Tourniquet-induced lower limb ischemia/reperfusion reduces mitochondrial function by decreasing mitochondrial biogenesis in acute kidney injury in mice.

The mechanisms by which lower limb ischemia/reperfusion induces acute kidney injury (AKI) remain largely uncharacterized. We hypothesized that tourniquet-induced lower limb ischemia/reperfusion (TILLIR) would inhibit mitochondrial function in the renal cortex. We used a murine model to show that TILLIR of the high thigh regions inflicted time-dependent AKI as determined by renal function and histology. This effect was associated with decreased activities of mitochondrial complexes I, II, V and citrate synthase in the kidney cortex. Moreover, TILLIR reduced mRNA levels of a master regulator of mitochondrial biogenesis PGC-1α, and its downstream genes NDUFS1 and ATP5o in the renal cortex. TILLIR also increased serum corticosterone concentrations. TILLIR did not significantly affect protein levels of the critical regulators of mitophagy PINK1 and PARK2, mitochondrial transport proteins Tom20 and Tom70, or heat-shock protein 27. TILLIR had no significant effect on mitochondrial oxidative stress as determined by mitochondrial ability to generate reactive oxygen species, protein carbonylation, or protein levels of MnSOD and peroxiredoxin1. However, TILLIR inhibited classic autophagic flux by increasing p62 protein abundance and preventing the conversion of LC3-I to LC3-II. TILLIR increased phosphorylation of cytosolic and mitochondrial ERK1/2 and mitochondrial AKT1, as well as mitochondrial SGK1 activity. In conclusion, lower limb ischemia/reperfusion induces distal AKI by inhibiting mitochondrial function through reducing mitochondrial biogenesis. This AKI occurs without significantly affecting PINK1-PARK2-mediated mitophagy or mitochondrial oxidative stress in the kidney cortex.

Impact of proximal and distal cuff inflation on brachial artery endothelial function in healthy individuals.

PURPOSE: In this study, we examined whether the decrease in endothelial function associated with short-term exposure to elevated retrograde shear rate (SR), could be prevented when combined with a concurrent drop in transmural pressure in humans. METHODS: Twenty-five healthy individuals reported to our laboratory on three occasions to complete 30-min experimental conditions, preceded and followed by assessment of endothelial function using flow-mediated dilation (FMD). We used cuff inflation for 30-min to manipulate retrograde SR and transmural pressure in the brachial artery. Subjects underwent, in randomised order: (1) forearm cuff inflation to 60 mmHg (distal cuff; causing increase in retrograde SR), (2) upper arm cuff inflation to 60 mmHg (proximal cuff; causing increase in retrograde SR + decrease in transmural pressure), and (3) no cuff inflation (Control). RESULTS: The distal and proximal cuff conditions both increased brachial artery retrograde SR (p < 0.001) and oscillatory shear index (p < 0.001). The Control intervention did not alter SR patterns or FMD (p > 0.05). A significant interaction-effect was found for FMD (p < 0.05), with the decrease during distal cuff (from 6.9 ± 2.3% to 6.1 ± 2.5%), being reversed to an increase with proximal cuff (from 6.3 ± 2.0 to 6.9 ± 2.0%). The proximal cuff-related increase in FMD could not be explained by the decrease in antegrade or increase in retrograde shear. CONCLUSION: This study suggests that a decrease in transmural pressure may ameliorate the decline in endothelial function that occurs following exposure to elevated retrograde shear in healthy individuals.

Acute cardiovascular response to unilateral, bilateral, and alternating resistance exercise with blood flow restriction.

