Evaluation of Mimesys phosphorylcholine (PC)-coated oxygenators during cardiopulmonary bypass in adults

A new generation of coating extracorporeal circuitry with biocompatible polymers has entered the North American perfusion market. This new biomimetic coating process uses synthetic phosphorylcholine (PC) containing polymers to bond covalently to the surface of the Sorin Monolyth oxygenator, under the brand name of Mimesys. In part one of a three-part investigation, 160 Mimesys-coated oxygenators were randomly evaluated against 36 uncoated oxygenators for blood flow, hemodynamic resistance, and pressure differentials. In part two, retrospective analysis of platelet data collected in this study was compared with platelet data collected from a previous investigation using uncoated Monolyth oxygenators with albumin and crystalloid perfusates. Part three examined the risk-adjusted clinical outcomes of 71 patients treated with Mimesys-coated oxygenators, compared with 71 case-matched patients treated with uncoated oxygenators. There was no difference found in the Mimesys-coated group, when compared to the control group, with regard to pressure differentials or hemodynamic resistance. However, we conclude that platelet protection with PC-coated Monolyth's using crystalloid perfusates, was similar to platelet protection with albumin perfusates, and significantly better than uncoated Monolyths using crystalloid perfusates.     

Acute methemoglobinemia during cardiopulmonary bypass caused by intravenous nitroglycerin infusion

The case of a patient is presented who was undergoing coronary bypass grafting and who, during cardiopulmonary bypass, became severely cyanotic because of methemoglobinemia after intravenous infusion of nitroglycerin. His condition responded promptly and favorably to the withdrawal of the offending agent and to administration of methylene blue.     

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。     

In vivo uptake and elimination of isoflurane by different membrane oxygenators during cardiopulmonary bypass

BACKGROUND: Volatile anesthetics are frequently used during cardiopulmonary bypass (CPB) to maintain anesthesia. Uptake and elimination of the volatile agent are dependent on the composition of the oxygenator. This study was designed to evaluate whether the in vivo uptake and elimination of isoflurane differs between microporous membrane oxygenators containing a conventional polypropylene (PPL) membrane and oxygenators with a new poly-(4-methyl-1-pentene) (PMP) membrane measuring isoflurane concentrations in blood. METHODS: Twenty-four patients undergoing elective coronary bypass surgery with the aid of CPB were randomly allocated to one of four groups, using either one of two different PPL-membrane oxygenators for CPB or one of two different PMP-membrane oxygenators. During hypothermic CPB, 1% isoflurane in an oxygen-air mixture was added to the oxygenator gas inflow line (gas flow, 3 l/min) for 15 min. Isoflurane concentration was measured in blood and in exhaust gas at the outflow port of the oxygenator. Between-group comparisons were performed for the area under the curve (AUC) during uptake and elimination of the isoflurane blood concentrations, the maximum isoflurane blood concentration (C(max)), and the exhausted isoflurane concentration (F(E)). RESULTS: The uptake of isoflurane, expressed as AUC of isoflurane blood concentration and a function of F(E), was significantly reduced in PMP oxygenators compared to PPL oxygenators (P < 0.01). C(max) was between 8.5 and 13 times lower in the PMP-membrane oxygenator groups compared to the conventional PPL-membrane oxygenator groups (P < 0.01). CONCLUSIONS: The uptake of isoflurane into blood via PMP oxygenators during CPB is severely limited. This should be taken into consideration in cases using such devices.     

Complement activation during cardiopulmonary bypass. Comparison of bubble and membrane oxygenators

A prospective randomized trial involving 91 patients undergoing cardiopulmonary bypass compared the effects of bubble oxygenators (with and without methylprednisolone sodium succinate) and membrane oxygenators on complement activation and transpulmonary sequestration of leukocytes. Patients were divided as follows: Group I, 30 patients, bubble oxygenator; Group II, 31 patients, bubble oxygenator and methylprednisolone sodium succinate (30 mg/kg); Group III, 30 patients, membrane oxygenator. In Group I, C3a increased from 323 +/- 171 ng/ml during cardiopulmonary bypass to 1,564 +/- 785 ng/ml at 25 minutes after bypass (p less than 0.0001). A significant decrease in C3a was found in Groups II and III compared to Group I (p less than 0.0001). C5a did not change significantly during cardiopulmonary bypass in any group. Reestablishment of pulmonary circulation at the end of bypass produced significant transpulmonary leukocyte sequestration in Group I; the median cell difference was 1,700/microliter. Transpulmonary sequestration was significantly (p less than 0.0001) less in Group II (median cell difference = 200/microliter) and in Group III (median cell difference = 400/microliter) than in Group I. We conclude that cardiopulmonary bypass with a bubble oxygenator alone initiates significantly (p less than 0.0001) more C3a activation and leukocyte sequestration than when methylprednisolone sodium succinate (30 mg/kg) is given 20 minutes before the start of cardiopulmonary bypass with a bubble oxygenator or when a silicone membrane oxygenator is used.     

