Lecture 5: Fluid and Electrolyte Imbalance - Na, K Flashcards
What are the 2 main causes of intracellular edema?
- Depression of metabolic systems of tissues
- Lack of adequate nutrition to the cells
*Cells lack the resources needed to drive the Na+-K+-ATPase pump, causing Na+ to accumulate in cells –> H2O rushes in
What 3 factors are working to prevent extracellular edema?
- Interstitium normally has low compliance
- Lymph flow can increase 10-50 fold
- Increased amts of protein-poor capillary fluid flow wash protein out from the interstitial space, thereby decreasing capillary filtration pressure
With ACE inhibition the GFR falls, but serum levels of what will rise?
Creatinine
Using the mnemonic SALT LOSS what are the sx’s of hyponatremia?
- Stupor/coma
- Anorexia, N/V
- Lethargy
- Tendon reflexes decreases
- Limp muscles (weakness)
- Orthostatic hypotension
- Seizures/HA
- Stomach cramping
What are some of the main causes of Euvolemic Hyponatremia?
- SIADH
- Drugs/Stress
- Glucocorticoid deficiency
- Hypothyroidism
- Primary polydipsia
What are 2 major causes of increased effective circulating volume which can cause hypervolemic hyponatremia?
1) Acute renal failure
2) Advanced chronic renal failure
What are some of the major causes of decreased effective circulating volume which can cause hypervolemic hyponatremia?
- CHF
- Liver disease
- Sepsis
- Nephrotic syndrome
- Pregnancy
- Anaphylaxis
What is the correct way to tx a patient with hyponatremia that is only a level 1 (no or minimal symptoms)?
- Fluid restriction
- Consider vaptan under select circumstances (i.e., can’t tolerate fluid restriction, need to correct [Na+] for surgery, etc..)
What is the correct way to tx a patient with hyponatremia that is a level 2 (moderate sx’s)?
- Vaptan or hypertonic NaCl
- Followed by fluid restriction
What is the correct way to tx a patient with hyponatremia that is a level 3 (severe sx’s)?
Hypertonic NaCl, followed fluid restriction or vaptan
Why does hyponatremia need to be corrected slowly?
Overly rapid correction —> osmotic demyelination syndrome
What is the rate that can be used to correct hyponatremia in someone who is acute symptomatic?
- 2.5 mEq/L/h to get to safe zone
- Should NOT increase more than 20 mEq/L/day
What is the rate that can be used to correct hyponatremia in someone that has chronic (>48 hrs) hyponatremia?
- Should be ~0.5 mEq/L/h until 120 mEq Na+/L
- Total increase should not exceed 8-12 mEq/L/day and no more than 18 mEq/L in first 48 hrs
What is one of the major tumors that can cause SIADH?
Oat-cell carcinoma of the lung
What are 3 situations in which hypernatremia is commonly seen?
Often a known indicator of?
- Not uncommon in those living alone who fall at home
- Known indicator of neglect in nursing homes
- People in the desert without enough water
What are 5 causes of Hyprvolemic Hypernatremia?
- Administration of hypertonic saline or hypertonic sodium bicarbonate
- Hypertonic dialysis
- Hypertonic feedings
- Primary hyperaldosteronism
- Cushing syndrome
What are 3 causes of Euvolemic Hypernatremia?
- Diabetes insipidus (central or nephrogenic)
- Hypodipsia = diminished thirst
- Insensible dermal and skin losses (only if hypodipsic)
What are 2 causes of Hypovolemic Hypernatremia?
- Lack of access to water
- “Broken” thirst mechanisms
Using the mnemonic TRIP, what are the symptoms of Hypernatremia?
- Twitching, tremors, hyperreflexia
- Restlessness, irritable, confusion, etc. (due to brain cell shrinkage)
- Intense thirst, dry mouth, decreased urine output
- Pulmonary and peripheral edema
What to use for treatment of hypovolemic hypernatremia?
Isotonic saline
In hypervolemic/euvolemic hypernatremia what is used as treatment?
HYPOtonic IV solutions (i.e., D5W, half-normal saline, quarter-normal saline)
What is the rate of infusion for correcting hypernatremia?
