tag:blogger.com,1999:blog-4230162007222918868.post5091407815455859671..comments2023-09-19T05:50:03.130-04:00Comments on Renal Fellow Network: Hyponatremia and ESRDGearoid McMahonhttp://www.blogger.com/profile/08049723797363526138noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-4230162007222918868.post-50973785713844478882017-02-07T08:50:10.046-05:002017-02-07T08:50:10.046-05:00I posted a comment on Feb 3...not sure where it we...I posted a comment on Feb 3...not sure where it went so I'll repeat. <br /><br />If PNa = 138, then: <br /><br />"Active" PNa = plasma water Na x Gibbs-Donnan factor for monovalent cation = 138/0.93 x 0.96 = 142, i.e. minimally different from dialysate Na of 140.Odednoreply@blogger.comtag:blogger.com,1999:blog-4230162007222918868.post-54367428868530944642017-02-06T11:57:48.167-05:002017-02-06T11:57:48.167-05:00I believe the answer to Dr. Rodby's question i...I believe the answer to Dr. Rodby's question is in the Donnan Effect (as I mentioned before) which occurs at the level of the dialysis filter membrane where protein form a barrier which complexes with sodium and precludes passage of free sodium ions. This enough to compensate for any difference in Na between plasma and dialysate. You can find a comprehensive review about this phenomenon in: Flanigan MJ. Sodium flux and dialysate sodium in hemodialysis. Semin Dial. 1998;11:298-304.Dr. Helbert Rondonhttps://www.blogger.com/profile/04527191513403619201noreply@blogger.comtag:blogger.com,1999:blog-4230162007222918868.post-22684280884725709502017-02-03T17:32:50.399-05:002017-02-03T17:32:50.399-05:00thanks so much - these responses are why i've ...thanks so much - these responses are why i've always loved this blog :)devikahttps://www.blogger.com/profile/10487149851662910526noreply@blogger.comtag:blogger.com,1999:blog-4230162007222918868.post-73583562134089648982017-02-03T11:09:17.202-05:002017-02-03T11:09:17.202-05:00"So, why is dialysate Na 140? and shouldn'..."So, why is dialysate Na 140? and shouldn't that lower our dialysis patient's PNa to the 130s? Using his same calculation, a HD pt with a PNa of 138 has a water Na of 148, and dialysis against a water Na of 140 would only drop that patient? "<br /><br />I believe I have found the answer. When in doubt go back to your mentors.<br />Answer and Full disclosure to follow! (gotta finish a manuscript first).<br /><br />rogerRoger Rodbynoreply@blogger.comtag:blogger.com,1999:blog-4230162007222918868.post-73060749989551858942017-02-03T10:05:55.717-05:002017-02-03T10:05:55.717-05:00Excellent post Devika. You may find interesting, ...Excellent post Devika. You may find interesting, couple of other posts on this topic from @ajkdblog and @errantnephron here :<br />https://twitter.com/LangoteAmit/status/827532329652465665Amit Langotehttps://www.blogger.com/profile/18377319083887261181noreply@blogger.comtag:blogger.com,1999:blog-4230162007222918868.post-89514186350827647242017-02-02T09:27:37.360-05:002017-02-02T09:27:37.360-05:00Dr. Nair,
nice job and discussion, these are diffi...Dr. Nair,<br />nice job and discussion, these are difficult cases. See <br /><br />http://community.asn-online.org/communities/community-home/digestviewer/viewthread?MessageKey=e2a71c91-9e27-4a42-b4b2-744ff2d6979c&CommunityKey=a62ccc6b-c43d-4ace-9208-29db8277db99&tab=digestviewer#bme2a71c91-9e27-4a42-b4b2-744ff2d6979c <br /><br />for a nice thread on this.<br /><br />As for CRRT v HD for hypoNa, certainly CRRT, being as slow as you want it, is easier to control the rate and magnitude of Na change. <br /><br />Dr. Rondon's point is well taken, the rate suggestions came from the fact that ODS was seen when a certain increase was seen over a certain time (change/time = rate), a rate less than that seen with ODS was suggested. But the better way to think about it is what change do you want in osmolality and why. If a patient is symptomatic, do you really want to raise their PNa by 1/2 meq/hour? Of course not you want to raise it immediately, but don't overshoot and that is why bolus 3% may be the best way to go. bolus check bolus check bolus check stop stop stop (and watch for a water diuresis in cases of non ESRD & AKI). <br /><br />Your ESRD (or AKI) pt is trickier, and I think you did well. Your concern is not raising it too much, you do not want to be the "second" case of ODS from HD, as ODS is catastrophic.<br /><br />He brings up a very interesting point that I never thought about (yikes), and that is the effect of the Na of dialysate being lower than we think (poorly worded but you get it). Normal Saline is 154 meq/l for that exact reason, the plasma water Na concentration is ~154, but measures at 140s because of the effect of proteins and lipids in the blood (in effect we all have pseudohyponatremia). <br /><br />So, why is dialysate Na 140? and shouldn't that lower our dialysis patient's PNa to the 130s? Using his same calculation, a HD pt with a PNa of 138 has a water Na of 148, and dialysis against a water Na of 140 would only drop that patient? <br /><br />Roger Rodby, MD<br />Rush, Chicago<br />rogerrodby@mac.com<br /><br />PS, thanks for the Donnan explanation, I've been working on that for years, still not there since for every negative anion (albumin in this case) there is a cation too, so why would albumin selectively hold Na?<br /><br /> Roger Rodbynoreply@blogger.comtag:blogger.com,1999:blog-4230162007222918868.post-40931525928625104872017-02-02T01:54:05.383-05:002017-02-02T01:54:05.383-05:00Thanks for the very helpful comments - agree that ...Thanks for the very helpful comments - agree that using low blood flows was probably not needed and that low dialysate [Na] would have been enough. His only additional risk factor for possible ODS was chronic alcoholism and lack of uremia (if we think uremia is protective as discussed above), but these were probably not significant enough to warrant conservative measures. Would be interested in hearing how patients requiring more urgent RRT needs would be managed.devikahttps://www.blogger.com/profile/10487149851662910526noreply@blogger.comtag:blogger.com,1999:blog-4230162007222918868.post-79938811813198650572017-02-01T21:25:49.149-05:002017-02-01T21:25:49.149-05:00Nice post. A common misconception is that the rate...Nice post. A common misconception is that the rate of sodium correction (e.g. 1 mEq/L/h) is important when in reality there is no evidence for this (Kidney Int. 1992 Jun;41(6):1662-7). The actual absolute magnitude of correction is what matters (e.g. < 8 or < 10 mEq/L per 24h depending on the risk of ODS). As you mentioned there are several ways you can deal with hyponatremia in ESRD. Extremely low Na should merit reduction of blood flow as you explain in your post but I am not sure that decreasing the blood flow in this particular patient with a Na of 122 was necessary unless you believe the patient was at an extremely high risk for ODS. Perhaps just using the lowest Na dialysate available (130) would have been enough. We cannot compare apples with oranges. Na concentration in the dialysate or Na "bath" is Na dissolved in water. The Na of 122 is not Na dissolved in water but in total plasma (or serum) which is only 93% water. So the actual Na concentration of the patient in water is 122/0.93 or 129. So, not that much different from Na in dialysate. Also the transfer of Na from dialysate to patient is greatly reduced due to the Donnan effect (negative charges from albumin attract cations like Na and do not allow easy transfer of Na+ into the patient). Dr. Helbert Rondonhttps://www.blogger.com/profile/04527191513403619201noreply@blogger.com