Ischemic Preconditioning Attenuates Pulmonary Dysfunction After Unilateral Thigh Tourniquet–Induced Ischemia–Reperfusion

Role of remote ischaemic conditioning in fracture healing and orthopaedic surgery-a systematic review and narrative synthesis

INTRODUCTION

Remote ischaemic conditioning (RIC) involves the use of controlled and transient ischemia and reperfusion cycles, commonly of the upper or lower limb, to mitigate cellular damage from ischaemic events. Studies have demonstrated that RIC may have anti-inflammatory and cardiovascular protective effects and thus could represent a novel therapeutic strategy to improve outcomes following orthopaedic surgery. This review aimed to comprehensively describe the current pre-clinical and clinical evidence for RIC in orthopaedics.

METHODS

MEDLINE and EMBASE via OVID (1966-March 2024) were searched using a systematic search strategy for randomised controlled trials (RCTs) investigating the effects of RIC on fracture, bone healing, and orthopaedics. Both pre-clinical and clinical RCTs were included.

RESULTS

Three pre-clinical RCTs (comprising of 198 rats in models of experimental fracture) met the inclusion criteria. These showed that RIC was associated with enhanced callus formation (volume and biomechanical strength) post-fracture, reduced oxidative stress and upregulated osteoblastic activity. Sixteen clinical RCTs, involving 628 patients, investigated RIC in 6 different elective orthopaedic procedures (knee, lower limb, cervical, shoulder, general, hip fracture). RIC protocols varied in cycle frequency, duration, and pressure, but all were given as a single dose at induction of anaesthesia. Significant results included reductions in oxidative stress, improved cerebral and peripheral oxygenation, and reduced pain scores and analgesia use. Only 1 study (n = 648) evaluated RIC in acute hip fracture and demonstrated an early cardioprotective effect.

CONCLUSION

The potential therapeutic effects of RIC in orthopaedic surgery is supported by preliminary evidence from pre-clinical and clinical studies. Trials to date are largely small but warrant investigation in well-powered multicentre RCTs. There are still many unanswered questions about the optimal RIC parameters (cuff pressure, frequency and duration) in orthopaedic surgery and determining which patients may benefit most from this therapy.

Remote ischaemic preconditioning and survival in noncardiac surgery: a meta-analysis of randomised trials

BACKGROUND

Remote ischaemic preconditioning (RIPC) is an intervention involving brief periods of limb ischaemia to protect remote organs from subsequent ischaemic injury. Although evidence exists on the beneficial effects of RIPC on biomarkers, its effect on survival is unknown. We performed a meta-analysis of randomised controlled trials (RCTs) to evaluate whether RIPC improves survival in noncardiac surgery.

METHODS

We searched several electronic databases for randomised trials comparing RIPC vs a control group in adult noncardiac surgical settings. The primary outcome was mortality at the longest follow-up available. We conducted a random-effects meta-analysis to calculate the risk ratio (RR) and 95% confidence intervals (CIs). Bayesian statistics were used to estimate the probability of mortality benefit (RR <1).

RESULTS

We identified 72 RCTs, which included 7457 subjects. Mortality was reported in 28 RCTs and was lower in the RIPC group compared with the control group (88/2122 [4.1%] vs 102/1767 [5.8%]; RR 0.74, 95% CI 0.57-0.98, P=0.03; I2=0%; moderate certainty; number needed to treat = 67), corresponding to a 97.0% probability of any reduction in mortality. RIPC was also associated with a reduced incidence of postoperative stroke (moderate certainty) and with a shorter duration of hospital stay (low certainty).

CONCLUSIONS

Remote ischaemic preconditioning was associated with improved survival and reduced postoperative stroke and hospital stay in noncardiac surgery. These findings warrant careful considerations of the benefits of RIPC and support the need for a large, multicentre RCT to confirm these promising results.

SYSTEMATIC REVIEW PROTOCOL

CRD42024588358 (PROSPERO).

Renoprotective effects of remote ischemic preconditioning on acute kidney injury induced by repeated tourniquet application in patients undergoing extremity surgery

Objective

Limb ischemia-reperfusion injury caused by repeated tourniquet application usually leads to acute kidney injury, adversely affecting patient prognosis. This study aimed to investigate the renoprotective effect of remote ischemic preconditioning (RIPC) in patients undergoing extremity surgery with repeated tourniquet application.

Methods

64 patients were enrolled and randomly divided into an RIPC group and a control group, with 32 patients in each. Pretreatment was administered before surgery, and baseline characteristics were collected. Perioperative surgical characteristics, renal biomarkers, oxidative stress markers, inflammatory factors, and postoperative conditions were recorded.

Results

2 participant were excluded from each group, leaving 30 patients per group. There were no significant differences between the two groups regarding baseline characteristics and perioperative surgical characteristics (p > 0.05). Compared to the control group, the RIPC group showed a significant decrease in BUN and SCr at 48 h postoperatively (p < 0.05). Levels of Cys-C, [TIMP-2] × [IGFBP-7], KIM-1, IL-18, and NGAL were significantly reduced at the first and second tourniquet releases and at 24 h postoperatively in the RIPC group (p < 0.05). From the first tourniquet release to 48 h postoperatively, MDA levels were significantly lower (p < 0.05) and SOD levels were significantly higher (p < 0.05) in the RIPC group compared to the control group. Postoperative conditions did not differ significantly between the groups.

Conclusion

RIPC effectively mitigated acute kidney injury caused by repeated tourniquet application, offering a robust method for perioperative renal protection in patients undergoing extremity surgery. Future studies should explore the underlying mechanisms and long-term clinical outcomes of RIPC in broader patient populations.

Clinical trial registration

https://www.chictr.org.cn/showproj.html?proj=231266.

