What it’s like to be a female anesthesiologist…

To promote the series #asawoman started by @nataliecrawfordmd (from Instagram)
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Throughout medical school, residency, fellowship, even now in private practice… patients have often judged a book by its cover. They’ve thought I was their nurse, volunteer, high school student or college student shadowing, almost everything but the person who will lead their anesthetic care. While this can seem deflating given all the extra work and studies one puts in to become a physician, I’ve changed my mindset re: my patients’ initial thoughts on me.
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First of all, thank goodness they think I’m super young! I have my mom’s genes and beautiful skin to thank!! At this rate, I hope I start to look 30 when I hit 50. When patients ask my age, I happily oblige them with a bold 39. Then I see a look of relief over their faces. I, of course, ask them how old they think I am….and I get the range of: just graduated college to mid-20s. Awesome!! I use it as a bonding moment and icebreaker with my patients. Sometimes with the right patient, I joke with them that it’s my first day… it usually entertains a good laugh. Then, I go into an overly technical schpeel on risks/benefits of anesthesia, expectations, PACU recovery. This typically solidifies to the patient that it’s not my first day on the job. Additionally, many patients tell me in the PACU that they feel better than their prior experience or better than their expectation and are quite grateful for my care.
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There are a lot of men in my anesthesia group. Sometimes, after I introduce myself to the patient, they’re shocked that a woman anesthesiologist would be delivering their care. In this day and age, I’m shocked that a lot of patients still assume that a male physician will oversee their care. When caring for female patients with this mentality, I purposefully address a gentle and vigilant anesthetic plan. With my male patients with this mentality, often times they’re happy to talk about the “happy juice” cocktail they’ll get and some much deserved relaxation knowing that I will carry a watchful eye over their surgery and anesthetic.
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Lastly, since becoming pregnant with my first and currently pregnant with my second… I feel I have a better understanding of the worried/concerned parents who are at the bedside to be with their child about to enter surgery.  Oftentimes, the parents think I’m young and want to know where I trained and when I graduated.  I offer them this info, and continue speaking to the patient (their child) about their concerns or questions.  I make sure the parents know everything that will go on re: anesthetic plan, how the patient will feel in recovery and risks/benefits of anesthesia options.  I TAKE MY TIME with the parents and the patient.  While my age and gender often work against me (even though it shouldn’t!), I make sure the controllable worries by the parents are addressed.  I speak to the parents after the surgery.  They go into the recovery room and see their child (older than 13 at our hospital) comfortable and recovering.  While I can’t change my appearance (nor would I want to…), I can change perceptions of women physicians.  We are every bit as capable of everything our male colleagues can do.  In addition, we tackle pregnancy, motherhood, businesses, and everything in between.  #asawoman As A Woman, I feel more empowered now than ever before.

Women in Anesthesiology

American Medical Women’s Association

American College of Physicians: Women in Medicine

Bias, Bravery, and Burnout: The Journey of Women in Medicine

Interested in Medical School? Start Early.

A friend of mine’s son is just about to graduate from high school.  He’s interested in medical school, and his mom asked me what advice I would give to help him pick a college knowing that he has an interest in medicine.

Keep in mind: I am not a counselor or an advisor.  I am a physician, and this is what worked for me.

My advice:

1. If you’re interested in medicine…. start early.
   • The college and medical school application process are getting more competitive.  Students are bright, prepared, and eager.  Let’s start with the basics.  Are you sure you’re interested in medicine?  Like really interested?  Sure, the media portrays some glamour lifestyles for physicians… but it’s not all glitz and glam.  You’ll put in at least a decade of extra work vs. your peers who get a job right out of college.  While they’re building their nest egg, you are not.   
   • Luckily, I stumbled upon my interest in medicine at an early age when my family practice physician encouraged me to pursue it.  He proved to be a great mentor as I was able to shadow him and really get a feel of his day and what he does.
2. Once you’ve decided medicine in your passion… solidify that decision.
   • Volunteer at the hospital.  Observe your physician.  Volunteer to help people.  If this excites you, you’re on the right track.  Put yourself in situations where you can get involved in medicine.  Read and research what medical school is like.  Reach out to a medical school and see if you can get more information: chat with a medical student, find out if anyone needs help with a research project.
3. Do well in school.
   • This is a must.  Applicants are incredibly competitive and intelligent with tons of extracurriculars on their resumes.  Get good grades.  Do well on your SAT/ACT and then do well on the MCAT.  Your grades and your test scores are the most basic comparison tool for schools to compare applicants.  Doing well gets you noticed.
4. Get involved and signup for extracurricular activities.
   • Once you’ve put in the work for good grades and test scores… get involved.  This could be anything: sports, clubs, arts/music, babysitting/caring for loved ones, volunteering, job in a lab, travel/cultural growth.  The key is to show that you’re well-rounded and multifaceted all while achieving the good grades.  Once the colleges and med schools have seen your test scores, they’ll next use your extracurricular activities to help separate out the different applicants.  The key is maintaining good grades while all these other activities are happening.  AAMC fact sheet for medical schools.

