Behind the Knife ABSITE 2026 - Quick Hits 4

</span> All right, dudes and dudettes, welcome back to the Abcite Review. We have one more episode. Quick hits, key terms, associations, all that good stuff ready for you today. All right, we are rocking and rolling here. We're going to have one more episode. Nina, you get to start us off with trauma, burn, and critical care. Patrick: Let's talk GCS. I have a patient who opens their eyes to pain. They're speaking and using inappropriate words. and they withdraw from pain. What is their GCS? Yeah, so their GCS is going to be nine. So open size to pain earns them two points. Inappropriate words is three points. And then withdrawing from pain is four. Patrick: I always remember GCS because I write it the same way in every single note I ever do. I do four, five, six EVM. And every single time I write a trauma note, I have to assign somebody's EVM score in order to remember it. All right, what are some of the basics to head</p><p><span style="color:#808080">

</span> trauma treatment? Yeah, your main goal here is going to be avoiding secondary injury. Patrick: Really, in a lot of TBI, the injury has happened, you just want to make, not make it worse. So, in general, for these injuries, you want to maintain an ICP of less than 20. To do that, you'll elevate the head of bed. You want to get euboxia as one of our attendings calls it. So you want a normal O2, you want a normal end tidal CO2, you want normal blood pressure and normothermia. Patrick: You can consider hypoventilation if they're actively herniating, but in general you don't want to target any particularly low PaCO2. So most people recommend targeting a PaCO2 of between 30 and 45. And then you can use adjuncts like sedation and paralytics, CSF drains and medications like mannitol or hypertonic saline. Patrick: And what about cerebral perfusion pressure? What's the what do we want for that? Yeah. So for cerebral perfusion pressure, you're going to target a CPP</p><p><span style="color:#808080">

</span> of 50 to 70. Okay, this is a little bit controversial, but how long do we often give anti epileptic medications following a severe traumatic brain injury? Patrick: Yeah, typically you can think about these for about seven days after injury. All right, and we're not giving steroids to any of our head injured patients, correct? That's right. All right, so the Acute Restorative Stress Syndrome is diagnosed with the Berlin criteria. What is that? Yeah, so ARDS is diagnosed if you have bilateral opacities, that kind of fluffy chest x ray, not cardiogenic in origin, a P to F ratio of under 300, and it has to be acute, the A in ARDS, so an onset of less than a week. Patrick: You can also then grade it by severity, so mild ARDS has a P to F ratio of 200 and 300, moderate is 100 to 200, and severe ARDS is less than 100. Okay, when it comes to burns, I'm going to use silver sulfadiazine. What are some of the key features or things I need to think about when it comes to using that topical</p><p><span style="color:#808080">

</span> medication? Patrick: Yeah, so silver sulfadiazine has pretty limited scar penetration and isn't effective against some of the gram negative rods that you may see in burn injured patients like pseudomonas. You also can't use it in patients who have a sulfa allergy or G6PD deficiencies because they'll get methamglobulinemia. Patrick: And then really it can also result in neutropenia. So those are just the things you'll watch out for in patients getting wound care with silver sulfadiazine. How about silver nitrate? This also has pretty limited eschar penetration and is ineffective against some of those GNRs, including sued and also can result in some electrolyte imbalances, right? Patrick: So a key question, stem burn patient using topicals. They have electrolyte imbalances. That'd be silver nitrate. Last methanide acetate. Yeah, this one will give you a better escarp penetration, but it is pretty painful for patients. It also gives you better coverage of bacteria but can also result in metabolic acidosis. Patrick: So keep an eye out for that. Okay. Fractional excretion of</p><p><span style="color:#808080">

