The role of mechanical ventilation in primary graft dysfunction in the postoperative lung transplant recipient: A single center study and literature review

Background

Primary graft dysfunction (PGD) is still a major complication in patients undergoing lung transplantation (LTx). Much is unknown about the effect of postoperative mechanical ventilation on outcomes, with debate on the best approach to ventilation.

Aim/Purpose

The goal of this study was to generate hypotheses on the association between postoperative mechanical ventilation settings and allograft size matching in PGD development.

Method

This is a retrospective study of LTx patients between September 2011 and September 2018 (n = 116). PGD was assessed according to the International Society of Heart and Lung Transplantation (ISHLT) criteria. Data were collected from medical records, including chest x‐ray assessments, blood gas analysis, mechanical ventilator parameters and spirometry.

Results

Positive end‐expiratory pressures (PEEP) of 5 cm H₂O were correlated with lower rates of grade 3 PGD. Graft size was important as tidal volumes calculated according to the recipient yielded greater rates of PGD when low volumes were used, a correlation that was lost when donor metrics were used.

Conclusion

Our results highlight a need for greater investigation of the role donor characteristics play in determining post‐operative ventilation of a lung transplant recipient. The mechanical ventilation settings on postoperative LTx recipients may have an implication for the development of acute graft dysfunction. Severe PGD was associated with the use of a PEEP higher than 5 and lower tidal volumes and oversized lungs were associated with lower long‐term mortality. Lack of association between ventilatory settings and survival may point to the importance of other variables than ventilation in the development of PGD.

[Lungtransplantation in Sweden - over 1 200 patients transplanted since 1990]

Lung transplantation is an accepted treatment for end stage lung diseases and performed at two national centers in Sweden - Gothenburg and Lund. Since the start in 1990 over 1 200 patients have been transplanted.  The indications are severe progressive lung diseases with short expected survival or severe negative effects on daily life. There are several contraindications among which severe other organ disease, recent malignancy or psychiatric disease are most important.  The most common causes for lung transplantation are chronic obstructive pulmonary disease (COPD), interstitial pulmonary disease, cystic fibrosis and pulmonary hypertension.  Long term survival after 5 years is 63 %, and after 10 years 48 %, which is better than the results reported in the international registry (57 % and 36 % respectively).   Lung transplantation is today a therapy for end stage pulmonary diseases with acceptable survival results. It is likely that the number of patients will increase in the future.

Sevoflurane provides better haemodynamic stability than propofol during right ventricular ischaemia-reperfusion

OBJECTIVES

To assess whether sevoflurane provides better haemodynamic stability than propofol in acute right ventricular (RV) ischaemia-reperfusion.

METHODS

Open-chest pigs (mean ± standard deviation, 68.8 ± 4.2 kg) anaesthetized with sevoflurane (n = 6) or propofol (n = 6) underwent 60 min of RV free wall ischaemia and 150 min of reperfusion. Haemodynamic parameters and blood flow in the 3 major coronary arteries were continuously monitored. Biomarkers of cardiac ischaemia were analysed.

RESULTS

Mean arterial pressure and stroke volume decreased, whereas pulmonary vascular resistance increased equally in both groups. Heart rate increased 7.5% with propofol (P < 0.05) and 17% with sevoflurane (P < 0.05). At reperfusion, left atrial pressure and systemic vascular resistance decreased with sevoflurane. While RV stroke work (mmHg·ml) and cardiac output (l·min-1) decreased in the propofol group (4.2 ± 1.2 to 2.9 ± 1.7 and 2.65 ± 0.44 to 2.28 ± 0.56, respectively, P < 0.05 both), they recovered to baseline levels in the sevoflurane group (4.1 ± 1.5 to 4.0 ± 1.5 and 2.77 ± 0.6 to 2.6 ± 0.5, respectively, P > 0.05). Circumflex and left anterior descending coronary artery blood flow decreased in both groups. Right coronary artery blood flow (ml·min-1) decreased with propofol (38 ± 9 to 28 ± 9, P < 0.05), but not with sevoflurane (28 ± 11 to 28 ± 17, P > 0.05). Biomarkers of cardiac ischaemia increased in both groups.

CONCLUSIONS

Compared to propofol, sevoflurane-anaesthetized pigs showed higher RV stroke work, cardiac output and right coronary artery blood flow during reperfusion. These findings warrant a clinical trial of sevoflurane in RV ischaemia in humans.

Ten year follow-up of lung transplantations using initially rejected donor lungs after reconditioning using ex vivo lung perfusion

Background

In 2006 and 2007 we performed double lung transplantation with marginal donor lungs assessed and reconditioned by Ex Vivo Lung Perfusion (EVLP), using a technique developed by Professor Stig Steen. Here we present a 10-year follow-up comparing the outcomes of lung transplantations performed at our clinic using EVLP lungs vs. conventional lungs.

Method

Between 2006 and 2007, 21 patients (6 EVLP, 15 conventional) underwent double lung transplantation (LTx) with follow-up on May 2017 at Lund University Hospital, Sweden. Pulmonary function was measured at 3/6/12 months, and annually thereafter for a period of 10 years in addition to survival and freedom from chronic lung allograft dysfunction (CLAD) being analyzed.

Results

Regarding Forced Expiratory Volume in 1 s (FEV1) and 6MWT at 3, 6, and 12 months and annually thereafter, no difference in median FEV1 nor 6MWT was found for EVLP-LTx vs. conventional-LTx (p > 0.05). No difference was shown in post-operative survival between EVLP-LTx vs. conventional LTx for patients with an overall survival up to 10-years (p > 0.05). The same pattern was shown in sub analyses for patients with a limited survival up to 1 and 5 years (p > 0.05).

Conclusion

No superiority was found in conventional-LTx over EVLP-LTx, neither in long-term survival nor pulmonary function. No difference in CLAD-free survival was seen between the two groups. We believe that EVLP is a safe and effective method to use in LTx, greatly increasing the donor pool by improving marginal lungs and providing an objective assessment of the viability of marginal donor lungs.

