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Historically, ambulance services in the UK have been perceived as an emergency service, responding to 999 calls by stabilising the patients condition sufficiently so they can be rapidly transported to the nearest emergency department (ED) for definitive care. It's response to traumatic injuries, such as simple lacerations, had been little more than first aid. This involved basic assessment of the wound, applying pressure to stop bleeding and bandaging (Institute of Healthcare and Development 200?). With no provision for wound care management, including closure, patients requiring this would have needed to attend their local ED or minor injury unit (MIU). Depending on the seriousness of the wound, a patient could be transported by ambulance or advised to transport themselves.
Taking Healthcare to the patient by the Department of Health (DOH) identified that although 77% of emergency calls to the ambulance service result in a patient being transported to hospital, at least 50% (1 million patients) of these could have been treated at scene, at home or in the community (Department of Health 2005). Recent reforms have advised that more patients should be treated in the community and that there was a need for an increase to traditional paramedics' education and scope of practice in order to meet the demographic demands of 999 users (DOH 2005).
Several studies have demonstrated that between 25-40% of ED attendances are for conditions that could be managed in primary care. Such attendances have ultimately led to an increased workload for ED staff and compromise their capability of dealing with urgent and emergent cases. The emergency care practitioner (ECP) is a relatively new concept developed in response to these demands and needs, as an alternative to the traditional ambulance approach. ECP's are able to deliver high quality urgent care and treat more NHS patients with injury or illness within their own homes. With the advent of the ECP role, many simple wounds / lacerations are suitable for treatment and closure in the pre-hospital setting (Snooks et al ).
As an ECP, employed by an ambulance service, part of my role is to 'see and treat' patients presenting with minor wounds, thus avoiding unnecessary transport to the ED. This not only affords the patient the most appropriate and timely care but also helps to take the burden off already overstretched EDs. Pre-hospital management of wounds involves primary closure. This is the bringing together of wound edges with sutures, adhesive strips, tissue adhesive or staples and is associated with wounds which are clean of debris (Eliya & Banda 2011). Whilst there is no definitive 'cut off time' from injury to closure, it is generally accepted that the longer the time interval the higher the risk of wound infection. This time interval has long been the topic of debate and highly variable, with time periods ranging from 3-24 hours.
The ambulance service I am employed by has a blanket, 6 hour time of injury to wound closure cut off. Any wounds presenting outside this timescale must be evaluated in the ED (Appendix 1). Contrary to this directive, anecdotally, I have been advised by other healthcare professionals that they have used primary closure on wounds up to 12 hours old. Indeed, from personal experience, when I have checked on patient's I have transported to the ED because they fell outside the 6 hour window, I have found they have had no 'special' treatment and their wounds have been simply cleaned and closed.
There are often instances when patients present outside of this 6 hour window. This can be for a combination of factors for example; patients may initially care for their wounds themselves thinking that they do not require any specialist care or elderly patients may fall and sustain lacerations before being found several hours later. Perhaps the biggest impact on the ability of ambulance services to provide home wound care is, that despite the inception of the ECP programme being less than 10 years, at the time of studying this dissertation some ambulance services have already scrapped their ECP service and my ambulance service has seen a reduction in ECP numbers with no active recruitment. Ambulance services are still predominantly judged and funded solely on their ability to respond to 75% of life threatening call within 8 minutes. Whilst funding has been ploughed in to meet the 20% of patients that fall within the 8 minute response time it has been cut to the urgent care service that ECPs provide to the 80% of 999 users with non-life threatening or even non-urgent clinical conditions (Woollard et al 2010). From personal experience, the reduction from a 24/7 to a more sporadic ECP service has meant delays in attending patient's presenting with simple wounds, pushing them closer towards or over the 6 hour injury to closure window. This combination of factors has led me to question this blanket, 6 hour closure time. Could, for example, an elderly patient with a head laceration, attended by an ambulance at midnight, stay at home and await wound closure from an ECP that starts their day shift at 07:00?
This paper will take the form of a critical literature review. This research will not consider traumatic wounds caused by animal or human bites and will concentrate on simple lacerations without underltying tendon, bone or visceral damage as these are outside the scope of ECP practice. The aim of this paper is to answer the following research question: Are wounds closed by primary repair, after 6 hours in the pre-hospital setting, at increased risk of infection?
