Pharmacokinetic interactions augment toxicities of sirolimus/cyclosporine combinations

This study correlated the dynamic effects of sirolimus (rapamycin; RAPA) and cyclosporine (CsA) alone versus in combination to produce renal dysfunction, myelosuppression, or hyperlipidemia, with their corresponding blood and tissue concentrations. After salt-depleted rats were treated with RAPA (0.4 to 6.4 mg/kg per d) and/or CsA (2.5 to 20.0 mg/kg per d) for 14 d, the GFR, lipid levels, bone marrow cellularity, and CsA/RAPA concentrations in whole blood versus liver or renal tissues were measured, and the median effect model was used to discern the type of drug interactions. Compared with vehicle controls (1.98 +/- 0.34 ml/min), GFR values were reduced only by large doses of drug monotherapy, namely RAPA (3.2 mg/kg per d = 1.2 +/- 0.02 ml/min or 6.4 mg/kg per d = 1.3 +/- 0.2 ml/min; both P < 0.01) or CsA (10.0 mg/kg per d = 1.2 +/- 0.1 ml/min or 20.0 mg/kg per d = 0.8 +/- 0.4 ml/min; both P < 0.01). In contrast, hosts that were treated with smaller doses of CsA/RAPA combinations showed more pronounced effects in reduction of GFR values: 2.5/0.4 mg/kg per d, modestly (1.5 +/- 0.5 ml/min; P < 0.01); 5.0/0.8 mg/kg per d, moderately (0.23 +/- 0.01 ml/min; P < 0.001); and higher-dose groups, markedly. The exacerbation of renal dysfunction seemed to be due to a pharmacokinetic interaction of RAPA to greatly increase CsA concentrations in whole blood and, particularly, in kidney tissue. In contrast, the pharmacodynamic effects of CsA to potentiate two RAPA-mediated toxicities-myelosuppression and increased serum cholesterol/low-density lipoprotein cholesterol-occurred independently of pharmacokinetic interactions. RAPA aggravates CsA-induced renal dysfunction owing to a pharmacokinetic interaction, whereas CsA produces a pharmacodynamic effect that augments RAPA-induced myelosuppression and hyperlipidemia.     

A short-term combination therapy with cyclosporine and rapamycin or leflunomide induces long-term heart allograft survival in a strongly immunogenic strain combination in rats

Abstract  Synergism between cyclosporine (CsA) and rapamycin (RAPA) or leflunomide (LF) was studied in a strongly immunogenic cardiac allograft model in rats. In the absence of immunosuppression, PVG recipients rejected WKAH heart grafts after a mean survival time (MST) of 5.2 ± 1.1 days. A dose of 7.5 mg/kg per day CsA did not prolong graft survival (MST 5.6 ± 1.2 days). CsA given at 10 mg/ kg per day for 30 days extended MST of the grafts to 48 ± 7 days. A short course of combination therapy consisting of adding a non-therapeutic dose of RAPA or a subthera-peutic dose of LF to a 1-month course of CsA resulted in permanent graft survival. These data suggest that RAPA and LF synergize with CsA enabling not only the lowering of the dose of CsA, but also inducing transplantation tolerance.     

The impact of the lung allocation scoring system at the single national Veterans Affairs Hospital lung transplantation program

Objective: The lung allocation score (LAS) has changed the distribution of donor lungs for transplantation. This study was undertaken to evaluate the impact of the LAS on a unique patient population undergoing lung transplantation (LTX) at the single national Veterans Affairs (VA) LT center. Methods: One hundred and ten consecutive VA patients underwent LTX between 1994 and 2007. Patients transplanted using the LAS (LAS, n = 26) were compared to patients transplanted prior to introduction of the LAS (pre-LAS, n = 84). Results: Waiting time decreased from 353.8 ± 254.7 (pre-LAS) to 238.0 ± 306.6 (LAS) days (p < 0.01). Recipient diagnoses have changed with an increase in idiopathic pulmonary fibrosis [11% (9/84) pre-LAS vs 46% (12/26) LAS, p < 0.01] and a decrease in emphysema [57% (48/84) pre-LAS vs 35% (9/26) LAS, p < 0.01]. Mean LAS calculation was 33.1 ± 2.9 for pre-LAS versus 41.9 ± 9.8 for the LAS (p < 0.01). Postoperative complications did not differ between the groups. Length of hospital stay decreased from 44.3 ± 42.9 (pre-LAS) to 18.1 ± 12.3 (LAS) days (p < 0.01). Hospital mortality and 1-year survival did not differ between the pre-LAS and LAS groups (7% vs 8%; p = 0.72 and 92% [95% confidence interval (CI) 86–98] vs 92% [CI 82–100]; p = 0.23, respectively). Conclusions: The LAS appears to be achieving its objectives by reducing waitlist time and altering the distribution of lung disease being transplanted on the basis of medical necessity in the U.S. VA population. In addition, the LAS does not appear to have adversely affected short-term post-transplant outcomes in our recipient cohort.     

