Excellent. Thank you Dr. Diaz and thank you to members of SCCM for the privilege of the podium. It's an honor to present. I have three financial disclosures, all of which are listed there. I have three objectives for the talk. First, I want to help you appreciate the epidemiology and significance of chest wall injury in the United States. Second, I'll discuss the pertinent components of chest wall anatomy and pathology of rib fractures. And third, and really the focus of the talk, I'm going to describe the current state of non-surgical pain management strategies for mechanically ventilated patients. So let's talk briefly about the epidemiology and significance of chest wall injury. I really like to describe the epidemiology of rib fractures as the three C's. They're common, catastrophic, and costly. The reality is, as a rib fracture, they're frequently encountered in the trauma bay in the ICU. Approximately 10 to 40% of patients will present as a trauma in the United States with a rib fracture, which equates to 4 to 17 million injury-associated rib fractures seen in the U.S. per year. Now, rib fractures are also catastrophic due to their morbidity, causing pneumonia, among other conditions. And concerningly, there's a stepwise increase in the morbidity based on the number of ribs fractured. Rib fractures can also be fatal for patients with clinical flail chest. There's an associated 16% mortality, which jumps to about 42% in the presence of concomitant pulmonary contusion. Finally, rib fractures are costly. In 2017, it cost about $8,000 per rib fracture for a patient hospitalized for chest wall trauma. Patients with rib fractures also take a mean 44 days to return to work, and over 60% of patients with clinical flail chest haven't returned to work in five years. So why are rib fractures so morbid? Understanding the chest wall provides some insight into the pathology we witness with untreated rib fractures. Now, the function of the chest wall is really twofold. First, to enable volumetric change, which facilitates gas exchange, and then second, protection of underlying visceral structures. And the bony infrastructure of the chest wall is the foundation for these functions. The bony structure is composed of seven true ribs with direct cartilaginous connection to the sternum, three false ribs attached to the ribs of seven, and two floating ribs, ribs 11 and 12. The sternum is composed of the manubrium body and xiphoid, and finally, the costus sternal and costal margin connect all of these bony structures. And the muscles that contribute to the first function of respiration are predominantly the diaphragm and intercostal muscles. The phrenic nerve originating from the anterior rami of the C3 to C5 nerve roots provides a motor sensory and sympathetic innervation of the diaphragm. The intercostal muscles are innervated by the corresponding intercostal nerves running under the rib and the intercostal groove. And importantly, because of the close proximity of the intercostal nerve to the rib, when a rib is fractured, there is direct mechanical trauma that repeatedly plagues that intercostal nerve. And the bony structure of the chest wall moves a lot, and it comes as no surprise to this group, 16 to 20 times per minute. Now, with each breath, the sternum moves anteriorly and superiorly, the pump handle movement, and at the same time, the ribs are moving superiorly and laterally, the bucket handle movement. And combining these two movements enable the volumetric change needed to drive pressure differentials in the chest. Now, in addition to the muscles of respiration, there are a number of other important muscles that contribute to the structure of the chest wall. On the interior chest wall, we have the external oblique, pectoralis major, pectoralis minor, serratus anterior, and the intercostal muscles I just described. Similarly, posteriorly, the chest is protected by the latissimus dorsi, the ascending, transverse, and descending portions of the trapezius, rhomboid major and minor, serratus posterior, and the rector spinae. Combined, all of these muscular structures provide structure and function to the chest wall, and the muscles and fascia that surround them also provide opportunity for the plane blocks that I'm going to discuss a little bit later. Now, before we talk about how to treat pain associated with rib fractures, I want to talk a little bit about the anatomy of the rib fractures themselves. As a rib fracture is not a rib fracture is not a rib fracture. I think we can all agree that the three mechanisms of injury that you see here are likely to be associated with considerably different forces. The fractures likely, after getting thrown and trampled by a bull, are going to be a lot different than the fractures from ground level fall. So while both pictures of eggs are correctly termed cracked, there is quite a bit of difference between the cracked egg on the left and the cracked egg on the right. And the same is true of rib fractures. There are important anatomic distinctions that need to be made to delineate what is a, quote, fractured rib. And being able to distinguish between these and the severity of rib fractures is important as we talk about treatment options. So to address variability and nomenclature, in 2019, the Chest Wall Injury Society released a taxonomy document where we as a society provided standardized terminology for rib fractures. Now, there are three important takeaways. The first is the complexity of the fracture. In the upper diagram, you can see the difference in fracture morphology, ranging from a simple fracture on the left to a complex fracture on the right. In the diagram