胎羊心脏转流模型的建立

目的　探讨胎羊心脏转流模型的建立及其对胎羊、胎盘的影响。方法　选用 6头怀孕山羊 ,切开子宫 ,暴露胎羊 ,正中开胸 ,经肺总动脉插 10F动脉管 ,右心房插 12～ 14F静脉管。离心泵连接动静脉插管 ,常温转流 3 0min。监测胎羊血压、心率、血气等数据。结果　胎羊体重 (1.80± 0 .2 7)kg ,灌注流量 (3 65± 48)ml·kg-1·min-1。转流中胎羊血压、心率稳定 ,血气结果在生理范围内。转流后 1h ,pH值下降 ,二氧化碳分压 (PCO2 )增高 ,与转流前比较差异有显著性 (P <0 .0 5 )。胎羊存活不超过 2h。结论　使用离心泵建立胎羊心脏转流模型 ,胎盘能够发挥体外循环氧合器的作用 ,但是体外循环对胎盘长期功能和胎羊存活不利     

胎羊体外循环中胎盘一氧化氮合酶的变化

目的 探讨胎羊体外循环中胎盘一氧化氮合酶（NOS）的变化。方法孕120-140d母羊8只，随机分为对照组和转流组，每组4只。对照组假手术，转流组运用离心泵和胎盘建立胎羊体外循环，转流30min。记录转流前、后胎羊平均动脉压、脐动脉流量和动脉血气值，计算胎盘血管阻力，检测胎羊血浆内皮素-1（ET-1）、一氧化氮（NO）和胎盘组织NOS活性，RT-PCR半定量分析eNOSmRNA转录状况。结果转流组胎羊体外循环结束后胎盘血管阻力上升，转流后2h胎盘NOS活性增强，胎盘eNOS转录水平增高（P〈0．05），与对照组比较差异有统计学意义（P〈0．05）。转流组胎羊血浆ET-1进行性增加，与对照组之间的差异也有统计学意义（P〈0．05）。两组之间血浆NO的变化没有显著差异。结论胎羊体外循环中胎盘组织NOS活性增强，不能降低胎盘血管阻力，NOS的变化可能是胎盘血管阻力增高的一种代偿。     

两种体外循环回路对瑞芬太尼的吸附作用

目的 比较希健-I型和AFFINITY(R) NT成人膜式氧合器体外循环回路对预冲液中瑞芬太尼的吸附作用.方法 实验分为3组(n=6):希健-I型成人膜式氧合器体外循环回路组(A组)、AFFINITY(R) NT成人膜式氧合器体外循环回路组(B组)和玻璃容器组(C组).将预冲液(6%羟乙基淀粉1000 ml和乳酸钠林格氏液500 ml)预冲入成人膜式氧合器体外循环装置或玻璃容器中,然后从静脉贮血器的静脉端或玻璃容器口注入瑞芬太尼,终浓度为100 ng/ml.于注入瑞芬太尼后2、5、10、15 min时,从静脉贮血器的动脉端或玻璃容器中抽取预冲液2 ml,采用气相色谱法检测瑞芬太尼的浓度.结果 三组不同时点间瑞芬太尼浓度比较差异无统计学意义(P>0.05).与C组比较,A组和B组各时点瑞芬太尼浓度下降(P<0.01);与B组比较,A组各时点瑞芬太尼浓度下降(P<0.01).结论 希健-I型和AFFINITY(R) NT成人膜式氧合器体外循环回路对瑞芬太尼均有吸附作用,前者的吸附作用大于后者.     

