Gastric Ultrasound for the Regional Anesthesiologist and Pain Specialist

This article in our series on point-of-care ultrasound (US) for the regional anesthesiologist and pain management specialist describes the emerging role of gastric ultrasonography. Although gastric US is a relatively new point-of-care US application in the perioperative setting, its relevance for the regional anesthesiologist and pain specialist is significant as our clinical practice often involves providing deep sedation without a secured airway. Given that pulmonary aspiration is a well-known cause of perioperative morbidity and mortality, the ability to evaluate for NPO (nil per os) status and risk stratify patients scheduled for anesthesia is a powerful skill set. Gastric US can provide valuable insight into the nature and volume of gastric content before performing a block with sedation or inducing anesthesia for an urgent or emergent procedure where NPO status is unknown. Patients with comorbidities that delay gastric emptying, such as diabetic gastroparesis, neuromuscular disorders, morbid obesity, and advanced hepatic or renal disease, may potentially benefit from additional assessment via gastric US before an elective procedure. Although gastric US should not replace strict adherence to current fasting guidelines or be used routinely in situations when clinical risk is clearly high or low, it can be a useful tool to guide clinical decision making when there is uncertainty about gastric contents. In this review, we will cover the relevant scanning technique and the desired views for gastric US. We provide a methodology for interpretation of findings and for guiding medical management for adult patients. We also summarize the current literature on specific patient populations including obstetrics, pediatrics, and severely obese subjects. Accepted for publication April 14, 2018. Address correspondence to: Stephen C. Haskins, MD, Department of Anesthesiology, Hospital for Special Surgery, 535 E 70th St, New York, NY 10021 (e-mail: haskinss@hss.edu). The authors declare no conflict of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.rapm.org). Copyright © 2018 by American Society of Regional Anesthesia and Pain Medicine.

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Anatomical basis for simultaneous block of greater and third occipital nerves, with an ultrasound-guided technique

Abstract

Purpose

In some headache disorders, for which the greater occipital nerve block is partly effective, the third occipital nerve is also suggested to be involved. We aimed to establish a simple technique for simultaneously blocking the greater and third occipital nerves.

Methods

We performed a detailed examination of dorsal neck anatomy in 33 formalin-fixed cadavers, and deduced two candidate target points for blocking both the greater and third occipital nerves. These target points were tested on three Thiel-fixed cadavers. We performed ultrasound-guided dye injections into these points, examined the results by dissection, and selected the most suitable injection point. Finally, this target point was tested in three healthy volunteers. We injected 4 ml of local anesthetic and 1 ml of radiopaque material at the selected point, guided with a standard ultrasound system. Then, the pattern of local anesthetic distribution was imaged with computed tomography.

Results

We deduced that the most suitable injection point was the medial head of the semispinalis capitis muscle at the C1 level of the cervical vertebra. Both nerves entered this muscle, in close proximity, with little individual variation. In healthy volunteers, an anesthetic injected was confined to the muscle and induced anesthesia in the skin areas innervated by both nerves.

Conclusions

The medial head of the semispinalis capitis muscle is a suitable landmark for blocking the greater and third occipital nerves simultaneously, by which occipital nerve involvement in various headache disorders may be rapidly examined and treated.

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The history and progress of local anesthesia: multiple approaches to elongate the action

Abstract

Analgesia and temporary inhibition of motor activity without interfering with central nervous function have been the essential merits of local anesthesia. Local anesthetics originated from cocaine have played a major role in local analgesia. However, the relatively short duration of action of local anesthetics has been a concern in intra- and post-operative analgesia. From the early age of modern local anesthesia, physicians and medical scientists had been struggling to control the active duration of local anesthetics. Such approach includes: development of long-acting local anesthetics, with physical tourniquet techniques, co-administration of other medicines such as vaso-constrictive agents or analgesics, development of mechanical devices to continuously or intermittently administer local anesthetics, and utilization of pharmaceutical drug delivery systems. In this review, the historical sequence of studies that have been performed in an effort to elongate the action of local anesthetics is presented, referring to epoch-making medical and scientific studies.

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Accuracy of identifying the cricothyroid membrane in children using palpation

Abstract

Accurate identification of the cricothyroid membrane (CTM) has paramount importance in the event of a 'cannot intubate, cannot oxygenate' scenario. We sought to determine the ability of anesthesiologists to correctly identify the CTM in obese and non-obese children. Anesthesiologists were asked to mark the entry point of the cricothyroidotomy device with an ultraviolet invisible pen on obese and non-obese (BMI < 95th percentile for age and sex) children aged 7–12 years. A correct estimation was defined as a mark made between the upper and lower borders of the CTM and within the 3-mm midline. Twenty anesthesiologists palpated 30 obese and 50 non-obese children. The CTM was accurately identified with digital palpation in a total 55% of children, and there were no differences inaccurate identification rates of the CTM between obese and non-obese children [57 vs. 54%, respectively; median difference 3%; 95% confidence interval (− 20 to 25%); p = 0.82]. Accuracy was not correlated with any demographic or morphometric features of the children. Percutaneous identification of the CTM in children aged 7–12 years was poor and not significantly different for obese and non-obese children. Pre-procedural ultrasonography may help to identify the landmarks for cricothyroidotomy.

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Opioids, gliosis and central immunomodulation

Abstract

Neuropathic pain is a common health problem that affects millions of people worldwide. Despite being studied extensively, the cellular and molecular events underlying the central immunomodulation and the pathophysiology of neuropathic pain is still controversial. The idea that 'glial cells are merely housekeepers' is incorrect and with respect to initiation and maintenance of neuropathic pain, microglia and astrocytes have important roles to play. Glial cells differentially express opioid receptors and are thought to be functionally modulated by the activation of these receptors. In this review, we discuss evidence for glia-opioid modulation of pain by focusing on the pattern of astrocyte and microglial activation throughout the progress of nerve injury/neuropathic pain. Activation of astrocytes and microglia is a key step in central immunomodulation in terms of releasing pro-inflammatory markers and propagation of a 'central immune response'. Inhibition of astrocytes before and after induction of neuropathic pain has been found to prevent and reverse neuropathic pain, respectively. Moreover, microglial inhibitors have been found to prevent (but not to reverse) neuropathic pain. As they are expressed by glia, opioid receptors are expected to have a role to play in neuropathic pain.

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Editorial Board w/barcode

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Table of Contents

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