Reduced effect of ischemic preconditioning against endothelial ischemia-reperfusion injury with cardiovascular risk factors in humans

Immediate Increase in the Root Mean Square of Successive Differences after Three Bouts of Remote Ischemic Preconditioning: A Randomized Controlled Trial

(1) Background: Remote ischemic preconditioning (RIPC) is an intervention involving the application of brief episodes of ischemia and reperfusion to distant tissues to activate protective pathways in the heart. There is evidence suggesting the involvement of the autonomic nervous system (ANS) in RIPC-induced cardioprotection. This study aimed to investigate the immediate effects of RIPC on the ANS using a randomized controlled trial. (2) Methods: From March 2018 to November 2018, we conducted a single-blinded randomized controlled study involving 51 healthy volunteers (29 female, 24.9 [23.8, 26.4] years). Participants were placed in a supine position and heart rate variability was measured over 260 consecutive beats before they were randomized into either the intervention or the SHAM group. The intervention group underwent an RIPC protocol (3 cycles of 5 min of 200 mmHg ischemia followed by 5 min reperfusion) at the upper thigh. The SHAM group followed the same protocol but on the right upper arm, with just 40 mmHg of pressure inflation, resulting in no ischemic stimulus. Heart rate variability measures were reassessed afterward. (3) Results: The intervention group showed a significant increase in RMSSD, the possible marker of the parasympathetic nervous system (IG: 14.5 [5.4, 27.5] ms vs. CG: 7.0 [-4.3, 23.1 ms], p = 0.027), as well as a significant improvement in Alpha 1 levels compared to the control group (IG: -0.1 [-0.2, 0.1] vs. CG: 0.0 [-0.1, 0.2], p = 0.001). (4) Conclusions: Our results hint that RIPC increases the RMSSD and Alpha 1 parameters showing possible immediate parasympathetic modulations. RIPC could be favorable in promoting cardioprotective or/and cardiovascular effects by ameliorating ANS modulations.

A Single Bout of Remote Ischemic Preconditioning Suppresses Ischemia-Reperfusion Injury in Asian Obese Young Men

Remote ischemic preconditioning (RIPC) has been shown to minimize subsequent ischemia-reperfusion injury (IRI), whereas obesity has been suggested to attenuate the efficacy of RIPC in animal models. The primary objective of this study was to investigate the effect of a single bout of RIPC on the vascular and autonomic response after IRI in young obese men. A total of 16 healthy young men (8 obese and 8 normal weight) underwent two experimental trials: RIPC (three cycles of 5 min ischemia at 180 mmHg + 5 min reperfusion on the left thigh) and SHAM (the same RIPC cycles at resting diastolic pressure) following IRI (20 min ischemia at 180 mmHg + 20 min reperfusion on the right thigh). Heart rate variability (HRV), blood pressure (SBP/DBP), and cutaneous blood flow (CBF) were measured between baseline, post-RIPC/SHAM, and post-IRI. The results showed that RIPC significantly improved the LF/HF ratio (p = 0.027), SBP (p = 0.047), MAP (p = 0.049), CBF (p = 0.001), cutaneous vascular conductance (p = 0.003), vascular resistance (p = 0.001), and sympathetic reactivity (SBP: p = 0.039; MAP: p = 0.084) after IRI. However, obesity neither exaggerated the degree of IRI nor attenuated the conditioning effects on the measured outcomes. In conclusion, a single bout of RIPC is an effective means of suppressing subsequent IRI and obesity, at least in Asian young adult men, does not significantly attenuate the efficacy of RIPC.

Tefillin use induces preconditioning associated changes in heart rate variability

Short bouts of occlusion of blood flow can induce a preconditioning response that reduces subsequent damage from longer periods of ischemia. It has been shown that ischemic preconditioning (IPC) can be elicited remotely (RIPC) through limitation of blood flow and as recently described via only pain sensation. Non-obstructive banding (NOB) through the donning of tefillin (a box with sacred texts attached to a leather strap that is traditionally bound to the non-dominant arm of Jewish adults during morning prayers) has been shown to elicit an RIPC response at least partially through pain sensation. This study evaluated the effects of NOB on heart rate variability (HRV) dependent factors that are known to be affected by various RIPC stimuli. We recruited 30 healthy subjects and subjected them to NOB versus control and found various HRV markers associated with RIPC to be changed in the NOB group. This finding provides further evidence that tefillin, likely through NOB induced RIPC changes, may still be a viable clinical pathway to prevent and decrease the morbidity associated with ischemic events.

