Paracanthal "One-Snip" Decompression in a Cadaver Model of Retrobulbar Hemorrhage.

PURPOSE: The authors assess the effectiveness of a modified paracanthal or "one-snip" procedure compared with the traditional lateral canthotomy and inferior cantholysis in the reduction of intraocular pressure (IOP) and proptosis in a human cadaveric model of retrobulbar hemorrhage. METHODS: This study comprised a comparative interventional study in a cadaveric model of retrobulbar hemorrhage. Six orbits of 3 fresh cadavers were included in the study. Baseline measurements of IOP and proptosis were recorded for all 6 orbits before and after simulation of retrobulbar hemorrhage as previously described. Right orbits (n = 3) underwent traditional lateral canthotomy and inferior cantholysis. Left orbits (n = 3) underwent modified paracanthal or "one-snip" procedure. The primary outcome measures were reduction in IOP and proptosis between the 2 techniques. RESULTS: Following lateral canthotomy and inferior cantholysis of each right orbit, the average IOP dropped to 14 mm Hg (range of 11-18 mm Hg), corresponding to a mean decrease of 32 mm Hg. Following the "one-snip" procedure of each left orbit, the average IOP dropped to 19 mm Hg with a range of 16 to 23 mm Hg, corresponding to a mean decrease of 22 mm Hg. There was no statistically significant difference in IOP reduction (p = 0.36) or proptosis reduction (p = 0.23) between the 2 treatment groups. CONCLUSIONS: Compared with traditional lateral canthotomy xand inferior cantholysis, the modified paracanthal or "one-snip" procedure is effective for IOP reduction and led to mild improvement of proptosis in a cadaveric model of retrobulbar hemorrhage. The authors hope this study helps improve orbital compartment syndrome outcomes by providing an option that more providers will feel comfortable performing and therefore decreasing time to surgical decompression.

Deoxycholic Acid and the Marginal Mandibular Nerve: A Cadaver Study.

BACKGROUND: One of the rare but serious complications observed with deoxycholic acid administration is damage to the marginal mandibular nerve. In this study, we evaluated if deoxycholic acid directly induces histologic damage to fresh cadaveric marginal mandibular nerve. METHODS: A segment of marginal mandibular nerve was harvested from 12 hemifaces of 6 fresh cadavers. The nerve specimen was exposed to either 0.9% sterile saline for 24 h, deoxycholic acid (10 mg/ml) for 20 min, or deoxycholic acid (10 mg/ml) for 24 h. The nerve specimens were then fixed in glutaraldehyde for a minimum of 24 h. Toluidine blue stained sections were evaluated for stain intensity using light microscopy and color deconvolution image analysis. Supraplatysmal fat was harvested as a positive control and exposed to the same treatments as the marginal mandibular nerve specimens, then evaluated using transmission electron microscopy. RESULTS: Toluidine blue staining was less in the marginal mandibular nerve exposed to deoxycholic acid when compared to saline. The specimen exposed to deoxycholic acid for 24 h showed less toluidine blue staining than that of the nerve exposed to deoxycholic acid for 20 min. Transmission electron microscopy of submental fat exposed to deoxycholic acid revealed disruption of adipocyte cell membrane integrity and loss of cellular organelles when compared to specimens only exposed to saline. CONCLUSIONS: Deoxycholic acid (10 mg/ml) damages the marginal mandibular nerve myelin sheath in fresh human cadaver specimens. Direct deoxycholic acid neurotoxicity may cause marginal mandibular nerve injury clinically. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Neutrophils Fuel Effective Immune Responses through Gluconeogenesis and Glycogenesis.

Neutrophils can function and survive in injured and infected tissues, where oxygen and metabolic substrates are limited. Using radioactive flux assays and LC-MS tracing with U-13C glucose, glutamine, and pyruvate, we observe that neutrophils require the generation of intracellular glycogen stores by gluconeogenesis and glycogenesis for effective survival and bacterial killing. These metabolic adaptations are dynamic, with net increases in glycogen stores observed following LPS challenge or altitude-induced hypoxia. Neutrophils from patients with chronic obstructive pulmonary disease have reduced glycogen cycling, resulting in impaired function. Metabolic specialization of neutrophils may therefore underpin disease pathology and allow selective therapeutic targeting.