If you’re in high school and interested in medicine:

• Get good grades and do well on SAT/ACT (consider college prep courses to help)
• If you’re able to take honors classes or AP classes and do well, definitely sign up for these.  It’s another way to separate yourself from other applicants.
• Volunteer at your local hospital and/or doctor’s office
• Get a job at a research lab or hospital
• Get involved in extracurricular activities
• Talk to your high school counselor about career paths
• Attend career fairs (my school offered a career night in medicine where we got to go into the operating room) and college fairs on getting into medical school
• Ask a college pre-med what they’re taking and how to do well in college
• If you’re torn between two schools on your college list, consider taking a good look at the college that may also be linked to a medical school.  There’s a good chance that some of the medical school professors will be teaching some of the upper level physiology or anatomy college courses.  Some of the professors may also sit on the admissions committee to medical school.  Lastly, it may be easier to get involved in clinical research or scientific studies that the medical school professors are working on… and that would be a great way to introduce yourself to medical school staff as well as get a stellar recommendation letter to show off your work ethic and dependability.

If you’re in college and interested in medicine:

• Get good grades and do well on the MCAT (consider prep course to help)
• Get a major in something you’re interested in (you do NOT have to be a pre-med major… you just have to take the pre-med prerequisites to take the MCAT and apply for medical school).  Even though I majored in biomedical science (a pre-med major at Texas A&M), I would have done biomedical engineering if I had a do-over.  Science and math have always been my interests…the engineering major would have given me a nice background beyond my pre-med major.
• Talk to your college counselor/advisor early (freshman year)
• If you get into an honors program in college (usually based on your SAT/ACT scores), go for it.  Typically the honors classes are smaller and are a fantastic way to build report with your professor as well as get deeper into the subject matter.  Plus, being in the honors program will further help you standout on your application to medical school.
• Volunteer at the local hospital.  Although you may start out as a volunteer, see if you can get into the OR (operating room) as well as outpatient clinics.  This will expose you to a wide variety of practices: surgery, anesthesiology, pathology, internal medicine, family practice, OB/GYN, specialties, etc.
• Get involved in extracurricular activities in college.  There are a ton of clubs and interest groups in college.  If you don’t find one you like, start your own!
• Need a job in college?  Consider getting one in the research lab or at a medical school or in a hospital.
• Consider doing summer school to get some credits out of the way.  When I was in college, 12 credits was a full-time student.  I always took 15 credits because I thought I could handle it.  (Now I cannot recommend the following…) My junior year in college, I signed up for 21 credits to see if I could handle a medical school work load.  It was a tough semester, but I did it and got a 4.0.  I wouldn’t recommend that route because you need to focus on grades… but it worked for me.
• Apply to a lot of medical schools (in-state and out-of-state).  I grew up in Texas and at the time they had a Texas match with 7 medical schools.  I only applied to the Texas (in-state) medical schools because I knew that was all I could afford.  Keep in mind your debt burden: a $9,000/yr education vs a $30,000/yr is a big difference.  I chose an option that made the most sense to me — I didn’t want to be in debt forever.  In fact, I highly recommend reading this book: The White Coat Investor: A Doctor’s Guide To Personal Finance And Investing.  If I had that available to me, I would’ve read that in high school… re-read it in college… read it again in medical school… and read it again throughout life.  Yes, I’m constantly revisiting this book because it is that good.
• Interviews: honestly, I can’t remember if I interviewed for medical school or not (geez that makes me sound old!).  If you do have interviews… put your best foot forward and practice interviews with your friends/parents/professors/etc.  Be positive, engaging, and professional.  Interviewers DO judge a book by its cover.
• Once you’ve applied to medical school, sit back and wait for your results to roll in.  Honestly rank the schools you would like to go that caters to your learning style/goals/etc.  My medical school (UTMB) was one of the first in the country to incorporate systems-based learning and problem-based learning.
  • Systems-based = learn subject material based on the different organ systems vs. separate anatomy, physiology, pharmacology, pathology, etc.  (I learned based on the cardiovascular/gastrointestinal/genitourinal/neurological system, which included the anatomy, physiology, pharmacology, pathology, etc related to that system.  I thought it was a more intuitive way to learn medicine) .
  • Problem-based learning involved small groups where we would discuss medical cases, labs, clinical problems, etc.  It was a nice environment to express yourself as well as work together in a team.  This is how the real-world works where you talk to your colleagues to work through various medical issues.  It supports professionalism and engages a teamwork mentality.
• Lastly, thank the people who helped you get here.  It’s easy to overlook your mentors, friends, professors, and family.  As you enter the medical school/medicine world, your family will learn along the way that you made a commitment to a profession that will take priority over them.  You will miss weekends, evenings, date nights, holidays, anniversaries, etc.  Not only will you sacrifice a lot to get to medical school… you’ll continue making sacrifices once you’re out practicing medicine in the real world.

