Hypernatremia and hyponatremia-Paulson Flashcards
Hypernatremia is defined as:
Elevated serum sodium > 145 mEq/L
Hypernatremia: MC etiology?
**most often from water depletion (think elderly Pt with dementia who doesn’t remember to drink H20)
Remember Sodium is the main extracellular _____
cation
Which Pt demographic is at the highest risk for hypernatremia?
Elderly patients with ↓ thirst and ↓ access to fluids are at highest risk
General- Hypo/hypernatremia
Sodium concentration can increase or decrease.
Define hypervolemia
fluid volume is increased
Define hypovolemia
fluid volume is decreased
Euvolemia=
Fluid volume is relatively unchanged
Pathophysiology Hypernatremia: again, what is the MC cause?
-Almost always from inadequate fluid intake or excess water loss –Think: elderly, dementia patients who forget to drink fl
Water losses: (can occur through?) list 3 ex’s
-Skin -GI tract -Urine
Describe how water can be lost through urine
-Osmotic diuresis -Diabetes insipidus (central or nephrogenic) -Diuretics can waste water and/or sodium (ie thiazide diuretics)
Describe the Pathophys: -Hypervolemic hypernatremia
-Iatrogenic from hypertonic saline or dialysis (specifically normal saline, giving a Pt extra fluids (volume)) -Hyperaldosteronism (increased aldosterone INCREASES the amount of Na reabsorbtion–> causes water to follow and be absorbed)
Describe the Pathophys: -Hypovolemic hypernatremia
-Renal losses from renal disease or diuretics -Extrarenal losses (ie diarrhea, vomiting)
Describe the Pathophys: -Euvolemic hypernatremia
-Hypodipsia (=decreased thirst and water intake, ie diabetes inspididus) -Diabetes insipidus
Hypernatremia: Clinical Features -Early Sx? -Next? -Neuro Sx? -S/s of dehydration?
-Early sx: anorexia, restlessness, n/v -Next: progressive AMS: lethargy or irritability 1st, then stupor or coma -Neurologic s/s: twitching, hyperreflexia, ataxia, tremor, seizures -S/S of dehydration: Dry MM, tenting/poor skin turgor, lack of tears, ↓ salivation, tachycardia, hypotension, oliguria/anuria
Diabetes insipidus=
=production of dilute urine -central diabetes insipidus= decreased posterior pituitary production of ADH (antidiuretic hormone) -Nephrogenic DM Inspidus= reduced sensitivity of the kidneys to ADH (so someone with diabetes insipidus IS NOT reabsorbing water as they should)
Osmotic diuresis=
take in some solute that does NOT get reabsorbed into your body (ie glucose, urea, manatol) NOT sodium (not an electrolyte solute), and what happens is all the water follows that solute and you end up with increased urine
Chronic hypernatremia: -defined as?
Chronic: has been present ≥ 2 days -Less likely to provoke neurologic s/s -Many patients have underlying neuro disease (impaired thirst) -Undergo brain adaptation to hypernatremia
Acute Hypernatremia: -is defined as? -more likely to provoke _____ sx?
More likely to provoke neurologic s/s (notes: rapid decrease in brain volume, can cause SAH (subarachnoid hem. and irreversible brain damage)
Hypernatremia: -diagnostic labs
-Cause is usually obvious from the history -**BMP–> Sodium >145 -Urine & plasma osmolality if etiology unclear
what can the urine and plasma osmolarity tell you?
-If hypernatremic & plasma osmolality >295, normal response would be to ↑ ADH production –> excrete low volumes (<500 mL/day) of very concentrated urine (with osmolality >800) -If so, there’s an extrarenal cause -If urine osmolality < plasma –> DI (notes: plasma osmolarity–> looks at
Hypernatremia: tx?
Give dilute fluids to correct the deficit & replace ongoing losses
Chronic hypernatremia: tx?
-Chronic: Correction must be slow –To avoid rapid fluid movement into the brain –>cerebral edema –Can lead to seizures and coma -D5W IV at a rate of **1.35 mL/hr x weight in kg –For a 50 kg patient, this would work out to about 70 mL/hr –The goal of this regimen is to lower the serum sodium by a max of 10 mEq/L over a 24 hour period -*Recheck serum sodium/glucose 4-6 hours after tx initiation (D5W=half normal saline)!!! never use normal saline
Acute hypernatremia: tx?
Acute: -D5W IV at a rate of 3-6 mL/kg per hour -Monitor sodium & glucose Q1-2H until Na < 145 –At this point, you can decrease the rate to 1 mL/kg per hour until they reach a sodium of 140. -Goal is to reduce the sodium by 1-2 mEq/L each hour
Calculated Free water deficit
Calculated free water deficit: Water deficit = Current TBW x ((serum [Na]/140) - 1) *this is used to figure out the fluids you need to replace) free water= electrolyte free water= pure water that has been depleted from the Pt’s body -dont memorize this calc just focus on treatment options
Rate of correction (for water deficit): -Chronic?
Chronic: no more than 10 mEq/L per day -Total amount for 1st day: 3 ml/kg of body weight x 10 –>Then divide that number by 24 hours
Rate of correction (for water deficit): -acute?
Acute: Lower to near normal in the first 24 hours -Hourly rate > total water deficit ÷ 24 hours -Also account for ongoing losses
Hypernatremia: prognosis
-Mortality rates of 40-60% –Many with underlying severe diseases -Associated with increased M&M (mortality and morbidity): -Perioperative 30-day mortality -Perioperative major coronary events -Pneumonia -VTE
Hyponatremia is defined as:
-Sodium < 135 mEq/L -*MC electrolyte disorder seen in hospitalized patients
Describe the 2 scenarios where a Pt can be hyponatremic
-Hypervolemic: Fluid overload Water is either added or retained –> the amount of sodium in the serum is diluted -Hypovolemic: Water and sodium is lost (but more sodium than water) –>can be through renal loses and extrarenal losses
Hyponatremic: -describe Hypervolemic causes
=Fluid overload –Water is either added or retained –> the amount of sodium in the serum is diluted **Ex’s= CHF, cirrhosis, IVF, nephrotic syndrome
Hyponatremic: -Describe Hypovolemic causes –Renal losses vs Extrarenal losses?
