Shock in Pediatric

Shock is most simply conceptualised as failure of the circulation to provide adequate delivery of oxygen and essential nutrients to the tissues to ensure normal cell respiration. The process leading to this state may be single or multifactorial. In the management of sick and injured children, the emphasis lies in swift recognition of shock followed by rapid assessment of the nature of the circulatory failure. The latter is essential because avoidance of significant morbidity and mortality relies on the clinician’s ability to determine the origin(s) of the shock accurately and initiate appropriate and specific management.

At a cellular level inadequate oxygen delivery leads to lactic acid formation and the development of metabolic acidosis. Up to a point the body compensates for this by redistributing blood flow away from non-essential tissues (e.g. mesenteric circulation, skin) to the vital organs (e.g. brain and heart). This state of compensated shock is completed by increased extraction of oxygen from the blood by these essential organs to maintain oxygen delivery. Uncompensated shock develops when despite these mechanisms the pathological insult makes it impossible for the body’s vital organs to overcome the inadequacy of oxygen delivery. Untreated, uncompensated shock will inevitably lead to a spiralling deterioration. An inflammatory cascade ensues at the endothelium causing cellular tissue damage. If prolonged, this damage becomes irreversible and indeed restoration of adequate circulation at this stage may lead to reperfusion injury, itself exacerbating the damage. Multi-organ failure will follow, which in many cases will be unrecoverable. However, compensated and early, uncompensated shock are treatable and so this chapter focuses on the clinician’s recognition, assessment and initial management of shock in the Pediatric Emergency Department.

Heart Condition During Shock

Shock can be thought of in terms of three key elements that affect the heart’s ability to provide an adequate circulation, namely preload, contractility and afterload.

Preload

Preload refers to the degree of tension placed upon the cardiac muscle as it begins to contract. It is usually considered to be the end-diastolic pressure at the completion of ventricular filling. A sufficient degree of stretch to the myocardium is required to produce a level of contraction as governed by the Frank-Starling mechanism. This stretch is produced by venous return, itself inherently linked to actual circulating volume. A fall in circulating volume will reduce venous return, myocardial stretch, force of myocardial contraction and cardiac output.

Contractility

The force generated during ventricular contraction defines ventricular contractility. Contractility is maximised in a neutral homeostatic environment when myocardial oxygen delivery is adequate, acidosis absent, electrolytes in balance, etc. Improvement in contractility increases cardiac output through improved stroke volume.

Afterload

Afterload may be thought of as the resistance against the heart as it exerts its force during contraction. It is actually the pressure created in the artery leading from the ventricle during ventricular systole. Whilst it is true that too high an afterload would result in a reduction in the output by the ventricle, too low an afterload itself poses significant problems since adequate organ perfusion relies on a finely balanced relationship between preload, contractility and afterload.

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Drowning Resuscitation Management in Pediatric

Management

Treatment of the victim of near-drowning can be attempted even before rescue from the water. Having said this, basic life support is difficult unless the rescuer has a firm foothold. Rescuers must always make a safe approach, otherwise further unnecessary deaths may occur.

Once on dry land the child’s airway should be opened and cleared but attempts at emptying the lungs of water are time wasting and fiitile. Fluid filled lungs have reduced compliance and so require higher inflation pressures. Resuscitation follows standard guidelines and most survivors will usually start to breathe after about 5 minutes.

The stomach is often full of water and vomiting often follows successful resuscitation attempts. Stomach decompression and intubation guards against this and both should be achieved once resuscitation has got underway. Once the child has been intubated, continuous positive airways pressure (CPAP) and positive end expiratory pressure (PEEP) are useful in ventilating stiff lungs.

Near-drowning can be complicated by a number of other factors, which must be borne in mind during resuscitation attempts. Many drowning incidents result from children falling or diving into water. In these circumstances the child could also have been injured and the rescuer should assume this until it can be ruled out. Particularly when there has been a diving accident in shallow water, there is significant risk of a cervical spine injury and the neck must be adequately immobilized until this possibility can be excluded.

The large surface area: volume ratio of children means that even during warm weather hypothermia is a common feature of near-drowning. A core temperature should be determined at an early stage during resuscitation using a low reading thermometer.

Hypothermia is a mixed blessing. Although its presence hampers resuscitation attempts, rapid cooling slows the metabolic rate and protects the vital organs. Children have survived long periods of submersion in cold water and resuscitation attempts should be equally prolonged. Survival has been recorded in children after an hour following submersion in cold water. Cardiac arrhythmias are frequently seen at low body temperatures, which also make them all the more difficult to treat. Ventricular fibrillation is often refractory at core temperatures below 30°C. Resuscitation should not be abandoned until the child has been rewarmed to at least 33°C. A child should not be declared dead until it is ‘warm and dead’.

Rewarming

The techniques used to rewarm a child depend on the degree of hypothermia. Methods are divided into external and core rewarming but must not hamper CPR.

External rewarming alone is usually adequate where core temperature is more than 32° C. Below 32°C, core warming is necessary. The means used depend on the skills of the rescuers and the facilities available

Means of external rewarming, temperature >32°C

• Remove wet clothing

• Dry child

• Wrap in warmed blankets

• Use radiant heat lamp

Means of core rewarming, temperature <32°C

• Infusion of warm intravenous fluids (at 43°C)

• Ventilation with warm gases (at 43°C)

• Instillation of warm fluids into body cavities (at 43°C)*

• Cardiac bypass

*Instillation of warm fluids into body cavities is used by some, but thought to

confer no advantage to others.

Indicators of outcome

Abandoning resuscitating is always a difficult decision and should ideally be made by a senior doctor. As already mentioned, despite an initially poor outlook, children have still survived. A number of factors may help when coming to a decision. The majority of successful resuscitations occur in children who have had submersion times of less than 10

minutes

Indicators of good outcome

• Submersion for <10 minutes

• Submersion in cold water

• Initial core temperature below 33°C preserves vital organ (especially brain)

function

• Initial spontaneous breath in first few minutes

Indicators of poor outcome

• No spontaneous respiratory attempt within 40 minutes

• Arterial pO2 less than 8.0 kPa (60 mmHg) despite resuscitation

• Blood pH below 7.0 despite resuscitation

• Persisting coma

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Drowning Case in Pediatric

Definition

Drowning is defined as death by asphyxiation following submersion in a fluid, which is usually water. During the initial resuscitation it does not seem to make any difference whether this is fresh or salt water. Near-drowning occurs when the victim recovers, however briefly, following submersion.

Epidemiology

Bodies of water act as a strong draw for children and are a favored play area. Every year hundreds of children drown and this is a significant cause of death particularly in the under 4–year-olds who are often oblivious to the potential dangers. Carers should be ever mindful of this and should never leave children unsupervised especially if they suffer with epilepsy. Whether it be the garden pond or the unattended bathtub, they are all potential death traps. Children should be encouraged to learn to swim from an early age.

Pathophysiology

In drowning accidents, the primary event is a respiratory arrest eventually leading to a secondary cardiac arrest. A child submerged in water will initially hold their breath and their heart rate slows as part of the diving reflex. If this process continues, hypoxia develops and the child then becomes tachycardic. Eventually the child will take a breath and inhale water, which on contact with the glottis results in laryngospasm and secondary apnoea. In about 10% of cases no water actually enters the lungs in what is known as ‘dry drowning’. In the remaining cases, secondary apnoea is followed by the disappearance of laryngeal spasm and the development of involuntary respiration. Water and debris are then drawn down into the lungs. The child becomes progressively more hypoxic and acidotic, with a terminal bradycardia or arrhythmia acting as the prelude to eventual cardiac arrest.

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