Engaging patients and caregivers in establishing research priorities for aortic dissection

Objectives:

The aim of this study was to establish the top 10 research uncertainties in aortic dissection together with the patient organization Aortic Dissection Association Scandinavia using the James Lind Alliance concept.

Methods:

A pilot survey aiming to identify uncertainties sent to 12 patients was found to have high content validity (scale content validity index = 0.91). An online version of the survey was thereafter sent to 30 patients in Aortic Dissection Association Scandinavia and 45 caregivers in the field of aortic dissection. Research uncertainties of aortic dissection were gathered, collated and processed.

Results:

Together with research priorities retrieved from five different current guidelines, 94 uncertainties were expressed. A shortlist of 24 uncertainties remained after processing for the final workshop. After the priority-setting process, using facilitated group format technique, the ranked final top 10 research uncertainties included diagnostic tests for aortic dissection; patient information and care continuity; quality of life; endovascular and medical treatment; surgical complications; rehabilitation; psychological consequences; self-care; and how to improve prognosis.

Conclusion:

These ranked top 10 important research priorities may be used to justify specific research in aortic dissection and to inform healthcare research funding decisions.

Impact of donor chest radiography on clinical outcome after lung transplantation

Background

Organ donation guidelines recommend a “clear” conventional bedside chest radiograph before lung transplantation despite only moderate accuracy for cardiopulmonary abnormalities.

Purpose

To evaluate the influence of donor image interpretation on lung transplantation outcome in recipients by following early and late complications, one-year survival, and to correlate imaging findings and blood gas analysis with lung transplantation outcome in recipients.

Material and Methods

In 35 lung donors from a single institution clinical reports and study reviews of imaging findings of the mandatory bedside chest radiographs and blood gas analyses were compared with clinical outcome in 38 recipients. Hospitalization time, peri- and postoperative complications, early complications (primary graft dysfunction, infection), 30-day and one-year survival, and forced expiratory volume in 1 s percentage of predicted normal value (FEV1%) at one-year follow-up were analyzed.

Results

Findings in clinical reports and study reviews differed substantially, e.g. regarding reported decompensation, edema, infection, and atelectasis. No correlation was shown between imaging findings in clinical report or study review and blood gas analyses in the lung donors compared to postoperative outcome in recipients.

Conclusion

The interpretation of the mandatory chest radiograph in its present form does not influence one-year outcome in lung transplantation. Larger imaging studies or a change in clinical routine including computed tomography may provide evidence for future guidelines.

Double lung, unlike single lung transplantation might provide a protective effect on mortality and bronchiolitis obliterans syndrome

Background

Survival after lung transplantation (LTx) is often limited by bronchiolitis obliterans syndrome (BOS).

Method

Survey of 278 recipients who underwent LTx. The endpoint used was BOS (BOS grade ≥ 2), death or Re-lung transplantation (Re-LTx) assessed by competing risk regression analyses.

Results

The incidence of BOS grade ≥ 2 among double LTx (DLTx) recipients was 16 ± 3% at 5 years, 30 ± 4% at 10 years, and 37 ± 5% at 20 years, compared to single LTx (SLTx) recipients whose corresponding incidence of BOS grade ≥ 2 was 11 ± 3%, 20 ± 4%, and 24 ± 5% at 5, 10, and 20 years, respectively (p > 0. 05). The incidence of BOS grade ≥ 2 by major indications ranked in descending order: other, PF, CF, COPD, PH and AAT1 (p < 0. 05). The mortality rate by major indication ranked in descending order: COPD, PH, AAT1, PF, Other and CF (p < 0. 05).

Conclusion

No differences were seen in the incidence of BOS grade ≥ 2 regarding type of transplant, however, DLTx recipients showed a better chance of survival despite developing BOS compared to SLTx recipients. The highest incidence of BOS was seen among CF, PF, COPD, PH, and AAT1 recipients in descending order, however, CF and PF recipients showed a better chance of survival despite developing BOS compared to COPD, PH, and AAT1 recipients.

Predictors and impact of massive bleeding in acute type A aortic dissection

Objectives

Bleeding complications associated with acute type A aortic dissection (aTAAD) are a well-known clinical problem. Here, we evaluated predictors of massive bleeding related to aTAAD and associated surgery and assessed the impact of massive bleeding on complications and survival.

Methods

This retrospective study of 256 patients used Blood Conservation Using Antifibrinolytics in a Randomized Trial (BART) criteria to define massive bleeding, which was met by 66 individuals (Group I) who were compared to the remaining patients (Group II). Multivariable logistic regression was used to identify independent predictors of massive bleeding and in-hospital mortality, Kaplan-Meier estimates for analysis of late survival, and Cox regression analysis to evaluate independent predictors of late mortality.

Results

Independent predictors of massive bleeding included symptom duration (odds ratio [OR], 0.974 per hour increment; 95% confidence interval [CI], 0.950-0.999; P  =   0.041) and DeBakey type 1 dissection (OR, 2.652; 95% CI, 1.004-7.008; P  =   0.049). In-hospital mortality was higher in Group I (30.3% vs 8.0%, P  <0.001). Kaplan-Meier estimates of survival indicated poorer survival for Group I at 1, 3 and 5 years (68.8 ± 5.9% vs 92.8 ± 1.9%; 65.2 ± 6.2% vs 85.3 ± 2.7%; 53.9 ± 6.9% vs 82.1 ± 3.3 %, respectively; log rank P  <   0.001). Re-exploration for bleeding was an independent predictor of in-hospital (OR, 3.109; 95% CI, 1.044-9.256; P  =   0.042) and late mortalities (hazard ratio, 3.039; 95% CI, 1.605-5.757; P  =   0.001).

Conclusions

Massive bleeding in patients with aTAAD is prompted by shorter symptom duration and longer extent of dissection and has deleterious effects on outcomes of postoperative complications as well as in-hospital and late mortalities.

Experiences of supportive care when waiting for a lung re-transplantation

Objectives:

Lung transplant patients and their next of kin share the experiences of illness but little is known in the face of a lung re-transplantation. To describe patients’ and next of kin’s experiences of supportive care while awaiting lung re-transplantation and the objective was to highlight a small group with special circumstances and needs.

