Table 1.

Mean concentrations of select solutes in plasma and CSF of healthy adult humans.

	Blood plasma a,b	Interstitial fluid/CSFa,b
Na+	150	147
Cl–	99	113
K+	4.63	2.86
Mg2+	1.61	2.23
Ca2+	2.25	1.25
HCO3–	26.8	23.3
Total protein (mg/dL)	6987.2	39.2
Osmolality (mosm/kg)	289	289
pH	7.397	7.3
pCO2	41.1	50.5

^aUnless otherwise specified, concentrations are shown as mEq/kg.

^bAdapted from Irani.²⁶¹