Limb Remote Ischemic Preconditioning Research Articles

Pretreatment with remote ischemic conditioning attenuates testicular damage after testicular ischemia and reperfusion injury in rats.

Testicular torsion is a urological emergency. However, surgical detorsion of the torsed spermatic cord can cause testicular reperfusion injury. Although remote ischemic preconditioning (RIPC) has been convincingly shown to protect organs against ischemia/reperfusion (I/R) injury, little is known regarding the effect of RIPC on testicular torsion/detorsion-induced reperfusion injury. Therefore, we aimed to evaluate the effect of RIPC on testes after testicular I/R injury in a rat model in vivo. Male Sprague-Dawley rats were randomly classified into 4 groups: sham-operated (sham), testicular I/R (TI/R), or remote liver (RIPC liver) and limb (RIPC limb) ischemic preconditioning groups. Testis I/R was induced by 3 h of right spermatic cord torsion (720° clockwise), and reperfusion was allowed for 3 hours. In the RIPC group, four cycles of 5 min of ischemia and 5 min of reperfusion were completed 30 min prior to testicular torsion. The ERK1/2 inhibitor U0126 was administered intravenously at the beginning of reperfusion (1 mg/kg). The testes were taken for the oxidative stress evaluations, histology, apoptosis, immunohistochemical and western blotting analysis. Remote liver and limb ischemic preconditioning attenuated ipsilateral and contralateral testicular damage after testicular I/R injury. For example. RIPC reduced testicular swelling and oxidative stress, lessened structural damage, and inhibited the testicular inflammatory response and apoptosis. Furthermore, RIPC treatment enhanced testicular ERK1/2 phosphorylation postI/R. Inhibition of ERK1/2 activity using U0126 eliminated the protection offered by RIPC. Our data demonstrate for the first time that RIPC protects testes against testicular I/R injury via activation of the ERK1/2 signaling pathway.

Three Dimensional-Arterial Spin Labeling Evaluation of Improved Cerebral Perfusion After Limb Remote Ischemic Preconditioning in a Rat Model of Focal Ischemic Stroke.

PurposeTo investigate the application value of 3D arterial spin labeling (3D-ASL) for evaluating distal limb ischemic preconditioning to improve acute ischemic stroke (AIS) perfusion.Materials and MethodsA total of 40 patients with AISs treated in our hospital from January 2020 to December 2020 were recruited, and 15 healthy individuals who were examined in our hospital during the same period were included as the control group; all of these participants were scored on the National Institutes of Health Stroke Scale (NIHSS) and examined by MRI. Sequences included conventional sequences, diffusion-weighted imaging (DWI), magnetic resonance angiography (MRA), and 3D-ASL, and cerebral infarct volume and cerebral blood flow (CBF) in the area of the infarct lesion were measured. After 3 months of treatment, patients with AIS were scored on the modified Rankin Scale (mRS) and divided into good prognosis and poor prognosis groups. In total, 55 adult male Sprague–Dawley rats were divided randomly into three groups: 20 in the middle cerebral artery occlusion (MCAO) group, 20 in the MCAO + limb remote ischemic preconditioning (LRP) group, and 15 in the sham group. In total, 48 h after the procedures, conventional MRI, DWI, and 3D-ASL sequence data were collected, and 2,3,5-trphenyltetrazolium chloride monohydrate (TTC) staining and behavioral scoring were performed. CBF was recorded in the infarct lesion area and the corresponding contralateral area, and the affected/contralateral relative values (rCBF) were calculated to compare the differences in rCBF between different groups. The pathological changes in brain tissues were observed by HE staining, and the expression of vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) in brain tissues was detected by immunofluorescence and real-time quantitative polymerase chain reaction (RT-qPCR). The protein expression of VEGF was detected by western blotting.ResultsHypertension and internal carotid atherosclerosis are high-risk factors for ischemic stroke, and CBF values in the infarct area are significantly lower than those in the corresponding areas on the contralateral side. NIHSS and mRS scores and CBF values have higher specificity and sensitivity for the prognosis of patients with AIS. LRP significantly reduces the infarct area, improves behavioral deficits in rats with cerebral ischemia, reduces neurological injury and histological damage, protects vascular structures, and promotes neovascularization. In addition, 3D-ASL showed a significant increase in brain tissue perfusion in the ischemic area after LRP, and the expression of VEGF and CD31 showed a significant positive correlation with CBF values.ConclusionThree dimensional (3D) ASL can be used to evaluate LRP to improve stroke perfusion, and its protective effect may be closely related to LRP-induced vascular regeneration.

