Ultrafiltration of the priming blood before cardiopulmonary bypass attenuates inflammatory response and improves postoperative clinical course in pediatric patients

Whole blood transcriptomics reveals granulocyte colony-stimulating factor as a mediator of cardiopulmonary bypass-induced systemic inflammatory response syndrome

Objectives

Systemic inflammatory response syndrome (SIRS) is a frequent complication of cardiopulmonary bypass (CPB). SIRS is associated with significant morbidity and mortality, but its pathogenesis remains incompletely understood, and as a result, biomarkers are lacking and treatment remains expectant and supportive. This study aimed to understand the pathophysiological mechanisms driving SIRS induced by CPB and identify novel therapeutic targets that might reduce systemic inflammation and improve patient outcomes.

Methods

Twenty-one patients undergoing cardiac surgery and CPB were recruited, and blood was sampled before, during and after surgery. SIRS was defined using the American College of Chest Physicians/Society of Critical Care Medicine criteria. We performed immune cell profiling and whole blood transcriptomics and measured individual mediators in plasma/serum to characterise SIRS induced by CPB.

Results

Nineteen patients fulfilled criteria for SIRS, with a mean duration of 2.7 days. Neutrophil numbers rose rapidly with CPB and remained elevated for at least 48 h afterwards. Transcriptional signatures associated with neutrophil activation and degranulation were enriched during CPB. We identified a network of cytokines governing these transcriptional changes, including granulocyte colony-stimulating factor (G-CSF), a regulator of neutrophil production and function.

Conclusions

We identified neutrophils and G-CSF as major regulators of CPB-induced systemic inflammation. Short-term targeting of G-CSF could provide a novel therapeutic strategy to limit neutrophil-mediated inflammation and tissue damage in SIRS induced by CPB.

Impact of pre-bypass ultrafiltration on prime values and clinical outcomes in neonatal and infant cardiopulmonary bypass

BACKGROUND

A standard blood prime for cardiopulmonary bypass (CPB) in congenital cardiac surgery may possess non-physiologic values for electrolytes, glucose, and lactate. Pre-bypass Ultrafiltration (PBUF) can make these values more physiologic and standardized prior to bypass initiation. We aimed to determine if using PBUF on blood primes including packed red blood cells and thawed plasma would make prime values more predictable and physiologic. Additionally, we aimed to evaluate whether the addition of PBUF had an impact on outcome measures.

METHODS

Retrospective review of consecutive patients ≤ 1 year of age undergoing an index cardiac operation on CPB between 8/2017 and 9/2021. As PBUF was performed at the perfusionists' discretion, a natural grouping of patients that received PBUF vs. those that did not occur. Differences in electrolytes, glucose, and lactate were compared at specific time points using Fisher's exact test for categorical variables and the Wilcoxon rank sum test for continuous variables. Clinical outcomes were also assessed.

RESULTS

In both cohorts, the median age at surgery was 3 months and 47% of patients were female; 308/704 (44%) of the PBUF group and 163/414 (39%) of the standard prime group had at least one preoperative risk factor. The proportion of PBUF circuits which demonstrated more physiologic values for glucose (318 [45%]), sodium (434, [62%]), potassium (688 [98%]), lactate (612 [87%]) and osmolality (595 [92%]) was significantly higher when compared to standard prime circuit levels for glucose (8 [2%]), sodium (13 [3%], potassium (150 [36%]), lactate (56 [13%]) and osmolality (23 [6%]) prior to CPB initiation. There were no differences in clinical outcomes or rates of major adverse events between the two cohorts.

CONCLUSIONS

PBUF creates standardized and more physiologic values for electrolytes, glucose, and lactate before the initiation of bypass without significant impacts on in-hospital outcomes.

Blood Conservation and Hemostasis Management in Pediatric Cardiac Surgery

Pediatric cardiac surgery is associated with significant perioperative blood loss needing blood product transfusion. Transfusion carries serious risks and implications on clinical outcomes in this vulnerable population. The need for transfusion is higher in children and is attributed to several factors including immaturity of the hemostatic system, hemodilution from the CPB circuit, excessive activation of the hemostatic system, and preoperative anticoagulant drugs. Other patient characteristics such as smaller relative size of the patient, higher metabolic and oxygen requirements make successful blood transfusion management extremely challenging in this population and require meticulous planning and multidisciplinary teamwork. In this narrative review we aim to summarize risks and complications associated with blood transfusion in pediatric cardiac surgery and also to summarize perioperative coagulation management and blood conservation strategies.