The endothelin receptor antagonist, L-754,142 does not prevent cyclosporine a-induced osteopenia in rats

Cyclosporine A (CsA) is a potent immunosuppressive agent widely used to prevent allograft rejection.In vivo administration of CsA is associated with the development of high-turnover osteopenia. Endothelin-1 (ET), a vasoconstrictive peptide, has been implicated in CsA-induced nephrotoxicty and hypertension. Recent evidence suggests that endothelin plays a pivotal role in bone metabolism. The present study was designed to investigate whether L-754,142 (ETRA), the combined endothelin A and B receptor antagonist, when given to rats, would favorably modify the bone loss caused by CsA. Fifty, 5-month-old male Sprague-Dawley rats were randomly divided into five groups of 10 rats each. The first group served as a basal control. The remaining four groups received, by daily gavage for 28 days, (1) a combined CsA and ETRA vehicle, (2) CsA, 10 mg/kg, (3) ETRA, 30 mg/kg, and (4) CsA, 10 mg/kg and ETRA, 30 mg/kg, respectively. Rats were weighed and venous blood was collected on days 0, 14, 28 for determination of BUN, creatinine, calcium, PTH, osteocalcin, and 1,25(OH)₂D. Tibiae, after double labeling, were removed following sacrifice for histomorphometry. Both CsA-treated rats and CsA/ETRA-treated rats demonstrated trabecular osteopenia with raised serum osteocalcin, and 1,25(OH)₂D levels when compared to control animals (P<0.05). Rats given CsA alone developed renal impairment, as shown by an increased BUN. The combination group did not develop renal impairment. The results suggest that endothelin may contribute to the development of CsA-induced nephrotoxicity, which was prevented by ETRA, but does not seem to play a role in CsA-induced osteopenia.     

Intrasplenic Liver Parenchymal Cells in Conjunction with Low-Dose Rapamycin and Cyclosporine Induce a Unique and Specific Prolongation of Rat Cardiac and Small Bowel Allograft Survival

These experiments investigated the immunosuppressive properties of liver tissue. Brown Norway (BN; RT1ⁿ) rat heart allografts survived in untreated control Wistar Furth (WFu; RTl^u) rat recipients for 6.2 ± 1.5 days, while allografts in animals that received rapamycin (RAPA) 0.0075 mg/kg/day and cyclosporine (CsA) 0.375 mg/kg/day delivered for 14 days by continuous intravenous infusion (civi) using osmotic pumps in conjunction with intrasplenic (i.s.) saline survived to 18.4 ± 1.3 days. i.s. addition of 3 M-KCl extracted BN hepatic antigen or unpurified BN hepatocytes (liver parenchymal cells—5 × 10⁷/kg), which exhibited a 4.8% class II antigen expression, and which alone failed to prolong allograft survival (MST = 6.0 ± 1.4 days), increased heart allograft survival to 25.3 ± 2.3 and 27.2 ± 1.9 days, respectively (p < 0.01). Hepatocyte purification using Dynabeads and Percoll reduced class II expression to 0.9% and increased allograft survival to 32.8 ± 1.6 days (p < 0.01). In contrast, the effect of 5 × 10⁸/kg BN erythrocytes, exhibiting only 0.1% class II expression, was much less (23.8 ± 1.9 days). Administration i.s. of BN splenocytes or nonparenchymal liver cells, demonstrated by flow cytometry to exhibit a 47.3 or 55.1% expression of class II antigen, respectively, failed to induce any significant increase in allograft survival (18.4 ± 4.6 and 19.4 ± 0.5 days, respectively). Survival of BN rat small bowel allografts was increased in Lewis (LEW; RTl¹) rat recipients treated with RAPA, CsA, and unfractionated BN hepatocytes from 10.2 ± 1.9 to 21.2 ± 1.5 days. Pretreatment with i.s. BN hepatocytes, 14 days prior to harvesting, reduced WFu lymphocyte responses to allogeneic stimulation with BN or ACI spleen cells by 75 and 70%, respectively. Addition of 1 × 10⁵ unpurified donor-specific BN or third-party Buffalo (BUF; RTl^b) hepatocytes, but not supernatant, to the responder wells of MLCs resulted in a 61 and 40% suppression, respectively, of the WFu lymphocyte response induced by BN allogeneic stimulation. These findings suggest that while class I MHC expression has a significant role to play in exerting the immunosuppressive effects of hepatocytes, other influences more specific to liver may also prevail.     

