Neurologic monitoring for special cardiopulmonary bypass techniques

Selective Antegrade Cerebral Perfusion With or Without Additional Lower Body Perfusion During Aortic Arch Reconstruction in Infants

BACKGROUND

Aortic arch reconstruction is often challenging, especially in infants, owing to its high postoperative complication risks. This study aimed to compare the effectiveness between selective antegrade cerebral perfusion (SACP) alone and SACP in combination with continuous lower body perfusion with descending aortic cannulation (DAC) in preserving renal function, and to determine the influence of perfusion strategy on the postoperative course of infants who underwent aortic arch reconstruction.

MATERIAL AND METHODS

A total of 121 infants who underwent aortic arch reconstruction between January 2008 and December 2018 were included in the analysis. Patients (median age: 29 days, range: 3-270 days) were divided into the following groups: those who underwent repair with SACP (SACP group, 79 patients) and those who underwent additional lower body perfusion (DAC group, 42 patients).

RESULTS

Three (7.1%) and nine (11.4%) patients died in the DAC and SACP groups, respectively (P = .54). The SACP group had more patients requiring renal replacement therapy (P = .002) and higher incidence of second stage acute kidney injury (AKI) development (Kidney disease improving global outcomes (KDIGO) criteria; P = .032). The SACP group had higher frequency of open chest postoperatively than the DAC group (P = .011). The DAC group had lower vasoactive inotropic score (VIS) at the first postoperative day (P < .001) and shorter intensive care unit length of stay (P = .050). There was no difference in neurological complications between the groups (P = .061). High VIS was associated with early mortality (odds ratio [OR]: 1.79 [1.33-2.41], P < .001) and AKI (OR: 1.60 [1.35-1.91], P < .001). The DAC perfusion strategy with minimal hypothermia was associated with lower risk of AKI (OR: 0.91 [0.84-0.98], P = .016).

CONCLUSION

Antegrade cerebral perfusion with continuous lower body perfusion via DAC could effectively be used for improving early postoperative results among infants undergoing procedures that include aortic arch reconstruction.

Staged Versus Complete Repair in the Symptomatic Neonate With Tetralogy of Fallot

BACKGROUND

The optimal management of tetralogy of Fallot (TOF) in symptomatic neonates remains unknown. We compared outcomes for those undergoing palliation vs complete repair in the neonatal period.

METHODS

In a retrospective cohort study of symptomatic neonates with TOF who had a neonatal complete repair (group 1, n = 112) or staged repair (group 2, n = 26) from 2000 to 2013, we compared outcomes at 4 time points: neonatal complete repair vs palliation (group 1 vs 2A), neonatal vs later complete repair (group 1 vs 2B), the single vs combined admissions to achieve a complete repair (group 1 vs group 2A + 2B), and cumulative events 2 years after complete repair for both groups.

RESULTS

Demographics, anatomy, comorbidities, surgical approach, and mortality were similar between groups 1 and 2. Group 1 had a longer duration of cardiopulmonary bypass and deep hypothermic circulatory arrest and more postprocedure cardiac events compared with group 2A; a longer duration of intubation, intensive care, and postprocedure hospital stay compared with groups 2A and 2B; and a longer total hospital stay compared with group 2B. With combined admissions for group 2, there was no difference in the total duration of intensive care, total hospital stay, or reinterventions compared with group 1.

CONCLUSIONS

Both management options result in similar survival; however, early morbidity was greater with neonatal complete repair. The impact of increased neonatal exposures, such as cardiopulmonary bypass, deep hypothermic circulatory arrest, and intensive care, on neurocognitive development requires further study but should be considered when choosing an optimal strategy.

Neonatal brain protection in cardiac surgery and the role of intraoperative neuromonitoring

Improving mortality rates in children undergoing surgery for congenital heart disease has enabled a shift in focus to improving morbidity, particularly with respect to neurological complications. Various factors have been implicated in influencing neurological outcomes. We share our experience in formulating a customized cardiopulmonary bypass (CPB) protocol based on currently available evidence. Theoretical advantages of intraoperative neuromonitoring during CPB, specifically use of near-infrared spectroscopy, will be discussed in the context of methodologies to monitor cerebral perfusion during surgery.