below, you will see a pictorial representation of displacement. The rib fracture on the left is an undisplaced fracture with greater than 90% cortical contact, where on the right is a displaced rib fracture with no cortical contact. The third important taxonomic distinction made by the CEWS document is that between clinical flail chest and a radiographic flail segment. Clinical flail chest is paradoxical movement of the chest wall during respiration, which you can see here in the video. Similar, but not identical, is a radiographic flail segment, which is three or more ribs broken in two or more places. Clinical flail chest is actually a relatively rare clinical entity, while radiographic flail segment is common. Patients with flail chest, by definition, will have a radiographic flail segment, but a patient with a radiographic flail segment might not and often doesn't have clinical flail chest. Now that we have a common vernacular and you see the terminology I'm going to be using to describe different types of rib fractures, I want to transition and discuss how these rib fractures then result in the pathology we see among injured patients. I like to describe the natural history of under- or untreated rib fractures as the rib fracture train of pain. When a patient comes in with rib fractures, the uniform primary complaint is pain, which in and of itself isn't too much of a problem, but once that pain train leaves the station, patients are off for a pretty rocky ride. With pain, a patient starts to splint. This impairs the patient's ability to deep-breathe to cough. The patient begins to hypoventilate, further limiting their ability to clear their airway. Then a patient begins to develop atelectasis, increasing the potential for a mucus plug. This atelectasis, combined with the potential for underlying pulmonary contusion, sets the patient to develop hypoxemia and ventilation perfusion mismatch. To compensate, the patient becomes more tachypneic. Their breathing goes up, their kidney worsens, until the patient eventually develops respiratory fatigue, causing their train to fall off the cliff, ultimately requiring intubation. Which really brings us to the primary focus of this talk, the non-surgical pain management of mechanically ventilated patients with injured patients with rib fractures. Now, currently we do have interventions to help stop this pain train in its tracks, preferably before a patient gets intubated. These interventions, including opiates, NSAIDs, and local and systemic lidocaine, ketamine, among others, are important ways we address acute chest wall pain in both the intubated and non-intubated patients. In addition to mechanical ventilation to address hypoxemia and VQ mismatch, we can also use ECMO for salvage therapy. But for the rest of the talk, we'll discuss interventions to address pain, control for rib fractures in the mechanically ventilated patient. Now, given that we're going to be focusing on the mechanically ventilated patient, I'm prompted to not discuss multimodal pain regiments and pulmonary hygiene bundles, which are more commonly implemented in an attempt to mitigate the need for intubation. Instead, I will describe the existing data for local regional pain control options and systemic therapy with lidocaine or ketamine. So I'm going to begin by briefly reviewing the five common local regional pain control options, epidural catheters, paravertebral blocks, serratus anterior blocks, erector spinae blocks, and intercostal nerve blocks. Now, an epidural involves placement of a small catheter into the epidural space using southerner technique, allowing for bolus or continuous administration of local anesthesia or opioids. The medication then distributes locally throughout the epidural space, disrupting nerve transmission within the spinal cord, spinal nerve roots, and dorsal root ganglia. However, contraindications, including coagulopathy, concomitant injuries, or increased intracranial pressure, as long as this is one of the more challenging blocks to place, can limit applicability in trauma patients. The paravertebral block involves injection of local anesthesia into the space immediately lateral to where the spinal nerves emerge from the intervertebral formula. As the local anesthesia spreads throughout the fascial plane, unilateral sensory motor and sympathetic blockade can be achieved, and a single injection or continuous catheter can deliver an infusion. The serratus anterior block accesses the serratus anterior fascial plane, either superficial or deep to the serratus anterior muscle. Injection of local anesthesia into this plane targets the lateral cutaneous branches of the thoracic intercostal nerves, providing targeted anesthesia to the anterior two-thirds of the chest wall. The erector spinae block involves introducing a catheter or needle through the trapezius, rhomboid, and erector spinae muscles, accessing the suberector, spina, and fascial plane using the transverse process of the spine as a landmark. Local anesthesia is applied into this space, and while the exact mechanism of action remains controversial, it is generally thought that diffusion of local anesthetic into the paravertebral space or blockage of the ventral and dorsal or rheumae of the spinal nerves results in analgesia. Finally, the intercostal nerve block involves application of local anesthetic to individual intercostal nerves of a given rib. This enables blockage of the ipsilateral sensory and motor fibers of the intercostal nerve, but is limited by minimal diffusion. So for mechanically ventilated patients with rib fractures, there really are two questions in my mind. First, should