Sequestration of Dexmedetomidine in Ex Vivo Cardiopulmonary Bypass Circuits.

Dexmedetomidine (DEX) is a sedative used in combination with other drugs in neonates and infants undergoing cardiac surgery using cardiopulmonary bypass (CPB). This study aimed to evaluate the disposition of DEX after administration to the ex vivo CPB circuits following different bolus doses and continuous infusion of DEX, including the effect of circuit coating, temperature, and modified ultrafiltration (MUF). Cardiopulmonary bypass circuits were setup ex vivo and primed with reconstituted blood. Dexmedetomidine was administered to the circuit (as a single bolus or single bolus along with continuous infusion). The circuit was allowed to equilibrate during the first 5 minutes, blood samples were collected at multiple time points (5-240 minutes). Blood samples were processed to collect plasma and analyzed for DEX with a validated assay. The majority of DEX sequestration in ex vivo CPB circuits occurred within the first 15 minutes. The percent of DEX remained in plasma pre-MUF (16-71%) and post-MUF (22-92%) varied depending on the dose and dosing scheme. Modified ultrafiltration significantly increased the plasma concentration of DEX in 19 of 23 circuits by an average of 12.1 ± 4.25% (p < 0.05). The percent sequestration of DEX was lower in CPB circuits at lower DEX doses compared to higher doses. A combination of DEX initial loading dose and continuous infusion resulted in steady concentrations of DEX over 4 hours. At therapeutically relevant concentrations of DEX (485-1,013 pg/ml), lower sequestration was observed in ex vivo CPB circuits compared to higher doses. The sequestration of DEX to circuits should be considered to achieve the optimal concentration of DEX during CPB surgery.

Rise in Angiopoietin-2 Following Neonatal Cardiac Surgery Is Associated With Adverse Clinical Outcomes.

OBJECTIVES: Neonatal cardiac surgery for congenital cardiac defects is associated with significant morbidity and mortality, and there is a need for early identification of patients at highest risk of adverse outcomes. Because vascular endothelial injury mediates damage across organ systems, we measured serum biomarkers of endothelial injury in neonates following cardiopulmonary bypass and examined their associations with short-term outcomes. DESIGN: Prospective cohort study. SETTING: Pediatric cardiac ICU. PATIENTS: Thirty neonates less than 2 weeks old undergoing repair of congenital cardiac defects with cardiopulmonary bypass. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Biomarkers of endothelial integrity, angiopoietin-1 and angiopoietin-2, were measured preoperatively and at 24 hours postoperatively. A composite adverse outcome was defined as any of the following: stroke, need for renal replacement therapy, extracorporeal membrane oxygenation support, cardiac arrest, or death. Associations of biomarkers with adverse outcomes were examined using Wilcoxon rank-sum test. There was an increase in angiopoietin-2 from preoperatively to 24 hours postoperatively (p < 0.0001) and a decrease in angiopoietin-1 from preoperatively to 24 hours postoperatively (p < 0.0001). Patients with greater rise in angiopoietin-2 from preoperatively to 24 hours postoperatively had greater risk of composite adverse outcome (p = 0.04). They had a trend toward higher Vasoactive-Inotropic Score (p = 0.06) and a higher prevalence of low cardiac output syndrome (p = 0.06). Twenty-four hour postoperative angiopoietin-2 level was associated with the composite adverse outcome (p = 0.03). The rise in angiopoietin-2 level from preoperatively to 24 hours postoperatively directly correlated with cardiopulmonary bypass duration (r = 0.47; p = 0.01). CONCLUSIONS: In neonatal cardiac surgery, longer duration of cardiopulmonary bypass is directly associated with greater endothelial injury as measured by increased serum levels of angiopoietin-2. Angiopoietin-2 levels 24 hours postoperatively were significantly associated with a composite adverse outcome. Postoperative angiopoietin-2 level may serve as an early indicator of patients in need of closer monitoring and protective intervention. Further research into endothelial protective strategies is warranted.

Results of a phase 1 multicentre investigation of dexmedetomidine bolus and infusion in corrective infant cardiac surgery.