</span> sodium. What is the formula? How do you remember it? Oh yes, sweet FINA. So I use this in case of an AKI to identify how the kidneys are handling sodium. You calculate it by taking the urinary sodium times the plasma creatinine over the plasma sodium times the urine creatinine. Patrick: And then it'll give you a ratio. So a FINA of less than 1 percent indicates a pre renal AKI, whereas a FINA of greater than 2 percent indicates an intra or post renal AKI. Right. So U. P. Over P. U. And you sodium first creating second. All right. So the respiratory quotient is something that comes up on the ab site. Patrick: I'm an intensivist and I don't use it frequently or ever in practice. But what are we talking about when we look at the respiratory quotient? What might indicate? Yeah, for some reason Absite loves this. So the respiratory quotient measures the volume of CO2 produced versus the volume of oxygen consumed. Patrick: So it's basically a measure of energy expenditure and fuel</p><p><span style="color:#808080">

</span> sources have characteristic respiratory quotients. So fat has an RQ of 0. 7, protein 0. 8, and carbs of 1. If you have a respiratory quotient of greater than one, that indicates that you might be overfeeding your patient. Whereas a respiratory quotient under 0. Patrick: 7 indicates starvation or ketosis. All right. And what are some of the basic nutritional requirements when it comes to our ICU patients? Yep, so for a normal adult, they need about 25 to 30 kilocalories per kilogram per day and one gram of protein per kilogram per day. In a hypermetabolic state, which is a lot of our trauma or other critically ill patients, this will increase, so those patients require 30 to 35 kilocalories per kilo per day, or 1. Patrick: 5 to 2 grams of protein per kilo per day. Finally, you've got the special case of burns, which is super highly metabolic. And those patients require kilocalories per kilo per day and 2 to 2. 5 grams of protein per</p><p><span style="color:#808080">

</span> kilo per day. All right, true rapid fire. I have concern for rectal injury. How do I diagnose it? Patrick: Take a look, do a proctoscopy. Okay, I've confirmed the rectal injury, how do I treat it? Divert them. Okay, I got a bad liver injury, there's persistent bleeding, and I did a perineal maneuver that didn't help. Where's the bleeding coming from? Yeah, you're gonna look for an IBC injury or a hepatic vein injury. Patrick: Big scary. Yeah. What injuries are associated with chance fractures? duodenal or pancreatic injuries. Okay. I have an open book pelvic fracture. How do I start by treating it in the trauma bay? Yeah. Put a binder on that patient and don't put it over their ASIS, put it over their greater trokes. These are patients where you can consider angioembolization in the IR suite if it's available or pre peritoneal pelvic packing. Patrick: Yeah. Or both sometimes. What am I going to see if I have an intra peritoneal bladder injury when it comes to, let's say, a CT a cystography? Yes, if you</p><p><span style="color:#808080">

</span> injected contrast into the into the bladder, then a intraperitoneal bladder injury will show up on your CT as contrast that kind of pulls around and outlines the small bowel. Patrick: These you want to repair surgically, so you're going to take them to the operating room and repair the bladder in two layers with absorbable suture. All right, and contrast that with an extra peritoneal bladder injury. Yeah, this one you won't see as clear delineation of things. You'll see kind of a flame like extravasation of extraperitoneal contrast into the retroperitoneum, and these ones are great because you don't have to take them necessarily to the OR. Patrick: You can treat these generally with a Foley catheter for about two weeks. Great. What are some key features of the pregnant trauma patient that shows up in your bay? Yeah, so the first thing you want to do is estimate the gestational age of the fetus. So, they, if the uterus is palpable at the level of the umbilicus, that generally indicates a gestational age of about 20 weeks. Patrick: And most fetuses or in most places in the United States, the fetus is considered viable if it's over 24</p><p><span style="color:#808080">

