The diagnostic value of pleural fluid pH

Video-Assisted Thoracoscopic Surgery in Community-Acquired Thoracic Empyema: Analysis of Risk Factors for Mortality

Background: Thoracic empyema is a disease with high mortality and morbidity. Video-assisted thoracoscopic surgery (VATS) is recommended to treat advanced stage empyema. The purpose of this study was to explore risk factors associated with post-surgery mortality for community-acquired empyema. Patients and Methods: We retrospectively reviewed 440 patients who received VATS for community-acquired empyema, higher than stage 2, in a tertiary medical center in Taiwan. Patients' age, comorbidities, pleural effusion analysis, and post-surgery outcome were compiled. Cox regression model for survival was applied to identify risk factors of 90-day death after surgery. Results: Fifty-three patients (12.05%) had died within 90 days post-surgery. The risk factors of mortality were advanced age (hazard ratio [HR], 1.027; 95% confidence interval [CI], 1.001-1.052), chronic kidney disease (HR, 5.322; 95% CI, 2.635-10.746), cancer (HR, 6.038; 95% CI, 2.737-13.321), pleural effusion pH ≤7 (HR, 2.61; 95% CI, 1.344-5.069), pleural effusion protein ≤4 (HR, 2.021; 95% CI, 1.035-3.947), and late surgery (HR, 3.014; 95% CI, 1.595-5.696). The 90-day mortality in the early surgery group versus the late group was 6.85% versus 26.05%. The increased mortality risk from late surgery was observed in most subgroups, except for patients who were female, had chronic renal disease, and had coronary artery disease. Conclusions: Patients who are elderly, have chronic kidney disease, cancer history, low pleural effusion pH, low pleural effusion protein, and late surgery are associated with post-surgery mortality for community-acquired advanced empyema. Early VATS surgery for advanced empyema or treatment failure of chest tube drainage appears to beneficial and is recommended.

Pleural Fluid Analysis: Are Light's Criteria Still Relevant After Half a Century?

Fifty years from their initial description, Light's criteria are still unhesitatingly accepted as the default reference test for separating pleural transudates and exudates. Efforts should be focused not so much on trying to find an even more reliable technique for categorizing PEs but on improving the misclassification rate of transudates that characterize Light's criteria. Despite their shortcomings, Light's criteria may well continue their reign for another 50 years. Long live the Light's criteria!

Relationship of pleural fluid pH and glucose: a multi-centre study of 2,971 cases

Background

Pleural fluid pH and glucose levels are both recommended in the workup of pleural effusions. Whether their levels correlate and predict each other or contribute independent knowledge is unclear. We aimed to investigate the pH/glucose relationship, assess their concordance and ascertain whether performing both tests provides additional information to performing either test alone.

Methods

The pH and glucose measurements from 2,971 pleural fluid samples, from three centers in Spain, UK and Australia, were categorized into Cancer (n=1,045), Infection (n=544), Tuberculosis (n=249) and Others (n=1,133) groups. The relationship between pH and glucose values and their concordance at clinically relevant cutoffs (pH 7.2 and glucose 3.3 mmol/L) were assessed.

Results

The mean pH of the cohort was 7.38 (SD 0.22) and median glucose 5.99 (range, 0.00-29.36) mmol/L. A regression model of the relationship between glucose (log-transformed) and pH with a restricted cubic spline showed linear (P<0.01) and nonlinear effects (P<0.01). The relationship was strong with a narrow confidence interval but the prediction interval was wide. Most (91.9%) samples were concordant using pH and glucose levels at cutoffs of 7.20 and 3.30 mmol/L respectively. Using pH alone, without glucose, captured 95.0% of the infection-related effusions with either pH or glucose below cutoff and glucose alone identified 91.7%.

Conclusions

Pleural fluid pH and glucose have a strong non-linear relationship but, in most situations, the level of one cannot accurately predict the other. Concordance rates were high and either test is sufficient in the majority of cases.

The management of benign non-infective pleural effusions

The evidence base concerning the management of benign pleural effusions has lagged behind that of malignant pleural effusions in which recent randomised trials are now informing current clinical practice and international guidelines.

The causes of benign pleural effusions are broad, heterogenous and patients may benefit from individualised management targeted at both treating the underlying disease process and direct management of the fluid. Pleural effusions are very common in a number of non-malignant pathologies, such as decompensated heart failure, and following coronary artery bypass grafting. Pleural fluid analysis forms an important basis of the diagnostic evaluation, and more specific assays and imaging modalities are helpful in specific subpopulations.

Options for management beyond treatment of the underlying disorder, whenever possible, include therapeutically aspirating the fluid, talc pleurodesis and insertion of an indwelling pleural catheter. Randomised trials will inform clinicians in the future as to the risks and benefits of these options providing a guide as to how best to manage patient symptoms in this challenging clinical setting.

