CAPS - The use of urine sodium to creatinine ratio as a marker of total body sodium in infants with intestinal failure - Sara Choi

Next, we have a presentation that was presented by Sarah Choi from British Columbia Children's Hospital. Uh, she presented on the use of urine sodium to creatinine ratio as a marker of total body sodium in infants with intestinal failure. After that, we'll hear from Doctor Paul Wales from Cincinnati Children's Hospital to fill us in on his thoughts, and Sarah wasn't able to be here today, but one of the authors on the paper, Doctor Hannah Piper, will be here, uh, for the discussion. So let's start there. Good morning. My name is Sarah and I am a 3rd year medical student at the University of British Columbia. To begin, none of the authors have anything to disclose. Infants with intestinal failure have compromised intestinal function, putting them at increased risk of malabsorption and electrolyte and fluid deficits. Sodium depletion can go unrecognized, resulting in poor growth, refractory to increased caloric intake, and as a result, many infants receive sodium supplementation as part of their clinical management. As it has been shown to be associated with weight gain and overall growth. However, it is difficult to determine how much sodium should be supplemented as serum sodium does not reflect total sodium stores. Ideally, the fractional excretion of sodium would be used as an optimum measure of total body sodium, however, is inconvenient in the pediatric population as it requires a paired urine and blood sample. Currently at BC Women's Hospital, urine sodium is used as a non-invasive marker to estimate total body sodium in infants with intestinal failure, with a value above 30 suggesting sodium sufficiency. However, one caveat of the urine sodium is that it doesn't account for volume status, therefore can result in oversupplementation or under supplementation with sodium. The urine sodium to urine creatinine ratio offers a non-invasive measure, which accounts for variable urine flow and has shown to be strongly correlated with FINA, thus potentially acting as a more accurate marker of sodium status. However, the use of the ratio has not yet been validated in this population. In this study, we aim to evaluate the use of urine sodium to creatinine ratio compared to urine sodium, and determine its correlation to sodium intake and growth. We conducted a retrospective chart review looking at all infants with intestinal failure who are part of the intestinal rehabilitation program over a two-year period. We collected data on patient demographics, etiology of intestinal failure, weekly nutritional intake, urine electrolytes, as well as weekly anthropometrics during their time with the program. And our goal was to determine the correlation between urine sodium and the ratio with growth, sodium intake, and determine a ratio cutoff value to target in this population. Infants without weekly urine electrolyte values and those being treated with diuretics were excluded. 22 infants were identified with a median gestational age of 31 weeks, median birth weight of 1.9 kg, and median age of enrollment at 8 days. We had a range of etiologies with gastroschisis being the most common. Each infant had an average of 3 data points. When evaluating the entire data set, there was no significant correlation between either urine sodium or the ratio with daily weight gain, and this is likely because there are various factors that can affect weight gain. However, we did exclude data points during treatment with diuretics, as fluid shifts can significantly account for weight changes. We did find that the ratio was more strongly associated with sodium intake when compared to urine sodium alone. And this is again likely because urine sodium does not account for urine flow. Plot Association showed that urine sodium values above 29, and ratio values above 35 best predicted adequate weight gain. The urine sodium threshold of 29 is similar to previous studies, as it is generally accepted that urine sodium values above 30 is suggestive of sodium sufficiency. And in the majority of urine sodium and ratio values, both markers were concordant, meaning that if urine sodium value met the threshold, then the ratio also met the threshold. However, in 19% of the time, the values were discordinate. In conclusion, we analyzed infants with intestinal failure, followed by a single center intestinal rehabilitation team for potential use of the ratio as a marker of sodium status. We found that both markers were not significantly correlated with weight gain, however, urine sodium to creatinine ratio significantly correlated with sodium intake. Urine sodium to creatinine values above 35 best predicted adequate weight gain, therefore suggesting sufficient sodium stores. Our findings can be used to guide further validation studies. I would like to thank everyone that has helped me throughout this project, and with that, I conclude my presentation and would be happy to take any questions. Thank you very much. I'm Paul Well, and I'm, I'm coming to you from outside. I'm on the way to the airport. So I hope everybody can hear me. Thanks for inviting me to participate in this great event, and thanks for asking me to, to review this paper. I, I encourage the audience to, to highly consider voting for this paper because it's, it has a massive clinical importance. This is often an underappreciated problem. A lot of our patients that have stomas, uh, even those without intestinal failure, they, they, they run the risk of sodium depletion, which does have a significant impact on their growth. Stomas and high stool losses are a large source of sodium bicarb, as well as mag magnesium loss. And sodium status needs to be thought of, especially in the setting of a baby that you're managing that is experiencing poor weight gain in the, in the exposure to what you believe to be adequate calories. Um, it's important to remember that when we replace sodium, it does help restore growth, but it doesn't allow catch up growth. And therefore, it's important that we track these patients serially, so that we can detect a trend evolving, so that we can avoid sodium depletion happening in the first place. Um, this has huge implications for practice. Um, as the author stated, uh, uh, um, you know, the, the FEMA is a little bit more complicated, uh, fraction excretion of sodium is a little bit more complicated because it does require simultaneous blood sampling. But I would argue that if, if it becomes part of practice to order urine one minute left in discussion at the time that. That someone's doing um their, their TPN blood work, it's easy to calculate that ratio. Um. And it's important to follow those trends. I would argue that, that having potassium chloride and an osmolaity added to the urine lytes in addition to just the sodium gives you a better picture of, of whether someone is truly sodium depleted. If we see their potassium level higher than their sodium level, that often will tell you that the aldosterone pathway is turned on. Um, Doctor Piper, uh, Really good paper, hugely important. Um, where do you wanna take this project next? Um, yeah, thanks, Paul, and, um, thanks for having me here. Um, I, I think the next step is to just implement this, you know, and start making it routine practice, um, and then to look and see, uh, prospectively, sort of how it, it holds up and refine. Some guidelines around parameters, I think it's an easy test to get and uh we're hoping that it becomes used uh more commonly, um, throughout North America. Mhm. Definitely a big problem, um, amazing paper. Uh, I see why it was chosen. I agree with you, Paul. This is, uh, critically important to patient care. Hannah, uh, Doctor Piper, thank you for presenting. Doctor Well, thanks for commenting.