Plasma cytokines do not reflect expression of pro- and anti-inflammatory cytokine mRNA at organ level after cardiopulmonary bypass in neonatal pigs

Whole Blood Reactivity to Viral and Bacterial Pathogens after Non-Emergent Cardiac Surgery during the Acute and Convalescence Periods Demonstrates a Distinctive Profile of Cytokines Production Compared to the Preoperative Baseline in Cohort of 108 Patients, Suggesting Immunological Reprogramming during the 28 Days Traditionally Recognized as the Post-Surgical Recovery Period

The release of danger signals from tissues in response to trauma during cardiac surgery creates conditions to reprogram the immune system to subsequent challenges posed by pathogens in the postoperative period. To demonstrate this, we tested immunoreactivity before surgery as the baseline (tbaseline), followed by subsequent challenges during the acute phase (t24h), convalescence (t7d), and long-term recovery (t3m). For 108 patients undergoing elective heart surgery, whole blood was stimulated with lipopolysaccharide (LPS), Influenza A virus subtype N2 (H3N2), or the Flublok™ vaccine to represent common pathogenic challenges. Leukocytosis, platelet count, and serum C-reactive protein (CRP) were used to measure non-specific inflammation. Cytokines were measured after 18 h of stimulation to reflect activation of the various cell types (activated neutrophils-IL-8; activated T cells-IL-2, IFNγ, activated monocyte (MO)-TNFα, IL-6, and deactivated or atypically activated MO and/or T cells-M-CSF, IL-10). IL-2 and IL-10 were increased at t7d, while TNFα was suppressed at t24h when LPS was utilized. Interestingly, M-CSF and IL-6 production was elevated at seven days in response to all stimuli compared to baseline. While some non-specific markers of inflammation (white cell count, IL-6, and IL-8) returned to presurgical levels at t3m, CRP and platelet counts remained elevated. We showed that surgical stimulus reprograms leukocyte response to LPS with only partial restoration of non-specific markers of inflammation.

Renal and Cerebral Hypoxia and Inflammation During Cardiopulmonary Bypass

Cardiac surgery-associated acute kidney injury and brain injury remain common despite ongoing efforts to improve both the equipment and procedures deployed during cardiopulmonary bypass (CPB). The pathophysiology of injury of the kidney and brain during CPB is not completely understood. Nevertheless, renal (particularly in the medulla) and cerebral hypoxia and inflammation likely play critical roles. Multiple practical factors, including depth and mode of anesthesia, hemodilution, pump flow, and arterial pressure can influence oxygenation of the brain and kidney during CPB. Critically, these factors may have differential effects on these two vital organs. Systemic inflammatory pathways are activated during CPB through activation of the complement system, coagulation pathways, leukocytes, and the release of inflammatory cytokines. Local inflammation in the brain and kidney may be aggravated by ischemia (and thus hypoxia) and reperfusion (and thus oxidative stress) and activation of resident and infiltrating inflammatory cells. Various strategies, including manipulating perfusion conditions and administration of pharmacotherapies, could potentially be deployed to avoid or attenuate hypoxia and inflammation during CPB. Regarding manipulating perfusion conditions, based on experimental and clinical data, increasing standard pump flow and arterial pressure during CPB appears to offer the best hope to avoid hypoxia and injury, at least in the kidney. Pharmacological approaches, including use of anti-inflammatory agents such as dexmedetomidine and erythropoietin, have shown promise in preclinical models but have not been adequately tested in human trials. However, evidence for beneficial effects of corticosteroids on renal and neurological outcomes is lacking. © 2021 American Physiological Society. Compr Physiol 11:1-36, 2021.

