Glucocorticoids Alter the Balance Between Pro- and Anti-inflammatory Mediators in the Myocardium in a Porcine Model of Brain Death

Hurdles to Cardioprotection in the Critically Ill

Cardiovascular disease is the largest contributor to worldwide mortality, and the deleterious impact of heart failure (HF) is projected to grow exponentially in the future. As heart transplantation (HTx) is the only effective treatment for end-stage HF, development of mechanical circulatory support (MCS) technology has unveiled additional therapeutic options for refractory cardiac disease. Unfortunately, despite both MCS and HTx being quintessential treatments for significant cardiac impairment, associated morbidity and mortality remain high. MCS technology continues to evolve, but is associated with numerous disturbances to cardiac function (e.g., oxidative damage, arrhythmias). Following MCS intervention, HTx is frequently the destination option for survival of critically ill cardiac patients. While effective, donor hearts are scarce, thus limiting HTx to few qualifying patients, and HTx remains correlated with substantial post-HTx complications. While MCS and HTx are vital to survival of critically ill cardiac patients, cardioprotective strategies to improve outcomes from these treatments are highly desirable. Accordingly, this review summarizes the current status of MCS and HTx in the clinic, and the associated cardiac complications inherent to these treatments. Furthermore, we detail current research being undertaken to improve cardiac outcomes following MCS/HTx, and important considerations for reducing the significant morbidity and mortality associated with these necessary treatment strategies.

Medical Management of Brain-Dead Organ Donors

With improving healthcare services, the demand for organ transplants has been increasing daily worldwide. Deceased organ donors serve as a good alternative option to meet this demand. The first step in this process is identifying potential organ donors. Specifically, brain-dead patients require aggressive and intensive care from the declaration of brain death until organ retrieval. Currently, there are no specific protocols in place for this, and there are notable variations in the management strategies implemented across different transplant centers. Some transplant centers follow their own treatment protocols, whereas other countries, such as Bangladesh, do not have any protocols for potential organ donor care. In this review, we discuss how to identify brain-dead donors and describe the physiological changes that occur following brain death. We then summarize the management of brain-dead organ donors and, on the basis of a review of the literature, we propose recommendations for a treatment protocol to be developed in the future.

A porcine model to study the effect of brain death on kidney genomic responses

Introduction

A majority of transplanted organs come from donors after brain death (BD). Renal grafts from these donors have higher delayed graft function and lower long-term survival rates compared to living donors. We designed a novel porcine BD model to better delineate the incompletely understood inflammatory response to BD, hypothesizing that adhesion molecule pathways would be upregulated in BD.

Methods

Animals were anesthetized and instrumented with monitors and a balloon catheter, then randomized to control and BD groups. BD was induced by inflating the balloon catheter and animals were maintained for 6 hours. RNA was extracted from kidneys, and gene expression pattern was determined.

Results

In total, 902 gene pairs were differently expressed between groups. Eleven selected pathways were upregulated after BD, including cell adhesion molecules.

Conclusions

These results should be confirmed in human organ donors. Treatment strategies should target involved pathways and lessen the negative effects of BD on transplantable organs.

The role of hormone replacement therapy in the intensive care management of deceased organ donors: a primer for nurses

Donation after brain death remains the primary contributor to the supply of organs available for transplantation in the United States. After brain death, both a surge of catecholamines and a dysregulation of the neurohormonal axis may result in hypotension, decreased organ perfusion, and reduced viability of organs to be transplanted. Hormone replacement therapy is widely used to maintain organ perfusion and has been shown to increase the number of organs procured. This article reviews the literature and mechanisms supporting the use of hormone replacement therapy in brain-dead organ donors and provides clinicians with information regarding the administration, monitoring, and preparation of thyroid hormone, arginine vasopressin, and corticosteroids.

Roles of inflammation and apoptosis in experimental brain death-induced right ventricular failure

BACKGROUND

Right ventricular (RV) dysfunction remains the leading cause of early death after cardiac transplantation. Methylprednisolone is used to improve graft quality; however, evidence for that remains empirical. We sought to determine whether methylprednisolone, acting on inflammation and apoptosis, might prevent brain death-induced RV dysfunction.

METHODS

After randomization to placebo (n = 11) or to methylprednisolone (n = 8; 15 mg/kg), 19 pigs were assigned to a brain-death procedure. The animals underwent hemodynamic evaluation at 1 and 5 hours after Cushing reflex (i.e., hypertension and bradycardia). The animals euthanized, and myocardial tissue was sampled. This was repeated in a control group (n = 8).