Methods:

Using qualitative content analysis, seven adult patients and seven next of kin were consecutively selected from a regional lung transplantation centre and individually interviewed shortly after decision about lung re-transplantation.

Results:

The experiences of supportive care were captured in one main category: ‘once again haunted by death’ and three sub-categories: ‘when life turns and death once again snorts down your neck’, ‘the importance of information’, and ‘perceptions of support’. A complex interaction between the experience of waiting, and communication patterns, emotional states, and social support was shown.

Conclusion:

This study provides insights into the complex interaction between the experience of waiting for a second lung transplant and communication patterns, emotional states, social support and social roles between patients, next of kin, healthcare professionals, and the health and social welfare system. There is a need for developing supportive care programme to achieve the best possible care.

Protection of pulmonary graft from thrombosis in donation after cardiac death: effect of warm ischaemia versus cold ischaemia

OBJECTIVES

The use of donation after cardiac death (DCD) to overcome organ shortage is slowly moving into the clinic. In this study, we compare the protective effect of warm ischaemia versus cold ischaemia on thrombotic formation in non-heparinized pulmonary grafts.

METHODS

Twelve Landrace pigs were randomized into two groups: warm ischaemia and cold ischaemia. Ventricular fibrillation without the administration of heparin was induced to mimick an uncontrolled DCD situation. The animals were then exposed to either 1 h of cold ischaemia (insertion of drain and installation of cold fluid in the pleuras) or warm ischaemia (body temperature). After 1 h, the pulmonary artery was opened and the pulmonary arterial branches were then macroscopically studied for thrombotic material.

RESULTS

After 60 min, the temperature was 36.6 ± 0.0°C in the warm ischaemic group and 14.6 ± 0.1°C in the cold ischaemic group (P < 0.001). In the warm ischaemic group, no thrombotic material could be found in the pulmonary artery in the animals examined and in the cold ischaemic group 6.8 ± 0.2 ml thrombotic material was found in the pulmonary artery (P < 0.001). In the warm ischaemic group, no thrombotic material could be found in the arterial branches of the pulmonary artery and in the cold ischaemic group 2.3 ± 0.1 ml thrombotic material was found in the arterial branches of the pulmonary artery (P < 0.001).

CONCLUSIONS

Warm ischaemia rather than cold ischaemia seems to protect the pulmonary graft from thrombosis in uncontrolled non-heparinized DCD pigs.

25-year follow-up after lung transplantation at Lund University Hospital in Sweden: superior results obtained for patients with cystic fibrosis

OBJECTIVES

In Sweden, two centres perform lung transplantation for a population of about 9 million and the entire population is covered for lung transplantation by government health insurance. Lund University Hospital is one of these centres. This retrospective report reviews the 25-year experience of the Skåne University Hospital Lung Transplant Program with particular emphasis on short-term outcome and long-term survival but also between different subgroups of patients and types of transplant [single-lung transplantation (SLTx) versus double-lung transplantation (DLTx)] procedure performed.

METHODS

Between January 1990 and June 2014, 278 patients underwent lung transplantation at the Skåne University Hospital Sweden. DLTx was performed in 172 patients, SLTx was performed in 97 patients and heart-lung transplantation was performed in 9 patients. In addition, 15 patients required retransplantation (7 DLTx and 8 SLTx).

RESULTS

Overall 1-, 5-, 10-, 15- and 20-year survival rates were 88, 65, 49, 37 and 19% for the whole cohort. DLTx recipients showed 1-, 5-, 10- and 20-year survival rates of 90, 71, 60 and 30%, compared with SLTx recipients with 1-, 5-, 10- and 20-year survival rates of 83, 57, 34 and 6% (P < 0.05), respectively. Comparing the use of intraoperative extracorporeal membrane oxygenation, extracorporeal circulation (ECC) and no circulatory support in the aspect of survival, a significant difference in favour of intraoperative ECC was seen.

CONCLUSIONS

Superior long-term survival rates were seen in recipients diagnosed with cystic fibrosis, α1-antitrypsin deficiency and pulmonary hypertension. DLTx showed better results compared with SLTx especially at 10 years post-transplant. In the present study, we present cumulative incidence rates of bronchiolitis obliterans syndrome of 15% at 5 years, 26% at 10 years and 32% at 20 years post-transplant; these figures are in line with the lowest rates presented internationally.

Sevoflurane anesthesia during acute right ventricular ischemia in pigs preserves cardiac function better than propofol anesthesia

BACKGROUND

The intention of the present study was to evaluate possible cardioprotective properties of inhalation anesthesia with sevoflurane.

METHODS AND MATERIALS

A porcine, open-chest model of right ventricular ischemia was used in 7 pigs receiving inhalation anesthesia with sevoflurane. The model was earlier developed and published by our group, using pigs receiving intravenous anesthesia with propofol. They served as controls. The animals were observed for three hours after the induction of right ventricular ischemia by ligation of the main branches supplying the right ventricular free wall.

RESULTS

In the sevoflurane group, the cardiac output recovered 2 hours after the induction of ischemia and intact right ventricular stroke work was observed. In the propofol group, no such recovery occurred. The release of troponin T was significantly lower than in the sevoflurane group.

CONCLUSIONS

Inhalation anesthesia with sevoflurane seems superior to intravenous anesthesia with propofol in acute right ventricular ischemic dysfunction.

Lungs exposed to 1 hour warm ischemia without heparin before harvesting might be suitable candidates for transplantation

Background

The limiting factor for lung transplantation is the lack of donor organs. The usage of lungs from donation after cardiac death (DCD) would dramatically increase donor availability. In the present paper we wanted to investigate lungs exposed to 1 h of warm ischemia without heparin followed by flush-perfusion and cold storage compared to lungs harvested from heart beating donors (HBD) using standard harvesting technique.