Use of a simply modified drainage catheter for peritoneal dialysis treatment of acute renal failure associated with cardiac surgery in infants

Acute renal failure (ARF) is a common complication in infants who undergo cardiac surgery in the intensive care unit. We report on a modified drainage catheter used in peritoneal dialysis (PD) for the treatment of ARF associated with cardiac surgery in infants. Thirty-nine infants with congenital heart disease undergoing cardiac surgery who developed ARF at our center between January 2009 and January 2012 were assessed. A modified drainage catheter for PD was used in these infants. Their demographic, clinical, and surgical data were analyzed. Thirty infants with ARF were cured by PD, and the other 9 died in the first 48 hours because of the severity of the acute cardiac dysfunction. All these infants were dependent upon mechanical ventilation during the postoperative period and used vasoactive drugs. In the survival group, the interval between the procedure and initiation of PD was 13.6 ± 6.5 (range, 6-30) hours. PD duration was 3.9 ± 0.9 (3-6) days. Minor complications were encountered in some patients (asymptomatic hypokalemia, hyperglycemia, and thrombocytopenia). These complications were readily treated by drugs or resolved spontaneously. Hemodynamics, cardiac function, and renal function improved significantly during PD. These data suggest that PD using a modified drainage catheter for ARF after cardiac surgery in infants is safe, feasible, inexpensive, and yields good results.

The impact of Staphylococcus aureus concentration on the development of pulmonary lesions and cytokine expression after intravenous inoculation of pigs

Acute respiratory distress syndrome is a common complication in severe sepsis. In pigs, the lungs play an important role in clearing systemic bacterial infections due to pulmonary intravascular macrophages found specifically in pigs. However, this increases the exposure of the porcine lungs to pathogens and potential injury. The authors propose that increasing the concentration of the inoculum without changing the bacterial dose will lead to severe sepsis with pronounced pulmonary lesions. This could potentially create a risk of cytokine spillover to the circulation, leading to an increased systemic response. Eight Danish Landrace pigs, approximately 10 weeks old, were inoculated twice with a low or once with a high concentration of Staphylococcus aureus. Three pigs were sham-inoculated. The animals were grouped based on macro- and microscopic lung lesions. The mRNA expression of local pulmonary inflammatory markers was compared to protein levels of systemic inflammatory markers. The most severe pulmonary lesions were observed in animals receiving the high S. aureus concentration, indicating that severity of lesions is dependent on inoculum concentration rather than total numbers of bacteria. Furthermore, local mRNA expression of inflammatory cytokines appeared to be dependent on the magnitude and severity of tissue destruction, including the ability to confine the lesions. Increasing mRNA levels of serum amyloid A could be a confident marker of severity of pulmonary lesions. Since no correlation was observed between local and systemic levels of inflammatory cytokines, this finding could indicate an ability of the porcine lung to compartmentalize the local inflammatory response and thus restrict systemic contribution.

[Evaluation of cytokine levels and pulmonary function in patients undergoing coronary artery bypass graft]

BACKGROUND AND OBJECTIVES

Systemic inflammatory response syndrome is commonly observed in coronary artery bypass grafts (CABG) with cardiopulmonary bypass (CB). The objective of this study was to evaluate the systemic and pulmonary levels of cytokines and their correlation with lung function in patients undergoing myocardial revascularization (MR) with CB.

METHODS

This study was approved by the Institutional Ethics Committee, and 13 patients undergoing MR with CB were evaluated. After anesthetic induction and at the end of CB, plasma and bronchoalveolar lavage levels of IL-1β, IL-6, IL-8, IL-10, and TNF-α were determined. The duration of CB and surgery, PaO(2)/FiO(2) ratio, alveolar-arterial oxygen gradient (A-a gradient), shunt, and lung compliance were evaluated. Results were submitted to analysis of variance for repeated measurements (*p < 0.05) and Spearman's correlation coefficient.

RESULTS

We observed increased levels of cytokines in plasma and bronchoalveolar lavage after CB and a direct relationship between the increase in IL-1β and decrease in lung compliance (p = 0.0439), as well as the inverse relationship between the increase in IL-10 and a decrease in compliance (p = 0.0325). The increase in IL-6 was directly related to the duration of CB (p = 0.012), while the increase in IL-8 was directly related to the duration of surgery (p < 0.0001). Levels of interleukin-1β, IL-8, and TNF-α in bronchoalveolar lavage were higher than in plasma.

CONCLUSIONS

There is an increase in cytokine levels in plasma and bronchoalveolar lavage after CB, as well as a correlation between increased cytokine levels and CB duration and surgery and changes in lung compliance.

Methylprednisolone Fails to Preserve Pulmonary Surfactant and Blood–Air Barrier Integrity in a Porcine Cardiopulmonary Bypass Model

BACKGROUND

Pulmonary inflammation after cardiac surgery with cardiopulmonary bypass (CPB) has been linked to respiratory dysfunction and ultrastructural injury. Whether pretreatment with methylprednisolone (MP) can preserve pulmonary surfactant and blood-air barrier, thereby improving pulmonary function, was tested in a porcine CPB-model.