AIM: Blood flow restriction (BFR) exercise is a common alternative to traditional high-load resistance exercise used to increase muscle size and strength. Some populations utilizing BFR at a low load may wish to limit their cardiovascular response to exercise. Different contraction patterns may attenuate the cardiovascular response, but this has not been compared using BFR. PURPOSE: To compare the cardiovascular response to unilateral (UNI), bilateral (BIL), and alternating (ALT) BFR exercise contraction patterns. METHODS: Twenty healthy participants performed four sets (30 s rest) of knee extensions to failure, using 30% one-repetition maximum, 40% arterial occlusion pressure, and each of the three contraction patterns (on different days, at the same time of day, separated by 2-10 days, randomized). Cardiovascular responses, presented as pre- to post-exercise mean changes (SD), were measured using pulse wave analysis and analyzed with Bayesian RMANOVA. RESULTS: ALT caused greater changes in: aortic systolic [ΔmmHg: ALT = 21(8); UNI = 13(11); BIL = 15(8); BF10 = 29.599], diastolic [ΔmmHg: ALT = 13(8); UNI = 7(11); BIL = 8(8); BF10 = 5.175], and mean arterial [ΔmmHg: ALT = 19(8); UNI = 11(11); BIL = 13(7); BF10 = 48.637] blood pressures. Aortic [ΔmmHg bpm: ALT = 4945(2340); UNI = 3294(1408); BIL = 3428 (1461); BF10 = 113.659] and brachial [ΔmmHg bpm: ALT = 6134(2761); UNI = 4300(1709); BIL = 4487(1701); BF10 = 31.845] rate pressure products, as well as heart rate [Δbpm: ALT = 26(14); UNI = 19(8); BIL = 19(11); BF10 = 5.829] were greatest with ALT. Augmentation index [Δ%: UNI = -6(13); BIL = - 7(11); ALT = - 5(16); BF10 = 0.155] and wave reflection magnitude [Δ%: UNI = - 5(9); BIL = - 4(7); ALT = - 4(7); BF10 = 0.150] were not different. CONCLUSION: Those at risk of a cardiovascular event may choose unilateral or bilateral BFR exercise over alternating until further work determines the degree to which it can be tolerated.

Knee extension with blood flow restriction: Impact of cuff pressure on hemodynamics.

INTRODUCTION: Blood flow restriction (BFR) exercise has emerged as a method of increasing muscle size and strength with low intensity resistance training. While the cuff pressures used during BFR are typically a percentage of resting arterial occlusion pressure (AOP), the impact these cuff pressures have on blood flow during lower body exercise is unknown. PURPOSE: To determine how various cuff pressures impact blood flow and tissue perfusion during exercise. METHODS: Eleven healthy male participants completed four sets of knee extension (30 reps per set at 30% max torque) with 0%, 60%, 80%, and 100% of arterial occlusion pressure (AOP) was applied to the proximal portion of the thigh. Femoral artery blood flow, tissue oxygenation, and central hemodynamics were continuously recorded before, during, and after exercise. Electromyography (EMG) amplitude was recorded from the vastus lateralis during exercise. RESULTS: Blood flow increased during exercise compared to rest across all cuff pressures (p < 0.001), however compared to 0%, the absolute blood flow was reduced by 34 ± 17%, 45 ± 22%, and 72 ± 19% for 60, 80, and 100% AOP, respectively. Furthermore, each cuff pressure resulted in similar relative changes in blood flow before, during, and after exercise. During exercise, tissue saturation index (TSI) decreased as cuff pressure increased (p ≤ 0.005) with the exception of 80 to 100% AOP. Deoxyhemoglobin increased (p ≤ 0.001) with cuff pressure. CONCLUSION: Our data indicate that while BFR knee extension elicits an absolute hyperemic response at cuff pressures up to 100% resting AOP, the relative reductions in blood flow are consistent across rest, exercise and recovery.

Does 24-h ambulatory blood pressure monitoring act as ischemic preconditioning and influence endothelial function?

Ischemic preconditioning can exert a powerful protection against a subsequent period of ischemia, via repeated inflation and deflation of a blood pressure cuff. Most often, damages of ischemia-reperfusion injury and benefits of preconditioning are evaluated via endothelial function. The ambulatory blood pressure monitoring constitutes repeated bouts of ischemia for 24 h. We examined whether repeated bouts of ischemia accumulated over 24 h influenced endothelial function. Twenty-two apparently healthy non-medicated middle-aged subjects 41 (8) years participated in the study. This study was registered with ClinicalTrials.gov (NCT03303404). Flow-mediated dilation (FMD) was measured as an index of endothelium-dependent vasodilation. The ambulatory blood pressure monitoring device went through an average of 110 (13) inflation/deflation cycles, which resulted in 46 (6) min of cumulative ischemic stimuli. Following 24-h of ambulatory blood pressure monitoring, FMD did not change significantly 6.6 (2.0) vs. 6.8 (2.7)%. Similarly, shear rate and reactive hyperemia were unchanged. We concluded that ambulatory blood pressure monitoring did not influence endothelium-dependent vasodilation acting via ischemic preconditioning.

The Effect of Remote Ischaemic Preconditioning on Arterial Stiffness in Patients Undergoing Vascular Surgery: A Randomised Clinical Trial.

