Cardiopulmonary bypass in neonates and infants: advantages of high flow high hematocrit bypass strategy-clinical practice review.

Cardiopulmonary bypass is an integral and indispensable part of surgical repair of congenital heart defects. While the complications and morbidity secondary to the use of cardiopulmonary bypass has decreased considerably, there remains a significant incidence of clinically relevant renal and neurological injury. To provide more physiological delivery of oxygenated blood to the end-organs, our center has been successfully using a high-flow, high hematocrit cardiopulmonary bypass strategy since 2006. The essential components of this strategy include maintaining high flows (typically 200 mL/kg/min in neonates, 150-175 mL/kg/min in older infants weighing <10 kg, and 2.6 L/min/m2 in older children) throughout the duration of cardiopulmonary bypass irrespective of patient temperature, as well as maintaining a hematocrit of at least 32% on cardiopulmonary bypass. The incidence of post-operative acute kidney injury (around 3%) and clinical acute neurological events (<1%) with this strategy is considerably less when compared to other contemporary publications using the conventional cardiopulmonary bypass strategy. In this review, we discuss the rationale behind our approach and present evidence to support the high-flow, high-hematocrit strategy. We also discuss the practical aspects of our strategy and describe the adjuncts we use to derive additional benefits. These adjuncts include the use of a hybrid pH/alpha stat strategy during cooling/rewarming, aggressive use of conventional ultrafiltration during cardiopulmonary bypass, a terminal hematocrit of 40-45%, and avoidance of milrinone and albumin in the early peri-operative period. This results in a very low incidence of post-operative bleeding, facilitates chest closure in the operating room even in most neonates, helps in reducing the need for post-operative blood product transfusion and helps in achieving a favorable post-operative fluid balance early after surgery.

Incidence of Acute Neurological Events in Neonates and Infants Undergoing Cardiac Surgery Using a High-Hematocrit/ High-Flow Bypass Strategy.

Background: The incidence of new acute neurological injury occurring in neonates and infants during cardiac surgery utilizing cardiopulmonary bypass is reportedly 3% to 5%. In 2013, we adopted a high flow rate, and high hematocrit bypass strategy, and sought to assess the incidence of early neurological injuries associated with this strategy. Methods: Neonates and infants undergoing cardiopulmonary bypass between January 2013 and December 2019 (n = 714) comprise the study. Adverse neurological events (ANEs) were defined as any abnormality of pupils, delayed awakening, seizures, focal neurological deficits, concerns prompting neurological consultation, or any abnormality on neurological imaging in the postoperative period. Our bypass strategy included a high flow rate (150-200 mL/kg/min), without reduction of flow rates during cooling and maintaining a target hematocrit on bypass > 32% with a terminal hematocrit of > 42%. Results: Median weight at the time of the procedure was 4.6 kg (IQR 3.6-6.1 kg) with the smallest patient weighing 1.36 kg. There were 46 premature patients (6.4%). There were 149 patients (20.9%) patients who underwent deep hypothermic circulatory arrest with a median time of 26 min (IQR 21-41 min). Hospital mortality was 3.5% (24/714, 95% CI: 2.28-5.13). The incidence of neurological events as defined above was 0.84% (6/714, 95% CI: 0.31-1.82). Neurological imaging identified ischemic injury in 4 patients and intraventricular hemorrhage in 2. Conclusions: High flow/high hematocrit bypass strategy was associated with a low incidence of ANE in this vulnerable population.

Current surgical techniques in the management of the symptomatic neonate with severe Ebstein anomaly: Too much, too little, or just enough?

The management of severely symptomatic neonates with Ebstein anomaly is challenging during the early neonatal period. Initial management goals should focus on mitigating a central shunt; providing respiratory mechanical support; providing an adequate but not excessive source of pulmonary blood flow; and minimizing pulmonary vascular resistance. For most patients thus stabilized, definitive repair should be prudently deferred until it is safe for a bailout bidirectional Glenn anastomosis to be added, usually at age 3 to 4 months. For those who remain critical, initial ligation of the large ductus and placing a more peripheral aortopulmonary shunt, or ligating the main pulmonary artery, should be weighed against a primary biventricular repair (Knott-Craig repair), or the Starnes' single-ventricle palliation. The Da Silva cone biventricular repair should generally be avoided during the early neonatal period. An initial Starnes' repair can be potentially converted to a biventricular repair in later infancy.