MATERIALS AND METHODS

After randomizing pigs to placebo (PLA; n = 5) or MP (30 mg/kg, MP; n = 5), animals were subjected to 3 h of CPB with 1 h of cardioplegic cardiac arrest. Hemodynamic data, plasma tumor necrosis factor-alpha (TNF-alpha, ELISA), and pulmonary function parameters were assessed before, 15 min after CPB, and 8 h after CPB. Lung biopsies were analyzed for TNF-alpha (Western blot) or blood-air barrier and surfactant morphology (electron microscopy, stereology).

RESULTS

Systemic TNF-alpha increased and cardiac index decreased at 8 h after CPB in PLA (P < 0.05 versus pre-CPB), but not in MP (P < 0.05 versus PLA). In both groups, at 8 h after CPB, PaO2 and PaO2/FiO2 were decreased and arterio-alveolar oxygen difference and pulmonary vascular resistance were increased (P < 0.05 versus baseline). Postoperative pulmonary TNF-alpha remained unchanged in both groups, but tended to be higher in PLA (P = 0.06 versus MP). The volume fraction of inactivated intra-alveolar surfactant was increased in PLA (58 +/- 17% versus 83 +/- 6%) and MP (55 +/- 18% versus 80 +/- 17%) after CPB (P < 0.05 versus baseline for both groups). Profound blood-air barrier injury was present in both groups at 8 h as indicated by an increased blood-air barrier integrity score (PLA: 1.28 +/- 0.03 versus 1.70 +/- 0.1; MP: 1.27 +/- 0.08 versus 1.81 +/- 0.1; P < 0.05).

CONCLUSION

Despite reduction of the systemic inflammatory response and pulmonary TNF-alpha generation, methylprednisolone fails to decrease pulmonary TNF-alpha and to preserve pulmonary surfactant morphology, blood-air barrier integrity, and pulmonary function after CPB.

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.

Insulin alters cytokine content in two pivotal organs after brain death: a porcine model

BACKGROUND

To optimize the quantity and quality of organs available for transplantation, it is crucial to gain further insight into the treatment of brain dead organ donors. In the current study we hypothesized that insulin treatment after brain death alters cytokine content in the heart, liver, and kidney.

METHODS

Sixteen brain dead pigs (35-40 kg) were treated with either (1) no insulin [brain dead without insulin treatment treatment (BD)], or (2) insulin infusion intravenously (i.v.) at a constant rate of 0.6 mU/kg/min during 360 min [brain dead with insulin treatment (BD+I)]. Blood glucose was clamped at 4.5 mmol/l by infusion of 20% glucose. Blood samples for insulin, glucose, catecholamines, free fatty acids, and glucagon were obtained during the experimental period. Six hours after brain death biopsies were taken from the heart, liver, and kidney. These were analyzed for cytokine mRNA and proteins [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, and IL-10].

RESULTS

The BD+I compared with the BD animals had lower IL-6 concentrations in the right ventricle of the heart (P=0.001), in the renal cortex (P=0.04) and in the renal medulla (P=0.05), and lower IL-6 mRNA in the renal medulla (P=0.0002). Furthermore, the BD+I animals had lower concentrations in the renal medulla of IL-10 (P=0.01), and tended to have lower TNF-alpha in the renal cortex (P=0.06) than the BD animals. In the right ventricle of the heart TNF-alpha mRNA and IL-10 mRNA were higher in the BD+I than in the BD group (P=0.002 and 0.004).

CONCLUSION

Insulin has anti-inflammatory effects on cytokine concentration in the heart and kidney after brain death.

Risk factors for acute renal failure requiring dialysis after surgery for congenital heart disease in children

BACKGROUND

Limited data exist on the risk factors for acute renal failure (ARF) following cardiac surgery in children with congenital heart disease. This cohort study was conducted to examine this subject, as well as changes in the incidence of ARF from 1993 to 2002, the in-hospital mortality and the time spent in the intensive care unit (ICU).

