Electrolytes

Question 1

Potassium

general

Answer 1

In kidneys, the majority of filtered K+ is resorbed in the proximal tubular system

Selective secretion or absorption in the distal tubule determines net K+
Limit of renal K+ excretion 10 mEq/ L
Excretion affected by circulating Aldosterone, cellular and extracellular K+, tubular urine flow rates, & acid-base disturbances

Question 2

potassium

normal range

Answer 2

3.5-5.0 mEq/L

Question 3

Potassium

Function

Answer 3

NA+/K+-ATPase
Nerve transmission
Skeletal muscle contraction
Cardiac muscle function
Renal and fluid ion balance
Potassium channels
Nerve action potentials

Question 4

Hypokalemia

causes

Answer 4

K level < 3.5 mEq/L

Hypokalemia occurs from one of 3 pathologic mechanisms:
Deficient intake
Anorexia, alcohol use disorder

Increase excretion
Diuretics, Hyperglycemia, 1° or 2° Aldosteronism, Elevated ACTH, Corticosteroid excess

GI loss
Colon, rectum- high K content
Gastric- hypokalemic hypochloremic met. Alkalosis

Other: Licorice, Acute Leukemia, Iatrogenic

Question 5

Hypokalemia

Clinical Symptoms

Answer 5

Skeletal muscle weakness/malaise
Fatigue
Weakness/cramps
Paresthesias
Paralysis (flaccid paralysis if severe)
N/V/C – paralytic ileus
Polydipsia
Polyuria/Nocturia

Usually asymptomatic until < 3.0 mEq/L

Question 6

Hypokalemia

Clinical Signs

Answer 6

hypotension
Diminished/ absent DTRs

Cardiac abnormalities-EKG changes
Ventricular arrhythmias, flatten T waves, U waves, depressed ST segments, and ventricular ectopy, cardiac arrest

May be acidotic

Usually asymptomatic until < 3.0 mEq/L

Question 7

hypokalemia

ECG changes

Answer 7

Although the ECG is a fairly good indicator of hyperkalemia, it is not reliable for detecting hypokalemia. However, when ECG changes are seen they tend to be those that are shown in this figure.

A : normal
B : shows flattening of the T wave, which is the earliest change
C and D :A “U wave” then develops, associated with ST-T wave flattening and sometimes slight ST depression. A “pseudo P-pulmonale” pattern may be seen.
E and F : ST depression is more noticeable and the U wave increases in amplitude until ultimately the U wave overtakes the T wave. At this point distinguishing between the T wave and U wave may be almost impossible (“Q-U” prolongation).

Note - The ECG changes of hypomagnesemia are identical to those of hypokalemia.

with K think t wave

Question 8

Hypokalemia

Treatment

Answer 8

Replace potassium (10 mEq of KCl will increase serum K approximately 0.1 mEq/L)

Orally (preferred)
Normal renal fxn
Do not exceed 40 mEq/h

IV (if emergent)
Do not exceed 10 mEq/h
Repeat as often as necessary
ECG monitor, mandatory if rate > 10 mEq/h
Avoid dextrose solutions-will drop K level

Rapid correction
Hyperkalemia
Arrhythmias

Make sure Mg is normal. If not, correct hypomagnesemia (K+ will normalize)

Correct hypocalcemia and hypokalemia together

Question 9

hypokalemia

Answer 9

if oral - should take 4 hours for K/ 24 hours for Mg
if IV - should take 1 hour for K/

Question 10

Hyperkalemia

general and causes

Answer 10

K level > 5.2 mEq/L

Physiologic Response
Rapid urinary excretion

Etiology
Impaired renal potassium excretion
Hypoaldosteronism
Shift from inside cells to extracellular fluid
Medications : ACE/ARB/Spironolactone

Laboratory error:
Hemolysis
Patients with hyperkalemia and no kidney injury/disease who are not taking medications that cause hyperkalemia should have repeat blood draw to rule out spurious hyperkalemia

Question 11

Answer 11

Question 12

Hyperkalemia

Clinical Manifestations

Answer 12

Peripheral muscle weakness and fatigue
SOB/Respiratory paralysis

CARDIAC abnormalities
EKG with peaked T waves at K of 6.0-7.0
flat p wave
increased PR interval
decreased QT interval
wide QRS
depressed ST segment
K of 8.0 or higher the QRS merge with T , V-fib, cardiac arrest

Question 13

hyperkalemia

Answer 13

A: normalB: shows peaking of the T wave, which is the earliest change (K+ about 6-7 mEq/L)

C: The T wave becomes taller and more peaked (K+ about 7-8 mEq/L); it almost looks like the Empire State building (tall, peaked, with a narrow base). Contrast with the T wave that is sometimes seen in healthy individuals as a normal variant (shaded box) in which the T wave is rounded, its sides are not symmetric, and it has a broad base.

