Interleukin-8 secretion following cardiopulmonary bypass in children as a marker of early postoperative morbidity

Dexmedetomidine Pharmacokinetics and a New Dosing Paradigm in Infants Supported With Cardiopulmonary Bypass

BACKGROUND

Dexmedetomidine is increasingly used off-label in infants and children with cardiac disease during cardiopulmonary bypass (CPB) and in the postoperative period. Despite its frequent use, optimal dosing of dexmedetomidine in the setting of CPB has not been identified but is expected to differ from dosing in those not supported with CPB. This study had the following aims: (1) characterize the effect of CPB on dexmedetomidine clearance (CL) and volume of distribution (V) in infants and young children; (2) characterize tolerance and sedation in patients receiving dexmedetomidine; and (3) identify preliminary dosing recommendations for infants and children undergoing CPB. We hypothesized that CL would decrease, and V would increase during CPB compared to pre- or post-CPB states.

METHODS

Open-label, single-center, opportunistic pharmacokinetics (PK) and safety study of dexmedetomidine in patients ≤36 months of age administered dexmedetomidine per standard of care via continuous infusion. We analyzed dexmedetomidine PK data using standard nonlinear mixed effects modeling with NONMEM software. We compared model-estimated PK parameters to those from historical patients receiving dexmedetomidine before anesthesia for urologic, lower abdominal, or plastic surgery; after low-risk cardiac or craniofacial surgery; or during bronchoscopy or nuclear magnetic resonance imaging. We investigated the influence of CPB-related factors on PK estimates and used the final model to simulate dosing recommendations, targeting a plasma concentration previously associated with safety and efficacy (0.6 ng/mL). We used the Wilcoxon rank sum test to evaluate differences in dexmedetomidine exposure between infants with hypotension or bradycardia and those who did not develop these adverse events.

RESULTS

We collected 213 dexmedetomidine plasma samples from 18 patients. Patients had a median (range) age of 3.3 months (0.1-34.0 months) and underwent CPB for 161 minutes (63-394 minutes). We estimated a CL of 13.4 L/h/70 kg (95% confidence interval, 2.6-24.2 L/h/70 kg) during CPB, compared to 42.1 L/h/70 kg (95% confidence interval, 38.7-45.8 L/h/70 kg) in the historical patients. No specific CPB-related factor had a statistically significant effect on PK. A loading dose of 0.7 µg/kg over 10 minutes before CPB, followed by maintenance infusions through CPB of 0.2 or 0.25 µg/kg/h in infants with postmenstrual ages of 42 or 92 weeks, respectively, maintained targeted concentrations. We identified no association between dexmedetomidine exposure and selected adverse events (P = .13).

CONCLUSIONS

CPB is associated with lower CL during CPB in infants and young children compared to those not undergoing CPB. Further study should more closely investigate CPB-related factors that may influence CL.

Effects of on-pump versus off-pump coronary artery bypass grafting on myocardial metabolism

BACKGROUND

On-pump coronary artery bypass grafting (ON-PCABG) and off-pump coronary artery bypass grafting (OF-PCABG) greatly affect myocardial metabolism (MCMB). However, no study has systematically explored and compared the impacts of ON-PCABG and OF-PCABG on MCMB. This study will aim to explore and to compare the effects of ON-PCABG and OF-PCABG on MCMB systematically.

METHODS

We will conduct the comprehensive literature search from the following electronic databases from inception to the present: Cochrane Library, EMBASE, MEDILINE, CINAHL, AMED and 4 Chinese databases without language restrictions. This systematic review will only concern randomized controlled trials (RCTs) and case-control studies of ON-PCABG and OF-PCABG on MCMB. The methodological quality of each entered study will be assessed by using Cochrane risk of bias tool.

RESULTS

Primary outcomes include myocardial cellular markers, myocardial lactate, oxygen utilization, pyruvate, and intramyocardial concentrations of glucose, urea and lactate. Secondary outcome comprises of glutathione, superoxide dismutase, myeloperoxidase, and oxidative stress and any other complications post surgery.

CONCLUSION

This study will provide a high-quality synthesis and will assess and compare the effects of ON-PCABG and OF-PCABG on MCMB based on the current relevant literature evidence.

DISSEMINATION AND ETHICS

The results will be submitted to peer-reviewed journals for publication. This study does not require ethic approval, because it only analyzes the data from published literature.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019125381.

