Cytokine release assays: current practices and future directions.

As a result of the CD28 superagonist biotherapeutic monoclonal antibody (TGN 1412) "cytokine storm" incident, cytokine release assays (CRA) have become hazard identification and prospective risk assessment tools for screening novel biotherapeutics directed against targets having a potential risk for eliciting adverse pro-inflammatory clinical infusion reactions. Different laboratories may have different strategies, assay formats, and approaches to the reporting, interpretation, and use of data for either decision making or risk assessment. Additionally, many independent contract research organizations (CROs), academic and government laboratories are involved in some aspect of CRA work. As a result, while some pharmaceutical companies are providing CRA data as part of the regulatory submissions when necessary, technical and regulatory practices are still evolving to provide data predictive of cytokine release in humans and that are relevant to safety. This manuscript provides an overview of different approaches employed by the pharmaceutical industry and CROs, for the use and application of CRA based upon a survey and post survey follow up conducted by ILSI-Health and Environmental Sciences Institute (HESI) Immunotoxicology Committee CRA Working Group. Also discussed is ongoing research in the academic sector, the regulatory environment, current limitations of the assays, and future directions and recommendations for cytokine release assays.

Reference values for the water load test in healthy school children and adolescents.

BACKGROUND AND STUDY AIM: The water load test (WLT) is an easy and cheap tool, useful in evaluating gastric accommodation and visceral hypersensitivity. This test can be used in diagnosing functional gastrointestinal disorders, like functional dyspepsia. Our main aim was to propose reference values for the WLT. Our secondary aim was to correlate the water volume drunk with the students' gender, age, and anthropometric measures. PATIENTS AND METHODS: We performed the WLT in students aged 8 to 17 years. Students drank water ad libitum for 3 minutes or until pain, satiety or vomiting occurred. We correlated anthropometric variables with water volumes drunk. Upper and lower limit for the maximum tolerated volume were calculated as the 5th and 95th percentile. Pain and nausea were recorded before and after the test. RESULTS: We evaluated 99 students, with a median age (inter quartile range) of 11 years 10-13 years) and 55.6 % were girls. Median water volume drank was 380 ml (190-540 ml). Boys (523 ml, interquartile range : 275-760 ml) drank more water than girls (380 ml, interquartile range : 190-570 ml) (p = 0.016). There was a significant correlation between water volume drank and students´ age, weight, height, and body mass index. Of the students that completed the WLT, 22.2 % had nausea and 30.3 % had mild abdominal pain after the test. CONCLUSIONS: We proposed reference values for the WLT in children aged 8 to 17 years. Adverse effects are minimal, it is safe to perform, and well tolerated.

BK Virus Nephropathy in Kidney Transplantation: An Approach Proposal and Update on Risk Factors, Diagnosis, and Treatment.

BK virus belongs to Polyomaviridae family; it causes 95% of nephropathy cases related to polyomavirus, with the other 5% caused by JC virus. Nephropathy jeopardizes graft function, causing a premature failure of the graft in 1%-10% of patients with kidney transplants. Nowadays, antiviral effective treatment is unknown, which is why blood and urine screening of renal transplantation patients has become the most important recommendation to guide the decrease of immunosuppression, and the only proven method to decrease poor outcomes. Different interventions, such as cidofovir, leflunomide, fluoroquinolones, and intravenous immunoglobulin, have been attempted with no improvement at all. This review aims to summarize the most relevant features of BK virus, historical issues, transmission mechanisms, risk factors, and therapeutic interventions.

Diffusing capacity limitations of the extent of lung volume reduction surgery in an animal model of emphysema.

