Lecture 5: Fluid and Electrolyte Imbalance - Na, K

Question 1

What are the 2 main causes of intracellular edema?

Answer 1

1. Depression of metabolic systems of tissues
2. 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

Question 2

What 3 factors are working to prevent extracellular edema?

Answer 2

1. Interstitium normally has low compliance
2. Lymph flow can increase 10-50 fold
3. Increased amts of protein-poor capillary fluid flow wash protein out from the interstitial space, thereby decreasing capillary filtration pressure

Question 3

With ACE inhibition the GFR falls, but serum levels of what will rise?

Answer 3

Creatinine

Question 4

Using the mnemonic SALT LOSS what are the sx’s of hyponatremia?

Answer 4

• Stupor/coma
• Anorexia, N/V
• Lethargy
• Tendon reflexes decreases
• Limp muscles (weakness)
• Orthostatic hypotension
• Seizures/HA
• Stomach cramping

Question 5

What are some of the main causes of Euvolemic Hyponatremia?

Answer 5

• SIADH
• Drugs/Stress
• Glucocorticoid deficiency
• Hypothyroidism
• Primary polydipsia

Question 6

What are 2 major causes of increased effective circulating volume which can cause hypervolemic hyponatremia?

Answer 6

1) Acute renal failure
2) Advanced chronic renal failure

Question 7

What are some of the major causes of decreased effective circulating volume which can cause hypervolemic hyponatremia?

Answer 7

• CHF
• Liver disease
• Sepsis
• Nephrotic syndrome
• Pregnancy
• Anaphylaxis

Question 8

What is the correct way to tx a patient with hyponatremia that is only a level 1 (no or minimal symptoms)?

Answer 8

• Fluid restriction
• Consider vaptan under select circumstances (i.e., can’t tolerate fluid restriction, need to correct [Na+] for surgery, etc..)

Question 9

What is the correct way to tx a patient with hyponatremia that is a level 2 (moderate sx’s)?

Answer 9

• Vaptan or hypertonic NaCl
• Followed by fluid restriction

Question 10

What is the correct way to tx a patient with hyponatremia that is a level 3 (severe sx’s)?

Answer 10

Hypertonic NaCl, followed fluid restriction or vaptan

Question 11

Why does hyponatremia need to be corrected slowly?

Answer 11

Overly rapid correction —> osmotic demyelination syndrome

Question 12

What is the rate that can be used to correct hyponatremia in someone who is acute symptomatic?

Answer 12

• 2.5 mEq/L/h to get to safe zone
• Should NOT increase more than 20 mEq/L/day

Question 13

What is the rate that can be used to correct hyponatremia in someone that has chronic (>48 hrs) hyponatremia?

Answer 13

• 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

Question 14

What is one of the major tumors that can cause SIADH?

Answer 14

Oat-cell carcinoma of the lung

Question 15

What are 3 situations in which hypernatremia is commonly seen?

Often a known indicator of?

Answer 15

1. Not uncommon in those living alone who fall at home
2. Known indicator of neglect in nursing homes
3. People in the desert without enough water

Question 16

What are 5 causes of Hyprvolemic Hypernatremia?

Answer 16

1. Administration of hypertonic saline or hypertonic sodium bicarbonate
2. Hypertonic dialysis
3. Hypertonic feedings
4. Primary hyperaldosteronism
5. Cushing syndrome

Question 17

What are 3 causes of Euvolemic Hypernatremia?

Answer 17

1. Diabetes insipidus (central or nephrogenic)
2. Hypodipsia = diminished thirst
3. Insensible dermal and skin losses (only if hypodipsic)

Question 18

What are 2 causes of Hypovolemic Hypernatremia?

Answer 18

1. Lack of access to water
2. “Broken” thirst mechanisms

Question 19

Using the mnemonic TRIP, what are the symptoms of Hypernatremia?

Answer 19

• Twitching, tremors, hyperreflexia
• Restlessness, irritable, confusion, etc. (due to brain cell shrinkage)
• Intense thirst, dry mouth, decreased urine output
• Pulmonary and peripheral edema

Question 20

What to use for treatment of hypovolemic hypernatremia?

Answer 20

Isotonic saline

Question 21

In hypervolemic/euvolemic hypernatremia what is used as treatment?

Answer 21

HYPOtonic IV solutions (i.e., D5W, half-normal saline, quarter-normal saline)

Question 22

What is the rate of infusion for correcting hypernatremia?

Answer 22

Correct over 48 hours at ≤ 0.5 mEq/L/hr (i.e., < 12 mEq/L/day)

Question 23

What are the effects of hyperkalemia vs. hypokalemia on the cardiac conduction system?

