209  Locke Summer Bootcamp H2o And Na

209.1 Summary

• Disturbances of Water and Sodium
• Roadmap
• How does hyponatremia cause problems?
• Hyponatremia: Resident-level algorithm
• Hyponatremia: Fellow-level algorithm

209.2 Slide outline

209.2.1 Slide 1

• Disturbances of Water and Sodium
• Brian Locke, MD
• 2022 Fellow Bootcamp ### Slide 2
• Roadmap
• Disorders of Water
• Hyponatremia
• Fellow-level schema
• When to use DDAVP clamp
• Hypernatremia
• Why all our ARDS patients are hypernatremia and why Orme’s approach works
• Disorders of Sodium
• Congestion
• Diuresis vs Natriuresis
• Inadequate dosing of lasix
• When to stop ### Slide 3
• How does hyponatremia cause problems?
• Why does DKA cause “hyponatremia” on labs, but symptoms of “hypernatremia” (thirst/dehydration, AMS) ### Slide 4
• How does hyponatremia cause problems?
• Osmolarity: number of particles in 1L ( that drops the freezing point 1.86 Kelvin; independent of size/weight of particles)
• Osmolality: number of particles of 1kg of solvent.
• Tonicity: effective osmolality of solutes that can act across a semi-permeable membrane
• Osm: property of particle in solution; Tonicity property of solution in relationship to a semipermeable membrane (cell membrane)
• Na+: exerts osmotic pressure
• Glu: moves across semipermeable membranes w/ insulin – transient (usually)
• Urea, ethanol, lactate: passively moves across semipermeable membrane: no osmotic pressure ### Slide 5
• Hyponatremia: Resident-level algorithm
• Na+ low enough to care?
• Are they hyperosmolar?
• Lab error? (lipemic, m-prot)
• Kidneys appropriate?
• Serum Osm ### Slide 6
• Hyponatremia: Resident-level algorithm
• Na+ low enough to care?
• Are they hyperosmolar?
• Lab error? (lipemic, m-prot)
• Kidneys appropriate?
• ADH present
• No ADH present
• Serum Osm
• Urine Osm
• Serum too dilute, urine should be ultra-dilute ### Slide 7
• Hyponatremia: Resident-level algorithm
• Na+ low enough to care?
• Are they hyperosmolar?
• Lab error? (lipemic, m-prot)
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (0.75l/hr max UOP)
• Beer: EtOH, C6H12O6
• Tea/Toast (100 mOsm-> 2L max)
• Impaired Range (~100 mOsm/kg)
• AKI, CKD, Old Age…
• Serum Osm
• Urine Osm
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 8
• Hyponatremia: Resident-level algorithm
• Na+ low enough to care?
• Are they hyperosmolar?
• Lab error? (lipemic, m-prot)
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (0.75l/hr max UOP)
• Beer: EtOH, C6H12O6
• Tea/Toast (100 mOsm-> 2L max)
• Impaired Range (~100 mOsm/kg)
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Serum Osm
• Urine Osm
• Urine Na
• (Why not FENa?)
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 9
• Hyponatremia: Resident-level algorithm
• Na+ low enough to care?
• Are they hyperosmolar?
• Lab error? (lipemic, m-prot)
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (0.75l/hr max UOP)
• Beer: EtOH, C6H12O6
• Tea/Toast (100 mOsm-> 2L max)
• Impaired Range (~100 mOsm/kg)
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• Serum Osm
• Urine Osm
• Urine Na
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 10
• TODO: No text extracted from this slide. ### Slide 11
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Are they hyperosmolar?
• Lab error? (lipemic, m-prot)
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• Clinical Situation (IVIG?)
• Low USpec Grav: specific, not sensitive
• What happened with 1L NS in ED? ### Slide 12
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• What happened with 1L NS in ED?
• 1542 MEqmOsm Na Cl allows 6L free water loss if ADH gone