Reversal of digital vasospasm by glyceryl trinitrate patch.

Localized digital ischaemia following tourniquet deflation is an event producing considerable concern after surgical procedures on the hand, and is more common when severe pre-operative deformity has been radically corrected. We describe three such cases of digital ischaemia, occurring immediately after the release of severe flexion contractures of the digits. Our cases were treated successfully by the application of a proximal cutaneous glyceryl trinitrate patch, which produced prompt recovery of the circulation in the affected digits. We suggest that this simple technique has an important role as theraputically, and possibly also as a diagnostic aid, in the evaluation and management of the post-operative ischaemic digit prior to re-exploration being undertaken.     

A profile of intravenous nitroglycerin use in cardiopulmonary bypass surgery

We studied the indications for use, time to onset of effect, approximate effective concentration and therapeutic success of commercially prepared intravenous nitroglycerin (NTG) in 50 patients undergoing cardiopulmonary bypass (CPB) surgery, Nitroglycerin was used to treat systemic or pulmonary hypertension, myocardial ischaemiaand ventricular failure. Twenty-one patients had more than one indication for NTG use. Nineteen of 22 patients with pulmonary hypertension, 12 of 13 patients with ischaemic changes, and 13 of 15 patients with ventricular failure improved during intravenous NTG administration. Hypertension during CPB was ameliorated in only six often instances. The time to onset of effect ranged from 4.1 ± 0.8 to 7.8 ± 2.8 minutes and the mean approximate effective NTG concentration varied from 1.7 ± 0.3 to 2.9 ± 0.7 μg · kg^-1 ± min^-1 (doses only approximate due to our use of an infusion system which absorbs NTG). Complications from intravenous NTG administration were not seen. We conclude that this NTG preparation facilitates treatment of prebypass hypertension, pulmonary hypertension, myocardial ischaemiaand ventricular failure but is less effective for the treatment of hypertension during CPB.     

Washin and washout of isoflurane administered via bubble oxygenators during hypothermic cardiopulmonary bypass

Washin and washout of a volatile anesthetic given through the oxygenator during hypothermic (23.4 +/- 2.1 degrees C) cardiopulmonary bypass were studied in nine patients. The authors administered isoflurane and measured its partial pressure in arterial (Pa) and venous (Pv) blood and the gas exhausted from the oxygenator (PE) at 1, 2, 4, 8, 16, 32, and 48 min during washin. These measurements were repeated during washout, which coincided with rewarming. During washin, PE, Pa, and Pv progressively rose toward inlet gas partial pressure (PI). Equilibration of Pa with PI was 41% after 16 min, 51% after 32 min, and 57% after 48 min of washin. During washout, Pa declined to 24% of its peak after 16 min and to 13% after 32 min. Washin and washout were considerably slower in mixed venous blood. Washin of isoflurane appeared to occur more slowly during cardiopulmonary bypass than during administration via the lungs in normothermic patients, presumably because hypothermia increases tissue capacity, compensating for the effect of hemodilution that otherwise would decrease the blood/gas partition coefficient. During rewarming, washout appeared to occur as rapidly as from the lungs of normothermic patients. This may have resulted from the declining blood/gas partition coefficient (due to rewarming) and relatively limited tissue stores of isoflurane. The relationship between exhaust and arterial partial pressures was reasonably consistent; for clinical purposes, measurement of PE can be used to estimate Pa.     

Different oxygenators for cardiopulmonary bypass lead to varying degrees of human complement activation in vitro

Complement activation was studied in vitro with six different membrane and bubble oxygenators for cardiopulmonary bypass. There was a similar increase in terminal (C5 to C9) activation with all oxygenators (p less than 0.001), ranging from 281% (117% to 444%) to 453% (225% to 680%) after 60 minutes (median and 95% confidence intervals). C3 activation was not observed with a hollow fiber membrane and a soft shell bubble oxygenator. On the other hand, a capillary membrane, a sheet membrane, a nonporous membrane, and a hard shell bubble oxygenator all induced a similar increase in C3 activation (p less than 0.01), ranging from 107% (23% to 346%) to 272% (88% to 395%) after 60 minutes. The differences in C3 activation could not be explained by the blood contact materials or any other single factor known to induce activation, which suggests that overall complement activation during cardiopulmonary bypass is a multifactorial effect. The tubing set per se induced only minor C3 activation but contributed to the overall formation of terminal complement complex. The study further indicates that an arterial line blood filter prevents activated neutrophils from being reinfused to the patient and should be used regardless of type of oxygenator.     

