Remote Ischemic Preconditioning Decreases Oxidative Lung Damage After Pulmonary Lobectomy: A Single-Center Randomized, Double-Blind, Controlled Trial

Effect of Remote Ischemic Conditioning on Organ Transplantation: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Remote ischemic conditioning (RIC) has shown great advantages in protecting organs from ischemia-reperfusion loss and applied research on RIC continues to increase. We performed a systematic review and meta-analysis to comprehensively investigate the value of RIC for different organ transplantation.

METHODS

We searched PubMed, EMBASE, and the Cochrane Library from inception to November 1, 2023, for randomized controlled trials investigating whether RIC has an advantage in organ transplantation (including heart, lung, liver, and kidney) compared with controls. The primary outcomes varied according to the transplanted organ, including liver transplantation (graft loss, early allograft dysfunction, acute kidney injury, days in hospital, and mortality); kidney transplantation (delayed graft function, acute rejection (AR), graft loss, 50% decrease in serum creatinine, glomerular filtration rate, days in hospital, and mortality); heart and lung transplantation (AR, mortality). Two investigators independently selected suitable trials, assessed trial quality, and extracted the data.

RESULTS

A total of 11 randomized controlled trials were included in this study, including six kidney transplants, three liver transplants, and one heart and lung transplant each, with 561 RIC cases and 564 controls, and a total of 1125 patients. The results showed that RIC did not reduce mortality in transplant patients compared with controls (liver transplant: RR0.9, 95% confidence interval [0.31-2.66]; kidney transplant: RR 0.76, 95% confidence interval [0.17-3.33]), graft failure rate (liver transplantation: RR 0.3, 95% confidence interval [0.07, 1.19]; kidney transplantation: RR 0.89, 95% confidence interval [0.35, 2.27]), length of hospital stay (liver transplantation: standard mean difference [SMD] 0.14, 95% confidence interval [-0.15, 0.42]; kidney transplantation: SMD -0.1, 95% confidence interval [-0.3, 0.11]). In addition, RIC did not improve early liver function after liver transplantation (RR 0.97, 95% confidence interval [0.55,1.7]), acute kidney injury after liver transplantation (RR 1.17 95% confidence interval [0.9, 1.54]), delayed functional recovery after renal transplantation (RR 0.84, 95% confidence interval [0.62, 1.15]), AR rate (RR 1.04, 95% confidence interval [0.72, 1.49]), 50% serum creatinine decline rate (RR 1.1, 95% confidence interval [0.88, 1.37]), glomerular filtration rate 3 months after surgery (SMD 0.13, 95% confidence interval [-0.05, 0.31]) and postoperative 12 months glomerular filtration rate (SMD 0.13, 95% confidence interval [-0.06, 0.31]).

CONCLUSION

Remote ischemic modulation does not improve clinical outcomes in patients undergoing organ transplantation (heart, lung, liver, and kidney).

Transcutaneous electrical acupoint stimulation improves pulmonary function by regulating oxidative stress during one-lung ventilation in patients with lung cancer undergoing thoracoscopic surgery: a randomized controlled trial

BACKGROUND

Our aim was to evaluate the efficacy of transcutaneous electrical acupoint stimulation (TEAS) on oxidative stress induced by one-lung ventilation, lung function, and postoperative quality of recovery in patients with lung cancer.

METHODS

The participants (n = 80) were assigned to the sham group and TEAS group. TEAS on bilateral Feishu (BL13), Zusanli (ST36), and Hegu (L14) was performed 30 minutes before induction of anesthesia and continued until the end of the surgery. In the sham group, the same acupoints were selected without electrical stimulation. PaO2/FiO2, intrapulmonary shunt ratio (Qs/Qt), alveolar-arterial oxygen tension (A-aDO2), and respiratory index (RI) were calculated to evaluate lung function before one-lung ventilation (T0), 30 min after one-lung ventilation (T1), 1 h after one-lung ventilation (T2), and 10 min after resuming two-lung ventilation (T3). The levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were detected to estimate oxidative stress at T0, T1, T2, and T3. Secondary outcomes included removal time of thoracic drainage tube, duration of intensive care unit (ICU) stay, length of postoperative hospitalization, the incidence of postoperative pulmonary complications, and the Quality of Recovery-15 (QoR-15) score on postoperative day 1 and 2.

RESULTS

TEAS significantly increased PaO2/FiO2 at T1 and T2, while Qs/Qt, A-aDO2, and RI decreased remarkably from T1 to T3 (P < 0.05). Meanwhile, TEAS obviously decreased MDA and increased SOD activity at T2 and T3 (P < 0.05). Furthermore, TEAS also markedly shortened the length of ICU stay and hospital stay after surgery, whereas the QoR-15 score on postoperative day 1 and 2 was significantly higher (P < 0.05).

