Pediatric Chest Trauma

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Pediatric thoracic trauma is the second highest cause of pediatric trauma mortality. It is critical for emergency care providers to be aware of the anatomic and physiologic differences in children, which result in significantly different injury patterns than adults. The authors highlight the essential steps for diagnosis and management of pediatric thoracic injuries.

— Ann M. Dietrich, MD, Editor

Introduction

Trauma is the most common cause of morbidity and mortality in pediatric patients.¹ In 2020, there were an estimated 4.1 million injuries among the 76 million children in the United States, with the majority unintentional, and treated and discharged.² Fortunately, the rate of pediatric deaths from trauma has decreased over time, with fewer hospitalizations likely due to improved preventive campaigns and medical care.³

Thoracic trauma encompasses around 10% of all pediatric trauma and is the second highest cause of pediatric trauma mortality following head trauma.⁴ The significant morbidity and mortality make thoracic trauma an important injury pattern to discuss, especially as the anatomy in children allows for differences in pathology from that seen in adults.

Thoracic trauma affects the lungs, heart, great vessels, aorta, tracheobronchial tree, chest wall structures (ribs, sternum, muscles), and, in rare cases, the proximal esophagus.⁴ This article will review the epidemiology of pediatric thoracic trauma, anatomical differences between children and adults, and a general approach to assessing and managing thoracic injuries. The bulk of this review will be on specific thoracic injuries in order of incidence rates, with attention to their diagnosis and management.

Etiology and Epidemiology

Blunt or penetrating mechanisms can cause thoracic trauma. Blunt trauma accounts for 85% to 90% of all injuries.⁵ In the United States, gunshot wounds are more likely than stabbing injuries in cases of penetrating trauma (60% vs. 33%).⁶ The most common etiology is motor vehicle accidents, both passenger and pedestrian, followed by falls and bicycle injuries.^5,7 While motor vehicle collisions have been the most common cause of all traumatic injuries, firearms recently have become the leading cause of death. The rate bypassed that of motor vehicle collisions in 2020, with the majority of deaths due to homicides. Although school shootings have increased dramatically, they only account for 1% of pediatric firearm mortalities.⁸ It is unclear how many of these deaths are due to a thoracic injury. However, a study on injury characteristics of nonfatal mass shooting participants (ages 1-89 years) demonstrated a thoracic injury in 10.1% of cases.⁹

Significant trauma associated with bicycle injuries was most commonly associated with a direct strike to the chest from the handlebar resulting in blunt trauma.⁹ All-terrain vehicles (ATVs) are frequent sources of injury in children and have a similar mechanism to motor vehicle accidents.¹⁰ A variety of injuries can occur to any number of the structures within the chest or thorax. The most common injury reported in children is a pulmonary contusion. Tracheal, diaphragm, and great vessel injuries are rare.¹

It is common for thoracic trauma to be associated with other traumatic injuries. More than 50% of thoracic injuries are associated with multi-trauma.^1,4 The mortality rate increases from 5% in isolated thoracic trauma to 20% with a single concomitant injury, and up to 30% with a head injury.^1,4 Most of these deaths are due to the associated injury.¹ Penetrating thoracic injuries do have high mortality rates, however.¹ Two studies have demonstrated possible indicators that increase the odds of thoracic trauma in a child with multitrauma.^11,12 These include low systolic blood pressure (age-adjusted), elevated respiratory rate (age-adjusted), abnormal chest auscultation, abnormal findings on chest exam, Glasgow Coma Scale (GCS) less than 15, femur fracture, and oxygen saturation less than 95%.^11,12 Five percent of patients in one study had none of these predictors and still had a thoracic injury, leading the authors to recommend that chest radiography should remain part of a pediatric trauma resuscitation.¹¹

Finally, abuse must be considered an etiology for any pediatric patient’s thoracic injuries. Rib fractures, specifically isolated posterior rib fractures, frequently are associated with abuse.¹³ Uncommonly, rib fractures can occur from resuscitation-related chest compressions; however, they are more likely to be located anteriorly. Sternal fractures and lateral clavicle fractures also are concerning for abuse.¹³ In polytrauma (multiple traumatic injuries), rib fractures can be present in 60% of patients.⁶

Pathophysiology and Anatomical Considerations

Blunt trauma includes compression, crushing, or acceleration/deceleration forces to the thorax resulting in injury, whereas penetrating trauma ranges from stab/puncture to gunshot wounds.¹⁴ Most traumatic injury mechanisms are caused by high kinetic energy transfer.¹

Children have several anatomical differences compared to adults. These differences and the high-energy mechanism change the pathology seen in pediatric thoracic injury patterns. The trachea is narrower and easily compressed. Small changes in the airway diameter can easily cause respiratory distress.⁴ The chest wall is more compliant, and the ribs are more flexible, as they have yet to be wholly ossified. The chest wall has less muscle mass, allowing more significant energy transfer to underlying tissue. This results in a decreased incidence of rib fractures and increased incidence of pulmonary contusions, making pulmonary contusions the most common thoracic injury in pediatrics.^1,4 These differences also are why more force is needed to cause rib fractures. A high-energy impact always must be considered when rib fractures are present and nonaccidental trauma is on the differential.^1,4,15 The chest wall is fully developed around age 13 years, when traumatic injuries mimic adult injuries, such as rib fractures being more likely.¹

The mediastinum is not fixed in pediatric patients, allowing visceral organs (heart and lungs) to move and become displaced. This mobility can result in the compression of critical structures as well as loss of preload, leading to hypotension. This mobility also makes vascular injuries less likely.¹³ However, less muscle mass means that penetrating chest trauma is more likely to injure multiple thoracic structures. Lastly, children younger than 10 years of age have a lower functional residual capacity and higher metabolic rate than adults. Therefore, more oxygen is needed, and there is less space to hold an additional reserve of oxygen, which can result in a quick onset of hypoxemia.⁴

Clinical and Diagnostic Considerations

All pediatric traumas should be evaluated and treated using Advanced Trauma Life Support (ATLS) guidelines and algorithms: primary survey, interventions, secondary survey, and adjuncts. This framework systematically approaches pediatric trauma patients.^13,14 The primary survey assesses the airway, breathing, circulation, and disability (GCS). Children have a lower overall blood volume than adults and a more robust cardiovascular response to acute blood loss. Given these differences, tachycardia may be the only warning sign of impending hemorrhagic shock, since hypotension is a very late sign of shock in children.¹⁶ Hypotension in infants is a systolic blood pressure less than 70 mmHg; in children 1-10 years of age, it is less than 70 + (age in years × 2) mmHg, and in children older than 10 years of age, it is less than 90 mmHg.¹⁷ Additionally, it is crucial to note that children have differing normal-range vitals based on age. (See Table 1.)

