Assessing a Safe Interval for Subsequent Negative Pressure Wound Therapy Change After Initial Placement in Acute, Contaminated Wounds

Background. Negative pressure wound therapy (NPWT) is empirically expanding across the globe. Yet published data with NPWT in acute, contaminated wounds is limited, and several concerns arise regarding contemporary acute wound care NPWT practice. Specifically, there are no evidence-based time intervals specifying when NPWT should be changed after initial placement in such cases; therefore, NPWT was studied in acute, contaminated wounds. Methods. The authors retrospectively reviewed 86 consecutive patients, and a total of 97 contaminated wounds. All wounds were class IV, based on Centers for Disease Control and Prevention (CDC) criteria. All patients were managed with NPWT. Patient and wound-specific variables were analyzed. Outcome endpoints included durability of wound closure and death. Results. Mean time of subsequent NPWT after initial placement was 2.9 days, median time 3 days, mode 2 days, and standard deviation (SD) 1.24 days. Durability of wound closure was 73/79 (92%). Deaths were noted in 6/86 (7%) of patients. No deaths appeared related to NPWT. Conclusions. Based on the findings in this study, analyzing NPWT in the largest known patient cohort of this type, a time interval of 1.7 days to 4.1 days (mean time 2.9 days, SD 1.24), between initial and subsequent placement of NPWT in acute, contaminated wounds is safe and effective.

Negative pressure wound therapy (NPWT) came into widespread clinical use in 1997 after the publication of a subatmospheric wound care technique.¹ Foam or gauze is placed into the wound, which is then covered by a plastic drape and the system set to suction via tubing. The subatmospheric wound care technique has US Food and Drug Administration (FDA) indications in “chronic, acute, traumatic, subacute and dehisced wounds, partial-thickness burns, ulcers (such as diabetic or pressure), flaps, and grafts.” The vacuum-assisted closure device (V.A.C., Kinetic Concepts, Inc, San Antonio, TX) is the most widely available commercial product, though at least 9 proprietary products exist worldwide.^2,3   Negative pressure wound therapy is in widespread use with more than 338 million vacuum-assisted therapy days reported worldwide during a 2-year period from 2009-2011, (oral communication, Steven Jackson, director of regulatory compliance, KCI, 7/1/2011), with availability in 25 countries as of 2012. These figures demonstrate an expanded clinical use of NPWT in acute wound care across the globe. This includes empiric applications of NPWT in contaminated wounds, of which there is currently limited published data.^4-14 Such contemporary empiric NPWT practice has involved treatment of wounds sustained in military conflicts, terrorist attacks, natural disasters, and developing countries.^15-17 In addition, the value of NPWT in helping to stabilize patients with acute, complex, and contaminated wounds for transport is undergoing formal evaluation by the United States military.⁷   Though there is limited published data on the use of NPWT in acute, contaminated wounds, contemporary writings specifically denote “monitoring closely,” stating such wounds “may require more frequent dressing changes.”¹⁸ These concerns appear to arise from a theoretic potential for sepsis with the use of NPWT in necrotic and/or infected wounds.¹⁹ Albeit rare, there are case reports detailing such occurrences,^6,17,20 yet published recommendations are scant and without reference relating to a defined time interval for subsequent NPWT changes after initial placement in acute, contaminated wounds.²¹ Therefore, the authors studied this paradigm to guide evidence-based practice.   In an effort to most accurately address the proposed question, the authors restricted the study to patients with acute, contaminated wounds. All wounds met class IV Centers for Disease Control and Prevention (CDC) criteria for contamination (ie, tissue necrosis and/or infection).²² Also, as the vast majority of patients in this cohort met sepsis criteria, this further defined the acuity of these wounds and corroborated the characteristics of the patient cohort being evaluated. The results of this study provide evidence-based guidance for a safe and efficacious time interval of subsequent NPWT change after initial placement in acute, contaminated wounds.

