Tins lyte abnormalaties

Question 1

Substances that contribute most to osmotic pressure in ECG

Answer 1

Na+, HCO3-, CL- and glucose

Question 2

Formulation to calculate effective osmolality (tonicity)

Answer 2

2XNA+ + glucose/18 (range 275-290mOsm/L)

Question 3

Fluid percentages

Answer 3

TBW 60%
ICF 40%
ECF 20% of which 15% IF and 5% IVF
IF = interstitial fluid (extravascular) and IVF is intravascular

Question 4

Hyponatremia definition

Answer 4

Serum Na+ <138 mEq/L

Symptomatic at 135

Question 5

Epidemiology of hyponatremia

Answer 5

Mild is common (15-30%) but only 4% have sodium below 130mEq/L
50% of cases are iatrogenic

Question 6

Hyperosmolar hyponatremia

Answer 6

> 295 mOsm/kg H2O

common in hyperglycemia, each 100mg/dL in plasma glucose above normal (100mg/dL) drops serum Na+ by 1.6 mEq

Question 7

Iso-osmolar hyponatremia

Answer 7

275-295 mOsm/kg
Severe hyperproteinemia or hyperlipidemia causes displacement of serum water (some labs use instruments to avoid this lab error)

Question 8

MDMA hyponatremia

Answer 8

Induces inappropriate secretion of ADH and causes increased gut water reabsorption

Question 9

Clinical features of hyponatremia

Answer 9

Moderately severe start at 130mEq/L
Headache, nausea, disorientation, confusion, agitation, ataxia and areflexia
Severe ate 120mEq/L Intractable vomiting, seizures, coma, resp arrest from brainstem herniation

Question 10

Post exercise hyponatremia

Answer 10

From too much solute free fluid. Check for bloating, nausea, vomiting and edema at wrists and fingers

Question 11

Osmotic Demyelination Syndrome

Answer 11

Rapid correction of hyponatremia (<12 mEq/L/24h) as water moves from cells to ECF (intracellular dehydration)
Symptoms are dysarthia, dysphagia, lethargy, parapereis or quadriparesis, seizurescomadeath

Question 12

Hypernatremia definition

Answer 12

Na+ > 145mEq/L AND hyperosmolality (>295 mOsm/L)

Question 13

Patho hypernatremia

Answer 13

Deficit in TBW or less commonly net gain of Na+
Needs a limit of sense of thirst, availability of water, kindeys ability to concentrate urine
May cause intracranial hemorrhage if too quick
Severity of symptoms based on onset (fast onset = worse symptoms like hyponatremia)

Question 14

Hypovolemic hypernatremia

Answer 14

Decreased TBW and total body Na+ with a relatively greater decrease in TBW)

Question 15

Hypervolemic hypernatremia

Answer 15

Increased total Na+ with normal or increased TBW

Question 16

Normovolemic hypernatremia

Answer 16

Normal sodium with decreased TBW

Question 17

Clinical features of hypernatremia

Answer 17

Nausea, vomiting, lethargy, weakness, increased thirst, low water intake, salt intake, polyuria (greater than 3000mL/hr of urine/24h)

Question 18

Hypernatremia predisposing risk factors

Answer 18

Beeties, hypercalcemia hypokalemia, lactulose, loop diuretics, lithium, demeclocycline or NSAIDS (interstitial nephritis)

Question 19

Hypernatremia physical exam

Answer 19

Hypotension, tachycardia, orthostatic pressure, sunken eyes, dry mucous membranes, altered mental status, poor skin turgor, edema in hypervolemic hypernatremia
Cushings syndrome - moon face, fatty deposits

Question 20

TX hypernatremia

Answer 20

Tx volume deficits first
then cause (diabetes insipidus) vomiting diarrhea fever then free water deficit

Question 21

Diabetes insipidus

Answer 21

Ability of kidney to reabsorb free water is compromised
Neurogenic due to inadequate ADH
Nephrogenic from renal causes (v2R receptors don’t respond properly to ADH)

Question 22

Diabetes insipidus characterized by

Answer 22

polyuria, polydipsia, increased volume of hypo-osmolar urine

Question 23

Normal K+

Answer 23

98% intracellular, 75% in muscles
150mEq/L intracellular
3.5-5 mEq/L extracellular

Question 24

K+ in the kidneys

Answer 24

Filtered freely through renal glomerulus then reabsorbed in proximal and ascending tubules, secreted in distal tubule in exchange for Na+

