Thoracocentesis

Thoracocentesis· Clinical Value, Complications, Technical Problems, and Patient Experience TImothy R. Collins, M.D.; and Steven A Sahn, M.D., RC.C.P.

A prospective study of 129consecutive thoracocenteses in 86 patients at a university medical center evaluated the clinical value, complications, and patient experience with thoracocentesis. Pleural Ouid analysis in conjunction with the clinical presentation placed 78 pleural fluids into diagnostic categories: de6nitive 14 (18 percent), presumptive 44 (56 percent), and nondiagnostic 20 (26 percent), Fourteen of 78 (18 percent) of the nondiagnostic Ouids were useful, while only six (8 percent) were not useful clinically; therefore, 92 percent of thoracocenteses provided clinically useful information. Using sequential data analysis, initial diagnostic categorizations of eight of 78 patients were upgraded from presumptive or nondiagnostic to definitive based on data available !4 hours following thoracocentesis. Thus, 70 patients were categorized based on the pleural Ouid data obtained within the 6rst 24 hours of thoracocentesis. Thirtyfour objective complications occurred in 26 of 129 (20 percent) thoracocenteses. The most common complications

were pneumothorax, 15 of129 (12 percent), and cough, 12 of 129(9 percent), Sixty-6ve subjective complications occurred in 56 of 123 (46 percent) thoracocenteses. Anxiety, 26 of 123 (21 percent), and site pain, 24 of 123 (20 percent), were the most common subjective complications noted. Thirty technical problems occurred in 129(23 percent) thoracocenteses with blood contamination, 14of 129(11 percent), and dry tap, nine of 129 (7 percent), being the most common. We conclude that diagnostic thoracocentesis is a clinically valuable procedure if used in conjunction with the patient presentation with an understanding of its limitations for providing a speci6c etiologic diagnosis. When performed by physicians in training, the number of complications are substantial and the operator often underestimates the degree of patient discomfort. Awareness of the clinical value and complications of thoracocentesis should lead to improved use and safety of this procedure.

Bowditch and Wyman' established thoracocentesis as a clinical diagnostic procedure in 1850. Subse-

fects of thoracocentesis were not mentioned and generally have been presented as isolated case reports, 16-12 although series reporting pneumothoraces alone do exist. 13.1" A prospective evaluation of clinical usefulness, complications, and patient experience with thoracocentesis has not been done to our knowledge and was the purpose of this study. It was designed to assess the diagnostic value, incidence of complications and technical problems, and the patients' perception of thoracocentesis. In addition, the methodology allowed simulation of the clinical situation with sequential data analysis.

quent generations of physicians have performed thoracocenteses and have found a specific etiologic diagnosis to be elusive. More than 50 diseases cause effusions through one of six mechanisms.v' Pleural effusions caused by a single disease vary in clinical fluid characteristics, and pleural fluid analyses from unrelated diseases often yield similar results.Y" Despite these inherent complexities, previous studies suggest that evaluation of pleural fluid results in an etiologic diagnosis in 62 to 88 percent of patients. 6-9 These earlier investigations, however, did not provide diagnostic standards allowing critical assessment of the diagnostic accuracy of the clinical evaluations. In addition, analysis of pleural fluid was not applied to the patient presentation in an attempt to determine how often clinically useful information was obtained in undiagnosed cases. Technical problems and adverse ef*From the Division of Pulmonary Sciences, University of Colorado Health Sciences Center, Denver, and the Division of Pulmonary and Critical Care Medicine, Medical University of South Carolina, Charleston. Presented in part at the Scientific Sessions of the American Federation for Clinical Research, Western Section, Cannel, CA, February 11, 1983, and American Thoracic Society, Kansas City, Kansas, May 10, 1983. Manuscript received August 7; revision accepted November Il, Reprint requests: Dr. Sahn, Pulmonary/Critical Care Medicine, Medical University of South Carolina, Charleston 29425