The objectives of this research are:
To explore the factors which influence the timing of wound closure in the pre-hospital setting.
To determine risk factors associated with primary wound closure outside the 6 hour window.
Acute traumatic wounds are a common reason why people go to the ED or MIU. During the year 2010-11, there were 625,144 ED and MIU attendances in England for lacerations. This accounted for 6.5% of total attendances (NHS 2012). Whilst there are no figures available for ambulance service attendances to patients presenting with traumatic wounds, a recent paper revealed that in a six month period, ECPs in a large metropolitan ambulance service attended 1555 calls for laceration / haemorrhage (Mason et al 2009). Traumatic wounds can range from relatively minor lacerations to those with widespread tissue damage and even amputation. The extent to which the tissue is damaged depends on the mechanism of injury and the object causing the injury. Complicated lacerations involving fractures, tendon damage, nerve or arterial injuries are treated in the operating theatre (Capella and Hollander 2003). For this reason they are outside the remit of the ECP and unsuitable for home closure.
The ECP's aim in wound care is to attain a functional closure with minimum scarring which is achieved primarily by preventing wound infection (Wedmore 2005). These priorities were echoed in a report by Singer et al (2000), who advise that according to patients, what was most important to them are optimal cosmetic effect, least painful repair, restoring function and avoiding infection. As with any traumatic injury, resuscitative and stabilising measures need to be undertaken before wounds can be assessed and treated (Caroline 2010). Simplistically, wound closure involves cleaning the wound and re-approximating the wound edges until natural healing occurs.
There are several ways to achieve wound closure and clinical skill is required in deciding which is the most appropriate way for the wound to heal (Hollander 1999). Primary wound closure, known as healing by first intention represents closure of a wound at the time of initial presentation. Wound edges are opposed and the wound closed with sutures, adhesive strips, tissue adhesive or staples. It is associated with faster healing, better cosmetic effect and reduced patient discomfort when compared with secondary closure. Healing by secondary intention involves leaving the wound open with healing occurring by the formation of granulation tissue from the bottom of the wound. Wounds managed by delayed primary closure are classified as healing by tertiary or third intention. This closure method is most often used when there is considerable bacterial contamination or delayed presentation. The wound is left open and observed until there is no evidence of inflammation or infection after which the wound edges are opposed. Risk of infection and tissue loss are higher during the days that the wound is left open (Hess 2002)
Surgical wounds can be classified as clean, clean contaminated, contaminated and dirty (Berard and Gandon 1964). Acute traumatic wounds, in comparison to surgical incisions, are by their very nature already exposed to infective agents and the time delay between injury and treatment is longer so are classified as contaminated or dirty (Forsch 2008). This classification system, however, does not state what time span constitutes 'fresh' or 'old' traumatic wounds. All wounds that present to the ED, and therefore the ECP in the pre-hospital field, are potentially contaminated with bacteria. There is, however, credible evidence to suggest that traumatic wound infections are caused by organisms secondary within the hospital or patient's home and not by initial contamination (Harley 2002). Multiple surgical and wound studies have demonstrated that wounds contaminated with more than 105 per gram of bacteria tissue are a high risk of infection. The result of this can be delayed wound healing (Lorenz 2008).
The optimum timing for primary wound closure has long been the topic of debate, with recommendations from surgeons ranging from closure within half an hour of wounding to leaving the wound open to heal by secondary intention (Hepburn 1919). Traditionally it has been taught that there is a 'golden period' within which lacerations can be closed primarily. Baar et al (2010) suggest that the idea of a golden period was derived by Paul Leopold Friedrich in 1898. In this study of guinea-pigs, the skin was lacerated in the tricep region and then contaminated with house dust and mud. With an interval of 30 minutes the wounds were cleaned. The results showed that all the guinea-pigs with wound cleaning up to 6 hours survived and all the guinea-pigs with wound cleaning after 8.5 hours died. Wedmore (2005), however, suggests that this golden period is derived from work by Robson et al (1973) who showed that 3-5 hours after tissue became burned, bacteria proliferated to a level that was associated with infection. Most authors since have established that there is a relationship between time of injury to wound closure and the risk of infection without providing credible evidence to support this. Clinical textbooks have cited time scales of up to 24 hours, depending on contamination and anatomical location, but there is little agreement on the cut-off time that constitutes the golden period (WHO 2010, Trott 1997, Purcell 2003). Douglas Lindsey author of Simple surgical emergencies, cited by Zethahala et al (2012) is highly critical of the notion of a golden period stating that it 'must have been passed on, like herpes and hepatitis by close oral contact, for it is hard to find in current texts'.
