Propofol Attenuates Endotoxin-Induced Endothelial Cell Injury, Angiotensin-Converting Enzyme Shedding, and Lung Edema

Dexmedetomidine only regimen for long-term sedation is associated with reduced vasopressor requirements in septic shock patients: A retrospective cohort study from MIMIC-IV database

Background

Previous studies have shown that dexmedetomidine (DEX) may be associated with reduced vasopressor requirements in septic shock patients, however, long-term DEX-only sedation in reducing vasopressor requirements is still controversial.

Methods

A retrospective study was conducted among patients with septic shock on mechanical ventilation using the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. The primary outcome was the ratio of norepinephrine equivalent dose to mean arterial pressure (NEq/MAP) in the first 72 h after DEX or other sedatives for sedation. The secondary outcomes were key organ function parameters, 28-day mortality, and 90-day mortality. Univariate, propensity score matching (PSM), and generalized linear mixed model (GLMM) analyses were performed.

Results

DEX was associated with decreased NEq/MAP in the first 72 h (difference = 0.05, 95% CI = -0.02-0.08, p = 0.002) after adjusting for confounders in the GLMM analysis. The DEX group was also associated with a lower heart rate, cardiac output (CO), lactate level, aspartate transaminase (AST) level, and higher PaO2/FiO2 ratio (p < 0.0125). Moreover, DEX only sedation was associated with reduced 90-day mortality (OR = 0.60, 95% CI = 0.37-0.94, p = 0.030).

Conclusion

DEX may be associated with decreased vasopressor requirements, improved AST and PaO2/FiO2 levels, and reduced 90-day mortality in patients with septic shock, which warrants further study.

Therapeutic approaches targeting renin-angiotensin system in sepsis and its complications

Sepsis, caused by the inappropriate host response to infection, is characterized by excessive inflammatory response and organ dysfunction, thus becomes a critical clinical problem. Commonly, sepsis may progress to septic shock and severe complications, including acute kidney injury (AKI), acute respiratory distress syndrome (ARDS), sepsis-induced myocardial dysfunction (SIMD), liver dysfunction, cerebral dysfunction, and skeletal muscle atrophy, which predominantly contribute to high mortality. Additionally, the global pandemic of coronavirus disease 2019 (COVID-19) raised the concern of development of effectve therapeutic strategies for viral sepsis. Renin-angiotensin system (RAS) may represent as a potent therapeutic target for sepsis therapy. The emerging role of RAS in the pathogenesis of sepsis has been investigated and several preclinical and clinical trials targeting RAS for sepsis treatment revealed promising outcomes. Herein, we attempt to review the effects and mechanisms of RAS manipulation on sepsis and its complications and provide new insights into optimizing RAS interventions for sepsis treatment.

Differences between Total Intravenous Anesthesia and Inhalation Anesthesia in Free Flap Surgery of Head and Neck Cancer

BACKGROUND

Many studies have evaluated risk factors associated with complications after free flap surgery, but these studies did not evaluate the impact of anesthesia management. The goal of the current study was to evaluate the differences between patients who received inhalation and total intravenous anesthesia (TIVA) in free flap surgery.

METHODS

One hundred and fifty-six patients who underwent free flap surgery for head and neck cancer were retrospectively divided into the TIVA (96 patients) and the inhalation group (87 patients). Perioperative hemodynamic data and postoperative medical complications were determined by documented medical records.

RESULTS

Ninety-six patients in the TIVA group were compared with 87 patients who received inhalation anesthesia. There were no differences in gender, age, classification of physical status based on American Society for Anesthesiologists (ASA) score, and cormobidities between the two groups. Patients in the TIVA group required less perioperative crystalloid (4172.46 ± 1534.95 vs. 5183.91 ± 1416.40 ml, p < 0.0001) and colloid (572.46 ± 335.14 vs. 994.25 ± 434.65 ml, p < 0.0001) to maintain hemodynamic stability. Although the mean anesthesia duration was shorter in the TIVA group (11.02 ± 2.84 vs. 11.70± 1.96 hours, p = 0.017), the blood loss was similar between groups (p = 0.71). There was no difference in surgical complication rate, but patients in the TIVA group developed fewer pulmonary complications (18 vs. 47, p = 0.0008). After multivariate regression, patients in the TIVA group had a significantly reduced risk of pulmonary complication compared with the inhalation group (Odds ratio 0.41, 95% CI 0.18-0.92).