Donor-specific antigen and cyclosporine in rat islet allografts

Combination therapy with one dose of 3 M KCl extracted donor-soluble antigen (Ag) and a short course of cyclosporine (CsA) has proven to prolong the survival of kidney allografts by enhancing specific T-suppressor populations. This regimen is tested in rat islet allografts in this study (Lewis to ACI). A 3-day perioperative course of 10 mg/kg/day CsA on Days -1, 0, and 1 did not prolong graft survival (MST = 10.7 +/- 2.5 days vs 9.4 +/- 1.2 days in controls). When this course of CsA therapy was combined with a single dose of donor antigen on Day -1, the survival time was prolonged slightly but significantly (MST = 14.0 +/- 5.8 days). Three cycles of a 3-day course of CsA therapy at 7-day intervals, a total of nine doses of 10 mg/kg/day CsA, were effective in delaying rejection of islet allografts (MST = 26.4 +/- 30.3). Moreover, combined therapy with donor antigen and three cycles of a 3-day course of CsA prolonged the survival of islet allografts (MST = 57.7 +/- 51.4 days) with 50% of recipients still normoglycemic at 60 days after transplantation. These findings indicate that the combination therapy of donor antigen with a short course of CsA has a powerful effect to prevent the rejection of islet allografts, as shown in kidney allografts, in rats.     

Brain preservation with selective cerebral perfusion for operations requiring circulatory arrest: protection at 25 °C is similar to 18 °C with shorter operating times

Background: Hypothermic circulatory arrest (HCA) is employed for aortic arch and other complex operations, often with selective cerebral perfusion (SCP). Our previous work has demonstrated real-time evidence of improved brain protection using SCP at 18 °C. The purpose of this study was to evaluate the utility of SCP at warmer temperatures (25 °C) and its impact on operating times. Methods: Piglets undergoing cardiopulmonary bypass (CPB) and 60 min of HCA were assigned to three groups: 18 °C without SCP, 18 °C with SCP and 25 °C with SCP (n = 8 animals per group). CPB flows were 100 ml kg⁻¹ min⁻¹ using pH-stat management. SCP flows were 10 ml kg⁻¹ min⁻¹ via the innominate artery. Cerebral oxygenation was monitored using NIRS (near-infrared spectroscopy). A microdialysis probe placed into the cerebral cortex had samples collected every 15 min. Animals were recovered for 4 h after separation from CPB. All data are presented as mean ± standard deviation (SD; p < 0.05, significant). Results: Cerebral oxygenation was preserved during deep and tepid HCA with SCP, in contrast to deep HCA without SCP (p < 0.05). Deep HCA at 18 °C without SCP resulted in significantly elevated brain lactate (p < 0.01) and glycerol (p < 0.01), while the energy substrates glucose (p < 0.001) and pyruvate (p < 0.001) were significantly depleted. These derangements were prevented with SCP at 18 °C and 25 °C. The lactate/pyruvate ratio (L/P) was profoundly elevated following HCA alone (p < 0.001) and remained persistently elevated throughout recovery (p < 0.05). Piglets given SCP during HCA at 18 °C and 25 °C maintained baseline L/P ratios. Mean operating times were significantly shorter in the 25 °C group compared to both 18 °C groups (p < 0.05) without evidence of significant acidemia. Conclusion: HCA results in cerebral hypoxia, energy depletion and ischaemic injury, which are attenuated with the use of SCP at both 18 °C and 25 °C. Procedures performed at 25 °C had significantly shorter operating times while preserving end organs.     

15AU81, a prostacyclin analog, enhances donor-specific hepatocytes to prolong the survival of rat heart but not small bowel allografts

