Length of Stay and Opioid Dose Requirement with Transversus Abdominis Plane Block vs Epidural Analgesia for Ventral Hernia Repair.

BACKGROUND: Major abdominal operations often requires postoperative opioid analgesia. However, there is growing recognition of the potential for abuse. We previously reported a significant reduction in opioid consumption after implementation of an Enhanced Recovery after Surgery protocol after ventral hernia repair focusing on opioid reduction. Epidural use was routine for postoperative pain control in this protocol. Recently, we have transitioned to transversus abdominis plane (TAP) block instead of epidural analgesia. We hypothesize that this modification reduces length of stay and lowers opioid use in ventral hernia repair. METHODS: All patients undergoing open ventral hernia repair were recorded prospectively in the Americas Hernia Society Quality Collaborative database. All patients receiving either TAP or epidural between February 2015 and March 2018 were identified. Additional review was performed to quantify opioid use in morphine milligram equivalents (MMEs). Primary outcomes were length of stay and opioid use. RESULTS: Epidural was used in 172 patients and TAP block in 74. There were no significant comorbidity differences between groups. The TAP group had a slightly higher BMI (33.6 kg/m2 vs 28.3 kg/m2) and slightly smaller hernias (8.8 cm vs 10.8 cm). There was no difference in 30-day surgical site infections. Hospital length of stay was significantly shorter with TAP block (2.4 vs 4.5 days; p < 0.001). Total MME requirements for patients receiving TAP block were lower than those with epidural during postoperative days 1 and 2 (mean 40 vs 54.1 MMEs; p = 0.033 and 36.1 vs 52.5 MMEs; p = 0.018). CONCLUSIONS: Use of TAP block significantly reduces length of stay and decreases opioid dose requirements in the early postoperative period compared with epidural analgesia.

Asymmetrical stimulus generalization following differential fear conditioning.

Rodent ultrasonic vocalizations (USVs) are ethologically critical social signals. Rats emit 22kHz USVs and 50kHz USVs, respectively, in conjunction with negative and positive affective states. Little is known about what controls emotional reactivity to these social signals. Using male Sprague-Dawley rats, we examined unconditional and conditional freezing behavior in response to the following auditory stimuli: three 22kHz USVs, a discontinuous tone whose frequency and on-off pattern matched one of the USVs, a continuous tone with the same or lower frequencies, a 4kHz discontinuous tone with an on-off pattern matched to one of the USVs, and a 50kHz USV. There were no differences among these stimuli in terms of the unconditional elicitation of freezing behavior. Thus, the stimuli were equally neutral before conditioning. During differential fear conditioning, one of these stimuli (the CS(+)) always co-terminated with a footshock unconditional stimulus (US) and another stimulus (the CS(-)) was explicitly unpaired with the US. There were no significant differences among these cues in CS(+)-elicited freezing behavior. Thus, the stimuli were equally salient or effective as cues in supporting fear conditioning. When the CS(+) was a 22kHz USV or a similar stimulus, rats discriminated based on the principal frequency and/or the temporal pattern of the stimulus. However, when these same stimuli served as the CS(-), discrimination failed due to generalization from the CS(+). Thus, the stimuli differed markedly in the specificity of conditioning. This strikingly asymmetrical stimulus generalization is a novel bias in discrimination.