Opioid-induced Loss of Local Anesthetic Potency in the Rat Sciatic Nerve

Duration of peripheral nerve blocks in opioid-tolerant individuals: A study protocol

BACKGROUND

Peripheral nerve blocks effectively alleviate postoperative pain. Animal studies and human research suggest that opioid tolerance may reduce the effectiveness of local analgesics. The reduced effectiveness has been observed in opioid-tolerant humans and animals undergoing spinal and infiltration anaesthesia with both lidocaine and bupivacaine. However, the impact on peripheral nerve blocks in humans has not been evaluated. This study aims to assess the onset time and duration of a radial nerve block in opioid-tolerant individuals compared to opioid-naive individuals. We hypothesise that peripheral nerve blocks may be less effective in producing sensory and motor blockades in opioid-tolerant individuals compared to their opioid-naive counterparts.

METHODS

Twenty opioid-tolerant individuals will be matched by sex and age with opioid-naïve counterparts. Participants will receive an ultrasound-guided radial nerve block. The primary outcome is the difference in the duration of sensory nerve blockade between the two groups. The secondary outcomes include the onset time of sensory blockade, onset time of motor blockade, and difference in duration of motor nerve blockade.

CONCLUSION

This study will compare the effectiveness of a peripheral nerve block between opioid-tolerant and opioid-naïve individuals. Any found differences could support a specific postoperative protocol for opioid-tolerant individuals regarding the use of peripheral nerve blocks.

INFLUENCE OF DIFFERENT TYPES OF ANESTHESIA FOR LAPAROSCOPIC HYSTERECTOMY ON THE DYNAMICS OF STRESS HORMONES

The aim of the study – to evaluate the influence of different variants of anesthesia, including low-opioid (LOA) and opioid-free anesthesia (OFA), on the dynamics of the stress response during laparoscopic hysterectomy. Materials and methods: 102 patients were randomly allocated into 3 groups: 37 women assigned to receive a standard opioid-based anesthesia (OBA group), 33 women – LOA group and 32 patients OFA group. Results: The patients of OFA group after induction and intubation of the trachea showed a significant (p<0.05) increase in cortisol level by 155.4 % and 160.9 % compared with the OBA group and LOA group. After completion of the hysterectomy, regardless of the variant of anesthesia, the level of cortisol exceeded the preoperative one (pOBA=0.116, pLOA=0.049, pOFA=0.043). Two hours after surgery with standard anesthesia (OBA group) there was a further increase in the concentration of cortisol in the blood, exceeding the initial values by 142.9 % (p=0.043). Patients in the LOA group and OFA group tended to decrease cortisolemia. The changes in adrenaline & glucose levels were somewhat similar. Conclusion: Use of OFA is accompanied by an aggravation of the stress response at the stage of hysterectomy, which is manifested by an increase in the level of adrenaline and cortisol. The most adequate perioperative protection is inherent in low-opioid anesthesia, which is accompanied by a lower release of stress hormones during hysterectomy and in the postoperative period. Opioid-based anesthesia provides adequate intraoperative protection, but is accompanied by insufficient postoperative analgesia.

Ex Vivo Whole Nerve Electrophysiology Setup, Action Potential Recording, and Data Analyses in a Rodent Model

Ex vivo rodent whole nerves provide a model for assessing the effects of interventions on nerve impulse transmission and consequent sensory and/or motor function. Nerve impulse transmission can be measured through sciatic nerve compound action potential (CAP) recordings. However, de novo development and implementation of an ex vivo whole nerve resection protocol and an electrophysiology setup that retains nerve viability, that produces low noise CAP signals, and that allows for data analysis is challenging. Additionally, some of the existing literature lacks detail and accuracy and may be out of date. This article describes detailed protocols for rodent ex vivo sciatic nerve dissection and handling; importance of an optimal physiologic solution; computer-aided designs for 3D printing of readily adaptable ex vivo rodent whole nerve electrophysiology chambers; construction of low-cost, effective suction electrodes; setup and use of nerve stimulators and amplifiers; acquisition of low noise, small voltage CAP data and digital conversion; use of software for data analyses of CAP components; and tips for troubleshooting. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Electrophysiology wiring and hardware setup Support Protocol 1: 3D printing an electrophysiology chamber Support Protocol 2: Building suction electrodes Basic Protocol 2: Sciatic nerve dissection and compound action potential recording Basic Protocol 3: Data export and analysis Support Protocol 3: Preparation of HEPES-buffered physiologic solution.

Cerebrospinal Fluid and Spinal Anesthesia Parameters in Healthy Individuals versus Opium-addict Patients during Lower Limb Surgery

Background

Studies have reported lower pain threshold, spinal anesthesia duration, and level of sensory block in addicts compared to non-addict patients undergoing spinal anesthesia for surgery. Moreover, blood gas and cerebrospinal fluid (CSF) were likely to be affected as well. The aim in the present study is to evaluate CSF and spinal parameters in addict versus non-addict patients during lower limb surgery.