Limb Remote Ischemic Preconditioning Applied During Sevoflurane Anesthesia Does Not Protect the Lungs in Patients Undergoing Adult Heart Valve Surgery.

Two consistent overall cell protective preconditioning treatments should provide more protection. We hypothesized that limb remote ischemic preconditioning (RIPC, second preconditioning stimulus) applied during sevoflurane inhalation (first preconditioning stimulus) would provide more protection to the lungs of patients undergoing adult heart valve surgery. In this randomized, placebo-controlled, double-blind trial, 50 patients were assigned to the RIPC group or the placebo group (1:1). Patients in the RIPC group received three 5-min cycles of 300 mmHg cuff inflation/deflation of the left-side lower limb before aortic cross-clamping. Anesthesia consisted of opioids and propofol for induction and sevoflurane for maintenance. The primary end point was comparison of the postoperative arterial-alveolar oxygen tension ratio (a/A ratio) between groups. Secondary end points included comparisons of pulmonary variables, postoperative morbidity and mortality and regional and systemic inflammatory cytokines between groups. In the RIPC group, the a/A ratio and other pulmonary variables exhibited no significant differences throughout the study period compared with the placebo group. No significant differences in either plasma or bronchoalveolar lavage levels of TNF- α were noted between the groups at 10 min after anesthetic induction and 1 h after cross-clamp release. The percentage of neutrophils at 12 h postoperation was significantly increased in the RIPC group compared with the placebo group (91.34±0.00 vs. 89.42±0.10, P = 0.023). Limb RIPC applied during sevoflurane anesthesia did not provide additional significant pulmonary protection following adult valvular cardiac surgery.

Remote ischemic preconditioning improves tissue oxygenation in a porcine model of controlled hemorrhage without fluid resuscitation

Remote ischemic preconditioning (RIPC) involves deliberate, brief interruptions of blood flow to increase the tolerance of distant critical organs to ischemia. This study tests the effects of limb RIPC in a porcine model of controlled hemorrhage without replacement therapy simulating an extreme field situation of delayed evacuation to definitive care. Twenty-eight pigs (47 ± 6 kg) were assigned to: (1) control, no procedure (n = 7); (2) HS = hemorrhagic shock (n = 13); and (3) RIPC + HS = remote ischemic preconditioning followed by hemorrhage (n = 8). The animals were observed for 7 h after bleeding without fluid replacement. Survival rate between animals of the RIPC + HS group and those of the HS group were similar (HS, 6 of 13[46%]-vs-RIPC + HS, 4 of 8[50%], p = 0.86 by Chi-square). Animals of the RIPC + HS group had faster recovery of mean arterial pressure and developed higher heart rates without complications. They also had less decrease in pH and bicarbonate, and the increase in lactate began later. Global oxygen delivery was higher, and tissue oxygen extraction ratio lower, in RIPC + HS animals. These improvements after RIPC in hemodynamic and metabolic status provide essential substrates for improved cellular response after hemorrhage and reduction of the likelihood of potentially catastrophic consequences of the accompanying ischemia.

