Thoracic injuries in childhood

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3.3 Thoracic injuries in childhood

Phil Aplin

Essentials

1 Thoracic injuries in children are common, are usually due to blunt trauma and are often associated with other injuries.
2 The pathophysiological differences in children depend principally on their age and size. These must be appreciated in order to optimise outcome.
3 The most common injuries are pulmonary contusions, rib fractures, pneumothoraces and haemothoraces. These can usually be managed by a combination of adequate oxygenation, IV fluids, thoracostomy tube drainage and analgesia.
4 Injuries to the aorta and diaphragm may be clinically occult and CXR findings are often non-specifically abnormal. Further diagnostic evaluation is always indicated in suspect cases.
5 Surgical intervention is uncommonly required, but is indicated in cases of massive haemothorax, cardiac tamponade, major airway and oesophageal injury, as well as in aortic and diaphragmatic injuries.
6 ED thoracotomy is principally indicated in cases of penetrating chest trauma and an arrest or pre-arrest presentation.

Introduction1–4

Traumatic injury is the most common cause of morbidity and mortality in childhood and thoracic injuries are secondary to head injuries as a cause of mortality. Isolated chest injuries have a mortality of around 5% but this increases substantially when combined with head and/or abdominal injury to as high as 20%. Injuries to the great vessels, bronchi, lung lacerations and cardiac tamponade are the chest injuries most likely to cause early death. Small children provide a small target in blunt trauma, so multiple injuries should be expected.

A recent review of an Australian trauma registry database found multiple body region injury to be almost universal (99%) in cases of severe blunt chest trauma. The most frequent associated serious injuries were head (46%), lower extremity (32%) and abdominopelvic injury (30%). By far and away the commonest chest injuries were pulmonary contusion, haemopneumothorax and rib fractures.

The common mechanisms of injury vary with the age of the child. Overall, the majority (60–80%) are due to blunt trauma and involve a motor vehicle in over half. In infants and toddlers common mechanisms include being injured as passengers in motor vehicle collisions (MVC) or as pedestrians struck or run over by a vehicle (commonly in the driveway of the family home). Falls (from stairs, balconies, etc.) occurs mainly in this age group. Child abuse also tends to predominate in this age group and should always be considered. In school age children motor vehicle and bicycle related trauma is common and sporting (± extreme sports) injuries increase in frequency with age. With adolescence the occurrence of penetrating trauma emerges with an associated increased mortality risk, also inexperienced teenage drivers have an increased incidence of MVC. Drug and alcohol intoxication is often associated with personal/interpersonal violence in this older age group.

There are a number of anatomical and physiological features of small children that must be appreciated when managing paediatric chest trauma. These are summarised in Table 3.3.1.

Table 3.3.1 Important pathophysiological differences between children and adults in chest trauma

• Small target – multiple injuries common
• Narrow airway – prone to obstruction
• Anterior larynx – difficult intubation
• Increased surface area – increased risk of hypothermia
• Increased oxygen consumption, diaphragmatic breathing, low functional residual capacity – prone to hypoxia
• Increased pliability of ribs – decreased incidence of rib fractures
• Response to blood loss – hypotension is a late sign of shock
• Developmental considerations – paediatric coma scoring

Initial approach in the ED5

Initial management follows the usual priorities. After ensuring airway patency, breathing should be assessed. High-flow oxygen should be applied. Signs of respiratory compromise and tension pneumothorax should be managed by needle decompression prior to chest X-ray (CXR) followed by chest tube insertion. A large haemothorax may compromise ventilation as well as circulation, requiring early chest tube placement and fluid resuscitation, whilst an orogastric tube (OGT) should be placed early to decompress the stomach, as gastric distension may compromise ventilation. Mechanical ventilation should be instituted for signs of ongoing respiratory distress/respiratory failure not relieved by optimisation of oxygen delivery, chest tube insertion, closure of open chest wounds and OGT placement. Ongoing signs of circulatory compromise without evidence of blood loss should raise the possibility of cardiac tamponade and myocardial contusion in a child with chest injuries. A portable CXR should be the first radiological test ordered. FAST (focused abdominal scan in trauma) scanning should occur early in the resuscitation of a child, where available, and imaging of the pericardium should always be included to detect haemopericardium. The vast majority of chest injuries in childhood can be managed non-operatively. Drainage of pericardial blood may occasionally be performed in the emergency department (ED) in an unstable patient if operative intervention is not immediately available. Other indications for operative intervention are listed in Table 3.3.2. CT imaging of the chest should be used selectively. It is indicated in high impact trauma and when multiple injuries are present or suspected, particularly severe head injury where there is a high likelihood of associated severe chest injury.

