Hemothorax

Overview

Definition

A hemothorax is defined as a collection of fluid with a hematocrit of at least 50% accumulated in the potential space between the parietal and visceral pleura of the lungs.

Epidemiology

• In the United States, an estimated 300,000 cases are reported annually.
• Associated with chest trauma and particularly motor vehicle accidents
• Chest trauma seen in 60% of polytrauma

Etiology

The source of blood may be the chest wall, lung parenchyma, heart, or great vessels from either traumatic or non-traumatic causes.

Traumatic causes:

• Lung parenchymal injury:
  • Most common cause
  • More commonly small (< 10%)
  • Often self-limited
• Arterial injury:
  • Intercostal artery injury (most common)
  • Internal mammary artery injury
  • Great large vessels (rare, but life threatening)
• Iatrogenic:
  • Central venous catheter placement
  • Thoracostomy tube placement

Non-traumatic causes:

• Malignancy
• Anticoagulant medications
• Coagulopathies
• Aortic dissection or aneurysm
• Tuberculosis and necrotizing infections

Pathophysiology

Hemodynamic component:

Large volume loss (each hemothorax can contain up to 40% of total circulating blood volume) into the pleura can lead to decreased cardiac function due to:

• Decreased preload by constricting the vena cava
• Increased restriction of movement of the cardiac wall
• Increased hydrostatic pressure leading to pulmonary hypertension

Respiratory component:

Blood collecting in the pleura decreases the lung’s functional vital capacity by:

• Causing hypoventilation (decreased tidal volume)
• Creating ventilation/perfusion (V/Q) mismatch
• Leading to anatomic shunting

Clinical Presentation

Symptoms

• Shortness of breath
• Chest pain

Signs

• Ipsilateral absent or ↓ breath sounds
• Tracheal deviation
• Dullness on percussion
• Crepitus
• Signs of hemorrhagic shock in large hemothoraces:
  • Hypotension
  • Tachycardia
  • Tachypnea
  • ↓ Jugular venous pressure

Diagnosis

Diagnosis is established by utilizing history, physical, and appropriate imaging. In cases of trauma, use of the primary survey is paramount to rapid diagnosis and treatment.

Imaging

• Chest X-ray: best initial diagnostic study
  • Upright imaging shows layering of blood.
  • Supine imaging shows haziness or opacity (whiteout).
  • May also show free air if a pneumothorax is present
• Ultrasound of the lungs (thorax sonography):
  • Part of the Extended Focused Assessment with Sonography for Trauma (eFAST) exam
  • Able to be obtained quickly
  • Can show complex fluid in the pleural cavity
  • More sensitive than a chest X-ray in detecting a hemothorax, but is technician dependent
• Chest computed tomography (CT)—definitive imaging choice:
  • Should only be obtained if the patient is stable 
  • CT can show other associated pathology.
  • CT angiogram can show the source of bleeding.

Management and Complications

Management

• Airway, breathing, and circulation (ABC) assessment → administer 100% oxygen → establish intravenous (IV) access
• Stabilize the patient (fluid resuscitation and blood transfusion as necessary).
• Reverse anticoagulants, if necessary.
• Provide analgesia appropriate to the level of the patient’s pain.
• Insert a chest tube (thoracostomy) for large hemothoraces or in an unstable patient:
  • Chest tube inserted on the midaxillary line at the 5th intercostal space
  • Used to drain the hemothorax
  • Monitor output of the hemothorax.
• Surgical intervention (thoracotomy) is indicated when:
  • Evacuating > 1,500 mL of blood directly after inserting a chest tube
  • Continued high output → collecting of > 1 L (1,000 mL) of blood over 4 hours or > 200 mL/hour for 3 consecutive hours

Complications

• Impaired ventilation on the affected side:
  • Leads to respiratory distress
  • May require intubation
• Empyema:
  • Retained blood collection develops a bacterial infection.
  • 5% of cases
• Fibrothorax:
  • Formation of scar tissues within the lungs due to blood irritation
  • 1% of cases

Differential Diagnosis

• Pneumothorax: abnormal collection of air in the pleural space due to laceration of the lungs. Types of pneumothorax include spontaneous pneumothorax and traumatic pneumothorax. Patients have dyspnea, chest pain, decreased breath sounds, and hyper-resonance on percussion. Treatment includes needle decompression and chest tube placement.
• Pleural effusion: accumulation of fluid in the pleural cavity. Can be caused by many conditions, including infection, malignancy, and heart failure. Symptoms include chest pain, dyspnea, and orthopnea. Diagnosis is by imaging, and pleural fluid analysis helps determine the etiology. Management is dependent on the underlying condition and severity, but may include monitoring, thoracentesis, chest tube placement, or surgery.
• Atelectasis: condition characterized by the collapse of alveoli, and eventually, lobar lung collapse and complete obstruction. Patients present with respiratory distress (dyspnea, tachypnea, tachycardia) and hypoxemia. Physical examination of the lungs reveals dullness to percussion and decreased breath sounds. Chest X-ray shows lung opacification. Management is aimed at ventilatory support. 
• Pulmonary embolism (PE): obstruction of pulmonary arteries, most often due to thrombus migration from the deep venous system. Signs and symptoms include pleuritic chest pain, dyspnea, tachypnea, and tachycardia. Severe cases are life threatening. Chest CT with angiography is the primary method of diagnosis. Management includes oxygenation, anticoagulation, and thrombolytic therapy for unstable patients.