Background: Single-centre series of the management of patients with ruptured abdominal aortic
aneurysm (AAA) are usually too small to identify clinical factors that could improve patient outcomes.
Methods: IMPROVE is a pragmatic, multicentre randomized clinical trial in which eligible patients with
a clinical diagnosis of ruptured aneurysm were allocated to a strategy of endovascular aneurysm repair
(EVAR) or to open repair. The influences of time and manner of hospital presentation, fluid volume
status, type of anaesthesia, type of endovascular repair and time to aneurysm repair on 30-day mortality
were investigated according to a prespecified plan, for the subgroup of patients with a proven diagnosis
of ruptured or symptomatic AAA. Adjustment was made for potential confounding factors.
Results: Some 558 of 613 randomized patients had a symptomatic or ruptured aneurysm: diagnostic
accuracy was 91·0 per cent. Patients randomized outside routine working hours had higher operative
mortality (adjusted odds ratio (OR) 1·47, 95 per cent confidence interval 1·00 to 2·17). Mortality rates
after primary and secondary presentation were similar. Lowest systolic blood pressure was strongly
and independently associated with 30-day mortality (51 per cent among those with pressure below 70
mmHg). Patients who received EVAR under local anaesthesia alone had greatly reduced 30-day mortality
compared with those who had general anaesthesia (adjusted OR 0·27, 0·10 to 0·70).
Conclusion: These findings suggest that the outcome of ruptured AAA might be improved by wider use
of local anaesthesia for EVAR and that a minimum blood pressure of 70 mmHg is too low a threshold
for permissive hypotension.