Effects of crystalloid and colloid priming strategies for cardiopulmonary bypass on colloid oncotic pressure and haemostasis: a meta-analysis

Optimization of cardiopulmonary bypass prime fluid to preserve microcirculatory perfusion during on-pump coronary artery bypass graft surgery: PRIME study protocol for a double-blind randomized trial

BACKGROUND

Acute microcirculatory perfusion disturbances and organ edema are important factors leading to organ dysfunction during cardiac surgery with cardiopulmonary bypass (CPB). Priming of the CPB system with crystalloid or colloid fluids, which inevitably leads to hemodilution, could contribute to this effect. However, there is yet no optimal evidence-based strategy for this type of priming. Hence, we will investigate different priming strategies to reduce hemodilution and preserve microcirculatory perfusion.

METHODS

The PRIME study is a single-center double-blind randomized trial. Patients undergoing elective coronary artery bypass graft surgery with CPB will be randomized into three groups of prime fluid strategy: (1) gelofusine with crystalloid, (2) albumin with crystalloid, or (3) crystalloid and retrograde autologous priming. We aim to include 30 patients, 10 patients in each arm. The primary outcome is the change in microcirculatory perfusion. Secondary outcomes include colloid oncotic pressure; albumin; hematocrit; electrolytes; fluid balance and requirements; transfusion rates; and endothelial-, glycocalyx-, inflammatory- and renal injury markers. Sublingual microcirculatory perfusion will be measured using non-invasive sidestream dark field video microscopy. Microcirculatory and blood measurements will be performed at five consecutive time points during surgery up to 24 h after admission to the intensive care unit.

DISCUSSION

PRIME is the first study to assess the effect of different prime fluid strategies on microcirculatory perfusion in cardiac surgery with CPB. If the results suggest that a specific crystalloid or colloid prime fluid strategy better preserves microcirculatory perfusion during on-pump cardiac surgery, the current study may help to find the optimal pump priming in cardiac surgery.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05647057. Registered on 04/25/2023.

CLINICALTRIALS

gov PRS: Record Summary NCT05647057, all items can be found in the protocol.

Effects of albumin and crystalloid priming strategies on red blood cell transfusions in on-pump cardiac surgery: a network meta-analysis

BACKGROUND

In on-pump cardiac surgery, the albumin priming strategy could maintain colloid osmotic pressure better than crystalloid solutions and reduce excessive perioperative fluid balance. However, a high-quality meta-analysis is required to compare the safety of these approaches in perioperative red blood cell (RBC) transfusions. Owing to limited direct evidence, we conducted a network meta-analysis (NMA) to increase the pool of studies and provide indirect evidence.

METHODS

The pre-defined primary outcomes were intraoperative and the first 24 h postoperative RBC transfusion volume in units. The pre-defined secondary outcome was postoperative blood loss (the first 24 h). We reviewed all randomized controlled trials comparing albumin, crystalloid, and artificial colloid priming strategies. Studies that only displayed pre-defined outcomes could be included. A pairwise meta-analysis was performed on studies that directly compared the pre-defined outcomes between albumin and crystalloids. Additionally, a random-effects network meta-analysis (NMA) model was employed to generate indirect evidence for the pre-defined outcomes between albumin and crystalloids.

RESULTS

The literature search identified 830 studies,10 of which were included in the final analysis. Direct meta-analysis indicated that crystalloid priming significantly decreased total perioperative RBC transfusions (MD: -0.68U; 95%CI: -1.26, -0.09U; P = 0.02) and intraoperative RBC transfusions (MD: -0.20U; 95%CI: -0.39, -0.01U; P = 0.03) compared to albumin. Postoperative RBC transfusions showed a decreasing trend in the crystalloid group; however, the difference was not statistically significant. (MD: -0.16U; 95%CI: -0.45, 0.14U; P = 0.30). After including indirect evidence, the NMA results continued to demonstrate a higher RBC receiving with the albumin priming strategy compared to crystalloids, although the differences did not reach statistical significance. For postoperative blood loss, direct evidence showed no significant differences between albumin and crystalloid priming strategies. However, NMA evidence displayed that albumin exist higher probability of reducing postoperative blood loss than crystalloid.