The New Orientation of Postoperative Analgesia: Remote Ischemic Preconditioning

Purpose of Review

Postoperative analgesia is currently a significant topic in anesthesiology. Currently, the predominant approach for achieving multimodal analgesia involves the utilization of pharmacotherapy and regional anesthesia procedures. The primary objectives of this approach are to mitigate postoperative pain, enhance patient satisfaction, and diminish overall opioid usage. Nevertheless, there is a scarcity of research on the use of remote ischemia preconditioning aimed at mitigating postoperative pain.

Recent Findings

Transient stoppage of blood flow to an organ has been found to elicit remote ischemia preconditioning (RIPC), which serves as a potent intrinsic mechanism for protecting numerous organs. In addition to its established role in protecting against reperfusion injury, RIPC has recently been identified as having potential benefits in the context of postoperative analgesia.

Summary

In addition to traditional perioperative analgesia, RIPC provides perioperative analgesia and organ protection.

Efficacy of remote ischaemic preconditioning on outcomes following non-cardiac non-vascular surgery: a systematic review and meta-analysis

BACKGROUND

Remote ischaemic preconditioning (RIPC) has been investigated as a simple intervention to potentially mitigate the ischaemic effect of the surgical insult and reduce postoperative morbidity. This review systematically evaluates the effect of RIPC on morbidity, including duration of hospital stay and parameters reflective of cardiac, renal, respiratory, and hepatic dysfunction following non-cardiac non-vascular (NCNV) surgery.

METHODS

The electronic databases PubMed, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched from their inception date to November 2021. Studies investigating the effect of local preconditioning or postconditioning were excluded. Methodological quality and risk of bias were determined according to the Revised Cochrane risk-of-bias tool for randomised trials (RoB 2). Calculation of the odds ratios and a random effects model was used for dichotomous outcomes and mean differences or standardised mean differences as appropriate were used for continuous outcomes. The primary outcomes of interest were cardiac and renal morbidity, and the secondary outcomes included other organ function parameters and hospital length of stay.

RESULTS

A systematic review of the published literature identified 36 randomised controlled trials. There was no significant difference in postoperative troponin or acute kidney injury. RIPC was associated with lower postoperative serum creatinine (9 studies, 914 patients, mean difference (MD) - 3.81 µmol/L, 95% confidence interval (CI) - 6.79 to - 0.83, p = 0.01, I² = 5%) and lower renal stress biomarker (neutrophil gelatinase-associated lipocalin (NGAL), 5 studies, 379 patients, standardized mean difference (SMD) - 0.66, 95% CI - 1.27 to - 0.06, p = 0.03, I² = 86%). RIPC was also associated with improved oxygenation (higher P_aO₂/F_iO₂, 5 studies, 420 patients, MD 51.51 mmHg, 95% CI 27.32 to 75.69, p < 0.01, I² = 89%), lower biomarker of oxidative stress (malondialdehyde (MDA), 3 studies, 100 patients, MD - 1.24 µmol/L, 95% CI - 2.4 to - 0.07, p = 0.04, I² = 91%)) and shorter length of hospital stay (15 studies, 2110 patients, MD - 0.99 days, 95% CI - 1.75 to - 0.23, p = 0.01, I² = 88%).

CONCLUSIONS

This meta-analysis did not show an improvement in the primary outcomes of interest with the use of RIPC. RIPC was associated with a small improvement in certain surrogate parameters of organ function and small reduction in hospital length of stay. Our results should be interpreted with caution due to the limited number of studies addressing individual outcomes and the considerable heterogeneity identified.

TRIAL REGISTRATION

PROSPERO CRD42019129503.

Effect of Remote Ischaemic Preconditioning on Perioperative Endothelial Dysfunction in Non-Cardiac Surgery: A Randomised Clinical Trial

Endothelial dysfunction result from inflammation and excessive production of reactive oxygen species as part of the surgical stress response. Remote ischemic preconditioning (RIPC) potentially exerts anti-oxidative and anti-inflammatory properties, which might stabilise the endothelial function after non-cardiac surgery. This was a single centre randomised clinical trial including 60 patients undergoing sub-acute laparoscopic cholecystectomy due to acute cholecystitis. Patients were randomised to RIPC or control. The RIPC procedure consisted of four cycles of five minutes of ischaemia and reperfusion of one upper extremity. Endothelial function was assessed as the reactive hyperaemia index (RHI) and circulating biomarkers of nitric oxide (NO) bioavailability (L-arginine, asymmetric dimethylarginine (ADMA), L-arginine/ADMA ratio, tetra- and dihydrobiopterin (BH4 and BH2), and total plasma biopterin) preoperative, 2–4 h after surgery and 24 h after surgery. RHI did not differ between the groups (p = 0.07). Neither did levels of circulating biomarkers of NO bioavailability change in response to RIPC. L-arginine and L-arginine/ADMA ratio was suppressed preoperatively and increased 24 h after surgery (p < 0.001). The BH4/BH2-ratio had a high preoperative level, decreased 2–4 h after surgery and remained low 24 h after surgery (p = 0.01). RIPC did not influence endothelial function or markers of NO bioavailability until 24 h after sub-acute laparoscopic cholecystectomy. In response to surgery, markers of NO bioavailability increased, and oxidative stress decreased. These findings support that a minimally invasive removal of the inflamed gallbladder countereffects reduced markers of NO bioavailability and increased oxidative stress caused by acute cholecystitis.

