Search this site

< Back Pulmonary Embolism...pending Diagnosis and Treatment of Pulmonary Embolism Previous Next

< Back Hemorrhoids What are hemorrhoids? Patient information: Hemorrhoids [American College of Colon and Rectal Surgeons] Patient education: Hemorrhoids (Beyond the Basics) [UpToDate] Hemorrhoids are a normal part of anorectal anatomy. They are blood vessels in the end of the rectum and at the anal verge. External hemorrhoids overlie the external anal sphincter (at the anal verge) and the internal hemorrhoids overlie the internal anal sphincter (inside the rectum). The hemorrhoids fill with blood and help maintain continence (avoid leaking stool). See images below. Anything that increases pressure in the abdomen, including prolonged straining, coughing, pregnancy, and an enlarged prostate requiring straining to urinate, can lead to abnormally large venous plexuses, which are what most people know as hemorrhoids. Internal hemorrhoids are lined by the same tissue as the rest of the GI tract, which secretes mucus. External hemorrhoids are lined by the same tissue as the rest of the skin on our bodies. Source: UpToDate Images: Internal and External Hemorrhoids Symptoms When hemorrhoids become abnormally large as a result of prolonged straining, typically from constipation, they can cause pain and bleeding. Internal hemorrhoids- dull/ achy pain and bleeding with bowel movements. In addition, if internal hemorrhoids prolapse (move from inside the rectum out onto the perianal skin), which typically occurs with bowel movements, this can cause issues with perianal moisture, itching and skin irritation. This is caused by the mucus from the overlying tissue. Prolapsed hemorrhoids can sometimes reduce spontaneously (return to their normal location in the rectum) or might require manual reduction (might have to be pushed back in after having a bowel movement). If internal hemorrhoids External hemorrhoids- bleeding with bowel movements. Acute pain can occur when an external hemorrhoid becomes thrombosed (acutely filled with blood clot→ overlying skin gets stretched→ severe pain). What is conservative management for hemorrhoids? See “ Anorectal Disease: How do I prevent anorectal disease? ” Improving bowel habits is the first-line treatment for hemorrhoids. See patient handouts below. Sitz baths- fill a tube with water as warm as you can tolerate, and soak your bottom after every bowel movement and at least 3 times per day. For itching: moisture in the perianal skin can cause itching. Improving bowel habits and gentle perianal skin hygiene can improve this. Zinc oxide can be used as a topical barrier twice daily. For protruding or swollen internal hemorrhoids: hold the hemorrhoid tissue with a Tucks pads (witch hazel) to decrease the swelling, allowing the hemorrhoid tissue to be reduced. Patient Info- Hemorrhoids .pdf Download PDF • 58KB Patient Info- Fiber Guide .pdf Download PDF • 68KB What is the operative management of hemorrhoids? Acute thrombosis of external hemorrhoids- most patients will have resolution of symptoms with conservative management described above. However, if you present within the first 48-72 hours, the hemorrhoid can be excised. Incision and drainage alone is not recommended, given high rates of recurrence. If symptoms have been present for more than 72 hours, surgery is more likely to create more discomfort, and therefore it is typically avoided. Large external hemorrhoids or mixed internal and external hemorrhoids with prolapse- typically managed with hemorrhoidectomy or hemorrhoidopexy. Internal hemorrhoids- banding is the most common treatment. Other options include sclerotherapy and infrared coagulation. Previous Next

How to be a Terrible First Date Dating, Pt 1 How to be a Terrible First Date I've been dabbling in the world of online dating for years. Some dates have been more successful than others. But until this point, I've always had pleasant encounters. That all changed with my last couple of dates. I've been shocked to discover how different people can behave in public compared to the persona they project via text. I always imagined people would be more reckless in their text and more personable in real life. Oh, how wrong I was… My first date was a few months after I moved to town. We video chatted a handful of times before we met, and he seemed like a nice normal guy. The first clue should have been when he told me he had a lawsuit against him related to a business deal. I'm too trusting and gave him the benefit of the doubt. So…what went wrong? First, he spent the beginning of the date asking me leading judgmental questions. How many guys have I dated/ slept with, etc, etc. He proceeded to tell me I was promiscuous (really? I've dated like 7 people and I'm 35 years old). Next, he proceeded to discuss pornography and sexual preferences. Then he asked whether I thought people could know each other if they don't live together before getting married, and he told me I was wrong when I said yes. Next, he insinuated that he didn't believe that I'm a surgeon. Weird, but whatever. He went on to Google me in front of me. Like, legit. Probably spent about 10 minutes staring at his phone while I ate my dinner. A couple times I told him he should probably pay attention to the person who took time out of their day to come to meet him… Then he decided to tell me he didn't believe I was Hispanic because Hispanic women wear a lot of makeup. He found a picture from a few years ago when I was applying for a job and told me if I put in some effort, I could look better. I told him I'm so much more than my appearance, and I don't value myself based on looks. After a complete shitshow for the first half, I told him I'd give him a chance to start over and consider a different approach. I gave him the benefit of the doubt that he was just nervous. Unfortunately, he didn't adjust his approach in the second half. He then told me more details about his legal issues. Seriously, he spent a year in a work camp for white-collar criminals. He reminisced about the friends he made and the work he did. I had a hard time keeping a straight face. And the cherry on top of the terrible date? He lied about his height. He wasn't 5'6. I'm 5'3 and he didn't have an inch on me. Note- I'm not against short guys. I AM against guys who lie about their height. Don't be that guy. *Note- Grammarly assessed the tone of this post as "sad" and "disapproving". I'm impressed. Previous Next

< Back Nasogastric Tubes Nasogastric tubes (NGTs) are frequently placed in surgical patients to decompress the stomach and minimize nausea/ vomiting while allowing bowel rest. For intubated ICU patients, this is frequently an orogastric tube, passed from the mouth to the stomach. The anatomy of an NGT Lumen: this is the inner cylindrical hollow conduit that allows gastric contents to be suctioned out and potentially allows medication and nutrition to be given (depending on the clinical situation). Multiple holes to allow gastric contents to be suctioned into the lumen of the tube Side port: if nasogastric tubes were like straws, with only one lumen, they would adhere tightly to the stomach wall when suction was applied. Thankfully, NG tubes have a side port (the blue ventilation port) that allows air to flow into the stomach, preventing the tube from giving the stomach a suction hickey. Markings on the tube indicate how far the tube has been inserted. A white line along the length of the tube (radiopaque). When viewed on an x-ray, the tube position can be confirmed by noting the location of the break in the radio-opaque line, which corresponds with the most proximal hole in the tube. Basic Equipment There is some basic equipment that you need to have at the bedside before inserting an NGT The NG tube and a packet of lubricant A large basin (in case the patient vomits) Suction tubing to connect to a canister with working suction Cup of water with straw (if not contraindicated) Placement Preparation Picking your tube size. Tubes range from 8-18 French. For adults, use 16 or 18. Avoid using a pediatric tube or anything smaller than a 16 Fr. Small tubes will just end up clogged. You can consider having one size smaller just in case you meet a lot of resistance and want to attempt a smaller caliber. Running the tube underwater. Some suggest that warm water helps by making the tube more pliable, others say cold water helps by making the tube softer. I haven't found one to be more helpful than the other. Try and see what works for you. Explain the procedure to the patient. Advise them that they might gag and vomit, and that’s ok. It’s not unexpected when you have a plastic tube through your nose and esophagus. Have the basin ready. Tell the patient their job is to swallow and keep swallowing. Tell them they might feel an urge to cough or gag, but they should try to resist that and focus on swallowing. If not contraindicated (ie aspiration risk, etc), have the patient hold a cup of water (with straw) in the hand opposite from where you're standing. Note- bowel obstruction is not a contraindication- once you place the tube, you will evacuate whatever the patient swallowed. Positioning and insertion Raise the head of the bed and have the patient upright as much as possible and have them put their chin to their chest. Lubricate