Perform diagnostic thoracentesis if the etiology of the effusion is unclear or
Pleural effusions do not require thoracentesis if too small to safely aspirate or, in clinically stable patients, ifexplained by underlying congestive heart failure (especially bilateral effusions) or by recent thoracic or abdominal surgery.
Relative contraindications to diagnostic thoracentesis
Complications of diagnostic thoracentesis include pain at the puncture site, cutaneous or internal bleeding, pneumothorax, empyema, and spleen/liver puncture.
Pneumothorax complicates approximately 12% of thoracenteses but requires treatment with a chest tube in <5% of cases.
Significant chronic obstructive or fibrotic lung disease increases the risk of symptomatic pneumothorax complicating thoracentesis.
In patients with large, freely flowing effusions and no relative contraindications to thoracentesis, diagnostic thoracentesis usually can be performed safely, with the puncture site initially chosen based on the chest radiograph and the level of dullness to percussion determined by physical examination.
Once the site is disinfected with Betadine and sterile drapes are placed, confirm the correct location for thoracentesis by aspirating pleural fluid through a 22-gauge needle before introducing larger bore thoracentesis needles or catheters.
Usually, pleural fluid is obtained with the 1.5-inch-long, 22-gauge needle used for local anesthesia, but for patients with larger amounts of subcutaneous tissue, a 3.5-inch-long, 22-gauge spinal needle with inner stylet removed can be used to find the effusion.
When possible, patients should be sitting upright for thoracentesis. Patients should not lean forward because doing so causes pleural fluid to move to the anterior costophrenic space.
For debilitated and ventilated patients who cannot sit upright, obtain pleural fluid by puncture over the eighth rib at the mid-to-posterior axillary line.
Supplemental oxygen often is administered during thoracentesis, both to offset hypoxemia produced by changes in ventilation-perfusion relationships as fluid is removed and to facilitate reabsorption of pleural air if pneumothorax complicates the procedure.
The incidence of complications from thoracentesis is lower when a more experienced clinician performs the procedure. Consequently, a skilled and experienced clinician should perform thoracentesis in patients who have a higher risk of complications or relative contra-indications for thoracentesis or who are unable to sit upright.
Therapeutic thoracentesis to remove larger amounts of pleural fluid is used to alleviate dyspnea and to prevent ongoing inflammation and fibrosis in parapneumonic effusions. In addition to the precautions listed under diagnostic thoracentesis above, note 3 additional considerations when performing therapeutic thoracentesis.
1. To avoid producing a pneumothorax during removal of large quantities of fluid, perform therapeutic thoracentesis with a catheter rather than a sharp needle. Various specially designed thoracentesis trays are available for introducing small catheters into the pleural space. Alternatively, newer systems using spring-loaded, blunt-tip needles that avoid lung puncture are available now.
2. Monitor oxygenation closely during and after thoracentesis because arterial oxygen tension paradoxically might worsen after pleural fluid drainage. Patients should wear supplemental oxygen during the procedure.
3. Only remove moderate amounts of pleural fluid to avoid re-expansion of pulmonary edema and to avoid causing a pneumothorax. Removal of 400-500 mL of pleural fluid might be enough to alleviate symptoms. The recommended limit is 1000-1500 mL at a single thoracentesis. Alternatively, some experts recommend monitoring pleural fluid pressure if large-volume thoracentesis is planned. Avoid rapid fluctuations of pleural pressure from positive to negative during thoracentesis, especially pressures below -20 cm H2O.
Although small, freely flowing para-pneumonic effusions can be drained by therapeutic thoracentesis, most complicated parapneumonic effusions and empyemas require drainage by tube thoracostomy.
Traditionally, large-bore chest tubes (20-36F) have been used to drain thick pleural fluid and break up loculations in empyemas.
However, such tubes are not always well tolerated by patients and are difficult to direct correctly into the pleural space.
More recently, small-bore tubes (8-14F) inserted at the bedside or under radiographic guidance have been shown to provide adequate drainage, even when empyema is present. These tubes cause less discomfort and are more likely to be situated successfully within a pocket of pleural fluid.
Insertion of additional pleural catheters, usually under radiographic guidance, or instilling fibrinolytics (such as streptokinase or urokinase) through the pleural catheter can drain multiloculated pleural effusions
Pleurodesis or pleural sclerosis
Pleurodesis or pleural sclerosis is used most often for recurrent malignant effusions, such as in patients with lung cancer or metastatic breast or ovarian cancer.
Given the limited life expectancy of these patients, the goal of therapy is to palliate symptoms while minimizing patient
discomfort and the duration of hospitalization and overall costs.
Pleural fluid pH might provide a useful guide to the overall life expectancy of patients with recurrent malignant effusions. In one series, 7 patients who had malignant pleural effusions with a pH <7.3 had a mean survival of about 2 months.
Outpatient serial thoracenteses aimed at draining enough pleural fluid to minimize dyspnea might be appropriate for some patients with malignant pleural effusions.
Unfortunately, pleural effusions can reaccumulate rapidly, and the risk of com-plications increases with repeated drainage.
A variety of irritating agents, including talc, quinacrine hydrochloride, bleomycin sulfate (Blenoxane), and doxycycline, can sclerose the pleural space and effectively prevent recurrence of the malignant pleural effusion.
Talc is the most effective sclerosing agent and can be given as slurry through chest tubes or pleural catheters, though insufflation of talc at either thoracotomy or thoracoscopy might be more effective.
Doxycycline and bleomycin also are effective in the majority of patients and can be administered more easily through small-bore catheters but are substantially more expensive than talc.
All sclerosing agents can produce fever, chest pain, and nausea.
Talc rarely causes more serious adverse effects, such as microemboli and granulomatous tissue reactions.
Injection of 50 mL of 1% lidocaine hydrochloride prior to instillation of the sclerosing agent might help alleviate pain. Additional analgesia might be required in some cases.
Clamp chest tubes for approximately 2 hours after instillation of the sclerosing agent.
Rotating the patient through different positions does not appear necessary to ensure distribution of the sclerosing agent throughout the pleural space.
Pleural sclerosis is likely to be successful only if the pleural space is drained completely before pleurodesis and if the lung is fully re-expanded to appose the visceral and parietal pleura after sclerosis.
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