (i.e. the epidermis (outermost thin layer), stratum corneum (outer layer) and the dermis (deepest layer)) and based on either clinical observation, or objective assessment, or both. Clinical evaluation often relies on features of the burn wound's appearance, such as blanching, capillary return, presence and degree of fixed capillary staining, and evaluation of retained light touch and pinprick sensation. Objective assessment tools such as laser doppler flowmetry, laser doppler imaging or indocyanine green video angiography, may be used to measure blood flow into the tissue and, therefore, depth of burn injury (Demling 2005).

First‐degree, or superficial, burns are confined exclusively to the epidermis or outer surface of the skin, and generally are not significant injuries, as they heal rapidly and spontaneously. Second‐degree, or partial‐thickness, burns involve varying amounts of the dermis. These may become deeper, and heal with variable amounts of scarring, the degree of which depends partly on the depth of the burn.

The superficial partial‐thickness burn is a sub‐category of partial‐thickness burns. This type of burn extends through the epidermis into the papillary (superficial) layer of the dermis. These wounds become erythematous, i.e. the skin reddens because the dermal tissue has become inflamed. One hallmark of the superficial partial‐thickness burn is blanching followed by rapid capillary refill when pressure is applied to the reddened area and subsequently released (Demling 2005; Johnson 2003). Thin‐walled, fluid‐filled blisters develop within minutes of the injury. As these blisters break, the exposed nerve endings transmit superficial pain, light touch and temperature, making these wounds extremely painful. The wound is moist because the characteristic waterproofing of the epidermis has been lost, allowing body fluid to leak onto the wound surface. Also, moderate oedema is usually present, due to the involvement of the dermal blood vessels in this type of injury (Demling 2005; Johnson 2003).

Deep partial‐thickness burns extend downward into the reticular (deeper) layer of the dermis and present as mixed red or waxy white. Areas of redness will continue to blanch when pressure is applied, but capillary refill may be absent, or sluggish, when pressure is released. Blisters are usually absent; however, the exposed surface of the wound is wet or moist, in a similar way to superficial partial‐thickness burns. Oedema is marked, and sensation is altered in areas of a deep partial‐thickness burn (Demling 2005; Johnson 2003).

Description of the intervention

Since the biology of wound healing has become better understood, many strategies have been developed to try to manipulate this wound healing process (Banwell 1999), and to minimise the progression of burn wounds by involving deeper tissue in the acute phase. These strategies range from use of a variety of skin substitutes and dressings, such as polyurethane films and hydrocolloids (Wasiak 2005), to the use of more complex and experimental techniques, such as hyperbaric oxygen therapy (Villanueva 2004), application of growth factors and cytokine biology (Atiyeh 2005). One way of manipulating the wound environment with a view to promoting healing is to apply negative pressure wound therapy (NPWT) across the wound surface via a dressing (Ubbink 2008). There are a number of terms to describe the treatment of a wound with NPWT including: subatmospheric pressure, vacuum‐sealing technique, sealed surface wound suction, vacuum assisted closure (VAC), negative pressure therapy or dressing, foam suction dressing, vacuum compression, vacuum pack technique, negative pressure dressing and foam suction dressing (Banwell 2004a). For the purposes of this review, all variations of this intervention will be referred to as NPWT. In NPWT a dressing is applied to a burn and a negative pressure (vacuum) applied though it, with tissue fluid being collected into a canister. NPWT was developed in the 1990s, and its uptake by the healthcare systems of developed countries has been dramatic. A US Department of Health report estimated that Medicare payments for NPWT pumps and associated equipment increased between 2001 and 2007 from USD 24 million to USD 164 million (an increase of almost 600%) (Department of Health and Human Services 2009).

How the intervention might work

Negative pressure is purported to induce an interstitial gradient shift which can cause a reduction in oedema, and a secondary increase in dermal perfusion, thus aiding in the removal of blood or serous fluid (Banwell 2004a). It is also postulated that the ability of NPWT to produce a mechanical stress or force that has a direct effect in cellular activity, and, in particular, the development of new blood vessels, may also contribute to a decrease in burn wound progression. The maintenance of a moist environment that provides optimal conditions for epithelialisation and the prevention of tissue desiccation is also potentially advantageous (Banwell 1999; Banwell 2004a; Pham 2003).

