Retention of polyurethane foam fragments during VAC therapy: a complication to be considered

Abstract

Vacuum‐assisted closure (VAC) therapy is a closed‐loop, non‐invasive active system, characterised by a controlled and localised negative pressure applied on porous polyurethane absorbent foams. It promotes healing of acute and chronic wounds. Therapeutic effects of VAC therapy have been proved and demonstrated; however, this method can have some disadvantages. Even if it is a quite versatile device, only qualified medical/paramedical personnel should use it in order to avoid possible complications that can occur after an improper application. In this report, 11 cases of foam‐fragment retention within the wound are presented. This rare complication did not promote healing, but further hindered it. On the basis of our experience, it is mandatory to define the indications, benefits and limitations of VAC therapy.

Introduction

The majority of acute pressure sores have the capacity to heal rapidly. Nevertheless, wider and chronic sores can require weeks or months to heal, a process that can be further delayed by infections, vascular insufficiency, high local pressure or by other causes 1. Difficult pressure sores are a common problem 2. A wide range of treatments are available to treat chronic ulcers, such as simple or advanced medications, compressive bandage, antimicrobials, surgical revision with grafts or flaps 3 and vacuum‐assisted closure (VAC) therapy 4, 5.

The practice to expose a wound to a negative atmospheric pressure for a long period of time in order to promote wound healing was first described by Fleischmann et al. in 1993; this technique was successful on 15 patients with open fractures 6.

The VAC therapy is a sophisticated system that allows carrying out a medication that maintains a humid, closed, sterile and isolated environment 4, 5, 6. Essentially, the technique is simple to be performed: a piece of foam of porous polyurethane with an open‐cell structure is cut according to the size of the wound and is set on top of the wound itself. The whole area is then covered with a transparent adhesive membrane that adheres tightly to the healthy skin surrounding the wound. A drainage tube, which is connected to a vacuum source, is then linked in order to suck wound fluids through the foam and these are collected into a tank to be subsequently disposed. The plastic membrane prevents the air penetration and allows creating a partial vacuum in the wound. The foam ensures that the whole surface of the wound is equally exposed to the negative pressure 4, 5, 6. This treatment presents standardised indications in acute and chronic sores 5.

In our opinion, the broad diffusion of VAC therapy devices, the great marketing pressure exerted on medical/paramedical personnel and an improper training could lead to inappropriate use that can be harmful. The focus of this report is on a rare complication of VAC therapy, that is, the retention of foam fragments within the wound that hinder the healing process.

Patients and methods

Since January 2004, among all patients presenting chronic ulcers and followed up in our department, a total of 345 patients were treated with a VAC therapy. The average time required to achieve complete healing in this patient group was 60 days and this was achieved with different treatment modalities including conservative wound management, surgical debridement and use of skin grafts and flaps associated to VAC therapy.

The retention of polyurethane foam fragments within the wound was evidenced in 11 paraplegic patients (10 males and 1 female) aged 24–55 years (average: 30 years).

According to medical history, the 11 paraplegic patients presented a medullary trauma that resulted in a condition of paraplegia. Between 6 and 24 months after the trauma, the patients developed grade III and grade IV pressure sores 7 as a consequence of the forced decubitus, the partial immobility and the sensitivity loss.

Therefore, the initial therapeutic modality consisted of a conservative wound management and VAC therapy (KCI Licensing, Inc., San Antonio, TX). Before applying the device, the lesion was disinfected with sodium hypochlorite solution and then irrigated with saline solution. Antibiotics were administered only to patients with clear symptoms and signs of infection according to antibiogram after positive wound swabs. The VAC polyurethane foams were applied in a single layer directly on the wound, avoiding their overlapping. An average of 1·4 foams of 18 × 12·5 × 3·3 cm in dimension was used for a single patient (Table 1). Dressing change was performed every 3–5 days for 4–8 weeks (average 6·3 weeks) for a total dressing changes of 6–28 (average 14·5; Table 1). A crescent negative pressure level from 50 to 125 mmHg in a continuous mode was achieved. This approach allowed an initial temporary wound improvement but without obtaining healing. Subsequently, a progressive wound worsening was noted with symptomatic foul‐smelling discharge with positive germ culture and progressive wound enlargement (Figure 1).

Table 1.