Delta chemokine (fractalkine)--a novel mediator of pulmonary arterial hypertension in children undergoing cardiac surgery

BACKGROUND

Fractalkine (FKN), a unique chemokine associated with pulmonary hypertension, may be involved in the acute stress response that regulates inflammation after cardiopulmonary bypass (CPB) surgery. We characterized FKN levels and correlated them with clinical parameters in children undergoing cardiac surgery involving CPB.

METHODS

Twenty-seven consecutive patients, aged 30 days to 11.5 years, who underwent surgery for correction of congenital heart defects, were prospectively studied. Serial blood samples were collected preoperatively, upon termination of CPB, and at six points postoperatively. Plasma was recovered immediately, aliquoted, and frozen at -70° C until assayed. Clinical and laboratory data were collected.

RESULTS

Baseline FKN levels were skewed between patients. Patients with low FKN levels showed significantly higher levels of oxygen saturation in room air compared to patients with high FKN levels (p<0.05). Moreover, there was a positive correlation between preoperative pulmonary arterial hypertension and FKN levels (p<0.05). Surprisingly, FKN elevation from preoperative to postoperative levels displayed no discernible pattern.

CONCLUSIONS

FKN levels significantly correlate with preoperative hypoxemia and PAH, suggesting that FKN may be up-regulated during hypoxemia. CPB is not associated with acute changes in circulating FKN levels. The role of FKN in the postoperative course should be further investigated.

Myocardial TLR4 is a determinant of neutrophil infiltration after global myocardial ischemia: mediating KC and MCP-1 expression induced by extracellular HSC70

Cardiac surgery with global myocardial ischemia-reperfusion (I/R) induces a myocardial inflammatory response that impairs cardiac recovery. Chemokines contribute to the overall myocardial inflammatory response through inducing leukocyte infiltration. Although Toll-like receptor 4 (TLR4) has an important role in postischemic myocardial injury, the relative roles of myocardial tissue and leukocyte TLR4 in leukocyte infiltration, as well as the role of TLR4 in myocardial chemokine expression, are unclear. Our recent study, in an isolated mouse heart model of global I/R, found that the 70-kDa heat shock cognate protein (HSC70) is released from cardiac cells and mediates the expression of cardiodepressant cytokines via a TLR4-dependent mechanism. In the present study, we tested the hypotheses that myocardial tissue TLR4 has a major role in mediating neutrophil infiltration and that myocardial TLR4 and extracellular HSC70 contribute to the mechanisms underlying cardiac chemokine response to global I/R. We subjected hearts isolated from TLR4-defective and TLR4-competent mice to global I/R and examined myocardial neutrophil infiltration and expression of keratinocyte-derived chemokine (KC) and monocyte chemoattractant protein-1 (MCP-1). TLR4-defective hearts exhibited reduced neutrophil infiltration regardless of the phenotypes of neutrophils perfused during reperfusion and expressed lower levels of KC and MCP-1. HSC70-specific antibody reduced myocardial expression of KC and MCP-1 after I/R. Furthermore, perfusion of HSC70 increased KC and MCP-1 expression in TLR4-competent hearts but not in TLR4-defective hearts, and HSC70 also induced the chemokine response in macrophages in a TLR4-dependent fashion. A recombinant HSC70 fragment lacking the substrate-binding domain was insufficient to induce chemokine expression in hearts and cells. This study demonstrates that myocardial tissue TLR4, rather than neutrophil TLR4, is the determinant of myocardial neutrophil infiltration after global I/R. TLR4 mediates myocardial chemokine expression, and the mechanisms involve extracellular HSC70. These results imply the HSC70-TLR4 interaction as a novel mechanism underlying the myocardial chemokine response to global I/R.

Patterns and prognostic value of troponin, interleukin-6, and leptin after pediatric open-heart surgery

PURPOSE

Leptin and interleukin-6 (IL-6) are inversely correlated and associated with decreased survival in critically ill patients. We investigated changes in leptin, IL-6, and troponin in children undergoing open-heart surgery, hypothesizing that IL-6 and troponin will increase after cardiopulmonary bypass (CPB) and will be negatively correlated with leptin.

PATIENTS AND METHODS

Serial blood samples were collected from 21 patients 24 hours before and up to 48 hours after surgery.

RESULTS

Leptin levels decreased by 50% during CPB (P < .001), then gradually increased, reaching baseline levels 12 hours after surgery. The IL-6 levels increased (P < .001) during CPB, peaking 2 hours after surgery and remaining slightly elevated at 24 hours after surgery (P < .001). Leptin and IL-6 were negatively correlated (R = -0.448, P < .001). Troponin levels increased during CPB (P < .001). Postoperative leptin and troponin were inversely correlated (r = -0.535, P < .001). Patients with modest elevations in troponin levels (<20 microg/L) had a shorter aortic clamp and CPB time (P < .01), lower IL-6 peak levels (P = .03), and shorter duration of ventilation and inotropic support compared with patients with peak troponin levels greater than 20 microg/L.