BACKGROUND: Dexmedetomidine (DEX) is increasingly used intraoperatively in infants undergoing cardiac surgery. This phase 1 multicentre study sought to: (i) determine the safety of DEX for cardiac surgery with cardiopulmonary bypass; (ii) determine the pharmacokinetics (PK) of DEX; (iii) create a PK model and dosing for steady-state DEX plasma levels; and (iv) validate the PK model and dosing. METHODS: We included 122 neonates and infants (0-180 days) with D-transposition of the great arteries, ventricular septal defect, or tetralogy of Fallot. Dose escalation was used to generate NONMEM® PK modelling, and then validation was performed to achieve low (200-300 pg ml-1), medium (400-500 pg ml-1), and high (600-700 pg ml-1) DEX plasma concentrations. RESULTS: Five of 122 subjects had adverse safety outcomes (4.1%; 95% confidence interval [CI], 1.8-9.2%). Two had junctional rhythm, two had second-/third-degree atrioventricular block, and one had hypotension. Clearance (CL) immediately postoperative and CL on CPB were reduced by approximately 50% and 95%, respectively, compared with pre-CPB CL. DEX clearance after CPB was 1240 ml min-1 70 kg-1. Age at 50% maximum clearance was approximately 2 days, and that at 90% maximum clearance was 18 days. Overall, 96.1% of measured DEX concentrations fell within the 5th-95th percentile prediction intervals in the PK model validation. Dosing strategies are recommended for steady-state DEX plasma levels ranging from 200 to 1000 pg ml-1. CONCLUSIONS: When used with a careful dosing strategy, DEX results in low incidence and severity of adverse safety events in infants undergoing cardiac surgery with cardiopulmonary bypass. This validated PK model should assist clinicians in selecting appropriate dosing. The results of this phase 1 trial provide preliminary data for a phase 3 trial of DEX neuroprotection. CLINICAL TRIALS REGISTRATION: NCT01915277.

Adrenergic receptor genotypes influence postoperative outcomes in infants in the Single-Ventricle Reconstruction Trial.

OBJECTIVES: Adrenergic receptor (ADR) genotypes have been associated with adverse outcomes in heart failure. Our objective was to evaluate the association of ADR genotypes with post-Norwood outcomes in infants with hypoplastic left heart syndrome (HLHS). METHODS: Infants with HLHS participating in the Pediatric Heart Network Single-Ventricle Reconstruction Trial underwent genotyping for 4 single-nucleotide polymorphisms in 3 ADR genes: ADRB1_231A/G, ADRB1_1165G/C, ADRB2_5318C/G, and ADRA2A_2790C/T. The association of genotype with freedom from serious adverse events (SAEs) (death, transplant, extracorporeal membrane oxygenation, cardiopulmonary resuscitation, acute shunt failure, unplanned reoperations, or necrotizing enterocolitis) during 14 months' follow-up was assessed with Cox regression and the association with post-Norwood complications was assessed with Poisson regression. Models were adjusted for clinical and surgical factors. RESULTS: The study included 351 eligible patients (62% male; 83% white). The mean age at Norwood procedure was 5.6 ± 3.6 days. A total of 152 patients had SAEs during 14-month follow-up including 84 deaths and 10 transplants. ADRA2A_2790CC genotype had lower SAE-free survival compared with CT/TT genotypes during follow-up (Log rank test, P = .02), and this association was independent of clinical and surgical risk factors (adjusted Cox regression, hazard ratio 1.54 [95% confidence interval 1.04, 2.30] P = .033). Post-Norwood complication rate did not differ by genotype. CONCLUSIONS: Infants with HLHS harboring ADR genotypes that are associated with greater catecholamine release or sensitivity had lower event-free survival after staged palliation. Excess catecholamine activation may adversely affect cardiovascular adaptation after the Norwood procedure. Future studies should explore whether targeting adrenergic activation in those harboring risk genotypes can improve outcomes. (ClinicalTrials.gov number NCT00115934).

Fluid Overload Is Associated With Late Poor Outcomes in Neonates Following Cardiac Surgery.

OBJECTIVES: Acute kidney injury is a severe complication of cardiac surgery associated with increased morbidity and mortality; yet, acute kidney injury classification for neonates remains challenging. We characterized patterns of postoperative fluid overload as a surrogate marker for acute kidney injury and as a risk factor of poor postoperative outcomes in neonates undergoing cardiac surgery. DESIGN: Retrospective cohort study. SETTING: Single, congenital heart center destination program. PATIENTS: Four hundred thirty-five neonates undergoing cardiac surgery with cardiopulmonary bypass from January 2006 through December 2010. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Demographics, diagnosis, and perioperative clinical variables were collected, including daily weights and serum creatinine levels. A composite poor clinical outcome (death, need for renal replacement therapy or extracorporeal life support within 30 postoperative days) was considered the primary outcome measure. Twenty-one neonates (5%) had a composite poor outcome with 7 (2%) requiring renal replacement therapy, 8 (2%) requiring extracorporeal life support, and 14 (3%) dying between 3 and 30 days post surgery. Neonates with a composite poor outcome had significantly higher maximum fluid overload (> 20%) and were slower to diurese. A receiver-operating characteristic curve determined that fluid overload greater than or equal to 16% and serum creatinine greater than or equal to 0.9 on postoperative day 3 were the optimal cutoffs for significant discrimination on the primary outcome (area under the curve = 0.71 and 0.76, respectively). In multivariable analysis, fluid overload greater than or equal to 16% (adjusted odds ratio = 3.7) and serum creatinine adjusted odds ratio 0.9 (adjusted odds ratio = 6.6) on postoperative day 3 remained an independent risk factor for poor outcome. Fluid overload greater than or equal 16% was also significantly associated with cardiac arrest requiring cardiopulmonary resuscitation, prolonged ICU stay, and chest reexploration. CONCLUSIONS: This study highlights the importance of monitoring fluid balance in the neonatal cardiac surgical population and suggests that daily fluid overload, a readily available, noninvasive marker of renal function, may be a sensitive and specific predictor of adverse outcomes.

