Targeting the opioid remifentanil: Protective effects and molecular mechanisms against organ ischemia-reperfusion injury

Opioids are widely used in clinical practice by activating opioid receptors (OPRs), but their clinical application is limited by a series of side effects. Researchers have been making tremendous efforts to promote the development and application of opioids. Fortunately, recent studies have identified the additional effects of opioids in addition to anesthesia and analgesia, particularly in terms of organ protection against ischemia-reperfusion (I/R) injury, with unique advantages. I/R injury in vital organs not only leads to cell dysfunction and structural damage but also induces acute and chronic organ failure, even death. Early prevention and appropriate therapeutic targets for I/R injury are crucial for organ protection. Opioids have shown cardioprotective effects for over 20 years, especially remifentanil, a derivative of fentanyl, which is a new ultra-short-acting opioid analgesic widely used in clinical anesthesia induction and maintenance. In this review, we provide current knowledge about the physiological effects related to OPR-mediated organ protection, focusing on the protective effect and mechanism of remifentanil on I/R injury in the heart and other vital organs. Herein, we also explored the potential application of remifentanil in clinical I/R injury. These findings provide a theoretical basis for the use of remifentanil to inhibit or alleviate organ I/R injury during the perioperative period and provide insights for opioid-induced human organ protection and drug development.

Dexmedetomidine Prolongs the Analgesic Effects of Periarticular Infiltration Analgesia following Total Knee Arthroplasty: A Prospective, Double-blind, Randomized Controlled Trial

BACKGROUND

Periarticular infiltration analgesia (PIA) is widely administered to relieve postoperative pain following total knee arthroplasty (TKA). The present study aimed to evaluate the effect of prolonging the analgesic duration by adding dexmedetomidine to PIA for pain management after TKA.

METHODS

One hundred and sixteen patients were randomly allocated into 3 groups based on PIA regimens including Group R (ropivacaine), Group E (ropivacaine plus epinephrine), and Group D (ropivacaine plus dexmedetomidine). The primary outcomes were postoperative visual analog scale (VAS) scores, time until the administration of first rescue analgesia, and opioid consumption. The secondary outcomes included postoperative inflammatory biomarkers and functional recovery. The tertiary outcomes were postoperative complications and adverse events.

RESULTS

The patients in Group D had significantly lower resting VAS scores than those in Groups R and E at 6 hours after surgery. Group R showed the higher pain scores at rest and motion than Groups D and E 12 hours postoperatively. The use of dexmedetomidine or epinephrine postponed the time until the administration of first rescue analgesia and led to lower opioid consumption in the first 24 hours after TKA. The levels of IL-8 and TNF-α in Groups D and E were significantly lower than those in Group R on postoperative Day 3. Furthermore, no significant differences were observed in functional recovery, postoperative complications, or adverse events among the three groups.

CONCLUSIONS

Adding dexmedetomidine as an adjuvant to PIA could potentiate and prolong the analgesic effect in the early stage following TKA without increasing the risk of adverse events.

Dexmedetomidine postconditioning provides renal protection in patients undergoing laparoscopic partial nephrectomy: A randomized controlled trial

Background: For localized disease, partial nephrectomy of small tumors continues to be the gold-standard treatment. However, temporary clamping is routinely performed during this process to control renal blood flow, which can cause renal ischemic/reperfusion injury. We evaluated whether dexmedetomidine postconditioning (DPOC) can reduce renal ischemic/reperfusion injury for patients receiving laparoscopic partial nephrectomy (LPN).

Methods: This randomized double-blind controlled trial included 77 patients who were scheduled for LPN at our hospital. Patients were randomly allocated to the DPOC or control group. DPOC was performed via intravenous administration of dexmedetomidine at 0.6 μg kg−1 for 10 min immediately after unclamping the renal artery. In the control group, saline was administered in place of dexmedetomidine under the same protocol. All participants underwent a 6-month follow-up. The primary outcome were the values of 99mTc-DTPA-GFR in the affected kidney at one and 6 months post-LPN.