Thoracic injuries may manifest a variety of findings during the primary survey. Patients can present with respiratory distress and/or signs of hemorrhage. Therefore, thoracic injuries must be considered based on the reported mechanism of injury and any abnormal findings with the primary survey. Any life-threatening injuries, such as tension pneumothorax, identified on the primary survey should be addressed before progressing to the secondary survey or obtaining imaging. Hypoxia and hypotension from the primary survey and thoracic signs/symptoms, decreased GCS, abnormal chest auscultation, and femur fracture from the secondary survey increase the odds of having a thoracic injury.^11,12 Signs and symptoms to evaluate include tachypnea, tachycardia, hypotension, chest wall tenderness, trachea deviation, jugular venous distention, chest wall deformity, chest wall bruising, chest wall crepitus, crackles or wheezing on lung exam, and decreased heart sounds on auscultation.^1,4 However, sometimes there are minimal or no external signs of thoracic trauma.⁴

A chest radiograph often is the initial imaging modality and can be obtained easily during the initial trauma assessment after the primary survey. Chest X-rays can detect several injuries, including pneumothorax, hemothorax, pulmonary contusions, diaphragm injury, and rib fractures. However, it is limited compared to computed tomography (CT). CT increases the sensitivity of identifying injuries and better characterizes injuries. However, the risks and benefits of CT scans must be considered, since children are four times more sensitive to radiation exposure from CT because of their life expectancy and cell division rate.⁷

Currently, the Pediatric Trauma Society has no formal guideline on the use of chest X-ray vs. CT; however, they did highlight studies that demonstrated CT use increases radiation exposure with little changes in management,¹⁸ making CT less ideal for use in pediatric trauma evaluations. One study showed that 42% more injuries were identified in children after using CT as a diagnostic tool. However, the management only changed in 2% (4/139) of patients within the study, and two of those four patients underwent further diagnostic imaging that was negative.¹⁹ Another study demonstrated a change in management of 8.7% of patients, with most changes focused on splints or non-weight-bearing status for fractures.²⁰ Therefore, chest X-rays should be used initially as a screening tool for suspected thoracic trauma in most pediatric trauma patients. However, if there is a more significant concern for possible great vessel or tracheobronchial injuries, then CT is a more appropriate and sensitive tool for identifying injuries.

One facility implemented and published a protocol to obtain a chest CT if there was mediastinal widening on a chest X-ray or vehicle-related mechanism combined with positive chest X-ray findings (abnormal findings consistent with injury or concern for injury). This protocol helped significantly reduce the amount of CTs used with no increase in clinically significant missed injuries.²¹ Obtaining a CT should not delay transport to a pediatric trauma center.¹³

Ultrasound is another diagnostic tool available for pediatric patients. While the modality has some benefits, it is used less than chest X-rays or CTs. Advantages of ultrasound include no ionizing radiation and it can be applied in real time in the trauma bay or even shortly afterward to assess the lungs and heart. It can be beneficial in identifying a pericardial effusion and for procedures (nerve blocks or pericardiocentesis). Pneumothorax may be diagnosed by observing the absence of lung sliding over multiple areas.^1,4 Although pneumothorax identification on ultrasound is well reported in the adult literature, one study demonstrated a sensitivity as low as 45% in pediatrics; however, the undetected pneumothoraxes were small and required no intervention.²²

Pleural effusions and pulmonary contusions can be diagnosed by identifying B-lines resulting from the edema.^1,4 A meta-analysis in 2015 reported better screening results for chest ultrasonography compared to radiography in detection of pulmonary contusion. However, there were limitations based on operator and characteristics of device.²³ Pleural effusions have been identified by ultrasound in other pediatric studies and can detect effusions as small as 10 mL to 20 mL vs. the minimal amount of 200 mL in chest radiographs.^24,25

Another ultrasound sign to assess for possible pleural effusion is the spine sign. A lower frequency transducer is used to evaluate the left or right upper quadrants in a similar viewing area for Focused Assessment with Sonography in Trauma (FAST). Typically, vertebral bodies are not well visualized in this view on ultrasound. However, if fluid is present, this will increase the transmission of ultrasound waves and enhance the visualization of vertebral bodies. Two prospective studies on adults had a sensitivity of 74% and 79% and a specificity of 93% for the spine sign.^26,27

While there are benefits in obtaining both consultative ultrasounds through the radiology department or point-of-care ultrasounds by a provider, there are significant drawbacks. Ultrasounds are very operator dependent. They also lack the sensitivity and specificity for identifying life-threatening traumatic injuries compared to cross-sectional imaging. Ultrasound is a valuable imaging adjunct but requires more research in pediatric trauma for further use. A randomized controlled trial is underway to further assess ultrasound in pediatric thoracic trauma.²⁶ Therefore, its use should be provider- and institutional-dependent.²⁸

General Management Considerations

The primary survey identifies life-threatening injuries. Oxygen therapy is beneficial in reversing hypoxia and may be delivered through a nasal cannula, nonrebreather mask, high-flow nasal cannula, continuous positive airway pressure (CPAP), or bilevel positive airway pressure (BiPAP). If the patient cannot maintain their airway, an advanced airway should be placed using rapid sequence intubation. In a patient with hypoxia or hemodynamic instability suspected of a pneumothorax or hemothorax, needle decompression and tube thoracostomy may be required. All medications given and equipment used are based on a child’s weight, which can be obtained quickly from a caregiver, scale, or bed weight. If no weight is available, then use a length-based tool such as the Broselow Pediatric Resuscitation Tape.¹³ (See Table 2.)

