Hypertonicity: Pathophysiologic Concept and Experimental Studies

Meta-analysis Comparing Outcomes of Two Different Negative Pressure Therapy Systems in Closed Incision Management

BACKGROUND

Closed incision negative pressure therapy (ciNPT) is an emerging approach to managing closed incisions of patients at risk of postoperative complications. There are primarily 2 different commercially available ciNPT systems. Both systems consist of a single-use, battery-powered device and foam- or gauze-based peel-and-place dressing designed for closed incisions. These systems vary in design, and there are no data comparing outcomes between the 2 systems.

METHODS

We performed 2 separate meta-analyses to compare surgical site infection (SSI) rates postuse of (1) ciNPT with foam dressing (FOAM) versus conventional dressings and (2) ciNPT with multilayer absorbent dressing (MLA) versus conventional dressings.

RESULTS

Seven articles and 2 abstracts met inclusion criteria in the FOAM group (n = 489) versus the control group (n = 489) in meta-analysis 1; 7 articles and 1 abstract met inclusion criteria in the MLA group (n = 532) versus the control group (n = 540) in meta-analysis 2. Meta-analysis 1 showed that patients in the control group were 3.17 times more likely to develop an SSI compared with patients in the FOAM group [weighted mean odds ratios of FOAM group versus control group was 3.17 (P < 0.0001) with the 95% confidence intervals of 2.17-4.65]. Meta-analysis 2 showed no significant difference in SSI rates between patients in the MLA group and patients in the control group [weighted mean odds ratios of MLA group versus control group was 1.70 (P = 0.08) with the 95% confidence intervals of 0.94-3.08].

CONCLUSIONS

Comparing outcomes of two different ciNPT systems with a common comparator (conventional dressings) may provide an interim basis for comparing ciNPT systems until further comparative evidence is available. More comparative research is required to determine outcomes in clinical practice.

A Comparative Trial of Incisional Negative-Pressure Wound Therapy in Abdominoplasty

The risk for minor local complications for abdominoplasty remains high despite advances in strategies in recent years. The most common complication is the formation of seroma with reported rates ranging from 15% to 40%. The use of incisional negative-pressure wound therapy (iNPWT) on closed surgical sites has been shown to decrease the infection, dehiscence, and seroma rates. Thus, this article aims to determine whether an iNPWT dressing, Prevena Plus, is able to reduce postoperative drainage and seroma formation in patients who undergo abdominoplasty. Sixteen consecutive patients who underwent abdominoplasty by a single surgeon were dressed with standard dressings and iNPWT dressings. Total drain output, day of drain removal, and adverse events were compared between cohorts with a minimum follow-up of 6 months. The iNPWT group demonstrated a significantly less amount of fluid drainage with a mean total fluid output of 370 ± 275 ml compared to 1269 ± 436 ml mean total drainage from controls (P < 0.001). Time before removal of both drains was almost halved in the iNPWT group with an average of 5.3 ± 1.6 days, which was significantly less than the average time of 10.6 ± 2.9 days seen in control patients (P < 0.001). No observed adverse events were recorded in either group. Our findings show that iNPWT for a closed abdominoplasty incision decreases the rate of postoperative fluid accumulation and results in earlier drain removal.

Cost-effectiveness analysis of single use negative pressure wound therapy dressings (sNPWT) compared to standard of care in reducing surgical site complications (SSC) in patients undergoing coronary artery bypass grafting surgery

Background

There is a growing interest in using negative pressure wound therapy in closed surgical incision to prevent wound complications which continue to persist following surgery despite advances in infection measures.

Objectives

To estimate the cost-effectiveness of single use negative pressure wound therapy (sNPWT) compared to standard of care in patients following coronary artery bypass grafting surgery (CABG) procedure to reduce surgical site complications (SSC) defined as dehiscence and sternotomy infections.

Method

A decision analytic model was developed from the Germany Statutory Health Insurance payer’s perspective over a 12-week time horizon. Baseline data on SSC, revision operations, length of stay, and readmissions were obtained from a prospective observational study of 2621 CABG patients in Germany. Effectiveness data for sNPWT was taken from a randomised open label trial conducted in Poland which randomised 80 patients to treatment with either sNPWT or standard care. Cost data (in Euros) were taken from the relevant diagnostic related groups and published literature.

Results

The clinical study reported an increase in wounds that healed without complications 37/40 (92.5%) in the sNPWT compared to 30/40 (75%) patients in the SC group p = 0.03. The model estimated sNPWT resulted in 0.989 complications avoided compared to 0.952 and the estimated quality adjusted life years were 0.8904 and 0.8593 per patient compared to standard care. The estimated mean cost per patient was €19,986 for sNPWT compared to €20,572 for SC resulting in cost-saving of €586. The findings were robust to a range of sensitivity analyses.

Conclusion

The sNPWT can be considered a cost saving intervention that reduces surgical site complications following CABG surgery compared to standard care. We however recommend that additional economic studies should be conducted as new evidence on the use of sNPWT in CABG patients becomes available to validate the results of this economic analysis.

