Hemothorax

The lungs are surrounded by two layers of tissue called the pulmonary pleurae. In most healthy people, these two layers are tightly apposed, separated only by a small amount of pleural fluid. In certain disease states, the space between these two layers, called the pleural cavity, swells with fluid. This accumulation of fluid in the pleural cavity is called pleural effusion. Pleural effusions are given specific names depending on the nature of the fluid: hydrothorax for serous fluid, pyothorax for pus, hemothorax for blood, and urinothorax for urine. == Signs and symptoms ==

Signs and symptoms include anxiety, rapid breathing, restlessness, shock, and pale, cool, clammy skin. When the affected area is percussed, a dull feeling may be observed. Neck veins may be flat and breathing sounds reduced. It can also cause a collapsed lung (atelectasis). == Causes ==

Hemothoraces are classified in three broad categories according to the cause and in order of frequency: traumatic, iatrogenic, or nontraumatic. All three categories have the potential to affect major arteries and result in death by blood loss. In blunt traumatic cases, hemothorax typically occurs when rib fracture damages the intercostal vessels or the intraparenchymal pulmonary vessel, while in penetrating trauma, hemothorax occurs due to injuries directly affecting blood vessels in the thoracic wall, lung parenchyma, or the heart. Minor chest trauma can cause hemothorax when the blood's ability to clot is diminished as result either of anticoagulant medications or when there are bleeding disorders such as hemophilia. Iatrogenic Iatrogenic hemothorax can occur as a complication of heart and lung surgery, for example the rupture of lung arteries caused by the placement of catheters, thoracotomy, thoracostomy, or thoracentesis. The most common iatrogenic causes include subclavian venous catheterizations and chest tube placements, with an occurrence rate of around 1%. Nuss procedure, or endoscopic treatment of esophageal varices. Catamenial hemothorax represents 14% of cases of thoracic endometriosis syndrome while catamenial pneumothorax is seen in 73%, catamenial hemoptysis in 7%, and pulmonary nodules in 6%. ==Mechanism==

When a hemothorax occurs, blood enters the pleural cavity. The blood loss from the circulation has several effects. Firstly, as blood builds up within the pleural cavity, it begins to interfere with the normal movement of the lungs, preventing one or both lungs from fully expanding and thereby interfering with the normal transfer of oxygen and carbon dioxide to and from the blood. Secondly, blood that has been lost into the pleural cavity can no longer be circulated. Hemothoraces can lead to significant blood loss – each half of the thorax can hold more than 1500 milliliters of blood, representing more than 25% of an average adult's total blood volume. The body may struggle to cope with this blood loss, and tries to compensate by maintaining blood pressure by forcing the heart to pump harder and faster, and by squeezing or constricting small blood vessels in the arms and legs. These compensatory mechanisms can be recognised by a rapid resting heart rate and cool fingers and toes. If the blood within the pleural cavity is not removed, it will eventually clot. This clot tends to stick the parietal and visceral pleura together and has the potential to lead to scarring within the pleura, which if extensive leads to the condition known as a fibrothorax. Furthermore, as enzymes in the pleural fluid begin to break down the clot, the protein concentration of the pleural fluid increases. As a result, the osmotic pressure of the pleural cavity increases, causing fluid to leak into the pleural cavity from the surrounding tissues. ==Diagnosis==

Hemothoraces are most commonly detected using a chest X-ray, although ultrasound is sometimes used in an emergency setting. In cases where the nature of an effusion is in doubt, a sample of fluid can be aspirated and analysed in a procedure called thoracentesis. Chest X-ray A chest X-ray is the most common technique used to diagnosis a hemothorax. X-rays should ideally be taken in an upright position (an erect chest X-ray), but may be performed with the person lying on their back (supine) if an erect chest X-ray is not feasible. On an erect chest X-ray, a hemothorax is suggested by blunting of the costophrenic angle or partial or complete opacification of the affected half of the thorax. On a supine film the blood tends to layer in the pleural space, but can be appreciated as a haziness of one half of the thorax relative to the other. A small hemothorax may be missed on a chest X-ray as several hundred milliliters of blood can be hidden by the diaphragm and abdominal viscera on an erect film. Supine X-rays are even less sensitive and as much as one liter of blood can be missed on a supine film. Other methods Ultrasonography may be used to detect hemothorax and other pleural effusions. This technique is of particular use in the critical care and trauma settings as it provides rapid, reliable results at the bedside. Ultrasound can cause issues in people who are morbidly obese or have subcutaneous emphysema. When CT is unavailable in the current setting or the person cannot be moved to the scan, ultrasound is used. Magnetic resonance imaging (MRI) can be used to differentiate between a hemothorax and other forms of pleural effusion, and can suggest how long the hemothorax has been present for. Fresh blood can be seen as a fluid with low T1 but high T2 signals, while blood that has been present for more than a few hours displays both low T1 and T2 signals. MRI is used infrequently in the trauma setting due to the prolonged time required to perform an MRI, and the deterioration in image quality that occurs with motion. Distinguishing the pleural fluid from blood by colour is impossible when the hematocrit value is over 5%. Hemothorax can itself be a rare complication of thoracentesis if the intercostal artery is punctured. == Treatment ==

