Strong-ion gap approach in patients with cardiogenic shock following ST-elevation myocardial infarction

OBJECTIVE: Assess if acid-base evaluation by Stewart's approach had a clinical role in cardiogenic shock (CS) following ST-elevation myocardial infarction (STEMI). SETTING: There are three widely used approaches to investigate metabolic acidosis: base excess (BE), anion gap (AG) and the Stewart's approach or strong ion gap (SIG). Available studies suggest the usefulness of SIG in sepsis and trauma. No data are so far available in CS. MEASUREMENTS AND RESULTS: We enrolled 63 consecutive patients with CS following STEMI submitted to Percutaneous Coronary Intervention (PCI). On admission, the APACHE II (Acute physiology and chronic health evaluation II) score and HOMA (Homeostasis model assessment) index were assessed together with glomerular filtration rate (eGFR), quantitative BE, AG, lactate values and 12 h lactate clearance. Non-survivors showed a higher incidence of PCI failure, higher APACHE II score, lower LVEF, lower eGFR, lower 12 h lactate clearance; a higher admission lactate and more negative BE. No difference was detectable in AG and SIG. Only 3 patients exhibited pathological values of SIG (≥ 2) and only 1 of these patients died. CONCLUSIONS: According to our data the SIG approach does not seem to add further information to usual parameters in acid-base evaluation or early risk stratification in CS patients.