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70 Intensive Care

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and the tachypnoea that results may be a useful clinical marker. should be initiated simultaneously, and neither should delay the other.
It is important to remember that children have robust compensatory In patients with suspected or known cardiomyopathy, clinicians must
mechanisms, and blood pressure may be preserved even in moderate be cautious with aggressive fluid resuscitation because overdistention
circulatory insufficiency. A fall in blood pressure is a late ominous sign of a poorly functioning myocardium is likely to cause the patient to
and defines decompensated shock. Normal cardiovascular parameters deteriorate. In these patients, it is often advisable to give smaller fluid
in children are given in Table 12.3. boluses and assess their effects on an ongoing basis.
Patients with poor physiological reserve as well as those who
Table 12.3: Normal paediatric cardiovascular parameters.
do not respond to fluid resuscitation may benefit from invasive
Age (years) Heart rate (beats per minute) Mean blood pressure haemodynamic monitoring to more accurately titrate their fluid and
(mm Hg) inotropic therapies. 28,29,35–44
Neonate 100–180 40–60 In evaluating the cardiovascular system, it is important to confirm sinus
1 100–200 50–100 rhythm on an ECG by establishing that every QRS complex is preceded
by a P wave and that every P wave is followed by a QRS complex. More
2 80–160 50–100
definitive assessment with cardiac ultrasound is helpful but not often
5 80–150 60–90
available in the acute situation. Arrhythmias are uncommon in critically ill
10 60–120 60–90 children without structural heart disease, and sinus tachycardia is commonly
15 50–120 65–95 present. In the presence of tachycardia that persists when measures such as
fever, hypovolaemia, anxiety, and pain are controlled. Tachyarrhythmias
such as supraventricular tachycardia (SVT), atrial fibrillation, and ventricular
Cardiac output depends on the following factors: tachycardia must be considered.
45
• Preload: Affected by circulating blood volume and effective delivery When measures such as fluid therapy and maintaining sinus rhythm
to the heart do not produce an adequate cardiac output, the circulation may be
supported further by using vasoactive drugs to increase cardiac inotropy
• Afterload: Systolic blood pressure and vascular tone
and chronotropy and/or vasoconstrict the peripheral vascular system.
• Inotropic state: Cardiac contractility Invasive pressure monitoring of central venous or arterial pressure,
where available, may provide cardiovascular information to further
• Chronotropy: Heart rate as well as rhythm
guide volume and pharmacological support. First-line vasoactive drugs
commonly used in the intensive care environment include dopamine
and adrenaline, both of which increase heart rate and contractility as
In supporting circulation, the goal is to optimise cardiac output. well as increasing systemic vascular resistance to varying degrees that
The most common clinical situation resulting in shock is hypovo- generally favour increased cardiac output. Noradrenaline is primarily a
laemia secondary to dehydration or blood loss. vasoconstrictor, and its use is limited to the less common situations in
which vasodilatation is present, such as in the older child with sepsis
or following cardiac surgery when an increase in systemic vascular
In surgical pre- and postoperative patients, hypovolaemia may be resistance is desirable. Milrinone, a phosphodiesterase inhibitor, is
exacerbated by distributive shock due to losses into third spaces as a increasingly used for inotropic support, especially following cardiac
result of increased capillary permeability. It is therefore of the utmost surgery when diastolic function in addition to systolic function may
importance to restore adequate intravascular volume promptly by using be impaired. Most patients will respond to a simple approach using
isotonic crystalloid or colloid. If there has been significant haemorrhage, a single inotropic agent. Detailed and repeated clinical examination,
packed red blood cells should be considered. It is essential to rule out haemodynamic monitoring and—if available—cardiac imaging enables
a cardiogenic cause of shock to avoid excessive fluid administration vasoactive support with one or more agents tailored according to the
and overloading a compromised heart. This is usually distinguishable patient’s individual requirements. 46–49
by clinical examination to rule out signs of heart failure, such as Specific Organ System Dysfunction
cardiomegaly or hepatomegaly, as well as with electrocardiogram Neurology
(ECG) monitoring and chest x-ray, which may demonstrate congestive
heart failure or pulmonary oedema and an increased heart shadow. In Acute neurological abnormality may result from a primary disorder of the
children, distention of neck veins is a less reliable sign. nervous system or from the consequences of severe illness in other organ
Fluid resuscitation in an attempt to restore intravascular volume systems. Children with respiratory or cardiovascular compromise are often
is best initiated by using boluses of 20 ml/kg crystalloid or colloid hypoxic with varying degrees of impairment of their levels of conscious-
solutions, titrated to clinical markers of cardiac output (heart rate, urine ness. This may range from irritability and lethargy to seizures or coma.
output, capillary refill, and level of consciousness). Numerous clinical Seriously ill children are often hypotonic but may exhibit more worrying
trials have attempted to determine the optimal fluid in paediatric signs of abnormal posturing and eventually respiratory arrest. Primary neu-
resuscitation. The choice of fluid is controversial, but because no clear rological disease, such as acute meningitis or encephalitis, trauma, a mass
benefit has been demonstrated for crystalloid over colloid, the choice lesion, or intoxication may present with a similar spectrum of nonspecific
must be dictated by availability as well as local policy in the acute abnormalities. In the early stages of assessment, it is important to stabilise
situation. 30–34 The femoral vein is frequently used to provide central airway, breathing, and circulation, as previously noted, to ensure optimal
venous access, enabling administration of vasoactive drugs, parenteral oxygenation of the brain, regardless of aetiology.
nutrition and drugs in higher concentration than would be tolerated in a Causes of decreased level of consciousness include hypoxia; hypotension
peripheral venous cannula. or shock; infection; metabolic disturbances (e.g., hypoglycaemia); toxins or
Large fluid deficits typically exist in sepsis, and initial volume drugs; trauma, especially head injury, including nonaccidental injury; and
resuscitation usually requires 40–60 ml/kg, but may be as much as 200 intracerebral haemorrhage.
ml/kg. It is important to note that at the same time as providing ongoing Once oxygenation and appropriate circulation are restored, the diagnosis
fluid resuscitation, respiratory support in the form of intubation and may be clarified with a more detailed history and physical examination to
ventilation may be required. Airway and respiratory support, if needed, elicit specific signs. Radiological imaging, such as computed tomography