Diabetic foot wounds: the value of negative pressure wound therapy with instillation

Abstract

Chronic wounds such as diabetic foot wounds are a tremendous burden to the health care system and often require a multidisciplinary approach to prevent amputations. Advanced technologies such as negative pressure wound therapy (NPWT) and bioengineered tissues have been successfully used in the treatment of these types of complex wounds. However, the introduction of NPWT with instillation (NPWTi) has provided an alternative treatment for treating complex and difficult‐to‐heal wounds. This article provides an overview of NPWT and the new NPWTi system and describes preliminary experience using NPWTi on patients with complicated infected diabetic foot wounds after surgical debridement and in a multidisciplinary setting.

Introduction

Chronic wounds form a tremendous burden to the health care system, accounting for about $20 billion in health care costs per year worldwide 1. Foot ulceration is the precursor to approximately 85% of all diabetic amputations, with an estimated 14–20% of patients with foot ulcers undergoing an amputation 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Infection of the ulcer further increases the risk of amputation. If these patients were initially treated by a multidisciplinary team, major amputations could be prevented in 80–90% of them with limb‐threatening ischaemia 16, 17, 18, 19, 20, 21 and in 95% with infection 22, 23, 24, 25. This is significant considering that amputations are related to high morbidity or mortality rates and a financial burden of up to $60 000 per patient.

The treatment of the diabetic foot wounds requires a multidisciplinary approach. The treatment of peripheral vascular disease, infection and pathological plantar pressure plays a significant role in the global management of complex wounds. The topical treatment of wounds using advanced wound dressings has not shown consistent results. More promising perspectives have been obtained in the treatment of neuropathic wounds owing to the introduction of bioengineered tissue in clinical practice 26, 27, 28, 29 and negative pressure wound therapy (NPWT) via Vacuum‐Assisted Closure Therapy (V.A.C.® Therapy; KCI USA, Inc., San Antonio, TX).

This NPWT system uses a reticulated open‐cell foam that is modelled to fit into the wound. The foam is subsequently covered and sealed with a semi‐occlusive film. The tubing pad is attached to a 2‐cm² aperture, which is cut on the surface of the dressing, thereby allowing a connection with the foam, whereas the other end of the tubing system is attached to the therapy unit that delivers negative pressure to the wound and provides either continuous or intermittent pressure.

NPWT has been shown to help wound healing in various ways. Tests on animals have demonstrated that NPWT decreased bacterial burden in wounds, changing them from infected wounds to colonised wounds within 4–5 days of treatment 30. Other postulated mechanisms of action that might affect wound healing are the induction of an increased local wound perfusion 31, 32, the induction of microdeformations at the wound surface and the removal of infectious material and wound fluids, including inhibitory factors 31, 32, 33. These mechanisms may explain how NPWT stimulates granulation tissue formation in comparison with wet‐to‐moist dressings. NPWT has also been shown to be an effective treatment of both complicated and non‐complicated ulcerated wounds 30, 31, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44.

Prior to 2006, only two randomised controlled trials (RCTs) that had evaluated the clinical effectiveness of NPWT in the treatment of diabetic foot wounds were found in the literature 35, 37. In the first study, McCallon et al. included only ten patients but found faster healing and greater wound surface reduction when NPWT was used compared with gauze dressings 35. In the second study, Armstrong and Lavery 37 published a large multicentre RCT investigating the effectiveness of NPWT on open diabetic foot amputations. The control group was treated with advanced moist wound dressings according to standard guidelines of the participating centres. Treatment with NPWT resulted in a statistically significant reduction in healing time, a higher percentage of healed wounds and a potential reduction in the number of reamputations 37. However, less than 50% of the patients reached complete healing during the 112‐day follow‐up period. Besides treating ulcerated chronic wounds, it has been shown that NPWT is effective in improving the qualitative and quantitative take‐rate of skin grafts in venous leg ulcers 45 and several other wound types but not in diabetic foot ulcers 46, 47.

Previous authors, most notably Fleischmann as well as Svedman, have discussed the infusion of a variety of solutions into the wound 48, 49, 50, 51, 52, 53, 54, 55. The initial work of Fleischmann led to the development of the V.A.C.® Instill Wound Therapy System (KCI USA, Inc.), which combines NPWT with instillation (NPWTi) and consists of a vacuum port and an infusion port with two clamps to allow for separate infusion and vacuum periods. This process involves a ‘hold’ cycle during which fluid is held in the foam during a pause in NPWT.