Significant blood loss should be identified early in the trauma resuscitation, focusing on the child’s pulse rate, peripheral perfusion and blood pressure. (See Table 3.) Any external bleeding should be controlled with direct pressure or a tourniquet as appropriate. Two peripheral intravenous (IV) lines should be initiated; if IVs access cannot be obtained promptly, intraosseous access should be obtained. Initial fluid resuscitation should begin with a 20 mL/kg bolus of warmed crystalloid fluid, since children are more prone to hypothermia.¹³ Normal saline is preferred for more significant volume resuscitation for patients with suspected traumatic brain injury, because it is believed to minimize fluid shifts into damaged brain tissue.^29-31 The fluid bolus should be infused rapidly using a rapid infuser or pressure bag. The patient’s vitals should be reassessed for response to fluids. Similar to recommendations for adult hemorrhagic shock, a recent consensus paper supports the prioritization of blood products over crystalloids for resuscitation of a child in hemorrhagic shock.³² Blood products should be administered in increments of 10 mL/kg aliquots. If there is a high suspicion of hemorrhagic shock, the institution’s massive transfusion protocol (MTP) should be activated. MTP allows for a more balanced resuscitation and helps with coagulopathy.¹³ Whole blood is being studied in adults with some success, but there are limited data in children.³³ Thromboelastography (TEG), if available, also can be considered. TEG can assess clot initiation, clot kinetics, and fibrinolysis to assess a patient’s potential coagulopathies in real time to aid in giving more goal-directed product administration. TEG is becoming a standard of care in adults and is being studied in the pediatric population.³⁴ Tranexamic acid (TXA) can be used since it has a low risk of harm, but there is unclear effectiveness of TXA in the current literature.³⁵

Monitoring for hemodynamic improvement includes normalization of the heart rate and mental status, return of skin color, increased systolic blood pressure, return of peripheral pulses, and adequate urinary output based on age (over time). Patients should be transferred to a facility with pediatric capabilities once stabilized and depending on injury findings.^13,36

If a patient requires cardiopulmonary resuscitation (CPR) for cardiopulmonary arrest, Pediatric Advanced Life Support (PALS) recommendations should be followed. Patients arriving at the hospital in active arrest have a poor prognosis.¹⁴ One study demonstrated a 26% survival rate for traumatic arrest in which CPR had been initiated.³⁷ A recent study specifically looking at children without signs of life on arrival to the emergency department (ED) found in 114 patients there were no survivors. The authors recommend no ED thoracotomy for pediatric patients with no signs of life on arrival to the ED.³⁸ The Eastern Association for the Surgery of Trauma (EAST) recommends against thoracotomy in pulseless patients without signs of life after a blunt injury.³⁹ Trauma EAST guidelines recommend thoracotomy in patients with penetrating injuries and signs of life.³⁹

One study demonstrated that adolescents had better outcomes than younger children with thoracotomy but still worse results than adults.⁴⁰ Another study found a 90% mortality rate in penetrating pediatric trauma patients and 88% mortality in blunt pediatric trauma patients.³⁸ Additionally, no patients who arrived at the hospital without signs of life and underwent thoracotomy survived.³⁸ Finally, an ED thoracotomy must be performed only at a center with access to pediatric surgical specialists who can assist in the definitive management of the patient.

Lastly, the resuscitative endovascular balloon occlusion of the aorta (REBOA) can be considered for temporary hemorrhage control in select cases. The advanced procedure involves placing an endovascular balloon into one of three zones of the aorta, typically through femoral access, to tamponade a possible injury site and control traumatic hemorrhage. Zone one of the aorta extends from the origin of the left subclavian artery to the celiac artery and can be approximately measured to the location of the xiphoid. A prior joint statement has stated that there is no high-grade evidence that REBOA improved outcomes or survival compared to standard treatment and that it is associated with significant complications (spinal cord ischemia, reperfusion injuries to organs, arterial disruption from access, aortic rupture from the balloon).⁴¹ It also typically is used for major bleeding below the level of the diaphragm, although no high-grade evidence exists to define specific indications. REBOA in thoracic vessel injury is limited in case reports, and thoracotomy was preferred for hemorrhage control. Also, REBOA should be performed only by a surgeon or interventionalist responsible for definitive hemorrhage control or a physician trained in REBOA with direct consultation by another physician to provide definitive hemorrhage control.⁴¹ A retrospective study from Japan’s Trauma Data Bank found that 0.3% of pediatric traumas received REBOA, with 27.8% being young children and 72.2% being adolescents.⁴² One study identified 11 pediatric patients who underwent REBOA using the Aortic Occlusion for Resuscitation in Trauma Acute Care Surgery Registry. This small cohort, which had a median age of 17 years, had a 30% survival rate.⁴³ A gap analysis at a single site center over 10 years identified that 0.6% of all pediatric trauma cases may have been amenable to REBOA. Additionally, 42% of patients severely injured and possible candidates for REBOA had died due to hemorrhage.⁴⁴ REBOA may be considered in pediatric trauma, but there are limited data on this intervention in pediatrics, and most literature is case reports.¹

Specific Injuries

Pulmonary Contusion and Lung Parenchymal Injury

When a high-energy force damages the alveolar space causing hemorrhage, edema, and subsequent inflammation, a patient may develop pulmonary contusions or parenchymal injuries. These injuries can cause a consolidation in the alveoli leading to inadequate ventilation and causing hypoxia (due to a ventilation-perfusion mismatch).⁴ Patients may present with respiratory distress, hypoxia, localized tenderness, abnormal breath sounds over a consolidated area, resting tachypnea, and hemoptysis (uncommon). It takes hours for these to appear from the initial injury to the subsequent inflammation and edema, and it sometimes can take up to 48-72 hours for symptom onset. Because of this delay, a pulmonary contusion may not be seen on an initial chest X-ray or be underestimated on radiography. If findings are present, they will appear as a nonanatomic area of consolidation, sparing the periphery. Although CT is more sensitive than chest radiograph at identifying pulmonary contusions , they are not always clinically significant. Pulmonary contusion severity as imaged on chest radiographs, not CT, correlates with impairment of oxygenation, carbon dioxide exchange, and duration of mechanical ventilation.⁴⁵ Almost one-third of patients can develop respiratory failure that may require mechanical ventilation. In patients requiring mechanical ventilation primarily cuffed endotracheal tubes should be used, since the cuff prevents leakage of positive pressure ventilation, often needed to ventilate patients with these injuries adequately. Additionally, cuffed tubes offer better protection against aspiration, and should not be overinflated to prevent airway damage.⁴⁶

