A crucial administration timing separates between beneficial and counterproductive effects of opioids on postoperative pain

The Effect of Lidocaine Splash Block Followed by Suspensory Ligament Massage in Female Dogs Undergoing Ovariohysterectomy: A Prospective Study

The administration of lidocaine as part of multimodal analgesia in dogs undergoing ovariohysterectomies demonstrates variable analgesic efficacy. The aim of this prospective, double-blinded clinical study was to evaluate the effectiveness of lidocaine 2% irrigation on the ovarian suspensory ligament, followed by localised massage, in achieving sufficient intraoperative analgesia. Thirty-eight female dogs were randomly divided to two groups and received either a splash block of 0.5 ml lidocaine 2% on each ovarian suspensory ligament (GL) or an equal volume of saline (GNS). All dogs were premedicated with dexmedetomidine (5 μg·kg-1) and buprenorphine (20 μg·kg-1) intramuscularly and meloxicam (0.2 mg·kg-1) subcutaneously. Anaesthesia was induced with propofol and maintained with isoflurane. The surgical procedure was initiated after an adequate depth of anaesthesia was achieved. Heart rate (HR), respiratory rate (fR) and mean arterial pressure (MAP) were continuously monitored. Fentanyl (2 μg·kg-1) was administered as rescue analgesia in case of a 30% increase in HR, fR, or MAP, compared to their values before manipulation of the ovaries. Data were analysed using a mixed model for repeated measures ANOVA and Pearson's Chi-Square test. The need for rescue analgesia differed significantly between the two groups (p < 0.0005). In GNS, 89.47% (17/19) of the dogs required rescue analgesia, compared to 10.53% (2/19) of the dogs in GL. The relative risk of rescue for the GNS compared to the GL was approximately 8.5. In conclusion, intraoperative analgesia during ovariohysterectomies in dogs can be enhanced using a lidocaine 2% splash block combined with massage of the ovarian suspensory ligament.

Opioid-Free Anesthesia and Postoperative Outcomes in Cancer Surgery: A Systematic Review

BACKGROUND

Surgery is an essential component of the treatment of solid tumors, but the perioperative course can be complicated by different factors (including anesthesia). Opioid-free anesthesia (OFA) may mitigate adverse outcomes of opioid-based anesthesia (OBA), but major questions remain on the actual impact in terms of analgesia and the improvement of surgical outcomes. To address this issue, we present a systematic review to evaluate the efficacy of OFA compared to OBA in the specific subset of cancer patients undergoing surgery.

METHODS

following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA), we searched MEDLINE, Embase and the Cochrane CENTRAL Library to include randomized controlled trials (RCTs) on adults undergoing oncological surgery, comparing OFA and OBA up to March 2022. Additional papers were added from the reference lists of identified sources. Papers were manually reviewed by two independent authors to ascertain eligibility and subsequent inclusion in qualitative analysis.

RESULTS

only two studies were eligible according to inclusion criteria. It was not possible to perform any meta-analysis. The two studies included patients undergoing prostate and gynecologic surgery on 177 patients, with significant heterogeneity in the outcomes.

CONCLUSIONS

randomized controlled trial specifically addressed to cancer patients are lacking. A knowledge gap exists, neither confirming nor rejecting the capacity of OFA to improve early postoperative outcomes in cancer surgery. Long-term consequences on specific oncological outcomes are far from being elucidated. We expect a growing body of literature in the coming years. Further studies are required with homogeneous methodology and endpoints.

Perioperative Opioid Administration

Opioids form an important component of general anesthesia and perioperative analgesia. Discharge opioid prescriptions are identified as a contributor for persistent opioid use and diversion. In parallel, there is increased enthusiasm to advocate opioid-free strategies, which include a combination of known analgesics and adjuvants, many of which are in the form of continuous infusions. This article critically reviews perioperative opioid use, especially in view of opioid-sparing versus opioid-free strategies. The data indicate that opioid-free strategies, however noble in their cause, do not fully acknowledge the limitations and gaps within the existing evidence and clinical practice considerations. Moreover, they do not allow analgesic titration based on patient needs; are unclear about optimal components and their role in different surgical settings and perioperative phases; and do not serve to decrease the risk of persistent opioid use, thereby distracting us from optimizing pain and minimizing realistic long-term harms.

Novel bifunctional hybrid compounds designed to enhance the effects of opioids and antagonize the pronociceptive effects of nonopioid peptides as potent analgesics in a rat model of neuropathic pain

ABSTRACT

The purpose of our work was to determine the role of nonopioid peptides derived from opioid prohormones in sensory hypersensitivity characteristics of neuropathic pain and to propose a pharmacological approach to restore the balance of these endogenous opioid systems. Nonopioid peptides may have a pronociceptive effect and therefore contribute to less effective opioid analgesia in neuropathic pain. In our study, we used unilateral chronic constriction injury (CCI) of the sciatic nerve as a neuropathic pain model in rats. We demonstrated the pronociceptive effects of proopiomelanocortin- and proenkephalin-derived nonopioid peptides assessed by von Frey and cold plate tests, 7 to 14 days after injury. The concentration of proenkephalin-derived pronociceptive peptides was increased more robustly than that of Met-enkephalin in the ipsilateral lumbar spinal cord of CCI-exposed rats, as shown by mass spectrometry, and the pronociceptive effect of one of these peptides was blocked by an antagonist of the melanocortin 4 (MC4) receptor. The above results confirm our hypothesis regarding the possibility of creating an analgesic drug for neuropathic pain based on enhancing opioid activity and blocking the pronociceptive effect of nonopioid peptides. We designed and synthesized bifunctional hybrids composed of opioid (OP) receptor agonist and MC4 receptor antagonist (OP-linker-MC4). Moreover, we demonstrated that they have potent and long-lasting antinociceptive effects after a single administration and a delayed development of tolerance compared with morphine after repeated intrathecal administration to rats subjected to CCI. We conclude that the bifunctional hybrids OP-linker-MC4 we propose are important prototypes of drugs for use in neuropathic pain.

Opioid free anesthesia: evidence for short and long-term outcome

The introduction of synthetic opioids in clinical practice played a major role in the history of anesthesiology. For years, anesthesiologists have been thinking that opioids are needed for intraoperative anesthesia. However, we now know that opioids (especially synthetic short-acting molecules) are definitely not ideal analgesics and may even be counterproductive, increasing postoperative pain. As well, opioids have revealed important drawbacks associated to poor perioperative outcomes. As a matter of fact, efforts in postoperative pain management in the last 30 years were driven by the idea of reducing/eliminating opioids from the postoperative period. However, a modern concept of anesthesia should eliminate opioids already intra-operatively towards a balanced, opioid-free approach (opioid-free anesthesia - OFA). In OFA drugs and techniques historically proven for their efficacy are combined in rational and defined protocols. They include ketamine, alpha-2 agonists, lidocaine, magnesium, anti-inflammatory drugs and regional anesthesia. Promising results have been obtained on perioperative outcome. For sure, analgesia is not reduced with OFA, but it is effective and with less opioid-related side effects. These benefits may be of particular importance in some high-risk patients, like OSAS, obese and chronic opioid-users/abusers. OFA may also increase patient-reported outcomes; despite it is difficult to specifically rule out the effect of intraoperative opioids. Finally, few data are available on long-term outcomes (persistent pain and opioid abuse, cancer outcome). New studies and data are required to elaborate the optimal approach for each patient/surgery, but interest and publication are increasing and may open the road to the wider adoption of OFA.