孕羊深低温体外循环对胎羊温度和血流动力学及血气的影响

目的探讨孕羊深低温体外循环(CPB)对胎羊温度、血流动力学和血气的影响。方法5头健康怀孕山羊常规建立CPB,转流降温、复温各1 h。监测孕羊和胎羊的温度、心率、平均动脉压、血气值。结果孕羊最低温度(17．4±1．5)℃,胎羊最低温度(24．6±1．5)℃。降温期胎羊温度始终高于孕羊温度,复温期孕羊-胎羊温差逆转,转流结束胎羊温度低于孕羊温度。降温期胎羊心率逐渐减慢,复温期不能恢复正常心率。低温转流15 min,胎羊pH值从转流开始的7．30± 0．03降到7．17±0．07(P<0．05)、PO_2从转流开始的(32．5±4．0)mmHg(1 mmHg=0．133 kPa)降到(17．5±3．0)mm Hg(P<0．05),PCO_2从转流开始的(44．8±2．2)mm Hg升到(56．8±5．1)mm Hg(P<0．05),BE值从转流开始的(-3．2±0．6)升到(-5．7±1．3)(P<0．05),此后血气值进一步恶化,复温阶段胎羊血气值也没有好转。CPB结束胎羊存活率为60％。结论孕羊深低温CPB 影响胎盘的热交换和气体交换功能,对胎羊存活不利。     

中国体外循环8年动态分析

目的 了解近8年来中国体外循环的发展动态,对我国未来体外循环的发展提出预测和建议.方法 2003年至2010年,逐年对全国开展心脏手术的医院进行问卷调查,内容涉及开展体外循环(on-pump)心脏手术和非体外循环(off-pump)心脏手术例数、氧合器使用情况及体外膜肺氧合(extracorporeal membrane oxygenation,ECMO)例数.收集并计算各年度各类氧合器的使用构成比;按手术例数对医院进行分级,计算不同级别医院所占比例.结果 2010年全国心脏手术170 547例,其中体外循环136753例.2010年进口膜式氧合器使用比例较2003年升高(59.75％对43.22％),鼓泡式氧合器比例显著降低(43.78％对14.59％),国产膜式氧合器使用比例也有所升高(13.00％对25.66％).2010年全国开展ECMO的医院共44家,总例数206例;年手术量＞1000例的医院32家,占43％;手术量＜50例的医院255家,占3％.结论 中国体外循环近年来发展速度较快,膜式氧合器使用率逐年上升,鼓泡式氧合器使用率逐年下降;未来需进一步集中体外循环医疗资源.     

两种氧合器对心肺转流炎症反应的影响

目的动态监测室间隔缺损修补术患者在心肺转流(CPB)各时段血清可溶性细胞间粘附分子(sICAM-1)、可溶性E-选择素(sE-selection)及肿瘤坏死因子α(TNF-α)的变化规律,并比较西京-90鼓泡式氧合器和希健-Ⅱ膜式氧合器对其的影响。方法选择择期行室间隔缺损修补术的患者30例,随机均分为鼓泡式氧合器组(B组)和膜式氧合器组(M组)。所有患者分别在麻醉后CPB开始前(T1)、主动脉阻断开放前(T2)、CPB结束时(T3)、术后2h(T4)、6h(T5)、24h(T6)及48h(T7)取静脉血5ml用ELISA法测定sICAM-1、sE-selection及TNF-α的浓度。结果两组患者血清中的TNF-α于T2时开始显著升高,T4时达到峰值(P<0·01)。sICAM-1于T5时开始升高,T6时达峰值。sE-selection于T4时开始升高,T5时达峰值(P<0·01)。M组大部分时点TNF-α、sICAM-1、sE-selection的浓度均低于B组。结论希健-Ⅱ膜式氧合器引起的炎症反应较轻。     

不同氧合器对体外循环心脏手术患儿中性粒细胞凋亡的影响

目的 研究小儿体外循环(cardiopulmonary bypass,CPB)中不同氧合器对中性粒细胞(PMN)凋亡的影响,为减轻体外循环伞身炎症反应提供新的思路.方法 将60例室间隔缺损患儿随机分为两组(n=30):西京-90鼓泡式氧合器组(B组)和希健-Ⅱ膜式氧合器组(M组).分别于CPB前、CPB结束时、CPB结束后4、8、24 h 5个时点采取静脉血,以伞血细胞计数仪测定PMN数量,流式细胞仪测定PMN凋亡率和PMN表面黏附分子CD11b表达变化,ELISA法测定血浆弹性蛋白酶浓度.结果 两组患者CPB结束后PMN凋亡率明显降低(P<0.05),PMN数量、CD11b表达、血浆弹性蛋白酶浓度明显升高(P<0.05),在CPB结束时及CPB结束后4、8 h PMN凋亡率M组均高于B组(P<0.05);而PMN数量、CD11b表达、血浆弹性蛋白酶水平B组均高于M组(P<0.05).CPB结束后24 h PMN数量B组高于M组(P<0.05).结论 与西京-90鼓泡氧合器相比,应用希健-Ⅱ膜式氧合器可以减轻CPB对PMN凋亡的抑制,进而减轻全身炎症反应.     

