Efficient extra- and intracellular alkalinization improves cardiovascular functions in severe lactic acidosis induced by hemorrhagic shock.

Background: Lactic acidosis is associated with cardiovascular failure. Buffering with sodium bicarbonate is proposed in severe lactic acidosis. Bicarbonate induces carbon dioxide generation and hypocalcemia, both cardiovascular depressant factors. The authors thus investigated the cardiovascular and metabolic effects of an adapted sodium bicarbonate therapy, including prevention of carbon dioxide increase with hyperventilation and ionized calcium decrease with calcium administration.

Methods: Lactic acidosis was induced by hemorrhagic shock. Twenty animals were randomized into five groups: (1) standard resuscitation with blood retransfusion and norepinephrine (2) adapted sodium bicarbonate therapy (3) nonadapted sodium bicarbonate therapy (4) standard resuscitation plus calcium administration (5) hyperventilation. Evaluation was focused in vivo on extracellular pH, on intracellular pH estimated by P nuclear magnetic resonance and on myocardial contractility by conductance catheter. Aortic rings and mesenteric arteries were isolated and mounted in a myograph, after which arterial contractility was measured.

Results: All animals in the hyperventilation group died prematurely and were not included in the statistical analysis. When compared with sham rats, shock induced extracellular (median, 7.13; interquartile range, [0.10] vs. 7.30 [0.01]; P = 0.0007) and intracellular acidosis (7.26 [0.18] vs. 7.05 [0.13]; P = 0.0001), hyperlactatemia (7.30 [0.01] vs. 7.13 [0.10]; P = 0.0008), depressed myocardial elastance (2.87 [1.31] vs. 0.5 [0.53] mmHg/μl; P = 0.0001), and vascular hyporesponsiveness to vasoconstrictors. Compared with nonadapted therapy, adapted bicarbonate therapy normalized extracellular pH (7.03 [0.12] vs. 7.36 [0.04]; P < 0.05), increased intracellular pH to supraphysiological values, improved myocardial elastance (1.68 [0.41] vs. 0.72 [0.44] mmHg/μl; P < 0.05), and improved aortic and mesenteric vasoreactivity.

Conclusions: A therapeutic strategy based on alkalinization with sodium bicarbonate along with hyperventilation and calcium administration increases pH and improves cardiovascular function.