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Tuesday, March 12, 2013

How to make your own ultrasound gel

I have been doing lots of bedside ultrasound lately and realized how useful it would be in areas far off the beaten track, like Haiti, for instance. With a bedside ultrasound (mine fits in my pocket) I could diagnose heart disease, kidney and gallbladder problems, various cancers as well as lung and intestinal diseases.

Then I realized that I would have to take a whole bunch of ultrasound gel with me, which would mean that I would have to check luggage, which is a real pain when traveling light to a place where luggage disappears. I heard that you can use water, or spit, in a pinch, or even lotion, though oil-based coupling media apparently break down the surface of the transducer.

Ultrasound requires an aqueous interface between the transducer and the skin or else all you see is black. Ultrasound gel is a clear goo, looks like hair gel or aloe vera, and is made by several companies out of various combinations of propylene glycol, glycerine, perfume, dyes, phenoxyethanol or carbapol R 940 polymer, along with lots of water. It is hard to find this information, but it is available in the material data safety sheets for the various companies that make it. The recipes are proprietary. Ultrasound gel is not super expensive, but it is not that easy to find in a store or in a developing country. It costs about $25 for 5 liters on Amazon, or $5 for a nice 8.7 oz squeeze bottle. It smells ever so slightly medicinal and leaves a sticky, then white residue as it dries.

There should really be some sort of powder that you mix up with water that makes ultrasound gel so we don't have to be shipping the water part of it, which is undoubtedly about 99% of the contents, long distances. But there isn't a powder. I have been looking. No instant ultrasound gel.

With a mixture of optimism and singularity of purpose I went to the kitchen and tried out six different recipes for an aqueous goo that would transmit sound waves. I thought that I could make ultrasound jam out of water and pectin, but that doesn't really work. Obviously there is something magic about fruit that makes pectin gel, maybe the acid or the sugar. Without fruit, even no-sugar pectin becomes about the consistency of spit. (I also tried spit, which does work, but has various obvious drawbacks.) I tried plain gelatin and water and got beautiful clear gelatin, which falls off the transducer, and kind of works, but is also messy. I tried corn starch and water, as if making extremely boring gravy. That was lovely and white, but the water wants to come out of it so it just slides off the transducer. I tried tapioca flour which I boiled with water, producing a nice clear, very mucoid gel which dries like glue on the skin and is very uncomfortable. I tried xanthan gum, a bacterial polysaccharide used to bind and thicken, boiled and cooled, and although it thickens the water it is slimy and falls off the transducer and makes a mess.

The recipe that worked (and worked great) is guar gum, salt and water. Guar gum has been used for a very long time in countries like India and Pakistan to thicken food and is now used often by people who can't eat gluten, to thicken gravies and make breads. Guar gum is the ground endosperm of the guar bean, which is very rich in a carbohydrate that avidly absorbs water. Guar beans are also eaten green and the pods are used as a vegetable ingredient after shelling out the beans. Guar gum is available in the flour section of many grocery stores and costs about $10 for a 220 gram bag. It is purported to be good for diarrhea, constipation, diabetes and lowering cholesterol. It has been added to infant tube feed formula in intensive care units to decrease stool frequency.

I messed with the recipe awhile and came up with a very nice slightly caramel tinged ultrasound gel this way:
1. Mix 2 teaspoons of guar gum with 1-2 teaspoons of salt. (The amount of salt isn't vitally important since it is just added to keep the guar gum from clumping. Using slightly less than a teaspoon of salt per 2 cups makes a gel with which is isotonic, which would be ideal for use near eyes or other mucus membranes or on open wounds).
2. Boil two cups of water.
3. Slowly sprinkle the guar gum/salt mixture into the boiling water while stirring vigorously with a fork or whisk.
4. Boil for about 1-2 minutes until thick and well mixed.
5. Cool before using. Save lives.

I tried it and it works at least as well as the proprietary stuff, and probably doesn't dry out quite as fast. It wipes off easily and doesn't leave a sticky film. Even though it is not entirely transparent, there is no reduction in the quality of the ultrasound image compared with the standard clear ultrasound gel.

It costs about 25 cents for a half pint, is sterile when you have finished making it and is completely non-toxic. The ingredients are available in many developing countries, not to mention the U.S. It is edible. It is not particularly bacteriostatic, though it could be made bacteriostatic with a little EDTA (but then it wouldn't be edible). It is probably best made and used for two or three days, then discarded if unused, though I kept some in a clean bottle at room temperature and it was stable and smelled fresh for over a week.

