Bicarbonate does not increase left ventricular contractility during L-lactic acidemia in pigs

Area of Science:

• Cardiovascular Physiology
• Acid-Base Balance
• Pharmacology

Background:

• Lactic acidosis is known to impair left ventricular contractility.
• The efficacy of bicarbonate therapy in improving cardiac function during lactic acidosis remains debated.

Purpose of the Study:

• To investigate the direct effects of bicarbonate on left ventricular contractility during experimentally induced lactic acidosis in vivo.
• To determine if sodium bicarbonate administration enhances myocardial function under conditions of metabolic acidosis.

Main Methods:

• Anesthetized pigs underwent L-lactic acid infusion to induce lactic acidosis, with beta-blockade and atrial pacing.
• Hemodynamics and left ventricular mechanics were measured, including pressure-volume relationships to assess contractility (Emax).
• Animals were randomized to receive either sodium bicarbonate or saline infusion.

Main Results:

• Bicarbonate infusion led to a decrease in mean arterial pressure without increasing cardiac output, similar to saline.
• Left ventricular contractility, assessed by Emax, did not significantly improve after bicarbonate administration.
• The effects of bicarbonate on hemodynamics and contractility were not significantly different from those of saline.

Conclusions:

• Sodium bicarbonate infusion does not directly enhance left ventricular contractility during lactic acidemia in pigs within the studied pH range.
• These findings suggest that the direct inotropic effects of bicarbonate on the heart are minimal under these experimental conditions.