</span> weeks old. Great. You want to position these patients left side down to deload the CAVA. You want to do fetal monitoring if the patient has a viable fetus. You'll do a pelvic exam in these patients to look for blood or clear fluid, which could indicate rupture of membranes. Patrick: And then finally, in this case, if you have a patient who would otherwise get a trauma CT scan and it's clinically indicated, you will do a CT scan. Don't worry about the radiation exposure. All right. So I've got a patient that I'm concerned about compartment syndrome. What are those six Ps? How am I going to treat it? Patrick: Yeah, I basically just put this one in here to say the word poikilothermia. So the six P's include pain, pallor, poikilothermia, pulselessness, heresies, and paralysis. And for a patient with a concern for compartment syndrome, it's a clinical diagnosis, I'm doing a fasciotomy as soon as I can. Right, so the six P's are cute and all, but this is a clinical diagnosis. Patrick: If the clinical context is appropriate for it, you have concern that the patient</p><p><span style="color:#808080">

</span> has compartment syndrome. Don't delay, just perform that fasciotomy. How do I work up a patient with a penetrating injury to the extremity, among other things? Yeah, so these are patients where you're going to get an ABI or BBI, and that should be about one in patients. Patrick: Right, so ankle brachial index or brachial brachial index. All right, so I have a kidney laceration. This is a little bit different than spleen and liver. How so, how am I going to approach these? Yeah, you generally want to spare the kidney if you can they're more likely to heal on their own and not bleed out because they're in a contained space in Gerotis fascia. Patrick: So they can be decompressed with ureteral stents or percutaneous drains. As long as the kidney is viable when you explore in the operating room, you can leave it be and leave drains. Right. But injury to the pancreatic head, how do I approach treating that? Yep, so you suck the head and you eat the tail, right? Patrick: So you're gonna put drains into a pancreatic head injury,</p><p><span style="color:#808080">

</span> and then you'll perform an ERCP to look for a ductal injury. If you find one, you can stent across it. Rarely in really severe injuries, you may have to perform a trauma whipple. Contrast that with the laceration to the tail of the pancreas and one that involves the duct. Patrick: Yep, you're going to eat the tail, so you're going to do a distal pancreatectomy. If you can spare the spleen, you will. Okay. I have a patient who was in a blunt I guess I'd say a high speed car accident. And there's a little bit of funniness on the CT scan. Maybe mention of a little bit of bowel thickening, a small amount of free fluid in the pelvis. Patrick: And they have a high white blood cell count. What am I going to do with them? Yeah, this is a great case for an occult injury, usually to a hollow viscera. So you're going to do a diagnostic lab to take a look. Okay. I have a penetrating injury to the anterior wall of the stomach. What am I obligated to do? Patrick: Lip it over and look at the posterior wall. You can have two injuries that you don't want to miss. Yeah. What's the main treatment for aortic dissection? At least initially. Yeah, so</p><p><span style="color:#808080">

</span> this is going to be your impulse for control. So keeping your heart rate and your blood pressure within normal limits and you typically are going to want to start with an esmol drip for that. Patrick: I have a blunt aortic injury with pseudoaneurysm. Let's say at the isthmus Well, how do I treat that? Yeah, you're going to call your vascular colleagues and you're going to get an EVAR going stat. I have a penetrating injury to the heart. What's next? Medium sternotomy. You want to intubate these patients in the operating room because if you wait around too long in the trauma bay, you're going to be very sad when you induce anesthesia. Patrick: All right. What's the difference between neurogenic shock and spinal shock? So neurogenic shock often will present with hypotension, maybe with bradycardia, especially if it's a higher level neurologic injury. Spinal shock is an absence of reflexes that you'll often see. Often the bulbocavernosis reflex will be go, will go, and this occurs immediately after an injury. Patrick: an injury, but eventually these reflexes will return. Any residual</p><p><span style="color:#808080">

