Abstract ID: A19
Abstract Title: Spinal 2-Chloroprocaine: The effect of added clonidine
Poster Type: Poster
ABSTRACT BODY
Introduction: 2-chloroprocaine (2-CP) in a preservative free form was used for spinal anesthesia (1) until reports of neurotoxicity were presented in the 1980’s. These were described after inadvertent intrathecal injections of 2-CP containing the antioxidant bisulfite during epidural anesthesia (2). Preservative free 2-CP is again commercially available and has gained interest as an alternative short acting spinal anesthetic. Forty milligrams of 2-CP has been established as an effective dose for attaining spinal anesthesia in surgical patients and the addition of fentanyl increased both the height and duration of the block (3). Clonidine in the reduced dose of 15 micrograms has been shown to increase the block height and duration of analgesia when added to intrathecal bupivicaine, but did not prolong the motor block (4). The aim of this study was to evaluate if a shorter duration of adequate anesthesia can be achieved with reducing the 2-CP dose to 30mg, and if adding the adjunct clonidine improves the quality of the block.
Materials and Methods: Eight healthy volunteers received two spinal anesthetics containing either 2-CP with clonidine 15 mcg or 2-CP with saline in a double-blinded randomized crossover manner. All spinals were performed in the left lateral position. To simulate surgical conditions, transcutaneous electrical stimulation (TES), tolerance to thigh tourniquet, motor strength and pinprick anesthesia were assessed. Time to lower extremity movement, ambulation and voiding were also assessed to simulate criteria for outpatient discharge.
Results: There was no significant difference between 2-CP alone and with clonidine in regards to peak block height (T8, range T6-L2 vs T8, range T4-T11, p=.57), time to 2 segment regression (50 ± 22 min vs 50 ± 9 min, Figure 1), tolerance to thigh tourniquet (33 ± 12 min vs 46 ± 11 min, p=.057), TES to non-dependent S1 (43 ± 39 min vs 76 ± 41 min, p=.08), and TES to T12 & T10 dermatomes (p=.09 & p=.72). There was a significant difference between 2-CP alone and with clonidine when testing regression to L1 (51 ± 23 min vs 76 ± 11 min, p=.002), time for return of gastrocnemius and quadriceps strength (p=.006 & p=.04), return of lower extremity movement (65 ± 13 min vs 79 ± 19 min, p=.004), complete regression (99 ± 18 min vs 131 ± 15 min, p=.001), TES to dependent S1 (52 ± 30 min vs 93 ± 19 min, p=.006), TES to non-dependent L3 (57 ± 27 min vs 93 ± 18 min, p=.001), TES to dependent L3 (59 ± 26 min vs 88 ± 18 min, p=.005), and ambulation (99 ± 18 min vs 131 ± 15 min, p=.001). Two subjects receiving 2-CP alone experienced sparing of S1 TES tolerance, but this was not seen with added clonidine.
Discussion: 2-chloroprocaine 30mg alone produced adequate spinal anesthesia, but one subject only achieved a peak block height of L2. The addition of clonidine to 2-CP did not increase the peak block height. Tolerance time to a thigh tourniquet was prolonged with clonidine but was not significant. The addition of clonidine increases the duration of both the sensory and motor blockade, and may be beneficial when added to low dose spinal 2-CP.
References: 1)Anesthesiology 1952;13:287-96. 2)Anesth Analg 1982;61:158-9. 3)Anesth Analg 2004;98(in press). 4)Anesth Analg 2003;96:1496-1502.
ATTACHED FILES
Reg Anesth Pain Med 2004; 29(2):A19