Evaluation of acid-base balance in ST-elevation myocardial infarction in the early phase: a prognostic tool?

OBJECTIVES: Metabolic acidosis has been described after myocardial infarction, but little data are available on the acid-base imbalance in ST-elevation myocardial infarction (STEMI) submitted to mechanical revascularization, and earlier studies on this topic differ with respect to patients' selection criteria, treatment and evaluated parameters.

METHODS: We assessed admission base excess, anion gap, and lactate in 445 consecutive patients with STEMI submitted to primary percutaneous coronary intervention and whether its evaluation could help in identifying patients at a higher risk for in-hospital mortality and complications (acute pulmonary edema and arrhythmias).

RESULTS: At backward stepwise logistic regression analysis, the following variables were independently associated with intra-ICCU mortality: age [odds ratio (OR) 1.05; 95% confidence interval (CI) 1.02-1.10; P = 0.006], estimated glumerular filtration rate (OR 0.98; 95% CI 0.96-0.99; P= 0.010), Tn I (OR 1.006; 95% CI 1.004-1.008; P <0.001), and base excess (OR 0.90; 95% CI 0.82-0.99; P = 0.038); Hosmer-Lemeshow v2: 5.69, P = 0.681. At backward stepwise logistic regression analysis, the following variables were independently associated with intra-ICCU complications: left ventricular ejection fraction (OR 0.95; 95% CI 0.91-0.98; P = 0.005) and lactic acid (OR 1.31; 95% CI 1.10-1.57; P =0.003); Hosmer-Lemeshow v2: 4.11, P = 0.847.

CONCLUSION: According to our findings, the evaluation of base excess and lactate in the early phase of STEMI provides the bedside clinicians with useful tools for early risk stratification. In fact, base excess proved to be an independent predictor for intra-ICCU mortality, whereas lactate represented an independent marker for intra-ICCU complications.