</span> deficits that are still persistent after the other reflexes return are typically permanent. And how do I like to resuscitate trauma patients? You're going to limit your crystalloid resuscitation, preferably give them whole blood or one to one to one product resuscitation. Patrick: Balanced resuscitation. What are the three main goals of a damage control laparotomy? So you want to control bleeding, control contamination, and get the heck out of there. So these are patients you want to leave temporarily closed and so you can get them up to the ICU and restart resuscitating them. Patrick: Right. What are some of the indications for damage control surgery? So these are patients who you're worried that they might die on the operating room table. So patients who are kind of in that lethal triad of acidosis, coagulopathy, and hypothermia. Patients who have competing injuries that are also urgent and need to be addressed, like brain injuries patients who are best served by packing, so these are like your severe liver injuries that require packing and then a trip to IR potentially from</p><p><span style="color:#808080">

</span> the operating room, or those patients who have kind of sketchy findings but things you want to take a second look at, so bowel ischemia, duodenal, or pancreatic injuries. Patrick: So I use a FAST exam to look for free fluid within the abdominal cavity. That being said, FAST exam does not show me fluid where? In the retroperitoneum, so you can't really ultrasound that very well. And so this might include aortic injuries, IBC injuries, kidney injuries, and severe pelvic fractures. So you can miss some pretty important stuff there. Patrick: Okay, I have a sick patient who's in the trauma bay and they're going to need to be intubated. What do I need to think about first? I have a feeling we're going to have a episode about this at some point, but we are going to try to resuscitate that patient in the trauma bay before we try to intubate. Patrick: What's the anatomic structure you're going through when placing a crick and why are you going through that area? Yeah, crikes are there to have emergency airway access. You want a prominent, easy to access point, which is the cricofibroid membrane. All right,</p><p><span style="color:#808080">

</span> Dan, let's talk pediatric surgery. How do I calculate maintenance IV fluids for tiny people? Patrick: Yeah, so I want to think of the 4 2 1 rules. So 4 cc's per kg for the first 10 kilos, 2 cc's per kg for the next 10 kilos, and 1 cc per kg for every kilo over 20. And the AAP recommends that patients 28 days to 18 years of age that require maintenance IV fluid should receive isotonic fluids with appropriate KCL and dextrose because they significantly decrease the risk of developing hyponatremia. Patrick: Can you describe the difference between pulmonary sequestration and a congenital pulmonary airway malformation or CPAM? Yeah, so a sequestration is you have no communication with the airway and you and usually find this systemic blood supply coming off the aorta and these can be intralobar or extralobar. Patrick: Whereas CPAM, the congenital pulmonary airway malformation, this is a portion of malformed lung</p><p><span style="color:#808080">

</span> that communicates with the airway. Both can present with infection most commonly and the treatment of each is lobectomy. What's the most common mediastinal mass in children? So neurogenic tumors, such as a neurofibroma or neuroganglioma are most common. Patrick: This is in the posterior area of the metastatum. And if you have a, an anterior metastatum mass lymphoma is the most common. And we covered this earlier, but what's the most common colitical cyst and how you're going to treat it? Yes. This is that type one where you have the dilation of the entire CBD and this is treated with resection and hepatico J. Patrick: Okay. Tell me about CDH or continual diaphragmatic hernia. So 80 percent of these are on the left side and we think of left posterior being the bactelic or back into the left. And then you can have an anterior CDH, which is called the more gag knee. A majority of these have other associated abnormalities and in regards to management of these overall, you want to stabilize before surgery. Patrick: So this may</p><p><span style="color:#808080">

</span> require intubation either with standard vent or oscillator. These patients may need ECMO. We'll place an NG tube to decompress the bowel and pump them with fluids. What's the number one solid abdominal malignancy in children? Yes, this is a neuroblastoma, most commonly found in the adrenals. Patrick: These may spontaneously regress, and these are much lower risk if diagnosed less than one year of age, and treatment of these is chemo and surgery. All right, what is a Wilms tumor and how do we treat it? So Wilms tumor is nephroblastoma. So it's usually an asymptomatic abdominal mass. It frequently metastasizes to bone and lung. Patrick: And for treatment, you want to think of nephrectomy, plus or minus chemotherapy. And when you are resecting these, the biggest thing is you do not want to spill the tumor because that will upstage it. How do you kids typically present when they have pyloric stenosis? And then furthermore, how do we work them up and treat them? Patrick: Yes, this is a 3 to 5</p><p><span style="color:#808080">