Benign pleural effusion management is challenging and based on limited evidence. Treatment options are discussedhttp://ow.ly/10EOSN

A 22-year-old man with pleural tuberculosis associated hydropneumothorax: Case report and literature review

A 22-year-old Asian male presented with fever, non-productive cough, right-sided pleuritic chest pain and was found to have a large right hydropneumothorax. A chest tube was placed. Pleural fluid analysis revealed a lymphocytic predominant exudate and he was subsequently started on four-drug daily anti-tuberculosis therapy (isoniazid, ethambutol, rifampin, pyrazinamide). Pleural biopsy revealed acid-fast bacilli. Given his persistent pleural effusion, he was given four doses of intrapleural tissue plasminogen activator (tPA) and dornase alpha (DNase) via his chest tube over a period of 6 days resulting in clinical and radiologic improvement. Pleural biopsy and pleural fluid culture specimens later revealed Mycobacterium tuberculosis. Intrapleural tPA-DNase therapy has demonstrated improved resolution of infections and shortened hospitalizations for parapneumonic infectious effusions. However, there is little literature on the use of intrapleural fibrinolytics specifically for pleural tuberculosis associated effusions. Furthermore, the American Thoracic Society does not comment on therapeutic thoracentesis or intrapleural fibrinolytic therapy in their recommendations for treatment of pleural tuberculosis. In our case of pleural TB-associated hydropneumothorax, the use of intrapleural tPA-DNase therapy facilitated pleural fluid drainage and resulted in near-complete resolution of the effusion.

Pneumonia and empyema: causal, casual or unknown

Parapneumonic effusions complicating pneumonia are associated with increased morbidity and mortality. Along with increased mortality, complicated parapneumonic effusion and empyema often necessitate prolonged treatment, longer hospital stay and interventions. Parapneumonic effusions arise from inflammation in the lungs and pleural space from direct invasion of bacteria, cascade of inflammatory events and bacteriologic virulence features. Patient factors and comorbidities also contribute to the pathophysiology of parapneumonic effusion development. The evolution of parapneumonic effusion can be divided into three progressive stages: (I) exudative stage; (II) fibrinopurulent stage; and (III) organizing stage with pleural peel formation. These stages can help categorize effusions into groups in order to evaluate the risk of a complicated course requiring intervention. We recommend that clinical data be evaluated and a stepwise approach be taken in management of these patients. This review article discusses current understanding of the development and relationship of parapneumonic effusions with pneumonia.

Do we measure pleural fluid pH correctly?

PURPOSE OF REVIEW

This review analyzes the current literature available on appropriate measurement of pleural fluid pH and currently used methods of measurement.

RECENT FINDINGS

Current literature continues to support the superiority of blood gas analyzers (BGAs) in the accurate measurement of pleural fluid pH. Despite the compelling evidence, roughly 30-50% of the laboratories across the United States continue to use inaccurate methods for pleural fluid pH measurement. Nearly 40% of pulmonologists were incorrect in believing their laboratory uses BGA for the analysis of pleural fluid pH.

SUMMARY

It is apparent that the clinical utility of pleural fluid pH is often undermined by its inappropriate measurement. Physicians must be made aware of their laboratory's method of measurement if pleural fluid pH is to be used in the evaluation of pleural diseases. If pleural fluid pH measurement is not done accurately, then other pleural fluid characteristics may be used to aid the clinician.

Optically-gated self-calibrating nanosensors: monitoring pH and metabolic activity of living cells

Quantitative detection of biological and chemical species is critical to numerous areas of medical and life sciences. In this context, information regarding pH is of central importance in multiple areas, from chemical analysis, through biomedical basic studies and medicine, to industry. Therefore, a continuous interest exists in developing new, rapid, miniature, biocompatible and highly sensitive pH sensors for minute fluid volumes. Here, we present a new paradigm in the development of optoelectrical sensing nanodevices with built-in self-calibrating capabilities. The proposed electrical devices, modified with a photoactive switchable molecular recognition layer, can be optically switched between two chemically different states, each having different chemical binding constants and as a consequence affecting the device surface potential at different extents, thus allowing the ratiometric internal calibration of the sensing event. At each point in time, the ratio of the electrical signals measured in the ground and excited states, respectively, allows for the absolute concentration measurement of the molecular species under interest, without the need for electrical calibration of individual devices. Furthermore, we applied these devices for the real-time monitoring of cellular metabolic activity, extra- and intracellularly, as a potential future tool for the performance of basic cell biology studies and high-throughput personalized medicine-oriented research, involving single cells and tissues. This new concept can be readily expanded to the sensing of additional chemical and biological species by the use of additional photoactive switchable receptors. Moreover, this newly demonstrated coupling between surface-confined photoactive molecular species and nanosensing devices could be utilized in the near future in the development of devices of higher complexity for both the simultaneous control and monitoring of chemical and biological processes with nanoscale resolution control.

Getting the most from pleural fluid analysis

Virtually, every pulmonary disease and most non-pulmonary diseases may be associated with a pleural effusion. The presence of a pleural effusion allows the clinician to 'diagnose' or narrow the differential diagnosis and aetiology of the fluid collection. However, pleural fluid analysis (PFA) in isolation rarely provides a definitive diagnosis. This review discusses the rationale for evaluating patients with a pleural effusion. If the clinician obtains a detailed history, performs a comprehensive physical examination, reviews pertinent blood tests, and evaluates the chest imaging findings prior to thoracentesis, there should be a high likelihood of establishing a firm clinical diagnosis based on the appropriate PFA. This manuscript reviews the clinical presentation, chest imaging findings, duration and natural course of specific pleural effusions to help narrow the range of pre-thoracentesis diagnoses. A diagnosis of transudative effusion confirms an imbalance in hydrostatic and oncotic pressures, normal pleura and a limited differential diagnosis, which is typically apparent from the clinical presentation. Exudates are the result of infections, malignancies, inflammation, impaired lymphatic drainage or the effects of drugs, and pose a greater diagnostic challenge. The differential diagnosis for a pleural exudate can be narrowed if LDH levels exceed 1000 IU/L, the proportion of lymphocytes is ≥80%, pleural fluid pH is <7.30 or there is pleural eosinophilia of >10%.