Down-Regulation of Nogo-A and PirB in Ischemic Cortex with Remote Ischemic Preconditioning in Mice

Objectives: The present study aims to investigate the effect of Limb Remote Ischemic Preconditioning (LRIP) on the expression of Nogo-A and PirB in the cortex of mice with focal cerebral ischemia, and related pathways involving in axonal regeneration and neurological function recovery after cerebral ischemia. Methods: Adult male C57/BL6 mice were divided into sham-operated (sham), transient Middle Cerebral Artery Occlusion (MCAO), LRIP and anti- PirBAb treatment group. Samples were collected 48h after cerebral ischemia. The histopathologic changes were assessed by 1,3,5-Triphenyl-2H-Tetrazolium Chloride (TTC), and Hematoxylin and Eosin (HE) staining and TUNEL method. The expression of Nogo-A and PirB were determined by immunofluorescence, RT-PCR and Western blot respectively. Results: TTC staining showed that LRIP treatment reduced the infarct size of mice and anti-PirBAb treatment further decline the infarct size, which was accompanied with the decline of neurological deficit score and reduction of neuronal damage. LRIP treatment also reduced the TUNEL positive cells induced by MCAO and anti-PirBAb treatment further strengthened the effect of LRIP. Except sham group, the expressions of Nogo-A and PirB in other three groups all increased with varying degrees, among which MCAO group was the highest, LRIP group was the second and the anti-PirBAb group was the lowest. The expressions of growth associated protein 43 (GAP43) showed opposite tendency. Conclusions: LRIP plays beneficial influence on cerebral ischemia. LRIP and PirB inhibition combination has a better protective effect on nervous system after cerebral ischemia in mice.

ZNF667 attenuates leukocyte-endothelial adhesion via downregulation of P-selectin in skin flap following remote limb ischemic preconditioning.

We assessed the effects and potential mechanism of romote ischemic preconditioning (RIPC) on leukocytes-endothelium cell adhesion in the flap microvessel after ischemia-reperfusion (I/R) injury. Eight hours after reperfusion, edema and intravascular leukocyte aggregation were reduced and microvessels were more obvious in the group with superficial inferior epigastric artery (SIEA) perforator flap (SIEA-flap) subjected to RIPC than in the I/R group. Zinc finger protein 667 (ZNF667) was significantly increased but P-selectin was decreased in the flaps subjected to RIPC, compared to those in the I/R group. The low expression of P-selectin was associated with ZNF667 expression and activation in human dermal microvascular endothelial cells in response to hypoxic preconditioning. ZNF667 bound to the P-selectin promoter region, suppressing its transcription through a special core sequence. The ablation of P-selectin by small interfering RNA effectively prevented the leukocytes-endothelium cell adhesion effect of ZNF667-knockdown. ZNF667 upregulation attenuates leukocyte-endothelial cell adhesion by negatively regulating the expression of P-selectin in SIEA-flap subjected to RIPC.

Time-efficient physical activity interventions to reduce blood pressure in older adults: a randomised controlled trial.

BackgroundHypertension is a risk factor for both cardiovascular and cerebrovascular disease, with an increasing incidence with advancing patient age. Exercise interventions have the potential to reduce blood pressure in older adults, however, rates of exercise uptake and adherence are low, with ‘lack of time’ a commonly cited reason. As such, there remains the need for time-efficient physical activity interventions to reduce blood pressure in older adults.ObjectiveTo compare the effect of three, novel time-efficient physical activity interventions on resting blood pressure in older adults.MethodsForty-eight, healthy, community-dwelling older adults (mean age: 71 years) were recruited to a 6-week randomised control trial. Resting blood pressure was measured before and after one of three supervised, time-efficient interventions: high-intensity interval training (HIIT) on a cycle ergometer; isometric handgrip training (IHG); unilateral, upper limb remote ischaemic preconditioning (RIPC) or non-intervention control.ResultsBoth HIIT and IHG led to a statistically significant reduction in resting systolic blood pressure (SBP) of 9 mmHg, with no significant change in the RIPC or control groups. There was no change in diastolic blood pressure or pulse pressure in any group.ConclusionsSupervised HIIT or IHG using the protocols described in this study can lead to statistically significant and clinically relevant reductions in resting SBP in healthy older adults in just 6 weeks.

Safety and Tolerability of Both Arm Ischemic Conditioning in Patients With Major Depression: A Proof of Concept Study.

