Increased ischemia-reperfusion blood flow impairs the skeletal muscle contractile function

Protective Role of Chronic Exercise Training in Modulating the Impact of Hyperglycemia on Vascular Sensitivity to Ischemia-Reperfusion

Hyperglycemia (HG) is associated with increased mortality and morbidity in acute ischemic events. Regardless of the tissue or organs involved, the vascular endothelium is a key target of ischemia-reperfusion (I/R) injury severity. Among endothelium-protective strategies, exercise has been widely described as useful. However, whether this strategy is able to impact the deleterious effect of HG on endothelial function during I/R has never been challenged. For this, 48 male Wistar rats were randomized into 4 groups: sedentary (Sed) or exercised (Ex, 45 min/day, 5 days/week for 5 weeks) rats, treated (hyperglycemic, HG) or not (normoglycemic, NG) with streptozotocin (40 mg/kg, 48 h before procedure). Vascular I/R (120/15 min) was performed by clamping the femoral artery. Arterial and downstream muscular perfusions were assessed using laser speckle contrast imaging. Vascular endothelial function was assessed in vivo 15 min after reperfusion. HG was responsible for impairment of reperfusion blood flow as well as endothelial function. Interestingly exercise was able to prevent those impairments in the HG group. In agreement with the previous results, HG increased reactive oxygen species production and decreased nitric oxide bioavailability whereas exercise training normalized these parameters. It, therefore, appears that exercise may be an effective prevention strategy against the exacerbation of vascular and muscular damage by hyperglycemia during I/R.

Efficacy of non-surgical interventions for promoting improved functional outcomes following acute compartment syndrome: A systematic review

Background

Acute compartment syndrome (ACS) is a devastating complication which develops following a traumatic extremity injury that results in increased pressure within osteofascial compartments, thereby leading to ischemia, muscle and nerve necrosis, and creates a life-threatening condition if left untreated. Fasciotomy is the only available standard surgical intervention for ACS. Following fasciotomy the affected extremity is plagued by prolonged impairments in function. As such, an unmet clinical need exists for adjunct, non-surgical therapies which can facilitate accelerated functional recovery following ACS. Thus, the purpose of this systematic review was to examine the state of the literature for non-surgical interventions that aim to improve muscle contractile functional recovery of the affected limb following ACS.

Methods

English language manuscripts which evaluated non-surgical interventions for ACS, namely those which evaluated the function of the affected extremity, were identified as per PRISMA protocols via searches within three databases from inception to February 2022. Qualitative narrative data synthesis was performed including: study characteristics, type of interventions, quality, and outcomes. Risk of bias (RoB) was assessed using the Systematic Review Centre for Laboratory Animal Experimentation’s (SYRCLE) RoB tool and reported level of evidence for each article.

Results

Upon review of all initially identified reports, 29 studies were found to be eligible and included. 23 distinct non-surgical interventions were found to facilitate improved muscle contractile function following ACS. Out of 29 studies, 15 studies which evaluated chemical and biological interventions, showed large effect sizes for muscle function improvement.

Conclusions

This systematic review demonstrated that the majority of identified non-surgical interventions facilitated an improvement in muscle contractile function following pathological conditions of ACS.

Our contemporary understanding of the aetiology of pressure ulcers/pressure injuries

In 2019, the third and updated edition of the Clinical Practice Guideline (CPG) on Prevention and Treatment of Pressure Ulcers/Injuries has been published. In addition to this most up‐to‐date evidence‐based guidance for clinicians, related topics such as pressure ulcers (PUs)/pressure injuries (PIs) aetiology, classification, and future research needs were considered by the teams of experts. To elaborate on these topics, this is the third paper of a series of the CPG articles, which summarises the latest understanding of the aetiology of PUs/PIs with a special focus on the effects of soft tissue deformation. Sustained deformations of soft tissues cause initial cell death and tissue damage that ultimately may result in the formation of PUs/PIs. High tissue deformations result in cell damage on a microscopic level within just a few minutes, although it may take hours of sustained loading for the damage to become clinically visible. Superficial skin damage seems to be primarily caused by excessive shear strain/stress exposures, deeper PUs/PIs predominantly result from high pressures in combination with shear at the surface over bony prominences, or under stiff medical devices. Therefore, primary PU/PI prevention should aim for minimising deformations by either reducing the peak strain/stress values in tissues or decreasing the exposure time.