Patients' casistic evidencing wound characteristics, treatment frequency and lasting with foams used and germs involved with targeted therapy required

Case study	Lesion site	Lesion dimension	Treatment lasting (weeks)	Foams used (18 ×  12·5 × 3·3 cm)	Dressing changes	Germ infection	Antibiotic therapy
1	Sacral	12 × 10 cm	7	1	16	Staphylococcus aureus	Levoxacin (500 mg twice a day iv for 2 weeks)
	Trochanteric	8 × 9 cm
2	Sacral	8 × 9 cm	7	1	9	Proteus mirabilis	Amoxicillin + clavulanic acid (2·2 g twice a day iv for 2 weeks)
3	Ischiatic	9 × 6 cm	4	1	6	Staphylococcus aureus	Levoxacin (500 mg twice a day iv for 10 days)
4	Sacral	12 × 12 cm	8	2	22	Enterococcus faecalis	Levoxacin (500 mg twice a day iv for 2 weeks)
	Trochanteric	10 × 11 cm
5	Trochanteric	9 × 7 cm	4	1	7	Staphylococcus aureus	Minocycline (100 mg twice a day iv for 10 days)
6	Ischiatic	2 × 12 cm	5	1	9	Staphylococcus aureus	Levoxacin (500 mg twice a day iv for 12 days)
	Trochanteric	5 × 11 cm
7	Sacral	9 × 11·5 cm	5	1	9	Enterococcus faecalis	Levoxacin (500 mg twice a day iv for 12 days)
8	Sacral	12 × 11 cm	8	2	28	Pseudomonas aeruginosa	Levoxacin (500 mg twice a day iv for 12 days)
	Ischiatic	9 × 6 cm
	Trochanteric	8 × 9 cm
9	Sacral	10 × 9 cm	7	2	20	Enterococcus faecalis	Amoxicillin + clavulanic acid (2·2 g twice a day iv for 2 weeks)
	Trochanteric	9 × 11 cm
	Trochanteric	7 × 8 cm
10	Ischiatic	8 × 12 cm	8	2	22	Enterococcus faecalis	Levoxacin (500 mg twice a day iv for 2 weeks)
	Sacral	12 × 12 cm
	Trochanteric	12 × 9 cm
11	Sacral	11·5 × 9 cm	6	1	11	Staphylococcus aureus	Amoxicillin + clavulanic acid (2·2 g twice a day iv for 2 weeks)
	Ischiatic	10 × 7 cm

Figure 1.

Pre‐operative view of pressure sores in the trochanteric, left ischiatic and sacralis regions.

In the 11 paraplegic patients, chronic ulcers were lasting from 2 to 4 years; this was the reason to request specialist consultation that required hospitalisation. The therapeutic indication was surgical debridement and eventual wound coverage with skin flaps.

Clinical, laboratory, haemato‐chemical and instrumental examinations showed full‐thickness wounds extending to the underlying bone structures, measuring 2–12 cm in diameter, in the ischiatic, sacralis and trochanteric regions. Wound swabs showed multiple germ infections (Proteus mirabilis, Enterococcus faecalis, Staphylococcus aureus, etc.) with increased inflammatory parameters, without hyperpyrexia and probable osteomyelitis. Surgical debridement of wounds was performed, and tissue and bone biopsies were taken for histological and cultural examinations. During surgery, fragments of VAC foam, up to 5 × 6 cm size, were identified deeply into the wounds within tissue tunnels and removed. These fragments were also sent for cultural examination (Figure 2). Foam‐fragment retention occurred at a negative pressure level between 100 and 125 mmHg. A targeted antibiotic therapy based on previous antibiograms was started, a copious irrigation of wound bed was executed and reconstruction with skin and fasciocutaneous flaps was performed. Confirmation of germ growth was found at the third postoperative day both in tissue samples and in VAC foam fragments, but not in bone biopsies. The antibiotic therapy was then adjusted and continued as required (Table 1). The histological examinations showed tissue fragments with intense inflammatory response and a pseudo‐epitheliomatous reaction with no sign of neoplasm degeneration. The postoperative course was uneventful. The flaps remained vital and the patients were discharged between 2 and 3 weeks after surgery. Patients were followed up from 1 to 3 years after surgery without an evidence of recurrence.

Figure 2.

Intra‐operative view showing a VAC therapy foam fragment in the left trochanteric pressure sore.