local regional blocks be used to augment, commonly used systemic therapy, i.e., systemic opioids and other sedation agents in patients with rib fractures? And two, if they're going to be used, what local regional blocks should be used? Let's begin with the first question. I would argue that the answer to the first question really is a strong maybe. I'll explain my reasoning by going through the Eastern Association for the Surgery of Trauma Guidelines from 2016. In these guidelines, the authors actually address this question directly with three of the five PICO questions that they used to address the benefit of epidural, paravertebral, and intercostal nerve blocks compared to non-regional pain control modalities. After application of rigorous systematic review methodology, the authors used 12 studies for the meta-analyses. Of note, the acceptable quantitative data was sparse for paravertebral and intercostal blocks, so the authors only reported quantitative data combined for meta-analyses for epidural catheters. So when comparing pain scores at 24, 48, and 72 hours, the epidural analgesia group had lower pain scores at 24 and 48 hours, but not at 72, and the analysis was limited as the result was largely driven by a single study. The total number of patients was small, and heterogeneity was high. Similarly, for pulmonary complications, there was no difference between epidural analgesia and opioid controller groups with very high heterogeneity and wide confidence intervals. And due to the very high heterogeneity of results reported for pulmonary function tests, the meta-analysis was actually not performed for this outcome, and due to the absence of RCTs for mechanical ventilation, quantitative analysis was also not possible. But it was noted that among the three RCTs that reported duration of mechanical ventilation, the duration of mechanical ventilation was shorter. Among the three observational trials that reported need for mechanical ventilation, patients managed with an epidural had a 2.2-fold greater odds of requiring mechanical ventilation. There were no difference in mortality between treatment modalities with high heterogeneity between studies, and all had a high risk of bias. For hospital length of stay among RCT, epidural use was not associated with an increased length of stay, but among the observational studies, epidural use was associated with a two-day increased length of stay. Similar but not identical discrepancies were found when evaluating ICU length of stay. Among the RCTs, epidural analgesia was associated with shorter number of ICU days, but when evaluating only the high methodologic studies, no difference was found. So for mechanically ventilated trauma patients with river fractures, should local regional blocks be used? I use them in my practice, and I know they're commonly used in other trauma centers. But actually based on available data, I think support could best be listed as maybe. Maybe epidurals improve pain control, maybe they shorten the duration of mechanical ventilation, and maybe they decrease the time a patient spends in the ICU. But should local regional blocks be offered to all patients? I think the data is far from clear. Which brings us to the second question. If a local regional block is to be used, what block should be offered? And interestingly and unfortunately, the data here is similarly quite sparse. There have been no RCTs comparing efficacy of these five interventions head-to-head in patients with river fractures, and the data is even more sparse among mechanically ventilated patients. But I'll briefly describe some of the data that's available to help inform answers to this question. In 2009, Moda et al. performed a single institution retrospective intervention study comparing thoracic epidurals to thoracic perivertebral blocks. Patients were evenly divided into treatment arms. Unfortunately, no distinction was made from mechanically ventilated patients, and as you can see from the graph on the right, the authors found that both thoracic epidural and perivertebral blocks both provided good pain relief and improved respiratory function, but there was no significant intergroup difference. However, hypotension was more common in the epidural group. This was followed by a study by Brett et al. in 2015 who reported a single institution retrospective cohort study comparing intercostal nerve block to epidural among patients with rib fractures. 107 patients were included, with slightly more in the intercostal nerve block arm. For the composite primary endpoint of pneumonia respiratory failure, no difference was identified. In 2019, Lynch et al. performed a multi-institution retrospective cohort study comparing intercostal nerve blocks to epidurals, including 85 people, evenly distributed. Only eight patients total in this group were intubated, and no difference was found between groups. Unfortunately, no data was available on length of mechanical ventilation in pneumonia. In 2020, Ball et al. performed a single institution retrospective study comparing epidurals and perivertebral blocks to serratus anterior blocks and critically injured patients using historically matched controls. Of the 39 patients included in this study, 24 patients had been intubated prior to the blocks being placed with near equal distribution between groups. However, the pre-block RISB differed between the two interventions groups. There was no difference in the amount of the RISB change between groups. Finally, in 2020, Sheetz et al. performed a single institution retrospective review of patients comparing those who received epidurals to those who received intercostal nerve blocks with liposomal bupivacaine. 