RESULTS

At 5 hours after the Cushing reflex, brain death resulted in increased pulmonary artery pressure (27 ± 2 vs 18 ± 1 mm Hg) and in a 30% decreased ratio of end-systolic to pulmonary arterial elastances (Ees/Ea). Cardiac output and right atrial pressure did not change. This was prevented by methylprednisolone. Brain death-induced RV dysfunction was associated with increased RV expression of heme oxygenase-1, interleukin (IL)-6, IL-10, IL-1β, tumor necrosis factor (TNF)-α, IL-1 receptor-like (ST)-2, signal transducer and activator of transcription-3, intercellular adhesion molecules-1 and -2, vascular cell adhesion molecule-1, and neutrophil infiltration, whereas IL-33 expression decreased. RV apoptosis was confirmed by terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling staining. Methylprednisolone pre-treatment prevented RV-arterial uncoupling and decreased RV expression of TNF-α, IL-1 receptor-like-2, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and neutrophil infiltration. RV Ees/Ea was inversely correlated to RV TNF-α and IL-6 expression.

CONCLUSIONS

Brain death-induced RV dysfunction is associated with RV activation of inflammation and apoptosis and is partly limited by methylprednisolone.

A standardized model of brain death, donor treatment, and lung transplantation for studies on organ preservation and reconditioning

BACKGROUND

We set a model of brain death, donor management, and lung transplantation for studies on lung preservation and reconditioning before transplantation.

METHODS

Ten pigs (39.7 ± 5.9 Kg) were investigated. Five animals underwent brain death and were treated as organ donors; the lungs were then procured and cold stored (Ischemia). Five recipients underwent left lung transplantation and post-reperfusion follow-up (Graft). Cardiorespiratory and metabolic parameters were collected. Lung gene expression of cytokines (tumor necrosis factor alpha (TNFα), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interferon gamma (IFNγ), high mobility group box-1 (HMGB-1)), chemokines (chemokine CC motif ligand-2 (CCL2-MCP-1), chemokine CXC motif ligand-10 (CXCL-10), interleukin-8 (IL-8)), and endothelial activation markers (endothelin-1 (EDN-1), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), selectin-E (SELE)) was assessed by real-time polymerase chain reaction (PCR).

RESULTS

Tachycardia and hypertension occurred during brain death induction; cardiac output rose, systemic vascular resistance dropped (P < 0.05), and diabetes insipidus occurred. Lung-protective ventilation strategy was applied: 9 h after brain death induction, PaO2 was 192 ± 12 mmHg at positive end-expiratory pressure (PEEP) 8.0 ± 1.8 cmH2O and FiO2 of 40%; wet-to-dry ratio (W/D) was 5.8 ± 0.5, and extravascular lung water (EVLW) was 359 ± 80 mL. Procured lungs were cold-stored for 471 ± 24 min (Ischemia) at the end of which W/D was 6.1 ± 0.9. Left lungs were transplanted and reperfused (warm ischemia 98 ± 14 min). Six hours after controlled reperfusion, PaO2 was 192 ± 23 mmHg (PEEP 8.7 ± 1.5 cmH2O, FiO2 40%), W/D was 5.6 ± 0.4, and EVLW was 366 ± 117 mL. Levels of IL-8 rose at the end of donor management (BD, P < 0.05); CCL2-MCP-1, IL-8, HMGB-1, and SELE were significantly altered after reperfusion (Graft, P < 0.05).

CONCLUSIONS

We have set a standardized, reproducible pig model resembling the entire process of organ donation that may be used as a platform to test in vivo and ex vivo strategies of donor lung optimization before transplantation.

Brain death increases COX-1 and COX-2 expression in the renal medulla in a pig model

BACKGROUND

Brain death is linked to a systemic inflammatory response that includes prostaglandins and cytokines among its mediators. The levels of cyclooxygenase-1 and cyclooxygenase-2 (COX-1 and COX-2) affect graft survival, but it remains unknown whether these enzymes are modified during brain death. The aims of this study were to investigate the organ expression of COX and to analyse the cytokine response in the plasma, cerebrospinal fluid (CSF), and organs in a porcine model of intracerebral haemorrhage and brain death.