the end of the tube. Place the tip of the tube just inside the nares and then advance parallel to the floor…not up. You can place your hand on the back of the patient's head to gently keep their head from flying back, which is the natural reaction to a huge piece of plastic in your nose. Keep advancing the tube while encouraging the patient to swallow. The gastroesophageal (GE) junction is usually about 40 cm from the beginning of the esophagus. The tube must get past the GE junction to effectively decompress the stomach. Post-placement Connect your tube to suction. There is a small plastic connector with tapered ends- one end connects to the suction tubing and the other end connects to the clear port. You can place to low intermittent or continuous suction- this is usually provider or institution dependent. You do NOT need a chest x-ray to confirm that an NGT is in the stomach before you place it to suction- if gastric contents are being suctioned, this confirms the position. You DO need a radiograph before instilling medication or enteral feeds. Risks of nasogastric tubes Non-functional tube- an NGT is nothing more than a straw or a garden hose- except for one thing. If you were to place a garden hose into someone's stomach and apply suction, it would just adhere to the stomach wall. This can lead to suction hickeys, which are precursors to ulcers/ bleeding. But most importantly, this will cause the tube to be ineffective. The solution is the blue ventilation port- it allows air to pass into the stomach and keeps the tube from being suctioned against the stomach wall. [this was explained above in the anatomy section- but it's so important that it deserves repetition] Naso-pulmonary tube- accidental insertion into the lung. For an awake interactive patient, this will be evident by your patient's reaction- if they have a tube in their lung, they will cough. This can even cause a pneumothorax (personally never seen it, but it's been described). In an intubated patient, it might not be noticed until x-ray for checking placement. Tube curled and tip directed upward in the esophagus. Two risks- ineffective gastric decompression and misdirected meds and feeds (back up in esophagus instead of into stomach). Aspiration- an NGT essentially stents the lower esophageal sphincter open. So if your patient is lying flat (ie asleep), you MUST ensure that the NGT is functional. Especially in the case of a bowel obstruction (patient can vomit and aspirate) or if your patient has decreased mobility and isn’t able to reposition themselves quickly to avoid aspirating. Clogged tube- risk of aspiration, inability to give meds/ enteral nutrition. The anti-reflux valve You might notice another piece of plastic in the NGT packaging. I didn't mention the anti-reflux valve, that short blue and white plastic piece that suspiciously seems to fit perfectly into the blue ventilation port. According to the manufacturer (CR Bard), this piece of plastic is supposed to be inserted at the end of the blue port and allow air entrainment to prevent the suction hickey on the stomach. It also prevents gastric contents that reflux into the port from spilling onto the sheets. HOWEVER-- the caveat is that when gastric contents are refluxing into the blue ventilation port, it's supposed to be take as an indicator that the valve must be removed and air must be flushed into the blue ventilation port. This is the reason the anti-reflux valves are despised by most surgeons- once the blue ventilation port is coated with gastric contents, if they're not flushed, the NGT is essentially converted to a straw. Yes, the port may spit up some gastric contents. However, the solution is NOT to replace the anti-reflux valve into the blue side port. Instead, the solution is to flush air into the blue port to clear it out . This is the primary task of maintaining a functional tube. You should hear faint sounds of air movement when you listen to the blue port- this means it’s working! [see video] The problem, and the reason we routinely throw these away, is the fact that they aren’t routinely removed and flushed, so they get clogged. When the blue port is clogged, the tube becomes non-functional, which can lead to gastric distension, nausea/ vomiting, and aspiration. “Minimal output” is not always reassuring with an NGT- it might be because the patient is improving, but it’s just as likely that the tube isn’t working because it isn't being maintained correctly. It's not an exaggeration to say this is a life or death issue. An elderly patient with a bowel obstruction and a non-functional tube→ gastric distention + widely patent gastroesophageal