Departure of Substances From the Spinal Theca

Studies With a Radioactive Spinal Anaesthetic

“…Since the appearance of the drug in the blood stream is almost immediate (Howarth and Cooper, 1949) it seemed that a direct venous drainage was the most likely route of departure for a substance administered intrathecally. Further studies have in a large measure confirmed this belief (Howarth and Cooper, 1949). It has G. 9.-Monkey d 7.5 kg.…”

“…Some part of the drug containing benzene nuclei persists for considerable periods in the blood, and blood DBP can pass the choroid plexus. Of all the channels draining the spinal subarachnoid space, the venous route appears to be the most important (Howarth and Cooper, 1949). This is not clear in contemporary teaching.…”

“…In the decrement curves there is no striking difference between those of DBP, sodium, phosphorus, and bromine, and there is no reason to believe that any of the latter three substances is retained within the theca (Howarth and Cooper, 1949). Even in the roots the total amount of DBP retained must be small.…”

“…The substances were found in the blood stream as soon as the injection was completed (Howarth and Cooper, 1949).…”

“…It has never been suggested that sodium, phosphorus, or bromine suffer such fixation; none the less, compounds of these elements do not appear within the cephalic reaches of the spinal subarachnoid space in any significant amount after intrathecal injection. Further, the rapid appearance of these substances in the venous system clearly points to a more likely mechanism (Howarth and Cooper, 1949).…”