General anaesthesia was induced with midazolam 0.1 mg*kg-1, propofol 2 mg*kg-1, cisatracurium 0.15 mg*kg-1 and fentanyl 1.5 µg*kg-1. Anaesthesia was maintained with one minimal alveolar concentration sevoflurane. Fractional doses of fentanyl 1-3 µg*kg-1 were administered if heart rate or mean blood pressure rose more than 20% above the base-line value obtained just before surgery commenced. After surgery, if a patient complained of pain then she/he was given i.v. oxycodone by an anaesthetist before commencing the patient controlled analgesia (PCA). The PCA solution was oxycodone (1mg*ml-1) and the PCA was programmed to allow a self-administered bolus dose of 1mg oxycodone with a lockout time of 5 min. During the night, basal rate oxycodone was 2-4 mg per hour. Additionally, patients were given 1g intravenous paracetamol every 6h and 100mg of intravenous ketoprofen every 12h, if required.

Before induction of general anesthesia thoracic paravertebral block was performed. General anaesthesia was induced with midazolam 0.1 mg*kg-1, propofol 2 mg*kg-1, cisatracurium 0.15 mg*kg-1 and fentanyl 1.5 µg*kg-1. Anaesthesia was maintained with one minimal alveolar concentration sevoflurane. Fractional doses of fentanyl 1-3 µg*kg-1 were administered if heart rate or mean blood pressure rose more than 20% above the base-line value obtained just before surgery commenced. After surgery, if a patient complained of pain then she/he was given i.v. oxycodone by an anaesthetist before commencing the patient controlled analgesia (PCA). The PCA solution was oxycodone (1mg*ml-1) and the PCA was programmed to allow a self-administered bolus dose of 1mg oxycodone with a lockout time of 5 min. During the night, basal rate oxycodone was 2-4 mg per hour. Additionally, patients were given 1g intravenous paracetamol every 6h and 100mg of intravenous ketoprofen every 12h, if required.

Before the induction of general anaesthesia a single-shot ThPVB was performed at the Th3 to Th4 level, approximately, 2.5 to 3 cm lateral to tip of a spinous process. A preblock ultrasound examination was undertaken to assess the depth of the transverse process and the pleura. An insulated 10 cm long needle was used and this was connected to a peripheral nerve stimulator with a set current of 2.5 milliampere(mA). The current was gradually reduced as the needle was inserted until the appearance of visible intercostal muscles activity with a current of 0.3 to 0.5mA (paravertebral space identification). Plain bupivacaine (0.3 ml*kg-1) was then injected after a negative aspiration test for air or blood. The efficacy of the blockade to cold was checked after 20 min with a plastic ampoule of saline kept in the freezer. Testing was symmetrical on both sides of thorax. A difference in sensation to cold between the blocked and unblocked sides was taken to indicate an effective block.

α-amylase activity assay was performed by a static method with AMYLAZA kit (Aqua-Med Łodz, Poland). The samples were diluted 100 times using 0,9% chloride solution. 2-chloro-4-nitrofenylo-maltotrioside is a substrate in this method. The reaction was performed in pH 6,0 MES buffer at 37 ° C rendering a colored reaction product. The product was then analyzed via spectrophotometry at 405 nm. Results are presented in salivary α-amylase activity units (U/ml). Measurement imprecision of the method was 4.1%. Material was collected after enrollment to the study (T0), six hours after the surgery (T1) and 24 hours after the surgery (T2).

The commercial ELISA (Diapra, Italy) was used to determine the concentration of cortisol. The analytical procedure was in accordance with the manufacturer's instructions in the technical manuals supplied with the kits. Absorbance readings were taken using a µQuant reader (Biotek, USA), while results were processed using KCJunior (Biotek, USA). The sensitivity of the method was 0,12 ng/ml for cortisol. The method's imprecision was 6.2%. Material was collected after enrollment to the study (T0), six hours after the surgery (T1) and 24 hours after the surgery (T2).

The commercial ELISA (Diapra, Italy) was used to determine the concentration of testosterone. The analytical procedure was in accordance with the manufacturer's instructions in the technical manuals supplied with the kits. Absorbance readings were taken using a µQuant reader (Biotek, USA), while results were processed using KCJunior (Biotek, USA). The sensitivity of the method was 3,28 pg/ml for testosterone. The method's imprecision was 7.9%. Material was collected after enrollment to the study (T0), six hours after the surgery (T1) and 24 hours after the surgery (T2).

The commercial ELISA (Immunodiagnostic AG, Niemcy.) were used to determine the concentration of sIgA. The analytical procedure was in accordance with the manufacturer's instructions in the technical manuals supplied with the kits. Absorbance readings were taken using a µQuant reader (Biotek, USA), while results were processed using KCJunior (Biotek, USA). Material was collected after enrollment to the study (T0), six hours after the surgery (T1) and 24 hours after the surgery (T2).

Pain intensity at rest was recorded with Numerical Rating Scale (NRS) at 0, 6, 12, 18 and 24 postoperative hours. Patient determined intensity of symptoms on a 10 grade scale, where 0 corresponded to no pain and 10 corresponded to the strongest possible pain.