The effect of intravenous anesthetics on ischemia-reperfusion injury

Remimazolam alleviates myocardial ischemia/reperfusion injury and inflammation via inhibition of the NLRP3/IL‑1β pathway in mice

Remimazolam (Rema) is a novel anesthetic that is widely used in anesthesia and sedation in critically ill patients. Notably, Rema exerts effects in patients through activation of the γ‑aminobutyric acid (GABA) receptor. GABA may alleviate myocardial ischemia/reperfusion (I/R) injury; however, the impact of Rema and underlying molecular mechanism in myocardial I/R injury remain to be fully understood. Therefore, the present study aimed to investigate the effects of Rema on cardiac I/R injury and to determine the underlying mechanisms. An acute myocardial I/R model was established by ligating the left anterior descending artery in adult male C57BL/6 mice (8‑10 weeks). Cultured Raw264.7 cells treated with lipopolysaccharide (LPS) were also used to investigate the effect of Rema on macrophages. The results of the present study revealed that Rema improved I/R‑induced cardiac dysfunction by increasing the ejection fraction value and reducing the myocardial infarction area. In addition, Rema also alleviated I/R‑induced cardiac inflammatory cell infiltration based on H&E and immunofluorescence staining. Transmission electron microscopy and ROS measurements showed that Rema improved I/R‑induced mitochondrial structural disruption and oxidative stress in cardiomyocytes. Transcriptomics analysis and reverse transcription‑quantitative PCR revealed that Rema alleviated I/R‑induced release of inflammatory factors and cytokines by inhibiting the expression of IL‑1β, IL‑6, C‑C chemokine receptor 2 and C‑X‑C motif chemokine ligand 5. Rema also inhibited I/R‑induced CD68+ cell proliferation, IL‑1β release, and NOD‑like receptor thermal protein domain associated protein 3 (NLRP3) and IL‑1β expression. The results of in vitro assays revealed that Rema inhibited LPS‑induced increases in IL‑1β, IL‑6 and TNF‑α expression and release in cultured RAW264.7 macrophages. In conclusion, the present study revealed that Rema may alleviate I/R‑induced cardiac dysfunction and myocardial injury by inhibiting oxidative stress and inflammatory responses via the NLRP3/IL‑1β pathway.

Efeitos hemodinâmicos e respiratórios em ovinos submetidos a quatro modalidades de ventilação e anestesiados com isoflurano ou propofol

O objetivo deste estudo foi avaliar diferentes modalidades ventilatórias em ovinos anestesiados com isoflurano ou propofol. Foram utilizadas 12 ovelhas, adultas, mestiças, com 12 meses de idade, pesando 32±5 kg, comprovadamente hígidas. Após instrumentação com os animais conscientes em decúbito lateral direito, foi administrado morfina (0,3 mg kg-1) e detomidina (20 mcg kg-1) como MPA. Foram induzidas à anestesia geral com propofol (4 mg kg-1) e intubadas. Neste momento, foram alocadas em dois grupos: PG (n=6), manutenção com infusão contínua de propofol (0,5 mg kg min-1), e IG (n=6) com anestesia inalatória com isoflurano (1,3 V%). Todas foram mantidas por 30 minutos em cada modalidade ventilatória: ventilação espontânea (VE), ventilação mecânica ciclada a volume (VV), ventilação mecânica ciclada a pressão (VP) e ventilação mecânica ciclada a pressão com PEEP (VPP). A FC e o IC foram maiores em IG e já o IRVS foi maior em PG. Os valores de hemoglobina, fração de shunt intrapulmonar e o volume corrente foram maiores no PG. Os animais apresentaram alcalose metabólica em ambos os grupos. O isoflurano promoveu maior hipotensão, diminuição da complacência pulmonar, aumento da resistência das vias aéreas, menores valores de PaO2 e maiores valores de PaCO2 em todas as modalidades ventilatórias. A VPP promoveu maior complacência pulmonar e índice de oxigenação, maiores valores de PaO2 e menores valores de shunt intrapulmonar. Conclui-se que o propofol e a VPP promoveram maior estabilidade hemodinâmica em ovelhas.