A not so simple effusion

We describe the case of a patient with an empyema, how it forms and what the evidence behind the treatment options are with specific reference to intrapleural thrombolytic therapy.

An update in the management of malignant pleural effusion

Malignant pleural effusion (MPE) usually presents in the disseminated and advanced stage of malignancy. Dyspnea is the debilitating symptom which needs palliation in these patients. Various modalities are available in the management of MPE. Careful consideration of the patient's expected survival and quality of life is needed when deciding the optimum treatment modality in such patients. In this article, different modalities of the palliative management of MPE are discussed with an attempt to derive a treatment algorithm for the management of MPE.

A systematic approach to the investigation and diagnosis of a unilateral pleural effusion

Fluid in the pleural space is a common sequela of a wide range of diseases which may be pulmonary, pleural or extrapulmonary. As the differential diagnosis is wide, a systematic approach to investigation and diagnosis is recommended. This review highlights the important features and recommendations for the investigation of a unilateral pleural effusion, a common condition encountered by the general physician. The aim of this study was to assist with a speedy diagnosis of the underlying pathology, using appropriate investigative techniques, while minimising the use of invasive procedures.

Diagnosis and management of malignant pleural effusions

Malignant pleural effusions (MPEs) complicate the clinical course of patients with a broad array of malignancies, which are most often due to lymphomas or carcinomas of the breast, lung, gastrointestinal tract or ovaries. Patients may present with a MPE as the initial manifestation of a cancer or develop an effusion during the advanced phases of a known malignancy. In either circumstance, the median survival after presentation with a MPE is 4 months. Effusions may result from direct pleural invasion (MPE) or indirect effects (paraneoplastic effusions), such as impairment of fluid efflux from the pleural space by lymphatic obstruction or pleural effects of cancer radiation or drug therapy. Because only 50% of patients with cancer who develop a pleural effusion during their clinical course have a MPE, careful evaluation of the effusion to establish its aetiology is required to direct therapy. Management is palliative with interventions directed towards decreasing the volume of intrapleural fluid and the severity of associated symptoms.

The value of pleural fluid analysis

Pleural fluid analysis in isolation may have clinical value. To have the greatest diagnostic impact, the clinician must formulate a prethoracentesis diagnosis based on the clinical presentation, blood tests, and radiographic imaging. With this approach, a definitive or confident clinical diagnosis can be expected in up to 95% of patients. The information in this report should allow the clinician to achieve this goal.

Recent advances in the diagnosis and management of malignant pleural effusions

Malignant pleural effusions (MPEs) are an important complication for patients with intrathoracic and extrathoracic malignancies. Median survival after diagnosis of an MPE is 4 months. Patients can present with an MPE as a complication of far-advanced cancer or as the initial manifestation of an underlying malignancy. Common cancer types causing MPEs include lymphomas, mesotheliomas, and carcinomas of the breast, lung, gastrointestinal tract, and ovaries. However, almost all tumor types have been reported to cause MPEs. New imaging modalities assist the evaluation of patients with a suspected MPE; however, positive cytologic or tissue confirmation of malignant cells is necessary to establish a diagnosis. Even in the presence of known malignancy, up to 50% of pleural effusions are benign, underscoring the importance of a firm diagnosis to guide therapy. Rapidly evolving interventional and histopathologic techniques have improved the diagnostic yield of standard cytology and biopsy. Management of an MPE remains palliative; it is critical that the appropriate management approach is chosen on the basis of available expertise and the patient's clinical status. This review summarizes the pathogenesis, diagnosis, and management of MPE. Studies in the English language were identified by searching the MEDLINE database (1980-2007) using the search terms pleura, pleural, malignant, pleurodesis, and thoracoscopy.

Use of Heparinized versus Non-Heparinized Syringes for Measurements of the Pleural Fluid pH

BACKGROUND

Pleural fluid (PF) pH measurement is important for establishing a diagnosis and for guiding clinical management. The current standard practice is to collect PF samples for pH measurement in heparinized syringes at room temperature and to instantaneously process these samples.

OBJECTIVE

The purpose of this study is to investigate the effect of collecting PF in heparinized versus non-heparinized syringes at room temperature on PF pH measurements when processed at various time intervals.

METHODS

From 50 consecutive thoracenteses, 1 ml of PF was collected anaerobically in each of six 3-ml syringes. Only three syringes were coated with heparin. The samples were processed for PF pH measurements at time 0 (T(0)) and 1 h (T(1)) and 2 h (T(2)) after collection. All specimens were preserved at room temperature, until the measurements were carried out in duplicates by a calibrated blood gas analyzer.