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 13
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• What happened with 1L NS in ED?
• 1542 MEqmOsm Na+Cl allows 6L free water loss if ADH gone!
• What if ADH to cause min Uosm:
• 150? 300? 600?
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 14
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• What happened with 1L NS in ED?
• 1542 MEqmOsm Na+Cl allows 6L free water loss if ADH gone!
• What if ADH to cause min Uosm:
• 150? (2L, Na up) 300? (1L, na unchanged) 600? (500 cc, na down)
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 15
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• What will happen if we restore EABV to kidneys?
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 16
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• What will happen if we restore EABV to kidneys?
• All the way off: 6L of UOP for 1L NS
• Part of the way off: 1L-5L off
• Uosm, Una reflect a physiologic state, not a diagnosis – can cycle them
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L
• Δ Urine Osm
• Δ Urine Na ### Slide 17
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• Your intern gave 1L IVF and the patient’s UOP is now 400 cc/hr. What category were they in?
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 18
• Hyponatremia: Fellow-level algorithm
• Na+ low enough to care?
• Kidneys appropriate?
• ADH present
• No ADH present
• Uosm: 50 – 1200 mOsm/kg
• < 50 osm per L H2O
• Polydipsia (H2O up)
• Beer: EtOH, C6H12O6
• Tea/Toast (osm down)
• Impaired Range
• AKI, CKD, Old Age…
• Appropriate?
• Not Appropriate:
• SIADH etc.
• ADH like a vasopressor (decreased EABV)
• Hypovolemic
• Hypervolemic
• Maldistributed
• Your intern gave 1L IVF and the patient’s UOP is now 400 cc/hr. What category were they in?
• How could we stop this?
• Do not wait for next Na
• 60kg -> 600 mOsm/d solute
• 50 mOsm: max 12L
• 1200 mOsm: min 0.5L ### Slide 19
• DDAVP clamp:
• ALL of 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
• 2 options:
• D5W to match the urine output (that’s a lot of D5; ‘iatrogenic polydipsia’)
• Give ADH back (useful whenever UOP high or might become high)
• 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 20
• Hyponatremia: summary
• Tools for residents: Serum Osm, Urine Osm, Urine Na (FENa)
• Tools for fellows: UOP, response to solutes, clinical circumstance, cycling the labs prn
• If the ED gave 1L IVF and the [Na] didn’t budge or worsened:
• SIADH etc., or appropriate ADH presence from hypervol/maldistributed
• If the ED gave 1L IVF and the patient is making more than 250+ cc/hr
• They either had no ADH to start, or reason for ADH is gone (hypovol)
• Start DDAVP 2 mcg IV q8h ### Slide 21
• Hypernatremia
• 60kg -> 600 mOsm/d solute; 50 mOsm: max 12L; 1200 mOsm/L: min 0.5L
• With normal solute intake and less than 500cc water, you’d get hypernatremic
• If you have Diabetes Insipidus, your maximum concentration drops. If max Uosm 600 mOsm/L, then <1L leads to hypernatremia. If Uosm 300, <2 L leads to hypernatremia, etc.
• High urine output, CNS tumor, long term lithium and hypernatremic? Check Uosm
• 1200 mOsm minimum of 1L of maximally concentrated UOP ### Slide 22
• Does someone who eats 2g of Na/d drink the same H2O as someone who eats 4g of Na/d?
• Yes – at steady state – in out.
• Over a large range of sodium intake, urine production and thus fluid intake will be constant
• More natriuresis occurs in people who eat more salt. ### Slide 23
• Physiology Review
• Large bolus of free water?
• ADH shuts off. Kidneys produce dilute urine. Electrolytes and volume status unchanged.
