[intro music]
[Dr. Shapiro] This is Dr. Samantha Shapiro, executive editor of Harrison's Principles of Internal Medicine. Harrison's Podclass is brought to you by McGraw Hill's AccessMedicine, the online medical resource that delivers the latest trusted content from the best minds in medicine. And now onto the episode.
[intro music]
[Dr. Handy] Hi everyone, welcome back to Harrison's Podclass. We're your co-hosts. I'm Dr. Cathy Handy.
[Dr. Wiener] And I'm Dr. Charlie Wiener, and we're joining you from the Johns Hopkins School of Medicine. Welcome to episode 112, a 23-year-old with anorexia nervosa. Okay, Cathy, today you're working with your colleagues in psychiatry, caring for a 23-year-old woman with severe anorexia nervosa. She has agreed to be admitted to the hospital for inpatient multidisciplinary therapy, including placement of an NG tube for enteral nutrition. On physical examination, her blood pressure is 90/60 with a heart rate of 110. Her respiratory rate is 12 with an oxygen saturation of 96% on room air. She has a temperature of 96 degrees Fahrenheit and a BMI of 14 kilograms per meter squared. She appears markedly malnourished with reduced muscle mass and subcutaneous fat. She has 1+ pitting edema to her knees.
[Dr. Handy] Let's pause here for a minute because she sounds really sick and does merit a lot of attention.
[Dr. Wiener] Tell me why you said she's really sick.
[Dr. Handy] So she has what sounds like starvation-related malnutrition from prolonged semi-starvation based on her body mass index and her clinical exam. I suspect that if we did labs, we'd see marked reduction in her albumin, her prealbumin, and other markers of nutrition. And I'd also be very concerned that she has vitamin deficiencies, particularly the water-soluble vitamins.
[Dr. Wiener] What stood out for you on her physical exam besides her notably reduced BMI?
[Dr. Handy] Well, let's go over that quickly, including her BMI. So remember, the BMI is the weight in kilograms divided by the square of height in meters. BMI normally ranges from 20 to 25 kilograms per meter squared, and BMI less than 15 is usually seen in severe starvation disease. On physical examination, the hallmarks of starvation-related malnutrition are muscle atrophy and loss of subcutaneous fat. Notably, the muscle atrophy may involve the respiratory muscles and the heart, which are obviously concerning. These patients also may be hypothermic, as is ours, and they often have edema because of their increased extracellular volume and hypoalbuminemia.
[Dr. Wiener] Okay. Well, let's get to the question which asks, all of the following are concerning potential complications of refeeding in this patient, except? And the options are A. cardiac arrhythmias; B. hypokalemia; C. hypomagnesemia; D. hypophosphatemia; or E. osmotic diuresis.
[Dr. Handy] This is a good question because as I mentioned, this woman has life-threatening malnutrition, and it turns out that even refeeding has hazards. I will say that the decision to go with enteral nutrition in this patient versus voluntary nutrition is obviously complex, and I credit her psychiatrist and the patient for adopting this approach. The patient must have realized that she'd been unable to adequately participate in voluntary nutrition, so elected this approach. But remember, we also have to be careful to avoid aspiration because she may have reduced gut motility.
[Dr. Wiener] Okay. Well, let's talk about and tell me about the refeeding syndrome.
[Dr. Handy] The refeeding syndrome can occur in patients with starvation related to malnutrition in the first days to week of nutritional repletion if carbohydrates and sodium are introduced too rapidly. Carbohydrate provision stimulates insulin secretion, which owing to its anti-natriuretic effect, expands the extracellular fluid volume, especially when excessive sodium is provided. So refeeding edema can be minimized by severely limiting sodium provision and increasing carbohydrate provision slowly.
[Dr. Wiener] Okay, so the osmotic diuresis is not really a complication of enteral therapy then?
[Dr. Handy] Yeah, E. is the best answer to the question, but osmotic diuresis is something that you do have to watch closely for if you're giving a patient parenteral nutrition because in those cases hyperglycemia is common.
[Dr. Wiener] Okay, so the other options that I listed are true, let's discuss them one by one.
[Dr. Handy] The combination of carbohydrate refeeding and new protein synthesis may cause symptomatic hypophosphatemia, hypokalemia, and hypomagnesemia, the mechanisms are all related to the new catabolism in the starved cells. Carbohydrates may stimulate enough intracellular glucose 6-phosphate and glycogen synthesis to seriously lower serum phosphate concentrations and the nitrogen catabolism new cell synthesis and cellular rehydration will cause the electrolytes to go from the extracellular to the intracellular space.
[Dr. Wiener] So obviously, in this patient, we should monitor those electrolytes frequently as we start the refeeding.
[Dr. Handy] Yes and supplement as indicated.
[Dr. Wiener] Okay. Well, what about the cardiac arrhythmias?
[Dr. Handy] Not only arrhythmias but even left heart failure may occur during refeeding. The electrolyte disturbances we just discussed may lead to arrhythmias, and remember, I mentioned that these patients may develop myocardial atrophy and reduced cardiac function. Refeeding with volume, glucose and calories may increase cardiac demands because resting energy expenditure will increase. All of these factors may conspire to cause LV failure and/or life-threatening arrhythmias.
[Dr. Wiener] Okay. Anything else you want to mention?
[Dr. Handy] Yeah, I mentioned that these patients are also likely to have vitamin deficiencies. We've discussed acute thiamine deficiency or Wernicke's encephalopathy before, and that can be a devastating but preventable complication. So make sure you give thiamine before the glucose as well.
[Dr. Wiener] Great. I'm glad you reminded us of that prior episode too. Okay, so the teaching points in this case are that starvation-related malnutrition is largely a clinical diagnosis based on a reduced BMI, muscle atrophy and a loss of subcutaneous fat. These patients are seriously ill, and even though in need of desperate need of refeeding, even that puts them at risk of a variety of electrolyte abnormalities, extracellular volume expansion and potential cardiac complications. Therefore, it should be done with care under close monitoring.
[Dr. Handy] And you can read more about this in the chapter on enteral and parenteral nutrition.
[outro music]
[Dr. Shapiro] Thanks for listening to Harrison's Podclass. You can listen to this episode and more on accessmedicine.com, which includes the complete Harrison's Principles of Internal Medicine text, Harrison's Review Questions, which complement and expand upon the questions in this episode, and much more. AccessMedicine.com may already be available to you via your academic institution. Check it out!
[outro music]