Hyponatremia

Exam 1, Dr. Wai

135-145 mEq/L

normal range for serum Na

Hyponatremia

Na < 135 mEq/L

Hypernatremia > 145mEq/L

sodium

• accounts for 90% of osmotic activity in the ECF

• plasma sodium concentration reflects water balance

hyponatremia

• most common electrolyte disorder

• common both inpatient and in ambulatory setting

steps to diagnose hyponatremia

1. assess osmolality

2. assess volume status

280-285 mOsm

normal serum osmolality

hypovolemic hypotonic hyponatremia

• diminished skin turgor, intraocular tension, dry mucous membranes, orthostatic hypotension, tachycardia

euvolemic hypotonic hyponatremia

• normal: pulse, BP, skin turgor

• no edema

hypervolemic hypotonic hyponatremia

• edema, dyspnea on exertion, pulmonary rales, ascites, anascara

clinical manifestations of hyponatremia

• CNS dysfunction

  • many are asymptomatic when Na > 120

  • more obvious symptoms when there is a large or rapid decrease in Na levels

• symptoms:

  • mild: nausea and malaise

  • moderate: disorientation, headache, restlessness, lethargy

  • severe: seizures, coma, respiratory arrest, permanent brain damage, brain stem herniation, death

osmotic demethylation

• serious adverse effect if you try to correct hyponatremia too fast

isotonic hyponatremia

• normal plasma osmolarity, low serum Na

• also called pseudohyponatremia

• sodium displaced in ECF

causes of isotonic hyponatremia

• hypertriglyceridiemia

• hyperproteinemia

• multiple myeloma

isotonic hyponatremia (psuedohyponatremia) treatment

• none, correct underlying problem

hypertonic hyponatremia

• increase in plasma osmolality and decrease in Na levels

  • caused by a shift of water from the ICF to the ECF

hypertonic hyponatremia causes

• mannitol administration/infusions

• hyperglycemia ****

hypertonic hyponatremia treatment

• manage underlying causes (diabetic ketoacidosis)

• hyperglycemia→ give insulin

hyoptonic hyponatremia

• most common cause of hyponatremia

• differentiate by volume status

<100 mEq/kg

• urine osmolarity _____

• normal water excretion → intake problem (polydipsia, low solute intake)

>100mEq/kg

• urine osmolality ___

• impaired water excretion

• rule out hypothyroid, adrenal suffiiciency

• evaluate urine sodium

> 20 mEq/L

• urine sodium ____

• renal losses

• DIURETICS

• adrenal insufficiency

• SIADH

<20 mEq/L

• urine sodium _____

• extrarenal losses (GI, skin, lung)

• heart failure, cirrhosis, nephrosis

• polydipsia, low solute intake (tea and toast or beer protomania)

hypovolemic hypotonic hyponatremia

• loss of water and sodium

• GI salt loss → D/V, NG suction

• skin losses→ excessive sweating, burns

• Renal losses→ renal disease, diuretics****

• sodium loss »» water loss

thiazide diuretics

• most common renal cause of hypovolemic hypotonic hyponatremia

decrease

• hypovolemic hypotonic hyponatremia effect on TBW and TBNa

hypovolemic hypotonic hyponatremia laboratory values

• renal: UOsm high, UNa high

• nonrenal- IOsm high, UNa low

hypovolemic hypotonic hyponatremia clinical presentation

• orthostasis, hypotension, tachycardia, dry mucuous membranes, CNS changes

hypovolemic hypotonic hyponatremia chronic treatment

• 0.9% NaCl until vital signs stable, then maintenance fluid (D5-1/2 NS)

drug induced hypovolemic hypotonic hyponatremia

• very common

• most cases of severe hyponatremia have been due to a thiazide type diuretic

• risk factors: elderly, low body mass, low potassium

thiazide mechanism

• interferes with sodium reabsorption in distal convoluted tubule (DCT)

• blocks Na reabsorption at Na/Cl cotransporter

• produces volume depletion which stimulate ADH release

• enhanced water reabsorption

• medullary concentration gradient unaffected

hypovolemic hypotonic hyponatremia goal

• reverse the hypotonicity without causing osmotic demthylation

hypovolemic hypotonic hyponatremia treatment

• chronic cases- give 0.9% NaCl

• correct at maximum rate of 10-12mEq/L/day

• slower for more severe

• monitor sodium every 4 hours

• can fgive DDVAP 2mg IV and D5W if start to overcorrect

• treat underlying cause: permanently discontinue thiazide diuretics

10-12

correct hypovolemic hypotonic hyponatremia at a maximum rate of ___ mEq/L/day

4

monitor sodium every __ hours for hypovolemic hypotonic hyponatremia

hypovolemic hypotonic hyponatremia treatment for acute or lifethreatening

• seizures or coma- 3% NaCL

• risk of cerebral edema or brain herniation outweighs risk of correcting sodium too rapidly

