Electrolytes Flashcards
normal serum K+
3.5 - 5.5 mEq/L
most abundant intracellular cation
K+
regulates RMP
K+
low K+ hyperpolarizes/depolarizes membrane
hyperpolarizes
high K+ hyperpolarizes/depolarizes membrane
depolarizes
Which organ is the most important regular of K+ homeostasis?
kidneys
Etiologies of hypokalemia ( < 3.5)
S/S hypokalemia
- skeletal muscle cramps
- weakness
- paralysis
EKG findings hypokalemia
- long PR & QT interval
- flat T wave
- U wave
Etiologies of hyperkalemia (> 5.5)
S/S hyperkalemia
cardiac rhythm disturbances
EKG findings hyperkalemia
5.5 - 6.5 = peaked T waves
6.5 - 7.5 = flat p wave, prolonged PR interval
7.0 - 8.0 = prolonged QRS
8.5 or greater = sine wave –> VFIB
Hyperkalemia Tx
- Calcium
- insulin + D50
- bicarb
- hyperventilate
- B2 agonist (albuterol)
- K+ wasting diuretics
- Kayexalate
- Dialysis
Max rate K+ should be administered through peripheral line
10 mEq/hour
Max rate K+ should be administered through central line
20 mEq/hour
normal serum Na+
135 - 145 mEq/L
Most abundant extracellular cation
Na+
Primary determinant of serum osmolarity
Na+
At what Na+ level should you consider delaying surgery?
less than 130
Hyponatremia
< 135
S/S hyponatremia
130 - 135 = no s/s to mild s/s
125 - 129 = N/V, malaise
115 - 124 = HA, lethargy, altered LOC
115 or less = SZ, coma, cerebral edema, resp arrest
Hyponatremia Tx
Goals:
- restore Na+ by manipulating serum osmolality & fluid balance w/ H2O restriction
- IVF based on tonicity
-diuretics
Hypernatremia
> 145
S/S hypernatremia
Based on serum osmolality:
350 - 375 = HA, agitation, confusion
376 - 400 = weakness, tremors, ataxia
401 - 430 = hyperreflexia, muscle twitching
431 or more = SZ, coma, death
Hypernatremia Tx
same goals as hyponatremia
Na+ should be corrected no more than ____ mEq/L/hour
1-2
Treating hyponatremia too quickly may cause:
central pontine myelinolysis
Treating hypernatremia too quickly may cause:
cerebral edema
normal serum Ca+ (total)
8.5 - 10.5 mg/dL
normal ionized Ca+
4.65 - 5.28 mg/dL
or
2.2 - 2.6 mEq/L
Parathyroid hormone & calcitonin feedback loop
Etiologies of hypocalcemia
- hypoparathyroidism
- vit D deficiency
- renal osteodystrophy
- pancreatitis
- sepsis
S/S hypocalcemia
- skeletal muscle cramps
- nerve irritability –> paresthesia & tetany
- laryngospasm
- mental status changes –> SZ
- Chvostek sign: tapping on angle of jaw –> facial contraction ipsilateral side
- Trousseau sign: inflate BP cuff 3 min –> muscle spasm of hand & forearm
EKG hypocalcemia
long QT interval
Hypocalcemia Tx
- Ca+
- vit D
Etiologies of hypercalcemia
- hyperparathyroidism
- CA
- thyrotoxicosis
- thiazide diuretics
- immobilization
S/S hypercalcemia
- nausea
- abdominal pain
- HTN
- psychosis
- mental status changes –> SZ
EKG hypercalcemia
short QT interval
Hypercalcemia Tx
- 0.9% NaCl
- Loop diuretic (lasix)
What hormone raises Ca+?
parathyroid hormone
What hormone lowers Ca+?
calcitonin
normal serum Mg+
1.7 - 2.4 mg/dL or 1.5 - 3 mEq/L
Calcium antagonist
Mg+
Clinical uses of Mg+
- pre-eclampsia
- opioid-sparing technique
- acute bronchospasm
- cardiac rhythm disturbance (torsades)
Which is correct about magnesium sulfate?
A. produces vasoconstriction
B. decreases sensitivity to NDNMBs
C. NMDA receptor blockade
D. increases uterine tone
C
Which is false about magnesium sulfate?
A. tocolytic
B. bronchodilator
C. antiepileptic
D. potentiates catecholamine release
D
Etiology of hypomagesemia
- poor intake
- alcohol abuse
- diuretics
- critical illness
- common w/ hypokalemia
S/S hypomagnesemia
EKG findings not significant unless very low –> long QT
Etiologies of hypermagnesemia
- excessive administration
- renal failure
- adrenal insufficiency
S/S hypermagnesemia
EKG changes not significant unless very high –> heart block
Hypermagnesemia can ___________ neuromuscular blockade with sux & nondepolarizers.
potentiate
How does Mg+ work as an opioid-sparing drug?
antagonizes NMDA receptor