CONCLUSIONS

Total intravenous anesthesia was associated with significantly fewer pulmonary complications in patients who received free flap reconstruction.

Propofol prevents lung injury after intestinal ischemia-reperfusion by inhibiting the interaction between mast cell activation and oxidative stress

AIMS

Both mast cells and oxidative stress are involved in acute lung injury (ALI) induced by intestinal ischemia-reperfusion (IIR). The aim of this study was to investigate whether propofol could improve IIR-induced ALI through inhibiting their interaction.

MAIN METHODS

Repetitive, brief IIR or IIR+compound 48/80 was performed in adult Sprague-Dawley rats pretreated with saline, apocynin or propofol. And their lungs were excised for histology, ELISA and protein-expression measurements 2h after reperfusion.

KEY FINDINGS

Rats pretreated with saline developed critical ALI 2h after IIR. We found significant elevations in lung injury scores, lung wet/dry ratio and gp91phox, p47phox, intercellular cell adhesion molecule-1 protein expressions and higher level of malondialdehyde, interleukin-6 contents, and myeloperoxidase activities, as well as significant reductions in superoxide dismutase activities, accompanied with increases in mast cell degranulation evidenced by significant increases in mast cell counts, β-hexosaminidase concentrations, and tryptase expression. And the lung injury was aggravated in the presence of compound 48/80. However, pretreated with propofol and apocynin not only ameliorated the IIR-mediated pulmonary changes beyond the biochemical changes but also reversed the changes that were aggravated by compound 48/80.

SIGNIFICANCE

Propofol protects against IIR-mediated ALI, most likely by inhibiting the interaction between oxidative stress and mast cell degranulation.

LPS-induced effects on angiotensin I-converting enzyme expression and shedding in human pulmonary microvascular endothelial cells

Angiotensin I-converting enzyme (kininase II, ACE, and CD143) availability is a determinant of local angiotensin and kinin concentrations and their physiological actions. Until now, it is unclear whether the decrease of pulmonary ACE activity in sepsis-described in clinical studies-is due to an enzyme compensatory downregulation (reduced ACE-mRNA expression) to shedding of ACE or endothelial damage. To address these questions, ACE distribution under septic conditions was studied in vitro by treating pulmonary microvascular endothelial cells (HPMEC) and human umbilical vein endothelial cells (HUVEC) with lipopolysaccharide from Escherichia coli (LPS). Primary isolated HUVEC and HPMEC were compared by detecting ACE activity, membrane-bound ACE, as well as shedding and mRNA production of ACE with and without LPS (1 ng/ml-1 μg/ml). ACE mRNA expression was detected by real-time PCR, and shedded ACE was measured in cell culture supernatant by ELISA. Additionally, membrane-bound protein expression was investigated by immunohistochemistry in situ. In septic ARDS, the distribution of ACE protein was significantly reduced in all lung endothelial cells (p<0.001). After stimulation with LPS, cultivated HPMEC showed more markedly than HUVEC, a concentration-dependent reduction of ACE protein expression compared to the respective untreated controls. Real-time PCR demonstrated a reduced ACE mRNA expression after LPS stimulation, predominantly in HPMEC. Specifically, in HPMEC, a concentration-dependent increase of shedded ACE was shown 24 h after LPS treatment. HPMEC cultures are an apt model for the investigation of pulmonary ACE expression in sepsis. This study suggests that reduced pulmonary microvascular endothelial ACE expression in septic ARDS is caused by two processes: (initial) increased shedding of ACE accompanied by a compensatory downregulation of ACE-mRNA and membrane-bound protein expression.