Patients were included in the study population if they had an acute wound diagnosed ≤ 24 hours prior to, or subsequent to, the time of hospital admission, and requiring surgical intervention. Wound etiologies were traumatic, infectious, or postsurgical. Presence of wound contamination was required (eg, tissue necrosis and/or infection). All wounds were Class IV based on US CDC criteria.²² “Open abdomen” wounds (ie, defects below the level of the midline fascia) were excluded.   Data were collected from one surgeon’s records at Christiana Care Health System, Newark, DE. This methodology limited variables in wound care management. Inpatient and outpatient records were reviewed.   Indications for surgery followed practice standards of care. History, physical examination, and laboratory and radiographic data were utilized in decision making. Evidence of or concern for tissue necrosis; presence of or concern for undrained and infected fluid not amenable or appropriate to lesser invasive approaches; and spreading/necrotizing soft tissue infection prompted surgical intervention.   Surgical care was provided in the operating room under general anesthesia or monitored anesthesia care. Intraoperative care involved sharp, blunt, and/or hydromechanical (Versajet, Smith and Nephew, St. Petersburg, FL) resection of all grossly necrotic tissue.   Complete evacuation of infected fluid was done. Intraoperative pulse irrigation (InterPulse Powered Lavage System, Stryker Medical, Portage, MI) was used in all cases except for one. Intraoperative cultures, (swab and/or tissue) were taken in cases where there was concern for deep space infection, spreading soft tissue infection, or resistant organisms.   Negative pressure wound therapy via the vacuum-assisted closure system was used in all wounds except the few cases where cross-covering physicians were involved (7/97 wounds). A gauze-based NPWT was applied in these select cases, with a vacuum-assisted closure system instituted, or wound closure done thereafter. All patients meeting clinical parameters of sepsis and/or with signs of wound infection were treated with antibiotics. Specialists in Infectious Disease were consulted in cases where resistant microbial organisms and/or osteomyelitis were identified.   The above wound care strategies were implemented in similar fashion in each case. Care was provided predominantly by a surgeon who was board-certified in General Surgery and Surgical Critical Care. Cross coverage was provided by a limited number of partnering surgeons.   Informed consent for surgery and the use of NPWT was obtained in all cases. Informed consent was obtained from patients or surrogates if the patient was unable to provide consent. The study design was reviewed and accepted by the Christiana Care Health System’s Institutional Review Board.