AAMC fact sheet for medical schools

My Training:

• St. John’s Episcopal Private School: Pre-K to 4th grade
• Jackson Elementary school: 4th – 5th grade
• Madison Middle School: 6th – 8th grade
• Cooper High school: 9th – 12th grade
• Texas A&M University: Summa Cum Laude, B.S. in biomedical science, University Honors, Undergraduate Research Scholar
• University of Texas Medical Branch: AOA, Gold Humanism Honor Society
• University of Texas at Austin transitional year: Internship
• Massachusetts General Hospital: Anesthesia residency
• University of California San Diego: Cardiothoracic Anesthesia fellowship

My Job:

• Anesthesia Service Medical Group (ASMG)
• All M.D. group doing our own anesthetic cases.
• Looking for a job?
• FAQ

Work-Life Balance and taking care of yourself

The ASA 2017 had an interesting self-study module called Physician Wellness Beyond the Usual Suspects.  It was a great learning tool to focus on the importance of the anesthesiologist to consider their own stress levels and seeing how to best mitigate the issues that could be problematic.

Check out these great articles from that self-study module:

• Time in the bank: A Stanford plan to save doctors from burnout
• Holmes and Rahe stress scale
• Suffering in silence: a qualitative study of second victims of adverse events
• On the Road to Professionalism

Key points:

• Understand your own stress levels.
• Make changes: speak to your staff, your administrators, your hospital to see what’s available to help you cope
• Get help
• Sometimes you can’t fix everything… and ultimately that’s ok.

“It is obvious that we can no more explain a passion to a person who has never experienced it than we can explain light to the blind.”

-T. S. Eliot

Dr. Atul Gawande: “What are the outcomes that matter?” — A Penned Point

The real surprise – to me, at least – came more than halfway through Dr. Atul Gawande’s keynote address at the opening session of the American Society of Anesthesiologists’ annual meeting in Boston. Much of his talk on October 21 celebrated the virtues of checklists and teamwork, topics that have turned into best-selling books for the…

via Dr. Atul Gawande: “What are the outcomes that matter?” — A Penned Point

The physician anesthesiologist vs. CRNA debate

Why is this even a debate?

It seems to me that the CRNA-led debate is financial… once you tease through all the fluff.

So here’s some literature I found:

• Evidence-based review did NOT find nurse anesthetists’ care equal to that of physician anesthesiologists
• Unsupervised anesthesia care by a nurse anesthetist is a threat to patient safety
• Anesthesiologist Direction and Patient Outcomes
• Is Physician Anesthesia Cost-Effective?
• I chose not to include biased studies where sick patients were not compared as well as morbidity and mortality.

As an anesthesiologist, I work in an MD-only anesthesia group. This is by choice: I prefer doing my own cases and being responsible for my own liabilities. The times I have required an anesthetic, I have requested a physician anesthesiologist. As a resident, I had very good insurance coverage, so I wanted a physician for my surgery. At that time, I was ok with having a resident anesthesiologist paired with an attending anesthesiologist for my case. My second surgery was done at my current hospital, and we only have MD anesthesiologists. Perhaps I’m biased? I know and I understand the path/journey/training it takes to get to become a physician anesthesiologist. I want someone who is well-trained, independently thinks, vigilant, and knowledgeable.