Surfactant protein A (SP-A) and angiotensin converting enzyme (ACE) as early biomarkers for pulmonary edema formation in ventilated human lung lobes

OBJECTIVE

Ex vivo perfused and ventilated lung lobes frequently develop pulmonary edema. We were looking for a suitable and early detectable biomarker in the perfusion fluid indicating lung cell damage and loss of tissue integrity in ventilated human lung lobes. Therefore, we elucidated whether surfactant protein A (SP-A) and angiotensin-converting enzyme (ACE) were measurable in the perfusion fluid and whether they were suitable indicators for edema formation occurring within the experimental time frame of 1-2 h.

METHODS

Patients (n = 39) undergoing a lobectomy, bilobectomy or pneumonectomy due to primary bronchial cell carcinoma were included in the studies. Lung lobes were extracorporally ventilated and perfused for up to 2 h. Two different perfusion fluids were used, plain perfusion buffer and perfusion buffer containing packed erythrocytes or buffy coats. Perfusion fluid samples were analyzed for SP-A and ACE using immunoassays served as perfusion fluids.

RESULTS

SP-A and ACE concentrations were analyzed in fluid sample sets of 39 and 33 perfusion experiments, respectively. Degrees of edema formation were arbitrarily classified into three groups (≤ 29, 30-59, ≥ 60 % weight gain). The maximum increase of SP-A and ACE concentrations in the perfusate was significantly higher for more pronounced edemas in case of perfusions using a mixture of blood components and buffer. Interestingly, the time courses of ACE and SP-A were highly similar.

CONCLUSION

We suggest that SP-A and ACE are promising early biochemical markers for the development for pulmonary edema formation in the ex vivo lung lobe perfusion.

LPS activates ADAM9 dependent shedding of ACE from endothelial cells

Angiotensin-I converting enzyme (ACE) is a zinc dependent peptidase with a major role in regulating vasoactive peptide metabolism. ACE, a transmembrane protein, undergoes proteolysis, or shedding, by an as yet unidentified proteinase to release a catalytically active soluble form of the enzyme. Physiologically, soluble ACE in plasma is derived primarily from endothelial cells. We demonstrate that ACE shedding from confluent endothelial cells is increased in response to bacterial lipopolysaccharide, but not phorbol esters. Characterisation of lipopolysaccharide stimulated shedding showed that there is a lag phase before soluble ACE can be detected which is sensitive to inhibitors of translation, NF-κB, TNFα and TNFR-I/II. The shedding phase is less sensitive to these inhibitors, but is ablated by BB-94, a Matrix Metalloproteinase (MMP)/A Disintegrin and Metalloproteinase (ADAM) inhibitor. Tissue Inhibitor of Metalloproteinase (TIMP) profiling suggested a requirement for ADAM9 in lipopolysaccharide induced ACE shedding, which was confirmed by depletion with siRNA. Transient transfection of ADAM9 and ACE cDNAs into HEK293 cells demonstrated that ADAM9 requires both membrane anchorage and its catalytic domain to shed ACE.

Propofol increases the Ca2+ sensitivity of BKCa in the cerebral arterial smooth muscle cells of mice

AIM

Propofol has the side effect of hypotension especially in the elderly and patients with hypertension. Previous studies suggest propofol-caused hypotension results from activation of large conductance Ca(2+)-sensitive K channels (BKCa). In this study, the effects of propofol on the Ca(2+) sensitivity of BKCa were investigated in mice cerebral arterial smooth muscle cells.

METHODS

Single smooth muscle cells were prepared from the cerebral arteries of mice. Perforated whole-cell recoding was conducted to investigate the whole-cell BKCa current and spontaneous transient outward K(+) current (STOC). Inside-out patch configuration was used to record the single channel current and to study the Ca(2+)- and voltage-dependence of BKCa.