孕羊低温体外循环对胎羊血流动力学以及碳水化合物代谢的影响北大核心CSCD

目的 探讨孕羊低温体外循环（CPB）对胎羊血流动力学以及碳水化合物代谢的影响.方法 孕羊20头,随机分成对照组,开胸不建立体外循环;常温CPB组（35～36℃）、浅低温组CPB（32～34℃）和中低温CPB组（28～31℃）,建立常规体外循环,转流降温、复温30 min.分别监测孕羊和胎羊的心率、平均动脉压、胎羊脐动脉和颈内动脉的搏动指数（pulse index,PI）,孕羊与胎羊血糖、乳酸含量和HCO-3值的变化.结果 母羊和胎羊平均动脉压差异无统计学意义（P＞0.05）.浅低温组和中低温组颈内动脉PI值较对照组和常温组显著增高（P＜0.05）,脐动脉PI值组间差异无统计学意义,但随体外循环时间的延长而增高.血糖水平胎羊各组间差异无统计学意义（P＞0.05）,但中低温CPB组中胎羊显著低于孕羊（P＜0.05）.中低温CPB组胎羊血乳酸随时间延长有上升趋势（P＜0.05）,而且显著高于孕羊（P＜0.05）,但各CPB组间血乳酸差异无统计学意义.结论 孕羊低温体外循环降温时,胎羊心率明显下降,复温后胎羊心率能回复正常,体外循环对胎羊平均动脉压无明显影响,但低温降低胎羊脑部和脐动脉的血流;低温体外循环导致胎羊血糖水平降低,而血乳酸浓度显著增高.     

840例复旦膜式氧合器的临床应用

复旦膜式氧合器是最早的国产膜式氧合器之一 ,上海市胸科医院自 1994年 9月至 2 0 0 0年 8月共应用 840例 ,现将临床应用经验总结如下。1　临床资料与方法本组共 840例 ,男 5 11例 ,女 32 9例。年龄 1.5～ 44岁 ,体表面积 0 .5～ 1.6 m2 。手术方式 :房间隔缺损修补术 34 5例 ,室间隔缺损修补术 32 8例 ,左心房粘液瘤摘除术 46例 ,肺动脉狭窄 39例 ,主动脉狭窄 31例 ,三房心纠治术 2 5例 ,其他复杂畸形纠治术 2 6例。全组病例采用常规体外循环方法 ,无血预充 ,中深度血液稀释 ,中度低温。2　结　　果全组病例体外循环时间 2 0～ 15 6分钟 ,…     

不同体外循环回路对预充液舒芬太尼浓度的影响

目的 评价不同体外循环回路对预充液舒芬太尼浓度的影响.方法 实验分为3组(n=6):西京90型大号鼓泡式氧合器体外循环回路组(Ⅰ组)、Termo Capiox SX18成人膜式氧合器体外循环回路组(Ⅱ组)和玻璃容器组(Ⅲ组).将预充液(琥珀酰明胶液1000 ml和乳酸钠林格氏液1000ml)预充入大号鼓泡式氧合器、膜式氧合器体外循环装置或玻璃容器中,从静脉贮血器的静脉端或玻璃容器口快速加入舒芬太尼15μg(浓度为7.5 ng/ml).于注入舒芬太尼后1、3、5、10、20、30、40、50、60、70、80、90 min时,从静脉贮血器的动脉端或玻璃容器中抽取预充液1 ml,采用气相色谱质谱法检测舒芬太尼的浓度.结果 与Ⅲ组比较,Ⅰ组和Ⅱ组各时点预充液舒芬太尼浓度降低(P＜0.05)；与Ⅱ组比较,Ⅰ组各时点预充液舒芬太尼浓度降低(P＜0.05).结论 西京90型大号鼓泡式氧合器和TermoCapiox SX18成人膜式氧合器体外循环回路对舒芬太尼均有吸附作用,且前者吸附作用强于后者.     