OBJECTIVE: The purpose of this study was to investigate in an elastase-induced emphysema rabbit model the effects of increasing resection volumes during lung volume reduction surgery on pulmonary compliance, forced expiratory air flow, and diffusing capacity to assess factors limiting optimal resection. METHODS: Emphysema was induced in 68 New Zealand White rabbits with 15,000 units of aerosolized elastase. Static respiratory system compliance, forced expiratory flow, and single-breath diffusing capacity were measured before the induction of emphysema, after the induction of emphysema, and 1 week after a bilateral upper and middle lobe lung volume reduction operation. RESULTS: Static respiratory system compliance with 60 mL insufflation above functional residual capacity increased with emphysema induction and then decreased progressively with resection of larger volumes of lung tissue (P =.001 by analysis of variance). Expiratory flow improved after lung resection in the rabbits with large resection volumes. In contrast, diffusing capacity tended to deteriorate with larger resection volumes (P =. 18). CONCLUSION: Improvements in respiratory system compliance and forced expiratory flow after lung volume reduction operations may account for the improvements seen clinically. Declines in diffusing capacity with extensive lung reduction may limit the clinical benefits associated with greater tissue resection volumes. Future investigations with animal models may reveal other physiologic parameters that may further guide optimal lung volume reduction procedures.

Survival after unilateral versus bilateral lung volume reduction surgery for emphysema.

OBJECTIVE: Bilateral staple lung volume reduction surgery (LVRS) immediately improves pulmonary function and dyspnea symptoms in patients with advanced heterogeneous emphysema to a greater degree than do unilateral procedures. However, the long-term outcome after these surgical procedures needs to be critically evaluated. We compare 2-year survival of patients who underwent unilateral versus bilateral video-assisted LVRS in a large cohort treated by a single surgical group. METHODS: The cases of all 260 patients who underwent video-assisted thoracoscopic stapled LVRS from April 1994 to March 1996 were analyzed to compare results after unilateral versus bilateral procedures. Overall survival was calculated by Kaplan-Meier methods; Cox proportional hazard methods were used to adjust for patient heterogeneity and baseline differences between groups. RESULTS: Overall survival at 2 years was 86.4% (95% CI 80. 9%-91.8%) after bilateral LVRS versus 72.6% (95% CI 64.2%-81.2%) after unilateral LVRS (P =.001 for overall survival comparison). Improved survival after bilateral LVRS was seen among high- and low-risk subgroups as well. Average follow-up time was 28.5 months (range, 6 days to 46.6 months) for the bilateral LVRS group and 29.3 months (range, 6 days to 45.0 months) for the unilateral LVRS patients. CONCLUSIONS: Comparison of unilateral versus bilateral thoracoscopic LVRS procedures for the treatment of emphysema reveals that bilateral LVRS by video-assisted thoracoscopy resulted in better overall survival at 2-year follow-up than did unilateral LVRS. This survival study, together with other studies demonstrating improved lung function after bilateral LVRS, suggests that bilateral surgery appears to be the procedure of choice for patients undergoing LVRS for most eligible patients with severe heterogeneous emphysema.

Transplant center characteristics and clinical outcomes after hematopoietic stem cell transplantation: what do we know?

Center effects are differences in outcome among treatment centers that cannot be explained by identifiable differences in patients treated or specific treatments applied and are presumed to result from differences in the ways health care is delivered. This paper will briefly review studies of association between treatment center factors and clinical outcomes in general medicine and surgery and look more closely at studies involving hematopoietic stem cell transplantation. We will also attempt to identify conceptual domains to study further the processes and mechanisms that may be associated with better outcomes.

Outpatient total body irradiation as a component of a comprehensive outpatient transplant program.

Outpatient total body irradiation (TBI) as part of a comprehensive outpatient transplant program was delivered to 142 of 167 (85%) consecutive patients receiving TBI-based conditioning therapy. Outpatients received either a single fraction of 500 cGy (110 patients) or 1200 cGy in six fractions over 3 days (32 patients). Patients were assessed daily and were administered oral ondansetron and dexamethasone for prophylaxis of nausea and vomiting as well as i.v. hydration. Accommodation during outpatient TBI-based conditioning was either the patient's home if within 30 min of the hospital, a hotel on the hospital grounds or on a closed hospital ward. None of the 142 patients required admission to the inpatient program during their TBI. There was no difference in 100-day mortality between those receiving TBI as an outpatient (9%) vs as an inpatient (16%). Of four deaths occurring within the first 14 days post transplant, none could be attributed to receiving TBI as an outpatient. Two hundred and six inpatient days were saved through the delivery of outpatient TBI. A comprehensive outpatient program, appropriate patient selection, daily hydration, the use of prophylactic 5HT3 antagonist anti-emetic therapy all contribute to the safe delivery of outpatient TBI.