The effects of ischaemic conditioning on lung ischaemia-reperfusion injury

Ischaemia-reperfusion injury (IRI) encompasses the deleterious effects on cellular function and survival that result from the restoration of organ perfusion. Despite their unique tolerance to ischaemia and hypoxia, afforded by their dual (pulmonary and bronchial) circulation as well as direct oxygen diffusion from the airways, lungs are particularly susceptible to IRI (LIRI). LIRI may be observed in a variety of clinical settings, including lung transplantation, lung resections, cardiopulmonary bypass during cardiac surgery, aortic cross-clamping for abdominal aortic aneurysm repair, as well as tourniquet application for orthopaedic operations. It is a diagnosis of exclusion, manifesting clinically as acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Ischaemic conditioning (IC) signifies the original paradigm of treating IRI. It entails the application of short, non-lethal ischemia and reperfusion manoeuvres to an organ, tissue, or arterial territory, which activates mechanisms that reduce IRI. Interestingly, there is accumulating experimental and preliminary clinical evidence that IC may ameliorate LIRI in various pathophysiological contexts. Considering the detrimental effects of LIRI, ranging from ALI following lung resections to primary graft dysfunction (PGD) after lung transplantation, the association of these entities with adverse outcomes, as well as the paucity of protective or therapeutic interventions, IC holds promise as a safe and effective strategy to protect the lung. This article aims to provide a narrative review of the existing experimental and clinical evidence regarding the effects of IC on LIRI and prompt further investigation to refine its clinical application.

Timing is everything: Exercise therapy and remote ischemic conditioning for acute ischemic stroke patients

Physical exercise is a promising rehabilitative strategy for acute ischemic stroke. Preclinical trials suggest that exercise restores cerebral blood circulation and re-establishes the blood–brain barrier’s integrity with neurological function and motor skill improvement. Clinical trials demonstrated that exercise improves prognosis and decreases complications after ischemic events. Due to these encouraging findings, early exercise rehabilitation has been quickly adopted into stroke rehabilitation guidelines. Unfortunately, preclinical trials have failed to warn us of an adverse effect. Trials with very early exercise rehabilitation (within 24 h of ischemic attack) found an inferior prognosis at 3 months. It was not immediately clear as to why exercise was detrimental when performed very early while it was ameliorative just a few short days later. This review aimed to explore the potential mechanisms of harm seen in very early exercise administered to acute ischemic stroke patients. To begin, the mechanisms of exercise’s benefit were transposed onto the current understanding of acute ischemic stroke’s pathogenesis, specifically during the acute and subacute phases. Then, exercise rehabilitation’s mechanisms were compared to that of remote ischemic conditioning (RIC). This comparison may reveal how RIC may be providing clinical benefit during the acute phase of ischemic stroke when exercise proved to be harmful.

Pulmonary effects of dexmedetomidine infusion in thoracic aortic surgery under hypothermic circulatory arrest: a randomized placebo-controlled trial

Dexmedetomidine has emerged as a promising organ protective agent. We performed prospective randomized placebo-controlled trial investigating effects of perioperative dexmedetomidine infusion on pulmonary function following thoracic aortic surgery with cardiopulmonary bypass and moderate hypothermic circulatory arrest. Fifty-two patients were randomized to two groups: the dexmedetomidine group received 1 µg/kg of dexmedetomidine over 20 min after induction of anesthesia, followed by 0.5 µg/kg/h infusion until 12 h after aortic cross clamp (ACC)-off, while the control group received the same volume of normal saline. The primary endpoints were oxygenation indices including arterial O2 partial pressure (PaO2) to alveolar O2 partial pressure ratio (a/A ratio), (A-a) O2 gradient, PaO2/FiO2 and lung mechanics including peak inspiratory and plateau pressures and compliances, which were assessed after anesthesia induction, 1 h, 6 h, 12 h, and 24 h after ACC-off. The secondary endpoints were serum biomarkers including interleukin-6, tumor necrosis factor-α, superoxide dismutase, and malondialdehyde (MDA). As a result, dexmedetomidine did not confer protective effects on the lungs, but inhibited elevation of serum MDA level, indicative of anti-oxidative stress property, and improved urine output and lower requirements of vasopressors.

Effect of remote ischaemic preconditioning on mortality and morbidity after non-cardiac surgery: meta-analysis

BACKGROUND

Remote ischaemic preconditioning (RIPC) has been shown to have a protective role on vital organs exposed to reperfusion injury. The aim of this systematic review was to evaluate the effects of non-invasive RIPC on clinical and biochemical outcomes in patients undergoing non-cardiac surgery.

METHODS

A systematic literature search of PubMed, EMBASE, Scopus, and Cochrane databases was carried out in February 2020. RCTs investigating the effect of non-invasive RIPC in adults undergoing non-cardiac surgery were included. Meta-analyses and trial sequential analyses (TSAs) were performed on cardiovascular events, acute kidney injury, and short- and long-term mortality.

RESULTS

Some 43 RCTs including 3660 patients were included. The surgical areas comprised orthopaedic, vascular, abdominal, pulmonary, neurological, and urological surgery. Meta-analysis showed RIPC to be associated with fewer cardiovascular events in non-cardiac surgery (13 trials, 1968 patients, 421 events; odds ratio (OR) 0.68, 95 per cent c.i. 0.47 to 0.96; P = 0.03). Meta-analyses of the effect of RIPC on acute kidney injury (12 trials, 1208 patients, 211 events; OR 1.14, 0.78 to 1.69; P = 0.50; I2 = 9 per cent), short-term mortality (7 trials, 1239 patients, 65 events; OR 0.65, 0.37 to 1.12; P = 0.12; I2 = 0 per cent), and long-term mortality (4 trials, 1167 patients, 9 events; OR 0.67, 0.18 to 2.55; P = 0.56; I2 = 0 per cent) showed no significant differences for RIPC compared with standard perioperative care in non-cardiac surgery. However, TSAs showed that the required information sizes have not yet been reached.

CONCLUSION

Application of RIPC to non-cardiac surgery might reduce cardiovascular events, but not acute kidney injury or all-cause mortality, but currently available data are inadequate to confirm or reject an assumed intervention effect.

