Alteration of Pressure-Induced Vasodilation in Aging and Diabetes, a Neuro-Vascular Damage

Evaluation of Shear Force Redistribution and Microclimate in Foam Dressings Indicated for Pressure Injury Prevention

OBJECTIVE

To understand the performance of a border and silicone version of a next-generation multilayered foam dressing (dressings A and B) compared with three commercially available wound dressings (dressings C, D, and E) in bench tests relevant for pressure injuries.

METHODS

Two methods were used. The first measured shear force transmission through dressings in low- and high-shear force scenarios compared with a control with no dressing. The second measured the dressings' microclimate (heat and moisture) compared with two controls: one with high moisture output and one with no moisture output. Statistical significance was determined using a 95% CI and t test with α = .05.

RESULTS

In the low-shear scenario, dressing A showed the lowest force transmission, whereas dressing B was not significantly different from dressings C and E. In the high-shear scenario, dressing D had a significantly higher percentage of transmitted forces compared with the other dressings, with dressing A showing the lowest force transmission but no significant differences among the other three dressings. Regarding microclimate, dressing A showed no significant difference in relative humidity in the dressing-indenter and dressing-surface interfaces, suggesting good breathability. Dressing E had the highest temperature at the indenter-dressing interface, significantly different from the other dressings ( P < .05).

CONCLUSIONS

The study found that a next-generation foam dressing (dressing A) had better breathability and lower shear force transmission than other available dressings. This study emphasized the importance of understanding the physical properties of dressings to choose the most appropriate product based on individual patient needs, wound characteristics, and environmental conditions.

Improving Microcirculation With Nerve Decompression: The Missing Link in Treatment of Diabetic Neuropathy and Diabetic Foot Ulcer

Sympathetic dysfunction in skin is well known in diabetic peripheral neuropathy. This produces dry, cracked, peeling skin susceptible to infection and also epidermal microcirculation insufficiency. Impaired autonomic neurovascular control opens dermal arterio-venous anastomoses and shunts microcirculation away from the epidermis and impairs skin oxygenation and nutrition. Few recognise that diabetic neuropathy includes swelling-induced entrapment neuropathy. Multiple peripheral nerves, swollen by the secondary polyol metabolic pathway, suffer local compressions at fibro-osseous tunnels. This includes the C-fibres controlling autonomic functions which constitute most of the nerve axons. No current standard of care therapy addresses the sympathetic-regulated neurovascular impairment of skin microcirculation in diabetes. Epineurolysis surgery for peripheral nerve decompression relieves local axonal compressions and generates recovery of sub-epidermal capillary flow. Clinical and animal diabetes studies have demonstrated objective improvements to epidermal hypoxia, demyelination and axonal histology. Seven surgery studies find an average 1.39% recurrence and zero amputations after prior Risk Class 3 wound healing in a mean of 1.78 years of follow-up. Deficits of electrophysiology, transcutaneous oxygenation and vasa nervorum circulation also improve. Surgically improved microcirculation is physiology-based. Nerve decompression minimises diabetic peripheral neuropathy, avoids initial diabetic foot ulcers, promotes neuropathic diabetic foot ulcer healing and minimises ulcer recurrences and subsequent amputation. The observational studies of these important benefits suggest wide application to the complications of diabetes neuropathy and beg for academic attention to Level 1 EBM confirmation.

Corneal confocal microscopy detects early nerve regeneration after pharmacological and surgical interventions: Systematic review and meta-analysis

Corneal confocal microscopy (CCM) is an ophthalmic imaging technique that enables the identification of corneal nerve fibre degeneration and regeneration. To undertake a systematic review and meta-analysis of studies utilizing CCM to assess for corneal nerve regeneration after pharmacological and surgical interventions in patients with peripheral neuropathy. Databases (EMBASE [Ovid], PubMed, CENTRAL and Web of Science) were searched to summarize the evidence from randomized and non-randomized studies using CCM to detect corneal nerve regeneration after pharmacological and surgical interventions. Data synthesis was undertaken using RevMan web. Eighteen studies including 958 patients were included. CCM identified an early (1-8 months) and longer term (1-5 years) increase in corneal nerve measures in patients with peripheral neuropathy after pharmacological and surgical interventions. This meta-analysis confirms the utility of CCM to identify nerve regeneration following pharmacological and surgical interventions. It could be utilized to show a benefit in clinical trials of disease modifying therapies for peripheral neuropathy.

Where Art Thou O treatment for diabetic neuropathy: the sequel

INTRODUCTION

Having lived through a pandemic and witnessed how regulatory approval processes can evolve rapidly; it is lamentable how we continue to rely on symptoms/signs and nerve conduction as primary endpoints for clinical trials in DPN.

