A practical approach to paediatric emergencies in the radiology department

Cardiac arrest in children is seldom a primary event, but is usually preceded by a period of respiratory or cardiovascular insufficiency leading to hypoxaemia and shock [2]. During this phase considerable organ damage, in particular to the kidneys, liver, gut and brain, can occur before the circulation fails completely (Fig. 1). The prognosis for children following a cardiac arrest is extremely poor, but the prodromal phase is usually detectable clinically, so the emphasis of paediatric emergency medicine is on the early recognition of and intervention in respiratory impairment and shock [3].

A specific pathological diagnosis of the cause of impairment of the child’s vital functions is less important to effective intervention than a global physiological appreciation of the mechanisms involved. To simplify and accelerate decision-making in an emergency, the ABCD (Airway, Breathing, Circulation, Disability) approach is widely adopted for both diagnosis and management. In contrast to adults, the majority of acute life-threatening events in children have a respiratory cause [2]. Use of the ABCD approach prioritizes the actions to be taken in a medical emergency in a logical order such that the flow of adequately oxygenated blood to the vital organs is maintained or restored.

Recognition of deranged vital functions is essential to effective intervention. Using the ABCD approach incorporated into a rapid clinical examination it is possible to assess the condition of the child in less than a minute to confirm or refute a suspicion of respiratory insufficiency or shock (Table 1).

Using a few simple interventions it is possible to prevent further deterioration in the vital functions of a child with incipient respiratory or circulatory failure until help arrives. A detailed discussion of specific therapy of the underlying conditions is outside the scope of this article, which therefore focuses on the general principles involved (Fig. 3). For the calculation of drug and fluid doses the weight of a child under 10 years of age can be estimated using the formula 8 + (age × 2), although this formula may need to be adjusted for different populations [3, 9, 10].

The essence of the initial management of all acute life-threatening disorders in children, including neurological conditions, is to improve the provision of oxygenated blood to the tissues and this can be approached logically using the ABC system. Therefore, severely ill children should be given a high concentration of oxygen, for which there are few contraindications, although the lowest oxygen concentration necessary to maintain an adequate oxygen saturation should be used in premature neonates, those with duct-dependent congenital heart disease and in heart failure with a large left-to-right shunt.

The first step is to open the upper airway using an appropriate manual manoeuvre such as the jaw-thrust, in which the lower jaw is lifted anteriorly with the fingers behind the mandibular angle. This lifts the tongue from the posterior pharyngeal wall. With a little practice the jaw thrust can be maintained with one hand leaving the other free for manual ventilation if needed. A simple device such as a Guedel airway may be helpful in maintaining airway patency and, for those with the necessary experience, a laryngeal mask is often superior. However, neither device will be tolerated by the child with intact pharyngeal reflexes in whom their use may precipitate vomiting and aspiration [11]. Opening the airway and delivering supplementary oxygen may be all that is required in some circumstances such as airway obstruction due to sedative overdose.

If the child is breathing inadequately despite a patent upper airway, artificial ventilation should be started using a suitable system and 100% oxygen. A self-inflating bag is probably the easiest system for the infrequent user, but care should be taken to ensure that this is properly assembled by testing its functionality before use. Such devices need to be attached to an oxygen reservoir if a high oxygen concentration is to be achieved. The adequacy of artificial ventilation is assessed by visual inspection of thoracic expansion and the response of the vital signs. An increase in oxygen saturation is a reassuring sign of improving oxygenation, but gives little information as to the adequacy of ventilation, for which end-tidal carbon dioxide measurement is more reliable.

Supplementary oxygen is also indicated in impending or established shock, which also requires intravascular fluids, inotropes and vasoactive agents in varying proportions according to the type of shock. Hypovolaemic shock, which may occur in dehydration from, for instance, abdominal emergencies, or following trauma, requires replacement fluid in aliquots of 20 ml/kg followed by reassessment of the circulation. Septic shock may require very large quantities of fluid replacement, inotropes and vasoconstrictors. Cardiogenic shock generally requires inotropic support, often in combination with agents to reduce the afterload, such as phosphodiesterase inhibitors, and may respond to a single dose of 10 ml/kg of intravenous fluid, but excessive fluid administration should be avoided. The management of anaphylactic shock is discussed below.