Remote Ischemic Preconditioning in Non-cardiac Surgery: A Systematic Review and Meta-analysis

BACKGROUND

Remote ischemic preconditioning (RIPC) may mitigate physiological stress related to surgery. There is no clear consensus on conduct of RIPC studies, or whether it is effective. The aim of this study was to (i) assess delivery of RIPC, (ii) identify reported outcomes, (iii) measure effect on key clinical outcomes.

METHODS

This review was registered on PROSPERO (CRD:42020180725). EMBASE and Medline databases were searched, and results screened by two reviewers. Full-texts were assessed for eligibility by two reviewers. Data extracted were methods of RIPC and outcomes reported. Meta-analysis of key clinical events was performed using a Mantel-Haenszel random effects model. The TIDieR framework was used to assess intervention reporting, and Cochrane risk of bias tool was used for all studies included.

RESULTS

Searches identified 25 studies; 25 were included in the narrative analysis and 18 in the meta-analysis. RIPC was frequently performed by occluding arm circulation (15/25), at 200 mmHg (9/25), with three cycles of 5 min ischemia and 5 min of reperfusion (16/25). No study fulfilled all 12 TIDieR items (mean score 7.68). Meta-analysis showed no benefit of RIPC on MI (OR 0.71 95% CI 0.48-1.04, I2 = 0%), mortality (OR 0.56, 95% CI 0.31-1.01, I2 = 0%), or acute kidney injury (OR 0.72 95% CI 0.48-1.08).

CONCLUSIONS

RIPC could be standardized as 200 mmHg pressure in 3 × 5 min on and off cycles. The signal of benefit should be explored in a larger well-designed randomized trial.

Which Anesthesia Regimen Is Best to Reduce Pulmonary Complications After Head and Neck Surgery?

OBJECTIVES/HYPOTHESIS

The differences between intravenous and inhalation anesthesia in clinical postoperative pulmonary complications (PPCs) have been studied in cardiac and lung resection surgery. Clinical evidence for the effects of these two anesthetics on PPCs in other types of surgery is still missing. We aimed to assess the impact of sevoflurane and propofol on the incidence of PPCs in patients undergoing surgery for head and neck cancer.

STUDY DESIGN

Double-blind, randomized, controlled trial.

METHODS

We assigned 220 adults at intermediate-to-high risk of PPCs scheduled for head and neck cancer surgery with radial forearm or fibular flap reconstruction to either propofol or sevoflurane as a general anesthetic. The occurrence of pulmonary complications according to the Clavien-Dindo score was defined as the primary (within 7 days after surgery) outcome.

RESULTS

The PPC incidence during 7 days after surgery was 32.4% and 18.2% in the propofol and sevoflurane groups, respectively (P = .027). The corresponding incidence of PPCs in patients who underwent tracheotomy at the end of surgery in the two groups was 44.8% and 24.5%, respectively (P = .030). In addition, the Clavien-Dindo classification showed significant differences between groups in minor complications (grades I and II) but not in major complications (grades III-V).

CONCLUSIONS

Compared with intravenous anesthesia, the administration of sevoflurane reduces the incidence of minor PPCs (grades I and II) in moderate- and high-risk patients who have undergone tracheotomy after head and neck cancer surgery with radial forearm or fibular flap reconstruction.

LEVEL OF EVIDENCE

2 Laryngoscope, 131:E108-E115, 2021.

Understanding and Optimizing Tourniquet Use During Extremity Surgery

Tourniquet use during extremity surgery is commonplace and a relatively safe practice. The surgical team's knowledge of the patient history, proper assessment, and indications and contraindications for and risks of tourniquet use can prevent unwanted outcomes. Exploration of these critical areas reinforces perioperative nurses' awareness and understanding of safe tourniquet use. Additionally, a review of the physiological effect of tourniquets on the skin, the body's response to local compression, the risk of vascular compromise, and the effect of the tourniquet on postoperative pain and swelling provides insight into AORN recommended practice guidelines. This article summarizes the indications and assessments for and risks of tourniquet use for patients during extremity surgery. An understanding of these topics can improve surgical outcomes and promote safe perioperative care.

Protective Effects of Dexmedetomidine and Oxycodone in Patients Undergoing Limb Ischemia-Reperfusion

Background

Tourniquet-related complications are a common clinical problem. In the present study, we compared the effects of dexmedetomidine vs. oxycodone in patients undergoing limb ischemia-reperfusion.

Material/Methods

Fifty-four patients undergoing unilateral lower-extremity surgery under combined spinal and epidural anesthesia were randomly assigned to a control (ischemia-reperfusion, I/R) group, a dexmedetomidine (Dex) group, and an oxycodone (Oxy) group. Tourniquet-induced hemodynamic parameters changes among groups were compared. The serum concentration of malondialdehyde (MDA), superoxide dismutase (SOD), tumor necrosis factor-a (TNF-α), interleukin-6 (IL-6), fatty acid binding protein 3 (FABP3), endothelin-1 (ET-1), and brain-derived neurotrophic factor (BDNF) were measured using ELISA before anesthesia and at 30 min and at 6 h after tourniquet release.

Results

In the control group, tourniquet use caused significant increases in systolic arterial pressure (SAP), mean arterial pressure (MAP), diastolic arterial pressure (DAP), and rate-pressure product. Compared with Oxy, Dex significantly decreased heart rate (HR). Both Dex and Oxy lowered SAP compared with the control group. No significant difference was observed in DAP between Dex and Oxy. The levels of MDA, TNF-α, IL-6, FABP3, and ET-1 were significantly higher, while the SOD and BDNF were significantly lower compared to baseline in the I/R group, but the variation range of those agents was significantly smaller in the Dex and Oxy groups, and the measured values were comparable between the 2 groups.