MATERIALS AND METHODS

Data Collection Information was collected by one author (1:R.C.) from consecutive patients undergoing thoracocentesis on medical services in one of three university affiliated hospitals served by the same housestaff who rotated among the threehospitals-The UDiversityof Colorado Health Sciences Center (UH), The Denver Veterans Hospital (VAH), and Denver General Hospital (DGH)-during the following periods: Sept-Oct 1981(VAH), Jan-Feb 1982(DGH), May-July1982(UH), Oct-Dec 1982 (UH), Jan-May 1983 (UH, VAH). Patients undergoing simultaneous pleural biopsy were excluded. Operators were medicine housestaff (103), supervised medical students (20), pulmonary fellows (four),and attendings (two). Interviews with the performer or the supervisor of the thoracocentesis and, when possible, with the patient were conducted. All patient charts, pathology reports, and CHEST / 91 / 6 / JUNE, 1987

817

chest radiographs, and radiograph reports were reviewed to confirm interview details, to abstract laboratory data and to ascertain followup information.

Data Analysis Etiologic diagnosis and clinical usefulness was assessed using pleural8uid data obtained from diagnostic thoracocentesis. No protocol was used to guide the operators in the technique of thoracocentesis or in the request of laboratory tests. Tests were ordered selectively by the housestaff based on their perception of relevant diagnoses. Thoracocenteses were diagnostic, therapeutic, or both, based on the intent of the performer at the time of thoracocentesis. Diagnostic thoracocentesis was defined as the removal of30 to 50 ml of pleural 8uid for measurement of laboratory tests; therapeutic thoracocentesis entailed the removal of several hundred milliliters of 8uid to relieve symptoms. Diagnostic value and clinical usefulness were assessed as follows: the patient history, physical examination, chest radiograph, laboratory tests, and pleural 8uid characteristics were presented to a pulmonary specialist (S.A.S.), who had no prior knowledge of the patient. Based on this information, the patients pleural effusion was placed by the specialist into one of three diagnostic categories: 1. Definitive: The pleural 8uid data independent of other clinical information was sufficient to establish an etiologic diagnosis. This could occur in malignancy (positive pleural8uid cytology), bacterial empyema (aspiration of pus and/or a positive gram stain or culture), tuberculous pleurisy (positive AFB stain or culture), other infections (fungal, parasitic), lupus pleuritis (presence of pleural8uid LE cells), and esophageal rupture (pleural8uid pH - 6.00 and high amylase). 2. Presumptive: The pleural fluid data supported the clinical impression and was compatible with that single diagnosis. A presumptive diagnosis could occur with congestive heart failure, parapneumonic effusions, paramalignant effusion, cirrhosis, trauma, pulmonary embolism, and postcardiac injury syndrome. The following criteria were established to help place patients into these presumptive diagnostic categories: Congestiveheart failure: unilateral or bilateral transudative effusions in the setting of clinical congestive heart failure, the manifestations of which could include an enlarged heart, distended neck veins, a cardiac gallop, elevated central venous pressure, elevated mean pulmonary capillary wedge pressure, low cardiac index, and response to therapy. Parapneumoniceffusion: an ipsilateral polymorphonuclear predominant exudate in the setting of clinical pneumonia or lung abscess with negative Gram stain and culture. Ibramalignante/fu8ion:J!5 a mononuclear cell predominant exudate (occasionally a transudate) with negative cytology for neoplasia, in the setting of a known malignancy and with the exclusion of other diseases. Mechanisms of paramalignant effusion formation include lymphatic obstruction, atelectasis, postobstructive pneumonitis, superior vena caval obstruction, etc. Cirrhosis:a transudative effusion in the setting of clinical, or biopsyproved cirrhosis with ascites. 7rauma: a grossly bloody exudate (RBC count>100,0001....1) in the setting of chest trauma, with the exclusion of iatrogenic causes. Pulmonary embolism: an exudative or transudative pleural effusion associated with a high probability lung scan or a positive angiogram. Postcardiac injury syndrome:18 an exudative pleural effusion (70 percent bloody, 30 percent serous) occurring days to weeks following pericardial or myocardial injury (myocardial infarction, cardiac surgery) associated with fever, pleuropericarditis, and alveolar infiltrates. 3. Nondiagnostic: The pleural 8uid data did not help to distinguish between two or more possible causes suggested by the clinical history. An example was a patient with a history of tuberculosis with chronic renal failure on dialysis and a lymphocyte-predominant, exudative pleural effusion (tuberculosis vs uremic pleurisy). This category was subdivided into useful and not useful. The 8uid was useful when the analysis eliminated a clinically suspected diagnosis from further consideration, eg, empyema. The 8uid was not useful when

818

its analysis provided no further diagnostic information to help distinguish possible causes and where empyema was not a consideration. The determination of an exudative versus a transudative effusion was not considered sufficient information to classify the effusion as clinically useful.