Due to my direct involvement with patients presenting with wounds on a daily basis and due to impact the reduction in ECP numbers is having on my ability to treat them within the stipulated 6 hour window, this topic is of particular interest to me. Home closure of wounds can be particularly beneficial for children, the elderly, disabled and cognitively impaired when a journey to the ED may be logistically difficult and distressing (O'Donnell et al 2002). To treat patients in the community without the need for ED attendance is the ethos at the core of my work and it is for this reason I wish to study the timing of primary wound closure. Through this literature review I aim to provide the reader with a clear rationale and a logical argument in answering the research question: Are wounds closed by primary repair, after 6 hours in the pre-hospital setting, at increased risk of infection?
This account of the methodology aims to provide the reader with clear and concise information regarding how and why the literature was attained and reviewed. This dissertation will be produced through the use of a literature review. It will attempt to inform and guide the reader toward a new perspective on the subject of the timing of primary wound closure in the pre-hospital setting and the risk of infection. Its aim is to methodically study, review and interpret the current knowledge and evidence around this subject.
There has been a dramatic increase in the volume of health and social care literature over the last few decades. This increased volume has meant that healthcare professionals are often unable to keep up to date with all the publications in their field of practice and are often presented with conflicting research results. This rapid accumulation of information has made it difficult to ensure clinical practice is based on dependable sources of research. Literature reviews seek to accumulate past research, summarise major issues and disseminate the information acquired by all past research efforts of a particular discipline (Evans & Kowanko 2000).
A literature review is an appropriate methodology for this dissertation as it will build on the work of others (Terryberry 2005). By acknowledging published research and literature a greater insight on a topic can be achieved and can point to an area of future study. It will not produce new evidence but integrate the current knowledge into a concise secondary document. By reviewing the evidence against current practice gaps in knowledge may be identified which may be addressed. From a pragmatic point of view, due to personal, financial and ethical constraints undertaking primary data collection would simply not be possible. This review may, however, propose further primary research in its findings.
Many health care decisions are now being made on the basis of reviews rather than primary research; therefore, they must be undertaken with the same rigour as the original primary research. There is always a potential for bias whenever literature is collected appraised and synthesised. The literature review could be used to promote the opinions and ideas of the reviewer by only including research that is of a particular point of view. The reviewer must remain impartial and objective throughout the process in order to achieve the maximum rigour and validity.
French et al (2001), describe the literature review as having three main steps, the first two being, the search for relevant literature and critical appraisal. Only once these two elements have been successfully undertaken can the third step, the synthesis of findings take place.
There are a broad range of electronic databases available which may be used to obtain information for research. The accessibility of these databases, and their relevance to the search strategy and discipline being researched need to identified as the initial step Aveyard (2007). MEDLINE and EMBASE for example, provide a broad range of literature in many health care areas but do not record all the publications from all medical journals. The Cochrane library deals specifically with systematic reviews and randomised controlled trials (RCT), whereas CINAHL references a much wider range of publications and non-research publications. Choosing which databases will give the most information rich results can be an onerous one, which is best undertaken with the expert help of an academic librarian.
Internet searching can also be a useful means of retrieving grey literature, such as unpublished papers, reports and conference abstracts. Identifying and scanning specific relevant websites will usually be more practical than using a general search engine such as 'Google' (Centre for reviews and dissemination 2009). In addition to databases and search engines journals are a good source of information and can provide more up to date information than other sources (Parahoo 1997). Other strategies include browsing the library, speaking with experts in the particular field of interest and hand searching through journals.
