Cerebrospinal Fluid Neurotransmitter Changes During the Perioperative Period in Patients Undergoing Total Knee Replacement

Effect of classical music on light-plane anaesthesia and analgesia in dogs subjected to surgical nociceptive stimuli

The objectives of this prospective, randomized, blinded, crossover, experimental study were to detect the potential anaesthetic- and analgesic-sparing effects of classical music provided to dogs undergoing skin surgery, and to investigate the role of substance P as an intraoperative pain indicator. Twenty dogs were included, each subjected to three different treatments: Chopin music, Mozart music and no music. They were premedicated with acepromazine, butorphanol and meloxicam and anaesthetized with propofol and isoflurane. Fentanyl was used as rescue analgesia. The anaesthetic depth was monitored by using the bispectral index along with standard anaesthetic monitoring, and autonomic nervous system responses were used to monitor the adequacy of analgesia. Furthermore, measurements of substance P serum concentration were carried out. Dogs exposed to music required less isoflurane and fentanyl. Furthermore, a statistically significant effect of time on substance P concentration was observed regardless of exposure to music, and there was a significant interaction effect between different timepoints and the type of acoustic stimulus. Classical music seems to have an isoflurane and fentanyl sparing effect on dogs undergoing minor surgery. Following surgical stimulation, the serum substance P concentration increases rapidly, and thus appears to be a potentially useful pain indicator.

Gabapentin and postoperative pain and opioid consumption: A double-blind randomized controlled trial of perioperative pain management for sinus surgery

BACKGROUND

The link between post-operative narcotic prescription and opioid misuse has spurred a nationwide effort to reduce perioperative opioid use. Previous work has suggested that perioperative gabapentin may reduce post-operative pain and opioid consumption across different procedures, although the optimal regimen remains to be defined.

METHODS

Chronic rhinosinusitis (CRS) patients undergoing functional endoscopic sinus surgery (FESS) with or without septoplasty were randomized to receive a 7-day pre- and post-operative course of placebo or gabapentin, starting at 300 mg daily and titrated to 300 mg three times daily, in a double-blind fashion. Primary endpoint was pain level using a validated visual analog scale (VAS). Secondary endpoints included post-operative opioid consumption and side effects, as well as modified Lund-Kennedy endoscopy, Lund-Mackay, and SNOT-22 scores.

RESULTS

Analysis of 35 patients (20 gabapentin, 15 control) showed no significant difference in mean postoperative VAS (p = 0.18) or postoperative opioid consumption between the placebo and gabapentin groups (2.3 and 4.8 oxycodone tablets respectively, p = 0.18). 15 of 35 patients did not require any post-operative oxycodone tablets, and only two patients required more than six tablets.

CONCLUSION

Preliminary results show no significant change in pain after FESS with or without septoplasty in patients taking 7-day pre- and post-operative gabapentin versus placebo. Results also showed no significant difference in opioid consumption between the treatment and placebo groups. Post-operative pain scores and opioid requirements are both quite low following FESS. Many patients do not need opioids at all, suggesting that routine initial post-operative opioid prescriptions can be limited accordingly.

The preemptive effects of oral pregabalin on perioperative pain management in lower limb orthopedic surgery: a systematic review and meta-analysis

BACKGROUND

To systematically review the literature and provide a comprehensive understanding of the preemptive effects of oral pregabalin on perioperative pain management in lower limb orthopedic surgery.

METHOD

We searched three electronic databases for randomized controlled trials comparing the results of preoperative pregabalin and placebo in patients undergoing lower limb orthopedic surgery. Data analyses were conducted using RevMan 5.4.

RESULTS

Twenty-one randomized controlled trials met our inclusion criteria. The cumulative opioid consumption within 24 and 48 h postoperatively in the pregabalin group was significantly less than that in the placebo group. The pooled static pain intensity at all time points within the first day was significantly lower in the pregabalin group than in the placebo group. Lower dynamic pain intensity at 48 h was detected in the pregabalin group than in the placebo group. Meanwhile, pregabalin led to a lower incidence of nausea but appeared to be associated with a higher incidence of dizziness and sedation. Subgroup analyses showed that no difference was detected between subgroups stratified by dosing regimen or pregabalin dose in the results of opioid consumption, pain intensity and incidence of complications.