CONCLUSIONS

Lower leptin and higher IL-6 levels correlated with troponin, a marker of myocardial injury. Because leptin may have cardioprotective effects, the postoperative drop in its levels may further contribute to myocardial dysfunction.

Reconstituted fresh whole blood improves clinical outcomes compared with stored component blood therapy for neonates undergoing cardiopulmonary bypass for cardiac surgery: a randomized controlled trial

OBJECTIVE

This study compared the effects of reconstituted fresh whole blood against standard blood component therapy in neonates undergoing cardiac surgery.

METHODS

Patients less than 1 month of age were randomized to receive either reconstituted fresh whole blood (n = 31) or standard blood component therapy (n = 33) to prime the bypass circuit and for transfusion during the 24 hours after cardiopulmonary bypass. Primary outcome was chest tube drainage; secondary outcomes included transfusion needs, inotrope score, ventilation time, and hospital length of stay.

RESULTS

Patients who received reconstituted fresh whole blood had significantly less postoperative chest tube volume loss per kilogram of body weight (7.7 mL/kg vs 11.8 mL/kg; P = .03). Standard blood component therapy was associated with higher inotropic score (6.6 vs 3.3; P = .002), longer ventilation times (164 hours vs 119 hours; P = .04), as well as longer hospital stays (18 days vs 12 days; P = .006) than patients receiving reconstituted fresh whole blood. Of the different factors associated with the use of reconstituted fresh whole blood, lower platelet counts at 10 minutes and at the end of cardiopulmonary bypass, older age of cells used in the prime and throughout bypass, and exposures to higher number of allogeneic donors were found to be independent predictors of poor clinical outcomes.

CONCLUSIONS

Reconstituted fresh whole blood used for the prime, throughout cardiopulmonary bypass, and for all transfusion requirements within the first 24 hours postoperatively results in reduced chest tube volume loss and improved clinical outcomes in neonatal patients undergoing cardiac surgery.

Preferential existence of death-inducing proteins in the human cardiomyopathic left ventricle

INTRODUCTION

Idiopathic or acquired dilated cardiomyopathy (DCM) is a leading health threat resulting in considerable mortality and serious long-term disability with a substantial economic healthcare expenditure. The purpose of this study was to investigate the modulation of apoptotic signaling genes in human cardiomyopathy.

METHODS

Cardiac tissue was obtained from six heart transplant recipients (age = 43 +/- 7 y) with DCM. Equivalent control specimens were taken from six healthy heart donors (age = 33 +/- 4 y). The mRNA expression of death-inducing proteins, the death (DRs) and decoy receptors (DcRs), in the four cardiac chambers was quantified using real time polymerase chain reaction LightCycler (Roche Diagnostics GmbH, Mannheim, Germany). Immunodetectable receptor protein expression was quantified densitometrically. Data were analyzed by analysis of variance and unpaired Student's t-test.

RESULTS

In DCM tissues, DR1 mRNA was elevated by 42.7% (P < 0.01) in the left ventricle (LV) and 56.4% (P < 0.001) in the left atrium (LA), while DR2 increased by 112.5% (P < 0.00001) in LV and 45.8% (P < 0.05) in LA. Increase in DR4 was 29.6% (P < 0.01) in LV, 82.5% (P < 0.01) in the right ventricle (RV), 210.8% (P < 0.01) in LA, and 99.1% (P < 0.01) in the right atrium (RA). DR5 was elevated by 66.7% (P < 0.01) in LV, 181.8% (P < 0.005) in LA, and 90.2% (P < 0.05) in RA. DcR1 decreased by 30.8% in LV, 44% (P < 0.05) in LA, and 12.5% in RA; DcR3 by 67.1% (P < 0.0001) in LV, 82.4% (P < 0.0001) in RV, 85.1% (P < 0.0001) in LA, and 84.6% (P < 0.0001) in RA. The trends in mRNA expression were comparable to the changes in protein expression.

CONCLUSIONS

Left heart-sided increase of death-inducing proteins in human cardiomyopathy is suggestive of their potential modulatory roles in death-related signaling in the pathogenesis of end-stage myocardial failure.

