Acid-base imbalance in uncomplicated ST-elevation myocardial infarction: The clinical role of tissue acidosis

Little information is available on acid-base imbalance in uncomplicated ST-elevation myocardial infarction (STEMI) submitted to primary percutaneous intervention (PCI). We therefore assessed acid-base imbalance in 257 consecutive uncomplicated STEMI patients submitted to PCI to determine whether its evaluation could help in identifying patients at higher risk for in-hospital complications (acute pulmonary edema and dysrhythmias). A basic metabolic profile was performed at hospital admission, that is before PCI. After PCI, we measured: creatinine, uric acid and NT-pro BNP and serum electrolytes. Peak troponin I was also considered. Acidemia was present in 11 patients (4. 2%), HCO₃ <22 in 62 (24. 1%). Base excess <-3 was detectable in 70 patients (27. 2%), anion gap > 12 in 13 (5. 1%), Cl/Na <0. 79 in 93 patients (38. 5%). Patients with a Cl/Na <0. 79 had a lower LVEF (p = 0. 042) and higher values of NT-pro-BNP (p = 0. 019) and of latency (p = 0. 029) together with a higher length of stay (p = 0. 017) and a higher incidence of in-hospital complications (p = 0. 017). At backward stepwise regression analysis, the following variables resulted independent predictors of in-hospital complications: base excess OR 1. 47 (95% CI 1. 04-2. 10) p = 0. 031; Cl/Na ratio O. R. 1. 85 (95% CI 1. 05-3. 27) p = 0. 035. In STEMI patients submitted to mechanical revascularization the evaluation of acid-base status and, in particular the detection of even mild degrees of acidosis may help in risk stratification for in-hospital complications. A Cl/Na <0. 79 ratio and a base excess are independent predictors for in-hospital complications.