Table 3.3.2 Indications for operative intervention in chest trauma

• Great vessel injury
• Pericardial tamponade
• Large haemothoraces
• Tracheobronchial injuries
• Oesophageal injury
• Diaphragmatic lacerations
• Open pneumothorax with major chest wall defect
• Penetrating chest trauma that crosses the mediastinum

Once stabilised, thoracic CT scan may be indicated to further delineate the extent of pulmonary injury, evaluate the great vessels and detect pneumothoraces. Analgesia should be initiated early in appropriate doses.

Chest wall injury6

Rib fractures

The elasticity and flexibility of the younger child’s chest wall leads to a lower incidence of rib fractures. Significant underlying intrathoracic injury can occur in the absence of rib fractures. In the 0- to 3-year age group rib fractures should raise the concern of abuse: in one study 2/3 of 0–3-year-olds with rib fractures were victims of abuse, and a careful assessment of all aspects of the clinical presentation is mandatory. Radiological findings suggestive of abuse include: multiple fractures, fractures of varying ages and bilateral fractures. A bone scan is a more sensitive test in the setting of potential abuse.

Rib fractures in children are a marker of potential severe associated injuries. Multiple rib fractures (>1) increase the risk of severe intrathoracic injury, multiple injuries and mortality. Fracture of the first rib requires significant force, mandating a high degree of suspicion of associated injuries to the great vessels and the trachea.

Flail chest injuries are rare in children and clearly indicate serious injury, with reduced ventilatory effectiveness and associated lung contusions contributing to the significant potential for respiratory failure. Assisted ventilation is indicated for those with respiratory failure despite optimal non-invasive ventilation and analgesia or associated injuries, particularly to the head.

Management of rib fractures involves analgesia, treatment of associated injuries, ongoing assessment of the child’s respiratory status and close observation for complications that may arise. Analgesic options in the ED include oral paracetamol (also available intravenously (IV)) and anti-inflammatories, intranasal fentanyl and titrated IV narcotics. Prevention of atelectasis and pneumonia is a priority.

Pulmonary injury7,8

Contusion

In children it is important to appreciate that significant lung injury can occur in the absence of rib fractures or other external signs of chest wall injury. Pulmonary contusion most commonly results from blunt injury and requires significant force. Pathological findings are intra-alveolar haemorrhage, consolidation and oedema causing V/Q mismatch, reduced lung compliance and subsequent hypoxaemia. CXR findings of increased pulmonary opacity may be present in the ED but may evolve over time. Computerised tomography (CT) scanning of the thorax may reveal contusion that is not evident on the initial plain films. Approximately half of the CXRs showing pulmonary contusion show other abnormalities, most commonly fractured ribs and pneumo/haemothoraces.

Management of pulmonary contusion involves:

• Maintenance of oxygenation. Supplemental 02 is initially delivered by high flow mask (10–15 L min–1). Persisting hypoxaemia requires non-invasive or invasive ventilatory support depending on severity and associated injuries.
• Pain relief should be provided as indicated.
• Excessive intravenous fluids should be avoided.
• Respiratory physiotherapy is useful.

Both acute respiratory distress syndrome and pneumonia may complicate pulmonary contusion.

Pneumothorax4,9

Traumatic pneumothoraces vary in their size and clinical significance. They occur in about 1/3 of children with significant thoracic trauma and associated injuries are common. All pneumothoraces should be considered as having the potential to cause cardiorespiratory compromise. The clinical signs of pneumothorax (PTX) vary from nothing to decreased air entry, hyperresonance and subcutaneous emphysema.

