PERSPECTIVE ARTICLE
Complications of negative pressure wound therapy: A mini review Zonghuan Li, MD; Aixi Yu, MD, PhD Department of Micro-Orthopedics, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China
Reprint requests: Prof. A. Yu, Department of Micro-Orthopedics, Zhongnan Hospital of Wuhan University, No. 169 Donghu Road, Wuchang District Wuhan, Hubei 430071, China. Tel: +86 27 83782519; Fax: +86 27 83782519; Email: [email protected]
ABSTRACT Negative pressure wound therapy, with its wide indications and narrow contraindications, has been widely used for various complicated wounds. Despite its excellent properties in promoting wound healing, there are sporadic but increasing reports on the complications. These complications included bleeding, infection, pain, rupture of the heart, and death in the short term. When used for the long term, the therapy may decrease life quality, increase anxiety, and lead to malnutrition. In this review, we briefly summarize the complications of negative pressure wound therapy.
Manuscript received: April 18, 2013 Accepted in final form: April 22, 2014 DOI:10.1111/wrr.12190
Negative pressure wound therapy (NPWT), first applied clinically in 1993 by Fleischmann et al.,1 has been widely used for the management of acute and chronic wounds. Since its invention, wound treatment has changed greatly. With advances in techniques, complicated wounds, for example, compound bone and soft tissue defects,2 could be managed by NPWT. The basic mechanisms for promoting wound healing are as the following: (1) increasing wound blood supply; (2) facilitating the elimination of necrotic tissue and foreign matter; (3) reducing peripheral edema of the wound; and (4) promoting granulation tissue formation and epithelialization by stimulating the overexpression of healing-related factors, including vascular endothelial growth factor, epidermal growth factor, etc. Nothing is perfect, and NPWT is no exception; complications are infrequent but can be life-threatening. These include bleeding, infection, pain, rupture of heart, death, life quality, anxiety, and malnutrition, which drew the attention of Food and Drug Administration (FDA).3 Until now, no review has been performed to discuss the complications of NPWT. In this review, we focus on NPWT-related complications.
SEARCH STRATEGY We systematically searched PubMed and Google Scholar without using time parameters, and reference lists of relevant studies were also checked. Free terms used were “NPWT,” “negative pressure wound therapy,” “TNP,” “topical negative pressure,” “vacuum assisted closure,” “complication,” “safety,” “infection,” “bleed,” “death,” etc. Titles and abstracts were screened to identify eligible studies. Wound Rep Reg (2014) 22 457–461 © 2014 by the Wound Healing Society
COMPLICATIONS Bleeding
When NPWT was applied, bleeding occurred mainly in two circumstances. First, an objective coagulation disorder was ignored by the clinician;4 this can be avoided as long as practitioners are vigilant. Second, the NPWT device was placed directly over an exposed heart or a blood vessel. Especially for vessels after anastomosis, suction may stave the thin-walled vessels and lead to bleeding. Vos et al.5 reported a patient with proximal anastomosis who bled several times after NPWT. To prevent vessels from bleeding, a rigid barrier was placed between the wound bed and the foam. Experimental research showed that both wound contraction and wound fluid removal were similar in the absence and presence of a rigid barrier.6 Moreover, the rigid barrier counteracted the reduction in blood flow of a wound bed caused by NPWT and did not influence the pressure transduction.7 Moveable fragments from the wound bed will migrate by the power of suction and cause injury topically. Kiessling et al.8 reported a case of tremendous bleeding caused by mobilized fragments due to the suction effect. They suggested that loose fragments should be removed before any vacuum sealing treatment. Agnogenic bleeding was reported in another study.9 When
FDA Mini-VAC NPWT RCT
Food and Drug Administration Minimally invasive vacuum-assisted closure Negative pressure wound therapy Randomized controlled trial
457
Complications of NPWT
blood-tinged fluid was drained in the tube and bottle, NPWT was discontinued, and the active bleeding ceased. Death might occur after the rupture of the heart or aorta, but if the steps to stop bleeding and perform a blood transfusion were taken in a timely manner, this risk could be avoided. In another case with complications, a 51-year-old man refused to receive a blood transfusion for religious reasons and died from intraoperative and postoperative blood loss with NPWT.10
Li and Yu
and fragments of foam remained. Thus, patients experienced more pain. Pain during NPWT was associated with the dressing in the wound bed and the value of negative pressure. Dressing changes were far less painful in gauze-based NPWT17 and at low-pressure NPWT.18 Additionally, pain was also reduced when NPWT was followed by a topical anesthetic instillation.19 To address the issue clearly, large-scaled RCTS are needed. Rupture of heart
