Sketchy Medicine | doodles for studying

Time 2020-11-16 13:04:07

Web Name: Sketchy Medicine | doodles for studying

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This is not an exhaustive overview of the muscles of the arm and forearm, but it demonstrates some of the tricky relationships that often catch people up. Some of the key points of compression are also noted and the muscles are coloured per their innervation. One thing not mentioned in the doodle that is important to notice is the way that the aponeurosis of the biceps veers medially (ulnarly) this is why it is also a supinator and not just an elbow flexor. I ve drawn the brachial plexus before showing more of its anatomical relationships (which is actually why the trunks and cords are named as they are). As I m gearing up studying, I created this more schematic diagram of the plexus, including the distal targets (mostly the muscles but some sensory too).Hopefully this will help you figure out where is the lesion? when you are faced with a brachial plexus question on your exams (and in life) as well.I ve also included a printable version for your printing and pasting-up-to-the-wall-to-passively-absorb pleasure.Long thoracic: serratus anteriorDorsal scapular: rhomboids, levator scapulaeSuprascapular: supraspinatus, infraspinatus, sensory to the AC GH jointsNerve to subclavius: subclaviusLateral pectoral: pec major (clavicular head), sensation to pecSuperior subscapular: subscapularis (upper part)Thoracodorsal (aka middle subscapular): lat dorsiInferior subscapular: subscapularis (lower part), teres majorMedial pectoral: pec minor, pec major (sternocostal head)Medial cutaneous n. of arm: sensory to medial surface of arm (tiny area)Medial cutaneous n. of forearm (antebrachial cutaneous): sensory to skin over biceps and medial forearmBrachial Plexus Part 1 anatomical relationsPeripheral nerve branches and compression neuropathyFind that lesion! (deep tendon reflexes of the arm)Share the knowledge:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Tumblr (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on Pinterest (Opens in new window)Click to email this to a friend (Opens in new window)Click to print (Opens in new window) When to use vancomycinThe most common use for vancomycin is in invasive Gram positive infectionsYou need to considerInfection sitePatient weightKidneyfunctionPathogen susceptibilityPharmacokineticsVancomycin has bad oral bioavailability so it s almost never used as a pillOccasionally it is orally to supplement C. diff infections (because that s going on in the GI tract)Volume of distribution: IV serum 0.4-1 L / kgNormally vancomycin doesn t cross the blood brain barrier very well, but in the setting of meningitis the inflamed meninges increases permeabilityAdverse effectsRedman syndrome: A histamine-like flushing during or immediately after dose. Occurs mostly on the face and neck. This is NOT life threateningTreatment: anti-histamine, pause infusion, then restart at a slower rateIf the reaction is severe, stop the infusion, give antihistamines, wait until symptoms resolve before restarting. When you restart, give the infusion reaaaalllllly slooooooowly (over more than 4 hours)DosingThis is where vancomycin can get tricky, because you are aiming for a target trough (between dose) serum concentrations.Generally the target is 10 mcg/ml, but this may need to be higher for treating MRSA or osteomyelitisTrough concentrations should be measured 30 minutes before the 4th doseany time a course of vanco is started orthe dose is changedMonitor creatinine at least once a week (remember that whole nephrotoxicity bit)Starting dose should be 15-20 mg/kg (based on actual not ideal body weight) every 12 hours. This usually works out to 1-2 g IV Q12H. If the kidneys are not working well, reduce the dose.ReferencesUpToDate.com Vancomycin: Parenteral dosing, monitoring, and adverse effects in adults Renal replacement therapy (RRT) is a process of removing waste products and excess free water from the blood during renal failure and critical illness.Common indications for RRT can be remembered with the mnemonic AEIOU:(Metabolic)AcidosisElectrolyte abnormalities (especially severe hyperkalemia)Ingestions/toxins (aspirin, lithium, methanol, ethylene