CONCLUSIONS

TEAS could reduce oxidative lung injury during one-lung ventilation, thereby protecting pulmonary function and effectively accelerating the early recovery of patients with lung cancer.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR2000038243).

Effect of remote ischemic preconditioning on lung function after surgery under general anesthesia: a systematic review and meta-analysis

Remote ischemic preconditioning (RIPC) protects organs from ischemia-reperfusion injury. Recent trials showed that RIPC improved gas exchange in patients undergoing lung or cardiac surgery. We performed a systematic search to identify randomized controlled trials involving RIPC in surgery under general anesthesia. The primary outcome was the PaO2/FIO2 (P/F) ratio at 24 h after surgery. Secondary outcomes were A-a DO2, the respiratory index, duration of postoperative mechanical ventilation (MV), incidence of acute respiratory distress syndrome (ARDS), and serum cytokine levels. The analyses included 71 trials comprising 7854 patients. Patients with RIPC showed higher P/F ratio than controls (mean difference [MD] 36.6, 95% confidence interval (CI) 12.8 to 60.4, I2 = 69%). The cause of heterogeneity was not identified by the subgroup analysis. Similarly, A-a DO2 (MD 15.2, 95% CI - 29.7 to - 0.6, I2 = 87%) and respiratory index (MD - 0.17, 95% CI - 0.34 to - 0.01, I2 = 94%) were lower in the RIPC group. Additionally, the RIPC group was weaned from MV earlier (MD - 0.9 h, 95% CI - 1.4 to - 0.4, I2 = 78%). Furthermore, the incidence of ARDS was lower in the RIPC group (relative risk 0.73, 95% CI 0.60 to 0.89, I2 = 0%). Serum TNFα was lower in the RIPC group (SMD - 0.6, 95%CI - 1.0 to - 0.3 I2 = 87%). No significant difference was observed in interleukin-6, 8 and 10. Our meta-analysis suggested that RIPC improved oxygenation after surgery under general anesthesia.Clinical trial number: This study protocol was registered in the University Hospital Medical Information Network (registration number: UMIN000030918), https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000035305.

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.

Primary graft dysfunction following lung transplantation: From pathogenesis to future frontiers

Lung transplantation is the treatment of choice for patients with end-stage lung disease. Currently, just under 5000 lung transplants are performed worldwide annually. However, a major scourge leading to 90-d and 1-year mortality remains primary graft dysfunction. It is a spectrum of lung injury ranging from mild to severe depending on the level of hypoxaemia and lung injury post-transplant. This review aims to provide an in-depth analysis of the epidemiology, pathophysiology, risk factors, outcomes, and future frontiers involved in mitigating primary graft dysfunction. The current diagnostic criteria are examined alongside changes from the previous definition. We also highlight the issues surrounding chronic lung allograft dysfunction and identify the novel therapies available for ex-vivo lung perfusion. Although primary graft dysfunction remains a significant contributor to 90-d and 1-year mortality, ongoing research and development abreast with current technological advancements have shed some light on the issue in pursuit of future diagnostic and therapeutic tools.

Effect of remote ischemic preconditioning on postoperative gastrointestinal function in patients undergoing laparoscopic colorectal cancer resection

PURPOSE

Patients undergoing laparoscopic colorectal cancer resection have a high incidence of postoperative gastrointestinal dysfunction (POGD). Remote ischemic preconditioning (RIPC) is an organ protection measure. The study investigated the effect of RIPC on postoperative gastrointestinal function.

METHODS

In this single-center, prospective, double-blinded, randomized, parallel-controlled trial, 100 patients undergoing elective laparoscopic colorectal cancer resection were randomly assigned in a 1:1 ratio to receive RIPC or sham RIPC (control). Three cycles of 5-min ischemia/5-min reperfusion induced by a blood pressure cuff placed on the right upper arm served as RIPC stimulus. Patients were followed up continuously for 7 days after surgery. The I-FEED score was used to evaluate the patient's gastrointestinal function after the surgery. The primary outcome of the study was the I-FEED score on POD3. Secondary outcomes include the daily I-FEED scores, the highest I-FEED score, the incidence of POGD, the changes in I-FABP and the inflammatory markers (IL-6 and TNF-α), and the time to first postoperative flatus.

