Surgical demands
Surgery is the third largest cause of death after ischaemic heart
disease and stroke accounting for almost 8 % of all deaths
globally18. Given the ageing population and projected
burden of vascular arterial occlusive/aneurysmal disease, surgery
remains a major concern for healthcare providers. Importantly, the ‘high
risk’ surgical patient accounts for 13% of cases yet contributes to a
disproportionate >80% of all postoperative deaths and
complications19. This is especially the case for TAAA
patients given the extensive repair required and prolonged recovery time
with increasing interest direct towards the ‘gold-standard’ assessment
of CRF via CPET to provide more objective insight into surgical risk
stratification.
An adequate, albeit presently undefined CRF conferring improved
physiological reserve is required in order for a patient to tolerate
extensive open TAAA repair, given that single lung ventilation is
obligatory in order to expose the thoracic aorta following collapse of
the left lung (Figure 1). Acceptable preoperative spirometry assessment
of the pulmonary circulation may consist of an FEV1>1 L and arterial partial pressure of carbon dioxide
<45 mmHg19. Postoperative pulmonary
complications and reintubation rates of up to 15% in the highest volume
centres indicate that this remains a major cause of morbidity following
TAAA surgery20. Pulmonary complications occur in up to
36% of patients and any adverse lung function tests preoperatively,
highlighted through spirometry and arterial blood gas analysis, may be
advised to undergo a regime including physical exercise, spirometry
training and bronchodilator therapy21. Other factors
reducing prolonged ventilator support included preservation of the
central tendon of the diaphragm by circumferential division and
avoidance of excessive blood products22.
Postoperatively, adequate pulmonary function is essential for
perioperative survival as all patients will be intubated in the
immediate and extensive postoperative recovery phase.