Infection
It was controversial whether NPWT facilitated the clearance of bacteria. We evaluated the effect of NPWT on bacterial load in an animal study. The results showed that infection could be controlled efficiently, and NPWT showed good ability to reduce bacterial counts in wound bed.11 Theoretically, the infection rate is minimized by NPWT, but no prospective randomized controlled trials (RCTs) have proven this. Six patients with complex pleural empyemas were managed with minimally invasive vacuum-assisted closure (Mini-VAC) therapy. Local infection was controlled and sepsis was satisfactory. Mini-VAC therapy reduced the empyema cavity and improved the lung function.12 However, in some cases, NPWT resulted in an increased incidence of infections. In an in vitro wound model study, bacterial load did not decrease using an NPWT dressing.13 Clinically, NPWT powered by continuous electricity removed exudate, kept the wound clean, and facilitated wound healing. When power was off, sponges covering the wound were foreign and acted as the source of infection. If the sponges fell out of place, the wound bed was open to the environment and the risk of infection increased. Collinge and Reddix14 reported that twelve patients had problems after power was turned off, and five patients were infected. This is different in China because central negative pressure was applied; unless there was air leakage, wounds would not be infected. During NPWT therapy, there is also potential risk of infection after bleeding. Blood clots lingering beneath the sponge serve as a culture medium for bacteria. Thus, once the bleeding is suspected, the treatment should be discontinued. Pain
Pain was usually experienced by wounded patients, especially during dressing changes. Patients treated with NPWT needed fewer dressing changes and thus suffered less pain theoretically. An observational study by Stansby et al.15 assessed the pain levels of NPWT for diabetic patients with foot ulcers or amputation wounds. At the time of dressing application, activation and deactivation of NPWT, and dressing removal, most patients reported experiencing mild or no pain. Notably, however, the study was noncontrolled and most patients had concurrent neuropathies, which might affected the pain experience. The results were totally different in traumatic patients without neuropathies in a comparative study. The pain levels for traumatic patients before, during NPWT, and at the dressing change were measured by a verbal numerical scale. The results confirmed high levels of pain for patients treated with foam-based NPWT.16 More adhesive and poriferous properties of foam made it possible for eugenic granulation tissue to grow. At the dressing change, the wound bed was disrupted 458
Right ventricle heart rupture was a rare but life-threatening complication associated with NPWT. When the NPWT device was applied to a sternal wound, the high negative pressure pulled the heart toward the sharp edges of the sternum, which may have injured the right ventricle. Vos et al. reported a patient with poststernotomy mediastinitis treated by NPWT. After 10 days, mediastinal bleeding led to an acute bulging of the sponges. After removal of the sponges, the bleeding was localized to the right atrium.20 Another study21 reported five cases of NPWT-related bleeding due to the rupture of right ventricle. In this study, they presented two key measures to avoid the lethal complications (cover the heart and fixate the sternum). To cover the heart, a rigid disc was usually used. Interestingly, the benefit of a rigid disc was far greater than just cardioprotection. Research on pigs revealed that the left pleural cavity was effectively drained when a disc was inserted between the heart and the sharp sternum, but it was not drained at all using conventional NPWT.22 Furthermore, NPWT with a disc had a lower influence on blood pressure and less bleeding compared with conventional NPWT.23 Death
In 2009, the FDA warned of the risk of death related to NPWT.3 Most reported deaths occurred during long-term wound care at home. Therefore, patients needed adequate training before they applied NPWT at home.3 Currently, NPWT is the ideal choice for patients with abdominal wall defects or abdominal sepsis. Previously, researchers mistakenly assumed that the risk of death for open abdominal patients increased with the application of NPWT.24 Recently, a large-sample study revealed that 97/355 (27.3%) and 66/223 (29.6%) deaths occurred in NPWT and non-NPWT, respectively. The absolute risk of death in the non-NPWT group was 3.7% greater than in the NPWT group (p = 0.40).25 Major bleeding and heart rupture could also lead to deaths, as discussed above. Quality of life
