D. Scott Lawson

Outcomes Before and After Implementation of a Pediatric Rapid-Response Extracorporeal Membrane Oxygenation Program

BACKGROUND Rapid-response extracorporeal membrane oxygenation (RR-ECMO) has been implemented at select centers to expedite cannulation for patients placed on ECMO during extracorporeal cardiopulmonary resuscitation (ECPR). In 2008, we established such a program and used it for all pediatric venoarterial ECMO initiations. This study was designed to compare outcomes before and after program implementation. METHODS Between 2003 and 2011, 144 pediatric patients were placed on venoarterial ECMO. Records of patients placed on ECMO before (17 ECPR and 62 non-ECPR) or after (14 ECPR and 51 non-ECPR) RR-ECMO program implementation were retrospectively compared. RESULTS The peak performance of the ECMO team was assessed by measuring ECMO initiation times for the ECPR patient subgroup (n = 31). There was a shift toward more ECPR initiations achieved in less than 40 minutes (24% pre-RR-ECMO versus 43% RR-ECMO; p = 0.25) and fewer requiring more than 60 minutes (47% pre-RR-ECMO versus 21% RR-ECMO; p = 0.14) after program implementation, although these changes did not reach statistical significance. After multivariable risk adjustment, RR-ECMO was associated with a 52% reduction in neurologic complications for all patients (adjusted odds ratio, 0.48; 95% confidence interval, 0.23 to 0.98; p = 0.04), but the risk of in-hospital death remained unchanged (adjusted odds ratio, 0.99; 95% confidence interval, 0.50 to 1.99; p = 0.99). CONCLUSIONS Implementation of a pediatric RR-ECMO program for venoarterial ECMO initiation was associated with reduced neurologic complications but not improved survival during the first 3 years of program implementation. These data suggest that development of a coordinated system for rapid ECMO deployment may benefit both ECPR and non-ECPR patients, but further efforts are required to improve survival.

Kinetics of procalcitonin and C-reactive protein and the relationship to postoperative infection in young infants undergoing cardiovascular surgery

Background:The utility of procalcitonin (PCT) and C-reactive protein (CRP) as infectious biomarkers following infant cardiothoracic surgery is not well defined.Methods:We designed a prospective cohort study to evaluate PCT and CRP after infant cardiothoracic surgery. PCT and CRP were drawn preoperatively and 24/72 h postoperation or daily in delayed sternal closure patients. Presence of infection within 10 d of surgery, vasoactive-inotropic scores at 24 and 72 h, and length of intubation, intensive care unit stay, and hospital stay were documented.Results:PCT and CRP were elevated at 24 h. PCT then decreased while CRP increased in patients undergoing delayed sternal closure or cardiopulmonary bypass. In the delayed sternal closure group, PCT was significantly higher on postoperative days 2–5 in patients who ultimately developed infection. Higher PCT was independently associated with increased vasoactive-inotropic score at 72 h. CRP did not correlate with infection or postoperative support.Conclusion:PCT rises after cardiothoracic surgery in infants but decreases by 72 h while CRP remains elevated. Sternal closure may affect CRP but not PCT. PCT is independently associated with circulatory support requirements at 72 h postoperation and with development of infection. PCT may have greater utility as a biomarker in this population.

Evaluation of a preprimed microporous hollow-fiber membrane for rapid response neonatal extracorporeal membrane oxygenation.

Delays in initiating extracorporeal membrane oxygenation (ECMO) in the critically ill pediatric patient may lead to adverse outcomes. Maintaining a primed ECMO circuit can considerably reduce the initiation time. The predominant concerns precluding this practice are a decrease in oxygenator efficiency due to the saturation of microporous hollow fibers and compromised sterility when the oxygenator has been primed for 30 days. For institutions using a hollow-fiber oxygenator for ECMO, there are no data reporting pre-primed hollow-fiber oxygenator viability. This study reports the efficiency of oxygen transfer and the sterility of the Carmeda Minimax Plus (Medtronic, Inc, Minneapolis, MN) oxygenator after being crystalloid primed for 30 days. A total of 10 Minimax Plus oxygenators were tested for oxygen transfer in a laboratory setting utilizing fresh whole bovine blood. The control group (n=5) were tested immediately after priming. The test group (n=5) were oxygenators primed for 30 days with crystalloid solution and left stagnant until tested. Prior to testing, all oxygenators were circulated for 5 min and samples drawn to test for circuit sterility. Venous inlet saturations were manipulated to achieve three levels of testing: venous saturation (SvO2) of 55% for an oxygen challenge, SvO2 of 65% to comply with AAMI standards, and SvO2 of 75% to assess oxygen transfer rates and peak PaO2 achievement. Blood flow for all tests was maintained at 2 L/min with 1:1 blood to gas flow ratio and 100% FiO2. Samples were drawn pre- and postoxygenator at 1- and 6-hour time intervals to compute actual oxygen transfer values. All cultures from the test group priming solution produced no microbial growth after 30 days of stagnant prime. Average oxygen transfer values (ml/O2/min) for the control group after 1 hour of continuous use were 130.1±15.5 (@55% SvO2), 113.7±10.4 (@65% SvO2),97.7±8.9 (@75% SvO2). After 6 hours, the average transfer values increased to 134.2±13.2 (@55% SvO2), 118.76±6.6 (@65% SvO2) and 98.9±8.3 (@75% SvO2). The average oxygen transfer values after 1 hour for oxygenators primed for 30 days were 114.9±10.0 (@55% SvO2), 112.4±8.2 (@65% SvO2) and 89.6±16.0 (@75% SvO2). After 6 hours of use, the average transfer values all decreased to 111.4±2.1 (@55% SvO2, p <0.05 versus control), 104.0±5.6 (@65% SvO2, p<0.05 versus control) and 88.4±3.2 (@75% SvO2, p<0.05 versus control). In conclusion, there was a decrease in the average oxygen transfer values for the test group after 6 hours versus the control. The modest loss of oxygen transfer ability observed can be considered acceptable due to the amount of surface area of the Minimax Plus oxygenator when used on a neonate, making it feasible to adopt the practice of prepriming the Minimax oxygenator for neonatal ECMO.

