Temporal patterns of interstitial pyruvate and amino acids after subarachnoid haemorrhage are related to the level of consciousness--a clinical microdialysis study.

BACKGROUND

Temporal patterns of brain interstitial amino acids after subarachnoid haemorrhage (SAH) were studied in relation to energy metabolite levels and to the severity of the initial global ischaemia as reflected by the level of consciousness at admission.

METHODS

Intracerebral microdialysis was used to measure brain interstitial amino acids and the energy metabolites glucose, lactate, and pyruvate during five days in 19 patients. Patients who were conscious (n = 11) were compared to those who were unconscious on admission (n = 8).

RESULTS

Eight non-transmitter amino acids (alanine, asparagine, glutamine, isoleucine, leucine, phenylalanine, serine and tyrosine), as well as glycine and pyruvate showed a pattern of increasing concentrations starting at 60-70 h after the onset of SAH. The conscious patients showed more pronounced elevations of non-transmitter amino acids, glycine, taurine and pyruvate compared to the unconscious patient group. Pyruvate levels were initially critically low for all patients, then normalised in the conscious patients but remained low in the unconscious group.

CONCLUSIONS

There was an increase of the cerebral interstitial levels of non-transmitter amino acids and glycine which correlated temporally to pyruvate levels, more pronounced in patients conscious on admission. Pyruvate levels in these patients normalised, but remained reduced in the unconscious patients. The increase of the non-transmitter amino acids and glycine could reflect an increased amino acid turnover in an attempt at repairing the injured brain, which could have been hampered by the lower pyruvate levels. Interstitial pyruvate may be a useful marker of the energy metabolic situation in the acutely injured brain.