PTH and Pleural effusion: Duration of chest tube drainage (in d) Duration of ICU-Stay (in d) Amount of pleural effusion (in ml) Postoperative stay (in d) Postoperative biochemical levels  Serum calcium (in mmol/l) 1  Serum parathyroid hormone (in pg/ml) 2 NRS  Postoperative Day 1  Postoperative Day 3  Postoperative Day 7 Follow-up (in month)