Insensible water loss from the medtronic minimax oxygenator : An in vitro study

The purposes of this study were to quantify the insensible water loss that occurs across the Medtronic Minimax oxygenator and to estimate the resultant rise in fluid sodium concentration. A Carmeda®-coated extracorporeal membrane oxygenation circuit connected to a Medtronic Minimax Plus oxygenator was primed with normal saline and attached to a closed reservoir. The gas sweep was randomly assigned to one of three rates: 2, 5, or 10 LPM (liters per minute). Each sweep rate was run in triplicate. The sodium concentration of the circuit was assessed after 12 and 24 hours of each trial. At the end of each 24-hour run, the evaporative loss was calculated. The average insensible water losses were 6.9 ± 0.4 ml/h, 16.6 ± 1.5 ml/h, and 34.4 ± 0.3 ml/h at gas sweep rates of 2, 5, and 10 LPM, respectively (p < 0.0001). Daily evaporative water losses for the membrane can be estimated to be 82.7 ± 2.2 ml for each 1 LPM of sweep gas flow for a normal saline pump flow of 300 ml/min. In a closed circuit, a faster sweep gas rate is associated with a more rapid rise in sodium concentration (p < 0.0001).

Venous line filtration: a novel technique for cases involving inferior vena caval and right atrial tumor and associated thrombus: a two-case series:

Two patients are presented with right atrial tumors, who were considered to be at risk for tumor thrombus migration down the venous line into the cardiopulmonary bypass (CPB) circuit during surgical excision, which may lead to compromised or interrupted venous drainage. An arterial line filter was placed in the venous line to capture any material that might become dislodged and embolize into the circuit. Vacuum-assisted venous drainage, at approximately -50 mmHg, was used to overcome any resistance caused by the filter in the venous line. In one case, tumor thrombus obstructed the filter, requiring the use of the bypass line around the filter, so venous return could be maintained. In both cases, thrombus was found in the filter. The first case was a 44-year-old female (81 kg, 137 cm, body surface area (BSA) 1.66 m2) who presented with a metastatic pheochromocytoma with associated thrombus arising from the left adrenal gland and extending into the inferior vena cava (IVC) and right atrium. The second case was a 37-year-old male (95 kg, 178 cm, BSA 2.17 m2), who presented with a very large angiosarcoma tumor involving almost the entire right atrium. We have shown that venous line filtration with vacuum-assisted venous drainage can be performed safely, and should be considered in cases where there is tumor thrombus in the vena cava or right atrium, which may threaten venous return.

Hemolysis generation from a novel, linear positive displacement blood pump for cardiopulmonary bypass on a six kilogram piglet: a preliminary report

Background: Current blood pumps used for cardiopulmonary bypass generally fall into two different pump design categories; non-occlusive centrifugal pumps and occlusive, positive-displacement roller pumps. The amount of foreign surface area of extracorporeal circuits correlates with post-operative morbidity due to systemic inflammation, leading to a push for technology that reduces the amount of foreign surfaces. Current roller pumps are bulky and the tubing forms an arc in the pumping chamber (raceway), positioning the inlet 360 degrees from the outlet, making it very difficult to place the pump closer to the patient and to efficiently reduce tubing length. These challenges put existing roller pumps at a disadvantage for use in a compact cardiopulmonary bypass circuit. Centrifugal blood pumps are easier to incorporate into miniature circuit designs. However, the prime volumes of current centrifugal pump designs are large, especially for pediatric extracorporeal circuits where the prime volumes are too great to be of clinical value. Method: We describe a preliminary report on a novel, occlusive, linear, single-helix, positive-displacement blood pump which allows for decreased prime volume and surface area of the extracorporeal circuit. This new experimental pump design was used to perfuse a 6 kilogram piglet with a pediatric cardiopulmonary bypass circuit for two hours of continuous use. Blood samples were obtained every thirty minutes and assayed for plasma free hemolysis generation. Conclusions: The results from this initial experiment showed low plasma free hemoglobin generation and encourages the authors to further develop this concept.

Review articles: Cold agglutinins and hypothermic cardiopulmonary bypass

As hypothermic cardiopulmonary bypass has become more commonplace over the past 20 years, so has the problem of management of the patient with cold agglutinins. The perfusionist must understand the implications of the presence of cold agglutinins and formulate a plan to manage each particular patient with the cardiac surgeon.