There is an increase in morbidity and mortality if a patient develops pediatric acute respiratory distress syndrome (PARDS). About 20% of patients will develop pneumonia, but antibiotics are controversial for prevention.^4,7,47 Patients with minor pulmonary contusions should receive supplemental oxygen, pulmonary hygiene, and fluid restriction as necessary to maintain oxygenation. Children with severe contusions in addition to mechanical ventilation may require additional therapies to maximize gas exchange, which may include high positive end-expiratory pressures, inhaled nitric oxide, high frequency oscillating , or even extra-corporeal membrane oxygenation.^4,28 Patients can develop pneumatoceles and pseudocysts that usually resolve independently in months.⁴

Pneumothorax and Hemothorax

A pneumothorax will occur as an isolated injury in 30% of cases of pediatric chest trauma.⁷ Penetrating chest trauma is more likely to cause this injury in 67% of cases compared to blunt trauma at 38%.⁶ Patients may present with tachypnea, decreased breath sounds, chest wall crepitus, chest wall injury, jugular venous distention, displaced apex heartbeat, loss of breath sounds to one side, hypotension, or contralateral deviation of the trachea. A tension pneumothorax is a life-threatening condition and should be suspected if tracheal deviation, hypotension, loss of breath sounds, and jugular venous distention are present. Tension pneumothorax occurs when the air overfills the pleural space, causing lung and mediastinal displacement. Shock and cardiac arrest can occur secondary to obstruction of the vena cava, leading to a decreased preload and reduced diastolic filling. Penetrating trauma can cause an open pneumothorax where air fills the pleural space from the external wound, causing tension physiology, or a lung laceration from the injury leaks air into the cavity.^1,4,5

Hemothorax typically occurs due to an injury to the intrathoracic vessels, parenchyma, or a rib fracture that damages the intercostal vessels. High energy is transmitted from blunt trauma, causing shearing forces that can tear the mediastinal vessel. This results in hemorrhage into the lung cavity, potentially displacing the lung.^5,7 These injuries occur in 13% to 29% of pediatric blunt trauma and result in increased mortality.⁷

A chest X-ray may demonstrate air in the pleural space with or without displacement of the mediastinum, hyperlucency at the apex, hyperlucency at mediastinal structures, the deep sulcus sign, hyperlucency at the diaphragm, and loss of lung markings.^1,4,48 CT can increase the sensitivity of identifying a pneumothorax or hemothorax. An occult pneumothorax is identified on CT but not chest X-ray. An occult pneumothorax rarely changes management and usually can be observed for resolution.^1,4,16,17 Point-of-care bedside ultrasound can be considered to assess for possible pneumothorax, with variable sensitivity, by identifying absent lung sliding.^1,4,22

Pneumothorax and hemothorax may be treated with chest tube placement or observed for resolution with expectant management. A patient rapidly deteriorating from a tension pneumothorax requires an emergent needle decompression followed by chest tube thoracostomy. Additional chest tubes may need to be placed if there is a significant or ongoing hemothorax or pneumothorax.

One study assessed observation vs. tube thoracostomy for pediatric patients with asymptomatic, non-occult pneumothorax due to blunt trauma. The observation group had complete resolution of their pneumothorax without further intervention and had a shorter hospital stay than the tube thoracostomy group.¹⁸ Patients should undergo exploratory thoracoscopy or thoracotomy in an operating room if they have continuing bleeding that exceeds 20% to 25% of the blood volume initially of drainage or 2 mL/kg/hour.^4,49 Leaving a hemothorax undrained can allow the collected blood to cause a fibrotic reaction, resulting in atelectasis, which can cause lung entrapment, pneumonia, and empyema.¹

Needle decompression is similar in children and adults and may be done in the second intercostal space (ICS), mid-clavicular line (MCL), or the fourth or fifth ICS. ATLS currently recommends the latter. A CT-based study recommends at the fourth ICS, to reduce the risk of injury to the intercostal vessels and intrathoracic structures, a 22 G/2.5 cm needle for infants, a 20 G/3.2 cm needle for 5-year-old children, and an 18 G/4.5 cm needle for 10-year-old children. In small infants and newborns, the use of a 24 G cannula may be considered. ²⁸ Children have less muscle and fat to penetrate prior to entering the pleural cavity; therefore, caution must be taken with longer needles, which potentially can injure underlying structures. Chest tubes are proportionally smaller in children. The Broselow Tape or other length-based measurement tape can help identify the appropriate thoracostomy tube size. Another way to estimate chest tube size is by taking the endotracheal tube size and multiplying it by 4.³⁴ Tube thoracostomy placement is similar in children and adults at the fifth ICS anterior to the midaxillary line. The incision should occur above the sixth rib to avoid the neurovascular bundle along the posterior ribs. The chest tube should be directed superiorly and posteriorly along the inside of the chest cavity.

If needle decompression occurs, a chest tube must be placed. After a chest tube is placed, it will need to be secured to the patient, and an occlusive dressing placed over the insertion site to prevent air from entering the pleural cavity. The chest tube then should be connected to a chest drainage system. Finally, chest tube placement should be confirmed with a chest X-ray and to re-assess the pneumothorax or hemothorax.^14,50

The pleural cavity already has a negative pressure, so a sealed system is required to prevent the introduction of air or fluid. Chest tubes are connected to this closed system to allow air or fluid drainage while preventing inflow. The chest tube is connected to tubing that empties into a drainage system. The drainage system should always be below the patient to allow gravity-dependent drainage. The amount of fluid drained can be monitored. A water seal chamber acts as a one-way valve allowing air to exit the pleural cavity during each expiration but not allowing re-entry due to the pressure difference. There is a dry suction port on most commercial systems. This port connects to wall suction, which should be placed on continuous if used. The amount of actual suction is controlled on the drainage system and is commonly set to -20 mmHg. Air bubbling in the water chamber is seen due to air entry in the design, which can be seen when a pneumothorax is present. It is essential to check the entire system for other possible air leaks, including the occlusive dressing.⁵⁰

Rib and Sternal Fractures

Because of their unique physiology, rib fractures are uncommon in children. Children have incompletely ossified and flexible bones, meaning that a significant amount of force is required for rib fractures to occur. If rib fractures are present, there is a very high likelihood of other injuries, such as lung, brain, and abdominal injuries. Given this, a detailed search must occur for co-injuries when rib fractures are found. Rib fractures often present with shortness of breath and chest wall pain. There may be signs of bruising or deformity along the chest wall. A flail chest may occur when a segment of three consecutive ribs moves freely and opposite the chest wall during respiration, causing a paradoxical chest wall motion and respiratory distress. Lower segments of rib fractures can injure the liver or spleen, and an increasing number of rib fractures can increase the chance of a hemothorax.^4,5 Rib fractures may be identified on chest X-ray; however, CT is more sensitive at identifying fractures and can better show displacement.⁵

