Safety guidelines regarding thoracentesis include: 1. avoid performing bilateral operations or in patients on positive pressure ventilation (potentially catastrophic complications); 2. to avoid REPE, <1500 ml of fluid per puncture; 3. avoid thoracentesis in patients with coagulopathy or thrombocytopenia who are not transfused with blood products. And these lack the support of evidence in the literature. In light of this, Professor Jeffrey H Barsuk of Northwestern University and others have studied this, and the article was recently published in Thorax. The study was a cohort study of inpatients who underwent thoracentesis at Cedars-Sinai Medical Center (CSMC) from August 2001 to October 2013. Data were collected on fluid volume, operative margin, presence of positive pressure ventilation in the patient, number of needle insertions through the supine position, medically induced pneumothorax, REPE, and bleeding at 24 hours postoperatively. Patient distribution characteristics and clinical features were obtained through electronic medical record queries. It was found that 9320 patients underwent thoracentesis at CSMC, of which 4618 patients underwent thoracentesis during this study period. Medically induced pneumothorax occurred in 57 (0.61%), REPE in 10 and bleeding in 17 (0.18%). The occurrence of medically induced pneumothorax was significantly associated with fluid aspirations >1500 ml, unilateral treatment and more than 1 needle puncture of the skin. The risk of REPE increased by 0.18% for every 1 ml of fluid pumped. Patient characteristics and partial thromboplastin time and platelet count were not significantly associated with bleeding. These results indicate that the complication rate of thoracentesis is low. Large pleural effusions and operator experience were the main factors influencing the results of this study. Current clinical guidelines and practice patterns may not reflect best evidence-based practice. This study strongly recommends that decisions about whether to perform bilateral operations, how much pleural fluid to exclude, and whether to transfuse blood products in patients on positive pressure ventilation need to be made by experienced clinicians who have comprehensive information about the patient.