Virtual endoluminal aortic root views determined at coronary CT angiography - an important tool for improving anomalous coronary artery visualization and surgical planning.

Anomalous origin of the coronary arteries, though uncommon, is of great clinical concern. It can be the cause of sudden cardiac death and abnormal cardiac hemodynamics. Advances in electrocardiographically (ECG)-gated multi-detector CT have increased diagnostic accuracy in detecting anomalous origin of coronary arteries and their interarterial and intramural courses. Recent advances in multi-detector CT image processing software have allowed the creation of virtual endoluminal views of the aortic root and improved assessment of the intramural course (the length and relationship to the intercoronary commissure) of the coronary artery, which is of considerable surgical importance. We review our experience with virtual endoluminal imaging in our first 19 cases of interarterial coronary artery anomalies (17 cases of interarterial with intramural segment and 2 cases of purely interarterial course) diagnosed preoperatively and proven surgically.

Impact of Different Cardiopulmonary Bypass Strategies on Renal Injury After Pediatric Heart Surgery.

BACKGROUND: The purpose of this study is to compare the incidence and severity of acute kidney injury (AKI) after open heart surgery in neonates and infants for two different cardiopulmonary bypass (CPB) strategies. METHODS: In all, 151 infants undergoing cardiac surgery were prospectively enrolled between June 2017 and June 2018 at two centers, one using conventional CPB (2.4 L · min-1 · m-2, 150 mL · kg-1 · min-1) with reduction of flow rates with moderate hypothermia and with a targeted hematocrit greater than 25% (center 1, n = 91), and the other using higher bypass flow rates (175 to 200 mL · kg-1 · min-1) and higher minimum hematocrit (greater than 32%) CPB (center 2, n = 60). The primary endpoint was the incidence of postoperative AKI as defined by Acute Kidney Injury Network criteria and risk factors associated with AKI. RESULTS: Preoperative characteristics and complexity of surgery were comparable between centers. The overall incidence of early postoperative AKI was 10.6% (16 of 151), with 15.4% (14 of 91) in center 1 and 3.3% (2 of 60) in center 2 (P = .02). Mean lowest flow rates on CPB were 78 mL · kg-1 · min-1 vs 118 mL · kg-1 · min-1 and mean highest hematocrit on separation from CPB were 33% vs 43% at center 1 and 2, respectively (P < .001). Center 1 used less packed red blood cells but more fresh frozen plasma than center 2 (P = .001). By multivariate analysis, only lower flows on CPB (78 vs 96 mL · kg-1 · min-1, P = .043) and lower hematocrit at the end of CPB (33% vs 37%, P = .007) were associated with AKI. CONCLUSIONS: In this contemporary comparative study, higher flow rates and higher hematocrit during cardiopulmonary bypass were associated with better preservation of renal function.

Single Institution Experience With International Referrals for Pediatric Cardiac Surgery.

BACKGROUND: Pediatric cardiac surgery in developing countries poses many challenges. The practice of referring patients from abroad via nongovernmental organizations has occurred for many years. We describe our experience with international referrals for pediatric cardiac surgery via Gift of Life Mid-South to the Heart Institute, Le Bonheur Children's Hospital in Memphis, Tennessee. METHODS: We performed a retrospective descriptive review of data collected in our Society of Thoracic Surgeons Congenital Heart Surgery Database (STS CHSD) along with data from our electronic medical record from January 1, 2007, to December 31, 2017. Available data included patient demographics, diagnoses, surgical procedure, entire inpatient length of stay (LOS), complications, and operative mortality. Cardiac surgeries were grouped according to the Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery Congenital Heart Surgery Mortality Categories (STAT Mortality Categories). Complications were defined according to the STS CHSD. RESULTS: In this retrospective descriptive study, case complexity level varied; however, 38% cardiac surgeries were in STAT Mortality Category 3 or 4. Honduras was the most common referral source with a total of 18 countries represented. Operative mortality remained very low (1 [1.4%] of 71 cardiac surgeries) despite patients being referred beyond infancy. There were an increasing number of complications and longer inpatient LOS (with greater variance) in STAT Mortality Category 4. CONCLUSIONS: International patients referred for congenital heart surgery can be successfully treated with an acceptable mortality rate despite late referrals. Inpatient LOS is related to surgical complexity. Follow-up studies are needed to determine the long-term outcomes of these patients.

