See also Allergy and immunology, chapter 19.

The life-threatening clinical manifestations are:

• Hypotension due to vasodilatation and loss of plasma volume due to increased capillary permeability.
  
• Bronchospasm.
  
• Upper airways obstruction due to laryngeal or pharyngeal oedema.

Immediate treatment

• Vasopressor and bronchodilator therapy: give adrenaline 10 mcg/kg (0.01 mg/kg) at 0.01 mL/kg of 1 : 1000 solution by intramuscular (i.m.) injection or 0.01 mg/kg (i.e. 0.1 mL/kg of 1 : 10 000 solution) by slow i.v. injection (over 10 min). A continuous infusion (0.1–1.0 mcg/kg per min) may be required if manifestations are prolonged. Note: Do not use subcutaneous adrenaline, as absorption is less reliable.
  
• Oxygen by mask: mechanical ventilation may be required.
  
• I.v. volume expander: give 0.9% saline at 20 mL/kg. Give repeat boluses of 10–20 mL/kg until the blood pressure is restored.
  
• Bronchodilator therapy with salbutamol: continuous nebulised (0.5%) or i.v. 5 mcg/kg per min for 1 h, then 1 mcg/kg per min thereafter. Secondary therapy with a steroid, aminophylline and an antihistamine may be helpful for prolonged bronchospasm and capillary leak.
  
• Relief of upper airway obstruction: mild to moderate oedema may respond to inhalation of nebulised 1% adrenaline (1 mL per dose diluted to 4 mL) or 5 mL of nebulised 1 : 1000 solution, but intubation of the trachea may be required.
  
• Anaphylaxis can be biphasic and the patient may deteriorate again over the next few hours.
  
• All patients with anaphylaxis should be observed carefully for at least 12 h, followed up for allergen testing, provided with self-injectable adrenaline and a Medi-alert bracelet.

Allergic oedema causing acute larygeal obstruction

Treat with nebulised 1% adrenaline 1 mL per dose diluted to 4 mL, or 5 mL of 1 : 1000 solution. Refer to an intensive care specialist or anaesthetist for endotracheal intubation, or an ENT surgeon for tracheostomy.

The normal circulating blood volume is 70–80 mL/kg. A child may lose a substantial volume of blood without developing hypotension. Cardiac output and blood pressure are preserved by tachycardia and vasoconstriction, so hypotension is a late sign of blood loss.

• Control external haemorrhage by direct wound pressure, arterial vessel pressure or a tourniquet and elevation of the injured area.
  
• Administer oxygen by mask.
  
• Insert a large-bore i.v. cannula, preferably in the upper limb. Two cannulae are usually required.
  
• Withdraw blood for group and cross-match.
  
• Infuse rapidly by pressure 20 mL/kg of 0.9% saline solution. This may also be administered rapidly by syringing with the aid of a three-way tap. Titrate additional volume to the heart rate, blood pressure and other indices of perfusion. Further boluses of 10–20 mL/kg 0.9% saline solution may be given.
  
• If exsanguinating, transfuse urgently with (in order of preference):

– crossmatched blood, or

– un-crossmatched blood of the same group as the patient, or

– un-crossmatched O-negative blood.

• Warm the blood.
  
• Monitor blood pressure, heart rate, oxygenation and urine output.
  
• Measure the central venous pressure, serum calcium, serum potassium, coagulation and acid–base status if a massive transfusion is required. Calcium (10% calcium chloride 0.2 mL/kg) and fresh frozen plasma are usually needed after 1–2 blood volumes have been transfused.
  
• Investigate and surgically explore internal haemorrhage if necessary.

Hypotension is due to vasodilatation, (early) leakage of fluid from capillary beds and depression of myocardial contractility.