junction + laying flat at night→ aspiration, pneumonia, death. Functional tubes are also crucial for patients with foregut procedures. For example, a repair of a stomach or proximal small bowel injury can be protected by a functional nasogastric tube- this minimizes air/ fluid passing by and exerting pressure on the repair. Please note- the blue ventilation port MAY reflux and spill out gastric contents. Two solutions are to place a chux under the end or to place the syringe of a Toomey at the end (see video). Just remember- if this happens, do NOT solve the problem by inserting the anti-reflux valve. Instead, use a Toomey syringe to flush air into the blue ventilation port. CAUTION! There are caveats to this- specifically patients with foregut surgery (anywhere from the mouth through the first part of the small intestine). Patients with these clinical scenarios should have explicit instructions to the nursing staff on how the tubes are to be maintained. But it makes too much noise?! A patient who can complain about a whistling NGT is a patient who is much less likely like to aspirate and need to be intubated than a patient who doesn't have a whistling NGT. But it makes a mess?! See solutions above- chux pad or place a Toomey syringe. How to maintain a functional NGT https://video.wixstatic.com/video/3b6ff6_0ae99743e4244ce6a94c3c6bdd532efd/1080p/mp4/file.mp4 How to use the anti-reflux valve https://video.wixstatic.com/video/3b6ff6_346b85a924454960bd6c4afe6ab037d0/1080p/mp4/file.mp4 So those are the basics. If I didn’t teach you any handy tricks, hold on for one last disclosure… the final secret to my success. I've used this trick many times for patients who are overly anxious or distressed at the process of having an NGT placed. For example, the patient who has had traumatic NGT placements previously (patients have shared so many horror stories with me) or is on edge in general. Two years ago, I was managing a burn patient in the ED. While the ED physician was prepping for a nasal laryngoscopy, he showed me a trick that I still use to this day. Using CTAs (cotton tip applicators, or Q-tips if you insist on a brand name), he anesthetized the patient's nasal passage with viscous lidocaine. He covered the cotton tip of 1-2 CTAs with the clear hair-gel consistency goop (the lidocaine), and then slowly advanced this along the nasal passage. Initially, they sat right inside the opening of the nares, resting for maybe 30-45 seconds. Then the lidocaine was reapplied, and the CTAs were advanced slightly to repeat the process. This continued through the entire length of the nasal passage. In addition to the nasal anesthetic, the patient was given a medicine cup with more viscous lidocaine to swallow. *Note- warn the patient that they MIGHT get the sensation that they can't breathe. They will still be able to breathe fine, but when the upper airway is anesthetized, it alters the sensation of airflow. Previous Next

< Back More Information on Acute Care Surgery The Beginnings of Acute Care Surgery: A Paradigm Shift in Surgical Emergencies. Nelson BV and Talboy GE. Acute Care Surgery: Redefining the General Surgeon. Mo Med. Sep-Oct 2010;107(5):313-315. Acute Care Surgery from the perspective of acute care surgeons. Santry HP et al. A qualitative analysis of acute care surgery in the United States: It’s more than just “a competent surgeon with a sharp knife and a willing attitude.” Surgery. 2014 May;155(5):809–825. A detailed timeline of our history. The AAST History of Acute Care Surgery . Previous Next

Medical Literature Evidence-Based Medicine After you have established a firm foundation of the basics of your chosen specialty, you're ready to develop regular habits to stay up to date on the newest research. Evidence-based medicine is the basis of high-quality patient care, but it can seem overwhelming to try to keep up with the ever-growing body of research. There are countless journals, and it would be time-consuming to search them regularly. So how does one go about navigating the vast ocean of available data? Registering for email alerts is a simple way to get notified when there are new publications. With a quick skim through the article titles to see if anything is relevant, followed by a review of the abstract/ article itself, you can be on the cutting edge of the latest information in your field. Several require individual registration, but it's a very simple and quick process. Many journals require a subscription, often available through your medical school or hospital library. If you are military, you have access to AMEDD Virtual Library (abundant medical resource collection). Thankfully, three