It is quite thick, like regular ultrasound gel, so it is a bit of a trick to get it into a squeeze bottle. A large bore funnel works, or the cooled gel can be squeezed into the bottle out of the cut end of a plastic bag. It can also be kept in a jar and used with a spoon.

This is kind of exciting. Now I will no longer be dependent on ultrasound gel manufacturers. If I was in Haiti, either I or someone at the house where I was staying could make up a batch of this the night before clinic and I would have fresh clean ultrasound gel with which I could be generous in my scans. The water wouldn't even have to be sterile since the stuff is boiled when it is made. Let there now be ultrasound in places that Amazon.com does not reach!

Janice Boughton, MD, ACP Member, practiced in the Seattle area for four years and in rural Idaho for 17 years before deciding to take a few years off to see more places, learn more about medicine and increase her knowledge base and perspective by practicing hospital and primary care medicine as a locum tenens physician. She lives in Idaho when not traveling. Disturbed by various aspects of the practice of medicine that make no sense and concerned about the cost of providing health care to every American, she blogs at Why is American Health care so expensive?, where this post originally appeared.

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Members of the American College of Physicians contribute posts from their own sites to ACP Internistand ACP Hospitalist. Contributors include:

Albert Fuchs, MD
Albert Fuchs, MD, FACP, graduated from the University of California, Los Angeles School of Medicine, where he also did his internal medicine training. Certified by the American Board of Internal Medicine, Dr. Fuchs spent three years as a full-time faculty member at UCLA School of Medicine before opening his private practice in Beverly Hills in 2000.

And Thus, It Begins
Amanda Xi, ACP Medical Student Member, is a first-year medical student at the OUWB School of Medicine, charter class of 2015, in Rochester, Mich., from which she which chronicles her journey through medical training from day 1 of medical school.

Auscultation
Ira S. Nash, MD, FACP, is the senior vice president and executive director of the North Shore-LIJ Medical Group, and a professor of Cardiology and Population Health at Hofstra North Shore-LIJ School of Medicine. He is Board Certified in Internal Medicine and Cardiovascular Diseases and was in the private practice of cardiology before joining the full-time faculty of Massachusetts General Hospital.

Zackary Berger
Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews.

Controversies in Hospital Infection Prevention
Run by three ACP Fellows, this blog ponders vexing issues in infection prevention and control, inside and outside the hospital. Daniel J Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. Michael B. Edmond, MD, FACP, is a hospital epidemiologist in Richmond, Va., with a focus on understanding why infections occur in the hospital and ways to prevent these infections, and sees patients in the inpatient and outpatient settings. Eli N. Perencevich, MD, ACP Member, is an infectious disease physician and epidemiologist in Iowa City, Iowa, who studies methods to halt the spread of resistant bacteria in our hospitals (including novel ways to get everyone to wash their hands).

db's Medical Rants
Robert M. Centor, MD, FACP, contributes short essays contemplating medicine and the health care system.

Suneel Dhand, MD, ACP Member
Suneel Dhand, MD, ACP Member, is a practicing physician in Massachusetts. He has published numerous articles in clinical medicine, covering a wide range of specialty areas including; pulmonology, cardiology, endocrinology, hematology, and infectious disease. He has also authored chapters in the prestigious "5-Minute Clinical Consult" medical textbook. His other clinical interests include quality improvement, hospital safety, hospital utilization, and the use of technology in health care.

DrDialogue
Juliet K. Mavromatis, MD, FACP, provides a conversation about health topics for patients and health professionals.

Dr. Mintz' Blog
Matthew Mintz, MD, FACP, has practiced internal medicine for more than a decade and is an Associate Professor of Medicine at an academic medical center on the East Coast. His time is split between teaching medical students and residents, and caring for patients.

Everything Health
Toni Brayer, MD, FACP, blogs about the rapid changes in science, medicine, health and healing in the 21st century.

FutureDocs
Vineet Arora, MD, FACP, is Associate Program Director for the Internal Medicine Residency and Assistant Dean of Scholarship & Discovery at the Pritzker School of Medicine for the University of Chicago. Her education and research focus is on resident duty hours, patient handoffs, medical professionalism, and quality of hospital care. She is also an academic hospitalist.

Glass Hospital
John H. Schumann, MD, FACP, provides transparency on the workings of medical practice and the complexities of hospital care, illuminates the emotional and cognitive aspects of caregiving and decision-making from the perspective of an active primary care physician, and offers behind-the-scenes portraits of hospital sanctums and the people who inhabit them.