Methods

Twelve Swedish domestic pigs were randomized into two groups. Six pigs (DCD group) underwent ventricular fibrillation and were then left untouched for 1 h after declaration of death. They did not receive heparin. The lungs were then harvested and flush-perfused with Perfadex® solution and the organs were stored at 8 °C for 4 h. Six pigs (HBD group) received heparin and the lungs were harvested and flush-perfused with Perfadex® solution and the organs were stored at 8 °C for 4 h. Lung function was evaluated, using ex vivo lung perfusion (EVLP), with blood gases at different oxygen levels, pulmonary vascular resistance (PVR), lung weight, and macroscopic appearance.

Results

At FiO₂ 1.0, the PaO₂ in the DCD group was 51.7 ± 2.0 kPa and in the HBD group 68.6 ± 2.4 kPa (p < 0.01). Significantly lower PVR levels were measured in the DCD group (372 ± 31 dyne x s/cm⁵) compared to the HBD group (655 ± 45 dyne x s/cm⁵) (p < 0.001). There was no significant difference between groups in weight, compliance or signs of pulmonary thrombosis or embolization.

Conclusions

It seems as if DCD lungs exposed to 1 h of warm ischemia before 4 h of cold storage has satisfying oxygenation capacity, low PVR, normal weight and no signs of thrombosis or embolization. According to our study it seems as lungs exposed to 1 h warm ischemia without heparin might be good candidates for transplantation.

Generalized ischaemia in type A aortic dissections predicts early surgical outcomes only

OBJECTIVES

In patients with acute type A aortic dissection (aTAAD), early post-surgical outcomes are largely influenced by preoperative conditions, specifically localized or generalized ischaemia. Such states are reflected in the recent Penn classification. Our aim was to determine the impact of preoperative ischaemia (by Penn class) on in-hospital and long-term mortality.

METHODS

All consecutive patients (n = 341) surgically treated for aTAAD between 1998 and 2014 were recruited for a retrospective observational study. Parameters impacting in-hospital and long-term mortality were identified through univariable and multivariable analyses.

RESULTS

In-hospital mortality rates by Penn class were as follows: Class Aa, 11%; Class Ab, 14%; Class Ac, 42% and Class Abc, 29%. Both Ac [odds ratio (OR) = 4.4; 95% confidence interval (CI), 1.92-9.80] and Abc (OR = 3.72; 95% CI, 1.26-10.99) classifications independently predicted in-hospital mortality, as did cardiopulmonary bypass time (OR = 1.01; 95% CI, 1.00-1.01). Relative to Class Aa patients, survival did not differ significantly in Class Ac and Abc subsets (log-rank P = 0.365 and P = 0.716, respectively), once 30-day postoperative deaths were excluded. The leading cause of late mortality was cardiac failure or myocardial infarction (29%), followed by aortic rupture (25%). Independent predictors of long-term mortality after aTAAD were age [hazard ratio (HR) = 1.08; 95% CI, 1.05-1.10] and supracoronary replacement graft (HR = 2.27; 95% CI, 1.1-4.75).

CONCLUSIONS

Penn classes Ac and Abc were identified as an independent risk factor for in-hospital mortality, whereas neither Penn class nor organ-specific ischaemia significantly impacted long-term survival. Regardless of ischaemic manifestations at presentation, the prognosis of patients surviving both surgery and early postoperative period proved acceptable.

Can post-sternotomy mediastinitis be prevented by a closed incision management system?

Post-sternotomy mediastinitis is a serious complication after cardiothoracic surgery and contribute significantly to post-operative morbidity, mortality, and healthcare costs. Negative pressure wound therapy is today's golden standard for post-sternotomy mediastinitis treatment. A systematic literature search was conducted at PubMed until October 2012 to analyse whether vacuum-assisted closure technique prevents mediastinitis after clean surgical incisions closure. Today's studies showed reduction of post-sternotomy mediastinitis including a beneficial socio-economic impact. Current studies, however included only high-risk patients, hence furthermore, larger randomised controlled trials are warranted to clarify the benefit for using surgical incision vacuum management systems in the general patient population undergoing sternotomy and clarify risk factor interaction.

Use of incisional negative pressure wound therapy on closed median sternal incisions after cardiothoracic surgery: clinical evidence and consensus recommendations

Negative pressure wound therapy is a concept introduced initially to assist in the treatment of chronic open wounds. Recently, there has been growing interest in using the technique on closed incisions after surgery to prevent potentially severe surgical site infections and other wound complications in high-risk patients. Negative pressure wound therapy uses a negative pressure unit and specific dressings that help to hold the incision edges together, redistribute lateral tension, reduce edema, stimulate perfusion, and protect the surgical site from external infectious sources. Randomized, controlled studies of negative pressure wound therapy for closed incisions in orthopedic settings (which also is a clean surgical procedure in absence of an open fracture) have shown the technology can reduce the risk of wound infection, wound dehiscence, and seroma, and there is accumulating evidence that it also improves wound outcomes after cardiothoracic surgery. Identifying at-risk individuals for whom prophylactic use of negative pressure wound therapy would be most cost-effective remains a challenge; however, several risk-stratification systems have been proposed and should be evaluated more fully. The recent availability of a single-use, closed incision management system offers surgeons a convenient and practical means of delivering negative pressure wound therapy to their high-risk patients, with excellent wound outcomes reported to date. Although larger, randomized, controlled studies will help to clarify the precise role and benefits of such a system in cardiothoracic surgery, limited initial evidence from clinical studies and from the authors' own experiences appears promising. In light of the growing interest in this technology among cardiothoracic surgeons, a consensus meeting, which was attended by a group of international experts, was held to review existing evidence for negative pressure wound therapy in the prevention of wound complications after surgery and to provide recommendations on the optimal use of negative pressure wound therapy on closed median sternal incisions after cardiothoracic surgery.

The Duration of Negative Pressure Wound Therapy Can Be Reduced Using the HeartShield Device in Patients With Deep Sternal Wound Infection

BACKGROUND

Heart rupture resulting in lethal bleeding is a devastating complication associated with negative pressure wound therapy (NPWT) in patients with deep sternal wound infection (DSWI). We have previously reported that the use of a protective HeartShield device in combination with NPWT decreases the risk of damage to the heart. This article presents a retrospective analysis of NPWT duration with and without the HeartShield device.

