Fluids, Electrolytes, Acid-Base Disorders, and Nutrition Support

vi.

If the patient has a TBI, it can be difficult to ascertain whether the patient has cerebral salt

wasting syndrome (CSWS) or SIADH. The main difference between these 2 clinical scenarios

is the patient’s volume status. Those with CSWS are typically hypovolemic, whereas those

with SIADH are euvolemic.

CSWS

SIADH

Decreased serum sodium

Decreased ECF

Normal or expanded ECF

Negative sodium balance

Variable sodium balance

CVP/PCWP/EDVI decreased

CVP/PCWP/EDVI normal or increased

Urine osmolality increased

Urine sodium increased

CVP = central venous pressure; CSWS = cerebral salt wasting syndrome; ECF = extracellular fluid; EDVI = end diastolic volume index; PCWP = pulmonary capillary

wedge pressure.

Treatment of hyponatremia

Typically reserved for acute (less than 48 hours) hyponatremia and/or severe symptoms (mental

Immediate treatment with hypertonic saline therapy (3% NaCl) should be adjusted to achieve

a serum Na concentration increase of 5 mEq/L in the first hour, and limit to a total of 10 mEq/L

increase during the first 24 hours and additional 8 mEq/L during every 24 hour thereafter

correction could lead to central pontine myelinolysis. An updated guideline recommendation

from the American Society of Nephrology recommends considering the risk of central pontine

myelinolysis to further determine correction goals. Patients with heightened risk include those

with a sodium of 105 mEq/L or less, alcohol use disorder, hypokalemia, malnutrition, and

advanced liver disease. Discontinue hypertonic saline when goal serum sodium change has

been achieved or symptoms have improved (whichever occurs first).

Mechanism

Examples

Mixed or uncertain

Opiates

Barbiturates

Nonsteroidal anti-inflammatory agents

Angiotensin-converting enzyme inhibitors

SSRIs

Cyclophosphamide

MDMA

ADH = antidiuretic hormone; MDMA = methylenedioxymethamphetamine; SSRI = selective serotonin reuptake inhibitor.