HYPEROSMOLARITY DOES NOT CONTRIBUTE TO TRANSIENT RADICULAR IRRITATIONAFTER SPINAL-ANESTHESIA WITH HYPERBARIC 5-PERCENT LIDOCAINE

Background and Objectives. In addition to major neurologic injury, loc al anesthesia toxicity may also include less severe but more common ne urologic side effects. The authors recently observed symptoms suggesti ve of transient radicular irritation in one third of patients after sp inal anesthesia with hyperbaric 5% lidocaine, whereas evidence of neur ologic symptoms was lacking with hyperbaric 0.5% bupivacaine. The purp ose of this prospective double-blinded study was to evaluate if the hi gh osmolarity of hyperbaric 5% lidocaine solution might contribute to the development of transient radicular irritation. Methods. Forty-four patients undergoing brief gynecologic procedures under spinal anesthe sia were randomly allocated to receive 1.5 mL of one of three study dr ugs. 5% lidocaine in 7.5% dextrose (drug A), 0.5% bupivacaine in 8.25% dextrose (drug B), or 5% lidocaine in 2.7% dextrose (drug C). Drug C was prepared by the pharmacy (University Hospital, Basel, Switzerland) with an osmolarity similar to that of drug B. Drugs A and B were comm ercially available. Patients were evaluated on postoperative day 1 for symptoms of transient radicular irritation by an anesthesiologist who was unaware of the drug given or details of the anesthetic technique. Results. Symptoms suggestive of transient radicular irritation were o bserved with a similar high incidence in patients receiving both lidoc aine preparations, but in no patient receiving hyperbaric 0.5% bupivac aine (P < .01). Conclusions. The results suggest that transient radicu lar irritation did not result from the marked hyperosmolarity of the h yperbaric 5% lidocaine. However, because lidocaine and bupivacaine wer e not administered at equipotent dosages, the relative potential for b oth drugs to induce transient radicular irritation remains tb be deter mined.