Page 321 - ACCCN's Critical Care Nursing

298 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

Ventilatory Support ● pulmonary hypertension from cardiac failure or valve
Ventilation should be approached according to the disease
general principles described in Chapter 15. As anaesthe- ● cardiogenic shock/post-pump failure
sia is not typically reversed at the end of the operation, ● systemic inflammatory response syndrome due to car-
patients are generally admitted apnoeic, and within 1–3 diopulmonary bypass
hours return to wakefulness and spontaneous breathing. ● early or rapid weaning that is undertaken before com-
plete readiness, leading to failure at weaning attempt
Ensuring a secure airway is an initial priority; the follow- ● surgical pain limiting spontaneous effort and poten-
ing should be undertaken: tially leading to atelectasis or sputum retention.
● Confirmation of endotracheal tube position and its
security immediately on admission: Approaches to weaning
● auscultation for equal bilateral air entry to rule out As patients often have no underlying pulmonary pathol-
right main bronchus intubation, ogy, and have been ventilated for brief periods only, rapid
● recording of the ETT insertion length should be weaning phases have become the norm in most centres.
sufficient In many instances, as soon as the patient wakes and
● postoperative chest X-ray, taken within 30 minutes, begins spontaneous breathing activity he/she may be
should also be examined for ETT positioning suitable for at least a trial of spontaneous breathing in
● Initial ETT care: CPAP mode, usually with some modest level of pressure
● assessment for air leak around the cuff (via perfor- support (e.g. 5–10 cm H 2O). If tolerated and the patient
mance of minimal occlusive volume or pressure maintains an adequate minute volume, SpO 2 and PaCO 2 ,
tests) then extubation may be considered within as little as
● ETT is adequately secured and positioned so as not another 30 minutes. Normal demonstrations of airway
to apply undue pressure against soft tissues of the protection capability (e.g. neuromuscular control, gag,
mouth and lips. swallow, cough and patient strength) should be sought
There has been a general trend to more rapid ventilatory before extubation (see Chapter 15 for details).
weaning in recent years, and in some centres ‘fast-track’ These short ventilation times and rapid weaning carry a
cardiac surgical recovery includes extubation at the end greater risk of weaning failure. Patients may initially wake
of the operation before transfer to a recovery unit for and appear to sustain spontaneous ventilation well for
suitable patients. Indices of respiration show no improve- some time, only to lapse back under anaesthetic influ-
ment when intubation is maintained for longer com- ence. A return to greater ventilatory support may be
30
pared with early extubation, and pooled results from necessary. Additionally, demonstrations of spontaneous
randomised early extubation trials show earlier ICU dis- breathing for as little as 30 minutes may be insufficient
charge and shorter lengths of stay (by 1 day) when early for patients to fail, as they have not exceeded reserves.
extubation is undertaken. 31 Failure to wean carries greater significance in the cardiac
Apart from these fast-track approaches, ventilation is surgical patient with existing pulmonary hypertension, as
commonly employed for 2–6 hours in the uncomplicated respiratory acidosis causes pulmonary vasoconstriction,
patient. Reasons for continuing ventilation beyond this abruptly worsening pulmonary hypertension and the risk
time frame may include: of pulmonary oedema and/or right ventricular failure.
● intraoperative neurological event Where ventilation has been more prolonged due to
● gas exchange deficit with unresolved hypoxaemia postoperative pulmonary problems, weaning may be
● ventilatory inadequacy approached more cautiously, as might be applied to the
● significant haemodynamic insufficiency general longer-term ventilated patient. Gradual manda-
● patients returning from theatre late in the evening tory rate reduction or increasing periods of spontaneous
may sometimes continue ventilation overnight to ventilation interspersed with periods of greater assistance
optimise postextubation breathing ability. have been used. 31
For many patients, ventilation is provided purely for
initial airway and apnoea protection rather than for treat- Assessment and Management of
ment of pulmonary deficits. In the absence of pulmonary Postoperative Bleeding
disease, many centres provide fairly uniform approaches The harvest sites for radial arteries or saphenous veins are
to parameter settings that aim at sustaining ventilation uncommon sources of significant blood loss and are gen-
and oxygenation, while limiting traumatic risk to the erally easily managed with dressings or compression.
lungs (see Table 12.1). However, approaches to ventila- Intrathoracic bleeding, however, may be torrential and
tion will need to be tailored in the presence of operative threaten life. Occasionally surgical bleeding from the
complications or coexisting lung disease. aorta, arterial grafts or myomectomy sites may exceed
replacement capabilities, and at times patients succumb
Ventilation challenges specific to the postcardiac surgical to overwhelming haemorrhage. Maintenance of drain
setting include:
patency and strict recording of losses and total fluid
● atelectasis due to operative access balance are paramount, and fluid balance assessments
● pneumothorax (pleural opening for grafts, or over shorter intervals, even every 5–10 minutes, become
ventilation-induced trauma) necessary during active bleeding. Because of the potential