By: Amy Walker,
on 11/12/2015
We are used to lines that guide – from those that keep our words straight on the page to those that direct planes down runways or trains along tracks. Moving from lines that guide our direction to guidelines that direct our behaviour, particularly in clinical medicine, is a very exciting time.
The post Tracheal Intubation Guidelines appeared first on OUPblog.
By: Amelia Carruthers,
on 10/16/2015
Today (Friday 16th October) is World Anaesthesia Day. To mark this occasion, we have selected ten of the most interesting events in the history of anaesthesia. From the discovery of diethyl ether by Paracelsus in 1525, to James Young Simpson's first use of chloroform in 1847, and the creation of the first specialist anaesthetic society in 1992 - anaesthesia is a medical discipline with a fascinating past.
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By: Joe Hitchcock,
on 1/16/2015
“Sorry mate, I didn’t see you.” It’s a common refrain heard after many a road-traffic collision. So common, in fact, that if you say “SMIDSY” to a UK motorcyclist, they’ll most likely wince and offer a story of how they or a colleague came to grief. Perhaps you’ve had SMIDSY said to you, or even had to utter those words yourself?
SMIDSY describes the all-too-common type of motorbike accident when a car pulls out at an intersection. The driver’s sure that the road is clear, but discovers too late that something is coming. Even if you haven’t been involved in such an incident, you can probably recall some occasion on which you were driving and had a near miss with a car or bike you’d swear wasn’t there a moment ago.
It turns out that these sorts of events might be more complicated than first appear. It’s quite possible for you to look right at the other vehicle, but for your brain to fail to process the information associated with it. These sorts of situational awareness failures may in fact result from a well-described, but not well-known, psychological phenomenon called “inattentional blindness”.
Most people believe their senses work a bit like a video camera. You direct attention towards an object and your brain automatically and reliably records. Although this is our day-to-day experience, perception is in reality a much more active process, with a number of filters operating between information arriving, and you becoming consciously aware of it.
A potentially limitless amount of information exists in the environment around you, but little of it is relevant from moment to moment. Rather than ‘clutter up’ consciousness with a surfeit of useless information, the subconscious monitors these unnecessary items and only ‘alerts’ the consciousness when something relevant occurs.
Under normal circumstances your brain is fairly efficient at subconsciously monitoring events around you. Imagine holding a conversation in a noisy restaurant: you are probably only consciously aware of the conversation you are directly involved in (your primary task), but if your name is mentioned elsewhere, you will turn around to find out why. Your brain has been subconsciously monitoring that stream of conversation, and when something personally relevant occurs (your name is a very powerful trigger, carrying a high degree of ‘cognitive saliency’) you can devote your attention to it.
Problems occur when you have to concentrate harder on a primary task. The more cognitive demands placed on you, the narrower your focus becomes. It’s surprising how big an event you might miss: the classic demonstration of this effect is known as the “Invisible Gorilla” and was devised by Harvard psychologists Dan Simons and Christopher Chabris in 1999. Observers were asked to follow two teams of basketball players, counting the passes made by one of the teams. Caught up in the counting task, 50% of the participants failed to notice as a collaborator, dressed in a gorilla costume, marched between the players and stopped to beat her chest before marching out again. Making the primary task more difficult, by asking the observers to count bounce- and aerial-passes separately, caused the noticing rate to fall to 33%. Most observers were inattentionally blind to the gorilla and many expressed shock when shown their error, some even accusing the experimenters of showing two different videos. Although these perceptual errors are an innate and universal feature of human cognitive architecture, it’s a common finding that insight into their effects is very poor. Almost everyone significantly overestimates their ability to notice the unexpected.
Increasing workload has been well described as a risk for this form of perceptual error. Interestingly, people with professional basketball experience are much more likely to notice the gorilla in the Simons video, but athletes from other disciplines perform much as the general public does. Whilst expertise is certainly protective to a degree (although does not eliminate the risk altogether), it does seem to be very task-specific.
How does inattentional blindness affect medical practice? The short answer is that no-one really knows. High-profile disasters such as the case of Elaine Bromiley make vivid reminders of the devastating consequences of medical errors, however, it is well recognized that daily errors occur in every institution around the world. In the UK, errors account for 2.5% of the national health budget annually.
Loss of situational awareness is thought to be the leading cause of error in time-critical situations, and there can be no doubt that clinicians labor under mentally taxing circumstances. Of course, doctors are well trained. Training brings expertise, and surely expertise protects against perceptual error? Possibly, but perhaps not to the extent that you might expect.