RESULTS

PF pH values were significantly lower with heparinized versus non-heparinized syringes at all time intervals (T(0): pH heparinized = 7.378 +/- 0.107 vs. pH non-heparinized = 7.390 +/- 0.108; T(1): pH heparinized = 7.378 +/- 0.115 vs. pH non-heparinized = 7.389 +/- 0.111; T(2): pH heparinized = 7.367 +/- 0.105 vs. pH non-heparinized = 7.389 +/- 0.121). In the heparinized syringes, there was a significant decrease in PF pH values at T(2) versus T(0) and T(1). There were no significant changes in PF pH values over time in the non-heparinized syringes.

CONCLUSIONS

For serial PF pH measurements, the same type of syringes (either heparinized or non-heparinized) should be consistently used. With heparinized syringes, processing of PF pH measurements should be performed within 1 h after collection.

Diagnosis and treatment of tuberculous pleural effusion in 2006

Tuberculous (TB) pleural effusion occurs in approximately 5% of patients with Mycobacterium tuberculosis infection. The HIV pandemic has been associated with a doubling of the incidence of extrapulmonary TB, which has resulted in increased recognition of TB pleural effusions even in developed nations. Recent studies have provided insights into the immunopathogenesis of pleural TB, including memory T-cell homing and chemokine activation. The definitive diagnosis of TB pleural effusions depends on the demonstration of acid-fast bacilli in the sputum, pleural fluid, or pleural biopsy specimens. The diagnosis can be established in a majority of patients from the clinical features, pleural fluid examination, including cytology, biochemistry, and bacteriology, and pleural biopsy. Measurement of adenosine deaminase and interferon-gamma in the pleural fluid and polymerase chain reaction for M tuberculosis has gained wide acceptance in the diagnosis of TB pleural effusions. Although promising, these tests require further evaluation before their routine use can be recommended. The treatment of TB pleural effusions in patients with HIV/AIDS is essentially similar to that in HIV-negative patients. At present, evidence regarding the use of corticosteroids in the treatment of TB pleural effusion is not clear-cut.

Pleural effusions of extravascular origin

Most pleural effusions are caused by hydrostatic and oncotic pressure imbalance, inflammation or infection, or abnormalities in lymphatic drainage. A select number of effusions are caused by fluid of extravascular origin. Some of these effusions result from complications of treatment, whereas others are a ramification of the underlying disease. The incidence, pathogenesis, clinical presentation, chest radiographic manifestations, pleural fluid analysis, diagnosis, and management are discussed.

[Changes in the acid-base equilibrium of pleural fluid during the first 2 hours after thoracentesis]

OBJECTIVE

The aim of this study was to assess changes in the acid-base equilibrium of pleural fluid during the first 2 hours after thoracentesis and to determine whether, as with arterial blood, it is important to keep the fluid on ice.

PATIENTS AND METHODS

A prospective, descriptive, comparative study was performed in 53 consecutive patients with pleural effusion. Thoracentesis was performed and pleural fluid was collected in 5 heparinized syringes to determine the pH, PO2, and PCO2 at baseline and at 30, 60, 90, and 120 minutes. In the first 26 patients, pleural fluid was collected in a further 4 syringes that were kept on ice prior to performing the same measurements at 30, 60, 90, and 120 minutes.

RESULTS

The patients had a mean (SD) age of 70 (14) years, 66% were smokers, 72% were men, 63% had right-sided pleural effusion, 85% had unilateral effusion, and 15% had massive effusion. In 10 patients the effusion was a transudate, in 35 it was lymphocytic, and in 8 it was neutrophilic. The etiology was benign in 34 cases and neoplastic in 19 cases. The baseline pH was 7.35 (0.1) and baseline values of PO2 and PCO2 were 57.8 (20) mm Hg and 53.7 (15) mm Hg, respectively. No significant changes were observed in the first 2 hours for either pH or PCO2, whereas PO2 did undergo a significant change over this period. The difference between the baseline value and the value obtained at 120 minutes was 0.005 (0.02) for pH, 12.5 (19) mm Hg for PO2, and 0.8 (3) mm Hg for PCO2, with correlation coefficients of 0.97, 0.49, and 0.98, respectively. Comparison of values by simple regression analysis did not reveal a significant difference in the changes in pH, PO2, or PCO2 associated with keeping samples on ice. Multivariate analysis revealed that neoplastic effusion and a higher red blood cell count in pleural fluid had a significant influence on pH changes.

CONCLUSIONS

The pH and PCO2 of pleural fluid did not change significantly during the first 2 hours following thoracentesis, whereas PO2 did undergo a significant change. Keeping samples on ice during this period is unnecessary. Only a higher red blood cell count in pleural fluid and neoplastic effusion had a limited effect on changes in the pH of samples from our patients during the first 2 hours following thoracentesis.

Percutaneous management of parapneumonic effusions

Parapneumonic effusions continue to be a significant source of morbidity and mortality. Treatment at earlier stages before fibrous peel and loculations occur has a much better prognosis. Using image guidance, addition of intracavitary fibrinolytic instillation, close follow-up with drainage of residual or new collections are some of the other factors that improve prognosis. In this article, we discussed treatment strategies, percutaneous management of parapneumonic effusions, its alternatives and results.