Wounds involving the extremities, defined as distal to the axilla or inguinal crease, were present in 41/97 (42%). Wounds involving the torso, head, and neck were present in 56/97 (58%). (Due to contiguity, 2 wounds involved a combination of extremity and torso locations). Tissue necrosis was present in 84/97 (87%) of wounds. Depth of necrosis was skin only in 0/84(0%) wounds; skin and subcutaneous tissue in 13/84 (15%) wounds; skin, subcutaneous tissue and fascia in 38/84 (45%) wounds; skin, subcutaneous tissue, fascia, and muscle in 21/84 (25%) wounds; and skin, subcutaneous tissue, fascia, muscle, and bone in 8/84 (10%) wounds. Necrosis within muscle only (myositis), was present in 3/84 (4%) wounds.   Traumatic amputations from an inciting event were involved in 5/41 (12%) wounds. Subsequent amputation due to irrecoverable tissue loss and/or infection occurred in 3/41 (7%) extremity wounds. Of these, 1/3 (33%) wounds did not have NPWT applied at initial presentation, but rather after the amputation was completed on hospital day 4; and in 2/3 (66%) wounds, future amputation was anticipated based on concurring opinions at the time of initial evaluation (pre-NPWT). Thus, precipitation of amputation from the use of NPWT seems unlikely. Refractory osteomyelitis was present in 1/41 (2%) wounds, but the patient declined a recommended amputation and was lost in follow-up. Loss of function of the lower extremity was noted in 1/41 (2%) wounds, and amputation was recommended, but the patient refused and was also lost in follow-up. Overall 10/41 (24%) of extremity wounds involved an amputation or advisement thereof.   Infection was present in 86/97 (89%) of the wounds. This was confirmed by wound purulence and/or cultures in 83/86 (97%). For the purposes of this study, cultures were considered relevant if obtained during the narrow time interval defined as ≤ 48 hours prior to, or ≤ 24 hours after the initial surgery and use of NPWT, rather than at any time in the patient’s hospitalization. In 2/86(2%) patients, clinical criteria for wound infection were present despite negative initial cultures. However, subsequent cultures were positive, corroborating initial clinical concern. In 1/86(1%), the patient did not have positive cultures, but improved with evacuation of an infected hematoma and the use of broad-spectrum systemic antibiotics.   Trauma was the etiology in 25/97 (26%) of wounds, infection in 69/97 (71%) of wounds,and decubiti in 3/97 (3%) of wounds. Of those related to a primary infectious cause, 6/69 (9%) wounds were postsurgical, 7/69 (10%) wounds were Fournier’s gangrene, and 8/69 (12%) wounds involved pyomyositis. An uncontrolled enteric fistula (present prior to the use of NPWT) was the etiology in 1/97 (1%) of the cases. Bowel perforations led to 4/97 (4%) wounds.   All wounds, 97/97 (100%), met CDC Class IV criteria due to the presence of contamination: infection and/or tissue necrosis.²² Classification of the type of contamination was infection in 86/97(89%) of wounds, with or without associated necrosis; and tissue necrosis in 11/97 (11%), without evidence of infection. All wounds with infection were treated with systemic antibiotics. All wounds with tissue necrosis required sharp/excisional debridement in the operating room.   Based on established international criteria, 78/86 (91%) of patients met SIRS/sepsis criteria: 4/86 (5%) of patients met SIRS criteria; 24/86 (28%) of patients met sepsis criteria; 19/86 (22%) of patients met severe sepsis criteria; and 31/86 (36%) patients met septic shock criteria.^23-25 The cause of SIRS/sepsis was due to the acute wound etiology (trauma or infection) in all cases.   The average surface area was 619 cm² where length and width was measured. The average wound volume was 786 cm³.   Negative pressure wound therapy. The timing of initial placement of the NPWT was at the first surgical intervention (T-0) in 81/97 (84%) wounds; at the second surgical intervention (T -1) in 9/97 (9%) wounds; at the third surgical intervention (T-2) in 6/97 (6%) wounds; and at the fourth surgical intervention (T-3) in 1/97 (1%) wounds. In cases where NPWT was placed other than (T-0), this was due to partnering physicians providing the initial surgical intervention and not electing to institute NPWT at that time. As these cases included wound contamination and/or infection on re-evaluation, they met inclusion criteria for this study. Timing of initial NPWT placement was then noted.   The vacuum-assisted polyurethane system was used in 96/97 (99%) wounds, and the polyvinyl sponge in 1/97 (1%) wounds. Polyvinyl sponges were used when there was exposed bowel. Gauze-type NPWT was used in 7/97 (7%) wounds (elected by partnering physicians at the time of their surgical intervention). In 6 of these cases, foam-based NPWT was used at the subsequent surgical intervention. The remaining patient had subsequent delayed primary closure.   Timing of NPWT dressing changes was determined based on current clinical standards combined with individual patient and wound assessments.^20,22,26 Due to the presence of tissue necrosis and/or infection in the initial stages of these cases, the NPWT system was changed more frequently during the early phases of wound care in this cohort. The average time to initial NPWT change postplacement was 2.9 days (Figure 1, Figure 2).   Purulence. Purulence was present in 62/97 (64%) wounds. This was noted as a separate wound parameter irrespective of any cultures that were taken. Purulence was defined by typical appearance, and recorded as present if there was at least enough volume to be collected by syringe.   Wound culture. Wounds were cultured if there was concern for infection based on clinical evaluation; hence, not all wounds were cultured (eg, traumatic wounds at initial intervention). In order to corroborate the acuity of these wounds, to clarify their feature at initial evaluation, and to standardize wound assessments, cultures were recorded at the initial time of surgery and at the placement of NPWT (time interval defined as cultures ≤ 48 hours prior to, or ≤ 24 hours after the initial surgery and use of NPWT). Cultures were positive in 62/69 (90%) wounds.   Type and timing of wound closure. Wounds were closed with delayed primary suturing, split thickness skin grafts, and/or secondary intention healing. The average time to closure was 17.1 days.   Wounds excluded from the time-to-closure calculation were as follows: 4/97 (4%) due to patient death prior to wound closure; 2/97 (2%) due to comorbidities delaying wound closure (eg, presence of malignancy and cerebrovascular accident); and 7/97 (7%) secondary intention “closures,” (ie, due to lack of accepted published criteria for defining wound “closure” in secondary intention healing).^3,26 Additional exclusions included 2/97 (2%) wounds lost in follow-up, and 1/97 (1%) wounds wherein the patient refused split-thickness skin graft.   Comorbidities. Patient comorbidities were recorded based on a physiologic systems approach. Comorbidities were defined as a system abnormality that predated the current hospital admission. Obesity, if present, was noted as well, and body mass index recorded.   Note, specific acute organ system abnormalities were not recorded in Table 1 (unless contributing to a patient’s death), as their presence was represented in the diagnosis of severe sepsis and/or septic shock.   Wound related complications. This was addressed via assessing the durability of wound closure. For the purposes of this study durability of wound closure was defined as either a delayed primary closure that required reopening or a partial take of a split thickness skin graft. Wound complications were present in 6/81 (8%) cases (Table 2).   Deaths. Patient deaths were noted in 6/86 (7%) cases. No deaths appeared directly related to NPWT.