METHODS

Twenty pigs were randomly assigned to either a brain death group or a control group. Brain death was induced by an intracerebral injection of blood, and the animals were observed over the next 8 h. Tissue samples were tested for COX-1, COX-2 messenger RNA (mRNA) expression (heart, lung, and kidney), haeme oxygenase-1 (HO-1) (kidney), interleukin-1β (IL-1β), IL-6, IL-8, IL-10, and tumour necrosis factor-α. These cytokines were also measured at eight time points in the plasma and CSF.

RESULTS

At the organ level, the levels of COX-1 and COX-2 mRNA expression were increased only in the renal medulla (P = 0.03 and P = 0.02, respectively). The cytokine levels in the tissue, plasma, and CSF revealed no differences between the groups. HO-1 expression decreased (P = 0.0088).

CONCLUSION

Brain death increases the expression of COX-1 and COX-2 mRNA in the renal medulla. The release of cytokines into the plasma and CSF did not vary between the groups.

Effects of methylprednisolone on inflammatory activity and oxidative stress in the lungs of brain-dead rats

OBJECTIVE:

To evaluate the effects that early and late systemic administration of methylprednisolone have on lungs in a rat model of brain death.

METHODS:

Twenty-four male Wistar rats were anesthetized and randomly divided into four groups (n = 6 per group): sham-operated (sham); brain death only (BD); brain death plus methylprednisolone (30 mg/kg i.v.) after 5 min (MP5); and brain death plus methylprednisolone (30 mg/kg i.v.) after 60 min (MP60). In the BD, MP5, and MP60 group rats, we induced brain death by inflating a balloon catheter in the extradural space. All of the animals were observed and ventilated for 120 min. We determined hemodynamic and arterial blood gas variables; wet/dry weight ratio; histological score; levels of thiobarbituric acid reactive substances (TBARS); superoxide dismutase (SOD) activity; and catalase activity. In BAL fluid, we determined differential white cell counts, total protein, and lactate dehydrogenase levels. Myeloperoxidase activity, lipid peroxidation, and TNF-α levels were assessed in lung tissue.

RESULTS:

No significant differences were found among the groups in terms of hemodynamics, arterial blood gases, wet/dry weight ratio, BAL fluid analysis, or histological score-nor in terms of SOD, myeloperoxidase, and catalase activity. The levels of TBARS were significantly higher in the MP5 and MP60 groups than in the sham and BD groups (p < 0.001). The levels of TNF-α were significantly lower in the MP5 and MP60 groups than in the BD group (p < 0.001).

CONCLUSIONS:

In this model of brain death, the early and late administration of methylprednisolone had similar effects on inflammatory activity and lipid peroxidation in lung tissue.

Combined donor simvastatin and methylprednisolone treatment prevents ischemia-reperfusion injury in rat cardiac allografts through vasculoprotection and immunomodulation

BACKGROUND

Ischemia-reperfusion injury (IRI) and allograft dysfunction remain as two of the major clinical challenges after heart transplantation. Here, we investigated the effect of donor treatment with simvastatin and methylprednisolone on microvascular dysfunction and immunomodulation during IRI in rat cardiac allografts subjected to prolonged ischemia time.

METHODS

The DA rats received simvastatin, methylprednisolone, or both 2 hr before heart donation. The allografts were subjected to 4-hr hypothermic preservation and transplanted to the fully major histocompatibility complex-mismatched WF rat recipients.

RESULTS

Six hours after reperfusion, donor treatment either with simvastatin alone or with high dose of methylprednisolone alone or in combination with simvastatin and methylprednisolone significantly reduced cardiac troponin T release and the number of allograft infiltrating ED1 macrophages MPO neutrophils. However, the combination donor treatment was superior in the prevention of IRI and significantly prolonged allograft survival. Donor simvastatin treatment inhibited allograft microvascular RhoA GTPase pathway activation, whereas methylprednisolone prevented activation of innate immune response and mRNA expression of hypoxia-inducible factor-1α and its multiple target genes.

CONCLUSIONS

Our results show that donor treatment in combination with simvastatin and methylprednisolone prevents IRI and has beneficial effect on allograft survival in rat cardiac allografts. Minimizing microvascular injury and the activation of innate immunity may offer a novel therapeutic strategy to expand the donor pool and furthermore improve the function of the marginal donor organs.