publishers (LWW Wolters Kluwer , Springer and Elsevier ) have centralized their journals, so you can quickly subscribe to several journals [these journals are designated by L, S or E]. Medicine and Critical Care Journal of the Ameri can Medical Association New England Journal of Medicine Intensive Care Medicine Critical Care Medicine (L) Current Opinions in Critical Care (L) Journal of Intensive Care (S) Critical Care (S) Journal of Critical Care (E) Critical Care Clinics (E) Surgery World Journal of Surgery World Journal of GI Surgery JAMA Surgery J Gastrointestinal Surg Advances in Surgery Annals of Surgery (L) Annals of Surgery Open (L) BMC Surgery (S) Surgery (E) American Journal of Surgery (E) Journal of the American College of Surgeons (E) Surgical Clinics of North America (E) Advances in Surgery (E) Trauma and Emergency Surgery European J Trauma and Emergency Surgery Trauma Surgery and Acute Care Open Journal of Trauma and Acute Care Surgery (L) World Journal of Emergency Surgery (S) World Neurosurgery (E) Other Specialities Journal of Neurotrauma World Journal of Cardiology JAMA Cardiology JAMA Neurology JAMA Network Open Anesthesia and Analgesia (L) Current Opinion in Anesthesiology (L) Current Opinion in Clinical Nutrition (L) Current Opinion in Infectious Diseases (L) Current Opinion in Neurology (L) Diseases of the Colon and Rectum (L) Journal of the American College of Cardiology (E)

Surgery trainee education. Trauma surgeon. Acute Care Surgery. Collaboration Interested in being a guest contributor? Any suggestions and contributions will be promptly reviewed and added to the appropriate page/ subpage. The contributor will be noted on the website- you can choose if you want your name or Twitter handle or whatever other identification you would like (or none at all if you would like to be anonymous). Content currently under development. Note- this list is NOT all-inclusive. Database of clinical vignettes in key topics of trauma, critical care and emergency general surgery. Focused on more complex scenarios (ie not run-of-the-mill appendicitis)! Please check out the vignettes I currently have to get an idea of what I’m trying to create- and reach out with any suggestions or cases. Literature reviews - deep dives, high-yield articles, etc Procedural or skill tutorials (pre-peritoneal packing, using the ultrasound in critical care, reading a chest x-ray). Each tutorial is followed by a list of primary sources, encouraging readers to pull information from multiple references. If there is any particular procedure or skill that you would like to create a tutorial for, or something that is currently on the website that you would like to enhance (for example, more advanced ultrasound techniques or ventilator settings), please feel free to reach out with suggestions! There is a wide array of other content that you can add to as well. Note templates Recommendations on networking opportunities Recommendations on social media accounts to follow Educational resources (textbooks, journal articles, training courses, web based open access medical education) Please send me an email (form at the bottom of the page) or contact me on Twitter @doc_on_the_run if you have any questions or want to submit something.

Surgery trainee education. Trauma surgeon. Acute Care Surgery. FAQs Why did you make this website? Over these years of learning about the practice of surgery, I've also learned a lot about myself. I am not an expert, and I did not follow a typical pathway- but I have some knowledge and resources to share. As I transition into my new Acute Care Surgeon role after 17 years in training, I'm pausing to share my experience, tips for success, and random nuggets of wisdom. This will be a work in progress, and I look forward to seeing how it evolves. My goal is to share my experience and knowledge in the hopes of helping those who desire to follow this path. But why do we need another medical education website? There are so many good resources already... There are endless ways to explain clinical concepts- pictures, text, analogies, clinical cases, podcast discussions of cases or principles, review articles, etc. There are also different learning styles. When I was trying to grasp advanced ventilator management, I read basic critical care textbooks, a book dedicated solely to ventilator management, and various websites and journal articles. This website is another way to interact with the information. Hopefully you will understand some of the concepts in a new way that helps you remember and apply them in clinical scenarios. In addition, I have also tried to create a comprehensive collection of all