Association between admission Braden Skin Score and delirium in surgical intensive care patients: an analysis of the MIMIC-IV database

Abstract

Background: The Braden Skin Score (BSS), a tool for assessing pressure ulcers, is increasingly recognized for its prognostic value in various disorders. However, its link to critical delirium in surgical patients remains understudied. This study aimed to explore the association between BSS upon admission and the risk of delirium in SICU patients.

Methods: This retrospective observational cohort study used data from the Medical Information Mart for Intensive Care (MIMIC)-IV database. The primary outcome was incidence of delirium. Feature importance of BSS was initially assessed using a machine learning algorithm, while restricted cubic spline (RCS) models and multivariable logistic analysis evaluated the relationship between BSS and delirium. Additionally, Kaplan-Meier analysis and mediation analysis were conducted to explore interactions among BSS, delirium, and short-term mortality.

Results: A total of 4,899 patients were included in the study, among whom 1,491 were diagnosed with delirium. The Boruta algorithm identified BSS as a significant predictor of delirium occurrence. RCS models demonstrated a non-linear positive relationship between BSS and delirium. Based on RCS curves, the optimal threshold for BSS was established at 16, thereby categorizing participants into two groups: those with BSS < 16 and those with BSS ≥ 16. Multivariable logistic regression analysis revealed that lower BSS was positively correlated with an increased risk of delirium. These findings exhibited robust consistency across subgroup analyses and sensitivity analyses. Furthermore, patients in lower BSS groups had a higher 90-day mortality, with delirium mediating an indirect effect on this outcome.

Conclusion: The low BSS was independently associated with an increased risk of delirium in critically ill surgical patients. Patients exhibiting a BSS below 16 demonstrated heightened susceptibility to the onset of delirium, thereby necessitating vigilant monitoring and timely intervention. Larger prospective studies are needed to confirm these findings.

Keywords: Braden Skin Score; MIMIC-IV database; delirium; risk factors; surgical intensive care unit.

Figure 1

The flowchart of this study.

Figure 2

Feature selection utilizing the Boruta algorithm. The horizontal axis lists variable names, while the vertical axis shows their corresponding Z values. The box plot illustrates these Z values during model computation. Green boxes indicate important variables, and red boxes represent unimportant ones. BSS, Braden Scale Score; BUN, blood urea nitrogen; CPD, Chronic pulmonary disease; CVD, Cerebrovascular disease; GCS, Glasgow Coma Score; HCO₃, Bicarbonate; ICU, intensive care unit; INR, international normalized ratio; MBP, mean blood pressure; MV, mechanical ventilation; PT, Prothrombin time; PTT, partial thromboplastin time; RRT, renal replacement therapy; SOFA, the Sequential Organ Failure Assessment; SpO₂, oxyhemoglobin saturation; T, temperature; WBC, white blood cell.

Figure 3

RCS analyses for the relationship between BSS and delirium. The horizontal dashed line indicates a hazard ratio of 1.0, with the cut-off value for BSS set at 16. (A) Model 1: no adjustments; (B) Model 2: sex, age, race, vital signs (HR, respiratory rate, temperature, and SpO₂), and laboratory indicators (white blood cell, platelet, hemoglobin, glucose, creatinine, blood urea nitrogen, potassium, calcium, and international normalized ratio); (C). Model 3: based on Model 1 and Model 2 and further adjusted for congestive heart failure, cerebrovascular disease, dementia, renal disease, liver disease, sepsis, and Glasgow Coma Score.

Figure 4

Subgroup analysis regarding the association between BSS and the risk of delirium. BSS, Braden Scale Score; OR, odds ratio, CI, confidence interval.

Figure 5

Relationship between BSS, delirium, and short-term mortality. (A) Patients were categorized into four groups based on their admission BSS (BSS < 16 or BSS ≥ 16) and the presence of delirium. The Kaplan–Meier curves showed the cumulative 90-day survival rates for each group, with differences analyzed using the log-rank test. (B) The total effect, including direct and indirect effects, was assessed using mediation analysis with 1,000 bootstrap iterations. A significant effect was indicated if the 95% confidence interval (CI) did not include zero. ADE average direct effect, ACME average causal mediation effect.