Does Flexible Arterial Tubing Retain More Hemodynamic Energy During Pediatric Pulsatile Extracorporeal Life Support?

The objective of this study was to evaluate the hemodynamic performance and energy transmission of flexible arterial tubing as the arterial line in a simulated pediatric pulsatile extracorporeal life support (ECLS) system. The ECLS circuit consisted of a Medos Deltastream DP3 diagonal pump head, Medos Hilite 2400 LT oxygenator, Biomedicus arterial/venous cannula (10 Fr/14 Fr), 3 feet of polyvinyl chloride (PVC) arterial tubing or latex rubber arterial tubing, primed with lactated Ringer's solution and packed red blood cells (hematocrit 40%). Trials were conducted at flow rates of 300 to 1200 mL/min (300 mL/min increments) under nonpulsatile and pulsatile modes at 36°C using either PVC arterial tubing (PVC group) or latex rubber tubing (Latex group). Real-time pressure and flow data were recorded using a custom-based data acquisition system. Mean pressures and energy equivalent pressures (EEP) were the same under nonpulsatile mode between the two groups. Under pulsatile mode, EEPs were significantly great than mean pressure, especially in the Latex group (P < 0.05). There was no difference between the two groups with regards to pressure drops across ECLS circuit, but pulsatile flow created more pressure drops than nonpulsatile flow (P < 0.05). Surplus hemodynamic energy (SHE) levels were always higher in the Latex group than in the PVC group at all sites. Although total hemodynamic energy (THE) losses were higher under pulsatile mode compared to nonpulsatile mode, more THE was delivered to the pseudopatient, particularly in the Latex group (P < 0.05). The results showed that the flexible arterial tubing retained more hemodynamic energy passing through it under pulsatile mode while mean pressures and pressure drops across the ECLS circuit were similar between PVC and latex rubber arterial tubing. Further studies are warranted to verify our findings.

Does an Open Recirculation Line Affect the Flow Rate and Pressure in a Neonatal Extracorporeal Life Support Circuit With a Centrifugal or Roller Pump?

The objective of this study is to evaluate the impact of an open or closed recirculation line on flow rate, circuit pressure, and hemodynamic energy transmission in simulated neonatal extracorporeal life support (ECLS) systems. The two neonatal ECLS circuits consisted of a Maquet HL20 roller pump (RP group) or a RotaFlow centrifugal pump (CP group), Quadrox-iD Pediatric oxygenator, and Biomedicus arterial and venous cannulae (8 Fr and 10 Fr) primed with lactated Ringer's solution and packed red blood cells (hematocrit 35%). Trials were conducted at flow rates ranging from 200 to 600 mL/min (200 mL/min increments) with a closed or open recirculation line at 36°C. Real-time pressure and flow data were recorded using a custom-based data acquisition system. In the RP group, the preoxygenator flow did not change when the recirculation line was open while the prearterial cannula flow decreased by 15.7-20.0% (P < 0.01). Circuit pressure, total circuit pressure drop, and hemodynamic energy delivered to patients also decreased (P < 0.01). In the CP group, the prearterial cannula flow did not change while preoxygenator flow increased by 13.6-18.8% (P < 0.01). Circuit pressure drop and hemodynamic energy transmission remained the same. The results showed that the shunt of an open recirculation line could decrease perfusion flow in patients in the ECLS circuit using a roller pump, but did not change perfusion flow in the circuit using a centrifugal pump. An additional flow sensor is needed to monitor perfusion flow in patients if any shunts exist in the ECLS circuit.