the useful resources I know, like apps and open access medical education resources (websites, clinical guidelines, etc) in one place for trainees to What does Doc on the Run mean? The summer before my last year of medical school was the start of my running career. My focus was enjoying the outdoors, not pace or distance. During my residency, I met someone who helped me refine my running. I started timing myself, training, and racing. Within a year or two, I pushed through personal barriers to become a "runner." My first half marathon was on Thanksgiving in my third year of surgical residency. I am at the end of my formal training, I am now an Acute Care Surgeon. As a surgeon, there are numerous factors that I can't control. It's fast-paced, demanding, and dynamic. I enjoy the organized chaos and high-stakes cases. Running is key to my work-life balance. Unlike in the operating room or the trauma bay, I have control over most aspects of my runs- pace, distance, route, and thoughts. It's not chaotic- it's basically the polar opposite of my work. During the day, my mind is going a million miles an hour. When I run, everything becomes clearer- I can solve problems, mull over ideas, or process dilemmas. And perhaps the most concrete impact is the runner's high that I enjoy after finishing. I have continued to run 10Ks, 10 milers, and the occasional 5K or 15K. I have learned more about the science of running (HR training zones, different paces for tempo/ interval/ long runs/ short runs) and I've learned how to adapt training schedules to fit my life. Unfortunately, I have suffered my share of injuries, including most recently nerve impingement in my foot. While I may have scaled back, running will always be part of my identity. Did you really build this website yourself? Yes, I did. No, I didn't do all the intricate coding by myself. But I did design, format, and create the content. So are you a computer/ technology guru? Whatever I know about technology, I learned from my brother and from spending many hours researching problems online. While my parents might consider me an expert, I literally just search online to solve most issues. When I get to the end of the internet and still haven't found the solution, my next step is Apple tech support (obviously only if the problem is with my iPhone or Mac). What did you learn while making this website? - Formatting the working space on a website - URL redirect - Domains and subdomains - Search engine optimization (SEO) - Establishing custom domains - Which text/ background colors are easiest to read - Anchors If you weren't an Acute Care Surgeon, what would you do? I'd be a chef. I love cooking! Is there anything that is overwhelmingly gross in your job? I have had almost every body fluid on me- stool, urine, blood, etc. So very little grosses me out. But I can't stand oral or nasal secretions (aka saliva, slobber, snot, etc.).

< Back Ultrasound: Cardiac Exam Purpose: identify possible causes of hemodynamic instability, respiratory distress, assessment of volume status. Probe The phased array can be used for the entire exam. The curvilinear can also be used for the subxiphoid and IVC views. Views There are 4 basic views, including the parasternal long axis, parasternal short axis, the apical four chamber and the subcostal view. Additionally, the inferior vena cava can be visualized. Cardiac ultrasound is more challenging to learn than most other ultrasound studies, because probe usage (position, angle, rotation, translation, etc) have drastic impact on visualization. It’s necessary to understand what is shown in each view, so take time reviewing these so you can have a better appreciation for what you are seeing when you perform a study on a real patient. One recommendation, if it is difficult to visualize the heart, moving the patient into the lateral decubitus with their left side down can significantly improve visualization as the heart is closer to the chest wall in this position. For video and pictorial explanations of the views, please refer to these sites. Basic Cardiac Views, #1 Basic Cardiac Views, #2 Findings Gross abnormalities- decreased ventricular function, arrhythmias Profound hypovolemia Small hyperdynamic left ventricle with end-systolic collapse Inferior vena cava- assess volume status, either static measurement of diameter or calculation of collapsibility (>50% correlates with volume responsiveness). Respiratory variation (collapsibility/distensibility index). Takotsubo cardiomyopathy Akinesia of the apical and mid-ventricular segment, hypercontractile basal segments. Apical sparing (dilated). Acute cor pulmonale Respiratory disorder→ pulmonary hypertension→ right heart failure. Dilated right heart. Cardiac tamponade Effusion with end-diastolic collapse of the right atrium, effusion in front of the aorta Pulmonary embolism Free-floating thrombus in the right ventricle or pulmonary artery; right ventricular dilation/ systolic dysfunction; septal bowing into the left ventricle; dilated IVC without inspiratory collapse. Most sensitive/ specific indirect sign- right ventricular apical sparing (McConnell's sign). References Guidelines for Performing a Comprehensive Transthoracic Echocardiographic Examination in Adults: Recommendations from the American Society of Echocardiography Previous Next