METHODS

One thousand, one hundred and twenty-eight children, operated on for congenital heart disease between 1993 and 2002, were identified from our prospectively collected ICU database to obtain data on potential risk factors.

RESULTS

A total of 130 children (11.5%) developed ARF after surgery. A young age [> or =1.0 vs. <0.1 year; odds ratio (OR), 0.23; 95% confidence interval (CI), 0.12-0.46], high Risk Adjusted Classification of Congenital Heart Surgery (RACHS-1) score (OR, 2.72; 95% CI, 1.66-4.45) and cardiopulmonary bypass (CPB) (<90 min vs. none; OR, 2.68; 95% CI, 1.03-6.96; > or =90 min vs. none; OR, 12.94; 95% CI, 5.46-30.67) were independent risk factors for ARF. The risk of ARF decreased during the study period. Children with ARF spent a significantly longer time in the ICU (2-7 days vs. <2 days, P = 0.002; > or =7 days vs. <2 days, P < 0.001) compared with non-ARF patients, and showed increased in-hospital mortality (20% vs. 5%, P < 0.001).

CONCLUSION

A young age, high RACHS-1 score and CPB were independent risk factors for ARF after surgical procedures for congenital heart disease in children. The risk of ARF decreased during the study period. Children with severe ARF spent a longer time in the ICU, and the mortality in ARF patients was higher than that in non-ARF patients.

Oxygenation and release of inflammatory mediators after off-pump compared with after on-pump coronary artery bypass surgery

BACKGROUND

In a previous study, we showed that oxygenation was impaired for up to 5 day after conventional coronary artery bypass grafting (CABG). As cardiopulmonary bypass (CPB) may have a detrimental effect on pulmonary function, we hypothesized that coronary revascularization grafting without the use of CPB (OPCAB) would affect post-operative oxygenation and release of inflammatory mediators less compared with CABG.

METHODS

Low-risk patients scheduled for elective coronary revascularization were randomly assigned to one of two groups (CABG, n = 17 or OPCAB, n = 18). Two parameters of oxygenation, shunt (%) and ventilation-perfusions mismatch, described as DeltaPO(2) (kPa), were estimated for up to 5 days post-operatively. Systemic release of interleukin (IL)-6, -8 and -10, C-reactive protein (CRP) and neutrophils were measured in peripheral blood samples for up to 3 days post-operatively. The lungs participation in the cytokine response was evaluated from mixed venous blood samples taken within the first 16 h post-operatively.

RESULTS

OPCAB was followed by a higher shunt (P = 0.047), with no difference (P = 0.47) in the deterioration of DeltaPO(2) between the groups. OPCAB was followed by an attenuated systemic release of IL-8 (P = 0.041) and IL-10 (P = 0.006), while the release of IL-6 (P = 0.94), CRP (P = 0.121) and neutrophils (P = 0.078) did not differ between the groups. Indications of an uptake of cytokines in the lungs were found after OPCAB.

CONCLUSIONS

When comparing OPCAB with CABG, oxygenation was more affected and only part of the systemic inflammatory response was attenuated.

Induction of tumor necrosis-alpha, p38 and JNK in the spinal cord following acute heart injury in the rat model

BACKGROUND

It is still not known whether the spinal cytokine signaling pathways are involved in the pathophysiologic mechanism of the acute phase of heart disease. This study examines the expression pattern of tumor necrosis factor-alpha (TNF-alpha) and its two related mitogenic-activated protein kinases, p38 and Jun-N-terminal kinase (JNK), in the spinal cord in response to acute cardiac injury (ACI).

METHODS

The ACI rat model was established by intra-myocardial injection of formalin. At the indicated times after the establishment of ACI, the thoracic segments of the spinal cord were harvested and Western blot was performed to determine the expression of TNF-alpha, p38 and JNK. The localization of the cytokine and the kinases was determined by immunohistochemistry and double immunofluorescence.

RESULTS

In response to ACI, TNF-alpha protein was up-regulated and reached a peak level at 6 h after ACI. The up-regulated TNF-alpha was distributed in all the laminae in the spinal cord and mainly localized in the neurons, as determined by immunohistochemistry and double immunofluorescence. In response to ACI, p38 and JNK were also up-regulated in the spinal cord. The expression profiles of p38 and JNK were similar to that of activated TNF-alpha following ACI.