Pleural effusion

Pleural disease remains a commonly encountered clinical problem for both general physicians and chest specialists. This review focuses on the investigation of undiagnosed pleural effusions and the management of malignant and parapneumonic effusions. New developments in this area are also discussed at the end of the review. It aims to be evidence based together with some practical suggestions for practising clinicians.

C-Reactive Protein in Lymphocytic Pleural Effusions: A Diagnostic Aid in Tuberculous Pleuritis

BACKGROUND

C-reactive protein (CRP) pleural fluid levels have been found to be higher in tuberculosis and parapneumonic effusions than in other causes of pleural effusion.

OBJECTIVE

The aim of this study was to analyze whether CRP (a simple and inexpensive test) may be a diagnostic aid for tuberculosis in lymphocytic pleural effusions.

METHODS

One hundred and forty-four patients with a lymphocytic pleural effusion (more than 50% lymphocytes in the differential white blood cell count) were included. The patients were 93 men (65%) and 51 women (35%), aged 64 +/- 18 years (mean +/- SD). The diagnoses were as follows: tuberculosis, 20; pleural effusion associated with malignancy, 69; transudates, 38; other benign exudates, 17.

RESULTS

The CRP pleural fluid level was higher in tuberculous pleuritis (54 +/- 24 mg/l) than in lymphocytic effusions of other origin (21 +/- 16 mg/l; p < 0.001). High CRP levels (>or=50 mg/l) have a high specificity for tuberculosis (95%), and low levels (<30 mg/l) have a high sensitivity (95%) for excluding disease.

CONCLUSIONS

CRP pleural fluid level determination is useful in the diagnostic workup of lymphocytic pleural effusions. High CRP levels are very suggestive of tuberculous pleuritis, and low CRP levels make this diagnosis unlikely.

Accuracy of computed tomography attenuation values in the characterization of pleural fluid: an ROC study

RATIONALE AND OBJECTIVES

To assess the accuracy of computed tomography (CT) in characterizing pleural fluid based on attenuation values.

MATERIALS AND METHODS

Protocol was approved by the local institutional review board and informed consent was waived. We retrospectively analyzed 145 pleural effusions of 145 patients (mean/standard deviation age: 60.7/15.9 years; 69 females) who underwent CT of the thorax and diagnostic thoracentesis within 7 days of each other. Effusions were classified as transudates or exudates using laboratory markers based on Light's criteria. The mean Hounsfield units (HU) of an effusion was determined by a region of interest on the three slices with the greatest anteroposterior diameter. A receiver operating characteristic curve was constructed to determine threshold values for classification on the basis of mean HU and to examine overall accuracy, using the area under the curve (A(z)).

RESULTS

Of the 101 exudates and 44 transudates, the mean attenuation of exudates (17.1 HU/standard deviation 4.4) was significantly higher than transudates (12.5 HU/6.3), (P < .001). There was a modest but significant positive relationship between mean HU and laboratory markers, with the strongest relationship with pleural/serum protein (r = 0.57, P < .001) and total pleural protein (r = 0.56, P < .001). The overall accuracy of attenuation values for identifying exudates was moderate, Az = 0.775, standard error = 0.039, with the largest limitation being the overlap with transudates in the 10-20 HU range, which constituted 66% (90/145) of the total effusions measured.

CONCLUSION

Although the mean attenuation of exudates is significantly higher than transudates, the clinical use of CT numbers to characterize pleural fluid is not recommended, as their accuracy is only moderate. Moreover, there is a notable overlap in attenuation values between transudates and exudates for a majority of effusions.

Multilevel and Continuous Pleural Fluid pH Likelihood Ratios for Draining Parapneumonic Effusions

BACKGROUND

Although clinical practice guidelines endorse the use of pleural fluid pH to select patients with parapneumonic effusions for pleural drainage, no studies have reported likelihood ratios for pleural fluid pH.

OBJECTIVES

We derived and tested the value of continuous likelihood ratios for selecting pneumonia patients for pleural drainage.

METHODS

Patient level pleural fluid pH results were obtained from a registry of primary studies that assessed the discriminative properties of pH. Multilevel likelihood ratios were calculated for four pH intervals. Continuous likelihood ratios were derived from logistic regression using discrete pH values. Binary, multilevel and continuous likelihood ratios were compared to evaluate the statistical (chi2) and clinical advantages of continuous likelihood ratios.

RESULTS

Hundred and ninety-seven pleural fluid pH results were retrieved from published reports and categorized into four pH ordinal intervals. Multilevel likelihood ratios ranged from a low of 0.13 (95% CI, 0.04-0.41) for pH values >7.40 to a high of 15.80 (95% CI, 7.04-35.45) for pH values < or =7.00. Logistic regression derived the following equation for continuous likelihood ratios: exp[-7.168(measured pH - 7.207)]. Continuous likelihood ratios offered more diagnostic information both statistically (p < 0.005) and clinically compared with binary and multilevel likelihood ratios.

CONCLUSIONS

Analysis of a patient registry allows the derivation of an exponential equation that calculates continuous likelihood ratios for discrete pleural fluid pH values. Continuous likelihood ratios provide more clinically and statistically significant information compared with binary and multilevel likelihood ratios for calculating posttest probabilities of the need to drain parapneumonic effusions.

