Oxygenator impact on voriconazole in extracorporeal membrane oxygenation circuits.

INTRODUCTION: To determine the oxygenator impact on alterations of voriconazole in a contemporary neonatal/pediatric (1/4 inch) and adolescent/adult (3/8 inch) extracorporeal membrane oxygenation circuit including the Quadrox-i® oxygenator. METHODS: Simulated closed-loop extracorporeal membrane oxygenation circuits (1/4 and 3/8 inch) were prepared with a Quadrox-i pediatric and Quadrox-i adult oxygenator and blood primed. In addition, 1/4- and 3/8-inch circuits were also prepared without an oxygenator in series. A one-time dose of voriconazole was administered into the circuits, and serial pre- and post-oxygenator concentrations were obtained at 5 minutes, 1, 2, 3, 4, 5, 6, and 24 hour time points. Voriconazole was also maintained in a glass vial and samples were taken from the vial at the same time periods for control purposes to assess for spontaneous drug degradation. RESULTS: For the 1/4-inch circuit, there was an approximate mean of 64-67% voriconazole loss with the oxygenator in series and mean of 15-20% voriconazole loss without an oxygenator in series at 24 hours. For the 3/8-inch circuit, there was an approximate mean of 44-51% voriconazole loss with the oxygenator in series and a mean of 8-12% voriconazole loss without an oxygenator in series at 24 hours. The reference voriconazole concentrations remained relatively constant during the entire study period demonstrating that the drug loss in each size of the extracorporeal membrane oxygenation circuit with or without an oxygenator was not a result of spontaneous drug degradation. CONCLUSION: This ex vivo investigation demonstrated substantial voriconazole loss within an extracorporeal membrane oxygenation circuit with an oxygenator in series with both sizes of the Quadrox-i oxygenator at 24 hours and no significant voriconazole loss in the absence of an oxygenator. Further evaluations with multiple dose in vitro and in vivo investigations are needed before specific voriconazole dosing recommendations can be made for clinical application with extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation and V/Q ratios: an ex vivo analysis of CO2 clearance within the Maquet Quadrox-iD oxygenator.

While hypercapnia is typically well treated with modern membrane oxygenators, there are cases where respiratory acidosis persists despite maximal extracorporeal membrane oxygenation support. To better understand the physiology of gas exchange within the membrane oxygenator, CO2 clearance within an adult Maquet Quadrox-iD oxygenator was evaluated at varying blood CO2 tensions and V/Q ratios in an ex vivo extracorporeal membrane oxygenation circuit. A closed blood-primed circuit incorporating two Maquet Quadrox-iD oxygenators in series was attached to a Maquet PLS Rotaflow pump. A varying blend of CO2 and air was connected to the first oxygenator to provide different levels of pre-oxygenator blood CO2 levels (PvCO2) to the second oxygenator. Varying sweep gas flows of 100% O2 were connected to the second oxygenator to provide different V/Q ratios. Exhaust CO2 was directly measured, and then VCO2 and oxygenator dead space fraction (VD/VT) were calculated. VCO2 increased with increasing gas flow rates with plateauing at V/Q ratios greater than 4.0. Exhaust CO2 increased with PvCO2 in a linear fashion with the slope of the line decreasing at high V/Q ratios. Oxygenator dead space fraction varied with V/Q ratio-at lower ratios, dead space fraction was 0.3-0.4 and rose to 0.8-0.9 at ratios greater than 4.0. Within the Maquet Quadrox-iD oxygenator, CO2 clearance is limited at high V/Q ratios and correlated with elevated oxygenator dead space fraction. These findings have important implications for patients requiring high levels of extracorporeal membrane oxygenation support.

Hypothermic Oxygenated New Machine Perfusion System in Liver and Kidney Transplantation of Extended Criteria Donors:First Italian Clinical Trial.