I’m sure there are great CRNAs out there… but when I was a resident… we used to supervise CRNAs in our final training year…. and it was scary some of things they would do. Who extubates from a trach R&R on 30% FiO2? Yeah, that particular CRNA told me they had 30 years experience. 30 years experience of doing something wrong doesn’t equate to 30 years of knowledgeable experience. And let’s not forget that CRNAs need a 15 minute morning break, 30 minute lunch break, and 15 minute afternoon break and they go home when their “shift” ends (even if it’s in the middle of a complex case). I take a break when I can… I eat lunch and take a bathroom break when I can…. and I choose to stay and finish complex cases for better continuity of care.

Would you want a nurse practitioner or physician assistant solely performing your surgery without a surgeon? I know I would NOT. I think there’s plenty of room for teamwork in healthcare. This is how to improve hospital efficiency and patient care. My fear is if CRNAs gain independence for purely financial reasons. But then, they will have to carry their own liability, cover their own breaks, take night call and discover that they had it so good in a healthcare team.

Opinions from other physician anesthesiologists:

• Proof that CRNAs don’t care about patient access to anesthesia
• Numbers don’t lie: Anesthesiologists are more qualified than CRNAs
• Doctor by your side: Get the Facts
• How MD anesthesiologists have become victims of their own excellence
• CSA legal analysis: Unauthorized opt-out of Medicare requirement
• Karen Sibert MD: Nurse anesthesia supervision and online opinion
• Unsupervised anesthesia care by a nurse anesthetist is a threat to patient safety
• CSA: Role of a physician anesthesiologist
• ASA: Patients demand physicians provide anesthesia care
• Primer on the anesthesia care team model
• Physician-led anesthesia is safe anesthesia
• ASA: Doctors and nurses are simply not one and the same
• Independent nurse practitioners are not the primary care solution

 

Bottom line in my opinion:

• Physicians endure years of grueling medical education that starts with the why, how, and treatment of disease. This is followed with years of residency training specifically in anesthesia. There’s also further training in the form of a fellowship for specialized fields.
• Getting into medical school is an extremely competitive process. You take the top 1% of college graduates and high MCAT scores to get into medical school.  The board certification for becoming certified in anesthesiology is quite complex and difficult in both the written and oral board exams.
• I will continue to be FOR team-based physician-led anesthesia care.

HeartWare vs. HeartMate LVAD

A couple of weeks ago, I took care of a patient who desperately needed to get better from acute CHF.  At that time, we placed the patient on an impella… but the next day, it was deemed that he needed ECMO to reperfuse his organs.  After a week on ECMO with continued impella support, ECMO was titrated down and off while maintaining 3.9L/min flow from the impella.  During the wean off ECMO, the patient had been extubated and was mentating clearly and interacting appropriately.

Fast forward a couple days after getting extubated, the patient was ripe for an LVAD.  But which one? (We ended up placing the patient on HeartWare LVAD).

YouTube: LVAD 101 – Anatomy & Physiology

YouTube: LVAD Pathophysiology

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HeartWare

HeartWare brochure

YouTube vid of HeartWare (no sound) ; Vid of HeartWare with detailed explanation

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HeartMate II

HeartMate II website

YouTube vid of HeartMate II

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Summary

• Cost-effectiveness: HeartWare > HeartMate II (UK NHS study, April 2014)
• LV Geometry: HeartWare = HeartMate II (J CT Surg, 2013)
• Stroke & GI bleed risk: HeartWare > HeartMate II (J Card Surg 2013)
• Risk of device failure: HeartWare < HeartMate II
• ENDURANCE trial: Randomized patients eligible for DT 2:1 to the HeartWare centrifugal flow LVAD versus the HeartMate II axial flow LVAD. The trial did reach its primary noninferiority endpoint of stroke free survival at 2 years (55.0% in the HeartWare patients versus 57.4% in the HeartMate II patients). Of note, a change in the design of the HeartWare device during the trial (sintering of the inflow cannula) appeared to decrease the incidence of pump thrombosis. Overall, the stroke rate was higher in the HeartWare arm whereas device malfunctions requiring exchange or urgent transplantation were more common in the HeartMate II arm. Data analysis suggested that better blood pressure control in the HeartWare arm may decrease the stroke rate and a second cohort of patients is being enrolled with more attention being paid to blood pressures management.

