The effect of excessive gas to blood ratios in an ECMO oxygenator.

INTRODUCTION: Oxygenators for paediatric Extracorporeal Membrane Oxygenation (ECMO) are required to operate over a wide range of flow rates, in a patient group ranging from neonates through to fully grown adolescents. ECMO oxygenators typically have a manufacturer's stated maximum gas: blood flow rate (GBFR) ratio of 2:1, however, many patients require greater ratios than this for adequate CO2 removal. Mismatches in GBFR in theory could result in high gas phase pressures. These increased pressures in theory could cause the formation of gross gaseous microemboli (GME) placing the child at higher risk of neurological injury. METHODS: We evaluated 6 paediatric and 6 adult A.L.ONE™ ECMO oxygenators and assessed their gas phase pressures and GME release, in an ex vivo setting, in GBFR ratios up to greater than 2, across a range of gas flow (1L - 10 L/min) rates with a fraction of inspired oxygen (FiO2) content of 50% and 100%. RESULTS: There were no increases above 10 mmHg observed in gas phase pressures in GBFR >= 2:1 in either adult or paediatric oxygenators. Laboratory examination of GME activity demonstrated a small increase in post-membrane GME release over the study period. GME release was unaffected by FiO2 setting or gas flow rate, with a maximum volume of < 6 µL in both paediatric and adult oxygenators. CONCLUSIONS: In an ex vivo setting, increasing GBFR above 2:1 in a paediatric oxygenator, and to a GBFR of 2:1 in an adult oxygenator did not significantly increase gas phase pressures, and no oxygenator membrane rupture was observed. There were no associations between gas flow rates and GME production.

Lung transplantation in an 18-month-old with donor specific antibodies - The use of intraoperative, targeted plasma exchange.

BACKGROUND: Sensitised patients undergoing Human Leukocyte Antigen-incompatible transplantation are at increased risk of hyperacute rejection and may be predisposed to antibody-mediated rejection, chronic lung allograft dysfunction and higher mortality. CASE: We present a case of primary lung transplantation in the setting of late identification of donor specific antibodies treated with intraoperative target plasma exchange. The patient was treated with fresh human plasma to a final volume of 1.5 times the patient's systemic circulation. From a pre-transplant mean fluorescence intensity of 5002, donor-specific antibodies were undetectable following plasma exchange on single antigen bead assay. CONCLUSIONS: This method represents a potential desensitisation technique for use in the intraoperative period.

Intraoperative anti-A/B immunoadsorption is associated with significantly reduced blood product utilization with similar outcomes in pediatric ABO-incompatible heart transplantation.

BACKGROUND: Intraoperative anti-A/B immunoadsorption (ABO-IA) was recently introduced for ABO-incompatible heart transplantation. Here we report the first case series of patients transplanted with ABO-IA, and compare outcomes with those undergoing plasma exchange facilitated ABO-incompatible heart transplantation (ABO-PE). METHODS: Data were retrospectively analysed on all ABO-incompatible heart transplants undertaken at a single centre between January 1, 2000 and June 1, 2020. Data included all routine laboratory tests, demographics and pre-operative characteristics, intraoperative details and post-operative outcomes. Primary outcome measures were volume of blood product transfusions, maximum post-transplant isohaemagglutinin titres, occurrence of rejection and graft survival. Secondary outcome measures were length of intensive care and hospital stay. Demographic and survival data were also obtained for ABO-compatible transplants during the same time period for comparison. RESULTS: Thirty-seven patients underwent ABO-incompatible heart transplantation, with 27 (73%) using ABO-PE and 10 (27%) using ABO-IA. ABO-IA patients were significantly older than ABO-PE patients (p < 0.001) and the total volume of blood products transfused during the hospital admission was significantly lower (164 [126-212] ml/kg vs 323 [268-379] ml/kg, p < 0.001). No significant differences were noted between methods in either pre or post-transplant maximum isohaemagglutinin titres, incidence of rejection, length of intensive care or total hospital stay. Survival comparison showed no significant difference between antibody reduction methods, or indeed ABO-compatible transplants (p = 0.6). CONCLUSIONS: This novel technique appears to allow a significantly older population than typical to undergo ABO-incompatible heart transplantation, as well as significantly reducing blood product utilization. Furthermore, intraoperative anti-A/B immunoadsorption does not demonstrate increased early post-transplant isohaemagglutinin accumulation or rates of rejection compared to ABO-PE. Early survival is equivalent between ABO-IA, ABO-PE and ABO-compatible heart transplantation.

Plasticizer di(2-ethylhexyl)phthalate (DEHP) release in wet-primed extracorporeal membrane oxygenation (ECMO) circuits.

