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- Decrease in K+ causes decreased excitability of cells, therefore cells are less responsive to normal stimuli.
- *Huge effect on cardiac muscle
What causes hypokalemia?
- Diuretics (Lasix)
- Digitalis (Digoxin competes with K+ in Na/K+ ATP pump)
- Water intoxication
- Diarrhea/Laxative abuse
What do you do if your patient has hypokalemia?
- Encourage potassium rich foods
- K+ replacement (IV or PO)
- Monitor lab values
- D/C potassium-wasting diuretics
- Treat underlying cause
An increase in K+ causes increased excitability of cells
What causes hyperkalemia?
- Increase in K+ intake
- Renal failure *most common
- K+ sparing diuretics
What do you do if your patient has hyperkalemia?
- Eliminate K+ administration
- Increase K+ excretion (Lasix, Kayexalate)
- Infuse glucose and insulin
- Cardiac moniroting
What causes hyponatremia?
- Excessive diaphoresis
- Wound drainage
- Low salt diet
- Renal disease
What do you do if your patient has hyponatremia?
- FVD: IV therapy to restore both fluid and Na
- FVE: Administer osmotic diuretic (Mannitol) to excrete water rather than sodium
- Increase oral sodium intake and restrict oral fluid intake
What causes hypernatremia?
- Renal failure
- Increase in oral Na intake
- Na containing IV fluids
- Decreased urine output with increased urine concentration
What do you do if your patient has hypernatremia?
- FVD: 0.45% NS. If caused by both Na and fluid loss, will administer NaCl. If inadequate renal excretion of sodium, will administer diuretics
- Mild: Ensure water intake
What causes hypocalcemia?
- Decreased oral intake
- Lactose intolerance
- Decreased vitamin D intake
- End stage renal disease
- Acute pancreatitis
- Removal or destruction of parathyroid gland
What does a positive Trousseau's sign indicate?
What does a positive Chvostek's sign indicate?
What do you do if your patient has hypocalcemia?
- Calcium supplements
- Vitamin D (helps Ca+ absorption)
- High calcium diet
- Seizure precautions
What causes hypercalcemia?
- Excessive Ca+ intake
- Excessive vitamin D intake
- Renal failure
What do you do if your patient has hypercalcemia?
- Eliminate calcium administration
- Drug therapy
- Isotonic NaCl
- Calcium reabsorption inhibitors (Phosphorus)
- Cardiac monitoring
Diseases of the cardiovascular system:
- 1. HTN
- 2. CHF
- 3. Coronary artery disease
- 4. MI
- 5. Cardiac arrhythmia
What drug classes are used to treat cardiovascular disease?
- Sympatholytic drugs
- Vasodilator drugs
- Calcium channel blockers
- Angiotensin (ACE) inhibitors
What is CHF?
- Contractile function is reduced
- CO unable to maintain BP
- Blood accumulates in heart (dilatation), lungs (pulmonary congestion), abdomen (ascites), and lower extremities (peripheral edema)
- Patient is weak and has difficulty breathing
What is the action of diuretics?
- Increase sodium excretion and relax arterial blood vessels (vasodilation)
- Elimination of excess fluid allows the heart to function more efficiently
What kind of diuretics are used in patients with reduced renal function?
What are common adverse effects of diuretic therapy?
Excessive loss of fluid, sodium and potassium
How do beta blockers lower BP?
By decreasing heart rate and increasing cardiac output
What is the action of calcium channel blockers?
Block the influx of calcium into the heart and arterial blood vessels to vasodilate and lower blood pressure, cardiac work, and oxygen demand
What are calcium channel blockers used to treat?
Hypertension, angina pectoris, cardiac arrhythmias
Calcium channel blocker drugs:
- Verapamil and diltiazem act on both the heart and blood vessels to lower BP
- Nifedipine and other calcium channel blockers lower BP by vasodilatoin
What are the adverse effects of calcium channel blockers?
- Excessive vasodilation
- Cutaneous flushing
What is the action of angiotensin (ACE) inhibitors?
- Block angiotensin receptors on blood vessels and adrenal cortex
- These drugs produce vasodilation and decrease the activity of aldosterone
What is the action of nitrates?
- Stimulate the formation of nitric oxide, a potent vasodilator of blood vessels
- Vasodilation of veins and arteries decreases cardiac work and cardiac oxygen consumption to relieve the pain of MI
What are adverse effects of nitrates?
- Vasomotor flushing, dizziness, and headache are common
- Sudden drop in BP, fainting, tachycardia
- *Patients should be seated when taking these drugs sublingually
What are nitrates used to treat?
- Acute attacks of angina
- Prevent anginal attacks
What is the action of beta blockers?
- Sympathetic beta receptor stimulation of the heart increases heart rate, force of contraction, and oxygen consumption
- Blockade of beta receptors decreases cardiac work and cardiac oxygen demand
Cardiac glycoside drugs:
What is the main pharmacological effect of Digoxin?
- Increase the contractile force of myocardial contractions
- Decrease heart rate and atrioventricular conduction
Effects of hypokalemia on Digoxin:
Increase drug toxicity and can cause cardiac arrhythmias
Effects of hyperkalemia on Digoxin:
Decrease the action of Dig
Effects of hypercalcemia on Digoxin:
Increase the actions and toxicity
What are the adverse effects of Digoxin?
- Dizziness, nausea, vomiting
- Visual disturbances "halo effect" around lights signal overdose
- Bradycardia, ectopic beats, and a variety of other cardiac arrhythmias can occur and can be life threatening
Class 1 local anesthetic-type antiarrhythmic drug:
What is the action of Lidocaine?
Block the Na+ channel
Class 2 antiarrhythmic drug:
What is the action of Propranolol?
Primarily blocks cardiac beta receptors to slow heart rate, AV conduction, and prolong the refractory period
Class 3 antiarrhythmic drug:
What is the action of Amiodarone?
Interferes by blocking the potassium channel
Class 4 antiarrhythmic drug:
Verapamil and diltiazem