Managing the inflammatory response after cardiopulmonary bypass: review of the studies in animal models

Remimazolam inhibits postoperative cognitive impairment after cardiopulmonary bypass by alleviating neuroinflammation and promoting microglia M2 polarization

Postoperative cognitive impairment (POCD) is a complication of cardiopulmonary bypass (CPB). Remimazolam is an ultra-short acting benzodiazepine that can be used for anesthesia or sedation during surgery. This study investigated the role of remimazolam in inflammasome activation and microglia polarization using CPB rat model and lipopolysaccharide (LPS)-induced microglia model. The cognitive function of rats was evaluated by Morris water maze. TUNEL assay was performed to detect apoptosis. Inflammatory cytokines concentration were analyzed by enzyme-linked immunosorbent assay. Reverse transcription-polymerase chain reaction was used to assess the expression of inflammasome and M1/M2-related microglia markers. Flow cytometry was performed to evaluate the expression of CD16/32 and CD206 in microglia. The results showed that remimazolam improved the memory and learning abilities in CPB rats. CPB rats and LPS-treated microglia showed increased apoptosis, pro-inflammatory cytokines level, and inflammasome expression as well as decreased microglia activation, while the results were reversed after remimazolam treatment. Besides, remimazolam treatment promoted the expression of M2-related markers in LPS-treated microglia. Nigericin treatment reversed the increased M2-related mRNA levels and the decreased apoptosis and inflammatory responses induced by remimazolam treatment. In conclusion, remimazolam attenuated POCD after CPB through regulating neuroinflammation and microglia M2 polarization, suggesting a new insight into the clinical treatment of POCD after CPB.

Does remote ischemic preconditioning affect the systemic inflammatory response by modulating presepsin levels?

OBJECTIVE

We investigated the effect of Remote Ischemic Preconditioning (RIPC) on the inflammatory response during CPB by means of serum presepsin levels at preoperative and postoperative 1st and 24th h.

METHODS

In this prospective, randomized, cross-sectional study we included 81 patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass (CPB). Patients were randomized and RIPC was applied to 40 patients in the study group before anesthesia. The remaining 41 patients were determined as the control group. The relationships between RIPC and factors such as presepsin, C-reactive protein (CRP), and leukocyte levels were investigated.

RESULTS

There was no significant difference between the groups in postoperative leukocyte and CRP values (p = 0.52, p = 0.13, respectively). When the preoperative and postoperative first hour presepsin values of the patients were compared, no significant difference was found in the control group (p = 0.17), but a significant difference was found in the study group (p < 0.05). When the presepsin values were compared between the groups, a significant difference was found only in the postoperative first hour value (p < 0.05).

CONCLUSIONS

It was observed that RIPC application caused to increase the presepsin levels in the postoperative first hour significantly in the study group (p < 0.05).

Plasma S100β and neuron-specific enolase, but not neuroglobin, are associated with early cognitive dysfunction after total arch replacement surgery: A pilot study

To investigate whether plasma concentrations of S100β protein, neuron-specific enolase (NSE), and neuroglobin (NGB) correlate with early postoperative cognitive dysfunction (POCD) in patients undergoing total arch replacement.This prospective study analyzed 40 patients who underwent total arch replacement combined with stented elephant trunk implantation at our hospital between March 2017 and January 2019. Cognitive function was assessed using the Mini-mental State Examination (MMSE) preoperatively, on the day after extubation and on day 7 after surgery. Plasma levels of S100β, NSE, and NGB POCD were assayed preoperatively and at 1, 6, and 24 hours after cardiopulmonary bypass. POCD was defined as a decrease of at least 1 unit in the MMSE score from before surgery until day 7, and patients were stratified into those who experienced POCD or not. The 2 groups were compared in clinicodemographic characteristics and plasma levels of the 3 proteins.Plasma levels of all 3 biomarkers increased significantly during and after cardiopulmonary bypass. Levels of S100β and NSE, but not NGB, were significantly higher in the 15 patients who showed POCD than in the remainder who did not. For prediction of early POCD, S100β showed an area under the receiver operating characteristic curve (AUC) of 0.71 (95% confidence interval [CI] 0.55-0.87), sensitivity of 48%, and specificity of 87%. The corresponding values for NSE were 0.77 (95%CI 0.60-0.94), 92%, and 67%. Together, S100β and NSE showed an AUC of 0.81 (95%CI 0.66-0.96), sensitivity of 73%, and specificity of 80%. NGB did not significantly predict early POCD (AUC 0.62, 95%CI 0.43-0.80).Plasma S100β protein and NSE, but not NGB, may help predict early POCD after total arch replacement.