Question 25

Things that cause K+ shift

Answer 25

Surgical stress, trauma, burns, acid-base imbalance, catabolic states, increased extracellular osmolality, insulin deficiency
(possible to have hyperk+ with reduced TB K+ and other way around)

Question 26

K+ and pH

Answer 26

K+ rises 0.6mEq/L for every 0.1 decrease in PH and vice versa through H+ and K+ exchange

Question 27

HypoK+ definition

Answer 27

Serum <3.5mEq/L
Common are fasting, eating disorders, ETOH abuse, alkolosis, insulin, B2-agonists, hypokalemia periodic paralysis
Vomiting, nasogastric suction, diarrhea
Diuretics, hyperaldosteronism, osmotic diuresis, toxins

Question 28

HypoK+ manifestations

Answer 28

Effect every system
Makes resting membrane more electronegative, enhancing depol and delays repol
Prolonged QT, flattened T waves, appearance of U waves
Starts at <2.5mEq/L usually

Question 29

Arrythmias of hypoK+

Answer 29

A fib, torsades, v tach and v fib

Question 30

HyperK definition

Answer 30

> 5.5 mEq/L

Question 31

Diuretics that cause hypoK

Answer 31

Carbonic anhydrase inhibitors, loop diuretics, thiazide-like diuretics)
Alkalosis is another common cause
Excessive Chaw, licorice, hyperaldosteronism can also cause it
Same with heavy sweat, heat stroke, fever, hypomagensia, leukemia, hypothermia

Question 32

Causes of pseudo hyperK

Answer 32

Tourniquet use, hemolysis, leukocytosis, thrombocytosis

Question 33

Intra to extracellular shifts causing hyperK

Answer 33

Acidosis, exercise, B-blockade, insulin deficiency, dig

Question 34

HyperK diuretics

Answer 34

Renal failure is a common cause of hyper K+
Potassium-sparing diuretics, b-blockade, NSAIDS, ACE inhibitors and Angio II blockers
Aldosterone deficiency

Question 35

HyperK in da heart

Answer 35

Less electronegative resting membrane, partial depol which reduces activation of voltage-dependent sodium channels. Slower and reduced amplitude of action potential
Calcium antagonizes effects of hyperK by raising threshold potential and restoring membrane potential

Question 36

ECG changes in hyper K

Answer 36

Long PRI, peaked T waves, short QT, flattening of P wave, QRS widening and eventuall QRS degradation into sinusoidal pattern

Question 37

Three tx modalities for hyper K

Answer 37

Membrane stabilization
Intracellular shift of K+
Removal/excretion
All three sequentially in rapid succession as they have different onset and duration
Treat pH if acidy, if not acidy the shift won’t work as well

Question 38

Dougs that block renal excretion of K+

Answer 38

ACE inhibitors, Angio II receptor blockers, K+sparing diuretics and NSAIDS

Question 39

Magnesium

Answer 39

total body 24 grams or 2000 mEq

50-70% fixed in bone and only slowly exchangable, rest is mostly ICF (second most abundant intracellular cation)

Question 40

Normal Mg2+

Answer 40

1.5-2.5mEq/L

Question 41

Major causes of hypomagnesia

Answer 41

ETOH, malnutrition, cirrhosis, pancreatitis, excessive GI fluid losses
TX of DKA w/o mag (especially if malnourished) can cause this

Question 42

Hypomagnesia presentation

Answer 42

If normal calcium, hyperreflxia, tremor, tetany or convulsions

Question 43

Tetany

Answer 43

Intermittent muscular spasms

Question 44

Hyperalimentation

Answer 44

IV nutrients

Question 45

Chvostek sign

Answer 45

Hypocalcemia typically, but possible in respiratory alkalosis or hypomagnesemia
Tapping infront of tragus or at angle of jaw will illicit a facial spasm (stimulating facial nerve cause a facial nerve spasm)

Question 46

Trousseau sign

Answer 46

Flexion of the wrist and fingers after a BP cuff is inflated past systolic and remains there for 3 mins. Indicates hypocalcemia (sensitivity 94%) also could be hypomagnesia

Question 47

ECG changes in hypomagnesemia

Answer 47

Similar to hypokalemia and or hypocalcemia

Hypomagensemia may be secondary to hypoalbuminemia