Conclusions

Compared with Dex, Oxy was not inferior in mitigating tourniquet-induced hyperdynamic response, ameliorating the inflammatory reaction, and protecting remote multiple organs in lower-extremity surgery patients.

Reduction of elevated lipids and low-density lipoprotein oxidation in serum of individuals with subclinical hypoxia and oxidative stress supplemented with lycosome formulation of docosahexaenoic acid

Thirty two individuals aged 40-65 years old with a moderate hyperlipidemia (serum triglycerides > 150 mg/dl and LDL from 130 to 160 mg/dl) were supplemented once daily for 30 days with a 250 mg conventional formulation of docosahexaenoic acid (DHA) without lycopene (CF-DHA) or 250 mg of lycosome-formulated DHA containing 7 mg of lycopene (LF-DHA). It was shown that ingestion of CF-DHA led to a transient increase in serum DHA level after 2 weeks of the trial, whereas LF-DHA did not cause significant changes in serum DHA. However, there was a noticeable increase in serum eicosapentaenoic acid levels exceeding the pretreatment value by 42.8% and 39.1% after the 2nd and 4th weeks of LF-DHA ingestion. Patients supplemented with LF-DHA showed a significant (19.5 mg/dl, p < 0.05) decline in LDL, which was accompanied by a corresponding decrease in total serum cholesterol and a much stronger reduction in serum triglyceride levels (reduction of medians by 27.5 mg/dl). No changes in HDL were observed. LF-DHA caused a significant decline in the serum level of malonic dialdehyde (MDA), whereas the components of LF-DHA, lycopene and DHA, ingested as two separate formulations had a less significant effect on serum MDA. Moreover, LF-DHA increased both the plasma oxygen transport and tissue oxygen saturation by the end of the observational period, while lycopene or DHA taken alone, or both of them co-ingested separately had none or a much less effect on the oxygen turnover parameters.

Use of Tourniquets in Limb Trauma Surgery

Although tourniquets are commonly used in patients with limb trauma patients, both in the acute and elective settings, no set protocols exist for their indications, contraindications, or proper use. This article addresses the current literature on optimal pressure, timing, cuff design, and complications of tourniquets in trauma patients. General issues are discussed, followed by those specific to upper and lower extremities. Lastly, serious complications, such as pulmonary embolism, are described.

Pharmacokinetics and Oxidation Parameters in Volunteers Supplemented with Microencapsulated Docosahexaenoic Acid

Context:

Docosahexaenoic acid (DHA) is an omega-3 fatty acid essential for cardiovascular health, brain development, and reproductive function. Due to hydrophobicity and low DHA bioavailability, new microencapsulated DHA formulations are under development.

Aim:

This study aims to evaluate DHA pharmacokinetics (PKs) and biological oxidation parameters in volunteers ingesting a newly developed lutein-containing lycosomal formulation of DHA (LF-DHA).

Materials and Methods:

A total of 32 healthy volunteers (40–65 years old) with signs of oxidative stress (OS) and subclinical hypoxia were orally supplemented for a month with 250 mg of regular DHA (1^st group) or a combination of lutein (7.0 mg) and zeaxanthin (1.4 mg) (2^nd group). The third group received regular DHA (250 mg) co-ingested with lutein/zeaxanthin (7.0/1.4 mg), whereas the 4^th group was given LF-DHA containing lutein/zeaxanthin (7.0/1.4 mg). PK, OS, and oxygenation parameters were analyzed.

Results:

LF-DHA improved the PKs of DHA enhancing its serum concentrations time dependently by 34.6% and 94.1% after 2^nd and 4^th weeks, respectively. DHA and lutein ingested either alone or simultaneously as two separate formulations reduced the levels of OS markers. However, LF-DHA inhibited the malonicdialdehyde (MDA) and oxidized low-density lipoprotein values were better than other formulations. LF-DHA also enhanced the plasma oxygen and tissue oxygen saturation. This effect was significantly higher than in other groups.

Conclusion:

LF-DHA eliminates the need in high-dose DHA supplementation protocols and confers a higher DHA bioavailability, thereby improving the parameters of biological oxidation and tissue respiration in affected individuals.

Assessment of the Pneumatic Ischemia Technique Using the Limb Occlusion Pressure During Upper Limb Surgery

PURPOSE

The purpose of our study was to evaluate effective ischemia and its associated complications using the limb occlusion pressure technique versus standard pneumatic ischemia technique.

DESIGN

Single-centered randomized, controlled clinical trial.

METHODS

One hundred sixty participants were randomized into two equal and parallel groups: (1) intervention group-LOP technique, and (2) control group-standard pneumatic ischemia technique.

FINDINGS

Anesthetic incidences (need to administer analgesics for pain and/or hypnotics for anxiety) were similar in both groups. Statistically significant differences were observed for pain, hyperemia, and hospitalization, with higher values in the control group. Patients in the intervention group had, at 95% confidence, a 2.9 times greater chance of having optimal ischemia (assessed as 9 on the analog scale) than patients in the control group (odds ratio, 2.9; 95% confidence interval, 1.4 to 6.1).

CONCLUSIONS

Intervention group patients had lower indexes of hyperemia, pain, and hospital stay.

