Clinical significance of specific gravity of spinal anaesthetic agents. Two double-blind studies with hyperbaric 5% lidocaine.

In two double-blind studies two hyperbaric 5% lidocaine solutions containing glucose in concentrations of 75 mg/ml and 50 mg/ml, respectively, were compared. The onset and total onset time, spread, intensity, duration of analgesia and motor block were studied. The spinal anaesthesia was given with the patient either sitting or in the lateral recumbent position. A tendency to a longer duration of anaesthesia near dermatomes Th X-L II and L IV-L V was noted in the group of patients in the sitting position and receiving lidocaine with a lower glucose concentration. Otherwise there were no differences between the two lidocaine solutions. The result shows that the glucose concentration can be reduced from 75 to 50 mg/ml in "heavy" lidocaine without any clinical disadvantage. This means a more isotonic solution in relation to the cerebrospinal fluid, resulting in milder osmotic effects on interspinal structures.