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Most studies of chronic nerve compression focus on large nerve function in painful conditions, and only few studies have assessed potential changes in the function of small nerve fibers during chronic nerve compression and recovery from compression. Cutaneous pressure-induced vasodilation is a neurovascular phenomenon that relies on small neuropeptidergic fibers controlling the cutaneous microvasculature. We aimed to characterize potential changes in function of these small fibers and/or in cutaneous microvascular function following short-term (1-month) and long-term (6-month) nerve compression and after release of compression (ie, potential recovery of function). A compressive tube was left on one sciatic nerve for 1 or 6 months and then removed for 1-month recovery in Wistar rats. Cutaneous vasodilator responses were measured by laser Doppler flowmetry in hind limb skin innervated by the injured nerve to assess neurovascular function. Nociceptive thermal and low mechanical thresholds were evaluated to assess small and large nerve fiber functions, respectively. Pressure-induced vasodilation was impaired following nerve compression and restored following nerve release; both impairment and restoration were strongly related to duration of compression. Small and large nerve fiber functions were less closely related to duration of compression. Our data therefore suggest that cutaneous pressure-induced vasodilation provides a non-invasive and mechanistic test of neurovascular function that gives direct information regarding extent and severity of damage during chronic nerve compression and recovery, and may ultimately provide a clinically useful tool in the evaluation of nerve injury such as carpal tunnel syndrome., (Copyright © 2011 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.)

Background: Little is known about the prevalence of proximal (hip, buttock, lower back) claudication after aortobifemoral bypass (AF2B) grafting and its hemodynamic effects at the buttock level., Methods: Forty-eight patients performed a treadmill test before and within 6 months after AF2B. The San Diego Claudication Questionnaire and the chest-corrected decrease from rest of transcutaneous oxygen pressure on buttocks were used to study exercise-induced proximal claudication and regional pelvic blood flow impairment. A decrease from rest of transcutaneous oxygen pressure value <-15 mm Hg was used to indicate regional blood flow impairment (RBFI)., Results: Patients had the following characteristics: 39 were men and 9 were women, 60 +/- 9 years, lowest ankle-to-brachial index (ABI) of 0.55 +/- 0.18 and maximal walking distance (MWD) on treadmill of 188 +/- 192 m at inclusion. ABI and MWD were significantly improved after surgery at 0.83 +/- 0.19 and 518 +/- 359 m (P < 0.0001). Unilateral or bilateral RBFI at the buttocks was found in 39 versus 29 patients before and after AF2B, respectively. Proximal claudication with underlying RBFI on one or both sides on treadmill were observed in 29 patients before AF2B, and in 9 of 26 (41%) versus 6 of 22 (23%) patients in end-to-end versus end-to-side proximal aorto-graft anastomosis of the AF2B, respectively (P < 0.05)., Conclusion: A significant increase in MWD and ABI, but little improvement of proximal perfusion is observed after surgery, a finding that is expected from the absence of hypogastric artery revascularization. The prevalence of proximal claudication and proximal blood flow impairment is higher in case of end-to-end when compared with end-to-side proximal aorto-graft anastomosis, confirming the role of collaterals such as lumbar arteries in the buttock circulation during exercise in patients suffering from peripheral arterial disease. Proximal claudication on treadmill early after surgery affects almost one third of the patients and must not be underestimated among patients receiving AF2B. Attempts at hypogastric artery revascularization, if possible, might be preferable to decrease the risk of proximal claudication after AF2B.

Background: We sought to identify whether transcutaneous oxygen tension (tcPo2) measurements could be used to noninvasively detect lesions in the arterial network supplying blood flow to the hypogastric circulation., Methods and Results: A study was undertaken in vascular patients with suspected (PC, n=43) and not with suspected (NPC, n=34) proximal ischemia. TcPo2 was measured on both buttocks and with a chest reference electrode. Arteriography on the right or left side was positive for stenoses (> or =75%) or occlusion of one or more of the following arteries: the aorta, the common iliac arteries, or the internal iliac arteries. The arteriography was compared with the resting tcPo2 values (REST) and with the minimal value (MIN) and maximal change from rest normalized to eventual chest changes (DROP) recorded during or after a treadmill test. REST, MIN, and DROP were, respectively, as follows in positive versus negative arteriograms (mean+/-SD; in mm Hg): 80.2+/-10.9 versus 78.6+/-11.5 (P>0.05), 55.2+/-20.0 versus 69.9+/-15.8 (P<0.001), and -31.8+/-17.6 versus -9.5+/-6.4 (P<0.0001) in PC and 78.9+/-14.0 versus 80.5+/-14.3 (P>0.05), 64.4+/-21.0 versus 75.1+/-14.6 (P<0.02), and -24.1+/-13.5 versus -8.7+/-4.8 (P<0.0001) in NPC. In PC and NPC respectively, with a cutoff point of -16 and -15 mm Hg, DROP showed, respectively, 83%/82% and 79%/86% sensitivity/specificity in the diagnosis of positive arteriograms., Conclusions: Proximal ischemia is a frequent finding in vascular patients. TcPo2 measurement on the buttocks during exercise is a sensitive and specific indicator for lesions in the arterial tree toward the hypogastric circulation. Potentially it could objectively assess the response to endovascular or surgical approaches to iliac lesions.