Inflammatory signalling associated with brain dead organ donation: from brain injury to brain stem death and posttransplant ischaemia reperfusion injury

Brain death is associated with dramatic and serious pathophysiologic changes that adversely affect both the quantity and quality of organs available for transplant. To fully optimise the donor pool necessitates a more complete understanding of the underlying pathophysiology of organ dysfunction associated with transplantation. These injurious processes are initially triggered by catastrophic brain injury and are further enhanced during both brain death and graft transplantation. The activated inflammatory systems then contribute to graft dysfunction in the recipient. Inflammatory mediators drive this process in concert with the innate and adaptive immune systems. Activation of deleterious immunological pathways in organ grafts occurs, priming them for further inflammation after engraftment. Finally, posttransplantation ischaemia reperfusion injury leads to further generation of inflammatory mediators and consequent activation of the recipient's immune system. Ongoing research has identified key mediators that contribute to the inflammatory milieu inherent in brain dead organ donation. This has seen the development of novel therapies that directly target the inflammatory cascade.

Graft-specific immune cells communicate inflammatory immune responses after brain death

BACKGROUND

Donor brain death (BD) triggers inflammatory graft activation that leads to impaired graft quality and outcome. We used a mouse BD model to investigate graft inflammation in cardiac transplants from immune-competent and immune-deficient donor animals. Effects of donor T-cell depletion were tested in an additional group of cardiac transplant recipients.

METHODS

We analyzed systemic and graft-specific inflammatory activation after BD in donors and in syngeneic recipients of hearts retrieved from BD donors. To dissect the role of donor-specific immune cells in communicating BD-triggered inflammation, immune-deficient T-cell-, B-cell-, and natural killer cell-deficient Rag2/double knockout mice and naïve C57BL6 treated with anti-thymocyte globulin (Thymoglobulin; Genzyme Transplant, Cambridge, MA) were observed.

RESULTS

Donor BD boosted lymphocyte activation in donors and recipients of syngeneic BD grafts. Lymphocyte activation was mitigated in recipients of immune-deficient and Thymoglobulin-treated BD donor grafts. Likewise, systemic and intra-graft levels of inflammatory cytokines interleukin -1, interleukin-6, interferon-γ, and tumor necrosis factor-α were significantly reduced in immune-deficient and anti-thymocyte globulin-treated recipients. Dense lymphocyte infiltrates were detected in the hearts from untreated BD donors; in contrast, the hearts from donors treated with Thymoglobulin demonstrated a preserved structure with minimal infiltrates comparable with naïve controls.

CONCLUSION

BD triggers inflammatory graft activation communicated through intra-graft immune cells. Donor treatment with Thymoglobulin prevented inflammatory immune activation and improved graft quality to levels comparable to living donor organs.

Effects of brain death on organ quality and transplant outcome

The inferiority of organs from brain dead donors is reflected by impaired graft survival and patient outcome. Brain death effects hemodynamic stability, hormonal changes, and neuroimmunologic effects and unleashes a cascade of inflammatory events. Despite considerable efforts in experimental and clinical research, most of the mechanisms linked to brain death are only appreciated on a descriptive level. This overview presents our current understanding of the pathophysiology and consequences of brain death on organ injury and summarizes available therapeutic interventions.

Management of the heartbeating brain-dead organ donor

The main factor limiting organ donation is the availability of suitable donors and organs. Currently, most transplants follow multiple organ retrieval from heartbeating brain-dead organ donors. However, brain death is often associated with marked physiological instability, which, if not managed, can lead to deterioration in organ function before retrieval. In some cases, this prevents successful donation. There is increasing evidence that moderation of these pathophysiological changes by active management in Intensive Care maintains organ function, thereby increasing the number and functional quality of organs available for transplantation. This strategy of active donor management requires an alteration of philosophy and therapy on the part of the intensive care unit clinicians and has significant resource implications if it is to be delivered reliably and safely. Despite increasing consensus over donor management protocols, many of their components have not yet been subjected to controlled evaluation. Hence the optimal combinations of treatment goals, monitoring, and specific therapies have not yet been fully defined. More research into the component techniques is needed.

Endocrine changes in brain death and transplantation

Following brain death (BD) many hormonal changes occur. These include an increase and then a fall in the levels of circulating catecholamines, reduced levels of anti-diuretic hormone and cortisol as well as alterations in the hypothalamic-pituitary thyroid axis consistent with the non-thyroidal illness syndrome. In an era when the numbers of potential recipients listed for transplantation are greater than the number of donors, with an increasing donor age, a detailed knowledge of the endocrine changes and pathophysiological consequences of these is essential to optimise the management of the brain-stem dead organ donor. There still remains significant debate as to whether hormone replacement therapy to correct the observed changes is beneficial.