AREAS COVERED

Small (Aδ and C) fibers are key to the genesis of pain, regulate skin blood flow, and play an integral role in the development of diabetic foot ulceration but continue to be ignored. This article challenges the rationale for the FDA insisting on symptoms/signs and nerve conduction as primary endpoints for clinical trials in DPN.

EXPERT OPINION

Quantitative sensory testing, intraepidermal nerve fiber density, and especially corneal confocal microscopy remain an after-thought, demoted at best to exploratory secondary endpoints in clinical trials of diabetic neuropathy. If pharma are to be given a fighting chance to secure approval for a new therapy for diabetic neuropathy, the FDA needs to reassess the evidence rather than rely on 'opinion' for the most suitable endpoint(s) in clinical trials of diabetic neuropathy.

Pharmacological applications of nitric oxide-releasing biomaterials in human skin

Nitric oxide (NO) is an important endogenous molecule that plays several roles in biological systems. NO is synthesized in human skin by three isoforms of nitric oxide synthase (NOS) and, depending on the produced NO concentration, it can actuate in wound healing, dermal vasodilation, or skin defense against different pathogens, for example. Besides being endogenously produced, NO-based pharmacological formulations have been developed for dermatological applications targeting diverse pathologies such as bacterial infection, wound healing, leishmaniasis, and even esthetic issues such as acne and skin aging. Recent strategies focus mainly on developing smart NO-releasing nanomaterials/biomaterials, as they enable a sustained and targeted NO release, promoting an improved therapeutic effect. This review aims to overview and discuss the main mechanisms of NO in human skin, the recent progress in the field of dermatological formulations containing NO, and their application in several skin diseases, highlighting promising advances and future perspectives in the field.

Alpha-Lipoic Acid Supplementation Restores Early Age-Related Sensory and Endothelial Dysfunction in the Skin

Many changes characterize skin aging, and the resulting dysfunctions still constitute a real challenge for our society. The aim of this study was to compare the skin aging of two rat strains, Wistar and Brown Norway (BN), considered as "poorly aging" and "healthy aging" models, respectively, and to assess the effect of alpha-lipoic acid (LPA), especially on skin microcirculation. To this purpose, various skin characteristics were studied at 6, 12, and 24 months and compared to the results of LPA treatment performed at 12 or 24 months. Skin aging occurred in both strains, but we showed an early occurrence of different age-related disorders in the Wistar strain compared to BN strain, especially regarding weight gain, glycemia dysregulation, basal skin perfusion, endothelial function, and skin resistance to low pressure. LPA treatment tended to improve skin resistance to low pressure in BN but not in Wistar despite the improvement of basal skin perfusion, endothelial function, and skin sensory sensitivity. Overall, this study confirmed the healthier aging of BN compared to Wistar strain and the positive effect of LPA on both general state and skin microcirculation.

Newborn and elderly skin: two fragile skins at higher risk of pressure injury

Skin is a key organ maintaining internal homeostasis by performing many functions such as water loss prevention, body temperature regulation and protection from noxious substance absorption, microorganism intrusion and physical trauma. Skin ageing has been well studied and it is well known that physiological changes in the elderly result in higher skin fragility favouring the onset of skin diseases. For example, prolonged and/or high-intensity pressure may suppress local blood flow more easily, disturbing cell metabolism and inducing pressure injury (PI) formation. Pressure injuries (PIs) represent a significant problem worldwide and their prevalence remains too high. A higher PI prevalence is correlated with an elderly population. Newborn skin evolution has been less studied, but some data also report a higher PI prevalence in this population compared to older children, and several authors also consider this skin as physiologically fragile. In this review, we compare the characteristics of newborn and elderly skin in order to determine common features that may explain their fragility, especially regarding PI risk. We show that, despite differences in appearance, they share many common features leading to higher fragility to shear and pressure forces, not only at the structural level but also at the cellular and molecular level and in terms of physiology. Both newborn and elderly skin have: (i) a thinner epidermis; (ii) a thinner dermis containing a less-resistant collagen network, a higher collagen III:collagen I ratio and less elastin; (iii) a flatter dermal-epidermal junction (DEJ) with lower anchoring systems; and (iv) a thinner hypodermis, resulting in lower mechanical resistance to skin damage when pressure or shear forces are applied. At the molecular level, reduced expression of transforming growth factor β (TGFβ) and its receptor TGFβ receptor II (TβRII) is involved in the decreased production and/or increased degradation of various dermal extracellular matrix (ECM) components. Epidermal fragility also involves a higher skin pH which decreases the activity of key enzymes inducing ceramide deficiency and reduced barrier protection. This seems to be correlated with higher PI prevalence in some situations. Some data also suggest that stratum corneum (SC) dryness, which may disturb cell metabolism, also increases the risk of PI formation. Besides this structural fragility, several skin functions are also less efficient. Low applied pressures induce skin vessel vasodilation via a mechanism called pressure-induced vasodilation (PIV). Individuals lacking a normal PIV response show an early decrease in cutaneous blood flow in response to the application of very low pressures, reflecting vascular fragility of the skin that increases the risk of ulceration. Due to changes in endothelial function, skin PIV ability decreases during skin ageing, putting it at higher risk of PI formation. In newborns, some data lead us to hypothesize that the nitric oxide (NO) pathway is not fully functional at birth, which may partly explain the higher risk of PI formation in newborns. In the elderly, a lower PIV ability results from impaired functionality of skin innervation, in particular that of C-fibres which are involved in both touch and pain sensation and the PIV mechanism. In newborns, skin sensitivity differs from adults due to nerve system immaturity, but the role of this in PIV remains to be determined.