Cerebral perfusion during cardiopulmonary bypass in children: correlations between near-infrared spectroscopy, temperature, lactate, pump flow, and blood pressure

Near-infrared spectroscopy (NIRS) is a noninvasive modality to monitor regional brain oxygenation (rSO(2) ). In this study, we aimed to investigate the correlation between cerebral rSO(2) and lactate, pump flow, hematocrit, pCO(2) , and mean blood pressure (MBP) during cardiopulmonary bypass (CPB). Between March and September 2011, 50 pediatric patients who underwent congenital heart surgery were enrolled into the study. Ages ranged from 6 days to 168 months (median 14 months). A NIRS sensor (Somanetics 5100B, Troy, MI, USA) was placed on the right forehead of patients. CPB period was divided into five stages: 1-at the beginning of CBP, 2-cooling at 32°C, 3-at final hypothermic temperature, 4-rewarming at 32°C, 5-before weaning from CPB. Data collection included measurements of each parameter at five stages of CPB. Data were analyzed using multivariate analysis within groups and Spearman's correlation to test association between parameters. Lactate levels increased significantly from stage 1 to stage 5 during CPB (P < 0.05). There was no significant correlation between cerebral rSO(2) and MBPs, pump flows, hematocrit, or pCO(2) during CPB. Cerebral rSO(2) levels showed changes between the stages; there was a significant increase during cooling period, compared to stage 1 (P < 0.05). Significant changes during cooling stage did not happen for other parameters. At stage 3, there was a negative correlation between lactate level and MBP. At stage 4, there was no significant change in cerebral rSO(2) levels despite decreased MBP. At the warming stage, low MBPs, but normal rSO(2) values, are observed despite increased pump flows. Increased rSO(2) levels despite insignificant changes at other parameters during the cooling stage of CPB may show that optimal pump flow with adequate intravascular volume may provide effective cerebral perfusion even without changes in MBP. Considering normal rSO(2) values during CPB in this study, it may be speculated that brain protection can be assessed by using NIRS and applying a standard bypass protocol.

Principles of antegrade cerebral perfusion during arch reconstruction in newborns/infants

Antegrade cerebral perfusion (ACP) is a cardiopulmonary bypass technique that uses special cannulation procedures to perfuse only the brain during neonatal and infant aortic arch reconstruction. It is used in lieu of deep hypothermic circulatory arrest (DHCA), and thus has the theoretical advantage of protecting the brain from hypoxic ischemic injury. Despite this, recent comparative studies have shown no difference in neurodevelopmental outcomes with ACP versus DHCA for neonatal arch repair. This article presents animal and human data demonstrating that ACP flows less than 30 mL/kg/min are inadequate for many patients, and may be the explanation for lack of outcome difference versus DHCA. A technique for ACP, its physiologic basis, and a neuromonitoring strategy are presented, and then the results of an outcome study are reviewed, showing that with ACP technique at higher flows of 50 to 80 mL/kg/min guided by neuromonitoring, periventricular leukomalacia is eliminated on postoperative brain magnetic resonance imaging after neonatal cardiac surgery.

Factors influencing neurologic outcome after neonatal cardiopulmonary bypass: what we can and cannot control

Advances in cardiopulmonary bypass and surgical techniques have led to progress in the early repair of congenital heart defects in children. However, as increasing numbers survive their initial cardiac operation, an awareness is emerging that significant early and late neurologic morbidities continue to complicate otherwise successful operative repairs. Adverse neurologic outcomes after neonatal cardiac surgery are multifactorial and relate to both fixed and modifiable mechanisms. The purpose of this review is to (1) review mechanisms of brain injury after neonatal cardiopulmonary bypass, (2) examine risk factors, and (3) speculate on how investigations may improve our understanding of neurologic injury.

Pediatric cardiac surgery without homologous blood transfusion, using a miniaturized bypass system in infants with lower body weight

OBJECTIVE

We have established a low-priming volume cardiopulmonary bypass system for pediatric heart surgery to avoid homologous blood transfusion. The priming volume of our system is down to 140 mL for patients weighing less than 7 kg. We can prime the bypass circuits without blood products for patients weighing more than 4 kg.

METHODS

Seventy consecutive patients weighing 4 to 7 kg underwent heart surgery with a bloodless prime from October 2003 to September 2006. The type of procedures (Risk Adjustment in Congenital Heart Surgery category) included the following: category 1: atrial septal defect (n = 3); category 2: ventricular septal defect, tetralogy of Fallot, bidirectional Glenn shunt, and others (n = 55); category 3: atrioventricular septal defect, double-outlet right ventricle, and others (n = 8); category 4: Rastelli procedure for transposition of the great arteries (n = 3); and category 6, Damus-Kaye-Stansel procedure (n = 1). Transfusion criteria were hematocrit less than 20%, mixed venous oxygen saturation less than 70%, regional cerebral oxygenation less than 50%, and plasma lactate level greater than 4.0 mmol/L during bypass.

RESULTS

The mean age and body weight were 7.3 +/- 5.4 months and 5.4 +/- 0.8 kg, respectively. Forty-five patients (64%) underwent transfusion-free procedures. Preoperative hematocrit, age, body weight, complexity of procedure and cardiopulmonary bypass time were compared between patients with and without transfusion. Bypass time and Risk Adjustment in Congenital Heart Surgery risk category in patients with transfusion were significantly greater than those in patients without (P < .0001, and P < .05, respectively). Body weight in patients without transfusion was significantly greater than that in patients with (P < .01). In multiple regression analysis, the determinants of blood transfusion were the bypass time and body weight (odds ratio 1.026, 95% confidence interval 1.011-.040, P < .0001, and odds ratio 0.366, 95% confidence interval 0.171-0.785, P < .01).

