Hyponatremia and Hypernatremia
Hyponatremia
Defined as sodium concentration < 135 mEq/L
Generally considered a disorder of water as opposed to disorder of salt
Results from increased water retention
Normal physiologic measures allow a person to excrete up to 10 liters of water per day which protects against hyponatremia
Thus, in most cases, some impairment of renal excretion of water is present
Volume status helps predict cause
Deplesional HyponatHypovolemic Hyponatremia
Diarrhea ,Vomiting
Adrenal insufficiency(Addison disease(
Thiazide overdose..loss of Na.
Decrease intake of Na, Excessive sweating→ increased thirst → intake of excessive amounts of pure water only without Na
.
4
• (Delusional Hyponat.)
• Euvolemic• SIADH
• Primary Polydipsia
• Hypervolemia
• Cirrhosis and CHF, Nephrotic Synd
5
Clinical manifestations of Hyponatremia
Neurological symptoms
Lethargy, headache, confusion, apprehension, depressed reflexes, seizures and coma
Muscle symptoms
Cramps, weakness, fatigue
Gastrointestinal symptoms
Nausea, vomiting, abdominal cramps, and diarrhea
Psuedohyponatremia –
High blood sugar (DKA) or protein level (multiple myeloma) can cause falsely depressed sodium levelsNormal ADH response to low sodium is to be suppressed to allow maximally dilute urine to be excreted thereby raising serum sodium level
Causes of Hyponatremia can be classified based on ADH level
_ Hyponatremia with ADH inappropriately elevated
(SIADH)
_appropriately suppressed eg. Primary polydypsia
ADH elevation
Conditions which ADH is elevatedVolume Depletion
True volume depletion (i.e. bleeding)Effective circulating volume depletion (i.e. heart failure and cirrhosis)
Increase plasma Osmolality(NR..275-290 mOsm/kg)
SIADH
Main diagnostic criteria for SIADH
Clinical EuvolemiaHyponatremia below 130 mmol/l
Urine osmolality isnot minimally low(as one expect (
Usually more than 150 mOmol/kg,though generally greater than 400-500 mOsm/kg in setting of low serum osmolality (below 270 mOsm/kg)
Urine sodium is not minimally low ie greater than 30 mEq/L
Normal hepatic, renal and cardiac function
Normal thyroid and adrenal function
SIADH
Caused by
CNS disease – tumor, infection, CVA, SAH,
Pulmonary disease – TB, pneumonia, positive pressure ventilation
Cancer – Lung, pancreas, thymoma, ovary, lymphoma
Drugs – NSAIDs, SSRIs, diuretics, TCAs
Surgery - Postoperative
Idopathic – most common
First step in Assessment: Are symptoms present?
Hyponatremia can be asymptomatic and found by routine lab testingIt may present with mild symptoms such as nausea and malaise (earliest) or headache and lethargy
Or it may present with more severe symptoms such as seizures, coma or respiratory arrest
WHAT NEXT?With no severe symptoms : fluid restriction started, next step is
to assess volume status to help determine cause
Hypovolemic – urine output, dry mucous membranes, sunken eyes
Euvolemic – normal appearing
Hypervolemic – Edema, past medical history, Jaundice (cirrhosis), S3 (CHF)
Workup for Hyponatremia
3 mandatory lab testsSerum Osmolality
Urine Osmolality
Urine Sodium Concentration
Additional labs depending on clinical suspicion
TSH, cortisol (Hypothryoidism or Adrenal insufficiency)
Albumin, LFTs, B.glucose ,Keton in urine,and S.Protein electrphoresis (psuedohyponatremia…..DKA,MM) Chest Xray (small cell carcinoma؟
Treatment is based on symptoms &type of Hyponatremia
Patients with serum sodium above 120 are generally asymptomaticSymptoms tend to occur at serum sodium levels lower than 120 or when a rapid decline in sodium levels occur
Patients can have mild symptoms at sodium concentrations of 110-115 mEq/L when this level is reached gradually
If Hyponat. Develops over hours or days..morbidity high due to cerebral oedema relatively rapid correction with starting bolus of 100 ml of 3% hypertonic saline which generally raise serum sodium level by 2-3 mEq/L
Goals for correction : gradual correction
2 mEq/L per hour for first 3-4 hours until symptoms resolve
Increase by no more than 10-12 mEq/L in first 24 hrs
Increase by no more than 18 mEq/L in first 48 hrs
What if little to no symptoms are present :
For Delusional HyponatremiaOral fluid restriction is the first step
No more than 600-1000 mL per day
Removal of cause of SIADH,
Demeclocycline 600-900 mg
If volume depletion (Deplesional Hypovolemic) is present, isotonic (0.9%) saline can be given intravenously
Hypervolemic Hyponatremia : treat underlying cause ,Causious Duiretics with fluid restriction. K sparing duiretics are especially benificial in states of Secondary Hyperaldoseronism
*Serum sodium levels should be drawn every 4-6 hours or more frequently if hypertonic saline is used
Hypertonic saline contains 500 mEq/L of sodium
Normal saline contains 154 mEq/L of sodiumWhat if the sodium increases too fast?
The serious complication of replacing sodium too fast is Central Pontine Myelinolysis which is a form of osmotic demyelinationSymptoms generally occur 2-6 days after elevation of sodium and usually either irreversible or only partially reversible
Symptoms include: dysarthria, dysphagia, paraparesis, quadriparesis, lethargy, coma or even death
Summary of Hyponatremia
Hyponatremia has variety of causesTreatment is based on symptoms
Severe symptoms = Hypertonic Saline
Mild or no symptoms = Fluid restriction
Overcorrection, more than 12 mEq increase in 24 hours must be avoided with monitoring
Serum Osmolality, Urine Osmolality and Urine sodium concentration are initial tests to order
Hypernatremia
Produced by either administration of hypertonic fluids or much more frequently, loss of thirst or failure of ADH mechanismsWater moves from ICF → ECF
&Cells dehydrate
Because of extremely efficient regulatory mechanisms such as ADH and thirst, hypernatremia generally occurs only in people with prolonged lack of thirst mechanism
Patients with loss of ADH - Diabetes Insipidus(DI(usually can compensate with increased fluid intake
Causes of Hypernatremia
• sweat losses in prolonged fever…..loss of pure water.• Insufficient intake of water (hypodipsia(
GIT losses
Diabetes Insipidus (both central and nephrogenic(
Osmotic Diuresis – DKA
Hypothalamic lesions which affect thirst function – Causes include tumors, granulomatous diseases or vascular disease
Sodium Overload – Infusion of Hypertonic sodium bicarbonate for metabolic acidosis
Hypernatremia
Initial symptoms include lethargy, weakness and irritabilityCan progress to twitching, seizures, obtundation or coma
Resulting decrease in brain volume can lead to rupture of cerebral veins leading to hemorrhage
Severe symptoms usually occur with rapid increase to sodium concentration
Sodium concentration greater than 180 mEq are associated with high mortality
Diagnosis of Hypernatremia
Same labs as workup for hyponatremia: Serum osmolality, urine osmolality and urine sodiumIf urine osmolality is lower than serum osmolality then DI is suspected
Administration of Desmopressin-DDAVP will differentiate
types of DI
* Urine osmolality will increase in central DI, no response in nephrogenic DI
Treatment of hypernatremia
Typical fluids given in form of Dextrose 5%Same as hyponatremia, sodium should not be lowered by more than 12 mEq/L in 24 hours
Overcorrection can lead to cerebral edema which can lead to encephalopathy, seizures or death
Comments
Post a Comment