The search strategy requires the identification of the terms that best describe the most important ideas and concepts for the review. Alternatives for these words such as abbreviations, related terms and synonyms should also be used to ensure and inclusive search (Leach et al 2009). When searching electronically, using Boolean operators AND/OR/NOT/NEAR can be used to expand or reduce or exclude. Variations in language and country specific terms also need to be taken into account (Crookes & Davies 1998)
The inclusion and exclusion criteria should be clearly defined prior to starting the literature search to reduce the risk of bias being introduced by the researcher during the selection process (Evans 2000). Rather than focusing on the results of studies, selection should be based on population, intervention, outcomes and research method. The inclusion criteria should capture all studies of interest. If the criteria are too narrowly defined there is a risk of missing potentially relevant studies and the generalisability of the results may be reduced. On the other hand, if the criteria are too broad the review may contain information which is hard to compare and synthesise. Inclusion criteria also need to be practical to apply; if they are too detailed, screening may become overly complicated and time consuming. (Horwitz 1995).
Greenhalgh (1997) suggests that each type of research can be assigned into a hierarchy of evidence. This is based on the credibility of the research design and confidence in the results. This can help a researcher to make a decision about the type and level of evidence a literature search has generated. The order of this hierarchy is:
Systematic reviews and meta-analyses
Randomised controlled trials with definitive results
Randomised controlled trials with non-definitive results
Cross sectional surveys
Such hierarchies have been criticised as allowing RCTs too much authority. Not all research questions can be answered through RCTs, either because of practical issues or because of ethical issues It must be remembered that no one piece of research is deemed to be perfect, even systematic reviews have their flaws and low grade evidence can have value (Saks & Allsop 2007).
With the advent of evidence based healthcare, there is a need to make a judgement about the quality of research obtained and its usefulness within the study (Humphries 1999). Evidence based care is the: "Conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients". (Sackett et al 1996, p1). Most clinical opinions and treatments should be critically assessed to be evidence based and this is now fundamental to the quality standards in the NHS (Martin and Meek 1999).
Critical appraisal is an objective critique and structured approach of examining a piece of research in order to decide its validity and identify flaws, potential bias, strengths and weaknesses (Aveyard 2007). Critical appraisal is at the core of the literature review as it assesses the scientific quality of a paper, including methodology, methods, analysis, discussion and recommendations (Leach 2005). In order to evaluate the literature Critical appraisal means being able to look at a piece of research in objective and structured way in order to decide on its validity when compared to other research.
To aid the process of critical appraisal it is recommended that a critical appraisal tool is used as a guide to evaluate the literature and thus developing a consistent approach to the critique (MacCauley et al 1998). This can ensure that all papers are reviewed systematically and with equal rigour. Although it has been identified that there are 121 critical appraisal tools available via the internet and electronic database there is no gold standard for any individual study design Katrak et al 2004). Critical Appraisal Skill Programme (CASP) framework has been identified as being particularly useful for undergraduate students as it does not have a generic format but provides a tool for most of the studies that are likely to be encountered. CASP asks 10 questions which the reviewer needs to consider in order to critically analyse each paper.
Any research must consider the implication of ethics. A literature review being a secondary study, does not require direct contact with any individuals, however, there are ethical aspects that have to be considered during the process. It is necessary to critique the ethical aspects of the published studies being reviewed to ensure they were conducted in an ethical manner. Informed consent should not be presumed in secondary analysis, given that it is usually not feasible to seek additional consent, a professional judgement may have to be made about whether re-use of the data breaches the contract made between subjects and the primary researchers (Hinds et al 1997). Heaton (1998) and Thorne (1998) advise that such judgements need to be based on whether the new questions posed by secondary research shift the focus of the initial intention of the primary research.
This chapter will explain how data for this study were searched, selected for inclusion and critically appraised.
In order to locate evidence relating to the research question a comprehensive search was undertaken to elicit pertinent studies. To ensure that a wide range of articles were found, four databases were searched: CINAHL, MEDLINE, PuBMED and Cochrane. The literature search used the following terms 'traumatic wound* OR laceration* AND 'age OR time' AND 'infection' (Appendix B).