• ROADMAP study: (Risk Assessment and Comparative Effectiveness of Left Ventricular Assist Device and Medical Management in Heart Failure Patients) was an observational study of the Thoratec HeartMate II LVAD compared to optimal medical management in patients with advanced heart failure. Thirty day mortality was the same in both groups (1%) while one year survival was 80% in the LVAD group compared to 64% in the medical group (on an as treated basis). Functional status and quality of life improved significantly more in the LVAD group (analyzed by 6 minute walk, health related quality of life, and NYHA class). Unfortunately, adverse events in the LVAD group remained similar to what was previously reported in the DT trial, with bleeding being the most frequent adverse event.
• Bridge to Transplant: HeartWare = HeartMate II (Ann Thor Surg, Feb 2014)
• ADVANCE trial (bridge to transplant): 94% survival at 180 days with HeartWare
• PPT: LVAD Update 2015
• Anesthesia for LVAD
  • Anesthesia for LVAD, 2011
  • Anesthesiology 2003: Considerations in patients with LVAD
  • SCA 2009: PBLD Anesthesia for LVAD
• TEE:
  • Echo in Management of LVADs: ASE Guidelines 2015
  • SCA 2012: PPT TEE for VAD
  • SCA: TEE to detect VAD complications
  • SCA 2013: TEE evaluation of devices and cannula

Ventricular Assist Devices: Impella

“There’s an emergent case coming for impella placement.”

Impella?  I’ve read about these devices and I’m familiar with managing patients on LVADs as well as providing anesthesia for LVAD placement.  But, I’ve never done an Impella on a critically unstable patient.

YouTube video describing the purpose and placement of the Impella

Cath Lab Digest: Overview of Impella 5.0

Anesthesia & Analgesia; January 2012. Echo rounds: The Use of TEE for Confirmation of Appropriate Impella 5.0 Device Placement.

From A&A Echo Rounds

 YouTube video similar to our axillary artery conduit (we had to go left sided bc of a prior AICD in the patient’s right chest) for Impella 5.0

JCVA, June 2010. Review Articles: Percutaneous LVAD: Clinical Uses, Future Applications, and Anesthetic Considerations.

Left Atrial Occlusion Devices

Our hospital is starting to do more left atrial occlusion devices for people who have afib and aren’t able to tolerate blood thinners. Currently, two types are offered by our cardiologists: Watchman procedure (endocardial) vs Lariat procedure (epicardial).

Lariat

It look and acts similar to a lariat or lasso.  An external guide wire with a magnet at its tip is introduced outside the heart towards the left atrial appendage (LAA). Another wire with a magnet at its tip is introduced from a groin vein and it traverses the interatrial septum to sit at the most distal point inside the LAA. The magnets “connect” and the lariat is introduced along the external guide wire and essentially lassos the LAA.

Watchman

A large occlusion device is inserted via a groin vein and traverses the interatrial septum into the proximal (base or largest opening) left atrial appendage. The device gets deployed and successfully occludes the LAA.

PPT on Watchman from Boston Scientific

Is one better than the other?

Endocardial (Watchman) vs epicardial (Lariat) left atrial appendage exclusion devices: Understanding the differences in the location and type of leaks and their clinical implications.  Pillarisetti J, et al. Heart Rhythm. 2015.

CONCLUSION: The Lariat device is associated with a lower rate of leaks at 1 year as compared with the Watchman device, with no difference in rates of cerebrovascular accident. There was no correlation between the presence of residual leak and the occurrence of cerebrovascular accident.

Anesthesia

For these cases, we typically have a good flowing peripheral IV and intubate these patients for general anesthesia. There’s a fair amount of TEE required for placement and verification of correct positioning of the device. Both procedures require transseptal access. Watch for hypotension as there is a risk for pericardial effusion.

TEE for Lariat

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TEE for Watchman

Echo Essentials for Endoluminal LAA Closure: April 2014 Cardiac Interventions Today

The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation: J Vis Exp. 2012; (60): 3671

Anesthesia and Transesophageal Echocardiography for WATCHMAN Device Implantation: December 2016Volume 30, Issue 6, Pages 1685–1692.

Transesophageal echocardiographic diagnosis of a WATCHMAN left atrial appendage closure device thrombus 10 years following implantation: Echocardiography 2017; 34: 128–130.