Small to medium sized pneumothoraces may not be visible on a portable supine CXR. Ultrasound of the chest may be incorporated into the FAST scan protocol to detect pneumothoraces and haemothoraces. The sensitivity of ultrasound in detecting these complications of chest trauma is superior to supine CXR but CT scanning remains the gold standard. Subtle signs on CXR include increased radiolucency on the ipsilateral side and a deep sulcus sign. Small pneumothoraces are commonly revealed on CT scan of the chest and/or abdomen. The significance and hence management of these small pneumothoraces is debated. A small uncomplicated PTX in a stable patient with isolated chest trauma, who is not likely to require positive pressure ventilation or prolonged transport (particularly aeromedical), can be considered for observation, high-flow O2 and analgesia in a high-dependency unit setting. Most other traumatic pneumothoraces require the insertion of a formal chest drain.

Tension pneumothorax

This is a clinical condition resulting from increasing intrathoracic pressure, lung collapse and mediastinal shift with subsequent impaired gas exchange, decreased venous return and cardiovascular collapse. The diagnosis is clinical and treatment should precede radiology in clear-cut cases. Signs are of ↓ air entry, hyperresonance and hyperexpansion plus ↓ movement of the affected side. The signs of tracheal deviation and elevation of the jugular venous pressure (JVP) may be difficult to detect in children who have short necks. JVP elevation may also be absent if there is associated hypovolaemia. Patients are always tachypnoeic with respiratory distress and tachycardia, but hypotension is a late sign if solely due to a tension PTX. Immediate needle decompression with a 16G cannula inserted into the 2nd intercostal space in the mid clavicular line should occur whilst preparing for formal intercostal tube insertion via a lateral approach.

However, hypotension and/or hypoxaemia may have other causes in the traumatised child. The differential diagnosis of a tension PTX includes: haemorrhage; pericardial tamponade; haemothorax (which may cause tension); pulmonary contusion; and air embolism. Common, easily preventable/treatable causes that may occasionally be confused with a tension PTX are intubation of the right main-stem bronchus and gastric distension. Endotracheal tubes (ETT) must be inserted the appropriate distance (age/2 + 12 cm) and movement of the child’s neck minimised. This is particularly so in small children where neck flexion (tube pulled out) or extension (tube down the [R] main bronchus) may result in the malposition of the ETT. An orogastric tube should be placed early.

Open pneumothoraces may occur with penetrating chest trauma. Respiratory compromise relates to the effects of the PTX, underlying lung injury and a ‘sucking chest wound’ if the defect is large enough. If the diameter of the chest wound is approximately 2/3 or greater than that of the trachea, air will preferentially be sucked into the chest on inspiration, leading to acute severe respiratory compromise. Management requires urgent wound coverage on three sides only with an occlusive dressing, to prevent the development of an iatrogenic tension PTX, and chest tube placement away from the wound. Once the chest drain is in place the wound can be sealed and arrangements made for definitive surgical care. Significant ongoing respiratory distress is an indication for mechanical ventilation.

Pulmonary lacerations5

Pulmonary lacerations are principally caused by penetrating injuries but can occur with blunt mechanisms especially associated with rib fractures. They usually result in a haemothorax (sometimes massive) or PTX and rarely can be complicated by air embolism. Air embolism typically occurs after the initiation of positive pressure ventilation and causes sudden haemodynamic deterioration with or without focal neurological signs. Development of a tension PTX, pericardial tamponade or massive haemothorax are the main other possibilities in the chest for such a sudden deterioration. Lung hyperinflation due to overly aggressive positive pressure ventilation may also cause cardiorespiratory compromise and risk barotrauma.

In the setting of deterioration after initiation of ventilation, by far the most likely cause is the development of tension PTX, which should be managed as above. In the rare event of air embolism, if suspected, management includes 100% oxygen, and reduction of the ventilation pressures. Emergency thoracotomy with clamping of the hilum on the affected side and aspiration of ventricular air has occasionally been life saving.