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.

Red cell transfusion management for patients undergoing cardiac surgery for congenital heart disease

BACKGROUND

Congenital heart disease is the most commonly diagnosed neonatal congenital condition. Without surgery, only 30% to 40% of patients affected will survive to 10 years old. Mortality has fallen since the 1990s with 2006 to 2007 figures showing surgical survival at one year of 95%. Patients with congenital heart disease are potentially exposed to red cell transfusion at many points in the surgical pathway. There are a number of risks associated with red cell transfusion that may be translated into increased patient morbidity and mortality.

OBJECTIVES

To evaluate the effects of red cell transfusion on mortality and morbidity on patients with congenital heart disease at the time of cardiac surgery.

SEARCH METHODS

We searched 11 bibliographic databases and three ongoing trials databases including the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 5, 2013), MEDLINE (Ovid, 1950 to 11 June 2013), EMBASE (Ovid, 1980 to 11 June 2013), ClinicalTrials.gov, World Health Organization (WHO) ICTRP and the ISRCTN Register (to June 2013). We also searched references of all identified trials, relevant review articles and abstracts from between 2006 and 2010 of the most relevant conferences. We did not limit the searches by language of publication.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing red cell transfusion interventions in patients undergoing cardiac surgery for congenital heart disease. We included participants of any age (neonates, paediatrics and adults) and with any type of congenital heart disease (cyanotic or acyanotic). We excluded patients with congenital heart disease undergoing non-cardiac surgery. No co-morbidities were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We contacted study authors for additional information.

MAIN RESULTS

We identified 11 trials (862 participants). All trials were in neonatal or paediatric populations. The trials covered only three areas of interest: restrictive versus liberal transfusion triggers (two trials), leukoreduction versus non-leukoreduction (two trials) and standard versus non-standard cardiopulmonary bypass (CPB) prime (seven trials). Owing to the clinical diversity in the participant groups (cyanotic (three trials), acyanotic (four trials) or mixed (four trials)) and the intervention groups, it was not appropriate to pool data in a meta-analysis. No study reported data for all the outcomes of interest to this review. Risk of bias was mixed across the included trials, with only attrition bias being low across all trials. Blinding of study personnel and participants was not always possible, depending on the intervention being used.Five trials (628 participants) reported the primary outcome: 30-day mortality. In three trials (a trial evaluating restrictive and liberal transfusion (125 participants), a trial of cell salvage during CPB (309 participants) and a trial of washed red blood cells during CPB (128 participants)), there was no clear difference in mortality at 30 days between the intervention arms. In two trials comparing standard and non-standard CPB prime, there were no deaths in either randomised group. Long-term mortality was similar between randomised groups in one trial each comparing restrictive and liberal transfusion or standard and non-standard CPB prime.Four trials explored a range of adverse effects following red cell transfusion. Kidney failure was the only adverse event that was significantly different: patients receiving cell salvaged red blood cells during CPB were less likely to have renal failure than patients not exposed to cell salvage (risk ratio (RR) 0.26, 95% confidence interval (CI) 0.09 to 0.79, 1 study, 309 participants). There was insufficient evidence to determine whether there was a difference between transfusion strategies for any other severe adverse events.The duration of mechanical ventilation was measured in seven trials (768 participants). Overall, there was no consistent difference in the duration of mechanical ventilation between the intervention and control arms.The duration of intensive care unit (ICU) stay was measured in six trials (459 participants). There was no clear difference in the duration of ICU stay between the intervention arms in the transfusion trigger and leukoreduction trials. In the standard versus non-standard CPB prime trials, one trial examining the impact of washing transfused bypass prime red blood cells showed no clear difference in duration of ICU stay between the intervention arms, while the trial assessing ultrafiltration of the priming blood showed a shorter duration of ICU stay in the ultrafiltration group.

AUTHORS' CONCLUSIONS

There are only a small number of small and heterogeneous trials so there is insufficient evidence to assess the impact of red cell transfusion on patients with congenital heart disease undergoing cardiac surgery accurately. It is possible that the presence or absence of cyanosis impacts on trial outcomes, which would necessitate different clinical management of two groups. Further adequately powered, specific, high-quality trials are warranted to assess this fully.