OBJECTIVES: The main aim of this study was to evaluate the effect of remote ischaemic preconditioning (RIPC) on arterial stiffness in patients undergoing vascular surgery. METHODS: This was a randomised, sham controlled, double blind, single centre study. Patients undergoing open abdominal aortic aneurysm repair, surgical lower limb revascularisation surgery or carotid endarterectomy were recruited. A RIPC or a sham procedure was performed, using a blood pressure cuff, along with preparation for anaesthesia. The RIPC protocol consisting of four cycles of 5 min of ischaemia, followed by 5 min of reperfusion was applied. Arterial stiffness and haemodynamic parameters were measured pre-operatively and 20-28 h after surgery. Two primary outcomes were selected: augmentation index and pulse wave velocity. RESULTS: Ninety-eight patients were randomised. After dropouts 44 and 46 patients were included in the RIPC and sham groups, respectively. Both groups were comparable. There were no statistically significant differences in augmentation index (p = .8), augmentation index corrected for heart rate of 75 beats per minute (p = .8), pulse wave velocity (p = .7), large artery elasticity indices (p = .8), small artery elasticity indices (p = .6), or mean arterial pressure (p = .7) changes between the RIPC and sham groups. There occurred statistically significant (p ≤ .01) improvement in augmentation index (-5.8% vs. -5.5%), augmentation index corrected for a heart rate of 75 beats per minute (-2.5% vs. -2%), small artery elasticity indices (0.7 mL/mmHg × 100 vs. 0.9 mL/mmHg × 100), and mean arterial pressure post-operatively in both the RIPC and the sham groups (change median values in RIPC and sham groups, respectively). CONCLUSIONS: RIPC had no significant effect on arterial stiffness, but there was significant improvement in arterial stiffness after surgery in both groups. Arterial stiffness and haemodynamics may be influenced by surgery or anaesthesia or oxidative stress or all factors combined. Further studies are needed to clarify these findings. CLINICALTRIALS.GOV: NCT02689414.

Remote Limb Ischemic Conditioning and Motor Learning: Evaluation of Factors Influencing Response in Older Adults.

Remote limb ischemic conditioning (RLIC) is a clinically feasible method of promoting tissue protection against subsequent ischemic insult. Recent findings from our lab demonstrated that RLIC robustly enhances motor learning in young, healthy humans. The next step is to determine which individuals would receive maximum benefit from RLIC before applying these findings to clinical rehabilitation populations such as stroke. Numerous factors, such as age, sex, body mass index (BMI), and cardiovascular comorbidities may influence the response. Sixty-nine participants aged 40-80 were randomized to receive either RLIC (n = 33) or sham (n = 36) conditioning. Participants underwent seven consecutive sessions consisting of RLIC or sham conditioning with a blood pressure cuff on the upper extremity and motor training on a stability platform balance task, with two follow-up sessions. Balance change (post-test-pre-test) was compared across participants, groups, and the factors of age, sex, BMI, and comorbidities. Participants in both groups improved their performance on the balance task from pre- to post-test. Overall balance change was independently associated with age and BMI. There was no difference in balance change between RLIC and Sham groups. However, RLIC significantly enhanced balance performance in participants with no comorbidities. Compared with our previous study in young adults, middle-aged and older adults demonstrated smaller improvements on the balance task. RLIC enhanced learning in middle-aged and older adults only in the absence of pre-defined comorbidities. RLIC may be a promising tool for enhancing motor recovery, but the accumulation of comorbidity with age may decrease its effectiveness.

The Effects of Intermittent Whole-Body Hypoxic Preconditioning on Patients with Carotid Artery Stenosis.

OBJECTIVE: To study the effects of intermittent whole-body hypoxic preconditioning on patients with carotid artery stenosis. METHODS: Fifty patients with carotid artery stenosis were selected and randomly divided into a hypoxic intervention group (HIG) and a control group (CG). Both groups were treated with a hypoxic respiration device for 7 days (HIG: 18% oxygen, CG: 21% oxygen). Venous blood samples were taken preoperatively and postoperatively. The subjects' vital signs were recorded during and after the intervention. After the completion of the trial, the concentrations of hemoglobin, hypoxia inducible factor-1α, erythropoietin, vascular endothelial growth factor, neuron-specific enolase, S100ß protein, brain-derived neurotrophic factor, serum aspartate transaminase, serum alanine aminotransferase, serum creatinine, and blood urea nitrogen were measured in the previously selected blood samples. RESULTS: During the intervention, the vital signs of the HIG were significantly different from those of the CG (P < 0.05). In the HIG, postoperative concentrations of hemoglobin, erythropoietin, hypoxia inducible factor-1α, and vascular endothelial growth factor were significantly more than the preoperative values (P < 0.05). In the CG, postoperative concentrations of neuron-specific enolase and S100ß protein were more than the preoperative values (P < 0.05). The concentrations of brain-derived neurotrophic factor, serum aspartate transaminase, serum alanine aminotransferase, serum creatinine, and blood urea nitrogen showed no significant differences between their preoperative and postoperative values in either the HIG or the CG (P > 0.05). CONCLUSIONS: Intermittent hypoxic preconditioning can change the vital signs and hematologic indexes of patients with carotid artery stenosis without causing new postoperative complications or organ damage.