D: P wave amplitude decreases, the PR interval lengthens, and the QRS widens (K+ >8 mEq/L).

E: P waves disappear (sino- ventricular rhythm) and the QRS becomes sinusoid (K+ >10 mEq/L).V Fib usually follows.

Question 14

Hyperkalemia-

work up
Labs – to determine cause

Answer 14

To determine potential cause (Electrolytes and EKG done)

Renal function assessment for renal failure

Urine K, Na, and osmolality

CBC (low Hg, Hct, or abnormal red cell suggests hemolysis/severe leukocytosis or a questions if it is pseudo-hyperkalemia

Metabolic panel – low bicarb (metabolic acidosis), hyperglycemia, elevated LDH, uric acid, phosphate, ALT, CK (rhabdomyolysis)

Serum cortisol, renin, aldosterone (adrenal insuff.)

check Mg as well

Question 15

Hyperkalemia

Treatment
mild/moderate vs severe

calcium gluconate** will correct hyper K in 5 minutes. likely to see on PANCE

Answer 15

Mild to Moderate (no cardiac abnormalities)
Restrict K+ intake, stop K+ sparing diuretics, address volume or acid-base disorders
Give K+ wasting diuretics

Severe or if cardiac abnormalities present
10% calcium gluconate IV over 5 min to reduce muscle excitability
Use 10 to 30 mL, action is quick (1-2 min)
Redistribute potassium from extracellular space to intracellular space
Using rapid-acting insulin (5 to 10 U) drives K+ into the cells
Given with 25 g glucose 50% IV over 5 min
Sodium bicarb IV (helpful if acidotic)
β₂-adrenergic agonist (Albuterol) 0.5% 20 mg in 4mL normal saline by nebulizer (onset is 15-30 min)

Dialysis (Decrease total body potassium level)
Identify and treat correctable causes

Kayexalate by mouth or enema binds and removes K- gives diarrhea

Question 16

Hypochloremia

General and Causes

Answer 16

Normal serum chloride 98-110 mEq/L
Hypochloremia < 98 mEq/L

Due to
Loss of gastric contents (N/V, NGT)
Excess extracellular water (hypotonic fluid admin., SIADH)
Renal losses caused by diuretics
Renal failure
During respiratory acidosis (kidneys resorb bicarb, Cl- excreted)

Question 17

Hypochloremia

Clinical Sx and Tx

Answer 17

No specific S/S
(typically co-exist with Na def – Na and Cl stick together)

TX: NaCl or KCl (if K def too)

Question 18

Hyperchloremia

general and causes

Sx / Tx

Answer 18

Serum Cl- >110 mEq/L
Uncommon in the surgical pt
Most commonly caused by administration of chloride rich IV fluids (0.9% NaCl)
In association with hyperchloremic metabolic acidosis, RTA, hypernatremia, iatrogenic,

No specific s/s

Treat underlying disorder. Used balanced solutions.

Question 19

Calcium

general

Answer 19

Normal serum calcium 8.5-10.5 mEq/L (ionized 4.75-5.30mg/dL)
Hypocalcemia < 8.5 mEq/L (corrected for albumin)
Hypercalcemia >11 mEq/L
Most found in hydroxyapatite crystals in bone

40% bound to plasma protein (albumin)
Correct serum Ca++ in hypoalbuminemic pts
Corrected serum Ca++ = measure Ca++ + (0.8 X [4-measured albumin in g/dL])

50% ionized and physiologically active

Resorption Increased by
PTH or metabolic alkalosis

Half of serum calcium is free while the other half is bound to albumin

Question 20

calcium

function

Answer 20

Neural signaling
Bone mineralization
Cardiac function
Skeletal muscle contraction
Digestive system function

Question 21

Physiology of Calcium

Answer 21

Stimulates osteoclasts to break down bone – releasing calcium and phosphorus

Increases reabsorption of calcium by kidneys

Blocks reabsorption of phosphate by kidneys, leading to urinary phosphate loss.

