THE NEURONAL ENVIRONMENT AFTER SUBARACHNOID HEMORRHAGE - CORRELATION OF AMINO-ACID AND NUCLEOSIDE LEVELS WITH POSTOPERATIVE RECOVERY

The study explores biochemically the neuronal environment adjacent to a subarachnoid haemorrhage in 11 patients after neurosurgical clipping of an arterial aneurysm. Extracellular fluid (ECF) from the rectus gyrus and subarachnoid fluid (SAF) were sampled with microdialysis probes. The concentrations of amino acids and nucleosides were monitored in 60 min samples collected over 2-4 days. The patients were 33-67 years of age. Surgery was performed 0-5 days after rupture of the aneurysm in 8 patients. One patient was operated on after 15 months. Clipping of aneurysms without prior haemorrhage was performed in two cases. Markedly elevated concentrations of the excitatory amino acid glutamate was observed in the ECF of only one patient who underwent surgery within 8 hours after the haemorrhage. Moderate glutamate elevations were seen in two patients and of aspartate in another patient. Five patients displayed periods of varying length of specifically elevated taurine concentrations in ECF or SAF. Transient periods of high concentrations of glycine and serine were seen in two patients. Even though average concentrations of all amino acids were fairly similar in the ECF and SAF, the pattern of changes vs. time differed markedly in the two compartments. Presently, we conclude that the level of consciousness in the post-operative phase was inversely related to total amino acid concentration in the ECF. Furthermore, while the ECF concentrations of taurine and glycine increased both specifically and transiently in several patients, excitatory amino acid levels were not appreciably elevated subsequent to the neurosurgical intervention. No pattern of amino acid concentrations could clearly serve as an indicator of haemorrhage or disturbed blood-brain barrier (BBB) function.