Sex specific factors regulating pressure and flow

Abstract

Over the last decade, there have been many published reports on sex differences in blood pressure regulation between young men and young women. The autonomic nervous system is a primary contributor to both acute and long-term blood pressure regulation. Sex differences in blood pressure regulation likely have effects that extend beyond mean arterial pressure, and which can affect blood flow and tissue function. This short review will include recent literature from our laboratory focusing on autonomic control of the circulation, specifically age and sex hormone related differences in central hemodynamics and cerebral blood flow, and discuss potential clinical implications.

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Beyond Ultrasound Guidance for Regional Anesthesiology.

Despite its popularity, ultrasound (US)-guided regional anesthesiology is associated with significant limitations. The latter can be attributed to either the US machine (ie, decreased ability to insonate deep neural structures, as well as the thoracic spine) or the operator. Shortcomings associated with the operator can be explained by errors in perception (ie, ambiguous criteria for needle/catheter tip-to-nerve proximity and subparaneural local anesthetic injection) or interpretation. Perhaps the greatest confusion afflicting US-guided regional anesthesiology originates from an intellectual misconception pertaining to its application. Increasingly, authors are using US to identify interfascial planes where local anesthetic can be injected thereby "discovering" new truncal blocks. Often these novel blocks suffer from a lack of proper randomized, comparative validation. Fortunately, solutions have been proposed to remedy many shortcomings associated with US guidance. The inability of US to reliably insonate deep neural structures can be circumvented with adjunctive neurostimulation. Fluoroscopy and waveform analysis have been proven to increase the success rate of thoracic epidural blocks. For continuous nerve blocks, combined US-neurostimulation may provide an objective end point (ie, an evoked motor response) for neural proximity and subparaneural positioning of the catheter tip. Finally, the solution to the plethora of nonvalidated US-guided blocks is both elegant and simple. New nerve blocks should answer a specific clinical need, and their first descriptions should take the form of an adequately powered, observer-blinded, randomized comparison against the established standard of care or, at the very least, a large case series (eg, a Brief Technical Report). Copyright (C) 2017 by American Society of Regional Anesthesia and Pain Medicine.

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Optimal Point of Insertion and Needle Angle in Neuraxial Blockade Using a Midline Approach: A Study in Computed Tomography Scans of Adult Patients.

Background and Objectives: Neuraxial blockade using a midline approach can be challenging. Part of this challenge lies in finding the optimal approach of the needle to its target. The present study aimed at finding (1) the optimal point of insertion of the needle between the tips of 2 adjacent spinous processes and (2) the optimal angle relative to the skin at which the needle should approach the epidural or subarachnoid space. Methods: A computer algorithm systematically analyzed computed tomography scans of vertebral columns of a cohort of 52 patients. On midsagittal sections, the possible points of insertion of a virtual needle and the corresponding angles through which the epidural or subarachnoid space can be reached were calculated. Results: The point chosen to introduce the needle between 2 adjacent spinous processes determines the range of angles through which the epidural or subarachnoid space can be reached. At the thoracic interspaces 1-2 through 3-4, thoracic interspaces 5-6 through 9-10, and at the lumbar vertebral interspaces 2-3 through 4-5, the optimal point of insertion is slightly inferior to the point halfway between the tips of the spinous processes. For thoracic interspace 4-5, the optimal point of insertion is slightly superior to the point halfway between the tips of the spinous processes. For the other interspaces, the optimal point of insertion is approximately halfway between the tips of the spinous processes. The optimal angle to direct the needle varies from 9 degrees at the thoracolumbar junction and at the lumbar interspaces 3-4 and 4-5, to 53 degrees at the thoracic interspace 7-8. Conclusions: Our study has resulted in practical suggestions-based on accurate, reproducible measurements in patients-as to where to insert the needle and how to angulate the needle when performing neuraxial anesthesia using a midline approach. Copyright (C) 2017 by American Society of Regional Anesthesia and Pain Medicine.

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Neuromuscular Monitoring in the Perioperative Period.

Neuromuscular monitoring devices were introduced into clinical practice in the 1970s. Qualitative neuromuscular monitors, or peripheral nerve stimulators, provide an electrical stimulus to a motor nerve and the response of corresponding muscle subjectively evaluated. A standard peripheral nerve stimulator provides several patterns of nerve stimulation, including train-of-four (TOF), double-burst, tetanic, and post-tetanic count. Qualitative (and quantitative) monitors are needed to determine onset of neuromuscular blockade, maintain the required depth of muscle relaxation during the surgical procedure, and assess an appropriate dose of reversal agent. However, absence of fade measured with a peripheral nerve stimulator does not exclude residual neuromuscular block; TOF ratios as low as 0.4-0.6 may be present when fade is no longer observed. In addition, the risk of incomplete neuromuscular recovery may be influenced by monitoring site. The adductor pollicis is more sensitive to the effects of neuromuscular blocking agents (compared to the muscles surrounding the eye), and monitoring at this site may more accurately reflect recovery of pharyngeal muscles (the last muscles to recover from the effects of neuromuscular blocking agents, in which dysfunction may persist even at a TOF ratio of 1.0). Quantitative monitors are devices that measure and quantify the degree of muscle weakness and display the results numerically. Several different technologies have been developed, including mechanomyography, electromyography, acceleromyography, kineograph, and phonomyography. Lower doses of anticholinesterases may be used to effectively reverse neuromuscular blockade at TOF ratios of 0.4-0.6; quantitative monitoring is required to determine that this level of neuromuscular recovery has occurred. As clinical tests of muscle strength, peripheral nerve stimulators are unable to determine whether full recovery of neuromuscular function is present at the end of the surgical procedure. The use of quantitative monitors is essential in excluding clinically important muscle weakness (TOF ratios

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Prolongation of Apnea Time in Obese Patients-Concerns With Rate of Rise of CO2.

No abstract available

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The Coagulation Profile of End-Stage Liver Disease and Considerations for Intraoperative Management.

The coagulopathy of end-stage liver disease results from a complex derangement in both anticoagulant and procoagulant processes. With even minor insults, cirrhotic patients experience either inappropriate bleeding or clotting, or even both simultaneously. The various phases of liver transplantation along with fluid and blood product administration may contribute to additional disturbances in coagulation. Thus, anesthetic management of patients undergoing liver transplantation to improve hemostasis and avoid inappropriate thrombosis in the perioperative environment can be challenging. To add to this challenge, traditional laboratory tests of coagulation are difficult to interpret in patients with end-stage liver disease. Viscoelastic coagulation tests such as thromboelastography (Haemonetics Corporation, Braintree, MA) and rotational thromboelastometry (TEM International, Munich, Germany) have helped to reduce transfusion of allogeneic blood products, especially fresh frozen plasma, but have also lead to the increased use of fibrinogen-containing products. In general, advancements in surgical techniques and anesthetic management have led to significant reduction in blood transfusion requirements during liver transplantation. Targeted transfusion protocols and pharmacologic prevention of fibrinolysis may further aid in the management of the complex coagulopathy of end-stage liver disease. (C) 2017 International Anesthesia Research Society

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The Perioperative Surgical Home: A New Role for the Acute Pain Service.

No abstract available

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