Sequential Data Analysis To simulate the availability of information in the clinical setting and to assess the impact of delayed test results in determining diagnostic value and clinical usefulness, the pleural 8uid data were analyzed in sequential fashion as would be available to the clinician at three periods (see below). Each period corresponded to when a specific test result generally would be available for interpretation. Data from each period were presented sequentially to the pulmonary specialist. The patient's effusion was categorized for each time before laboratory data were presented from subsequent periods. If more than one thoracocentesis was performed, interval clinical history was provided.

If a given test was ordered, the results would be available for analysis during the specific time periods as follows: 1. First 24 hours: color and odor; WBC and RBC counts, differential WBC count; gram and AFB stain; pH; glucose, LDH, and protein concentration; LE cells. 2. 24 to 72 hours: aerobic and anaerobic cultures; cytology; titers of antinuclear antibody and rheumatoid factor and complement levels; triglyceride and cholesterol concentrations. 3. 72 hours to 6 weeks: fungal and tuberculosis cultures. The above tests represent the commonly available laboratory studies and approximate "tum-around" times. Performers ordered tests with discrimination and never ordered the complete inventory of tests. Complications Complications were assessed through performer and patient interviews and validated by chart analysis and review of chest radiographs or radiology reports. Objective complications were those observed by the operator at the time of thoracocentesis or during the subsequent 48 hours. Subjective complications were those experienced by the patient and reported by the operator or by the patient from a list of possible complications presented during the interview. Operators and patients were asked to quantify the patient's thoracocentesis site pain, anxiety and generalized chest pain on a scale of 0 to 10 (0= none, IO=severe). A response of2 or greater was considered clinically important. Technical problems in obtaining fluid were assessed by operator interviews and validated by chart and laboratory data review Technical problems were based on the outcomes of thoracocentesis. Equipment problems such as catheter occlusion, stop-cock malfunction, or needle gauge or length problems were not recorded separately. Technical problems were defined as follows: (I) dry thoracocentesis: no 8uid obtained; (2) traumot1e thoracocentuis: bloody fluid that clotted or had an hematocrit similar to peripheral blood; (3) blood contaminatedfluid: the performer reported that the pleural fluid was contaminated by blood during removal (serous fluid followed by bloody 8uid or vice versa); (4)insufficientfluid: obtained a quantity of8uid insufficient for the planned diagnostic tests; and (5) wrong side: thoracocentesis performed on the side opposite the effusion.

Statistical Analysis Data analysis was performed on a per patient and a per thoracocentesis basis. The results of diagnostic categorization are presented on a per patient basis, using the first thoracocentesis from which analyzable 8uid was obtained. The results of complications and technical problems are presented on a per thoracocentesis basis. >t analysis was applied to assess associations between variables. 11 Thoracocentesis (Collins, 8ahn)

RESULTS

Eighty-six (86) patients underwent 129 thoracocenteses. There were 54 men and 32 women ranging in age from 22 to 96 years, with a mean age of 56.4 years. Thirty-five patients had two or more thoracocenteses. The ratio of number of patients to number of thoracocenteses from each hospital medical service was: University Hospital, 46/62; Veterans Hospital, 27/47; Denver General Hospital, 13/20. The reason for the first thoracocentesis performed on each patient was diagnostic only in 65 of86 (76 percent) and diagnostic and! or therapeutic in 21 of 86 (24 percent). The indication for all thoracocenteses including a subsequent thoracocentesis was diagnostic only in 84 of 129 (65 percent) and diagnostic and/or therapeutic in 45 of 129 (35 percent). Therapeutic thoracocenteses were grouped with diagnostic plus therapeutic procedures for the purpose of analysis of complications.