CONCLUSIONS

This study shows that cardiac injury can induce the activation of spinal TNF-alpha, p38 and JNK. The activated spinal cytokine signaling may contribute to disease progression in the acute phase of cardiac injury in clinical practice.

Procedure-induced Inflammation and Endothelial Cell Activation in an Artificially Ventilated and Circulated Porcine Double-Lung Model

Systemic inflammation is induced during extracorporeal circulation, resulting in an increased bleeding tendency and endothelial cell activation. Lungs from seven piglets were perfused by autologous blood in an extracorporeal circuit, where the lungs and the left atrium were attached to polyvinyl chloride (PVC) tubings and the blood circulated by a roller pump. The trachea was intubated and attached to a ventilator. The lungs maintained good gas exchange, despite a slight increase in lactate levels. Plasma tPA increased slightly over time, suggesting endothelial cell activation. Activation of inflammatory systems was reflected in increased levels of plasma interleukin (IL)-6 and IL-10. A model for the study of lung endothelial activation during extracorporeal circulation has been shown to be reproducible. The lung tissue was shown to be capable of gas exchange and activation of endothelial cells and procedure-induced inflammation were noted.

Interleukin-10 and its role in clinical immunoparalysis following pediatric cardiac surgery

OBJECTIVE

A systemic insult is associated with subsequent hyporesponsiveness to endotoxin (as measured by ex vivo tumor necrosis factor [TNF]-alpha production) and an increased risk of late nosocomial infection in some patients. When combined with low monocyte surface major histocompatibility complex class II expression, this state of altered host defense is now commonly referred to as immunoparalysis. This study was undertaken to delineate the relationship between observed levels of the anti-inflammatory cytokine interleukin-10, common genetic polymorphisms that influence these levels, and the occurrence and severity of endotoxin hyporesponsiveness in children following elective cardiac surgery requiring cardiopulmonary bypass.

DESIGN

A prospective observational clinical study.

SETTING

A tertiary pediatric cardiac center.

PATIENTS

Thirty-six infants and children <2 yrs of age undergoing elective cardiac surgery requiring cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We investigated the production of TNF-alpha, interleukin-6, interleukin-8, interleukin-1 receptor antagonist, and interleukin-10 in whole blood in response to lipopolysaccharide (Neisseria meningitides 10 ng/mL) in samples drawn before, during, and up to 48 hrs after surgery. Patients were genotyped for the -1082, -819, and -592 interleukin-10 promoter polymorphisms. Whole blood cytokine response to lipopolysaccharide was reduced postoperatively to </=50% of preoperative levels for all cytokines measured. Stimulated cytokine production was lowest in cases with the highest postoperative plasma interleukin-10 levels, which were in turn associated with the GCC haplotype. Those patients in whom the whole blood response to endotoxin was maintained (TNF-alpha >100 pg/mL) over the first 48 hrs were more likely to have an uncomplicated short stay (odds ratio 4.7, 95% confidence interval 1-22).

CONCLUSIONS

Immediately following cardiac surgery, many children become relatively refractory to lipopolysaccharide stimulation. This immunoparalysis appears to be related in part to high circulating levels of interleukin-10 and places these patients at increased risk of postoperative complications. Interleukin-10 genotype may be a risk factor for immunoparalysis.

Tumor necrosis factor-alpha and interleukin-10 gene expression in peripheral blood mononuclear cells after cardiac surgery

OBJECTIVE

Cytokine response after cardiac surgery may be genetically influenced. A study was carried out to investigate the relation between cytokine gene expression in peripheral blood mononuclear cells, genotype, and clinical events after cardiac surgery.

DESIGN

A case-control study was performed.

SETTING

Cardiac intensive care unit in a university hospital.

SUBJECTS

A total of 82 patients having elective cardiac surgery were divided into those having uncomplicated recovery (n = 48) or recovery complicated by hyperlactatemia or requirement for inotropic support (n = 34).

INTERVENTIONS

The relative change in peripheral blood mononuclear cell tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) messenger RNA 1 and 6 hrs after cardiopulmonary bypass was compared with a baseline preoperative level using quantitative reverse transcriptase polymerase chain reaction. DNA was analyzed for carriage of TNF-alpha and IL-10 polymorphic alleles.

