Novel Non-Drug Method of Increasing Spinal Analgesic Duration Without Increasing Side Effects during CSE Labor Analgesia
Abstract Number: 106
Abstract Type: Original Research
INTRODUCTION: Adding adjuvants to intrathecal bupivacaine in combined spinal epid analgesia (CSE) may provide longer spinal analgesic duration (SAD), but also increases side effects of pruritus & motor block. Injecting normal saline (NS) into the epid space after an intrathecal local anesthetic injection has resulted in inconsistent extension of block level. Most studies were limited by small samples, small epid injectate or variable time interval after spinal drug has setup. The effect of pre-existing epid volume injectate on a subsequent spinal block (SAB) has not been studied. We hypothesized SAD & SAB level are increased by injecting 15mL epid NS PRIOR to intrathecal bupivacaine. Our secondary goal is to examine the volume effect of pre-existing epid injectate on subsequent SAB characteristics.
METHODS: After IRB approval, 25 of 60 planned labor patients were randomized in a double blind fashion to receive 0 mL (Gp N) or 15 ml (Gp S) epid NS, followed by 3mg isobaric intrathecal bupivacaine. In both groups, a standard CSE kit was used (17g Tuohy, 27g Whitacre), with LOR & needle-thru-needle technique. In Gp N, no NS was given. In Gp S, 15 mL NS was injected over 10-20 seconds epidurally PRIOR to insertion of spinal needle followed by intrathecal dose. Patients were assessed every 5 mins X 20 mins & then every 20 mins until additional analgesia requested. We defined SAD, our primary outcome, as interval from spinal injection to patient requesting additional analgesia. To detect a 30% mean difference between gps in SAD, priori power analysis showed 29/gp is needed (power 0.8, α 0.05). ANOVA, Chi-Squares, Fishers exact tests & unpaired t-tests were used as appropriate. P<0.05 is significant.
RESULTS: Interim results included 25 subjects (14 Gp N, 11 Gp S). Demographics were similar between groups. SAD was significantly longer in Gp S (P<0.029). Though maximum sensory or motor block levels were similar between gps, all of Gp S & only 61% of Gp N had a sensory level ≥T8. 64% (Gp N) & 91% (Gp S) achieved comfort(VPS<=3) in <5mins after SAB, while 36% (Gp N) & 55% (Gp S) required ephedrine. 71% (Gp N) & 100% (Gp S) had epid cath inserted without issues (blood/CSF/paresthesia).
CONCLUSION: Our interim results suggest 15 mL epid NS injected PRIOR to SAB significantly increased SAD of isobaric 3mg bupivacaine without increasing side effects. The lack of difference in block height between gps may be due to the isobaricity & small dose of bupivacaine.