Hyponatremia Flashcards
hypovolemia
- define
- what causes it?
- contraction of the EVF (extracellular fluid volume)
- due to combined salt and water loss
what is hyponatremia and what causes it
- a decrease in Na+ serum concentration
- defined as serum [Na+] below 135 mEq/L
- due to either loss of Na+ or or dilution of Na+ due to excessive body water
what serum [Na+] constites mild, moderate and severe hyponatremia
- Mild :130-134 mEq/L - often asymptomatic
- Moderate: 120-129 mEq/L
- Severe: <120 mEq/L
at what serum [Na] might neurological symptoms present?
115 mEq/L
various symptomatology seen in hyponatremia
- Mild or absent symptoms
- Moderately severe symptoms:
- Nausea without vomiting
- Confusion
- Headache
- Severe symptoms:
- Vomiting
- Cardiorespiratory arrest
- Seizures
- Reduced consciousness/ coma
major causes of hyponatremia
- vomitting, diarrhea: fluid and Na+ loss
- diuretics: fluid and Na+ loss
- inadequate salt intake
- gastrointestinal suckling
- mannitol:
- dilution hyponatremia
- a shift of fluid from teh ICF to the ECF due to hypertonicity in the ECF dilutes serum Na+ and lowers serum Na+ concentration
what is normal serum osmolality?
280-295 mosm/kg
how to calculate serum osmolality
2 [Na+] + [glucose]/18 + BUN/2.8
ADH
- where is it synthesized
- when it is released
- what does it do
- a hormone synthesized by the hypothalamus
- stored in the pituitary and released in states of high serum osmolality
- __acts on distal collecting tubule and collecting ducts to increase their permeability to water
- is a vasoconstrictor
what compartments make hole the total body water?
how much volume does each contain?
what is hypoosmolality
- serum osmolality less than 280 mOsm/Kg
- indicates excess total body water relative to body solutes
IV infusions are administered into what fluid compartment?
into the insterstitium (component of ECV)
what is hypertonic hyponatremia?
what are examples?
- hyponatremia due to overall hypertonicity ( > 290 mOsm) caused by a different solute in the extracellular space that draws water from the ICV into the ECV, thus diluting soeium
- hyperglycemia - high serum glucose
-
hypertonic infusions (these are administered into the interstitial space, cause a hypertonic ECV)
- glucose infusion
- mannitol infusion - given for cerebral edema
- maltose - given alongside IgG administration
isotonic hyponatremia
- define
- what causes it?
- hyponatremia seen when ECV osmolarity overall normal (270-290)
- caused by:
-
psueodhyponatremia: fake lab error resulting from
- hyperlipidemia
- hyperproteinemia
- gycine in TURP: isotonic glycine given in trans urethral prostate resection
hypotonic hyponatremia
- hyponatremia in the context of low overall osmolarity (<270 Mosm) in the extracellular space
- three types of hopotonic hyponatremia
- hypovolemic
- euvolemic
- hypervolemic
- three types of hopotonic hyponatremia
hypovolemic hyponatremia
- describe the fluid/solute status of the extracellular space
- what are causes of this state?
- this is a type of hypotonic hyponatremia ( <270 mosm)
- due to a loss of both total body water and total body sodium but a proportionally LARGER loss of sodium
- causes:
- GI losses:
- vomitting
- diarrhea
- blood loss
- Renal loss:
- diruetics
- adrenal insufficiency: Na+ wasting
- GI losses:
define euvolemic hyponatremia
a type of hypotonic hyponatremia where
- TBW has increased
- total salt is normal
what pathological states can cause euvolemic hyponatremia?
- SIADH: syndrome of innapropriate ADH secretion
- psychogenic polydispia
both lead to elevated total body water in the context of normal total body salt
define hypervolemic hyponatremia
a type of hypotonic hypontremia where
- BOTH TBW and total body Na+ increase
- relatively LARGER increase in TBW with respect to total body Na+
what pathological states can lead to hypervolemic hyponatremia?