A wet-primed ready-to-use extracorporeal membrane oxygenation (ECMO) circuit is used in some centres for rapid deployment of ECMO during cardiopulmonary resuscitation. Yet, the potential release of plasticizer di(2-ethylhexyl)phthalate (DEHP) from the polyvinyl chloride tubing in the circuit during storage is a concern. In this study, a high performance liquid chromatography method was used to determine the concentration of DEHP in the priming solution (Plasmalyte) from an ECMO circuit stored for up to 14 days at 8 degrees C. No accumulation of DEHP in the circulating fluid was detected. The results provide important information for centres where ECMO circuits are kept wet-primed prior to clinical use.

Impact of rapid leukodepletion on the outcome of severe clinical pertussis in young infants.

OBJECTIVES: Bordetella pertussis is a common, underrecognized, and vaccine-preventable cause of critical illness with a high mortality in infants worldwide. Patients with severe cases present with extreme leukocytosis and develop refractory hypoxemia and pulmonary hypertension that is unresponsive to maximal intensive care. This may reflect a hyperviscosity syndrome from the raised white blood cell (WBC) count. Case reports suggest improved outcomes with exchange transfusion to reduce the WBC count. Our objective was to quantify possible benefits of aggressive leukodepletion. METHODS: We, as a regional PICU and extracorporeal membrane oxygenation referral center, adopted a strategy of aggressive leukodepletion in January 2005. The impact of this strategy on crude and case mix-adjusted survival of all infants who were critically ill with B pertussis were compared with control subjects from January 2001 to December 2004 and Extracorporeal Life Support Organisation registry data. RESULTS: Nineteen infants (7 [37%] boys) received intensive care for B pertussis from 2001 to 2009. Admission WBC counts were equivalent in 2 time periods: 2001-2004 (mean: 52,000/µL) and 2005-2009 (mean: 75,000/µL). In 2001-2004, 5 (55%) of 9 patients survived the ICU. Between 2005 and 2009, 9 (90%) of 10 patients survived. When case-mix adjustment for age, WBC count, and extracorporeal membrane oxygenation referral were considered, the 2001-2004 predicted survival (4.4 [49%] of 9.0) was equivalent to the observed mortality (4.0 [44%] of 9.0). Between 2005 and 2009, observed mortality (1.0 [10%] of 10.0) was significantly better than predicted (4.7 [47%] of 10.0). CONCLUSIONS: Leukodepletion should be considered in critically ill infants with B pertussis and leukocytosis.

A wet-primed extracorporeal membrane oxygenation circuit with hollow-fiber membrane oxygenator maintains adequate function for use during cardiopulmonary resuscitation after 2 weeks on standby.

OBJECTIVE: To assess the durability of wet-preprimed extracorporeal membrane oxygenation (ECMO) circuits for potential use in resuscitation after a 2-wk period of storage. DESIGN: Experimental laboratory study. SETTING: Tertiary care pediatric cardiac intensive care unit. SUBJECTS: None. INTERVENTIONS AND MEASUREMENTS: 14 ECMO circuits (polyvinyl chloride and super-Tygon tubing with hollow-fiber oxygenator, Medos Hilite 800LT) were primed with crystalloid under sterile conditions and stored for 0 (control, n = 4), 7 (n = 5) and 14 (n = 5) days and maintained at 8 degrees C on pump at 10 rpm and gas flow at 0.2 L/min. Daily samples were inspected for plasticizers by means of high-performance liquid chromatography and for microorganisms by culture and polymerase chain reaction techniques. After storage, the oxygenators were primed with red blood cells (hemoglobin, 12 g/dL) and tested in vitro with a deoxygenator according to Association for Advancement of Medical Instrumentation standards. Oxygen and CO(2) transfer rates were calculated by standard formulae at maximum blood flow (800 mL/min) and maximum sweep gas flow (1.6 L/min). MAIN RESULTS: Oxygen transfer was linearly related to venous oxygen saturation, increasing by 11 mL/min for each 10% decrease in venous oxygen saturation. Estimated oxygen transfer at venous oxygen saturation of 60% was 45.8 mL/min (95% confidence interval [CI], 43.5-48.1) for controls, 51.0 mL/min (95% CI, 48.9-53.2) for 7-day oxygenators, and 49.0 mL/min (95% CI, 47.8-50.1) for 14-day oxygenators. CO(2) transfer declined to 29.2 mL/min at 14 days of storage, a mean fall of 11.5 mL/min (95% CI, 4.2-18.7) in comparison with 7-day storage. All circuits were free from microbes/microbial DNA. Plasticizer levels fell below the lower limit of detection (0.003 microg/mL) at 7 and 14 days. CONCLUSIONS: A wet-preprimed ECMO circuit with hollow-fiber membrane oxygenator can be stored for up to 2 wks with adequately preserved function if prepared appropriately. These data may improve safe access to rapid-response ECMO support.