Impact of hollow-fiber membrane surface area on oxygenator performance: Dideco D903 Avant versus a prototype with larger surface area

This study compares the gas transfer capacity, the blood trauma, and the blood path resistance of the hollow-fiber membrane oxygenator Dideco D 903 with a surface area of 1.7 m2 (oxygenator 1.7) versus a prototype built on the same principles but with a surface area of 2 m2 (oxygenator 2). Six calves (mean body weight: 68.2 +/- 3.2 kg) were connected to cardiopulmonary bypass (CPB) by jugular venous and carotid arterial cannulation, with a mean flow rate of 4 l/min for 6 h. They were randomly assigned to oxygenator 1.7 (N = 3) or 2 (N = 3). After 7 days, the animals were sacrificed. A standard battery of blood samples was taken before the bypass, throughout the bypass, and 24 h, 48 h, and 7 days after the bypass. The oxygenator 2 group showed significantly better total oxygen and carbon dioxide transfer values throughout the perfusion (p < .001 for both comparison). Hemolytic parameters (lactate dehydrogenase and free plasma hemoglobin) exhibited a slight but significant increase after 5 h of bypass in the oxygenator 1.7 group. The pressure drop through the oxygenator was low in both groups (range, 43-74 mmHg). With this type of hollow-fiber membrane oxygenator, an increased surface of gas exchange from 1.7 m2 to 2 m2 improves gas transfer, with a limited impact on blood trauma and no increase of blood path resistance.     

The relationship between oxygenator exhaust P(CO2) and arterial P(CO2) during hypothermic cardiopulmonary bypass

During cardiopulmonary bypass the partial pressure of carbon dioxide in oxygenator arterial blood (P(a)CO2) can be estimated from the partial pressure of gas exhausting from the oxygenator (P(E)CO2). Our hypothesis is that P(E)CO2 may be used to estimate P(a)CO2 with limits of agreement within 7 mmHg above and below the bias. (This is the reported relationship between arterial and end-tidal carbon dioxide during positive pressure ventilation in supine patients.) During hypothermic (28-32 degrees C) cardiopulmonary bypass using a Terumo Capiox SX membrane oxygenator, 80 oxygenator arterial blood samples were collected from 32 patients during cooling, stable hypothermia, and rewarming as per our usual clinical care. The P(a)CO2 of oxygenator arterial blood at actual patient blood temperature was estimated by temperature correction of the oxygenator arterial blood sample measured in the laboratory at 37 degrees C. P(E)CO2 was measured by connecting a capnograph end-to-side to the oxygenator exhaust outlet. We used an alpha-stat approach to cardiopulmonary bypass management. The mean difference between P(E)CO2 and P(a)CO2 was 0.6 mmHg, with limits of agreement (+/-2 SD) between -5 to +6 mmHg. P(E)CO2 tended to underestimate P(a)CO2 at low arterial temperatures, and overestimate at high arterial temperatures. We have demonstrated that P(E)CO2 can be used to estimate P(a)CO2 during hypothermic cardiopulmonary bypass using a Terumo Capiox SX oxygenator with a degree of accuracy similar to that associated with the use of end-tidal carbon dioxide measurement during positive pressure ventilation in anaesthetized, supine patients.     

