NOREPINEPHRINE PROLONGS TETRACAINE SPINAL-ANESTHESIA IN SURGICAL PATIENTS - A PRELIMINARY-STUDY

We conducted a double-blinded examination of the effects of norepineph rine as a vasoconstrictor on the onset and duration of tetracaine spin al anesthesia in 80 surgical patients. The patients were randomly allo cated to four groups (n = 20 in each group). Each patient received 10 mg of tetracaine in a volume of 2.0 mL which contained either 0 mug/mL , 5 mug/mL, 10 mug/mL, or 15 mug/mL of norepinephrine. The onset of sp inal anesthesia was determined by the time to reach Th-10 level as wel l as by the time required to obtain the highest level of sensory analg esia. The time for two-segment regression and full-motor recovery were defined as the duration of spinal anesthesia. The time to reach Th-10 , the highest analgesia level, and the time to obtain the highest anal gesia level did not differ among the groups. Two-segment regression wa s prolonged significantly by 175%, 103%, and 106% as compared with the plain tetracaine group, in 5 mug/mL, 10 mug/mL, and 15 mug/mL of nore pinephrine groups, respectively. Motor recovery also was extended sign ificantly by 111%, 152%, and 121% as compared with the plain tetracain e group, in 5 mug/mL, 10 mug/mL, and 15 mug/mL of norepinephrine group s, respectively. There were no differences in the changes of arterial blood pressure and heart rate associated with the addition of norepine phrine among the groups, We conclude that norepinephrine provides a cl inically meaningful prolongation of the duration of tetracaine spinal anesthesia.