Bicarbonate buffered ultrafiltration leads to a physiologic priming solution in pediatric cardiac surgery

Unmasking culprits: novel analysis identifies complement factors as potential therapeutic targets to mitigate inflammation during children's heart surgery

BACKGROUND

Cardiopulmonary bypass (CPB) causes systemic inflammation during pediatric cardiac surgery, which can contribute to post-operative organ dysfunction and prolonged recovery. This study aims to identify key inflammatory mediators related to this clinically significant immunologic response.

METHODS

Pediatric patients were enrolled in a single-arm prospective clinical study (NCT05154864) and received standard cardiac operation, CPB and subzero-balance ultrafiltration. Arterial samples were taken before CPB initiation and immediately after weaning, and concentrations of 33 inflammatory mediators were assayed. A principal component analysis with hierarchical clustering (PCA-HCPC) included inflammatory mediator concentrations measured at the end of CPB, validated peak post-operative clinical scores, ventilation time and intensive care length of stay. Mahalanobis distance assessed statistical differences between clusters. Spearman's correlation described the linear relationship between mediator concentrations at the end of CPB and intensive care length of stay. Results are median (IQR).

RESULTS

Forty consecutive patients were enrolled; the majority were male (58%), age of 7.3 (1.7-39.0) months and weight of 6.7 (4.6-14.9) kg. The PCA-HCPC revealed activated complement factors along with all peak clinical scores and prolonged intensive care requirements in the same cluster. Cytokine, chemokine, and leukocyte adhesion molecule concentrations were found in two other distinct clusters (Mahalanobis distance = 16.5; p = 0.004 and Mahalanobis distance = 17.4; p = 5.8 × 10-4). Mediator concentrations of C2 (Rho = 0.50; p = 0.001), C3 (Rho = 0.58; p = 1.1 × 10-4), C3b (Rho = 0.47; p = 0.002), C5 (Rho = 0.48; p = 0.002) and C5a (Rho = 0.63; 1.7 × 10-5) showed linear correlations with intensive care unit length of stay.

CONCLUSIONS

Activated complement factors, but not pro-inflammatory cytokines or chemokines, were most related to cardiopulmonary dysfunction and prolonged recovery in this novel analysis. Investigation of therapies that inhibit complement to dampen CPB-associated inflammation and enhance recovery after pediatric cardiac surgery is warranted. Trial Registration ClinicalTrials.gov, NCT05154864.

Sanguineous cardiopulmonary bypass prime accelerates the inflammatory response during pediatric cardiac surgery

BACKGROUND

The inflammatory response to cardiopulmonary bypass (CPB) in pediatric patients remains an unresolved challenge. Sanguineous CPB prime, composed of allogenic blood products, is one potentially important stimulus. This study aims to identify specific inflammatory mediators active in sanguineous CPB prime and their impact on the inflammatory response at CPB initiation.

METHODS

In a post-hoc analysis of a prospective observational cohort study (NCT05154864), where pediatric patients undergoing cardiac surgery with CPB were enrolled after informed consent, patients were grouped by CPB prime type (sanguineous vs crystalloid). Arterial samples were collected post-sternotomy as a baseline and again at CPB initiation from all patients. In the sanguineous group, CPB prime samples were also collected after buffered ultrafiltration but before CPB initiation. Luminex® measured concentrations of 24 inflammatory mediators for comparison between groups. Statistical analyses were by Mann-Whitney test and Wilcoxon signed-rank test. Data are presented as median [IQR].

RESULTS

Forty consecutive pediatric patients participated. The sanguineous group (n = 26) was younger (4.0 [0.2 - 6.0] vs 48.5 [39.0 - 69.5] months; p = 2.6 × 10-7) and smaller (4.9 [34 - 6.6] vs 17.2 [14.9 - 19.6] kg; p = 2.6 × 10-7) than the crystalloid group (n = 14). Despite this, baseline concentrations of 20 complement and cytokine concentrations were comparable between groups (p > 0.05) while four showed differences between groups (p < 0.05). The sanguineous prime contained supraphysiologic concentrations of complement mediators: C2, C3, C3a, C3b, and C5a. Correspondingly, upon CPB initiation, patients receiving sanguineous prime exhibited a significantly larger burden of C2, C3, C3b, C5, and C5a (p < 0.001) relative to the crystalloid group. Cytokine and chemokine mediators were present at trace levels in the sanguineous prime.

CONCLUSIONS

Sanguineous prime contains activated complement that accelerates the inflammatory response at CPB initiation in neonates and infants. Immunomodulatory interventions targeting complement during CPB prime preparation could offer substantial benefits for these vulnerable patients.