Typically, multimodal pain control is the mainstay of treatment in children. Pharmacological options include acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), lidocaine patches, and nerve blocks (epidural, rib blocks, erector spinae blocks).²⁸ Adequate pain control allows patients to take deep breaths and open the lungs to help with ventilation and prevent pneumonia. Rib fixation is supported in adult literature. There is no current evidence for rib fixation in pediatric patients; however, there are some case reports.^28,51 Nonaccidental trauma should be considered in children with rib fractures and an inconsistent mechanism of injury or lack of a history of trauma.⁵² In children younger than 12 months of age without a history of known trauma, rib fractures are more likely to be caused by nonaccidental trauma.⁵³

Sternal fractures are rare and occur at less than one per 100,000.⁵⁴ This injury is likely seen in motor vehicle accidents in older children whose chest wall has matured with adult-like physiology. One study demonstrated that sternal fractures are associated with other injuries, increased need for mechanical ventilation, higher level care, and increased mortality.⁵⁴ Another study showed that many sternal fractures could be isolated and, if stable, have lower morbidity.⁵⁵ There is a concern for possible underlying blunt cardiac injury with these fractures. Similar to rib fractures, the management is pain control and pulmonary hygiene.

Pneumomediastinum

Pneumomediastinum is the presence of gas in the mediastinum. This area is bounded by the thoracic outlet superiorly, the diaphragm inferiorly, the sternum anteriorly, the vertebral column posteriorly, and the parietal pleura laterally. Penetrating trauma can introduce air into the mediastinum. Blunt trauma can injure the trachea or esophagus, causing air to be released into the mediastinum. Spontaneous pneumomediastinum can occur through the Macklin phenomenon: Increased intra-alveolar pressure results in alveolar rupture, allowing air to dissect into the peri-bronchial and perivascular sheaths that spread into the mediastinum and surrounding tissue.⁵⁶

Symptoms can include chest pain, shortness of breath, neck pain, coughing, abdominal pain, and emesis. Subcutaneous emphysema also can be present, with tachycardia, voice hoarseness, and tachypnea. Pneumomediastinum typically can be detected on chest X-ray, and CT can increase that sensitivity but is unnecessary if the patient is asymptomatic. CT also helps increase the sensitivity of finding an underlying injury, such as esophageal perforation. Frequently, these injuries commonly can be observed and will resolve on their own. However, surgery may be indicated due to a significant underlying injury to the trachea, esophagus, or diaphragm.^4,56

Tracheal Injuries, Esophageal Injuries, and Diaphragm Rupture

Tracheobronchial injuries are infrequent in the pediatric population; however, they carry relatively high morbidity and mortality when they do occur, which most commonly is within 2 cm to 3 cm of the carina (75% to 90%).⁵⁷ These injuries can be lethal up to 33% of the time in the first hour.^5,7 Patients commonly present with respiratory distress, hemoptysis, and subcutaneous emphysema.⁵⁷ Patients also can present with mediastinal air into the neck, causing subcutaneous emphysema, stridor, hoarse voice, and difficulty swallowing. Most of these injuries can be detected on CT, but further exploration with bronchoscopy may be needed.^4,5 Patients likely will need their airways secured with intubation and surgery to address the injury. The airway should be secured below the leakage site.⁵⁷

The esophagus is a posterior structure generally protected in the thorax. Esophageal injuries are rare; however, they can rupture because of increased intra-abdominal pressures. This typically occurs in the esophagus’s distal third, with a rupture into the left chest.^1,4 Patients may have chest pain, epigastric pain, respiratory distress, and subcutaneous emphysema. A chest X-ray can detect pleural effusions and mediastinal air; however, CT is more sensitive. Water-soluble esophagogram (not barium, since this can damage and worsen respiratory distress) and esophagoscopy can further detect perforations. Antibiotics and fluids should be started promptly if there is a high suspicion of esophageal rupture. Children, unlike adults, often can be observed with esophageal injuries and not require surgery. Patients must be on parenteral nutritional therapy until the perforation heals.^5,58

Diaphragm injuries commonly occur due to the abdomen being forcibly compressed, causing stress on the diaphragm as a result of the high pressures. These injuries usually occur to the left diaphragm, posterolateral aspect. Liver and spleen injuries frequently are associated with diaphragmatic injuries associated with blunt trauma. Rupture of the diaphragm can result in herniation of the stomach and bowel into the chest, which occurs in 1% of pediatric blunt chest trauma.⁴⁹ Patients often will have abdominal and chest pain and may have signs and symptoms of respiratory distress. A chest X-ray can identify lung opacities, pleural effusions, displacement of the stomach bubble, high-riding hemidiaphragm, and possible nasogastric tube in the chest (if one was placed). Identifying this injury on a chest X-ray before placing a chest tube is crucial, since the chest tube may result in additional significant damage. These injuries otherwise require surgical intervention.

Cardiac Injuries

There is limited research on pediatric blunt cardiac injury. Most patients with cardiac injuries from thoracic trauma will die in the prehospital period. Most cardiac injuries are due to a blunt mechanism; however, penetrating injuries can cause lacerations to the heart.¹ Cardiac laceration has a high mortality rate, with a 30% survival rate. Survival rates are higher in stab wounds than gunshot wounds.⁵⁹

Patients can experience electrical or structural complications from these injuries. Electrical complications often result in arrhythmias, while structural damages can affect cardiac output. EAST guidelines recommend an electrocardiogram (ECG) in all patients with blunt cardiac injury to assess for arrhythmia. This typically is paired with troponin testing, and if both are normal, this injury can be ruled out; however, it is unclear, based on existing literature, the generalizability of this approach to the pediatric patient.⁵⁹ Echocardiogram often is used further to assess the structure and function of the heart if an injury is suspected. One series of 266,045 pediatric patients found the incidence of blunt cardiac injury (BCI) was less than 0.2%, with a mortality of 26%. In this study, the strongest independent risk factors for BCI were pulmonary contusions and hemothorax.⁶⁰

