Electrolyte Abnormalities Flashcards
T/F fluid control is one of the most influential aspects of what we do.
True
How is total water broken down in the body by weight?
- 60% of total body weight is water
- 40% intracellular
- 20% extracellular
How much of extracellular fluid is interstitial vs plasma?
- 75% interstitial
- 25% plasma volume
How does total body water vary with men, women and infants?
- 55% of mans weight
- 45% of woman’s weight
- 80% of infants weight
Obese individuals have less total body water than non obese
What electrolytes dominate in intracellular fluid?
- high concentration of K+
- mg+
- Na/K+ ATPase pump and active transport maintain high [K+] inside cell and [Na] outside of cell
Extracellular fluid primarily contains which electrolytes?
- high concentration of Na+ (primary cation) and Cl- (primary anion)
Intravascular fluid (plasma) controls fluid movement how?
- high concent. Of osmotically active plasma proteins—-> albumin
- capillary membrane not permeable to albumin- remains in vascular space
Fluid movement is affected by:
- properties of membranes separating compartments
- concentration of osmotically active substances within a compartment
What is the chief focus of fluid treatment for us?
- intravascular fluid space—> it the only thing we can get into and control
What is the difference between hydrostatic pressure and oncotic pressure?
- hydrostatic pressure: pushing pressure, water pressure, pressure of fluid going out—-> BP
- oncotic pressure: pulling pressure from proteins
What are starling forces effected by?
- hydrostatic pressures in capillary vs interstitium
- oncotic pressures in capillary vs interstitium
Which factors affect fluid movement?
- osmolarity
- # of osmoles of solute/Liter of solution
- osmolality
- # of osmoles of solute/Kg of solvent
- tonicity
- how solution affects cell volume
- isotonic, hypotonic, hypertonic
What is an isotonic solution?
-285mosm/L
How do you increase osmolarity or osmolality?
-increase the amount of solute (water value will remain the same, 1L or 1kg)
What is the difference between hypovolemia and dehydration?
- hypovolemia: fluid body has is still at normal balance
- loss of extracellular fluids, decrease in circulation fluid
- absolute loss of fluid from the body.
- dehydration: unbalanced
- concentration disorder
- insufficient water present in relation to Na levels
What is the most common electrolyte abnormality in hospitalized patients?
Hyponatremia
What causes hyponatremia?
Vomiting Diarrhea Diuretics Adrenal insufficiency SIADH Renal failure/nephrotic syndrome Water intoxication CHF Liver failure
What are clinical manifestations of hyponatremia?
- neuro-
- HA. - coma
- malaise. - cerebral edema
- agitation. - confusion
- GI-
- anorexia
- n/v
- Muscular-
- cramps, weakness
- *** since Na doesn’t cross the BBB, you get higher levels of Na inside the brain comparatively. H2O follows Na—> cerebral edema that can lead to DEATH
What is the treatment of hyponatremia?
- fluid restriction
- admin hypertonic saline and osmotic or loop diuretic
- correction of serum Na level too quickly can lead to neuro damage and demyelination
—> correct slowly: 1-2 mEq/L- no more than 10-15 mmol in 24 hours
What causes hypernatremia?
- most common cause I’d water deficiency d/t:
- excessive water loss or inadequate intake
Also caused by:
- excessive water loss or inadequate intake
- extra Na intake/administration
- 1Ëš hyperaldosteronism
- DI
- renal dysfunction
- impaired thirst
What are clinical manifestations of hypernatremia?
- Neuro:
- thirst
- weakness
- seizures
- hallucinations
- irritability
- coma
- disorientation
- intracranial bleeding
- CV:
- hypervolemia
- renal:
- polyuria or oliguria- renal insufficiency
In hypernatremia, what happens to the brain?
Na+ in vasculature is in excess relative to brain Na+ levels
—> H2O in brain follows this Na+, dehydrating the brain, and pulls so hard it can rip the vessels- causing intracranial bleeding
How is hypernatremia treated?
Replace the water deficit
- increase 1-2mEq/hr until pt clinically stable, gradually over a 24 hr time frame
What is a major function of K+?
Largely responsible for resting membrane potential
- balanced by GI absorption and renal excretion
What causes hypokalemia?
- GI losses
- systemic alkalosis
- DKA
- diuretics
- SNS stimulation
- poor dietary intake
- most common electrolyte abnormality in our clinical practice ***
- thiazide diuretics —>11xs more likely to have low K+
- men 2xs as likely as women
What are clinical manifestations of hypokalemia?
-CV: ST depression Presence of U wave Flattened/inverted T waves Ventricular ectopy -Neuromuscular: Weakness (resp. Muscle) Depressed reflexes Confusion ** serum k <2.5–> parasthesias, fasiculations, muscle weakness
How is hypokalemia treated?
- slow IV supplementation
Anesthesia related concerns:- increased risk of myocardial irritability when K+ <2.6
- avoid hyperventilation of lungs—> alkalosis causes low K(uses k in blood to drive pH one way or another)
- avoid rapid infusion of K (40 mEq/hr MAX)
—> too fast will hyperpolarize the heart and stop it from beating
What causes hyperkalemia?
