Faculty Bibliography

BACKGROUND: Sudden death is a well-recognized complication of heart transplantation. Little is known about the incidence and risk factors for sudden death after transplant in children. The purpose of this study was to determine the incidence of and risk factors for sudden death. METHODS: This retrospective multicenter cohort study used the Pediatric Heart Transplant Study Group (PHTS) database, an event-driven registry of children aged <18 at listing undergoing heart transplantation between 1993 and 2007. Standard Kaplan-Meier and parametric analyses were used for survival analysis. Multivariate analysis in the hazard-function domain was used to identify risk factors for sudden death after transplant. RESULTS: Of 604 deaths in 2,491 children who underwent heart transplantation, 94 (16%) were classified as sudden. Freedom from sudden death was 97% at 5 years, and the hazard for sudden death remained constant over time at 0.01 deaths/year. Multivariate risk factors associated with sudden death included black race (hazard ratio [HR], 2.6; p < 0.0001), United Network of Organ Sharing (UNOS) status 2 at transplant (HR, 1.8; p = 0.008), older age (HR, 1.4/10 years of age; p = 0.03), and an increased number of rejection episodes in the first post-transplant year (HR, 1.6/episode; p = 0.03). CONCLUSION: Sudden death accounts for 1 in 6 deaths after heart transplant in children. Older recipient age, recurrent rejection within the first year, black race, and UNOS status 2 at listing were associated with sudden death. Patients with 1 or more of these risk factors may benefit from primary prevention efforts.

BACKGROUND: Fast-tracking and early endotracheal extubation have been described in patients undergoing surgery for congenital heart disease (CHD); however, criteria for patient selection have not been validated in a prospective manner. Our goal in this study was to prospectively identify factors associated with the decision to defer endotracheal extubation in the operating room (OR). METHODS: We performed a prospective observational study of 275 patients (median age 18 months) at the Mount Sinai Medical Center (MSMC), New York, New York, and 49 patients (median age 25 months) at the University of Tokyo Hospital (UTH), Tokyo, Japan, undergoing surgery for CHD requiring cardiopulmonary bypass. These patients were all eligible for fast-tracking, including extubation in the OR immediately after surgery, according to the respective inclusion/exclusion criteria applied at the 2 sites. RESULTS: Eighty-nine percent of patients at the MSMC, and 65% of patients at the UTH were extubated in the OR. At the MSMC, all patients without aortic cross-clamp, and patients with simple procedures (Risk Adjustment for Congenital Heart Surgery [RACHS] score 1) were extubated in the OR. Among the remaining MSMC patients, regression analysis showed that procedure complexity was still an independent predictor for not proceeding with planned extubation in the OR. Extubation was more likely to be deferred in the RACHS score 3 surgical risk patients compared with the RACHS score 2 group (P = 0.005, odds ratio 3.8 [CI: 1.5, 9.7]). Additionally, trisomy 21 (P = 0.0003, odds ratio 9.9 [CI: 2.9, 34.5]) and age (P = 0.0015) were significant independent predictors for deferring OR extubation. We tested our findings on the patients from the UTH by developing risk categories from the MSMC data that ranked eligible patients according to the chance of OR extubation. The risk categories proved to predict endotracheal extubation in the 49 patients who had undergone surgery at the UTH relative to their overall extubation rate, despite differences in anesthetic regimen and inclusion/exclusion criteria. CONCLUSIONS: Preoperatively known factors alone can predict the relative chances of deferring extubation after surgery for CHD. The early extubation strategies applied in the 2 centers were successful in the majority of cases.

OBJECTIVES: To determine if a relationship exists between regional oxyhemoglobin saturation (rSO(2)) measured at various body locations by near-infrared spectroscopy (NIRS) and blood lactate level in children after cardiac surgery. DESIGN: A prospective, observational study. SETTING: A pediatric cardiac intensive care unit in a university hospital. PARTICIPANTS: Twenty-three children undergoing repair of congenital heart disease. Patients with single-ventricle physiology and/or residual intracardiac shunts were excluded. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Cerebral, splanchnic, renal, and muscle rSO(2) values were recorded every 30 seconds via NIRS for 24 hours postoperatively. Blood lactate levels measured minimally at 0, 2, 4, 6 and 24 hours postoperatively were correlated with rSO(2) values derived by averaging all values recorded during the 60 minutes preceding the blood draw. Twenty-three patients were enrolled with 163 lactate measurements and more than 39,000 rSO(2) observations analyzed. Cerebral rSO(2) had the strongest inverse correlation with lactate level followed by splanchnic, renal, and muscle rSO(2) (r = -0.74, p < 0.0001, r = -0.61, p < 0.0001, r = -0.57, p < 0.0001, and r = -0.48, p < 0.0001, respectively). The correlation improved by averaging the cerebral and renal rSO(2) values (r = -0.82, p < 0.0001). Furthermore, an averaged cerebral and renal rSO(2) value <or=65% predicted a lactate level >or=3.0 mmol/L with a sensitivity of 95% and a specificity of 83% (p = 0.0001). CONCLUSIONS: Averaged cerebral and renal rSO(2) less than 65% as measured by NIRS predicts hyperlactatemia (>3 mmol/L) in acyanotic children after congenital heart surgery. Hence, this noninvasive, continuous monitoring tool may facilitate the identification of global hypoperfusion caused by low cardiac output syndrome in this population

Near infrared spectroscopy (NIRS) is a noninvasive method for the in vivo monitoring of tissue oxygenation. Originally used predominantly to assess cerebral oxygenation, NIRS has gained widespread popularity in many clinical settings in all age groups. Changes in regional tissue oxygenation as detected by NIRS may reflect the delicate balance between oxygen delivery and consumption in more than one organ system. However, more studies are required to establish the ability of NIRS monitoring to improve patient outcome. This review provides a comprehensive description of NIRS in children.