An optimized low-pressure tourniquet murine hind limb ischemia reperfusion model: Inducing acute ischemia reperfusion injury in C57BL/6 wild type mice

Acute ischemia reperfusion injury in skeletal muscle remains an important issue in several fields of regenerative medicine. Thus, a valid model is essential to gain deeper insights into pathophysiological relations and evaluate possible treatment options. While the vascular anatomy of mice regularly prevents sufficient vessel occlusion by invasive methods, there is a multitude of existing models to induce ischemia reperfusion injury without surgical procedures. Since there is no consensus on which model to prefer, this study aims to develop and evaluate a novel, optimized low-pressure tourniquet model. C57BL/6 mice underwent an ischemic procedure by either tourniquet or invasive artery clamping. A sham group served as control. With exception of the sham group, mice underwent 2 hours of ischemia followed by 4 hours of reperfusion. Groups were compared using microcirculatory and spectroscopic measurements, distinctions in tissue edema, histological and immunohistochemical analyses. Both procedures led to a significant decrease in tissue blood flow (- 97% vs. - 86%) and oxygenation (- 87% vs. - 75%) with a superiority of the low-pressure tourniquet. Tissue edema in the tourniquet cohort was significantly increased (+ 59%), while the increase in the clamping cohort was non-significant (+ 7%). Haematoxylin Eosin staining showed significantly more impaired muscle fibers in the tourniquet group (+ 77 p.p. vs. + 11 p.p.) and increased neutrophil infiltration/ROI (+ 51 vs. + 8). Immunofluorescence demonstrated an equal increase of p38 in both groups (7-fold vs. 8-fold), while the increase in apoptotic markers (Caspase-3, 3-Nitrotyrosine, 4-Hydroxynonenal) was significantly higher in the tourniquet group. The low-pressure tourniquet has been proven to produce reproducible and thus reliable ischemia reperfusion injury. In addition, significantly less force was needed than previously stated. It is therefore an important instrument for studying the pathophysiology of ischemia reperfusion injury and for the development of prophylactic as well as therapeutic interventions.

Pattern of presentation of pressure ulcers in traumatic spinal cord injured patients in University College Hospital, Ibadan

The neurosurgery division in University College Hospital (U.C.H.) admits approximately one traumatic spinal cord injured (SCI) patient per week, most of whom stay a minimum of 42 days on admission. A common complication in these patients is the development of pressure ulcers, which contributes to a longer hospital stay and increased hospital expenses. The purpose of this study was to investigate the pattern of presentation of pressure ulcers in patients on admission and to propose policies or protocols to reduce the incidence. It is a prospective study of traumatic SCI patients managed on the neurosurgery ward from January 2003 to June 2004. The data was analysed using descriptive statistics. Sixty-seven patients were studied. The average hospital stay was 73 days. Thirteen (20%) of the patients were admitted with pressure ulcers, 32 (47·7%) developed it after admission. As much as 87·5% of pressure ulcers seen in the course of this study which occurred on admission in U.C.H. was in the first week of admission, 6·25% in the second week and the remaining 6·25% in the third week. Pressure ulcers were distributed as follows; 69% (42) in the sacral region, 18% (11) trochanteric, 5% (3) scalp, 1·5% (1) ankle, 1·5% (1) ischial tuberosity, the remaining 5% in other sites. Preventive measures for pressure ulcers consisted of basic skin care, pressure dispersion using fenestrated foams and alternating weight-bearing sites by regular turning. Pressure ulcers are commonest in the sacral and gluteal regions and tend to occur within the first week of admission in the neurosurgical wards.

Hypertonic saline reduces skeletal muscle injury and associated remote organ injury following ischemia reperfusion injury

BACKGROUND AND PURPOSE

Pharmacological modulation of skeletal muscle reperfusion injury after traumaassociated ischemia may improve limb salvage rates and prevent the associated systemic sequelae. Resuscitation with hypertonic saline restores the circulating volume and has favorable effects on tissue perfusion and blood pressure. We evaluated the effects of treatment with a bolus of hypertonic saline on skeletal muscle ischemia reperfusion (IR) injury and the associated end-organ injury.

METHODS

Adult male Sprague-Dawley rats (n = 27) were randomized into 3 groups: (1) a control group, (2) an IR group treated with normal saline, and (3) an IR group treated with hypertonic saline. Bilateral hindlimb ischemia was induced by application of a rubber band proximal to the level of the greater trochanters for 2.5 h. The treatment groups received either normal saline (4 mL/kg) or hypertonic saline (4 mL/kg) prior to tourniquet release. Following 12 h of reperfusion, the tibialis anterior muscle was dissected and muscle function was assessed electrophysiologically. The animals were then killed, and skeletal muscle and lung tissue were harvested for evaluation.

RESULTS

Hypertonic saline significantly attenuated skeletal muscle reperfusion injury, as shown by reduced myeloperoxidase content, wet-to-dry ratio, and electrical properties of skeletal muscle. There was a corresponding reduction in lung injury, as demonstrated by reduced myeloperoxidase content and reduced wet-to-dry ratio.

INTERPRETATION

Treatment with hypertonic saline attenuates skeletal muscle ischemia reperfusion injury and its associated systemic sequelae.