RESULTS

Propofol (56 and 112 μmol/L) increased the macroscopic BKCa and STOC currents in a concentration-dependent manner. It markedly increased the total open probability (NPo) of single BKCa channel with an EC(50) value of 76 μmol/L. Furthermore, propofol significantly decreased the equilibrium dissociation constant (K(d)) of Ca(2+) for BKCa channel. The K(d) value of Ca(2+) was 0.881 μmol/L in control, and decreased to 0.694, 0.599 and 0.177 μmol/L, respectively, in the presence of propofol 28, 56 and 112 μmol/L. An analysis of the channel kinetics revealed that propofol (112 μmol/L) significantly increased the open dwell time and decreased the closed dwell time, which stabilized BKCa channel in the open state.

CONCLUSION

Propofol increases the Ca(2+) sensitivity of BKCa channels, thus lowering the Ca(2+) threshold of the channel activation in arterial smooth muscle cells, which causes greater vasodilating effects.

Management of mechanical ventilation during laparoscopic surgery

Laparoscopy is widely used in the surgical treatment of a number of diseases. Its advantages are generally believed to lie on its minimal invasiveness, better cosmetic outcome and shorter length of hospital stay based on surgical expertise and state-of-the-art equipment. Thousands of laparoscopic surgical procedures performed safely prove that mechanical ventilation during anaesthesia for laparoscopy is well tolerated by a vast majority of patients. However, the effects of pneumoperitoneum are particularly relevant to patients with underlying lung disease as well as to the increasing number of patients with higher-than-normal body mass index. Moreover, many surgical procedures are significantly longer in duration when performed with laparoscopic techniques. Taken together, these factors impose special care for the management of mechanical ventilation during laparoscopic surgery. The purpose of the review is to summarise the consequences of pneumoperitoneum on the standard monitoring of mechanical ventilation during anaesthesia and to discuss the rationale of using a protective ventilation strategy during laparoscopic surgery. The consequences of chest wall derangement occurring during pneumoperitoneum on airway pressure and central venous pressure, together with the role of end-tidal-CO2 monitoring are emphasised. Ventilatory and non-ventilatory strategies to protect the lung are discussed.

Lung injury following thoracic aortic occlusion: comparison of sevoflurane and propofol anaesthesia

BACKGROUND

Halogenated anaesthetics have been shown to reduce ischaemia-reperfusion injuries in various organs due to pre- and post-conditioning mechanisms. We compared volatile and total intravenous anaesthesia with regard to their effect on remote pulmonary injury after thoracic aortic occlusion and reperfusion.

METHODS

Eighteen pigs were randomized after sternotomy and laparotomy (fentanyl-midazolam anaesthesia) to receive either sevoflurane or propofol in an investigator-blinded fashion. Ninety minutes of thoracic aortic occlusion was induced by a balloon catheter. During reperfusion, a goal-directed resuscitation protocol was performed. After 120 min of reperfusion, the anaesthetic regimen was changed to fentanyl-midazolam again for another 180 min. The oxygenation index and intra-pulmonary shunt fractions were calculated. After 5 h of reperfusion, a bronchoalveolar lavage was performed. The total protein content and lactate dehydrogenase activity were measured in epithelial lining fluid (ELF). Alveolar macrophage oxidative burst was analysed. The wet to dry ratio was calculated and tissue injury was graded using a semi-quantitative score. Ten animals (n=5 for each anaesthetic) without aortic occlusion served as time controls.

RESULTS

The oxygenation index decreased and the intra-pulmonary shunt fraction increased significantly in both occlusion groups. There were no significant differences between sevoflurane and propofol with respect to the oxygenation index, ELF composition, morphologic lung damage, wet to dry ratio and alveolar macrophage burst activity. Differences were, however, seen in terms of systemic haemodynamic stability, where catecholamine requirements were less pronounced with sevoflurane.

CONCLUSION

We conclude that the severity of remote lung injury was not different between sevoflurane and propofol anaesthesia in this porcine model of severe lower-body ischaemia and reperfusion injury.