Page 716 - ACCCN's Critical Care Nursing

Paediatric Considerations in Critical Care 693

perfusion (V/Q) mismatch due to lower airway obstruc- unresponsive to inhaled bronchodilators and steroids. It
tion, in addition to hypoventilation, hypercarbia, and is a bronchodilator, improving diaphragmatic contractil-
pulmonary vasoconstriction related to acidosis. Hypoxae- ity and a central respiratory stimulant. However, the
mia can result in further bronchoconstriction, hypoten- narrow therapeutic window and side effects of induced
sion, systemically-reduced oxygen availability, increased nausea and/or vomiting represent a non-negligible risk
myocardial oxygen consumption and neurological symp- of complication, thus its use should be limited to manag-
toms such as agitation, confusion or decreased level of ing asthma not responsive to other agents. 138
consciousness. Bronchodilators may worsen hypoxaemia Ventilation may be required when there is profound hy-
through worsening V/Q mismatch or bronchoconstric- poxaemia, severe muscle fatigue or decreased level of
tion, due to the hyperosmolarity of the nebulised solu- consciousness. 130,139 However, as asthmatic children are
tion. In addition, rapid changes to the compliance of the at higher risk of complications such as barotrauma and
airways together with hyperexpanded lungs may result in air trapping, there is a higher risk of death associated
airway collapse.
with ventilation in this group of patients. Non-invasive
Oxygen delivery is achieved by high-flow oxygen mask positive pressure ventilation (NPPV) is the first choice,
with a reservoir bag. All nebuliser therapy should be with some evidence that it rapidly corrects gas exchange
oxygen-driven. However, if hypoxaemia persists despite abnormalities and assists with respiratory muscle
maximal bronchodilator therapy and oxygen administra- fatigue. 140-142 The contraindications for NPPV include
tion, then mask continuous positive airway pressure cardiac/respiratory arrest, severe encephalopathy, haemo-
(CPAP) may be considered. dynamic instability, facial surgery/deformity, high risk for
aspiration, nonrespiratory organ failure, severe upper
β 2 -agonists, anticholinergics and steroids form the foun- gastrointestinal bleeding, unstable arrhythmia and upper
dation of acute severe asthma management, but for chil- airway obstruction. 142
dren over 40 kg and those who have reached puberty it
may be more appropriate to administer IV adrenaline. Intubation may be necessary when signs of deterioration
β 2 -agonists act by relaxing bronchial smooth muscle, are present, such as elevated carbon dioxide levels,
improving mucociliary transport and inhibiting media- exhaustion, alteration of mental status, haemodynamic
tor release. In severe to life-threatening asthma, nebu- instability and refractory hypoxaemia. 142 Because of high
lised salbutamol is preferred. 134 Inhaled salbutamol airway pressures, a cuffed endotracheal tube should
combined with magnesium sulfate improves pulmonary be used.
function. 135 Adverse effects of β 2 -agonists’ administra- Children with acute asthma may have a raised metabolic
tion include hypokalaemia, tachycardia, tremors, agita- rate and increased insensible losses, together with reduced
tion and hyperglycaemia. Mild lactic acidosis may also oral intake. With increased intrathoracic pressure due to
occur. Intravenous salbutamol infusion should be con- air trapping, even mild dehydration may compromise
sidered when there is severe, life-threatening asthma cardiac output. Therefore, adequate fluid replacement is
refractory to inhaled treatment. Inhaled salbutamol may necessary. In addition, pulmonary secretions will thicken
be discontinued once IV infusion has commenced, but and plug the airways if fluid intake is inadequate. Main-
should be reestablished before ceasing the infusion. In tenance fluids should be provided until the child’s con-
acute severe episodes, salbutamol is usually given every dition and oral intake improve. 143
20 minutes; if there is little response, continuous nebu-
liser therapy may be required. In this instance, a feeding
tube is inserted into the nebuliser and the chamber NURSING THE VENTILATED CHILD
replenished as it empties. Anticholinergics, in combina- Principles of mechanical ventilation were covered in
tion with β 2 -agonists, improve lung function by aug- Chapter 15. Issues such as gastric decompression, ade-
menting the action of β 2 -agonists, blocking irritant quate analgesia and sedation and undertaking steps to
receptors and bronchodilation of larger airways. 136 prevent accidental extubation are similar to those for
Corticosteroids decrease airway inflammation, enhancing adults. Specific considerations for ventilating infants and
the β 2 -agonists’ effects, and reduce mucus production. children include:
Oral and intravenous methods of administration are l Most children are oxygenated before, during and after
similarly efficacious. The effects of systemic steroids are suctioning with 100% O 2 . 144 The child’s clinical status
apparent within 3–4 hours of administration, with is monitored throughout the procedure.
maximal benefit achieved within 6–12 hours. There is l Heated humidification is preferred in children as they
little evidence to support giving inhaled steroids during have limited respiratory reserve and are prone to
an acute episode. 137 airway blockage. 145,146
Magnesium sulphate promotes smo3oth muscle relax- l Endotracheal suctioning does not require normal
147-149
ation by inhibiting uptake of calcium. Intravenous mag- saline instillations.
nesium sulfate has demonstrated efficacy in acute severe l To prevent iatrogenic atelectasis, the suction catheter
asthma and inhaled magnesium sulphate combined with size should be less than or equal to two-thirds the
a β 2 -agonist results in improved pulmonary function. 135 internal diameter of the ETT. Suction pressure should
be limited to −60 mmHg (−8 kPa) for infants, and
Aminophylline has shown some benefit in regards to up to −200 mmHg (−27 kPa) for adolescents. A
improved lung function in severe asthma that is suction regulator is useful to monitor the amount of