How does the makeup of CSF compare with plasma?
- Despite their common origin, CSF and plasma have a number of important differences:
- Na+, Cl– and Mg2+concentrations are higher
- K+ and Ca2+ concentrations are lower than plasma
- Protein is <1% of plasma resulting in reduced buffering capability and a lower pH
CSF
Plasma
Sodium
(mmol/L)
(mmol/L)
140
140
Calcium
(mmol/L)
(mmol/L)
1.2
(∼50% that of plasma)
(∼50% that of plasma)
2.2-2.6
Potassium
(mmol/L)
(mmol/L)
3.0
4.0-5.0
Chloride
(mmol/L)
(mmol/L)
120
96-106
Bicarbonate
(mmol/L)
(mmol/L)
24
Equal
Equal
24
Glucose
(mmol/L)
(mmol/L)
4
(∼60% that of plasma)
(∼60% that of plasma)
6
pCO2 (kPa)
6.6
5.2
pH
7.32
(0.08 lower than plasm)
(0.08 lower than plasm)
7.40
Protein
(g/L)
(g/L)
0.2-0.4
(<1% that of plasma)
(<1% that of plasma)
70
Specific Gravity
1.004-1.007
1.010
WCC
(per mm3)
(per mm3)
0-5
(usually lymphocytes and monocytes)
(usually lymphocytes and monocytes)
4,000-11,000