</span> week old that's presenting to the Evie with projectile vomiting every time they feed after vomiting. They seem to be hungry again on abdominal examination. Usually, when they're in the or their abdomen is relaxed. You can feel this firm all of like mass in regards to the. Notorious labs for this. Patrick: It's the hypochloric hypokalemic metabolic alkalosis, which needs to be fixed prior to surgery. So you really want to resuscitate these patients and correct their electrolytes before going to the O. R. These patients can be diagnosed with ultrasound. And you can think of pyloric stenosis being pie 3. Patrick: 14. So muscle thickness is greater than three and the length is greater than. Thank you. One four or so you give length greater than 14 millimeters and we're going to treat these patients with the pylor myotomy How about intussusception in children? What's the most common cause and how do they present? Patrick: Yeah, so this is commonly a patient may have some sort of a virus and then they get inflamed pyre patches Which</p><p><span style="color:#808080">

</span> can be the lead point to these intussusception It can also be caused by lymphoma or meckles and then you want to reduce these with an air contrast enema Right. Air contrast enema. All right. Patrick: Do I know Teresa? How do these kids present? How are we treating them? Yeah. So a lot of these are actually found prior to birth or just shortly after birth. With a large double bubble sign seen on x ray. They had bilious vomiting. This is number one cause of duodenal obstruction in newborns, and it's due to a failure of recanalization of the bowel, which compared to jejunal atresia is caused by intrauterine vascular accident. Patrick: And so 20 percent of these patients usually have Down syndrome as well. So you want to make sure you do a good cardiac screening in this patient population. And so, treatment for this is the duodenal duodenostomy. What's the most common type of tracheoesophageal fistula? So this is the type C, which is the most common. Patrick: It's about 90%. So this is proximal esophageal</p><p><span style="color:#808080">

</span> atresia with a distal te fistula. And what kind of abnormalities are associated with these findings? Yeah, so you really wanna think of the ral being in vertebral, anorectal, cardiac te fistula, radius, renal and limbs. All right, Dan, I got a newborn who's not pooping. Patrick: What's one of the top things you want to think about? Yeah, so there's a lot to think about here. But one thing is to think about is meconium ileus. And so with this, you'll have a distal ileal obstruction. Usually diagnose and treat this with a gastrographin enema and N acetylcysteine enemas. And you want to check for cystic fibrosis. Patrick: Another one too is Hirschsprung's you want to think about. Great. And necrotizing enterocolitis in a child these often present with bloody stools after formula feeding in a premature infant. How am I going to diagnose that and what's the treatment? Yeah. So it's very common to see pneumatosis intestinalis on x ray, which is that air in the wall of the bowel. Patrick: If</p><p><span style="color:#808080">

</span> it gets pretty severe, you can have some portal venous gas as well. So primarily you want to. Stop feeds, make the patient NPO, start antibiotics, resuscitate this patient, and have a low threshold to operate if they have perforation. Okay. Describe the difference between gastroschisis and an emphylocele. Patrick: Yeah. So gastroschisis, this is the right of, on the right side of the umbilicus, it does not have any sac to it. It has a low risk of associated abnormalities compared to the emphylocele, which is the O, which I think of as the umbilicus. It comes out from the umbilicus. It does have a sac around it and has a higher risk of other associated abnormalities. Patrick: I've also seen that O for omphalocele drawn like a heart, so it tells you they're going to have cardiac abnormalities and need an echo. Great, so let's finish up with the most painful section, biostatistics. This is going to be Dan and Nina. You guys get to play together. Dan, What's a cohort study? Patrick: Yeah, so this is an</p><p><span style="color:#808080">

