Adequate blood pressure control is one of the major concerns for patients undergoing surgical procedures. Longer-term outcomes may be affected by extended periods of less severe hypotension in patients surviving the immediate perioperative period. Little is known about what blood pressure may be acceptable to reduce immediate peri-operative complications and any long term adverse outcomes.
This multicentre retrospective cohort study aimed to determine the association of intraoperative hypotensive exposures with 30-day postsurgical mortality. The group aimed to create a (logarithmic) ratio scale quantifying risk associated with hypotensive exposures. Retrospective intraoperative data was obtained for 152,445 non-cardiac cases and MAP values were extracted. Multivariate regression analysis of the ‘development’ group was used to assess the factors associated with increased 30-day mortality. The developed algorithm was tested on a larger ‘validation’ group within the cohort study.
Progressively greater hypotensive exposures were associated with greater 30-day mortality. In the development cohort, covariable-adjusted (age, Charlson score, case duration, history of hypertension) exposure limits were identified for time accumulated below each of the thresholds that portended certain identical (5%–50%) percentage expected increases in the odds of mortality. These exposure time limit sets were shorter in patients with a history of hypertension. A novel risk score, the SLUScore (range 0–31), was conceived as the number of exposure limits exceeded for one of these sets (20% set). A SLUScore of > 0 found to have an increased risk of 30-day mortality.
The SLUScore aimed to develop a novel way to identify patients at risk of increased mortality die to intraoperative hypotension. With the information presented it is difficult to assess what the SLUScore calculates. This paper does not allow confidence in the data interpretation due to the lack of clear results and methodology. The authors suggest including the score in new anaesthetic machines, although the feasibility of this is not readily apparent due to the final patient SLUScore only being available on case conclusion. The development of new technology aiming to reduce risk within anaesthesia should be embraced however due to significant conflicts of interest, the results of this paper are not such to allow any change in anaesthetic management of intraoperative hypotension currently.