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What lytes are responsible for the resting membrane potential?
Na+ and K+
What is the normal intracellular concentration of K+?
150 mEq/L, is the MAJOR intracellular Ion
What it the normal plasma concentration of K+?
3.5 to 5 mEq/L
What is the difference between serum and plasma?
- plasma is the portion of the blood that has not clotted
- serum indicates portion of blood that has clotted
What is the Serum K+ concentration?
.5mEq higher than plasma because of lysis of cells
What maintains the high K+ gradient in the cell?
the Na+/K+ ATPase pump
The ATPase pump moves 3 Na+ ions out of the cell for every___ K+ ions into the cell. Why is ATP needed?
2, K+ is moving against the gradient.
What two substances help to move K+ into the cells?
Acidosis both metabolic and respiratory will shift K+ where?
out of the cells
Where does metabolic and respiratory alkalosis shift K+?
into the cell
How much K+ does the average person take in each day?
50 - 150 mEq/day
How is K+ excreted from the body?
- mainly through the kidney's
- some through the faecal route
T or F: We usually excrete about the same amount of potassium that we take in per day?
How low does GFR need to be to ineffectively clear K+?
What are the MAJOR regulators of k+?
What needs to be considered with a pt on an ACEI?
HyperK+, because aldosterone is blocked thereby increasing K+.
What drugs often cause hypokalemia?
- various hormones
- chemotherapeutic drugs (less common)
Is plasma concentration a good indicator of total body K+?
T or F: Acute hypoK causes hyperpolarization of the cell.
What maintains the relative negativity of the cell membrane?
Na/K ATPase pump
What is normal charge inside the cell?
-70 to -90 mVolts inside the cell
Hyperpolarization makes it more difficult for the cell to generate an action potential. What lyte imbalance causes this?
How do the sedative hypnotic drugs work?
by hyperpolarizing the cell membranes in the CNS via Cl- ions when they attach to the GABA receptor.
What is Threshhold?
The charge at which an action potential is generated
What is the consequence of hyperpolarizing the cardiac cell membranes of the normal pacemakers via hypok+?
could see some ventricular escape beats
What ECG changes might we see with hypok?
- flat or inverted T's
- prominent U's
- ST depression
Pt's on Digoxen may be at risk for increase dig toxicity because of what?
hypoK causes more binding of dig
A high Na and K diet can contribute to what?
How does HypoK affect Diabetic pt's?
- impaired insulin secretion
- decreased organ sensitivity to insulin
Is there a suggested level of K below which surgery is contraindicated?
We can expect to more rhythme disturbances below what level of K?
3.5, especially cardiac pt's
Treatments for hypo K
- potassium replacements
- correction of acid base balance
- removal of medications creating problem
How much does a normal dose of succ increase the K level?
.5 of a mEq
Why does succ increase the K level?
the fasiculations of succ cause a release of Intracellular K into the interstitium.
What pt population is at increased risk for hyperK due to succ admin, why?
- Denervation injury
- burn pt's
- result of upregulation of cholinergic receptors, Succ is contraindicated
Below what level of K is the effect of succ on the heart minimal?
6 mEq however we might see tall peaked T's
As the level of K rises what occurs with the ECG tracing
first tall peaked T's then lengthened PR, followed by a more sine wave appearance QRS eventually leading to cardiac standstill
What imbalances increase K's effect on the heart?
hypoNa+, Hypo Ca++, or acidosis
K levels above 7 present with what specific problems?
- Flaccid paralysis
- impaired phonation
- Resp Arrest
What meds cause an elevated K?
- K sparing diuretics
What predisposing factors will make a pt more prone to hyperK?
- Renal insufficiency
- hypoaldosteronism (same mechanism as ACEI)
How do we treat hyperK?
- Eliminate the cause
- reverse membrane ecitability
- remove K from body
- move K+ from ECF to ICF Via Glucose and insulin
What does Ca-gluconate do in lieu of hyperK?
- Depresses cardiac excitation
- stabilizes the rhythm
How do Beta2 agents help in hyperK?
Increase skeletal uptake of Ca++. (albuterol)
How can we remove K from the body?
- Furosemide if kidneys are functioning
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