Remote Ischemic Preconditioning in High-risk Cardiovascular Surgery Patients: A Randomized-controlled Trial.

Remote ischemic preconditioning (RIPC) may reduce biomarkers of ischemic injury after cardiovascular surgery. However, it is unclear whether RIPC has a positive impact on clinical outcomes. We performed a blinded, randomized controlled trial to determine if RIPC resulted in fewer adverse clinical outcomes after cardiac or vascular surgery. The intervention consisted of 3 cycles of RIPC on the upper limb for 5 minutes alternated with 5 minutes of rest. A sham intervention was performed on the control group. Patients were recruited who were undergoing (1) high-risk cardiac or vascular surgery or (2) cardiac or vascular surgery and were at high risk of ischemic complications. The primary end point was a composite outcome of mortality, myocardial infarction, stroke, renal failure, respiratory failure, and low cardiac output syndrome, and the secondary end points included the individual outcome parameters that made up this score, as well as troponin-I values. A total of 436 patients were randomized and analysis was performed on 215 patients in the control group and on 213 patients in the RIPC group. There were no differences in the composite outcome between the 2 groups (RIPC: 67 [32%] and control: 72 [34%], relative risk [0.94 {0.72-1.24}]) or in any of the individual components that made up the composite outcome. Additionally, we did not observe any differences between the groups in troponin-I values, the length of intensive care unit stay, or the total hospital stay. RIPC did not have a beneficial effect on clinical outcomes in patients who had cardiovascular surgery.

Long-term outcome following remote ischemic postconditioning during percutaneous coronary interventions-the RIP-PCI trial long-term follow-up.

The clinical value of ischemic conditioning during percutaneous coronary intervention (PCI) and mode of administration is controversial. Our aim was to assess the long-term effect of remote ischemic postconditioning among patients undergoing PCI. We randomized 360 patients undergoing PCI who presented with a negative troponin T at baseline into 3 groups: 2 groups received remote ischemic postconditioning (with ischemia applied to the arm in 1 group and to the thigh in the other group), and the third group acted as a control group. Remote ischemic postconditioning was applied during PCI immediately following stent deployment, by 3, 5-minute cycles of blood pressure cuff inflation to >200 mm Hg on the arm or thigh (20 mm Hg to the arm in the control), with 5-minute breaks between each cycle. There were no differences in baseline characteristics among the 3 groups. Periprocedural myocardial injury occurred in 33% (P = 0.64). After 1 year, there was no difference between groups in death (P = 0.91), myocardial infarction (P = 0.78), or repeat revascularization (P = 0.86). During 3 years of follow-up, there was no difference in death, myocardial infarction, and revascularization among the groups (P = 0.45). Remote ischemic postconditioning during PCI did not affect long-term cardiovascular outcome. A similar effect was obtained when remote ischemia was induced to the upper or lower limb. ClinicalTrials.gov Identifier: NCT00970827.

Effect of non-invasive remote ischemic preconditioning on intra-renal perfusion in volunteers.

Remote ischemic preconditioning may attenuate renal injury and protect the kidney during subsequent inflammatory or ischemic stress. However, the mechanism of such a protection is not well understood. The aim of this study was to investigate the impact of remote ischemic preconditioning on renal resistivity index (RRI) in nine healthy volunteers. In six volunteers, four cycles of 4-min inflation of a blood pressure cuff were applied to one upper arm, followed by 4-min reperfusion with the cuff deflated. RRI was determined using Doppler echography during each cuff deflated period. Measures were also performed in three volunteers without preconditioning. The median value of RRI significantly decreased progressively from 0.59 [0.53-0.62] before the remote conditioning (baseline) to 0.49 [0.46-0.53] at the end of the experiment (p < 0.001) whereas there was no change in controls. In this study, for the first time, we have clearly shown in a small group of subjects that remote ischemic preconditioning can induce a significantly decrease in RRI through increased intra-renal perfusion.

Characterization of muscle oxygenation response to vascular occlusion: implications for remote ischaemic preconditioning and physical Performance.

