Undersea and Hyperbaric Medicine Section Newsletter - April 2013
Important Dates - Undersea and Hyperbaric Medicine Section Newsletter, April 2013
Bruce J. Derrick, MD
Undersea & Hyperbaric Medical Society – Annual Scientific Meeting
June 13-15, 2013. Orlando, FL
ACEP13 Scientific Assembly
October 14-17, 2013. Seattle, WA
Book your hotel early! Visit https://www.acep.org/sahotels/
Duke Dive Medicine– Fellow’s eConference:
This is a monthly, live, web-based “e-conference” designed to share and discuss diving and other hyperbaric medicine related cases. Thank you to everyone who has been participating, especially all of the fellows who have put together excellent presentations! Upcoming dates and presenters are as follows:
Tuesday, May 7th: University of Pennsylvania
Tuesday, June 4th: Duke
Email Bruce J. Derrick, MD for information about how to participate.
Section Update - Undersea and Hyperbaric Medicine Section Newsletter, April 2013
Tracy Leigh LeGros, MD, PhD, UHM/ABEM, FACEP
What a great time we had at ACEP in Denver this year. Our section meeting was very exciting and we were given a great lecture by Dr. Robert Sanders on Altitude and Diving. I was happy to see all of you and hope to see all of you next year in Seattle. Now for some updates.
Promotion of the UHM Section in ACEP News
Some of our members, including Drs. Norma and Derek Cooney, Dr. Robert Sanders, Dr. Tracy LeGros, Dr. Heather Murphy-Lavoie, and Dr. Bruce Derrick, have agreed to write 300 - 500 word articles for inclusion in ACEP News. This is going to promote our section well. The topics we will be presenting include HBO Fellowships, Sudden Sensorineural Hearing Loss, Central Retinal Artery Occlusion, Emergent Indications and Dysbarisms. However, if ANY OF YOU have any ideas or would like to write such an article (or would like help in doing so) please contact any of us on this listserv and we would be glad to facilitate this.
Let the Showdown Begin!!!
For too long we have heard from a select few that the Scheinkestel and the Annane Studies on carbon monoxide treatment with HBO prove that HBO is not efficacious in the treatment of CO poisoning. Well we intend to set the record straight! We have proposed to debate two of the foremost lecturers in emergency medicine. Stephen Thom, MD, PhD, UHM, FACEP and Tracy LeGros, MD, PhD, UHM, FACEP will argue the pro side of the debate. Dr. William Mallon and Dr. Jerome Hoffman will argue the con side. We are very excited and grateful that ACEP has accepted this proposal.
Even More Hyperbaric ACEP Lectures on the Horizon
In addition to the Showdown lecture, we have also proposed EIGHT additional lectures to the ACEP educational committee. These lectures were developed during a brainstorming session with Drs. Norma Cooney, Derek Cooney, Robert Sanders, Heather Murphy-Lavoie and Tracy LeGros. It was convened at a very nice hotel in Denver and some really nice topics were developed. Dr. Kivela, our ACEP Board Liaison during this session was very supportive of the submission of topics for future courses at Scientific Assembly, as well as articles for ACEP News showcasing indications for hyperbaric medicine. I hope the course proposals get approved and the submissions to ACEP News are published. There is even talk of having our own HBO tract or Section Spotlight. Wouldn't that be great!
We would like to welcome Vidor Friedman, MD, FACEP who is the new Board Liaison for the UHM Section.
Keep tuned, there is more to come.
Those are the updates as far as I am aware. We have changes in leadership within our section, and our new leaders will introduce themselves to you. They are very dynamic and have great ideas. We are in good hands. See you in Seattle!
Injecting Oxygen Into a Vein - Undersea and Hyperbaric Medicine Section Newsletter, April 2013
Suraj Yalamuri, MD
Imagine for a moment that you are currently in the middle of a difficult intubation and it is unsuccessful. Now imagine that you are no longer able to ventilate the patient and his oxygen saturation is rapidly dropping. At this point most of us are probably working our way through the difficult airway algorithm and as you probably guessed, we need to start preparing for an emergency invasive airway access. But what if you could buy some time by injecting something into a peripheral vein? How does 15 minutes during which the patient’s oxygen saturation can be maintained without any cardiac or neurological compromise sound? A research group from Boston Children’s Hospital has developed a way of delivering oxygen intravenously and has demonstrated the survival of animals with complete asphyxia for 10-15 minutes. The study was performed by Kheir et al and is titled Oxygen Gas-Filled Microparticles Provide Intravenous Oxygen Delivery.1
These gas filled microparticles are lipid coated microbubbles. Lipid coated microbubbles are a relatively new class of agents that are currently being used in medicine for both diagnostic and therapeutic applications. One such example is the use of perfluorocarbon (PFC) stabilized microbubbles that are used in diagnostic ultrasound imaging.2 Additionally, specific drugs or genes have been incorporated into these stabilized microbubbles for targeted delivery.3 For example, a peptide targeting activated GPII-bIIIa receptors in platelets can be locally injected to detect and/or enhance a clot in the left atrial appendage that can then be visualized through echocardiography.4
For oxygenation, the most promising research has been in using gaseous PFC compounds. These micron-sized spherical structures are able to change shape by either storing oxygen in an oxygen rich environment and appearing spherical or degassing in an oxygen poor environment and taking on more of a crescent shape. In this manner their function is similar to hemoglobin.5 They are synthetic blood substitutes and their efficacy has been proven in animal trials where PFC gas has been shown to maintain survival of severely anemic rats or in pigs that are in hemorrhagic shock.6,7 However, these blood substitutes are still dependent on an intact airway and lungs that are essential for gas exchange as the microbubbles themselves do not contain any oxygen.