Prostacyclin analogs have previously been shown to have not only cytoprotective but also independent immunosuppressive effects. The effect of one such analog, 15AU81, to enhance the immunosuppressive effects of liver was investigated. We have previously demonstrated that cyclosporine (CsA) in conjunction with rapamycin (RAPA) potentiates class I+, class II- donor-specific hepatocytes to prolong rat cardiac and small bowel allograft survival. Brown Norway (BN; RT1n) hepatocytes alone (5 x 10(7)/kg, administered intrasplenically) failed to prolong the survival of BN heart allografts in Wistar Furth (WFu; RT1u) recipients, beyond that of untreated controls (MST = 7.2 +/- 0.8 days). Survival of BN hearts was increased to 11.4 +/- 1.7 days in WFu recipients treated with BN hepatocytes and 50 microg/kg/day 15AU81 administered by continuous s.c. infusion for 14 days using osmotic pumps (p < 0.05). The further addition of RAPA 0.0075 mg/kg/day and CsA 0.375 mg/kg/day delivered for 14 days by continuous i.v. infusion (CIVI) using osmotic pumps (a combination that alone prolonged BN heart allografts in WFu hosts to 18.4 +/- 1.3 days and in conjunction with BN hepatocytes prolonged survival to 27.2 +/- 1.9 days) prolonged allograft survival to 35.2 +/- 5.2 days. In contrast, the survival of small bowel allografts was not enhanced by 15AU81 administration. Survival of BN small bowel transplants in LEW recipients treated with hepatocytes alone (MST = 11.6 +/- 1.5 days) or hepatocytes plus 15AU81 (MST = 10.0 +/- 1.0 days) was similar to controls (MST = 10.2 +/- 1.9 days). Treatment with hepatocytes and RAPA/CsA increased survival to 21.2 +/- 1.5 days. The further addition of 15AU81 failed to augment this (MST = 17.0 +/- 1.9 days). In vitro WFu lymphocyte proliferative responses from animals pretreated with BN hepatocytes, 15AU81, or both treatments, for 2 weeks prior to harvesting, exhibited a reduction of at least 50%, compared to untreated controls upon allostimulation with irradiated BN or ACI spleen cells. These findings demonstrate that 15AU81 interacts favorably with hepatocytes either alone or in conjunction with RAPA and CsA to enhance their immunosuppressive effects on rat heart allograft survival. The failure to enhance small bowel allograft survival may be explained by the inability at this low dosage of 15AU81 to influence the intense graft versus host reaction elicited by small bowel transplants.     

Anesthésie pour sténose du pylore. Evaluation de l'association propofol-anesthésiques halogénés

This study was aimed at evaluating haemodynamic changes during an anaesthetic sequence for full stomach, using propofol as induction agent and volatile anaesthetics for maintenance of anaesthesia in infants scheduled for surgical cure of hypertrophic pyloric stenosis. After correction of preoperative blood electrolyte and metabolic disturbances with appropriate i.v. hydrating solutions, anaesthesia was induced with propofol and suxamethonium. Infants were divided in two groups according to the volatile anaesthetic agent used for maintenance of anaesthesia after tracheal intubation : halothane (n = 16) or isoflurane (n = 15). The two groups were identical regarding weight (4.28 ± 0.6 vs 4.14 ± 0.76 kg), age (1.6 ± 0.9 vs 1.5 ± 0.6 months), preinduction heart rate (155 ± 22 vs 151 ± 22 b · min⁻¹) and systolic-diastolic arterial pressure (96 ± 18/58 ± 12 vs 105 ± 16/67 ± 15 mmHg). Propofol and suxamethonium doses were identical, 3.9 ± 1 mg · kg⁻¹ and 1.3 ± 0.6 mg · kg⁻¹ respectively in halothane groupe, vs 4.3 ± 0.8 mg · kg⁻¹ and 1.3 ± 0.4 mg · kg⁻¹ in isoflurane group. Heart rate did not change after induction of anaesthesia, while arterial blood pressure decreased significantly (p < 0.001). However, blood pressure remained within the normal range for age throughout the procedure. Mean duration of surgery was shorter in halothane group (64 ± 16 vs 79 ± 17 min, p < 0.05), however time-interval from the end of surgery to tracheal extubation (12 ± 6 vs 15 ± 8 min) was short and identical in the two groups. It is concluded that propofol seems to be appropriate for infants requiring a rapid i.v. sequence induction for “full-stomach”, as haemodynamic changes remain minimal.     

Mizoribine--an inosine monophosphate dehydrogenase inhibitor--acts synergistically with cyclosporine A in prolonging survival of murine islet cell and heart transplants across major histocompatibility barrier