With the aim to explore innovative tools for organ preservation, especially in marginal organs, we hereby describe a clinical trial of ex-vivo hypothermic oxygenated perfusion (HOPE) in the field of liver (LT) and kidney transplantation (KT) from Extended Criteria Donors (ECD) after brain death. A matched-case analysis of donor and recipient variables was developed: 10 HOPE-ECD livers and kidneys (HOPE-L and HOPE-K) were matched 1:3 with livers and kidneys preserved with static cold storage (SCS-L and SCS-K). HOPE and SCS groups resulted with similar basal characteristics, both for recipients and donors. Cumulative liver and kidney graft dysfunction were 10% (HOPE L-K) vs. 31.7%, in SCS group (p = 0.05). Primary non-function was 3.3% for SCS-L vs. 0% for HOPE-L. No primary non-function was reported in HOPE-K and SCS-K. Median peak aspartate aminotransferase within 7-days post-LT was significantly higher in SCS-L when compared to HOPE-L (637 vs.344 U/L, p = 0.007). Graft survival at 1-year post-transplant was 93.3% for SCS-L vs. 100% of HOPE-L and 90% for SCS-K vs. 100% of HOPE-K. Clinical outcomes support our hypothesis of machine perfusion being a safe and effective system to reduce ischemic preservation injuries in KT and in LT.

Hypothermic effects on gas exchange performance of membrane oxygenator and blood coagulation during cardiopulmonary bypass in pigs.

INTRODUCTION: Whether hypothermic cardiopulmonary bypass could attenuate both blood coagulation and platelet activation compared to normothermic cardiopulmonary bypass remains elusive. METHODS: Biocompatibility of a polymer-coated cardiopulmonary bypass circuit was comparatively assessed by plasma proteomics between juvenile pigs undergoing hypothermic (23°C) cardiopulmonary bypass and those undergoing normothermic (37°C) cardiopulmonary bypass (n = 6, respectively). Plasma samples were taken three times: 5 minutes after initiation of cardiopulmonary bypass (T5, before cooling), just before declamping and rewarming (Tc), and just before termination of cardiopulmonary bypass (Trw, 120 minutes). Proteomic analysis was quantitively performed by isobaric tags for relative and absolute quantification labeling. Thrombin-antithrombin complexes (TAT III) were measured by enzyme immunoassay, and vitamin K-dependent protein C (PROC), ß-thromboglobulin (TG), and P-selectin were measured by enzyme-linked immunosorbent assay. Blood gas analyses evaluated oxygenator performance. RESULTS: Hypothermic cardiopulmonary bypass had a significantly higher PaO2 at Tc and lower PaCO2 at Trw than normothermic cardiopulmonary bypass. Two hundred twenty-four proteins were identified with statistical criteria of both protein confidence (>95%) and false discovery rate (<5%). Six of these proteins significantly decreased at Tc than at T5 in hypothermic cardiopulmonary bypass (p = 0.02-0.04), with three related to platelet degranulation. Protein C decreased at Trw compared with T5 in normothermic cardiopulmonary bypass (p = 0.04). Thrombin-antithrombin complex had a slightly larger increase with normothermic cardiopulmonary bypass at Trw than with hypothermic cardiopulmonary bypass. ß-thromboglobulin and P-selectin levels were significantly lower at Trw with hypothermic cardiopulmonary bypass than with normothermic cardiopulmonary bypass (p = 0.04). CONCLUSION: Hypothermic cardiopulmonary bypass attenuated platelet degranulation/blood coagulation and maintained better oxygenator performance compared to normothermic cardiopulmonary bypass in juvenile pigs.

Life span of different extracorporeal membrane systems for severe respiratory failure in the clinical practice.

Over the past decade, veno-venous extracorporeal membrane oxygenation (vvECMO) has been increasingly utilized in respiratory failure in patients. This study presents our institution´s experience focusing on the life span of ECMO systems reflecting the performance of a particular system. A retrospective review of our ECMO database identified 461 adult patients undergoing vvECMO (2010-2017). Patients that required more than one system and survived the first exchange >24 hours (n = 139) were included. Life span until the first exchange and exchange criteria were analyzed for all systems (PLS, Cardiohelp HLS-set, both Maquet Cardiopulmonary, Rastatt, Germany; Deltastream/Hilite7000LT, iLA-activve, Xenios/NovaLung, Heilbronn, Germany; ECC.O5, LivaNova, Mirandola, Italy). At our ECMO center, the frequency of a system exchange was 30%. The median (IQR) life span was 9 (6-12) days. There was no difference regarding the different systems (p = 0.145 and p = 0.108, respectively). However, the Deltastream systems were exchanged more frequently due to elective technical complications (e. g. worsened gas transfer, development of coagulation disorder, increased bleedings complications) compared to the other exchanged systems (p = 0.013). In summary, the used ECMO systems are safe and effective for acute respiratory failure. There is no evidence for the usage of a specific system. Only the increased predictability of an imminent exchange preferred the usage of a Deltastream system. However, the decision to use a particular system should not depend solely on the possible criteria for an exchange.

