Disorders of the Pleura and Mediastinum

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Disorders of the Pleura and Mediastinum

• Dr. Gerrard Uy

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Pleural Effusion

• Presence of an excess quantity of fluid in the
  pleural space
• The pleural space lies between the lungs and
  chest wall and normally contains a very thin
  layer of fluid

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Etiology

• Pleural fluid accumulates when pleural fluid
  formation exceeds absorption
• Normally, pleural fluid enters the pleural space
  from the capillaries in the parietal pleura and
  removed via the lymphatics

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Approach to Patient

• Determining the cause is essential
• 2 types of effusion
• Transudate
• Occurs when systemic factors that influence the
  formation and absorption of pleural fluid are
  altered
• Leading cause heart failure and cirrhosis
• Exudate
• Occurs when local factors that influence the
  formation and absorption of pleural fluid are
  altered
• Leading cause pneumonia, malignancy, pulmonary
  embolism

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Lights Criteria

• Used to determine the type of pleural fluid
• Criteria
• Pleural fluid protein/serum protein gt 0.5
• Pleural fluid LDH/serum LDH gt 0.6
• Pleural fluid LDH gt 2/3 normal upper limit for
  serum
• Misidentify 25 of transudates as exudates

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Effusion Due to Heart Failure

• Most common cause of pleural effusion is left
  ventricular failure
• Isolated right sided pleural effusions are more
  common than left sided pleural effusion
• If diagnosis is established, patients are best
  treated with diuretics
• NT pro BNP gt 1500 pg/ml is diagnostic of effusion
  secondary to congestive heart failure

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Hepatic Hydrothorax

• Occurs in 5 of patients with cirrhosis and
  ascites
• Direct movement of peritoneal fluid through small
  openings in the diaphragm into the pleural space
• Effusion is usually right sided

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Parapneumonic effusion

• Most common cause of exudative pleural fluid in
  the united states
• Empyema refers to a grossly purulent effusion
• the presence of free pleural fluid can be
  demonstrated with a lateral decubitus radiograph,
  CT scan, or ultrasound
• If free fluid gt 10mm, a therapeutic thoracentesis
  should be performed

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Parapneumonic effusion

• Indications for considering CTT insertion
• Loculated pleural fluid
• Pleural fluid phlt7.2
• Pleural fluid glucoselt3.3mmol/L(lt60mg/dl)
• Positive gram stain or culture of the pleural
  fluid
• Presence of gross pus in the pleural space

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Effusion secondary to Malignancy

• Secondary to metastatic disease
• Second most common type of exudative pleural
  effusion
• Most common tumors causing malignant pleural
  effusion
• Lung carcinoma
• Breast carcinoma
• lymphoma

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Effusion secondary to Malignancy

• Diagnosis is usually made via cytology of the
  pleural fluid
• If cytology is negative, thoracoscopy is the best
  next procedure if malignancy is highly suspected
• If unavailable, needle biopsy of the pleura is
  the alternative

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Mesothelioma

• Primary tumors arising from mesothelial cells
  that line the pleural cavities
• Related to asbestos exposure
• Thoracoscopy or open pleural biopsy is usually
  necessary to establish the diagnosis

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Chylothorax

• Accumulation of chyle in the pleural space
• Occurs when the thoracic duct is disrupted
• Most common cause is trauma
• Thoracentesis reveals a milky fluid with a
  triglyceride level gt 110 gm/dl
• Treatment of choice is CTT insertion and
  administration of octreotide

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Hemothorax

• Blood in the pleural space
• Hematocrite should be obtained from the pleural
  fluid
• True hemothorax if hematocrit is greater than
  half of the peripheral blood
• CTT insertion, thoracoscopy and thoracotomy

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Other Causes of pleural effusion

• Esophageal rupture
• Pancreatitis
• Intraabdominal abscess
• Meigs Syndrome benign ovarian tumor ascited
  and pleural effusion