glycol)(Volume)OverloadUremiaThere are many different variations of RRT, but the main principles behind it can be quite simple.In hemodialysis, diffusionis responsible for removing unwanted solutes and water. The setup involves a semipermeable membrane that can allow water and some water-soluble molecules to pass. Blood will flow on one side of the membrane, under pressure, while the dialysate (contains glucose and some electrolytes) generally flows on the other side in the opposite direction. This creates a suitable concentration gradient for unwanted molecules to pass into the dialysate, while excess water is forced across the membrane based on the amount of pressure is applied by the dialysis circuit.In hemofiltration,blood is pushed across a semipermeable membrane, under pressure. Most of the plasma water is able to pass through the membrane, while unwanted molecules get stuck in the membrane (convection). A substitution fluid may be added back to the blood, in order to dilute out waste molecules (e.g., urea), replace useful molecules (e.g., bicarbonate), and to avoid losing too much fluid from the patient s circulation.Some modes of RRT will involve both hemodialysis and hemofiltration. Others only use one of these mechanisms.ReferencesButcher BW, Liu KD. 2013. Renal replacement therapy and rhabdomyolysis. In: Critical Care Secrets (Parsons and Wiener-Kronish, Eds.) Mosby, Philadelpia PA.Hoste E, Vanommeslaeghe. 2017. Renal replacement therapy. In: Textbook of Critical Care (Vincent, Abraham, Moore, Kochanek, and Fink, Eds.) Elsevier, Philadelphia PA.Ricci Z, Romagnoli S, Ronco C. 2015. Extracorporeal support therapies. In: Miller s Anesthesia (Miller, Ed.) Elsevier/Saunders, Philadelphia PA. Hypothermia is when you get really cold. Generally, hypothermia is defined as a core temperature less than 35C (95F). The Swiss staging system is fairly commonly used for correlating core temperature and clinical signs:Stage I (35 32C; 90 95F): conscious, shiveringStage II (28 32C; 82 90F): altered mental status, not shiveringStage III (24 28C; 75 82F): unconscious, not shivering, vital signs presentStage IV ( 24C; 75F): apparent death (but resuscitation possible!)Stage V ( 13.7C; 58F): death due to irreversible hypothermiaHealthy people have fairly effective mechanisms for maintaining a normal temperature (37C; 99F) (e.g., shivering, peripheral vasoconstriction) but these can be overwhelmed by extreme cold (Primary Hypothermia). Some comorbid patients can develop hypothermia even in a warm environment (Secondary Hypothermia). For instance, severely-burned patients can have increased heat loss, while acute spinal cord injury can impair peripheral thermoregulation.For the development of hypothermia, it is sometimes helpful to remember that heat can be lost by 4 physical mechanisms:Radiation: heat exchange by infrared electromagnetic radiationEvaporation: molecules converting from liquid to gas phase (e.g., sweat)Convection: heat exchange by air/fluid currentsConduction: heat exchange by direct contact with a colder surfaceBrown DJA, Brugger H, Boyd J, Paal P. 2012. Accidental hypothermia. NEJM; 367:1930.Zafran K, Mechem CC. 2017. Accidental hypothermia in adults. In: UpToDate. Waveform capnography is a commonly used monitor in the operating room, and is increasingly seen in non-operating room environments too! The capnographic waveform can be described as having several phases:Phase 0 (inspiratory baseline) represents the inspiratory phase of the respiratory cycle.Phase 1 is the initial part of expiration, when dead space gases are being exhaled. Since the exhaled gas in this phase did not take part in gas exchange, the PCO2 is 0.Phase 2 (expiratory upstroke) involves exhaled gases from alveoli reaching the detector. There is a sharp rise in PCO2 during this phase.Phase 3 is a (more or less) flat plateau showing continued exhalation of alveolar gas. The last, maximal part of this phase is the end-tidal point (ETCO2), which is usually 35-40 mmHg. ETCO2 tends to be 2-5 mmHg lower than PaCO2, though this difference can be increased/decreased under a variety of conditions, such as ventilation-perfusion mismatch.The shape of the capnograph waveform can tell you a lot!For example:A slanting upslope can represent