Differential effects of ketamine and MK-801 on A-fiber and C-fiber responses of spinal wide dynamic range neurons in the cat

Efficacy and Safety of Adding Ketamine to Lidocaine in Intravenous Regional Anesthesia: A Meta-analysis of Randomized Controlled Trials

PURPOSE

To systematically evaluate the efficacy and safety of adding ketamine (K) to lidocaine (L) for intravenous regional anesthesia (IVRA).

DESIGN

A systematic review and meta-analysis.

METHODS

A comprehensive search of the Cochrane library, Embase, PubMed, Web of Science, and ProQuest databases, and the Google Scholar search engine was conducted from inception to March 2023. All retrieved articles were imported into Endnote X20 software and independently screened by two researchers according to predetermined inclusion and exclusion criteria. The data were analyzed using Revman 5.4 software and the assessed outcomes included the time of sensory and motor block onset, time of sensory and motor block recovery, fentanyl consumption, time of tourniquet pain onset, intraoperative and postoperative visual analog scale scores, and complications.

FINDINGS

A total of 532 patients from 11 randomized controlled trials were included in the meta-analysis. The results showed that the time of sensory (P < .00001) and motor block onset (P < .00001) were shorter in the L + K group than in the L-only group. The time of sensory (P = .01) and motor block recovery (P = .006) and time of tourniquet pain onset (P < .00001) were longer in the L + K group than in the L-only group. There was a significant reduction in fentanyl consumption (P = .0002) in the L + K group compared to the L-only group. Moreover, the visual analog scale scores in the L + K group were significantly lower than the L-only group 10 minutes (P = .04), 20 minutes (P = .0004), 30 minutes (P < .00001), and 40 minutes (P < .0001) after tourniquet inflation, and 5 minutes (P < .00001), 15 minutes (P = .04), 30 minutes (P = .008), 1 hour (P = .002), 2 hours (P < .00001), and 4 hours (P < .00001) after tourniquet deflation. There was no evidence that the use of K as an adjuvant in IVRA increased adverse effects.

CONCLUSIONS

The addition of K to L in IVRA shortened the onset time, prolonged the block time, and reduced intraoperative and postoperative pain without increasing complications.

Electrophysiological studies on the role of the NMDA receptor in nociception in the developing rat spinal cord

The present study investigated the effects of spinally applied N-methyl-D-aspartate (NMDA) antagonists 2-amino-5-phosphonovaleric acid (AP5) and ketamine on convergent neurones in the deep dorsal horn of rats, in vivo at different postnatal ages (P) 14, 21, 28, and 56 days. AP5 inhibited the primary afferent fibre input, the C fibre, post-discharge and windup evoked responses in a dose-dependent manner at each age, and was significantly more effective in the pups than adult rats (P<0.03 at 100-microg dose). AP5 100 microg abolished windup almost completely in the pups, whilst the adults required 10-fold higher doses. In contrast there was no difference in ketamine potency between age groups. Windup in the ketamine groups was reduced in a dose-dependent manner equally across all the age groups. The differential inhibitory effects of AP5 and ketamine may be due to postnatal changes in density, localisation and receptor subunit composition, altering receptor affinity and kinetics.