Microcirculatory effects of local and remote ischemic preconditioning in supraceliac aortic clamping

Short-Term Preconditioning With Blood Flow Restricted Exercise Preserves Quadriceps Muscle Endurance in Patients After Anterior Cruciate Ligament Reconstruction

Surgical ACL reconstruction performed with a tourniquet induces compression and ischemic stress of the quadriceps femoris (QF) muscle which can accelerate postoperative weakness. Given that low-load blood flow restricted (BFR) exercise is potent in enhancing muscle oxygenation and vascular function, we hypothesized that short-term preconditioning with low-load BFR exercise can attenuate QF muscle endurance deterioration in the postoperative period. Twenty subjects undergoing arthroscopic ACL reconstruction performed 5 exercise sessions in the last 8 days prior to surgery. They were assigned into either BFR group, performing low-load BFR knee-extension exercise, or SHAM-BFR group, replicating equal training volume with sham occlusion. Blood flow (near-infrared spectroscopy) and surface EMG of QF muscle during sustained isometric contraction at 30% of maximal voluntary isometric contraction (MVIC) torque performed to volitional failure were measured prior to the intervention and again 4 and 12 weeks after surgery. There was an overall decrease (p = 0.033) in MVIC torque over time, however, no significant time-group interaction was found. The time of sustained QF contraction shortened (p = 0.002) in SHAM-BFR group by 97 ± 85 s at week 4 and returned to preoperative values at week 12. No change in the time of sustained contraction was detected in BFR group at any time point after surgery. RMS EMG amplitude increased (p = 0.009) by 54 ± 58% at week 4 after surgery in BFR group only. BFm increased (p = 0.004) by 52 ± 47% in BFR group, and decreased (p = 0.023) by 32 ± 19% in SHAM-BFR group at week 4 after surgery. Multivariate regression models of postoperative changes in time of sustained QF contraction revealed its high correlation (R2 = 0.838; p < 0.001) with changes in BFm and RMS EMG in the SHAM-BFR group, whereas no such association was found in the BFR group. In conclusion, enhanced endurance of QF muscle was triggered by combination of augmented muscle fiber recruitment and enhanced muscle perfusion. The latter alludes to a preserving effect of preconditioning with BFR exercise on density and function of QF muscle microcirculation within the first 4 weeks after ACL reconstruction.

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

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

Local and remote ischemic preconditioning protect against intestinal ischemic/reperfusion injury after supraceliac aortic clamping

OBJECTIVES

This study tests the hypothesis that local or remote ischemic preconditioning may protect the intestinal mucosa against ischemia and reperfusion injuries resulting from temporary supraceliac aortic clamping.

METHODS

Twenty-eight Wistar rats were divided into four groups: the sham surgery group, the supraceliac aortic occlusion group, the local ischemic preconditioning prior to supraceliac aortic occlusion group, and the remote ischemic preconditioning prior to supraceliac aortic occlusion group. Tissue samples from the small bowel were used for quantitative morphometric analysis of mucosal injury, and blood samples were collected for laboratory analyses.

RESULTS

Supraceliac aortic occlusion decreased intestinal mucosal length by reducing villous height and elevated serum lactic dehydrogenase and lactate levels. Both local and remote ischemic preconditioning mitigated these histopathological and laboratory changes.

CONCLUSIONS

Both local and remote ischemic preconditioning protect intestinal mucosa against ischemia and reperfusion injury following supraceliac aortic clamping.

Pinacidil pretreatment improves vascular reactivity after shock through PKCα and PKCε in rats

We investigated the beneficial effect of pinacidil pretreatment on vascular reactivity, calcium sensitivity, and animal survival after hemorrhagic shock, its relationship to protein kinase Cα (PKCα), protein kinase Cε (PKCε), and adenosine. Using hemorrhagic shock rats, the protective effects of different extents of pinacidil pretreatment on vascular reactivity and in which the roles of PKCα, PKCε, and adenosine were observed. Pinacidil pretreatment significantly improved shock-induced decrease of vascular reactivity of superior mesenteric artery, which was antagonized by the PKCα antagonist Gö-6976 (5 × 10 mole/L) and PKCε pseudosubstrate inhibitory peptide (1 × 10 mole/L). Pinacidil pretreatment induced the translocation of PKCα and PKCε from the cytoplasm to the membrane. This translocation of PKCα and PKCε was eliminated by adenosine A1 receptor antagonist DPCPX (1 × 10 mole/L). As compared with simple fluid resuscitation, combination with pinacidil pretreatment significantly improved the vascular reactivity and survival rate of hemorrhagic-shocked rats. These results suggested that pinacidil pretreatment could induce good protective effects on vascular reactivity and calcium sensitivity after hemorrhagic shock mainly through the activation of PKCα and PKCε via adenosine A1 receptor, and this protective effect made an important contribution to the overall outcome of shock therapy.