Fatigue and Generalize Weakness (Selby) Flashcards
Why is obstructive sleep apnea a cardiac concert?
Obstructive sleep apnea can lead to CVD
Discuss the pathophysiology of HFrEF
Decreased cardiac contractility leads to back flow of blood into the pulmonary veins and decreased CO. This leads to systolic HF
What are the long-term effects of a lowered RMP?
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
Discuss the pathophysiology of HFpEF
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
How is obstructive sleep apnea dx?
Polysomnography (sleep study)
What lab in addition to measuring urine sodium level and urine osmolality might you want to order if considering SIADH in your ddx?
Serum uric acid– low serum uric acid is associated with SIADH
Why does demyelination occur if correction is too fast?
Brain cells shrink, axonal shear damage occurs and there is a disruption in the BBB
What are some examples of hypervolemic hypoosmotic hyponatremia?
If urine Na+ >20mEq/L: nephrotic syndrome, heart failure, cirrhosis
If urine Na+ <20mEq/L: acute or chronic kidney failure (low GFR)
How does a high K+ concentration effect membrane potential?
Makes membrane potential less negative
When do we usually see vfib with hyperkalemia?
[serum K+] ~ >9mmol/L
Which type of hyponatremia involves ↓total body water and ↓total body Na+?
Hypovolemic hypoosmotic hyponatremia
What is the most common malignancy associated with ectopic ADH production?
Small cell lung cancer
What is the dx if serum osmolality is normal (280-295 mOsm/kg) with hyponatremia?
Iso-osmotic hyponatremia
How would you tx euvolemic hypoosmotic hyponatremia?
Water restriction, hypertonic saline, furosemide, salt or urea tablets
How does tx for acute versus chronic hyponatremia differ?
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
How does the kidney regulate urinary K+ secretion?
The distal part of the nephron regulates urinary K+ secretion via principle cells (secretion) and alpha-intercalated cells (reabsorption)
Define hyponatremia (value)
<135 mEq/L
How would you tx hypervolemic hypoosmotic hyponatremia?
Water restriction, furosemide
What does tx of hyponatremia depend on?
Severity of hyponatremia, duration of hyponatremia and presence of sx
What is the general rule of thumb regarding the timespan for correcting hyponatremia?
Serum sodium should be corrected over the same time period it took to become low
What is the systemic diagnostic approach hyponatremia?
- measure serum osmolality
- if hypo-osmotic hyponatremia, assess volume status of patient
- if hypo-osmotic hyponatremia, measure random urine sodium level and urine osmolality
What are some examples of hypovolemic hypoosmotic hyponatremia?
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
What is the difference between the immediate response and long-term control of potassium homeostasis?
Immediate response= transcellular shift
Long-term control= renal excretion
List some non-osmotic stimuli for ADH release
Baroreceptors (carotid sinus, aortic arch)
Nausea
Hypoxia
Pain
Medications (opiates, antipsychotics, antidepressants)
Pregnancy
What is the most common sleep-related breathing disorder?
Obstructive sleep apnea
How would you tx hypovolemic hypoosmotic hyponatremia?
No sx: isotonic saline
Sx: hypertonic saline
When should you order a transtubular potassium gradient (TTKG) test?
NEVER– invalid test
How is obstructive sleep apnea tx?
Weight loss, CPAP or BiPAP
Alt tx: oral appliances, upper airway surgery, hypoglossal nerve stimulation, etc.
Which type of HF do we usually see concentric remodeling? What about eccentric remodeling?
Concentric remodeling: HFpEF (diastole, EF>50%)
Eccentric remodeling: HFrEF (systole, EF<40%)
What are some major adverse clinical manifestations of hyperkalemia?
Cardiac arrhythmias– vfib, bradycardia from AV block, systole
Skeletal muscle weakness– respiratory failure from diaphragm weakness
Metabolic acidosis
How to you categorize the severity of obstructive sleep apnea?
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
Why is SIADH considered a dx of exclusion?
Must rule of adrenal, thyroid, pituitary adrenal insufficiency and diuretic use
What is the most common medication associated with hyponatremia?
Hydrochlorothiazide (HCTZ)
Discuss the NYHA classes of HF
Class I: asymptomatic
Class II: minor sx with modest exertion
Class III: moderate sx with minor exertion
Class IV: sx at rest
What is the normal value for serum osmolality?
280-290 mOsm/kg
What does the fractional excretion of K+ (FEK) tell us?
<10% indicates renal etiology
>10% indicates extra-renal etiology
What does hyponatremia primarily result from?
Increases in TBW > changes in total body sodium
Increases in TBW occur due to excessive water intake and/or decreased renal excretion
What are some risk factors for obstructive sleep apnea?
Older age (>60YO), male sex, obesity, large neck circumference, tonsillar/adenoid hypertrophy, nasal obstruction, etc.
What is the dx if serum osmolality is high (>295 mOsm/kg) with hyponatremia?
Hyper-osmotic hyponatremia (consider glucose, mannitol, glycerol and sorbitol intake)
What should you do if serum sodium correction is done too quickly?
Consider 5% dextrose in water (D5W) and DDAVP and/or discontinuation of some therapies
What are some examples of euvolemic hypoosmotic hyponatremia?
If urine Na+ >20mEq/L: SIADH, hypothyroidism, cortical deficiency, drugs/diuretics, pain, nausea, stress/psychosis
If urine Na+ <20mEq/L: primary polydipsia
When do we usually see clinical manifestations of hyponatremia? What sx do we see?
Serum sodium <125 mEq/L– headache, fatigue, lethargy, dizziness, nausea, confusion, gait instability, psychosis, seizures, coma from cerebral edema
What is the sodium correction for hyperglycemia?
Na decreases 1.6 mEq/L for every 100 mg/dL increase in glucose
What are some clinical manifestations of obstructive sleep apnea?
Loud snoring, awakening with gasping or choking, daytime sleepiness or fatigue, poor concentration, morning headaches
Which type of hyponatremia involves ↑total body water and ↑total body Na+?
Hypervolemic hypoosmotic hyponatremia
Which type of hyponatremia involves ↑total body water and no change in total body Na+?
Euvolemic hypoosmotic hyponatremia
What is important to note about the timing of labs in renal cases?
All labs need to be drawn simultaneously and it is best to avoid tx until labs are drawn as they can alter lab values
What is the key ECG change with see with hyperkalemia?
Peaked T-waves
