Management of deep hypothermic (DH) cardiopulmonary bypass (CPB), a critical neuroprotective strategy, currently relies on non-invasive temperature to guide cerebral metabolic suppression during complex cardiac surgery in neonates. Considerable inter-subject variability in temperature response and residual metabolism may contribute to the persisting risk for postoperative neurological injury. To characterize and mitigate this variability, we assess the sufficiency of conventional nasopharyngeal temperature (NPT) guidance, and in the process, validate combined non-invasive frequency-domain diffuse optical spectroscopy (FD-DOS) and diffuse correlation spectroscopy (DCS) for direct measurement of cerebral metabolic rate of oxygen ( CMRO2). During CPB, n = 8 neonatal swine underwent cooling from normothermia to 18℃, sustained DH perfusion for 40 min, and then rewarming to simulate cardiac surgery. Continuous non-invasive and invasive measurements of intracranial temperature (ICT) and CMRO2 were acquired. Significant hysteresis ( p < 0.001) between cooling and rewarming periods in the NPT versus ICT and NPT versus CMRO2 relationships were found. Resolution of this hysteresis in the ICT versus CMRO2 relationship identified a crucial insufficiency of conventional NPT guidance. Non-invasive CMRO2 temperature coefficients with respect to NPT ( Q10 = 2.0) and ICT ( Q10 = 2.5) are consistent with previous reports and provide further validation of FD-DOS/DCS CMRO2 monitoring during DH CPB to optimize management.

The objective of this study is to evaluate three different diameters of arterial tubing and three diameters of arterial cannulae in terms of pressure drop, and hemodynamic energy delivery in simulated neonatal/ pediatric cardiopulmonary bypass (CPB) circuits. The CPB circuit consisted of a Terumo Capiox Baby FX05 oxygenator (Terumo Corporation, Tokyo, Japan), arterial tubing (1/4 in, 3/16 in, or 1/8 in × 150 cm), and a Medtronic Bio-Medicus arterial cannula (8, 10, or 12 Fr; Medtronic, Inc., Minneapolis, MN, USA). The pseudo patient's pressure was maintained at 50 mm Hg. The circuit was primed using lactated Ringer's solution and heparinized packed human red blood cells (hematocrit 30%). Trials were conducted at different flow rates and temperatures (35 and 28°C). Flow and pressure data were collected using a custom-based data acquisition system. Using 8 Fr arterial cannula at 500 mL/min, small diameter arterial tubing generated higher circuit pressure (294.6 ± 0.1 mm Hg [1/8 in], 213.5 ± 0.5 mm Hg [3/16 in], 208.4 ± 0.4 mm Hg [1/4 in] at 35°C) and arterial line pressure drop (158.3 ± 0.1 mm Hg [1/8 in], 79.6 ± 0.1 mm Hg [3/16 in], 62.1 ± 0.1 mm Hg [1/4 in] at 35°C). Using 10 Fr arterial cannula at 1000 mL/min, pre-oxygenator pressures were 266.8 ± 0.2 mm Hg (3/16 in) and248.0 ± 0.3 mm Hg (1/4 in); arterial line pressure drops were 111.6 ± 0.0 mm Hg (3/16 in) and 74.0 ± 0.1 mm Hg (1/4 in) at 35°C. When using 12 Fr arterial cannula at 1500 mL/min, preoxygenator pressures reached 324.4 ± 0.3 mm Hg (3/16 in) and 302.5 ± 0.4 mm Hg (1/4 in); arterial line pressure drops were 154.0 ± 0.1 mm Hg (3/16 in) and 92.0 ± 0.2 mm Hg (1/4 in) at 35°C. Pressure drops across arterial line tubing were main CPB circuit pressure drops. High flow rate, hypothermia, small diameter arterial tubing. and arterial cannula created more hemodynamic energy at the preoxygenator site, but energy loss across CPB circuit also increased. Although small diameter (<1/ 4 in ID) arterial tubing may decrease total CPB priming volume, it also led to significantly higher circuit pressure, higher pressure drop, and more hemodynamic energy loss across CPB circuit. Larger diameter arterial cannula had less pressure drop and allowed more hemodynamic energy delivery to the patient.

CF VAD implantation with AVV excision can successfully support complex pediatric patients in a wide range of size and anatomy (small chambers, systemic right ventricles). This technique may allow for CF VAD implantation in patients previously deemed too small for such support.

Abstract OBJECTIVES Controversy remains regarding the use of deep hypothermic circulatory arrest (DHCA) in neonatal cardiac surgery. Alterations in cerebral mitochondrial bioenergetics are thought to contribute to ischaemia–reperfusion injury in DHCA. The purpose of this study was to compare cerebral mitochondrial bioenergetics for DHCA with deep hypothermic continuous perfusion using a neonatal swine model. METHODS Twenty-four piglets (mean weight 3.8 kg) were placed on cardiopulmonary bypass (CPB): 10 underwent 40-min DHCA, following cooling to 18°C, 10 underwent 40 min DHCA and 10 remained at deep hypothermia for 40 min; animals were subsequently rewarmed to normothermia. 4 remained on normothermic CPB throughout. Fresh brain tissue was harvested while on CPB and assessed for mitochondrial respiration and reactive oxygen species generation. Cerebral microdialysis samples were collected throughout the analysis. RESULTS DHCA animals had significantly decreased mitochondrial complex I respiration, maximal oxidative phosphorylation, respiratory control ratio and significantly increased mitochondrial reactive oxygen species (P &lt; 0.05 for all). DHCA animals also had significantly increased cerebral microdialysis indicators of cerebral ischaemia (lactate/pyruvate ratio) and neuronal death (glycerol) during and after rewarming. CONCLUSIONS DHCA is associated with disruption of mitochondrial bioenergetics compared with deep hypothermic continuous perfusion. Preserving mitochondrial health may mitigate brain injury in cardiac surgical patients. Further studies are needed to better understand the mechanisms of neurological injury in neonatal cardiac surgery and correlate mitochondrial dysfunction with neurological outcomes.