It was controversial whether NPWT benefits or hurts the quality of life for patients. NPWT accelerated wound healing dramatically and improved mental and physical health. Thus, patients felt well subjectively and lived a happy life in spite of the inconvenience of carrying NPWT devices. Several studies supported this idea. Karatepe et al.26 performed a RCT in 67 diabetic patients to assess the change of life quality. The results showed quality of life scores improved remarkably after NPWT treatment. In another study by Immer et al.,27 the quality of life was evaluated in patients with deep sternal Wound Rep Reg (2014) 22 457–461 © 2014 by the Wound Healing Society
Li and Yu
wound infections. The results showed the quality of life was better after treatment by NPWT. However, some researchers insisted that no significant difference existed with respect to life quality between the conventional dressings and NPWT. Vuerstaek et al.28 reported that quality of life improved but did not differ significantly after NPWT during the first week, and in the second week, the improvements vanished. Ousey et al.29 measured the quality of life for patients treated with NPWT or standard wound care at weeks 1, 2, 4, 8, and 12. Nevertheless, no real difference was achieved over the 12-week period. Furthermore, some patients experienced exacerbation of physical functioning symptoms, limited mobility, pain, odor, and itching.30,31 NPWT is aimed to provide healing benefits to patients, but the intervention may occasionally cause unintentional harm. The treatment was powered by central negative pressure or a portable machine, which may limit the activities of patients.31 Other decreases in quality of life included poor appetite, sleep problems, and even a change of cognitive status.32 A severe deterioration in quality of life might bring about the discontinuation of NPWT and the failure of treatment. Anxiety
Despite NPWT gaining satisfying results in wound healing, some patients were not willing to continue the treatment. Although anxiety also existed in patients treated with conventional dressing, patients treated by NPWT were more nervous and aggressive than usual. Anxiety scores were significantly higher in the NPWT group than in the gauze group. This interesting phenomenon might be mainly correlated with pain, restrictions of activities, and unfamiliarity with this form of treatment.33 Loss of protein and malnutrition
Wound exudates have high protein content, glucose, and other essential nutrients that facilitated wound healing.34 With the effect of continuous suction, these compositions were removed from wound bed and more protein, glucose, and other nutrients were mobilized from the body. It formed a vicious circle and there are great losses of proteins in wound exudates by NPWT. A prospective study35 showed that NPWT created more exudate and wound-related protein loss than burn wounds. Furthermore, NPWT was not efficacious for malnourished patients (albumin
Complications of negative pressure wound therapy: A mini review Zonghuan Li, MD; Aixi Yu, MD, PhD Department of Micro-Orthopedics, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China
Reprint requests: Prof. A. Yu, Department of Micro-Orthopedics, Zhongnan Hospital of Wuhan University, No. 169 Donghu Road, Wuchang District Wuhan, Hubei 430071, China. Tel: +86 27 83782519; Fax: +86 27 83782519; Email: [email protected]
ABSTRACT Negative pressure wound therapy, with its wide indications and narrow contraindications, has been widely used for various complicated wounds. Despite its excellent properties in promoting wound healing, there are sporadic but increasing reports on the complications. These complications included bleeding, infection, pain, rupture of the heart, and death in the short term. When used for the long term, the therapy may decrease life quality, increase anxiety, and lead to malnutrition. In this review, we briefly summarize the complications of negative pressure wound therapy.
Manuscript received: April 18, 2013 Accepted in final form: April 22, 2014 DOI:10.1111/wrr.12190
Negative pressure wound therapy (NPWT), first applied clinically in 1993 by Fleischmann et al.,1 has been widely used for the management of acute and chronic wounds. Since its invention, wound treatment has changed greatly. With advances in techniques, complicated wounds, for example, compound bone and soft tissue defects,2 could be managed by NPWT. The basic mechanisms for promoting wound healing are as the following: (1) increasing wound blood supply; (2) facilitating the elimination of necrotic tissue and foreign matter; (3) reducing peripheral edema of the wound; and (4) promoting granulation tissue formation and epithelialization by stimulating the overexpression of healing-related factors, including vascular endothelial growth factor, epidermal growth factor, etc. Nothing is perfect, and NPWT is no exception; complications are infrequent but can be life-threatening. These include bleeding, infection, pain, rupture of heart, death, life quality, anxiety, and malnutrition, which drew the attention of Food and Drug Administration (FDA).3 Until now, no review has been performed to discuss the complications of NPWT. In this review, we focus on NPWT-related complications.
