Sodium and Potassium Disorders (CMPP)

What is the #1 determinant for serum osmolality

Na

What is the predicted osmolality forumla

(2*Na) + (Glucose / 18) + (BUN/2.8)

What factors are needed for hpyonatermia to develop

Increase in intravascular H2O

Inability of the body to respond by limiting intake and excreted diluted urine

What can cause hyponatermia

Polydipsia

Decrease in effective circulation

SIADH

Hyponatremic Dehydration

Pseudohyponatermia

How does polydipsia induce hyponatermia

More water is ingested than can be excreted by kidny

What is the most diluted urine can be made

50 mOsm/L

What can cause hyponatermia secondary to polydipsia

Psychogenic Polydipsia

Beer Potomania

Psychogenic Polydipsia

• A psychiatric craving for excessive amount of water

uncommon cause of hyponatermia

Beer Potomania

A polydipsia due to massive consumption of beer

Uncommon cause of hyponatermia

At what volume of beer will potomania be induced

> 4 L

Where does ADH come from

Posterior Pit

What is the order of favor for the body with osmolality, Na, and volume

1. Volume

2. Osmolality

3. Na

What does decreases effective circulation cause hyponatermia

Increases the secretion of ADH → More retained water

Syndrome of Inappropriate ADH (SIADH)

A condition where ADH is secreted in absence of hypovolemia or high osmolality

What can cause SIADH

Pulm:

• Pnuemonia

• TB

• Acute Failure

• Mechanical Ventilator

Neuro/Psych

• Meningitis

• Encephalitis

• CVA

• Trauma

• Psychosis

Malignancy

• Paraneoplastic Syndrome

Drugs

• Nacrotics

• Chemo

• TCAs

• Anticonvulsants

• Antipsychotics

How is SIADH dx

Hyponatermia

Low Serum Osmolality

High Urine Osmolality

Euvolmeic

How does hyponatermia cause cerebral edema

Low serum osmolality causes fluid to leave circulation and go into brain tissue

What is normal Na range

135-145

When does symptoms of hyponatremia onsent

Na < 125

What chagnes the presentation of hyponatermia

Rapidity

Magnitude

How does acute onset hyponatremia present

• (Na = 120-125) Nausea + Malaise

• (Na = 115-120) Headaches + Lethargic + Confusion

• (Na < 115) LETHAL + Stupor + Seizure + Coma

Acute Onset Hyponatremia

A decrease in Na that develops < 3 days

Chronic Hyponatermia

A decrease in Na that developed over > 3 days

How does chronic hyponatremia present

Often asymptomatic

Pseudohyponatermia

A condition where serum Na is low but serum osmolality is nornal

What can cause pseudohyponatermia

False Positive

Elevated Plasma Protein (Multiple Myeloma)

Hypertrigylceridemia

Hyperglycemia

Mannitol

How does hyperglycemia cause pseudohyponatermia

High Glucose causes water to be drawn into vascualture

The extra water dilutes the pre-existing Na

No S/S as osmolality is normal

What is a normal serum glucose

70-100

What is the relation of glucose to Na

For every 100 mg/dL increase in glucose above 100 mg/dL, Na will decrease by 2 mEq/L

What is normal serum osmolality

275-290

What causes the S/S of hyponatremia

Low osmolality

A patient has a low Na, low osmolality, and low urine osmolality. What is the likely cause?

Psychogenic Polydipsia or Beer Potomonia

A patient has a low Na and normal serum osmolality. What is the likely cause

Pseudohyponatermia

A patient has a low Na, low serum osmolality, high urine osmolality, and hypervolemic. What is the likely cause?

Low effective circulation (CHF / Cirrhosis / Nephrotic Syndrome)

A patient has a low Na, low serum osmolality, high urine osmolality, and euvolemic. What is the likely cause?

SIADH

A patient has a low Na, low serum osmolality, high urine osmolality, and hypovolemic. What is the likely cause?

Hyponatermic Dehyrdation

Hyponatermic dehydration

A condition in which the body is losing Na faster than water.

Caused in conditions like diarrhea

What is the most important factor in tx of hyponatermia

Pateint Presenation

Tx for Asymptomatic Hyponatermia

Slowly fix over several days

Fix underlying psuedohyponatremia

Pontine Myelinolysis

Irreversible neuronal damage caused by a dramatic shift of water out of the brain, often fatal

Can be induced when tx hyponatermia too quick

At what rate is pontine myelinolysis a significant risk

Correction of Na > 12 mEq over 24 hours

Tx for Hypovolemic Hyponatermia

0.9 NS

Tx for Hypervolemic Hyponateremia

Fluid Restriction

Loop Diuretic

Tx for Euvolemic Hyponatermia

Fluid Restriction (~800)

Tx for Severe Symptomatic (Intractable Seizure) Hyponatremia

3% NS at rate greater than Na by 1-2mEq/L for 3-4 hours

Slow rate once patient stops seizing

Hypernatermia

A serum Na > 145

What is the body defense for hypernatermia

Osmoreceptors trigger release of ADH and thrist via hypothalamus

What can cause hypernatermia

Diarrhea (#1)

Fluid Evaporation (Skin and Lungs)

Burns

Hypodipsia

Loop Diuretics

Osmotic Diuresis

DI

Diabetes Inspidius (DI)