=Water and sodium is lost (but more sodium than water) -Renal losses: Diuretics, especially **thiazide diuretics -Extrarenal losses: Diarrhea, sweating, blood loss, fluid shifts
Pathophysiology- Euvolemic Hyponatremia: -list possible causes (5)
-Adrenal insufficiency -Polydipsia -Hypothyroidism -Syndrome of Inappropriate Antidiuretic Hormone (SIADH) -Reset Osmostat
Pathophysiology- Euvolemic Hyponatremia: -Polydipsia–> can be primary or _____
psychogenic
Pathophysiology- Euvolemic Hyponatremia: -List causes of Syndrome of Inappropriate Antidiuretic Hormone (SIADH) (list 4)
-Intracranial pathology -Paraneoplastic syndrome (tumor secretes ADH) -Pulmonary disease -Medications: SSRI, cyclophosphamide (think brain bleed, brain tumor= ie any intracranial pathology, stroke, OR pulmonary disease (lung cancer, COPD, and MEDS are a big one)
Reset osmostat=
=the kidneys retains their ability to approp. concentrate the urine, but the threshold for ADH secretion gets reset DOWNWARDS–> so Pt’s have a chronic mild or low hyponatremia –sometimes considered a variant of SIADH
Meds that cause hyponatremia: (slide 16 any are possible, but Paulson listed these main ones)
-thiazide diuretics -antipsychotics -SSRI’s (are huge cause of hyponatremia!!!) -say they’re euvolemic and they are on an SSRI–> titrate the SSRI down, or switch meds
Classification by tonicity: (another method of classification for hyponatremia-tonicity describes the serum osmolality) -3 types of tonicity
-Hypotonic -Isotonic -Hypertonic
Describe Hyptonic
=less concentrated than normal saline *-SIADH *-Effective arterial blood volume depletion–>CHF, cirrhosis, diuretics *-Endocrine d/o: hypothyroid, adrenal insufficiency *-Advanced renal failure (lose the ability to concentration our urine properly, so water can be retained, serum is more dilute than it should be)
Describe Isotonic=
=same concentration **-Pseudohyponatremia: ↑ serum lipids or proteins can lead to an erroneous measurement of sodium levels KNOW THIS–> is someone has a high lipid level or serum protein (ie multiple myeloma increase in bence jones)–> can lead to a “fakeout” of sodium level (there is a reduction in the fraction (portion of serum) that is water and sodium so you get an artificially low sodium level)
Describe hypertonic=
=more concentrated than normal saline **-Significant hyperglycemia Mannitol, maltose, or sucrose retention **-These solutes cause a shift of water out of cells–> sodium is diluted KNOW this–> Pt that is signif. hyperglycemic, water that was inside cells is now in the serum–> causes serum dilution of sodium– just correct the sodium level for this
Algorithmic for hyponatremia
slide 18
Hyponatremia: clinical features -at what sodium serum level are Pts symptomatic? -S/Sx?
-Usually not symptomatic until Na is 125-130 -May complain of: anorexia, n/v, lethargy, disorientation, headache, seizures -Signs: Weakness, agitation, hyporeflexia, orthostatic hypotension, delirium, coma, seizure, respiratory arrest, brainstem herniation
Another cause of hyponatremia?
contrast agents
Hyponatremia: diagnostic labs?
-Focus on finding underlying cause *-1st: BMP + serum osmolality –Osmolality can further direct you to a hypotonic, isotonic, or hypertonic cause -Urine osmolality & electrolytes also helpful -Other possibilities: TSH, plasma cortisol, ACTH stimulation test, brain or lung imaging
Serum sodium algorithm (starting with plasma osmolality)
slide 21 , Paulson not testing on this but schoenwald might -first use your inspection skills and check their volume status first and go from there
d
slide 22
Classifications of hyponatremia: -acute ? -subacute? -chronic ?
-Acute: developed within the last 24 hours -Subacute: 24-48 hours -Chronic: >48 hours
Classifications of hyponatremia: -severe? -moderate -mild?
-Severe: Sodium is ≤ 120 -Moderate: 121-129 -Mild: 130-135
Hyponatremia: tx?
-Identify & treat underlying cause -If symptomatic, even if mild, need emergency therapy –Hypertonic saline -Goal is to raise Na by 4-6 over a couple hours –Should alleviate symptoms & prevent herniation –Check sodium Q2H -For non-emergency therapy, the goal is to bring Na up slowly -Overly rapid correction can cause osmotic demyelination syndrome (aka central pontine myelinolysis)
Hyponatremia: tx -Hypovolemic?
tx with Isotonic saline
Hyponatremia: tx -Hypervolemic?
-CHF, cirrhosis: diuresis, fluid restriction, sodium restriction -Renal failure: fluid restriction, dialysis, sodium restriction
Hyponatremia: tx -Euvolemic
-Fluid restriction –SIADH- may add salt tabs and/or a loop diuretic
What is an off-label med used for SIADH?
*Demeclocycline
When is Demeclocycline used? -S/E?
-Often used for patients who don’t respond to salt tabs/loop diuretics -S/E: renal toxicity (especially for patients with cirrhosis), can cause nephrogenic DI, intracranial hypertension