SUBJECTS AND PATIENTS

The study included 6 patients treated with the HeartShield device in combination with NPWT and 6 patients treated with conventional NPWT during the same time period. The duration of active treatment time was measured.

RESULTS

The median duration of NPWT was 8 days (range: 6-14 days) in the HeartShield device NPWT group and 14 days in the conventional group (range: 10-18 days). The difference was statistically significant (P < .05).

CONCLUSIONS

It appears that the treatment of patients with DSWI with the HeartShield device reduces the duration of NPWT.

Anatomic feasibility of endovascular reconstruction in aortic arch aneurysms

The purpose was to estimate the proportion of current open aortic arch reconstructions that might be feasible for endovascular repair. From all elective repair made in Southern Sweden in one center between 2005 and 2012, 129 open and eight endovascular aortic arch repairs were identified. The anatomy of the ascending arch and descending aorta as well as the arch vessels was categorized from multiplanar and axial computed tomography scans. Of 129 open cases, only two (1.5%) were suitable for endovascular repair. Among 137 all arch open and endovascular arch reconstructions performed during the study period, only 10 (7%) were candidates for endovascular repair. The most common exclusion for endovascular repair was an excessively large ascending aortic diameter. In conclusion, only a small proportion of patients having an open arch repair are suitable for endovascular arch repair, a finding related to the large diameter of the ascending aorta.

Use of bacteria- and fungus-binding mesh in negative pressure wound therapy provides significant granulation tissue without tissue ingrowth

OBJECTIVE

Bacteria- and fungus-binding mesh traps and inactivates bacteria and fungus, which makes it interesting, alternative, and wound filler for negative pressure wound therapy (NPWT). The aim of this study was to compare pathogen-binding mesh, black foam, and gauze in NPWT with regard to granulation tissue formation and ingrowth of wound bed tissue in the wound filler.

METHODS

Wounds on the backs of 8 pigs underwent 72 hours of NPWT using pathogen-binding mesh, foam, or gauze. Microdeformation of the wound bed and granulation tissue formation and the force required to remove the wound fillers was studied.

RESULTS

Pathogen-binding mesh produced more granulation tissue, leukocyte infiltration, and tissue disorganization in the wound bed than gauze, but less than foam. All 3 wound fillers caused microdeformation of the wound bed surface. Little force was required to remove pathogen-binding mesh and gauze, while considerable force was needed to remove foam. This is the result of tissue growth into the foam, but not into pathogen-binding mesh or gauze, as shown by examination of biopsy sections from the wound bed.

CONCLUSIONS

This study shows that using pathogen-binding mesh as a wound filler for NPWT leads to a significant amount of granulation tissue in the wound bed, more than that with gauze, but eliminates the problems of ingrowth of the wound bed into the wound filler. Pathogen-binding mesh is thus an interesting wound filler in NPWT.

A porcine model for acute ischaemic right ventricular dysfunction

OBJECTIVES

To establish an experimental model for acute ischaemic isolated right ventricular dysfunction and the subsequent haemodynamic changes.

METHODS

An open-chest porcine model with ischaemic dysfunction of the right ventricle induced by ligation of the three main branches supporting the right ventricular free wall. Invasive monitoring of mean arterial blood pressure (MAP), central venous pressure (CVP), left atrial pressure (LAP) and right ventricular pressure (RVP); ultrasonic measurement of cardiac output (CO) and calculation of haemodynamic parameters such as stroke volume (SV), systemic vascular resistance (SVR), pulmonary vascular resistance (PVR) and right ventricular stroke work (RVSW) using standard formulae.

RESULTS

The ischaemic challenge to the right ventricle resulted in a significant (≥30%) reduction in RVSW associated with an increase (6-25%) in CVP and reduction (8-18%) in pulmonary artery pressure (PAP) despite unchanged PVR, all reflecting the failing right ventricle. There was also a significant drop in CO (14-22%) despite unchanged LAP indicating lessened transpulmonary delivery of left ventricular preload due to the failing right ventricle causing the haemodynamic compromise rather than left ventricular failure. Supraventricular and ventricular arrhythmias occurred in three and two out of seven pigs, respectively-all of which except one were successfully resuscitated with cardioversion and/or defibrillation.

CONCLUSIONS

This novel open-chest porcine model of induced ischaemia of the right ventricular free wall resulted in significant haemodynamic compromise confirmed using standard haemodynamic measurements making it useful for further research on acute, ischaemic isolated right ventricular failure.

C-reactive protein and leucocyte counts drop faster using the HeartShield® device in patients with DSWI

Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier disc (HeartShield™) has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up by the negative pressure and damaged by the sharp sternum bone edges. Seven patients treated with conventional NPWT and seven patients treated with NPWT with a protective barrier disc (HeartShield) were compared with regard to bacterial clearance and infection parameters including C-reactive protein levels and leucocyte counts. C-reactive protein levels and leucocyte counts dropped faster and bacterial clearance occurred earlier in the HeartShield® group compared with the conventional NPWT group. Negative biopsy cultures were shown after 3·1 ± 0·4 NPWT dressing changes in the HeartShield group, and after 5·4 ± 0·6 NPWT dressing changes in the conventional NPWT group (P < 0·001). All patients were followed up with clinical check-up after 3 months. None of the patients in the HeartShield group had any signs of reinfection such as deep sternal wound infection (DSWI) or sternal fistulas, whereas in the conventional NPWT group, two patients had signs of sternal fistulas that demanded hospitalisation. HeartShield hinders the right ventricle to come into contact with the sharp sternal edges during NPWT and thereby protects from heart damage. This study shows that using HeartShield is beneficial in treating patients with DSWI. Improved wound healing by HeartShield may be a result of the efficient drainage of wound effluents from the thoracic cavity.

