Intraoperative hypotension has been associated with postoperative morbidity and early mortality. Postoperative hypotension, however, has been less studied. This study examines postoperative hypotension, hypothesizing that both the degree of hypotension severity and longer durations would be associated with myocardial injury.
This single-center observational cohort was comprised of 1,710 patients aged 60 yr or more undergoing intermediate- to high-risk noncardiac surgery. Frequent sampling of hemodynamic monitoring on a postoperative high-dependency ward during the first 24 h after surgery was recorded. Multiple mean arterial pressure (MAP) absolute thresholds (50 to 75 mmHg) were used to define hypotension characterized by cumulative minutes, duration, area, and time-weighted-average under MAP. Zero time spent under a threshold was used as the reference group. The primary outcome was myocardial injury (a peak high-sensitive troponin T measurement 50 ng/l or greater) during the first 3 postoperative days.
Postoperative hypotension was common, e.g., 2 cumulative hours below a threshold of 60 mmHg occurred in 144 (8%) patients while 4 h less than 75 mmHg occurred in 824 (48%) patients. Patients with myocardial injury had higher prolonged exposures for all characterizations. After adjusting for confounders, postoperative duration below a threshold of 75 mmHg for more than 635 min was associated with myocardial injury (adjusted odds ratio, 2.68; 95% CI, 1.46 to 5.07, P = 0.002). Comparing multiple thresholds, cumulative durations of 2 to 4 h below a MAP threshold of 60 mmHg (adjusted odds ratio, 3.26; 95% CI, 1.57 to 6.48, P = 0.001) and durations of more than 4 h less than 65 mmHg (adjusted odds ratio, 2.98; 95% CI, 1.78 to 4.98, P < 0.001) and 70 mmHg (adjusted odds ratio, 2.18; 95% CI, 1.37 to 3.51, P < 0.001) were also associated with myocardial injury. Associations remained significant after adjusting for intraoperative hypotension, which independently was not associated with myocardial injury.
In this study, postoperative hypotension was common and was independently associated with myocardial injury.
- Recent studies have demonstrated associations of postoperative hypotension after noncardiac surgery, defined using varying definitions (categorical or continuous), with adverse outcome including myocardial injury with a varying influence of intraoperative hypotension. The authors have previously reported an association considering mean arterial pressure quartiles assessed by high sensitivity troponin T levels. In this study, they evaluated multiple absolute mean arterial pressure (MAP) thresholds and temporal time-weighted characterizations of hypotension in the first 24 h after surgery in patients admitted to a high-dependency unit with continuous blood pressure monitoring. Myocardial injury was assessed using serial high sensitivity troponin sampling on the first 3 postoperative days.
- Postoperative hypotension occurred in from 8 to 48% of patients using MAP thresholds from 60 to 75 mmHg. Myocardial injury (peak high sensitivity troponin T 50 ng/l or greater) was associated with higher prolonged durations for all of the MAP thresholds investigated (50 to 75 mmHg). After adjustment for relevant potential clinical confounders, adjusted odds ratios ranged from 2.18 to 3.26 based on the assessed thresholds and characterizations. In contrast to other studies, intraoperative hypotension had no independent effect on myocardial injury.
- The results may have been influenced by selection of a relatively higher-risk cohort, possible influence of unblinded measurements on clinical decision-making, lack of consideration of clinical processes used to treat intraoperative blood pressure, unavailability of preoperative troponin values, and other potential confounders.