Myocardial contusion is the most common traumatic cardiac injury (95% of BCIs).¹⁶ Patients generally present with substernal chest pain. Cardiac arrhythmias and hypotension also may be present. ECG changes can include arrhythmias, diffuse S-T changes, or heart block. Troponin may be elevated, and echocardiography can show wall motion changes consistent with contusion or hematoma. This injury usually is self-limited, although aneurysm formation can be a complication.¹⁶ Patients should be monitored on continuous telemetry until free of arrhythmia for 24 hours. Dobutamine can be considered for blood pressure support for hypotensive patients secondary to myocardial contusion who are not responsive to fluid resuscitation. Severe injuries have been managed by intra-aortic balloon pumps and extracorporeal membrane oxygenation; however, this is exceedingly rare in the pediatric population.⁵⁹

Cardiac tamponade can occur in blunt or penetrating trauma. A pericardial effusion of blood or other fluid (rarely air) can form between the heart and pericardium, leading to impaired cardiac filling during diastole and leading to an obstructive shock state. Beck’s triad of muffled heart sounds, hypotension, and distended neck veins is present in 90% of cases. Other findings include narrow pulse pressure and pulsus paradoxus.^1,4,16,59 It is challenging to accurately auscultate muffled sounds in the trauma bay, and severe blood loss may not cause distended neck veins, leading to diagnostic difficulty.⁵⁸ Bedside ultrasonography can help identify cardiac tamponade quickly in the trauma bay. If tamponade physiology is present in an unstable patient, pericardiocentesis should be done to remove the fluid around the heart. The procedure uses a needle inserted into the subxiphoid space at a 45-degree angle with the needle directed toward the left shoulder while aspirating to get a return of blood. The procedure also can be done with ultrasound guidance to help avoid further injury to the heart or possible pneumothorax. If pericardiocentesis is unsuccessful or a penetrating injury is likely causing the tamponade, then a resuscitative thoracotomy is indicated to identify the potential injury. Finally, a pericardiocentesis can have a false-negative result secondary to clotting.^14,59

Commotio cordis is a life-threatening arrhythmia due to a direct blow to the heart. The direct impact is precisely timed to the repolarization phase of the cardiac cycle, which can cause ventricular tachyarrhythmia. Several cases of this have been reported to occur during various sporting activities. Patients should be resuscitated quickly with CPR and defibrillation, since defibrillation can help break the arrhythmia. Survival rates can be 80% to 100% if defibrillation can be completed rapidly.^16,59

Great Vessel and Aortic Injuries

Injuries to the aorta and great vessels are highly lethal; however, mediastinal mobility makes injuries to the aorta and other great vessels rare. These typically occur in blunt trauma cases in children as a result of high-energy mechanisms and rapid decelerations. The aorta at the level of the ligamentum arteriosum is the most common area affected.⁴⁹ These injuries can be challenging to detect and can present with abdominal pain, chest pain, tachycardia, hypotension, and sudden and disastrous clinical deterioration. A chest X-ray may show mediastinal widening and loss of the aortic knob, increasing suspicion of an aortic injury. The thymus can mask features on the chest X-ray, especially in younger children. Other findings can be seen, including first or second rib fractures and pleural effusions. If there is a high clinical concern, a CT angiogram may help further identify these injuries and mediastinal hematoma, pseudoaneurysm, focal dissection, thrombus, and intimal irregularity.

Prompt surgical repair is the definitive treatment. Pain control and beta-blocker therapy are indicated until surgery can occur. Beta-blockers will help reduce the heart rate and blood pressure to help mitigate shearing forces.^1,4,5

Chylothorax

A chylothorax usually occurs from blunt trauma and is rare in children. Hyperextension of the spine with fractures from the spine or posterior ribs causes injury to the thoracic duct, which can cause a pleural effusion. Tube thoracostomy can help remove the fluid. The fluid will appear milky and have triglyceride levels greater than 110 mg/dL, chylomicrons, predominance of lymphocytes, and low cholesterol levels. These injuries usually are managed nonoperatively by tube thoracostomy, medium-chain fatty acid diet, or parenteral nutrition. Surgery is indicated if the chylous fluid expressed exceeds 100 mL per year of age or fails to resolve.⁵⁹

Traumatic Asphyxia

This phenomenon, also known as Perthes syndrome, occurs when the thorax is compressed, causing an inability to breathe. It is a rare condition in children, with the incidence not known. The incidence in adults is reported as one in 18,500 accidents.⁶¹ An article by Byard and colleagues reported only six pediatric cases over 35 years from 1966-2000.⁶² The compressive force causes global hypoxia and increased intrathoracic and mediastinal pressures. Increased intrathoracic pressure causes right atrial blood to be pushed into the innominate artery and jugular veins, which leads to capillaries rupturing in the cervicofacial region. This increased pressure causes facial and bulbar petechia and subconjunctival hemorrhages. Global hypoxia will result in cyanosis and loss of consciousness. If this force is not removed, the patient will die. If the compressive force is removed, children can re-oxygenate and have a good prognosis.^1,14,49

Disposition Considerations

Transfer guidelines should be in place for hospitals that are designated trauma centers as part of the designation process. Table 4 is a sample compilation of guidelines that are recommended by American Academy of Pediatrics and National Highway and Transportation Safety Administration published standards across the nation at other trauma centers regarding transport.⁶³

Conclusion

Trauma is the most common cause of morbidity and mortality in children, with thoracic trauma having the second highest mortality rate. Thoracic trauma can include injuries to the chest wall, ribs, lungs, trachea, esophagus, heart, and great vessels, resulting in various injury patterns. Most injuries are due to blunt mechanisms, with motor vehicle accidents being the most common cause.

The injury patterns in children are different from adults due to anatomical differences. These differences include a flexible chest wall, incompletely ossified bones, increased metabolic rates, and mediastinal mobility. Pulmonary contusions are the most common injury pattern, and rib fractures are rare in children because of those anatomical differences. Children also are more likely to have pneumothoraxes. Therefore, it is essential to conduct a primary survey to identify life-threatening injuries and a detailed secondary survey of the chest to identify more subtle injuries. Based on the mechanism and physical exam findings, a chest X-ray should be obtained in the trauma bay to assess for injuries. CT is unnecessary for every pediatric trauma and should be obtained on a case-by-case basis. Ultrasound has a limited role in pediatric thoracic trauma based on current literature.

Management primarily is based on the injury pattern, with most patients requiring observation, oxygen, and pain control. More serious injuries may require surgical intervention. Patients with severe injuries should be transferred to a pediatric trauma center for further management.