Prevention of postoperative bleeding after complex pediatric cardiac surgery by early administration of fibrinogen, prothrombin complex and platelets: a prospective observational study

Background

Postoperative bleeding is a major problem in children undergoing complex pediatric cardiac surgery. The primary aim of this prospective observational study was to evaluate the effect of an institutional approach consisting of early preventive fibrinogen, prothrombin complex and platelets administration on coagulation parameters and postoperative bleeding in children. The secondary aim was to study the rate of re-intervention and postoperative transfusion, the occurrence of thrombosis, length of mechanical ventilation, ICU stay and mortality.

Methods

In fifty children (age 0–6 years) with one or more predefined risk factors for bleeding after cardiopulmonary bypass (CPB), thrombelastography (TEG) and standard coagulation parameters were measured at baseline (T1), after CPB and reversal of heparin (T2), at sternal closure (T3) and after 12 h in the ICU (T4). Clinical bleeding was evaluated by the surgeon at T2 and T3 using a numeric rating scale (NRS, 0–10).

Results

After CPB and early administration of fibrinogen, prothrombin complex and platelets, the clinical bleeding evaluation score decreased from a mean value of 6.2 ± 1.9 (NRS) at T2 to a mean value of 2.1 ± 0.8 at T3 (NRS; P <  0.001). Reaction time (R), kinetic time (K), maximum amplitude (MA) and maximum amplitude of fibrinogen (MA-fib) improved significantly (P <  0.001 for all), and MA-fib correlated significantly with the clinical bleeding evaluation (r = 0.70, P <  0.001). The administered total amount of fibrinogen (mg kg^− 1) correlated significantly with weight (r = − 0.42, P = 0.002), priming volume as percentage of estimated blood volume (r = 0.30, P = 0.034), minimum CPB temperature (r = − 0.30, P = 0.033) and the change in clinical bleeding evaluation from T2 to T3 (r = 0.71, P <  0.001). The incidence of postoperative bleeding (> 10% of estimated blood volume) was 8%. No child required a surgical re-intervention, and no cases of thrombosis were observed. Hospital mortality was 0%.

Conclusion

In this observational study of children with an increased risk of bleeding after CPB, an early preventive therapy with fibrinogen, prothrombin complex and platelets guided by clinical bleeding evaluation and TEG reduced bleeding and improved TEG and standard coagulation parameters significantly, with no occurrence of thrombosis or need for re-operation.

Trial registration

German Clinical Trials Register DRKS00018109 (retrospectively registered 27th August 2019).

Comparison of the trometamol-balanced solution with two other crystalloid solutions for fluid resuscitation of a rat hemorrhagic model

Currently, the optimal resuscitation fluid remains debatable. Therefore, in the present study, we designed a trometamol-balanced solution (TBS) for use as a resuscitation fluid for hemorrhagic shock. Hemorrhagic shock was induced in 18 male Wistar-Kyoto rats, which were assigned to normal saline (NS), Ringer's solution (RS), and TBS groups. During the hemorrhagic state, their hemodynamic parameters were recorded using an Abbott i-STAT analyzer with the CG4+ cartridge (for pH, pressure of carbon dioxide, pressure of oxygen, total carbon dioxide, bicarbonate, base excess, oxygen saturation, and lactate), the CG6+ cartridge (for sodium, potassium, chloride, blood glucose, blood urea nitrogen, hematocrit, and hemoglobin), and enzyme-linked immunosorbent assay kits (calcium, magnesium, creatinine, aspartate aminotransferase, alanine aminotransferase, bilirubin, and albumin). Similar trends were found for the parameters of biochemistries, electrolytes, and blood gas, and they revealed no significant changes after blood withdrawal-induced hemorrhagic shock. However, the TBS group showed more effective ability to correct metabolic acidosis than the NS and RS groups. TBS was a feasible and safe resuscitation solution in this study and may be an alternative to NS and RS for resuscitation in hemorrhagic shock patients without liver damage.

Recent innovations in perfusion and cardiopulmonary bypass for neonatal and infant cardiac surgery

The development and refinement of cardiopulmonary bypass (CPB) has made the repair of complex congenital heart defects possible in neonates and infants. In the past, the primary goal for these procedures was patient survival. Now that substantial survival rates have been achieved for even the most complex of repairs in these patients, focus has been given to the reduction of morbidity. Although a necessity for these complex neonatal and infant heart defect repairs, CPB can also be an important source of perioperative complications. Recent innovations have been developed to mitigate these risks and is the topic of this review. Specifically, we will discuss improvements in minimizing blood transfusions, CPB circuit design, monitoring, perfusion techniques, temperature management, and myocardial protection, and then conclude with a brief discussion of how further systematic improvements can be made in these areas.