CONCLUSIONS

It is possible to do complex transfusion-free procedures safely for patients weighing more than 4 kg by using the low-priming volume circuit. The limiting factors of bloodless heart surgery are not preoperative hematocrit and complexity of procedure but the cardiopulmonary bypass time and the patient's body weight.

Monitoring cerebral oxygenation in a pediatric patient undergoing surgery for vascular ring

Regional cerebral oxygenation can be monitored using near-infrared spectroscopy (NIRS). Inadequacy of collateral cerebral circulation and regional cerebral ischemia during cardiac and vascular surgery may be detected by the use of NIRS monitoring. We report a 2-year-old child who underwent surgical repair of vascular ring and subclavian reimplantation, where use of NIRS helped in early detection and timely intervention to prevent prolonged cerebral ischemia.

An Evaluation of Bilateral Monitoring of Cerebral Oxygen Saturation During Pediatric Cardiac Surgery

Cerebral oximetry is a technique that enables monitoring of regional cerebral oxygenation during cardiac surgery. In this study, we evaluated differences in bi-hemispheric measurement of cerebral oxygen saturation using near-infrared spectroscopy in 62 infants undergoing biventricular repair without aortic arch reconstruction. Left and right regional cerebral oxygen saturation index (rSO2i) were recorded continuously after the induction of anesthesia, and data were analyzed at 12 time points. Baseline rSO2i measurements were left 65 +/- 13 and right 66 +/- 13 (P = 0.17). Mean left and right rSO2i measurements were similar (< or =2 percentage points/absolute scale units) before, during, and after cardiopulmonary bypass, irrespective of the use of deep hypothermic circulatory arrest. Further longitudinal neurological outcome studies are required to determine whether uni- or bi-hemispheric monitoring is required in this patient population.

Tissue oxygenation index is a useful monitor of histologic and neurologic outcome after cardiopulmonary bypass in piglets

OBJECTIVE

Tissue oxygenation index is a novel monitoring indicator derived by near-infrared spectroscopy. We hypothesized that tissue oxygenation index could predict a minimum safe flow rate for specific bypass conditions.

METHODS

Thirty-six piglets (age, 43 +/- 5 days; weight, 9.0 +/- 1.1 kg) underwent cardiopulmonary bypass with cerebral near-infrared spectroscopy (NIRO-300; Hamamatsu Photonics K.K., Hamamatsu City, Japan). Animals were cooled for 40 minutes to 15 degrees C, 25 degrees C, or 34 degrees C (pH-stat, hematocrit value of 20% or 30%, and pump flow of 100 mL . kg -1 . min -1), followed by low-flow perfusion (10, 25, or 50 mL . kg -1 . min -1) for 2 hours. Neurologic and behavioral evaluations were determined for 4 days. The brain was then fixed for histologic assessment. Tissue oxygenation index was defined as the average signal during low-flow bypass.

RESULTS

Animals with an average tissue oxygenation index of less than 55% showed cerebral injury, whereas animals with an index of greater than 55% showed minimal or no evidence of injury. Correlations were found between average tissue oxygenation index and histologic score (Spearman rho = -0.65, P < .001) and neurologic deficit score (Pearson r = -0.50, P = .002) on the first postoperative day. Temperature (P < .001), flow rate (P < .001), and hematocrit value (P = .002) were multivariable predictors of tissue oxygenation index, as determined by means of multivariable analysis of variance.

CONCLUSION

Tissue oxygenation index is a useful monitor for defining the minimum safe flow rate during cardiopulmonary bypass. An index value of less than 55% is a strong predictor of neurologic injury.

Central nervous system outcomes in children with complex congenital heart disease

PURPOSE OF REVIEW

To provide a brief overview of our current understanding of the types of neurodevelopmental sequelae in congenital heart disease survivors and to review the most recent studies from the past year, which have focused on 4 interrelated issues: (1) outcome studies, (2) the mechanism and etiology of central nervous system injury in children with CHD, (3) perioperative monitoring for brain injury, and (4) strategies for neuroprotection during cardiac surgery.

RECENT FINDINGS

As the number of survivors of surgery for complex congenital heart disease continues to rise, it is recognized that there is an increased incidence of adverse neurological outcomes in the survivors. In particular, a pattern similar to that seen in premature infants is emerging, including learning disabilities, behavioral abnormalities, inattention and hyperactivity. Imaging studies have revealed a high prevalence of structural brain abnormalities and periventricular leukomalacia, fetal and postnatal cerebral blood flow is abnormal, postnatal oxygen delivery is decreased, and intraoperative support techniques and postoperative low cardiac output are associated with cerebral hypoperfusion.

SUMMARY

The causes of these late developmental abnormalities are most likely sequential, cumulative and multifactorial.