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary bypass was longer in duration in the complicated group. TNF-alpha gene expression decreased and IL-10 gene expression increased in peripheral blood mononuclear cells after surgery when compared with preoperative levels. One hour after cardiopulmonary bypass, the complicated group had more TNF-alpha and less IL-10 messenger RNA production than the uncomplicated group. The IL-10/TNF-alpha ratio was greater in uncomplicated than in complicated recovery patients. An IL-10 haplotype was identified that was less frequent in the complicated group. There was no difference between groups in TNF-alpha genotype. On multivariate analysis, cardiopulmonary bypass time and the IL-10/TNF-alpha messenger RNA ratio were independent predictors of outcome.

CONCLUSIONS

There is a predominant anti-inflammatory cytokine response after uneventful cardiac surgery. IL-10 may have a protective role after cardiac surgery.

Gene expression of pulmonary cytokines after sevoflurane or thiopentone anaesthesia in pigs

BACKGROUND

Volatile anaesthetics have diverse inflammatory effects on the lungs. They increase gene expression of some pro-inflammatory cytokines in alveolar macrophages whereas in alveolar type II cells they seem to decrease secretion and gene expression of pro-inflammatory cytokines. We have previously detected increased leukotriene C4, nitrate and nitrite concentrations in bronchoalveolar lavage fluid after sevoflurane anaesthesia. In the current study, we measured gene expression of inflammatory cytokines in the lung tissue and plasma concentrations of cytokines in pigs after thiopentone or sevoflurane anaesthesia.

METHODS

Sixteen pigs were randomly selected to receive either a continuous thiopentone infusion (control group, n = 8) or sevoflurane (n = 8) at 4.0% inspiratory concentration (1.5 MAC) in air for 6 h. Tissue samples were collected at the end of the study for measurement of gene expression of inflammatory cytokines. Blood samples were collected during anaesthesia for measurement of plasma cytokine concentrations.

RESULTS

Compared with thiopentone anaesthesia, lower gene expression of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in lung tissue was observed after sevoflurane anaesthesia. Of measured cytokines IL-1beta, TNF-alpha, IL-6, IL-8 and IL-10 only plasma concentrations of IL-6 could be measured during the study without a difference between the groups.

CONCLUSION

Lower gene expression of TNF-alpha and IL-1beta was found in the intact porcine lung tissue after sevoflurane anaesthesia compared with thiopentone anaesthesia. Clinical significance of this finding is unknown.

Evidence that acute hyperinsulinaemia increases the cytokine content in essential organs after an endotoxin challenge in a porcine model

BACKGROUND

Insulin has anti-inflammatory effects, as evaluated by its ability to reduce the plasma concentrations of cytokines. However, the inflammatory processing at the organ level is far less well established. The cytokine content in several organs after endotoxin (lipopolysaccharide, LPS) exposure and the effect of hyperinsulinaemia was examined.

METHODS

Pigs (35-40 kg) were randomized into four groups, anaesthetized and mechanically ventilated for 570 min: group 1 (anaesthesia only; n = 10), group 2 (hyperinsulinaemic euglycaemic clamp, HEC; n = 9), group 3 (LPS; n = 10) and group 4 (LPS + HEC; n = 9). LPS was infused intravenously for 180 min (total dosage, 10 microg/kg). At the end of the study, i.e. 330 min after the termination of LPS or equivalent, cytokine mRNA and cytokine protein contents in the lungs, heart, liver, adipose tissue and spleen were measured.

RESULTS

Hyperinsulinaemia led to increased interleukin-10 (IL-10) protein content in the heart and liver (by 40% and 28%, respectively) in comparison with normoinsulinaemic animals (P < 0.01 and P = 0.02, respectively), and increased tumour necrosis factor-alpha (TNF-alpha) protein content in the heart (P = 0.02). Animals exposed to LPS exhibited reduced TNF-alpha, IL-6 and IL-8 protein content in the heart (P = 0.02, P < 0.001 and P = 0.01, respectively). In the kidneys and adipose tissue, a particularly large cytokine protein content was observed.

CONCLUSION

The findings strongly substantiate the role of insulin as an immune-modifying hormone at organ level during baseline and after an endotoxin challenge. Moreover, the kidneys and adipose tissue appear to be pivotal organs in terms of cytokine content shortly after endotoxin exposure, but the complexity remains to be clarified.

