The effect of dehydration on the elimination of aqueous contrast media from the subarachnoid space.

The frequency of side effects and complications from aqueous myelography is increased by dehydration. To study the effect of dehydration on the elimination of water-soluble contrast medium from the lumbar subarachnoid space, we measured iodine concentrations in the cerebrospinal fluid, serum, and urine for 24 hours after myelography in "hydrated" and "dehydrated" monkeys. Dehydrated animals were fasted for 12 hours prior to and 24 hours after myelography; hydrated animals received oral fluids ad libitum and 300 ml of intravenous fluids. Dehydrated animals had a lower concentration of contrast medium in the blood than hydrated animals. Dehydration slows the elimination of aqueous contrast medium from the lumbar subarachnoid space.