Of the 412 patients, 56.17% were male. The mean age was 65.9 ± 16.2 years. The anatomical location of the GI perforation was: 39.1% in the lower gastrointestinal tract (LGI) including the colon, rectum, and anus; 33.3% in the upper gastrointestinal tract (UGI), from the distal esophagus to the duodenum; and 26% in the small intestine (Fig. 2). The incidence of multiple perforations was 1.7%, with simultaneous perforations in the small intestine and LGI tract occurring in 1.0%, followed by perforations in the UGI and LGI tracts in 0.5%, and perforations involving the UGI tract and small intestine in 0.2% of the cases. The mean TTS was 9.7 ± 7.8 h. The average operating time was 2.52 ± 1.21 h. The mean ICU stay was 4.4 ± 7.7 days and mean total hospital stay was 20.5 ± 25.0 days. In the non-survivors group, the mean time from admission to mortality was 9.5 ± 8.7 days. Three hundred seventy-six patients (91.01%) survived. However, 36 patients (0.09%) expired after surgery.
The anatomical location of GI perforation. *GI, gastrointestinal
Based on 30-day mortality, the participants were allocated to two groups: survivors and non-survivors. The association between demographics and factors associated with postoperative 30-day mortality is presented in Table 1.
The non-survivors had significantly older age (65.04 ± 16.31 versus 75.33 ± 11.32 years, P < 0.001), longer operating time (2.48 ± 1.18 versus 2.91 ± 1.42 h, P = 0.042) and shorter hospital stays (21.57 ± 25.79 versus 9.56 ± 8.79 days, P < 0.001) compared with the survivors. Sex (57.18 versus 44.44%, P = 0.195, in male), BMI (23.26 ± 9.61 versus 30.9 ± 38.84, P = 0.378), length of stay in the ICU (4.2 ± 7.82 versus 6.11 ± 6.54 days, P = 0.161), and TTS (9.67 ± 7.71 versus 10.2 ± 9.3 h, P = 0.701) were not statistically significantly different from 30-day mortality after surgery.
The non-survivors group showed higher APACHE II score (23.01 ± 8.66 versus 40.32 ± 9.16, P < 0.001); serum lactate (2.77 ± 3.18 versus 6.68 ± 5.52, P = 0.002); and BUN (25.58 ± 16.62 versus 39.7 ± 31.78, P = 0.012) compared with the survivors group. However, the non-survivors group showed a lower level of pH (7.39 ± 0.07 versus 7.3 ± 0.15, P = 0.005) and HCO3 (20.72 ± 4.25 versus 16.27 ± 6.39, P = 0.001) compared with the survivors group. Lower serum hemoglobin (Hb) levels (12.57 ± 2.62 versus 11.74 ± 2.5, P = 0.07); higher serum CRP (9.84 ± 11.35 versus 13.71 ± 12.26, P = 0.057); and Cr (1.3 ± 1.08 versus 1.82 ± 1.51, P = 0.053) levels were observed in the non-survivors group, without statistical significance. There was no significant difference between the two groups regarding the underlying diseases, such as hypertension, diabetes, cardiovascular disease, cerebrovascular diseases, and cancer. The anatomical location of perforation was also compared between the two study groups. There was no significant difference in perforation of the UGI tract (35.2% versus 22.22%, P = 0.166) or small intestine (28.86% versus 27.79%, P = 1.000). Although not statistically significant, in the LGI tract (37.77% vs. 55.56%, P = 0.056), there was a tendency for more LGI perforations in the non-survivors group. The number of patients transferred from other hospitals was 132 (35.1%) in the survivors group and 11(30.6%) in the non-survivors group, with no significant difference (P = 0.715).
The multivariable logistic regression analysis revealed that a higher APACHE score (OR, 1.3; P < 0.001; 95% CI: 1.17–1.43) and longer total hospital stays (OR, 0.89; P = 0.005; 95% CI: 0.83–0.96) were independent and significant indicators for postoperative 30-day mortality (Fig. 3).
Multivariable logistic regression analysis of factors influencing 30-day mortality after surgery for gastrointestinal perforation
In receiver operating characteristic analysis, the area under the curve (AUC) of APACHE II score were 0.903 (95% CI: 0.835 to 0.980). The optimal cut off value of APACHE II score was 32.5 (Fig. 4).
The area under the curve (AUC) and the optimal cut off value of APACHE II score. *APACHE, acute physiology and chronic helath evaluation
Using the restricted cubic spline curve, the predictive value of mortality temporarily increased at the beginning when the TTS was only approximately 1–2 h. Subsequently, the mortality rate continued to decrease until a waiting time of 16 h. The curve began to ascend at 16 h as the diverging point and continued to increase thereafter (Fig. 5).
Restricted cubic spline curve (RCS) for probability of mortality rates over time from admission to surgery (TTS). Solid lines represent the estimated adjusted probability of mortality, and shaded bends represent 95% confidence intervals
Since the mortality rate increased at 16 h after TTS in the RCS curve model, a subgroup analysis using propensity score matching was performed by dividing the patients into two groups based on a waiting time of 16 h. Table 2 presents the clinical characteristics and outcomes between the two groups. Using the propensity-matched cohort, no significant differences were observed between the two groups regarding surgical outcomes: 30-day mortality (11.4% versus 5.7%; P = 0.669); ICU stay (4.3 ± 7.5 versus 4.3 ± 5.2, P = 0.985); and total hospital stay (17.4 ± 17.0 versus 24.7 ± 23.4, P = 0.140); and transfer from other hospitals (45.7% versus 34.3%; P = 0.464). However, the patients who waited over 16 h group before surgery had a significantly higher rate of readmission to the ICU (3 (8.6%) versus 11 (31.4%); P = 0.036) compared with the under 16 h group.
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