In-Vitro Evaluation of Two Types of Neonatal Oxygenators in Handling Gaseous Microemboli and Maintaining Optimal Hemodynamic Stability During Cardiopulmonary Bypass.

Objective: Usually only FDA-approved oxygenators are subject of studies by the international scientific community. The objective of this study is to evaluate two types of neonatal membrane oxygenators in terms of transmembrane pressure gradient, hemodynamic energy transmission and gaseous microemboli capture in simulated cardiopulmonary bypass systems. Methods: We investigated the Braile Infant 1500 (Braile Biomédica, São José do Rio Preto, Brazil), an oxygenator commonly used in Brazilian operating rooms, and compared it to the Dideco Kids D100 (Sorin Group, Arvada, CO, USA), that is an FDA-approved and widely used model in the USA. Cardiopulmonary bypass circuits were primed with lactated Ringer's solution and packed red blood cells (Hematocrit 40%). Trials were conducted at flow rates of 500 ml/min and 700 ml/min at 35ºC and 25ºC. Real-time pressure and flow data were recorded using a custom-based data acquisition system. For gaseous microemboli testing, 5cc of air were manually injected into the venous line. Gaseous microemboli were recorded using the Emboli Detection and Classification Quantifier. Results: Braile Infant 1500 had a lower pressure drop (P<0.01) and a higher total hemodynamic energy delivered to the pseudopatient (P<0.01). However, there was a higher raw number of gaseous microemboli seen prior to oxygenator at lower temperatures with the Braile oxygenator compared to the Kids D100 (P<0.01). Conclusion: Braile Infant 1500 oxygenator had a better hemodynamic performance compared to the Dideco Kids D100 oxygenator. Braile had more gaseous microemboli detected at the pre-oxygenator site under hypothermia, but delivered a smaller percentage of air emboli to the pseudopatient than the Dideco oxygenator.

In-vitro evaluation of two types of neonatal oxygenators in handling gaseous microemboli and maintaining optimal hemodynamic stability during cardiopulmonary bypass

Abstract Objective: Usually only FDA-approved oxygenators are subject of studies by the international scientific community. The objective of this study is to evaluate two types of neonatal membrane oxygenators in terms of transmembrane pressure gradient, hemodynamic energy transmission and gaseous microemboli capture in simulated cardiopulmonary bypass systems. Methods: We investigated the Braile Infant 1500 (Braile Biomédica, São José do Rio Preto, Brazil), an oxygenator commonly used in Brazilian operating rooms, and compared it to the Dideco Kids D100 (Sorin Group, Arvada, CO, USA), that is an FDA-approved and widely used model in the USA. Cardiopulmonary bypass circuits were primed with lactated Ringer's solution and packed red blood cells (Hematocrit 40%). Trials were conducted at flow rates of 500 ml/min and 700 ml/min at 35ºC and 25ºC. Real-time pressure and flow data were recorded using a custom-based data acquisition system. For gaseous microemboli testing, 5cc of air were manually injected into the venous line. Gaseous microemboli were recorded using the Emboli Detection and Classification Quantifier. Results: Braile Infant 1500 had a lower pressure drop (P<0.01) and a higher total hemodynamic energy delivered to the pseudopatient (P<0.01). However, there was a higher raw number of gaseous microemboli seen prior to oxygenator at lower temperatures with the Braile oxygenator compared to the Kids D100 (P<0.01). Conclusion: Braile Infant 1500 oxygenator had a better hemodynamic performance compared to the Dideco Kids D100 oxygenator. Braile had more gaseous microemboli detected at the pre-oxygenator site under hypothermia, but delivered a smaller percentage of air emboli to the pseudopatient than the Dideco oxygenator.

Randomized trial on the effect of sevoflurane on polypropylene membrane oxygenator performance.