Relationship between amount of lung resected and outcome after lung volume reduction surgery.

BACKGROUND: Lung volume reduction surgery (LVRS) is being actively investigated for palliative treatment of severe emphysema. Considerable focus is directed toward patient selection and outcomes of LVRS. However, there is little information available regarding surgical methods to guide optimal extent of resection. We hypothesized that acute improvement and long-term survival after bilateral staple LVRS would be related to the extent of tissue resected. METHODS: The relationship between acute improvement in forced expiratory volume in 1 second and forced vital capacity was examined as a function of the total grams of lung tissue resected in 237 patients who underwent bilateral staple LVRS by a single group of surgeons. Overall survival was assessed based on extent of resection by quartiles of tissue weight resected using Kaplan-Meier survival methods. RESULTS: Improvement in forced expiratory volume in 1 second and forced vital capacity correlated with extent of tissue resected (p < 0.01), although there was considerable variability to individual response (r = 0.3). In contrast, there was no apparent relationship between the amount of tissue resected and overall postoperative survival (p = 0.7). CONCLUSIONS: There is a correlation between the amount of tissue resected and improvement in forced expiratory volume in 1 second and forced vital capacity after bilateral staple LVRS, with generally greater postoperative improvement after larger volume resections. However, there does not appear to be greater long-term survival with larger volume resections despite greater improvement in spirometry. This study suggests that factors other than improvement in spirometric variables may govern optimal LVRS resection volumes and long-term outcome. Future studies will clearly be needed in this important area of LVRS emphysema research.

Compliance and functional residual capacity after staple versus combined staple/holmium laser lung volume reduction surgery in a rabbit emphysema model.

BACKGROUND: There is some evidence to suggest that laser exposure, when added to standard staple reduction techniques, may result in improved physiologic response to lung volume reduction surgery (LVRS). In this study, we compared physiologic responses of staple LVRS with combined staple/laser in a rabbit emphysema model. METHODS: Ninety-three New Zealand White rabbits underwent emphysema induction with aerosolized elastase 4 weeks before surgery and were killed 1 week after surgery. Treatment groups were bilateral moderate volume staple LVRS (< or =3 g, n = 39), combined moderate volume staple (< or =3 g)/holmium laser LVRS (n = 18), large-volume staple LVRS (> or =3 g, n = 27), or sham surgery (n = 9). RESULTS: Decrease in postoperative static respiratory system compliance by combined moderate-volume staple/laser treatment (1.22 cc/cm H2O) was similar to large-volume staple resection (1.40 cc/cm H2O, p = 0.39), and superior to moderate staple resection (0.82 cc/cm H2O, p = 0.01) or sham surgery (0.09 cc/cm H2O, p = 0.0001). Functional residual capacity decrease was greater after combined moderate staple/laser resection (6.46 cc) than large-volume staple resection (4.52 cc, p = 0.33), moderate-volume staple resection (4.59 cc, p = 0.43), or sham surgery (4.10 cc, p = 0.29). Perioperative mortality was highest after laser/staple LVRS (22%, 4/18). CONCLUSIONS: In this rabbit model, combined staple/ holmium laser reduction for emphysema results in significant improvement in compliance and trends toward improvement in functional residual capacity above staple reduction alone, but with higher mortality.

Photodynamic therapy for patients with advanced non-small-cell carcinoma of the lung.