Gut Check
Ryan Madanick, MD, ACP Member, is a gastroenterologist at the University of North Carolina School of Medicine, and the Program Director for the GI & Hepatology Fellowship Program. He specializes in diseases of the esophagus, with a strong interest in the diagnosis and treatment of patients who have difficult-to-manage esophageal problems such as refractory GERD, heartburn, and chest pain.

I'm dok
Mike Aref, MD, PhD, FACP, is an academic hospitalist with an interest in basic and clinical science and education, with interests in noninvasive monitoring and diagnostic testing using novel bedside imaging modalities, diagnostic reasoning, medical informatics, new medical education modalities, pre-code/code management, palliative care, patient-physician communication, quality improvement, and quantitative biomedical imaging.

Informatics Professor
William Hersh, MD, FACP, Professor and Chair, Department of Medical Informatics & Clinical Epidemiology, Oregon Health & Science University, posts his thoughts on various topics related to biomedical and health informatics.

David Katz, MD
David L. Katz, MD, MPH, FACP, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care.

Just Oncology
Richard Just, MD, ACP Member, has 36 years in clinical practice of hematology and medical oncology. His blog is a joint publication with Gregg Masters, MPH.

KevinMD
Kevin Pho, MD, ACP Member, offers one of the Web's definitive sites for influential health commentary.

MD Whistleblower
Michael Kirsch, MD, FACP, addresses the joys and challenges of medical practice, including controversies in the doctor-patient relationship, medical ethics and measuring medical quality. When he's not writing, he's performing colonoscopies.

Medical Lessons
Elaine Schattner, MD, FACP, shares her ideas on education, ethics in medicine, health care news and culture. Her views on medicine are informed by her past experiences in caring for patients, as a researcher in cancer immunology, and as a patient who's had breast cancer.

Mired in MedEd
Alexander M. Djuricich, MD, FACP, is the Associate Dean for Continuing Medical Education (CME), and a Program Director in Medicine-Pediatrics at the Indiana University School of Medicine in Indianapolis, where he blogs about medical education.

More Musings
Rob Lamberts, MD, ACP Member, a med-peds and general practice internist, returns with "volume 2" of his personal musings about medicine, life, armadillos and Sasquatch at More Musings (of a Distractible Kind).

Prescriptions
David M. Sack, MD, FACP, practices general gastroenterology at a small community hospital in Connecticut. His blog is a series of musings on medicine, medical care, the health care system and medical ethics, in no particular order.

Reflections of a Grady Doctor
Kimberly Manning, MD, FACP, reflects on the personal side of being a doctor in a community hospital in Atlanta.

The Blog of Paul Sufka
Paul Sufka, MD, ACP Member, is a board certified rheumatologist in St. Paul, Minn. He was a chief resident in internal medicine with the University of Minnesota and then completed his fellowship training in rheumatology in June 2011 at the University of Minnesota Department of Rheumatology. His interests include the use of technology in medicine.

Technology in (Medical) Education
Neil Mehta, MBBS, MS, FACP, is interested in use of technology in education, social media and networking, practice management and evidence-based medicine tools, personal information and knowledge management.

Peter A. Lipson, MD
Peter A. Lipson, MD, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. The blog, which has been around in various forms since 2007, offers musings on the intersection of science, medicine, and culture.

Why is American Health Care So Expensive?
Janice Boughton, MD, FACP, practiced internal medicine for 20 years before adopting a career in hospital and primary care medicine as a locum tenens physician. She lives in Idaho when not traveling.

World's Best Site
Daniel Ginsberg, MD, FACP, is an internal medicine physician who has avidly applied computers to medicine since 1986, when he first wrote medically oriented computer programs. He is in practice in Tacoma, Washington.

Other blogs of note:

American Journal of Medicine
Also known as the Green Journal, the American Journal of Medicine publishes original clinical articles of interest to physicians in internal medicine and its subspecialities, both in academia and community-based practice.

Clinical Correlations
A collaborative medical blog started by Neil Shapiro, MD, ACP Member, associate program director at New York University Medical Center's internal medicine residency program. Faculty, residents and students contribute case studies, mystery quizzes, news, commentary and more.

Interact MD
Michael Benjamin, MD, ACP member, doesn't accept industry money so he can create an independent, clinician-reviewed space on the Internet for physicians to report and comment on the medical news of the day.

PLoS Blog
The Public Library of Science's open access materials include a blog.

White Coat Rants
One of the most popular anonymous blogs written by an emergency room physician.

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