All citations were initially examined on screen to identify potentially relevant papers. Those papers thought to be relevant or possibly relevant were retrieved in full and compared with the inclusion / exclusion criteria. The authors of these papers and their reference lists were then separately searched upon to help identify other relevant articles that may not have been found in the wider search. The Emergency Medicine Journal and the Journal of Paramedic Practice were searched separately as these are the most information rich source for pre-hospital and emergency care. Checking for abstracts from conferences and meetings, contacting authors or experts in wounds care was not undertaken due to time and financial constraints.
Inclusion / exclusion criteria
Initially, the time frame for inclusion, was research no older than 20 years, however, it quickly became apparent that the majority of research relating to the 'golden period' of wound closure is significantly older than that. The inclusion time frame was, therefore, changed to include this 'seminal' work and extend to 1980. No geographical restrictions were applied. There was no ethnographic exclusion to this study, to reflect the multi-cultural diversity of the United Kingdom no ethnographic parameters were placed on this study. Studies that included complicated lacerations involving fractures, tendon damage, nerve or arterial injuries that required repairs and those that required extensive debridement, were already infected or heavily contaminated were excluded from this research. Such wounds are beyond the scope of the ECP and require specialist treatment.
Criteria for including and excluding studies for this review:
Children and adults of all ages
Primary and secondary research directly related to the timing of primary wound closure
English language or already translated papers
Published literature only
By using a systematic methodology a thorough search of the literature has been carried out. The literature was compared to the hierarchy of evidence to determine the quality of the research and then appraised using a critical appraisal tool. In order to evaluate the literature to be reviewed the CASP appraisal system was used against each piece of research. This appraisal tool was chosen as it is a system I am familiar with and have used throughout my university studies. The next chapter will discuss and explore the results of this search strategy.
The search strategy yielded 400 papers which were reduced to 6, once reviewed and inclusion/ exclusion criteria had been applied. A Cochrane review by Eliya & Banda (2011) initially looked promising: a systematic review looking at the primary closure versus delayed closure for non-bite traumatic wounds with 24 hours post injury. As their inclusion criteria were for RCTs only and none have been undertaken their research was not concluded. Several papers, Rutherford et al (1980) Alkan et al (1984), were found that looked in to infection after wound closure in the ED, however, time to closure was not a parameter that was measured so these were excluded.
Of the six papers identified five were prospective observational studies and one was a RCT. In the RCT by Morgan et al (1980) randomization was based on what type of antibiotic the patient received for infection prophylaxis rather than wound age, time to closure was measured for analysis. For this reason the paper by Morgan et al (1980) was considered an observational study for this dissertation, as recommended by ?. I did not find any literature on the timing of primary wound closure in the pre-hospital setting. This was unsurprising as it is recognised that ambulance service research is in its infancy compared to other disciplines (Siriwardena et al 2009). There was research literature in to the role of the ECP, but none pertaining to specific interventions such as wound closure. The studies identified all had ED, MIU or equivalent setting. As it is the intervention i.e. wound closure rather than the setting that was important for this dissertation it was felt that these were appropriate for inclusion. The critiques of these articles can be seen in table format in Appendix C.
Given the frequency that traumatic wounds occur and present themselves to EDs and the ambulance service, the question of timing in primary wound closure has been researched very little and there is a significant dearth of literature on this topic. The literature that was selected for this study it very much divided into research from the 1980s and early 1990's and research that has been carried out over the last five years. There is little consensus of opinion and significant heterogeneity among the studies. Due to this diversity, in depth statistical analysis was unable to be carried out. The main results, however, will be reported, critiqued and analysed. A mind map was used to map the main themes that emerged (Appendix c).
Time to closure
An often cited study, by Berk et al (1988), explored the question of whether a simple wound presenting for care later than 12 to 24 hours after injury could be closed safely. This was a third world study in an ED in Jamaica. They identified that a 'golden period' did exist and that wounds on any 'body locale' could be safely closed by primary intention up to 19 hours and wounds on the head had no cut off time. There was a relatively small sample of 372 cases. Although the results initially looked impressive and were backed up with effective data analysis the study suffered from a 45% attrition rate. Interestingly, 132 of the 204 patients that were followed up had a wound to closure time in excess of 12 hours. On initial review this appears to be a particularly high ratio when compared to other studies, however, wound closure was carried out by a 'wound officer' who worked daily, but only between the hours of 16:00 and 22:00. This may account for the high number of patients delaying presentation and also the author's interest in researching safe primary closure after 12 hours. Despite the noted flaws, the American College of Emergency Physicians (ACEP) specifically references Berks et al (1988) in its clinical policy for penetrating injury of the extremity (ACEP 1999).