RESULTS

A total of 100 patients were enrolled in the study, of which 13 patients were excluded. Finally, 87 patients were included in the analysis, 44 patients in the RIPC group and 43 patients in the sham-RIPC group. Patients assigned to the RIPC group had a lower I-FEED score on POD3 compared with the sham-RIPC group (mean difference 0.86; 95% CI: 0.06 to 1.65; P = 0.035). And patients in the RIPC group were also associated with a lower I-FEED score on POD4 vs the sham-RIPC group (mean difference 0.81; 95% CI: 0.03 to 1.60; P = 0.043). Compared with the sham-RIPC group, the incidence of POGD within 7 days after surgery was lower in the RIPC group (P = 0.040). At T₁, T₂, and T₃ time points, inflammatory factors and I-FABP were considerably less in the RIPC group compared to the sham-RIPC group. The time to the first flatus and the first feces was similar in both groups.

CONCLUSION

RIPC reduced I-FEED scores, decreased the incidence of postoperative gastrointestinal dysfunction, and lowered concentrations of I-FABP and inflammatory factors.

A Meta-Analysis of Remote Ischemic Preconditioning in Lung Surgery and Its Potential Role in COVID-19

Purpose: To determine the effects of remote ischemic preconditioning (RIPC) on pulmonary gas exchange in people undergoing pulmonary surgery and discuss a potential role of RIPC in COVID-19. Method: A search for studies examining the effects of RIPC after pulmonary surgery was performed. RevMan was used for statistical analyses examining measures of A-ado2, Pao2/Fio2, respiratory index (RI), a/A ratio and Paco2 obtained earlier after surgery (i.e., 6-8 hours) and later after surgery (i.e., 18-24 hours). Results: Four trials were included (N = 369 participants). Significant (p < 0.05) overall effects of RIPC were observed early after surgery on A-ado2 and RI (SMD -0.84 and SMD -1.23, respectively), and later after surgery on RI, Pao2/Fio2, and a/A ratio (SMD -0.39, 0.72, and 1.15, respectively) with the A-ado2 approaching significance (p = 0.05; SMD -0.45). Significant improvements in inflammatory markers and oxidative stress after RIPC were also observed. Conclusions: RIPC has the potential to improve pulmonary gas exchange, inflammatory markers, and oxidative stress in people with lung disease undergoing lung surgery and receiving mechanical ventilation. These potential improvements may be beneficial for people with COVID-19, but further investigation is warranted.

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.

Repeated intermittent hypoxic stimuli to operative lung reduce hypoxemia during subsequent one-lung ventilation for thoracoscopic surgery: A randomized controlled trial

Background

An intervention to potentiate hypoxic pulmonary vasoconstriction may reduce intrapulmonary shunt and hypoxemia during one-lung ventilation. Previous animal studies reported that repeated intermittent hypoxic stimuli potentiated hypoxic pulmonary vasoconstriction, but no clinical study has examined the effects of this intervention on hypoxemia during one-lung ventilation. We thus performed a single-center, parallel-group, double-blind, randomized controlled trial to investigate whether repeated intermittent hypoxic stimuli to the operative lung reduce hypoxemia during the subsequent one-lung ventilation for thoracoscopic surgery.

Methods

Patients undergoing one-lung ventilation were randomized into two groups (n = 68 each). Before one-lung ventilation, in the intermittent hypoxia group, the nondependent lung was not ventilated for 2 min and then ventilated for 2 min while the dependent lung was continuously ventilated. This was repeated five times. In the continuous normoxia group, both lungs were ventilated for 20 min. We measured SpO₂, PaO₂, FiO₂, PaCO₂, SaO₂, and central venous oxygen saturation during one-lung ventilation. The primary outcome was the number of patients with hypoxemia defined as a SpO₂ <95% during one-lung ventilation, which was analyzed with a chi-squared test.

Results

Hypoxemia was less frequent in the intermittent hypoxia group than in the continuous normoxia group during OLV [6/68 (8.8%) vs 17/68 (25.0%), risk ratio (95% CI) 0.35 (0.15–0.84), p = 0.012]. The PaO₂ (p = 0.008 for 30 min and 0.007 for 60 min) and PaO₂/FiO₂ (p = 0.008 for both) were higher 30 and 60 min after starting one-lung ventilation, and the alveolar-arterial pressure gradient (p = 0.010) and shunt index (p = 0.008) were lower 30 min after starting one-lung ventilation in the intermittent hypoxia group than in the continuous normoxia group. Postoperative adverse events did not differ significantly between groups.

Conclusions

Repeated intermittent hypoxic stimuli to the operative lung seemed to potentiate hypoxic pulmonary vasoconstriction, and thus reduced hypoxemia during the subsequent one-lung ventilation.