From JACC: Cardiovascular Interventions
Volume 7, Issue 11, November 2014 DOI: 10.1016/j.jcin.2014.05.026 PDF Article

Percutaneous Left Atrial Appendage Closure
Procedural Techniques and Outcomes

3D Echo inside the Cath Lab – A must in LAA Closure. London, 2016.

ECHONOMY:Tools for Echocardiographic Calculations

YouTube: LEFT ATRIAL APPENDAGE CLOSURE PROCEDURE : Role of Transesophageal Echocardiography

YouTube: TCTAP 2015 SHD Live Case Session: LAA Closure

YouTube: How to image the inter-atrial septum using 3D-TEE “RATLe-90 maneuver”

YouTube: TOE in LA Appendage Assessment by Jason Sharp

**ASEcho.org 2017**

WATCHMAN:

 

Baseline TEE:

·       Full Scripps TEE protocol

·       Measure the LAA at the following views:

o   0°, 45°, 90°, 135°

·       Report the LAA maximal orifice, as well as the LAA dimensions at each angle using the following Xcelera drop-downs under “Left Atrium”:

 

·       Comment on presence or absence of atrial thrombus or “smoke”

·       Optional: Comment on LAA shape (ie: cauliflower, chicken wing, windsock, cactus)

 

 

Intra-Procedural TEE:

·       Comment on presence or absence of atrial thrombus

·       Report the LAA maximal orifice using the following Xcelera drop-down under “Left Atrium”:

·       Enter LAA device size and implantation date under the “History” section in Xcelera

·       Comment on the presence or absence of a residual leak using the following Xcelera drop-down under “Left Atrium”:

 

·       If a residual leak is present, comment on the size (mm) of the leak using the following Xcelera drop-down under “Left Atrium”:

 

·       Iatrogenic ASD with direction of shunting

·       Comment on any post-procedure pericardial effusion (compare to baseline)

 

 

Post-Procedure Discharge TTE (pt. in hospital):

·       LIMITED 2D TTE to rule out pericardial effusion (unless order specifies otherwise)

·       Spectral Doppler for respirophasic flow changes if an effusion is present

 

 

45-Day, 6 Month, 1 year and 2 year F/U TEEs:

·       Comment on presence or absence of atrial thrombus

·       Comment on the presence or absence of a residual leak using the following Xcelera drop-down under “Left Atrium”:

 

·       If a residual leak is present, comment on the size (mm) of the leak using the following Xcelera drop-down under “Left Atrium”:

 

·       Carry over LAA device size and implantation date under the “History” section in Xcelera

·       Comment on Iatrogenic ASD with direction of shunting, if still present

Career path: anesthesiologist

If you’re an anesthesiologist or in anesthesiology, you should check out this guy’s blog. He’s real and states it how it is. 

Lately, I’ve been feeling a lot of what he describes here: http://www.blog.greatzs.com/2016/03/a-hard-days-night.html?m=1

I think in residency it was a tad easier to deal with the insane work hours bc all my friends were in the same boat. We all suffered together and had minimal free time. But now in the real world, where a lot of my friends are non-medical or have better work hours… I see a huge discrepancy in free time available. It’s taking a toll on me bc I want that free time too and I find myself overwhelmed with being a “Yes” person and ignoring “me”. Lately, it’s catching up and I need a disconnect. 

But apparently, according to this recent report, I’m not working that hard.  Maybe hospital administrators should know that OR efficiency (or lack thereof) is the bottleneck.  Perhaps parallel incentives where productivity-based pay instead of salaries would provide a bit of motivation. 

And I completely agree with this guy’s assessment and wonderment of trying to become an intensivist. I chose anesthesiology for a reason, not ICU, not internal medicine, etc. 

Your brain under anesthesia

Anesthesiology 10 2015, Vol.123, 937-960. Clinical Electroencephalography for Anesthesiologists: Part I: Background and Basic Signatures
Patrick L. Purdon, Ph.D.; Aaron Sampson, B.S.; Kara J. Pavone, B.S.; Emery N. Brown, M.D., Ph.D.

