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Effect of Temperature on Combined Spinal-Epidural Dosing on Labor Analgesia Duration
Abstract Number: F-22
Abstract Type: Original Research
Background: Previous studies have illustrated the influence of local anesthetic temperature on baricity and viscosity; and cold solution may prolong intrathecal analgesic duration. On the contrary, recent studies have shown cold epidural solution has a shortened duration of analgesia. The goal of this study is to compare the analgesic duration of intrathecal medication at different temperatures used for combined spinal-epidural (CSE) in laboring patients.
Methods: After IRB approval, informed consent was planned from 60 women presenting for vaginal delivery requesting epidural analgesia. Patients were randomized to either a room temperature (RT) group or a cold temperature (CT) group. Spinal doses consisted of one mL of bupivacaine 1.75 mg plus fentanyl 15 mcg. CSE was performed in a sitting position using LOR with saline technique at L3-4/L4-5 level with a 17 –G Tuohy needle and a 27-G Whitacre spinal needle via needle thru needle technique. Spinal dose was administered after spontaneous clear CSF return. The temperature of the spinal drug was measured by an infrared thermometer prior to injection. Subsequently, epidural catheters were not tested or dosed until patient request. The primary outcome was intrathecal analgesia duration. Patients were monitored for vital signs, VAS pain scores, sensory level, and side effects (pruritus, N/V) every 5 mins for 15 mins, then every 15 mins until patients requested more analgesia. Unpaired t-test, Chi-squares and Mann-Whitney U test were applied as appropriate with P<0.05 considered significant.
Preliminary Results: Twenty-nine of the total 60 patients (17 in RT group, 12 in CT group) were enrolled (all 60 pts to be completed by April 2014). Mean intrathecal analgesic duration was 72 min ± 26 min for RT group and 94 min ± 28 min for CT group (P< 0.039). Demographics and secondary outcomes were similar between groups (Table 1).
Conclusion: Results suggest a trend toward prolonged labor analgesia with cold intrathecal CSE solution without increasing side effect. The extended duration may be due to the change in drug baricity and viscosity, whereas temperature dependent changes in pH may be more important with epidural application. Our study supports previous findings and suggests this phenomenon persists even with small volume concentrations of intrathecal medications. However, one limitation is that the effect of temperature on the pharmacodynamics of intrathecal opioid is not known.