Page 387 - ACCCN's Critical Care Nursing

364 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

COLLABORATIVE PRACTICE patient–ventilator synchrony, especially when non-
The key principles of management are treatment of the conventional modes of ventilation are used. Improve-
precipitating cause and providing supportive care during ments in oxygenation are usually observed and may be
the period of acute respiratory failure. 6,45 Mortality rates attributed to reduction in oxygen consumption and
from ARDS have decreased over time; this is not attrib- improved chest wall compliance. The use of NMBAs,
uted solely to the use of low tidal volume ventilation however, is also associated with an increased risk of
promoted by the ARDS Network group, but to other myopathy, so any benefits gained should be weighed
51
44
advances in critical care. Specific strategies include cau- against known risks.
tious fluid management, adequate nutrition, prevention Inhaled nitric oxide (iNO) therapy may be used to
of ventilator-associated pneumonia, prophylaxis for deep improve oxygenation through selective vasodilation of
venous thrombosis and gastric ulcers, weaning of seda- the pulmonary blood vessels, promoting improvement in
tion and mechanical ventilation as early as possible, and ventilation–perfusion matching. Despite the lack of evi-
physiotherapy and rehabilitation (similar to ARF man- dence regarding its effectiveness in improving outcomes
agement). Management involves a coordinated collab- of patients with ARDS, its use is reasonably widespread.
orative approach including supportive ventilation, patient Improvement in oxygenation should be observed within
positioning and medication administration. the first hour of treatment to support its ongoing use.
51
Some groups have reported the use of iNO to be harmful
Ventilation Strategies and recommend that it not be used, given the lack of
52
The key focus of ventilation in ARDS is the prevention of evidence demonstrating reduction in mortality. A similar
refractory hypoxaemia rather than reversing it after it effect, in terms of pulmonary vasodilation, has been
develops. The use of small tidal volumes and adequate achieved using inhaled prostacyclines and this remains
levels of PEEP, along with careful attention to fluid status under investigation as an alternative therapy. 51
and patient–ventilator synchrony, may be sufficient to A number of medications are currently being investigated
maintain oxygenation at an appropriate level while mini- to treat ARDS in acute and subacute exudative phases.
mising further damage from barotrauma and nosocomial These include agents that target the disrupted surfactant
pneumonia. 6,47 The use of rescue therapies is controversial system (exogenous surfactant therapy), oxidative stress
as none to date have reduced mortality when studied in and antioxidant activity (antioxidants), neutrophil
large heterogeneous populations of patients with ARDS. recruitment and activation, expression and release of
Some therapies however demonstrated improved oxygen- inflammatory mediators (corticosteroids), activation of
ation, which may be an important goal in many patients the coagulation cascade (immunomodulating agents and
who experience severe hypoxaemia. The key focus of statins), and microvascular injury and leak (beta 2 -
rescue ventilatory strategies is alveolar recruitment, includ- agonists). The use of low-dose corticosteroids has been
53
ing higher levels of PEEP, use of airway pressure release associated with improved outcomes for patients with
ventilation (APRV), high-frequency oscillatory ventilation ARDS, although its use remains controversial and
54
(HFOV) and high-frequency percussive ventilation further investigation is recommended.
(HFPC) (see Chapter 15). If hypoxaemia is severe, extra-
corporeal life support may also be considered. As there is
no evidence to support the use of one strategy over another, SPECIAL CONSIDERATIONS
the choice of therapy is often based on equipment avail- ALI and ARDS occur in pregnancy usually as a result of
ability and clinician expertise. An evidence based approach aspiration pneumonitis, sepsis or pneumonia. Manage-
is likely to involve lung-protective ventilation (volume ment of ventilation is similar to the non-pregnant patient,
and pressure limitation with modest PEEP) requiring per- although consideration of the impact on the fetus is
missive hypercapnia and permissive hypoxaemia. 49 important in medication usage and ventilatory manage-
ment. Elderly patients who develop ARDS are likely to
6
Prone Positioning experience an increased severity of disease, yet have a
Use of prone positioning in patients with ARDS was mortality rate comparable to other patients. Develop-
described almost 30 years ago as a means of improving ment of other organ dysfunction depends on the presence
oxygenation. This improvement is largely due to the of chronic conditions such as renal and cardiovascular
effect that the prone position has on chest wall and lung diseases. 55
compliance. The result is a more homogenous ventilation
of the lungs and improved ventilation–perfusion match- ASTHMA AND CHRONIC
ing. Investigation into the effectiveness of this as a OBSTRUCTIVE PULMONARY DISEASE
6
therapy in ARDS has noted improvement in oxygenation,
but no corresponding improvement in mortality. It is Asthma is defined as a respiratory condition where airflow
therefore recommended as a rescue therapy for the patient limitation may be fully or partially reversible either spon-
at risk of death from hypoxia, rather than as a routine taneously or with treatment. 56-58 COPD is a respiratory
treatment. See Chapter 15 for further discussion. condition defined by a largely fixed airflow limitation.
50
The partial airway responsiveness to therapy in COPD
Medications results in a clinical overlap between COPD, asthma and
A number of non-ventilatory strategies may form part of chronic bronchitis. A non-proportional Venn diagram
the treatment of patients with ARDS. Neuromuscular (see Figure 14.2), originally used by the American Tho-
59
blocking agents (NMBAs) are used to promote racic Society and now in the Australian and New Zealand