Patients with advanced non-small-cell lung carcinoma (NSCLC) have poor prognoses and experience negative sequelae of disease. Patients often suffer from dyspnea and/or hemoptysis, with overall pulmonary compromise. Patients with advanced, inoperable disease have limited options for treatment. This study summarizes our early experience and findings using photodynamic therapy (PDT) as an effective modality in the palliation of hemoptysis, dyspnea, and physical airway obstruction in cases of inoperable lung cancer. A retrospective review was conducted for the first 10 patients diagnosed with stage III/IV obstructive NSCLC who underwent PDT at our institution. Endobronchial lesions were identified by bronchoscopy. Treatments were initiated 48 hours after intravenous injection of 2 mg/kg of the photosensitizing agent porfimer sodium (Photofrin, QLT PhotoTherapeutics, Vancouver, BC). The porfimer sodium was then activated by illumination with a 630 nm wavelength light using a Coherent argon ion laser through a flexible bronchoscope. Repeated bronchoscopies were performed 1-3 days following initial PDT for evaluation and airway debridement. In 8 cases, a second treatment of PDT was administered within 72 hours of the first injection. One patient received a third treatment several months later. Three patients also received endobronchial stents after PDT. Overall, all 10 patients responded to PDT. Physical airway obstruction was reduced in all patients, with a noted improvement in bronchoscopic luminal diameter. Acute hemoptysis resolved in all 7 symptomatic patients. Median survival was 5.5 months post-PDT, while median survival postdiagnosis was 10.5 months. Three patients are alive at the time of this review at 5-21 months following therapy. Patients with unresectable late-stage NSCLC have few options for treatment. Our early experience with PDT indicates effective relief of hemoptysis, dyspnea, and airway obstruction and improves their quality of life.

Evidence for selective degradation of platelet GP IIb/IIIa complex after prolonged in vitro ventricular assist.

BACKGROUND: Left ventricular assist devices (VAD) have improved survival in patients with end-stage heart failure. Past studies have shown that interactions between blood and synthetic surfaces promote initial bleeding and later thromboembolism. The exact mechanism of blood activation during VAD circulation remains unclear. The purpose of this study was to test the hypothesis that platelet glycoprotein (GP) IIb/IIIa receptor degradation occurs during clinical use of ventricular assist devices. METHODS: Five in vitro nonpulsatile centrifugal VAD circuits were simulated for 4 days using 450 mL of fresh human whole blood. Temperature, activated clotting time, pH, pCO2, pO2, Ca++, and glucose were maintained at physiologic values. Flow was maintained at a constant 2.0 L/min/m2. We examined whole blood platelet aggregation induced by ristocetin, collagen, and adenosine diphosphate (ATP). We also examined whole blood platelet degranulation induced by collagen and ADP. RESULTS: Platelet aggregation in response to ristocetin, collagen, and ADP irreversibly and progressively declined with prolonged circulation in the VAD. While ADP-induced aggregation declined within the first hour, ristocetin and collagen-induced aggregation declined after 10 hours. Collagen-induced platelet degranulation decreased similar to aggregation, whereas ADP-induced degranulation continued and was preserved throughout the experiment. CONCLUSIONS: These results suggest prolonged circulation of human blood in a VAD circuit irreversibly impair platelet aggregation. The response of circulating platelets to individual agonists suggests that this platelet degradation is partially receptor specific. In our VAD system, ADP-stimulated platelet aggregation is more rapidly degraded with circulation. These results offer preliminary evidence that circulation of human blood in a VAD circuit leads to early degradation of the platelet GP IIb/IIIa complex. GP IIb/IIIa complex degradation is likely to be the mechanism of early VAD associated bleeding.

Alternative pathway of complement is activated during in vitro ventricular assist.

BACKGROUND: Although ventricular assist devices (VAD) have improved survival in selected patients, their use continues to be complicated by thromboembolism and end-organ failure. Complement activation may play a role in the pathogenesis of these complications. Previous studies have found that the complement common terminal pathway is activated during VAD circulation. C3a levels rise dramatically during VAD use. Because the C3a fragment is generated by either the alternative or classical pathway, the purpose of this study is to determine the relative importance of the respective pathways in complement activation during in vitro VAD circulation. METHODS: Six in vitro VAD circuits were simulated for 3 days using 450 mL of human blood. Temperature, activated clotting time, pH, pCO2, pO2, Ca2+, and glucose were maintained at physiologic levels. Enzyme immunoassays were used to measure concentrations of fragment Bb to indicate alternative pathway activation and fragment C4d to indicate classical pathway activation. RESULTS: Fragment Bb concentrations rise from 1.92 to 10.77 micrograms/mL during the first 6 hours of circulation. Thereafter, Bb levels plateau. C4d concentrations slowly rise from a baseline of 1.49 to 6.84 micrograms/mL in 72 hours. CONCLUSIONS: These findings suggest that both the alternative and classical pathways of complement are activated during VAD circulation. Alternative pathway activation precedes classical pathway activation during in vitro VAD circulation and may be of greater clinical importance during clinical VAD circulation.