Haemothorax9,10

Clinically relevant haemothoraces occur in about 15% of cases of blunt chest trauma but are more common if the injury is penetrating. The source of bleeding is most commonly from lacerations to the lung, intercostal or internal mammary vessels or occasionally from mediastinal vessel injury (often fatal). Each hemithorax can hold up to 40% of a child’s blood volume.

The clinical presentation is of varying degrees of hypovolaemia and respiratory compromise depending on the amount of blood lost into the chest, associated pneumothorax and the development of increased intrathoracic pressure. Chest examination reveals reduced air entry and dullness to percussion ± signs of tension. Management is with a chest drain. Drainage of massive haemothoraces may precipitate further bleeding as the tamponade effect is removed.

Blood loss from the chest tube, haemodynamic response to resuscitation, mechanism of injury (blunt vs. penetrating) and associated injuries (especially head) are used by cardiothoracic surgeons in determining the need for thoracotomy.

Indications for thoracotomy include:

• initial drainage exceeding >15 mL kg–1 of estimated blood volume;
• continued bleeding greater than 1–2 mL kg–1 hr–1;
• increasing bleeding;
• significant residual haemothorax post-tube drainage.

Management involves oxygenation and ventilatory support if indicated, urgent chest tube placement of the appropriate size via the lateral approach directed posteriorly and volume resuscitation. The concept of hypovolaemic resuscitation in uncontrolled traumatic haemorrhage has not been evaluated in children. However, it is important to consider early surgical intervention in any patient who is haemodynamically compromised due to haemorrhage or showing signs of ongoing bleeding.

Longer-term complications of haemothoraces include haematoma organisation with secondary lung entrapment and empyema formation. Prophylactic antibiotics are indicated when chest tubes are placed for penetrating trauma. The adult trauma literature suggests a reduced infection rate even in previously closed traumatic haemothoraces requiring drainage.

Tracheobronchial injuries10

These uncommon injuries may occur with penetrating or severe blunt trauma and have a high mortality if not recognised and treated rapidly. In blunt trauma intrathoracic airway injuries usually occur near the origin of the main stem bronchi. Typically they present with respiratory distress and signs of subcutaneous (SC) emphysema, pneumomediastinum and a tension PTX. Haemoptysis also occurs. In the case of PTX urgent chest tube placement is required and typically a large air leak will continue and there will be failure of lung expansion on CXR. At this point an airway injury is usually considered. A second chest tube should be placed and urgent cardiothoracic surgical consultation obtained. Once stabilised, a CT scan may be helpful in further injury delineation and assessing lung inflation, as massive SC emphysema can make CXR interpretation very difficult. Bronchoscopy is useful as a diagnostic modality in suspected tracheobronchial injury and operative intervention is often required.

Mediastinal injury5,9,10

Aortic transection

Aortic rupture is a rare event in young children but the incidence increases withadolescents involved in high speed MVCs. About 80% occur at the aortic isthmus just distal to the origin of the left subclavian artery. Most are rapidly fatal at the scene. Diagnosis in hospital depends on clinical suspicion based on mechanism of injury, physical signs (often absent) and CXR findings. CXR in cases of aortic rupture is usually abnormal but findings are non-specific (Table 3.3.3) and the suspicion of aortic injury on clinical or radiological grounds requires further diagnostic imaging.

Table 3.3.3 CXR signs of aortic injury

• Widened mediastinum (mediastinum to chest ratio >0.25)
• Loss or abnormal contour of aortic knob
• Depression of left mainstem bronchus
• Deviation of the trachea to the right
• Deviation of the oesophagus (NG or OG tube) to the right
• Left pleural cap
• Left haemothorax
• Upper rib fractures

NG, nasogastric; OG, orogastric.

