Evaluation of Subcutaneous Tissue Gases and pH during Induction of Acidosis and Alkalosis

Abstract

Peripheral tissue oxygen utilization was studied during hypoxic-induced acidosis and sodium bicarbonate-induced alkalosis in 8 domestic pigs by measurements of subcutaneous oxygen tension (P_scO₂), carbon dioxide tension (P_scCO₂) and pH (pH_sc) in relation to central hemodynamic parameters and oxygenation. Hypoxic-induced acidosis resulted in a decrease in P_scCO₂ and arterial oxygen tension (P_aO₂) to one third of baseline values (p < 0.05), an increase in P_scCO₂ and arterial carbon dioxide tension (P_aCO₂) from 41 to 55 and 34 to 39 mm Hg, respectively (p < 0.05), and a decrease in pH_sc from 7.47 to 7.30 (p < 0.05). P_scO₂ and P_aO₂ increased during reversal of hypoxia and infusion of bicarbonate (p < 0.05), without reaching baseline values. In parallel P_scCO₂ decreased and pH_sc increased but changes lagged behind changes in blood gases. Alkalosis established by further infusion of bicarbonate resulted in a decrease in P_aO₂ to 62 mm Hg whereas P_scO₂ remained below baseline values (p < 0.05). Correction of oxygen utilization in the subcutaneous tissue as measured by the markers P_scCO₂ and pH_sc is slower than indicated by changes in tissue oxygen tension, blood gases and pH. Overcompensation of acidosis with bicarbonate resulting in alkalosis impairs oxygenation.