Inflammatory response after neonatal cardiac surgery and its relationship to clinical outcomes

BACKGROUND

Cardiac surgery in infants results in a profound inflammatory response secondary to cardiopulmonary bypass (CPB) and the need for blood products. It is not clear how this inflammatory response modulates postoperative course or whether quantification of proinflammatory cytokines can aid with risk stratification. In this study, we prospectively assessed a panel of candidate markers to determine the time course for inflammation and the association of specific markers with clinical outcomes defined as intensive care unit length of stay (LOS).

METHODS

We obtained preoperative blood samples from 92 neonates undergoing surgery with CPB and then serially for 5 days after surgery. Numerous interleukins were assayed along with tumor necrosis factor (TNF)-alpha and interferon (INF)-gamma. The most common surgical procedures were arterial switch procedure (n = 35) and Norwood operation (n = 34). Multivariate analysis was performed to determine if inflammatory mediators could independently predict prolonged intensive care unit LOS.

RESULTS

Compared with the presurgery level, there were statistically significant increases (p < 0.005) for 8 out of 11 inflammatory markers: INF-gamma, interleukin (IL)-10, IL-13, IL-2, IL-5, IL-8, TNF-alpha, and IL-6 after surgery. The only cytokine on the first postoperative day that was independently associated with prolonged length of stay was IL-8 (p = 0.002). Cytokine values measured on postoperative day 3 were most valuable in predicting prolonged LOS. A model that included use of circulatory arrest, and day 3 measures of IL-6 and IL-8 yielded an area under of the curve of 0.88 (95% confidence interval 0.79 to 0.96) for predicting a prolonged LOS.

CONCLUSIONS

In summary, neonatal heart surgery for complex lesions elicits a broad inflammatory response. This early inflammatory response appears nonspecific and did not predict clinical course. Persistence of specific inflammatory mediators on the third day after surgery, however, provided important prognostic information. As such, select cytokines may serve as valuable biomarkers in this population. Whether strategies targeting specific cytokines can alter clinical course is not known.

Risk of extracorporeal life support circuit-related hyperkalemia is reduced by prebypass ultrafiltration

OBJECTIVES

Pediatric patients who receive large volume blood transfusions are at risk for experiencing transfusion-related hyperkalemic cardiac arrest. Prebypass ultrafiltration of blood used to prime cardiopulmonary bypass circuits is commonly used in pediatric cardiac surgery to create a more physiologic and electrolyte balanced priming solution prior to initiation of cardiopulmonary bypass. This study was undertaken to determine the efficacy of prebypass ultrafiltration in normalizing extracorporeal life support circuit priming solution before initiating extracorporeal life support.

DESIGN

Prospective study.

SETTING

PICU and neonatal ICU in a tertiary academic center.

PATIENTS

Patients requiring venovenous extracorporeal life support.

INTERVENTIONS

Prebypass ultrafiltration of extracorporeal life support circuits.

MEASUREMENTS AND MAIN RESULTS

Hematocrit, electrolyte, and lactate concentrations were measured in blood-primed extracorporeal life support circuits before and after ultrafiltration and in blood collected from patients before and after initiation of extracorporeal life support. Clinically significant elevation of K concentration was observed in all extracorporeal life support circuits prior to prebypass ultrafiltration, despite the fact that 93% of red blood cell units were collected ≤ 7 days prior to use. Prebypass ultrafiltration significantly reduced concentrations of K (10.9 vs 6.0 mEq/L, p = 0.001) and lactate (7.0 vs 3.6 mmol/L, p < 0.001) and increased hematocrit (37% vs 48%, p < 0.001) and concentrations of ionized calcium (0.64 vs 1.16 mg/dL, p < 0.001) and Na (129 vs 144 mEq/L, p < 0.001). Serum electrolyte concentrations remained within the normal physiologic range in all patients following initiation of venovenous extracorporeal life support with circuits that underwent prebypass ultrafiltration.

CONCLUSIONS

Prebypass ultrafiltration normalizes the electrolyte balance of blood-primed extracorporeal life support circuits. Prebypass ultrafiltration processing may reduce the risk of transfusion-related hyperkalemic cardiac arrest in small children who require venovenous extracorporeal life support.