Inflammatory response during hyperglycemia and hyperinsulinemia in a porcine endotoxemic model: the contribution of essential organs

BACKGROUND

During euglycemia acute hyperinsulinemia diminishes the cytokine response to endotoxin [Lipopolysaccharide (LPS)] exposure. In this study we elucidated whether acute hyperglycemia and hyperinsulinemia modify the cytokine content in several organs during LPS challenge in a porcine model.

METHODS

Pigs (35-40 kg) were randomized to either normoglycemia (group 1, n = 8) or hyperglycemia and hyperinsulinemia (group 2, n = 8), anesthetized and mechanically ventilated. Both groups received a 180-min intravenous infusion of LPS (total 10 microg kg(-1)). Groups 1 and 2 were clamped at plasma glucose concentrations of 5 mM and 15 mM, respectively. Group 1 maintained a baseline insulin level while the hyperglycemic group exhibited increased insulin levels.

RESULTS

Circulating cytokines, cytokine mRNA and cytokine protein content were examined in the heart, liver, kidneys, lungs, spleen, adipose and muscle tissue. After LPS exposure, in both groups vast and equal plasma cytokines were elicited by approximately 70-5000-fold. A 10-fold higher level of IL-10, IL-6 and TNF-alpha protein was found in kidney tissue compared to the other organs together with a 3-10-fold increase of TNF-alpha in adipose tissue. However, cytokine mRNAs as well as organ function were without statistical difference between the groups.

CONCLUSION

Endotoxemia elicited a pronounced cytokine response in both plasma and at organ level. The kidneys and adipose tissue showed the highest cytokine protein content. Acute hyperglycemia apparently counteracts the well-established anti-inflammatory effects of insulin on the inflammatory response in a LPS challenged porcine model. Whether the observation can be extrapolated to more long-term stress-exposure remains to be clarified.

Periventricular leukomalacia following neonatal and infant cardiac surgery

The dramatic reduction in surgical mortality following repair of congenital heart defects has been accompanied by increasing recognition of adverse neurodevelopmental sequelae in some children. Neurodevelopmental abnormalities following neonatal and infant cardiac surgery include mild cognitive impairment, expressive speech and language abnormalities, impaired attention and executive function, impaired visual and spatial motor skills, as well as learning disabilities. These defects result in a significant need for early intervention, as well as rehabilitative and special education services. Central nervous system injury following repair of congenital heart defects results from a complex interaction of patient specific and environmental factors. Recent studies suggest that cerebral white matter injury characterized by periventricular leukomalacia (PVL) is common in infants with congenital heart disease particularly following cardiac surgery. Studies at our institution show that this occurs in greater than 50% of neonates following cardiac surgery, but is rare in older infants. Prolonged exposure to cardiopulmonary bypass (with or without deep hypothermic circulatory arrest) is a risk factor for PVL, possibly secondary to the systemic inflammatory response to cardiopulmonary bypass. Hypotension and hypoxemia in the early postoperative period, especially diastolic hypotension, significantly increase the risk of PVL. Future studies are needed to determine significance of PVL as a marker for long-term developmental dysfunction.

Inflammatory response to cardiac surgery: cardiopulmonary bypass versus non-cardiopulmonary bypass surgery

Cardiac surgery has been routinely performed using cardiopulmonary bypass (CPB) ever since its clinical introduction during the 1950s. CPB is, however, associated with an intense inflammatory response because of conversion to laminar flow, blood contact with the artificial bypass surface, cold cardiac ischaemia and hypothermia. The inflammatory reaction can intensify to a systemic inflammatory response syndrome (SIRS) associated with serious morbidity and mortality. Strategies to suppress inflammation had some success but fell short of controlling SIRS. The development of cardiac immobilization techniques allowing complete revascularization has caused a renaissance of coronary artery bypass grafting surgery on the beating heart (OPCAB). This strategy avoids all inflammation caused by CPB and reduces the pro-inflammatory stimulus to sternotomy and the revascularization procedure itself. This review summarises the pathophysiological features of the inflammatory response to CPB, revisits therapeutic anti-inflammatory strategies designed to suppress CPB-induced inflammation and balances the clinical evidence available comparing off-pump and on-pump revascularization.