Validation of association of the apolipoprotein E ε2 allele with neurodevelopmental dysfunction after cardiac surgery in neonates and infants.

OBJECTIVE: Apolipoprotein E (APOE) genotype is a determinant of neurologic recovery after brain ischemia and traumatic brain injury. The APOE ε2 allele has been associated with worse neurodevelopmental (ND) outcome after repair of congenital heart defects (CHD) in infancy. Replication of this finding in an independent cohort is essential to validate the observed genotype-phenotype association. METHODS: The association of APOE genotype with ND outcomes was assessed in a combined cohort of patients with single-ventricle CHD enrolled in the Single Ventricle Reconstruction and Infant Single Ventricle trials. ND outcome was assessed at 14 months using the Psychomotor Development Index (PDI) and Mental Development Index (MDI) of the Bayley Scales of Infant Development-II. Stepwise multivariable regression was performed to develop predictive models for PDI and MDI scores. RESULTS: Complete data were available for 298 of 435 patients. After adjustment for preoperative and postoperative covariates, the APOE ε2 allele was associated with a lower PDI score (P = .038). Patients with the ε2 allele had a PDI score approximately 6 points lower than those without the risk allele, explaining 1.04% of overall PDI variance, because the ε2 allele was present in only 11% of the patients. There was a marginal effect of the ε2 allele on MDI scores (P = .058). CONCLUSIONS: These data validate the association of the APOE ε2 allele with adverse early ND outcomes after cardiac surgery in infants, independent of patient and operative factors. Genetic variants that decrease neuroresilience and impair neuronal repair after brain injury are important risk factors for ND dysfunction after surgery for CHD.

Getting personal: understanding how genetic variation affects clinical outcomes in patients with tetralogy of Fallot.

The work by Jeewa et al. is an important step toward "personalizing" or individualizing our approach to care of patients with tetralogy of Fallot. Although future studies will need to confirm the potential role of HIF1A-mediated signaling in right ventricular remodeling, it raises the possibility that modulation of the HIF1A signaling pathway or its downstream effectors such as TGF-ß may allow better preservation of ventricular function in patients with TOF. Furthermore, directed genotyping for HIF1A and other genetic variants may help identify patients at risk for adverse outcomes. This study demonstrates the potential for genetics-of- outcomes studies to evaluate novel therapeutic targets and to identify at-risk populations that may require specific therapeutic considerations.

Efficacy and safety of aprotinin in neonatal congenital heart operations.

BACKGROUND: Aprotinin has been associated with significant morbidity and mortality in adults, leading to its withdrawal from the market and clinical substitution with the lysine analogs, tranexamic acid and ε-aminocaproic acid. Neonates undergoing cardiopulmonary bypass are especially at risk for perioperative bleeding, yet little data exist comparing lysine analogs with aprotinin. METHODS: Neonates undergoing cardiopulmonary bypass (January 2006 to December 2009) were included in this single-institution, retrospective cohort study. Preoperative, intraoperative, and postoperative data were analyzed. The relationship between demographic, surgical risk data, and outcomes were analyzed. Markers of effectiveness included transfusion requirement, duration of operation, duration of ventilation, and intensive care unit length of stay. Markers of safety included reexploration, renal dysfunction, neurologic complications, and death. RESULTS: Of 423 included neonates, 271 (64%) received aprotinin and 152 (36%) a lysine analog. Infants who received aprotinin had a higher baseline creatinine and lower weight and gestational age. The aprotinin group experienced shorter time to surgical closure, lower blood product use, and lower rates of reexploration and postoperative renal dysfunction compared with the lysine-analog group. There was no difference in duration of ventilation or intensive care unit stay, neurologic outcomes, or death. CONCLUSIONS: Neonates who received aprotinin had significantly lower intraoperative transfusion requirements and shorter surgical closure times. The aprotinin group was less likely to require surgical reexploration and had a lower rate of renal injury. These data illustrate the need for further research regarding safety and efficacy of aprotinin in a larger sample of children undergoing cardiac operations.