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* From the Interventional Pulmonology Section, Pulmonary and Critical Care Medicine Division, University of California, San Diego Medical Center/Thornton Hospital, La Jolla, CA.
Correspondence to: Henri G. Colt, MD, FCCP, Associate Professor of Medicine, University of California, San Diego Medical Center/Thornton Hospital, 9310 Campus Point Dr 0976, La Jolla, CA 92037; e-mail: hcolt{at}ucsd.edu
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Abstract |
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 TOP Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Design: Prospective, nonrandomized cohort study.
Setting: Pulmonary Special Procedures Unit of a university medical center.
Methods: Thoracentesis using either a 22-gauge, a Boutin, or a Cope needle (depending on availability and operator preference) was performed by the pulmonary faculty or by pulmonary physicians-in-training under faculty supervision. In order to control for effusion size and the presence of loculations, chest radiography and pleural ultrasonography were performed prior to each thoracentesis. Potential patient-related and procedure-related risk factors for pneumothorax were analyzed at the procedure level using the presence or absence of pneumothorax on the postprocedure chest radiograph as the sole outcome variable.
Results: Two hundred fifty-five thoracenteses were performed in 205 adult patients (113 men and 92 women; mean age, 58.8 ± 18 years) over a 31/2-year period. One hundred fifty procedures were performed for diagnostic purposes, 28 procedures were performed for therapeutic purposes, and 77 procedures were performed for both diagnostic and therapeutic purposes. Based on the radiographic criteria, 152 effusions (60%) were small. Loculations were present in 76 patients (30%). Pneumothoraces occurred in 14 instances (5.4%), and chest tube drainage was required in 2 instances (0.78%). Hospitalization status, critical illness, effusion size or type, presence of loculations, operator, needle type, amount of fluid withdrawn, occurrence of dry tap, and type of thoracentesis were not associated with an increased frequency of pneumothorax. The only predictor variable demonstrating statistical significance was repeated thoracentesis.
Conclusion: The results of a bivariate analysis suggest that pneumothorax following thoracentesis is a rare event that is not easily predictable when the procedure is performed by experienced operators in a controlled setting.
Key Words: complications • pleural ultrasonography • pneumothorax • thoracentesis
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Introduction |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The authors of several reviews3 4 5 state that the incidence of thoracentesis-related pneumothorax varies between 3% and 19%. In fact, the frequency of thoracentesis-related pneumothorax in three large retrospective studies totaling 679 procedures was only 7.6%.6 7 8 Chest tubes were needed in 3.6% of all thoracenteses, representing almost half of all patients (48%) in whom pneumothorax occurred.
Similar figures have been cited in at least seven recently published prospective studies9 10 11 12 13 14 15 totaling 612 thoracenteses in 463 patients. In these studies, the overall frequency of thoracentesis-related pneumothorax was only 8.6% (53 pneumothoraces). Chest tubes were necessary in 2.6% of all thoracenteses performed, corresponding to 16 pneumothoraces (30.1%) of all patients in whom pneumothorax occurred.
Conventional wisdom would suggest, therefore, that thoracentesis is a safe procedure infrequently associated with adverse events that affect clinical management. Still, investigators strive to identify risk factors that, once controlled, could further decrease the incidence of thoracentesis-related complications. Interestingly, risk factors for pneumothorax in these studies are not consistently identified, but operator inexperience,9 16 17 the use of a large needle,7 9 therapeutic as opposed to diagnostic thoracentesis,10 12 the evacuation of a large volume of pleural fluid,7 10 the need for multiple needle passes,7 15 the presence of loculations,8 underlying neoplastic or chronic obstructive lung disease,17 and repeated thoracenteses in the same patient15 have each been described.
Intrigued by the diversity of results that potentially link various patient-related and procedure-related risk factors to pneumothorax, we intentionally adopted a sophisticated approach to all patients referred to our unit for this procedure, in order to further investigate the relationship between risk factors and thoracentesis-related pneumothorax. Our experience with this approach forms the basis of this report.
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Materials and Methods |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The following patient-related and procedure-related predictor variables were noted prospectively: the inpatient or outpatient hospitalization status; whether the patient was critically ill and hospitalized in the ICU; the size of the effusion, based on a review of preprocedure chest radiographs (large if fluid extended to or above the dome of the hemidiaphragm, and small if fluid or thickening was confined to the costophrenic angle or below the level of the dome of the diaphragm); whether thoracentesis was warranted for diagnostic or therapeutic purposes; the physician performing the procedure; the thoracentesis needle that was used, based on random physician preferences and needle availability (a simple 22-gauge needle attached to a 60-mL syringe, a reusable 3-mm Boutin pleural puncture needle equipped with a stopcock and blunt inner cannula, or a Cope inner trocar and hollow outer cannula); the indication for the procedure; whether thoracentesis was an initial or repeated procedure; whether loculations were present on sonography; the amount of fluid removed; whether the procedure was a dry tap; whether fluid was exudative or transudative; and the etiology of the pleural effusion.