Audit of topical glyceryl trinitrate for treatment of fissure-in-ano

PURPOSE: To clarify the clinical role of topical glyceryl trinitrate (GTN) in the management of anal fissures. PATIENTS AND METHODS: Fifty-six consecutive patients with fissure-in-ano attending a colorectal clinic from April 1997 to May 1998 included 16 acute and 40 chronic anal fissures. Patients were instructed to apply 0.2% 0.5 g of GTN to the painful area of the anus. Patients were followed-up in the clinic at 4, 8 and 12 weeks, and by telephone interviews at a median follow up of 10 months. RESULTS: Ten of 16 acute fissures (63%) were healed by 4 weeks and 13 (81%) by 8 weeks. Thirteen of 40 chronic fissures (33%) were healed by 8 weeks and 20 (50%) by 12 weeks. Seventeen patients (30%) underwent lateral sphincterotomy and all healed. There were five recurrences within 3 months of treatment with GTN. Thirty-four (61%) suffered from headaches, eight being severe headaches. None of the patients developed incontinence with GTN or lateral sphincterotomy. CONCLUSIONS: Treatment of fissure-in-ano using GTN ointment was effective in up to 50% of patients with chronic anal fissure, and has the benefit of being repeatable if the fissure recurs. Patients should be aware that treatment is likely to take some months to be effective and is associated with significant side effects in up to 15% of patients.     

Should the gas outlet port on membrane oxygenators be routinely scavenged during cardiopulmonary bypass?

Elimination of a volatile anesthetic agent administered prior to the start of bypass through the oxygenator has not been previously described. The purpose of this study was to determine the contamination risk from enflurane used before but not during cardiopulmonary bypass. Enflurane concentration was measured from the gas outlet port of a membrane oxygenator using infrared gas analysis in 11 cardiac surgical patients. The mean peak concentration at the gas outlet port in patients who had a final end-tidal concentration of < or = 0.3% was 0.08 +/- 0.04%, compared to 0.18 +/- 0.05% in patients with a final end-tidal concentration of more than 0.3%, P < 0.001. The elapsed time to reach peak concentration was 8.3 +/- 8.4 minutes, whereas the elapsed time from the peak concentration to 50% of the peak level was 63.1 +/- 25.1 minutes. At the time of peak enflurane release, a concentration of less than 2 ppm was measured at distances of 10 cm or less from the oxygenator gas outlet port in patients with an end-tidal enflurane of < or = 0.3%. In one patient with a final end-tidal enflurane of 1.1%, a contaminant level of 2 ppm could be measured at 95 cm from the oxygenator gas outlet port. This demonstrates that there is a potential risk of contamination from volatile anesthetics used immediately prior to extracorporeal circulation. Minimizing this risk may necessitate routine scavenging of the oxygenator, or simply avoiding increased concentrations of inhalation anesthesia before initiating cardiopulmonary bypass.     

Comparing oxygen transfer performance between three membrane oxygenators: effect of temperature changes during cardiopulmonary bypass

Recently, a new oxygenator (Dideco 903 [D903], Dideco, Mirandola, Italy) has been introduced to the perfusion community, and we set about testing its oxygen transfer performance and then comparing it to two other models. This evaluation was based on the comparison between oxygen transfer slope, gas phase arterial oxygen gradients, degree of blood shunting, maximum oxygen transfer, and diffusing capacity calculated for each membrane. Sixty patients were randomized into three groups of oxygenators (Dideco 703 [D703], Dideco; D903; and Quadrox, Jostra Medizintechnik AG, Hirrlingen, Germany) including 40/20 M/F of 68.6 +/- 11.3 years old, with a body weight of 71.5 +/- 12.1 kg, a body surface area (BSA) of 1.84 +/- 0.3 m(2), and a theoretical blood flow rate (index 2.4 times BSA) of 4.4 +/- 0.7 L/min. The maximum oxygen transfer (VO(2)) values were 313 mL O(2)/min (D703), 579 mL O(2)/min (D903), and 400 mL O(2)/min (Quadrox), with the D903 being the most superior (P < 0.05). Oxygen (O(2)) gradients were 320 mm Hg (D703), 235 mm Hg (D903), and 247 mm Hg (Quadrox), meaning D903 and Quadrox are more efficient versus the D703 (P < 0.05). Shunt fraction (Qs/Qt) and diffusing capacity (DmO(2)) were comparable (P = ns). Diffusing capacity values indexed to BSA (DmO(2)/m(2)) were 0.15 mL O(2)/min/mm Hg/m(2) (D703), 0.2 mL O(2)/min/mm Hg/m(2) (D903), and 0.18 mL O(2)/min/mm Hg/m(2) (Quadrox) with D903 outperforming D703 (P < 0.0005). During hypothermia (32.0 +/- 0.3 degrees C), there was a lower absolute and relative VO(2 )for all three oxygenators (P = ns). The O(2) gradients, DmO(2) and DmO(2)/m(2), were significantly lower for all oxygenators (P < 0.01). Also, Qs/Qt significantly rose for all oxygenators (P < 0.01). The oxygen transfer curve is characteristic to each oxygenator type and represents a tool to quantify oxygenator performance. Using this parameter, we demonstrated significant differences among commercially available oxygenators. However, all three oxygenators are considered to meet the oxygen needs of the patients.