Evaluation of Electrocardiogram Parameters and Heart Rate Variability During Blood Pressure Elevation by Phenylephrine in Cirrhotic Rats

Cirrhotic cardiomyopathy is a myocardial disease that may go undetected in the early stages due to peripheral vasodilatation. The aim of the study was to evaluate the electrocardiogram (ECG) and heart rate variability (HRV) after raising blood pressure by phenylephrine injection in rats with liver cirrhosis. Twenty male Sprague-Dawley rats were divided into the Sham and common bile duct ligation (CBDL) groups. After 44 days, animals were anesthetized and the right femoral artery and vein catheterized. After a steady-state period, a bolus injection of phenylephrine (PHE, 10 μg/μl/IV, baroreflex maneuver) was followed by a slow injection of PHE (100 μg/ml/5 min/IV, sustained maneuver). Rapid and slow injections of PHE resulted in a greater increase in mean arterial pressure (MAP) and a weaker bradycardia response in the CBDL group than in the Sham group. ECG analysis showed increased QT, QTc, JT, and T peak to T end in the CBDL group, which remained unchanged after PHE injection. On the other hand, the parasympathetic indices of the HF band and RMSSD, and the sympathetic index of the LF band after PHE injection were lower in the CBDL group than in the Sham group.ECG data indicated prolonged ventricular depolarization and repolarization, independent of blood pressure levels in cirrhosis. On the other hand, after PHE injection, the parasympathetic and sympathetic components of HRV decreased, regardless of the duration of elevated blood pressure. We suggest that HRV analysis can provide a useful approach to assess cardiac dysfunction associated with elevated blood pressure in cirrhosis.

Protective Effect of Oxygen and Isoflurane in Rodent Model of Intestinal Ischemia-Reperfusion Injury

Animal research in intestinal ischemia-reperfusion injury (IRI) is mainly performed in rodent models. Previously, intraperitoneal (I.P.) injections with ketamine-xylazine mixtures were used. Nowadays, volatile anesthetics (isoflurane) are more common. However, the impact of the anesthetic method on intestinal IRI has not been investigated. We aim to analyze the different anesthetic methods and their influence on the extent of intestinal IRI in a rat model. Male Sprague-Dawley rats were used to investigate the effect of I.P. anesthesia on 60 min of intestinal ischemia and 60 min of reperfusion in comparison to hyperoxygenation (100% O₂) and volatile isoflurane anesthesia. In comparison to I.P. anesthesia with room air (21% O₂), supplying 100% O₂ improved 7-day survival by cardiovascular stabilization, reducing lactic acidosis and preventing vascular leakage. However, this had no effect on the intestinal epithelial damage, permeability, and inflammatory response observed after intestinal IRI. In contrast to I.P. + 100% O₂, isoflurane anesthesia reduced intestinal IRI by preventing ongoing low-flow reperfusion hypotension, limiting intestinal epithelial damage and permeability, and by having anti-inflammatory effects. When translating the aforementioned results of this study to clinical situations, such as intestinal ischemia or transplantation, the potential protective effects of hyperoxygenation and volatile anesthetics require further research.

Pharmacological Conditioning of the Heart: An Update on Experimental Developments and Clinical Implications

The aim of pharmacological conditioning is to protect the heart against myocardial ischemia-reperfusion (I/R) injury and its consequences. There is extensive literature that reports a multitude of different cardioprotective signaling molecules and mechanisms in diverse experimental protocols. Several pharmacological agents have been evaluated in terms of myocardial I/R injury. While results from experimental studies are immensely encouraging, translation into the clinical setting remains unsatisfactory. This narrative review wants to focus on two aspects: (1) give a comprehensive update on new developments of pharmacological conditioning in the experimental setting concentrating on recent literature of the last two years and (2) briefly summarize clinical evidence of these cardioprotective substances in the perioperative setting highlighting their clinical implications. By directly opposing each pharmacological agent regarding its recent experimental knowledge and most important available clinical data, a clear overview is given demonstrating the remaining gap between basic research and clinical practice. Finally, future perspectives are given on how we might overcome the limited translatability in the field of pharmacological conditioning.

Anti-metastatic effect of midazolam on melanoma B16F10 cells in the lungs of diabetic mice

Midazolam is an anesthetic agent commonly used for anesthesia and sedation in surgery. However, there is no information on the role of midazolam in hyperglycemia-induced cancer metastasis to date. In this study, we investigated the effects of midazolam on inhibiting metastases in the lungs of diabetic mice and on human pulmonary microvascular endothelial cells (HPMVECs). Subcutaneous injection of midazolam inhibited hyperglycemia-induced cancer metastasis in the lungs of diabetic mice. Midazolam also prevented the generation of ROS, activation of TGase, and subsequent vascular leakage in the lungs of diabetic mice. Furthermore, in vitro studies with HPMVECs confirmed that midazolam inhibited VEGF-induced intracellular events including ROS generation, TGase activation, and disruption of vascular endothelial-cadherins, thus preventing the permeability of endothelial cells. Notably, midazolam had no direct effect on the migration or proliferation of melanoma cells, instead acting upon endothelial cells. The midazolam-mediated inhibition of VEGF-induced intracellular events was reversed by treatment with the GABA_A receptor antagonist flumazenil. These findings suggest that midazolam prevents hyperglycemia-induced cancer metastasis by inhibiting VEGF-induced intracellular events and subsequent vascular leakage via the GABA_A receptors in the lungs of diabetic mice.