Remote ischaemic preconditioning is a non-invasive intervention with potential to protect a number of organs against ischaemia-reperfusion injury and possibly improve athletic performance. Little mechanistic evidence exists to support either limb choice or cuff inflation pressure that is most effective. This preliminary study aimed to establish the dose-response effect of different occlusion pressures on skeletal muscle oxygenation and blood flow in healthy males (n = 6). In a randomized controlled crossover study, cuff inflation pressures (140,160 and 180 mmHg) were used to induce limb ischaemia (× 3 cycles of 5-min) in upper (UL) and lower (LL) limbs on three separate occasions. Muscle oxygenation and blood flow properties of UL (flexor carpi ulnaris) and LL (vastus lateralis) were assessed using near infrared spectroscopy. Higher deoxyhaemoglobin (ΔHHb) values were consistently observed in UL (versus LL; P<0·05), no difference between pressures. Occlusion at 140 mm Hg failed to elicit decreases in tissue oxyhaemoglobin (ΔHbO2 ) from resting baseline (UL and LL), with significant HbO2 decreases only observed at 180 mmHg in LL (P<0·05). Increases in ΔHbO2 and muscle oxygenation index (Hbdiff ) above baseline were observed with cuff deflation, lasting up to 15 min into recovery in LL irrespective of occlusion pressure (P<0·05). Muscle oxygenation properties are influenced by choice of limb occluded and findings show that tissue ischaemia can be induced at much lower absolute pressures than traditionally used in RIPC studies. Blood flow and muscle oxygenation may be enhanced for at least 15 min following the last occlusion.

Preconditioning with peristaltic external pneumatic compression does not acutely improve repeated Wingate performance nor does it alter blood lactate concentrations during passive recovery compared with sham.

Application of dynamic external pneumatic compression (EPC) during recovery from athletic activities has demonstrated favorable effects on flexibility, soreness, swelling, and blood lactate (BLa) concentrations. However, the effects of "preconditioning" with a peristaltic pulse EPC device on subsequent performance and BLa concentrations have not been characterized. Herein, we demonstrate that pretreatment for 30 min with EPC has no effect on subsequent supramaximal exercise performance or BLa concentrations during passive recovery.

Effects of dexmedetomidine in conjunction with remote ischemic preconditioning on renal ischemia­reperfusion injury in rats / Efeitos de dexmedetomidina em conjunto com o pré-condicionamento isquêmico remoto em lesão de isquemia-reperfusão renal em ratos / Efectos de la dexmedetomidina en conjunto con el precondicionamiento isquémico remoto en la lesión de isquemia-reperfusión renal en ratones

Background and objectives: The aim of this study was to evaluate the effects of remote ischemic preconditioning by brief ischemia of unilateral hind limb when combined with dexmedetomidine on renal ischemia-reperfusion injury by histopathology and active caspase-3 immunoreactivity in rats. Methods: 28 Wistar albino male rats were divided into 4 groups. Group I (Sham, n = 7): Laparotomy and renal pedicle dissection were performed at 65th minute of anesthesia and the rats were observed under anesthesia for 130min. Group II (ischemia-reperfusion, n = 7): At 65th minute of anesthesia bilateral renal pedicles were clamped. After 60 min ischemia 24 h of reperfusion was performed. Group III (ischemia-reperfusion + dexmedetomidine, n = 7): At the fifth minute of reperfusion (100 μg/kg intra-peritoneal) dexmedetomidine was administered with ischemia-reperfusion group. Reperfusion lasted 24 h. Group IV (ischemia-reperfusion + remote ischemic preconditioning + dexmedetomidine, n = 7): After laparotomy, three cycles of ischemic preconditioning (10 min ischemia and 10 min reperfusion) were applied to the left hind limb and after 5 min with group III. Results: Histopathological injury scores and active caspase-3 immunoreactivity were significantly lower in the Sham group compared to the other groups. Histopathological injury scores in groups III and IV were significantly lower than group II (p = 0.03 and p = 0.05). Active caspase-3 immunoreactivity was significantly lower in the group IV than group II (p = 0.01) and there was no significant difference between group II and group III (p = 0.06). Conclusions: Pharmacologic conditioning with dexmedetomidine and remote ischemic preconditioning when combined with dexmedetomidine significantly decreases renal ischemia- reperfusion injury histomorphologically. Combined use of two methods prevents apoptosis via active caspase-3. .