PurposeA substantial proportion of patients with major depressive disorder (MDD) does not respond or cannot tolerate to currently available treatments. This study was to assess the safety and tolerability of Remote Limb Ischemic Preconditioning (RLIPC) as an adjunctive therapy in patients with MDD.Patients and MethodsEnrolled patients underwent RLIPC, five cycles of simultaneous bilateral arm ischemia, 5 min and followed by reperfusion of each cycle, and once daily for eight consecutive weeks. Depression and anxiety severity, and quality of life were assessed every 2 weeks. Descriptive analysis was used for safety and tolerability data.ResultsThirty-seven participants completed at least one RLIPC. Twenty-four of them (64.9%) completed the study. Twelve patients prematurely discontinued the study due to poor adherence, and one due to a mild side effect. The changes in HRSD-17, GAD-7 and QOL-6 total scores from baseline to the endpoint were significant from the end of second week treatment onwards. The responder and remission rates were 59.46% (22/37) and 54.05% (20/37) at the endpoint, respectively.ConclusionRLIPC was safe and well tolerated, and may be effective in reducing depressive symptoms in patients with MDD. Large studies are warranted to test its efficacy and safety as monotherapy or adjunctive therapy in the treatment of MDD.

Modulation of spinal cord excitability following remote limb ischemic preconditioning in healthy young men.

Remote limb ischemic preconditioning (RIPC) has shown to improve dynamic postural control in humans. However, studies on the underlying adaptations of spinal cord networks have never been performed. The present work addresses this issue by investigating parameters from the soleus H-reflex recruitment curve (RC), presynaptic mechanisms of reflex modulation (presynaptic inhibition-PSI, and post activation depression-PAD), and the excursion of the center of pressure (CP) recorded during 1min in upright stance over a compliant surface. A sham ischemic protocol (partial obstruction of blood flow) was applied to the contralateral thigh along four consecutive days. The same procedure was repeated with full obstruction (RIPC) three days after ending the sham protocol. Data were collected before and after both sham and RIPC protocols. The follow-up data were collected five days after the last ischemic intervention. Significant reduction was detected for both the fast oscillations of the CP (higher frequency components) and the parameter estimated from the RC corresponding to the high amplitude H-reflexes (p < 0.05). Even though the magnitude of effects was similar, it was washed out within three days after sham, but persisted for at least five days after RIPC. No significant differences were found for PSI and PAD levels across conditions. These findings indicate that RIPC leads to enduring changes in spinal cord excitability for the latest reflexively recruited motoneurons, along with improvement in balance control. However, these adaptations were not mediated by the presynaptic mechanisms currently assessed.

Hypoxia-Inducible Factor 1α and 2α Have Beneficial Effects in Remote Ischemic Preconditioning Against Stroke by Modulating Inflammatory Responses in Aged Rats

Limb remote ischemic preconditioning (RIPC) has been proven to alleviate stroke injury in young rats, but its protective effect and its mechanism in aged rats are still unclear. Hypoxia-inducible factor (HIF) is one of the important markers of stroke, and its high expression plays an important role in the pathogenesis of stroke. In this study, we tested the hypothesis that RIPC could regulate the expression of HIF, leading to reduced inflammatory responses in aged rats. Stroke was induced by transient middle cerebral artery occlusion (MCAo) in aged rats, and RIPC was conducted in both hind limbs. The HIF-1α and HIF-2α mRNA and protein were examined by real-time RT-PCR and western blotting (WB). Inflammatory cytokines in the peripheral blood and brain were measured using AimPlex multiplex immunoassays. The protein levels of p-Akt, Akt, p-ERK, and ERK were examined by WB. We investigated that RIPC reduced the infarct size, improved neurological functions, and decreased the expression of HIF-1α and HIF-2α in the ischemic brain. RIPC reduced the levels of IL-1β, IL-6 and IFN-γ in the peripheral blood and the levels of IL-1β and IFN-γ in the ischemic brain 48 h post-stroke. Moreover, intraperitoneal injection of the HIF inhibitor, acriflavine hydrochloride (ACF), abolished the protection of RIPC with respect to infarct size and neurological functions and neutralized the downregulation of pro-inflammatory IL-1β, IL-6 and IFN-γ. ACF also reversed the activation of the Akt signaling pathway induced by RIPC following stroke. HIF may play a key role in RIPC, which was likely mediated by the Akt signaling pathway and systemic modulation of the inflammatory response in aged rats.