Impact of liver damage on blood-borne variables and pulmonary hemodynamic responses to hypoxia and hyperoxia in anesthetized rats

BACKGROUND

Liver disorders may be associated with normal pulmonary hemodynamic, hepatopulmonary syndrome (HPS), or portopulmonary hypertension (POPH). In this study, we aimed to investigate the effect of the severity of liver dysfunctions on blood-borne variables, and pulmonary hemodynamic during repeated ventilation with hyperoxic and hypoxic gases.

METHODS

Female Sprague Dawley rats were assigned into four groups of Sham (n = 7), portal vein ligation (PPVL, n = 7), common bile duct ligation (CBDL, n = 7), and combination of them (CBDL+ PPVL, n = 7). Twenty-eight days later, right ventricular systolic pressure (RVSP) and systemic blood pressure were recorded in anesthetized animals subjected to repeated maneuvers of hyperoxia (O₂ 50%) and hypoxia (O₂ 10%). Besides, we assessed blood parameters and liver histology.

RESULTS

Liver histology score, liver enzymes, WBC and plasma malondialdehyde in the CBDL+PPVL group were higher than those in the CBDL group. Also, the plasma platelet level in the CBDL+PPVL group was lower than those in the other groups. On the other hand, the serum estradiol in the CBDL group was higher than that in the CBDL+PPVL group. All the above parameters in the PPVL group were similar to those in the Sham group. During ventilation with hyperoxia gas, RVSP in the CBDL+PPVL group was higher than the ones in the other groups, and in the CBDL group, it was more than those in the PPVL and Sham groups. Hypoxic pulmonary vasoconstriction (HPV) was not detected in both CBDL+PPVL and CBDL groups, whereas, it retained in the PPVL group.

CONCLUSION

Severe liver damage increases RVSP in the CBDL+PPVL group linked to the high level of ROS, low levels of serum estradiol and platelets or a combination of them. Furthermore, the high RVSP at the noted group could present a reliable animal model for POPH in female rats.

[The effects of remifentanil used during cesarean section on oxidative stress markers in correlation with maternal hemodynamics and neonatal outcome: a randomized controlled trial]

BACKGROUND AND OBJECTIVE

Remifentanil is used to attenuate maternal hemodynamic response to intubation and surgical stress during Induction-Delivery period of cesarean section. The goal was to compare the effects of two remifentanil dosing regimens on oxidative stress level, in correlation with its hemodynamic and neonatal effects.

METHODS

Fifty-one patients, 17 per group, enrolled for elective cesarean section were randomly divided by computer-generated codes into three parallel groups: (A) patients received a 1μg.kg^-1 remifentanil bolus immediately before induction, followed by 0.15μg.kg^-1.min^-1 infusion, that was stopped after skin incision; (B) patients received a 1μg.kg^-1 remifentanil bolus immediately before induction; (C) (control), patients did not receive remifentanil until delivery. Maternal venous blood samples were taken at basal time, at extraction and 30minutes after the end of operation for spectrophotometrical determination of malondialdehyde and advanced oxidation protein products concentration. The same was conducted for umbilical venous sample.

RESULTS

Systolic blood pressure and heart rate remained significantly lower in group A compared to B and C during entire Induction-Delivery period (p<0.001, p=0.02 after intubation; p=0.006, p=0.03 after skin incision; p=0.029, p=0.04 after extraction; respectively). Malondialdehyde concentration was lower at time of extraction in maternal blood in group A compared to B and C (p=0.026). All neonatal Apgar scores were ≥ 8 and umbilical acid-base values within normal range.

CONCLUSIONS

The remifentanil dosing regimen applied in group A significantly attenuated lipid peroxidation and maternal hemodynamic response during entire I-D period, without compromising neonatal outcome.

From Ganglion Cell to Photoreceptor Layer: Timeline of Deterioration in a Rat Ischemia/Reperfusion Model