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 conditioning for acute respiratory distress syndrome in COVID-19

Acute respiratory distress syndrome and subsequent respiratory failure remains the leading cause of death (>80%) in patients severely impacted by COVID-19. The lack of clinically effective therapies for COVID-19 calls for the consideration of novel adjunct therapeutic approaches. Though novel antiviral treatments and vaccination hold promise in control and prevention of early disease, it is noteworthy that in severe cases of COVID-19, addressing "run-away" inflammatory cascades are likely more relevant for improvement of clinical outcomes. Viral loads may decrease in severe, end-stage coronavirus cases, but a systemically damaging cytokine storm persists and mediates multiple organ injury. Remote ischemic conditioning (RIC) of the limbs has shown potential in recent years to protect the lungs and other organs against pathological conditions similar to that observed in COVID-19. We review the efficacy of RIC in protecting the lungs against acute injury and current points of consideration. The beneficial effects of RIC on lung injury along with other related cardiovascular complications are discussed, as are the limitations presented by sex and aging. This adjunct therapy is highly feasible, noninvasive, and proven to be safe in clinical conditions. If proven effective in clinical trials for acute respiratory distress syndrome and COVID-19, application in the clinical setting could be immediately implemented to improve outcomes.

Protective effects of remote ischemic preconditioning against spinal cord ischemia-reperfusion injury in rats

OBJECTIVES

We aimed to investigate the protective effect of remote ischemic preconditioning against spinal cord ischemia and find a clue to its mechanism by measuring glutamate concentrations in the spinal ventral horn.

METHODS

Male Sprague-Dawley rats were divided into 5 groups (n = 6 in each group) as follows: sham; SCI (only spinal cord ischemia); RIPC/SCI (perform remote ischemic preconditioning before spinal cord ischemia); MK-801/RIPC/SCI (administer MK-801, N-methyl-D-aspartate receptor antagonist, before remote ischemic preconditioning); and MK-801/SCI (administer MK-801 without remote ischemic preconditioning). Remote ischemic preconditioning was achieved by brief limb ischemia 80 minutes before spinal cord ischemia. MK-801 (1 mg/kg, intravenous) was administered 60 minutes before remote ischemic preconditioning. The glutamate concentration in the ventral horn was measured by microdialysis for 130 minutes after spinal cord ischemia. Immunofluorescence was also performed to evaluate the expression of N-methyl-D-aspartate receptor 2B subunit in the ventral horn 130 minutes after spinal cord ischemia.

RESULTS

The glutamate concentrations in the spinal cord ischemia group were significantly higher than in the sham group at all time points (P < .01). Remote ischemic preconditioning attenuated the spinal cord ischemia-induced glutamate increase. When MK-801 was preadministered before remote ischemic preconditioning, glutamate concentration was increased after spinal cord ischemia (P < .01). Immunofluorescence showed that remote ischemic preconditioning prevented the increase in the expression of N-methyl-D-aspartate receptor 2B subunit on the surface of motor neurons (P = .047).

CONCLUSIONS

Our results showed that remote ischemic preconditioning prevented spinal cord ischemia-induced extracellular glutamate increase in ventral horn and suppressed N-methyl-D-aspartate receptor 2B subunit expression.

Remote Ischemic Preconditioning Prevents Postoperative Acute Kidney Injury After Open Total Aortic Arch Replacement: A Double-Blind, Randomized, Sham-Controlled Trial

BACKGROUND

Acute kidney injury is a common complication after open total aortic arch replacement but lacks effective preventive strategies. Remote ischemic preconditioning has controversial results of its benefit to the kidney and may perform better in high-risk patients of acute kidney injury. We investigated whether remote ischemic preconditioning would prevent postoperative acute kidney injury after open total aortic arch replacement.

METHODS

We enrolled 130 patients scheduled for open total aortic arch replacement and randomized them to receive either remote ischemic preconditioning (4 cycles of 5-minute right upper limb ischemia and 5-minute reperfusion) or sham preconditioning (4 cycles of 5-minute right upper limb pseudo ischemia and 5-minute reperfusion), both via blood pressure cuff inflation and deflation. The primary end point was the incidence of acute kidney injury within 7 days after the surgery defined by the Kidney Disease: Improving Global Outcomes criteria. Secondary end point included short-term clinical outcomes.