• For avg (10 mOsm/kg/day) diet, ADH fully off 50 mmol/L (maximally dilute) 70 kg person > 700 mmol load > 50 mmol/L excretion > 14L of free water can be excreted per day without perturbing sodium balance.
• Large bolus of sodium?
• Maximal natriuresis ~280 mmol/L (2x serum, roughly).
• Why? There is NO active sodium excretion along the nephron ### Slide 24
• The nephron doesn’t have a dedicated method to excrete sodium.
• Instead, the kidneys concentrate urine by increasing urea concentration in the medulla.
• Counter-intuitively, to maintain osmolality the major mechanism after an ingestion of salt is not thirst, but free water re-absorption in the kidney (ie. concentration of urine)
• It takes time to generate this gradient
• Kidneys retain water (with ADH) to maintain [Na] in serum in the interim
• Glucocorticoid driven catabolism to generate urea
• Increase urea in the renal medullary interstitium
• Increase osmotic gradient to reabsorb free water ### Slide 25
• If someone who normally eats low Na diet eats high Na diet, do they drink more water?
• Healthy people randomized to either low sodium (0.5 g) to regular (3.2g) diet, then swap
• After increased Na load: takes ~3-5 days to reach a new steady state with kidney able to match Na load
• On the first day: only half of excess Na load excreted
• The positive sodium balance caused fluid retention and an increase in body weight of over 1 kg.
• No difference in fluid intake (free-water reabsorption makes up difference) ### Slide 26
• Na and fluid loading in the ICU
• 1L of NaCl 3.5gm (154 mmol Na) ~7 gm NaCl
• Consider COVID-ARDS:
• ~750 cc/d NS from Ketamine, 350 cc/d from Fentanyl 100 cc/d ciastricurium, 200 from CTX
• ~4g of sodium just from sedation and NMB ### Slide 27
• ADH is also a weak Anti-natriuretic Hormone
• Healthy volunteers drank either:
• Low hydration: free water 0.25 mL/kg q30m (35 mL/hr for 70kg) or
• High hydration: water 2.0 mL/kg q30m ( 288 mL/h for 70kg).
• Then received 250cc 2% NaCl
• High hydration: excrete the extra sodium immediately.
• Low hydration cannot (ADH crosstalk, maximal concentration ability of kidneys)
• Meaning: the kidneys CANNOT create low free water, high Na urine ### Slide 28
• Physiology Review:
• The kidneys have mechanisms to quickly adjust free water clearance.
• The kidney does not have a fast mechanism to increase natriuresis – it takes several days and catabolism to achieve this.
• Limitation in free water hampers natriuresis due to ADH crosstalk.
• While the kidney is adapting to a new baseline sodium intake, fluid retention occurs in the kidney (regardless how much fluid they drink).
• Therefore, it is very hard to achieve balanced I/O during salt loading ### Slide 29
• Bad ARDS Circle of Life
• Many Drips
• (in NS)
• Lasix & no
• free H2O
• Fluid Overload
• Hypernatremia ### Slide 30
• Single-day, point prevalence survey: 46 Australian and New Zealand ICUs on 21 September 2011
• Median sodium admin: 224.5 mmol (IQR, 144.9-367.6 mmol). 2.8 mmol/kg (IQR, 1.6-4.7 mmol/kg).
• Patients Day 2-10 of ICU admission:
• maintenance or replacement intravenous (IV) infusions, 69.3mmol; 30.9% of all sodium sources;
• IV fluid boluses, 36.5 mmol; 16.3%;
• IV drug boluses, 27.6 mmol; 12.3%;
• enteral nutrition, 26.5 mmol; 11.8%;
• IV drug infusions, 19.3 mmol; 8.6%;
• IV flushes, 16.6mmol; 7.4%;
• blood products, 13.5 mmol; 6%;
• IV antimicrobials, 11.2mmol; 5%;
• parenteral nutrition, 4.3 mmol; 1.9%.
• Median 5 grams of Na per day
• Double the usual intake ### Slide 31
• Why do we dissolve medications in NaCl?
• ICUs have pre-mixed versions of medications to deliver quickly (ie. antibiotics, fentanyl)
