Fluids, Electrolytes, Acid-Base Disorders, and Nutrition Support
Solutions
Sodium
(mEq/L)
Potassium
(mEq/L)
Chloride
(mEq/L)
Bicarbonate
(mEq/L)
Calcium
(mEq/L)
Magnesium
(mEq/L)
Osmolarity
(mOsm/L)
0.9% sodium chloride
(normal saline)
β
β
β
β
3% sodium chloride
(hypertonic saline)
β
β
β
β
Dehydration: Signs and symptoms include decreased urine output (unless patient has glycosuria or
diuretic therapy), increased blood urea nitrogen/serum creatinine ratio (BUN/SCr greater than 20),
insufficient net fluid balance (from intake and output documentation records), increased serum sodium,
poor skin turgor, dry mucous membranes, orthostatic hypotension, βcontraction alkalosis,β increased
losses
Fever
Skin losses through sweating
GI fluid losses (e.g., emesis, gastric suction, diarrhea, enterocutaneous fistula, surgical wounds,
drains)
weight gain, positive fluid balance
Excessive fluid and/or sodium intake
Impaired ability to excrete excess water and sodium (e.g., heart failure, cirrhosis with ascites, renal
failure)
Hyponatremia (see also the Neurocritical Care chapter for further reading on hyponatremia)
Classic evaluation
Exclude hyperglycemia, mannitol, and glycine for unmeasured effective osmoles (hypertonic
hyponatremia).
| (a) | Correct serum sodium for hyperglycemia (once the hyperglycemia is controlled, the |
|---|
serum sodium will rise).
| (1) | For every 100-mg/dL increase in BG greater than 100 mg/dL, serum sodium will fall |
|---|
by about 2.4 mEq/L (or vice-versa).
| (2) | Corrected serum Na = Measured serum Na + [(BG -100)/100 * 2.4] (Am J Med |
|---|
1999;106:399-403).
ii.
Exclude factitious/pseudo-hyponatremia (isotonic hyponatremia): Arguably still possible
during lipemia (triglycerides greater than 1000 mg/dL or hyperproteinemia (e.g., multiple
myeloma) if the serum is diluted under the assumption that the serum contains 7% solid-phase
iii.
Evaluate ECF volume (increased, normal, decreased): Evaluate patient for edema, fluid
balance on fluid intake/output records, hemodynamic markers, chest radiography: Pulmonary
infiltrates without pneumonia, enlarged heart or evidence of diseases with decreased urinary
water/sodium excretion (e.g., AKI, congestive heart failure, cirrhosis with ascites).
iv.
European guidelines suggest evaluating urine sodium and osmolality before ECF volume
2014;40(3):320-331).
Evaluate urine sodium and osmolality for hypotonic (serum osmolality less than 280 mOsm/
kg) hyponatremia in conjunction with volume status (hypovolemic, euvolemic, hypervolemic):