Preoperative low Geriatric Nutritional Risk Index increases intensive care unit admission risk in patients undergoing gastrointestinal tumor surgery.

Background: Gastrointestinal tumors are highly prevalent malignant tumors worldwide, and surgery is their primary treatment modality. Although the Geriatric Nutritional Risk Index (GNRI), a simple nutritional assessment tool, has been associated with prognosis in various diseases, its impact on ICU admission risk following gastrointestinal tumor surgery remains unclear. This study aims to investigate the relationship between preoperative GNRI and postoperative ICU admission risk. Methods: This retrospective cohort study analyzed 9,045 gastrointestinal tumor surgery patients from the INSPIRE database. Multivariable logistic regression with stepwise confounder adjustment was used to examine the GNRI-ICU admission association. Generalized additive models explored nonlinear relationships, while subgroup and sensitivity analyses verified result robustness. Results: Multivariable regression analysis demonstrated that preoperative GNRI decrease was significantly associated with increased risk of ICU admission in patients after gastrointestinal tumor surgery. The severe nutritional risk group (GNRI < 82) had a 2.01-fold higher risk of ICU admission compared to the no-risk group (GNRI > 98) (95% CI: 1.09-3.69). Nonlinear analysis identified GNRI = 89 as a key threshold ( Conclusion: Preoperative GNRI is an independent predictor for ICU admission following gastrointestinal tumor surgery, demonstrating a significant non-linear relationship with a critical threshold at GNRI = 89. The categorical risk stratification (GNRI < 82) provides clinically meaningful information for perioperative risk assessment.