The new advanced membrane gas exchanger

Current membrane oxygenators are constructed for patients with a body surface under 2.2 m(2). If the body surface exceeds 2.5 m(2), commercially available devices may not allow adequate oxygenation during cardiopulmonary bypass. To address this, a hollow-fiber oxygenator with an enlarged contact surface of 1.81 m(2) was tested. In an experimental set-up, six calves of mean weight 85.4 ± 3 kg were connected to cardiopulmonary bypass. They were randomly assigned to a standard oxygenator (n = 3; ADMIRAL, Euroset, Medola, Italy) with a surface of 1.35 m(2) or to an enlarged surface oxygenator (n = 3; AMG, Euroset). Blood samples were taken before bypass, after 10 min on bypass, and after 1, 2, 5 and 6 h of perfusion. Analysis of variance was used for repeated measurements. The mean flow rate was 6.5 l/min for 6 h. The total oxygen transfer at 6 h was significantly higher in the high-surface group (P < 0.05). Blood trauma, evaluated by plasma hemoglobin and lactate dehydrogenase levels, did not detect any significant hemolysis. Thrombocytes and white blood cell count profiles showed no significant differences between the two groups at 6 h of perfusion (P = 0.06 and 0.80, respectively). At the end of testing, no clot deposition was found in the oxygenator, and there was no evidence of peripheral emboli. The results suggest that the new oxygenator allows very good gas transfer and may be used for patients with a large body surface area.     

Oxygenator exhaust capnography as an index of arterial carbon dioxide tension during cardiopulmonary bypass using a membrane oxygenator

We have studied the relationship between the partial pressure of carbon dioxide in oxygenator exhaust gas (PECO2) and arterial carbon dioxide tension (PaCO2) during hypothermic cardiopulmonary bypass with non- pulsatile flow and a membrane oxygenator. A total of 172 paired measurements were made in 32 patients, 5 min after starting cardiopulmonary bypass and then at 15-min intervals. Additional measurements were made at 34 degrees C during rewarming. The degree of agreement between paired measurements (PaCO2 and PECO2) at each time was calculated. Mean difference (d) was 0.9 kPa (SD 0.99 kPa). Results were analysed further during stable hypothermia (n = 30, d = 1.88, SD = 0.69), rewarming at 34 degrees C (n = 22, d = 0, SD = 0.84), rewarming at normothermia (n = 48, d = 0.15, SD = 0.69) and with (n = 78, d = 0.62, SD = 0.99) or without (n = 91, d = 1.07, SD = 0.9) carbon dioxide being added to the oxygenator gas. The difference between the two measurements varied in relation to nasopharyngeal temperature if PaCO2 was not corrected for temperature (r2 = 0.343, P = < 0.001). However, if PaCO2 was corrected for temperature, the difference between PaCO2 and PECO2 was not related to temperature, and there was no relationship with either pump blood flow or oxygenator gas flow. We found that measurement of carbon dioxide partial pressure in exhaust gases from a membrane oxygenator during cardiopulmonary bypass was not a useful method for estimating PaCO2.      

Retinal microembolism and neuropsychological deficit following clinical cardiopulmonary bypass: comparison of a membrane and a bubble oxygenator. A preliminary communication

To observe and quantify cerebrovascular microembolic events in the central nervous system during cardiopulmonary bypass, 40 patients having elective uncomplicated coronary surgery had retinal fluorescein angiograms 5 min before bypass was discontinued. Each patient also had 10 neuropsychological tests before and after surgery. A Harvey H1700 bubble oxygenator was used for 23 patients and a Cobe CML sheet membrane oxygenator was used for 17 patients. All 23 (100%) of patients in the bubble oxygenator group had retinal microvascular occlusions consistent with microembolism compared to 8/17 (47%) in the membrane oxygenator group (P less than 0.001). In those retinas with occlusions, the mean resultant area of non-perfusion was less in the membrane oxygenator group (0.11 mm2; n = 8) than in the bubble oxygenator group (0.29 mm2; P less than 0.01). Arterial PO2 levels during bypass were similar in both groups at moderate hypothermia, but the mean PaO2 during rewarming was higher in the bubble oxygenator group (27 kPa) than in the membrane group (13 kPa; P less than 0.001). Neuropsychological deficits were more common and more severe after bubble oxygenation than after membrane oxygenation, but in this small patient group, the difference was not statistically significant. We conclude that flat sheet membrane oxygenation during cardiopulmonary bypass may confer significant protection against cerebrovascular microembolism.     

Prostaglandin synthesis inhibition prevents placental dysfunction after fetal cardiac bypass.