Discussion

Pressure sores represent a frightful complication in critical patients, particularly in traumatised ones with spinal cord injury, in virtue of possible opportunistic infections difficult to be eradicated. Such complex wounds set numerous problems in terms of the treatment modality. Although well‐standardised protocols on pressure sore treatment do exist, the same cannot be said about the existence of management protocols to help setting indications, timing and clinical priorities 8, 9, 10, 11. VAC therapy is indicated to treat these wounds and has gained a very important role in clinical management 6, 12, 13. Originally, this system was used for extremely debilitated patients, showing extensive loss of infected and chronic substances and regarded as non‐treatable 12.

The VAC therapy is a closed‐loop system that, by applying negative pressure (from 25 to 250 mmHg, either as continuous or intermittent cycle), allows removal of exudates and oedema, reduction of bacterial load and stimulation of wound healing 9. By using foam dressing, the negative pressure allows the retention of interstitial fluids that are subsequently collected in a tank and disposed. The evacuation of these fluids does not allow the formation of purulent surface that can be a fertile ground for subsequent colonisation by anaerobic germs. Furthermore, some studies have proved that the negative pressure application allows a dilation of the arterioles with a consequential rise in the blood flow, thus favouring the formation of the granulation tissue in the wound 12, 14. It also exerts a real mechanical traction that allows the wound margins to close, reducing its size. This accelerates the healing process with numerous and proved advantages both at a clinical and economic level. The VAC therapy is applied in many fields, from chronic to post‐traumatic ulcers, from post‐surgical wound dehiscence to post‐oncological loss of substance. Furthermore, the slow therapeutic action of VAC therapy has proved to be very useful for preparation of the area receiving skin graft, thereby improving the percentage of graft take 15, 16, 17, 18. Nowadays, there are different negative pressure therapy (NPT) systems available beside the KCI system, such as VISTA and EZCARE manufactured by Smith and Nephew (London, UK), SVEDMAN and SVED manufactured by Innovative Therapy, Inc. (Gaithersburg, MD) and others [Table 2 19]. The most important differences between these systems are the filler materials used such as foam or non‐adherent antimicrobial gauze, the connecting suction catheter as a flat drain or an integrated tubing with pressure sensor and the intensity of the negative pressure 20. Recently, KCI Licensing Inc. developed NPT pumps called ActiVAC and InfoVAC 19. These devices highly improved the technology and introduced a silver‐impregnated granular foam, which is an optimal source to treat infection 21.

Table 2.

Manufacturer and trade or brand names of NPT devices

NPT devices can have some disadvantages. In fact, even if it is a quite versatile tool, only qualified medical/paramedical personnel should handle it in order to avoid possible complications due to improper use 22.

After the approval of Food and Drug Administration for the treatment of non‐healing chronic wounds 23, VAC therapy indications have been subsequently extended [acute wounds, diabetic ulcers, pressure sores and partial‐ and full‐thickness burns 6]. Such guidelines have been accurately described by Mendez‐Eastman in 2001 13.

VAC therapy is contraindicated when there is a wound with a necrotic tissue at the bottom or when there is an ongoing osteomyelitis process underneath the wound, when arteries or blood vessels are exposed when a neoplasm process causes loss of substance or in cases in which there is a non‐enteric and unexplored fistula. Furthermore, this method is not indicated when there are not enough margins of healthy skin surrounding the wound that can adhere to the medication or when the wound is near a functional orifice. Finally, a special attention must be paid with metabolic or coagulation alterations.

Possible VAC therapy complications are toxic shock syndrome 24, bleeding complication 25, arterial erosion and haemorrhage 26, empyema 27, uncontrolled sepsis 28, 29 and major bleeding complications due to cardiac rupture 30. We also include cases of skin lesions that can occur if the foam is not perfectly applied on top of the wound margins, covering also the healthy skin surrounding the wound.

On the basis of our experience, a rare and more harmful complication is the retention of foam fragments within the wound. Such occurrence does not promote the healing process and creates a condition of chronic morbidity that is difficult to be managed. Indeed, the presence of a foreign body that, having collected the entire previous VAC cycle secretions, becomes a fertile field for bacterial colonisation, preventing the wound from healing.

Furthermore, it can become troublesome with differential diagnosis of more severe conditions, such as osteomyelitis, if the retention of the foam fragment is not detected.

According to our experience, we believe that defining indications, benefits and limits of the NPT as well as user guidelines is necessary in order to avoid the above‐described complications. The retention of foam fragment should be considered in cases of prolonged VAC therapy not bringing any benefit or even causing a possible worsening of the pathological condition.

In conclusion, we believe that NPT is a useful and efficient device to manage difficult wounds, but at the same time, patients undergoing such treatment must be carefully selected and, above all, qualified personnel must be involved.