Clinical Immersion
Zabel Plastic and Reconstructive Surgery
Clinical Immersion is a biomedical engineering course that focuses on first hand experience in a clinical setting to observe and look for needs that can be addressed by biomedical engineers. This course is easily one of my personal favorites at UD and taught me a lot about the beginning of the engineering design process, how to be observant and find the root causes of things through interviews and questions, and even what things I would like from my own future. I finished the course with a new view of healthcare that has encouraged me to continue on my own path to becoming a physician. Below is the final project that I completed during this course and highlights my experiences as well as defines one of the top needs I identified.
Overview
I had the opportunity to shadow Dr. David Zabel, the Chief of Plastic Surgery at Christiana Care Health Systems and the Medical Director of the St. Francis Hospital Wound Care Center. I was able to observe practices in multiple clinical settings including at Christiana Hospital, Wilmington Hospital, St. Francis Hospital, and Zabel Plastic and Reconstructive Surgery. During the month, I sat in on cosmetic consultations and procedures such as breast augmentations, otoplasties, and mole removals. However, the majority of the procedures and appointments I observed were centered around wound care and attempting to speed up or trigger the body's natural wound healing cycle. This included small scale procedures like debridement with q-tips to large scale debridement under general anesthetic to skin grafts and flaps. Dr. Zabel has an expertise in hand surgery as well so I was able to see the placement of screws to fix broken hands and amputations. Each and every experience showed me how many opportunities there are to improve medical care from a biomedical engineering perspective. I also was able to learn a lot more about biological and engineering design processes that went into the creating of many medical equipment that is currently used. One of the largest takeaways from this experience was what I learned about the day to day life of a surgeon and what it is like to work in the medical field. It is something that I will remember as I quickly move into my future career path.
Background and Motivation
During the month, I observed many procedures under local anesthesia which used lidocaine. Very quickly I realized how painful the numbing portion of the procedure is as patient after patient showed physical signs of pain from squeezing their hands and scrunching their face and verbal signs of pain like yelling in pain. After noticing this issue, I began recording the number of procedures under local anesthesia and how many patients exhibited signs of pain to test my hypothesis that the majority of people experience pain. In the end, out of 15 procedures performed in Dr. Zabels private office, only two patients did not show any signs of pain which was over my 75% metric. With permission, I questioned one of the two on how it felt and they stated that it did burn, but they found it equivalent to other things they have experienced and went into it expecting that same level of pain. From a series of discussions with Dr. Zabel and some patients that underwent the procedures followed by my own research, I found that the root of the pain was the extreme burning sensation caused by the acidic pH. Lidocaine based anesthetics are typically 1:100,000 epinephrine and have a pH averaging 3.93 which is much lower than physiological pH which ranges 7.35 to 7.45 which creates that burning feeling [1]. On top of that, some patients exhibited an extreme fear of needles that increased their anxiety before the numbing process even began. The application method of the anesthetic, needles, is only adding to the pain of the process as studies have shown fear of needles alone can increase the pain experienced by the patient and 25% of the population has this fear [2]. Overall, the entire local anesthesia process unnecessarily increases patient pain until the point at which it becomes effective at numbing the area. As seen in Figure 1, the plotting of pain scores after lidocaine injection, within the first minute after the injection, patients experience pain ranked as high as 50 on a 0-100 VAS pain ranking scale [3]. Local anesthetics are used in offices all over the world from plastic surgeons to dermatologists to dentists, and in reality most people will seek out or need a procedure that requires it [4]. Clearly, this has high potential to affect most of the population, so a treatment option that limits more than it causes would be beneficial to everyone.
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The Need
A way to completely numb specific areas in patients undergoing surgery under local anesthesia that minimizes pain during application.
Solution Landscape
Lidocaine
Summary: This is the currently used local anesthetic that numbs the area of interest by blocking the signals at the nerve endings. It does this by binding to the voltage gated sodium channels of neuron membranes therefore stabilizing them and preventing sensation of pain. Overall, it is the most effective, safest, and leastly costly solution used in the majority of local anesthesia procedures [5]
Benefits: FDA approved, easily kept at room temperature, very effective, causes minimal adverse reactions, works within 4 minutes, and exits the body within a few hours [5]
Risks: Average pH of 3.93 which causes pain to the patient, water based so must be injected with needles to pass the skins hydrophobic barrier, lidocaine in a cream form takes hours to work and is minimally effective [1, 6-7]
Buffered Lidocaine
Summary: This solution works the same way as lidocaine with the exception of it containing bicarbonate to increase the pH [8]
Benefits: Closer to physiological pH (7.35-7.45) to reduce burning pains by 1.5 points on a 10 point pain scale and equally as effective as the typical lidocaine [1, 8-9]
Risks: Not FDA approved, has a shelf life of 10 days, and required physicians or pharmacies to make the mixture on their own [8]
Septocaine (Articaine)
Summary: This is another local anesthetic which is used in place of lidocaine sometimes as they are statistically the same in effect created by blocking voltage gated sodium channels to prevent the sensation of pain [10].