• Some meds are sodium salts ( any negative ion paired with a sodium cation) – generally more soluble in water than the acid form
• A few medications must be given in NS
• It’s the default ### Slide 32
• TODO: No text extracted from this slide. ### Slide 33
• Clinical impact - TOPMAST trial
• Blind randomization of 70 patients undergoing major thoracic surgery to [Na] 154 mmol/L vs [Na] 54 mmol/L fluid
• Primary: Net fluid balance: Na154 +4.5L vs Na54 3.12L despite identical fluid infused
• Secondary:
• Pulmonary Edema: Na154 17%, Na54 3%
• Electrolyte abnormalities:
• Na154 – n3 had Na above 145.
• N24 had Cl- above ULN
• Na54 – n4 patients had Na
• below 135. ### Slide 34
• The patient is hypernatremic and congested:
• Reduce Na intake (The Orme approach- is the patient on Nepro?)
• Wait – their kidneys will adapt in 3-5 days
• Give them more D5w – this will allow natriuresis by decreasing ADH
• Maybe we should default to meds in D5w instead of NS?
• If you give 2L D5w… say next day the ins 3L, outs 3L – have you made progress? Stay tuned… ### Slide 35
• Bad ARDS Circle of Life
• Many Drips
• (in NS)
• Lasix & no
• free H2O
• Fluid Overload
• Hypernatremia
• Use D5W instead
• Driven By Na Overload
• Liberal free water can allow natriuresis ### Slide 36
• Congestion
• Disorders of H2O homeostasis: Hypernatremia and Hyponatremia
• Disorders of Na homeostasis: Congestion and Hypovolemia
• Yet
• On rounds, we present “(mLs) in and out” and not ”Na in and Na out”
• Why? ### Slide 37
• “Despite hospitalization for HF being exceptionally common, expensive, and morbid, we have not a single Class I Level of Evidence: A guideline recommendation to guide our care of these patients” ### Slide 38
• A patient is congested: what initial orders are important?
• Na restriction of 2g per day? Yes or No
• Fluid restriction of 2L per day? Yes or No
• Strict I/Os and Daily weights? Yes or No ### Slide 39
• Salt and Fluid Restriction ### Slide 40
• Salt and Fluid Restriction causes… thirst ### Slide 41
• What is the problem with I/O and Kg?
• Assumptions:
• For I/O to be a surrogate of net natriuresis:
• [Na] intake constant
• D5 / NS
• [UNa] constant
• Breaking phenomenon
• Recording is accurate.
• In reality, it is not ### Slide 42
• Natriuresis varies widely during diuresis
• Why might the Na concentration of urine vary between patients?
• Depends on ADH presence (among other other reasons).
• Tight water restriction ADH increase, natriuresis unchanged.
• Loose water restriction ADH decrease, natriuresis unchanged ### Slide 43
• Urine composition by time
• “the sodium content of diuretic-induced urine is highly variable and correlates only modestly with fluid and weight loss” ### Slide 44
• Braking Phenomenon (of natriuresis)
• Assume a patient makes no dietary changes
• Sodium clearance increases with ECF (true)
• Off diuretics, a patient takes in 3g of Na in 24h. They are at steady state. 3g of Na must be excreted in 24h. They are congested.
• If you start a diuretic, initially their ECF is unchanged (congested), but natriuresis increases.
• They eventually reach a new steady state (inout), but at a lower ECF ### Slide 45
• Discordant Diuresis and Natriuresis
• Net Na drops a little
• Net Na drops a lot
• Net I/O drops a little
• Not much response, normal [UNa]
• Good natriuresis, high [UNa]
• Net I/O drops a lot
• Good diuresis,
• Low [UNa]
• Good response, normal [Una] ### Slide 46
• Natriuresis based decongestion
• Simple: Spot urine Na > 100 2h after dose was probably effective (will lead to net 2g+ natriuresis in BID dosing)
• Complex: ### Slide 47
• Does it work?