In Vitro Evaluation of an Alternative Neonatal Extracorporeal Life Support Circuit on Hemodynamic Performance and Bubble Trap

The objective of this study was to evaluate an alternative neonatal extracorporeal life support (ECLS) circuit with a RotaFlow centrifugal pump and Better-Bladder (BB) for hemodynamic performance and gaseous microemboli (GME) capture in a simulated neonatal ECLS system. The circuit consisted of a Maquet RotaFlow centrifugal pump, a Quadrox-iD Pediatric diffusion membrane oxygenator, 8 Fr arterial cannula, and 10 Fr venous cannula. A "Y" connector was inserted into the venous line to allow for comparison between BB and no BB. The circuit and pseudopatient were primed with lactated Ringer's solution and packed human red blood cells (hematocrit 35%). All hemodynamic trials were conducted at flow rates ranging from 100 to 600 mL/min at 36°C. Real-time pressure and flow data were recorded using a data acquisition system. For GME testing, 0.5 cc of air was injected via syringe into the venous line. GME were detected and characterized with or without the BB using the Emboli Detection and Classification Quantifier (EDAC) System. Trials were conducted at flow rates ranging from 200 to 500 mL/min. The hemodynamic energy data showed that up to 75.2% of the total hemodynamic energy was lost from the circuit. The greatest pressure drops occurred across the arterial cannula and increased with increasing flow rate from 10.1 mm Hg at 100 mL/min to 114.3 mm Hg at 600 mL/min. The EDAC results showed that the BB trapped a significant amount of the GME in the circuit. When the bladder was removed, GME passed through the pump head and the oxygenator to the arterial line. This study showed that a RotaFlow centrifugal pump combined with a BB can help to significantly decrease the number of GME in a neonatal ECLS circuit. Even with this optimized alternative circuit, a large percentage of the total hemodynamic energy was lost. The arterial cannula was the main source of resistance in the circuit.

Effect of the Pulsatile Extracorporeal Membrane Oxygenation on Hemodynamic Energy and Systemic Microcirculation in a Piglet Model of Acute Cardiac Failure

The objective of this study was to compare the effects of pulsatile and nonpulsatile extracorporeal membrane oxygenation (ECMO) on hemodynamic energy and systemic microcirculation in an acute cardiac failure model in piglets. Fourteen piglets with a mean body weight of 6.08 ± 0.86 kg were divided into pulsatile (N = 7) and nonpulsatile (N = 7) ECMO groups. The experimental ECMO circuit consisted of a centrifugal pump, a membrane oxygenator, and a pneumatic pulsatile flow generator system developed in-house. Nonpulsatile ECMO was initiated at a flow rate of 140 mL/kg/min for the first 30 min with normal heart beating, with rectal temperature maintained at 36°C. Ventricular fibrillation was then induced with a 3.5-V alternating current to generate a cardiac dysfunction model. Using this model, we collected the data on pulsatile and nonpulsatile groups. The piglets were weaned off ECMO at the end of the experiment (180 min after ECMO was initiated). The animals did not receive blood transfusions, inotropic drugs, or vasoactive drugs. Blood samples were collected to measure hemoglobin, methemoglobin, blood gases, electrolytes, and lactic acid levels. Hemodynamic energy was calculated using the Shepard's energy equivalent pressure. Near-infrared spectroscopy was used to monitor brain and kidney perfusion. The pulsatile ECMO group had a higher atrial pressure (systolic and mean), and significantly higher regional saturation at the brain level, than the nonpulsatile group (for both, P < 0.05). Additionally, the pulsatile ECMO group had higher methemoglobin levels within the normal range than the nonpulsatile group. Our study demonstrated that pulsatile ECMO produces significantly higher hemodynamic energy and improves systemic microcirculation, compared with nonpulsatile ECMO in acute cardiac failure.