< Back Cardiac Physiology Cardiovascular Physiology Oxygen Delivery Adequate cardiovascular function is vital to maintaining perfusion to the organs and tissues in the body. Perfusion drives oxygen delivery (O2) and removal of byproducts of cell metabolism (CO2). The amount of oxygen that is delivered (DO2) is a function of cardiac output (CO; the volume of blood ejected from the heart every minute) and the arterial oxygen content (amount of oxygen in the blood). Cardiac output is determined by the volume of blood the heart pumps out into the body with each heartbeat (stroke volume, SV) and the frequency of the heartbeat (heart rate, HR). Stroke volume depends on preload (blood volume returned to the heart), contractility (effectiveness of cardiac muscle activity), and afterload (pressure in the peripheral vasculature that the heart has to overcome to eject blood). Arterial oxygen content (CaO2) is the amount of O2 in the blood that is ejected from the heart. This is determined by dissolved O2 + O2 bound to hemoglobin. Hemoglobin carries O2, and the percentage of Hgb molecules that are saturated (bound) with O2 is determined by arterial blood gas (SaO2, arterial oxygen concentration) or pulse oximetry (SpO2, peripheral arterial oxygen concentration). Pulse oximetry is non-invasive and is a reliable surrogate (as long as SaO2 >90%). The O2 carrying capacity of one gram of hemoglobin is 1.38 (this is a constant in the equation). So this is the first part of the equation: the number of hemoglobin molecules x the % of those molecules that are saturated with O2 x how much O2 saturated hemoglobin can carry . The second part of the equation is the dissolved oxygen (partial pressure of arterial oxygen, PaO2, reported as mmHg). This value is multiplied by the constant 0.003, which is the mL of O2 dissolved per mmHg plasma. This number is infinitesimally small relative to the other half of the equation and it is typically ignored when determining oxygen concentration. This means that the significant modifiable factor in CaO2 is Hgb. Oxygen has to have something to bind to (Hgb) because dissolved oxygen has minimal oxygen-carrying capacity. Oxygen delivery (DO2)= CO x CaO2 Cardiac Output (CO)= heart rate (HR) x SV Stroke volume (SV)= the volume of blood ejected from the heart each heartbeat. Arterial oxygen concentration (CaO2)= [1.38 x Hgb x SaO2] + [PaO2 x 0.003] How can oxygen delivery be increased? One of the components of the equation has to be adjusted. Increase cardiac output. Increase SV- use of an inotropic agent (* medication that increases the strength of the heart contraction), ensure adequate preload (volume resuscitation). Increase HR- use of a chronotropic agent (* medication that increases heart rate). Increase arterial oxygen content Increase blood hemoglobin concentration *See pharmacology below Oxygen Consumption Oxygen consumption (VO2) is determined by how much oxygen the peripheral tissues extract and use. It is the difference between oxygen delivery (DO2) and oxygen return(ed) (SvO2). Oxygen consumption (VO2)= DO2 - SvO2. Oxygen consumption is calculated by subtracting SvO2 or ScVO2 from the amount of oxygen delivered. Venous oxygen saturation (SvO2 or ScVO2)- concentration of oxygen in the blood returning to the heart. Measured with a central venous catheter. *See below under CV monitoring for more details. Cardiovascular Monitoring There are several techniques for monitoring cardiovascular parameters, ranging from non-invasive to maximally invasive. Non-invasive methods include telemetry, pulse oximetry, and blood pressure monitoring. The benefit of these devices is their simplicity of use and interpretation. But these are error-prone, and regarding blood pressure, it doesn't provide continuous monitoring. For more info, see lecture entitled " Hemodynamics ". Arterial lines can be placed to provide continuous cardiac monitoring. The arterial waveform can indicate specific pathology (see Edwards Quick Guide to Cardiovascular