The Effect of Transcutaneous Electrical Acupoint Stimulation on Inflammatory Response in Patients Undergoing Limb Ischemia-Reperfusion

Reperfusion after tourniquet use can induce inflammation and cause remote organ injury. We evaluated the therapeutic effect of transcutaneous electrical acupoint stimulation (TEAS) on inflammatory mediators and lung function in patients receiving lower limb tourniquets. Forty patients undergoing unilateral lower extremity surgery with tourniquet were randomly assigned to two groups: the TEAS group and ischemia-reperfusion (I/R) group. The C-C motif chemokine ligand 2 (CCL2), C-X-C motif chemokine ligand 8 (CXCL8), interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and arterial blood gas analysis were measured preoperatively and 6 h after tourniquet removal. The levels of CXCL8, IL-1, IL-6, TNF-α, and CCL2 were significantly increased compared to baseline values in both groups, but the increase was significantly smaller in the TEAS group. In the TEAS group, the partial pressure of oxygen and arterial-alveolar oxygen tension ratio were significantly decreased, and the alveolar-arterial oxygen tension difference and respiratory index were significantly increased, compared to those in the I/R group at 6 h after reperfusion. In conclusion, TEAS diminished the upregulation of proinflammatory factors in response to lower limb ischemia-reperfusion and improved pulmonary gas exchange.

Role of the plasma cascade systems in ischemia/reperfusion injury of bone

Ischemia/reperfusion (I/R) injury has been extensively studied in organs such as heart, brain, liver, kidney, and lung. As a vascularized organ, bone is known to be susceptible to I/R injury too, but the respective mechanisms are not well understood to date. We therefore hypothesized that, similar to other organs, plasma cascade-induced inflammation also plays a role in bone I/R injury. Reperfusion injury in rat tibia was induced by unilateral clamping of the femoral artery and additional use of a tourniquet, while keeping the femoral vein patent to prevent venous congestion. Rats were subjected to 4h ischemia and 24h reperfusion. Deposition of complement fragment C3b/c and fibrin as well as expression of tissue factor (TF), tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), and E-selectin was detected by immunohistochemistry. In plasma, the levels of high mobility group box1 (HMGB1) were measured by ELISA. The total level of complement in serum was assessed by the CH50 test. Our results show that deposition of C3b/c was significantly increased with respect to healthy controls in cortical bone as well as in marrow of reperfused limbs. C3b/c deposition was also increased in cortical bone, but not in bone marrow, of contralateral limbs. Deposition of fibrin, as well as expression of PAI-1, was significantly increased in bone after ischemia and reperfusion, whereas expression of tPA was reduced. These differences were most prominent in vessels of bone, both in marrow and cortical bone, and both in reperfused and contralateral limbs. However, PAI-1, was only increased in vessels of reperfused cortical bone and there were no significant changes in expression of E-selectin. With respect to solid bone tissue, a significant increase of C3b/c and fibrin deposition was shown in osteocytes, and for fibrin also in the bone matrix, in both contralateral and reperfused cortical bone compared with normal healthy controls. A slight expression of TF was visible in osteocytes of the normal healthy control group, while TF was not present in the experimental groups. Moreover, CH50 values in serum decreased over time and HMGB1 was significantly increased in plasma of animals at the end of reperfusion. We conclude that ischemia and reperfusion of bone leads to activation of the complement and coagulation systems and a downregulation of the fibrinolytic cascade. In the acute phase, a vascular inflammation induced by activation of the plasma cascade systems also occurs in the bone. This is similar to I/R injury of other vascularized organs and tissues.

Effect of two administration routes of Shenmai Injection () on pulmonary gas exchange function after tourniquet-induced ischemia-reperfusion

OBJECTIVE

To compare the effect between nebulized and intravenous administration of Shenmai Injection () on pulmonary gas exchange function of patients following tourniquet-induced lower limb ischemia-reperfusion.

METHODS

Thirty-eight patients scheduled for lower extremity surgery were randomized into three groups using the closed envelop method: Shenmai Injection was administered 30 min before tourniquet inflflation by nebulization [0.6 mL/kg in 10 mL normal saline (NS)] in the nebulization group or by intravenous drip (0.6 mL/kg dissolved in 250 mL of 10% glucose) in the intravenous drip group, and equal volume of NS was given intravenously in the NS group; 15 in each group. Arterial blood gases were analyzed, serum levels of malonaldehyde (MDA) and interleukine-6 (IL-6) and interleukine-8 (IL-8) were determined using the method of thiobarbituric acid reaction and enzyme-linked immuno sorbent assay respectively just before tourniquet inflflation (T0), and at 0.5 h (T1), 2 h (T2), 6 h (T3) after tourniquet deflflation.

RESULTS

Compared with baselines at T0, MDA levels signifificantly increased at T2, T3 in the NS group and at T3 in the nebulization group, and IL-6 and IL-8 levels were signifificantly increased at T2, T3 in NS, the intravenous drip and the nebulization groups (P <0.05). Arterial pressure of oxygen (PaO₂) at T3 was decreased, while alveolararterial oxygen tension showed difference (PA-aDO₂) at T3 in the NS group; RI at T3 in both intravenous drip and the nebulization groups were enhanced (P <0.05). Compared with the NS group, MDA and IL-8 levels at T2, T3, IL-6 at T3 in the intravenous drip group, and IL-8 at T3 in the nebulization group were all remarkably increased (P <0.05). Additionally, MDA level at T3 in the nebulization group was higher than that in the intravenous drip group (P <0.05).

CONCLUSIONS

Intravenous administration of Shenmai Injection provided a better protective effect than nebulization in mitigating pulmonary gas exchange dysfunction in patients following tourniquet-induced limb ischemia-reperfusion.

Remote ischemic preconditioning as prevention of transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a serious complication of transfusion medicine, considered now as the leading cause of transfusion-related mortality. It may occur in up to 1 in 5000 transfusions and carries an elevated morbidity and mortality. Clinically it presents as hypoxia and non-cardiogenic pulmonary edema, usually within 6h of transfusion. It consists of an immunological phenomenon involving the activation of neutrophils and endothelial injury, leading to capillary leak and pulmonary edema, mechanisms shared with lung ischemia-reperfusion (IR) injury. Brief and repetitive periods of ischemia in an organ or limb have been shown to protect against subsequent major IR injury in distant organs, a phenomenon called remote ischemic preconditioning (RIPC). Limb RIP has been shown to protect the lung against IR injury trough modulation of endothelial function as well as neutrophil activation and infiltration. The protective effects of RIPC on the lung have been confirmed in clinical trials of orthopedic and cardiothoracic surgery. RIPC is a safe, tolerable and cheap procedure. I propose that limb RIPC could be used as a preventive strategy against the development of TRALI.