Surgical therapy of certain congenital heart lesions in utero may have advantages over postnatal repair or palliation. For fetal heart operations to be done, it will be necessary to devise a method of fetal cardiac bypass. Previous studies in which standard cardiopulmonary bypass techniques were used have reported fetal death resulting from increased placental vascular resistance, which causes decreased placental blood flow and depressed respiratory gas exchange. The mechanism responsible for this increase in placental vascular resistance has remained unknown. In a series of 10 fetal cardiac bypass experiments we examined the role of prostaglandins as the mediators of this response. Observations were made during a 1-hour prebypass period, a 30-minute bypass period, and a 2-hour postbypass period. The cardiac bypass circuit consisted of a centrifugal pump, and bypass flows were adjusted to equal a normal fetal cardiac output of 400 ml/min/kg. In six of the experiments indomethacin (3 mg/100 ml) was added to the pump priming to block prostaglandin synthesis. By means of the microsphere technique, fetal cardiac output, placental blood flow, individual organ blood flow, and placental vascular resistance were determined at five times during the experiments: presternotomy, poststernotomy, during cardiac bypass, at 5 minutes after cessation of bypass, and 30 minutes after cessation of bypass. Fetal arterial blood gas measurements were made every 15 to 30 minutes. When indomethacin was used to inhibit prostaglandin synthesis, placental vascular resistance did not increase, placental blood flow did not decrease, and fetal blood gases remained at normal prebypass levels during and after fetal cardiac bypass. We propose that production of vasoactive prostaglandins is responsible for the increased placental vascular resistance and decreased placental blood flow observed after fetal cardiac bypass. An understanding of the mechanism responsible for the increased placental vascular resistance seen after fetal cardiac bypass will be an important first step before clinical application.     

Significance of the concentrated red cell and albumin priming method with particular reference to anaphylatoxin generation.

Anaphylatoxins generated by cardiopulmonary bypass were observed in basic and clinical studies (n = 120 in the latter). In vitro immunoglobulin fractions denatured by oxygen bubbling produced C4a, C3a, and C5a, but albumin identically treated did not. Therefore concentrated red cells with albumin were used to prime homologous blood for clinical application during cardiopulmonary bypass. Complement levels were compared with type of oxygenator (bubble or membrane) and the ratio of primed homologous blood to circulating autologous blood volume. With the bubble oxygenator at a low ratio of homologous to autologous blood (arbitrarily defined as less than 20%), C3a levels during cardiopulmonary bypass tended to be lower in the concentrated red cells plus albumin priming group than in the ordinary priming group (p less than 0.1, at 60 and 90 minutes of cardiopulmonary bypass). C4a and C3a levels increased less after protamine administration with concentrated red cells plus albumin priming (p less than 0.05, p less than 0.01, respectively, 90 minutes after protamine) than with ordinary priming. Such changes in the membrane oxygenator group were less remarkable. Thus C3a levels were approximately the same in both oxygenator groups primed with concentrated red cells plus albumin. The higher the homologous to autologous ratio, the steeper the C4a and C3a increase from the beginning of cardiopulmonary bypass with the bubble oxygenator. This tendency was less remarkable in the membrane oxygenator group. Early postoperative pulmonary function was improved by concentrated red cells plus albumin priming, especially in the bubble oxygenator group. In conclusion, (1) oxygenator systems primed with concentrated red cells plus albumin produced less anaphylatoxin than those with homologous blood, especially with the bubble oxygenator, and (2) our clinical results support the importance of immunoglobulin denatured by oxygen bubbling in anaphylatoxin generation (by means of the classical pathway), as shown by our in vitro study.     

Oxygenation strategy and neurologic damage after deep hypothermic circulatory arrest. I. Gaseous microemboli.

