title: Masked pneumothorax: risk of valveless trocar systems.
abstract: OBJECTIVE
  Unlike traditional valved trocars, the valveless trocar maintains pneumoperitoneum during laparoscopy by forming a CO(2) curtain at the proximal end of the trocar. This gas barrier instantaneously maintains exact intraperitoneal pressure that yields to the transient physiological changes seen with breathing. Due to this different mechanism of action, pneumothorax development may be masked by the valveless trocar system.
  
  
  METHODS
  We retrospectively reviewed 850 transperitoneal laparoscopic kidney and adrenal surgeries in which a valveless trocar system was used to determine any record of pneumothorax detected intraoperatively or postoperatively. A patient with pneumothorax was considered a case and anesthetic parameters were reviewed. A matched control group was generated from patients treated with transperitoneal laparoscopic kidney and adrenal surgery using the valveless trocar with no complications.
  
  
  RESULTS
  Pneumothorax was diagnosed in 10 patients (1.2%). Two cases were the result of intentional excision of the diaphragm, which were repaired intraoperatively, while 8 were not recognized until the postoperative period. Five of the patients (63%) with unintentional pneumothorax required chest tube placement for a mean of 2.4 days. The remaining 3 patients (37%) were treated conservatively and followed with serial chest x-rays. The only anesthetic variable that was significantly different between the groups was Δ end tidal CO(2) with greater fluctuations in end tidal CO(2) in the pneumothorax group than in controls (p = 0.03).
  
  
  CONCLUSIONS
  Pneumothorax is a rare complication of laparoscopic urological surgery that is usually recognized intraoperatively through physiological changes. Valveless trocar systems mask these findings and can delay identification until the postoperative period.
authors.affiliation: Arthur Smith Institute for Urology and Department of Anesthesia (MS), Hofstra North Shore-Long Island School of Medicine, New Hyde Park, New York 11042, USA. jhillelsohn@gmail.com
authors.forename: Joel H
authors.initials: JH
authors.lastname: Hillelsohn
authors.forename: Justin I
authors.initials: JI
authors.lastname: Friedlander
authors.forename: Neeti
authors.initials: N
authors.lastname: Bagadiya
authors.forename: Zhamshid
authors.initials: Z
authors.lastname: Okhunov
authors.forename: Mahyar
authors.initials: M
authors.lastname: Kashan
authors.forename: Mikhail
authors.initials: M
authors.lastname: Schwartzur
authors.forename: Louis
authors.initials: L
authors.lastname: Kavoussi
mesh_terms: D004867:Equipment Design; D004868:Equipment Failure; D005260:Female; D006801:Humans; D007049:Iatrogenic Disease; D010535:Laparoscopy / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011030:Pneumothorax / Q000209:etiology*; D012189:Retrospective Studies; D013525:Surgical Instruments / Q000009:adverse effects*