During the last 2 years, a new device has been developed as the next generation of instillation therapy. The V.A.C.Ulta™ Therapy System (KCI USA, Inc.) is an integrated system that allows standard NPWT as well as an instillation option using V.A.C. VeraFlo™ Therapy (KCI USA, Inc.). With this combination system, it is possible to deliver topical wound cleansing solutions to the wound bed. Complex and difficult‐to‐heal‐wounds can be managed, avoiding the need for a separate NPWT unit. This new NPWTi system uses dressings (V.A.C. VeraFlo Dressing; KCI USA, Inc.) specifically designed for instillation therapy, which have an open pore structure that is similar to the black foam dressings used with NPWT. These dressings have reduced hydrophobic properties and provide greater mechanical strength for use during instillation therapy, which may help to prevent tearing at dressing changes.

It is well recognised that wound preparation plays a key role in creating an optimal environment for wound healing. Regular cleansing of the wound can help to address the barriers to healing by removing devitalised tissue, debris, infectious materials and exudate and help prepare the wound bed for closure 56. Compared with swabbing or bathing, wound irrigation is considered to be the most consistently effective method of wound cleansing 57.

Initially, this new instillation system was used adjunctively in infected ulcers using antiseptic solutions; however, its use has now been expanded to include cleansing regimens that can help to remove debris, exudate, infectious materials and healing inhibitors 51, 58. Several publications describe various clinical applications of adjunctive instillation therapy, most of which focus on the treatment of wound infection. The instillation of polyhexanide [polyhexamethylene biguanide (PHMB)] solution showed effective treatment of soft tissue necrotising fasciitis and osteomyelitis when used in combination with other treatments 59, 60. Lehner et al. also reported that the same regimen was an effective adjunctive therapy for acutely and chronically infected orthopaedic implants 61. Table 1 lists the studies that demonstrate the clinical advantages of using NPWTi.

Table 1.

Literature review of instillation therapy

	Title	Study type	Aim	Method	Findings
Bernstein and Tam 62	Combination of subatmospheric pressure dressing and gravity feed antibiotic instillation in the treatment of post‐surgical diabetic foot wounds	Case series of five patients	To evaluate the effect of NPWT with instillation of saline, polymyxin B and bacitracin in the treatment of diabetic foot wounds	6 hours of NPWT at −125 mmHg followed by instillation of saline mix on five post‐surgical diabetic wounds	A decrease in hospital stay and amputation rate was observed Authors noted that with the addition of instillants, the wound fluid viscosity lowered, thus facilitating more efficient removal into the canister
Gabriel et al. 49	Negative pressure wound therapy with instillation: a pilot study describing a new method for treating infected wounds	Pilot study, NPWT with instillation: n = 15, control: n = 15	To compare the effect of NPWT with instillation to treatment with moist gauze wound care in patients with complex, infected wounds	Silver nitrate solution was instilled for 30 seconds with a 1‐second hold time followed by −125 mmHg of continuous NPWT for 2 hours	Patients treated with NPWT plus instillation required fewer treatment days, cleared the infection earlier, reached wound closure sooner and had fewer in‐hospital days (P < 0·001 for all results)
Timmers et al. 60	Negative pressure wound treatment with polyvinyl alcohol foam and polyhexanide antiseptic solution instillation in posttraumatic osteomyelitis	Retrospective case–control cohort study of 30 patients	To evaluate the effect of NPWT plus instillation in patients with osteomyelitis of the pelvis or lower extremity	Polyhexanide instillation solution was used Soak time was 10–15 minutes Pressure settings ranged from 300 to 600 mmHg Dressing changes took place every 3–4 days Mean duration of therapy was 19·0–22·4 days	Patients treated with negative pressure plus instillation had a lower infection recurrence rate compared with control (10% versus 58·5%, respectively, P < 0·0001) NPWTi patients also had a shorter total length of hospital stay and number of surgical procedure compared with control (all P < 0·0001)
Schintler et al. 59	The impact of V.A.C. Instill® in severe soft tissue infections and necrotising fasciitis	Case series of 15 patients treated with NPWT plus instillation	To evaluate the effect of NPWT with instillation on patients with skin and soft tissue infections	Polyhexanide instillation solution was used Wound size determined instillation time; 20‐minute dwell time for all cases Duration of therapy ranged from 4 to 18 days with dressing changes occurring every 2–4 days	Infection was controlled and complete healing occurred in all patients Authors concluded that treatment with NPWT and instillation is a viable option for difficult anatomical regions or cases of incomplete debridement
Lehner et al. 61	First experiences with negative pressure wound therapy and instillation in the treatment of infected orthopaedic implants: a clinical observational study	32 patients with an infected orthopaedic implant were included in this observational study	To observe the effect of NPWTi on orthopaedic implant retention following an acute or chronic infection	NPWTi settings varied on a case‐by‐case basis Instillation solution (compatible with dressings and NPWTi system) was at the discretion of the treating physician	27 of 32 patients (84·4%) retained their implant 19 patients with an acute infection and 8 patients with a chronic infection retained their implant at 4‐ to 6‐month follow‐up
Wolvos 63	The use of negative pressure wound therapy with an automated, volumetric fluid administration: an advancement in wound care	Pilot study including six patients treated with NPWTi with either Dressing A or Dressing B; Dressing A: n = 5, Dressing B: n = 1	To introduce initial clinical experience with NPWTi and a comparison of two different dressings	Microcyn® antiseptic solution was used as an instillate One patient was treated with NPWT only Instillation occurred every 2–4 hours Soak time consisted of 5–10 minutes followed by negative pressure at −100 to −125 mmHg	NPWT‐only patient with a different dressing on each half of wound demonstrated no difference in degree or quality of granulation tissue NPWTi was successful in treating multiple wound types No complications were observed