Justificativa e objetivos: Avaliar os efeitos do pré-condicionamento isquêmico remoto, mediante breve isquemia de membro posterior unilateral, em combinação com dexmedetomidina em lesão de isquemia-reperfusão renal por meio de histopatologia e imunorreatividade da caspase-3 ativa em ratos. Métodos: Foram divididos em quatro grupos 28 ratos machos albinos Wistar. Grupo I (Sham cirurgia controle], n = 7): laparotomia e dissecção do pedículo renal foram feitas em 65 minutos de anestesia e os ratos foram observados sob anestesia por 130 minutos. Grupo II (isquemia-reperfusão, n = 7): no 65° minuto de anestesia, os pedículos renais bilaterais foram pinçados; após 60 minutos de isquemia, foi feita reperfusão de 24 horas. Grupo III (isquemia-reperfusão + dexmedetomidina, n = 7): no quinto minuto de reperfusão, dexmedetomidina (100 mg/kg intraperitoneal) foi administrada ao grupo com isquemia-reperfusão. A reperfusão durou 24 horas. Grupo IV (isquemia-reperfusão + pré-condicionamento isquêmico remoto + dexmedetomidina, n = 7): após a laparotomia, três ciclos de pré-condicionamento isquêmico (10minutos de isquemia e 10minutos de reperfusão) foram aplicados no membro posterior esquerdo e depois de cincominutos ao grupo III. Resultados: Os escores de lesão histopatológica e imunorreatividade da caspase-3 ativa foram significativamente menores no grupo Sham em comparação com os outros. Os escores de lesão histopatológica dos grupos III e IV foram significativamente menores do que os do II (p = 0,03 e p = 0,05). A imunorreatividade da caspase-3 foi significativamente menor no grupo IV do que no II (p = 0,01) e não houve diferença significante entre os grupos II e III (p = 0,06). Conclusões: O condicionamento farmacológico com dexmedetomidina e o pré...

Introducción y objetivos: El objetivo de este estudio fue evaluar los efectos del precondicionamiento isquémico remoto mediante breve isquemia del miembro posterior unilateral en combinación con la dexmedetomidina en la lesión de isquemia-reperfusión renal por medio de histopatología e inmunoreactividad de la caspasa-3 activa en ratones. Métodos: 28 ratones machos albinos Wistar fueron divididos en 4 grupos. Grupo I (Sham cirugía control], n =7): se realizó laparotomia y disección del pediculo renal en 65 min de anestesia y los ratones fueron observados bajo anestesia durante 130min. Grupo II (isquemia-reperfusión, n = 7): en el sexagésimo quinto minuto de anestesia, los pídiculos renales bilaterales fueron pinzados; después de 60min de isquemia, se realizaron 24h de reperfusión. Grupo III (isquemia-reperfusión + dexmedetomidina, n = 7): al quinto minuto de reperfusión, la dexmedetomidina (100 μg/kg intraperitoneal) fue administrada en el grupo con isquemia-reperfusión; la reperfusión duró 24 h. Grupo IV (isquemia-reperfusión + precondicionamiento isquémico remoto + dexmedetomidina, n=7): después de la laparotomía, se aplicaron 3 ciclos de precondicionamiento isquémico (10 min de isquemia y 10 min de reperfusión) en el miembro posterior izquierdo y después de 5 min en el grupo in. Resultados: Las puntuaciones de lesión histopatológica e inmunoreactividad de la caspasa-3 activa fueron significativamente menores en el grupo Sham en comparación con los otros grupos. Las puntuaciones de lesión histopatológica de los grupos III y IV fueron significativamente menores que las del grupo II (p = 0,03 y p = 0,05). La inmunorreactividad de la caspasa-3 fue significativamente menor en el grupo IV que en el grupo II (p = 0,01) y no hubo diferencia significativa entre los grupos II ...

The angiogenic effects of ischemic conditioning in experimental critical limb ischemia.

