Chapter 21 - Fluids/Electrolytes

Question 1

Describe and approach to hyponatremia.

Answer 1

1) True/False (sOsm)
2) H2O Excretion normal/impaired (diuretic/low GFR)
3) ADH Active (Uosm > 100) or inactive (<100)
4) If inactive (appropriate) - polydipsia/beer potomania
5) If active - volume assessment
a) Hypovolemic - renal or extrarenal (FeNa)
b) Euvolemic - SIADH/endocrine/osmostat
c) Hypervolemia - CHF, cirrhosis vs renal failure (FeNa). SIADH possible.

Question 2

What is the treatment of acute symptomatic hyponatremia?

Answer 2

3% NaCl

Dose 25-150 mL

Bolus 100-150 if sz, infusion if symptomatic

Repeat q10min

Goal to raise Na 6-8mmol/L

Fluid restrict

Principles:
Defend Intravascular Volume
Don’t Allow Worsening of Na
Avoid Overcorrection
Correct Underlying Cause

DDAVP 1-2mcg q8h iv/sc to avoid massive shifts

Question 3

What is the major complication of overcorrection of hyponatremia and how is it managed?

Answer 3

Osmotic demyelination syndrome

May present up to 7 days post event.

Symptoms: ataxia, quadrapelegia, cranial nerve palsies, locked in syndrome

Risk factors: elderly, malnourished, chronic low Na, hypokalemia

Treat with relowering of Na and supportive measures.

Question 4

What are some symptoms of hyponatremia?

Answer 4

Twitching, weakness, hemiparesis, ataxia, coma, seizures.

Question 5

What are symptoms of hypernatremia?

Answer 5

Irritability, seizure, increased tone, coma

Question 6

Describe the urine findings for diabetes insipidus

Answer 6

Low urine osmolality (200-300)

Urine sodium 60-100

Inability to concentrate urine due to ADH deficiency (central - reduced production from pituitary, nephrogenic - ADH resistance)

Central will respond to ADH stimulation (Vasopressin challenge; 5U subcut will cause urine osm to increase to > 800 under water deprivation)

Question 7

What are the causes of hypernatremia?

Answer 7

Decreased intake, increased Na intake, hormone (cushing/aldostromism), water loss, drug effects

Question 8

What is the formula for free water deficit?

Answer 8

H2O def = (mNa/nNa) - 1

m = measured

n = normal

Generally 1L deficit will raise Na by 3-5mmol/L

Question 9

How does acidosis affect potassium?

Answer 9

For every 0.1 increase in pH potassium decreases by 0.5

Each 1 mmol/L of potassium serum change is equivalent to body deficit/surplus of 100-200 meq

Question 10

List EKG findings in hyperkalemia

Answer 10

6. 5-7.5: Long PR, Peaked Twave, Short QTc
7. 5-8: flat p, QRS prolongation

10-12: complete QRS degredation

Question 11

List treatments of hyperkalemia in order of time to effect.

Answer 11

Calcium Chloride (1amp)/Gluc (2-3amp)

Bicarb (1-2amp)

Ventolin (5mg)

Insulin/D50W (10/1)

Lasix (40)

Sodium Polystyrene (25-50g)

*Dialysis

Question 12

What are the causes of hypocalcemia?

Answer 12

Malabsorption: VitD Deficiency

Increased excretion: Diuretics, Renal failure, EtOH

Metabolic: Shock, Sepsis, Pancreatitis, Low Mg, Tranfusion

Endocrine: HypoPTH/PseudoPTH

Drugs (phosphates, gent/tobramycin, UFH, protamine, glucagon, steroids, Mg, Norepi)

Question 13

What are causes of hypercalcemia?

Answer 13

Malignancy

Endocrinopathy (hyperT4, Pheo, adrenal insuff, acromegaly, hyperPTH)

Drug (TZD, Li)

Granulomatous Disease (sarcoid, TB, histo, coccidiomycosis)

Immoblization

Question 14

What are clinical manifestations of hypocalcemia?

Answer 14

Weakness, fatigue

CNS - memory, confusion, psychosis, EPS, seizures

Derm: brittle hair, hyperpigmentation, dry skin

CV: CHF, vasoconstriction

MSK: spasms, cramps, weakness

Osteomalacia, cataracts, reduced insulin, rickets

Question 15

What are clinic manifestations of hypercalcemia?

Answer 15

Stones (nephrolithiasis)

Bones (osteolysis)

Moans (psychosis)

Groans (PUD, pancreatitis, constipation)

Question 16

What are EKG changes with hypocalcemia?

Answer 16

Long QT (primarily ST segment)

Question 17

What is the acute treatment of hypercalcemia?

Answer 17

BPA (pamidronate, etidronate, zoledronic acid)

Calcitonin 4U/kg

Fluids

Question 18

What are EKG manifestations of low Mg?

Answer 18

Increased PR, Increase QT, Increased QRS, ST depression, TWI

Question 19

What is acute treatment of hyperMg?

Answer 19

IV Fluids

Lasix IV

Calcium

Dialysis

Question 20

What populations get low Mg and how does it usually present?

Answer 20

Alcoholics, cirrhotics, prolonged IV fluids, hyperalimentation

Usually neuromuscular irritabilty, seizures, tremor

Question 21

Describe Chovseks and Trousseau signs

Answer 21

Chvostek - twitch of mouth with tap of nerve anterior to ear

Trousseau - BP cuff above SBP x 3 min, fingers extend at IP, flex at MTP, wrist flexion, arm pronation

Question 22

How does calcium and potassium affect digoxin?

Answer 22

Dig toxicity is increased with hypercalcemia and hypokalemia

Question 23

What is the pharmacological treatment for hyperphosphatemia?

Answer 23

Acetylzolamide