“Early” Delayed Sternal Closure Following Pediatric Cardiac Surgery

BACKGROUND

Delayed sternal closure is commonly used following pediatric cardiopulmonary bypass surgery for many reasons including support of the failing myocardium. We hypothesized that, as a result of improvements in perioperative care, sternal closure could be achieved at an earlier postoperative time than the 3 to 5 days typically reported in the literature.

METHODS

Retrospective chart review of all bypass surgery (n = 585) performed in a single center over a 3-year period (2000-2002).

RESULTS

We identified 66 children (11.3%), median age 5 days old, who underwent delayed sternal closure. In 60 of these patients, sternal closure was achieved at a median (interquartile) postoperative time of 21 hours (18 to 40 hours). The most common indication was inadequate hemostasis, although early sternal closure was also achieved in the subgroup with poor myocardial function as the primary indication at a median of 36 hours (21 to 44 hours). There was no noticeable hemodynamic, respiratory or metabolic compromise following sternal closure, although patients with poor myocardial function tended to have a lower mean blood pressure than those with inadequate hemostasis (ANOVA, p = 0.02). The overall mortality was 19.7% (13 of 66), with a median duration of ventilation and intensive care stay among survivors of 3.8 days (2.4 to 6.3 days) and 4.8 days (3.7 to 7.9 days), respectively.

CONCLUSIONS

Delayed sternal closure is possible at an earlier stage than previously reported.

Volume replacement with HES 130/0.4 may reduce the inflammatory response in patients undergoing major abdominal surgery

PURPOSE

To investigate the effects of intravascular volume replacement therapy on the inflammatory response during major surgery.

METHODS

Thirty-six patients scheduled for elective abdominal surgery were randomized to receive either 6% hydroxyethylstarch (130,000 Dalton mean molecular weight, degree of substitution 0.4; n = 18, HES-group) or lactated Ringer's solution (RL-group; n = 18) for intravascular volume replacement. Fluid therapy was given perioperatively and continued for 48 hr in the intensive care unit. Volume replacement was guided by physiological parameters. Serum concentrations of interleukin (IL)-6, IL-8 and IL-10 and soluble adhesion molecules (sELAM-1 and sICAM-1) were measured after induction of anesthesia, four hours after the end of surgery, as well as 24 hr and 48 hr postoperatively.

RESULTS

Biometric and perioperative data, hemodynamics and oxygenation were similar between groups. On average, 4470 +/- 340 mL of HES 130/0.4 per patient were administered in the HES-group compared to 14310 +/- 750 mL of RL in the RL-group during the study period. Release of pro-inflammatory cytokines IL-6 and IL-8 was significantly lower in the HES-group [(peak values) 47.8 +/- 12.1 pg*dL(-1) of IL-6 and 35.8 +/- 11.2 pg*mL(-1) of IL-8 (HES-group) vs 61.2 +/- 11.2 pg*dL(-1) of IL-6 and 57.9 +/- 9.7 pg*mL(-1) of IL-8 (RL-group); P < 0.05]. Serum concentrations of sICAM-1 were significantly higher in the RL-group [(peak values) 1007 +/- 152 ng*mL(-1) (RL-group) vs 687 +/- 122 ng*mL(-1), (HES group); P < 0.05)]. Values of sELAM-1 were similar in both groups.

CONCLUSION

Intravascular volume replacement with HES 130/0.4 may reduce the inflammatory response in patients undergoing major surgery compared to a crystalloid-based volume therapy. We hypothesize that this is most likely due to an improved microcirculation with reduced endothelial activation and less endothelial damage.

Chemokines and the inflammatory response following cardiopulmonary bypass--a new target for therapeutic intervention?--A review

This 10-year Medline search of English-language articles describing experimental and clinical studies on chemokines, cardiopulmonary bypass (CPB) and systemic or multiorgan failure revealed that chemokines are significantly involved in the pathogenesis of post-CPB syndrome. The post-CPB inflammatory response depends upon recruitment and activation of inflammatory cells. Leucocyte recruitment is a well-orchestrated process that involves several protein families, including pro-inflammatory cytokines, adhesion molecules and chemokines. Current anti-inflammatory therapies mostly act on the cells that have already been recruited. A more efficient therapy might be the prevention of excessive recruitment of particular leucocyte populations by antagonizing chemokine receptors which might act upstream of the current anti-inflammatory agents. The chemokines, which are a cytokine subfamily of chemotactic cytokines, participate in recognizing, recruiting, removing and repairing inflammation. As chemokines target specific leucocyte subsets, antagonism of a single chemokine ligand or receptor would be expected to have a circumscribed effect, thereby endowing the antagonist with a limited side-effect profile. Chemokines should be considered as possible targets for therapeutic intervention.