</span> observational study where you're looking at exposure versus non exposed. It can be prospective or retrospective. And one of the big things for AppCite is that you can calculate a risk ratio with a cohort study. Okay, Nina, a case control study. Yeah, so I think if this one is like the cheapo version where you wanted to do a cohort study, but you only have people who are picked based on their outcomes. Patrick: So you, instead of picking somebody based on exposure, like a cohort you pick based on outcome, it's also observational. These are all retrospective. You compare your cases to your controls, and they're good for rare diseases or diseases that are otherwise really hard to study. Your measure of risk here is an odds ratio after a case control study. Patrick: Excellent. Dan, type one error. Yeah, so this is when the null hypothesis is rejected incorrectly and the associated metric is the alpha value, which is associated with p value. Okay, Nina, type 2 error. Type 2 is when you accept the null hypothesis when it's actually</p><p><span style="color:#808080">

</span> incorrect. Your sample size is usually too small because type 2 error is decreased by increasing the power of your study. Patrick: I remember this by thinking about type 1 and type 2 error by the boy who cried wolf. So in that story, the villagers committed a type 1 and then a type 2 error in that order. All right, Dan if I say the P is less than 0. 05, how do you describe that in words? This is a less than 5 percent likelihood that the difference is due to chance alone. Patrick: Nina, what's a student's t test? sO your t test is going to compare the means between two independent groups, and this is for continuous data only, data that you can calculate a mean on. How about ANOVA, Dan? This compares means between over two independent groups, and this would be continuous variables only. Patrick: Okay. Paired at t test, Nina? This one's a little tricky, so it's still comparing means, still comparing between two separate groups, and still comparing continuous</p><p><span style="color:#808080">

</span> variables only, but the groups are the same people. So this would be what you'd use if you were, for example, comparing pre operative and post operative weights of patients who underwent a Roux en Y versus a sleeve gastrectomy, where each patient's serving as their own control. Patrick: All right, Dan. A chi squared. Okay. So this compares two groups with categorical variables. So example of categorical variables are hair color, eye color, gender, diagnosis of post op PE, or the development of a surgical site infection. Okay. And the most commonly tested biostat question, sensitivity, specificity, Positive predictive value and negative predictive value. Patrick: This is your four squared table. Nina, can you explain that to us a little bit? Yeah, this is tough to do without the visual of that four table, but I actually write that on every scrap sheet that I use during app site. So your top corner is going to be your. So your left side and your rows are going to be the test. Patrick: It's going to be yes or no. And then the top is going</p><p><span style="color:#808080">

</span> to be your disease, yes or no. So you'll end up with four boxes that say true positive, false positive, false negative, and true negative. I think of sensitivity as the likelihood of being positive in disease. Some people also say snout or sensitivity will rule out a diagnosis. Patrick: And this is going to be your true positive over your true positive plus false negative. Specificity, I think of in med school, my professor taught us that the NIH is very significant specific. And so you do negative in health is your specificity, and that's your true negative over your true negative plus false positives. Patrick: PPV and NPV are more relevant to the prevalence of diseases in the in the population. And this is actually how you would interpret and talk about a test in most cases with the patient, because typically they're getting a test result and what they want to know is, do I have the actual disease? So in positive predictive value, you're taking the true positives over the true positive plus the false</p><p><span style="color:#808080">

</span> positives. Patrick: Finally, in a negative predictive value, you're taking true negative over true negative plus false negative. We'll draw this out and put it in the show notes for this episode because it's painful to describe. All right. And that is a wrap. Thank you so much for listening. Nina and Dan, thank you so much for participating and for helping prepare this awesome review. Patrick: We wish you guys And gals, all the best of luck on the exam. We know you'll do fantastic again. Thanks for listening to behind the knife. Please do not be shy about leaving us a review, especially on Apple and Spotify. It does help us an awful lot. Dominate the day. We'll see you next time.</p></body></html>