The major outcome variable, thoracentesis-related pneumothorax, was defined as new evidence of air in the pleural space on postprocedure chest radiographs in patients with or without clinical symptoms, but in the absence of known trapped lung. Other complications were noted as part of our ongoing quality assurance program, but the results were not used for statistical analysis. Dry taps, defined as an attempt at thoracentesis without the recovery of enough pleural fluid for laboratory analysis, were not considered complications.
The data were analyzed at the procedure level (each patient could
contribute more than one procedure) using the presence or absence of
thoracentesis-related pneumothorax as the dichotomous outcome variable.
A bivariate analysis using contingency tables was performed to examine
associations between predictor variables and pneumothorax.
2 and associated p values were examined using
p 
0.05 as the threshold for statistical significance.
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Results |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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No statistically significant associations were found between patient-related risk factors and the occurrence of thoracentesis (Table 2 ). One hundred fifty-two procedures (60%) were performed primarily for diagnostic purposes. Although pneumothorax occurred more frequently in patients undergoing more than one thoracentesis (p < 0.05), none of the other procedure-related factors were significantly associated with the occurrence of pneumothorax (Table 3 ). In addition, after coding pneumothorax as a binary variable, with 1 equaling the presence of pneumothorax and 0 equaling no pneumothorax, a correlation was run between pneumothorax and the amount of fluid withdrawn. No statistical significance was found (r = 0.3). Dry taps occurred on 15 occasions (overall frequency, 6.7%), but they were not associated with a greater incidence of pneumothorax.
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Discussion |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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One limitation of this study, however, was our liberal use of pleural ultrasonography to control for the presence of loculations. It is unclear whether our use of pleural ultrasonography alone could explain the low incidence of pneumothorax or the infrequent need for tube thoracostomy. It is noteworthy that thoracentesis was always performed regardless of the results of the ultrasound examination, and that dry taps (n = 15) were not associated with an increased incidence of pneumothorax. Although dynamic signs such as anechoic appearance, flapping movements of atelectatic lung, and the visualization of internal septa or intrapleural debris suggest a pleural effusion,18 19 20 many pleural or chest wall abnormalities are hypoechoic, and some fluid collections appear as uniform echogenic structures.21 22 23 At the same time, pleural ultrasonography is not 100% specific, so dry taps are not always avoidable.
Another potential limitation of our study was (functionally speaking) that the procedures were performed at the attending level, because trainees performed the thoracentesis under direct faculty guidance, making the addressed issue of operator experience less clear. In fact, it is likely that operator skill was a major factor contributing to the low incidence of pneumothorax in our study. Because our complication rate was less than the pneumothorax rate (11 to 19%) described in studies10 12 14 in which house officers performed thoracentesis without faculty supervision, our results could be used to validate the findings of Bartter et al9 that thoracentesis is a low-risk procedure when performed by trained operators. The demonstrated safety of thoracentesis in a well-controlled environment also provides indirect evidence to support the argument of Doyle et al15 that routine chest radiography after thoracentesis is probably unwarranted.
Our study is larger than the retrospective studies of Jenkins et al6 or Moore et al.8 It is also larger than each of the seven prospective studies9 10 11 12 13 14 15 that addressed the risk for thoracentesis-related pneumothorax (Table 4 ). In contrast to the results presented by these and other investigators, we found no statistically significant association between the occurrence of pneumothorax and the type of needle used, the size of the effusion, the amount of fluid drained, the presence of loculations, the type of thoracentesis, or experience of the operator. Our complication rate is insufficient, however, to provide the statistical power necessary to refute these previously demonstrated relationships between risk factors and pneumo-thorax.
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In summary, we cannot unquestionably refute the relationships between potential risk factors and pneumothorax that have been described by previous investigators. Nevertheless, the results from this prospective bivariate analysis suggest that thoracentesis-related pneumothorax is rare and not easily predictable when the procedures are performed under faculty supervision in a controlled environment.
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Footnotes |
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Received for publication September 30, 1999. Accepted for publication February 2, 1999.
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