116 patients were included, although patients who were intubated before during the initial trauma assessment were excluded. In the reviewed group, only 12 patients were intubated with more in the epidural group. Authors found that patients with intercostal nerve blocks were less likely to require intubation, had shorter hospital lengths of stay, and ICU length of stay, but there was no difference in ventilator-to-days mortality. So to answer the question for mechanically ventilated patients with rib fractures, what local regional blocks should be used, I think the only reasonable answer, based on available data, is that it really depends. There is inadequate data to say that one local regional intervention is better than another for mechanically intubated patients with rib fractures. Local regional pain interventions should be offered, maybe, but they have to be tailored to each individual patient. Because the reality is that each of the possible local regional blocks options have unique features that make them more or less suitable for different fracture patterns, with contraindications that may limit applicability for the polytrauma patients, and possible side effects considerations that must be accounted for. And ultimately, one size of local regional block will not work for all patients, and having a multitude of block options with a clinical decision algorithm accounting for the risks and benefits of each block type is a sensible way to approach the decision about what block to obtain for a given mechanically intubated patient with rib fractures. Now, there are numerous examples of such guidelines. I've included the guideline we use at Stanford on the left, and the guideline published by University Hospital Plymouth as an example. I'm gonna transition and discuss another burr-going local regional pain control option, intercostal cryoneuralysis. Now, cryoneuralysis, or cryoablation, involves the direct application of cold to nerves, which destroys the nerve axon. However, the epineural and perineural tissue remain intact, providing a scaffold over which the axon can regenerate. Now, freezing the nerve provides durable, targeted analgesia for three to six months, and efficacy of intercostal cryoneuralysis has been demonstrated in patients undergoing thoracic and breast surgery, leading to decreased opioid requirements and reduced hospital length of stay. However, to date, this technology has not been specifically applied at a large scale to mechanically ventilated patients with rib fractures. Now, cryoneuralysis can be formed operatively or percutaneously using CT or ultrasound guidance. A cryoprobe is placed two to three centimeters from the spine at the location of the red dot on the image. This enables the interventionalist to target the ventral rami of the intercostal nerves. Then, temperatures of at least negative 60 degrees Celsius are applied for two minutes. The probe thaws, and then the probe is reapplied to another rib space. In the image series on the right, you can see on the upper image, the frozen probe applied intrathoracically, with the lower image showing the thawed probe having been moved down a rib space. Now, there are several caveats to this methodology. One can only target intercostal nerves three through nine. If you freeze too high, you can cause a Horner syndrome, and if you freeze too low, you get a pseudohernia. If freezing is performed too close to the spine, you can destroy the nerve root, and if freezing is performed too far out, you miss the recurrent cutaneous branch of the intercostal nerve. And similar to other local regional block options in trauma patients, data is sparse and not specific to mechanically ventilated patients. Briefly, there have been three major studies published with intrathoracic cryoneurolysis for patients with rib fractures. Let's see if I can go back there. Maybe not. But they're all single institution, and only one of the studies uses ultrasound to do percutaneous cryoneurolysis. I'm gonna spend the remainder of the time discussing the data to support systemic therapy with IV lidocaine or ketamine for pain control among mechanically ventilated patients. So similar to the local regional blocks, there are really two questions. Does IV lidocaine or ketamine have benefit in the pain treatment of mechanically ventilated patients with rib fractures, and should these two medications be used or supplant local regional blocks? And based on available data in mechanically ventilated patients, the answers to both questions are really unclear, to say the least. Now there are really four major studies evaluating the efficacy of systematic lidocaine in trauma patients with rib fractures, all published since 2020. In 2020, Lee et al. published a retrospective single institution study comparing outcomes among patients with traumatic rib fractures receiving IV lidocaine to those with an epidural. Of the 89 patients, there was no data on mechanically ventilated patients and ICU-specific outcomes. In this group, after accounting for epidural-administered opioids, the epidural group required more morphine equivalents within the first 48 hours, but otherwise there was no difference. Similar in 2020, Choi et al. published another single institution center comparison comparing patients with rib fractures receiving IV lidocaine to those who did not. Of 534 patients, 42% received IV lidocaine, with a greater proportion of patients receiving IV lidocaine being admitted to the ICU. Unfortunately, no subgroup analysis was performed on mechanically ventilated patients, and on adjusted analyses, the authors found no difference. This was followed