OBJECTIVES: Ischemic conditioning (IC) is a method of angiogenic stimulus for limb ischemia. Here, we aimed to investigate the effects of short-term repeated ischemic stimulus on critical lower limb ischemic injury. METHODS: Rats were divided into four groups consisting of 40 animals in each group: sham, ischemia, local IC, and remote IC groups. Right-leg critical limb ischemia was achieved through ligation of the iliac artery and vein in male Sprague-Dawley rats except the sham group. Repeated transient ischemia using the tourniquet method was used for IC of lower extremities in the local and remote groups. IC was performed on the right leg for the local group and on the left leg for the remote group. Ten rats in each group were sacrificed for evaluation on days 1, 7, 14, and 30. Endothelial progenitor cell (EPC) counts were measured. Gastrocnemius muscles were evaluated for the degree of ischemia. Laser Doppler blood flow measurements were performed in order to make comparison between the blood flows of the limbs of the groups. RESULTS: The blood flow in the right limb of rats in the sham (1.65 perfusion units [PU]) and local IC (1.67 PU) groups was significantly higher than the ischemic group (1.17 PU) (p = .001 and p = .022 respectively). The levels of EPCs in the ischemia (1.09 ± 0.5) and remote IC groups (1.36 ± 0.8) were significantly higher than the sham (0.38 ± 0.2) group on day 7 (p = .026 and p = .002 respectively). Remote IC and local IC groups exhibited increased histopathological ischemia on day 7 when compared with sham group (p = .001, p = .01 respectively). The angiogenic scores on the 7th, 14th and 30th days for local IC and remote IC groups were significantly higher than sham and ischemia groups. CONCLUSIONS: IC seems to be the potent activator of angiogenesis in ischemic tissue. This study provides preliminary data showing that repeated short ischemic stimuli may reduce critical ischemic injury by promoting angiogenesis.

Does limb preconditioning reduce pain after total knee arthroplasty? A randomized, double-blind study.

BACKGROUND: Total knee arthroplasty (TKA) can be associated with considerable postoperative pain. Ischemic preconditioning of tissue before inducing procedure-related underperfusion may reduce the postoperative inflammatory response, which further may reduce associated pain. QUESTIONS/PURPOSES: In this prospective, randomized study, we aimed at evaluating the impact of ischemic preconditioning on postoperative pain at rest and during exercise; use of pain medication; levels of systemic prothrombotic and local inflammatory markers; and length of stay and achievement of physical therapy milestones. METHODS: Sixty patients undergoing unilateral TKA under tourniquet were enrolled with half (N = 30) being randomized to an episode of limb preconditioning before induction of ischemia for surgery (tourniquet inflation). Pain scores, analgesic consumption, markers of inflammation (interleukin-6 [IL-6], tumor necrosis factor [TNF]-α in periarticular drainage), and periarticular circumference were measured at baseline and during 2 days postoperatively. Changes in prothrombotic markers were evaluated. RESULTS: Patients in the preconditioning group had significantly less pain postoperatively at rest (mean difference = -0.71, 95% confidence interval [CI] = -1.40 to -0.02, p = 0.043) and with exercise (mean difference = -1.38, 95% CI = -2.32 to -0.44, p = 0.004), but showed no differences in analgesic consumption. No differences were seen between the study and the control group in terms of muscle oxygenation and intraarticular levels of IL-6 and TNF-α as well as levels of prothrombotic markers. No differences were found between groups in regard to hospitalization length and time to various physical therapy milestones. CONCLUSIONS: Ischemic preconditioning reduces postoperative pain after TKA, but the treatment effect size we observed with the preconditioning routine used was modest. CLINICAL RELEVANCE: Given the ease of this intervention, ischemic preconditioning may be considered as part of a multimodal analgesic strategy. However, more study into the impact of different preconditioning strategies, elucidation of mechanisms, safety profiles, and cost-effectiveness of this maneuver is needed.

Remote ischemic preconditioning in percutaneous coronary revascularization: a double-blind randomized controlled clinical trial.

OBJECTIVE: To assess the impact of pre-procedural remote ischemic preconditioning on the incidence of myocardial complications following percutaneous coronary intervention. BACKGROUND: Ischemic preconditioning of a remote vascular territory improves the subsequent ischemic tolerance of distant organs. METHOD: The Myocardial Event Reduction with Ischemic Preconditioning Therapy (MERIT) trial recruited 80 consecutive patients undergoing elective angioplasty with drug-eluting stents to receive two 5-min lower limb tourniquet occlusions or an un-inflated tourniquet (controls) 1 h before the procedure. The primary outcome was troponin T level at 24 h. Secondary outcomes were intra-procedural chest pain and ST-segment deviation. RESULTS: 6 patients in the control group and 2 in the ischemic preconditioning group had pre-procedural raised troponin T (p = 0.23). This increased to 16 (40%) in the control group and 5 (12.5%) in the study group at 24 h (p = 0.01). Fewer patients in the study group experienced intra-procedural chest pain (1 vs. 7, p = 0.056). Mean ST-segment deviation time was 13 ± 35 s in the study group and 58 ± 118 s in the control group (p = 0.02). At a mean follow-up of 11 months, the major adverse cardiac event rate did not differ significantly between the groups. CONCLUSION: These data suggest that ischemic preconditioning reduces the absolute risk of post-procedure cardiomyocyte necrosis by 27.5%, and reduces intra-procedural chest pain and ST-segment deviation in patients undergoing percutaneous coronary interventions. We suggest its routine use in percutaneous coronary intervention, although the long-term prognostic impact in this patient group warrants further investigation.