Correction to: Limb Remote Ischemic Preconditioning Reduces Repeated Ketamine Exposure-Induced Adverse Effects in the Developing Brain of Rats.

The original version of this article unfortunately contained mistakes in Fig.2c, d and Funding section.

Abstract 216: Therapeutic Hypothermia Alone and in Combination With Preconditioning Improves Long Term Survival During Resuscitation of Hemorrhagic Shock

Background: We investigated the effects of hypothermia treatment alone and in combination with experimental bilateral lower limb remote ischemic preconditioning (RIPC) in rats undergoing experimental hemorrhagic shock. Previously we showed that RIPC alone improved survival. Methods: In the hypothermia alone study, adult Sprague Dawley rats (both genders) were randomized to hypothermia (n=16) or control group (n=15); in a combination study, rats were randomized to hypothermia plus RIPC (n=11) or control group (n=10). Rats were anesthetized with intraperitoneal ketamine/xylazine. Therapeutic hypothermia (Thermosuit) was started at 5 minutes after mean blood pressure (MBP) reached 30 mmHg. Core temperature was maintained at ~ 32 °C until blood volume was fully restored. RIPC was induced by 4 cycles of inflating small bilateral pressure cuffs to 200 mmHg around the femoral arteries for 5 minutes, followed by 5 minute deflation of the cuffs prior to hemorrhagic shock. In the control group, body temperature was maintained at 37 °C during the procedure. Hemorrhagic shock was induced by withdrawing blood from the carotid artery. Target mean blood pressure of 30 mmHg was maintained for 30 minutes followed by reinfusion of shed blood within the next 30 min. Rats were allowed recovery and the primary endpoint was survival rate at 6 weeks. Results: In the setting of hypothermia alone, 4 of 15 (26.7 %) rats in the control group and 11 of 16 (68.8 %; p = 0.032) rats in the hypothermia group survived at 6 weeks. In the combination study, 1 of 10 (10 %) rats in the control group and 7 of 11 (63.6 %; p = 0.024) rats in the hypothermia plus RIPC group survived at 6 weeks. Kaplan Meier Survival Curves are shown in Fig1. Conclusions: Hypothermia alone and combination with RIPC significantly improved long term survival in rats subjected to hemorrhagic shock. Hypothermia and RIPC did not show survival rates greater than hypothermia alone.

Limb Remote Ischemic Preconditioning for Intestinal and Pulmonary Protection during Elective Open Infrarenal Abdominal Aortic Aneurysm Repair: A Randomized Controlled Trial: Erratum.

Limb Remote Ischemic Preconditioning for Intestinal and Pulmonary Protection during Elective Open Infrarenal Abdominal Aortic Aneurysm Repair: A Randomized Controlled Trial: Erratum.

Limb Remote Ischemic Preconditioning Reduces Repeated Ketamine Exposure-Induced Adverse Effects in the Developing Brain of Rats.

Prolonged or repeated exposure to ketamine, a common anesthetic in pediatrics, has been shown to induce neurotoxicity and long-term neurocognitive deficits in the developing brain. Therefore, identification of potential therapeutic targets for preventing or alleviating such neurodegeneration and neuroapoptosis induced by ketamine is urgently needed. Remote ischemic preconditioning of the limb provides neuroprotection in different models of cerebral injury. Thus, the present study aimed to assess whether remote ischemic preconditioning could have a neuroprotective effect against neurotoxicity induced by ketamine. In our study, 96 newborn rats were assigned to one of four groups, including control, remote ischemic preconditioning, ketamine, and remote ischemic preconditioning plus ketamine. Ketamine was administered intraperitoneally in six doses of 20mg/kg at 2-h intervals. Limb remote ischemic preconditioning comprised four ischemia (5min)/reperfusion (5min) cycles in the right hind limb using an elastic rubber band tourniquet. Histopathological characteristics of cerebral damage were assessed by H&E staining and transmission electron microscopy. TUNEL assay, immunohistochemical staining and immunoblot were employed to evaluate neural cell apoptosis. Learning and memory were evaluated using the Morris water maze. The results showed increased cleaved caspase-3 protein levels in the cerebral cortex and the hippocampal CA1 region, severe cell damage and DNA breakage, and decreased spatial learning and memory abilities in the ketamine group in comparison with controls. Notably, these changes were significantly reduced by remote ischemic preconditioning. These findings suggest that remote ischemic preconditioning ameliorates neuroapoptosis and neurocognitive impairment after repeated ketamine exposure in newborn rats.