While NPWT is in widespread use and its role in acute wound care is empirically expanding,^{4-8,16,17,19,21,27,28} several concerns arise regarding contemporary acute wound care NPWT practice.   First, acute wounds often have tissue necrosis and/or infection. Contemporary, experiential NPWT practice is increasingly used in such cases, though published contraindications to NPWT include the presence of tissue necrosis and infection.^19,27,29 Second, acute wounds are often of infectious etiology; yet, current published literature does not confirm decreasing bacterial loads in wounds managed with NPWT.^30-33 Third, there are case reports of sepsis with the use of NPWT in infected wounds.^6,17,20 Fourth, wounds related to trauma, war, or a natural disaster have often been caused by significant force, resulting in large wounds, yet there is limited published literature on NPWT in such cases.^4-8 Fifth, NPWT in developing countries is expanding, proposed as being of “great value in treating severe wounds in underdeveloped countries.”^16-17 Yet lack of resources for comprehensive acute wound care, lack of sterile supplies, loss to follow-up, and lack of published data in this setting are noteworthy. Lastly, and of particular concern regarding the issues above, is that published literature is devoid of specific evidence-based reference defining the timing of subsequent NPWT after initial placement in acute, contaminated wounds. Reflecting this point are 2010 manufacturer’s recommendations for vacuum-assisted closure therapy, which state “…infected wounds must be monitored often and very closely. For these wounds, dressings may need to be changed more often than 48-72 hours…” ²⁰ Yet, 2012 manufacturer’s recommendations for the same therapy now omit a specific time period for dressing changes, stating instead, “…infected wounds should be monitored closely and may require more frequent dressing changes than non-infected wounds…”¹⁸ These revised recommendations thus denote best current clinical practice rather than specific evidence-based studies. The aim of this study, therefore, was to examine a large, consecutive cohort of acute, contaminated wounds, in hopes of providing an evidence basis assigning a safe and efficacious time interval for NPWT change after initial placement.   The wounds in this series were all contaminated, class IV based on CDC criteria; and the vast majority were infected. Many of the traumatic extremity wounds were created by such force that tissue destruction resulted in amputation, or was subsequently required. Wounds of infectious etiology were typically polymicrobial, necrotizing soft tissue processes. Average wound dimensions were large, with a mean area of 617 cm² (53 wounds) and a mean volume of 786 cm3 (43 wounds) with 1 linear wound measuring 45 cm. In all, the wounds in this cohort mirror current, global acute wound care using NPWT. Thus, results of this study are reasonably extrapolated to contemporary practice worldwide.   Though there are rare case reports of sepsis, and even Toxic Shock Syndrome developing from NPWT, the authors did not find sepsis to be a complication of NPWT in acute, contaminated wounds,^6,17,20 despite the class IV characteristics of all of the wounds in this patient cohort. The authors surmise that, though a theoretic risk of NPWT-related sepsis exists in acute, contaminated wounds, the risk is ameliorated by contemporary and comprehensive approaches to patient and wound care; namely, use of appropriate antibiotics, resuscitation techniques, meticulous and thorough operative wound intervention, as well as appropriate subsequent NPWT changes after placement.   As referenced in Table 2, there was no statistically significant association between any single patient comorbidity and a wound complication (as defined above). This likely reflects the acute nature of the wounds in this study’s cohort, as poor chronic wound healing in patients with comorbidities has been well established, particularly regarding tobacco abuse.   Notably, the actual time interval between initial application of NPWT and subsequent NPWT change in individual cases was assigned based on daily evaluations of the following variables: the clinical condition of the patient, the character of the NPWT drainage, and/or the “hold” of the NPWT system/suction. Thus, rather than assigning a predetermined time for subsequent NPWT after initial placement, daily reassessments were made based on the variables noted. In further evaluation of the appropriateness of this approach, the study specifically reviewed those wounds undergoing first subsequent NPWT changes on a) post-placement day ≤ 1 and b) post-placement day ≥ 4 (Tables 3 and 4). The data reflect a strong correlation between perceived preoperative clinical need of NPWT change and actual intraoperative findings at the time of that intervention.   In all patients meeting sepsis criteria and undergoing first NPWT dressing change on day 1 after initial placement, there were wound characteristics consistent with ongoing necrosis and/or abscess. In all of the patients not meeting sepsis criteria and undergoing first NPWT dressing change on day 1 after initial placement, there were no findings of residual necrosis and/or abscess. Thus surgical intervention and NPWT change appear appropriately determined by the presence or absence of sepsis criteria. (Of note, the 1 patient meeting septic shock criteria, and having the first NPWT dressing change within several hours of initial placement, was excluded due to the extremely short interval between initial placement of the NPWT and subsequent NPWT change.) Separately, in all of the patients meeting sepsis criteria, and undergoing first NPWT dressing change on day ≥ 4 after initial placement, there were wound characteristics consistent with ongoing necrosis. In all of the patients not meeting sepsis criteria, and undergoing first NPWT dressing change on day ≥ 4, there were no findings of necrosis and/or abscess. Therefore, surgical intervention and NPWT changes again appear appropriately determined by the presence or absence of sepsis criteria, with earlier intervention indicated when sepsis is present. Based on these findings, the authors recommend a patient and wound-directed approach to determining the timing of NPWT after initial placement in acute, contaminated wounds. In this regard, though preassigned NPWT changes are beneficial from a programmatic standpoint in wound care based on findings reflected in this study, such predetermined wound care interventions may need to be tailored in acute, contaminated wounds.

