The buffering ability of commonly employed cardiopulmonary bypass solutions and alkalizing agents.

This experiment evaluated the hydrogen ion (H + ) buffering capacity (BC) of solutions and alkalizing agents employed during cardiopulmonary bypass (CPB). A solution's BC can be determined when a known quantity of H + is titrated into the solution and the change ( ) in pH (-log of the hydrogen ion activity ([H + ] a )) is measured ( [H + ] a / mmole H + ). Eleven solutions were studied : Lactated Ringers (LR), 0.9% NaCl (NS), Plasma-Lyte A TM , Hespan TM (6% hetastarch), banked donor blood with citrate phosphate dextrose adenine (CPDA-1), fresh donor blood, THAM TM , sodium bicarbonate (NaHCO 3 ; 1 mEq/ml), high potassium crystalloid cardioplegic solution (HKCCPS), oxygenated crystalloid cardioplegic solution (OCCPS), and adult crystalloid priming solution (AP) per institutional protocol. The solutions were studied at three temperatures : 37°C, 28°C, and 18°C. The null hypothesis stated there was no difference in the BC of the solutions studied. The solutions were first titrated to the same starting pH of 8.0. The solutions were then titrated with a predetermined concentration of hydrochloric acid (HCl) to a pH of 7.0. A higher quantity of H + added to a solution indicated a greater ability of that solution to buffer H + within pH limits of 8.0 to 7.0. The data was analyzed with a two way ANOVA and Bonferonni method. A p value <0.05 was considered to be statistically significant. The significant results of our study indicated that THAM tm demonstrated the best BC, followed in decreasing order by NaHCO 3 , banked blood, fresh blood, HKCCPS, AP, OCCPS, Plasmalyte TM , LR, Hespan TM , and NS.