- states that decrease extracellular circulating blood volume (ECBV)
-
these states all lead to edema (either due to impaired fluid return to heart or low plasma oncotic pressure)
- CHF: weak heart function
- cirrhoris: low sythesis of plasma proteins
- nephrotic syndrome: innapropriate filtration of plasma proteins, leading to low serum plasma proteins
- renal railure (acute or chornic)
-
these states all lead to edema (either due to impaired fluid return to heart or low plasma oncotic pressure)
- low ECVB leads to –> increased Na+ and water retentention –> hypervolemia
- more water retention relative to sodium retention
what clinical presentations to look for in possible hypovlemia?
Examination of skin and mucous membranes
Low BP
Postural hypotension
Increased capillary refill
what clinical presentations to look for in possible hypervolemia?
JVD
Edema
what is the use of urine sodium concentration in the assesment of hyponatremia?
urine sodium concentration can be used to distinguish between hypovolemia (decreased by TBW and TBNa+, bigger drop in TBNa+) and euvolemia (increased TBW, normal TBNa+)
what specific history should you estbalish with a hyponatremic patients?
determine if they had recent surgery and involving administration of:
- large volumes hypotonic fluid
- ex: prostate or intrauterine procedures)
- large volume of hypertonic IV fluid
- mannitol, glycerol, IVIg
- they were treated with lipemic serum
what are the three main labs you should order for the diagnosis of hyponatremia?
- serum osmolality (normal: 270-290 mOsm)
- urine osmolality
- urine sodium concentration
what does urine osmolarity > 100 mOsm/kg indicate?
indicates in impaired ability of the kidney to dilute the urine.
- urine is therefore too concentrated
- usually secondary to increased ADH
other than the main labs, what labs to get for diagnosis of hyponatremia?
TSH/ FT4- to rule out hypothyroidsm
Uric acid: Low in SIADH
Cortisol- to rule out Adrenal insufficiency
Lipids/albumin
uric acid levels can be used to rule in what type of hyponatremia?
uric acid levels will be low in SIADH (type of euvolemic hyponatremia)
what type of imaging to get in patients with suspected SIADH or suspected cerebral salt wasting ?
had CT scan and chest radiography
based on plasma osmolality, volume status, and urine sodium, outline the diagnosis of the different subsets of hyponatremia
SIADH
- define
- list its causes
- what type of hyponatremia does ADH cause
- how to diagnose
- inappropriate ADH secretion
- excess water reaborption limits the ability of the kidney to dilute urine
- leads to a euvolemic hypotonic hyponatremia
- causes:
- neoplasms
- pneumonia
- menigitis
- drugs:
- SSRIs
- NSAIDS
- carbamazepine
- chemotherapy (cilastin)
- diagnosis:
- main labs
- low serum osmarility:
- < 270 mOsm (confirms hyponatremia)
-
check urine osmolalitity!
-
high serum osmolarity:
- > 100 mOsm/kg
-
high urine [na+]
- > 20 mEq/L
-
high serum osmolarity:
- low serum osmarility:
- other labs:
- REDUCED URIC ACID*
- main labs
discuss cardio, renal and hepatic function in SIADH
Normal renal, hepatic and cardiac function
psychogenic polydypsia
- define
- what type of hyponatremia does it lead
- how to diagnose
- caused by excessive intake of water
- this increases total body water and leads to severly diluted urine
- euvolemic hypotonic hyponatremia
- diagnosis:
- serum osmolarity low (< 270 mOsm)
-
check urine osmolality:
- low urine osmolaritity
- < 100 mOsm/kg
- < 20 mEq/L
- low urine osmolaritity
exercise associated hyponatremia - what is the serum/urine osmolarity
who is at risk?
what is the treatment?
-
excessive water intake seen in the context of marathons & other endurance events
- anyone who has prolonged exercise who is drinking lots of fluids is at risk
- urine osmolarity
- low ( < 100 mOSm)
- urine is dilute
- treatment:
- if pt is asymptomatic: water restriction
- if pt is symptomatic: give hypertonic saline
beer potomia
- excessive beer consumption
- beer has low solute/water ratio
- causes a hypotonic hyponatremia
- low urine osmolarity (< 100 mOsm/kg) like in EAH
- can also lead to malnutrition
- beer has low solute/water ratio
define acute, subuacte and chronic hypotranemia
Acute (< 24 hours)
Subacute (>24-48)
Chronic (>48hrs)
define mild, moderate and severe hyponatremia
Mild: 130-134 mEq/L
Mod: 120-129 mEq/L
Severe<120 mEq/L
hyponatremia treatment goals
- to oprevent further decline in the Na+ concentration
- to relieve symptoms of hyponatremia
excessive correction of hyponatremia can lead to what disease?
osmotic demylination syndrome
describe the presentation of ODS (osmotic demylination syndrome)
Paresis
Dysphagia
Dysarthria
Diplopia
Loss of consciousness Ataxia
Parkinsonism
what are the fluid replacement options for hyponatremia?
