Draft

143  Ddavp Clamp

143.1 Summary

  • Hyponatremia 501: DDAVP CLAMP
  • Roadmap
  • Two ways to get hyponatremic
  • Homeostasis Overwhelmed
  • Body using ADH as a Vasopressor
  • What happens when they get NS in the ED?
  • Flip the Script
  • Revisiting SIADH treatment
  • Giving DDAVP (ADH)
  • Case 1:

143.2 Slide outline

143.2.1 Slide 1

  • Hyponatremia 501: DDAVP CLAMP
  • Brian Locke, MD ### Slide 2
  • Roadmap
  • Why is the clamp helpful?
  • When should you clamp?
  • How should you clamp?
  • Does anything matter? ### Slide 3
  • Two ways to get hyponatremic
  • Homeostasis Overwhelmed
  • Anti-Diuretic Hormone
  • Appropriate response, but insufficient.
  • Kidney causes water retention
  • Too much free water to handle
  • Carbs, Fat, EtOH → CO2+H2O
  • Frail Kidneys
  • ADH (vasopressin) being used as an endogenous pressor
  • ADH inappropriately there
  • Low Urine Osm / spec grav
  • How low the urine osm & UOP differentiates
  • High Urine Osm / spec grav
  • Urine Na differentiates ### Slide 4
  • Homeostasis Overwhelmed
  • 60 kg person with an average diet: 600 mOsm/d solute.
  • Healthy individual:
  • max urine osm 1200 mOsm/L → L/d of urine?
  • min urine osm 50 mOsm/L → L/d of urine? ### Slide 5
  • Homeostasis Overwhelmed
  • 60 kg person with an average diet: 600 mOsm/d solute.
  • Healthy individual:
  • max urine osm 1200 mOsm/L → 0.5 L/d of urine (~ 50cc/hr, coincidence?)
  • min urine osm 50 mOsm/L → 12 L/d of urine? (~500cc/hr)
  • more than 12L of daily intake? hyponatremia
  • What is the maximum intake if:
  • Minimum urine osm increases to 100? 200? 400?
  • Solute intake doubles? Solute intake halves?
  • Minimum urine osm increases to 100 & 2x solute intake? 100 & ½?
  • GFR is too low to make 12L of urine? (AKI, CKD/Old age)
  • What happens when we give ADH
  • What happens when in ICU (NS…) ### Slide 6
  • Body using ADH as a Vasopressor
  • Inappropriate ADH
  • Kidneys trying, but overwhelmed
  • Urine Osm, Urine Na describe a physiologic state, not a diagnosis.
  • Physiologic states change
  • Repeat labs if you need to ### Slide 7
  • What happens when they get NS in the ED?
  • If ADH is present, urine output will be low and urine will be concentrated.
  • Very little free water is excreted, serum Na won’t rise.
  • If ADH is absent, urine output will be high (if GFR is) and urine will be dilute.
  • Lots of dilute urine serum sodium rises.
  • Unless using hypertonic, this is the ONLY way Na rapidly corrects.
  • Homeostatic Overload
  • Inappropriate ADH
  • ADH as Vasopressor
  • GFR OK and kidneys work very brisk UOP, rapid rise
  • [ADH was never present]
  • ADH present before and after little UOP or raise in Na
  • If body no longer needs ADH as pressor turns off, brisk UOP and Na rise.
  • [Cardiorenal+Hepatorenal ADH remains on] ### Slide 8
  • Flip the Script
  • A patient comes in with a Na of 120 and receives 1L of NS. What’s on the DDx if:
  • UOP 300/hr
  • Na rockets up
  • UOP 50/hr
  • Na jumps by 5
  • Na doesn’t change
  • Na drops
  • Options:
  • Polydipsia
  • Tea & Toast / Beer Potomania
  • Kidneys that don’t work good
  • Cardiorenal
  • Hepatorenal
  • Hypovolemia
  • SIADH ### Slide 9
  • Flip the Script
  • A patient comes in with a Na of 120 and receives 1L of NS. What’s on the DDx if:
  • UOP 300/hr
  • Na rockets up
  • UOP 50/hr
  • Na jumps by 5
  • Na doesn’t change
  • Na drops
  • Polydipsia
  • Tea & Toast / Beer Potomania
  • Hypovolemia [adh turned off]
  • Kidneys don’t work good (+/- any of left column0
  • ADH still present:
  • SIADH (min uosm ~300)
  • Cardiorenal
  • Hepatorenal
  • [hypovol insufficient]
  • SIADH
  • Options:
  • Tea & Toast / Beer Potomania Kidneys that don’t work good
  • Hypovolemia ### Slide 10
  • Revisiting SIADH treatment
  • Less ADH low min osm. More ADH higher min osm.
  • What is the maximum intake if (normal 12L max, 50 mOsm min urine osm):
  • Minimum urine osm increases to 100? 200? 400?
  • 6L, 3L, 1.5L
  • Solute intake doubles? Solute intake halves?
  • 2x (24L), 1/2x (6L)
  • What are the two ways to treat SIADH? ### Slide 11
  • Giving DDAVP (ADH)
  • Why?
  • To cause SIADH can’t overcorrect.
  • Then treat SIADH by either fluid restricting, giving solute, or both.
  • ALL the risk of over-correction comes from solute being given when ADH is low ( body can now dump free water at Uosm 50 osm/L)
  • Adrogue-Madias equation: 1L NS in 70kg w/ Na 105 -> 107.5
  • Overcorrection can only occur with brisk UOP (or crazy HS) ### Slide 12
  • Case 1:
  • Dx is psychogenic polydipsia. 15L/d. Na 120.
  • Is ADH high or low? (urine osm)
  • UOP is high or low before we act?
  • What would happen if you gave NS?
  • UOP: Serum Na:
  • What would happen if you gave DDAVP + NS/HS? ### Slide 13
  • Case 2:
  • Profoundly dehydrated. Na 120.
  • Is ADH high or low? (urine osm)
  • UOP is high or low before we act?
  • What would happen if you gave NS?
  • UOP: Serum Na:
  • What would happen if you gave DDAVP + NS/HS? ### Slide 14
  • Case 3:
  • CHF and cardiorenal synd. Na 120.
  • Is ADH high or low? (urine osm)
  • UOP is high or low before we act?
  • What would happen if you gave NS?
  • UOP: Serum Na:
  • What would happen if you gave DDAVP + NS/HS? ### Slide 15
  • When to clamp
  • When to Consider the Clamp
  • When it doesn’t matter (so probably don’t)
  • When not to clamp
  • Situations where ADH is off or going to turn off:
  • Polydipsia
  • Tea and Toast / Beer Potomania
  • Hypovolemia or correctable ↓EABV
  • SIADH (makes no physiologic difference because they’re already ‘clamped’)
  • Hepatorenal (they’re clamped and it’ll be hard to fix)
  • Low GFR (won’t overcorrect anyway)
  • Cardiorenal (it will get in the way of decongesting)
  • 2 options for when ADH is off:
  • Limit solute, give back D5W to match the urine output
  • Give ADH back ### Slide 16
  • 2 paths when ADH turns off: commit to one
  • Without DDAVP Clamp
  • With DDAVP Clamp
  • Very strict control of solute
  • Absolutely needs monitoring of UOP (foley)
  • Purpose; assess needed reaction to kidney
  • If managing based on labs, always 4-6h behind
  • Control of solute is less important
  • Monitoring UOP is less critical
  • Purpose: ensure your intervention is working
  • May be appropriate for milder hyponatremia and lower potential for over-correction (low GFR, inability to fully suppress ADH)
  • More appropriate for severe hyponatremia without hypervolemia, high potential for over-correction (high GFR, ability to fully suppress ADH)
  • Using a “reactive” DDAVP strategy (give DDAVP as needed for over-correction) retains the worst aspects of the standard management. ### Slide 17
  • How to DDAVP clamp:
  • DDAVP 2 mcg IV q8hr, continued until Na at target
  • Give 3% Saline to increase
  • Do nothing to keep unchanged
  • Give D5w to decrease ### Slide 18
  • Hyponatremia Pitfalls
  • Fixating on the diagnosis, not the physiologic state
  • Using ”reactive” DDAVP
  • Not paying attention to the UOP to tell when ADH turned off
  • Not paying attention to their solute inputs (esp if not clamping) ### Slide 19
  • Has there been a change?
  • https://reblocke.github.io/sodiumchange/ ### Slide 20
  • Does anything matter? 2 recent studies:
  • EHRs of 5 Toronto Hospitals
  • Inclusion: Inpt, 1st Na <130. 2010—2020. N22858
  • Exposure: Na, Comorbs, Corr.
  • Outcome: ODS on imaging [flag then review] or ICD for ODS.
  • Results: Mean Na 125. 17.7% over-corrected
  • 30% got CT, 6.6% got MRI
  • Devastating+Rare Hard to know ### Slide 21
  • Does anything matter? 2 recent studies:
  • EHRs of BWH+MGH 1993-2018
  • Inclusion: Inpt, 1st Na <120. N3274
  • Exposure: Na, Comorbs, Corr.
  • Outcome: CPM (NLP of MRI report), LOS, Mortality
  • Results: Mean Na 116.
  • Where did correction → CPM come from? ### Slide 22
  • Hyponatremia: summary
  • It is possible we are entirely mistaken about the cause of CPM / ODS
  • We know very little for certain, other than it is rare.
  • Standard of care, for now, is slow correction.
  • Probably net positive consequence to abandon this if slow corr causing harm
  • Tools for residents: Serum Osm, Urine Osm, Urine Na
  • Tools for fellows: UOP, response to solutes, clinical circumstance, cycling the labs prn
  • Reactive managementOK if mild, limited GFR/ADH suppression, Hypervolemia
  • Otherwise, commit to DDAVP + Hypertonic saline proactively ### Slide 23
  • Key References
  • https://www.coreimpodcast.com/2021/02/10/5-pearls-on-hyponatremia-episode-1/
  • Desmopressin to Prevent Rapid Sodium Correction in Severe Hyponatremia: A Systematic Review: DOI: 10.1016/j.amjmed.2015.04.040
  • NEJM Evidence Articles:
  • McMillan et al. 2022 DOI: 10.1056/EVIDoa2200215
  • Seethapathy et al. 2023 DOI: 10.1056/EVIDoa2300107

143.3 Learning objectives

  • Hyponatremia 501: DDAVP CLAMP
  • Roadmap
  • Two ways to get hyponatremic
  • Homeostasis Overwhelmed
  • Body using ADH as a Vasopressor

143.4 Bottom line / summary

  • Hyponatremia 501: DDAVP CLAMP
  • Roadmap
  • Two ways to get hyponatremic
  • Homeostasis Overwhelmed
  • Body using ADH as a Vasopressor

143.5 Approach

  1. TODO: Outline the initial assessment or decision point.
  2. TODO: Outline the next diagnostic or management step.
  3. TODO: Outline follow-up or escalation criteria.

143.6 Red flags / when to escalate

  • TODO: List red flags that require urgent escalation.

143.7 Common pitfalls

  • TODO: Capture common errors or missed steps.

143.8 References

TODO: Add landmark references or guideline citations.

143.9 Slides and assets

143.10 Source materials