Improved Long-term Survival with Remote Limb Ischemic Preconditioning in a Rat Fixed-Pressure Hemorrhagic Shock Model.

We investigated whether bilateral, lower limb remote ischemic preconditioning (RIPC) improved long-term survival using a rat model of hemorrhagic shock/resuscitation. Rats were anesthetized, intubated and ventilated, and randomly assigned to RIPC, induced by inflating bilateral pressure cuffs around the femoral arteries to 200mmHg for 5min, followed by 5-min release of the cuffs (repeated for 4cycles), or control group (cuffs were inflated to 30mmHg). Hemorrhagic shock was induced by withdrawing blood to a fixed mean blood pressure of 30mmHg for 30min, followed by 30min of resuscitation with shed blood. Rats remained anesthetized for 1h during which hemodynamics were monitored then they were allowed to survive for 6weeks. The percentage of estimated total blood volume withdrawn to maintain a level of 30mmHg was similar in both groups. RIPC significantly increased survival at 6weeks: 5 of 27 (19%) rats in the control group and 13 of 26 (50%; p = 0.02) rats in the RIPC group survived. Blood pressure was higher in the RIPC group. The diastolic internal dimension of the left ventricle, an indicator of circulating intravascular blood volume, was significantly larger in the RIPC group at 1h after initiation of resuscitation compared to the control group (p = 0.04). Left ventricular function assessed by fractional shortening was comparable in both groups at 1h after initiation of resuscitation. Blood urea nitrogen (BUN) was within normal range in the RIPC group (17.3 ± 1.2mg/dl) but elevated in the control group (22.0 ± 1.7mg/dl) at 48h after shock. RIPC significantly improved short-term survival in rats that were subjected to hemorrhagic shock, and this benefit was maintained long term. RIPC led to greater circulating intravascular blood volume in the early phase of resuscitation and improved BUN.

AKT and ERK1/2 activation via remote ischemic preconditioning prevents Kcne2-dependent sudden cardiac death.

Sudden cardiac death (SCD) is the leading global cause of mortality. SCD often arises from cardiac ischemia reperfusion (IR) injury, pathologic sequence variants within ion channel genes, or a combination of the two. Alternative approaches are needed to prevent or ameliorate ventricular arrhythmias linked to SCD. Here, we investigated the efficacy of remote ischemic preconditioning (RIPC) of the limb versus the liver in reducing ventricular arrhythmias in a mouse model of SCD. Mice lacking the Kcne2 gene, which encodes a potassium channel β subunit associated with acquired Long QT syndrome were exposed to IR injury via coronary ligation. This resulted in ventricular arrhythmias in all mice (15/15) and SCD in 5/15 mice during reperfusion. Strikingly, prior RIPC (limb or liver) greatly reduced the incidence and severity of all ventricular arrhythmias and completely prevented SCD. Biochemical and pharmacological analysis demonstrated that RIPC cardioprotection required ERK1/2 and/or AKT phosphorylation. A lack of alteration in GSK‐3β phosphorylation suggested against conventional reperfusion injury salvage kinase (RISK) signaling pathway protection. If replicated in human studies, limb RIPC could represent a noninvasive, nonpharmacological approach to limit dangerous ventricular arrhythmias associated with ischemia and/or channelopathy‐linked SCD.

Sevoflurane, Propofol and Carvedilol Block Myocardial Protection by Limb Remote Ischemic Preconditioning.