OBJECTIVES: Volatile anesthetics have cardioprotective properties that improve clinically relevant outcomes in cardiac surgery, and can be used during cardiopulmonary bypass (CPB) through adapted calibrated vaporizers together with air and oxygen (O2). The effect of volatile agents on the membrane oxygenator is unknown. The aim of this study was to evaluate, for the first time, the performance of semiporous polypropylene membrane oxygenators after the use of sevoflurane vaporized during CPB in cardiac surgery. DESIGN: A prospective, randomized, controlled trial. SETTING: Teaching hospital. PARTICIPANTS: Thirty-two consecutive patients scheduled to undergo coronary artery bypass graft with CPB. INTERVENTIONS: Patients were allocated randomly to receive either a volatile anesthetic (sevoflurane 1%-3%, 16 patients) or an intravenous hypnotic (midazolam, 16 patients) during CPB. After surgery, the membrane oxygenators used during CPB were tested with regard to O2 transfer, carbon dioxide transfer, and pressure drop. MEASUREMENTS AND MAIN RESULTS: The authors observed no protocol deviation or crossover. The performance of the membrane oxygenator was similar between the 2 groups, as documented by O2 transfer (55±6.4 mL/min/L in the sevoflurane group versus 57±4.7 mL/min/L in the midazolam group, p = 0.4), carbon dioxide transfer, and pressure drop. CONCLUSIONS: The use of sevoflurane during CPB in cardiac surgery does not affect membrane oxygenator performance.

Comparison of perfusion quality in hollow-fiber membrane oxygenators for neonatal extracorporeal life support.

Perfusion quality is an important issue in extracorporeal life support (ECLS); without adequate perfusion of the brain and other vital organs, multiorgan dysfunction and other deficits can result. The authors tested three different pediatric oxygenators (Medos Hilite 800 LT, Medtronic Minimax Plus, and Capiox Baby RX) to determine which gives the highest quality of perfusion at flow rates of 400, 600, and 800 mL/min using human blood (36 degrees C, 40% hematocrit) under both nonpulsatile and pulsatile flow conditions. Clinically identical equipment and a pseudo-patient were used to mimic operating conditions during neonatal ECLS. Traditionally, the postoxygenator surplus hemodynamic energy value (SHE(post), extra energy obtained through pulsatile flow) is the one relied upon to give a qualitative determination of the amount of perfusion in the patient; the authors also examined SHE retention through the membrane, as well as the contribution of SHE(post) to the postoxygenator total hemodynamic energy (THE(post)). At each experimental condition, pulsatile flow outperformed nonpulsatile flow for all factors contributing to perfusion quality: the SHE(post) values for pulsatile flow were 4.6-7.6 times greater than for nonpulsatile flow, while the THE(post) remained nearly constant for pulsatile versus nonpulsatile flow. For both pulsatile and nonpulsatile flow, the Capiox Baby RX oxygenator was found to deliver the highest quality of perfusion, while the Minimax Plus oxygenator delivered the least perfusion. It is the authors' recommendation that the Baby RX oxygenator running under pulsatile flow conditions be used for pediatric ECLS, but further studies need to be done in order to establish its effectiveness beyond the FDA-approved time span.

Evaluation of infant membrane oxygenator in sheep.

OBJECTIVE: To analyze the security and efficacy of a new membrane oxygenator, the so-called OXM - 1500. METHODS: From May 2005 to September 2006, six sheep of Santa Inês breed (five male and one female, respectively) were studied. The average body weight was 14.1 (+/-5) kg, body surface 0.6 (+/-0.2) m(2) and a mean age 3.8 (+/-1.5) months. All of them were submitted to extracorporeal circulation (CEC) with evaluation at 10, 30, 60, 120, 180 and 240 minutes. The following values were obtained: values of oxygen transference (TTO2) and carbon dioxide transference (TTCO2), haemoglobin (HBS) and free haemoglobin (HBL), the score of platelets and of leucocytes, and heat transference rate. RESULTS: TTO2 and TTCO2 were adequate. Lesion of the majority formed blood elements was insignificant; there no modifications in HBS, HBL levels; platelets and leucocytes decreased over time. Heat exchange was effective (p < 0.05). CONCLUSIONS: The membrane OXM--1500 infant oxygenator, tested in sheep, showed adequate oxygenation capacity, CO2 removal capacity, and small alteration of haemoglobin and platelets without significant decrease of leucocytes, as expected. Heat exchanger connected to the oxygenator was efficient in temperature changes.