A combined ultrafiltration strategy during pediatric cardiac surgery: a prospective, randomized, controlled study with clinical outcomes

OBJECTIVE

To investigate the clinical effects of a combined ultrafiltration strategy on the surgical treatment of pediatric patients with congenital heart diseases.

DESIGN

A prospective, randomized, controlled study.

SETTING

A single-institution study in an affiliated hospital of a university.

PARTICIPANTS

Sixty-five pediatric patients who underwent open heart surgery with cardiopulmonary bypass (CPB) to treat congenital heart disease were enrolled. The participants were randomized into 2 groups: conventional + modified ultrafiltration (MUF) (CM) group and prime + zero-balanced + MUF (PZM) group.

INTERVENTIONS

In the CM group (n = 33), conventional ultrafiltration was performed after removal of the aortic clamp, and MUF was performed after the completion of CPB. In the PZM group (n = 32), ultrafiltration was performed for the circuit prime solution, zero-balance ultrafiltration was performed after removal of the aortic clamp, and MUF was performed after the completion of CPB.

MEASUREMENTS AND MAIN RESULTS

The blood gas parameters and tumor necrosis factor alpha content in the priming solution and perioperative blood samples were analyzed. Postoperative parameters, including mechanical ventilation time, respiratory indices, intensive care unit time, and hospital time, also were recorded. One hospital death occurred in each group. No severe complications occurred in either group. The lactic acid, glucose, and tumor necrosis factor alpha contents in the priming solution and perioperative blood samples were significantly lower in the PZM group compared with the CM group. The respiratory indices were statistically significantly better in the PZM group compared with the CM group in the early postoperative period. No significant differences were found between the 2 groups regarding the postoperative ventilation time, inotropic support, homologous blood transfusion, drainage, intensive care unit time, or postoperative hospital time.

CONCLUSION

The combined use of ultrafiltration of prime solution, zero-balance ultrafiltration, and MUF strategy is associated with a modest improvement in pulmonary function compared with the combination of conventional and MUF strategies in the early postoperative period, but the principal clinical outcomes are similar.

Transfusion-free neonatal cardiopulmonary bypass using a TinyPump

BACKGROUND

We devised a miniaturized circuit incorporating a TinyPump in the venous line to amplify the venous return. We compared this system to the conventional blood-primed circuit and investigated whether this circuit could maintain hematocrit levels without blood transfusion and reduce coagulation and inflammatory cascades.

METHODS

Thirteen 1-week-old piglets (3.7 ± 0.2 kg) were divided into group M (miniaturized circuits with TinyPump-assisted venous drainage without blood, n = 7) and group C (conventional circuits with blood priming, n = 6). Cardiopulmonary bypass (CPB) was performed at 150 to 180 mL·kg(-1)·min(-1) for 2 hours, including 60 minutes of cardioplegic cardiac arrest. Modified ultrafiltration (MUF) was subsequently performed. Data were acquired before CPB and after the end of MUF.

RESULTS

The priming volume including the hemofilter circuit of the main circuit required 152 mL in group M and 300 mL in group C. The mean hematocrit values in group M and group C were not significantly different during CPB (21.5% ± 2.0% versus 23.2% ± 1.3%) or after MUF (30.7% ± 2.1% versus 32.9% ± 4.0%). After MUF, group M had lower thrombin-antithrombin complex levels (16.7 ± 5.0 ng/mL versus 28.4 ± 8.4 ng/mL, p < 0.01) and interleukin-8 levels (2,867 ± 758 pg/mL versus 13,730 ± 5,220 pg/mL, p < 0.01) than group C. The pulmonary vascular resistance index was lower in group M after MUF (4,105 ± 862 dynes·cm(-5)·kg(-1) versus 6,304 ± 1,477 dynes·cm(-5)·kg(-1), p < 0.01). The lung water content was also better in group M (83.7% ± 0.5% versus 84.9% ± 0.5%, p < 0.01).

CONCLUSIONS

The minicircuit with TinyPump-assisted venous drainage successfully maintained acceptable hematocrit levels and the cardiopulmonary function in neonatal piglets. Employing this technique may attenuate blood requirements and inflammatory responses, thereby improving the clinical outcomes of neonatal open-heart surgery.

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.