An earlier study by Morgan et al (1980) considered the delayed treatment of wounds of the hand and forearm under antibiotic cover. This study of 300 patients presenting to an ED in Scotland only enrolled patients with distal upper extremity wounds and classified them as superficial or deep. The deep wounds required exploration in theatres so only the figures for the simple wounds that were closed in the ED will be used for this dissertation. Opposing the views of Berk et al (1988), they identified that simple wounds on the hand and forearm should be closed at the earliest opportunity. They looked at three closure windows 0-4 hours, 4-12 hours and >12 hours. The results showed an increasing risk of infection of 6%, 15%, and 32% respectively. This study, however, only had 19 patients in this delayed closure group which somewhat minimizes its impact. A very broad definition of wound infection which included evidence of inflammation to presence of pus and discharge was used may also have added to the sensitivity.
Contrary to Morgan et al (1980), research by Baker and Lunati (1990) did not find any difference in infection rate for lacerations closed before (1.2%) or after six hours (1.3%) from the time of injury regardless of location. They prospectively studied the management and outcome of 2,834 children aged between one month and 18 years who presented to a large children's hospital ED in Philadelphia for laceration repair. The data from this large study were collected over a one year period; however, there was no report on lost-to-follow up rate which detracts from its rigour. As the mean age of the patients was 6.4 years old, it would be difficult to generalise these results onto the adult population.
Van Den Baar (2010) sought to provide evidence against any dogma that wounds older than six hours of trauma should not be sutured. There were 425 patients included in this prospective cohort study. Patients' wounds were all closed, regardless of the time after the wound. All patients were seen in 7-10 days for removal of stitches and to observe for wound infection. Only 17 of these patients were lost to follow up. Of the 408 patients who were followed, 45 had wounds older than six hours after trauma. 91% of all patients had no infection. 36 patients had redness of the suture sites or a worse complication. Eleven patients (2.7%) had general redness or pus at the site of the wound. Of those with a wound older than six hours, 3 out of 45 (6.7%) had wounds that were infected, versus 30 of 363 (9.1%) in wounds occurring less than six hours before primary closure (P=0.59).
In a small study of 297 participants, Waseem et al (2012) suggest a bimodal time distribution in infection rates following laceration repair. This study was carried out in a ma
The most up to date, and comprehensive study by Quinn et al (2012) looked at 2663 patients with lacerations presenting to the ED of three participating hospitals. The aim of the study was to determine risk factors associated with infection and traumatic lacerations and to see if a relationship exists between infection and time to wound closure after injury. 27 specific patient, laceration and treatment variables were collected by the treating physician. The main conclusions were that there is no true 'golden period' of laceration repair and that there was no association between the time from injury to wound closure and the development of infection. Patients were followed for 30 days to determine the development of infection and desire for scar revision. Suffered a 32% loss to follow up.
The rates of wound infection in early versus late primary closure are presented in Table 1. As already mentioned, Morgan et al (1980) presented rates of infection in three subgroups. In order to make comparisons easier the first two groups were combined to present figures of wounds closed under 12 hours and those closed after 12 hours. The results from Waseem et al (2012) are not included in the table as they chose to study median times of laceration repair and did not employ or report a cut off time to measure against.
Given that there is not standard cut off time for the golden period across these studies.
Three of the papers studied the rate of wound infection before and after a specifically defined golden period. The studies of Morgan et al (198) and Baker & Lunati (1990) reported wound age as one of the variable but this was not the primary intention of the studies.
When referring back to the original research question are wounds closed after 6 hours at increased risk of infection
From Table 1 it can be seen that two most recent studies have an increased infection rate in the early primary closure versus late primary closure group. Initially the infection rates for Berk et al (1988) look quite high, however, when the results were interrogated further they reveal a 18.2% infection rate in wounds closed under 6 hours a rate of 6% for those wounds closed between 7-12 hours with no infections reported from 13-19 hours. Unlike the other studies primary wound closure was carried out on patients who presented up to 48 hours after injury which has skewed the over 12 hour infection rate to 20%.