Correct over 48 hours at ≤ 0.5 mEq/L/hr (i.e., < 12 mEq/L/day)
What are the effects of hyperkalemia vs. hypokalemia on the cardiac conduction system?
- Hyperkalemia —> membranes hyperpolarized = less likely to fire = BRADYcardia
- Hypokalemia –> tachycardia
*This the opposite effect of what is occurring in cells
What will be seen on the ECG of someone with hyperkalemia?
Peaked T wave
What are some of the hormones/drugs, acid-base states, and deficiencies that cause an increase in K+ movement into cells?
- Insulin
- β2-agonist (epi) and α-blockers
- Aldosterone deficiency
- Alkalosis
- Hypoosmolarity
What are some of the factors (i.e., hormones, drugs, deficiencies, states) that cause an increase in K+ leaving the cell?
- α-agonist (NE, Epi)
- Insulin deficiency
- β2-blockers
- Acidosis
- Hyperosmolarity
- Exercise
- Cell lysis
Rapid absorption of K+ in diet into the ECF could lead to fatal hyperkalemia if not for its rapid redistribution into the ICF, which is most importantly due to what?
Insulin
What are the 5 major influences on segmental absorption of K+ in the nephron during times of normal/excess K+?
- Plasma [K+]
- Aldosterone
- ADH
- Acid-Base Balance
- Tubular fluid flow rate
Hyperkalemia will cause an increase in the release of what hormone?
Aldosterone
Using the mnemonic GRAPHIC IDEA what are the causes of Hypokalemia?
- GI losses (vomitting, diarrhea) Insufficient intake
- Renal tubular acidosis (type I and II) Diuretics
- Aldosterone Elevated β-adrenergic activity
- Paralysis (periodic) Alkalosis
- Hypothermia
- Insulin excess
- Cushing’s Syndrome
The most prominent signs/sx’s of hypokalemia will be in what system?
Neuromuscular
- Skeletal m. weakness
- Smooth m. weakness –> GI hypomobility causing ileus and constipation
What are three CV system signs/sx’s associated w/ hypokalemia?
- Ventricular arrhythmias
- HYPOtension
- Cardiac arrest
Hypokalemia will lead to what renal manifestations?
Impaired concentrating ability causes polyuria and nocturia
Effect of hypokalemia on blood glucose levels?
Hyperglycemia
What are the 3 main goals for treatment of Hypokalemia?
- Prevent life-threatening conditions
- Replace K+ deficit —> K+ replacement is mainstay
- Diagnose/correct underlying cause –> i.e., K+ losing diuretics
Preventing life-threatening conditions associated w/ hypokalemia is especially urgent if rapid K+ falls to what level?
< 2.5 mEq/L
Using the mnemonic RED FETS what are the causes of Hyperkalemia?
- Renal disease: ARF, CKD, type IV RTA
- Excessive intake: food, K+ IV fluids, blood transfusion
- Drugs: K+ sparing diuretics, K+ salts of penicillin
- Factitious: prolonged use of tourniquet, hemolysis
- Endocrine: Addison’s disease
- Tissue release: rhabdomyolysis, burns, hemolysis, cytotoxic therapy
- Shift out of cell: acidosis, β-antagonists, insulin deficiency, tissue damage
Which system will have the predominant and most important signs/sx’s of Hyperkalemia, what are they?
- Cardiac
- Abnormal heart rhythm, bradycardia
- Peaked T wave
What are 3 neuromuscular signs/sx’s of hyperkalemia?
- Numbness
- Weakness
- Flaccid paralysis
Emergency management of Hyperkalemia is divided into 3 categories, how are cardiac effects managed first?
Antagonize cardiac effects —> give IV calcium
In the treatment of Hyperkalemia what can be given to redistribute K+ intol cells?
- Give insulin + glucose (most reliable) or
- β2-agonist such as albuterol
In the management of hyperkalemia what can be given to facilitate K+ elimination?
- K+ losing diuretic
- Consider mineralocorticoid (pts w/ hypoaldosteronism)
- Cation exchange resin
- Dialysis
After effectively managing an emergency situation of hyperkalemia, what should be done?
Monitor intake (≤ 60 mEq/day), paying attention to hidden sources such as Abx
