[pH of the cerebro spinal fluid during subdural block (author's transl)]

This study was initiated by other authors who found that bupivacaine precipitated together with spinal fluid in vitro and who assumed that during spinal anaesthesia complications might be possible. Under the influence of several local anaesthetic agents the pH of the spinal fluid and in 160 cases the precipitation was examined. There was no precipitation. The experimental conditions were nearly in vivo conditions. The results differed clearly from those in vitro. While in vitro bupivacaine precipitated from a pH higher than 7.37 in concentrations higher than 0.8 mg/ml [2], the pH of the spinal fluid in vivo was lower than 7.35 continually and the concentration of bupivacaine not higher than 0.3 mg/ml. This means that the border of bupivacaine precipitation is by far not reached in vivo and that complications therefore are not possible.