Diagnostic Usefulness Seventy-eight patients (78/86, 91 percent) had fluids obtained that could be analyzed. Thus, eight patients were excluded from the evaluation of diagnostic usefulness. Of the 129 thoracocenteses, 97 fluids were analyzed (86 percent of all fluids obtained). All 97 fluids from these 78 patients were placed into diagnostic categories. Patient diagnostic categorization was not significantly different when results of the initial fluid analysis (one per patient for a total of 78) were compared to analysis of fluid from a subsequent thoracocentesis (for a total of97). Diagnostic value and clinical usefulness are, therefore, presented on a per patient basis. Pleural fluid analysis in conjunction with the clinical presentation helped place pleural fluids from these 78 patients into diagnostic categories as follows: definitive 14 (18percent), presumptive 44 (56 percent), and nondiagnostic 20 (26 percent). The nondiagnostic fluids were subdivided into useful 14 (18 percent) and not useful 6 (8 percent) (Table 1). When the definitive and presumptive categories were combined to form a clinical diagnostic category, 58 or 74 percent of the fluids were "diagnostic." When the nondiagnostic, useful fluids were combined with the "diagnostic" group, 72 (92 percent), provided information that was clinically useful. In six of 78 (8 percent) patients, pleural fluid analysis was not useful clinically. The determination of transudate vs exudate did not help distinguish between or among possible etiologic diagnoses in these six patients. The diagnostic usefulness of pleural fluid analysis did not correlate with patient age (S60 years or >60 years) or sex. When the effect of sequential data analysis from the three periods on initial diagnostic categorization was evaluated for the 78 patients, eight patients were

Table l-Diagnoaic CGNgona rfPl.ural Effuaiona (n = 78) No. of Patients ('1»

Category Definitive, 14 (18) Malignancy Bacterial empyema lbberculous pleurisy Presumptive 44 (56) Congestive heart failure Parapneumonic ParamaUgnant Other Cirrhosis, 5 1rauma, 2 Pulmonary embolism, 1 Postcardiac injury, syndrome, 1 Nondiagnostic, 20 (26) Useful Not useful

7

6

1

15 13 7 9

14 (18) 6 (8)

upgraded, five from presumptive to definitive and three from nondiagnostic to definitive ('D1ble 2). Of these eight definitive diagnoses, six patients had cytology positive for malignancy, one had a positive bacterial culture, and one a positive culture for tuberculosis. Fifteen patients had at least one subsequent thoracocentesis that provided analyzable fluid. Three patients with bilateral thoracocenteses had the same cause for each effusion. 1Wo patients had the initial diagnostic category upgraded from presumptive to definitive (empyema, cancer), while in ten patients the diagnosis remained unchanged after a subsequent thoracocentesis. Complications

Thirty-four objective complications occurred in 26 of 129 (20 percent) thoracocenteses ('D1ble 3). Pneumothorax occurred in 15 of 129 (12 percent) thoracocenteses. The pneumothorax was judged clinically unimportant (air entry through the needle or small pneumothorax) in eight and clinically important (large pneumothorax producing symptoms or a pneumothorax secondary to lung puncture in a patient with underlying lung disease) in seven. Chest tubes were placed in five of these seven patients, two after Table I-Diagraoatic CtJfegoristJdon tI8 After TIaoracocenIaia (n