airway obstruction (e.g., chronic obstructed pulmonary disease, bronchospasm, blocked endotracheal tube).In patients paralyzed with a neuromuscular blocker, as the paralytic wears off they may try to breathe asynchronously against the ventilator, producing a notch called a ‘curare cleft.’Quantitative capnography during resuscitation can be very useful. During CPR, there should be a visible waveform during high quality chest compressions; its absence may indicate accidental esophageal intubationA sudden loss is bad, as it means that the tube is fully obstructed or disconnected or that there has been a sudden loss of circulationYou can also just simply tell is someone is hypo- or hyperventilatingDorsch JA, Dorsch SE. 2007. Gas monitoring. In: Understanding anesthesia equipment (Dorsch and Dorsch, Eds.) Lippincott Williams Wilkins, Philadelphia PA.Kodali BS. 2013. Capnography outside the operating rooms. Anesthesiology; 118:192. Tumescent solution is also called Klein s Solution after the physician who characterized the recipe and the use of it.It s called tumescent because it makes things tumescent, which is a fancy word for swollen. Tumescent is a dilute solution of lidocaine, epinephrine, and sodium bicarbonate that is injected in the subcutaneous tissue (fat). The epinephrine is the most important ingredient as it causes vasoconstriction, this means that the blood loss that could be a big problem for large procedures like burn surgery and liposuction becomes much less of a big deal.The other interesting thing is that since fat is relatively avascular compared to other tissues, the safe amount of tumescent is much higher than what is normally stated for injections of lidocaine or epinephrine.For example, it was reported by Klein that the toxic dose of lidocaine for tumescent solution is 35 mg/kg of body weight.There are a few different recipes for tumescent anesthesia, the one presented in the doodle is the one first outlined by Klein, some use more or less lidocaine or epinephrine.ReferencesKucera IJ1, Lambert TJ, Klein JA, Watkins RG, Hoover JM, Kaye AD. Liposuction: contemporary issues for the anesthesiologist. J Clin Anesth. 2006, 18(5): 379-87.Klein JA. The tumescent technique. Anesthesia and modified liposuction technique. Dermatol Clin. 1990, 8(3): 425-37.Klein JA. Tumescent technique for local anesthesia improves safety in large-volume liposuction. Plast Reconstr Surg. 1993, 92: 1085-100. The carpal bone ossify aka turn into bone aka magically become visible on an x-ray in a predictable order.The easiest way to remember is that it starts at the capitate (smack dab in the middle) and then goes in a ulnarly-directed spiral. I was going to say clockwise or counter-clockwise but that would depend on which side of which hand you were looking at. So capitate, followed by hamate and then down to triquetrumand so on. Except for the pisiform, being a sesamoid bone it gets left behind and only develops yearslater.Capitate: 1-3 monthsHamate: 2-4 monthsDistal radius: 1 year The scaphoid shift testaka midcarpal shift test is a variation of the Watson Test for scaphoid instability. A positive test can be caused by scapholunate ligament laxity or injury.The Watson test evaluates scaphoid instability as the wrist is moved from radial to ulnar deviation (it s not an active test)To do the scaphoid shifttest (as described by Lane in 1993)Use the same hand as the patient s affected hand (suspicious of a right scaphoid problem? Use your right hand to test)Place your hand on the patient s so that your thumb is over the volar surface of the scaphoid tubercle (the distal pole). Don t apply any pressure (remember this area is probably at least a little sore and you want to remain friends for now)Gently movethe wrist through ulnar/radial deviation (you can be fancy and consider this your Watson Test) and flexion/extension to relax the patientWith the patient s wrist in neutral extension and neutral (or slight radial deviation), forcefully and quickly push the scaphoid tubercle in the dorsal directionAt this point, the patient is likely no longer your friendNote the degree of shift, any crepitus or clunk, and pain evoked.Remember to compare this to the opposite wrist

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