Accelerated recovery after coronary artery bypass surgery in patients with poor left ventricular function: preliminary report.

The success of "fast-track" accelerated recovery pathways in improving patient outcomes after coronary artery bypass graft surgery (CABG) has prompted expanded application. Although initially used only in routine cases, higher-risk cohorts may also benefit from this collection of management techniques. Twenty-seven consecutive patients with ejection fractions (EFs) less than or equal to 30 per cent (group I) undergoing CABG requiring cardiopulmonary bypass were started on our routine care path. The results of this effort were retrospectively compared with 27 concurrent patients with an EF greater than or equal to 50 per cent (group II) undergoing CABG at our institution. Outcome criteria included postoperative extubation (by 6 hours), transfer from intensive care unit (in < or = 24 hours), and hospital discharge on or before postoperative day 5. As anticipated, group I patients deviated from pathway criteria more frequently than did group II. However, despite severely compromised preoperative cardiac function, 52 per cent of group I patients were extubated within the first 6 hours postoperatively, 51 per cent were discharged from the intensive care unit on the 1st postoperative day, and 52 per cent were discharged from the hospital within the first 5 postoperative days. Group II patients' values for these parameters were 96, 96, and 70 per cent, respectively. No adverse effects could be attributed to pathway expectations. The results of this preliminary study suggest that accelerated care pathways may be safely applied to patients with severely low EFs and deserve further study.

An early comparison between endoscopic ultrasound-guided fine-needle aspiration and mediastinoscopy for diagnosis of mediastinal malignancy.

Precise mediastinal lymph node staging is essential in non-small cell lung cancer for proper evaluation and treatment. In addition to CT, mediastinoscopy is routinely used for staging and diagnosis of mediastinal malignancy. Recently, endoscopic ultrasound (EUS) combined with fine-needle aspiration (FNA) biopsy has been used to evaluate mediastinal disease. The purpose of this study was to assess and compare mediastinoscopy with EUS/FNA in the evaluation of mediastinal masses. From August 1995 to July 1997, 21 patients with suspected mediastinal malignancy underwent cervical mediastinoscopy with biopsy. During this same period, seven patients with suspected mediastinal malignancy were evaluated using EUS/FNA. All patients were retrospectively studied. Both mediastinoscopy and EUS/FNA were highly sensitive in diagnosing mediastinal malignancy (100% and 86%, respectively). Specificity and positive predictive value were 100 per cent for both procedures. Mediastinoscopy and EUS/FNA are highly accurate methods of staging mediastinal malignancy. Mediastinoscopy provides better access to the upper and anterior mediastinum, whereas EUS/FNA can safely be used to biopsy subcarinal and posterior mediastinal masses. Mediastinoscopy and EUS/FNA target different areas of the mediastinum and may be complimentary in the evaluation of mediastinal malignancy and staging of bronchogenic carcinoma.

Ex vivo cardiac allograft preservation by continuous perfusion techniques.

The current technique of cardiac preservation for clinical transplantation by infusion of cold cardioplegia and immersion of the heart in an isotonic saline bath at 4 degrees C limits safe tissue preservation time to 4 to 6 hours. The myriad of benefits to be gained by extending cardiac preservation time has prompted the search for alternatives to hypothermic immersion of the heart, the most promising of which involves techniques of coronary artery perfusion. Countless studies have shown the benefits of long-term storage of donor hearts by perfusion rather than the immersion technique. Continuous perfusion preservation has three basic advantages over simple immersion. Perfusion preservation with oxygen carrying solutions has the advantage of preventing ischemia, anaerobic metabolism, and reperfusion injury. Second, nutritional supplementation and provision of substrate can be more effectively delivered to myocardial cells. Third, continuous perfusion preservation effects the clearance of metabolic waste products from the coronary circulation. The composition of the ideal perfusion solution and optimal preservation conditions remain incompletely defined.

Platelet glycoprotein IIb/IIIa inhibitor attenuates complement activation during in vitro ventricular assist circulation.