Pundion cf 71tne

=78) G

Period Category

0-24 hr

24-72 hr

Definitive Presumptive Nondiagnostic Useful Not useful

6 49 23 17 6

13 45 20 14 6

72~wk

CHEST I 81 I 8 I JUNE. 1887

14

44

20 14 6

818

diagnostic and three after therapeutic thoracocentesis. Two of the five patients died within five days of pneumothorax. They were elderly patients with severe underlying disease. Pneumothorax occurred more frequently in patients with a malignancy (8 of 21) than in those without a malignancy (7 of 65) (p<0.01). Pneumothorax occurred more frequently in patients undergoing a therapeutic thoracocentesis (9 of 45) than those undergoing a diagnostic thoracocentesis (6 of 84) (p<0.05). Cough occurred in 12 of 129 (9 percent) thoracocenteses. The occurrence of cough. during .a thoracocentesis correlated with a higher occurrence of pneumothorax (five pneumothoraces in 12 patients with cough versus ten in 117 patients without cough) (p<0.01). Patient age (s60 years vs >60 years), operator experience (SIO vs >10 thoracocenteses), and catheter use (catheter vs needle alone) did not correlate with pneumothorax. Overall, objective complications occurred more frequently with therapeutic thoracocentesis, 23 of 45 (51 percent) than with diagnostic thoracocentesis, 11 of 84 (13 percent) (p<0.05). Other major and minor objective complications were sought but not found during the study period. .One patient with reexpansion pulmonary edema, a patient with inferior diaphragmatic artery laceration, 19 and an incident of the wrong patient undergoing thoracocentesis were noted before the study began. A patient with splenic laceration requiring emergency splenectomy was reported after the study closed. Following 123 thoracocenteses, the operator or supervisor was interviewed; and in 58 instances, the patient was interviewed. Reasons for failure of patient interviews were refusal, confusion, encephalopathy, poor memory, prompt discharge, and more than 72 hours after thoracocentesis. Sixty-five subjective complications occurred in 56 of 123 (46 percent) thoracocenteses (Table 3). Operators reported the following incidence of subjective complications: anxiety, 26 of 122 (21 percent); site pain, 24 of 123 (20 percent); dyspnea, six of123 (5 percent); generalized chest pain, six of 123 (5 percent); shoulder pain, two of 123 (2 percent); and abdominal pain, one of 123 (I percent). When patient and operator responses to the question of thoracocentesis site pain and anxiety were compared, most agreed that there was no pain or anxiety. However, when anxiety or pain were present, the operator tended to underestimate the degree of patient discomfort. Subjective complications were more likely with diagnostic plus therapeutic (27 of 45; 60 percent) than diagnostic (29 of78; 37 percent) thoracocentesis (p<0.05). Patients s60 years of age had more subjective complications than patients >60 years (35/60, 50 percent vs 21/63, 33 percent) (p<0.01). Pleural fluid was obtained in 113of 129 thoracocenteses. Thirty (30) technical problems were noted in 129 thoracocenteses (Table 4). There were 14 (11 percent) 820

Table 3-CompUcationB of Thoracocentesis Complication Objective (n = 129) Pneumothorax Cough Vasovagal reaction Retching Total Subjective (n = 123) Anxiety Site pain Dyspnea Generalized chest pain Shoulder pain Abdominal pain Total

n

Incidence, %

15 12 4 3

12 9

3 2

34

26

24 6 6

2

1 65

21 20 5 5 2 1

blood-contaminated fluids, nine (7 percent) dry procedures, three (2 percent) traumatic procedures, three (2 percent) insufficient fluids, and one (1percent) wrong side thoracocentesis. Only the blood-contaminated fluids could be analyzed. The other technical problems prevented 16 of129 (IS percent) of the thoracocenteses from yielding analyzable fluid. The incidence of technical problems did not correlate with patient age or operator experience but were more likely to occur with diagnostic, 25 of 84 (30 percent), than with diagnostic plus therapeutic thoracocentesis, five of 45 (11 percent) (p<0.05). When patients were asked to compare the discomfort of thoracocentesis with that of venipuncture, 21 of 58 (36 percent) reported less discomfort, 22 of 58 (38 percent) the same, and 15 of 58 (26 percent) reported more discomfort. When patients were asked to compare the discomfort of thoracocentesis with that of arterial puncture, 28 of 52 (54 percent) patients reported less, 18of 52 (35 percent) the same, and six of 52 (12percent) reported more discomfort. When patients were asked how they felt immediately after the procedure, 16 of 57 (28 percent) stated "better," 32 of 57 (56 percent) the "same," and nine of 57 (16percent) stated "worse." DISCUSSION

Our results show that pleural fluid analysis can yield clinically useful information in greater than 90 percent of patients; however, the diagnostic usefulness of thoracocentesis is enhanced by understanding its limiTable 4-Technical Problema ofThoracocentaia (n=1J9) Problem

n

Incidence, %

Blood contaminated fluid Dry tap Traumatic thoracocentesis Insufficient fluid Wrong side Total