Fluid balance concepts in medicine: Principles and practice

The regulation of body fluid balance is a key concern in health and disease and comprises three concepts. The first concept pertains to the relationship between total body water (TBW) and total effective solute and is expressed in terms of the tonicity of the body fluids. Disturbances in tonicity are the main factor responsible for changes in cell volume, which can critically affect brain cell function and survival. Solutes distributed almost exclusively in the extracellular compartment (mainly sodium salts) and in the intracellular compartment (mainly potassium salts) contribute to tonicity, while solutes distributed in TBW have no effect on tonicity. The second body fluid balance concept relates to the regulation and measurement of abnormalities of sodium salt balance and extracellular volume. Estimation of extracellular volume is more complex and error prone than measurement of TBW. A key function of extracellular volume, which is defined as the effective arterial blood volume (EABV), is to ensure adequate perfusion of cells and organs. Other factors, including cardiac output, total and regional capacity of both arteries and veins, Starling forces in the capillaries, and gravity also affect the EABV. Collectively, these factors interact closely with extracellular volume and some of them undergo substantial changes in certain acute and chronic severe illnesses. Their changes result not only in extracellular volume expansion, but in the need for a larger extracellular volume compared with that of healthy individuals. Assessing extracellular volume in severe illness is challenging because the estimates of this volume by commonly used methods are prone to large errors in many illnesses. In addition, the optimal extracellular volume may vary from illness to illness, is only partially based on volume measurements by traditional methods, and has not been determined for each illness. Further research is needed to determine optimal extracellular volume levels in several illnesses. For these reasons, extracellular volume in severe illness merits a separate third concept of body fluid balance.

Preliminary result with incisional negative pressure wound therapy and pectoralis major muscle flap for median sternotomy wound infection in a high-risk patient population

Deep sternal wound infection (DSWI) represents a dangerous complication that can follow open-heart surgery with median sternotomy access. Muscle flaps, such as monolateral pectoralis major muscle flap (MPMF), represent the main choices for sternal wound coverage and infection control. Negative pressure incision management system has proven to be able to reduce the incidence of these wounds' complications. Prevena™ represents one of these incision management systems and we aimed to evaluate its benefits. A total of 78 patients with major risk factors that presented post-sternotomy DSWI following cardiac surgery was selected. Thrity patients were treated with MPMF and Prevena™ (study group). Control group consisted of 48 patients treated with MPMF and conventional wound dressings. During the follow-up period, 4 (13%) adverse events occurred in the study group, whereas 18 complications occurred (37·5%) in the control group. Surgical revision necessity and mean postoperative time spent in the intensive care unit were both higher in the control group. Our results evidenced Prevena™ system's ability in improving the outcome of DSWI surgical treatment with MPMF in a high-risk patient population.

Evidence based review of negative pressure wound therapy

Vacuum-assisted closure, sometimes referred to as microdeformational wound therapy or most commonly negative pressure wound therapy (NPWT), has significantly improved wound care over the past two decades. NPWT is known to affect wound healing through four primary mechanisms (macrodeformation, microdeformation, fluid removal, and alteration of the wound environment) and various secondary mechanisms (including neurogenesis, angiogenesis, modulation of inflammation, and alterations in bioburden) which are described in this review. In addition, the technique has many established uses, for example in wound healing of diabetic and pressure ulcers, as well as burn and blast wounds. This therapy also has many uses whose efficacy has yet to be confirmed, for example the use in digestive surgery. Modifications of the traditional NPWT have also been established and are described in detail. This therapy has various considerations and contraindications which are summarized in this review. Finally, future perspectives, such as the optimal cycling of the treatment and the most appropriate interface material, are touched upon in the final segment. Overall, despite the fact that questions remain to be answered about NPWT, this technology is a major breakthrough in wound healing with significant potential use both in the hospital but also in the community.

Effect of a new incision management system (PREVENA®) on wound healing after endophlebectomy of the common femoral vein: a case series

Background

New endovascular techniques facilitate treatment of complex deep vein obstructions in cases of post-thrombotic syndrome. In a relevant number of these patients, endophlebectomy including the implantation of an arteriovenous fistula between the common femoral artery and the femoral vein is indispensable in order to establish a good inflow. These procedures display a high risk of wound complications. Despite conservative efforts to prevent these postoperative complications, wound healing problems occur in more than 20 % of cases. The present case report is the first description of wound dressing using a PREVENA® incision management system in cases of endophlebectomy.

Case presentation

A single center’s experience with the incision management system PREVENA®, which was used after endophlebectomy and venous stenting in complex hybrid procedures in three white men aged 46 years, 53 years, and 61 years is the subject of this case report. Although the surgical procedures were performed under therapeutical anticoagulation and took a couple of hours, no wound complications occurred.

Conclusions

These encouraging results underline a potential benefit of the incision management system PREVENA® in cases of complex venous recanalization including endophlebectomy of the femoral vein as well as the implantation of an arteriovenous fistula.