Fig. 2

Restricted cubic spline analysis of 30-day mortality with positive (a) and negative (b) fluctuations in Cl⁻ within 72 h according to the cumulative fluid balance during 72 h after ICU admission. Cumulative fluid balance (%) was calculated as: (Total input fluid – total output fluid, L) × 100 x weight in admission (kg)^− 1. Positive fluctuation in Cl⁻: Maximum Cl⁻ level within 72 h after ICU admission – Cl⁻ level upon ICU admission. Negative fluctuation in Cl⁻: Cl⁻ level upon ICU admission – minimum Cl⁻ level within 72 h after ICU admission