Ross-Konno Operation in an Infant With a Quadricuspid Pulmonary Valve and Anomalous Aortic Origin of the Right Coronary Artery.

Anomalous aortic origin of the right coronary artery from the left aortic sinus is a rare congenital anomaly that is generally repaired during adolescence when the condition is associated with symptoms. It is rarely diagnosed in infancy. Similarly, a quadricuspid pulmonary valve is also a rare finding, and there are scant data to evaluate whether this malformation of the pulmonary valve is suitable to be used for a Ross operation. This report describes a case in which both these anomalies coexisted in an infant who underwent a successful Ross-Konno operation.

Experience of a single institution with femoral vein homograft as right ventricle to pulmonary artery conduit in stage 1 Norwood operation.

OBJECTIVE: Femoral vein homograft can be used be used as valved right ventricle to pulmonary artery conduit in the Norwood operation. We describe the results of this approach, including pulmonary artery growth and ventricular function. METHODS: A retrospective chart review of 24 consecutive neonates with hypoplastic left heart syndrome or complex single ventricle undergoing this approach between June 2012 and December 2017 was performed. Conduit valve competency and ventricular function were estimated using transthoracic echocardiogram, and pulmonary artery growth was measured using Nakata's index. Changes in ventricular function pre-Glenn and at latest follow-up were assessed by ordinal logistic regression with a general linear model to account for the correlation within the same patient over time. RESULTS: Median age at surgery was 4 days, and mean weight was 3 kg. There was no interstage mortality. A total of 21 patients have undergone Glenn operation, and 9 patients have completed the Fontan operation. None of the conduits developed thrombosis. Sixty-three percent of conduits remained competent in the first month, and 33% remained competent after 3 months of operation. Catheter interventions on conduits were necessary in 14 patients. Median Nakata index at pre-Glenn catheterization was 228 mm2/m2 (interquartile range, 107-341 mm2/m2). Right ventricular function was preserved in 83% of patients at a median follow-up of 34 (interquartile range, 10-46) months. CONCLUSIONS: Femoral vein homograft as a right ventricle to pulmonary artery conduit in the Norwood operation is safe and associated with good pulmonary artery growth and preserved ventricular function as assessed by subjective echocardiography. Catheter intervention of the conduit may be necessary.

Utility of the Medtronic microvascular plug™ as a transcatheter implantable and explantable pulmonary artery flow restrictor in a swine model.

BACKGROUND: A surgical pulmonary artery band (PAB) is used to control excessive pulmonary blood flow for certain congenital heart diseases. Previous attempts have been made to develop a transcatheter, implantable pulmonary flow restrictor (PFR) without great success. We modified a microvascular plug (MVP) to be used as a PFR. The objectives of this study were to demonstrate feasibility of transcatheter implantation and retrieval of the modified MVP as a PFR, and compare PA growth while using the PFR versus PAB. METHODS AND RESULTS: The PFR was implanted in eight newborn piglets in bilateral branch pulmonary arteries (PAs). Immediately post-PFR implantation, the right ventricular systolic pressure increased from a median of 20-51 mmHg. Transcatheter retrieval of PFR was 100% successful at 3, 6, and 9 weeks and 50% at 12-weeks post-implant. A left PAB was placed via thoracotomy in four other newborn piglets. Debanding was performed 6-weeks later via balloon angioplasty. On follow-up, the proximal left PA diameters in the PFR and the PAB groups were similar (median 8 vs. 7.1 mm; p = 0.11); albeit the surgical band sites required repeat balloon angioplasty secondary to recurrent stenosis. By histopathology, there was grade II vessel injury in two pigs immediately post-retrieval of PFR that healed by 12 weeks. CONCLUSIONS: Transcatheter implantation and retrieval of the MVP as a PFR is feasible. PA growth is comparable to surgical PAB, which is likely to require reinterventions. The use of the MVP as a PFR in humans has to be trialed before recommending its routine use.

