By Q. Sven. Quincy University.
The superior and lateral lig- Vestibular nerve Incus aments lie roughly in the plane of the ossicular chain and an- Facial nerve chor the head and shaft of the malleus order claritin 10mg allergy treatment quotes. The anterior ligament Cochlear attaches the head of the malleus to the anterior wall of the nerve middle ear cavity discount claritin 10 mg without a prescription allergy medicine regulations, and the posterior ligament runs from the head of the incus to the posterior wall of the cavity. The sus- pensory ligaments allow the ossicles sufficient freedom to function as a lever system to transmit the vibrations of the tympanic membrane to the oval window. This mechanism is especially important because, although the eardrum is sus- pended in air, the oval window seals off a fluid-filled cham- ber. Transmission of sound from air to liquid is inefficient; if Pinna sound waves were to strike the oval window directly, 99. Al- though it varies with frequency, the ossicular chain has a Outer ear Middle Inner ear ear lever ratio of about 1. The brane is coupled to the smaller area of the oval window (ap- structures of the middle and inner ear are en- proximately a 17:1 ratio). These conditions result in a pres- cased in the temporal bone of the skull. Although the efficiency depends on the fre- slightly emphasize frequencies in the range of 1,500 to quency, approximately 60% of the sound energy that 7,000 Hz and aids in the localization of sources of sound. Wax-secreting glands line the canal, and its inner end is sealed by the tympanic membrane or eardrum, Approximate Stapedius axis of Superior muscle a thin, oval, slightly conical, flexible membrane that is an- rotation ligament chored around its edges to a ring of bone. An incoming Temporal bone pressure wave traveling down the external auditory canal causes the eardrum to vibrate back and forth in step with Scala vestibuli the compressions and rarefactions of the sound wave. Oval window Lateral The overall acoustic effect of the outer ear structures is to ligament produce an amplification of 10 to 15 dB in the frequency range broadly centered around 3,000 Hz. The next portion of the auditory sys- Basilar tem is an air-filled cavity (volume about 2 mL) in the mas- Incus membrane toid region of the temporal bone. The tube Eardrum opens briefly during swallowing, allowing equalization of Tensor tympani Round the pressures on either side of the eardrum. During rapid muscle window external pressure changes (such as in an elevator ride or during takeoff or descent in an airplane), the unequal Eustachian tube Scali forces displace the eardrum; such physical deformation tympani may cause discomfort or pain and, by restricting the mo- tion of the tympanic membrane, may impair hearing. Outer Middle Inner Blockages of the eustachian tube or fluid accumulation in ear ear ear the middle ear (as a result of an infection) can also lead to difficulties with hearing. Vibrations from the eardrum are transmitted by the lever system Bridging the gap between the tympanic membrane and formed by the ossicular chain to the oval window of the scala the inner ear is a chain of three very small bones, the ossi- vestibuli. The malleus (hammer) is attached to the pensory system for the ossicles, are not shown. The combination eardrum in such a way that the back-and-forth movement of the four suspensory ligaments produces a virtual pivot point of the eardrum causes a rocking movement of the malleus. The stapedius and tensor tympani muscles third bone, the stapes (stirrup). This last bone, through its modify the lever function of the ossicular chain. CHAPTER 4 Sensory Physiology 79 Sound transmission through the middle ear is also af- The process of sound transmission can bypass the ossic- fected by the action of two small muscles that attach to the ular chain entirely. If a vibrating object, such as a tuning ossicular chain and help hold the bones in position and fork, is placed against a bone of the skull (typically the mas- modify their function (see Fig. The tensor tympani toid), the vibrations are transmitted mechanically to the muscle inserts on the malleus (near the center of the fluid of the inner ear, where the normal processes act to eardrum), passes diagonally through the middle ear cavity, complete the hearing process. Bone conduction is used as a and enters the tensor canal, in which it is anchored. Con- means of diagnosing hearing disorders that may arise be- traction of this muscle limits the vibration amplitude of the cause of lesions in the ossicular chain. The actual process of sound transduction contraction changes the axis of oscillation of the ossicular takes place in the inner ear, where the sensory receptors chain and causes dissipation of excess movement before it and their neural connections are located. These muscles are activated by a between its structure and function is a close and complex reflex (simultaneously in both ears) in response to moder- one. The following discussion includes the most significant ate and loud sounds; they act to reduce the transmission of aspects of this relationship.
