hypobaric spinal anesthesia

hy·po·bar·ic spi·nal an·es·the·si·a

spinal anesthesia in which spread of local anesthetic solution in the subarachnoid space is controlled by adjusting the position of the patient when the density of the local anesthetic solution is made less than the density of cerebrospinal fluid (that is, hypobaric) by the addition of distilled water.