NPWT, negative pressure wound therapy; NPWTi, NPWT with instillation.

Case studies

The use of NPWTi in the treatment of diabetic foot ulcers is only recent. The following cases describe the preliminary experience using NPWTi on patients with complicated infected wounds after surgical debridement and in a multidisciplinary setting.

Case 1

A 68‐year‐old male with type 2 diabetes presented with a wet gangrene in the fourth and fifth toes of the right foot and compartment syndrome of the plantar aspect of the midfoot (Figure 1A). He presented a critical limb ischaemia treated with an angioplasty of superficial femoral artery and anterior tibial artery. An open amputation of the lateral rays was performed. Methicillin‐resistant Staphylococcus aureus (MRSA) was isolated and appropriate antibiotic therapy was used. During the postoperative period after debridement (Figure 1B) and bleeding control, NPWTi using polyhexanide (PHMB) was applied with a soak time of 15 minutes, followed by NPWT for 2 hours at −125 mmHg. NPWTi was carried out for 7 days with progression of granulation tissues to prepare the wound bed for dermal substitute application (Integra™ dermal regeneration template; Integra Lifescience, Plainsboro, NJ) (Figure 1C). The wound was completely healed at follow‐up (Figure 1D).

Figure 1.

(A) Initial presentation, (B) 11 days after surgical debridement, (C) 14 days after treatment with negative pressure wound therapy with instillation (NPWTi) using polyhexamethylene biguanide (left) and 42 days after coverage with dermal substitute (right). (D) Wound was completely healed at follow‐up.

Case 2

A 42‐year‐old male with type 1 diabetes presented with wet gangrene of the fourth ray of the right foot and with progression to necrotising fasciitis of the lateral aspect of the leg (Figure 2A). Critical limb ischaemia was assessed, and after emergent surgical debridement (Figure 2B), a percutaneous angioplasty below the knee of the anterior and posterior tibial artery was performed. MRSA and Serratia marcescens were isolated and appropriately treated with complex antibiotic regimen. NPWTi using polyhexanide (PHMB) was applied with a soak time of 15 minutes, followed by NPWT for 2 hours at −125 mmHg (Figure 2C). Wound received dermal replacement therapy followed by first skin graft application (Figure 2D). The wound healed after application of second graft (Figure 2E).

Figure 2.

(A) Initial presentation, (B) 3 days after surgical debridement and revascularisation, (C) 15 days after treatment with negative pressure wound therapy with instillation (NPWTi) using polyhexamethylene biguanide, (D) 60 days after dermal replacement therapy and first skin graft and (E) 30 days after healing with second skin graft application.

Conclusion

NPWTi has become an alternative option for treating complex, chronic wounds, which is supported by several studies in the literature. By using the new NPWTi system with automated volumetric fluid instillation, we have demonstrated its successful use for the treatment of DFUs. Larger studies are required to further investigate the efficacy of NPWTi on DFUs.

Dalla Paola L. Diabetic foot wounds: the value of negative pressure wound therapy with instillation.