Biomarkers for ischemic preconditioning: finding the responders

Ischemic preconditioning is emerging as an innovative and novel cytoprotective strategy to counter ischemic vascular disease. At the root of the preconditioning response is the upregulation of endogenous defense systems to achieve ischemic tolerance. Identifying suitable biomarkers to show that a preconditioning response has been induced remains a translational research priority. Preconditioning leads to a widespread genomic and proteonomic response with important effects on hemostatic, endothelial, and inflammatory systems. The present article summarizes the relevant preclinical studies defining the mechanisms of preconditioning, reviews how the human preconditioning response has been investigated, and which of these bioresponses could serve as a suitable biomarker. Human preconditioning studies have investigated the effects of preconditioning on coagulation, endothelial factors, and inflammatory mediators as well as on genetic expression and tissue blood flow imaging. A biomarker for preconditioning would significantly contribute to define the optimal preconditioning stimulus and the extent to which such a response can be elicited in humans and greatly aid in dose selection in the design of phase II trials. Given the manifold biologic effects of preconditioning a panel of multiple serum biomarkers or genomic assessments of upstream regulators may most accurately reflect the full spectrum of a preconditioning response.

The Delay Phenomenon: A Compilation of Knowledge across Specialties

Objective The purpose of this article is to review and integrate the available literature in different fields to gain a better understanding of the basic physiology and optimize vascular delay as a reconstructive surgery technique. Methods A broad search of the literature was performed using the Medline database. Two queries were performed using "vascular delay," a search expected to yield perspectives from the field of plastic and reconstructive surgery, and "ischemic preconditioning," (IPC) which was expected to yield research on the same topic in other fields. Results The combined searches yielded a total of 1824 abstracts. The "vascular delay" query yielded 76 articles from 1984 to 2011. The "ischemic preconditioning" query yielded 6534 articles, ranging from 1980 to 2012. The abstracts were screened for those from other specialties in addition to reconstructive surgery, analyzed potential or current uses of vascular delay in practice, or provided developments in understanding the pathophysiology of vascular delay. 70 articles were identified that met inclusion criteria and were applicable to vascular delay or ischemic preconditioning. Conclusion An understanding of IPC's implementation and mechanisms in other fields has beneficial implications for the field of reconstructive surgery in the context of the delay phenomenon. Despite an incomplete model of IPC's pathways, the anti-oxidative, anti-apoptotic and anti-inflammatory benefits of IPC are well recognized. The activation of angiogenic genes through IPC could allow for complex flap design, even in poorly vascularized regions. IPC's promotion of angiogenesis and reduction of endothelial dysfunction remain most applicable to reconstructive surgery in reducing graft-related complications and flap failure.

Protection of organs other than the heart by remote ischemic conditioning

Organ or tissue dysfunction due to acute ischemia-reperfusion injury (IRI) is the leading cause of death and disability worldwide. Acute IRI induces cell injury and death in a wide variety of organs and tissues in a large number of different clinical settings. One novel therapeutic noninvasive intervention, capable of conferring multiorgan protection against acute IRI, is 'remote ischemic conditioning' (RIC). This describes an endogenous protective response to acute IRI, which is triggered by the application of one or more brief cycles of nonlethal ischemia and reperfusion to one particular organ or tissue. Originally discovered as a therapeutic strategy for protecting the myocardium against acute IRI, it has been subsequently demonstrated that RIC may confer protection against acute IRI in a number of different noncardiac organs and tissues including the kidneys, lungs, liver, skin flaps, ovaries, intestine, stomach and pancreas. The discovery that RIC can be induced noninvasively by applying the RIC stimulus to the skeletal tissue of the upper or lower limb has facilitated its application to a number of clinical settings in which organs and tissues are at high risk of acute IRI. In this article, we review the experimental studies that have investigated RIC in organs and tissues other than the heart, and we explore the therapeutic potential of RIC in preventing organ and tissue dysfunction induced by acute IRI.

Ischemic preconditioning attenuates lipid peroxidation and apoptosis in the cecal ligation and puncture model of sepsis

Sepsis and septic shock are are among the major causes of mortality in intensive care units. The lung and kidney are the organs most affected by sepsis. Evidence exists that lipid peroxidation and apoptosis may be responsible for the high mortality due to sepsis. Ischemic preconditioning (IP) is a method for the protection of tissues and organs against ischemia/reperfusion injury by reducing reactive oxygen species levels, lipid peroxidation and apoptosis. In the present study, the effects of IP were investigated in cecal ligation and puncture (CLP)-induced sepsis in rats. The three groups of animals used in the present controlled study were the sham-operated group (sham, n=7), which only underwent a laparotomy; the sepsis group (sepsis, n=7), which underwent cecal ligation and perforation; and the IP + sepsis group (IP+sepsis, n=7), which underwent CLP immediately prior to the application of three cycles of IP to the hind limb. The study was terminated at 6 h after the induction of CLP. Blood, kidney and lung tissue samples were collected for the determination of serum creatinine, blood urea nitrogen (BUN), neutrophil gelatinase-associated lipocalin (NGAL) and lung tissue malondialdehyde (MDA) levels, as well as histological examination. The serum creatinine, plasma NGAL and lung tissue MDA levels in the sepsis group were significantly increased compared with those in the sham and the IP+sepsis groups (P<0.05). Alveolar macrophage counts, histological kidney and lung injury scores, kidney (caspase 3) and lung tissue immuonreactivity (M30) scores in the sepsis group were also significantly increased compared with those in the sham and IP+sepsis groups (P<0.05). The alveolar macrophage count in the IP+sepsis group was increased compared with that in the sham group (P<0.05). In conclusion, IP inhibits lipid peroxidation and attenuates histological injury and apoptosis in the lung and kidney during sepsis.