IntroductionMizoribine (MZR) is an inosine monophosphate dehydrogenase inhibitor. It has been widely used in Japan in the treatment of autoimmune diseases and is known to inhibit T and B cell proliferation. The aim of this study was to evaluate the efficacy of MZR as an immunosuppressive agent and determine its ability to synergize with a commonly used calcineurin inhibitor Cyclosporine A (CsA) in prolonging survival of murine islet cells and heart transplanted across major histocompatibility barrier.MethodsMurine allogeneic islet cell transplantation between Balb/c donor mice and C57BL/6 recipient mice and heterotopic heart transplantation was done between C3H/He donor mice and Balb/c recipient mice. Recipients were divided into groups based on immunosuppression: Group 1—No immunosuppression, Group 2—MZR alone (20 mg/kg/day), Group 3—CsA alone (20 mg/kg/day), Group 4—MZR + CsA (20 mg/kg/day). Donor specific IFN-γ, IL-10, IL-2, IL-4 secreting cells were enumerated by ELISpot. Serum cytokine and chemokine concentration was measured by Luminex.ResultsIslet cell allograft recipients treated with CsA and MZR had prolonged islet function compared to other groups [normoglycemia (blood glucose < 200 mg/dL) up to 32 ± 4 days, p < 0.05]. Similarly, heart allograft survival was significantly improved in mice treated with CsA and MZR compared to other groups (50% 30-day survival, p = 0.04). Donor specific IFN-γ, IL-4, IL-2 secreting cells were significantly decreased in recipients treated with CsA and MZR with marked increase in IL-10 secreting cells (p < 0.05). There was also an increase in serum IL-10 with decrease in IFN-γ, IL-4, IL-2, MCP-1, and IL-6 in mice treated with CsA and MZRConclusionMZR and CsA when used in combination are potent immunosuppressive agents in murine islet cell and heart transplantation models. These agents lead to a decrease in donor specific IFN-γ with increase in IL-10 secreting cells leading to improved allograft survival and function.     

The effect of donor-specific transfusion and cyclosporin A on small bowel transplantation in the rat

Pre-transplant blood transfusions are given as a means of desensitization to reduce the required dose of cyclosporin A (CsA). In this study, the effect of pretransplant blood transfusion on host survival and T-cell function against alloantigen were investigated. Male Lewis rats (RT1¹) were used as the recipients in all experiments, and male DA rats (RT1^a) were used as the blood and small bowel donors, and as a source of allogeneic stimulator cells. Male BUF rats (RT1^b) were used as donors of third party blood, and of allo-stimulator cells in a delayed-type hypersensitivity (DTH) response. In our experimental design, Lewis rats were divided into the following groups according to the type of administration: (1) a donor-specific blood transfusion (DST) 8 days preoperatively and a concurrent 5-day course of CsA at 10 mg/kg per day; (2) a nonspecific third party blood transfusion (NST) and CsA at 10 mg/kg per day from day 8 to day 4 preoperatively; (3) CsA alone from day 8 to day 4 preoperatively; (4) DST alone 8 days preoperatively; or (5) no treatment, being the control group. Postoperative treatment consisted of CsA at 2.5 mg/kg per day for 30 days. Rats conditioned with NST plus CsA, CsA alone, DST alone, and the untreated control rats survived for 7.2 ±1.2, 9.0 ± 2.2, 6.8 ± 0.4, and 7.4 ± 1.6 days, respectively. In contrast, the five rats conditioned with DST plus CsA survived for 100 days or more. This study demonstrates that long-term survival of a small bowel allograft can be achieved by host-conditioning with a combined treatment of DST and low-dose CsA.This paper was presented at the 10th Congress of the Asian Association of Pediatric Surgeons held in Seoul, Korea from March 26–29, 1990, and at the 90th Annual Meeting of the Japanese Surgical Society held in Sapporo, Japan in 1990.     

Lack of change of cancellous bone volume with short-term use of the new immunosuppressant rapamycin in rats

Summary Immunosuppressants have adverse effects on bone mineral metabolism in animal and human studies, with corticosteroids producing low-turnover osteopenia, and cyclosporin-A (CsA) producing high-turnover osteopenia. Rapamycin (RAPA) is a new immunosuppressant reported to be at least 10 times more potent than CsA, and acts via a different pathway to CsA and the other new immunosuppressant FK506. This study investigated the effects of RAPA on bone mineral metabolism in the rat. Forty-two, 10-week-old, male Sprague Dawley rats were divided into three groups, and treated according to the following protocol: group A (control) received RAPA vehicle by daily gavage for 14 days (n = 12); group B (high dose RAPA) received RAPA 2.5 mg/kg/day by daily gavage for 14 days (n = 15); group C (low dose RAPA) received RAPA 1.25 mg/kg/day by daily gavage for 14 days (n = 15). Rats were weighed and bled on days 0, 7, and 14 for measurement of blood ionized calcium, bone Gla protein (BGP), parathyroid hormone (PTH), and 1,25(OH)₂D. Tibial bone histomorphometry was determined on day 14 after double-calcein labeling. Weight gain was similar in the two groups treated with RAPA compared with control animals. High-dose RAPA (group B) transiently depressed serum BGP levels on day 7, with elevated blood ionized calcium levels on day 7, and lowered 1,25(OH)₂D levels on day 14. Serum PTH levels were unchanged. Low dose RAPA (group C) did not affect calciotropic hormones. Histomorphometric analyses of tibial metaphyses revealed that parameters of bone formation and resorption were not significantly different in the groups treated with RAPA (group B and C) compared with control animals (group A). Trabecular bone volume (BV/TV) in group B (high-dose RAPA) (15.39 ± 1.01%) and C (low-dose RAPA) (15.38 ±0.57%) was not significantly altered compared with group A (control) (16.42 ± 0.86%). Short-term treatment with RAPA, unlike CsA, does not result in excess resorption and loss of bone volume. The depressed serum 1,25(OH)₂D levels seen with high-dose RAPA therapy may adversely effect bone mineral metabolism in the long term.Presented in part at the American Federation for Clinical Research National Meeting. May 1992, Baltimore, MD     