Activation of JAK-STAT and nitric oxide signaling as a mechanism for donor heart dysfunction

BACKGROUND

Donor heart dysfunction (DHD) precluding procurement for transplantation occurs in up to 25% of brain-dead (BD) donors. The molecular mechanisms of DHD remain unclear. We investigated the potential role of myocardial interleukin (IL)-6 signaling through the JAK2-STAT3 pathway, which can lead to the generation of nitric oxide (NO) and decreased cardiac myocyte contractility.

METHODS

Hearts were procured using standard technique with University of Wisconsin (UW) solution from 14 donors with a left ventricular (LV) ejection fraction of <35% (DHD). Ten hearts with normal function (NF) after BD served as controls. LV IL-6 was quantitated by enzyme-linked immunoassay (ELISA) and JAK2-STAT3 signaling was assessed by expression of phosphorylated STAT3. Inducible NO synthase (iNOS) and caspase-3 were measured by activity assays.

RESULTS

Myocardial IL-6 expression was 8-fold greater in the DHD group vs NF controls. Phosphorylated STAT3 expression was 5-fold higher in DHD than in NF, indicating increased JAK2-STAT3 signaling. LV activity of iNOS was 2.5-fold greater in DHD than in NF. LV expression of the pro-apoptotic gene Bnip3 and caspase-3 activity were 3-fold greater in the DHD group than in the NF group.

CONCLUSIONS

Myocardial IL-6 expression is significantly higher in the setting of DHD compared with hearts procured with normal function. This may lead to increased JAK2-STAT3 signaling and upregulation of iNOS, which has been shown to decrease cardiac myocyte contractility. Increased NO production may also lead to increased apoptosis through upregulation of Bnip3 gene expression. Increased iNOS signaling may be an important mechanism of DHD and represents a novel therapeutic target to improve cardiac function after BD.

Mechanism of the protective effects of N-acetylcysteine on the heart of brain-dead Ba-Ma miniature pigs

BACKGROUND

Severe stress response induced by brain death leads to a marked increase in the expression of inflammatory cytokines regulated by nuclear factor-kappaB (NF-kappaB). N-acetylcysteine may inhibit activation of the NF-kappaB pathway. This study examined the expression of NF-kappaB in the hearts of brain-dead Ba-Ma miniature pigs and the protection potential of N-acetylcysteine.

METHODS

Ba-Ma miniature pigs were randomized into 3 groups: control group (Group C), N-acetylcysteine-free group (Group B), and N-acetylcysteine treatment group (Group N). At 6, 12, and 24 hours after the initial brain death, serum cardiac troponin-T (cTnT), tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 were examined. Heart tissue was taken 24 hours after the initial brain death. Structural changes of the heart and the expression of NF-kappaB were analyzed.

RESULTS

At 6 hours after the initial brain death, serum levels of cTnT, TNF-alpha, IL-1beta, and IL-6 in Groups B and N began to increase. Levels in Group B increased more dramatically than in Group N. At 24 hours, cardiocyte damage was documented, but the damage in Group N was less severe than that in Group B. The expression of NF-kappaB in Groups B and N increased, and expression in Group B increased more sharply than in Group N.

CONCLUSIONS

N-acetylcysteine can alleviate both structural and functional injury of the heart during brain death, which might be related to the inhibition of NF-kappaB expression and decreasing release of inflammatory mediators.

[Hormone modulation of organ donor. Utility of the steroids]

Recently, the work group made up of the National Transplant Organization (Organización Nacional de Trasplantes, ONT), Spanish Society of Intensive, Critical Medicine and Coronary Units (Sociedad Española de Medicina Intensiva, Crítica y de Unidades Coronarias, SEMICYUC) and other Scientific Societies have recommended using 15 mg/kg of methyl prednisolone during the management of lung donors after brain death. This recommendation is based on descriptive and retrospective studies. However, the review of different experimental and clinical studies also suggests a potential benefit of using steroids in either thoracic or abdominal organ donors during management strategies. In brain death management, early steroid administration may decrease cytokine production and also may prevent alterations induced by proinflammatoy mediators, stabilize cell membranes, reduce expression of cell surface adhesion molecules and avoid lipid peroxidation after the ischemic period. This could be beneficial in increasing number and quality of organs harvested and in decreasing rejection episodes after transplant. It would be very recommendable to carry out prospective and comparative studies to demonstrate these potential utilities. Meanwhile and knowing the deleterious effects of inflammatory activity arising during and after brain death, we recommend using 15 mg/kg of methyl prednisolone in the organ donor management, as soon as possible. The potential benefit of its immunomodulation effects, its low cost and the absence of major side effects can justify this recommendation.