A condition of ADH impairment

What are the types of DI

Central

Nephrogenic

Central DI

A condition of impaired secretion of ADH for posterior pit

What are the causes of Central DI

Idiopathic #1

Brain Tumors

Brain Surgery

Head Trauma

Nephrogenic DI

A condition in which the kidneys do not respond to ADH

What can cause Nephrogenic DI

Intrinsic Renal Disease

Meds (Lithium #1 cause)

What can cause primary hypodipsia

Access to water is limited

Homeostatic mechanisms fail

Hypothalamic Dysfunction

Can be from both primary and reason for problem to persist

What are secondary causes of hypodipsia

Institutionalized

Handicapped

P/O

Intubated

Dementia

Delirium

What neuro symptoms can be caused by hypernatermia

AMS

focal deficits

seizures

Renal Cause of Hypernatermia often presents with what

Polyuria

A patient has high serum Na and hypervolemia. What are the likely causes

Elevated aldosterone (Hyperaldosteronism)

Elevated corticosteroid (Cushing’s)

A patient has high Na, hypovolemia, low UOP, high urine osmolality, and low urine Na. What is the likely cause

Insensible loss

GI fluid loss

Primary Hypodipsia

A patient has high Na, hypovolemia, high UOP, and low urine osmolality. What is the likely cause?

DI

How can we tell the difference between DI types

DDVAP test

Desmopressin (DDVAP)

A synthetic form of ADH

DDVAP Test

A test used to determine if DI is central or nephrogenic

• If giving DDVAP increases urine osmolality by 50% = Central

• If giving DDVAP has no effect on urine osmolality = Nephrogenic

What is the #1 factor for tx of hypernatremia

Clinical Status (Neuro and Hemodynamic)

Correcting hypernatermia too rapid leads to

Cerebral Edema

Idiogenic Osmoles

Molecules created by brain cells when the body has a chronic hyperosmolality

Allows brain tissue to maintain osmotic balance

At what rate do we normally correct hypernatermia

5-8 mEq/L / day

Tx for Stable Hypervolemic Hypernatermia

Treat Underlying Disorder

Give fluids (PO>IV)

Tx for Stable Hypovolemic Hypernatermia

Calcaute free H2O deficit

Give fluid (PO>IV)

Tx for Neurogenically Unstable Hypernatermia

0.9 NS at 10-12 mEq/L correction rate

Tx for Hemodynamically Unstable Hypernatermia

0.9 NS

Move to 0.45 NS when stable

Tx for Central DI

DDAVP

Tx for Nephrogenic DI

Low Na Diet

Thiazide

What is normal serum K

3.5 - 5

What is the normal daily intake of K

20-60 mEq

What induces K execretion to increase

Aldosterone

What are the causes of hypokalemia

Decreased intake

Increased loss

Transcelluar Shift (Intracellular)

What can cause increased loss of K

GI Loss (Diarrhea and Vomiting)

Evaporative Loss

Hypovolemia (Due to RAAS)

Primary/Secondary Hyperaldosteronism

Cushing’s

What can cause K to shift into cells

Alkaemia

Exogenous Insulin

SABAs

Hypokalemic Periodic Paralysis

Hypokalemic Periodic Paralysis

Rare genetic disease that causes shifts in K and episodic weakness

At what level does hypokalemia present

K < 3.0

How does hypokalemia present

Fatigue

Muscle Weakness

Myalgia

Muscle Cramping

Ileus

Constipation

Cardiac Dysrhythmia

Hypoventilation

Paralysis

What is the realationship between K and acid-base disorders

K is needed to exchange H+ ion from cells

• In alkoloses, K is pushed into cells to pull out H (Hypokalemia)

• In acidosis, K is pulled out of cells to push in H (Hyperkalemia)

What is the maxmium excretion of K

25 mEq / day

A increased K in urine in setting of hypokalemia suggests

Renal Cause

What tests are good to order for hypokalemia?

ABGs

Serum Mg

EKG

Why do we take a Mg serum in the setting of hypokalemia

Mg deficiency can cause hypokalemia

What are the EKG findings for hypokalemia

Prominent U-wave (1st Sign)

ST-depression

Flattened T-wave

What are the route in which we can give KCl

PO

IV

What is the dosing for KCl for hypokalemia

10 mEq for every 0.1 mEq below 3.5

What is the maximum dosing for KCl

PO = 40 mEq q4h

IV = 40mEq/L at 20mEq/hr

Central Line = 100mEq at 20/hr

What is the risk of rapid correction of hypokalemia

V-tach / V-fib

Hyperkalemia

Serum K > 5.0

Pseudohyperkalemia

A false elevation of K due to hemolyzed blood

What are causes of true hyperkalemia

Decreased excretion (#1)

Transcellular Shift

Increased intake of K

What foods are high in K

Salt Subs

Bananas

Oranges

Potatoes

Spinach

Fish

Beans

Wjat can cause decreased excretion of K

Hypoaldosteronism

Adrenal Insufficiency

What can cause K transcellaur shift out of cell

Metabolic Acidosis

Muscle Relaxants / Paralytics

Rhabdomyolysis

Tumor Lysis Syndrome

What medications can induce hyperkalemia in kidney disease

Renin Inhibitors

ACEIs

ARBs

Aldosterone Antagonists (Spironolactone)

NSAIDs (Decrease GFR)