Avaliação de oxigenador de membrana infantil em ovinos / Evaluation of infant membrane oxygenator in sheep

OBJETIVO: Analisar a segurança e a eficácia de um novo oxigenador de membrana denominado OXM -1500. MÉTODOS: No período de maio de 2005 a setembro de 2006, foram estudados seis ovinos da raça Santa Inês, sendo cinco machos e uma fêmea, com peso corpóreo médio de 14,1 (±5) kg, superfície corpórea de 0,6 (±0,2) m² e idade média de 3,8 (±1,5) meses. Todos foram submetidos a circulação extracorpórea (CEC) com avaliação nos tempos 10, 30, 60, 120, 180 e 240 minutos, obtendo-se os valores de taxa de transferência de oxigênio (TTO2) e de taxa de transferência de gás carbônico (TTCO2), hemoglobina sérica (HBS) e livre (HBL), plaquetometria, leucometria e taxa de transferência de calor. RESULTADOS: Houve adequadas TTO2 e TTCO2. A lesão da maioria dos elementos figurados do sangue foi insignificante, sem alterações dos níveis de HBS, HBL, plaquetas e o número de leucócitos diminuíram com o tempo. A troca de calor foi efetiva (p < 0,05). CONCLUSÃO: O oxigenador de membrana infantil OXM1500, testado em ovinos, mostrou-se com capacidade adequada de oxigenação, remoção de gás carbônico e pequena alteração da hemoglobina e plaquetas, com diminuição do número de leucócitos de forma esperada. O trocador de calor acoplado ao oxigenador foi eficaz nas variações de temperatura.

OBJECTIVE: To analyze the security and efficacy of a new membrane oxygenator, the so-called OXM - 1500. METHODS: From May 2005 to September 2006, six sheep of Santa Inês breed (five male and one female, respectively) were studied. The average body weight was 14.1 (±5) kg, body surface 0.6 (±0.2) m² and a mean age 3.8 (±1.5) months. All of them were submitted to extracorporeal circulation (CEC) with evaluation at 10, 30, 60, 120, 180 and 240 minutes. The following values were obtained: values of oxygen transference (TTO2) and carbon dioxide transference (TTCO2), haemoglobin (HBS) and free haemoglobin (HBL), the score of platelets and of leucocytes, and heat transference rate. RESULTS: TTO2 and TTCO2 were adequate. Lesion of the majority formed blood elements was insignificant; there no modifications in HBS, HBL levels; platelets and leucocytes decreased over time. Heat exchange was effective (p < 0.05). CONCLUSIONS: The membrane OXM - 1500 infant oxygenator, tested in sheep, showed adequate oxygenation capacity, CO2 removal capacity, and small alteration of haemoglobin and platelets without significant decrease of leucocytes, as expected. Heat exchanger connected to the oxygenator was efficient in temperature changes.

A comparison of radiographic signs of pulmonary inflammation during ECMO between silicon and poly-methyl pentene oxygenators.

INTRODUCTION: The inflammatory response caused by extracorporeal membrane oxygenation (ECMO) is clearly visible within the first 24 h of cannulation. The inflammatory process affects all areas of the lung, even areas previously spared by the primary disease. OBJECTIVE: To compare the change in the radiographic signs of inflammatory response to ECMO between poly-methyl pentene and silicon oxygenators. STUDY DESIGN: Retrospective review of neonates and adults pre- and post-replacement of silicon oxygenators with poly-methyl pentene devices. Data were collected from Extracorporeal Life Support Organisation (ELSO) registry forms and patient records. Results were analysed by quantitative and semi-quantitative methods. RESULTS: There was a significant reduction in the radiographic signs of inflammatory response to ECMO, and a reduction in the time taken to revert to pre-ECMO state in the neonatal poly-methyl pentene group compared to silicon. However, there was no significant reduction in the duration of ECMO runs and the percentage survival between these groups in the neonates. In adults, there was no difference in severity of radiographic signs between groups. However, the inflammatory changes were relatively delayed in the adult poly-methyl pentene group. CONCLUSION: Polymethyl pentene (Medos) oxygenators have reduced the host's response phenomenon 'white out' in neonates, and caused a delayed response in adults. This is most likely a consequence of smaller blood contact surface area combined with the effect of heparin coating of the oxygenator membrane. However, recovery was not a function of the type of gas exchange device used.

Testing of heat exchangers in membrane oxygenators using air pressure.

