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Epidural and Intrathecal Analgesia
Published in Pamela E. Macintyre, Stephan A. Schug, Acute Pain Management, 2021
Pamela E. Macintyre, Stephan A. Schug
The spinal cord and brain are covered by three membranes, the meninges. The outer membrane is called the dura mater. The middle layer, the arachnoid, lies directly below the dura and both jointly form the dural sac. The inner layer, the pia mater, adheres to the surface of the spinal cord and brain. The epidural space lies outside the dura mater and is limited by the bones and ligaments of the spinal canal (Figure 9.1). It is a potential space filled primarily with fat and connective tissue, but it also contains blood vessels and is traversed by nerve roots. Inside the dural sac, which extends down to S2, is the subarachnoid or intrathecal space containing cerebrospinal fluid (CSF). It contains the spinal cord above the level of L1-2 and the cauda equina, comprising lumbar and sacral nerve roots, below L1-2.
Anatomy of the head and neck
Published in Helen Whitwell, Christopher Milroy, Daniel du Plessis, Forensic Neuropathology, 2021
The dura mater has two distinct layers, an outer layer that is fused to the periosteum lining the inner surface of the skull and an inner fibrous layer. Consequently, no epidural space exists superficial to this layer, unlike the situation found within the spinal canal of the vertebral column. However, there is a potential space, termed the ‘extradural space’, present that can serve as a reservoir for blood if the meningeal vessels become ruptured by trauma. The tightly adherent skull-dura layers serve to prevent spread of blood. Both layers of dura are separated by a thin gap layer, in which are found the major blood sinuses and other blood vessels. Arachnoid granulations project through the dura into the venous sinuses and serve to absorb CSF back into the venous system. All the venous sinuses drain eventually into the internal jugular veins of the neck.
Anterior Component Separation
Published in Jeff Garner, Dominic Slade, Manual of Complex Abdominal Wall Reconstruction, 2020
Elizabeth Tweedle, James Wheeler
Suction drains should be placed in the subcutaneous space and retro-rectus space on both sides and if the patient has a separate pocket of dissection, such as after endoscopic ACS, a drain should also be placed percutaneously into this potential space. The lipocutaneous flaps are carefully inspected and any devitalised skin debrided. It may well be necessary to trim the skin and tissue in the midline to produce a cosmetically acceptable closure and to reduce any potential dead space for seroma to accumulate in; while efforts are made to preserve it, patients should be consented that they may lose their umbilicus at this stage.
Acute subperiosteal orbital haematoma following general anaesthesia in the setting of recent trauma
Published in Orbit, 2022
Daniel T. Hogarty, Elad Ben Artsi, Brandon Thia, Robin Meusemann, Brent Gaskin
The pathophysiology of SOH involves bleeding within the potential space between the periosteum and orbital bone. This periosteum is normally loosely attached except around the orbital fissures, optic canal, arcus marginalis, suture lines, and foramina.2 A loose attachment has been postulated to be more prominent in younger patients.3,4 The potential space between the periosteum and orbital bone is traversed by a number of small diploic vessels that are part of the valveless orbital venous system that has the potential to transmit transient elevations in central venous pressure or intracranial pressure.2,5 Rupture of these diploic veins is the likely source of bleeding. SOH most commonly occurs in the superior orbit, as this area has the largest section of periosteum without firm adhesions.2
Challenges in surgical video annotation
Published in Computer Assisted Surgery, 2021
Thomas M. Ward, Danyal M. Fer, Yutong Ban, Guy Rosman, Ozanan R. Meireles, Daniel A. Hashimoto
As detailed in the subsequent challenges on spatial and temporal annotation, the balance between having flexible definitions that preserve clinical relevance and precise definitions that improve inter-rater reliability can be optimized by considering the specific phenomena of interest. Some variability in annotating clinical phenomena may be unavoidable as such variability may reflect inherent differences in the conceptualization of such phenomena by surgeons. For example, surgeons may differ in their interpretation of the correct surgical plane (i.e. the potential space between two structures through which a dissection can be performed) or in the amount of bleeding that qualifies as clinically significant. These underlying differences could provide clues on the difficulty of a surgical situation (e.g. significant adhesions or inflammation) and may require additional annotation from human experts. While high variability between annotators in such edge cases might threaten a project seeking to utilize automated methods, it can also serve as a useful metric to more closely study a clinical phenomenon through other methods that may be more appropriate (e.g. qualitative methods).
The ins and outs of drug-releasing vaginal rings: a literature review of expulsions and removals
Published in Expert Opinion on Drug Delivery, 2020
Peter Boyd, Ruth Merkatz, Bruce Variano, R. Karl Malcolm
The human vagina (derived from the same word in Latin meaning ‘sheath’ or ‘scabbard’) is a collapsed fibromuscular tube extending from the external genitalia to the cervix. It is best considered as a potential space that undergoes considerable distension during sexual intercourse and particularly childbirth. The overall shape of the vagina and its ability to stretch are affected by the laxity (looseness) and elasticity of the vaginal tissue and its relationship to other pelvic organs (discussed in Section 2.6) [32]. Earlier scientific studies investigating the dimensions of the human vagina were often performed either using cadavers or by making three-dimensional casts in live women by injecting various moldable materials, such as wax, rapidly solidifying dental impression paste, and silicone [33–35]. Recognizing that these casting methods and materials produced some degree of distension of the vagina, magnetic resonance imaging (MRI) of the live human vagina of women following administration and distribution of an aqueous vaginal gel has been reported as a means of more accurately capturing baseline dimensions [32]. In this study, a significant variation in mean vaginal length (cervix to introitus) was reported across 28 women (14 nulliparous and 14 parous) aged 18–45, with a mean value of 62.7 mm. Mean vaginal width decreased from proximal vagina (32.5 mm) to pelvic diaphragm (27.8 mm) and introitus (26.2 mm). Factors such as age, height, and parity (but not race) were positively associated with differences in baseline vaginal dimensions.