CONCLUSION

This meta-analysis supports the use of pregabalin preoperatively in patients undergoing lower limb orthopedic surgery. However, it was wary of the resulting increase in dizziness and sedation. There is no evidence to support the continued use of pregabalin postoperatively or using more than 150 mg of pregabalin per day.

TRIAL REGISTRATION

This study was registered on 09 November 2021 with INPLASY (registration number: INPLASY2021110031).

Meta-analyses of gabapentinoids for pain management after knee arthroplasty: A caveat emptor? A narrative review

The use of gabapentinoids for perioperative pain management after total knee arthroplasty has been the subject of nine systematic reviews and meta-analyses. A critical analysis of the clinical aspects of the methodology of these publications shows major flaws which limit the interpretation for the recommended use of perioperative gabapentinoids in pain management for unilateral primary total knee arthroplasty. Consequently, readers and authors of systematic reviews and meta-analyses should critically assess the clinical aspects of the included studies.

Immunomodulatory lipid mediator profiling of cerebrospinal fluid following surgery in older adults

Arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) derived lipids play key roles in initiating and resolving inflammation. Neuro-inflammation is thought to play a causal role in perioperative neurocognitive disorders, yet the role of these lipids in the human central nervous system in such disorders is unclear. Here we used liquid chromatography–mass spectrometry to quantify AA, DHA, and EPA derived lipid levels in non-centrifuged cerebrospinal fluid (CSF), centrifuged CSF pellets, and centrifuged CSF supernatants of older adults obtained before, 24 h and 6 weeks after surgery. GAGE analysis was used to determine AA, DHA and EPA metabolite pathway changes over time. Lipid mediators derived from AA, DHA and EPA were detected in all sample types. Postoperative lipid mediator changes were not significant in non-centrifuged CSF (p > 0.05 for all three pathways). The AA metabolite pathway showed significant changes in centrifuged CSF pellets and supernatants from before to 24 h after surgery (p = 0.0000247, p = 0.0155 respectively), from before to 6 weeks after surgery (p = 0.0000497, p = 0.0155, respectively), and from 24 h to 6 weeks after surgery (p = 0.0000499, p = 0.00363, respectively). These findings indicate that AA, DHA, and EPA derived lipids are detectable in human CSF, and the AA metabolite pathway shows postoperative changes in centrifuged CSF pellets and supernatants.

Gabapentinoids: pharmacokinetics, pharmacodynamics and considerations for clinical practice

The gabapentinoids are often recommended as first-line treatments for the management of neuropathic pain. The differing pharmacodynamic and pharmacokinetic profiles can have implications for clinical practice. This article has summarised these key differences. In addition to their use in managing neuropathic pain, gabapentinoids are increasingly being used for off-label conditions despite the lack of evidence. Prescription rates for off-label conditions have overtaken that for on-label use. Similarly, the use of gabapentinoids in the perioperative period is now embedded in clinical practice despite conflicting evidence. This article summarises the risks associated with this increasing use. There is increasing evidence of the potential to cause harm in vulnerable populations such as the elderly and increasing prevalence of abuse. The risk of respiratory depression in combination with opioids is of particular concern in the context of the current opioid crisis. This article describes the practical considerations involved that might help guide appropriate prescribing practices.

The Effect of Perioperative Pregabalin on Pain after Arthroscopic Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

