In the new era of ultrasound guidance: is pneumothorax from supraclavicular block a rare complication of the past?

Editor—Before the utilization of ultrasound, the complication of pneumothorax was a concern for many anaesthetists performing supraclavicular block (SCB). 2 Technological advances have made ultrasound guidance for regional nerve blocks a standard practice, and when coupled with SCB, have rendered pneumothorax an improbable complication. The incidence of clinicallysignificant pneumothoraxafteran ultrasound-guided SCB has not yet been determined in a large patient study. Therefore, we undertook a 5 yr retrospective study to determine: (i) incidence of pneumothorax as a complication of ultrasound-guided SCB and (ii) the reliability of ultrasound in preventing pneumothoraces in SCB. After IRB approval, we analysed data from June 2009 to December 2013 on all brachial plexus blocks performed at Harbor-UCLA Medical Center. These data were obtained from our electronic health record database (Fig. 1). All SCB were examined for the presence or absence of ultrasound utilization and the complication of pneumothorax. Recorded pneumothorax incidence was zero. All SCB procedures were performed under ultrasound guidance. To determine if the difference in pneumothorax incidence with the utilization of ultrasound was statistically significant from the incidence without the utilization of ultrasound, a x test was performed between our data and the data from the literature. Thompson’s report (0.8% incidence) without ultrasound for SCB was chosen for x test comparison since it was the largest study (n1⁄41248). x analysis returned a P-value of ,0.001. This comparison demonstrates that ultrasoundguided SCB allowed statistically significant reductions in the incidence of pneumothorax. Althoughthese twostudies aretheoretically incomparable because the groups were not randomized, both featured the largest sample sizes of SCBs and lowest incidence of pneumothorax. While assumption of variation in technique, needle insertion, method of injection, and operator’s experience level were different between these studies, ultrasound guidance was the only constant variable, implying proper use of ultrasound guidance is the largest factor in improving patient safety from a pneumothorax. With our study being the largest to date with 1419 patients without pneumothorax, similar conclusions can be inferred cumulatively from other studies utilizing ultrasound without pneumothorax. On the contrary, isolated case reports of pneumothorax as a complication of ultrasound-guided SCB show that the true incidence of pneumothorax is not zero, despite its zero incidence at our institution. Although our study and others have been able to obtain a zero rate of occurrence of pneumothorax, this does not imply zero risk of clinically relevant pneumothorax nor does it imply any information about the size of the risk. Hanley’s mathematical ‘rule of three’ provides a method of calculating theoretical maximum long-run risk with a 95% confidence interval, yielding a theoretical risk of 2:1000 of developing pneumothorax with ultrasound-guided SCB. Our 5 yr study shows that SCB are our preferred technique of regional anaesthesia for upper extremity surgery. SCB accounted for 72% of all brachial plexus blocks (Fig. 1), from which we can infer that the majority of upper extremity blocks are performed without fear of pneumothorax complications. At our teaching institution, ultrasound has been a routine practice since 2007, with faculty involvement in 100% of SCBs.