Why it is important to do this review

NPWT is an expensive, yet widely used, health technology. The US Food and Drug Administration approved the use of at least one NPWT system for use on partial‐thickness burns in 2003, and subsequently its use in burn wound management has been described by a number of clinicians (Kamolz 2004; Moisidis 2004; Schrank 2004). Yet it is unclear what evidence of the effectiveness of NPWT for treatment of partial‐thickness burns is available to guide both clinical and policy decision making. We plan to summarise the evidence to determine whether NPWT is safe, effective and beneficial to those patients with partial‐thickness burns.

Objectives

To compare the effects of NPWT with standard care or other adjuvant therapies in the healing of partial‐thickness burns in adults.

Methods

Criteria for considering studies for this review

Types of studies

We included all randomised controlled trials (RCTs) and controlled clinical trials (CCTs) that evaluated the effectiveness of NPWT for partial‐thickness burns, irrespective of publication status or language.

Types of participants

We included studies recruiting adults aged 18 years, or over, with a partial‐thickness burn, the severity of which could be determined either by clinical evaluation or objective assessment, or both. Clinical evaluation relied on burn wound appearance, blanching, capillary return, presence and degree of fixed capillary staining and evaluation of retained light touch and pinprick sensation. Objective assessment involved the measurement of tissue perfusion by methods such as laser doppler flowmetry, laser doppler imaging or indocyanine green video angiography.

Types of interventions

Studies were eligible if they compared NPWT with standard burn wound therapies in the treatment of partial‐thickness burns. Studies involving any mode of delivery of NPWT were eligible, including commercially available devices (such as VAC Pump, KCI Texas, USA), wall suction or surgical drainage bottles, as well as negative pressure cycles that vary in degree, application (including continuous and/or intermittent pressure cycles) and duration.

Types of outcome measures

Studies were eligible for inclusion if they reported any of the following outcome measures:

Primary outcomes

  • time to complete healing;

  • rate of change in wound area;

  • proportion of wound completely healed within the trial period.

Secondary outcomes

  • incidence of wound infection;

  • adverse events;

  • measures of satisfaction or patient preference;

  • quality of life.

Search methods for identification of studies

Electronic searches

The search methods section of the third update of this review can be found in Appendix 1

For the fourth update we conducted a streamlined search:

  • The Cochrane Wounds Group Specialised Register, comprising references identified from comprehensive electronic database searches, handsearches of relevant journals and abstract books of conference proceedings (searched 04 September 2014);

  • The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 8)

The following search strategy was used in The Cochrane Central Register of Controlled Trials (CENTRAL):
#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 ("vacuum assisted closure technique" or VAC):ti,ab,kw
#12 (#1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11)
#13 MeSH descriptor Burns explode all trees
#14 (burn or burns or burned):ti,ab,kw
#15 (#13 OR #14)
#16(#12 AND #15)

The search strategies for Ovid MEDLINE, Ovid EMBASE and Ovid CINAHL can be found in Appendix 2, Appendix 3 and Appendix 4, respectively. The Ovid MEDLINE search was combined with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity‐ and precision‐maximizing version (2008 revision); Ovid format (Lefebvre 2011). The EMBASE and CINAHL searches were combined with the trial filters developed by the Scottish Intercollegiate Guidelines Network (SIGN) (SIGN 2012). We did not apply language restrictions.

Searching other resources

For the original review we contacted authors of relevant studies to request details of unpublished or ongoing investigations and checked citations of retrieved studies for further trials. This process was not repeated for the updates. No new studies were identified for this update, so there were no additional reference lists to check.

Data collection and analysis

Selection of studies

Two review authors independently scanned records retrieved by the searches to exclude obviously irrelevant studies, and to identify trials that met the inclusion criteria. They retrieved, and independently reviewed, full text articles for the purpose of applying inclusion criteria. In all instances, differences of opinion were resolved by discussion.

