In the planned prospective randomized study, oxidative stress will be investigated by analyzing volatile organic compounds in the exhaled air in children. Children who have undergone open versus laparoscopic surgery for appendicitis will be compared. A better understanding of the effects of the surgical technique could be a prerequisite for an optimized surgical setting. It could also lead to recommendations for pre- or perioperatively antioxidative agents.

Aim of the study: In the planned prospective randomized study, oxidative stress will be investigated by analyzing VOCs (volatile organic compounds) in the exhaled breath in children undergoing open or laparoscopic surgery for appendicitis at the Department of Pediatric and Adolescent Surgery of the Medical University of Graz. A resulting better understanding of the effects of the surgical technique can a) be a pre-condition for an optimized surgical setting and b) possibly lead to recommendations of pre- or perioperatively antioxidatively active substances and c) be a base for future surgical procedures.

Study design: This is a prospective randomized pilot study in children and adolescents undergoing surgery due to acute appendicitis. Patients with complicated appendicitis and those with an intraoperatively caused disorder will be excluded. The operation within the context of this study is exclusively conducted by specialists of the Department of Pediatric and Adolescent Surgery of the Medical University of Graz, who perform both - open and laparoscopic surgical techniques. 40 patients aged 6-18 years suffering from acute appendicitis are to be included. These are divided into 2 groups. Group 1 (n = 20) with laparoscopic and group 2 (n = 20) with open appendectomy.

Recruitment and compensation of study participants: Parents/patients are made aware of the study by means of an information sheet and are provided with a declaration of consent if interested. Participants do not receive any compensation for participating in the study.

Sampling of exhaled VOCs (volatile organic compounds) using NTME (needle trap microextraction) for measurement OS (oxidative stress): Number of samples: 2 samples each from exhaled breath at the times defined below (in total n = 12). The time of sampling: t1 before anaesthetic introduction (n = 2); t2 after anesthetic introduction (n = 2); t3 15 minutes after cut (n = 2); t4 30 minutes after cut (n = 2); t5 45 minutes after cut (n = 2); t6 after seam (n = 2).

Analysis of exhaled VOCs for measurement OS: The exhaled breath samples taken are placed in an injector of a gas chromatograph into the inert carrier gas stream (He). The substances are assigned according to their retention time in the chromatogram and its mass spectrum. Unknown connections in the mass spectrum of exhaled breath is used as a basis for comparison with a reference database.

Sampling of blood markers for measurement OS: a) sampling times for WBCs, CRP: t1 = 1 sample preoperatively (before anaesthetic introduction) and t2 = 1 sample after 24 h. b) sampling times for malondialdehyde: t1 = 1 sample before anaesthetic introduction and t2 = 1 sample after suture.

Histopathological grading: The explanted vermiform appendix becomes the histopathological Refurbishment at the Institute of Pathology of the Medical University of Graz. There the classification is made according to the histopathological findings in 4 degrees of severity (acute focal appendicitis, acute suppurative appendicitis, acut gangrenous appendicitis, perforated appendicitis).

Sampling WBCs, CRP: These are carried out within the scope of routine diagnostics due to the clinical presentation of the AA (acute appendicitis).

Sampling VOCs: 2 breath samples are taken from each patient during expiration, taken from it. To collect the samples, the investigators use an automatic Sampling device connected directly to a capnometer. This system works with microextraction (NTME) and enables a automatic sampling of the alveolar air, i.e. in the plateau of the CO2 curve. The samples are sent to the Intitute of Rostock Medical Breath Analysis and Technologies (RoMBAT) as cooperation partner. This partner was selected because it already has extensive experience with the methodology and studies on oxidative stress during operations.

Malondialdehyde (MDA) sampling: Malondialdehyde is analysed at the Clinical Institute for Medical and Chemical Laboratory Diagnostics at the Medical University of Graz means of ultra-modern GC-MS method. For this purpose, the patient is assigned to the two Measuring times 2 x 400 μl EDTA plasma taken. The second sample serves only as a safety measure if repeat measurements are necessary. The samples obtained must be deep-frozen at -80 °C within 2 hours. . Subsequently (at the latest on the following day) the samples must be analyzed to the Institute.

Planned evaluation: The statistical investigations are carried out with SPSS 23.0®. Graphical representation of the data is performed with GraphPad Prism 7®. To investigate whether the main target variables (VOCs) differ in the course between the two groups, linear models are used for repeated measurements with group (open versus laparoscopic appendectomy) as intermediate subject factor and time of measurement (t1 to t6) as internal subject factor. In the case of deviations from the normal distribution, transformations are taken into consideration. The secondary targets, i.e. the changes in the serum markers on theTimes t1 and t6, are compared between the 2 groups (open versus laparoscopic appendectomy) by Mann-Whitney U-test (data not normally distributed) or independent T-test (with normal distribution). In order to establish relationships between the VOCs and the serum markers for oxidative stress at times t1 and t6 a correlation analysis is performed (depending on the data, Pearson or Spearman Rho). All statistical tests are carried out on two sides and all p-values are interpreted purely exploratively.

Inclusion Criteria:

• Age from 6-18 years
• reliable diagnosis of acute appendicitis
• surgical therapy using open/laparoscopic surgical technique
• given approval

Exclusion Criteria:

• Age not between 6 and 18 years
• chronic underlying disease/autoimmune disease
• complicated appendicitis (perforation, consecutive purulent peritonitis, abscess formation)
• infection outside acute appendicitis
• SIRS
• taking medications containing the cytochrome P450 (CYP) system affect including cortisone
• impaired liver function
• unaccepted consent

After obtaining written informed consent from patients/legal guardians the patients will be randomized 1:1 to one of the two surgical techniques. Randomization is carried out using the web-based "Randomizer for Clinical Trials" program at the Institute of Medical Informatics, Statistics and Documentation at the Medical University of Graz (www.randomizer.at).