14

11 7

9

3 3 1 30

2 2

1 23

Thoracocentesis (Collins, Sahn)

tations. A definitive etiologic diagnosis was made in 18 percent of our patients, a relatively low figure. Referral centers that might evaluate a population with a high incidence of malignancy have reported as high as 35 percent definitive diagnoses. 6,8 The major "diagnostic" value of thoracocentesis is in supporting a presumptive clinical diagnosis. Thus, the pleural fluid data are used to lend confidence to the clinical impression. In our study, a presumptive diagnosis was made in 56 percent of patients. Thus, a "cause" of the effusion could be determined in three of four patients. The clearer the clinical reasoning before thoracocentesis, the more helpful the pleural fluid data are in establishing a cause fur the effusion. Our study indicated that the information necessary to establish an etiologic diagnosis is available to the clinician in the first 72 hours followingthoracocentesis. The only exceptions to this would be in the diagnosis of tuberculous pleurisy and fungal infections in the pleural space. Since malignancy and empyema comprise the majority of the cases in the definitive category, it was not surprising that the etiology of the effusion was established 24 to 74 hours after thoracocentesis (see Table 2). Furthermore, all data needed to arrive at a presumptive diagnosis were available by 24 hours. We found that objective complications occurred in 20 percent of thoracocenteses. Pneumothorax was the most serious complication and occurred in 12 percent of procedures. This rate is similar to previously reported rates of 13 percent" and 9 percent" from prospective studies. Five of the 15 patients required a chest tube; this is comparable to the reports of others. 13,14 The role of pneumothorax and chest tube placement in the subsequent deaths of two elderly patients was not clearly causal but may have been contributory. Three factors associated with pneumothorax were identified: malignancy, cough during the procedure, and therapeutic thoracocentesis. In therapeutic thoracocentesis, use oflarger-bore needles and catheters and more manipulation of equipment as opposed to diagnostic procedures may explain this observation. Whether cough was the result or the cause of pneumothorax could not be determined. The physician should be alert to potential problems in this setting and take necessary precautions, such as use of a blunt-tipped needle's" or terminating the procedure if cough ensues. Other serious complications have been reported and based on our study occur in fewer than 1 percent of procedures. Such complications include: splenic rupture," abdominal hemorrhage," intrathoracic hemorrhage," unilateral pulmonary edema," air embolism, 10 death," catheter fragment left in pleural space," and tumor seeding of needle tract. II Splenic rupture, abdominal hemorrhage, and reexpansion pulmonary

edema were noted before and after the study and resulted in increased morbidity. Thoracocentesis is thought to cause minimal patient discomfurt; however; definite patient confirmation has been lacking. We observed. that the majority of patients considered discomfort from thoracocentesis to be similar or less than that associated with venipuncture or arterial puncture. Anxiety related to the thoracocentesis was common, and this may have heightened the perception of pain in some patients. The incidence of technical problems in this consecutive series was 23 percent, a frequency higher than anticipated. Technical problems occur more commonly in diagnostic than therapeutic thoracocentesis and include the inability to obtain fluid, insufficient fluid, or blood contamination. Better localization of fluid by ultrasound may obviate the above technical problems in instances of small or loculated effusions or pleural reaction simulating fluid.D.14 Blood contamination occurred frequently in diagnostic procedures. We think that this complication may contribute to the limited diagnostic value of pleural fluid RBC counts under 100,000/..,1.• We believe that performer-induced contamination may be a better explanation fur bloody transudative effusions than spontaneous hemorrhage." Because the majority of thoracocenteses were performed by housestaff the incidence of complications may relate to the experience of the operator, However; the numbers of thoracocenteses chosen to reflect operator experience « or >10) did not show different rates of complications; the data may be biased by patient selection, size of the effusion, guidance of a senior physician, and other variables. We suspect that physicians with more expertise, such as pulmonologists or experienced internists, would have fewer complications than the occasional operator; When thoracocentesis is performed as a diagnostic test, the clinician should be aware of the limitations of the procedure and have diagnostic possibilities in mind. The knowledge that most pleural fluid analyses do not provide a definitive etiology but support a clinical diagnosis should motivate the clinician to formulate a rational differential diagnosis prior to thoracocentesis. The pleural fluid findings then can be used to support or dispute the clinical diagnosis. Anxiety and discomfort, a common accompaniment of invasive procedures, can be minimized by explanation of the procedure and adherence to proper technique. ACKNOWLEDGMENTS: The authors wish to thank Drs. Richard Hamman and Gary Zerbe and the medicalhousestafF of the Unive~ si~ of Colorado Health Science Center fOr their cooperation, Dr. John HefInerforhelpfulsuggestions, and Leann HolstfOr secretarial assistance.

