Use of Sodium-Chloride Difference and Corrected Anion Gap as Surrogates of Stewart Variables in Critically Ill Patients

Abstract

IntroductionTo investigate whether the difference between sodium and chloride ([Na+] – [Cl−]) and anion gap corrected for albumin and lactate (AGcorr) could be used as apparent strong ion difference (SIDapp) and strong ion gap (SIG) surrogates (respectively) in critically ill patients.MethodsA total of 341 patients were prospectively observed; 161 were allocated to the modeling group, and 180 to the validation group. Simple regression analysis was used to construct a mathematical model between SIDapp and [Na+] – [Cl−] and between SIG and AGcorr in the modeling group. Area under the receiver operating characteristic (ROC) curve was also measured. The mathematical models were tested in the validation group.Resultsin the modeling group, SIDapp and SIG were well predicted by [Na+] – [Cl−] and AGcorr (R2 = 0.973 and 0.96, respectively). Accuracy values of [Na+] – [Cl−] for the identification of SIDapp acidosis (<42.7 mEq/L) and alkalosis (>47.5 mEq/L) were 0.992 (95% confidence interval [CI], 0.963–1) and 0.998 (95%CI, 0.972–1), respectively. The accuracy of AGcorr in revealing SIG acidosis (>8 mEq/L) was 0.974 (95%CI: 0.936–0.993). These results were validated by showing excellent correlations and good agreements between predicted and measured SIDapp and between predicted and measured SIG in the validation group (R2 = 0.977; bias = 0±1.5 mEq/L and R2 = 0.96; bias = −0.2±1.8 mEq/L, respectively).ConclusionsSIDapp and SIG can be substituted by [Na+] – [Cl−] and by AGcorr respectively in the diagnosis and management of acid-base disorders in critically ill patients.

Haploinsufficiency of the Mouse Atp6v1b1 Gene Leads to a Mild Acid-Base Disturbance with Implications for Kidney Stone Disease

“…This increase in blood Cl -concentration both in heterozygous and KO mice cannot be linked to dehydration as hematocrit levels were not different between the three strains of mice. Moreover, the calculated sodium-chloride difference, an index for metabolic acidosis versus dehydration [23] showed a significant lower value in KO mice compared to WT mice at the end of the acid load and an intermediate but not significant value for heterozygous animals. Once again, this may indicate an acid-base disturbance.Finally, the low pCO 2 may point to a partial respiratory compensation.…”

Different effects of fluid loading with saline, gelatine, hydroxyethyl starch or albumin solutions on acid-base status in the critically ill

“…We calculated the relative plasma volume changes in percentage from (Hb0/Hb90)–((1-Hct90/1-Hct0)), in which Hb is haemoglobin and Hct haematocrit, measured at 0 min and 90 min (Sysmex SE-9000, Sysmex Corporation, Kobe, Japan) [29]. We calculated, in each patient, the sodium chloride concentration difference as a measure of apparent strong ion difference and the corrected anion gap as a measure of strong ion gap [3,4,28]. The anion gap (AG) was calculated from sodium minus chloride and bicarbonate concentrations and the corrected AG from AG + (0.25 x (45-[albumin in g/L]))–(lactate in mmol/L) to estimate unmeasured, non-lactic acid, anions.…”

“…It decreases with an increase in unmeasured anions and concomintant acidosis. The difference between sodium and chloride concentration has been shown to correlate good with the SID and corrected anion gap as a measure for the strong ion gap [3,4]. …”

Les utilisations du trou anionique plasmatique corrigé pour le diagnostic de l’acidose métabolique

“…La différence [Na + ] -[Cl -] est quant à elle aux alentours de 36 ± 2 mEq/l. Ces deux paramètres ont, avant tout, été décrits comme étant de bons substituts du strong ion difference (SID) apparent de Stewart [43,44]. On notera qu'une hyponatrémie associée à une normochlorémie se traduira par une acidose, tandis qu'une hypernatrémie associée à une hyperchlorémie pourra ne pas provoquer d'acidose.…”