Increases conversion of inactive to active 1,25 vitamin D (which then increases calcium absorption from gut)

Question 22

Hypocalcemia

general and causes

Answer 22

Serum calcium < 8.5 mg/dL

Normal physiologic Response

Etiology
Malabsorption
Decreased intake
Vitamin D deficiency
Bowel surgery
Hypoparathyroidism
Decreased serum albumin
Chronic kidney disease
Decreased calcitriol
Hyperphosphatemia

Often seen in surgical patient/hospitalized patients
May be acute or chronic

Acute pancreatitis
Hypoparathyroidism
Severe soft tissue infections (necrotizing fasciitis)
Renal Insufficiency
Malabsorption syndromes
Chronic Diarrhea
Vitamin D def.
Hypomagnesemia
Hyperphosphatemia
Blood transfusion
Adverse effects of drugs
rhabdomyolysis
Tumor lysis syndrome
rickets
Genetic disorders
Chronic Diarrhea
Osteoblastic metastases
Prostate and breast cancer
DiGeorge syndrome
IBD
Fluid loss from pancreatic/ intestinal fistulas

Question 23

Hypocalcemia

Classifications of mild vs severe

Answer 23

Mild
Calcium level of 8.5-8.0
asymptomatic

Severe
Calcium level below 7.6
Symptomatic at any level below normal

Question 24

hypocalcemia

Clinical Manifestations

Answer 24

Circumoral tingling
Numbness/ tingling of fingertips
Muscle cramps
Wheezing/Dyspnea
Seizures
Palpitations/Chest pain
Confusion
Depression
Trousseau’s Sign :Carpal spasm elicited by inflation of BP cuff to 20 mmHg above systolic pressure for 3 min

Chvostek Sign :Twitching of circumoral muscles in response to tapping facial nerve anterior to ear

Wheezing
Irregular heart rhythm
Hyperactive DTRs
Tetany
Prolonged QT on EKG

Question 25

# Hypocalcemia Diagnostic evaluation

Answer 25

Serum Calcium or ionized Calcium Identify cause: Serum albumin, K, Mg, Phos, Alk, Vit D, PTH, Cr, CK Urinary calcium

Question 26

#Hypocalcemia Tx

Answer 26

Treatment depends on severity, how acutely it developed, and the degree of neuromuscular irritability. Treatment given to: **Asymptomatic patients with calcium < 7.6 mg/dL** Symptomatic pts **Preferred tx: Calcium gluconate 10 mL 10% (slow injection over 5 min)** Calcium gluconate diluted in 50 mL of 5% dextrose or 0.9% NaCl Monitor calcium levels. If persistent, may give calcium gluconate infusion 1.2 to 1.6 mg/kg of elemental Ca infused over 4 to 6 hrs increases serum Ca by 2 to 3 mg/dL If Ca persists (or likely to), give oral Vitamin D supplementation. If pt is also hypomagnesemic, must correct Mg first. If Chronic, give supplemental Ca with Vit D.

Question 27

# Hypercalcemia general and causes

Answer 27

Serum Ca > 10.5 mEq/L No formal classification, but may be described as mild, moderate, or severe Mild < 12 Moderate 12-14 Severe > 14 Occurs from one of three mechanisms: 1) increased bone resorption (example, lytic bone lesions) 2) Increased GI absorption of Ca (excessive PTH effects on 1,25 (OH)2D 3) Decreased renal Ca excretion (thiazide diuretics) May be classified if PTH are elevated or reduced PTH elevated: primary or tertiary hyperparathyroidism PTH reduced: malignancy, excess Vit. D, Drugs (thiazides. Lithium, estrogens/testosterone, milk-alkali syndrome, thyrotoxicosis, pheochromocytoma, acute adrenal insuf. Most common causes are primary hyperparathyroidism and malignancy.