CONCLUSION

Both direct and NMA evidence indicated that the albumin priming strategy resulted in more perioperative RBC transfusions than crystalloids. Considering the additional blood management burden, the application of an albumin-priming strategy in on-pump cardiac surgery still needs more consideration.

Comparison of six percent hydroxyethyl starch 130/0.4 and ringer's lactate as priming solutions in patients undergoing isolated open heart valve surgery: A double-blind randomized controlled trial

OBJECTIVES

Colloids are added to the priming solution of the cardiopulmonary bypass (CPB) pump to maintain colloid osmotic pressure and prevent fluid overload. This study aimed to compare the effects of 6% hydroxyethyl starch (HES) 130/0.4 and ringer's lactate (RL) priming solution on patients' outcomes undergoing isolated heart valve surgery with CPB.

METHODS

This randomized clinical trial included one hundred and 20 patients undergoing heart valve surgery, and those were allocated into two groups. Patients in the RL group received 1500 mL of RL, and those in the RL + HES group were given 500 mL of HES and 1000 mL of RL.

RESULTS

The patients' median age was 52 (IQR 42-60) and 50 (IQR 40-61) years in the RL + HES and the RL group, respectively (p = .71). The number of cases that required blood product transfusion in both the operating room and intensive care unit was also significantly higher in the RL + HES group compared to the RL group (RR 2.04, 95% CI 1.50-2.76; p < .01 and RR 1.42, 95% CI 1.01-2.01; p = .05, respectively). Declines in postoperative creatinine levels and platelet counts were higher in the RL + HES compared to the RL group (between-subjects effect p = .007 and p = .038, respectively), while the incidence of acute kidney injury was comparable between groups (RR 0.66, 95% CI 0.13-3.30; p = .55).

CONCLUSIONS

Among patients undergoing heart valve surgery with CPB, 6% HES added to RL for priming compared with only RL increased the risk of the need for blood product transfusion over the hospitalization period.

Development of new colloid osmotic pressure measurement method using ultrafiltration membrane during cardiopulmonary bypass

BACKGROUND

Clinical practice of measuring colloid osmotic pressure (COP) was abandoned after correcting hypoosmolarity did not improve overall patient outcomes. However, the use of albumin and colloidal solutions has contributed to maintaining intraoperative and postoperative fluid balance at lower levels. Reduced perioperative fluid balance is consistently reported to have positive effects on clinical outcomes. Priming solutions for cardiopulmonary bypass typically include colloids; however, the optimal type of priming solution has not yet been determined. Stricter COP management may further improve postoperative courses. To achieve this, the widespread adoption of a measurement method suitable for COP monitoring during cardiopulmonary bypass is required.

METHODS

A test circuit was made which measured COP using an ultrafiltration membrane method based on the changes in hydrostatic pressure that occurs across a semipermeable membrane. We then compared the measurements obtained using this method with colloidal osmometer measurements.

RESULTS

COP measurements were obtained for a total of 100 tests (10 times each for 10 test solutions). The evaluation parameters included simultaneous reproducibility, correlation with the colloid osmometer, and measurement time. The results demonstrated high accuracy of the ultrafiltration membrane method, simultaneous reproducibility within 3%, a high positive correlation with the colloid osmometer (correlation coefficient: R2 = 0.99; p < 0.01), and equal time required for measurement.

CONCLUSION

Measuring COP using ultrafiltration membranes solves problems within existing measurement methods. Although further improvements in the method are necessary, it has implications for future research and clinical applications.

Changes in colloid oncotic pressure during cardiac surgery with different prime fluid strategies

OBJECTIVE

In cardiac surgery, colloid oncotic pressure (COP) is affected by haemodilution that results from composition and volume of prime fluid of cardiopulmonary bypass (CPB). However, the extent to which different priming strategies alter COP is largely unknown. Therefore, we investigated the effect of different priming strategies on COP in on-pump cardiac surgery.