OBJECTIVES: Recent studies suggest that myocardial reperfusion injury is exacerbated by free radicals when pure oxygen is used during cardiopulmonary bypass. Partial replacement of the oxygenator gas mixture with nitrogen, however, such as has already been adopted clinically in many centers, could increase the risk of gaseous nitrogen microembolus formation and therefore of brain damage because of the low solubility of nitrogen, particularly under conditions of hypothermia. METHODS: Ten 7- to 10-kg piglets were cooled for 30 minutes to 15 degrees C on cardiopulmonary bypass and then rewarmed for 40 minutes to 37 degrees C. In 5 piglets cardiopulmonary bypass was normoxic and in 5 it was hyperoxic. In each group 3 bubble oxygenators without arterial filters and 2 membrane oxygenators with filters were used. Cerebral microemboli were monitored continuously by carotid Doppler ultrasonography (8 MHz) and intermittently by fluorescence retinography. RESULTS: Embolus count was greater with lower rectal temperature (P <.001), use of a bubble oxygenator (P <.001), and lower oxygen concentration (P =.021) but was not affected by the temperature gradient between blood and body during cooling or rewarming. CONCLUSIONS: Gaseous microemboli are increased with normoxic perfusion, but this is only important if a bubble oxygenator without a filter is used.     

Experimental evaluation of the Medtronic Maxima Forté hollow fiber membrane oxygenator.

A new hollow fiber membrane oxygenator, the Medtronic Maxima Forté, was tested for gas transfer, blood path resistance and blood handling characteristics in a standardized setting with surviving animals. Three calves (mean body weight: 71 +/- 9.6 kg) were placed on cardiopulmonary bypass at a mean flow rate of 50 ml/kg/min for six hours. The circuit included the Maxima Forté oxygenator. The animals were weaned from cardiopulmonary bypass and then from the ventilator. After seven days, the animals were sacrificed electively. Physiologic blood gas values could be maintained throughout perfusion in all animals. Mean pressure drop through the oxygenator varied between 49 mmHg and 66 mmHg. The respective baseline values for red blood cell count, white blood cell count and platelets were 8.90 +/- 1.26 10(6)/mm3, 7.46 +/- 3.17 10(3)/mm3. and 680 +/- 216 10(3)/mm3. Red blood cell and platelet counts dropped slightly to 7.26 +/- 1.61 10(6)/mm3 and 400 +/- 126 10(3)/mm3 at the end of the bypass, whereas the white blood cell count increased up to 9.13 +/- 5.25 10(3)/mm3. All three cell lines returned to near their baseline values after seven days. Blood trauma evaluated as a function of plasma hemoglobin (plasma Hb) and lactate dehydrogenase (LDH) showed stable values during all the perfusion time. Both peaked at 24 hours before returning to their baseline values at seven days. LDH showed a statistically significant variation: 3255 +/- 693 IU at 24 hours versus 2029 +/- 287 IU at baseline (p = 0.04). The variation of plasma Hb was not statistically significant (93.5 +/- 7.7 mumol/l at 24 hours versus 77.3 +/- 52.3 mumol/l at baseline) indicating a weak effect of the perfusion on blood trauma. The Medtronic Maxima Forté hollow fiber membrane oxygenator offered good gas exchange capabilities, a low pressure drop, and low blood trauma over a prolonged perfusion time of six hours in this evaluation.     

Silicone-Coated Polypropylene Hollow-Fiber Oxygenator: Experimental Evaluation and Preliminary Clinical Use

Background. A membrane oxygenator consisting of a microporous polypropylene hollow fiber with a 0.2-μm ultrathin silicone layer (cyclosiloxane) was developed. Animal experimental and preliminary clinical studies evaluated its reliability in bypass procedures.

Methods. Five 24-hour venoarterial bypass periods were conducted on dogs using the oxygenator (group A). In 5 controls, bypass periods were conducted using the same oxygenator without silicone coating (group B). As a preliminary clinical study, 14 patients underwent cardiopulmonary bypass with the silicone-coated oxygenator.

Results. Eight to 16 hours (mean, 12.2 hours) after initiation of bypass, plasma leakage occurred in all group B animals, but none in group A. The O₂ and CO₂ transfer rates after 24 hours in group A were significantly higher than at termination of bypass in group B (p < 0.005 and p < 0.03, respectively). Scanning electron microscopy of silicone-coated fibers after 24 hours of bypass revealed no damage to the silicone coating of the polypropylene hollow fibers. In the clinical study, the oxygenator showed good gas transfer, acceptable pressure loss, low hemolysis, and good durability.

Conclusions. This oxygenator is more durable and offers greater gas transfer capabilities than the previous generation of oxygenators.