Ann. Pak. Inst. Med. Sci. 2012; 8(1): 1-2      

Medicine is an ever  evolving science. The present day medicine is termed as evidence based medicine wherein practice and policies are guided by sound clinical and experimental evidence supporting the  benefits and safety of a given therapeutic modality. Over the last decade, Vacuum Assisted Closure therapy  (VAC therapy) has emerged as a novel adjunct to the management of surgical wounds across a range of specialties. ^1-3
How does the VAC therapy work?  Since the technique is relatively new, its exact mechanism of action still continues to be researched. A variety of interrelated factors have been identified to account for its favorable effects on wound  healing. These factors can be summarized into three  subgroups i.e.  removing, reducing and Improving.  Firstly the edematous tissue planes surrounding the wound are characterized by localized collection of interstitial fluid that contains inhibitory factors that suppress mitosis, fibroblasts activity, collagen production, and cell growth. The VAC therapy actively withdraws this fluid and its constituent   inhibitory factors.  Secondly the VAC therapy reduces the bacterial counts of the wound to a level far lower than what can cause infection.  Thirdly VAC therapy   improves the entire healing process through its direct and indirect effects. With removal of local edema, the microcirculation and lymphatic/ venous drainage is reestablished. The  delivery of oxygen and nutrients to the wound is optimized. The micromechanical forces of  low pressure suction exerts an Ilizarovian effect at cellular level, resulting in  increased expression of mRNA and protein synthesis. There is increased Angiogenesis. The moist environment provided by VAC technique promotes granulation tissue formation and healing. ^4-6  The wound if small is thus encouraged to close spontaneously. Larger and complex wounds are rendered  suitable for definitive reconstruction with skin graft or flap.
How can the VAC therapy be applied to a wound? Not surprisingly  with growing understanding of the mechanism involved, one can easily construct a  VAC dressing at bed side and  convert an open wound into a close controlled one.  Before its application to the wound, once  must make sure that wound is first adequately  debrided with excision of all devitalized tissues. Two sheets of  synthetic foam are then  tailored the size and shape of the wound and the wound is covered with them with a  Redivac suction drain placed  between the two sheets.  A transparent sealing plastic membrane sheet such as  Opsite or  plastic food wrap is then applied to the foam layers, making the system water tight and air tight. The suction drain is connected to Suction machine or wall vacuum suction maintained at 50-120 mmHg. It  is maintained for five  days, at which point the VAC dressing is removed.  A fresh VAC dressing may be applied for another five days and  the wound  re-evaluated for further definitive management. ¹
What kind of wounds are suitable for VAC therapy?   In fact the VAC therapy finds almost universal applicability across a range of wounds, with only few contraindications such as malignancy, bleeding diathesis and exposed major blood vessels. When employed, VAC therapy helps to temporize wounds, giving time for stabilization of the patient until complex reconstructive procedures can be instituted on a prepared wound bed. It is effective both in the  preparatory phase of wound prior to any  reconstruction and as postoperative dressings for securing skin grafts especially in wounds on difficult anatomic locations.^{1, 7-10}
Owing to its low cost, VAC therapy provides an economical alternative to the other available costly local wound management measures. Such economic implications of wound management are particularly important in the context of our limited health budgets. It also reduces the need for daily change of dressing thus comforting the patients on one hand  and reducing the work load of the  staff responsible for wound dressings on the other hand. With expeditious wound healing, the overall hospital stay of the patients is also reduced. ¹
Given the growing body of quality evidence, VAC therapy should be adequately employed particularly in the problem wounds and in the problem patients such as those with diabetes mellitus and peripheral vascular disease. Nonetheless once must not forget that  it is an adjunct to other established  wound care measures such as thorough debridement and not a substitute for them.

References

1. Saaiq M, Din HU, Khan MI, Chaudhery SM. Vacuum-assisted closure therapy as a pretreatment for split thickness skin grafts. J Coll Physicians Surg Pak. 2010; 20(10):675-9.

2. Baillot R, Cloutier D, Montalin L. Impact of deep sternal wound infection management with vacuum-assisted closure therapy followed by sternal osteosynthesis: a 15-year review of 23,499 sternotomies. Eur J Cardiothorac Surg. 2010; 37(4):880-7.

3. Blume P, Walters J, Payne W. Comparison of negative pressure wound therapy using vacuum-assisted closure with advanced moist wound therapy in the treatment of diabetic foot ulcers: a multicenter randomized controlled trial. Diabetes Care 2008; 31(4):631-6.

4. Morris GS, Brueilly KE, Hanzelka H. Negative pressure wound therapy achieved by vacuum-assisted closure: evaluating the assumptions. Ostomy Wound Manage. 2007; 53: 52–7.

5. Ubbink DT, Westerbos SJ, Nelson EA, Vermeulen H. A systematic review of topical negative pressure therapy for acute and chronic wounds. Br J Surg. 2008;95(6):685-92.

6. Saxena V, Hwang CW, Huang S, Eichbaum Q, Ingber D, Orgill DP. Vacuum-assisted closure: microdeformations of wounds and cell proliferation. Plast Reconstr Surg 2004; 114:1086-96.

7. Penn-Barwell JG, Fries CA, Street L, Jeffery S. Use of topical negative pressure in British servicemen with combat wounds. ePlasty 2011;11: 354-63.

8. Nather A, Chionh SB, Han AYY,1 Chan PPL, Nambiar A. Effectiveness of Vacuum-assisted Closure (VAC) Therapy in the Healing of Chronic Diabetic Foot Ulcers. Ann Acad Med 2010 ;39 ( 50): 353-8.

9. Stannard JP, Volgas DA, Stewart R, McGwin G, Alonso JE. Negative pressure wound therapy after severe open fractures: a prospective randomized study. J Orthop Trauma. 2009;23(8):552-7.

10. Petkar KS, Dhanraj P, Kingsly PM, Sreekar H, Lakshmanarao A, Lamba S, et al. A prospective randomized controlled trial comparing negative pressure dressing and conventional dressing methods on split thickness skin grafts in burned patients. Burns 2011;37:925-9.