Kheir et al used lipid-coated microbubbles as the vehicle for oxygen storage and delivery. However, these stabilized microbubbles contained oxygen gas at their core and were surrounded by a lipid monolayer. The bubbles were able to be suspended in an emulsion and did not coalesce. When the infusion was injected into a vein at a steady rate in an asphyxiated animal, the ~4 micron bubbles disintegrated into micelles in an oxygen poor environment and released the trapped oxygen gas that oxygenated nearby red blood cells. Since in this scenario there was no gas exchange in the lungs, there was a corresponding rise in arterial oxygen tension. Both cardiac damage and neurological compromise was prevented and the animals had significantly increased survival rates. These results were able to be maintained for as long as 10-15 minutes of continuous infusion.
While there have been advances in mechanical devices that aid intubation and/or ventilation, similar technical leap in a chemical agent that can maintain oxygenation has not been robust. The study by Kheir et al represents the first such leap. Successful translation of this breakthrough into the human patient population has the ability to stabilize the patient during the scenario described in the beginning and has the potential to dramatically improve outcomes in emergent situations.
1. Kheir JN, Scharp LA, Borden MA, et al. Oxygen gas-filled microparticles provide intravenous oxygen delivery. Sci Transl Med.
2. Harvey CJ, Lim AK, Blomley MJ, Taylor-Robinson SD, Gedroyc WM, Cosgrove DO. Detection of an occult hepatocellular carcinoma using
ultrasound with liver-specific microbubbles. Eur Radiol. 2002;12 Suppl 3:S70-73.
3. Kheirolomoom A, Dayton PA, Lum AF, et al. Acoustically-active microbubbles conjugated to liposomes: characterization of a proposed drug
delivery vehicle. J Control Rel. 2007;118(3):275-284.
4. Wu Y, Unger EC, McCreery TP, et al. Binding and lysing of blood clots using MRX-408. Invest Radiol. 1998;33(12):880-885.
5. Unger EC, Porter T, Culp W, Labell R, Matsunaga T, Zutshi R. Therapeutic applications of lipid-coated microbubbles. Adv Drug Deliv Rev.
6. Lundgren CE, Bergoe GW, Tyssebotn I. The theory and application of intravascular microbubbles as an ultra-effective means of transporting
oxygen and other gases. Undersea Hyperb Med. 2004;31(1):105-106.
7. Lundgren CE, Bergoe GW, Tyssebotn IM. Intravascular fluorocarbon-stabilized microbubbles protect against fatal anemia in rats. Artif Cells Blood
Substit Immobil Biotechnol. 2006;34(5):473-486.
ISSHL & Hyperbaric Oxygen Therapy: A Case Report - Undersea and Hyperbaric Medicine Section Newsletter, April 2013
Idiopathic Sudden Sensorineural Hearing Loss (ISSHL) & Hyperbaric Oxygen Therapy: A Case Report
Warren McCauley, MSIII
Idiopathic Sudden Sensorineural Hearing Loss (ISSHL) became an approved indication for hyperbaric oxygen therapy (HBOT) by the Undersea and Hyperbaric Medical Society (UHMS) in October 2011. ISSHL is defined as hearing loss greater than or equal to 30 dB occurring within three days over at least three contiguous frequencies. The recommendation for the initial treatment of ISSHL is systemic or local steroid therapy followed by 100 percent oxygen at 2.0 to 2.5 atmospheres for 90 minutes daily for 10 to 20 treatments.1 The treatment protocol and efficacy of HBOT more than 14 days after the initial event is debated. In this case report, we present a woman who experienced sudden unilateral hearing loss, the most common presentation of ISSHL, and her outcome after HBOT.