- increased total body K+
- renal failure
- K sparing diuretics
- excessive IV K
- excessive salt substitutes
- Altered distribution of K+
- metabolis/resp. Acidosis
- dig. Intox, ACE inhibitors, ARBS
- insulin deficiency
- hemolysis
- tissue/muscle damage after burns
- succinylcholine administration
—> normal k increase is 05.mEq- with muscle disorder and burns, up regulation of receptors can increase K up to 10mEq
- DO NOT GIVE SUCC. TO QUADS/PARAS OR BURN PTS ***
What are clinical manifestations of hyperkalemia?
- CV:
- tall peaked and elevated T waves
- widened QRS
- prolonged PR
- flattened/absence P waves
- ST depression
- cardiac arrest
What is the treatment of hyperkalemia?
- 1˚ goal—>avoid adverse cardiac effects.
1. ) stabilize cardiac membrane with IV Ca++
2. ) drive K+ into cells with insulin and glucose
3. ) get K+ out with Kayexalate
What are anesthesia/surgical related concerns for hyperkalemia?
If k+ >5.5 reschedule
5.5 is max for elective procedures
What is the role of magnesium, and where is it found?
- 40-60% stored in muscle and bone
- 30% intracellular
- 1% in serum
Regulated by kidneys and intestines - roles:
- co-factors in enzymatic reactions
- energy metabolism
- protein synthesis
- neuromuscular excitability
- function of Na/K ATPase
What causes hypomagnesemia? (<1.7 mEq/L)
- inadequate intake, starvation
- TPN without Mg+
- GI losses:
- diarrhea
- fistulas
- NG sanctioning
- vomiting
- chronic ETOH
What are chronic manifestations of hypomagnesemia?
- EKG:
- flat T waves
- U waves
- prolonged QT
- wide QRS
- atrial and ventricular PVCs
What is the treatment for hypomagnesemia?
IV Mg+: 1-2 G over 5 min, then 1-2 G/hr continuous infusion
What causes hypermagnesemia?
- Iatrogenic administration
- pre-eclampsia
- antacids/laxatives (tums, mag citrate, MOM)
- renal failure
- adrenal insufficiency
What are clinical manifestations of hypermagnesemia?
- 3-5 mEq/l ———> flushing, N/V
- 4-7 ——> drowsy, decreased deep tendon reflexes, weakness
- 5-10—-> bradycardia, hypotension
- 7-10——> loss of patellar reflex
- 10———> Respiratory depression
- 10-15—> respiratory paralysis
- 15-20—> cardiac arrest
( huge doses required to have these effects)
What is the treatment for hypermagnesemia?
- DC Mg supplement
- use Ca as an antagonist in urgent situations (bradycardia, heart block, resp depression)—-> Mg decreases resting potential, Ca increases resting potential
- Ca potentiates ND NMBs
How does Mg work for pain control?
Makes muscles relax (muscle pain)
- settles down NMDA receptors
- can eliminate acute migraines, pancreatic CA pain, and fibromyalgia pain
- enhances action of analgesics (IV, gas and spinal)
What is the norm for Mg?
1.4-2.2mEq/L
What is the function of calcium,and where is it found?
- 99% found in bones
- 1% in plasma and body cells
Function: - structural integrity of bones
- second messenger that couples cell membrane receptors to cellular responses
—-> muscular contraction, hormones, neuro transmission, coagulation, myocardial contractility
Which lab value is best to use for Ca and why?
Ionized Ca: physiologically active portion
- normal ionized Ca is 9-10.5 mg/dL
What drives Ca into bones? What pulls it out of bones?
- calcitonin drives Ca into bones
- parathyroid hormone pulls Ca out of bones
What causes hypocalcemia?
- hypoparathyroid
- malignancy
- chronic renal insufficiency
- hyperventilation—> alkalosis—>protein binding of Ca
- citrate of blood (transfused) binds to Ca and lowers Ca levels
What are clinical manifestations of hypocalcemia?
Neuromusc. Irritability:
- resting membrane potential and threshold potential narrow—> doesn’t take much to fire an impulse
- cramps
- weakness
- Chvostek’s sign
- Trousseau’s sign
- numbness
- tingling
What are clinical manifestations of hypocalemia?
CV: - dysrrhythmias - prolonged QT - T wave inversion - hypotension - decreased myocardial contractility Pulm: - laryngospasm - bronchospasm - hypoventilation
What is the treatment of hypocalcemia?
- infusion of Ca salts
- Ca chloride: best if available—> more bioavailable and quicker
- Ca gluconate: slower
- 3 G Ca gluconate = 1 G CaCl
What are causes of hypercalcemia?
- HYPERparathyroid (>50% cause)
- tumors/malignancy
- Ca mobilization from bone d/t immobility
What are clinical manifestations of hypercalcemia?
CV: - HTN - heart block - shortened QT - dysrhythmias Neuro musc: - muscle weakness - depressed deep tendon reflexes - sedation
How is hypercalcemia treated?
- treat underlying cause
- volume expansion with NS—> manage intraoperatively with enough IVF to maintain adequate UOP
- loop diuretics
- HD can filter out Ca if really bad *