REFERENCES 1 Garrison FH. Introduction to the history of medicine, 4th edt CHEST I 91 I 8 I JUNE, 1987

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Philadelphia: WB Saunders Co , 1929:632 2 Sahn SA. Evaluation of pleural effusions and pleural biopsy. In : Petty TL , ed . Pulmonary diagnostic techniques. Philadelphia: Lea ~ Febiger, 1975:105-31 3 Sahn SA. The differential diagnosis of pleural effusions. West J Med 1982; 137:99-108 4 Black LF. The pleural space and pleural liquid. Mayo Clin Proc 1972; 47:493-506 5 Light RW, MacGregor MI, Luchsinger PC , Ball WC. Pleural effusion : the diagnostic separation of transudates and exudates. Ann Intern Med 1972; 77:507-13 6 Hirsch A, Ruffic P, Nebut M, Bignon J, Chretien J. Pleural effusion: laboratory tests in 300 cases. Thorax 1979; 34:106-12 7 Leuallen EC, Carr DT. Pleural effusion: a statistical study. N Engl J Med 1955; 252:79-83 8 Storey DD, Dines DF, Coles DT. Pleural effusion: a diagnostic dilemma. JAMA 1976; 236:2183-86 9 Tinney WS, Olsen AM. The significance of fluid in the pleural space: a study of 274 cases. J Thorac Surg 1945; 14:248-52 10 Braveny I, Machka K. Delayed iatrogenic rupture of the spleen. Lancet 1980; 2:752-53 11 Trapnell DH, Thurston JB. Unilateral pulmonary edema after pleural aspiration. Lancet 1970; 1:1367-69 12 Sue DY, Lam K. Retention of catheter fragment after thoracocentesis. Postgrad Med 1982; 72:101-06 13 Shepard JW Thoracocentesis: a safer method. Am Rev Respir Dis 1980; 121(suppl):I88 14 Jenkins DW, McKinnay MK, Sepak MW, Booker JL . Veres needle in the pleural space. South Med J 1983; 76:1383-85

15 Sahn SA. Malignant pleural effusions. Clin Chest Med 1985; 6: 113-25 16 Stelzner 'I; King TE, Antony VB, Sahn SA. The pleuropulmonary manifestations of the postcardiac injury syndrome. Chest 1983; 84:383-87 17 Snedecor AW, Cochran WG . Statistical methods, 6th ed. Ames, Iowa: Iowa State University Press, 1978 18 Heffner JE, Sahn SA. Abdominal hemorrhage after perforation of a diaphragmatic artery during thoracocentesis. Arch Intern Med 1981; 141:1238 19 Carney M, Ravin CEo Intercostal artery laceration during thoracocentesis. Increased risk in elderly patients. Chest 1979; 75:520-22 20 Johnson RF, Dorasty JL. Pleural disease. In: Fishman P, ed . Pulmonary diseases and disorders. New York: McGraw Hill Book Co, 1980:1363 21 Simpson K. Death from vagal inhibition. Lancet 1949; 1:558-60 22 Agurlar-Torres FG, Schlueter Dp, Perlman L, Maskawa T. Subcutaneous implantation of an adenocarcinoma following thoracocentesis. Wise Med J 1977; 76:19-21 23 Hornsberger HR, Lee TG, Makieno PH . Rapid, inexpensive real-time directed thoracocentesis. Radiology 1983; 146:545-46 24 Hirsch JH , Rogers]V, Mack LA. Real-time sonography of pleural opacities. Am J Radioll981 ; 136:297-301 25 Light RW Approach to the patient. In : Light RW, ed . Pleural diseases. Philadelphia: Lea ~ Febiger, 1983:61-67 26 Light RW, Erozan YS, Ball WC. Cells in pleural fluid: their value in differential diagnosis. Arch Intern Med 1973; 132:845-60

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Thoracocentesis (Collins, SBhn)