SEARCH STRATEGY We systematically searched PubMed and Google Scholar without using time parameters, and reference lists of relevant studies were also checked. Free terms used were “NPWT,” “negative pressure wound therapy,” “TNP,” “topical negative pressure,” “vacuum assisted closure,” “complication,” “safety,” “infection,” “bleed,” “death,” etc. Titles and abstracts were screened to identify eligible studies. Wound Rep Reg (2014) 22 457–461 © 2014 by the Wound Healing Society
COMPLICATIONS Bleeding
When NPWT was applied, bleeding occurred mainly in two circumstances. First, an objective coagulation disorder was ignored by the clinician;4 this can be avoided as long as practitioners are vigilant. Second, the NPWT device was placed directly over an exposed heart or a blood vessel. Especially for vessels after anastomosis, suction may stave the thin-walled vessels and lead to bleeding. Vos et al.5 reported a patient with proximal anastomosis who bled several times after NPWT. To prevent vessels from bleeding, a rigid barrier was placed between the wound bed and the foam. Experimental research showed that both wound contraction and wound fluid removal were similar in the absence and presence of a rigid barrier.6 Moreover, the rigid barrier counteracted the reduction in blood flow of a wound bed caused by NPWT and did not influence the pressure transduction.7 Moveable fragments from the wound bed will migrate by the power of suction and cause injury topically. Kiessling et al.8 reported a case of tremendous bleeding caused by mobilized fragments due to the suction effect. They suggested that loose fragments should be removed before any vacuum sealing treatment. Agnogenic bleeding was reported in another study.9 When
FDA Mini-VAC NPWT RCT
Food and Drug Administration Minimally invasive vacuum-assisted closure Negative pressure wound therapy Randomized controlled trial
457
Complications of NPWT
blood-tinged fluid was drained in the tube and bottle, NPWT was discontinued, and the active bleeding ceased. Death might occur after the rupture of the heart or aorta, but if the steps to stop bleeding and perform a blood transfusion were taken in a timely manner, this risk could be avoided. In another case with complications, a 51-year-old man refused to receive a blood transfusion for religious reasons and died from intraoperative and postoperative blood loss with NPWT.10
Li and Yu
and fragments of foam remained. Thus, patients experienced more pain. Pain during NPWT was associated with the dressing in the wound bed and the value of negative pressure. Dressing changes were far less painful in gauze-based NPWT17 and at low-pressure NPWT.18 Additionally, pain was also reduced when NPWT was followed by a topical anesthetic instillation.19 To address the issue clearly, large-scaled RCTS are needed. Rupture of heart
Infection
It was controversial whether NPWT facilitated the clearance of bacteria. We evaluated the effect of NPWT on bacterial load in an animal study. The results showed that infection could be controlled efficiently, and NPWT showed good ability to reduce bacterial counts in wound bed.11 Theoretically, the infection rate is minimized by NPWT, but no prospective randomized controlled trials (RCTs) have proven this. Six patients with complex pleural empyemas were managed with minimally invasive vacuum-assisted closure (Mini-VAC) therapy. Local infection was controlled and sepsis was satisfactory. Mini-VAC therapy reduced the empyema cavity and improved the lung function.12 However, in some cases, NPWT resulted in an increased incidence of infections. In an in vitro wound model study, bacterial load did not decrease using an NPWT dressing.13 Clinically, NPWT powered by continuous electricity removed exudate, kept the wound clean, and facilitated wound healing. When power was off, sponges covering the wound were foreign and acted as the source of infection. If the sponges fell out of place, the wound bed was open to the environment and the risk of infection increased. Collinge and Reddix14 reported that twelve patients had problems after power was turned off, and five patients were infected. This is different in China because central negative pressure was applied; unless there was air leakage, wounds would not be infected. During NPWT therapy, there is also potential risk of infection after bleeding. Blood clots lingering beneath the sponge serve as a culture medium for bacteria. Thus, once the bleeding is suspected, the treatment should be discontinued. Pain
Pain was usually experienced by wounded patients, especially during dressing changes. Patients treated with NPWT needed fewer dressing changes and thus suffered less pain theoretically. An observational study by Stansby et al.15 assessed the pain levels of NPWT for diabetic patients with foot ulcers or amputation wounds. At the time of dressing application, activation and deactivation of NPWT, and dressing removal, most patients reported experiencing mild or no pain. Notably, however, the study was noncontrolled and most patients had concurrent neuropathies, which might affected the pain experience. The results were totally different in traumatic patients without neuropathies in a comparative study. The pain levels for traumatic patients before, during NPWT, and at the dressing change were measured by a verbal numerical scale. The results confirmed high levels of pain for patients treated with foam-based NPWT.16 More adhesive and poriferous properties of foam made it possible for eugenic granulation tissue to grow. At the dressing change, the wound bed was disrupted 458