• Collect blood for culture, but do not delay administration of an antibiotic if a blood sample cannot be collected. If no information is available regarding the source of pathogen, give flucloxacillin 50 mg/kg (max 2 g) i.v. 4 hourly and cefotaxime 50 mg/kg (max 2 g) i.v. 6 hourly. For particular circumstances consult the Antimicrobial guidelines. For shock due to meningococcaemia, which is usually accompanied by a purpuric rash, give cefotaxime 50 mg/kg (max 2 g) i.v. 6 hourly. Give benzylpenicillin 60 mg/kg (max 3 g) i. v. / i.m. 4 hourly if cefotaxime not available.
  
• Treat shock with 0.9% saline solution, 20 mL/kg initially – further boluses of 10–20 mL/ kg may be needed.
  
• Give oxygen and monitor blood gases. Mechanical ventilation may be required.
  
• Commence infusion of an inotropic agent. Dopamine (5–20 mcg/kg per min) is preferred. Administration via a central vein is preferred but it may be given via a peripheral vein as a dilute solution (e.g. 15 mg/kg in 500 mL at 10–40 mL/h = 5–20 mcg/kg per min). Dobutamine (5–20 mcg/kg per min) may be administered into a peripheral vein.
  
• Defer lumbar puncture, if indicated, until the child has been stabilised.

There is a global hypoxic–ischaemic injury often associated with lung damage from aspiration of water and gastric contents. The differences between freshwater and saltwater drowning are not usually clinically important.

• Adequate oxygenation and ventilation are of paramount importance. Mechanical ventilation is required for severe lung involvement, circulatory arrest or loss of consciousness. Lung hypoxic–ischaemic injury is compounded by pulmonary oedema or aspiration of water or gastric contents.
  
• Decompress the stomach, which is usually distended with air and water.
  
• Support the circulation with i.v. infusion of colloid (e.g. 4% albumin) or 0.9% saline solution and infusion of an inotropic agent (e.g. dopamine 5–20 mcg/kg per min into a central vein).
  
• If signs of cerebral oedema are present (i.e. a depressed conscious state) administer mannitol 0.25–0.5 g/kg i.v. once.
  
• Correct electrolyte disturbances; hypokalaemia is common.
  
• Administer benzylpenicillin 60 mg/kg (max 3 g) i.v. 6 hourly if ventilation is required (to prevent the complication of pneumococcal pneumonia).
  
• If CPR is required, prevent hyperthermia and induce controlled hypothermia (33–34 °C) for 72 h for cerebral protection.

The most common cause is laryngotracheobronchitis (croup) and occasional causes are epiglottitis, an inhaled foreign body, allergic oedema and trauma. The hallmark of obstruction is stridor, which when accompanied by a barking cough suggests croup, or when accompanied by dysphagia/drooling suggests epiglottitis. Severe obstruction stimulates forceful diaphragmatic contraction that results in a retraction of the rib cage, tracheal tug and abdominal protrusion on inspiration. Cyanosis and irregular respiratory effort are terminal signs.

Epiglottitis

See also Respiratory conditions, chapter 36, p. 513.

• Complete obstruction may occur in just a few hours. In general, tracheal intubation under anaesthesia is required. Arrange promptly.
  
• Keep the child as calm as possible in a seated position and administer oxygen by mask.
  
• If complete obstruction is imminent, summon immediate help from an intensivist or anaesthetist. If inexperienced, do not attempt intubation unless the child becomes comatosed. Intubate orally initially with a relatively small endotracheal tube. It may be hard to see the larynx because of secretions in the pharynx and the swollen epiglottis. Be prepared to aspirate the pharynx with a Yankauer sucker. Cricoid pressure is very helpful to visualise the vocal cords.
  
• If intubation proves to be impossible, attempt to ventilate with bag–valve–mask; a good technique may achieve adequate oxygenation and ventilation. If ventilation is impossible, perform cricothyrotomy or tracheostomy (see below).
  
• Antibiotic therapy: Ceftriaxone 100 mg/kg (max 2 g) i.v. followed by 50 mg/kg (max 2 g) 24 h later.