Comparative study of the microvascular blood flow in the intestinal wall, wound contraction and fluid evacuation during negative pressure wound therapy in laparostomy using the V.A.C. abdominal dressing and the ABThera open abdomen negative pressure therapy system

This study aimed to compare the changes in microvascular blood flow in the small intestinal wall, wound contraction and fluid evacuation, using the established V.A.C. abdominal dressing (VAC dressing) and a new abdominal dressing, the ABThera open abdomen negative pressure therapy system (ABThera dressing), in negative pressure wound therapy (NPWT). Midline incisions were made in 12 pigs that were subjected to treatment with NPWT using the VAC or ABThera dressing. The microvascular blood flow in the intestinal wall was measured before and after the application of topical negative pressures of −50, −75 and −125mmHg using laser Doppler velocimetry. Wound contraction and fluid evacuation were also measured. Baseline blood flow was defined as 100% in all settings. The blood flow was significantly reduced to 64·6±6·7% (P <0·05) after the application of −50mmHg using the VAC dressing, and to 65·3±9·6% (P <0·05) after the application of −50mmHg using the ABThera dressing. The blood flow was significantly reduced to 39·6±6·7% (P <0·05) after the application of −125mmHg using VAC and to 40·5±6·2% (P <0·05) after the application of −125mmHg using ABThera. No significant difference in reduction in blood flow could be observed between the two groups. The ABThera system afforded significantly better fluid evacuation from the wound, better drainage of the abdomen and better wound contraction than the VAC dressing.

Is it possible to further improve the function of pulmonary grafts by extending the duration of lung reconditioning using ex vivo lung perfusion?

BACKGROUND

The method of ex vivo lung perfusion (EVLP) has been suggested as a reliable means of differentiating between "good" and "poor" pulmonary grafts in marginal donors as, when grafts identified as good by this method are transplanted, the results do not differ from those using lungs fulfilling standard criteria. The EVLP method is also thought to improve pulmonary grafts by reducing lung edema and eliminating lung atelectasis. In the present study, we investigated whether the pulmonary graft could be further improved by extending the duration of EVLP.

METHODS AND MATERIALS

Six Landrace pigs were used. The lungs were reconditioned and evaluated, using the EVLP method, as double lungs. After the initial evaluation, EVLP was continued for a further 90 minutes.

RESULTS

The arterial oxygen level (pO2) was 60.8 ± 4.8 kPa after the standard 60 minutes of EVLP and 67.1 ± 2.2 kPa after 150 minutes (p = 0.48). The pulmonary vascular resistance was 453 ± 78 dyne*s/cm(5) after 60, 90, 120 and 150 minutes of EVLP (p = 1.0). The pulmonary artery pressure was 17.8 ± 1.0 mmHg after 60, 90, 120, and 150 minutes of EVLP (p = 1.0) and the pulmonary artery flow was 3.5 ± 0.4 l/min after 60, 90, 120, and 150 minutes of EVLP (p = 1.0). The mean weight of the pulmonary grafts after harvesting was 574 ± 20 g at the beginning of EVLP 541 ± 24 g and, after 150 min of EVLP, 668 ± 33 (p = 0.011).

CONCLUSIONS

The blood gases and hemodynamic parameters in the pulmonary grafts did not improve as a result of the extra 90 minutes of EVLP. However, the weight of the pulmonary graft increased significantly with increasing duration of EVLP, indicating lung perfusion injury.

Comparison of bacteria and fungus-binding mesh, foam and gauze as fillers in negative pressure wound therapy--pressure transduction, wound edge contraction, microvascular blood flow and fluid retention

Bacteria- and fungus-binding mesh binds with and inactivates bacteria and fungus, which makes it an interesting alternative, wound filler for negative pressure wound therapy (NPWT). This study was conducted to compare the performance of pathogen-binding mesh, foam and gauze as wound fillers in NPWT with regard to pressure transduction, fluid retention, wound contraction and microvascular blood flow. Wounds on the backs of 16 pigs were filled with pathogen-binding mesh, foam or gauze and treated with NPWT. The immediate effects of 0, -40, -60, -80 and -120 mmHg, on pressure transduction and blood flow were examined in eight pigs using laser Doppler velocimetry. Wound contraction and fluid retention were studied during 72 hours of NPWT at -80 and -120 mmHg in the other eight pigs. Pathogen-binding mesh, gauze and foam provide similar pressure transduction to the wound bed during NPWT. Blood flow was found to decrease 0.5 cm laterally from the wound edge and increase 2.5 cm from the wound edge, but was unaltered 5.0 cm from the wound edge. The increase in blood flow was similar with all wound fillers. The decrease in blood flow was more pronounced with foam than with gauze and pathogen-binding mesh. Similarly, wound contraction was more pronounced with foam, than with gauze and pathogen-binding mesh. Wound fluid retention was the same in foam and pathogen-binding mesh, while more fluid was retained in the wound when using gauze. The blood flow 0.5-5 cm from the wound edge and the contraction of the wound during NPWT were similar when using pathogen-binding mesh and gauze. Wound fluid was efficiently removed when using pathogen-binding mesh, which may explain previous findings that granulation tissue formation is more rapid under pathogen-binding mesh than under gauze. This, in combination with its pathogen-binding properties, makes this mesh an interesting wound filler for use in NPWT.

A rigid disc for protection of exposed blood vessels during negative pressure wound therapy

BACKGROUND

There are increasing reports of serious complications and deaths associated with negative pressure wound therapy (NPWT). Bleeding may occur when NPWT is applied to a wound with exposed blood vessels. Inserting a rigid disc in the wound may protect these structures. The authors examined the effects of rigid discs on wound bed tissue pressure and blood flow through a large blood vessel in the wound bed during NPWT.

METHODS

Wounds were created over the femoral artery in the groin of 8 pigs. Rigid discs were inserted. Wound bed pressures and arterial blood flow were measured during NPWT.

RESULTS

Pressure transduction to the wound bed was similar for control wounds and wounds with discs. Blood flow through the femoral artery decreased in control wounds. When a disc was inserted, the blood flow was restored.

CONCLUSIONS

NPWT causes hypoperfusion in the wound bed tissue, presumably as a result of mechanical deformation. The insertion of a rigid barrier alleviates this effect and restores blood flow.