The effects of remote ischemic preconditioning (RIPC) in cardiac surgery have been inconsistent. We investigated whether anesthesia or beta-blockers interfere with RIPC cardioprotection. Fifty patients undergoing cardiac surgery were randomized to receive limb RIPC (four cycles of 5-min of upper arm cuff inflation/deflation) in the awake state (no-anesthesia; n = 17), or under sevoflurane (n = 17) or propofol (n = 16) anesthesia. In a separate crossover study, 11 healthy volunteers received either carvedilol or no medication prior to RIPC. Plasma dialysates were obtained and perfused through an isolated male Sprague–Dawley rat heart subjected to 30-min ischemia/60-min reperfusion, following which myocardial infarct (MI) size was determined. In the cardiac surgery study, pre-RIPC MI sizes were similar among the groups (39.7 ± 4.5% no-anesthesia, 38.9 ± 5.3% sevoflurane, and 38.6 ± 3.6% propofol). However, post-RIPC MI size was reduced in the no-anesthesia group (27.5 ± 8.0%; p < 0.001), but not in the anesthesia groups (35.7 ± 6.9% sevoflurane and 35.8 ± 5.8% propofol). In the healthy volunteer study, there was a reduction in MI size with RIPC in the no-carvedilol group (41.7 ± 4.3% to 30.6 ± 8.5%; p < 0.0001), but not in the carvedilol group (41.0 ± 4.0% to 39.6 ± 5.6%; p = 0.452). We found that the cardioprotective effects of limb RIPC were abolished under propofol or sevoflurane anesthesia and in the presence of carvedilol therapy.

Protective Effect of Contralateral, Ipsilateral, and Bilateral Remote Ischemic Preconditioning on Spinal Cord Ischemia Reperfusion Injury in Rats.

To evaluate the effect of different remote ischemic preconditioning (RIPC) methods in spinal cord ischemia-reperfusion (IR) injury. A total of 36 rats were distributed to the 6 groups: sham surgery, control (only spinal cord IR), unilateral (hind limb RIPC before spinal cord IR), bilateral (hind limbs RIPC before spinal cord IR), ipsilateral (hind and fore limbs RIPC to the right before spinal cord IR), contralateral (right hind limb and left fore limb as RIPC before spinal cord IR). Thirty minutes after RIPC, the spinal cord was subjected to ischemia for 60 minutes. Seventy two hours after IR, all rats were evaluated by neurological function, histological and biochemical examinations. The mean Motor Deficit Index (MDI) scores in the ipsilateral, contralateral, and bilateral groups were lower than that of the unilateral group (p < 0.05). The mean malondialdehyde (MDA) in ipsilateral group was lower than were control group (p < 0.05). The mean total antioxidant capacity (TAC) and the mean number of normal motor neurons in the experimental groups were significantly higher than increased control group (p < 0.05). The mean plasma levels of catalase in the contralateral, ipsilateral, and bilateral groups were significantly increased compared to control group (p < 0.05). The mean scores of white matter damage in contralateral, bilateral, and unilateral groups were lower than control group (p < 0.05). The results of this study show that contralateral, ipsilateral, and bilateral limb RIPC may reduce the complications of spinal cord ischemic injury.

Abstract 186: Remote Limb Ischemic Preconditioning Improves Short and Long Term Survival and Maintains Intravascular Blood Volume During Resuscitation of Hemorrhagic Shock