Efficacy of rapamycin and FK 506 in prolonging rat hind limb allograft survival.

OBJECTIVE: Graft rejection and the toxicity of current immunosuppressive regimens preclude the application of microsurgical advances to transplantation of limbs or other nonessential parts. If limb transplantation is to become a clinical reality, newer, safer, more effective immunosuppressive agents are needed. SUMMARY BACKGROUND DATA: Rapamycin (RPM) and FK 506 are fungal macrolide antibiotics with effective immunosuppressive properties demonstrated in several animal models. RPM is more potent and effective than is FK 506 in rat cardiac allografts and has demonstrated synergy with cyclosporine (CsA) in limb allograft models. METHODS: An orthotopic rat hind limb allograft model (Brown-Norway [RT-1n] to Lewis [RT-1(1)] rats was used. RPM (doses, 3.0, 4.5, and 6.0 mg/kg/day) was administered intraperitoneally on postoperative days 1 to 14. FK 506 (6 mg/kg/day) was administered orally on postoperative 1 to 14 and 1 to 90 and at rejection onset (10 mg/kg/day for salvage). CsA with RPM (postoperative days 1 to 14) was used to assess synergy, with CsA alone serving as the control. Other controls included untreated and placebo-treated allografted animals. The permutation test and Mann-Whitney test were applied to the data. RESULTS: The mean survival times were assessed as follows: (1) control (placebo, untreated), 5 days; (2) RPM groups, 9.5, 10.6, and 8.7 days; (3) 14-day FK 506, 28 days; (4) 90-day FK 506, > 90 days; (5) CsA, 17.3 days; and (6) CsA with RPM, 19.3 days. FK 506 significantly prolonged graft survival compared with RPM (Permutation Test, p < 0.001 and Mann-Whitney Test, p < 0.05). FK 506 salvage reversed early rejection. High-dose RPM produced significant toxicity. Synergy between CsA and RPM was not demonstrated. CONCLUSIONS: FK 506 prolongs allograft survival, reverses early rejection, and prevents rejection without clinical toxicity when given continually. RPM does not prevent rejection in this model and produces significant toxicity at high doses. FK 506 may be a first step in making limb transplantation a clinical reality in reconstructive surgery.     

Minimised versus conventional cardiopulmonary bypass: outcome of high-risk patients

Background: Coronary artery bypass grafting (CABG) with extracorporeal circulation (ECC) is the gold standard for surgical coronary re-vascularisation. Recently, minimised extracorporeal circulation system (MECC) has been postulated a safe and advantageous alternative for multi-vessel CABG. Method: Between January 2004 and December 2007, 244 high-risk patients (logistic EuroScore (ES) > 10%) underwent CABG in our institution. ECC was used in 139 (57%) and MECC in 105 (43%) patients. Demographic data including age (MECC: 73.4 ± 7.4 years; ECC: 73.3 ± 6.4 years), ES (MECC: 19.2 ± 9.8%; ECC: 21.4 ± 11.9%), left-ventricular ejection fraction (MECC: 45.6 ± 16.1%; ECC: 43.1 ± 15.3%), diabetes mellitus (MECC: 14.3%; ECC: 15.1%) and COPD (MECC: 6.7%; ECC: 7.9%) did not differ between the two groups. Preoperative end-stage renal failure was an exclusion criterion. The clinical course and serological/haematological parameters in the ECC and MECC patients were compared in a retrospective manner. Results: Although the numbers of distal anastomoses did not differ between the two groups (MECC: 3.0 ± 0.9; ECC: 2.9 ± 0.9), ECC time was significantly shorter in the MECC group (MECC: 96 ± 33 min; ECC: 120 ± 50 min, p < 0.01). Creatinine kinase (CK) levels were significantly lower 6 h after surgery in the MECC group (MECC: 681 ± 1505 U l⁻¹; ECC: 1086 ± 1338 U l⁻¹, p < 0.05) and the need of red blood cell transfusion was significantly less after MECC surgery (MECC: 3 [range: 1–6]; ECC: 5 [range: 2–9] p < 0.05). Moreover, 30-day mortality was significantly lower in the MECC group as compared to the ECC group (MECC: 12.4%; ECC: 26.6, p < 0.01). Discussion: MECC is a safe alternative for CABG surgery. A lower 30-day mortality, lower transfusion requirements and less renal and myocardial damage encourage the use of MECC systems, especially in high-risk patients.     

