The hypothesis that sending blood-stained cerebrospinal fluid (CSF) through a
pneumatic tube causes in vitro haemolysis has been tested.
Spectrophotometric scanning of CSF supernatants demonstrated a significantly greater
absorbance at 415nm in those CSF samples that had been sent through the tube system
compared to those that had not (P=0·0034). It is concluded that
passage of blood-stained CSF down a pneumatic tube system causes in
vitro haemolysis, accompanied by the release of oxyhaemoglobin from the
lysed cells into the surrounding CSF. In view of this observation, it is recommended
that CSF samples requiring spectrophotometric analysis, as part of the investigation
of subarachnoid haemorrhage, should not be transported via a pneumatic tube
system.
