Spinal 2-chloroprocaine: the effect of added clonidine

Preservative-free 2-chloroprocaine (2-CP) is being investigated for short-acting spinal anesthesia. Clonidine improves the quality of spinal bupivacaine and ropivacaine, but in traditional doses (1-2 microg/kg) it produces systemic side effects. It has not been studied in combination with 2-CP. In this double-blind, randomized crossover study, we compared spinal 2-CP (30 mg) with and without clonidine (15 microg) in eight volunteers. Pinprick anesthesia, motor strength, tolerance to electrical stimulation and thigh tourniquet, and time to ambulation were assessed. Peak block height was similar between 2-CP (T8 [range, T6 to L2]) and 2-CP with clonidine (T8 [range, T4 to T11]) (P = 0.57). Sensory anesthesia was prolonged with clonidine at L1 (51 +/- 23 min versus 76 +/- 11 min; P = 0.002), as was complete block regression (99 +/- 18 min versus 131 +/- 15 min; P = 0.001). Lower extremity motor blockade was increased with clonidine (return to baseline Bromage score: 65 +/- 13 min versus 79 +/- 19 min, P = 0.004; return to 90% gastrocnemius strength: P = 0.003). Clonidine increased tourniquet tolerance from 33 to 45 min (P = 0.06) and increased time to ambulation, spontaneous voiding, and discharge (99 +/- 18 min versus 131 +/- 15 min for all; P = 0.001). There were no differences in hemodynamic measurements, and no subject reported transient neurologic symptoms. We conclude that small-dose clonidine increases the duration and improves the quality of 2-CP spinal anesthesia without systemic side effects.