Sodium Flashcards
Hypotonic hyponatremia :true hyponatremia
**serum osmolality <280 mOsm/kg
A)Hypovolemic : low urine sodium (<10meq/dl)
High(>20meq/dl)
B) euvolemic
C)hypervolemic (low urine Na+)
Causes of low urine sodium hypovolemic Hypotonic hyponatremia
kidneys absorb Na
External loses example diarrhea vomiting /nasal gastric suction diaphoresis /third spacing /Burns pancreatitis
Causes of high urine sodium hypotonic hyponatremia
Renal causes excessive diuretic use
Decreased aldosterone
Acute tubular necrosis
MOA for aldosterone ,ADH
Increases sodium resorption and then water follows
ADH: Increases water resorption Alone
Causes of euvolemic hypotonic hyponatremia
RATS :Renal tubular acdosis /Addison/thyroid( hypothyroidism) /Syndrome of inappropriate ADH secretion /psychogenic polydepsia -post operative
Causes of hypervolemic hypotonic hyponatremia
CHF
Nephrotic syndrome
liver diseases
Causes of syndrome of inappropriate ADH secretion
CNS pathologies
malignancy small cell lung carcinoma surgery (postoperative hyponatremia )
drugs
Drugs That’s causes syndrome of inappropriate ADH secretion (SIADH)
SSRIs-Oxytocin-carbamazepine-Haloperidol-Cyclophosphamide -certain antineoplastic agents
Clinical features of hyponatremia
Neurological symptoms due to water intoxication (cerebral edema)
a. Headache, delirium, irritability
b. Muscle twitching, weakness
c. Hyperactive deep tendon reflexes
Increased ICP, seizures, coma
GI-nausea, vomiting, ileus, watery diarrhea
• Cardiovascular hypertension due to increased ICP
Increased salivation and lacrimation
• Oliguria progressing to anuria- may not be reversible if therapy is the delayed and AKF develops
Gi symptoms due to hyponatremia
Nausea vomiting ileus watery diarrhea
Clinical features of hypernatremia
Altered mental status /restlessness /weakness /focal neurological deficit /confusion /seizure /coma
tissue and mucous membranes dryness decrease salivation
Diagnosis of hypernatremia
Urine volume should be low
Urine osmolarity should be more than 800 mOsm/kg
Desmopressin Is given to differentiates nephrogenic from central diabetes insipidus
Treatment of isovolemic
Hypernatremia if due to diabetes Insipidus
Vasopressin
Na
Associated with water homeostasis
ECF
An increase in sodium intake results in an increase ECF volume which result in an increase in GFR and sodium excretion through release of ANP and BNP from heart and dec renal renin secretion which inhibits epinephrine nor-epinephrine, ADH ,aldosterone
B. Sodium Homeostasis
1. Sodium is actively pumped out of cells and
1 to the extracellular
space. It is the main osmotically active cation o
2. An increase in sodium intake results in an increas
which results
in an increase in GFR and sodium excretion. This oce
hrough release
of ANP and BNP by the heart and decrease of renal renin
which together
promote natriuresis and inhibit norepinephrine, epinephrine, aldosterone, and ADH
release.
3. A decline in the extracellular circulating volume results in a decreased GFR and a reduction in sodium excretion. This is a response to the sympathetic nervous system increasing cardiac output as well as a decrease in renal perfusion pressure resulti: in activation of the renin-angiotensin-aldosterone system. Aldosterone increases Na reabsorption and potassium secretion from the late distal tubules.
4. Diuretics inhibit Na* reabsorption :Furosemide and other loop diuretics inhibit the Na-K-CI transporter in the thick ascending limb of the loop of Henle, whereas
thiazide diuretics inhibit the Na-CI° cotransporter at the early distal tubule. However, the majority of Na* reabsorion occurs in the proximal tubule. |
Water homeostasis
- Osmoreceptors in the hypothalamus are stimulated by plasma hypertonicity (
>295 mOsm/kg); activation of these stimulators produces thirst. - Hypertonic plasma also stimulates the secretion of antidiuretic hormone (ADH) from the posterior pituitary gland. When ADH binds to V2 receptors in the renal collecting ducts, water channels are synthesized and more water is reabsorbed.
- ADH is suppressed as plasma tonicity decreases.
- Ultimately, the amount of water intake and output (including renal, Gl, and insensible losses from the skin and the respiratory tract) must be equivalent over time to preserve a steady state.
Effect of water on Na
• Hyponatremia and hyper-natremia are caused by too much or too little water.
Excessive water intake alone rarely leads to hyponatremia because the kidneys have a great capacity to excrete water.
Effect of Na on water
• Hypovolemia and hyper-volemia are caused by too little or too much sodium.
