Background Despite a lack of evidence in the literature, several assumptions exist about the safety of thoracentesis in clinical guidelines and practice patterns. We aimed to evaluate specific demographic and clinical factors that have been commonly associated with complications such as iatrogenic pneumothorax, re-expansion pulmonary oedema (REPE) and bleeding.

Methods We performed a cohort study of inpatients who underwent thoracenteses at Cedars-Sinai Medical Center (CSMC) from August 2001 to October 2013. Data were collected prospectively including information on volume of fluid removed, procedure side, whether the patient was on positive pressure ventilation, number of needle passes and supine positioning. Iatrogenic pneumothorax, REPE and bleeding were tracked for 24 h after the procedure or until a clinical question was reconciled. Demographic and clinical characteristics were obtained through query of electronic medical records.

Results CSMC performed 9320 inpatient thoracenteses on 4618 patients during the study period. There were 57 (0.61%) iatrogenic pneumothoraces, 10 (0.01%) incidents of REPE and 17 (0.18%) bleeding episodes. Iatrogenic pneumothorax was significantly associated with removal of >1500 mL fluid (p<0.0001), unilateral procedures (p=0.001) and more than one needle pass through the skin (p=0.001). For every 1 mL of fluid removed there was a 0.18% increased risk of REPE (95% CI 0.09% to 0.26%). There were no significant associations between bleeding and demographic or clinical variables including International Normalised Ratio, partial thromboplastin time and platelet counts.

Conclusions Our series of thoracenteses had a very low complication rate. Current clinical guidelines and practice patterns may not reflect evidence-based best practices.