Table 2 Description of the structure of the algorithm
From: Analysis of acid–base disorders in an ICU cohort using a computer script
Level | Function |
|---|---|
1 ⇩ | Initial input variables are pCO2 and pH. The script estimates a most probable start-scenario including a primary disturbance for certain pH/pCO2 combinations (Table 1), on which further calculations are carried out in the next level |
2 ⇩ | The input variables are the primary disturbances from level 1. The compensation variables; pCO2 for metabolic and bicarbonate for respiratory disturbances are determined. Full compensation (100%) is defined according to the Boston formulas. If the compensation is partial the script defines a second disturbance that interacts with/counteracts the compensation mechanism |
3 ⇩ | The input variable is the diagnosis of metabolic acidosis from level 2. The script calculates the anion gap and the delta ratio to evaluate a possible tertiary disturbance in case of a primary or secondary disturbance of metabolic acidosis. Anion gap is calculated as [Na+] + [K+] − [Cl−] − [bicarbonate]. The traditional delta ratio was further calculated for all anion gaps > 16 using the formula [AG-12]/[24-bicarbonate] |
⇩⇩⇩ 4 | The results from the previous levels 1–2–3 are inserted in a final fourth evaluation filter, where the diagnosis is compared to special criteria. To date the fourth level is not fully built and it serves as possibility to further develop the script. Finally, a graph is drawn, where pH is placed on the X axis giving an instant understanding whether the result is an acidosis or an alkalosis. Bicarbonate level is placed on the Y axis. In addition, a superficial layer consisting of pCO2 isopleths, created using the Henderson–Hasselbach equation solved for bicarbonate, are placed on top of the graph |