Ionized magnesium in the cerebrospinal fluid of patients with head injuries.
BACKGROUND
In head injury patients, a decrease in the serum ionized magnesium (iMg) concentration is considered to be related to the severity of the injury, however, this phenomenon is still not completely understood. The cerebrospinal fluid (CSF) iMg concentration has not been well documented under such conditions and, moreover, its normal value has not yet been established. We hereby intended to investigate the role of the iMg concentration and other parameters in both the serum and CSF of head injury patients and identify any relationship with other parameters.


METHODS
The subjects consisted of head injury patients without any other serious injuries. Ten healthy volunteers were selected as control subjects. Arterial blood and CSF specimens were simultaneously obtained and measured. We measured the Glasgow Coma Scale scores (GCS), the intracranial pressure (ICP), pH, po2, pco2, sodium, potassium, iCa, iMg, glucose, lactate, urea nitrogen. All data are expressed as the mean+/-SD and the units of iMg and iCa (corrected under pH 7.40) are given in mmol/L.


RESULTS
In the healthy subjects, the iMg concentration in the serum/CSF was 0.48 +/- 0.02 / 0.66 +/- 0.14, and iCa was 1.14 +/- 0.05 / 0.94 +/- 0.07. The GCS of the 15 head injury subjects at examination was 8.7 +/- 4.5. When the subjects were divided into 3 groups according to the GCS level (3 and 4, 5-8, and > or =9) at the time of examination, the serum iMg concentration was thus found to be related to the severity of injury based on the GCS level (p = 0.028), but not the CSF iMg concentration (p = 0.89). No relationship was observed between the iMg concentration in the serum and CSF when all specimens were compared, but an extremely close correlation was seen in the group with GCS 3 and 4 (p < 0.0001, r = 0.995), although no such correlation was seen in the other 2 groups (p = 0.12, r = -0.56 in the group with GCS 5-8, and p = 0.26, r = -0.35 in the group with GCS > or = 9). There was a significant correlation between the serum iMg and iCa (p = 0.0093, r = 0.47), and also between the CSF iMg and iCa concentrations (p < 0.0001, r = 0.67).


CONCLUSIONS
The serum iMg concentration has been suggested to possibly affect the neurologic state through CSF iMg in patients with the most severe head injury. In patients with moderate or mild head injuries, however, the ionized magnesium concentration is also probably associated with the degree of neurologic deficit based on the ionized calcium level. The CSF and serum ionized magnesium dissociation may thus result from the slow movement of ionized magnesium through the blood brain barrier.
Sakamoto
Toshihisa
T
tskmt@me.ndmc.ac.jp
Takasu
Akira
A
Saitoh
Daizoh
D
Kaneko
Naoyuki
N
Yanagawa
Yoichi
Y
Okada
Yoshiaki
Y
D000293:Adolescent; D000328:Adult; D000368:Aged; D001812:Blood-Brain Barrier / Q000502:physiology; D002118:Calcium / Q000097:blood / Q000134:cerebrospinal fluid; D015600:Glasgow Coma Scale; D016489:Head Injuries, Closed / Q000097:blood / Q000134:cerebrospinal fluid*; D006801:Humans; D008274:Magnesium / Q000097:blood / Q000134:cerebrospinal fluid*; D008875:Middle Aged
D008274:Magnesium; D002118:Calcium