The treatment of all types of shock requires vascular access in the form of a peripheral venous cannula, a central venous catheter or an intraosseous device through which drugs and fluids are administered via the bone marrow cavity. Insertion of an intraosseous device can be easily learned and is safe and may even be faster to site than an intravenous cannula [12]. All drugs and intravenous fluids likely to be needed in an emergency can be administered intraosseously and blood concentrations are known to be similar to those following central venous infusion, provided the drugs are properly flushed [13, 14]. A drill for the insertion of an intraosseous device has recently been introduced and shows much promise as an even faster and more effective method of gaining vascular access in children [15].

Although the essence of the management of paediatric emergencies is the early recognition and treatment of potential respiratory failure and shock to prevent cardiopulmonary arrest, radiologists should also be aware of the current resuscitation guidelines for children, which are shown in Fig. 4. The relative infrequency and inhomogeneous nature of paediatric resuscitation means that good evidence of effect from clinical studies is hard to come by and many aspects of the guidelines have been decided by extrapolation from adult studies. For ease of teaching and retention the guidelines have been kept as simple as possible. As a consequence, guidelines for basic and advanced life support of children differ little from those for adults.

As respiratory causes are the most common causes of cardiopulmonary arrest, paediatric life support begins with opening of the airway and administration of five ventilations (rescue breaths) preferably with 100% oxygen. In the absence of sings of life, such as movement, coughing or reasonable attempts to breathe (but not agonal gasping), cardiac massage should be started by compressing the lower third of the sternum to one third of the thoracic depth at a rate of 100 compressions per minute. The best way to achieve this depends upon the child’s age. The most effective technique in infants is the method attributed to Thaler in which the thorax is encircled with both hands while the sternum is compressed with the thumbs one finger-breath above the xiphoid process (Fig. 5) [16]. In older children the lower third of the sternum is compressed with one or two hands according to the size of the child and of the rescuer. If the child is not intubated, compressions are briefly interrupted every 15 compressions to allow for two ventilations. However, higher ratios of compressions to ventilations may produce better coronary flow and the adult ratio of 30:2 is also advocated as an option for lone rescuers [13, 17]. Continuous thorax compressions are used in intubated children.

Paediatric advanced life support is aimed at maintaining adequate blood flow to vital organs while the cause is detected and treated. Cardiac arrhythmias are a less frequent cause of circulatory arrest than in adults. Nonetheless, it is important to exclude ventricular fibrillation by ECG monitoring as soon as possible, as the effectiveness of defibrillation decreases rapidly with time [18]. The recommended energy of manual defibrillation in children is 4 J/kg regardless of the type of defibrillator used. Children older than 8 years can be safely defibrillated according to the adult recommendations (150 J biphasic). Automatic external defibrillators can be safely used in children older than 1 year, and probably also in infants [19, 20].

The ECG of most children with a circulatory arrest will show either asystole or pulseless electrical activity that may take many forms from normal sinus rhythm to a wide complex “dying heart” rhythm. In both cases, it is important to maintain the artificial circulation with good oxygenation and thorax compressions and vasoconstriction with adrenaline 10 µg/kg every 3–5 min. Higher doses of adrenaline are no longer considered helpful [21]. At the same time the cause of the arrest should be actively sought. A widely used mnemonic for the potential causes of circulatory arrest is the “four H’s and four T’s” (Fig. 4), which can be applied to both children and adults, although the relative frequency of the underlying mechanism varies with age. In children, hypoxia is relatively more frequent and thromboembolism rare. Tension pneumothorax and cardiac tamponade, which may complicate invasive procedures, show similar clinical signs in adults and children and confirmation of the diagnosis radiographically or by echocardiography should present no problem in the radiology department. Treatment is by percutaneous drainage. In the case of a tension pneumothorax, immediate percutaneous thoracocentesis in the midclavicular line of the second intercostal space with a large intravenous cannula should be performed, followed by insertion of a thorax drain. Tension pneumoperitoneum, which may complicate reduction of intussusception, presents with severe respiratory embarrassment, and is also treated by immediate percutaneous drainage followed by surgical exploration [22].

As soon as the appropriate equipment and expertise is available, a child with a circulatory arrest should be intubated to guarantee the airway and allow optimal ventilation. Early intubation by inexperienced personnel has been show to not benefit the patient, and may be detrimental [23]. Therefore, bag-and-mask ventilation should be continued initially. Following intubation, thoracic compressions should be continuous at a rate of 100/minute. The recommended initial ventilation rate is 12–20/min depending on the age of the child, but may need to be adjusted according to blood gas analysis.

