Crystalloid fluids choices during cardiopulmonary bypass, outcomes of acid–base and lactate levels in cardio surgery

BACKGROUND: Ultrafiltration is integral to cardiopulmonary bypass, yet the optimal replacement fluid for zero-balance ultrafiltration requires further investigation to guide clinical practice. This study aimed to compare the efficacy of Normal saline, Ringer's solution, and Ringer's lactate on lactate management, acid-base balance, and clinical outcomes. METHODS: This semi-experimental study enrolled 90 patients undergoing cardiopulmonary bypass (CPB) into three groups of 30. In Group-R, Ringer's solution was used as replacement fluid in Z-BUF. In Group-RL, Ringer's lactate and in Group-NS, Normal saline was used. Lactate and pH levels were measured at five points: before CPB and after anesthesia induction, after cardioplegia, before starting Z-BUF, after Z-BUF and after CPB. RESULTS: While there was no significant difference in baseline lactate (T1), an increasing trend was observed up to T3. At T4, immediately after Z-BUF, lactate levels were significantly higher in Group-RL (3.5 ± 1.0 mEq/L) compared to Group-R (2.3 ± 1.0 mEq/L) and Group-NS (1.9 ± 0.6 mEq/L) (p < 0.05). By T5, lactate in Group-RL decreased, showing no significant difference between groups. There were no statistically significant differences in pH between groups at any time point. However, the magnitude of pH decrease from T3 to T4 was smaller in Group-RL (7.38 ± 0.05 to 7.37 ± 0.03) compared to Group-R (7.39 ± 0.05 to 7.35 ± 0.04) and Group-NS (7.41 ± 0.07 to 7.35 ± 0.05). CONCLUSION: While Ringer's lactate demonstrated favorable pH stability, its clinical superiority in preventing significant acidosis or reducing bicarbonate requirements, and the implications for postoperative nursing monitoring and fluid management protocols, require validation in larger trials.