The Role of Cutaneous Microcirculatory Responses in Tissue Injury, Inflammation and Repair at the Foot in Diabetes

Diabetic foot syndrome is one of the most costly complications of diabetes. Damage to the soft tissue structure is one of the primary causes of diabetic foot ulcers and most of the current literature focuses on factors such as neuropathy and excessive load. Although the role of blood supply has been reported in the context of macro-circulation, soft tissue damage and its healing in the context of skin microcirculation have not been adequately investigated. Previous research suggested that certain microcirculatory responses protect the skin and their impairment may contribute to increased risk for occlusive and ischemic injuries to the foot. The purpose of this narrative review was to explore and establish the possible link between impairment in skin perfusion and the chain of events that leads to ulceration, considering the interaction with other more established ulceration factors. This review highlights some of the key skin microcirculatory functions in response to various stimuli. The microcirculatory responses observed in the form of altered skin blood flow are divided into three categories based on the type of stimuli including occlusion, pressure and temperature. Studies on the three categories were reviewed including: the microcirculatory response to occlusive ischemia or Post-Occlusive Reactive Hyperaemia (PORH); the microcirculatory response to locally applied pressure such as Pressure-Induced Vasodilation (PIV); and the interplay between microcirculation and skin temperature and the microcirculatory responses to thermal stimuli such as reduced/increased blood flow due to cooling/heating. This review highlights how microcirculatory responses protect the skin and the plantar soft tissues and their plausible dysfunction in people with diabetes. Whilst discussing the link between impairment in skin perfusion as a result of altered microcirculatory response, the review describes the chain of events that leads to ulceration. A thorough understanding of the microcirculatory function and its impaired reactive mechanisms is provided, which allows an understanding of the interaction between functional disturbances of microcirculation and other more established factors for foot ulceration.

The effects of different accumulated pressure-time integral stimuli on plantar blood flow in people with diabetes mellitus

Background

Exercise, especially weight-bearing exercise (e.g. walking), may affect plantar tissue viability due to prolonged repetitive high vertical and high shear pressure stimulus on the plantar tissue, and further induce development of diabetic foot ulcers (DFUs). This study aimed to investigate the effects of different accumulated pressure-time integral (APTI) stimuli induced by walking on plantar skin blood flow (SBF) responses in people with diabetes mellitus (DM).

Methods

A repeated measures design was used in this study. Two walking protocols (low APTI (73,000 kPa·s) and high APTI (73,000 × 1.5 kPa·s)) were randomly assigned to ten people with DM and twenty people without DM. The ratio of SBF measured by laser Doppler flowmetry after walking to that before (normalized SBF) was used to express the SBF responses.

Results

After low APTI, plantar SBF of people with DM showed a similar response to people without DM (P = 0.91). However, after high APTI, people with DM had a significantly lower plantar SBF compared to people without DM (P < 0.05). In people with DM, plantar SBF in the first 2 min after both APTI stimuli significantly decreased compared to plantar SBF before walking (P < 0.05).

Conclusions

People with DM had a normal SBF response after low APTI walking but had an impaired SBF response after high APTI walking, which suggests that they should avoid weight-bearing physical activity with intensity more than 73,000 kPa·s and should rest for more than 2 min after weight-bearing physical activity to allow a full vasodilatory response to reduce risk of DFUs.

The risk of surgery-related pressure ulcer in diabetics: A systematic review and meta-analysis

Background and objective

Postoperative pressure ulcers are known as the most important quality indicators of intraoperative care that create critical and costly complications during hospital care. Accordingly, this study was performed to determine the risk factor for diabetes in postoperative pressure ulcers.