Inflammatory parameters after pleurodesis in recurrent malignant pleural effusions and their predictive value

Recurrent pleural malignant effusion is a common problem which can be treated by inducing symphysis of the pleural sheets. Many different drugs administered into the pleural space can be used to achieve this. The drugs cause an inflammatory response, which in turn is believed to cause the symphysis. Comparatively little has been published on the degree of pleural inflammation and the systemic response and whether this will affect the outcome. The aim of this study was to describe the systemic inflammatory reaction following instillation of a chemical agent into the pleura and to investigate whether this had any predictive value for the outcome (i.e. the pleurodesis). The markers investigated were simple ones: erythrocyte sedimentation rate, C-reactive protein, and leukocyte count from venous blood samples, and the fever reaction. Eighty-nine prospective patients with malignant pleural effusion who underwent pleurodesis with either talc (48 patients) or quinacrine (41 patients) were included in the study. Symphysis was achieved in 82 patients (92 per cent) and all had a prominent transitional elevation of the inflammatory parameters. The unsuccessful attempts caused negligible or very small elevations, but due to the small numbers only the degree of fever after 8 and 48 h showed a statistically significant difference. In conclusion, pleurodesis causes a systemic inflammation and there is a tendency to a correlation between the success of pleurodesis and the degree of inflammation. High fever and high inflammatory parameters including CRP are due to this inflammatory response and do not indicate infection.

Biochemical analysis of pleural, peritoneal and pericardial effusions

Body fluids other than blood, urine and cerebrospinal fluid are often submitted for biochemical analysis. Of these, pleural, peritoneal and pericardial fluids are the most common. Laboratory tests are a useful tool to assess the aetiology, pathophysiology and subsequent treatment of effusions. A wide range of biochemical tests may be requested. This review critically examines the various analytes that have been used to investigate these body fluids.

The management of pleural space infections

Pleural infection is responsible for significant morbidity and mortality worldwide, and its clinical management is challenging. The diagnosis of empyema and tuberculous pleurisy may be difficult, and these conditions may be confused with other causes of exudative pleural effusions. Complicated parapneumonic effusion or empyema may present with 'atypical' clinical features; delays in diagnosis are common and may contribute to the high mortality of these infections. Pleural aspiration is the key diagnostic step; pleural fluid that is purulent or that has a pH < 7.2, or organisms on Gram stain or culture, is an indication for formal intercostal drainage. In order to achieve a definitive diagnosis of tuberculous pleurisy, Mycobacterium tuberculosis must be isolated in the culture of pleural fluid, pleural tissue or sputum; demonstration of granulomas in pleural tissue is also suggestive of tuberculosis. The use of pleural fluid biochemical markers, such as adenosine deaminase, in the diagnosis of tuberculous pleurisy varies among clinicians; the diagnostic value of such markers is affected by the background prevalence of tuberculosis and the likelihood of an alternative diagnosis. Uncertainties also remain regarding the treatment of pleural infection. Treatment of complicated parapneumonic effusion and empyema involves prolonged courses of antibiotics and attention to the patient's nutritional state. The role of intrapleural fibrinolytics and the optimal timing of surgical intervention are unknown. The lack of clear predictors of clinical outcome in empyema contributes to the difficulty in treating this condition. The pharmacological treatment of tuberculous pleurisy is the same as for pulmonary tuberculosis; the precise role of steroids in the treatment of tuberculous pleurisy remains uncertain.

Pleural effusion: a structured approach to care

The accumulation of fluid in the pleural space is a common manifestation of a wide range of disease. This review provides a structured approach to the investigation of the patient with a pleural effusion. This should allow an accurate diagnosis to be made with the minimum number of invasive and time-consuming investigations.

Is it meaningful to use biochemical parameters to discriminate between transudative and exudative pleural effusions?

OBJECTIVES

The usefulness of biochemical criteria to separate pleural transudates from exudates is controversial, and the limitations of Light's criteria in patients receiving diuretic therapy is of general concern. We evaluated the added value of biochemical criteria to clinical judgment for separating transudates from exudates.

SETTING

A community teaching hospital.

DESIGN

A prospective, observational study for the evaluation of diagnostic tests.

PATIENTS AND MEASUREMENTS

In 249 consecutive patients referred for diagnostic thoracentesis, two physicians classified the pleural effusion as transudate or exudate based on all available information just before performing the thoracentesis. The sensitivity, specificity, and accuracy of the clinical presumption were compared with those of Light's criteria, and serum-pleural fluid albumin and protein gradients. The combined accuracy of biochemical and clinical criteria was also assessed.

RESULTS

The accuracy of Light's criteria (93%) was significantly higher than that showed by the initial clinical presumption (84%; p < 0.01) and that of the alternative biochemical criteria: serum-pleural fluid albumin gradient (87%; p < 0.03) and serum-pleural fluid protein gradient (86%; p < 0.01). In patients receiving diuretic therapy, the accuracy of Light's criteria was 83% (60 of 72 cases), neither different to that of the albumin gradient (88%; 63 of 72 cases) nor to that of the protein gradient (86%; 62 of 72 cases). When these alternative biochemical criteria were applied exclusively to patients receiving diuretics who were thought to have a transudative effusion by clinical criteria, but having fluid identified as exudative by Light's criteria, the results did not improve significantly. Using a multiparametric model for the population receiving diuretics, the accuracy was greater (93%; 67 of 72 cases) than that of Light's criteria but without reaching statistical significance (p = 0.12).