- normal saline
- lactated ringers
- hypertonic saline
- reserved for patients with moderate-severe hyponatremia (< 129 mEq/L)
acute hyponatremia
- what defines “acute”
- what is the goal of treatment
- what are the limitations of treatment
- acute: presented < 48 hrs ago
- goal is to raise [Na+] by 4-6 mmol
- takes about 6-8 hrs to correct, then maintain for 24 hrs
- blood [Na+] not to increase by more than 12 mEq in 24 hrs
chronic hyponatremia
- treatment goals
- what adjustments should be made regading risk of ODS?
- chronic hyponatremia: > 48 hours
- goal: raise [Na+] by 4-8 mmol/L in 24 hours
- accounting for ODS:
-
low risk for ODS:
- max correction of hyponatremia by an increase of 10-12 mmol/L in 24 hr period (or 18 mmol/L in 48 hr period)
-
high risk for ODS:
- max correction of of hyponatremia by an increase of 8 mmol/L in 24 hrs
-
possible high ODS risk pts:
- pt with [Na+] < 105 mEq/L
- hypokalemic pts
- malnourished pts
- alcoholic/liver diseases pts
-
low risk for ODS:
treatment of hypovolemic hyponatremic patients?:
- administer isotonic/hypertonic saline
- hypovolemia secondary to diuretic use may also need K+ repletion
how to treat euvolemic hyponatremia patients that are
asymptomatic
- f_ree water restriction_ (<1/day)
- treat SIADH, psychogenic polydispia, EAH this way
treatment for hypervolemic hyponatremic patients:
- give Na+ while restricting fluid
- vasopressin (receptor) antagonists
- if CHD:
- add loop diuretics and an ACE/ARB
how to treat hyponatremic patients that are overtly symptomatic - i.e., have seizures/severe neurological deficits
administer 3% hypertonic saline
furosemide
- what kind of drug?
- indications for use?
- how it is given?
- MOA and effects?
- when it is possibly contradindicated/when should it be used with caution?
- indications: hypervolemic hypontramia
- given with saline
- loop diuretic
- MOA: acts on the thin ascending loop of henle, on the NKCC (Na+/K+/2Cl-) transporter
- decreases Na+ reabsorption (as well as Cl, Mg++, Ca++, mildly K+), i_ncreasing free water excretion_
- use with caution in hypokalemic patients, since it can lead to K+ secretion in the collecting ducts
demeclocycline
- what kind of drug is it
- indications
- MOA
- a tetracycline antiobiotic
- MOA: binds 30s subunit inhibiting protein synthesis
- causes diuresis
- indication: in conjunction with fluid restriction, be used to treat SIADH
tolvaptan
- what kind of drug/MOA/effects
- what are is uses
- contraindications/cautions
- uses: hypervolemic or euvolemic hyponatremia
- is a vasopressin (ADH) antagonist
- MOA: binds vasopressin receptor V2, inhibiting ADH binding
- effects:
- increases urine output
- decrease urine osmlality (dilutes urine)
- normalizes serium sodiu mlevels
- cautions:
- do NOT use over 30 days or you risk liver injury
- if given to patients in a hospital: the hospital MUST have serum Na+ monitoring
- contraindicaitons: liver disease
covinaptan
what kind of drug/MOA/effects
uses
- a ADH(vasopressin) antagonists
- blocks V2 and V1a receptors
- MOA/effects are same as tolvaptan
- increased urine ouput
- decreased urine osmolality (dilute urine)
- MOA/effects are same as tolvaptan
- blocks V2 and V1a receptors
- indication: euvolemic and hypervolemic hyponatremia in patients that are hospitalized
- given IV