Materials and methods

The present study is a systematic review of PubMed, Scopus and the Web of Science databases with using standardized keywords of the performed English language articles between Jan 2010 to Jan 2020. The articles were searched independently by two related researchers to avoid possible biases. Then, all collected articles were reviewed, and articles with inclusion criteria were evaluated using a data collection table. It should be noted that the data were analyzed using STATA software version 11.1.

Results

Overall, the results showed that 19724 patients were identified from 15 studies conducted in Asia (six), the America (four), Europe (four), and Australia (one) from 1989 to 2019. The results showed that patients with diabetes were more likely to experience surgery-related pressure ulcers than patients without diabetes (The odds ratio of 1.52; the 95% confidence interval: 1.25–1.85).

Conclusion

In general, patients with diabetes increased the risk of surgery-related pressure ulcers about 1.5 times more than others. Accordingly, the reduction of surgery-induced pressure ulcers should be more extensively considered in patients with diabetes.

What is already known about the topic?•

Diabetes as a preoperative comorbidity should be added to risk assessment instruments for perioperative pressure ulcers, which may increase the accuracy of the prediction.

•

The excess risk of pressure ulcers associated with pre-existing diabetes was significantly higher in patients undergoing surgery, specifically in patients receiving cardiac surgery.

What this paper adds.•

Diabetes increases the risk of surgery-related pressure ulcers about 1.5 times. Therefore, it is necessary to provide Planned Cares to prevent, overcome, and decrease surgery-related pressure ulcers in patients with diabetes.

•

Previous meta-analysis reported that the risk of surgery-related pressure ulcers in diabetic patients was higher than non-diabetic patients in cardiac surgeries, while evidence for this claim was not observed in this study. Considering the long duration of liver resection surgery, the risk of pressure ulcers is higher than heart surgery

•

It is advised that standard wound measuring tools will apply for measuring wounds in the next prospective studies. It is also better to evaluate pressure ulcers at a specific time after surgery toward more carefully investigate the issue.

[Functional integrity of aging skin, from cutaneous biology to anti-aging strategies]

The skin is a sentinel organ making easily visible the passing of time. Chronological and environmental aging weakens skin structure and functions. The skin barrier, the elastic and mechanical properties of the cutaneous tissue as well as its vascular reactivity are impacted by aging. The barrier dysfunction in aged skin is caused by defects in epidermal keratinocytes renewal and differentiation notably linked to abnormal expression of microRNAs regulating cell death and autophagy. An abnormal balance between synthesis and degradation of matrix proteins modifies the mechanical properties of the dermis in aged skin. Finally, a reduction of the vascular reactivity linked to endothelial dysfunctions is observed in elderly people. These biological processes can be targeted by therapeutic approaches either topical or systemic, especially using anti-oxydants or senolytics. These anti-aging strategies might contribute to restore, at least in part, the functional integrity of aged skin.

A Synoptic Overview of Neurovascular Interactions in the Foot

Diabetes is a worldwide public health concern as it is associated with various complications. One of the major complications of diabetes is diabetic foot syndrome that results in catastrophic events such as ulceration and amputation. Therefore, the main four strategies of diabetic foot care involve risk prediction, prevention, and early diagnosis and prompt intervention. The drivers of ulceration are multifactorial, and importantly, include microcirculatory changes in the diabetic skin. Cutaneous microcirculation on the foot is greatly influenced by the small fibers which mediate thermal sensation and pain perception in addition to sympathetic activities such as thermoregulation and vasodilation. The interdependence between the neurovascular elements means with the loss of small fiber functions, the corresponding microcirculatory responses may be compromised. Thus, it can be hypothesized that the impairment of the microcirculation may follow the order of the corresponding small fiber nerve dysfunction or vice versa. In this review, select neurovascular investigations that inform the cutaneous microcirculatory and small fiber nerve function in response to pain, cold, and heat and pressure stimuli are reviewed and discussed in this order of sensory loss: the loss of pain, cold, warmth, touch and deep pressure sensation. We also discuss the neurological and vascular characteristics of each of these neurovascular responses. This review highlights the influence of small fibers on cutaneous microcirculation and the need for prospective studies that can determine the course of microcirculatory impairment over time. This, in turn, may help clarify the exact role of microcirculatory changes in the pathway of ulceration. The insights from this review can be pertinent to understand key microcirculatory disturbances and given that the microcirculatory impairment develops at an early stage, relevant interventions can be implemented to possibly reverse or regress the course of the disease. Therefore, knowledge of the neurovascular interactions aids to map the disease progression for early diagnosis and prevention of adverse complications.