Sodium dreadnaught

is Hard Joel M. Topf, MD Nephrology Sodium

Sodium is different ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Osmosis: the thought experiment

The movement of water in the body ,[object Object],[object Object],intracellular compartment extracellular compartment

[object Object],The movement of water in the body When the tonicity inside of cells increases, cells swell.

Why we care about osmolality ,[object Object]

So what about sodium? ,[object Object],[object Object],[object Object],[object Object]

Sodium is an indicator of osmolality ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Tonicity versus Osmolality ,[object Object],[object Object],[object Object],[object Object],[object Object],Only impermeable particles cause changes in cell volume.

Summary ,[object Object],[object Object],[object Object],[object Object]

Low sodium: hyponatremia ,[object Object],[object Object],[object Object]

Pseudohyponatremia: high osmolality ,[object Object],Hillier TA, Abbott RD, Barrett EJ. Am J Med 1999; 106: 399-403.

Pseudohyponatremia: high osmolality ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Pseudohyponatremia: high osmolality ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Hillier TA, Abbott RD, Barrett EJ. Am J Med 1999; 106: 399-403.

Hillier Study on Pseudohyponatremia Na = 140 - 0.016 Glucose Na = 140 - 0.024 Glucose Na = 141 - 0.016 Glucose Na = 151 - 0.04 Glucose

Pseudohyponatremia: high osmolality ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Pseudohyponatremia: Normal osmolality ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Participant summary report: surveys 1982-2002. Northfield, Ill.: College of American Pathologists, 1982-2002.

True hyponatremia ,[object Object]

True hyponatremia ,[object Object],Negative salt balance causes hypovolemia

[object Object],Causes of hyponatremia: Increased intake ,[object Object],clearing

Water clearance ,[object Object],[object Object],[object Object],[object Object]

Free water clearance and soup ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],In regards to sodium all that matters is the free water component

Free water clearance 0.5 liter free water Solute component (plasma osmolality 284 mOsm/kg) Use clearance to calculate the osmolar clearance 1 liter 142 mOsm/Kg 0.5 liter 284 mOsm/Kg

Free water clearance Solute component (Solute Clearance) ? 0.5 liter Zero mOsm/Kg Free water component (Free water Clearance) The free water component equals urine volume minus the solute component 1 liter 142 mOsm/Kg 0.5 liter 284 mOsm/Kg

Free water clearance 0.5 liter 568 mOsm/Kg 1 liter 284 mOsm/Kg -0.5 liter 568 mOsm/Kg

Free water clearance Solute component (plasma osmolality 284 mOsm/kg) Use clearance to calculate the osmolar clearance 1 liter 284 mOsm/Kg 0.5 liter 568 mOsm/Kg

Free water clearance Solute component (Solute Clearance) ? Free water component (Free water Clearance) 0.5 liter 568 mOsm/Kg – 0.5 liter Zero mOsm/Kg 1 liter 284 mOsm/Kg

Free water clearance: Implications Dilute urine increases serum osmolality Concentrated urine de-creases serum osmolality Dilute urine Solute free water Concentrated urine Negative free water Na + Na +

Free water clearance: The math

Free water clearance: Math Examples

Electrolyte free water clearance ,[object Object],[object Object]

Electrolyte free water clearance ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Electrolyte free water clearance ,[object Object],[object Object],[object Object],Free water clearance Electrolyte free water clearance

Electrolyte free water clearance: CHF vs. SIADH ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Etiology of hyponatremia ,[object Object],[object Object],Ingestion > EFW clearance

Etiology of hyponatremia ,[object Object],[object Object],[object Object],Hyponatremia is primarily due to an inability to produce dilute urine Dilute urine Solute free water

Etiology of Hyponatremia: 3 steps to generating dilute urine ,[object Object],[object Object],[object Object],1400 285 100 50

Failure to Generate dilute urine ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Failure to Generate dilute urine ,[object Object],[object Object],[object Object],[object Object],[object Object]

Failure to Generate dilute urine ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

ADH is normally used to regulate osmolality ,[object Object],[object Object],[object Object]

ADH is normally used to regulate osmolality We start with an increase in the plasma osmolality This is detected by the brain The brain releases ADH ADH acts on the kidney The kidney reacts by retaining water and producing a small amount of concentrated urine. The retained water goes here not here

ADH is also secreted when there is poor perfusion. ,[object Object],[object Object],[object Object]

SIADH: ADH release with no physiologic benefit ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Causes of SIADH ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The response to hyponatremia Low sodium concentration causes water to move into the cells. In the brain this causes an increase in ICP. Compensated chronic hyponatremia is essentially asymptomatic.

The problem with compensation The starting point is after compensation has reduced the amount of intracellular solute and the ICP Now, an over-eager intern sees the low sodium and starts an infusion of 3% NaCl to raise the sodium to normal. Sodium 108 The sodium draws water from the inside of the cells causing the brain to shrivel. The problem with interns Sodium 134

Central pontine myelinolysis ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Damned if you do. Damned if you don’t ,[object Object],[object Object]

Symptomatic vs. Asymptromatic ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Symptomatic vs. Asymptromatic ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Symptomatic vs. Asymptromatic ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Ayus JC, Arieff AI. JAMA 1999; 281: 2299-2304.

Conservative therapy for asymptomatic hyponatremia ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Conservative therapy for asymptomatic hyponatremia ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Water restriction is ineffective

[object Object],[object Object],[object Object],[object Object],Conservative therapy for asymptomatic hyponatremia

Acute symptomatic hyponatremia ,[object Object],[object Object],[object Object],[object Object]

Change in sodium formula ,[object Object],[object Object],[object Object],[object Object],[object Object],Change in sodium following one liter of any IVF. TBW = kg x 0.7 or 0.6 or 0.5 or 0.4 Na in 3%: 513 Na in 0.9%: 154 Na in 0.45%: 77 Na in 0.225%: 39

Change in Sodium Formula: Examples ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Hyponatremia: Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Hypernatremia ,[object Object],[object Object],[object Object],[object Object]

Causes of hypernatremia ,[object Object],[object Object],Generation ,[object Object],[object Object],[object Object],Maintenance ,[object Object],[object Object],[object Object]

[object Object],[object Object],Generation – Gain of sodium ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Generation – Loss of water ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Electrolyte free water clearance

Diabetes insipidis ,[object Object],[object Object],[object Object],[object Object]

Diabetes insipidis ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Maintenance of hypernatremia ,[object Object]

Inability to drink ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Summary of hypernatremia ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Hypernatremia is a sodium concentration > 145 mEq/L The development of hypernatremia is a two part processes:

Symptoms of hypernatremia ,[object Object],[object Object],[object Object],[object Object],[object Object]

Consequences of mismanagement ,[object Object]

Treatment ,[object Object],[object Object],[object Object],[object Object]

[object Object],The amount of fluid ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The rate of correction ,[object Object],[object Object],[object Object],[object Object]

Accounting for ongoing losses ,[object Object],[object Object],[object Object],[object Object],[object Object]

Treating hypernatremic patients ,[object Object],[object Object],[object Object],[object Object]

Hypernatremia summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Sodium dreadnaught

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