. 2018 Jul 15;596(23):5723–5756. doi: 10.1113/JP275376

Table 1.

Electrolyte concentration (mmol L⁻¹ or mEq kg⁻¹ H₂O) in CSF and plasma of embryos/newborns and adults

Species	Age	Units	Fluid	Na⁺	K⁺	Cl⁻	HCO₃ ⁻	Ca²⁺	Mg²⁺	Ref
Monkey, term 168 days	E50–60	mEq kg⁻¹ H₂O	CSF		3.6			3.8	1.85	1
			Plasma		4.1			4.9	1.5	1
	E90	mEq kg⁻¹ H₂O	CSF		3.2			3.5	2.3	1
			Plasma		4.0			5.0	1.5	1
	E130	mEq kg⁻¹ H₂O	CSF		2.9			2.9	2.2	1
			Plasma		3.8			4.9	1.5	1
	Adult	mEq kg⁻¹ H₂O	CSF		2.6			2.3	1.9	1
			Plasma		4.5			4.6	1.2	1
Rabbit, term 31 days	E23	mEq L⁻¹	CSF	142	4.1	113			1.5	2
			Plasma	143	6.5	104			3.2	2
	E27	mEq L⁻¹	CSF	140	4.0	110			1.6	2
			Plasma	147	6.0	108			3.6	2
	Adult	mEq L⁻¹	CSF	150	3.0	120			1.4	2
			Plasma	154	3.2	100			2.2	2
Rat, term 21 days	P0	mEq L⁻¹	CSF	144	3.8	109				2
			Plasma	150	6.5	102				2
	P8	mEq L⁻¹	CSF	144	3.8	107				2
			Plasma	166	7.1	98				2
	Adult	mEq L⁻¹	CSF	152	3.0	122				2
			Plasma	153	5.0	106				2
Sheep, term 150 days	E44–50	mEq L⁻¹	CSF	135	5.4	113		—	2.0	3
			Plasma	138	—	113		—	1.6	3
	E85–92	mEq L⁻¹	CSF	144	3.5	123		3.4	1.9	3
			Plasma	136	3.8	104		6.05	1.8	3
	Adult	mEq L⁻¹	CSF	148	3.1	128		2.45	1.8	3
			Plasma	138	3.4	115		3.4	1.4	3
Pig, term 115 days	5 cm CRL	mmol L⁻¹ H₂O	CSF	126		115				4
			Plasma†	125		112				4
	6.5 cm CRL	mmol L⁻¹ H₂O	CSF	120		115				4
			Plasma†	110		98				4
	12.5 cm CRL	mmol L⁻¹ H₂O	CSF	125		122				4
			Plasma†	105		96				4
Pony, term 342 days	E312	mmol L⁻¹	CSF	143	3.7	109				5
			Serum	134	5.7					5
	E342	mmol L⁻¹	CSF	143	2.9	112				5
			Serum*	—	—	—				5
	Adult	mmol L⁻¹	CSF	144	2.9	101				5
			Serum	132	4.7	94				5
Chick, hatch 20–21 days	E13	mEq L⁻¹	CSF	121	3.9	104				6
			Plasma	117	6.3	101				6
	E15	mEq L⁻¹	CSF	125	3.6	103				6
			Plasma	120	5.8	91				6
	E19	mEq L⁻¹	CSF	129	3.8	109				6
			Plasma	134	7.8	93				6
	Adult	mmol kg⁻¹ H₂O	CSF	159	4.2	142				7
			Plasma	160	4.7	115				7
Human, 38 weeks’ post–conception	P0–4 weeks	mmol L⁻¹	CSF	138	3.2	117		1.6		8
			Plasma	136	5.4	105		2.3		8
	P7–12 months	mmol L⁻¹	CSF	142	2.5	120		1.4		8
			Plasma	136	4.9	107		2.7		8
	P7–14 years	mm L⁻¹	CSF	141	2.8	122		1.3		8
			Plasma	138	4.6	107		2.7		8
	Adult	mEq kg⁻¹ H₂O	CSF	147	2.9	113	23	2.3	2.2	9
			Plasma	150	4.6	99	27	4.7	1.6	9

References: (1) Bito & Myers (1970), cisternal CSF; (2) Amtorp & Sorensen (1974), cisternal CSF; (3) Bradbury et al. (1972), cisternal CSF; (4) Flexner (1938), cisternal CSF; (5) Rossdale et al. (1982), atlanto‐occipital subarachnoid CSF; (6) Stastny & Rychter (1976), ventricular CSF; (7) Anderson & Hazelwood (1969), cisternal CSF; (8) Heine et al. (1981), lumbar CSF; (9) Davson & Segal (1996), lumbar CSF. Note differences in units. The most appropriate are mmol L⁻¹ or mEq kg⁻¹ H₂O as this allows for differences in protein concentration in CSF and plasma (see Davson, 1967, for discussion). These are markedly different early in development, as well as between CSF and plasma, see section on ‘Proteins in CSF’. ^*Not measured; ^†calculated from CSF/plasma ratios. CRL, crown rump length.