Modified and conventional ultrafiltration during pediatric cardiac surgery: Clinical outcomes compared

OBJECTIVE

This prospective study compared clinical outcomes after heart surgery between three groups of infants with congenital heart disease. One group received dilutional conventional ultrafiltration (group D), another received modified ultrafiltration (group M), and a third group received both dilutional conventional and modified ultrafiltration (group B). We hypothesized that group B patients would have the best clinical outcome.

METHODS

Children younger than 1 year undergoing heart surgery for biventricular repair by the same surgeon were randomly allocated to one of the three study groups. Patient management was standardized, and intensive care staff were blinded to group allocation. Primary outcome measure was duration of postoperative mechanical ventilation. Other outcome measures recorded included total blood products transfused, duration of chest tube in situ, chest tube output, and stays in intensive care and in the hospital.

RESULTS

Sixty infants completed study protocol. Mean age and weight were as follows: group D (n = 19), 61 days, 4.3 kg; group M (n = 20), 64 days, 4.5 kg; and group B (n = 21), 86 days, 4.4 kg. Preoperative and intraoperative characteristics were similar between groups. Ultrafiltrate volumes obtained were 196 +/- 93 mL/kg in group D, 105 +/- 33 mL/kg in group M, and 261 +/- 113 mL/kg in group B. There were no significant differences between groups for any outcome variable. Technical difficulties prevented completion of modified ultrafiltration in 2 of 41 infants.

CONCLUSION

There was no clinical advantage in combining conventional and modified ultrafiltration. Because clinical outcomes were similar across groups, relative risks of the ultrafiltration strategies may influence choice.

Aprotinin attenuates the elevation of pulmonary vascular resistance after cardiopulmonary bypass

Pulmonary vascular resistance (PVR) is generally believed to be elevated after cardiopulmonary bypass (CPB) due to whole body inflammation. Aprotinin has an antiinflammatory action, and it was hypothesized that aprotinin would attenuate the PVR increase induced by CPB. Ten mongrel dogs were placed under moderately hypothermic CPB for 2 hr. The experimental animals were divided into a control group (n=5, group I) and an aprotinin group (n=5, group II). In group II, aprotinin was administered during pre-bypass (50,000 KIU/kg) and post-bypass (10,000 KIU/kg) periods. Additional aprotinin (50,000 KIU/kg) was mixed in CPB priming solution. PVRs at pre-bypass and post-bypass 0, 1, 2, 3 hr were calculated, and lung tissue was obtained after the experiment. Post-bypass PVRs were significantly higher than prebypass levels in all animals (n=10, p<0.001). PVR elevation in group II was less than in group I at 3 hr post-bypass (p=0.0047). Water content of the lung was lower in group II (74+/-9.4%) compared to that of group I (83+/-9.5%), but the difference did not reach significance (p=0.076). Pathological examination showed a near normal lung structure in group II, whereas various inflammatory reactions were observed in group I. We concluded that aprotinin may attenuate CPB-induced PVR elevation through its anti-inflammatory effect.

Elimination of proinflammatory cytokines in pediatric cardiac surgery: analysis of ultrafiltration method and filter type

OBJECTIVE

This study was undertaken to assess whether different filter types or ultrafiltration methods influence inflammatory markers in pediatric cardiac surgery.

METHODS

Forty-one children younger than 5 years were prospectively randomized to groups A (polyamid filter with conventional ultrafiltration), B (polyamid filter with modified ultrafiltration), C (polysulfon filter with conventional ultrafiltration), and D (polysulfon filter with modified ultrafiltration). Interleukin 6, interleukin 10, tumor necrosis factor, terminal complement complex, and lactoferrin were measured before the operation (T0), before rewarming (T1), after ultrafiltration (T2), at 6 (T3) and 18 hours (T4) after the operation, and in the ultrafiltrate.

RESULTS

All markers changed with both ultrafiltration methods, both filter types, and in all groups (except tumor necrosis factor) along the T0 to T4 observation time (P <.0001). Their patterns of changes were different for terminal complement complex, with less decrease after use of the polysulfon filter (P <.05), and among groups A through D for interleukin 6 (P =.01), with more decrease in group C than group A (P <.02). Interleukin 10 decreased with the polyamid filter (P <.001) but not with the polysulfon filter. In the ultrafiltrate, tumor necrosis factor was higher with the polysulfon filter than the polyamid filter (6.8 +/- 5 pg/mL vs 4.0 +/- 3.7 pg/mL, P <.05). The ultrafiltrate/plasma ratio of interleukin 6 was higher with conventional ultrafiltration than modified ultrafiltration (0.018 +/- 0.017 vs 0.004 +/- 0.007, P <.005).