Systemic inflammation in the brain-dead organ donor

Brain death itself impairs organ function in the potential donor, thereby limiting the number of suitable organs for transplantation. In addition, graft survival of kidneys obtained from brain-dead (BD) donors is inferior to that of kidneys obtained from living donors. Experimental studies confirm an inferior graft survival for the heart, liver and lungs from BD compared with living donors. The mechanism underlying the deteriorating effect of brain death on the organs has not yet been fully established. We know that brain death triggers massive circulatory, hormonal and metabolic changes. Moreover, the past 10 years have produced evidence that brain death is associated with a systemic inflammatory response. However, it remains uncertain whether the inflammation is induced by brain death itself or by events before and after becoming BD. The purpose of this study is to discuss the risk factors associated with brain death in general and the inflammatory response in the organs in particular. Special attention will be paid to the heart, lung, liver and kidney and evidence will be presented from clinical and experimental studies.

Low dose methylprednisolone prophylaxis to reduce inflammation during one-lung ventilation

BACKGROUND

The specific aim of this study was to examine the efficacy of a low dose of methylprednisolone in minimizing inflammatory response in juvenile piglets when given 45-60 min prior to onset of one-lung ventilation.

METHODS

Twenty piglets aged 3 weeks were assigned to either the control group (n = 10) or methylprednisolone group (n = 10). The animals were anesthetized and after 30 min of ventilation, they had their left lung blocked. Ventilation was continued via right lung for 3 h. The left lung was then unblocked. Following another 30 min of bilateral ventilation, the animals were euthanized and both lungs were harvested. The methylprednisolone group had a single dose (2 mg x kg(-1)) of methylprednisolone given i.v. 45-60 min prior to onset of one-lung ventilation. Physiological parameters (PaO2, resistance, and compliance) and markers of inflammation (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-6, and IL-8) were measured at baseline and every 30 min thereafter. Lung tissue homogenates from both collapsed and ventilated lungs were analyzed for TNF-alpha, IL-1beta, IL-6, and IL-8.

RESULTS

The methylprednisolone group had higher partial pressure of oxygen (P = 0.01), lower plasma levels of TNF-alpha (P = 0.03) and IL-6 (P = 0.001) when compared with control group. Lung tissue homogenate in the methylprednisolone group had lower levels of TNF-alpha (P < 0.05), IL-1beta (P < 0.05), and IL-8 (P < 0.05) in both the collapsed and the ventilated lungs.

CONCLUSIONS

In a piglet model of one-lung ventilation, use of prophylactic methylprednisolone prior to collapse of the lung improves lung function and decreases systemic pro-inflammatory response. In addition, in the piglets who received methylprednisolone, there were reduced levels of inflammatory mediators in both the collapsed and ventilated lungs.

Does brain death induce a pro-inflammatory response at the organ level in a porcine model?

BACKGROUND

Organs from brain-dead donors have a poorer prognosis after transplantation than organs from living donors. A possible explanation for this is that brain death might initiate a systemic inflammatory response, elicited by a metabolic stress response or brain ischemia. The aim of this study was to investigate the effect of brain death on the cytokine content in the heart, liver, and kidney. In addition, the metabolic and hemodynamic response caused by brain death was carefully registered.

METHODS

Fourteen pigs (35-40 kg) were randomized into two groups (1) eight brain-dead pigs and (2) six pigs only sham operated. Brain death was induced by inflation of an epidurally placed balloon. Blood samples for insulin, glucose, catecholamine, free fatty acids (FAA), and glucagon were obtained during the experimental period of 360 min. At the conclusion of the experiment, biopsies were taken from the heart, liver, and kidney and were analyzed for cytokine mRNA and proteins [tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, and IL-10).

RESULTS

We found a dramatic response to brain death on plasma levels of epinephrine (P=0.004), norepinephrine (P=0.02), FAA (P=0.0001), and glucagon (P=0.0003) compared with the sham group. There was no difference in cytokine content in any organ between the groups.

CONCLUSION

In this porcine model, brain death induced a severe metabolic response in peripheral blood. At the organ level, however, there was no difference in the cytokine response between the groups.