Use of a hanging-weight system for liver ischemic preconditioning in mice.

Ischemic preconditioning (IP) represents a powerful experimental strategy to identify novel molecular targets to attenuate hepatic injury during ischemia. As a result, murine studies of hepatic IP have become an important field of research. However, murine IP is technically challenging, and experimental details can alter the results. Therefore, we systematically tested a novel model of hepatic IP by using a hanging-weight system for portal triad occlusion. This system has the benefit of applying intermittent hepatic ischemia and reperfusion without manipulation of a surgical clamp or suture, thus minimizing surgical trauma. Systematic evaluation of this model revealed a close correlation of hepatic ischemia time with liver damage as measured by alanine (ALT) and aspartate (AST) aminotransferase serum levels. Using different numbers of IP cycles and times intervals, we found optimal liver protection with four cycles of 3 min ischemia/3 min reperfusion as measured by ALT, AST, lactate dehydrogenase, and interleukin-6. Similarly, ischemia-associated increases in hepatic infarct size, neutrophil infiltration, and histological injury were maximally attenuated with the above regimen. To demonstrate transcriptional consequences of liver IP, we isolated RNA from preconditioned liver and confirmed transcriptional modulation of known target genes (equilibrative nucleoside transporters, acute-phase complement genes). Taken together, these studies confirm highly reproducible liver injury and protection by IP when using the hanging-weight system for hepatic ischemia and intermittent reperfusion. Further studies of murine IP may consider this technique.

Use of a hanging-weight system for isolated renal artery occlusion during ischemic preconditioning in mice.

Renal failure from ischemia contributes to morbidity and mortality. Ischemic preconditioning (IP) represents a powerful strategy for kidney protection, and recent advances in transgenic mice may help elucidate its molecular mechanisms. However, murine IP is technically challenging and experimental details significantly influence results. Thus we developed a novel model for renal IP using a hanging-weight system for isolated renal artery occlusion. In contrast to previous models, this technique eliminates the need for clamping the vascular pedicle (artery/vein). In fact, assessment of renal injury after different time periods of ischemia (10-60 min) revealed highly reproducible increases in plasma creatinine and potassium levels, while creatinine clearance, urinary flow and potassium/sodium excretion were significantly attenuated. Using different numbers of IP cycles, we found maximal protection with four cycles of 4 min of ischemia-reperfusion. In contrast, no significant renal protection was observed with IP of the vascular pedicle. To assess transcriptional responses in this model, we isolated RNA from preconditioned kidneys and found time-dependent induction of erythropoietin mRNA and plasma levels with IP. Taken together, this model provides highly reproducible renal injury and protection by IP, thus minimizing variability associated with previous techniques based on clamping of the renal pedicle. Further studies on renal ischemia/IP in mice may consider this technique.

Bloodless liver resection using the monopolar floating ball plus ligasure diathermy: preliminary results of 16 liver resections.

Blood loss during liver transection and ischemia-reperfusion injury associated with hepatic inflow occlusion are significant drawbacks during liver surgery. Sixteen patients underwent liver resection using the Monopolar Floating Ball (FB) plus LigaSure (LS) diathermy without occlusion of the hepatoduodenal ligament (group FB-LS). The liver parenchyma was precoagulated using the FB, and the uncovered tiny vessels were sealed using LS. Surgical outcomes were retrospectively compared with 16 well matched patients who underwent liver resection using the conventional clamp crushing method with Pringle's maneuver (group CC). The amount of blood loss during liver transection was significantly less in group FB-LS than in group CC [200 ml (0-990 ml) vs. 480 ml (120-1800 ml); p = 0.006]. The median time it took to complete the liver transection was significantly longer in group FB-LS than in group CC [144 minutes (43-335 minutes) vs. 58 minutes (18-94 minutes); p < 0.0001]. Hepatic inflow occlusion was temporally used in five patients in group FB-LS to achieve hemostasis in hepatic venous tributaries for 6, 10, 19, 26, and 61 minutes, respectively. Using these two electronic devices allows liver resection to be safely performed, with the advantage of minimal blood loss and a reduced inflow occlusion period compared to the conventional method. The major disadvantage may be a slower transection speed. A prospective randomized trial is needed to clarify the clinical benefits of liver resections performed using this novel technique.