What is the clinical evidence from this study?

Study design: Cohort. Population: Cardiac Surgery (n=6139). Intervention: Nocturnal blood pressure rising vs. Nocturnal blood pressure not rising. Primary outcome: 90-day mortality (HR 1.54, 95% CI 1.11-2.12).

March 16, 2026Open Access

Association between postoperative nocturnal blood pressure rising and mortality in patients receiving cardiac surgery: a retrospective cohort study

Key Result

Nocturnal blood pressure rising was associated with a 54% increased risk of 90-day mortality compared to those without nocturnal blood pressure rising (HR 1.54).

Key Points

This study aims to investigate the link between postoperative nocturnal blood pressure rising and mortality in cardiac surgery patients.
Retrospective cohort analysis of adult patients from the MIMIC-IV database.
Defined nocturnal blood pressure rising as mean arterial pressure exceeding diurnal levels within the first 24 hours post-surgery.
Outcomes assessed included 30-day, 90-day, and 1-year mortality.
Utilized restricted cubic splines, Kaplan-Meier survival curves, and Cox proportional hazards models for analysis.
Performed subgroup and sensitivity analyses to ensure robustness of findings.
Out of 6139 patients, 1997 (32.5%) displayed nocturnal blood pressure rising.
Higher mortality was observed at 90 days (3.3% vs. 2.0%) and 1 year (5.9% vs. 3.9%) for those with nocturnal BP rising.
Cox models indicated nocturnal BP rising significantly associated with 90-day mortality (HR: 1.54) and 1-year mortality (HR: 1.37).
No significant interaction between nocturnal BP rising and mortality was found in subgroup analyses.

Study Design

Type

Cohort (n=6,139)

Multicenter

Yes

Structured PICO

Does early postoperative nocturnal blood pressure rising increase mortality in adult patients receiving cardiac surgery?

Population

6,139 adult patients (≥18 years) undergoing coronary artery bypass grafting (CABG), valvular surgery, or a combination, admitted to the ICU postoperatively. Median age 69, 28.56% female. Excluded: ICU stay <24 hours, insufficient BP records, or inability to determine exact time of ICU admission.

Intervention

Early postoperative nocturnal blood pressure rising (defined as nocturnal mean arterial pressure exceeding diurnal mean arterial pressure within the first 24 hours postoperatively in the ICU)

Comparator

Non-nocturnal blood pressure rising (nocturnal mean arterial pressure less than or equal to diurnal mean arterial pressure)

Outcome

30-day, 90-day, and 1-year mortality (follow-up starting at ICU admission)hard clinical

Early postoperative nocturnal blood pressure rising is a common ICU hemodynamic pattern that independently predicts increased medium- and long-term mortality after cardiac surgery.

Main Result

Effect estimate: HR 1.54 (95% CI 1.11-2.12)

Absolute Event Rate: 3.3% vs 2%

Limitations

Potential selection bias due to exclusion of patients with ICU stay <24 hours.
Lack of preoperative blood pressure data could influence results.

Abstract

Postoperative blood pressure (BP) patterns may provide prognostic information in cardiac surgery patients, yet their clinical significance remains unclear. We investigated the association between early postoperative nocturnal BP rising and mortality in this population. This retrospective cohort study used the MIMIC-IV database (2008–2019) including adult patients undergoing coronary artery bypass grafting (CABG) or valvular surgery. Patients with an intensive care unit (ICU) stay less than 24 h, insufficient BP records, or indeterminate ICU admission were excluded. Nocturnal BP rising was defined as nocturnal mean arterial pressure (MAP) exceeding diurnal MAP within the first 24 h postoperatively. Outcomes included 30-day, 90-day, and 1-year mortality. Restricted cubic splines, Kaplan–Meier survival curves, and Cox proportional hazards models were used to assess associations between nocturnal BP rising and mortality, adjusting for confounders. Subgroup and sensitivity analyses were also conducted to confirm consistency and robustness. A total of 6139 patients were included in this study. Among them, 1997 (32.5%) exhibited nocturnal BP rising. Patients with nocturnal BP rising experienced higher mortality rates at 90-day (3.3% vs. 2.0%) and at 1-year (5.9% vs. 3.9%). Adjusted Cox models revealed that nocturnal BP rising was statistically associated with 90-day (HR: 1.54, 95% CI: 1.11–2.12) and 1-year mortality (HR: 1.37, 95% CI: 1.08–1.74), but not 30-day mortality. In subgroup analysis, there was no significant interaction effect between nocturnal BP rising and mortality across different subgroups. After a series of sensitivity analyses, the association remained consistent. Early postoperative nocturnal BP rising is common and independently associated with an increased risk of medium- and long-term mortality after cardiac surgery.

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