Application of established pathophysiologic processes brings greater clarity to diagnosis and treatment of hyponatremia

Table 3 Summary of volume studies by gold standard radio-isotope dilution methods in hyponatremic and normonatremic neurosurgical patients[45,46,50]

Ref.	n of patients	Low blood volume RSW	Increased blood volume SIADH	Urine Na mEq/L
Nelson et al[45] HN	12	10 (83%)	2	41-203
Wijdicks et al[46] HN	9	8 (89%)	1	--
NN	12	8 (67%)	4
Sivakumar et al[50] HN	18	17 (94%)		43-210

RSW much more common than SIAD. Printed with permission, Ref. [26]. SIADH: Syndrome of inappropriate anti-diuretic hormone; RSW: Renal salt wasting; HN: Hyponatremic; NN: Normonatremic.