THE ANTI-INFLAMMATORY EFFECT OF DIAZOXIDE IN CORONARY ARTERY BYPASS GRAFTING

Many therapeutic strategies have been designed to suppress the inflammatory response in patients undergoing coronary artery bypass grafting (CABG). Pharmacological preconditioning with diazoxide is an alternative in effective cardioprotective strategies, but more evidence is required to show its effect on the inflammatory response. Forty patients with stable angina who were scheduled for isolated elective CABG operations were randomized into control and diazoxide (DZX) groups. In the DZX group, 1.5 mg/kg diazoxide was infused intravenously in 5 min followed by a 5-min washout before commencing the cardiopulmonary bypass. In the control group, placebo infusion was given similarly. Blood samples for cytokine measurement were collected from the radial artery and coronary sinus perioperatively, and hemodynamic data were recorded. Thirty-six patients fulfilled the data collection. Cardiac index (CI) increased in both groups over time as compared with baseline. In the DZX group, the increase of CI was greater than that in the control group (P = 0.002). Systemic and coronary sinus plasma levels of IL-6, IL-8, and IL-10 increased significantly after reperfusion in both groups as compared with baseline (P < 0.05). IL-6 and IL-8 both reached the peak value at 6 h after cardiopulmonary bypass. IL-10 reached peak level at 20 min after reperfusion in both groups. There was significantly higher IL-10 in DZX groups (P = 0.015). The ratios of IL-6 to IL-10 and IL-8 to IL-10 were significantly lower in DZX groups than in controls (P = 0.025 and P = 0.041 for each, respectively). Pharmacological preconditioning with DZX in CABG patients shifts the circulating inflammatory cytokine balance toward the anti-inflammatory direction.

Glucocorticoids reduce cardiac dysfunction after cardiopulmonary bypass and circulatory arrest in neonatal piglets

OBJECTIVE

The hypotheses were that glucocorticoid administration could improve ventricular recovery by reducing cardiopulmonary bypass (CPB)-induced inflammatory response and that presurgical administration might be more effective than intraoperative dosing.

DESIGN

Animal case study.

SUBJECTS

Crossbred piglets (5-7 kg).

INTERVENTIONS

Piglets were cooled with CPB, followed by 120 mins of deep hypothermic circulatory arrest (DHCA). Animals were rewarmed to 38 degrees C, removed from CPB, and maintained for 120 mins. Methylprednisolone (60 mg/kg) was administered in the CPB pump prime (intraoperative glucocorticoid [intraop GC]) or 6 hrs before CPB (30 mg/kg) in addition to the intraoperative dose (30 mg/kg; pre- and intraop GC). Controls (no GC) received saline.

MEASUREMENTS AND MAIN RESULTS

In no GC, left ventricle (LV) positive change in pressure in time (+dP/dt) (mm Hg/sec) had a mean +/- SD of 1555 +/- 194 at baseline vs. 958 +/- 463 at 120 mins after CPB, p=.01). LV +dP/dt was maintained in glucocorticoid-treated animals (1262 +/- 229 at baseline vs. 1212 +/- 386 in intraop GC and 1471 +/- 118 vs. 1393 +/- 374 in pre-intraop GC). Glucocorticoids reduced myocardial interleukin-6 messenger RNA expression, measured by ribonuclease protection assay, at 120 mins after CPB compared with animals receiving saline (p<.05), although interleukin-6 plasma and LV protein concentrations were not affected. Interleukin-10 myocardial protein concentrations were elevated after CPB-DHCA with higher concentrations in glucocorticoid-treated animals (p<.05). Glucocorticoid treatment maintained myocardial concentrations of the inhibitor of nuclear factor-kappaB in the cytosol and decreased nuclear factor-kappaB concentrations detected in the nucleus in a DNA/protein interaction array.

CONCLUSIONS

Glucocorticoids improved recovery of LV systolic function in neonatal animals undergoing CPB-DHCA. Animals receiving glucocorticoids before CPB had better postoperative oxygen delivery than those receiving only intraoperative treatment. Maintenance of cardiac function after glucocorticoids might be due, in part, to alterations in the balance of pro- and anti-inflammatory proteins, possibly through nuclear factor-kappaB-dependent pathways.