Pressure transduction and fluid evacuation during conventional negative pressure wound therapy of the open abdomen and NPWT using a protective disc over the intestines

BACKGROUND

Negative pressure wound therapy (NPWT) has gained acceptance among surgeons, for the treatment of open abdomen, since very high closure rates have been reported with this method, compared to other kinds of wound management for the open abdomen. However, the method has occasionally been associated with increased development of fistulae. We have previously shown that NPWT induces ischemia in the underlying small intestines close to the vacuum source, and that a protective disc placed between the intestines and the vacuum source prevents the induction of ischemia. In this study we compare pressure transduction and fluid evacuation of the open abdomen with conventional NPWT and NPWT with a protective disc.

METHODS

Six pigs underwent midline incision and the application of conventional NPWT and NPWT with a protective disc between the intestines and the vacuum source. The pressure transduction was measured centrally beneath the dressing, and at the anterior abdominal wall, before and after the application of topical negative pressures of -50, -70 and -120 mmHg. The drainage of fluid from the abdomen was measured, with and without the protective disc.

RESULTS

Abdominal drainage was significantly better (p < 0. 001) using NPWT with the protective disc at -120 mmHg (439 ± 25 ml vs. 239 ± 31 ml), at -70 mmHg (341 ± 27 ml vs. 166 ± 9 ml) and at -50 mmHg (350 ± 50 ml vs. 151 ± 21 ml) than with conventional NPWT. The pressure transduction was more even at all pressure levels using NPWT with the protective disc than with conventional NPWT.

CONCLUSIONS

The drainage of the open abdomen was significantly more effective when using NWPT with the protective disc than with conventional NWPT. This is believed to be due to the more even and effective pressure transduction in the open abdomen using a protective disc in combination with NPWT.

The effects of variable, intermittent, and continuous negative pressure wound therapy, using foam or gauze, on wound contraction, granulation tissue formation, and ingrowth into the wound filler

OBJECTIVE

Negative pressure wound therapy (NPWT) is commonly used in the continuous mode. Intermittent pressure therapy (IPT) results in faster wound healing, but it often causes pain. Variable pressure therapy (VPT) has therefore been introduced to provide a smooth transition between 2 different pressure environments, thereby maintaining the negative pressure environment throughout the therapy. The aim of the present study was to examine the effects of IPT and VPT on granulation tissue formation.

METHOD

A peripheral wound in a porcine model was treated for 72 hours with continuous NPWT (-80 mm Hg), IPT (0 to -80 mm Hg), or VPT (-10 to -80 mm Hg), using foam or gauze as wound filler. Wound contraction and force to remove the wound filler were measured. Biopsies from the wound bed were examined histologically for granulation tissue formation.

RESULTS

Intermittent pressure therapy and VPT produced similar results. Wound contraction was more pronounced following IPT and VPT than continuous NPWT. Intermittent pressure therapy and VPT resulted in the formation of more granulation tissue than continuous NPWT. Leukocyte infiltration and tissue disorganization were more prominent after IPT and VPT than after continuous NPWT. Granulation tissue grew into foam but not into gauze, regardless of the mode of negative pressure application, and less force was needed to remove gauze than foam.

CONCLUSIONS

Wound contraction and granulation tissue formation is more pronounced following IPT and VPT than continuous NPWT. Granulation tissue grows into foam but not into gauze. The choice of negative pressure mode and wound filler is crucial in clinical practice to optimize healing while minimizing pain.

Negative pressure wound therapy-associated tissue trauma and pain: a controlled in vivo study comparing foam and gauze dressing removal by immunohistochemistry for substance P and calcitonin gene-related peptide in the wound edge

Pain upon negative pressure wound therapy (NPWT) dressing removal has been reported and is believed to be associated with the observation that granulation tissue grows into foam. Wound tissue damage upon removal of the foam may cause the reported pain. Calcitonin gene-related peptide (CGRP) and substance P are neuropeptides that cause inflammation and signal pain and are known to be released when tissue trauma occurs. The aim of this controlled in vivo study was to compare the expression of CGRP and substance P in the wound bed in control wounds and following NPWT and foam or gauze dressing removal. Eight pigs with two wounds each were treated with open-pore structure polyurethane foam or AMD gauze and NPWT of 0 (control) or -80 mm Hg for 72 hours. Following removal of the wound filler, the expression of CGRP and substance P was measured, using arbitrary units, in sections of biopsies from the wound bed using immunofluorescence techniques. Substance P and CGRP were more abundant in the wound edge following the removal of foam than of gauze dressings and least abundant in control wounds. The immunofluorescence staining of the wound edge for CGRP was 52 ± 3 au after the removal of gauze and 97 ± 5 au after the removal of foam (P <0.001). For substance P, the staining was 55 ± 3 au after gauze removal and 95 ± 4 au after foam removal (P <0.001). CGRP and substance P staining was primarily located to nerves and leukocytes. The increase in CGRP and substance P immunofluorescence was especially prominent in the dermis but also was seen in subcutaneous and muscle tissue. Using gauze may be one way of reducing NPWT dressing change-related pain. New wound fillers designed to optimize granulation tissue formation and minimize pain issues presumably will be developed in the near future.

Green foam, black foam or gauze for NWPT: effects on granulation tissue formation

OBJECTIVE

To compare the effects of green foam with black foam and gauze during negative pressure wound therapy (NPWT), with regard to wound bed appearance and granulation tissue formation, and monitoring of wound exudate.

METHOD

Wounds on the backs of eight pigs underwent 72 hours of NPWT plus either green polyurethane foam with an open pore structure, black polyurethane foam with an open pore structure or saline-moistened AMD gauze. Sections of biopsies from the wound bed, including the overlying dressing, were examined histologically with regard to microdeformation of the wound bed and granulation tissue formation. The force required to remove the wound fillers was measured.