by King et al. in 2022 who reported a retrospective single center study comparing patients with IV lidocaine to those receiving standard care. Unfortunately, patients with a GCS-14 were excluded, and when evaluating the patients who received IV lidocaine in a crossover fashion, the authors noted a reduction in opiates pain scores and hospital cost. In 2022, Pat and et al. published the only double-blinded RCT evaluating IV lidocaine compared to usual analgesics. The 34 patients were equally distributed into each arm, and no patient admitted to the ICU or mechanically ventilated patients were included. For all three of the four outcomes evaluated, pain scores at rest, patient satisfaction, and morphine equivalence, there was no difference between the treatment and the placebo arms. For ketamine, there's similarly sparse data, but there are two major studies performed in trauma patients. In 2018, Walters et al. performed a retrospective case control study comparing patients with one or more rib fractures and an injury severity score greater than or equal to 15 to either IV ketamine or standard care. While there was no information on mechanically ventilated patients reported in the study, patients receiving IV lidocaine had lower pain scores and less narcotic equivalent use. Additionally, among patients who received ketamine, they experienced significant drops in their average pain score and worse pain scores after the initiation of IV ketamine. Finally, in 2019, Carver and Kugler published a series of two papers describing a prospective single-center, double-blind RCT comparing ketamine to placebo among patients aged 18 to 64 and a second group of greater than or equal to 65. Of note, both study arms excluded patients with a GCS less than 13, and while there was an equal distribution of patients admitted to the ICU, there was no specific data on mechanically ventilated patients. I have findings from the Carter study displayed here, but the findings from both studies were the same. Low-dose ketamine failed to decrease the pain scores or morphine equivalence within the overall cohort, but among patients with an injury severity score greater than 15, the morphine equivalence were decreased with administration of ketamine, as can be seen in the table in the graph on the right. So just as with local regional blocks, the data is inconclusive, supporting IV lidocaine or IV ketamine as a pain control adjunct among the mechanically ventilated patients with rib fractures. It's unclear to what degree these therapies are really beneficial among injured, intubated trauma patients with rib fractures. But I use them and many other people use these adjuncts. So the decision to offer either of these two therapies to mechanically ventilated trauma patients with rib fractures really has to be individualized to each patient, understanding the contraindications to a given therapy and weighing the potential complications. Again, having a decision algorithm built into an institution's rib fracture management guideline is paramount to helping ensure providers are aware of the options available to patients and also help steer providers to the correct option for a given patient. So during this talk, we've achieved the learning objectives, we've discussed the epidemiology and significance of rib fractures, and I've provided a refresher on chest wall anatomy and pathology of rib fractures. Finally, I've discussed the non-surgical pain management strategy options exclusive of common IV narcotics and sedatives for mechanically injured patients. And hopefully you can see there's no one size fits all pain management approach to mechanically ventilated patients with rib fractures and that the quote best pain control, non-surgical pain control option really does depend on availability and interventional stability and the patient's injuries, because nearly all existing data is low quality data and it isn't specific to mechanically ventilated trauma patients. Risks and feasibility and availability must be balanced against benefit for each patient. And finally, interventions for management of rib fractures among intubated patients exist along a spectrum and not all therapeutic interventions are mutually exclusive. Yeah, I'll finish up with this slide. I'd like to finish with this following thought that I strongly believe mechanical problems need a mechanical fix. With each of the interventions I have described over the course of the talk, there are a number of potential complications and I didn't even have a chance to discuss the potential issues associated with systemic narcotics or sedatives commonly used among patients who are intubated. Because ultimately at the end of the day, these therapies in and of themselves are not adequate to digress a set of displaced rib fractures like you see on the 3D recon on the left. Because no matter how much narcotic you administer or how much vitakin you run into someone's veins, a mechanical problem needs a mechanical fix. And this isn't to say that these medical therapies aren't useful, they are absolutely essential to how we manage patients with rib fractures. But no amount of narcotic or gabapentin or epidural is going to adequately address the acute and long-term pain associated with displaced rib fractures such as those seen on the left. When we as healthcare providers rely only on medical therapy to address mechanical problems, we're like Superman trying to punch Chuck Norris. The mechanical problem isn't fixed and in escalating medical therapies, we create a lot of collateral damage. Thank you.

epidemiology

chest wall injuries

rib fractures

morbidity

pain management

mechanical fix