Neuronal damage and impaired vision in different retinal disorders are induced, among other factors, by ischemia/reperfusion (I/R). Since the mechanisms and the progression of ischemic injury are still not completely clarified, a timeline of this retinal degeneration is needed. In this study, we investigated protein and mRNA alterations at 2, 6, 12, and 24 h as well as 3 and 7 days after ischemia to determine the course of an ischemic insult through the whole retina. Moreover, functional analyses were performed at later stages. We detected a significant functional loss of cells in the inner nuclear layer and photoreceptors at 3 and 7 days. Additionally, the thickness of the whole retina was decreased at these points in time, indicating a severe degradation of all retinal layers. Immunohistological and qRT-PCR analyses of retinal ganglion cells (RGCs), glial cells, AII amacrine, cone and rod bipolar as well as cone and rod photoreceptor cells confirmed this first assumption. Our results show that all investigated cell types were damaged by ischemia induction. Especially RGCs, cone bipolar cells, and photoreceptor cones are very sensitive to I/R. These cells were lost shortly after ischemia induction with a progressive course up to 7 days. In addition, Müller cell gliosis was observed over the entire period of time. These results provide evidence, that I/R induces damage of the whole retina at early stages and increases over time. In conclusion, our study could demonstrate the intense impact of an ischemic injury. The ischemic defect spreads across the whole retina right up to the outer layers in the long-term and thus seems to impair the visual perception already during the stimulus processing. In addition, our findings indicate that the cone pathway seems to be particularly affected by this damage.

Guidelines for measuring cardiac physiology in mice

Cardiovascular disease is a leading cause of death, and translational research is needed to understand better mechanisms whereby the left ventricle responds to injury. Mouse models of heart disease have provided valuable insights into mechanisms that occur during cardiac aging and in response to a variety of pathologies. The assessment of cardiovascular physiological responses to injury or insult is an important and necessary component of this research. With increasing consideration for rigor and reproducibility, the goal of this guidelines review is to provide best-practice information regarding how to measure accurately cardiac physiology in animal models. In this article, we define guidelines for the measurement of cardiac physiology in mice, as the most commonly used animal model in cardiovascular research.

Listen to this article’s corresponding podcast at http://ajpheart.podbean.com/e/guidelines-for-measuring-cardiac-physiology-in-mice/.

A Review of Anesthetic Effects on Renal Function: Potential Organ Protection

BACKGROUND

Renal protection is a critical concept for anesthesiologists, nephrologists, and urologists, since anesthesia and renal function are highly interconnected and can potentially interfere with one another. Therefore, a comprehensive understanding of anesthetic drugs and their effects on renal function remains fundamental to the success of renal surgeries, especially transplant procedures. Some experimental studies have shown that some anesthetics provide protection against renal ischemia/reperfusion (IR) injury, but there is limited clinical evidence.

SUMMARY

The effects of anesthetic drugs on renal failure are particularly important in the context of kidney transplantation, since the conditions of preservation following removal profoundly influence the recovery of organ function. Currently, preservation procedures are typically based on the usage of a cold-storage solution. Some anesthetic drugs induce anti-inflammatory, anti-necrotic, and anti-apoptotic effects. A more thorough understanding of anesthetic effects on renal function can present a novel approach for developing organ-protective strategies. The aim of this review is to discuss the effects of different anesthetic drugs on renal function, with particular focus on IR injury. Many studies have demonstrated the organ-protective effects of some anesthetic drugs, specifically propofol, which indicate the potential of some anesthetics to introduce novel organ protective targets. This is not surprising, since lipid emulsions are major components of propofol, which accumulating data show provide organ protective effects against IR injury. Key Messages: Thorough understanding of the interaction between anesthetic drugs and renal function remains fundamental to the delivery of safe perioperative care and to optimizing outcomes after renal surgeries, particularly transplant procedures. Anesthetics can be repurposed for organ protection with more information about their effects, especially during transplant procedures. Here, we review the effects of different anesthetic drugs - specifically those that contain lipids in their structure, with special reference to IR injury.

A murine model of lung ischemia and reperfusion injury: tricks of the trade

BACKGROUND

Pulmonary ischemia-reperfusion injury (IRI) causes postoperative morbidity in patients undergoing lung transplantation, isolated lung perfusion, and cardiopulmonary bypass and may lead to potentially lethal pathologies such as respiratory shock. In-depth study of this pathology requires a reliable animal model. Mice are a popular species to develop experimental models because of their logistic advantages and the availability of knock outs. However, their small size warrants microsurgical techniques and a skilled surgeon.

MATERIALS AND METHODS

We developed a murine model of pulmonary anoxic IRI through hilar clamping using adult female Swiss mice. After left thoracotomy, we expose the pulmonary hilum keeping the ribs and the muscles of back and forepaw intact. A microvascular clamp is placed over the entire hilum, occluding bronchus, pulmonary artery, and vein.

RESULTS

Our model proved to be simple, reliable, and reproducible, showing minimal preoperative and postoperative mortality. Histopathologic analysis indicated all characteristic features of pulmonary IRI, such as an early recruitment of lymphocytes followed by neutrophil influx.

CONCLUSIONS

This article presents a murine surgery model for pulmonary IRI based on a muscle-sparing thoracotomy. The minimal approach limits manipulation of lung tissue, minimizing mortality and non-IRI-induced injury.