Pharmacokinetic profiles of cyclosporine in rats. Influence of route of administration and dosage

This study was performed to determine the influence of different routes of administration and of variable doses of cyclosporine (CsA) on the pharmacokinetics of CsA in the rat. Seven groups of 4 adult female Lewis rats were given CsA once daily for 5 days: group 1: 5 mg/kg of CsA p.o. (by gavage); group 2: 10 mg/kg of CsA p.o.; Group 3: 5 mg/kg of CsA i.m.; group 4: 10 mg/kg of CsA i.m.; Group 5: 5 mg/kg of CsA s.c.; group 6: 10 mg/kg of CsA s.c., group 7: 10 mg/kg CsA i.p. CsA plasma levels were determined by RIA at 0, 2, 4, 6, 8, and 24 hr on days 1 and 4. Ease of administration was greatest in the s.c. groups (3 and 4), in which no anesthesia, no restraining device, and no special skills were required. Peak CsA levels varied greatly from group to group, as did trough levels and CsA bioavailability, as determined by the total area under the plasma CsA concentration-time curve. All groups exhibited great variation of CsA plasma level in the 24-hr period following administration, except group 3, in which the peak-to-trough difference was only 26.8% of peak level, as opposed to values over 60% in all other groups. We conclude that: (1) CsA may be administered to rats through different routes to achieve adequate plasma levels; (2) the route and dosage will greatly influence the pharmacokinetic profile of CsA; and (3) the SC route, in addition to being the easiest, provides reproducible and steady CsA plasma levels, with little variation over a 24-hr period.     

Combination thalidomide and cyclosporine for cardiac allograft rejection. Comparison with combination methylprednisolone and cyclosporine

Combination CsA with corticosteroids is the most commonly used maintenance immunosuppressive regimen after cardiac transplantation, although their high-toxicity profiles frequently limit their clinical benefit. Immunosuppressive agents that would act synergistically with CsA but without the toxicity profile of corticosteroids would be clinically useful. Thalidomide was removed from the market due to its teratogenic effects, although it has known immunomodulatory activity. The purpose of this study was (1) to determine whether maintenance immunosuppression with thalidomide and subtherapeutic doses of CsA can help prevent rat cardiac allograft rejection; and (2) to compare its synergism with CsA to the commonly used corticosteroid, methylprednisolone. ACI-LEW allografts were all treated with subtherapeutic doses of CsA (10 mg/g/day, s.c.) for 4 days. When CsA was then discontinued, severe rejection developed by posttransplant day 14. Group 1 received CsA alone. Group 2 received in addition oral thalidomide 100 mg/day for 14 days. Groups 3, 4, and 5 received CsA and methylprednisolone (low dose: 0.2 mg/kg/day s.c.; moderate dose: 2.0 mg/kg/day s.c.; and high dose: 20 mg/kg/day s.c. Twelve histologic parameters of rejection were semiquantitatively graded 0-4, and total pathology scores were determined. The combination of thalidomide and subtherapeutic CsA significantly reduced the severity of myocardial necrosis, interstitial inflammation, interstitial edema, and the total pathology score. Thalidomide was found to be equally as effective as low-, moderate-, and high-dose methylprednisolone. The results of this study suggest the potential clinical role of CsA and thalidomide in maintenance immunosuppressive regimens, thereby avoiding the use of corticosteroids.     