CONCLUSIONS

Light's criteria are significantly superior to the clinical presumption to separate pleural transudates from exudates. In patients receiving diuretics, Light's criteria lose accuracy, which is similar to that showed by the use of alternative biochemical criteria alone or combined with clinical judgment.

Fatores preditivos para drenagem de derrames pleurais parapneumônicos em crianças

Objetivo: Avaliar os critérios de Light et al. para drenagem em derrames pleurais parapneumônicos (DPP) em crianças. Métodos: Estudo transversal prospectivo realizado com 85 crianças admitidas no Hospital da Criança Santo Antônio, Porto Alegre, no Estado do Rio Grande do Sul, região Sul do Brasil, que apresentaram pneumonia e derrame pleural confirmado por radiografia de tórax e/ou ultra-sonografia. Os critérios de exclusão foram: drenagem prévia, derrame associado com outras doenças. A análise do pH foi em aparelho de gasometria. Glicose e desidrogenase láctica foram analisadas por espectrofotometria. A indicação de drenagem foi feita pelo médico assistente sem participação dos pesquisadores. Resultados: Neste estudo, os DPP com pH menor que 7,2 e glicose igual ou inferior a 40mg/dl apresentaram índices de drenagem superiores aos da DHL > 1.000UI/l. O pH e a glicose apresentaram especificidades elevadas na predição de drenagem (89% e 88%) e superiores às da DHL (65%). Os mesmos resultados foram observados quando líquidos não purulentos foram analisados (pH < 7,2 -- 94%; glicose < 40 -- 88%; e DHL > 1.000 -- 68%). Em pacientes com pH < 7, DHL > 1.000UI/l e glicose < 40mg/dl predominaram líquidos com aspecto turvo ou purulento. Em torno de 21% dos pacientes com indicação de drenagem, segundo os critérios bioquímicos, encontrou-se líquido com aspecto límpido. Conclusões: Estes dados indicam que os exames bioquímicos podem apoiar a decisão de drenagem torácica de derrame pleural parapneumônico em líquidos não purulentos. A especificidade para drenagem foi de 89% para o pH, 88% para glicose e em torno de 65% para DHL.

Does pleural fluid pH change significantly at room temperature during the first hour following thoracentesis?

BACKGROUND

Usually, pleural fluid (PF) pH is measured immediately following thoracentesis, and if there is any delay in the measurement, the PF sample is preserved on ice.

OBJECTIVE

To determine if PF pH changes significantly at room temperature during the first hour following thoracentesis.

DESIGN

Prospective, self-controlled.

SETTING

Tertiary care center.

PATIENTS

All patients undergoing thoracentesis.

MEASUREMENTS

The PF pH of a sample collected in an arterial blood gas syringe was measured immediately following thoracentesis by an arterial blood pH/gas analyzer. Additional measurements were made at 5, 15, 30, 45, and 60 min from the first pH measurement (pH0), maintained at room temperature.

RESULTS

For 28 PF samples, pH0 (mean +/- SD) was 7.351 +/- 0.158, and the 60-min pH (pH60) was 7.359 +/- 0.161. The mean difference between pH60 and pH0 was 0.008 +/- 0.026, which was not significant, either clinically or statistically (p = 0.13). Similarly, the interim pH values (for measures at 5, 15, 30, 45 min after pH0) were not significantly different from pH0 (mean differences, 0.002, 0.003, 0.005, and 0.004, respectively; p values, 0.51, 0.21, 0.06, and 0.22, respectively).

CONCLUSIONS

The pleural fluid pH of a sample preserved at room temperature does not change significantly during the first hour following thoracentesis. Hence, contrary to the common medical practice, there is no need to perform the pH measurement within minutes after thoracentesis and to preserve a pleural fluid sample on ice.

Infection of the pleural space

Parapneumonic effusions are common accompaniments of pneumonia that require proper management to prevent progression to empyema. Management decisions require thoughtful individualization of care because of the multiple factors that affect outcome; no one algorithmic approach exists for all patients. Basic principles of care, however, apply to all patients and center on the early detection of infected pleural fluid and the rapid completion of effective pleural drainage and lung re-expansion, when indicated to decrease morbidity and mortality.

Evaluating pleural effusions. How should you go about finding the cause?

Although many pulmonary and systemic diseases are known to cause pleural effusions, analysis of the pleural fluid pinpoints the cause in most cases. Distinguishing pleural transudates from exudates is an important step. Transudate effusions are caused by a small, well-defined group of illnesses (e.g., cirrhosis, congestive heart failure). Exudative effusions, on the other hand, are associated with a wide variety of causes, including pneumonia, malignancy, TB, drug-induced reactions, and many others. Some effusions remain unexplained despite extensive tests. Surgical approaches may be appropriate for some of these patients, but the risks must be carefully weighed against the benefits.

