The significance of morphine concentrations in the cerebrospinal fluid in morphine caused deaths.

Morphine analysis was performed using a variety of immunoassay methods in blood, urine and the cisternal cerebrospinal fluid (CSF) from 23 patients dying opiate-related deaths. Of these, 16 were a result of intravenous morphine or heroin use. The blood and CSF morphine concentrations were determined using both fluorescence polarization immunoassay (FPIA) and radioimmunoassay (RIA), while urine was analyzed by enzyme multiplied immunoassay technique (EMIT). Urine morphine concentrations were greater than 0.300 microgram/mL in all but one case. Blood and CSF morphine concentrations were found to be poorly correlated, and it was concluded that one should not be used to predict the other. Following intravenous administration, CSF morphine concentrations of greater than 0.02 microgram/mL were however found to be consistent with death from morphine related respiratory depression. As intrathecal or epidural administration of morphine can greatly influence the CSF concentration without inducing respiratory depression, the site of collection of the CSF must be known, as must the route of administration in order to properly interpret CSF morphine concentrations.