Intravenous Phenylephrine Preconditioning of Cardiac Grafts From Non–Heart-Beating Donors

Background. Hypoxia and warm ischemia produce severe injury to cardiac grafts harvested from non–heart-beating donors. To potentially improve recovery of such grafts, we studied the effects of intravenous phenylephrine preconditioning.Methods. Thirty-seven blood-perfused rabbit hearts were studied. Three groups of non–heart-beating donors underwent intravenous treatment with phenylephrine at 12.5 (n = 8), 25 (n = 7), or 50 μg/kg (n = 7) before initiation of apnea. Non–heart-beating controls (n = 8) received saline vehicle. Hypoxic cardiac arrest occurred after 6 to 12 minutes of apnea, followed by 20 minutes of warm in vivo ischemia. A 45-minute period of ex vivo reperfusion ensued. Nonischemic controls (n = 7) were perfused without antecedent hypoxia or ischemia.Results. Phenylephrine 25 μg/kg significantly delayed the onset of hypoxic cardiac arrest compared with saline controls (9.6 ± 0.5 versus 7.7 ± 0.4 minutes; p = 0.00001), yet improved recovery of left ventricular developed pressure compared with saline controls (57.1 ± 5.3 versus 41.0 ± 3.4 mm Hg; p = 0.04). Phenylephrine 25 μg/kg also yielded a trend toward less myocardial edema than saline vehicle (p = 0.09).Conclusions. Functional recovery of nonbeating cardiac grafts is improved by preconditioning. We provide evidence that the myocardium can be preconditioned with phenylephrine against hypoxic cardiac arrest.(Ann Thorac Surg 1997;63:1664–8)     

Influence of internal mammary artery grafting and completeness of revascularization on long-term outcome in octogenarians

Background. It has been well established that complete revascularization with internal mammary artery (IMA) grafting is important in young patients undergoing coronary artery bypass grafting (CABG). Applying these principles to octogenarians remains controversial.Methods. From 1986 to 1999, 358 consecutive patients aged 80 to 94 years underwent CABG. Revascularization was complete in 291 (81%) and incomplete in 67 (19%). The IMA was used in 231 (65%) cases.Results. Operative mortality was 7% ± 1%, but was not statistically different with or without IMA grafting (IMA 5% ± 2% versus no IMA 10% ± 3%, p = 0.11) or complete revascularization (p > 0.41). Midterm survival improved with IMA grafting (70% ± 3% versus 56% ± 5% at 4 years, p < 0.03; 36% ± 4% versus 29% ± 5% at 8 years, p < 0.08), but was not significant beyond 8 years. Among 138 survivors, those with IMA grafts were more likely to be angina free (82% versus 53%, p < 0.001) and in New York Heart Association class I (60% versus 36%, p < 0.03). Survival, recurrent angina, and functional class were independent of completeness of revascularization (p > 0.21).Conclusions. IMA grafting improved survival, angina, and functional class of octogenarians, but complete revascularization did not have a similar impact.     

Effects of l-arginine administration before cardioplegic arrest on ischemia-reperfusion injury

Background. Administration of l-arginine during reperfusion or its addition to cardioplegic solution has been shown to protect myocardium against ischemia-reperfusion injury. This study aimed at evaluating the role of l-arginine in ischemia-reperfusion injury when administered intraperitoneally 24 hours before cardioplegic arrest.Methods. Two groups of Sprague-Dawley rats (control, n = 10; and l-arginine, n = 10) were studied in an isolated buffer-perfused heart model. Both groups were injected intraperitoneally 24 hours before ischemia. Before experimentation blood samples were collected for cardiac troponin I and cGMP analysis. In the coronary effluents, cardiac troponin I, adenosine, cyclic guanosine monophosphate, and nitric oxide metabolites were assayed.Results. Before heart excision, serum cardiac troponin I concentrations were higher in the l-arginine than in the control group (0.037 ± 0.01 versus 0.02 ± 0.05 μg · L⁻¹; p < 0.05). During reperfusion, cardiac troponin I release was lower in the l-arginine than in the control group (0.04 ± 0.01 versus 0.19 ± 0.03 ng · min⁻¹; p < 0.05). The coronary flow as well as the left ventricular developed pressure were higher in the l-arginine than in the control group before ischemia and remained so throughout the experimentation.Conclusions. These results indicate that l-arginine administered intraperitoneally 24 hours before cardioplegic arrest reduced myocardial cell injury and seems to protect myocardium against ischemia-reperfusion injury.     

Synergistic effect of rapamycin and cyclosporine in prevention of acute kidney allograft rejection in the mouse

The effect of rapamycin (RAPA) and cyclosporine A (CsA) monotherapy and combination therapy was examined in prevention of kidney allograft rejection in the mouse. Both drugs were administered orally for up to 14 days in BALB/c (H-2(d)) to C57BL/6 (H-2(b)) mice strong combination. Six groups were treated with RAPA and/or CsA. This study shows that concomitant therapy of RAPA and CsA produces strong synergistic interaction in prolonging renal allograft survival in mice when compared with monotherapy of RAPA or CsA.