Toll-like receptor 9 and the inflammatory response to surgical trauma and cardiopulmonary bypass

Objectives

Cardiac surgery can lead to post-operative end-organ complications secondary to activation of systemic inflammatory response. We hypothesize that surgical trauma or cardiopulmonary bypass (CPB) may initiate systemic inflammatory response via release of mitochondrial DNA (mtDNA) signaling Toll-like receptor 9 (TLR9) and interleukin-6 production (IL-6).

Materials and methods

The role of TLR9 in systemic inflammatory response in cardiac surgery was studied using a murine model of sternotomy and a porcine model of sternotomy and CPB. mtDNA and IL-6 were measured with and without TLR9-antagonist treatment. To study ischemia-reperfusion injury, we utilized an ex-vivo porcine kidney model.

Results

In the rodent model (n = 15), circulating mtDNA increased 19-fold (19.29 ± 3.31, p < 0.001) and plasma IL-6 levels increased 59-fold (59.06 ± 14.98) at 1-min post-sternotomy compared to pre-sternotomy. In the murine model (n = 11), administration of TLR-9 antagonists lowered IL-6 expression post-sternotomy when compared to controls (59.06 ± 14.98 vs. 5.25 ± 1.08) indicating that TLR-9 is a positive regulator of IL-6 after sternotomy. Using porcine models (n = 10), a significant increase in circulating mtDNA was observed after CPB (Fold change 29.9 ± 4.8, p = 0.005) and along with IL-6 following renal ischaemia-reperfusion. Addition of the antioxidant sulforaphane reduced circulating mtDNA when compared to controls (FC 7.36 ± 0.61 vs. 32.0 ± 4.17 at 60 min post-CPB).

Conclusion

CPB, surgical trauma and ischemic perfusion injury trigger the release of circulating mtDNA that activates TLR-9, in turn stimulating a release of IL-6. Therefore, TLR-9 antagonists may attenuate this response and may provide a future therapeutic target whereby the systemic inflammatory response to cardiac surgery may be manipulated to improve clinical outcomes.

Evaluation of Inflammation Caused by Cardiopulmonary Bypass in a Small Animal Model

Extracorporeal circulation (ECC) methods are being increasingly used for mechanical support of respiratory and cardio-circulatory failure. Especially, cardiopulmonary bypass (CPB) during cardiovascular surgery, sustenance of the patient’s life by providing an appropriate blood flow and oxygen supply to principal organs. On the other hand, systemic inflammatory responses in patients undergoing cardiovascular surgery supported by CPB contribute significantly to CPB-associated mortality and morbidity. Our previous research showed that CPB causes a systemic inflammatory response and organ damage in a small animal CPB model. We have been studying the effects of hyperoxia and blood plasma substitute on CPB. In this review, we present a study focusing on the systemic inflammatory response during CPB, along with our findings.

PaO2 greater than 300 mmHg promotes an inflammatory response during extracorporeal circulation in a rat extracorporeal membrane oxygenation model

Background

Extracorporeal membrane oxygenation (ECMO) is being increasingly used for mechanical support of respiratory and cardio-circulatory failure. An excessive systemic inflammatory response is observed during sepsis and after cardiopulmonary bypass (CPB) with similar clinical features. We hypothesized that hyperoxia condition encourages the systemic inflammatory response and organ disorder during ECMO. To prove this hypothesis correct, we investigated the systemic inflammatory responses at normal and high levels of arterial oxygen pressure (PaO₂) in the rat ECMO model.

Methods

Rats were randomly assigned to one of the following groups depending on the value of PaO₂ during ECMO: A group (n=11, PaO₂ 100–199 mmHg), B group (n=10, PaO₂ 200–299 mmHg), C group (n=8, PaO₂ 300–399 mmHg), and D group (n=11, PaO₂ >400 mmHg). Serum cytokine levels [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10)] were measured before, 60, and 120 min after the initiation of ECMO. The wet-to-dry weight (W/D) ratio of the left lung was also measured, and dihydroethidium (DHE) staining, reflecting superoxide generation, of lung and liver tissues was performed 120 min after ECMO initiation.

Results

In the C and D groups, the pro-inflammatory cytokines (TNF-α and IL-6) significantly increased during ECMO compared with the other groups. On the other hand, the increase in anti-inflammatory cytokines (IL-10) was more suppressed in the C and D groups than in the other groups. The W/D ratio increased significantly more in the C and D groups than in the other groups. In addition, DHE fluorescence had a tendency to increase as the PaO₂ rose.