Many of these patients were described by nurses as com- plaining vociferously of pain before they fell asleep and obstructed to the point of cardiorespiratory arrest order claritin 10 mg fast delivery allergy testing and pregnancy. Critical apneic episodes in these claims were observed with all routes of narcotic administration includ- ing intravenous and intramuscular injections purchase claritin 10mg allergy testing back, patient-controlled anal- gesia, and spinal and epidural administration. Chapter 10 / Anesthesiology 135 Prevention of claims like these is complicated by the fact that not all patients with OSA carry the diagnosis preoperatively. Although OSA is diagnosable through formal sleep studies, it also has clinical hallmarks. These include loud snoring—often requiring couples to sleep in separate rooms; obstruction noted by the sleeping partner, including episodes of gasping and choking while asleep; and exces- sive daytime somnolence with an uncontrollable sleepiness interfer- ing with professional or private life (15). Patients who exhibit these symptoms might not all have OSA if evaluated by formal sleep stud- ies, but it might be safer to treat them as if they did until proven otherwise (11). Children with obstruction secondary to adenotonsillar hypertrophy may also have clinical sleep apnea presenting with the same clinical signs. They can also be at risk post-tonsillectomies if medicated with parenteral narcotics. Risk-management suggestions include finding ways to monitor OSA patients appropriately postoperatively. Pulse oximetry currently has the ability to detect hypoxic episodes early, but oximeter alarms must be audible to hospital personnel if arrests are to be prevented. This can be accomplished in intensive care units or on wards that are staffed for this purpose. The administration of narcotics to OSA patients needs to be closely monitored. Pain medication orders for any given patient might be written by different individuals (e. Red-flagging the charts of OSA patients can warn all physicians and caregivers of the increased risk of narcotic administration. Patients who use continuous positive airway pressure masks at home should be advised in advance to bring them to the hospital and should use them postoperatively where appropriate. As pain is treated more aggressively, the tragic complication of respiratory arrest in patients with OSA may be seen more frequently. Anesthesiologists should be alert to signs of OSA and should consider routinely asking questions to identify those patients at risk (11). When Bad Claims Happen to Good Anesthesiologists Much has been written about the stress of being named in a malprac- tice lawsuit. Anesthesiologists may be particularly vulnerable in this circumstance because they do not have a consistent and loyal patient base and have only transient relationships with the other physicians with whom they work. As one anesthesiologist explained, “It’s like you’re only as good as your last case. The legal admonition not to speak to other physicians about the details of cases facing pos- sible litigation can leave an anesthesiologist feeling isolated and alone. However, in being sued, anesthesiologists are actually joining the ranks of the majority of their colleagues. One’s partners are more likely than not to have been involved in malpractice cases themselves, but this is not a topic that comes up frequently for discussion in the operating room. Malpractice lawsuits are an unpleasant but real part of life for most anesthesiologists with busy practices. Those who manage to avoid litigation entirely are just as likely to be lucky as unusually skilled. With 4% of anesthesiology claims generated solely by surgical complications, avoiding those is really a matter of luck. Naturally, physicians tend to dwell on the facts of cases with adverse outcomes. In retrospect, it can be frustrating how simple the steps that would have avoided a complication might seem. However, any one anesthetic may be acceptably accomplished in many different ways, so there will always be a number of alternatives to whatever choices a physician makes. From a medical-legal standpoint, the standard of care does not depend on 20/20 hindsight but rather on what a similarly trained physician might have chosen to do given similar circumstances.
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