Question 28

# Hypercalcemia clinical manifestations

Answer 28

Asymptomatic Symptomatic: Gastrointestinal Constipation Anorexia Renal Nephrolithiasis Neurologic Anxiety, lethargy Cardiac Arrhythmia – Short QT interval “moans, groans, pains, and stones”

Question 29

# Calcium

Question 30

# Hypercalcemia treatment

Answer 30

Restrict Ca++ Hydrate- IV ½ NS or NS Enhances urinary calcium excretion Saline diuresis lead to hypokalemia, hypomagnesemia, or other electrolyte imbalance Avoid fluid overload If severe, use bisphosphonates. (not used if hyperparathyroid) Drugs of choice are pamidronate and zoledronic acid. Corticosteroid-used long term to suppress calcium release from bone but take 1-2 weeks to show results Treat underlying cause

Question 31

# Magnesium general and function

Answer 31

2nd most abundant cation of the intracellular fluid Mg++ is tightly regulated by the gut, kidney, and bone. Function Activates enzymes ATP function in combination with phosphate Signal transduction pathways Nerve transmission

Question 32

# Hypomagnesemia general and cause | mild/mod/severe

Answer 32

Normal 1.8-2.1 mg/dL Mild 1.5-1.8 mg/dL Moderate 1-1.4 mg/dL Severe < 1mg/dL Common in critically ill pts Etiology Diminished absorption or intake Increased renal loss

Question 33

# Hypomagnesemia Clinical Manifestations

Answer 33

Most frequently, asymptomatic Clinical manifestations appear with more severe symptoms: N/V Anorexia Weakness Lethargy Cramps Fasciculations, tetany Carpopedal spasm Paresthesias Irritability, inattention Confusion

Question 34

# hypomagnesemia Cardiac Arrhythmias

Answer 34

(variety of atrial and ventricular arrhythmias – flattened T waves, prolonged QT interval, ST depression, and widened QRS complexes)

Question 35

# Hypomagnesemia Treatment

Answer 35

TX: oral, IV magnesium sulfate, hydration-watch in renal failure Management Chronic, asymptomatic PO Magnesium oxide Symptomatic IV Magnesium sulfate in 5% dextrose or normal saline Calcium and potassium replacement may be required, but patients with hypokalemia and hypocalcemia do not recover without magnesium supplementation Dose adjustments for patients with advanced chronic kidney disease

Question 36

# Hypermagnesemia general and causes

Answer 36

Serum magnesium > 2.2 mg/dL Rare However, magnesium toxicity is potentially fatal. Persistent hypermagnesemia most often seen in chronic renal insufficiency. These patients are taking large amounts of magnesium. May occur in patients given large doses of IV magnesium (ie, preeclampsia) May be seen in oral supplementation; however, the kidney is typically able to excrete excess magnesium. May be caused by: Eclampsia treatment Renal failure Rhabdomyolysis Dehydration Severe metabolic acidosis Adrenal Insufficiency Antacids

Question 37

# Hypermagnesemia Clinical Findings

Answer 37

Impaired neurologic function Muscle weakness Decreased deep tendon reflexes Obtundation, confusion Flaccid paralysis Impaired gastrointestinal function Ileus Cardiac abnormalities Prolonged QT interval Severe Respiratory paralysis Hypotension, cardiac arrest

Question 38

# Hypermagnesemia Tx

Answer 38

Discontinue exogenous sources Antacids, laxatives IV **Calcium chloride** Antagonizes magnesium Avoid use of magnesium in advanced chronic kidney disease Hemodialysis

Question 39

# Phosphorus general and function

Answer 39

Normal 3 to 4.5 mg/dL Total body content: 85% in bone, 14% intracellular, and 1% extracellular Daily intake is 800 to 1500 mg Present in many foods: dairy products, meats, grains Kidney secretes phosphorus Most filtered at the glomerulus **PTH increases renal phosphate excretion Vitamin D enhances intestinal phosphate absorption**

Question 40

# Hypophosphatemia etiology

Answer 40

Caused by : Decreased intake Impaired intestinal absorption Antacid use, TPN, Vit D. def Redistribution into cells or bone Hyperparathryoidism, cancer, steroids Renal losses Diuretics, hyperaldosteronism, burns, renal transplant, resp. alkalosis, SIADH, steroids Frequently depleted in alcoholism poor diet and renal loss Common in surgical pt Associated with Potassium and Magnesium losses

Question 41

# Hypophosphatemia clin man

Answer 41

Clinical Manifestations: Only observed if severe (< 1 mg/dL) Encephalopathy, dilated cardiomyopathy, generalized muscle weakness, rhabdomyolysis, and hemolysis.