Different oxidative stress marker levels in blood from the operated knee or the antecubital vein in patients undergoing knee surgery: a tourniquet-induced ischemia-reperfusion model

BACKGROUND

In knee surgery a tourniquet is usually applied in order to provide a bloodless surgical field. This study aims to compare, in a tourniquet-induced ischemia-reperfusion model, the glutathione oxidation and lipid peroxidation in two different blood sources: an operated knee drainage tube or the antecubital vein.

METHODS

Thirty-two patients undergoing total knee replacement were studied. We measured reduced glutathione (GSH), oxidized glutathione (GSSG), malondialdehyde (MDA) and other metabolic parameters in the blood from the operated knee (17 patients), or from the antecubital vein (15 patients) before tourniquet inflation (T(0)) and after tourniquet release at different times: 3, 10, and 60 minutes (T(1), T(2), and T(3), respectively).

RESULTS

We have found an early increase of approximately 100% in GSSG and MDA blood levels coinciding with a decrease in GSH levels at T(1)-T(3) in blood from the operated knee. These changes were also observed in blood from the antecubital vein at T(1) and T(2), but at lower levels than in blood from the operated knee.

CONCLUSIONS

There is an intense glutathione oxidation and lipid peroxidation in the operated knee after tourniquet deflation. The surgical drainage is a good source of blood for the determination of biomarkers in a tourniquet-induced ischemia-reperfusion model, because changes are observed more early and it is more direct than another source of systemic blood.

Cuff width increases the serum biochemical markers of tourniquet-induced skeletal muscle ischemia in rabbits

Tourniquet application is a widely accepted adjuvant technique in extremity surgery. The purpose of this prospective, randomized trial was to evaluate the effect of cuff width on skeletal muscle ischemia-reperfusion injury. A 2- or 4-cm wide curved tourniquet cuff was applied around the midthigh of 36 New Zealand White rabbits and inflated to a pressure of 200 or 400 mm Hg for 2 hours: group A=2 cm to 200 mm Hg; group B=2 cm to 400 mm Hg; group C=4 cm to 200 mm Hg; group D=4 cm to 400 mm Hg. Blood levels of potassium, lactic acid, urea, lactic dehydrogenase, and creatinine phosphokinase MM isoenzyme (CPK-MM) were measured as basic indicators for limb ischemia before tourniquet inflation and 1, 5, and 30 minutes after cuff release.Potassium values did not differ among the 4 groups. Lactic acid and urea concentrations were always higher in the 400 mm Hg groups (B and D) (P<.001). However, cuff width did not affect their levels (P>.16). Lactic dehydrogenase and CPK-MM values were also greater in the 400 mm Hg groups at all times (P<.001). Further subgroup analysis of 200 mm Hg pressure groups showed higher lactic dehydrogenase (P<.02) but not CPK-MM (P>.9) concentrations in group C than in group A during the 30-minute period. At 400 mm Hg, lactic dehydrogenase and CPK-MM values were higher in group D compared with group B only 30 minutes after cuff deflation (P<.001). Broad tourniquets are associated with significantly greater and prolonged elevation of serum biochemical markers of inducible skeletal muscle ischemia-reperfusion injury compared with narrow ones. This difference is more prominent when a wide cuff is inflated to a high pressure.

Assessment of endothelium and inflammatory response at the onset of reperfusion injury in hand surgery

Background

Activation of the endothelium, complement activation and generation of cytokines are known events during ischemia-reperfusion (I/R) that mediate tissue injury. Our aim was to elucidate their respective participation at the onset of the reperfusion phase. Tourniquet application in hand surgery causes short-term ischemia, followed by reperfusion and was therefore used as the model in this study.

Methods

Ten patients were included in the study after obtaining informed consent. A tourniquet was placed on the upper arm and inflated to 250 mmHg for 116 ± 16 min, during which the surgery was performed. Venous blood and tissue samples from the surgical area were taken at baseline as well as 0, 2, and 10 min after reperfusion and analyzed for the following parameters: Endothelial integrity and/or activation were analyzed by measuring heparan sulfate and syndecan-1 in serum, and vWF, heparan sulfate proteoglycan as well as CD31on tissue. Complement activation was determined by C3a and C4d levels in plasma, levels of C1-inhibitor in serum, and IgG, IgM, C3b/c, and C4b/c deposition on tissue. Cytokines and growth factors IL-5, IL-6, IL-7, IL-8, IL-10, IL-17, G-CSF, GM-CSF, MCP-1, TNFα, VEGF, and PDGF bb were measured in the serum. Finally, CK-MM levels were determined in plasma as a measure for muscle necrosis.

Results

Markers for endothelial activation and/or integrity as well as complement activation showed no significant changes until 10 min reperfusion. Among the measured cytokines, IL-6, IL-7, IL-17, TNFα, GM-CSF, VEGF, and PDGF bb were significantly increased at 10 min reperfusion with respect to baseline. CK-MM showed a rise from baseline at the onset of reperfusion (p < 0.001) and dropped again at 2 min (p < 0.01) reperfusion, suggesting ischemic muscle damage.

Conclusions

In this clinical model of I/R injury no damage to the endothelium, antibody deposition or complement activation were observed during early reperfusion. However, an increase of pro-inflammatory cytokines and growth factors was shown, suggesting a contribution of these molecules in the early stages of I/R injury.