Conclusions

These data demonstrate that it is better to avoid administration of too much oxygen during ECMO to attenuate lung injury linked to generation of superoxide and the systemic inflammatory response.

Extracorporeal life support and systemic inflammation

Extracorporeal life support (ECLS) encompasses a wide range of extracorporeal modalities that offer short- and intermediate-term mechanical support to the failing heart or lung. Apart from the daily use of cardiopulmonary bypass (CPB) in the operating room, there has been a resurgence of interest and utilization of veno-arterial and veno-venous extracorporeal membrane oxygenation (VA- and VV-ECMO, respectively) and extracorporeal carbon dioxide removal (ECCO₂R) in recent years. This might be attributed to the advancement in technology, nonetheless the morbidity and mortality associated with the clinical application of this technology is still significant. The initiation of ECLS triggers a systemic inflammatory response, which involves the activation of the coagulation cascade, complement systems, endothelial cells, leukocytes, and platelets, thus potentially contributing to morbidity and mortality. This is due to the release of cytokines and other biomarkers of inflammation, which have been associated with multiorgan dysfunction. On the other hand, ECLS can be utilized as a therapy to halt the inflammatory response associated with critical illness and ICU therapeutic intervention, such as facilitating ultra-protective mechanical ventilation. In addition to addressing the impact on outcome of the relationship between inflammation and ECLS, two different but complementary pathophysiological perspectives will be developed in this review: ECLS as the cause of inflammation and ECLS as the treatment of inflammation. This framework may be useful in guiding the development of novel therapeutic strategies to improve the outcome of critical illness.

Tadalafil: Protective Action against the Development of Multiple Organ Failure Syndrome

Introduction

Multiple organ failure syndrome (MOFS) is a pathology associated to unspecified and severe trauma, characterized by elevated morbidity and mortality. The complex inflammatory MOFS-related reactions generate important ischemia-reperfusion responses in the induction of this syndrome. Nitric oxide elevation, through the activation of cyclic guanosine monophosphate (cGMP), has the potential of counteracting the typical systemic vasoconstriction, and platelet-induced hypercoagulation. Tadalafil would possibly act protectively by reducing cGMP degradation with consequent diffuse vasodilatation, besides reduction of platelet-induced hypercoagulation, thus, preventing multiple organ failure syndrome development.

Methods

The experimental protocol was previously approved by an institution animal research committee. Experimental MOFS was induced through the stereotaxic micro-neurosurgical bilateral anterior hypothalamic lesions model. Groups of 10 Wistar rats were divided into:

a) Non-operated control;

b) Operated control group;

c) 2 hours after tadalafil-treated operated group;

d) 4 hours after tadalafil-treated operated group;

e) 8 hours after post-treated operated group. The animals were sacrificed 24 hours after the neurosurgical procedure and submitted to histopathologic examination of five organs: brain, lungs, stomach, kidneys, and liver.

Results

The electrolytic hypothalamic lesions resulted in a full picture of MOFS with disseminated multiple-organs lesions, provoked primarily by diffusely spread micro-thrombi. The treatment with tadalafil 2 hours after the micro-neurosurgical lesions reduced the experimental MOFS lesions development, in a highly significant level (P<0.01) of 58.75%. The treatment with tadalafil, 4 hours after the micro-neurosurgically-induced MOFS lesions, also reduced in 49.71%, in a highly significant level (P<0.01). Finally, the treatment with tadalafil 8 hours after the neurosurgical procedure resulted in a statistically significant reduction of 30.50% (P<0.05) of the experimentally-induced MOFS gravity scores.

Conclusion

The phosphodiesterase 5 inhibitor, tadalafil, in the doses and timing utilized, showed to protect against the experimentally-induced MOFS.

Aggressive re-warming at 38.5 °C following deep hypothermia at 21 °C increases neutrophil membrane bound elastase activity and pro-inflammatory factor release

Background

Cardiopulmonary bypass (CPB) is often performed under hypothermic condition. The effects of hypothermia and re-warming on neutrophil activity are unclear. This study aimed to compare the effects of different hypothermia and re-warming regimens on neutrophil membrane bound elastase (MBE) activity and the release of pro-inflammatory factors from neutrophils.

Methods

Human neutrophils were exposed to different hypothermia and re-warming regimens. MBE activity and the release of interleukin (IL)-β1, IL-6, IL-8, and tumor necrosis factor (TNF)-α were measured.

