Electrolyte Abnormalities Flashcards by Liz Pennington

Hyponatremia is defined by a serum Na of what?

Serum Na <135

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Hyponatremia is very common especially in which popultions?

hospitalized, ICU patients

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ADH is released in response two which two stimuli?

Osmotic stimuli from increases in serum osmolarity detected by osmoreceptors in the anterior hypothalamus

non-osmotic stimuli from decreases in BP or BV detected by aterial baroreceptors

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What are some other non-osmotic stimuli for ADH release?

Baroreceptors

Nausea

Hypoxia

Pain

Medications

Pregnancy

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Hyponatremia results primarily from increases in what?

increases in TBW, not changes in sodium

(can be from increase in fluid intake or decrease in water excretion)

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What are the clinical manifestations of hyponatremia?

depends on severity and acuity, most asymptomatic until levels are <125

headache
fatigie
dizziness
nausea
seizures
cerebral edema

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What is necessary when working up hyponatremia to minimize confusion on the underlying etiology?

a systematic approach

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Acute hyponatremia is a low Na level for how long?

<48hours

chronic >48hrs or unknown duration

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What are the two steps of approaching hyponatremia?

measure serum osmlarity to determine if hypotonic, isotonic or hypertonic hyponatremia is present
if hypotonic hyponatremia is present, then assess volume status by measuring random urine Na and urine osmolarity

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When assessing for hyponatremia, it is important that all labs be drawn (apart or simultaneously?)

simultaneously

best to avoid treatment until labs are drawn

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What are some exam findings indicative of hypovolemia?

hypotension

orthostatic VS +

tachycardia

poor cap refill

dry mucosa

flat JV

decreased urine output

>50% collapse of IVC during echo

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What are some exam findings of hypervolemia?

hypertension

sacral or LE edema

JVD

dilated IVC on echo

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What is a diagnosis of exclusion after ruling out cortisol deficiency, hypothyroidism and other causes?

What is the most common malignancy associated with this?

SIADH

Small cell lung cancer

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What drugs are associated with SIADH?

antidepressents

anti convulsants

antipsychotics

cyclophosphamide

opiates

MDMA

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What presents as a true hyponatremia with euvolemia and urine osm > 300?

SIADH

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How to treat acute hyponatremia?

can have rapid correction of Na with little risk of ODS

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how is chronic hyponatremia treated?

careful of rapid correction as pt is at higher risk of ODS

goal is to raise serum Na by 8-10mEq/day with no more than 18mEq/L within the first 48hrs

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For symptomatic hyponatremic patients give what to raise Na quickly (acute setting)?

Give hypertonic saline 3% solution

(raise it to 3-4 mEq/L to stop symptoms and then slowly raise back to normal)

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If Na is correcting too quickly, how can you lower it back to acceptable level to avoid ODS?

D5W

DDAAVP

d/c some therapies that may be raising Na too fast

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Besides hypertonic saline for SIADH, what else is used in treatment?

Water restriction

Furosemide

Salt/urea tablets

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What are four severe complications of hyponatremia?

Seizures

coma

Death from uncal herniation

ODS

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What is Osmotic Demyelination Syndrome?

ODS is delayed 2-6 days after rapid Na correction

Demyelination occurs in the pontine/extrapontine nucleus

can cause Locked-in syndrome

Diagnose via MRI, may take 4 weeks to show up

alcoholics are at high risk for this

Hypernatremia, often seen in infants and elderly, is defined as a serum Na of

Risk factors include:

>145

Trauma, burns, ICU patients, dementia, uncontrolled DM

What are the two underlying processes that lead to hypernatremia?

unreplaced water loss (fancy for dehydration)

-common in elderly due to impaired thirst mechanism

Sodium overload

What are the clinical manifestations of hypernatremia?

results in cell shrinkage as water moves out of cel into ECF causes irritability, AMS, lethargy, seizures, hyperreflexia, ICH acute-\<48hrs chronic-\>48hours or unknonw duration

While acute hypernatremia can be corrected with little risk, correcting chronic hypernatremia too rapidly can lead to ? What are the two steps of correction?

cerebral edema goal is to lower serum sodium by 10-12mEq/day 1. replace water deficit 2. correct underlying cause leading to water loss

Excess K is removed from the body by which organ?

Mostly via the **kidneys** with some loss in the feces Kidneys are primary regulator of K

Which part of the kidney regulates K secretion?

The distal part of the nephron principal cells for secretion a-intercalated cells for reabsorption

Serum K is regulated very closely, thus any small alteration in K can have what?

serious major clinical manifesations

Hyperkalemia is defined as serum K of

\>5.0 or 5.5meq/L affects up to 10% of hospitalized pts

high serum K can cause which cardiac complications?

V Fib Bradycardia from AV block Asystole

Hyperkalemia can also decrease ammioniogenesis and decrease NH4Cl excretion leading to what?

less net acid excretion and metabolic acidosis

high K concentration makes the membrane potential (more or less) negative?

less negative

A sinusoidal wave pattern seen on EKG correlates with which electrolyte abnormality?

Hyperkalemia (\>9) and V Fib

What are the two main reasons for hyperkalemia?

Transcellular shift Decreased renal K excretion

Transcellular shift leading to hyperkalemia can be from which causes?

Pseydhyperkalemia Metabolic acidosis insulin deficiency, hyperglycemia and hyperosmolality increased tissue catabolism meds exercise blood transfusion

What causes Pseudohyperkalemia

RBC hemolysis uring venipuncture clotted blood samples (check plasma to rule out) Leukocytosis

What are the causes of decreased ranl K excretion?

Low aldosterone secretion Aldosterone resistance AKI/CKD

A fractional excretion of K \<10% indicates A fractional excretion of K \>10% indicates

renal etiology of hyperkalemia extrarenal etiology of hyperkalemia

If peaked T waves are seen on EKG due to hyperkalemia, give what drug to stabilize cardiac membrane?

calcium gluconate

For transcellular shift leading to hyperkalemia, give which drugs?

insulin or dextrose B2 agonist

to remove excess K, give which drugs?

Sodium Polystyrene sulfonate Zirconium cycloslicate Patiromer

What are two general modifications to treat hyperkalemia regardless of cause?

low K diet d/c meds that increase K (ACEI, ARB, Ald blockers, K supplements)

Hypokalemia is defined as a serum K of

\<3.5 mEq/L affects up to 20% of hospitalized patients and is less common in outpatients

What are some cardiac complications associated with hypokalemia?

PACs PVCs tachycardia/bradycardia V. fib

What are some muscular complications of hypokalemia?

skeletal muscle weakness (diaphragm) rhabdomolysis

Hypokalemia is associated with which acid-base disturbance? What does low K do to the membrane potential?

metabolic alkalosis low K makes the membrane potential **_more_** negative

What are the three main reasons for hypokalemia?

1. transcellular shift 2. extrarenal loss 3. renal loss

What are some causes of transcellular shift leading to hypokalemia?

Insulin B2 agonist Metabolic alkalosis

What are the most common causes of **_extra_**renal loss leading to hypokalemia?

GI loss via vomiting, NG suctinoing, diarrhea Cutaneous loss via sweating

What are the causes of renal loss leading to hypokalemia?

diuretics increased mineralocorticoid activity (1' hyperaldosteronism, Cushing syndrom) hypomagnesemia

What are the urine labs to order to diagnose hypokalemia?

24hr urine K (nest method for assessing renal K excretion) Urine K/Cr ratio

how should hypokalemia be treated?

treat underlying cause give KCl K will increase by 0.1 units for every 10 units of KCl given replace Mg if low