Background: We further examined the protective effects of experimental bilateral lower limb remote ischemic preconditioning (RIPC) in rats undergoing experimental hemorrhagic shock. Methods: Sprague Dawley rats (both genders) were randomized into RIPC (n= 26) or control group (n= 27), and anesthetized with intraperitoneal ketamine/xylazine. RIPC was induced by 4 cycles of inflating small bilateral pressure cuffs to 200 mmHg around the femoral arteries for 5 minutes, followed by 5 minute deflation of the cuffs. Hemorrhagic shock was induced by withdrawing blood from the carotid artery. Target mean blood pressure of 30 mmHg was maintained for 30 minutes followed by reinfusion of shed blood within the next 30 min. Rats remained anesthetized for another 30 min before recovery; endpoints were survival at 72 hours and 6 weeks. Results: The % of estimated total blood volume withdrawn to maintain a level of 30 mmHg was similar in the RIPC group (41.7 ± 1.0 %) and control group (41.9 ± 1.0 %). Recovery of blood pressure during the early resuscitation phase was significantly improved in the RIPC group. The diastolic internal dimension of the left ventricle (echocardiogram), which indicates circulating intravascular blood volume, was significantly larger in the RIPC group at 1 hour after initiation of shed blood reinfusion (5.8 ± 0.1 mm) compared to 5.4 ± 0.1mm in the control group (p=0.04). Left ventricular fractional shortening was comparable between RIPC (50.9 ± 1.9 %) and control group (49.6 ± 1.8 %; p=0.64) at 1 hour after initiation of resuscitation. At 48 hours after shock, BUN was within normal range in the RIPC group (17.3 ± 1.2 mg/dl); but elevated in the control group (22.0 ± 1.7 mg/dl). At 72 hours after hemorrhagic shock injury, 6 of 27 (22.2 %) rats in the control group and 13 of 26 (50 %, p = 0.047) rats in the RIPC group survived. At 6 weeks, 5 of 27 (18.5 %) rats in the control group and 13 of 26 (50 %; p = 0.021) rats in the RIPC group survived. RIPC significantly increased survival rate at both 72 hours and 6 weeks. Conclusions: RIPC improved recovery of blood pressure and maintained more circulating intravascular blood volume in the early phase of resuscitation, improved BUN, and markedly and significantly improved short and long term survival in rats subjected to hemorrhagic shock.

Impact of Remote Ischemic Preconditioning Post-application Delay on Muscle Oxygenation during Subsequent Cycling Intervals

INTRODUCTION: Remote ischemic preconditioning (RIPC) involves brief, repeated bouts of manually-imposed blood flow restriction of the arms or legs. The alternating periods of occlusion and reperfusion lead to endothelial adaptations, capable of enhancing blood flow and oxygen delivery. PURPOSE: The aim of this study was to investigate the effect of a lower limb RIPC protocol, with either a 5-min or 45-min post-application delay, on muscle oxygen saturation within that same limb at rest and during short- duration intense cycling. METHODS: Subjects included recreationally aerobically trained college-aged students (23± 3 years, 173.5± 5.4 cm, 69.2± 4.0 kg, 15.2± 4.0 % BF, 2peak VO : 46.6± 1.1 mL•kg-1•min-1 at 215± 19 W). All subjects randomly completed four experimental trials: RIPC with 5-min delay, RIPC with 45-min delay, SHAM with 5-min delay, and SHAM with 45-min delay. For the RIPC conditions, each subject received 5-min of alternating-leg blood flow occlusion using a blood pressure cuff (220 mmHg) placed on the upper thighs for a total of 40 min. After a 5 or 45-min delay, the subjects completed 5, 1-min cycle sprints separated by 2 min of recovery. The SHAM conditions were identical to the RIPC, however, subjects laid supine for the same 40-min duration with alternating-leg cuff inflation to 20 mmHg. Muscle oxygen saturation was measured continuously using a portable NIRS-based sensor placed over the vastus lateralis (VL). RESULTS: RIPC decreased muscle oxygen saturation in the VL in a replicable manner (MD: 29.5± 13.4%, mean occlusion slope: -5.0± 2.4 %•min-1, mean reperfusion slope: 38.5± 22.4%•min-1) while SHAM conditions left muscle oxygen saturation largely unchanged (MD: 2.9± 1%). Mean VL oxygen saturation (RIPC45:71.9± 0.7%; RIPC5: 67.3± 1.7%; SHAM45: 72.0± 4.4%; SHAM5: 69.9± 3.0%) and preservation of muscle oxygen saturation (MD: RIPC45: -12.4± 6.2%; RIPC5: -14.4± 9.9%; SHAM45: -11.6± 6.4%; SHAM5: -13.0± 7.1%) during high intensity cycling intervals varied minutely between experimental conditions. CONCLUSIONS: The muscle oxygenation response during a standard occlusion/reperfusion protocol may lack assumed constancy. Furthermore, the use of RIPC and the length of the delay following RIPC did not greatly alter the muscle oxygenation response to repetitive high-intensity cycling intervals.