Results

Patient characteristics

A total of 41 patients were included in the study. The mean age was 60.9 ± 13.4 years, with a male predominance (56.1%; n = 23). The most frequent comorbidities were diabetes mellitus (46.3%; n = 19) and active smoking (29.3%; n = 12). The main sources of infection were urogenital (29.3%; n = 12), digestive (26.8%; n = 11), and skin and soft tissue infections (22.0%; n = 9).

At ICU admission, the MAP was 53.8 ± 8.5 mmHg, and 73.0% of patients (n = 30) presented with an altered Glasgow Coma Scale score. The overall 28-day mortality rate was 56.1% (n = 23).

Admission blood lactate levels according to outcome

The median blood lactate level at admission in the overall cohort (n = 41) was 3.1 mmol/L (IQR: 1.7-5.0). Patients who died within 28 days (n = 23; 56.1%) had higher admission lactate levels (median 3.9 mmol/L; IQR: 2.4-5.0) compared with survivors (n = 18; 43.9%; median 2.35 mmol/L; IQR: 1.5-4.0). However, this difference did not reach statistical significance (p = 0.231) (Figure 1).

Figure 1: Distribution of Admission Blood Lactate Levels According to 28-Day Outcome in Patients With Septic ShockBox-and-whisker plot showing the distribution of admission blood lactate levels in patients with septic shock according to 28-day outcome. The median lactate level was higher in non-survivors (3.9 mmol/L; interquartile range (IQR): 2.4–5.0) compared with survivors (2.35 mmol/L; IQR: 1.5–4.0). However, the difference between the two groups did not reach statistical significance (Mann–Whitney U test, p = 0.231).

Predictive performance of admission lactate for 28-day mortality

The ROC curve analysis was performed to assess the ability of admission blood lactate levels to predict 28-day mortality. The area under the ROC curve (AUC) was 0.610 (95% confidence interval (CI): 0.445-0.758; p = 0.227), indicating poor discriminative performance.

The optimal cutoff value identified using the Youden index was 2.4 mmol/L, corresponding to a sensitivity of 73.9% (n = 17/23) and a specificity of 55.6% (n = 10/18) (Figure 2).

Figure 2: Receiver Operating Characteristic (ROC) Curve of Admission Blood Lactate for Predicting 28-Day Mortality in Patients With Septic ShockReceiver operating characteristic (ROC) curve evaluating the discriminative performance of admission blood lactate levels for predicting 28-day mortality in patients with septic shock. The area under the curve (AUC) was 0.610 (95% confidence interval (CI): 0.445–0.758; p = 0.227). The optimal cutoff value identified using the Youden index was 2.4 mmol/L, corresponding to a sensitivity of 73.9% and a specificity of 55.6%. The dashed diagonal line represents the line of no discrimination.

Logistic regression analysis

In univariate logistic regression analysis, admission blood lactate was not significantly associated with 28-day mortality. Similarly, in multivariate analysis, admission lactate was not identified as an independent predictor of mortality (odds ratio (OR) = 1.42; 95% CI: 0.96-2.11; p = 0.08).