Anion gap in turpentine-induced pleural effusions. Correlation with pH and protein level

Since the pleural fluid proteins and lactate are unmeasured anions, the pleural fluid anion gap (Na+K-Cl-total CO2) should vary with the protein level and should be high in acidic effusions (which have high lactate levels). The anion gap is also convenient and inexpensive to measure, and less subject to artifact than the pH measurement. To test the hypothesis that the anion gap correlates with the pH, protein level, and other traditional pleural fluid measurements, we used a well-described model of turpentine-induced effusions in nine New Zealand white rabbits. Nonacidic exudative effusions were induced by an intrapleural injection of turpentine; acidic exudative effusions were induced by a second injection. Pleural fluid and blood were obtained just before (0 h) and 9, 24, 48, and 72 h after the second injection. We found the anion gap correlated with pH, the glucose, protein, and lactate dehydrogenase levels, pleural-fluid/plasma protein and lactate dehydrogenase ratios, and WBC count (all p < 0.001). The pH and protein ratio together accounted for 95% of all anion gap variation within individual subjects. We also found the influence of the PCO2 level on pH was not significant after taking into account the influence of the anion gap. These results suggest the anion gap may be useful in the clinical evaluation of pleural effusions and could potentially replace the pH measurement.

Pleural effusions in hospitalized patients receiving long-term hemodialysis

OBJECTIVE

To determine the incidence, causes, and clinical features of pleural effusions in hospitalized patients receiving long-term hemodialysis.

DESIGN

Retrospective.

PARTICIPANTS

One hundred patients receiving hemodialysis for at least 3 months with pleural effusion hospitalized at the Medical University of South Carolina hospitals.

RESULTS

The incidence of pleural effusions in hospitalized patients receiving long-term hemodialysis was 21%. The mean (+/- SEM) age was 55 +/- 1.4 years and the male to female and black to white ratios were 3:2. Pleural effusions resulted from heart failure in 46% and nonheart failure causes in 54%. Uremic pleurisy (n = 16), parapneumonic effusion (n = 15), and atelectasis (n = 11) accounted for most of the nonheart failure causes of pleural effusions. Three of 15 (20%) parapneumonic effusions were empyemas. The presence of chest pain was not different in patients with parapneumonic effusions than in other patients with nonheart failure effusion (all p = NS) but was more frequent compared to those with heart failure (p = 0.006). Patients with parapneumonic effusions (p = 0.0006) and atelectasis (p = 0.003) were more likely to have unilateral pleural effusions than patients with heart failure.

CONCLUSIONS

Pleural effusions are common in hospitalized patients receiving chronic hemodialysis. Although heart failure was the most common cause, other diseases were responsible for most of the effusions. The presence of a unilateral effusion suggests a diagnosis other than heart failure, most commonly parapneumonic effusion or atelectasis and deserves prompt thoracentesis as these effusions often cannot be reliably differentiated clinically. The reduced humoral and cellular immunity, in addition to delay in diagnosis because of an attenuated clinical response, may explain the high rate of empyemas in this study population.

The relationship between pleural fluid findings and the development of pleural thickening in patients with pleural tuberculosis

The objective of the study was to determine if residual pleural thickening after treatment for pleural tuberculosis could be predicted from the pleural fluid findings at the time of the initial thoracentesis. Forty-four patients initially diagnosed as having pleural tuberculosis between January 1986 and January 1988 were separated into two groups: the 23 patients in group 1 had residual pleural disease, while the 21 patients in group 2 had no residual pleural disease after treatment for their pleural tuberculosis was completed. The clinical characteristics of the two different groups did not differ significantly, but the patients in group 1 tended to be a little sicker in that the duration of their symptoms was longer, their hemoglobin values were lower, and weight loss and cough were more frequent. There were no significant differences in the pleural fluid findings in the two different groups. The mean pleural fluid protein level was 5.40 +/- 0.58 g/dl for group 1 and 5.17 +/- 0.80 g/dl for group 2, while the mean pleural fluid glucose level was 78.6 +/- 19.5 mg/dl for group 1 and 79.5 +/- 20.1 mg/dl for group 2. The mean pleural fluid lactate dehydrogenase (LDH) level in group 1 was 593 +/- 498 IU/L, while the mean level for group 2 was 491 +/- 198 IU/L. The presence of residual pleural thickening was not related to the chemotherapeutic regimen or the performance of a therapeutic thoracentesis. From this study we conclude that approximately 50 percent of patients with pleural tuberculosis will have residual pleural thickening when their therapy is completed, but that one cannot predict which patients will have residual pleural thickening from either their clinical characteristics or their pleural fluid findings.

Pleural fluid analysis in malignant mesothelioma. Prognostic implications

Pleural fluid characteristics of 26 patients diagnosed with malignant mesothelioma over an 18-year period were reviewed and compared with those of patients with effusions due to other malignancies. Survival from time of initial thoracentesis was directly correlated with pleural pH and decreased pleural fluid/serum glucose ratios but was not related to protein or LDH concentration. Decreased pleural fluid pH was statistically related to a decreased pleural fluid/serum glucose ratio. Patients with low pH (less than 7.30) pleural effusions had statistically decreased mean survival and decreased mean pleural fluid/serum glucose ratios compared with patients with normal pH (greater than or equal to 7.30). Patients with malignant mesothelioma pleural effusions had statistically decreased mean pleural fluid pH compared with patients with other malignant pleural effusions. Decreased levels of pleural fluid pH and pleural fluid/serum glucose ratios have negative prognostic significance and probably correlate with the degree of tumor bulk affecting the pleural surface.