Care ). In addition, an arterial line can report stroke volume variation. Stroke volume variation (SVV) is a surrogate of arterial pressure changes with inspiration/ expiration. If the change in pressure with respiratory cycles is >10-15%, it suggests the patient is fluid responsive, meaning they are likely to improve their preload (and cardiac output and blood pressure) with IV fluid administration. Central venous catheters can be placed to deliver intravenous medication as well as provide cardiac monitoring. A central venous catheter can measure the pressure of the blood returned to the right atrium (central venous pressure, CVP), which is a crude measurement of preload and right heart function. In addition, the oxygenation of the blood returning to the right heart (from the head and upper body) is reported as Central venous oxygenation saturation (ScVO2). ScVO2 reflects the balance between oxygen delivery and consumption. Arterial lines and central venous catheters are considered "minimally invasive". A pulmonary artery (PA) catheter is the most invasive device for cardiac monitoring. Similar to a central venous catheter, a PA catheter can determine the oxygenation of the blood returning to the right heart, which is the mixed venous oxygen saturation (SvO2). However, in contrast to the central venous catheter which is located in the superior vena cava (proximal to the right atria), this device is measuring blood oxygenation in the pulmonary artery (from the right ventricle), so it accounts for the blood from the entire body (unlike the ScVO2). Cardiac Pharmacology Vasoactive medications are frequently used in the ICU for the management of shock, heart failure, and other acute pathology. There are several key receptors, and understanding the function of each receptor is the key to using these different agents correctly. Receptors * α (alpha) 1- vasoconstriction * α2- inhibit norepinephrine release from presynaptic neurons * β (beta) 1- chronotrope (↑HR), inotrope (↑Ca in cardiac myocytes ↑contractility), dromotrope (↑cardiac impulse conduction velocity) * β2- vasodilation * Dopa 1- vasodilation * Dopa 2- neurotransmitter release Pharmacologic Agent Classification Each medication has a specific physiologic effect based on its particular mechanism of action. Agents may stimulate or inhibit receptors (see above) or alter the concentration of a key substance (cAMP, calcium, potassium, nitric oxide (NO)). Previous Next

11 < Back Board Examinations American Board of Surgery: General Surgery Boards Exam Prep Master the General Surgery Oral Boards by Dr Hassan Aziz . Dr Aziz reviews key surgical topics, including trauma, thoracic, pediatric, HPB, GI, breast cancer, endocrine, vascular. [Reference courtesy of Hassan Aziz, MD @Sharpknife_Aziz ] Surgical Education and Self-Assessment Program (SESAP). Resource for general surgeons- stay current with the latest surgical knowledge and prepare for examinations. American Board of Surgery: Surgical Critical Care Boards Exam Prep Evidence-Based Practice of Critical Care. 3rd edition, 2019. Reviews the literature regarding specific high yield critical care topics. Trauma, Critical Care, and Surgical Emergencies: A Case and Evidence-Based Textbook. 1st edition, 2010. 64 cases that review the basic principles of ACS. Previous Next

2 < Back Operating General Surgery Texts Chassin's Operative Strategy in General Surgery: An Expositive Atlas. 5th Edition, 2022. Zollinger's Atlas of Surgical Operations. 11th Edition, 2021. Operative Dictations in General and Vascular Surgery. 2012. Acute Care Surgery Texts Operative Techniques and Recent Advances in Acute Care and Emergency Surgery (Aseni). 1st edition, 2019. Surgical Decision Making in Acute Care Surgery. Atlas of Trauma/Emergency Surgical Techniques. Top Knife (Mattox). 1st edition, 2004. High yield of trauma operative management. Back to the basics. Atlas of Surgical Techniques in Trauma (Demetriades). 2nd edition, 2020. Anatomic Exposures in Vascular Surgery (Wind). 3rd edition, 2013. Key anatomic exposures for less commonly encountered injury patterns. Recommended by Dr. Feliciano at AAST 2020 Conference. Videos Surgical Stabilization of Rib Fractures and Cryoablation. Collection of videos of different surgical approaches. WebSurg. Free access to expert videos of minimally invasive surgery. Highly recommend. The Toronto Video Atlas of Surgery. Free access to expert videos of GI operative procedures. [Reference courtesy of EJS @ElliotJScottMD] Difficult Cholecystectomy: A learning module for laparoscopic cholecystectomy How to Tie Knots Like a Heart Surgeon How to Secure Chest Tubes (Soweto Tie) Previous Next