Dr. Joseph Esherick Monthly Blog – November 2011
Numerous studies have shown that ultrasound guidance lowers the rate of complications and increases the success rate for virtually every hospital procedure compared with traditional landmark-based techniques. This has proved to be the case for ultrasound-guided central lines, ultrasound-guided paracentesis, and ultrasound-guided lumbar punctures in obese patients. This essay will focus on ultrasound-guided thoracentesis which has a decreased rate of pneumothorax and need for tube thoracostomy compared with the blind approach.
Pleural effusions affect nearly 1.5 million people each year in the United States. Many of these people require thoracentesis for pleural fluid analysis to either determine the etiology of their pleural effusions or as a therapeutic procedure to relieve dyspnea and hypoxia. Examination of the pleural space with sonography is best carried out using a convex array 3.5- to 5 MHz probe. Ideally, the patient is in the sitting position and sonography should identify the uppermost extent of the pleural effusion and the location of the diaphragm. The depth of insertion can also be approximated by using the depth markers on the ultrasound screen. At this point, a mark can be made on the posterior thorax just above the rib at the optimal site for thoracentesis. The thoracentesis can then be carried out in standard fashion with the patient in the same sitting position. Alternatively, the convex array probe can be placed in a sterile sheath and the thoracentesis can be performed using real-time ultrasound guidance. The complication rate is identical with either technique for ultrasound-guided thoracentesis...
Ultrasound was first described as a technology to guide thoracentesis in 1986. Since then a number of studies have demonstrated a decreased rate of pneumothorax with ultrasound-guided thoracentesis versus physical exam-guided thoracentesis[3,4,5]. A study by Grogan et al. demonstrated a reduction in pneumothorax from 29% to 0% compared with exam-guided thoracentesis.3 Raptopoulos et al found a similar reduction in pneumothorax for ultrasound-guidance versus exam-guided thoracentesis (3% vs 18%). In addition, ultrasound guidance increases the success rate for thoracentesis; the success rate of a successful thoracentesis is as high as 88% when ultrasound is used after unsuccessful exam-guided thoracentesis. Furthermore, in circumstances of a “dry tap” with exam-guided thoracentesis, ultrasound revealed that 58% of needle insertions were below the diaphragm. Ultrasound guidance has also been shown to reduce the need for tube thoracostomy; a study by Barnes et al showed that tube thoracostomy was performed in 0.7% of patients who underwent ultrasound-guided thoracentesis versus 4.1% of patients who underwent exam-guided thoracentesis (p<0.05).
A systematic review and meta-analysis was performed in 2010 to determine the rate of pneumothorax following thoracentesis. Twenty four studies with a total of 6605 thoracenteses were analyzed. The overall pneumothorax rate was 6.0%, of which 34.1% required chest tube insertion. Ultrasound-guidance significantly lowered the risk of pneumothorax (OR = 0.3, 95% CI 0.2-0.7).
Currently, point-of-care ultrasound is a luxury for most hospitalists and emergency room physicians, and ultrasound-guidance for procedures is not mandatory. However, my suspicion is that the increased emphasis on patient safety by regulatory agencies such as the Joint Commission and the Agency for Healthcare Research and Quality (AHRQ) will soon lead to the strong encouragement of ultrasound-guided procedures, including ultrasound-guided thoracentesis. As this transition occurs, simulation based training courses will ensure that proceduralists receive hands-on instruction that will allow them to realize the lower complication rates associated with ultrasound-guided procedures.
Joseph Esherick, MD, FAAFP is the Associate Director of Medicine and the Medical ICU Director at the Ventura County Medical Center in Ventura, California. He is also an Associate Clinical Professor of Family Medicine at The David Geffen School of Medicine at UCLA. He received his medical degree from Yale University School of Medicine, New Haven, Connecticut, and completed a family practice residency at the Ventura County Medical Center, Ventura, California. He is board certified in family medicine and the author of the Tarascon Primary Care Pocketbook and the Tarascon Hospital Medicine Pocketbook. He instructs the Hospitalist Procedures course for the National Procedures Institute and is an editorial board member for Tarascon Publishing and for Elsevier’s First Consult.
Dr. Esherick is the author of some of Tarascon Publishing’s best-selling titles including:
The recently published Tarascon Medical Procedures Pocketbook, Tarascon Hospital Medicine Pocketbook and Tarascon Primary Care Pocketbook. Both titles are available in print and mobile (iPhone, Android and Blackberry).
 Feller-Kopman, D. Ultrasound-Guided Thoracentesis. Chest. 2006; 129: 1709-1714.
 Kohan JM et al. Value of chest ultrasonography versus decubitus roentgenography for thoracentesis. Am Rev Respir Dis. 1986; 133: 1124-1126.
 Grogan DR et al. Complications associated with thoracentesis: a prospective, randomized study comparing three different methods. Arch Int Med. 1990; 150: 873-877.
 Jones PW et al. Ultrasound-guided thoracentesis: is it a safer method? Chest. 2003; 123: 418-423.
 Raptopoulos V et al. Factors affecting the development of pneumothorax associated with thoracentesis. Am J Roentgenol. 1991; 156: 917-920.
 Weingardt JP et al. Ultrasound findings following failed, clinically directed thoracentesis. J Clin Ultrasound. 1994; 22: 419-426.
 Barnes TW et al. Sonographically guided thoracentesis and rate of pneumothorax. J Clin Ultrasound. 2005; 33: 442-446.
 Gordon CE et al. Pneumothorax Following Thoracentesis: A Systematic Review and Meta-analysis. Arch Intern Med. 2010; 170: 332-339.