REFERENCES

1. Pearson EG, Fitzgerald CA, Santore MT. Pediatric thoracic trauma: Current trends. Semin Pediatr Surg 2017;26:36-42.
2. Injury Prevention and Control. WISQARS (Web-based Injury Statistics Query and Reporting System). Centers for Disease Control and Prevention. https://www.cdc.gov/injury/wisqars/index.html. Published Feb. 9, 2023.
3. Shook JE, Chun TH, Conners GP, et al. Management of pediatric trauma. Pediatrics 2016;138:1-9.
4. Reynolds SL. Pediatric thoracic trauma: Recognition and management. Emerg Med Clin North Am 2018;36:473-483.
5. Tovar JA, Vazquez JJ. Management of chest trauma in children. Paediatr Respir Rev 2013;14:86-91.
6. Cooper A, Barlow B, DiScala C, String D. Mortality and truncal injury: The pediatric perspective. J Pediatr Surg 1994;29:33-38.
7. Minervini F, Scarci M, Kocher GJ, et al. Pediatric chest trauma: A unique challenge. J Visualized Surgery 2020;6:1-7.
8. Lee LK, Fleegler EW, Goyal MK, et al; AAP Council on Injury, Violence, and Poison Prevention. Firearm-related injuries and deaths in children and youth. Pediatrics 2022;150:1-22.
9. Czaja MP, Kraus CK, Phyo S, et al. Injury characteristics, outcomes, and health care services use associated with nonfatal injuries sustained in mass shootings in the US, 2012-2019. JAMA Netw Open 2022;5:1-13.
10. Biyyam DR, Hwang S, Patel MT, et al. CT findings of pediatric handlebar injuries. Radiographics 2020;40:815-826.
11. Weerdenburg KD, Wales PW, Stephens D, et al. Predicting thoracic injury in children with multitrauma. Pediatr Emerg Care 2019;35:330-334.
12. Holmes JF, Sokolove PE, Brant WE, Kuppermann N. A clinical decision rule for identifying children with thoracic injuries after blunt torso trauma. Ann Emerg Med 2002;39:492-499.
13. Mikrogianakis A, Grant V. The kids are alright: Pediatric trauma pearls. Emerg Med Clin North Am 2018;36:237-357.
14. American College of Surgeons Committee on Trauma. Advanced Trauma Life Support (ATLS®) Student Manual. 10th ed. American College of Surgeons; 2018.
15. Hagedorn KN, Johnston JH, Chinapuvvula NR, et al. Characterization of all-terrain vehicle-related chest injury patterns in children. Emerg Radiol 2019;26:373-379.
16. Sawaya DE, Colombani PM. Pediatric thoracic trauma. In: Puri P, Hollwarth M, eds. Pediatric Surgery: Diagnosis and Management. 1st ed. Springer Cham; 2009:133-141.
17. American Academy of Pediatrics. Part 4: Systematic Approach to the Seriously Ill or Injured Child. In: PALS: Pediatrics Advanced Life Support Provider Manual. American Heart Association; 2020.
18. Hughes BD, Landman M, Koberlein GC, et al. Pediatric trauma: Thoracic imaging assessment in the setting of blunt trauma. Pediatric Trauma Society. https://pediatrictraumasociety.org/multimedia/files/guidelines/Blunt-Imaging-Review.pdf
19. Golden J, Isani M, Bowling J, et al. Limiting chest computed tomography in the evaluation of pediatric thoracic trauma. J Trauma Acute Care Surg 2016;2:271-277.
20. Ugalde IT, Prater S, Cardena-Turanza M, et al. Chest x-ray vs. computed tomography of the chest in pediatric blunt trauma. J Pediatr Surg 2021;5:1039-1046.
21. Downie K, McIntir A, Tobias J, et al. Application of a thoracic CT decision rule in the evaluation of injured children: A quality improvement initiative. J Trauma Nurs 2023;1:48-54.
22. Vaszquez DG, Berg GM, Srour SG, Ali K. Lung ultrasound for detecting pneumothorax in injured children: Preliminary experience at a community-based Level II pediatric trauma center. Pediatr Radiol 2020;50:329-337.
23. Hosseini M, Ghelichkhani P, Baikpour M, et al. Diagnostic accuracy of ultrasonography and radiography in detection of pulmonary contusion; a systematic review and meta-analysis. Emerg (Tehran) 2015;3:127-136.
24. Musolino AM, Tomà P, De Rose C, et al. Ten years of pediatric lung ultrasound: A narrative review. Front Physiol 2022;12:1-22.
25. Cox M, Soudack M, Podberesky DJ, Epelman M. Pediatric chest ultrasound: A practical approach. Pediatr Radiol 2017;47:1058-1068.
26. Vargas CA, Quintero J, Figueroa R, et al. Extension of the thoracic spine sign as a diagnostic marker for thoracic trauma. Eur J Trauma Emerg Surg 2021;47:749-755.
27. Dickman E, Terentiev V, Likourezos A, et al. Extension of the thoracic spine sign: A new sonographic marker of pleural effusion. J Ultrasound Med 2015;34:1555-1561.
28. Hallbach JL, Ignacio RC. Thoracic and chest wall injuries. In: Kennedy AP, Ignacio RC, Ricca R, eds. Pediatric Trauma Care. 1st ed. Springer;2023:241-252.
29. Rossaint R, Afshari A, Bouillon B, et al. The European guideline on management of major bleeding and coagulopathy following trauma: Sixth edition. Crit Care 2023;27:1-45.
30. Zampieri FG, Damiani LP, Biondi RS, et al. Effects of balanced solution on short-term outcomes in traumatic brain injury patients: A secondary analysis of the BaSICS randomized trial. Rev Bras Ter Intesiva 2022;34:410-417.
31. Lombardo S, Smith MC, Semler MW, et al. Balanced crystalloid versus saline in adults with traumatic brain injury: Secondary analysis of a clinical trial. J Neurotrauma 2022;39:1159-1167.
32. Russell RT, Esparaz JR, Beckwith MA,et al. Pediatric traumatic hemorrhagic shock consensus conference recommendations. J Trauma Acute Care Surg 2022;94(1S Suppl 1):S2-S10.
33. Naiditch JA, Dingeldein M, Tuggle D. Evaluation, stabilization, and initial management after trauma. In: Zimmerman JJ, Rotta AT, Clark RSB, et al, eds. Fuhrman & Zimmerman’s Pediatric Critical Care, 6th ed. Elsevier; 2021:1363-1374.
