Management of priming fluids in cardiopulmonary bypass for adult cardiac surgery: network meta-analysis

Background Cardiopulmonary bypass (CPB) is frequently employed for cardiac surgery, and selecting a suitable priming fluid is a prerequisite for CPB. Currently, the commonly used priming fluids in clinics are classified as crystalloids and colloids, including balanced crystalloids, albumin, dextran, gelatin and hydroxyethyl starch (HES). This network meta-analysis compared the effects of eight fluids used during CPB in adults to determine optimal priming fluid during CPB surgery. Methods Randomised controlled trials assessing priming fluids for CPB in adult cardiac surgery published before 13 April 2023 were searched across Ovid MEDLINE(R) ALL, OVID EMbase, and Cochrane Central Register of Controlled Trials. Various priming fluids were classified into eight categories, including balanced crystalloids, 0.9% NaCl, iso-oncotic human albumin, hyperoncotic human albumin, HES with molecular weight 130k, HES with molecular weight 200k, gelatin and dextran. Results The NMA of platelet counts revealed no significant differences in any result. In direct comparison results, only the comparison of HES with molecular weight 130k vs. gelatin (standard mean difference = -0.40, 95% confidence interval [95%CI: -0.63, -0.16) revealed a significant difference. According to the SUCRA, balanced crystalloids had the highest platelet count, followed by gelatin, and HES with a molecular weight of 130k had the lowest platelet, followed by HES with a molecular weight of 200k. Conclusion Patients using dextran have a low mortality rate and a short mean CPB time, the use of balanced crystalloids is beneficial in terms of platelet count, and HES with molecular weight 130k is beneficial for postoperative urine volume at 24h. However, all priming fluids have pros and cons quite, and the optimal choice of priming fluids remains unsupported by current evidences. When performing CPB surgery, the type of priming fluid should be selected according to the actual situation in CPB for adult cardiac surgery. KEY MESSAGES When dextran was used as the CPB priming fluid, patients had the lowest mortality and shortest mean CPB time. With iso-oncotic HA, patients had the shortest length of ICU stay, the least blood loss 24h after surgery, and the lowest chest tube output 24h after surgery. The use of balanced crystalloids was beneficial for platelet count, the use of L-HES was beneficial for urine output 24h after surgery, and the use of H-HES resulted in the shortest hospital stay. In summary, each of these fluids has pros and cons quite, and an optimal choice of priming fluids during CPB surgery remains unsupported by current evidence. When performing CPB surgery, the type of priming fluids should be selected according to the actual condition of the patient's body.