Question 42

# hypophospatemia Dx

Answer 42

often done with history and physical exam Can measure 24 hr urine or fractional excretion in spot urine for phosphate normal response is for kidneys to reduce phosphate excretion to less than 100 mg/day

Question 43

# hypophosphatemia Tx

Answer 43

Treatment: If mild, no treatment – decrease intake. If symptomatic or having ongoing loss, Oral repletion: Na or KPO4 salts or skimmed milk IV phosphorus If on dialysis, use phosphate-containing dialysate

Question 44

# Hyperphosphatemia general and causes

Answer 44

Common Caused by: Excessive phosphate intake Increased intestinal absorption Laxatives and enemas, intoxication with Vit. D Redistribution from intracellular stores Massive cell lysis (rhabdomyolysis, tumor lysis syndrome), DKA Impaired renal excretion Acute or chronic renal failure, primary hypoparathyroidism Pseudohyperphosphatemia may occur in hemolytic specimens or hyperglobulinemic states (ie, multiple myeloma)

Question 45

# Hyperphosphatemia clin man

Answer 45

May cause Acute Renal Failure. Can cause hypocalcemia – tetany, hypotension, seizures, & cardiac arrhythmias

Question 46

# hyperphosphatemia Treatment

Answer 46

If acute, asymptomatic, and normal renal function, hyperphosphatemia will most likely resolve spontaneously. If symptomatic and impaired renal function, extracorporeal therapy to remove excess phosphate. Chronic Minimize dietary phosphorus intake Phosphate binders (calcium salts, lanthanum carbonate, or sevelamer) Aluminum hydroxide effective phosphate binder, but prolonged use leads to aluminum accumulation. (may cause encephalopathy and osteomalacia) hemodialysis

Question 47

1. Which of the following electrolyte abnormalities is commonly associated with hypomagnesemia? a. Hypercalcemia b. Hypernatremia c. Hypochloremia d. Hypokalemia

Answer 47

d. Hypokalemia

Question 48

1. Which of the following electrocardiogram findings is most associated with hypercalcemia? a. Elevated ST segment b. Increased QRS voltage c. Lengthened PR interval d. Short QT interval e. Widened T-waves

Answer 48

d. Short QT interval

Question 49

1. Which of the following is the most appropriate initial treatment of cardiac arrhythmia in a patient with hyperkalemia? a. Calcium gluconate b. Furosemide (Lasix) c. Insulin with glucose d. Sodium polystyrene (Kayexalate) e. Triamterene (Dyrenium)

Answer 49

a. Calcium gluconate

Question 50

Which of the following mediations is most likely to cause hyperkalemia? a. Acetazolamide (Diamox) b. Eplerenone (Inspra) c. Furosemide (Lasix) d. Hydrochlorothiazide (Microzide)

Answer 50

b. Eplerenone (Inspra)

Question 51

A 72-year old man is hospitalized for severe malnutrition. The patient is started on **total parenteral nutrition**. Which of the following electrolyte abnormalities should you be monitoring vigilantly? a.-hyperkalemia b. Hypermagnesemia c. Hypocalcemia d. hypophosphatemia

Answer 51

all of them

Question 52

Which of the following electrolyte abnormalities is associated with diuretic therapy ? a. Hyperkalemia b. Hypermagnesemia c. Hypomagnesemia d. hyperchloremia

Answer 52

c. Hypomagnesemia

Question 53

A 75-year-old man is admitted with congestive heart failure. His home medications include furosemide 80 mg daily and digoxin 0.125 mg daily. His admitting ECG reveals **flattened T waves and the prescence of U wave**. Which of the following serum electrolyte abnormalities is most likely for this patient? a. K 2.4 mEq/L b. K 5.7 mEq/L c. Calcium 12mg/dL d. Magnesium 1.2

Answer 53

a. K 2.4 mEq/L

Question 54

A 57-year-old woman presents to clinic with weight loss, fatigue, and recurrent nephrolithiasis. Her physical exam is unremarkable. Her laboratory evaluations reveals normal renal and hepatic function, ESR of 52 mm/h, TSH of 2.0, and a serum calcium of 17mg/dL. Which of the following is the most likely cause of the patient’s hypercalcemia? a. Thyrotoxicosis b. Hyperparathyroidism c. Excessive calcium supplements d. malignancy

Answer 54

d. malignancy | stones, bones, abdominal moans