34. Panapa M, Davenport M. Approaches to the hemorrhaging pediatric trauma patient. Trauma Reports 2021;22:1-12.
35. Kornelsen E, Kuppermann N, Nishijima DK, et al. Effectiveness and safety of tranexamic acid in pediatric trauma: A systematic review and meta-analysis. Am J Emerg Med 2022;55:103-110.
36. Floan GM, Calvo RY, Prieto JM, et al. Pediatric penetrating thoracic trauma: Examining the impact of trauma center designation and penetrating trauma volume on outcomes. J Pediatr Surg 2023;2:330-336.
37. Stewart S, Briggs KB, Fraser JA, et al. Pre-hospital CPR after traumatic arrest: Outcomes at a Level 1 pediatric trauma center. Injury 2023;54:15-18.
38. Prieto JM, Van Gent JM, Calvo RY, et al. Nationwide analysis of resuscitative thoracotomy in pediatric trauma: Time to differentiate from adult guidelines? J Trauma Acute Care Surg 2020;89:686-690.
39. Seamon MJ, Haut ER, Van Arendonk K, et al. An evidence-based approach to patient selection for emergency department thoracotomy: A practice management guideline from the Eastern Association for the Surgery of Trauma. J Trauma Acute Care Surg 2015;79:159-173.
40. Moore HB, Moore EE, Bensard DD. Pediatric emergency department thoracotomy: A 40-year review. J Pediatr Surg 2016;51:315-318.
41. Bulger EM, Perina DG, Qasim Z, et al. Clinical use of resuscitative endovascular balloon occlusion of the aorta (REBOA) in civilian trauma systems in the USA, 2019: A joint statement from the American College of Surgeons Committee on Trauma, the American College of Emergency Physicians, the National Association of Emergency Medical Services Physicians and the National Association of Emergency Medical Technicians. Trauma Surg Acute Care Open 2019;4:1-6.
42. Norri T, Miyata S, Terasaka Y, et al. Resuscitative endovascular balloon occlusion of the aorta in trauma patients in youth. J Trauma Acute Care Surg 2017;82:915-920.
43. Theodorou CM, Brenner M, Morrison JJ, et al. Nationwide use of REBOA in adolescent trauma patients: An analysis of the AAST AORTA registry. Injury 2020;51:2512-2516.
44. Theodorou CM, Trappey AF, Beyer CA, et al. Quantifying the need for pediatric REBOA: A gap analysis. J Pediatr Surg 2021;56:1395-1400.
45. Wylie J, Morrison G C, Nalk K, et al. Lung contusion in children—early computed tomography versus radiography. Pediatr Crit Care Med 2009;10:643-647.
46. Park S, Shin SW, Kim HJ, et al. Choice of the correct size of endotracheal tube in pediatric patients. Anesth Pain Med (Seoul) 2022;17:352-360.
47. Medar SS, Villacres S, Kaushik S, et al. Pediatric acute respiratory distress syndrome (PARDS) in children with pulmonary contusion. J Intensive Care Med 2021;36:107-114.
48. Piccolo CL, Ianniello S, Trinci M, et al. Diagnostic imaging in pediatric thoracic trauma. Radiol Med 2017;122:850-865.
49. Chung DH. Chapter 67: Pediatric surgery. In: Townsend CM, Evers BM, Beauchamp DR, et al, eds. Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice. 21st ed. Elsevier;2021:1844-1882.
50. Doyle GR, McCutcheon JA. Chapter 10.6: Chest tube drainage systems. In: Doyle GR, McCutcheon JA, eds. Clinical Procedures for Safer Patient Care. 1st ed. Bccampus;2015. https://opentextbc.ca/clinicalskills/chapter/10-7-chest-drainage-systems/
51. Polycarpou A, Kim BD. Pediatric surgical rib fixation: A collected case series of a rare entity. J Trauma Acute Care Surg 2021;91:947-950.
52. Ruest S, Kanaan G, Moore JL, et al. Pediatric rib fractures identified by chest radiograph: A comparison between accidental and nonaccidental trauma. Pediatr Emerg Care 2021;37:e1409-e1415.
53. Pain CW, Fakeye O, Christian CW, Wood JN. Prevalence of abuse among young children with rib fractures: A systematic review. Pediatr Emerg Care 2019;35:96-103.
54. Odegard MN, Endorf FW, Richardson CJ, et al. Analysis of pediatric sternal fractures using the Kid’s Inpatient Database (KID). Injury 2022;53:1627-1630.
55. Chalphin AV, Mooney DP. Pediatric sternal fractures: A single center retrospective review. J Pediatr Surg 2020;55:1224-1227.
56. Iteen AJ, Bianchi W, Sharman T. Pneumomediastinum. In: StatPearls. StatPearls Publishing;2022:1-21. Last updated May 1, 2023. https://www.ncbi.nlm.nih.gov/books/NBK557440/#_NBK557440_pubdet_
57. Reith A, Varga E, Kovacs T, et al. Contemporary management strategies of blunt tracheobronchial injuries. Injury 2021;52(Suppl 1):S7-S14.
58. Fitzgerald TN, Reed CR. Chapter 119: Pediatric thoracic trauma. In: Zimmerman JJ, Clark RSB, Fuhrman BP, et al, eds. Furhman & Zimmerman’s Pediatric Critical Care. 6th ed. Elsevier;2022:1401-1407.
59. Clancy K, Velopulos C, Bilaniuk JW, et al. Screening for blunt cardiac injury: An Eastern Association for the Surgery of Trauma practice management guideline. J Trauma 2012;73:301-306.
60. Emigh B, Grigorian A, Dilday J, et al. Risk factors and outcomes in pediatric blunt cardiac injuries. Pediatr Surg Int 2023;39:195.
61. Cortis J, Falk J, Rothschild MA. Traumatic asphyxia—fatal accident in an automatic revolving door. International Journal of Legal Medicine 2015;129:1103-1108.
62. Byard RW, Hanson KA, James RA. Fatal unintentional traumatic asphyxia in childhood. J Paediatrics Child Health 2003;39:31-32.
63. Pediatric Consultation and Transfer Guidelines. August 2011. https://media.emscimprovement.center/documents/SDakotaInterFacilityTransferGuidelines2125.pdf