Page 715 - ACCCN's Critical Care Nursing

692 S P E C I A LT Y P R A C T I C E I N C R I T I C A L C A R E

Asthma increasing, 126 is higher in boys 129,130 and in urban areas,
Asthma is a disease of the lower respiratory tract charac- but its mortality has declined over the past two decades,
126
terised by mucosal and immune system dysfunction. from 1–2/100,000 down to 0.8/100,000.
There is a complex interaction between bronchial wall
cells, inflammatory mediators and the nervous system. Clinical manifestations
The chronic inflammatory process causes narrowing of ICU admission is required when children present with
bronchial airways, thus obstructing airflow. This leads to respiratory failure due to an asthma exacerbation. Obesity
episodes of wheezing, breathlessness and chest tighten- and genetic predisposition may be important in reacting
ing that are usually reversible. 106 to β 2 -agonist therapy. These children exhibit clinical
131
Development of childhood asthma results from a com- features associated with respiratory distress. Pulsus para-
bination of genetic, environmental and socioeconomic doxus, a phenomenon of palpable changes in blood pres-
risk factors. 118-122 Increasing prevalence of asthma over sure that occur with respirations, may also be present and
the past 20–30 years may be linked to a higher inci- can also be noted on plethysmography. Arterial blood gas
dence of genetic predisposition, independent of envi- analysis usually reveals initially a mild respiratory alka-
ronmental factors. Some studies have identified links losis and hypoxaemia; however, more severe asthma may
between asthma and various regions of the human show combined respiratory and metabolic acidosis and
genome, but the linkages are not consistent. The CD14 hypercapnia as the child tires and is unable to eliminate
133
gene shows the best promise of linkage, with increased carbon dioxide.
expression or promotion of this gene associated with
123
atopy and asthma in early to late childhood. Certain Assessment and management
racial groups, such as African-Americans, when com- Assessment of asthma severity is based on criteria such as
pared to Americans of European origin, are also more the degree of respiratory failure as evidenced by cyanosis,
likely to develop asthma and have complications, par- length of sentences between breaths, retractions and
ticularly those traditionally from tropical regions. 124 hypoxia, as well as level of consciousness and degree of
Once asthma has developed, there are triggers that may pulsus paradoxus. There are many scores available to
precipitate an attack. These include viral illnesses, par- assist in determining the severity of asthma, including the
ticularly respiratory viruses, tobacco smoke exposure, National Asthma Campaign guidelines, the Pulmonary
house dustmites, exercise, pet hair, food and environ- Index Score, the Respiratory Failure Score and the Modi-
mental allergens. fied Dyspnoea Scale. Whatever method is used, assess-
Asthma is one of the commonest paediatric presentations ments should be frequent and response to treatment
to emergency departments and its worldwide prevalence recorded (see Table 25.6). Severe asthma that worsens
125
is growing with differences between populations. It is and/or does not respond to treatment warrants admis-
130
reported that as many as 20–30% of children in Wester- sion to a paediatric ICU.
nised countries, including Australia and New Zealand, The broad aims of management of severe asthma include
will develop wheeze or asthma symptoms; 126 the current maintaining oxygenation, rapid bronchodilation and
disease rate is between 9.6% in the US, 127 29.7% in the treating any cardiovascular compromise. In children with
UK, 128 and 31% in Australia. Asthma prevalence is severe asthma, hypoxaemia results from ventilation/
1

TABLE 25.6 Asthma severity assessment
Sign* Mild Moderate Severe Life threatening
Altered consciousness no no agitated agitated, confused, drowsy
Accessory muscle use no minimal moderate severe
Oximetry in air >94% 90–94% <90% <90%
Talks in sentences phrases words words
Pulsus paradoxus not present may be palpable palpable palpable
Pulse rate <100 tachycardia marked tachycardia marked tachycardia or bradycardia
Central cyanosis no no likely to be present likely to be present
Wheeze on auscultation variable moderate–loud often quiet often quiet
Physical exhaustion no no yes yes
Initial spirometry (if done; % of >60% 40–60% <40% <40%
best or predicted)
*The child should be assigned to the most severe grade in which any feature occurs. If the child has received treatment prior to arrival, he/she should be managed as
more severe than the clinical signs indicate.
Adapted from (132).