Serious dysrhythmias in children are rare, but occur more commonly than complete circulatory arrest, and may present as otherwise unexplained shock particularly in unmonitored infants. Supraventricular tachycardia is the most frequent and usually responds to a rapid intravenous bolus of adenosine 100 μ/kg, or to a second dose of 200 μg/kg. Failure to respond may be an indication for synchronous cardioversion with 1–2 J/kg, preferably under anaesthesia. Ventricular tachycardia may be secondary to electrolyte disorders or intoxication and is treated initially with an intravenous infusion of amiodarone 5 mg/kg, or by cardioversion as for supraventricular tachycardia. Vagal bradycardia is often transitory, but may require intravenous atropine 20 μg/kg (minimum dose 100 μg).

Life-threatening anaphylactic reactions are an uncommon but ever-present potential complication of the administration of contrast medium [24]. Severe anaphylaxis presents with the sudden onset of upper airway and respiratory symptoms (stridor, wheeze, respiratory embarrassment), shock (initially due to vasodilatation and fluid sequestration) and skin and/or mucosal changes. Circulatory arrest may follow. The onset may be delayed by 5–10 min following intravenous injection of the antigen [25]. If treated promptly and correctly, the prognosis is good; however, overtreatment of minor reactions and vasovagal episodes with adrenaline is believed to be associated with significant morbidity [26, 27]. A skin reaction on its own does not constitute an anaphylactic reaction.

If conscious, the child should be allowed to adopt the most comfortable position. Raising the legs may improve venous return, cardiac output and blood pressure in shock, but sitting upright may improve breathing if airway obstruction or wheeze is predominant. Immediate treatment of a severe reaction consists of high-flow oxygen, intramuscular adrenaline, vascular access and fluid in aliquots of 20 ml/kg. Intravenous adrenaline should only be given by those experienced in its use or if circulatory arrest occurs. The intramuscular dose of adrenaline is 10 μg/kg, repeated at intervals of 5 min according to the response, but recent British guidelines recommend a simplified dosage schema as shown in Fig. 6 [28]. Adrenaline helps to maintain the circulation by vasoconstriction and a positive inotropic effect, and is a bronchodilator. It may also help reduce the release of histamine and other mediators [29]. Large quantities of fluids may be needed. Patients should be monitored with ECG, pulse oximetry and noninvasive blood pressure monitoring. Antihistamines and steroids have a secondary role, but the latter may be useful if bronchospasm is prominent, in which case bronchodilator therapy, such as salbutamol, should also be given [30].

Cardiac arrest in the context of anaphylaxis is treated along standard lines as described above. Following the reaction all patients should be investigated to confirm the diagnosis and trigger agent [28].

Convulsions may occur during radiological examinations due to fever, head injury or other causes. Convulsions increase the cerebral oxygen requirement and that of other organs while reducing the effectiveness of ventilation. Cerebral hypoxia occurs when compensation mechanisms fail and the immediate goal of therapy is to stop the convulsion as soon as possible whilst maintaining cerebral oxygenation [31].

Immediate treatment (Fig. 7) consists of maintaining a patent upper airway, high-flow oxygen, and an anticonvulsant of which the benzodiazepines are the most commonly used. If the child has no vascular access, rectal diazepam 0.5 mg/kg or buccal midazolam 0.5 mg/kg may be given. The intravenous route should be used if available. The intravenous dose of diazepam is 0.25 mg/kg, but lorazepam 0.1 mg/kg may be equally effective and cause less respiratory depression. Blood glucose should be measured as hypoglycaemia is a potentially serious and easily treatable cause of convulsions particularly in small children [32]. Hypoglycaemia can be reversed with intravenous glucose 0.25–0.5 g/kg (equivalent to 2.5–5 ml 10% glucose per kilogram).

Guidelines have been produced for the drugs, equipment and monitoring that should be available in the radiology department for use in emergencies and during procedures under sedation [33, 34]. This equipment should be appropriate to the age of the patients attending the department and should be checked regularly. All staff should be aware of its location and the local system of activating the resuscitation team for children.

The general level of knowledge of the treatment of emergency situations among radiologists is believed to be amenable to improvement and the need for further training has been expressed [35, 36]. There is ample evidence that structured resuscitation training of health-care professionals can lead to an improvement in knowledge and skills, but retention times are short especially when these skills are rarely used [37‐39]. Retraining at intervals and mock emergency exercises can improve retention [40]. Radiology departments should consider their local educational needs in respect of paediatric emergencies and take steps to rectify these.