RESULTS

Significantly fewer patients developed postoperative acute kidney injury with remote ischemic preconditioning compared with sham (55.4% vs 73.8%; absolute risk reduction, 18.5%; 95% CI, 2.3%-34.6%; P = .028). Remote ischemic preconditioning significantly reduced acute kidney injury stage II-III (10.8% vs 35.4%; P = .001). Remote ischemic preconditioning shortened the mechanical ventilation duration (18 hours [interquartile range, 14-33] versus 25 hours [interquartile range, 17-48]; P = .01), whereas no significant differences were observed between groups in other secondary outcomes.

CONCLUSIONS

Remote ischemic preconditioning prevented acute kidney injury after open total aortic arch replacement, especially severe acute kidney injury and shortened mechanical ventilation duration. The observed renoprotective effects of remote ischemic preconditioning require further investigation in both clinical research and the underlying mechanism.

Anaesthetic management of organ transplant patients

In this paper we will describe anaesthetic management of solid organ and reconstructive transplantation (RT) patients. We will focus on similar underlying principles of reperfusion, ischaemic-reperfusion injury, preconditioning and extracorporeal donor organ preservation. Special concerns for anaesthetic management of these patients need to focus on pre-assessment, pre-operative optimisation, vascular access, fluid management, blood and products replacement, cardiovascular monitoring, use of inotropes and vasoconstrictors, maintaining electrolyte balance and regional anaesthesia. Despite the complexity and long duration of transplant procedures, fast-tracking to the surgical ward after transplantation is becoming more popular and its benefits are well recognised.

Remote ischemic conditioning: a promising therapeutic intervention for multi-organ protection

Despite decades of formidable exploration, multi-organ ischemia-reperfusion injury (IRI) encountered, particularly amongst elderly patients with clinical scenarios, such as age-related arteriosclerotic vascular disease, heart surgery and organ transplantation, is still an unsettled conundrum that besets clinicians. Remote ischemic conditioning (RIC), delivered via transient, repetitive noninvasive IR interventions to distant organs or tissues, is regarded as an innovative approach against IRI. Based on the available evidence, RIC holds the potential of affording protection to multiple organs or tissues, which include not only the heart and brain, but also others that are likely susceptible to IRI, such as the kidney, lung, liver and skin. Neuronal and humoral signaling pathways appear to play requisite roles in the mechanisms of RIC-related beneficial effects, and these pathways also display inseparable interactions with each other. So far, several hurdles lying ahead of clinical translation that remain to be settled, such as establishment of biomarkers, modification of RIC regimen, and deep understanding of underlying minutiae through which RIC exerts its powerful function. As this approach has garnered an increasing interest, herein, we aim to encapsulate an overview of the basic concept and postulated protective mechanisms of RIC, highlight the main findings from proof-of-concept clinical studies in various clinical scenarios, and also to discuss potential obstacles that remain to be conquered. More well designed and comprehensive experimental work or clinical trials are warranted in future research to confirm whether RIC could be utilized as a non-invasive, inexpensive and efficient adjunct therapeutic intervention method for multi-organ protection.

Limb Ischemic Conditioning Induces Oxidative Stress Followed by a Correlated Increase of HIF-1α in Healthy Volunteers

BACKGROUND

Local and remote ischemic preconditioning has been used as a protective intervention against ischemia/reperfusion (I/R) damage in several preclinical and clinical studies. However, its physiological mechanisms are not completely known. I/R increases the production of reactive oxygen species, which also serve as messengers for a variety of functions. Hypoxia-inducible factor 1 alpha (HIF-1α) is probably the most important transcription factor mediator of hypoxic signaling.

OBJECTIVE

We hypothesized that limb ischemic conditioning (LIC) induces a local oxidative/nitrosative stress and a correlated increase of HIF-1α plasma levels.

METHODS

An observational, prospective, and single-center study has been conducted in 27 healthy volunteers. LIC was applied: three cycles (5 min of ischemia followed by 5 min of reperfusion) using an ischemia cuff placed on the upper left arm. Time course of 8-isoprostane, nitrite, and HIF-1α levels was measured in blood plasma. Venous blood was sampled from the left arm before tourniquet inflation (basal) and after LIC: 1 min and 2 hr for 8-isoprostane and nitrite; and 1 min, 2 hr, 8 hr, 24 hr, and 48 hr for HIF-1α.

RESULTS

After LIC, we have found an early increase of 8-isoprostane and nitrite. HIF-1α increased at 2 and 8 hr after LIC. We found a direct correlation between HIF-1α and 8-isoprostane and nitrite plasma levels.

CONCLUSIONS

We concluded that LIC induces an early oxidative/nitrosative stress in the arm followed by an increase of HIF-1α plasma levels correlated with 8-isoprostane and nitrite levels, possibly as a local response.