In young children the normal thymic contour may give the impression of a widened mediastinum. Further imaging usually involves CT angiography, aortogram or transoesophageal echocardiography depending on availability, expertise and local practices. The absence of signs of dissection and mediastinal haematoma on CT angiography is used to exclude aortic injury. Occasionally, formal aortography or transoesophageal echocardiography will be performed to exclude possible aortic injury.

Management in confirmed cases is surgical. β-blockers may be commenced pre-operatively in haemodynamically stable patients to reduce vessel wall stress.

Cardiac injuries11

As with aortic injury, clinically significant cardiac injury from blunt trauma in children is uncommon and is usually associated with other intrathoracic injuries. Pericardial tamponade can certainly occur with blunt trauma, though it is more common in penetrating injuries (see below). Myocardial contusion may manifest as an arrhythmia or otherwise unexplained tachycardia and/or hypotension. Valvular injury and septal defects are also reported. Diagnosis suffers from the lack of a gold standard and the questionable clinical relevance of test results. Most of the evidence comes from adult trauma patients. A normal ECG has a high negative predictive value for the occurrence of clinically significant complications in suspected myocardial contusion. Evidence for the value of cardiac markers is lacking. Echocardiography is a very useful modality in assessing suspected clinically significant myocardial contusion such as the presence of unexplained hypotension, tachycardia or new murmurs.

In the absence of ECG abnormalities, hypotension or new murmurs, ongoing ECG monitoring is usually not required.

Commotio cordis12,13

The phenomenon of sudden cardiac arrest following a localised blow to the chest is well documented in children. In these cases autopsy fails to identify myocardial contusion, structural cardiac abnormality, conduction system or coronary artery pathology. The proposed theory is that a blow to the chest during the vulnerable phase of the electrical cycle induces ventricular fibrillation/ventricular tachycardia. Protective chest guards are recommended in at-risk sports.

Penetrating cardiac trauma14

In children this occurs predominantly in the adolescent age group. Cardiac lacerations may lead to rapid exsanguination or pericardial tamponade. Any penetrating chest or upper abdominal wound has the potential to injure the heart. Clinical signs of tamponade include tachycardia and elevation of the JVP (in the absence of hypovolaemia), with subsequent hypotension and cardiac arrest with pulseless electrical activity. The CXR is typically normal in the absence of associated mediastinal or lung injury. In trained hands and with satisfactory imaging conditions echocardiography has excellent accuracy in the detection of pericardial blood and can be done rapidly in the emergency department (ED). Management requires urgent cardiothoracic surgical involvement. A conscious patient with a perfusing blood pressure requires urgent surgery. A rapidly deteriorating patient in the ED requires needle pericardiocentesis if there is any surgical delay. Cardiac arrest with vital signs present at the scene and a short transit time to hospital or arrest in the ED is an indication for ED thoracotomy or pericardiocentesis depending on the skills of personnel available. Pericardiocentesis is performed using a long 16 or 18G over the needle cannula via the subxiphoid approach at a 35 degree angle to the skin and aiming at the left shoulder with ECG monitoring. Ultrasound control may assist where available. Aspiration of 10–20 mL may result in significant clinical improvements. The needle should be removed but the catheter should remain in place for repeat aspirations. Failure to aspirate blood does not exclude tamponade as the cannula may miss the pericardium or the pericardial blood may have clotted.

Diaphragmatic injury9,10,15

Diaphragmatic injury is another uncommon paediatric injury, but it is important nonetheless, as undiagnosed, complications eventually will arise, though this may take years. Left-sided injury is more common than right-sided in blunt trauma and associated intra-abdominal injury is common.

Upper abdominal penetrating trauma that injures intrathoracic structures (and vice versa) must also have caused diaphragmatic injury and requires repair. Diagnosis is difficult unless CXR reveals clear signs of herniated stomach or bowel or the nasogastric tube curling up into the thorax. More commonly the CXR is non-specifically abnormal with findings of an abnormal diaphragmatic contour with or without lower zone opacity. Often the diagnosis is made at laparotomy or laparoscopy for associated injuries. Barium studies are normal if bowel contents are not herniated. CT scanning may miss small tears. Magnetic resonance imaging may have a role in diagnosing these injuries. Suspected occult diaphragmatic lacerations in penetrating trauma can be investigated by laparoscopy/thoracoscopy or open operation.