Methods

In this case-control study, 22 opium addicts and 22 sex- and age- matched non-addicts undergoing lower limb surgery under spinal anesthesia were included. The CSF parameters, venous blood gas (VBG), and sensory and motor block findings were compared between the groups.

Findings

The addict and non-addict patients were similar regarding CSF and blood gas parameters except higher pH in VBG (7.39 ± 0.06 vs. 7.33 ± 0.11, P = 0.030) and CSF (7.39 ± 0.06 vs. 7.33 ± 0.11, P = 0.030) for addict patients. The addict patients had significantly later onset of sensory block (5.72 ± 1.57 vs. 3.16 ± 0.93 minutes, P < 0.001) and shorter motor block duration (137.72 ± 11.51 vs. 149.09 ± 14.44 minutes, P = 0.006), with no significant difference in the sensory block duration and motor block onset.

Conclusion

Addict patients have delayed onset of sensory block with shorter duration of motor block and lower sensory block level. Among the blood gas and CSF markers, only pH was significantly higher in addict patients, needing further evaluations; however, it seems that addiction has no significant effect on these parameters.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

A Multi-faceted Educational Approach for Pain Metric Recording Prior to Knee and Hip Arthroplasty: Effects on Documentation by an Acute Pain Service

Background

Despite the increased use of electronic medical records (EMRs) in past years, the recording of clinically useful baseline pain information may still be lacking. An educational effort targeted at the acute pain service and reinforced by electronic prompting may be an effective way to promote electronic documentation of relevant pain metrics. The objective of this study was to assess whether an educational effort with electronic prompting in the EMR promotes the documentation of baseline pain scores and preoperative opioid use by an acute pain service (APS).

Methods

A total of 98 patients were included in this study: 49 in the study group and 49 in the control group. The study group consisted of patients who underwent knee and hip arthroplasties after the institution of a multimodal analgesia educational program that also incorporated an electronic prompt to promote behavior change. Primary outcomes were the frequency of documentation of baseline pain scores and preoperative opioid use.

Results

After the implementation of the education initiative, 67% of the patients had baseline pain scores recorded in the preoperative APS documentation, compared to 20% in the control group (p = 0.0001). Preoperative opioid use was recorded in 24% of APS documentation within the control group, but this increased to 73% after the educational intervention (p = 0.0001). Documentation of resting pain scores on the day of surgery also increased from 59% to 87% (p = 0.0014).

Conclusions

The introduction of a multi-dimensional educational effort focused on baseline pain metric recording within the context of an analgesic change of practice increased assessment of both baseline pain and preoperative opioid use by APS. These results can be applied to other settings in which a focused change of practice is required and an electronic medical record already utilized.

Persistent Postsurgical Pain

The development of chronic pain is considered a major complication after surgery. Basic science research in animal models helps us understand the transition from acute to chronic pain by identifying the numerous molecular and cellular changes that occur in the peripheral and central nervous systems. It is now well recognized that inflammation and nerve injury lead to long-term synaptic plasticity that amplifies and also maintains pain signaling, a phenomenon referred to as pain sensitization. In the context of surgery in humans, pain sensitization is both responsible for an increase in postoperative pain via the expression of wound hyperalgesia and considered a critical factor for the development of persistent postsurgical pain. Using specific drugs that block the processes of pain sensitization reduces postoperative pain and prevents the development of persistent postoperative pain. This narrative review of the literature describes clinical investigations evaluating different preventative pharmacologic strategies that are routinely used by anesthesiologists in their daily clinical practices for preventing persistent postoperative pain. Nevertheless, further efforts are needed in both basic and clinical science research to identify preclinical models and novel therapeutics targets. There remains a need for more patient numbers in clinical research, for more reliable data, and for the development of the safest and the most effective strategies to limit the incidence of persistent postoperative pain.

Perioperative Management of Patients with Addiction to Opioid and Non-opioid Medications

PURPOSE OF REVIEW

With the rise of the opioid epidemic, anesthesiologists will find themselves faced with opioid-addicted patients more frequently. Addiction to opioids may also occur concurrently with abuse of other non-opioid medications. Our review article seeks to outline an armamentarium of pain management strategies in the perioperative period for these patients with addiction to opioid and non-opioid medications.

RECENT FINDINGS

Statistics from the CDC demonstrate a shocking increase in opioid prescription rates and opioid-related deaths. Furthermore, opioid-addicted patients have notoriously undertreated pain in the perioperative period. A multitude of strategies are available in the perioperative period to treat pain in these patients. Formulating treatment plans for opioid and non-opioid-addicted patients undergoing surgery should include considerations in the pre-, intra-, and post-operative period. Our review article outlines several non-opioid modalities which may be employed to treat pain in these patients; however, particularly in the opioid-addicted population, the practitioner must be aware that non-opioids alone may not suffice to treat post-surgical pain. Consultation with pain management may be warranted to optimize opioid and non-opioid treatment for these patients.