A few studies have looked into inattentional blindness in medical personnel, mainly by showing people items such as radiographs with a gorilla superimposed. These experiments showed large numbers of even experienced staff miss the anomaly. Our group in Oxford took this a little further, creating a recording of an adult resuscitation scenario into which we inserted a series of events, designed to test for the presence of different types of perceptual error. We showed this video to a more than 140 people and demonstrated that overall, more than seven people in ten missed events that would contribute to poor patient outcome (were they to be missed in ‘real life’). As one might expect, experts in the group (all experienced, accredited instructors of adult resuscitation) did perform better. In their case around six in ten missed it…
So does this prove that inattentional blindess is a problem for us, as experienced clinicians? Not yet, but it does raise some questions about how reliably individuals can maintain situational awareness, and offers some insight into the mechanisms by which even highly trained personnel might make mistakes. By research, using tools such as high-fidelity simulation, we can start to investigate how frequently perceptual errors actually do contribute to loss of situational awareness, who is most vulnerable to these effects, and most importantly, how can we mitigate them.
Heading image: Optics: page to a partwork on science, with pictures of optical phenomena. Coloured lithograph by J. Emslie, 1850. CC BY 4.0 via Wellcome Images.
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By: GeorgiaM,
on 12/11/2014
Many students, when asked by a teacher or professor to volunteer in front of the class, shy away, avoid eye contact, and try to seem as plain and unremarkable as possible. The same is true in dental school – unless it comes to laughing gas.
As a fourth year dental student, I’ve had times where I’ve tried to avoid professors’ questions about anatomical variants of nerves, or the correct way to drill a cavity, or what type of tooth infection has symptoms of hot and cold sensitivity. There are other times where you cannot escape having to volunteer. These include being the first “patient” to receive an injection from one of your classmate’s unsteady and tentative hands. Or having an impression taken with too much alginate so that all of your teeth (along with your uvula and tonsils) are poured up in a stone model.
But volunteering in the nitrous oxide lab … that’s a different story. The lab day is about putting ourselves in our patients’ shoes, to be able to empathize with them when they need to be sedated. For me, the nitrous oxide lab might have been the most enjoyable 5 minutes of my entire dental education.
In today’s dental practice, nitrous oxide is a readily available, well-researched, incredibly safe method of reducing patient anxiety with little to no undesired side effects. But this was not always the case.
The Oxford Textbook of Anaesthesia for Oral and Maxillofacial Surgery argues that “with increasingly refined diets [in the mid-nineteenth century] and the use of copious amounts of sugar, tooth decay, and so dentistry, were on the increase.” Prior to the modern day local anesthesia armamentarium, extractions and dental procedures were completed with no anesthesia. Patients self-medicated with alcohol or other drugs, but there was no predictable or controllable way to prevent patients from experiencing excruciating pain.
That is until Horace Wells, a dentist from Hartford, Connecticut started taking an interest in nitrous oxide as a method of numbing patients to pain.
Wells became convinced of the analgesic properties of nitrous oxide on December 11, 1844 after observing a public display in Hartford of a man inhaling the gas and subsequently hitting his shin on a bench. After the gas wore off, the man miraculously felt no pain. With inspiration from this demonstration and a strong belief in the analgesic (and possibly the amnestic) qualities of nitrous oxide, on December 12, Wells proceeded to inhale a bag of the nitrous oxide and have his associate John Riggs extract one of his own teeth. It was risky—and a huge success. With this realization that dental work could be pain free, Wells proceeded to test his new anesthesia method on over a dozen patients in the following weeks. He was proud of his achievement, but he chose not to patent his method because he felt pain relief should be “as free as the air.”
This discovery brought Wells to the Ether Dome at the Massachusetts General Hospital in Boston. Before an audience of Harvard Medical School faculty and students, Wells convinced a volunteer from the audience to have their tooth extracted after inhaling nitrous oxide. Wells’ success came to an abrupt halt when this volunteer screamed out in pain during the extraction. Looking back on this event, it is very likely that the volunteer did not inhale enough of the gas to achieve the appropriate anesthetic effect. But the reason didn’t matter—Wells was horrified by his volunteer’s reaction, his own apparent failure, and was laughed out of the Ether Dome as a fraud.
The following year, William Morton successfully demonstrated the use of ether as an anesthetic for dental and medical surgery. He patented the discovery of ether as a dental anesthetic and sold the rights to it. To this day, most credit the success of dental anesthesia to Morton, not Wells.
