Lower limit of adequate oxygen delivery for the maintenance of aerobic metabolism during cardiopulmonary bypass in neonates.

BACKGROUND: The objective of cardiopulmonary bypass (CPB) is to maintain an adequate balance between oxygen delivery (Do2) and consumption. The critical Do2 is that at which consumption becomes supply dependent. This study aimed to identify the critical Do2 in neonates, who have higher metabolic rates than adults. METHODS: In a retrospective cohort of neonates, Do2 was calculated from CPB parameters recorded during aortic cross-clamping. High lactate concentration measured after aortic unclamping (lactOFF) was used to identify anaerobic metabolism. Data were analysed using mixed linear and proportional odds regression models. The relationship between Do2 and temperature was analysed in a subgroup of patients with lactOFF <2.5 mM, thought to have had balanced oxygen delivery and consumption. The estimated regression coefficient was further used to adjust hypothetical Do2 thresholds, and Do2 excursions below the threshold were quantified as magnitude-durations. The lowest threshold that provided magnitude-durations and linked with an increase in lactOFF was used as the lowest suitable (critical) Do2 at 37°C. RESULTS: Overall, 22 896 time points were analysed in 180 neonates. In 40 patients with lactOFF <2.5 mM, Do2 varied by 22.87 (0.70) ml min-1 m-2 °C-1. When varying the Do2 threshold between 340 and 380 ml min-1 m-2, excursions below the threshold were linked with incremental lactOFF. A 100 ml m-2 excursion below the 340 ml min-1 m-2Do2 threshold increased the risk of a 1 mM increment in lactOFF by 22% (odds ratio: 1.22; 95% confidence interval: 1.02-1.45). CONCLUSIONS: It was found that 340 ml min-1 m-2 is likely to represent the lowest suitable Do2 required in neonates to maintain aerobic metabolism during normothermic CPB.

Impact of Heparin- or Nonheparin-Coated Circuits on Platelet Function in Pediatric Cardiac Surgery.

BACKGROUND: Extracorporeal circuit coating has been shown to improve coagulation derangements during pediatric cardiopulmonary bypass (CPB). This study compared platelet function and hemostasis activation in pediatric cardiac surgery conducted with nonheparin coating (Balance; Medtronic, Minneapolis, MN) versus heparin-based coating (Carmeda; Medtronic) circuits. METHODS: A prospective, randomized, double-center trial was conducted in children older than 1 month undergoing congenital heart disease treatment. Blood samples were collected at baseline (T0), 15 minutes after the start of CPB (T1), and 15 minutes (T2) and 1 hour after the conclusion of CPB (T3). The primary end point of the study was to detect potential differences in ß-thromboglobulin levels between the two groups at T2. Other coagulation and platelet function indicators were analyzed as secondary end points. RESULTS: The concentration of ß-thromboglobulin increased significantly at T2 in both groups. However, there was no significant difference between the groups across all time points. There was no difference in the secondary end points between the groups. CONCLUSIONS: The two circuits showed similar biological effects on platelet function and coagulation. This observation may be useful in optimizing the conduct of CPB and in rationalizing its cost for the treatment of congenital heart disease.

Low perfusion pressure is associated with renal tubular injury in infants undergoing cardiac surgery with cardiopulmonary bypass: A secondary analysis of an observational study.