The patient is a middle-aged female who went bed one evening in perfect health. She noted some increased fatigue during the day, but had no acute complaints. She woke up the next morning experiencing almost complete hearing loss in her left ear. The hearing loss was accompanied by mild tinnitus in the left ear. She denied any other symptoms at the time.
A pure tone audiogram on day 1 of her course showed mild sensorineural hearing loss on the right and greater than 50 dB hearing loss on the left with some sparing at 5000 Hz. The patient was prescribed prednisone 60 mg daily for 4 days; 40 mg daily for 2 days; followed by 20 mg daily for 2 days. Brain MRI with special attention to the internal auditory canals was unremarkable. She was re-evaluated on day 12 at which time it was felt her symptoms were due to an inflammatory process. Hyperbaric oxygen was mentioned as a potential therapy, but was not pursued.
She presented to another otolaryngologist on day 20 of her course. She was administered a steroid injection in her left ear, placed on oral prednisone 60 mg daily and a hyperbarics consult was then recommended. When she presented to the hyperbaric medicine clinic, she continued to complain of decreased hearing in her left ear, but the patient’s review of symptoms was otherwise negative. Pertinent physical exam findings included a mildly thickened, gray left tympanic membrane with a small perforation in the anterior inferior position. Hearing was completely absent to finger rub on the left with a negative Rinne test on the left and the Weber test lateralizing toward her right ear. HBOT at 2.0 atmospheres for 120 minutes was recommended and started the same day with the number of sessions to be determined depending on efficacy and clinical course. After three treatments, audiometry showed a 35 dB gain at 2000 Hz. Follow-up audiogram after eight total treatments showed no further change and HBOT was discontinued.
ISSHL is of clinical importance as it can significantly diminish one’s quality of life. In addition, the timing of therapy in relation to the initial event seems to be important to outcomes. A large scale review found that the most beneficial results are attained when HBOT is combined with corticosteroid treatment within 14 days of symptom onset. Average hearing gains were 19.3 dB for moderate hearing loss and 37.7 dB for severe hearing loss.2 Similarly, other studies have shown that the early (within the initial 10 days) administration of HBOT results in a greater likelihood of complete hearing restoration or significant improvement.3 With treatment protocols varying widely, especially between referring physicians and those who administer hyperbaric oxygen, our goal is to underscore the benefits of immediately implementing hyperbaric oxygen as a component of the therapeutic regimen.
This patient initially received a steroid taper which is in accordance with the UHMS recommendations. She then presented to an otolaryngologist 12 days into her course but it was not recommended to pursue HBOT at that time. This recommendation seems to be in agreement with some otorhinolaryngology literature which advises corticosteroids as the initial therapy but states that HBOT within three months of diagnosis of ISSHL may be of benefit.4 While there is not a definitive protocol in the treatment of ISSHL, the effects of hyperbaric oxygen in the subacute or chronic phases of the disease is largely unproven.5 However, the literature does support the idea that HBOT should be combined with steroid therapy, and has been found superior to oral steroids, intratympanic steroids, or hyperbaric oxygen therapy alone based on mean hearing gain.6
This patient presented to hyperbaric clinic 20 days removed from the initial onset of symptoms. She showed noticeable improvement in the low frequencies based on audiogram after three treatments. This initially suggested that treatment may be of benefit in the subacute to chronic phase of ISSHL in this patient. This outcome is in agreement with some prognostic factors shown to be associated with clinical improvement after HBOT, mainly profound hearing loss and low frequency hearing loss.7 Unfortunately, this patient did not continue to improve beyond her initial three HBOT sessions. We are also unable to delineate the effect of HBOT vs. intratympanic steroid injection in this patient given the time course of this case.
Currently, there is no definitive treatment protocol for ISSHL. Furthermore, the implementation of HBOT for ISSHL varies widely. Some of this variation may be attributed to conflicting published literature. This case highlights the potential utility of establishing a standard protocol for ISSHL therapy which could be utilized by otolaryngologists and hyperbaric physicians alike. HBOT remains an important intervention in the acute stage of ISSHL with outcomes being most substantial when combined with steroid administration.8 Additional research is needed to illicit the role of hyperbaric oxygen in the subacute and chronic stages of the ISSHL and its relationship to different treatment profiles.
1. Piper SM, LeGros TL, Murphy-Lavoie H. Idiopathic Sudden Sensorineural Hearing Loss. Undersea Hyperb Med Soc. 2011.
2. Murphy-Lavoie H, Piper S, Moon RE, et al Hyperbaric oxygen therapy for idiopathic sudden sensorineural hearing loss. Undersea Hyperb Med.