Right ventricle heart rupture was a rare but life-threatening complication associated with NPWT. When the NPWT device was applied to a sternal wound, the high negative pressure pulled the heart toward the sharp edges of the sternum, which may have injured the right ventricle. Vos et al. reported a patient with poststernotomy mediastinitis treated by NPWT. After 10 days, mediastinal bleeding led to an acute bulging of the sponges. After removal of the sponges, the bleeding was localized to the right atrium.20 Another study21 reported five cases of NPWT-related bleeding due to the rupture of right ventricle. In this study, they presented two key measures to avoid the lethal complications (cover the heart and fixate the sternum). To cover the heart, a rigid disc was usually used. Interestingly, the benefit of a rigid disc was far greater than just cardioprotection. Research on pigs revealed that the left pleural cavity was effectively drained when a disc was inserted between the heart and the sharp sternum, but it was not drained at all using conventional NPWT.22 Furthermore, NPWT with a disc had a lower influence on blood pressure and less bleeding compared with conventional NPWT.23 Death
In 2009, the FDA warned of the risk of death related to NPWT.3 Most reported deaths occurred during long-term wound care at home. Therefore, patients needed adequate training before they applied NPWT at home.3 Currently, NPWT is the ideal choice for patients with abdominal wall defects or abdominal sepsis. Previously, researchers mistakenly assumed that the risk of death for open abdominal patients increased with the application of NPWT.24 Recently, a large-sample study revealed that 97/355 (27.3%) and 66/223 (29.6%) deaths occurred in NPWT and non-NPWT, respectively. The absolute risk of death in the non-NPWT group was 3.7% greater than in the NPWT group (p = 0.40).25 Major bleeding and heart rupture could also lead to deaths, as discussed above. Quality of life
It was controversial whether NPWT benefits or hurts the quality of life for patients. NPWT accelerated wound healing dramatically and improved mental and physical health. Thus, patients felt well subjectively and lived a happy life in spite of the inconvenience of carrying NPWT devices. Several studies supported this idea. Karatepe et al.26 performed a RCT in 67 diabetic patients to assess the change of life quality. The results showed quality of life scores improved remarkably after NPWT treatment. In another study by Immer et al.,27 the quality of life was evaluated in patients with deep sternal Wound Rep Reg (2014) 22 457–461 © 2014 by the Wound Healing Society
Li and Yu
wound infections. The results showed the quality of life was better after treatment by NPWT. However, some researchers insisted that no significant difference existed with respect to life quality between the conventional dressings and NPWT. Vuerstaek et al.28 reported that quality of life improved but did not differ significantly after NPWT during the first week, and in the second week, the improvements vanished. Ousey et al.29 measured the quality of life for patients treated with NPWT or standard wound care at weeks 1, 2, 4, 8, and 12. Nevertheless, no real difference was achieved over the 12-week period. Furthermore, some patients experienced exacerbation of physical functioning symptoms, limited mobility, pain, odor, and itching.30,31 NPWT is aimed to provide healing benefits to patients, but the intervention may occasionally cause unintentional harm. The treatment was powered by central negative pressure or a portable machine, which may limit the activities of patients.31 Other decreases in quality of life included poor appetite, sleep problems, and even a change of cognitive status.32 A severe deterioration in quality of life might bring about the discontinuation of NPWT and the failure of treatment. Anxiety
Despite NPWT gaining satisfying results in wound healing, some patients were not willing to continue the treatment. Although anxiety also existed in patients treated with conventional dressing, patients treated by NPWT were more nervous and aggressive than usual. Anxiety scores were significantly higher in the NPWT group than in the gauze group. This interesting phenomenon might be mainly correlated with pain, restrictions of activities, and unfamiliarity with this form of treatment.33 Loss of protein and malnutrition
Wound exudates have high protein content, glucose, and other essential nutrients that facilitated wound healing.34 With the effect of continuous suction, these compositions were removed from wound bed and more protein, glucose, and other nutrients were mobilized from the body. It formed a vicious circle and there are great losses of proteins in wound exudates by NPWT. A prospective study35 showed that NPWT created more exudate and wound-related protein loss than burn wounds. Furthermore, NPWT was not efficacious for malnourished patients (albumin