• NCT04481919 RCT with hard outcome end-points ongoing ### Slide 48
• TODO: No text extracted from this slide. ### Slide 49
• How to dose:
• 1. DOSE trial: 2.5x home dose and IV
• 2. Assess:
• UOP should be 150 hr+ within 2h of IV dose (don’t wait 6 to see)
• UNa should be 50-70+
• Why are you not giving a higher dose?
• Would respond to
• low dose
• Needs high dose
• Give low dose
• 
• Delayed in needed care
• Give high dose
• What’s the harm? ### Slide 50
• Toxicity without volume depletion?
• 1985: Patient with oliguric AKI were given “1 g furosemide was given as a single injection over four hours. In the test group, frusemide was then continued either intravenously or orally in a dose of 3 g/24 hr until a urine output of 200 ml/hr was sustained or until the plasma creatinine fell …The serious complication of deafness occurred in two of 28 patients and in one of them this was permanent.”
• 2021: Yale Diuretic Protocol: “automated, nurse-driven, and called for administration of 2 to 12.5 mg IV bumetanide up to 3 times daily.” “rapidly escalated toward a peak of 1,500 mg IV furosemide equivalents per day that was reached in the first 2 days of the protocol in 86% of patients.” “No cases of ototoxicity (n409)
• Meta-analysis: OR 3 of developing ototoxicity when dose excess 1 GRAM daily (~40 mg/hr)
• NOT A NEPHROTOXIN ### Slide 51
• “Suspect near euvolemia due to contraction alkalosis”
• Loop diuretics create Chloride (and Sodium)-Rich urine
• Loosing Cl- rich, ‘bicarbonate poor’ urine will lead to development of alkalosis at ANY extracellular volume.
• Pendrin: Chloride – Bicarbonate exchanger to maintain neutrality
• Not “contraction” (albumin will not fix it), but “chloride depletion” (saline will). ### Slide 52
• Diurese until sCr clearly increases: No intrinsic renal injury from diuretic caused creatinine increase ### Slide 53
• Congestion: Review
• Realize that I/O’s are a surrogate for what we care about (Na flux)
• Salt and Fluid restrictions are TWDFNR in patients with normal [Na+]
• Give higher doses of loop diuretics
• Do not use elevated [HCO3-] as a reason to stop diuresing ### Slide 54
• Key References
• Hyponatremia:
• 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
• Hypernatremia:
• Fluid-induced harm in the hospital: look beyond volume and start considering sodium. From physiology towards recommendations for daily practice in hospitalized adults: https://doi.org/10.1186/s13613-021-00851-3
• Congestion:
• The use of diuretics in heart failure with congestion - a position statement from the Heart Failure Association of the European Society of Cardiology: https://onlinelibrary.wiley.com/doi/10.1002/ejhf.1369
• It Is Chloride Depletion Alkalosis, Not Contraction Alkalosis: https://doi.org/10.1681/ASN.2011070720

209.3 Learning objectives

• Disturbances of Water and Sodium
• Roadmap
• How does hyponatremia cause problems?
• Hyponatremia: Resident-level algorithm
• Hyponatremia: Fellow-level algorithm

209.4 Bottom line / summary

• Disturbances of Water and Sodium
• Roadmap
• How does hyponatremia cause problems?
• Hyponatremia: Resident-level algorithm
• Hyponatremia: Fellow-level algorithm

209.5 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.

209.6 Red flags / when to escalate

• TODO: List red flags that require urgent escalation.

209.7 Common pitfalls

• TODO: Capture common errors or missed steps.

209.8 References

TODO: Add landmark references or guideline citations.

209.9 Slides and assets

• Presentations/Locke - Summer Bootcamp H2O and Na.pptx

209.10 Source materials

• Presentations/Locke - Summer Bootcamp H2O and Na.pptx