Hemodiafiltration-A Technique for Physiological Correction of Priming Solution in Pediatric Cardiac Surgery: An In Vitro Study

Pediatric cardiopulmonary bypass (CPB) circuit invariably requires priming with packed red blood cells (PRBCs). Metabolic composition of stored PRBCs is unphysiological and becomes worse with increasing duration of storage. It is recommended to correct these abnormalities before initiation of CPB. We tested the hypothesis that hemodiafiltration of the prime with 0.45% saline is sufficient for reducing the metabolic load and reaching a physiologic state. In an in vitro study, 100 mL of blood each from 45 units of PRBCs stored for 3-20 days were used for priming the 45 neonatal CPB circuits. Based upon the method used for removal of excess crystalloid from the prime, circuits were divided into three groups. Group 1: Direct removal through manifold line. Group 2: Ultrafiltration of prime. Group 3: Hemodiafiltration of the prime. Blood gas analyses were obtained from the PRBCs and from the prime before and after removal of crystalloid. Both direct removal of crystalloid and ultrafiltration resulted in significant reduction in biochemical and metabolic load of blood (P < 0.001). However, the final composition of the prime was far from being physiological. Hemodiafiltration resulted in improvement of metabolic parameters to near physiological range (lactate: 33.8 ± 4.44 vs. 14 ± 2.53 mg/dL, pH: 7.05 ± 0.15 vs. 7.34 ± 0.06, bicarbonates: 4.83 ± 0.59 vs. 27.6 ± 2.94 meq/L; P < 0.001). Similarly, sodium (147.76 ± 12.73 vs. 144.6 ± 5.96 meq/L) and potassium (9.6 ± 2.83 vs. 4.23 ± 0.37 meq/L) also changed significantly (P < 0.001) to near physiologic range. Hemodiafiltraion of final prime is a simple, efficients and rapid method of correcting the biochemical parameters and reducing the metabolic load of stored PRBCs towards the physiological range before initiating the CPB.

Raman spectroscopy as a novel tool for monitoring biochemical changes and inter-donor variability in stored red blood cell units

Raman spectroscopy has been used to retrieve biochemical information from the supernatant of stored red blood cells (RBCs), demonstrating that some units of donated RBCs accumulate lactate much more readily than others.

Current ultrafiltration techniques before, during and after pediatric cardiopulmonary bypass procedures

Ultrafiltration, which is currently considered as a standard method to remove excess water administered during pediatric cardiopulmonary bypass (CPB), aims to minimize the adverse effects of hemodilution, such as tissue edema and blood transfusion. Three ultrafiltration techniques can be used before, during and after CPB procedures, including conventional ultrafiltration (CUF), modified ultrafiltration (MUF) and zero-balance ultrafiltration (Z-BUF). These methods are widely different, but they have common benefits on hemoconcentration, less requirement for blood products, and reduction of the systemic inflammatory responses (SIRS). The present review attempts to restate these ultrafiltration circuitries, application methods, end-points, and clinical impacts.

Bicarbonate-buffered ultrafiltration during pediatric cardiac surgery prevents electrolyte and acid-base balance disturbances

Pediatric cardiopulmonary bypass is still a challenge because of electrolyte disturbances and inflammation. Many investigations deal with different types of hemofiltration to reduce these potentially harmful side effects. We tested the hypothesis of whether bicarbonate-buffered hemofiltration of the priming solution minimizes electrolyte and acid-base disturbances during the initiation of cardiopulmonary bypass and whether bicarbonate-buffered hemofiltration performed during cardiopulmonary bypass could reduce cytokine levels. Twenty children younger than 2 years of age (mean age 166 ± 191 days; mean weight 6.42 ± 3.22 kg) scheduled for pediatric cardiac surgery with cardiopulmonary bypass were enrolled in this prospective clinical study. Cardiopulmonary bypass circuits were primed with a bicarbonate-buffered hemofiltration solution, gelatin and 1 unit of packed red blood cells. The priming was hemofiltered using an ultrahemofilter until approximately 1000 mL of ultrafiltrate was restored with the buffered solution. Further hemofiltration was performed throughout the whole bypass time, especially during rewarming. Blood gas analyses and inflammatory mediators were monitored during the operation. Blood gas analysis results after initiation of cardiopulmonary bypass and throughout the entire study remained within the physiologic ranges. Even potassium decreased from 4.0 ± 0.3 to 3.4 ± 0.4 mmol.l−1 after initiation of cardiopulmonary bypass. Plasma levels of tumor necrosis factor alpha decreased significantly (47 ± 44 vs. 24 ± 21 pg.mL−1) whereas complement factor C3a (5.0 ± 2.9 vs. 16.8 ± 6.6 ng.mL−1) and interleukin-6 (7.3 ± 15.2 vs. 110 ± 173 pg.mL−1) increased despite hemofiltration. In conclusion, this study shows that bicarbonate-buffered ultrafiltration is an efficient, simple and safe method for performing hemofiltration, both of the priming solution and during the entire bypass time. The use of a physiological restitution solution prevents electrolyte and acid-base balance disturbances. The elimination of inflammatory mediators seems to be as effective as other ultrafiltration methods.