Benefits: FDA approved and has higher efficacy requiring less injections [11]
Risks: Studies show it has higher adverse reactions in children, typically only used in dental procedures, requires injection to pass the skin's barrier, and has a low pH that causes pain [11]
Novocaine
Summary: Functions the same way as the other two anesthetic solutions in that it blocks voltage gated sodium channels to block nerve endings and eliminate the sensation of pain [12]
Benefits: Cheaper than lidocaine and is used all throughout Europe still [12]
Risks: It is banned in the US due to the high chance of allergic reactions to the ingredients used to store it at room temperature, has a long wait time until it numbs the area, has a very short lifespan in the body [12]
Coolsense
Summary: This is a local anesthetic that uses a cryo system to numb areas for painless injection procedures such as cannulation and works by cooling the area to slow blood flow which in turn reduces the feeling of pain [13].
Benefits: Proven to bring pain of injections down to a rating of 3 out of 10, good for use before other local anesthetics like lidocaine, FDA approved for reducing pain [14]
Risks: Must be kept in a freeze until use, minimal research on use during surgeries and still requires use of other anesthetics like lidocaine for larger procedures [14]
Physical Changes
Physical changes including but not limited to smaller diameter needle, perpendicular injection, pause after initial insertion, keep anesthetic on needle tip, and warming the solution.
Summary: All of these solutions attempt to minimize pain by allowing the anesthetic to come into contact with the nerves quicker or to reduce the chances of the needle hitting nerves and causing more pain. Smaller needles and perpendicular injection work by helping to avoid the needle coming into contact with nerves that would cause extra pain. Keeping anesthetic on the needle tip and warming the solution are thought to help numb the areas quicker before the needle is inserted to again help reduce pain [15]
Benefits: While there is no clinical rationale for use of only these methods, these techniques sometimes can reduce pain and are safe to do [15]
Risks: Variable in effectiveness but in the end does not reduce the pain much at all [15]
The Gap
In summary, lidocaine is the most commonly used anesthesia in clinical settings for all the reasons described above including its effectiveness and safety. The other -caine solutions work the same as lidocaine so can be used in place of it, but still with the same issue of causing excessive pain. Topical numbing tools like creams and coolsense are used in less medical settings and more cosmetic settings because they are not effective enough to eliminate pain during surgeries that go deeper than something such as a tattoo needle. The physical changes and coolsense tool are left up to the clinical themself on whether or not they use them and it is not heavily reported on how often they are used. Unfortunately, they are not very effective in blocking or reducing pain on their own so there is still a need for an effective way to numb an area before a procedure that doesn't hurt the patient. Looking into solutions currently being researched, buffered lidocaine has been in focus for the last 10 years, but has not led to any significant changes yet. However, buffered lidocaine is readily available all over Canada for use. One journal publication described that there are increasing rules and regulations being placed on the combination of bicarbonate and lidocaine and that many medical organizations such as American Academy of Dermatology Association are working with the FDA and CDC to try to keep physicians' ability to create this solution in their office. The search for a 100% effective numbing topical solution is ongoing with no promising findings yet. Overall, taking into account the current and emerging solutions, there is a clear need for a new local anesthetic method. Within that, there is the opportunity to optimize many parts of the procedure including shortening the time to work, reduce the costs (current solutions average about $10 for 100 mL of the solution), and make it a less painful experience for the patients.
Stakeholder Analysis
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Design Criteria
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Next Steps
Overall, I believe that the pain caused by local anesthetics is an unmet need due to the fact that the current solutions are causing exactly what they are trying to prevent. During a procedure, patients are not going into it expecting the very thing that is supposed to numb them to put them in excessive pain while it takes its time to work. Given a more effective solution that does not cause any painful sensations, patients will be more relaxed and feel comfortable going into these procedures. Moving forward with this identified need, it would need to be verified that it is a widely found need outside of the clinical setting I was observing in. Stakeholders that I did not have access to would need to be interviewed to identify their view point to verify the assumptions I made on their behalf. Lastly, a deeper dive into why other potential solutions did not pass or were effective may be useful to further define the exact gap that this new product would fill. However, I believe that there is a lot of potential in the biomedical engineering field to design a new and improved method of local anesthesia with a lot of potential solutions as the engineering design process unfolds.
Acknowledgements
I would like to thank Dr. Rooney for her help throughout the course and Dr. Zabel for allowing me to shadow him and teaching me more than I could have hoped to learn this winter.
References
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