• monitor every 2 hours

2

monitoring for acute or life threatening hypovolemic hypotonic hyponatremia is to monitor Na every __ hours

acute and severe symptom (seizures or coma)treatment for hypovolemic hypotonic hyponatremia

• hypertonic saline (3% NaCl) bolus 100ml over 10min (x 3 as needed)

acute and moderate symptom (confusion or lethargy) hypovolemic hypotonic hyponatremia treatment

• hypertonic saline (3% NaCl) continuous infusion 0.5-2ml/kg/hr

euvolemic hypotonic hyponatremia causes

• SIADH

• primary polydipsia

• tea and toast or beer protomania

• hypothyroidism

• hypocortisolism

euvolemic hypotonic hyponatremia

• water gain or rentention

• increase TBW

euvolemic hypotonic hyponatremia SIADH lab values

• Uosm high, UNA high

euvolemic hypotonic hyponatremia clinical presentation

• depends on severity of hyponatremia

  • seizures, lethargy

euvolemic hypotonic hyponatremia lab values for polydipsia

• UOsm low

• UNa low

euvolemic hypotonic hyponatremia chronic treatment

• water restriction, salt tablets, urea, loop diuretics, vaptans

syndrome of inappropriate antidiuretic hormone secretion (SIADH)

• most common cause of euvolemic hypotonic hyponatremia

• elevated levels of ADH that is inappropriate based on osmotic and volume stimuli

• induces reabsorption of water from the collecting duct which firther increases hyponatremia

• leads to a reduction in aldosterone secretion→ increases urinary Na excretion (high urine Na)

• component of increased water intake also involved

drugs that can cause SIADH

• antidepressants (Celexa, Prozac, Zoloft, Lexapro, Paxil- SSRIs), Trixyclics, and Venlafaxine

• antipsyhotics,vinca alkaloids, MDMA

• chemotherapy- vincristine, cyclophosphamide

• anticonvulsants- carbamazepine

mechanism of SIADH drug induction

• stimulate ADH release (central)

  • serotonin may stimulate ADH release

• potentiate the action of ADH (renal)

  • chlorporamide, carbamazepine, oxcarbazepine, and cyclophosphamide

euvolemic hypotonic hyponatremia reatment

• fluid restriction

• less than 1 liter per day

3% NaCl plus IV furosemide, monitor every 2 hours

life threateneing SIADH (coma/seizures) or acute (<48 hrs) euvolemic hypotonic hyponatremia treatment

chronic SIADH euvolemic hypotonic hyponatremia treatment

• stop causative agent or treat underlying cause

• fluid restriction less than 1 liter per day

• patients who do not respond to fluid restrcition in 1-2 wereks- may need medication treatment

• correct at maximum rate of 10-12 mEq/L/day

• monitor sodium every 4 hours

• medications: urea, salt tabs (500-2g TIB), topical dose 1 g TID)

urea, salt tablets

medications you can give for chronic SIADH euvolemic hypotonic hyponatremia treatment if fluid restriction is not working

hypervolemic hypotonic hyponatremia

• increase in water and sodium

• water gain »»» sodium gain

• mechanism- angiotensin II, aldosterone, norepi, ADH

• TBW increases

• TBNa increases

hypervolemic hypotonic hyponatremia causes

• heart failure

• liver cirrhosis

• kidney failure

hypervolemic hypotonic hyponatremia laboratory values

• UOsm high, UNa high

hypervolemic hypotonic hyponatremia clinical presentation

• peripheral and pulmonary edema, variable blood pressure

hypervolemic hypotonic hyponatremia chronic treatment

• Na restriction, water restriction, loop diuretics, vaptans

treatment in hypervolemic hypotonic hyponatremia with heart failure

• fluid restriction

• sodium restriction- less than 2g/day

• loop diuretics

• treat heart failure

treatment of hypervolemic hypotonic hyponatremia with cirrhosis

• fluid restriction

• sodium restriction- less than 2g/day

• diuretics (loop + mineralcorticoid receptor antagonist)

• treat ascited - GI section of therapeutics

hypertonic hyponatremia

21 yo M with DM 1 presents to ED the with nausea, vomiting, and confusion. He ran out of insulin 3 days ago.
 