All heat exchangers (HE) in membrane oxygenators are tested by the manufacturer for water leaks during the production phase. However, for safety reasons, it is highly recommended that HEs be tested again before clinical use. The most common method is to attach the heater-cooler to the HE and allow the water to recirculate for at least 10 min, during which time a water leak should be evident. To improve the detection of water leaks, a test was devised using a pressure manometer with an integrated bulb used to pressurize the HE with air. The cardiopulmonary bypass system is set up as per protocol. A pressure manometer adapted to a 1/2" tubing is connected to the water inlet side of the oxygenator. The water outlet side is blocked with a short piece of 1/2" deadend tubing. The HE is pressurized with 250 mmHg for at least 30 sec and observed for any drop. Over the last 2 years, only one oxygenator has been detected with a water leak in which the air-method leaktest was performed. This unit was sent back to the manufacturer who confirmed the failure. Even though the incidence of water leaks is very low, it does occur and it is, therefore, important that all HEs are tested before they are used clinically. This method of using a pressure manometer offers many advantages, as the HE can be tested outside of the operating room (OR), allowing earlier testing of the oxygenator, no water contact is necessary, and it is simple, easy and quick to perform.

Evaluation of coated oxygenators in cardiopulmonary-bypass systems and their impact on neurocognitive function.

INTRODUCTION: Coronary artery bypass graft surgery (CABG) using cardiopulmonary bypass (CPB) is assumed to be associated with a decline of neurocognitive functions. This study was designed to analyse the neurocognitive function of patients with coronary heart disease before and after CABG and to determine possible protective effects of oxygenator surface coating on neurological outcome. METHODS: Forty patients scheduled for selective CABG were prospectively randomized into two groups of 20 patients each according to the type of hollow-fibre membrane oxygenator used. Non-coated oxygenators (Group A) were compared to phosphorylcholine (PC)coated oxygenators (Group B). A battery of six neurological tests was administered preoperatively, 7-10 days and 4-6 months after surgery. RESULTS: One patient of Group A suffered from a perioperative stroke and died on postoperative day 3, presumably because of sudden heart failure. Two patients of Group A (10%) developed a symptomatic transitory delirious psychotic syndrome (STPT) on postoperative days 3 and 5. None of the patients of Group B had perioperative complications. The test analysis revealed a trend of declined neurocognitive function early after CABG, but did not show any difference in neurocognitive outcome between the two groups. DISCUSSION: PC coating of the oxygenators did not show any significant benefit on neurocognitive function after CABG using CPB.

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.

Accuracy of temperature measurement in the cardiopulmonary bypass circuit.

Oxygenator arterial outlet blood temperature is routinely measured in the cardiopulmonary bypass (CPB) circuit as a surrogate for the temperature of the arterial blood delivered to sensitive organs such as the brain. The aim of this study was to evaluate the accuracy of the temperature thermistors used in the Terumo Capiox SX25 oxygenator and to compare the temperature measured at the outlet of the oxygenator using the Capiox CX*TL Luer Thermistor with temperatures measured at distal sites. Five experimental stages were performed in vitro to achieve this aim. Under our experimental conditions, the luer thermistors accurately measured the temperature as referenced by a precision thermometer. In the CPB circuit, the difference between arterial outlet and reference thermometer temperature varied with outlet temperature over-reading at low temperatures and under reading at high temperatures. There was negligible heat loss (-0.4+/-0.1degrees C) measured at 4.5 m from the arterial outlet. The Terumo Capiox CX*TL Luer Thermistor is an accurate and reliable instrument for measuring temperature when incorporated into the Capiox Oxygenator. The accuracy in the measurement of temperature using these thermistors is affected by the thermistor immersion depth. Under reading of the arterial blood temperature by approximately 0.5 degrees C should be considered at normothermic temperatures, to avoid exceeding the maximum arterial blood temperature as described by institutional protocols. The accuracy of blood temperature measurements should be considered for all oxygenator arterial outlet temperature probes.

Temperature inaccuracies during cardiopulmonary bypass.