Results

Neutrophil MBE activity was significantly reduced after 60-min moderate (28 °C) or deep (21 °C) hypothermic treatment. Compared with normothermic (37 °C) re-warming, aggressive re-warming (38.5°) for 120 min following deep hypothermia (21 °C) dramatically increased neutrophil MBE activity (P < 0.05). Co-incubation of neutrophils with platelet-rich plasma further increased MBE activity significantly under all the tested temperature regimens. IL-β1 release from neutrophils was significantly higher after deep hypothermia (21 °C) followed by normothermic (37 °C) re-warming than after moderate hypothermia (28 °C) followed by normothermic re-warming (P < 0.05). Aggressive re-warming (38.5°) following deep hypothermia significantly increased the release of IL-β1, IL-8, and TNF-α from neutrophil compared with moderate re-warming (37 °C) (all P < 0.05).

Conclusion

Aggressive re-warming following deep hypothermia may contribute to CPB-associated tissue injury by increasing neutrophil MBE activity and stimulating pro-inflammatory factor release, thus, should be avoided. The optimal hypothermic temperature of CPB should be determined based on patient clinical characteristics and surgery type.

Hidrocortisona reduz as concentrações séricas dos biomarcadores inflamatórios séricos em pacientes submetidos a endarterectomia de carótida

ResumoContextoA hidrocortisona pode reduzir a concentração dos biomarcadores inflamatórios séricos e teciduais.ObjetivoAnalisar a atividade inflamatória da proteína C-reativa ultrassensível (PCR-US), do fator de necrose tumoral (FNT)-alfa e do fator de crescimento do endotélio vascular (FCEV) séricos e teciduais, mediante administração intraoperatória de hidrocortisona, após endarterectomia de artéria carótida (EAC).MétodoVinte e dois pacientes foram divididos em Grupo Controle (5 assintomáticos e 6 sintomáticos) – não foi administrada hidrocortisona – e Grupo 1 (4 assintomáticos e 7 sintomáticos) – foram administrados 500 mg intravenoso de hidrocortisona. O PCR-US, o FNT-alfa e o FCEV séricos foram dosados no pré-operatório e em 1 hora, 6 horas e 24 horas após a EAC. Na placa carotídea, mensuramos os níveis de FNT-alfa e FCEV.ResultadosO grupo 1 exibiu menor concentração sérica de FNT-alfa em 1 hora (p=0,031), 6 horas (p=0,015) e 24 horas (p=0,017) após a EAC, e menor concentração de FCEV em 1 hora (p=0,006) e 6 horas (p=0,005) após a EAC, em relação ao grupo controle. Os pacientes sintomáticos do grupo 1 exibiram menor concentração de FNT-alfa em 1 hora e 6 horas após a EAC, e menor concentração de FCEV em 1 hora após a EAC, em relação ao grupo controle. Não houve diferença estatística entre as concentrações teciduais de FNT-alfa e FCEV entre o grupo controle e o grupo 1.ConclusãoA hidrocortisona reduz as concentrações séricas pós-operatórias de FNT-alfa e FCEV, em especial nos sintomáticos; porém, não reduz os níveis teciduais destes biomarcadores.

Hydrocortisone supresses inflammatory activity of metalloproteinase-8 in carotid plaque

Objective

Matrix metalloproteinases are inflammatory biomarkers involved in carotid plaque instability. Our objective was to analyze the inflammatory activity of plasma and carotid plaque MMP-8 and MMP-9 after intravenous administration of hydrocortisone.

Methods

The study included 22 patients with stenosis ≥ 70% in the carotid artery (11 symptomatic and 11 asymptomatic) who underwent carotid endarterectomy. The patients were divided into two groups: Control Group - hydrocortisone was not administered, and Group 1 - 500 mg intravenous hydrocortisone was administered during anesthetic induction. Plasma levels of MMP-8 and MMP-9 were measured preoperatively (24 hours before carotid endarterectomy) and at 1 hour, 6 hours and 24 hours after carotid endarterectomy. In carotid plaque, tissue levels of MMP-8 and MMP-9 were measured.

Results

Group 1 showed increased serum levels of MMP- 8 (994.28 pg/ml and 408.54 pg/ml, respectively; P=0.045) and MMP-9 (106,656.34 and 42,807.69 respectively; P=0.014) at 1 hour after carotid endarterectomy compared to the control group. Symptomatic patients in Group 1 exhibited lower tissue concentration of MMP-8 in comparison to the control group (143.89 pg/ml and 1317.36 respectively; P=0.003). There was a correlation between preoperative MMP-9 levels and tissue concentrations of MMP-8 (P=0.042) and MMP-9 (P=0.019) between symptomatic patients in the control group.

Conclusion

Hydrocortisone reduces the concentration of MMP- 8 in carotid plaque, especially in symptomatic patients. There was an association between systemic and tissue inflammation.