Apolipoprotein E levels in pediatric patients undergoing cardiopulmonary bypass

Apolipoprotein E (apoE) may play a critical role in modulating the response to neurological injury after cardiopulmonary bypass (CPB) in children. Plasma samples were collected from 38 pediatric patients. Half of the patients received nonpulsatile flow and the other half underwent pulsatile flow during CPB. Plasma samples were collected at three time points: at baseline prior to incision (T1), 1 h after CPB (T2), and 24 h after CPB (T3). The study included 38 pediatric patients undergoing heart surgery (mean age 2.5 ± 2.1 years). Baseline apoE levels were low (<30 μg/mL) in 21 patients (55%). ApoE levels were significantly decreased at 1 h after CPB compared with baseline (22 ± 14 vs. 34 ± 18 μg/mL, P = 0.001). At 24 h after CPB, apoE levels were significantly increased compared with baseline (47 ± 25 vs. 34 ± 18 μg/mL, P = 0.002). Pulsatile mode was associated with lower apoE levels at 24 h after CPB compared with nonpulsatile mode (38 ± 14 vs. 57 ± 29 μg/mL, P = 0.018). ApoE levels correlated negatively with pump time (r = -0.525, P = 0.021) and cross-clamp time (r = -0.464, P = 0.045) at 24 h following CPB for the nonpulsatile group but not for the pulsatile group. In this cohort of young children with congenital heart disease, baseline apoE levels were low in the majority of patients prior to surgery. ApoE levels decreased further at 1 h after CPB, and then significantly increased by 24 h. The mode of perfusion and the duration of pump time and clamp time influence the apoE levels after CPB. An improved understanding of these mechanisms may translate into the development of new techniques to improve the clinical outcomes after pediatric CPB.

Potential Danger of Pre-Pump Clamping on Negative Pressure-Associated Gaseous Microemboli Generation During Extracorporeal Life Support--An In Vitro Study

The objectives of this study were to investigate the relationship between revolution speed of a conventional centrifugal pump and negative pressure at the inlet of the pump by clamping the tubing upstream of the pump, and to verify whether negative pressure leads to gaseous microemboli (GME) production in a simulated adult extracorporeal life support (ECLS) system. The experimental circuit, including a Maquet Rotaflow centrifugal pump and a Medos Hilite 7000 LT polymethyl-pentene membrane oxygenator, was primed with packed red blood cells (hematocrit 35%). Negative pressure was created in the circuit by clamping the tubing upstream of the pump for 10 s, and then releasing the clamp. An emboli detection and classification quantifier was used to record GME volume and count at pre-oxygenator and post-oxygenator sites, and pressure and flow rate data were collected using a custom-based data acquisition system. All trials were conducted at 36°C at revolution speeds of 2000-4000 rpm (500 rpm increment). The flow rates were 1092.5-4708.4 mL/min at the revolution speeds of 2000-4000 rpm. Higher revolution speed generated higher negative pressure at the pre-pump site when clamping the tubing upstream of the pump (-108.3 ± 0.1 to -462.0 ± 0.5 mm Hg at 2000-4000 rpm). Moreover, higher negative pressure was associated with a larger number and volume of GME at pre-oxygenator site after de-clamp (GME count 10,573 ± 271 at pre-oxygenator site at 4000 rpm). The results showed that there was a potential danger of delivering GME to the patient when clamping pre-pump tubing during ECLS using a centrifugal pump. Our results warrant further clinical studies to investigate this phenomenon.

Are perioperative near-infrared spectroscopy values correlated with clinical and biochemical parameters in cyanotic and acyanotic infants following corrective cardiac surgery?

Background:

Near-infrared spectroscopy (NIRS) is a useful non-invasive tool for monitoring infants undergoing cardiac surgery. In this study, we aimed to determine the NIRS values in cyanotic and acyanotic patients who underwent corrective cardiac surgery for congenital heart diseases.

Methods:

Thirty consecutive infants who were operated on with the diagnosis of ventricular septal defect (n=15) and tetralogy of Fallot (n=15) were evaluated retrospectively. A definitive repair of the underlying cardiac pathology was achieved in all cases. A total of six measurements of cerebral and renal NIRS were performed at different stages of the perioperative period. The laboratory data, mean urine output and serum lactate levels were evaluated along with NIRS values in each group.

Results:

The NIRS values differ in both groups, even after the corrective surgical procedure is performed. The recovery of renal NIRS values is delayed in the cyanotic patients.

Conclusion:

Even though definitive surgical repair is performed in cyanotic infants, recovery of the renal vasculature may be delayed by up to two days, which is suggestive of a vulnerable period for renal dysfunction.