Fatigue and Generalize Weakness (Selby)

Question 1

Why is obstructive sleep apnea a cardiac concert?

Answer 1

Obstructive sleep apnea can lead to CVD

Question 2

Discuss the pathophysiology of HFrEF

Answer 2

Decreased cardiac contractility leads to back flow of blood into the pulmonary veins and decreased CO. This leads to systolic HF

Question 3

What are the long-term effects of a lowered RMP?

Answer 3

Although initially a lower RMP will increase membrane excitability, long-term persistent depolarization leads to inactivation of sodium channels. This produces a net decrease in membrane excitability, leading to impaired cardiac conduction and/or neuromuscular weakness/paralysis

Question 4

Discuss the pathophysiology of HFpEF

Answer 4

Diastolic dysfunction results from decreased LV relaxation and compliance leading to ventricular stiffness and higher diastolic pressure, which is transmitted to the atria and pulmonary veins

Question 5

How is obstructive sleep apnea dx?

Answer 5

Polysomnography (sleep study)

Question 6

What lab in addition to measuring urine sodium level and urine osmolality might you want to order if considering SIADH in your ddx?

Answer 6

Serum uric acid– low serum uric acid is associated with SIADH

Question 7

Why does demyelination occur if correction is too fast?

Answer 7

Brain cells shrink, axonal shear damage occurs and there is a disruption in the BBB

Question 8

What are some examples of hypervolemic hypoosmotic hyponatremia?

Answer 8

If urine Na+ >20mEq/L: nephrotic syndrome, heart failure, cirrhosis

If urine Na+ <20mEq/L: acute or chronic kidney failure (low GFR)

Question 9

How does a high K+ concentration effect membrane potential?

Answer 9

Makes membrane potential less negative

Question 10

When do we usually see vfib with hyperkalemia?

Answer 10

[serum K+] ~ >9mmol/L

Question 11

Which type of hyponatremia involves ↓total body water and ↓total body Na+?

Answer 11

Hypovolemic hypoosmotic hyponatremia

Question 12

What is the most common malignancy associated with ectopic ADH production?

Answer 12

Small cell lung cancer

Question 13

What is the dx if serum osmolality is normal (280-295 mOsm/kg) with hyponatremia?

Answer 13

Iso-osmotic hyponatremia

Question 14

How would you tx euvolemic hypoosmotic hyponatremia?

Answer 14

Water restriction, hypertonic saline, furosemide, salt or urea tablets

Question 15

How does tx for acute versus chronic hyponatremia differ?

Answer 15

Acute hyponatremia (<48hr): can have rapid correction with little risk of osmotic demyelination syndrome (ODS)

Chronic hyponatremia (>48hr): must be careful of rapid correction of serum sodium as the patient is at a higher risk for osmotic demyelination syndrome (ODS). The goal is to raise serum sodium by 8-10 mEq/d with no more than 18 mEq/L within the first 48 hr

Question 16

How does the kidney regulate urinary K+ secretion?

Answer 16

The distal part of the nephron regulates urinary K+ secretion via principle cells (secretion) and alpha-intercalated cells (reabsorption)

Question 17

Define hyponatremia (value)

Answer 17

<135 mEq/L

Question 18

How would you tx hypervolemic hypoosmotic hyponatremia?

Answer 18

Water restriction, furosemide

Question 19

What does tx of hyponatremia depend on?

Answer 19

Severity of hyponatremia, duration of hyponatremia and presence of sx

Question 20

What is the general rule of thumb regarding the timespan for correcting hyponatremia?

Answer 20

Serum sodium should be corrected over the same time period it took to become low

Question 21

What is the systemic diagnostic approach hyponatremia?

Answer 21

1. measure serum osmolality
2. if hypo-osmotic hyponatremia, assess volume status of patient
3. if hypo-osmotic hyponatremia, measure random urine sodium level and urine osmolality

Question 22

What are some examples of hypovolemic hypoosmotic hyponatremia?

Answer 22

If urine Na+ >20mEq/L: renal fluid losses, diuretic excess, mineralocorticoid deficiency, cerebral salt wasting, salt-losing nephropathy, bicaronaturia with RTA, osmotic diuresis, ketonuria

If urine Na+ <20mEq/L: extra-renal fluid losses, vomiting, diarrhea, third spacing of fluids (burns, pancreatitis, blood loss), excessive sweating, lung losses

Question 23

What is the difference between the immediate response and long-term control of potassium homeostasis?