Lab results: Na 122, K 3.9, Cl 101, CO2 13, BUN 32, Cr 0.9, glucose 600, ketones 4.7.

Which most likely describes this type of hyponatremia?

vincristine, cyclophosphamide, zoloft, carbamazepine

57 yo F with stage IV breast cancer, depression, trigeminal neuralgia presents to the ED after new onset witnessed seizure at home. Her recent chemo tx: vincristine, cyclophosphamide.

Home meds: Zoloft 200 mg daily, carbamazepine 900 mg TID. 
Labs: Na 108, K 3.7, Cl 87, CO2 20, BUN 65, SCr 2.3, glucose 105. UOsm 248. UNa 62.

What is the most likely underlying cause of hyponatremia? (Select all that apply)

UOsm is high, UNa is high

57 yo F with stage IV breast cancer, depression, trigeminal neuralgia presents to the ED after new onset witnessed seizure at home. Her recent chemo tx: vincristine, cyclophosphamide.

Home meds: Zoloft 200 mg daily, carbamazepine 900 mg TID. 
Labs: Na 108, K 3.7, Cl 87, CO2 20, BUN 65, SCr 2.3, glucose 105. UOsm 248. UNa 62.

Interpretthe urine chemistries

fluid restrict, give 3% NaCl, monitor every 2-4 hours

57 yo F with stage IV breast cancer, depression, trigeminal neuralgia presents to the ED after new onset witnessed seizure at home. Her recent chemo tx: vincristine, cyclophosphamide.

Home meds: Zoloft 200 mg daily, carbamazepine 900 mg TID. 
Labs: Na 108, K 3.7, Cl 87, CO2 20, BUN 65, SCr 2.3, glucose 105. UOsm 248. UNa 62.

What is the most likely underlying cause of hyponatremia? (Select all that apply)

hypovolemic, HCTZ

85 yo F with HTN presents to the ED for N/V/D, orthostatic hypotension, and confusion x 3 days. Family thinks she caught a “stomach bug.” She hasn’t kept any liquids down. She continued taking her HCTZ 25 mg daily as prescribed. Her mucous membranes are dry.

Labs: Na 119, K 3.7, Cl 96, CO2 24, BUN 65, SCr 2.3, glucose 87. UOSm 532. UNa 46.

What is the most likely type of hyponatremia? What is the most likely underlying cause?

UOsm is high, UNa is high

85 yo F with HTN presents to the ED for N/V/D, orthostatic hypotension, and confusion x 3 days. Family thinks she caught a “stomach bug.” She hasn’t kept any liquids down. She continued taking her HCTZ 25 mg daily as prescribed. Her mucous membranes are dry.

Labs: Na 119, K 3.7, Cl 96, CO2 24, BUN 65, SCr 2.3, glucose 87. UOSm 532. UNa 46.

What is the most likely type of hyponatremia? What is the most likely underlying cause?

stop HCTZ, give 0.9% NaCl, 10-12 mEq/L/day

85 yo F with HTN presents to the ED for N/V/D, orthostatic hypotension, and confusion x 3 days. Family thinks she caught a “stomach bug.” She hasn’t kept any liquids down. She continued taking her HCTZ 25 mg daily as prescribed. Her mucous membranes are dry.

Labs: Na 119, K 3.7, Cl 96, CO2 24, BUN 65, SCr 2.3, glucose 87. UOSm 532. UNa 46.

What is the most likely type of hyponatremia? What is the most likely underlying cause?

3% NaCl, check electrolytes in 2-4 hours

A 32 yo previously healthy female collapsed at the finish line of a marathon with a new-onset, witnessed seizure. In the ED, her Na 117 mEq/L and vital signs stable. Yesterday, her Na 137 mEq/L at a routine lab draw.

What is the most appropriate treatment and monitoring?

hypervolemic, cirrhosis

A 48 yo male with 30-year alcohol use presents to the ED with shortness of breath and abdominal ascites. He gained 20 pounds over the last 3 weeks. He is diagnosed with new onset cirrhosis.

Labs: Na 118, K 3.4, Cl 104, CO2 22, BUN 20, SCr 1.2, glucose 193. SOsm 268. UOSm 170. UNa 16.

What is the most likely type of hyponatremia and underlying cause?