Hypoxia Modulates Platelet Purinergic Signalling Pathways.

BACKGROUND: Hypoxia resulting from ascent to high-altitude or pathological states at sea level is known to increase platelet reactivity. Previous work from our group has suggested that this may be adenosine diphosphate (ADP)-specific. Given the clinical importance of drugs targeting ADP pathways, research into the impact of hypoxia on platelet ADP pathways is highly important. METHODS: Optimul aggregometry was performed on plasma from 29 lowland residents ascending to 4,700 m, allowing systematic assessment of platelet reactivity in response to several platelet agonists. Aggregometry was also performed in response to ADP in the presence of inhibitors of the two main ADP receptors, P2Y1 and P2Y12 (MRS2500 and cangrelor, respectively). Phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a key determinant of platelet aggregation, was analysed using the VASPFix assay. RESULTS: Hypobaric hypoxia significantly reduced the ability of a fixed concentration of cangrelor to inhibit ADP-induced aggregation and increased basal VASP phosphorylation. However, in the absence of P2Y receptor inhibitors, we did not find evidence of increased platelet sensitivity to any of the agonists tested and found reduced sensitivity to thrombin receptor-activating peptide-6 amide. CONCLUSION: Our results provide evidence of increased P2Y1 receptor activity at high altitude and suggest down-regulation of the P2Y12 pathway through increased VASP phosphorylation. These changes in ADP pathway activity are of potential therapeutic significance to high-altitude sojourners and hypoxic sea level patients prescribed platelet inhibitors and warrant further investigation.

Thin Air, Thick Vessels: Historical and Current Perspectives on Hypoxic Pulmonary Hypertension.

The association between pulmonary hypertension (PH) and hypoxia is well-established, with two key mechanistic processes, hypoxic pulmonary vasoconstriction and hypoxia-induced vascular remodeling, driving changes in pulmonary arterial pressure. In contrast to other forms of pulmonary hypertension, the vascular changes induced by hypoxia are reversible, both in humans returning to sea-level from high altitude and in animal models. This raises the intriguing possibility that the molecular drivers of these hypoxic processes could be targeted to modify pulmonary vascular remodeling in other contexts. In this review, we outline the history of research into PH and hypoxia, before discussing recent advances in our understanding of this relationship at the molecular level, focussing on the role of the oxygen-sensing transcription factors, hypoxia inducible factors (HIFs). Emerging links between HIF and vascular remodeling highlight the potential utility in inhibiting this pathway in pulmonary hypertension and raise possible risks of activating this pathway using HIF-stabilizing medications.

Repeatability of Split-Spectrum Amplitude-Decorrelation Angiography to Assess Capillary Perfusion Density Within Optical Coherence Tomography.

BACKGROUND AND OBJECTIVE: To evaluate the repeatability of retinal thickness and vascular density measurements using split-spectrum amplitude-decorrelation angiography (SSADA) with optical coherence tomography (OCT). PATIENTS AND METHODS: Forty patients were divided into seven categories according to their diagnosis: no retinopathy (control), retinal vein occlusion, diabetes with no retinopathy, diabetes with retinopathy, non-exudative age-related macular degeneration (AMD), exudative AMD, and epiretinal membrane. Capillary density and retinal thickness measurements were taken and evaluated for reliability by determination of statistically significant differences and coefficient of variability (CoV) between measurements. RESULTS: No significant differences (P > .05) were found in any of the within-visit measurements. CoVs ranged from 0.26% to 52.76%, depending on the measure and the disease settings. CONCLUSION: The SSADA OCT angiography analysis has a low level of variability between measurements and, thus, is a reliable tool for evaluation of retinal perfusion. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e9-e19.].