3. Holy R, Navara M, Dosel P, et al. Hyperbaric oxygen therapy in idiopathic sudden sensorineural hearing loss (ISSNHL) in association with combined
treatment. Undersea Hyperb Med. 2011;238:137-42.
4. Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical practice guideline: sudden hearing loss. Otolaryngol Head Neck Surg. 2012; 146:S1-35.
5. Ohno K, Noguchi Y, Kawashima Y, et al. Secondary hyperbaric oxygen therapy for idiopathic sudden sensorineural hearing loss in the subacute
and chronic phases. J Med Dent Sci. 2010;57:127-32.
6. Alimoglu Y, Inci E, Edizer DT, et al. Efficacy comparison of oral steroid, intratympanic steroid, hyperbaric oxygen and oral steroid + hyperbaric
oxygen treatments in idiopathic sudden sensorineural hearing loss cases. Eur Arch Otorhinolaryngol. 2011;268:1735-41.
7. Korpinar S, Alkan Z, Yigit O, et al. Factors influencing the outcome of idiopathic sudden sensorineural hearing loss treated with hyperbaric oxygen
therapy. Eur Arch Otorhinolaryngol. 2011;268:41-7.
8. Suzuki H, Hasida K, Nguyen KH, et al. Efficacy of intratympanic steroid administration on idiopathic sudden sensorineural hearing loss in
comparison with hyperbaric oxygen therapy. Laryngoscope. 2012;122:1154-7.
Article You May Have Missed - Undersea and Hyperbaric Medicine Section Newsletter, April 2013
Bruce Derrick, MD
The following is a synopsis of a concise, yet substantive, article on carbon monoxide diagnosis, management and prevention that may be interesting and educational to emergency, critical care and hyperbaric physicians. If you would like to access the full article, the necessary details may be found below. Any views expressed in this synopsis are not representative of any institution.
Practice recommendations in the diagnosis, management, and prevention of carbon monoxide poisoning. In the American Journal of Respiratory and Critical Care Medicine. Published Dec 1, 2012.
Authors: Neil B. Hampson, MD, Claude A. Piantadosi, MD, Stephen R. Thom, MD, PhD, and Lindell K. Weaver, MD.
The authors of this article are experts in the field of hyperbaric medicine. They collaborated to compile this evidence-based consensus of recommendations and clinical practice guidelines to aid in the diagnosis, management and prevention of carbon monoxide (CO) poisoning. Spanning topics related to the basic science of CO mechanisms to clinical outcomes of poisoned patients, these four authors have published over 100 papers on carbon monoxide, and, in compiling this set of recommendations, the authors cite 94 separate references.1
The authors begin their practice recommendations by noting that CO toxicity is more than tissue hypoxia caused by the reversible formation of carboxyhemoglobin (COHb). Cellular mechanisms such as peroxynitrite production, lipid peroxidation, immune mediated injury and delayed inflammatory response are among the many underlying causes of the clinical presentation of CO poisoned patients and related delayed complications.1
According to the authors, the clinical diagnosis of acute CO poisoning should be made on the basis of exposure, the presence of symptoms, and be confirmed with laboratory measurement of the COHb level.1 The authors enter into a concise discussion of the available diagnostic testing modalities, when various diagnostic testing modalities’ use is appropriate, and interpretation of related results.
What management strategies do these four experts recommend given the varying evidence and opinions put forth by “the seven” clinical trials, Cochrane Reviews, and related clinical practice guidelines? I encourage you to read their well-researched practice recommendations; however, the take home point is that hyperbaric oxygen therapy IS recommended in many situations, and the sooner, the better. These authors also address certain specific circumstances and populations where hyperbaric therapy may or may not be appropriate.1
Follow-up is an important aspect of all emergency care and the authors note that carbon monoxide patients are no different. They have higher long-term mortality and may require long-term cardiology, neurology or psychiatric care. If deemed stable following treatment, the authors recommend that these patients be re-evaluated within 1-2 months after therapy. These patients may require thorough neuropsychiatric testing if they not determined to be at their baseline functioning when re-evaluated.1
The final section of the paper discusses the implementation of prevention strategies such as warning labels for charcoal briquettes, the use of CO detectors and ongoing legislative activities aimed at preventing accidental exposure. The authors agree that it is important that prevention strategies target all populations, across all socioeconomic ranges. As demonstrated by recent weather-related events, a sudden loss of electricity can impact any of us at any time.
As noted above, the authors have penned a concise, yet substantive, review for the practicing emergency physician, critical care physician and hyperbaric physician.
1. Hampson NB, Piantadosi CA, Thom SR, Weaver LK. Practice recommendations in the diagnosis, management, and prevention of
carbon monoxide poisoning. Am J Respir Crit Care Med. 2012;186(11):1095-1101.