Data extraction and management

The review authors extracted data independently from the studies using standardised forms. Data extracted included country of origin, health care setting, study design, baseline characteristics of participants by treatment group, inclusion and exclusion criteria, details of intervention and comparison, outcome measures and results. When missing or incomplete data were encountered, we contacted study authors with a request for information. All differences of opinion were resolved by discussion among the review authors.

Assessment of risk of bias in included studies

We undertook a quality assessment considering the adequacy of the randomisation and allocation concealment process, whether intention to treat (ITT) analysis was performed, the level of blinding and whether the follow‐up was complete. For this update the Cochrane Collaboration tool for assessing risk of bias was applied to included studies (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 5 for the criteria on which risk of bias judgements were made). A risk of bias table was completed for the eligible study. The review authors independently assessed the studies and any disagreements were resolved by discussion.

Assessment of heterogeneity

We planned to consider both clinical and statistical heterogeneity. Wherever appropriate, we planned to pool data using meta‐analysis (conducted using RevMan 5.1 (RevMan 2011)), that is where studies appeared similar in terms of wound type, intervention type, duration and outcome type. We planned to assess statistical heterogeneity using the chi² test (a significance level of P less than 0.1 was considered to indicate heterogeneity) and the I² estimate (Higgins 2003). The I² estimate examines the percentage of total variation across studies due to heterogeneity rather than to chance. Values of I² over 50 per cent indicate a high level of heterogeneity. In the absence of clinical heterogeneity and in the presence of statistical heterogeneity (I² over 50 per cent), we anticipated using a random‐effects model, however, we would not pool studies when heterogeneity was very high (I² over 75 per cent). Where there was no clinical or statistical heterogeneity we envisaged using a fixed‐effect model.

Data synthesis

Where possible, we planned to present the outcome results for each trial with 95% confidence intervals (CI). We planned to report estimates for dichotomous outcomes (e.g. burns healed during a particular time period) as risk ratios (RR). We decided to use the RR rather than odds ratio (OR), since ORs (when interpreted as RR) can give an inflated impression of the effect size when event rates are high, as is the case for many trials reporting healing (Deeks 2002). We planned to report outcomes relating to continuous data (e.g. percentage change in ulcer area) as mean differences (MD) and overall effect size (with 95% CI). Where a study reported time‐to‐healing data (the probability of healing over a consecutive time period) we planned to report and plot these data (where possible) using hazard ratio estimates. If studies reported time‐to‐event data (e.g. time to healing), did not report hazard ratios, or reported these data incorrectly as a continuous variable, then, where feasible, we planned to estimate this using other reported outcomes, such as the numbers of events, through the application of available statistical methods (Tierney 2007).

Where statistical data synthesis was not possible we planned to present a narrative synthesis.

Results

Description of studies

The searches for this fourth review retrieved seven references, none of which met the inclusion criteria for this review. We did not obtain any citations as full text. The searches for the third review update retrieved 27 references, none of which met the inclusion criteria.

The original searches for this review identified 60 references, of these 10 potentially relevant articles obtained as full text, with nine being excluded because they were either case reports, case series or narrative reviews (Adamkova 2005; Banwell 2004b; Haslik 2004; Moisidis 2004; Molnar 2004b; Nugent 2005; Schintler 2005), or did not address primary outcome measures (Kamolz 2004; Schrank 2004) (see Characteristics of excluded studies). We did not find additional studies when we examined citations of retrieved studies.

One study was included which formed the basis of this review (Molnar 2004a) ‐ this is a conference abstract reporting interim data. At the time of the original review we contacted the authors of this abstract, who stated that the abstract results were preliminary data that would be publishable in the foreseeable future (personal communication), as well as providing further details of the study population. In 2014, the author was contacted again, but, as yet, no further information has been received.

