Electrolyte Abnormalities Flashcards
Hyponatremia is defined by a serum Na of what?
Serum Na <135
Hyponatremia is very common especially in which popultions?
hospitalized, ICU patients
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
What are some other non-osmotic stimuli for ADH release?
Baroreceptors
Nausea
Hypoxia
Pain
Medications
Pregnancy
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)
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
What is necessary when working up hyponatremia to minimize confusion on the underlying etiology?
a systematic approach
Acute hyponatremia is a low Na level for how long?
<48hours
chronic >48hrs or unknown duration
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
When assessing for hyponatremia, it is important that all labs be drawn (apart or simultaneously?)
simultaneously
best to avoid treatment until labs are drawn
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
What are some exam findings of hypervolemia?
hypertension
sacral or LE edema
JVD
dilated IVC on echo
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
What drugs are associated with SIADH?
antidepressents
anti convulsants
antipsychotics
cyclophosphamide
opiates
MDMA
What presents as a true hyponatremia with euvolemia and urine osm > 300?
SIADH
How to treat acute hyponatremia?
can have rapid correction of Na with little risk of ODS
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
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)
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
Besides hypertonic saline for SIADH, what else is used in treatment?
Water restriction
Furosemide
Salt/urea tablets
What are four severe complications of hyponatremia?
Seizures
coma
Death from uncal herniation
ODS
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
- replace water deficit
- 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?
- transcellular shift
- extrarenal loss
- renal loss
What are some causes of transcellular shift leading to hypokalemia?
Insulin
B2 agonist
Metabolic alkalosis
What are the most common causes of extrarenal 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