Oesophageal injury5

This is essentially only seen in penetrating trauma and in these cases a high index of suspicion is required, as missed injuries cause inevitable serious morbidity and mortality. On initial CXR a finding of mediastinal air is an early clue. Over subsequent hours an evolving sepsis with pleural effusions and mediastinitis ensues. Conscious patients able to verbalise complain of chest and epigastric pain but this is difficult to interpret in the setting of other chest injuries. Suspicion of an oesophageal injury must be followed by a Gastrografin study, oesophagoscopy or both. If positive, broad-spectrum antibiotics and urgent surgery are required.

ED thoracotomy14

The only definite indication for thoracotomy in the ED is in the scenario of penetrating chest trauma with loss of vital signs shortly before arrival in the ED or during ED resuscitation, with the purpose of pericardial drainage, repairing penetrating injury to the heart or controlling bleeding from the hilum or lung. Open cardiac massage can also be performed as well as cross-clamping of the aorta. The universally poor outcome of blunt trauma patients who arrive at the ED with no vital signs/signs of life argues strongly against performing ED thoractomy in these patients. Blunt thoracic trauma patients who deteriorate in the ED despite full resuscitation may occasionally survive following ED thoracotomy but in general these very unstable patients should go to the operating theatre if possible.

Controversies

The use of intercostal catheters in small traumatic pneumothoraces is debated – especially with positive pressure ventilation. The maximum size that can safely be treated conservatively is not defined.
The role of ED thoracotomy, in low volume centres (which includes all Australasian paediatric centres), is not known.

References

1 Peclet M.H., Newman K.D., Eichelberger M.R., et al. Thoracic trauma in children: An indicator of increased mortality. J Pediatr Surg. 1990;25:961-965.

2 Black T.L., Snyder C.L., Miller J.P., et al. Significance of chest trauma in children. South Med J. 1996;89:494-496.

3 Nakayama D.K., Ramenofsky M.L., Rowe M.I. Chest injuries in children. Ann Surg. 1989;210:770-775.

4 Samarsekara S., Mikocka-Walus A., Butt W., Cameron P. Epidemiology of major paediatric chest trauma. J Paediatr Child Health. 2009;45:676-680.

5 Fleisher G.R., Ludwig S. Textbook of paediatric emergency medicine, 4th ed. Philadelphia: Lippincott Williams & Wilkins. 2000:1341-1360.

6 Garcia V.F., Gotschall C.S., Eichelberger M.R., et al. Rib fractures in children: A marker of severe trauma. J Trauma. 1990;30:695-700.

7 Bonadio W.A., Hellmich T. Post-traumatic pulmonary contusion in children. Ann Emerg Med. 1989;18:1050-1052.

8 Allen G.S., Cox C.S., Moore F.A., et al. Pulmonary contusion: Are children different? J Am Coll Surg. 1997;185:229-233.

9 Bliss D., Silen M. Paediatric thoracic trauma. Crit Care Med. 2002;30:1-13.

10 Wesson D.E. Thoracic injuries. In: O’Neill J.A., editor. Paediatric surgery. 5th ed. Mosby: St Louis; 1998:245-260.

11 Dowd M.D., Krug S. Pediatric blunt cardiac injury: Epidemiology, clinical features and diagnosis. J Trauma. 1996;40:1-12.

12 Cantor R.M., Leaming J.M. Evaluation and management of pediatric major trauma. Emerg Med Clin North Am. 1998;16:229-256.

13 Maron B.J. Blunt impact to the chest leading to sudden cardiac death from cardiac arrest during sports activities. N Engl J Med. 1995;333:337-342.

14 Polhgeers A., Ruddy R.M. An update on pediatric trauma. Emerg Med Clin North Am. 1995;12:267-287.

15 Jackimczyk K. Blunt chest trauma. Emerg Med Clin North Am. 1993;11:81-91.

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