The treatment of a hemothorax depends largely on the extent of bleeding. While small hemothoraces may require little in the way of treatment, larger hemothoraces may require fluid resuscitation to replace the blood that has been lost, drainage of the blood within the pleural space using a procedure known as a tube thoracostomy, and potentially surgery in the form of a thoracotomy or video-assisted thoracoscopic surgery (VATS) to prevent further bleeding. The thoracostomy tube is usually placed between the ribs in the sixth or seventh intercostal space at the mid-axillary line. Thoracostomy tubes with a diameter of 24–36 F (large-bore tubes) should be used, as these reduce the risk of blood clots obstructing the tube. Manual manipulation of chest tubes (referred to as milking, stripping, or tapping) is commonly performed to maintain an open tube, but no conclusive evidence has demonstrated that this improves drainage. Tubes should be removed as soon as drainage has stopped, as prolonged tube placement increases the risk of empyema. The procedure should ideally be performed within 72 hours of the injury as delay may increase the risk of complications. Prophylactic antibiotics are given for 24 hours in the case of trauma. ==Prognosis==

The prognosis following a hemothorax depends on its size, the treatment given, and the underlying cause. While small hemothoraces may cause few problems, in severe cases an untreated hemothorax may be rapidly fatal due to uncontrolled blood loss. If left untreated, the accumulation of blood may put pressure on the mediastinum and the trachea, limiting the heart's ability to fill. However, if treated, the prognosis following a traumatic hemothorax is usually favourable and dependent on other non-thoracic injuries that have been sustained at the same time, the age of the person, and the need for mechanical ventilation. Hemothoraces caused by benign conditions such as endometriosis have a good prognosis, while those caused by neurofibromatosis type 1 has a 36% rate of death, and those caused by aortic rupture are often fatal. It is more likely in people who develop shock, had a contaminated pleural space during the injury, persistent bronchopleural fistulae, and lung contusions. The likelihood of it can be reduced by keeping thoracostomy tubes sterile and by keeping the pleural surfaces close together to prevent fluid or blood from accumulating between the surfaces. The retained blood can irritate the pleura, causing scar tissue (adhesions) to form. If extensive, this scar tissue can encase the lung, restricting movement of the chest wall, and is then referred to as a fibrothorax. Less than 1 percent of cases go on to develop a fibrothorax. Cases with hemopneumothorax or infection more often develop fibrothorax. After the chest tube is removed, over 10% of cases develop pleural effusions that are mostly self-limited and leave no lasting complications. In such cases, thoracentesis is performed to eliminate the possibility of an infection being present. Other potential complications include atelectasis, lung infection, pneumothorax, sepsis, respiratory distress, hypotension, tachycardia, pneumonia, adhesions, and impaired lung function. == Epidemiology ==

Trauma to the thorax results in approximately 16,000 to 30,000 deaths every year. There are about 300,000 cases of hemothorax in the U.S every year. Polytrauma (injury to multiple body systems) involves chest injuries in 60% of cases and commonly leads to hemothorax. In a case study, 37% of people hospitalized for blunt chest trauma had traumatic hemothorax. Hemothorax commonly occurs with a displaced rib fracture. == Other animals ==

Horses poisoning In horses, hemothorax is uncommon and usually traumatic. It may occur along with pneumothorax. It is mainly diagnosed by ultrasound. Treatment involves supportive care, correction of the underlying cause, and occasionally drainage. The prognosis is variable. Hemothorax is usually caused by trauma to the thorax. It can result from any injury that involves the pleural, intercostal, intervertebral, cardiac, In less acute cases with slower bleeding, anemia and hypoproteinemia may gradually develop. but can be performed in case of infection or fluid levels resulting in respiratory compromise. However, drainage in contraindicated in cases caused by clotting disorders. Additionally, broad spectrum antibiotics can be given in the case of open trauma or pulmonary rupture. Supportive care may be required. It may include intranasal oxygen, painkillers, blood transfusions, and fluids. In order to avoid fluid overload, fluids are given slowly. The prognosis significantly depends on the underlying cause of the hemothorax. In cases caused by uncomplicated thoracic trauma, the prognosis may be good, but the prognosis is worse in cases that are complicated by pleuritis. Cases caused by cancer or clotting disorders have a poor prognosis, as do cases with massive bleeding due to injury to the heart or very large blood vessels. ==References==