Complement activity and platelet glycoprotein (GP) IIb/IIIa dysfunction have been demonstrated during in vitro ventricular assist device circulation. Platelets contain C1 serine protease inhibitor (C1 INH) in secretory granules, which normally regulates complement. Complement activity may result from a loss of platelet regulation on complement during ventricular assist device circulation as platelets lose viability. The purpose of this study was to assess the ability of a platelet GP IIb/IIIa receptor inhibitor to attenuate ventricular assist device associated complement activation during in vitro ventricular assisted circulation. Eight in vitro nonpulsatile centrifugal ventricular assist device circuits were simulated for 4 days using 450 ml fresh human whole blood. Cardiac index, temperature, pH, PO2, PCO2, Ca, glucose, and activated clotting time were maintained at physiologic levels. Levels of C1 INH and C3a were measured with and without a reversible glycoprotein IIb/IIIa inhibitor (MK-383). Concentrations of C1 INH increase on exposure to ventricular assist device, and decrease to a plateau within 12 hr. The decrease in circulating unbound C1 INH was attenuated with pre treatment with MK-383. Concentrations of C3a increase 34 fold within 4 hr of exposure to a ventricular assist device with and 22 fold without pre treatment with MK-383. These findings suggest that protection of the platelet GP IIb/IIIa complex delays complement activation during in vitro ventricular assist device circulation.

Cardiac function after eight hour storage by using polyethylene glycol hemoglobin versus crystalloid perfusion.

Efforts to extend myocardial preservation for transplantation by crystalloid perfusion have been limited by edema and compromised function. We hypothesized that hypothermic perfusion preservation with a polyethylene glycol (PEG) conjugated hemoglobin solution may extend preservation times. The purpose of this study was to compare cardiac function after continuous perfusion by using a hypocalcemic, normokalemic crystalloid perfusate with and without the addition of PEG-hemoglobin (Hb). The hearts of 20 anesthetized and ventilated New Zealand White rabbits were harvested after cold cardioplegic arrest. Group I (n = 10) hearts were continuously perfused with a hypocalcemic, normokalemic 3% bovine PEG-Hb solution at 20 degrees C and 30 mm Hg for 8 hours. Group II (n = 10) hearts were continuously perfused with an identical crystalloid solution without PEG-Hb for 8 hours under the same conditions as group I hearts. Cardiac function was measured with a left ventricular force transducer after transfer to a standard crystalloid Langendorff circuit at 37 degrees C and an aortic root pressure of 59 mm Hg. After 8 hours of perfusion preservation, heart rate was similar for groups I and II (p = not significant [NS]). Coronary blood flow after and during preservation was similar between PEG-Hb and crystalloid preserved hearts (p = NS). Left ventricular developed pressure, peak dP/dt, and peak -dP/dt were superior in hearts preserved with PEG-Hb. Percent water of total ventricular weight was 82.0% for group I and 81.6% for group II (p = NS). Continuous perfusion preservation of rabbit hearts for 8 hours with a hypocalcemic normokalemic PEG-Hb based solution at 30 mm Hg and 20 degrees C yields left ventricular function that is superior to perfusion with a similar crystalloid solution without PEG-Hb, despite similar myocardial edema and coronary flow. Extended cardiac perfusion preservation with this PEG-Hb based solution deserves further study, including comparison with traditional cardioplegic preservation solutions.

Protection of platelet glycoprotein IIb/IIIa receptor complex preserves platelet function during in vitro ventricular assisted circulation.

Platelet dysfunction probably contributes to bleeding associated with ventricular assist devices (VADs). Previous evidence suggests that VAD associated platelet dysfunction may be due to dysfunction of the platelet fibrinogen receptor. The purpose of this investigation was to test the hypothesis that selective protection of platelet fibrinogen receptor preserves platelet aggregating ability during in vitro ventricular assisted circulation. Eight in vitro nonpulsatile centrifugal VAD circuits were simulated for four days using 450 ml of fresh human whole blood. Temperature, activated clotting time, pH, PCO2, PO2, Ca2+, and glucose were maintained at physiologic values. Flow was maintained at a constant 2.0 L/min/m2. We examined whole blood platelet aggregation induced by ristocetin, collagen, and adenosine diphosphate (ADP). We added a highly specific reversible inhibitor (MK-383) of the glycoprotein (GP) IIb/IIIa receptor complex before start of circulation to the final four VAD experiments. ADP induced aggregation decreased within the first hour of circulation. Ristocetin and collagen induced aggregation decreased to negligible levels after 10 hours of circulation. With MK-383, ristocetin induced aggregation was preserved. Addition of MK-383 did not alter the decrease of ADP and collagen induced aggregation. These results suggest platelet aggregating ability is maintained with protection of the platelet fibrinogen receptor during in vitro ventricular assisted circulation.