Result: The GFR values in the DPOC group (35.65 ± 4.89 ml min−1.1.73 m−2) were significantly higher than those the control group (33.10 ± 5.41 ml min−1.1.73 m−2; p = 0.022) at 1 month after LPN. There was no statistically significant difference in GFR value between the two groups at 6 months after LPN.

Conclusion: DPOC provides therapeutic benefits to LPN patients, at least on a short-term basis, by alleviating renal ischemic/reperfusion injury.

Clinical Trial Registration: Chinese Clinical Trial Registry, identifier [ChiCTR-TRC-14004766].

Myostatin Deficiency Protects C2C12 Cells from Oxidative Stress by Inhibiting Intrinsic Activation of Apoptosis

Ischemia reperfusion (IR) injury remains an important topic in clinical medicine. While a multitude of prophylactic and therapeutic strategies have been proposed, recent studies have illuminated protective effects of myostatin inhibition. This study aims to elaborate on the intracellular pathways involved in myostatin signaling and to explore key proteins that convey protective effects in IR injury. We used CRISPR/Cas9 gene editing to introduce a myostatin (Mstn) deletion into a C2C12 cell line. In subsequent experiments, we evaluated overall cell death, activation of apoptotic pathways, ROS generation, lipid peroxidation, intracellular signaling via mitogen-activated protein kinases (MAPKs), cell migration, and cell proliferation under hypoxic conditions followed by reoxygenation to simulate an IR situation in vitro (hypoxia reoxygenation). It was found that mitogen-activated protein kinase kinase 3/6, also known as MAPK/ERK Kinase 3/6 (MEK3/6), and subsequent p38 MAPK activation were blunted in C2C12-Mstn^−/− cells in response to hypoxia reoxygenation (HR). Similarly, c-Jun N-terminal kinase (JNK) activation was negated. We also found the intrinsic activation of apoptosis to be more important in comparison with the extrinsic activation. Additionally, intercepting myostatin signaling mitigated apoptosis activation. Ultimately, this research validated protective effects of myostatin inhibition in HR and identified potential mediators worth further investigation. Intercepting myostatin signaling did not inhibit ROS generation overall but mitigated cellular injury. In particular, intrinsic activation of apoptosis origination from mitochondria was alleviated. This was presumably mediated by decreased activation of p38 caused by the diminished kinase activity increase of MEK3/6. Overall, this work provides important insights into HR signaling in C2C12-Mstn^−/− cells and could serve as basis for further research.

Effects of dexmedetomidine on the function of distal organs and oxidative stress after lower limb ischaemia-reperfusion in elderly patients undergoing unilateral knee arthroplasty

Aims

This study aims to evaluate the effects of dexmedetomidine on organ function, inflammation response, and oxidative stress in elderly patients following iatrogenic lower limb ischaemia–reperfusion (IR) during unilateral total knee arthroplasty.

Methods

Following unilateral total knee arthroplasty, 54 elderly patients were randomized to receive either intraoperative intravenous injection of dexmedetomidine (n = 27) or equivalent volume of 0.9% saline (n = 27). Blood samples were harvested at 5 minutes before lower limb tourniquet release (baseline); and 1, 6 and 24 hours after tourniquet release. Surrogate markers of cardiac, pulmonary, hepatic and renal function, oxidative stress, inflammatory response, along with parasympathetic and sympathetic activity were recorded and analysed.

Results

The levels of blood xanthine oxidase, creatine kinase, lactic acid and respiratory index increased in patients following tourniquet‐induced lower limb IR injury. Dexmedetomidine administration decreased the respiratory index (P = .014, P = .01, and P = .043) and the norepinephrine level (P < .001) at 1, 6 and 24 hours; and decreased the xanthine oxidase level (P = .049, P < .001) at 6 and 24 hours after tourniquet release compared with the Control group. Other measurements, including creatine kinase isoenzyme, lactate dehydrogenase, creatinine, urea nitrogen, glutamic–oxalacetic transaminase, glutamic–pyruvic transaminase, malondialdehyde, interleukin‐1, interleukin‐6 and tumour necrosis factor‐α, were not statistically significantly different between the 2 groups.