Objective: Vasopressin has been used to treat arterial hypotension associated with hyperdynamic vasoplegic states, but detrimental effects on splanchnic circulation have been reported. We tested the effects of a low-dose vasopressin analogue, terlipressin (6 microg/kg), on systemic and splanchnic hemodynamics in fluid-challenged endotoxic rats (lipopolysaccharide, 30 mg/kg in 1 hr)., Design: Prospective, randomized, controlled experimental study with repeated measures., Setting: Investigational animal laboratory., Subjects: A total of 77 rats were divided into five groups: group C, control (17 rats); group E, LPS (18 rats); group EF, LPS plus fluid challenge (18 rats); group EFT, LPS plus fluid challenge plus terlipressin (18 rats); and group ET, LPS plus terlipressin (seven rats)., Interventions: Rats were anesthetized, mechanically ventilated, and instrumented to measure heart rate, mean arterial pressure, and abdominal aortic and mesenteric vein indexed blood flows; ileal microcirculation was assessed by laser Doppler. After LPS infusion, rats experienced an endotoxic shock and were resuscitated after the allocation group. The fluid challenge was targeted to maintain mean arterial pressure of >90 mm Hg and aortic blood flow at baseline values., Measurements and Main Results: Terlipressin significantly (p <.05) increased mean arterial pressure without decreasing indexed aortic blood flow and heart rate in the fluid-challenged endotoxic rats (EFT) compared with EF rats and had detrimental effects in hypodynamic endotoxic rats (ET). Fluid challenge significantly (p <.05) increased mesenteric vein blood flow in both the EF and EFT groups, and terlipressin had no detrimental effect on mesenteric blood flow. Terlipressin significantly (p <.05) increased ileal microcirculation in fluid-challenged endotoxic rats (EF and EFT) but not in hypodynamic endotoxic rats (E and ET)., Conclusion: Low-dose terlipressin in fluid-challenged endotoxic rats improved systemic and splanchnic hemodynamics and improved the ileal microcirculation.

Unlabelled: We used controlled hypotension to obtain a bloodless cavity during middle ear surgery under an optical microscope. No previous study has assessed the effect of controlled hypotension on inner ear blood flow (IEF) autoregulation in humans receiving propofol or isoflurane anesthesia. In the present study, the IEF autoregulation was determined using laser Doppler flowmetry in combination with transient evoked otoacoustic emissions (TEOAEs) during controlled hypotension with sodium nitroprusside in 20 patients randomly anesthetized with propofol or isoflurane. A coefficient of IEF autoregulation (Ga) was determined during controlled hypotension, with a Ga value ranging between 0 (no autoregulation) and 1 (perfect autoregulation). During controlled hypotension with propofol, IEF remained stable (1%+/-6%; P > 0.05) but decreased by 25%+/-8% with isoflurane (P < 0.05). The Ga was higher during propofol anesthesia (0.62+/-0.03) than during isoflurane anesthesia (0.22+/-0.03; P < 0.0001). Under propofol anesthesia, there were individual relationships between TEOAE amplitude and change in IEF in four patients. Such a correlation was not observed under isoflurane anesthesia. These results suggest that human IEF is autoregulated in response to decreased systemic pressure. Furthermore, isoflurane has a greater propensity to decrease cochlear autoregulation and function than propofol., Implications: The present study shows that inner ear blood flow is autoregulated under propofol, but not isoflurane, anesthesia during controlled hypotension in humans during middle ear surgery. Further studies are needed to explore the postoperative auditory functional consequences of the choice of the anesthetic drug used in middle ear surgery.