Unprocessed electroencephalogram signatures of propofol-induced sedation and unconsciousness. (A) Awake eyes open electroencephalogram pattern. (B) Paradoxical excitation. (C) Alpha and beta oscillations commonly observed during propofol-induced sedation (fig. 5). (D) Slow-delta and alpha oscillations commonly seen during unconsciousness. (E) Slow oscillations commonly observed during unconsciousness at induction with propofol (fig. 6) and sedation with dexmedetomidine (fig. 11) and with nitrous oxide (fig. 13). (F) Burst suppression, a state of profound anesthetic-induced brain inactivation commonly occurring in elderly patients,68 anesthetic-induced coma, and profound hypothermia (fig. 6, B and D). (G) Isoelectric electroencephalogram pattern commonly observed in anesthetic-induced coma and profound hypothermia. With the exception of the isoelectric state, the amplitudes of the electroencephalogram signatures of the anesthetized states are larger than the amplitudes of the electroencephalogram in the awake state by a factor of 5 to 20. All electroencephalogram recordings are from the same subject. Reproduced, with permission, from Brown et al. Chapter 50 in Miller’s Anesthesia, 8th edition, 2014.

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The brain on propofol.  

A is adapted, with permission, from Purdon et al:Electroencephalogram signatures of loss and recovery of consciousness from propofol. Proc Natl Acad Sci U S A 2013; 110:E1142–51; and C is adapted, with permission, from Lewis et al. Rapid fragmentation of neuronal networks at the onset of propofol-induced unconsciousness. Proc Natl Acad Sci U S A2012; 109:E3377–86. Adaptations are themselves works protected by copyright. In order to publish this adaptation, authorization has been obtained both from the owner of the copyright of the original work and from the owner of copyright of the translation or adaptation.

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(A) At low doses, ketamine blocks preferentially the actions of glutamate N-methyl-d-aspartate receptors on γ-aminobutyric acid (GABA)ergic inhibitory interneurons in the cortex and subcortical sites such as the thalamus, hippocampus, and the limbic system. The antinociceptive effect of ketamine is due in part to its blockade of glutamate release from peripheral afferent (PAF) neurons in the dorsal root ganglia (DRG) at their synapses on to projection neurons (PNs) in the spinal cord. (B) Spectrogram showing the beta-gamma oscillations in the electroencephalogram of a 61-yr-old woman who received ketamine administered in 30 mg and 20 mg doses (green arrows) for a vacuum dressing change. Blocking the inhibitory action of the interneurons in cortical and subcortical circuits helps explain why ketamine produces beta oscillations as its electroencephalogram signature. (C) Ten-second electroencephalogram trace recorded at minute 5 from the spectrogram in B. A is reproduced, with permission, from Brown, Purdon, and Van Dort: General anesthesia and altered states of arousal: A systems neuroscience analysis. Annu Rev Neurosci. 2011;324:601–28. B and C were adapted from Purdon and Brown, Clinical Electroencephalography for the Anesthesiologist (2014), with permission, from the Partners Healthcare Office of Continuing Professional Development.69 Adaptations are themselves works protected by copyright. In order to publish this adaptation, authorization has been obtained both from the owner of the copyright of the original work and from the owner of copyright of the translation or adaptation.

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Spectrograms and time domain electroencephalogram signatures of dexmedetomidine-induced sedation. (A) Spectrogram of the electroencephalogram of a 59-kg patient receiving a 0.65 μg kg−1 h−1 dexmedetomidine infusion to maintain sedation. The spectrogram shows spindles (9 to 15 Hz oscillations) and slow-delta oscillations. (B) Ten-second electroencephalogram trace recorded at minute 60 from the spectrogram in A emphasizing spindles (red underlines). (C) Spectrogram of the electroencephalogram of a 65-kg patient receiving a 0.85 μg kg−1 h−1 dexmedetomidine infusion to maintain sedation. (D) Ten-second electroencephalogram trace recorded at minute 40 from the spectrogram in C showing the slow-delta oscillations. A–D were adapted, with permission, from Purdon and Brown, Clinical Electroencephalography for the Anesthesiologist (2014), from the Partners Healthcare Office of Continuing Professional Development.69 Adaptations are themselves works protected by copyright. In order to publish this adaptation, authorization has been obtained both from the owner of the copyright of the original work and from the owner of copyright of the translation or adaptation.