The included abstract (Molnar 2004a) reported that participants with bilateral thermal hand burns (treated for less than 24 hours post injury) had one hand randomised to receive NPWT (125 mmHg pressure) applied for 48 hours, whilst the other hand was treated with silver sulphadiazine (SSD). The study used a commercially available device (VAC Pump, KCI Inc, Texas, United States) to apply the negative pressure. All participants served as their own control. The trial reported outcome data at day 30 of a 60‐day study period. Outcome measures assessed were reported as: rate of burn healing by use of a Sigma Scan (Systat Software Inc, California, United States), volume of hand as determined by fluid displacement, range of motion, grip and pinch strength. The abstract did not clearly state how many people had been randomised, but reported that it presented results for the first 23 participants. Additional information supplied via personal communication with the author noted that the mean age of these 23 participants was 46 years and the total burn surface area (TBSA) ranged from five per cent to 40 per cent, with mean TBSA at 16 per cent.

Risk of bias in included studies

A full study report has not been identified, therefore the risk of bias assessment for Molnar 2004a was based on the conference abstract alone (see Characteristics of included studies). The study is described as "prospective, randomised, controlled, blinded, multi‐center and web‐based", however, the exact method of sequence generation was not specified in the abstract, and allocation concealment was also not reported. Due to the nature of NPWT, it is unlikely that the patients or treatment provider could have been blinded to the intervention. Molnar 2004a reported that, at strategic time points, a blinded principal investigator was used to determine the area of the burns to determine their rate of healing (personal communication with the author). Since the study was an interim report, judging risk of bias for 'incomplete outcome data' was not possible; no attrition was reported at this point in the trial. Burn wound progression and hand function were pre‐specified as outcomes in the abstract, both of which were reported (see risk of bias Figure 1).


Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Effects of interventions

Due to missing data, poor reporting or both, a formal statistical analysis was not possible. A series of outcome measures such as the reduction in hand oedema, the volume of fluid displaced, and grip and pinch strength were reported by Molnar 2004a, although these were not considered by our review. As a result we focused on the following outcome measures:

Primary outcomes

Time to complete healing

No data were reported for this outcome.

Rate of change in wound area

Molnar 2004a reported a significant difference in burn size at day three (P < 0.09) and day five (P < 0.04), but not at day 14. From the abstract it is not clear which group was favoured in the day 3 and 5 analysis. No data were presented beyond P values.

Proportion of wounds completely healed within the trial period

No data were reported for this outcome.

Secondary outcomes

Incidence of wound infection

No data were reported for this outcome.

Adverse events

Molnar 2004a reported that there were no discernable complications with NPWT treatment of the acute burns.

Measures of satisfaction or patient preference

No data were reported for this outcome.

Quality of life measures

No data were reported for this outcome.

Discussion

This systematic review summarises the best available evidence relating to safety and effectiveness of NPWT in adults with partial‐thickness burns. After an extensive search of the literature, only one RCT was found, which was an interim report judged to be at high risk of bias.

There is currently an absence of evidence regarding the use of NPWT for burn wounds, despite the theoretical considerations that may support the concept. Our results highlighted the need for high‐level, good‐quality research into the safety and effectiveness of NPWT in adults with partial‐thickness burns. The trial by Molnar 2004a was methodologically weak and poorly reported. There was no description of the randomisation process, and no mention of the degree of comparability of burn injury to both hands at baseline. Other weaknesses included: the absence of reporting on clinically relevant outcomes, such as rate of healing, time to complete healing, rate of change in wound area, and proportion of the wound completely healed within the trial period; lack of clarity regarding the definition and reduction of oedema formation; and the ongoing use of SSD as a comparator, as it is not only known to be toxic to regenerating epithelial cells (Wasiak 2005), but may place patients at increased risk of developing complications such as neutropenia (a lack of white blood cells), erythema multiforme (a rash usually resulting from a drug reaction), crystals in the urine and methaemoglobinaemia (oxidation of more than 1% of the haemoglobin in blood to the ferric state) (Subrahmanyam 1998).

The small sample size and preliminary analysis of only 23 patients precludes the drawing of any conclusions regarding the nature or frequency of adverse events.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Figuras y tablas -
Figure 1

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.