CONCLUSIONS

The polysulfon filter showed a filtration profile for inflammatory mediators superior to that of the polyamid filter for interleukin 6, tumor necrosis factor, and interleukin 10. Interleukin 6 was most efficiently removed by conventional ultrafiltration with a polysulfon filter, and tumor necrosis factor was best removed by modified ultrafiltration with a polysulfon filter, whereas other inflammatory mediators were not influenced by filter type or ultrafiltration method. Therefore combined conventional and modified ultrafiltration with a polysulfon filter may currently be the most effective strategy for removing inflammatory mediators in pediatric heart surgery.

Microvascular Inflammatory Response in Cardiac Surgery

Cardiac surgical procedures, with or without cardiopulmonary bypass, elicit a systemic inflammatory response in patients that induces the elaboration of multiple cytokines, chemokines, adhesion molecules, and destructive enzymes. This inflammatory reaction involves multiple interdependent and redundant cell types and humoral cascades, which allows for amplification and positive feedback at numerous steps. This systemic inflammatory response ultimately results in a broad spectrum of clinical manifestations, with multiple organ failure being the most severe form. Investigative efforts have focused on understanding the mechanism of this systemic inflammatory response syndrome in order to develop potential therapeutic targets to inhibit it, thereby possibly decreasing postoperative morbidity and mortality. Multiple therapeutic methods have been investigated, including pharmacologic inhibitors and modifications of surgical technique and the cardiopulmonary bypass circuit. Although studies have demonstrated that the use of these therapies in experimental and clinical settings has attenuated the systemic inflammatory response, they have failed to conclusively show clinical benefit from these therapies. These therapies may be too specific to minimize the deleterious effects of a systemic inflammatory response that results from the activation of multiple, interdependent, and redundant inflammatory cascades and cell types. Hence, further studies that investigate the molecular and cellular events underlying the systemic inflammatory response syndrome and the resultant effects of anti-inflammatory therapies are warranted to ultimately achieve improvements in clinical outcome after cardiac surgical procedures.

Bradykinin and histamine generation with generalized enhancement of microvascular permeability in neonates, infants, and children undergoing cardiopulmonary bypass surgery

OBJECTIVE

To investigate whether generation and liberation of bradykinin and histamine contribute to generalized edema formation in pediatric cardiopulmonary bypass surgery.

DESIGN

Prospective observational study.

SETTING

Pediatric heart surgery of a university hospital.

PATIENTS

Forty-one neonates, infants, and children undergoing cardiopulmonary bypass to correct congenital cardiac anomalies.

INTERVENTIONS

Plasma concentrations of bradykinin and histamine were determined before, during, and after cardiopulmonary bypass. Fluid balance was evaluated by control of fluid intake and output.

MEASUREMENTS AND MAIN RESULTS

The susceptibility to generalized edema formation increased significantly (r = -.457; p <.005) with decreasing age. Approximately three times higher plasma concentrations of bradykinin (p <.001) were found at the onset of anesthesia and during the total observation period in patients with a fluid retention of >6% of body weight compared with patients with a lower retention rate. Plasma bradykinin reached significantly (p <.01) higher peak concentrations of 237.9 +/- 58.6 fmol/mL during cardiopulmonary bypass and of 227.5 +/- 90.7 fmol/mL during the early postoperative period in patients with severe edema formation in contrast to only 86.6 +/- 10.9 and 65.5 +/- 26.8 fmol/mL in patients with minor fluid retention. A tendency (p =.06) to slightly increasing histamine concentrations from 2.07 +/- 0.13 nmol/L at baseline to 3.32 +/- 1.41 nmol/L during 90 mins of cardiopulmonary bypass was only observed in patients with high fluid retention.

CONCLUSIONS

Bradykinin seems to be essentially involved in the enhancement of microvascular permeability in pediatric cardiopulmonary bypass surgery, although a dominant causal role cannot be claimed by this study. Histamine, however, doesn't appear to play a major role and may only contribute as a cofactor. To what extent an increased expression of bradykinin-1 and bradykinin-2 receptors or a reduced potential of bradykinin-degrading enzymes is involved is the object of a further clinical study.