Cerebral hyperthermia caused by perfusate temperature greater than 37 degrees C during the rewarming phase of CPB has been linked to postoperative neurologic deficits. The purpose of this study was to determine the accuracy of the coupled temperature measurement system and the CDI 500 arterial temperature sensor. Seventeen patients undergoing CPB were divided into four groups, each with a different temperature probe coupled to the oxygenator. The coupled temperature measurement system and CDI temperature sensors were compared with an indwelling probe placed in direct contact with the arterial perfusate. Blood, bladder, room and water temperatures, arterial line pressure, blood flow, and hemoglobin were recorded while the patients were supported with CPB. The actual blood temperature was significantly higher than the coupled temperature measurement system for two of the four groups (mean = 1.61 degrees C and 0.91 degrees C, p < 0.0001). A significant positive correlation between the actual temperature and the coupled temperature measurement system error was observed for the same two groups (r = 0.44, p < 0.0001). The actual temperature was significantly higher than the CDI temperature in all patients (mean = 1.2 degrees C, p < 0.0001). The coupling mechanism on the oxygenator generates inconsistent temperature readings. The perfusionist should consider these inconsistencies when using coupled temperature measurements and may consider the use of a direct temperature measurement system. The CDI temperature error is probably the result of inadequate flow through the sensor. On the test circuit, the flow of 170 mL/min was inadequate for circuit temperature accuracy. The accuracy of the CDI temperature drastically improved when the flow-through the sensor was increased to approximately 400 mL/min. Thus, the perfusionist must ensure adequate flow through the sensor in order for the temperature mechanism to function properly. Finally, the perfusionist can prevent cerebral hyperthermia by not allowing water temperature to exceed 37 degrees C, when using a coupled temperature measurement system.

Doppler microembolic signals during cardiopulmonary bypass: comparison of two membrane oxygenators.

We undertook this study to evaluate the dependence of Doppler microembolic signal (MES) counts, detected during cardiopulmonary bypass, on the type of oxygenator used. A total of 90 patients, 71 men and 19 women, aged 60 +/- 10 years (mean +/- SD), undergoing elective cardiac surgery for coronary artery bypass grafting (one vessel, n = 6; two vessels, n = 24; three vessels, n = 33; four vessels, n = 9) or valve replacement (mitral valve, n = 2, aortic valve, n = 15, both valves, n = 1) were monitored with transcranial Doppler sonography during the complete surgical procedure. The surgical and anesthetic techniques were standardized in all patients, except for the type of membrane oxygenator used (COBE CML Duo, n = 55 or DIDECO D 703, n = 35). MES count was expressed as total number of MES detected in both middle cerebral arteries during cardiopulmonary bypass (CPB) and also as total MES number divided by the CPB duration in minutes (MES min(-1)). No significant differences in patients' age or sex and type and duration of operation were noted between the two groups. MES incidence while the patients were on cardiopulmonary bypass was 100%. MES counts during CPB were 309 (236-502) and 143 (86-233) for DIDECO and COBE oxygenators, respectively (p < 0.00001). MES min(-1) were also significantly higher in patients operated with DIDECO, as compared to COBE oxygenators (3.7 (2.4-5.6) versus 1.5 (1-2.4), respectively, p < 0.0001). Inter-observer variability was satisfactory (k = 0.72). Use of a DIDECO D 703 oxygenator resulted in significantly higher MES counts as compared to the COBE CML Duo oxygenator. The clinical relevance of this finding remains to be determined.

Lymphocyte's activation and apoptosis after coronary artery bypass graft: a comparative study of two membrane oxygenators--one with and another without a venous-arterial shunt.

Newer oxygenators with the latest technologies are designed to attenuate the immune response, including lymphopenia, prompted by cardiopulmonary bypass (CPB) in cardiac surgery. We evaluated the effect of CPB, comparing an oxygenator with a venous-arterial shunt and a conventional oxygenator with regard to lymphocyte's early activation and apoptosis induction and its implications in post-CPB lymphopenia. Patients undergoing coronary artery bypass graft surgery with CPB, using either a conventional oxygenator or one with a venous-arterial shunt, had blood samples drawn at anesthetic induction (baseline); the beginning and end of the CPB; and at 6, 12, and 24 hours after surgery. Analysis by flow cytometry was undertaken to assess the expression of lymphocyte surface markers (CD3+, CD25+, CD26+, CD69+) and apoptosis (annexin V). Twenty patients were studied; 10 used a conventional oxygenator, and 10 used an oxygenator with venous-arterial shunt. Postoperative lymphopenia (50% decrease), 35% increased expression of CD69+, and 56% decrease in annexin V were significant comparing baseline to 24 hour value, similarly in both groups. Early activation (expression of CD69+) and degree of apoptosis (expression of annexin V) of lymphocytes after CBP in cardiac surgery was similarly observed in both types of oxygenators. The observed lymphopenia after CPB does not appear to be secondary to apoptosis.