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Spectrograms and time domain electroencephalogram signatures of sevoflurane, isoflurane, and desflurane at surgical levels of unconsciousness. The inspired concentration of the anesthetics is the blue trace in the upper part of each panel. Green arrows below each panel are propofol bolus doses. (A) At sub-minimal alveolar concentrations (MACs) (minutes 40 to 60), the spectrogram of sevoflurane resembles that of propofol (fig. 6, A and B). As the concentration of sevoflurane is increased (minutes 100 to 120), theta (5 to 7Hz) oscillations appear. The theta oscillations dissipate when the sevoflurane concentration (blue curve) is decreased. (B) Ten-second electroencephalogram trace of sevoflurane recorded at minute 40 of the spectrogram in A. (C) The spectrogram of sevoflurane shows constant alpha, slow, delta and theta oscillations at a constant concentration of 3%. (D) Ten-second electroencephalogram trace of sevoflurane recorded at minute 30 of the spectrogram in C. (E) At sub-MAC concentrations (minutes 16 to 26), the spectrogram of isoflurane resembles that of propofol (fig. 6, A and B) and sub-MAC sevoflurane (A). Theta oscillations strengthen as the isoflurane concentration increases toward MAC. (F) Ten-second electroencephalogram trace of isoflurane recorded at minute 40 of the spectrogram in E. (G) At the sub-MAC concentrations shown here, the spectrogram of desflurane resembles propofol with very low theta oscillation power. (H) Ten-second electroencephalogram trace of isoflurane recorded at minute 40 of the spectrogram in G. A, C, E, and G were adapted, with permission, from Purdon and Brown, Clinical Electroencephalography for the Anesthesiologist (2014), from the Partners Healthcare Office of Continuing Professional Development.69 Adaptations are themselves works protected by copyright. In order to publish this adaptation, authorization has been obtained both from the owner of the copyright of the original work and from the owner of copyright of the translation or adaptation.

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Slow-delta and beta-gamma oscillations associated with nitrous oxide. (A) Prior to emergence, a patient was maintained on 0.5% isoflurane and 58% oxygen. At minute 82, the composition of the anesthetic gases was changed to 0.2% isoflurane (blue curve) in 75% nitrous oxide (green curve) and 24% oxygen. The total gas flow was increased from 3 to 7 l/min. The alpha, theta, and slow oscillation power decreased from minutes 83 to 85. At minute 86, the power in the theta to beta bands decreased considerably (blue area) as the slow-delta oscillation power increased. At minute 89, the slow-delta oscillation power decreased and the beta-gamma oscillations appeared at minute 90. The flow rates and anesthetic concentrations were maintained constant between minutes 82 and 91. Isoflurane was turned off at minute 91. (B) Ten-second electroencephalogram traces of the slow-delta oscillation at minute 86.7 and the beta-gamma oscillations at minute 90.8. A and B were adapted, with permission, from Purdon and Brown, Clinical Electroencephalography for the Anesthesiologist (2014), from the Partners Healthcare Office of Continuing Professional Development.69 Adaptations are themselves works protected by copyright. In order to publish this adaptation, authorization has been obtained both from the owner of the copyright of the original work and from the owner of copyright of the translation or adaptation.

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Different anesthetics (propofol, sevoflurane, ketamine, and dexmedetomidine), different electroencephalogram signatures, and different molecular and neural circuit mechanisms. (A) Anesthetic-specific differences in the electroencephalogram are difficult to discern in unprocessed electroencephalogram waveforms. (B) In the spectrogram, it is clear that different anesthetics produce different electroencephalogram signatures. The dynamics the electroencephalogram signatures can be related to the molecular targets and the neural circuits at which the anesthetics act to create altered states of arousal. Propofol and sevoflurane enhance γ-aminobutyric acid (GABA)ergic inhibition, sevoflurane binds at GABA receptors and other molecular targets, ketamine blocks N-methyl-d-aspartate (NMDA) glutamate receptors, and dexmedetomidine is a presynaptic alpha adrenergic agonist. A and B were adapted, with permission, from Purdon and Brown, Clinical Electroencephalography for the Anesthesiologist (2014), from the Partners Healthcare Office of Continuing Professional Development.69 Adaptations are themselves works protected by copyright. In order to publish this adaptation, authorization has been obtained both from the owner of the copyright of the original work and from the owner of copyright of the translation or adaptation.

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Key points:

• For the inhaled ether-derived anesthetics such as sevoflurane, isoflurane, and desflurane, we observed that, with the exception of the theta oscillations that appear around 1 MAC and beyond, their electroencephalogram patterns during maintenance and emergence closely resemble those seen in propofol. Nitrous oxide is known to be associated with increased beta and gamma oscillations and likely decreased slow-delta oscillations. However, we demonstrated that nitrous oxide also produces profound slow-delta oscillations during the transition from an inhaled ether anesthetic.
• An animated version of portions of parts I and II are available at www.AnesthesiaEEG.com.