Tirofiban administration attenuates platelet and platelet-neutrophil conjugation but not neutrophil degranulation during in vitro VAD circulation.

Ventricular Assist Devices (VADs) have been used as bridges to heart transplantation. However, VAD circulation is complicated by the incidence of thromboembolism, prolonged bleeding, and activation of the inflammatory cascade. We hypothesize that platelet and neutrophil activation are interrelated and linked to the activation of the glycoprotein (GP) IIb/IIIa platelet receptor. The purpose of this study is to evaluate the effects of Tirofiban, a platelet GP IIb/IIIa receptor inhibitor, on platelet and neutrophil activation during simulated VAD circulation. Two groups of five in vitro VAD circuits were simulated with and without Tirofiban using 450 cc of human blood. Blood samples were drawn at specific time intervals up to 72 hours, measuring leukotriene C4 (LTC4), platelet factor four (PF4), and neutrophil elastase. Tirofiban decreased serum levels of PF4 and LTC4 during VAD circulation. Neutrophil elastase secretion was not affected by Tirofiban administration. Preconditioning of VAD circulation with Tirofiban attenuated platelet activation as demonstrated by a decrease in serum PF4 levels. Tirofiban administration ameliorates the inflammatory response by altering platelet-neutrophil interaction as demonstrated by a decrease in LTC4 production. Continued elastase secretion indicates that the inflammatory response is not completely inhibited by Tirofiban administration. These results suggest that neutrophils may be activated by alternative mechanisms. Early complement activation has been demonstrated during in vivo and in vitro VAD circulation and may play a role in mediating inflammatory and thromboembolic reactions during VAD use.

Recovery of cardiac function after standard hypothermic storage versus preservation with Peg-hemoglobin.

Preservation of the heart for transplantation after infusion of cardioplegia and extirpation of a cardiac allograft results in an ischemic insult to the myocardium. This ischemic insult may lead to a loss of function in the transplanted heart. Hypothermic perfusion preservation with an oxygen hemoglobin carrying solution may avert ischemic injury and lead to improved recovery of cardiac function. The purpose of this study was to compare cardiac function after 8 hours of continuous hypothermic perfusion with a unique polyethylene-glycol-hemoglobin (PEG-Hb) solution to hearts preserved by 4 hours of hypothermic ischemic storage. Freshly extirpated hearts served as functional controls. The hearts of 26 anesthetized and intubated New Zealand white rabbits were harvested after cold cardioplegic arrest. Group I (n = 12) hearts were perfused with a PEG-Hb solution at 20 degrees C and 30 mm Hg for 8 hours. PO2 was maintained > or = 500 mm Hg. Group II (n = 7) hearts were preserved by cold ischemic storage for 4 hours at 4 degrees C. Group III (n = 7) were tested immediately after harvest. Left ventricular (LV) function was measured in the nonworking state at 15 minutes, 1 hour, and 2 hours after transfer to a standard crystalloid Langendorff circuit. Measurement of LV developed pressure, peak + dP/dt and -dP/dt revealed a superior trend between Group I and Group II hearts in comparison with freshly extirpated hearts. Heart rate was similar among all groups throughout testing (p = ns). Coronary blood flow was not significantly different between groups. Continuous perfusion preservation of rabbit hearts for 8 hours with PEG-Hb solution at 30 mm Hg and 20 degrees C yielded LV function that was similar to 4 hours of ischemic hypothermic storage. Furthermore, return of cardiac function after 8 hours of perfusion preservation using this PEG-Hb solution may be superior to that obtained in freshly extirpated hearts. These data suggest that some recovery of myocardial function may occur during perfusion preservation with this PEG-Hb solution after the ischemic insult of cardioplegic arrest. Continuous perfusion preservation using this PEG-Hb solution deserves further investigation in large animal transplant models.