Table 1.
Formulae used for calculations of acid–base variables used in the present study
| Parameter | Equation | Reference |
|---|---|---|
| Cl− corr | (Na+ normal/Na+ patient) × Cl− patient [Where Na+ normal is the reference interval mid‐point 148 mmol/L] | Meltesen & Bohn (2012) |
| HCO3 − act | 0.0307 × pCO2 × 10(pH – 6.105) | NCCLS (1994) |
| BEecf | HCO3 − act – 24.8 + (16.2 × (pH – 7.40)) | Shapiro et al. (1989) |
| AG | (Na+ + K+) – (Cl− + HCO3 −) | Dibartola (1992) |
| AGcorrected | AG + (0.42 x (3.8 – Alb (g/dL)) | Dibartola (1992) |
| Atot | (phosphate (mg/dL) × 0.58) + (albumin (g/dL) × 2.8) | Corey (2003) and Stewart (1983) |
| SIDapparent | [(Na+ + K+) – (Cl− + Lactate)] | Constable (2000) |
| SIDeffective | [HCO3 − + (albumin (g/dL) × 2.8) + (phosphate (mg/dL) × 0.58)] | Hopper et al. (2014a) |
| SIG | [(Na+ + K+) – (Cl− + Lactate)] ‐ [HCO3 − + (albumin (g/dL) × 2.8) + (phosphate (mg/dL) × 0.58)] | Constable & Stampfli (2005) and Hopper et al. (2014a) |
| SIGsimplified | Anion gap – (albumin × 4.9) | de Morais & Leisewitz (2012) |
| Water BE effect | (0.25 x (Na+ patient – Na+ normal)) | Dibartola (1992) |
| Chloride BE effect | Cl− normal – Cl− corrected | Dibartola (1992) |
| Phosphate BE effect | (0.58 × (phosphatenormal – phosphatepatient (mg/dL))) | Hopper et al. (2014a) |
| Albumin BE effect | (3.7 × (albuminnormal – albuminpatient (g/dL))) | Dibartola (1992) |
| Lactate BE effect | (–1) x lactatepatient | Hopper et al. (2014a) |
| XA‐ | BE – Sum of water, chloride, phosphorous, albumin and lactate effects | Hopper et al. (2014a) |
AG, anion gap; Atot, total plasma weak acids; BEecf, base excess (extracellular fluid); HCO3 − act, actual bicarbonate; SID, strong ion difference; SIG, strong ion gap; XA−, unmeasured anions.