Sodium

Question 1

Hypotonic hyponatremia :true hyponatremia

Answer 1

**serum osmolality <280 mOsm/kg

A)Hypovolemic : low urine sodium (<10meq/dl)
High(>20meq/dl)
B) euvolemic
C)hypervolemic (low urine Na+)

Question 2

Causes of low urine sodium hypovolemic Hypotonic hyponatremia

Answer 2

kidneys absorb Na
External loses example diarrhea vomiting /nasal gastric suction diaphoresis /third spacing /Burns pancreatitis

Question 3

Causes of high urine sodium hypotonic hyponatremia

Answer 3

Renal causes excessive diuretic use
Decreased aldosterone
Acute tubular necrosis

Question 4

MOA for aldosterone ,ADH

Answer 4

Increases sodium resorption and then water follows

ADH: Increases water resorption Alone

Question 5

Causes of euvolemic hypotonic hyponatremia

Answer 5

RATS :Renal tubular acdosis /Addison/thyroid( hypothyroidism) /Syndrome of inappropriate ADH secretion /psychogenic polydepsia -post operative

Question 6

Causes of hypervolemic hypotonic hyponatremia

Answer 6

CHF
Nephrotic syndrome
liver diseases

Question 7

Causes of syndrome of inappropriate ADH secretion

Answer 7

CNS pathologies
malignancy small cell lung carcinoma surgery (postoperative hyponatremia )
drugs

Question 8

Drugs That’s causes syndrome of inappropriate ADH secretion (SIADH)

Answer 8

SSRIs-Oxytocin-carbamazepine-Haloperidol-Cyclophosphamide -certain antineoplastic agents

Question 9

Clinical features of hyponatremia

Answer 9

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

Question 10

Gi symptoms due to hyponatremia

Answer 10

Nausea vomiting ileus watery diarrhea

Question 11

Clinical features of hypernatremia

Answer 11

Altered mental status /restlessness /weakness /focal neurological deficit /confusion /seizure /coma
tissue and mucous membranes dryness decrease salivation

Question 12

Diagnosis of hypernatremia

Answer 12

Urine volume should be low
Urine osmolarity should be more than 800 mOsm/kg
Desmopressin Is given to differentiates nephrogenic from central diabetes insipidus

Question 13

Treatment of isovolemic

Hypernatremia if due to diabetes Insipidus

Answer 13

Vasopressin

Question 14

Na

Answer 14

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. |

Question 15

Water homeostasis

Answer 15

1. Osmoreceptors in the hypothalamus are stimulated by plasma hypertonicity (
   >295 mOsm/kg); activation of these stimulators produces thirst.
2. 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.
3. ADH is suppressed as plasma tonicity decreases.
4. 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.

Question 16

Effect of water on Na

Answer 16

• 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.

Question 17

Effect of Na on water

Answer 17

• Hypovolemia and hyper-volemia are caused by too little or too much sodium.

Question 18

Hyponatremia

Answer 18

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.)

Question 19

Isotonic hyponatremia pseudo hyponatremia

Answer 19

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

Question 20

Hypertonic hyponatremia

Answer 20

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

Question 21

Diagnosis of hyponatremia

Answer 21

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

Question 22

Rx of Isotonic and hypertonic hyponatremias

Answer 22

-diagnose and treat the underlying disorder

Question 23

Treatment Of Hypotonic hyponatremia.

Answer 23

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.

Question 24

Hypernatremia

Answer 24

> 145 mmol/L
Inc Na in relation to water

Question 25

Causes of hypovolemic hypernatremia

Answer 25

(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

Question 26

Causes of Hypervolemic hypernatremia

Answer 26

• 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

Question 27

Causes of Isovolemic hypernatremia (sodium stores normal, water lost)

Answer 27

• Diabetes insipidus: central (usually due to CNS pathologies) or peripheral (causes include lithium toxicity, hypercalcemia, hypokalemia, renal disease, drugs)
• Insensible respiratory (tachypnea)

Question 28

Rx of Hypovolemic hypernatremia

Answer 28

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

Question 29

Rx of Hypervolemic hypernatremia

Answer 29

-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.

Question 30

Rx of Isovolemic hypernatremia

Answer 30

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

Question 31

Calculation of Maintenance Fluids

Answer 31

• 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

Question 32

Na correction

Answer 32

To decide whether correct it for 24 or 48 h we depends on degree of hypernatremia
It should Dec 12 meq/ day