Answer 23

• Hyperkalemia —> membranes hyperpolarized = less likely to fire = BRADYcardia
• Hypokalemia –> tachycardia

*This the opposite effect of what is occurring in cells

Question 24

What will be seen on the ECG of someone with hyperkalemia?

Answer 24

Peaked T wave

Question 25

What are some of the hormones/drugs, acid-base states, and deficiencies that cause an increase in K+ movement **into** cells?

Answer 25

- **Insulin** - **β₂-agonist** (epi) and **α-blockers** - Aldosterone deficiency - Alkalosis - Hypoosmolarity

Question 26

What are some of the factors (i.e., hormones, drugs, deficiencies, states) that cause an increase in K+ leaving the cell?

Answer 26

- **α-agonist** (NE, Epi) - Insulin **deficiency** - **β₂-blockers** - **Acidosis** - **Hyper**osmolarity - **Exercise** - **Cell lysis**

Question 27

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?

Answer 27

Insulin

Question 28

What are the 5 major influences on segmental absorption of K+ in the nephron during times of normal/excess K+?

Answer 28

1. Plasma [K+] 2. Aldosterone 3. ADH 4. Acid-Base Balance 5. Tubular fluid flow rate

Question 29

Hyperkalemia will cause an increase in the release of what hormone?

Answer 29

Aldosterone

Question 30

Using the mnemonic GRAPHIC IDEA what are the causes of Hypokalemia?

Answer 30

- **G**I losses (vomitting, diarrhea) **I**nsufficient intake - **R**enal tubular acidosis (type I and II) **D**iuretics - **A**ldosterone **E**levated β-adrenergic activity - **P**aralysis (periodic) **A**lkalosis - **H**ypothermia - **I**nsulin excess - **C**ushing's Syndrome

Question 31

The most prominent signs/sx's of hypokalemia will be in what system?

Answer 31

**Neuromuscular** - **Skeletal m. weakness** **- Smooth m. weakness** --\> GI hypomobility causing **ileus** and **constipation**

Question 32

What are three CV system signs/sx's associated w/ hypokalemia?

Answer 32

1. Ventricular arrhythmias 2. HYPOtension 3. Cardiac arrest

Question 33

Hypokalemia will lead to what renal manifestations?

Answer 33

Impaired concentrating ability causes **polyuria** and **nocturia**

Question 34

Effect of hypokalemia on blood glucose levels?

Answer 34

**Hyper**glycemia

Question 35

What are the 3 main goals for treatment of Hypokalemia?

Answer 35

1. **Prevent life-threatening conditions** 2. **Replace K+ deficit** ---\> **K+ replacement** is mainstay 3. **Diagnose/correct underlying cause** --\> i.e., K+ losing diuretics

Question 36

Preventing life-threatening conditions associated w/ hypokalemia is especially urgent if rapid K+ falls to what level?

Answer 36

\< 2.5 mEq/L

Question 37

Using the mnemonic RED FETS what are the causes of Hyperkalemia?

Answer 37

- **R**enal disease: ARF, CKD, type IV RTA - **E**xcessive intake: food, K+ IV fluids, blood transfusion - **D**rugs: K+ sparing diuretics, K+ salts of penicillin - **F**actitious: prolonged use of tourniquet, hemolysis - **E**ndocrine: Addison's disease - **T**issue release: rhabdomyolysis, burns, hemolysis, cytotoxic therapy - **S**hift out of cell: acidosis, β-antagonists, insulin deficiency, tissue damage

Question 38

Which system will have the predominant and most important signs/sx's of Hyperkalemia, what are they?

Answer 38

- **Cardiac** - Abnormal heart rhythm, **bradycardia** - **Peaked T wave**

Question 39

What are 3 neuromuscular signs/sx's of hyperkalemia?

Answer 39

1. Numbness 2. Weakness 3. Flaccid paralysis

Question 40

Emergency management of Hyperkalemia is divided into 3 categories, how are cardiac effects managed first?

Answer 40

**Antagonize cardiac effects** ---\> give **IV calcium**

Question 41

In the treatment of Hyperkalemia what can be given to redistribute K+ intol cells?

Answer 41

- Give **insulin + glucose (most reliable)** or - **β2-agonist** such as **albuterol**

Question 42

In the management of hyperkalemia what can be given to facilitate K+ elimination?

Answer 42

- **K+ losing diuretic** - Consider **mineralocorticoid** (pts w/ hypoaldosteronism) - Cation exchange resin - Dialysis

Question 43

After effectively managing an emergency situation of hyperkalemia, what should be done?

Answer 43

**Monitor intake** (≤ 60 mEq/day), paying attention to hidden sources such as Abx