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.