Croup

See also Respiratory conditions, chapter 36, p. 515.

• Avoid any examination that may distress the child.
  
• In severe obstruction, give an inhalation of nebulised 1% adrenaline 1 mL per dose diluted to 4 mL, or 5 mL of 1 : 1000 solution to obtain temporary relief.
  
• Give corticosteroid i.m/i.v. (e.g. dexamethasone 0.6 mg/kg).
  
• Obtain intensive care or anaesthetic help with a view to endotracheal intubation. If this is not available, intubate when the child is going into respiratory failure. Use an introducing stylet in an endotracheal tube of size 0.5–1 mm smaller than usually calculated by age in years; i.e. (age/4 + 4 mm).
  
• Children admitted to a general paediatric ward should not be administered oxygen. Decreased saturations are a marker of obstruction requiring medical review and often further adrenaline. Giving oxygen masks this.

Aspirated foreign body

See also Respiratory conditions, chapter 36, p. 518.

• Give first aid (back slaps, chest thrusts) if obstruction occurs, otherwise allow the child to cough. Do not instrument the airways if the child is coping, but summon an anaesthetist and ENT surgeon. Give oxygen.
  
• If complete obstruction occurs, attempt removal of an impacted laryngeal foreign body with forceps – if this is unsuccessful, perform cricothyrotomy or tracheostomy (see below).
  
• If respiratory failure is due to a foreign body lodged in the lower trachea or bronchi, attempt ventilation via an endotracheal tube while organising endoscopic removal.

Emergency relief of a totally obstructed upper airway

• Adequate oxygenation (but not normal ventilation) can be obtained by inserting a 14-gauge i.v. cannula percutaneously into the trachea via the cricothyroid membrane (which lies between the thyroid and cricoid cartilage); the patient should be lying straight, with the cannula in the midline and angled towards the feet. Remove the needle of the i.v. cannula; connect the cannula to a resuscitator or a bagging circuit using a connector from a 3.0 mm endotracheal tube. Oxygenate with sustained 100% oxygen inspirations. Alternatively, connect the cannula to the compressed wall oxygen supply via a three-way i.v. tap (to allow expiration) and a length of plastic tubing. A length of plastic tubing that has a side hole cut may also be used to allow expiration. Aid intermittent expiration by lateral chest compression.
  
• Alternatively, perform cricothyrotomy. Identify and maintain stabilisation of the thyroid– cricoid region with one hand. Incise the skin over the cricothyroid membrane. Bluntly dissect into the trachea with forceps in the midline or incise vertically with scalpel. Insert a small tracheostomy or endotracheal tube.
  
• Alternatively, perform percutaneous mini-tracheostomy.

See also Respiratory conditions, chapter 33.

Critical asthma

Children unresponsive to intermittent inhalation of salbutamol should receive:

• Continuous inhalation of undiluted 0.5% salbutamol solution nebulised with oxygen.
  
• Methylprednisolone 1 mg/kg i.v. (max 50 mg) 6 hourly.
  
• Nebulised ipratropium may be added as 250 mcg/dose diluted to 2–3 mL every 20 min × 3 and then 4–6 hourly (beware anticholinergic effects).
  
• I.v. salbutamol load 5 mcg/kg per min for 60 min followed by infusion 1–2 mcg/kg per min (beware hypokalaemia). Discuss with nearest paediatric ICU or retrieval service at this stage.
  
• Aminophylline (subject to prior theophylline use and serum level) 10 mg/kg (max. 500 mg) i.v. over 1 h. This can be followed by an infusion: 1.1 mg/kg per hour (age 1–9 years) or 0.7 mg/kg per hour (10 years to adult) or 6 hourly doses (each over an hour). Check level following loading dose.
  
• MgSO4 0.1 mmol/kg infused over 30 min.
  
• Refractory critical asthma – manage in ICU.

See also Neurologic conditions, chapter 33, p. 453.