Hypernatremia
Physiology of Serum Sodium
Composition of Serum
Serum Water : accounts for 93% of the serum volume
Serum sodium is restricted to the serum water fraction
Nonaqueous Components : accounts for 7% of the serum volume
Nonaqueous components are mainly lipids and proteins
Etiology of Hypernatremia
Water Loss Alone
Renal Water Loss
Central Diabetes Insipidus (DI) (see Diabetes Insipidus , [[Diabetes Insipidus]])
Hypothalamic Infiltration
Pituitary-Hypothalamic Surgery
Head Trauma (see Head Trauma , [[Head Trauma]])
Phenytoin (Dilantin) (see Phenytoin , [[Phenytoin]])
Encephalitis (see Encephalitis , [[Encephalitis]])
Nephrogenic Diabetes Insipidus (DI) (see Diabetes Insipidus , [[Diabetes Insipidus]])
Extra-Renal Water Loss
Fever (see Fever , [[Fever]]): insensible water loss from skin
Burns (see Burns , [[Burns]]): insensible water loss from skin
Hyperventilation : insensible water loss from lungs
Water + Sodium Loss
Renal Water + Sodium Loss
Chronic Kidney Disease (CKD) (see Chronic Kidney Disease , [[Chronic Kidney Disease]]): osmotic diuresis
Hyperglycemia (see Hyperglycemia , [[Hyperglycemia]]): osmotic diuresis
Mannitol (see Mannitol , [[Mannitol]]): osmotic diuresis
Extra-Renal Water + Sodium Loss
Sweating/Diaphoresis (see Diaphoresis , [[Diaphoresis]])
Sodium Gain
Excessive Sodium Administration
Adrenal Hyperfunction
Diagnosis of Hypernatremia
Laboratory Serum Sodium Measurement Technology
Flame Photometry Assay of Serum Sodium : measures sodium concentration in whole plasma
In the presence of hyperproteinemia or hyperlipidemia (with expansion of nonaqueous component of the serum), pseudohyponatremia may be seen with this assay method
Sodium-Selective Electrode Assay of Sodium : measures sodium activity in serum water -> this assay gives the true, physiologically relevant sodium concentration as it measures sodium activity in serum water alone
Indirect Potentiometry: current assay used in many hospital laboratories
Direct Potentiometry
Clinical Manifestations
Neurologic Manifestations
Ataxia (see Ataxia , [[Ataxia]])
Encephalopathy/Altered Mental Status
Irritability
Reversible Splenial Lesion Syndrome (RESLES) (see Reversible Splenial Lesion Syndrome , [[Reversible Splenial Lesion Syndrome]])
Seizures (see Seizures , [[Seizures]])
Spasticity
Thirst
Tremor (see Tremor , [[Tremor]])
Other Manifestations
Treatment
General Treatment Considerations
Calculate Free Water Deficit = (0.6) x (Wt in kg) x ((Serum Na/140)-1)
Note: total body water = 0.6 x BW in kg
Correct serum Na at <1 mEq/L per hr
Replace 50% of free water deficit over first 24 hrs, then rest over next 48 hrs
Treatment by Type
Hypovolemic : NS until euvolemic, then D5W
Hypervolemic : Lasix (or HD) + D5W
Central Diabetes Insipidus
Pitressin (see xxxx , [[]]: 2.5 U IM q48hrs
Desmopressin (DDAVP) (see Desmopressin , [[Desmopressin]]): 10-20 ug qday intranasal
Nephrogenic Diabetes Insipidus
References
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