Limitations of this study include the lack of a control group; yet, publications to date reflect the inherent difficulty of prospective, randomized trials in wound care.^{3,17,30,34-40} Though other observational study designs might have been used to compare wound care practices, the aim of this study was not to document wound care superiority with NPWT. Rather, it was to assess a safe and efficacious time interval for subsequent placement of NPWT after a clinical decision was made for its use in acute, contaminated wounds. Also, due to the lack of published data defining the optimal timing for subsequent NPWT after initial placement in contaminated wounds, literature-based guidance was lacking to assign a comparative control group.   Another potential limitation of this study relates to the heterogeneity of wound locations (albeit, limited to the torso and extremities), and etiology (traumatic and infectious). Yet with the stated aim, it was important to include the heterogeneity described as it mirrors current NPWT-related acute wound care practice.   In addition, this study reviewed the use a predominantly foam-based, as opposed to gauze-based, NPWT system. Thus the conclusion of this study may not reflect gauze-based NPWT in acute, contaminated wounds.   Due to the complexity of the wounds, and comorbidities of the patients in this study’s cohort, inpatient care, with access to daily wound and NPWT assessment, was deemed necessary during the initial patient care phase. It is unclear if the conclusions of this study would be similar if the patients received outpatient care for their acute, contaminated wounds. Lastly, though the time range of 1.7-4.1 days may not be specific enough to guide practice, the authors think the interval is definitive enough to be clinically useful.

Since NPWT is already in widespread use and empirically expanding in acute, contaminated cases, it is important to develop evidence-based practice when possible. This study defined a 1.7-4.1 day (2.9 mean, +/- 1 SD) interval as safe and effective for the subsequent placement of NPWT after initial placement in acute, contaminated wounds.

Ehyal Shweiki, MD, MS Bioethics, FACS is from the Thomas Jefferson University Hospital, Philadelphia, PA. Kathy E. Gallagher, MSN, FNP, FACCWS is from the Christiana Care Health System, Newark, DE.

Address correspondence to: Kathy E. Gallagher, MSN, FNP, FACCWS Surgical Critical Care Christiana Care Health System MAP 2, Suite 3301 4735 Ogletown Stanton Road Newark, DE 19713 kagallagher@christianacare.org

Disclosure: The authors disclose no financial or other conflicts of interest.