BACKGROUND: Earlier work on adults undergoing surgery with cardiopulmonary bypass suggests that there is a close relationship between the lower limit of the cerebral and renal autoregulation pressures. Although cerebral autoregulation during bypass in infants has been extensively investigated, the impact of bypass on kidney function is not well known. It is, nevertheless, acknowledged that the main pathophysiological process involved in cardiac surgery-related kidney damage is tubular injury, and that urine neutrophil gelatinase-associated lipocaline (uNGAL) is a reliable biomarker of injury. OBJECTIVE: To identify the most predictive bypass variable for the measurement of renal injury, its threshold value and the most predictive time below that threshold. DESIGN: Observational study linking electronically recorded bypass perfusion pressure and oxygen delivery rate with intra-operative uNGAL excretion. Variations in bypass variables were accounted for by their excursions below several thresholds. SETTING: French tertiary referral paediatric cardiac centre. PATIENTS: A total of 72 infants in whom uNGAL was measured within 1 h of bypass. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Renal injury, identified by a high creatinine normalised uNGAL concentration (>21.2 µg mmol). RESULTS: At the end of bypass, 43.75% of infants had high uNGAL. A more than 40% pressure drop below the normal age-standardised mean arterial pressure was associated with high uNGAL. Receiver operating curve [interquartile range] areas were 0.626 [0.501 to 0.752] for a more than 40% drop, and 0.679 [0.555 to 0.804] for a more than 50% drop. A more than 40% pressure drop for 19.5 min provided a 0.65 negative predictive value for high uNGAL, and a more than 50% pressure drop for 5.4 min provided a 0.67 negative predictive value. The link between uNGAL and oxygen delivery rate was negligible. CONCLUSION: Maintaining the perfusion pressure above 60% of the normal age-standardised mean arterial pressure may provide an effective renal protective strategy. TRIAL REGISTRATION: Registered on October 11, 2010, ClinicalTrials.gov Identifier: NCT01219998.

Cold histidine-tryptophan-ketoglutarate solution and repeated oxygenated warm blood cardioplegia in neonates with arterial switch operation.

BACKGROUND: The present study aimed to compare myocardial protection, as assessed by cardiac troponin-I release, and short-term outcomes between two groups of neonates undergoing the arterial switch operation (ASO) with either Custodiol cardioplegia (Custodiol HTK, Köhler Chemie GmbH, Bensheim, Germany) or repeated oxygenated warm blood cardioplegia. METHODS: A total of 218 neonates were enrolled retrospectively from February 2007 through February 2011. All analyses were stratified on the type of procedure (ASO±ventricular septal defect closure ± aortic arch repair). Troponin concentrations within the first week of surgery were analyzed using mixed models for repeated measurements. To counteract the confounding effect of the coronary anatomy, a sensitivity analysis was conducted after 1:1 matching. RESULTS: Overall 30 patients had Custodiol cardioplegia, and 188 had warm blood cardioplegia. High-risk coronary anatomy (single right coronary artery giving rise to the left, intramural course) was associated with higher troponin concentrations and a higher 30-day mortality rate postoperatively, and was more prevalent in the Custodiol group when compared with the warm blood cardioplegia group. Postoperative troponin concentrations were higher in the Custodiol group both before (p<0.001) and after matching on the coronary anatomy (p=0.03). The 30-day mortality rate was higher in the Custodiol group, 10% versus 1.1% (p=0.009), but only a nonsignificant trend was noted after matching. CONCLUSIONS: The use of Custodiol cardioplegia in neonates undergoing ASO was associated with a larger troponin release when compared with warm blood cardioplegia, suggesting poor myocardial protection. The difference noted in 30-day mortality was not due to the use of Custodiol.

Use of a miniaturized cardiopulmonary bypass circuit in neonates and infants is associated with fewer blood product transfusions.

Miniaturized bypass circuits, including the Kids D100 oxygenator and the D130 arterial filter, were specially designed to reduce blood transfusions in small infants undergoing cardiac surgery. This study compared the number of blood product transfusions and short-term outcome between patients younger than 1 year undergoing cardiac surgery with a conventional and a miniaturized bypass circuit, after controlling for baseline characteristics and surgical complexity by 1:1 matching. Adjusted odds ratios (ORs) and 95% confidence intervals for exposure to transfusions and to any additional transfusion were estimated from binary and polytomous regression models. Of the 804 patients enrolled retrospectively, 246 were analyzed after matching. The use of the miniaturized circuit required a lower priming volume, 265.5 vs. 432.4 mL, p < 0.001, fewer packed red blood cell (PRBC) transfusions, 1.4 vs. 2.0 U, p < 0.001, and fewer platelet transfusions on the day of surgery, 57.7% vs. 76.4%, p < 0.001. After adjustment for the use of antifibrinolytics, the ultrafiltration rate, and the year of surgery, the use of the miniaturized circuit was independently related to a reduced risk of additional PRBC transfusions, OR 0.04 (0.01, 0.13), and exposure to platelet transfusions, OR 0.78 (0.63, 0.96). Short-term outcome was similar.