METHODS

Patients (n = 60) were divided into 3 groups (n = 20 each), based on the center in which they were operated and the specific prime fluid strategy used in that center during the inclusion period. CPB prime fluids were either gelofusine-, albumin-, or crystalloid based, the latter two with or without retrograde autologous priming.

RESULTS

In all groups, COP was lowest after weaning from CPB and one hour after CPB. Between groups, COP was lowest with gelofusine prime fluid (16.4, 16.8 mmHg, respectively) compared with crystalloids (MD: -1.9; 95% CI:-3.6, -0.2; p = .02 and MD: -2.4, 95% CI: -4.2, -0.7; p = .002) and albumin (MD: -1.8, 95% CI: -3.5, -0.50; p = .041 and MD: -2.4, 95% CI: -4.1, -0.7; p = .002). In all groups, the decrease in COP one hour after bypass compared to baseline correlated positively with fluid balance at the end of surgery (p < .001).

CONCLUSIONS

COP significantly decrease during CPB surgery with the largest decrease in COP at the end of surgery, while at the same time fluid balance increases. We suggest that prime fluid strategy should be carefully selected when maintenance of COP during cardiac surgery is desirable.

Application of effective albumin concentration in treatment of chronic liver disease

Albumin is a non-glycosylated plasma protein. Besides the role of increasing blood volume and maintaining plasma colloid osmotic pressure, albumin also has multiple biological functions such as transport, antioxidant and anti-inflammatory effects, immune regulation, etc. In-depth studies on the structure and function of albumin have revealed that the post-transcriptional modification of albumin reduces the effective albumin concentration in patients with chronic liver disease, so the clinically effective albumin concentration rather than total albumin concentration can more accurately reflect the disease progression and prognosis, and more effectively guide exogenous albumin treatment in such patients. This article summarizes the clinical correlation between post-transcriptional modification of albumin and the liver and its related diseases, as well as the studies on effective albumin, in order to provide evidence-based information on effective albumin concentration and to better guide the clinical treatment of chronic liver disease.

Hemostatic effects of a dextran-based priming solution for cardiopulmonary bypass: A secondary analysis of a randomized clinical trial

INTRODUCTION

Intravascular fluids administered to patients may influence hemostasis. In patients undergoing cardiac surgery with cardiopulmonary bypass, the heart-lung machine is primed with 1300 ml of fluid. We assessed postoperative coagulation and platelet function in patients randomized to two different priming solutions, one colloid-based (dextran 40) and one crystalloid-based.

MATERIALS AND METHODS

Eighty-four elective cardiac surgery patients were randomized to either a dextran-based prime or Ringer's acetate with added mannitol. Blood samples were collected before, and 2 and 24 h after cardiopulmonary bypass. Coagulation was assessed by standard coagulation tests and rotational thromboelastometry. Platelet function was assessed with impedance aggregometry. Bleeding volumes and transfusion requirements were recorded.

RESULTS

Comparing the groups 2 h after bypass, the dextran group showed lower hemoglobin concentration, hematocrit, platelet count, and fibrinogen concentration, and higher INR and aPTT, as well as longer clot formation time (+41 ± 21 % vs. +8 ± 18 %, p < 0.001) and a larger reduction in fibrinogen-dependent clot strength (-37 ± 12 % vs. -7 ± 20 %, p < 0.001). Adenosine diphosphate-dependent platelet activation was reduced in the dextran group but not in the crystalloid group 2 h after bypass (-14 ± 29 % vs. -1 ± 41 %, p = 0.041). No significant between-group differences in hemostatic variables remained after 24 h, and no significant differences in perioperative bleeding volumes, re-explorations for bleeding, or transfusion rates were observed.

CONCLUSIONS

Compared to a crystalloid solution, a dextran-based prime had measurable negative impact on hemostatic variables but no detectable increase in bleeding volume or transfusion requirements in cardiac surgery patients.

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.