RESULTS

Wound exudate and bleeding could be easily seen when using gauze and green foam, but were not visible under the black foam. Such visibility facilitates monitoring of the wound status. No difference was found in the quantity or characteristics of the granulation tissue formed under the green foam or black foam. Both green foam and black foam resulted in more pronounced granulation tissue formation than gauze under negative pressure. There was also more leucocyte infiltration and tissue disorganisation under green foam and black foam than under gauze. All three wound fillers created microdeformation within the wound bed surface. Similar forces were required to remove green foam and black foam (5.0 ± 0.6 N for green foam and 4.0 ± 0.4 N for black foam), while less force was needed for gauze (2.1 ± 0.2 N). This may be a result of tissue ingrowth into the foam (357 ± 12µm for green foam and 362 ± 14µm for black foam), but not into gauze (0µm), as shown by examination of biopsy sections from the wound bed.

CONCLUSION

Green foam and black foam have similar biological effects on the wound bed. Bleeding and exudate can be more easily monitored when using green foam or gauze. Differences in the wound bed tissue morphology when using foam or gauze plus NPWT support clinical observations that granulation tissue under foam is thick but fragile, whereas that under foam is thinner but denser.

CONFLICT OF INTEREST

The study was supported by Mölnlycke Health Care AB.

A rigid barrier between the heart and sternum protects the heart and lungs against rupture during negative pressure wound therapy

Objectives

Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier has been suggested to offer protection against this lethal complication, by preventing the heart from being drawn up and damaged by the sharp edges of the sternum. The aim of the present study was to investigate whether a rigid barrier protects the heart and lungs against injury during NPWT.

Methods

Sixteen pigs underwent median sternotomy followed by NPWT at -120 mmHg for 24 hours, in the absence (eight pigs) or presence (eight pigs) of a rigid plastic disc between the heart and the sternal edges. The macroscopic appearance of the heart and lungs was inspected after 12 and 24 hours of NPWT.

Results

After 24 hours of NPWT at -120 mmHg the area of epicardial petechial bleeding was 11.90 ± 1.10 cm² when no protective disc was used, and 1.15 ± 0.19 cm² when using the disc (p < 0.001). Heart rupture was observed in three of the eight animals treated with NPWT without the disc. Lung rupture was observed in two of the animals, and lung contusion and emphysema were seen in all animals treated with NPWT without the rigid disc. No injury to the heart or lungs was observed in the group of animals treated with NPWT using the rigid disc.

Conclusion

Inserting a rigid barrier between the heart and the sternum edges offers protection against heart rupture and lung injury during NPWT.

Effects on drainage of the mediastinum and pleura during negative pressure wound therapy when using a rigid barrier to prevent heart rupture

Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) following cardiac surgery. The use of a rigid disc has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up towards, and damaged by, the sharp sternum edges. The aim of the present study was to compare the wound fluid evacuation from the pericardium and the left pleura when using NPWT with such a disc between the sternal edges and the heart, and when using conventional NPWT. Six pigs underwent median sternotomy followed by NPWT at -120 mmHg, using foam, with or without a rigid plastic disc between the heart and the sternal edges. A 250 ml saline was infused into the pericardium, and the time required for fluid evacuation was measured. A 500 ml saline was infused into the left pleura and the time for fluid evacuation measured. The pericardium was effectively drained of 250 ml fluid in both cases [conventional NPWT: 24 ± 0·7 seconds, NPWT with the disc: 25 ± 1·1 seconds (n.s.)]. The left pleura was effectively drained when using NPWT with the disc, but was not drained at all when using conventional NPWT. The left pleura could be effectively drained of 500 ml fluid when a rigid perforated plastic disc was inserted between the sternal edges and the heart during NPWT. Significantly less drainage of the left pleura was possible when using conventional NPWT without the disc. The pericardium was equally good drained using NPWT with or without the disc.

Haemodynamic effects of negative pressure wound therapy when using a rigid barrier to prevent heart rupture

Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up and damaged by the sharp sternum bone edges. The aim of this study was to investigate the haemodynamic effects of placing a rigid barrier over the heart to protect it from rupture during NPWT. Eight pigs underwent median sternotomy followed by NPWT at --70 and --120 mmHg, using foam, with or without a rigid plastic disc between the heart and the sternal edges. The heart frequency, cardiac output, mean systemic arterial pressure, mean pulmonary artery pressure, central venous pressure and left atrial pressure were recorded. Cardiac output was not affected by NPWT, regardless of whether a rigid barrier was used. Heart frequency decreased during NPWT without a disc, and showed a tendency towards a decrease when using a rigid disc. The blood pressure decreased during NPWT without a disc, and showed only a tendency towards a decrease when a disc was inserted between the heart and the sternum. In conclusion, the results of this haemodynamic study show that a rigid disc can safely be placed over the heart during NPWT, to prevent heart rupture. The haemodynamic effects of NPWT in sternotomy wounds are slightly reduced by the presence of the rigid disc.

The influence on wound contraction and fluid evacuation of a rigid disc inserted to protect exposed organs during negative pressure wound therapy

The use of a rigid disc as a barrier between the wound bed and the wound filler during negative pressure wound therapy (NPWT) has been suggested to prevent damage to exposed organs. However, it is important to determine that the effects of NPWT, such as wound contraction and fluid removal, are maintained during treatment despite the use of a barrier. This study was performed to examine the effect of NPWT on wound contraction and fluid evacuation in the presence of a rigid disc. Peripheral wounds were created on the backs of eight pigs. The wounds were filled with foam, and rigid discs of different designs were inserted between the wound bed and the foam. Wound contraction and fluid evacuation were measured after application of continuous NPWT at -80 mmHg. Wound contraction was similar in the presence and the absence of a rigid disc (84 ± 4% and 83 ± 3%, respectively, compared with baseline). Furthermore, the rigid disc did not affect wound fluid removal compared with ordinary NPWT (e.g. after 120 seconds, 71 ± 4 ml was removed in the presence and 73 ± 3 ml was removed in the absence of a disc). This study shows that a rigid barrier may be placed under the wound filler to protect exposed structures during NPWT without affecting wound contraction and fluid removal, which are two crucial features of NPWT.