Answer 23

Immediate response= transcellular shift

Long-term control= renal excretion

Question 24

List some non-osmotic stimuli for ADH release

Answer 24

Baroreceptors (carotid sinus, aortic arch)
Nausea
Hypoxia
Pain
Medications (opiates, antipsychotics, antidepressants)
Pregnancy

Question 25

What is the most common sleep-related breathing disorder?

Answer 25

Obstructive sleep apnea

Question 26

How would you tx hypovolemic hypoosmotic hyponatremia?

Answer 26

No sx: isotonic saline

Sx: hypertonic saline

Question 27

When should you order a transtubular potassium gradient (TTKG) test?

Answer 27

NEVER– invalid test

Question 28

How is obstructive sleep apnea tx?

Answer 28

Weight loss, CPAP or BiPAP

Alt tx: oral appliances, upper airway surgery, hypoglossal nerve stimulation, etc.

Question 29

Which type of HF do we usually see concentric remodeling? What about eccentric remodeling?

Answer 29

Concentric remodeling: HFpEF (diastole, EF>50%)

Eccentric remodeling: HFrEF (systole, EF<40%)

Question 30

What are some major adverse clinical manifestations of hyperkalemia?

Answer 30

Cardiac arrhythmias– vfib, bradycardia from AV block, systole

Skeletal muscle weakness– respiratory failure from diaphragm weakness

Metabolic acidosis

Question 31

How to you categorize the severity of obstructive sleep apnea?

Answer 31

Mild OSA: AHI= 5-14 events/hr
Moderate OSA: AHI≥ 15-29 events/hr
Severe OSA: AHI≥ 30 events/hr

AHI= apneas + hyponeas / total sleep time in hours

Question 32

Why is SIADH considered a dx of exclusion?

Answer 32

Must rule of adrenal, thyroid, pituitary adrenal insufficiency and diuretic use

Question 33

What is the most common medication associated with hyponatremia?

Answer 33

Hydrochlorothiazide (HCTZ)

Question 34

Discuss the NYHA classes of HF

Answer 34

Class I: asymptomatic
Class II: minor sx with modest exertion
Class III: moderate sx with minor exertion
Class IV: sx at rest

Question 35

What is the normal value for serum osmolality?

Answer 35

280-290 mOsm/kg

Question 36

What does the fractional excretion of K+ (FEK) tell us?

Answer 36

<10% indicates renal etiology

>10% indicates extra-renal etiology

Question 37

What does hyponatremia primarily result from?

Answer 37

Increases in TBW > changes in total body sodium

Increases in TBW occur due to excessive water intake and/or decreased renal excretion

Question 38

What are some risk factors for obstructive sleep apnea?

Answer 38

Older age (>60YO), male sex, obesity, large neck circumference, tonsillar/adenoid hypertrophy, nasal obstruction, etc.

Question 39

What is the dx if serum osmolality is high (>295 mOsm/kg) with hyponatremia?

Answer 39

Hyper-osmotic hyponatremia (consider glucose, mannitol, glycerol and sorbitol intake)

Question 40

What should you do if serum sodium correction is done too quickly?

Answer 40

Consider 5% dextrose in water (D5W) and DDAVP and/or discontinuation of some therapies

Question 41

What are some examples of euvolemic hypoosmotic hyponatremia?

Answer 41

If urine Na+ >20mEq/L: SIADH, hypothyroidism, cortical deficiency, drugs/diuretics, pain, nausea, stress/psychosis

If urine Na+ <20mEq/L: primary polydipsia

Question 42

When do we usually see clinical manifestations of hyponatremia? What sx do we see?

Answer 42

Serum sodium <125 mEq/L– headache, fatigue, lethargy, dizziness, nausea, confusion, gait instability, psychosis, seizures, coma from cerebral edema

Question 43

What is the sodium correction for hyperglycemia?

Answer 43

Na decreases 1.6 mEq/L for every 100 mg/dL increase in glucose

Question 44

What are some clinical manifestations of obstructive sleep apnea?

Answer 44

Loud snoring, awakening with gasping or choking, daytime sleepiness or fatigue, poor concentration, morning headaches

Question 45

Which type of hyponatremia involves ↑total body water and ↑total body Na+?

Answer 45

Hypervolemic hypoosmotic hyponatremia

Question 46

Which type of hyponatremia involves ↑total body water and no change in total body Na+?

Answer 46

Euvolemic hypoosmotic hyponatremia

Question 47

What is important to note about the timing of labs in renal cases?

Answer 47

All labs need to be drawn simultaneously and it is best to avoid tx until labs are drawn as they can alter lab values

Question 48

What is the key ECG change with see with hyperkalemia?

Answer 48

Peaked T-waves