The Influence Of Deliberate Hypotension To Spinal Cord Blood Flow And Evoked Potential

The spinal surgery has developed very fast in recent years.But sometimesthere is a massive bleeding in these operations.Deliberate hypotension isnow often used in spinal surgery to reduce the amount of bloodtransfusion.But hypotension may cause the ischemia of the spine andinduce injury of the central nervous system.This study investigated theeffect of the deliberate hypotension on spinal blood flow and evokedpotentials.Objective In order to evaluate the superiority of the controlledhypotension with nicadipine in spinal operation, the effect of nicardipineinduced hypotension on spinal cord blood flow(SCBF) and spinal cordevoked potentials(SCEPs) in dogs were investigated. Methods 6 adultmongrel dogs, weighing 12.0 kg to 16kg were used. Trachea and femoralartery were intubated after 2.5％thiopentone sodium(1ml·kg^-1, iv) andanesthesia was maintained with continuous intavenous injection of 2.5％thiopentone sodium(1.1ml·kg^-1·h^-1). Controlled hypotension was inducedby continuous iv nicardipine(8μg·kg^-1·min^-1), which was defined as60％of basal mean arterial pressure(MAP). MAP was monitored and thechanges of spinal cord evoked potentials(SCEPs) after nicardipine (8μ g·kg^-1·min^-1,iv) injection were observed by laser doppler flowmetry.Results Mean arterial blood pressure(MABP) decreased 42.9％withnicadipine, but there was little influence on SCBF. The amplitude ofmotor evked potential(MEP) did not change significantly while amplitudeof somatosensory evoked potential(SEP) fell at some extent. ConclusionNicardipine-induced hypotension only had less influence on SCEPs,which suggested that nicardipine probably could be safely used in spinaloperation.In the comparative analysis on the effect of controlled hypotension tospinal cord distraction injury, nicadipine had mild influence on SCBF andSEP. The latency and amplitude of the MEP remained unchanged.And thesusceptibility of the spine to distraction injury is not increased while inhypotension condition induced by nicadipine.