High acetylsalicylic acid dosing in infants after modified Blalock-Taussig shunt.

OBJECTIVE: Shunt-related adverse events are frequent in infants after modified Blalock-Taussig despite use of acetylsalicylic acid prophylaxis. A higher incidence of acetylsalicylic acid-resistance and sub-therapeutic acetylsalicylic acid levels has been reported in infants. We evaluated whether using high-dose acetylsalicylic acid can decrease shunt-related adverse events in infants after modified Blalock-Taussig. METHODS: In this single-centre retrospective cohort study, we included infants ⩽1-year-old who underwent modified Blalock-Taussig placement and received acetylsalicylic acid in the ICU. We defined acetylsalicylic acid treatment groups as standard dose (⩽7 mg/kg/day) and high dose (⩾8 mg/kg/day) based on the initiating dose. RESULTS: There were 34 infants in each group. Both groups were similar in age, gender, cardiac defect type, ICU length of stay, and time interval to second stage or definitive repair. Shunt interventions (18 versus 32%, p=0.16), shunt thrombosis (14 versus 17%, p=0.74), and mortality (9 versus 12%, p=0.65) were not significantly different between groups. On multiple logistic regression analysis, single-ventricle morphology (odds ratio 5.2, 95% confidence interval of 1.2-23, p=0.03) and post-operative red blood cells transfusion ⩾24 hours [odds ratio 15, confidence interval of (3-71), p<0.01] were associated with shunt-related adverse events. High-dose acetylsalicylic acid treatment [odds ratio 2.6, confidence interval of (0.7-10), p=0.16] was not associated with decrease in these events. CONCLUSIONS: High-dose acetylsalicylic acid may not be sufficient in reducing shunt-related adverse events in infants after modified Blalock-Taussig. Post-operative red blood cells transfusion may be a modifiable risk factor for these events. A randomised trial is needed to determine appropriate acetylsalicylic acid dosing in infants with modified Blalock-Taussig.

Successful Heart Transplantation in Two Infants With Dextrocardia-Heterotaxy Syndrome.

Infants with dextrocardia-heterotaxy syndrome pose significant surgical challenges to a successful orthotopic heart transplant. Herein we report on 2 infants with dextrocardia-heterotaxy syndrome who underwent complex heart transplantation. A combination of preoperative 3-dimensional chest computed tomography to predict optimal donor size and unique surgical technique resulted in successful outcomes.

Improved Outcomes in Management of Hypoplastic Left Heart Syndrome Associated With Congenital Diaphragmatic Hernia: an Algorithmic Approach.

Hypoplastic left heart syndrome (HLHS) is the second most common congenital heart disease associated with congenital diaphragmatic hernia (CDH). The reported survival rate of neonates with CDH and HLHS is only 1%-5%. We review our experience with CDH and HLHS and compare our outcomes with published literature. Retrospective review of all neonates with CDH and HLHS at our institution over a 10-year period was performed. The morphology of cardiac and diaphragm defects, clinical course, treatment strategies, and outcomes were reviewed, and an algorithmic approach was proposed. Five patients with CDH and HLHS were treated between 2006 and 2016. All had mitral stenosis with aortic stenosis. Four patients had a left-sided Bochdalek diaphragmatic hernia and 1 patient had a large bilateral Morgagni hernia. Two (2/4) of the Bochdalek hernias were associated with significant pulmonary hypoplasia and required patch closure of the CDH; both were palliated with percutaneous ductal stents and both died. Three patients underwent primary Norwood operation followed by repair of less severe CDH defect. All 3 patients are currently well and have survived bidirectional Glenn anastomosis; one patient is well after Fontan operation. Successful palliation of neonates with HLHS and associated CDH is possible in the current era. Outcome is determined primarily by the severity of the CDH and the degree of associated pulmonary hypoplasia. An algorithmic team approach is helpful in management of this difficult group of patients.