Lack of chlorpromazine effect on skeletal muscle metabolism after ischemia and a short reperfusion period

The great resistance of muscle to ischemia was used to study blood flow-dependent phenomena produced by anesthetic drugs in this condition. A short reperfusion period was used in order to favor metabolic changes indicative of an effect of chlorpromazine (CPZ) on blood flow. Gracilis muscles of dogs were submitted to 5 h of ischemia and 30 min of reperfusion. CPZ-treated animals were injected I.V. (2 mg/kg) 10 min before the beginning of ischemia. Biopsies provided the material for tissue measurements. Lactate content and pH were determined in blood samples collected from a muscle efferent vein. In both the CPZ-treated and nontreated groups, ischemia induced a decline in muscle glycogen content, with a corresponding increase in muscle lactate and a decrease in mitochondrial respiratory control ratio. After 30 min of reperfusion, tissue levels of lactate did not attain preischemic values but showed a clear decline in the two experimental groups, evidencing the reversible state of the muscle. All other metabolic parameters remained unchanged. Mitochondrial respiratory control remained functional during ischemia and reperfusion. Blood pH displayed similar changes in both groups. There was no metabolic indication that the drug affected blood flow during early reperfusion and/or of a greater sensitivity of muscle endothelial cells to anesthetic drugs.

The effect of perfusion with UW solution on the skeletal muscle and vascular endothelial exocrine function in rat hindlimbs

BACKGROUND

The effect of University of Wisconsin (UW) solution perfusion for extremity preservation is still unknown although it is widely used. The purpose of this study is to examine the effect of UW solution perfusion on skeletal muscle preservation in a rat model.

MATERIALS AND METHODS

Rat hindlimbs were amputated and either preserved with UW solution perfusion (UW perfusion group) or given no perfusion (no-perfusion group) for 5 h at 25 degrees C. They were then transplanted to other isogeneic rats. ATP in the muscle and serum creatine phosphokinase were measured after 24 h of reperfusion. The vascular endothelial function of the femoral artery rings was measured before and after 24 h of reperfusion in the presence or absence of indomethacin (cyclooxygenase inhibitor) and L-NMMA (nitric oxide synthase inhibitor). TEA (calcium-activated potassium channel inhibitor) was also used to verify the vasodilator function. Reperfusion blood flow was monitored during the first 2 h of reperfusion.

RESULTS

ATP in the UW perfusion group was significantly decreased after 24 h of reperfusion, while that in the no-perfusion group recovered. Reperfusion blood flow in the UW solution perfusion group was significantly lower than that in the no-perfusion group. Acetylcholine-induced relaxation in the UW perfusion group was significantly reduced before and after 24 h of reperfusion compared to that in the no-perfusion group and was mostly diminished by indomethacin and L-NMMA administration.

CONCLUSIONS

Skeletal muscle injury is augmented by UW solution perfusion, probably due to deterioration of the vascular endothelial function resulting in blood supply diminution.

Effect of nitric oxide on the contractile function of rat reperfused skeletal muscle

BACKGROUND

The involvement of nitric oxide (NO) in ischemia-reperfusion injury remains controversial and has been reported to be both beneficial and deleterious. The purpose of this study was to examine the contribution of NO and superoxide to skeletal muscle function using an ischemic revascularized hind limb model in rats.

PATIENTS AND MATERIALS

Warm ischemia produced by vascular pedicle clamping was sustained for 3 h. The animals were divided into four groups according to the solution administrated: (1) saline, (2) N-methyl-L-arginine acetate (L-NMMA), (3) L-NMMA + N-(N-L-g-glutamyl-S-nitroso-l-cysteinyl)glycine (S-nitrosoglutathione), or (4) superoxide dismutase (SOD). Saline, L-NMMA, or L-NMMA + S-nitrosoglutathione was infused for the first 2 h of reperfusion. The SOD was administered as an intravenous bolus 5 min before the onset of reperfusion. Postischemic blood flow was measured by a Doppler flow meter. Muscle contractile function was determined after 24 h of reperfusion.

RESULTS

Postischemic blood flow was significantly decreased by the L-NMMA infusion compared with that in the saline-treated group. No significant difference in postischemic blood flow was noted in the saline-, L-NMMA + S-nitrosoglutathione-, and SOD-treated groups. Contractile function of the gastrocnemius muscle in the L-NMMA-and SOD-treated groups, but not in the L-NMMA + S-nitrosoglutathione group, was significantly better than that in the saline-treated group.

CONCLUSION

Limiting postischemic blood flow and SOD infusion are both beneficial in decreasing the ischemia-reperfusion injury of skeletal muscle. S-Nitrosoglutathione infusion following suppression of endogenous NO production does not reduce ischemia-reperfusion injury.