Hyponatremia
Excess water
Na < 135 mmol/L
Symptoms when Na<120 mEq/L
An important exception is increased (ICP) (e.g., after head injury). As ECF osmolality decreases, water shifts into brain cells, further increasing ICP/Therefore. is critical to keep serum sodium normal or slightly high in such patients.)
Isotonic hyponatremia pseudo hyponatremia
Increase in plasma, solids, protein, and lipids artificially, lowers the plasma, sodium concentration but sodium level is normal
Caused by any conditions that increase protein or lipid levels
Hypertonic hyponatremia
Caused by the presence of osmotic substances that cause an osmotic shift of water out of cells these substances connect across the cell membrane and so create osmotic gradient
Substances :
glucose ( for every100 mg/dl inc in glu above normal The serum Na level dec 3 meq/L) , glycerol ,
Mannitol , Maltos ,
sorbitol,radio-contrast agent
Diagnosis of hyponatremia
I. Plasma osmolality-low in a patient with true hyponatremia
2. Urine osmolality
. Lowif the kidneys are responding appropriately by diluting the urine- for example, primary polydipsia
. Elevatedif there are increased levels of ADH- for example, SIADH, CHE, and hypothyroidism
3. Urine sodium concentration
a. Urine Na* should be low in the setting of hyponatremia
b. Urine Na* concentration 20 to 40 mmol/L is consistent wits SIADH salt-wasting nephropathy or hypoaldosteronism. Diuretics may produce this
c. Urine Na* concentration <25 mmol/L is consistent with hypovolemia
Rx of Isotonic and hypertonic hyponatremias
-diagnose and treat the underlying disorder
Treatment Of Hypotonic hyponatremia.
Mild (Na* 120 to 130 mmol/L)-
withhold free water, and allow the patient to reequilibrate spontaneously. In SIADH, salt tablets can also be used.
b. Moderate (Na* 110 to 120 mmol/L) - loop diuretics (given with saline to preven renal concentration of urine due to high ADH).
c. Severe (Na* <110 mmol/L) or if symptomatic:
give hypertonic saline to increse serum sodium by 1 to 2 mEq/L/hr until symptoms improve.
• Hypertonic saline rapidly increases the tonicity of ECF
- Do not increase sodium more than 8 mol/L during the first 24 hours. An overly rapid increase in serum sodium concentration may produce central
pontine demyelination
• however in symptomatic patients aim for correcting 4 - 6 mEq/L in first 6 hours. Make sure to check sodium levels frequently.
Hypernatremia
> 145 mmol/L
Inc Na in relation to water
Causes of hypovolemic hypernatremia
(sodium stores are depleted, but relatively more water has been lost)
• Renal lossfrom diuretics, osmotic diuresis (most commonly due to glycosuria in diabetics), renal failure
• Extrarenal loss–from diarrhea, diaphoresis, respiratory losses
Causes of Hypervolemic hypernatremia
• latrogenic-most common cause of hypervolemic hypernatremia (e.g., large amounts of parenteral NaHCO; TPN)
• Exogenous glucocorticoids
• Cushing syndrome
total parenteral nutrition
• Saltwater drowning
• Primary hyperaldosteronism
Causes of Isovolemic hypernatremia (sodium stores normal, water lost)
• Diabetes insipidus: central (usually due to CNS pathologies) or peripheral (causes include lithium toxicity, hypercalcemia, hypokalemia, renal disease, drugs)
• Insensible respiratory (tachypnea)
Rx of Hypovolemic hypernatremia
Give isotonic NaCl to achieve euvolemia and restore hemodynamics initially. Correction of hypernatremia can wait until the patient is hemodynamically stable, then replace the free water deficit
Rx of Hypervolemic hypernatremia
-Give diuretics (such as furosemide, to correct volume status) and D5W (to achieve normal sodium concentration) to remove excoss sodium
Dialyze patients with renal failure.
Rx of Isovolemic hypernatremia
Patients with diabetes insipidus require vasopressin (nephrogenic DI, unless hereditary, is rarely complete), low sodium diet, and thiazide diuretics. Prescribe oral fluids, or if the patient cannot drink, give D5W
Calculation of Maintenance Fluids
• 100/50/20 rule:
• 100 mL/kg for first 10 kg,
50 mL/kg for next 10 kg,
20 mL/kg for every 1 kg over 20
• Divide total by 24 for hourly rate
• For example, for a 70 kg man: 100 × 10 = 1,000; 50 × 10 = 500, 20 × 50 kg = 1,000. Total = 2,500. Divide by 24 hours: 104 mL/hr
Na correction
To decide whether correct it for 24 or 48 h we depends on degree of hypernatremia
It should Dec 12 meq/ day