What can be drawn from these results
It is difficult to compare Van Den Baar's research with those from the literature suggesting a maximum closing time of 19 hours, as the present study only included five patients with wounds seen after 19 hours. They concluded that they could not advocate a revised maximum time to closure
Two questions emerged from this initial analysis: What is an acceptable risk and how was wound infection diagnosed?
Whilst Quinn et al make a bold claim that the concept of a golden period not longer exists
What infection rate is acceptable?
The concept of risk is generally understood to refer to the combination of the probability and magnitude of some future harm. According to this understanding, risks are considered "high" or "low" depending on whether they are more (or less) likely to occur, and whether the harm is more (or less) serious. Hollander et al (1995) advised that the infection rate of lacerations treated in the ED is likely to be between 2% and 5%.
Why is there such a difference in results
Diagnosis of wound infection
Some of these differing rates may be explained by how infection was measured. On one end of the scale, because of the low incidence of infection in the cohort, Van den Baar et al (2010) decided to make their 'definition' of infection more sensitive by defining it as any sign of redness at the wound area. On the other extreme, Berk et al (1988) used dehiscence as their measure of infection. Dehiscence is the splitting open of a wound and is associated with wound infection but can also be caused by mechanical stress, haematoma and poor nutrition. Quinn et al (2012) only classified the wound as being infected if the patient was seen by a physician and subsequently treated with oral or intravenous antibiotics. Van den Baar et al (2010) was the only trial that independently validated the diagnosis of wound infection by one or more blinded assessors.
There is consensus in other areas and further themes emerged.
The most up to date paper found, by Quinn et al (2012),
Whilst the study by Berk et al (1988) showed increase risk
Extremity vs facial/scalp wounds
A clear pattern that emerged was that infection rates differ dependent on which anatomical regions are involved. In all the studies that enrolled head and neck wounds they were consistently and significantly less likely to become infected compared with the upper and lower extremities. Whilst this was recognised by both Berk et al (1988) and Baker and Lunati (1990) their studies did not include a significant amount of predictor variables to calculate if this was related to time of closure. Both Van den Baar et al (2010) who undertook a multivariate analysis, and Quinn et al (2012) identified a correlation between infection rate and wound location. They concluded, that not only are the lower extremities the most susceptible to infection with an infection rate of and 19.5% and 7.6% respectively, but that this risk factor is independent of time to closure time. Morgan et al (1980), however, is contradictory of this as they appear to directly relate location of injury to time since wounding, showing a progressive rate of infection as time to closure increases. Quinn et al (2012) are critical of the results of the Morgan et al (1980) citing comparatively high infection rates and their omission of decontamination methods as two reasons to question its validity. Whilst this study cannot simply be dismissed based on a hypothesis, it is accurate to say that advances in wound decontamination and the use of no touch aseptic technique have seen a reduction in infection over the last 20 years, so could have been a factor. These combined results imply that the highly perfused areas of the scalp and face are at lower risk of infection compared to the extremities, particularly the legs, which have an increased risk. Wounds to the lower extremities must be seen as a risk factor independent of any 'golden period' of wound closure.
It is well documented that the risk of wound infection is increased by any factor that debilitates the patient, impairs immune resistance or reduces tissue perfusion, Co--morbidities such as renal failure, cardiac conditions and diabetes mellitus, immunocompromised status, hypoxia/poor tissue. Despite this knowledge it was much understudied in these papers. Only two of the studies, Quinn et al (2012) and Waseem et al (2012) included underlying medical conditions in their studies. Van der Baar (2010) although aware of the possible effect it may have, did not undertake extensive analysis on co-morbidity as they thought that due to the large size of the cohort and the relatively young population it would have had little effect on the outcome. Quinn et al (2013) reported a 6.7% infection rate in patients with diabetes compared with 2.5% in patients without diabetes. Those who reported diabetes with complications had an infection rate of 33%.
The rates of wound infection in early
Van der Baar (2010) was the only study to take inital swabs
What is clear and a consensus of opinion in all the literature reviewed is that more research is needed into this area of pre-hospital care.
The major limitation and potential source of bias for all of the included trials was the study design was observational rather than RCT