Overview about the statistical models Effect of alcohol on BE levels:
The linear equation for predicting BE (dependent variable) from the BAL (independent variable) was as follows:
BE = -0.60 * BAL - 1.88 where BAL is given in per mille.
Number of patients: 11,882 95% confidence interval for BAL coefficient: -0.51 - -0.69 Pearson correlation coefficient: 0.119
Effect of Base Excess:
First approach to assess the effect of BAL and base excess on outcome (mortality).
The RISC II score is a combination of point weights for 15 different variables found to be significantly associated with mortality in a previous analysis (Lefering 2013). Higher points are associated with a better survival. This score also contains point weights for low BE. In the present analysis the effect of low BE is evaluated; therefore the points for BE were removed from the RISC II score in advance.
Logistic regression analysis in all patients (n=11,889) with hospital mortality as dependent variable. Independent predictors are: The RISC II score (without the points for base excess);
acidosis (defined as BE ≤ -6); BAL+; interaction of BAL+ and BE ≤ -6.
Nagelkerke’s R² = 0.591
Predictor Coefficient SE p value Odds
ratio
95% CI RISC II score without
BE
-0.931 0.023 <.001 0.394 0.377 – 0.412
BAL+ -0.348 0.146 .018 0.706 0.530 – 0.941
Acidosis (BE ≤ -6) +0.384 0.110 <.001 1.469 1.183 – 1.823 Interaction of BAL+
and acidosis
-0.030 0.231 .897 0.970 0.617 – 1.527
Constant -0.181 0.062 .004
Second approach to assess the effect of BAL and base excess on outcome (mortality).
For this approach, patient group was split into patients with BAL+ and BAL-. Then the effect of low BE was assessed in both subgroups. Again, the RISC II score was used as a summary of 15 important prognostic factors, where here also the point weights for BE were removed.
BAL+ subgroup (n=2417), Nagelkerke’s R² = 0.531
Predictor Coefficient SE p value Odds
ratio
95% CI RISC II score without
BE
-0.931 0.023 <.001 0.394 0.377 – 0.412
acidosis (BE ≤ -6) 0.393 0.210 .062 1.481 0.981 – 2.237
Constant -0.602 0.165 <.001
BAL - subgroup (n=9472), Nagelkerke’s R² = 0.602
Predictor Coefficient SE p value Odds
ratio
95% CI RISC II score without
BE -0.938 0.025 <.001 0.391 0.372 – 0.411
acidosis (BE ≤ -6) 0.379 0.111 .001 1.461 1.176 – 1.816
Constant -0.171 0.064 .008
Overview RISC II score
