The study was conducted between November 2016 and May 2018 in a single centre, St. Andrew's Centre for Plastic Surgery and Burns in Broomfield Hospital, in Chelmsford United Kingdom, including all immediate and delayed DIEP/MS-TRAM patients of two senior plastic surgeons, who agreed to participate and met the in-/exclusion criteria. All participants signed an informed consent. Randomisation was performed using the Trans European Network for Clinical Trials Service (TENALEA), which is an internet-based randomisation system. Patients were either allocated to the 'Group A - diathermy' or 'Group B - PEAK PlasmaBlade™. Blinding was broken after the last patient had completed the 6-week follow-up period.

All patients underwent a standardised DIEP or MS-TRAM breast reconstruction procedure. A scalpel was used to make the skin incision to the depth of the dermis. The raising of the flap was subsequently done either using the PEAK Plasma Blade™ or conventional diathermy. Before the abdominal closure two 15 French Blake drains were inserted and secured to the skin with a 2.0 Silk suture and connected to a low vacuum wound drainage system (85 kPa/neg 100mmHg). Every patient would wear an abdominal binder (9-inch, Marena) for 6 weeks post-operatively. Data on drain requirement, total daily abdominal drainage, pain, mobility and complications were collected during the inpatient stay. On day 0,1 and 2 also abdominal drain fluid was obtained. This was stored in labelled 1.5mL Eppendorf tubes in a -80°C freezer. The samples were sent to Myriad RBM, Inc. a clinical laboratory improvement amendments (CLIA) certified biomarker testing laboratory located in Austin, Texas (United States) for inflammatory cytokine analysis. Abdominal drains were removed when draining 30mL or less in 24 hours. Following discharge, patients were seen in the outpatient department after two and six weeks. At both follow-up appointments, data on complications were recorded. Also an abdominal ultrasound was performed using the V-Universal™ Stand portable ultrasound machine (SonoSite, Inc) to identify and measure abdominal seroma collections. Seromas were only aspirated if they were causing discomfort to the patient. After completion of the 6-week follow-up period patients were discharged from the study. All data were collected by the blinded principle study investigator and logged onto an electronic database.

Data from an in the investigator's unit conducted pilot study on drain requirement was used to perform a power calculation.This results in a minimal sample size of 53 patients for each group (106 overall).

Normal distribution was evaluated using the Shapiro-Wilk test, following this continuous data was analysed using the independent sample t-test or Mann-Whitney U Test to identify a statistically significant difference between the two groups. All right skewed was log transformed, if this resulted in a normal distribution the independent samples t-test was used to determine statistical significance. For categorical data the Pearson Chi-Square Test for numbers over 5 was used. If the count was equal to or less than 5 the Fisher's Exact Test was used to determine statistical significance. A value below or equal to 0.05 (2-tailed) was considered to be statistically significant. Linear regression (Cox proportional hazard model) was used to identify significant determinants for the time to drain removal. Variables that had a significant p-value in the univariate analysis were included in a multivariable analysis. Significant determinants could indicate confounding factors for which would be corrected. Logistic regression was used to identify determinants for complications and the presence of seroma at the 2- and 6-week abdominal ultrasound scan. Variables that had a significant p-value in the univariate analysis were included in multivariable analysis, if none of the determinates were significant p values \<0.10 were included in the multivariable analysis. Significant determinants could indicate confounding factors for which would be corrected.