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A Journal on Anesthesiology, Resuscitation, Analgesia and Intensive Care

Official Journal of the Italian Society of Anesthesiology, Analgesia, Resuscitation and Intensive Care
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Minerva Anestesiologica 2001 July-August;67(7-8):573-7

language: English

The minimum effective dose of 0.5% hyperbaric spinal bupivacaine for cesarean section

Danelli G., Zangrillo A., Nucera D., Giorgi E., Fanelli G., Senatore R., Casati A.

From the Department of Anesthesiology IRCCS H San Raffaele University of Vita-Salute, Milan


Back­ground. The aim of ­this pros­pec­tive, ­blind ­study was to deter­mine the min­i­mum effec­tive ­dose of hyper­bar­ic bupiv­a­caine ­required for cesar­e­an sec­tion.
Meth­ods. ­With Eth­i­cal Com­mit­tee approv­al and writ­ten con­sent, 24 ­healthy wom­en under­go­ing elec­tive cesar­e­an sec­tion ­received a com­bined spi­nal epi­du­ral anes­the­sia. We ­sought to deter­mine the min­i­mum effec­tive ­dose of spi­nal bupiv­a­caine ­using a stair­case meth­od. In ­each ­patient an arbi­trary ­dose of 0.5% hyper­bar­ic bupiv­a­caine in rela­tion to ­patient ­height was ­used. The ­initial ­dose was 0.075 mg/cm ­height, ­while the out­come of ­each ­patient’s ­response deter­mined the ­dose for the sub­se­quent ­patient. ­When suc­cess­ful spi­nal ­block (sen­so­ry lev­el ≥T4 ­with com­plete ­motor block­ade) was ­achieved with­in 20 min ­from spi­nal injec­tion, the ­dose of spi­nal bupiv­a­caine for the ­next ­patient was ­decreased by 0.01 mg/cm ­height. Con­verse­ly, ­when suc­cess­ful spi­nal ­block was not ­observed, the ­dose of spi­nal bupiv­a­caine for the ­next ­patient was ­increased by 0.01 mg/cm ­height. Sen­so­ry and ­motor ­blocks ­were eval­u­at­ed eve­ry 5 min by an inde­pen­dent, blind­ed observ­er. If suc­cess­ful spi­nal ­block was not ­achieved with­in the ­designed peri­od, a 5-8 ml epi­du­ral ­bolus of 2% lid­o­caine was giv­en to ­achieve ade­quate sur­gi­cal anes­the­sia.
­Results. No com­pli­ca­tions ­were report­ed dur­ing the ­study, and all wom­en deliv­ered ­their ­baby unevent­ful­ly (­APGAR ­scores 5 min ­after deliv­ery ­ranged ­from 9 to 10) with­in 5 min ­from uter­us inci­sion. The dura­tion of sur­gi­cal pro­ce­dure ­ranged ­from 30 to 48 min­utes. The ­dose of hyper­bar­ic bupiv­a­caine pro­vid­ing ade­quate sur­gi­cal anes­the­sia with­in 20 min ­from spi­nal injec­tion in 50% of sub­jects was 0.036 mg/cm ­height (95% con­fi­dence inter­vals: 0.031-0.041 mg/cm ­height). The ED95 cal­cu­lat­ed ­from the pro­bit trans­for­ma­tion to pro­vide effec­tive spi­nal anes­the­sia for cesar­e­an sec­tion was 0.06 mg/cm ­height.
Con­clu­sions. ­This pros­pec­tive, ­blind ­study dem­on­strat­ed ­that a ­dose as low as 0.06 mg/cm ­height rep­re­sents the ­dose of intra­the­cal bupiv­a­caine pro­vid­ing effec­tive spi­nal ­block in 95% of wom­en under­go­ing elec­tive cesar­e­an sec­tion.

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