Remote ischaemic preconditioning - translating cardiovascular benefits to humans

Remote ischaemic preconditioning (RIPC), induced by intermittent periods of limb ischaemia and reperfusion, confers cardiac and vascular protection from subsequent ischaemia–reperfusion (IR) injury. Early animal studies reliably demonstrate that RIPC attenuated infarct size and preserved cardiac tissue. However, translating these adaptations to clinical practice in humans has been challenging. Large clinical studies have found inconsistent results with respect to RIPC eliciting IR injury protection or improving clinical outcomes. Follow‐up studies have implicated several factors that potentially affect the efficacy of RIPC in humans such as age, fitness, frequency, disease state and interactions with medications. Thus, realizing the clinical potential for RIPC may require a human experimental model where confounding factors are more effectively controlled and underlying mechanisms can be further elucidated. In this review, we highlight recent experimental findings in the peripheral circulation that have added valuable insight on the mechanisms and clinical benefit of RIPC in humans. Central to this discussion is the critical role of timing (i.e. immediate vs. delayed effects following a single bout of RIPC) and the frequency of RIPC. Limited evidence in humans has demonstrated that repeated bouts of RIPC over several days uniquely improves vascular function beyond that observed with a single bout alone. Since changes in resistance vessel and microvascular function often precede symptoms and diagnosis of cardiovascular disease, repeated bouts of RIPC may be promising as a preclinical intervention to prevent or delay cardiovascular disease progression.

Delayed Cutaneous Microvascular Responses With Non-consecutive 3 Days of Remote Ischemic Preconditioning

The optimal frequency and duration of remote ischemic preconditioning (RIPC) that augments microvascular function is unknown. A single bout of RIPC increases cutaneous endothelial function for ∼48 h, whereas 1 week of daily RIPC bouts improves more sustained endothelium-independent function. We hypothesized that 3 days of RIPC separated by rest days (3QOD RIPC) would result in sustained increases in both endothelium-dependent and endothelium-independent functions. Cutaneous microvascular function was assessed in 13 healthy young participants (aged 20.5 ± 3.9 years; 5 males, 8 females) before 3QOD and then 24, 48, and 72 h and a week after 3QOD. RIPC consisted of four repetitions of 5 min of blood flow occlusion separated by 5 min of reperfusion. Skin blood flow responses to local heating (T_loc = 42°C), acetylcholine (Ach), and sodium nitroprusside (SNP) were measured using laser speckle contrast imaging and expressed as cutaneous vascular conductance (CVC = PU⋅mmHg^–1). Local heating-mediated vasodilation was increased 72 h after 3QOD and the increased responsivity persisted a week later (1.08 ± 0.24 vs. 1.34 ± 0.46, 1.21 ± 0.36 PU⋅mmHg^–1; ΔCVC, pre-RIPC vs. 72 h, a week after 3QOD; P = 0.054). Ach-induced cutaneous vasodilation increased a week after 3QOD (0.73 ± 0.41 vs. 0.95 ± 0.49 PU⋅mmHg^–1; ΔCVC, pre-RIPC vs. a week after 3QOD; P < 0.05). SNP-induced cutaneous vasodilation increased 24 h after 3QOD (0.47 ± 0.28 vs. 0.63 ± 0.35 PU⋅mmHg^–1; ΔCVC, pre-RIPC vs. 24 h; P < 0.05), but this change did not persist thereafter. Thus, 3QOD induced sustained improvement in endothelium-dependent vasodilation but was not sufficient to sustain increases in endothelium-independent vasodilation.

Beneficial postoperative micro-rheological effects of intraoperative administration of diclophenac or ischemic preconditioning in patients with lower extremity operations -Preliminary data

BACKGROUND

Ischemia-reperfusion (I/R) may worsen blood rheology that has been demonstrated by clinical and experimental data. It is also known that anti-inflammatory agents and preconditioning methods may reduce I/R injury.

OBJECTIVE

We aimed to analyze hemorheological alterations in elective knee operations and the effects of intraoperative nonsteroidal anti-inflammatory drug (NSAID) administration and application of ischemic preconditioning.

METHODS

Hemorheological variables of 17 patients with total knee replacement or anterior crucial ligament replacement were analyzed. The ischemic (tourniquet) time was 92±15 minutes. Seven patients did not receive NSAID (Control group), 5 patients got i.v. sodium-diclophenac 10 minutes before and 6 hours after reperfusion. Five patients had ischemic preconditioning (3×15 minutes). Blood samples were collected before the ischemia, 10 minutes after reperfusion, on the 1st and 2nd p.o. day.

RESULTS

Whole blood viscosity didn't show notable inter-group differences, except for a slight decrease in the preconditioning group. RBC deformability decreased, erythrocyte aggregation enhanced by the 1st and 2nd p.o. days in Control group. In NSAID and preconditioning groups the changes were moderate, aggregation values significantly lowered compared to the Control group.

CONCLUSION

Intraoperatively administered diclophenac or ischemic preconditioning could moderate the deterioration in micro-rheological parameters caused by I/R in patients.