After giving up dentistry, Horace Wells worked unsuccessfully as a salesman and traveled to Paris to see a presentation on updated anesthesia techniques. But his ego had been broken. After returning the U.S, he developed a dangerous addiction to chloroform (perhaps another risky experiment for patient sedation, gone awry) that left him mentally unstable. In 1848, he assaulted a streetwalker under the influence. He was sent to prison and in the end, took his own life.
This is the sad story of a man whose discovery revolutionized dentists’ ability to effectively care for patients while keeping them calm and out of pain. As a student at the University of Connecticut School of Dental Medicine, it is a point of pride knowing that Dr. Wells made this discovery just a few miles from where I have learned about the incredible effects of nitrous oxide. My education has taught me to use it effectively for patients who are nervous about a procedure and to improve the safety of care for patients with high blood pressure. This is a day we can remember a brave man who risked his own livelihood in the name of patient care.
Featured image credit: Laughing gas, by Rumford Davy. Public domain via Wikimedia Commons.
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By: Alice,
on 12/8/2012
The Mayo Clinic Scientific Press suite of publications is now available on Oxford Medicine Online. To highlight some of the great resources, we’ve pulled together some interesting facts about anesthesia from James Hebl and Robert Lennon’s Mayo Clinic Atlas of Regional Anesthesia and Ultrasound-Guided Nerve Blockade. Get free access to the Mayo Clinic suite for a limited time with this Facebook offer (watch out, it closes today!).
(1) Egyptian pictographs dating back to 3000 BC showing a physician compressing a nerve in the antecubital fossa while an operation is being performed on the hand.
(2) William Halsted, M.D. (1852–1922; Chair, Department of Surgery, Johns Hopkins Hospital), used cocaine as local infiltration as he dissected down toward major nerve trunks. He then injected cocaine around them, performing regional blockade under direct vision.
(3) In Paris in the early 1920s, a new technique for blocking the brachial plexus from an axillary approach was introduced. M. Reding, M.D., studying the anatomy of the axilla, discovered that the nerves of the plexus surround the artery in a fascial sheath. Thus, using the artery as a landmark, Reding found that the fascial compartment could be filled with local anesthetic to result in brachial plexus blockade. Reding blocked the musculocutaneous nerve, which lay outside the sheath, by infiltrating the coracobrachialis muscle.
(4) Paresthesia technique—the long-preferred method of regional anesthesiologists—was slowly replaced during the 1980s as peripheral nerve stimulation began to emerge. During its development, peripheral nerve stimulation was thought to provide superior localization of neural structures compared with blind paresthesia-seeking techniques. Peripheral nerve stimulators transmit a small electric current through a stimulating needle that, when in proximity to neural structures, causes depolarization and muscle contraction.
(5) In contemporary medical practice, regional anesthetic techniques have expanding socioeconomic and clinical implications. For example, studies evaluating patient satisfaction have found that perioperative analgesia and the avoidance of nausea and vomiting are consistently two of the highest concerns among patients.
(6) Ultrasound guidance may represent the 21st century’s version of Halsted’s anatomical dissection down to the brachial plexus.
Mayo Clinic Atlas of Regional Anesthesia and Ultrasound-Guided Nerve Blockade by James Hebl and Robert Lennon is a practical guide for residents-in-training and clinicians to gain greater familiarity with regional anesthesia and acute pain management to the upper and lower extremity. It emphasizes the importance of a detailed knowledge of applied anatomy to safely and successfully performing regional anesthesia. It also provides and overview of the emerging field of ultrasound-guided regional anesthesia, which allows reliable identification of both normal and variant anatomy. Mayo Clinic Atlas of Regional Anesthesia and Ultrasound-Guided Nerve Blockade contains more than 200 beautifully illustrated anatomic images important to understanding and performing regional anesthesia. Corresponding ultrasound images are provided when applicable.
The Mayo Clinic Scientific Press suite of publications is now available on Oxford Medicine Online. With full-text titles from Mayo Clinic clinicians and a bank of 3,000 multiple-choice questions, Mayo Clinic Toolkit provides a single location for residents, fellows, and practicing clinicians to undertake the self-testing necessary to prepare for, and pass, the Boards and remain up-to-date. Oxford Medicine Online is an interconnected collection of over 250 online medical resources which cover every stage in a medical career, for medical students and junior doctors, to resources for senior doctors and consultants. Oxford Medicine Online has relaunched with a brand new look and feel and enhanced functionality. Our aim is to ensure that the site continues to deliver the highest quality Oxford content whilst meeting the requirements of the busy student, doctor, or health professional working in a digital world.
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