Evaluation of subcutaneous tissue gases and pH during induction of acidosis and alkalosis. An experimental study in pigs.

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 (PscO2), carbon dioxide tension (PscCO2) and pH (pH(sc)) in relation to central hemodynamic parameters and oxygenation. Hypoxic-induced acidosis resulted in a decrease in P(sc)O(2) [corrected] and arterial oxygen tension (P(a)O(2)) to one third of baseline values (p < 0.05), an increase in PscCO2 and arterial carbon dioxide tension (PaCO2) 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). PscO2 and PaO2 increased during reversal of hypoxia and infusion of bicarbonate (p < 0.05), without reaching baseline values. In parallel PscCO2 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 PaO2 to 62 mm Hg whereas PscO2 remained below baseline values (p < 0.05). Correction of oxygen utilization in the subcutaneous tissue as measured by the markers PscCO2 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.