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Pneumothorax

• Presence of gas in the pleural space
• 4 categories
• Spontaneous pneumothorax
• Secondary pneumothorax
• Traumatic pneumothorax
• Tension pneumothorax

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Spontaneous Pneumothorax

• Occurs in the absence of an underlying disease
• Usually due to rupture of small apical blebs,
  small cystic spaces that lie immediately under
  the visceral pleura
• Occurs almost exclusively in smokers
• Simple aspiration, thoracoscopy and thoracotomy
  with stapling of blebs, CTT insertion

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Secondary Pneumothorax

• Most are due to COPD
• Pneumothorax in patients with lung disease are
  more life threatening than it is in normal
  individuals
• Usually treated with CTT

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Traumatic Pneumothorax

• Can result from both penetrating or non
  penetrating chest trauma
• Traumatic pneumothorax should be treated with CTT
  unless very small
• Iatrogenic pneumothorax most commonly caused by
  needle aspiration, thoracentesis and insertion of
  a central IV catheter

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Tension Pneumothorax

• Usually occurs during mechanical ventilation or
  resuscitative efforts
• Diagnosis is made by P.E. showing enlarged
  hemithorax with no breath sounds, hyperresonace
  to percussion, and shift of the mediastinum to
  the contralateral side
• Treated as a medical emergency
• A large bore needle should be inserted at the 2nd
  anterior ICS

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ARDS(Acute Respiratory Distress Syndrome)

• Dr. Gerrard Uy

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ARDS

• clinical syndrome of severe dyspnea of rapid
  onset, hypoxemia, and diffuse pulmonary
  infiltrates leading to respiratory failure
• Caused by diffuse lung injury
• The arterial (a) PO2 (in mmHg)/FIO2 (inspiratory
  O2 fraction) lt200 mmHg is characteristic of ARDS
• Acute lung injury (ALI) is a less severe form
• a PaO2/FiO2 ratio between 200-300 identifies
  patients who are likely to benefit from
  aggressive therapy

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ARDS

• caused by diffuse lung injury from many
  underlying medical and surgical disorders

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ARDS

• gt80 are caused by severe sepsis syndrome and/or
  bacterial pneumonia (4050), trauma, multiple
  transfusions, aspiration of gastric contents, and
  drug overdose
• older age, chronic alcohol abuse, metabolic
  acidosis, and severity of critical illness

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ARDS

• Natural history is marked by 3 phases

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Exudative Phase

• alveolar capillary endothelial cells and type I
  pneumocytes (alveolar epithelial cells) are
  injured
• Edema fluid
• Cytokines
• first 7 days of illness after exposure to a
  precipitating ARDS risk factor
• Dyspnea develops
• Chest radiograph reveals alveolar and
  interstitial opacities involving at least ¾ of
  the lung fields

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Proliferative Phase

• lasts from day 7 to day 21
• Most recover rapidly, off ventilation
• many still experience dyspnea, tachypnea, and
  hypoxemia
• first signs of resolution
• Shift of neutrophil to lymphocytes
• proliferation of type II pneumocytes along
  alveolar basement membranes

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Fibrotic Phase

• Many patients with ARDS recover lung function 3-4
  weeks after the initial pulmonary injury
• require long-term support on mechanical
  ventilators and/or supplemental oxygen
• extensive alveolar duct and interstitial fibrosis
• emphysema-like changes with large bullae

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Treatment

• General Principles
• (1) the recognition and treatment of the
  underlying medical and surgical disorders (e.g.,
  sepsis, aspiration, trauma)
• (2) minimizing procedures and their
  complications
• (3) prophylaxis against venous thromboembolism,
  gastrointestinal bleeding, and central venous
  catheter infections
• (4) the prompt recognition of nosocomial
  infections and
• (5) provision of adequate nutrition

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Prognosis

• Recent mortality estimates for ARDS range from
  41-65
• Mortality is largely attributable to nonpulmonary
  causes
• Sepsis and nonpulmonary organ failure account for
  gt80 of deaths
• Risk fasctor for mortality includes
• Advance age
• Preexsiting medical condition