Conclusions

Intraoperative dexmedetomidine administration in elderly patients dampens the deterioration in respiratory function and suppresses the oxidative stress response in elderly patients following iatrogenic lower limb IR injury.

Impact of Dexmedetomidine on Tourniquet-Induced Systemic Effects in Total Knee Arthroplasty under Spinal Anesthesia: a Prospective Randomized, Double-Blinded Study

Background

Clinical studies on the impact of dexmedetomidine on tourniquet-induced systemic effects have been inconsistent. We investigated the impact of dexmedetomidine on tourniquet-induced systemic effects in total knee arthroplasty.

Methods

Eighty patients were randomly assigned to either control (CON) or dexmedetomidine (DEX) group. The DEX group received an intravenous loading dose of 0.5 μg/kg DEX over 10 minutes, followed by a continuous infusion of 0.5 μg/kg/h from 10 minutes before the start of surgery until completion. The CON group received the same calculated volume of normal saline. Pain outcomes and metabolic and coagulative changes after tourniquet application and after tourniquet release were investigated.

Results

The frequency of fentanyl administration postoperatively, patient-controlled analgesia (PCA) volume at 24 hours postoperatively, total PCA volume consumed in 48 hours postoperatively, and VAS score for pain at 24 and 48 hours postoperatively were significantly lower in the DEX group than in the CON group. Ten minutes after the tourniquet release, the DEX group showed significantly higher pH and lower lactate level than those in the CON group. Antithrombin III activity and body temperature 10 minutes after tourniquet release were significantly lower in the DEX group than in the CON group. Ca²⁺, K⁺, HCO₃ ^-, base excess, and PCO₂ levels 10 minutes after tourniquet release were not significantly different between the two groups.

Conclusion

We showed that DEX attenuated pain and hemodynamic, metabolic, and coagulative effects induced by the tourniquet. However, these metabolic and coagulative changes were within normal limits. Therefore, DEX could be used as an analgesic adjuvant, but should not be considered for routine use to prevent the systemic effects induced by tourniquet use.

An optimized low-pressure tourniquet murine hind limb ischemia reperfusion model: Inducing acute ischemia reperfusion injury in C57BL/6 wild type mice

Acute ischemia reperfusion injury in skeletal muscle remains an important issue in several fields of regenerative medicine. Thus, a valid model is essential to gain deeper insights into pathophysiological relations and evaluate possible treatment options. While the vascular anatomy of mice regularly prevents sufficient vessel occlusion by invasive methods, there is a multitude of existing models to induce ischemia reperfusion injury without surgical procedures. Since there is no consensus on which model to prefer, this study aims to develop and evaluate a novel, optimized low-pressure tourniquet model. C57BL/6 mice underwent an ischemic procedure by either tourniquet or invasive artery clamping. A sham group served as control. With exception of the sham group, mice underwent 2 hours of ischemia followed by 4 hours of reperfusion. Groups were compared using microcirculatory and spectroscopic measurements, distinctions in tissue edema, histological and immunohistochemical analyses. Both procedures led to a significant decrease in tissue blood flow (- 97% vs. - 86%) and oxygenation (- 87% vs. - 75%) with a superiority of the low-pressure tourniquet. Tissue edema in the tourniquet cohort was significantly increased (+ 59%), while the increase in the clamping cohort was non-significant (+ 7%). Haematoxylin Eosin staining showed significantly more impaired muscle fibers in the tourniquet group (+ 77 p.p. vs. + 11 p.p.) and increased neutrophil infiltration/ROI (+ 51 vs. + 8). Immunofluorescence demonstrated an equal increase of p38 in both groups (7-fold vs. 8-fold), while the increase in apoptotic markers (Caspase-3, 3-Nitrotyrosine, 4-Hydroxynonenal) was significantly higher in the tourniquet group. The low-pressure tourniquet has been proven to produce reproducible and thus reliable ischemia reperfusion injury. In addition, significantly less force was needed than previously stated. It is therefore an important instrument for studying the pathophysiology of ischemia reperfusion injury and for the development of prophylactic as well as therapeutic interventions.