sodium homeostasis mohammed almeziny bspharm r,ph. msc phd clinical pharmacist
TRANSCRIPT
SODIUM HOMEOSTASIS
Mohammed Almeziny BsPharm R,Ph. Msc PhD
Clinical Pharmacist
Introduction
Sodium is the principle cation of extracellular fluid
The regulation of osmolarity (80%). The acid-base balance. The membrane potential of cells.
Introduction Cont’d
The total is 4200 mmol (60mmol/kg). 40% bone 50% extracellular 10
intracellular.
Daily requirement
1-3 mmol/kg/day
1 liter of 0.9% provides 154 mmol N+
HYPONATREMIA
Definition
Serum sodium concentration less than 132 mmol/l
The sodium con.. Is a reflection of water balance rather than total body sodium.
Type of hyponatremia
Hypovolemic hyponatremia Euvolemic hyponatremia Hypervolemic hyponatremia Redistributive hyponatremia Pseudohyponatremia
Hypovolemic hyponatremia
A decrease in total body water (TBW) and a greater decrease in total body sodium (Na+) occur. The extracellular fluid (ECF) volume is decreased.
Euvolemic hyponatremia
An increase in TBW with normal total sodium occurs. The ECF volume is increased minimally to moderately, but edema is not present.
Hypervolemic hyponatremia
An increase in total body sodium and a greater increase in TBW occur. The ECF is increased markedly, and edema is present.
Redistributive hyponatremia
A shift of water from the intracellular to the extracellular compartment occurs with a resultant dilution of sodium. The TBW and total body sodium are unchanged. This condition occurs with hyperglycemia.
Pseudohyponatremia
A dilution of the aqueous phase by excessive proteins or lipids occurs. The TBW and total body sodium are unchanged. This condition is seen with hypertriglyceridemia and multiple myeloma.
Diagnostic approach to hyponatremia
Normal (280mOsm)
Elevated(>280mOsm)
Low (<280 mOsm)
Measure serum Osmolality
Isotonic hyponatremia
Hypertonichyponatremia
Clinically assesECF volume
Next slideHyperlipidemiaHyperproteinemiaIsotonic infision
HyperglycemiaHypertonic infusion
Low ( BP, HR)
poor skin turgor
Elevated (edema)
Normal
Hypovolemic Hypotonic
hyponatremia
hypervolemicHypotonic
hyponatremia
IsovolemicHypotonic
hyponatremia
Total body Na deficitGI, skin,lung kidney
Adrenal insufficiency
Total body Na excessCHF, Liver damage
Nephrosis
Total body Na normalH2O intoxication
SIADH, Renal FailureK loss
Reset Osmstat
Diagnostic approach to hyponatremia cont’d
Interpreting Lab. Data
Urinary Sodium help to distinguish between renal and nonrenal losses.
urine sodium < 20 mEq/L. e.g cirrhosis, nephrosis, congestive heart failure SIADH will have urine sodium levels in excess of
20 mEq/L.
Causes
Drugs. thiazide diuretics, amiodarone, chlorpropamide, cyclophosphamide, clofibrate, carbamazepine, oxcarbazepine, opiates, oxytocin, desmopressin, vincristine, selective serotonin reuptake inhibitors, trazodone or tolbutamide
Causes cont’d
Adrenal Insufficiency and Adrenal Crisis
Congestive Heart Failure and Pulmonary Edema Gastroenteritis Hypothyroidism and Myxedema Coma Renal Failure, Acute Renal Failure, Chronic and Dialysis Complications Syndrome of Inappropriate Antidiuretic Hormone Secretion(SIADH).
Clinical presentation
Depend on the degree and the chronicity of hyponatremia.
120 mEq/L 110 mEq/L Most abnormalities on physical exam
are neurological in origin.
Clinical presentation cont’d
Anorexia Nausea and vomiting Difficulty concentrating Confusion Lethargy Agitation Headache Seizures
Calculate adult Na deficit in hyponatremia
Na mEq.=
(140 mEq/L - patient's serum Na) x (0.5X body weight).
An increase in serum sodium of 4-6 mEq/L is generally sufficient
0.5 mEq/L/hr or 12 mEq/L/day or 18 mEq/L/2 day’s.
Hypernatremia
Definition
Serum sodium concentration More than 145 mmol/l
The sodium con.. Is a reflection of water balance rather than total body sodium.
Etiology and Pathophysiology
Hypernatremia in adults has a mortality of 40 to 60%.
The elderly are particularly susceptible, especially in warm weather, due to a reduced thirst response and underlying diseases.
Principal Causes of Hypernatremia
Extrarenal losses GI: Vomiting,
diarrhea Skin: Burns,
excessive sweating Renal losses
Intrinsic renal disease
Loop diuretics Osmotic diuresis
(glucose, urea, mannitol)
Hypernatremia with hypovolemia (decreased TBW and Na; relatively greater decrease in TBW)
Principal Causes of Hypernatremia cont’d
Extrarenal losses Respiratory:
Tachypnea Skin: Fever,
excessive sweating Renal losses Central diabetes
insipidus
Nephrogenic diabetes insipidus
Other Inability to access
water Primary hypodipsia Reset osmostat
Hypernatremia with euvolemia (decreased TBW; near-normal total body Na)
Principal Causes of Hypernatremia cont’d
Hypertonic fluid administration (hypertonic saline, NaHCO3, total parenteral nutrition)
Mineralocorticoid excess Adrenal tumors secreting deoxycorticosterone Congenital adrenal hyperplasia (caused by 11-
hydroxylase defect)
Hypernatremia with hypervolemia rare
Symptoms and Signs
The major signs of hypernatremia result from CNS dysfunction due to brain cell shrinkage. Confusion, neuromuscular excitability, seizures, or coma may result; cerebrovascular damage with subcortical or subarachnoid hemorrhage and venous thromboses are frequent in patients dying from severe hypernatremia.
Treatment
Free water deficit =
TBW × [(plasma Na/140) − 1]
TBW = body wt x 0.6 = liters if hypernatremia is chronic or of unknown duration,
it should be corrected over 48 h, and the plasma osmolality should be lowered at a rate of no more than 2 mOsm/L/h to avoid cerebral edema caused by excess brain solute.
Loop diuretics
Treatment cont’d
In patients with hypernatremia and depletion of total body Na content (ie, who have volume depletion), the free water deficit is greater than that estimated by the formula.
In patients with hypernatremia and ECF volume overload (excess total body Na content), the free water deficit can be replaced with 5% D/W, which can be supplemented with a loop diuretic.
Treatment cont’d
In patients with hypernatremia and euvolemia, free water can be replaced using either 5% D/W or 0.45% saline.