Effects of sodium chloride and bicarbonate in shock with metabolic acidosis

Abstract

Metabolic acidosis from inadequate tissue perfusion has been thought to depress cardiovascular function, but this is difficult to quantify and separate from low blood flow and hypoxia. To evaluate this, equimolar hypertonic NaHCO3 [sodium bicarbonate] and NaCl (8.9 milliosmols in 5 ml/kg) and blood were compared in dogs in hemorrhagic shock. Cardiac output (CO.) and mesenteric blood flow (MF) approached preshock levels with both solutions, but blood pressure (BP) remained low. NaHCO3 raised pH to 7.38 and NaCl lowered pH by .03 from 7.15. At 15 min, CO., MF, BP, and systemic and mesenteric O2 consumption were comparable after both solutions but 1-2 times higher with blood. Hemodilution, volume bled to return to 30 mm Hg, plasma Na, K, osmolality, and duration of action were comparable after each. The correction of pH by NaHCO3 produced no greater blood flow, blood pressure, or oxygenation in animals with severe metabolic acidosis than NaCl. This suggests that metabolic acidosis produced by tissue hypoxia in shock may not significantly depress the circulation in the intact animal at the level and duration studied.