Pain after anterior cruciate ligament (ACL) reconstruction is usually intense in the early postoperative period, but the efficacy of a multimodal analgesia approach remains controversial. This study aimed to investigate the analgesic efficacy of pregabalin in multimodal analgesia after ACL reconstruction. Patients who underwent ACL reconstruction under spinal anesthesia and agreed to use intravenous patient-controlled analgesia (IV-PCA) were randomly administered placebo (control group, n = 47) or pregabalin 150 mg (pregabalin group, n = 46) 1 h before surgery and 12 h after initial treatment. Pain by verbal numerical rating scale (VNRS) at rest and with passive flexion of knee was assessed at postoperative 12, 24, and 36 h and 2 weeks. IV-PCA consumption, rescue analgesic use, and side effects were also evaluated. Lower scores of VNRS were obtained with passive flexion of knee in the pregabalin group than in the control group at postoperative 24 (7(4-8) vs. 8(6-9), p = 0.043) and 36 h (4(3-7) vs. 5(4-9), p = 0.042), and lower value of VNRS at rest was observed in the pregabalin group [0(0-1)] than in the control group [1(0-2)] at postoperative 2 weeks (p < 0.001). No differences were obtained for IV-PCA consumption, rescue analgesic use, and side effects except for dizziness for postoperative 12 h. Pregabalin as an adjuvant to multimodal analgesic regimen significantly reduced early postoperative pain in patients undergoing ACL reconstruction.

The cerebrospinal fluid and barriers - anatomic and physiologic considerations

The cerebrospinal fluid (CSF) space consists of the intracerebral ventricles, subarachnoid spaces of the spine and brain (e.g., cisterns and sulci), and the central spinal cord canal. The CSF protects the central nervous system (CNS) in different ways involving metabolic homeostasis, supply of nutrients, functioning as lymphatic system, and regulation of intracranial pressure. CSF is produced by the choroid plexus, brain interstitium, and meninges, and it circulates in a craniocaudal direction from ventricles to spinal subarachnoid space from where it is removed via craniocaudal lymphatic routes and the venous system. The CSF is renewed 3-5 times daily and its molecular constituents are mainly blood-derived (80%), while the remainder consists of brain-derived and intrathecally produced molecules (20%). The CSF space is separated from the vascular system by the blood-CSF barrier (BCB), whereas the blood-brain barrier (BBB), responsible for maintaining the homeostasis of the brain, is located between brain parenchyma and vascular system. Although both barriers have similar functions, they differ with regard to their morphologic and functional properties. Both barrier systems are permeable not only for small molecules, but also for macromolecules and circulating cells. The transport of molecules across the BBB and BCB is regulated by passive diffusion (e.g., albumin, immunoglobulins) and facilitated or active transport (e.g., glucose). The extracellular space volume, potassium buffering, CSF circulation, and interstitial fluid absorption are mainly regulated by aquaporin-4 channels, which are abundantly located at the blood-brain and brain-CSF interfaces. The composition of CSF shows a high dynamic range, and the levels of distinct proteins vary due to several influencing factors, such as site of production (brain or blood-derived), site of sampling (ventricular or lumbar), CSF flow rate (BCB function), diurnal fluctuations of CSF production rate, and finally, molecular size of blood-derived proteins (IgM vs. albumin) and circadian rhythm (glucose, prostaglandin D synthase). Alterations of lumbar CSF are mainly influenced by processes of the CNS located adjacent to the ventricular and spinal CSF space and less by pathologies in cortical areas remote from the ventricles.

Is perioperative pregabalin effective for reducing postoperative pain in major surgery?

INTRODUCTION

Pregabalin is a structural analog of γ-aminobutyric acid that may have a role in acute pain management. It has been used in the perioperative context, but there is controversy regarding its real clinical utility.

METHODS

To answer this question we used Epistemonikos, the largest database of systematic reviews in health, which is maintained by screening multiple information sources, including MEDLINE, EMBASE, Cochrane, among others. We extracted data from the systematic reviews, reanalyzed data of primary studies, conducted a meta-analysis and generated a summary of findings table using the GRADE approach.

RESULTS AND CONCLUSIONS

We identified 21 systematic reviews including 77 randomized trials. We concluded the use of perioperative pregabalin in major surgeries probably does not produce a clinically important decrease in acute postoperative pain. Although it could decrease nausea, postoperative vomiting and opioid requirements, it also produces an increase in sedation.

Noradrenaline, Serotonin, GABA, and Glycine in Cerebrospinal Fluid during Labor Pain: A Cross-Sectional Prospective Study

Background and Aims

The inhibitory pathways that play a role in spinal modulation include local interneurons and descending control. Clinical data regarding the role of these pathways in acute pain is lacking. Accordingly, the aim of this study was to evaluate cerebrospinal fluid (CSF) levels of noradrenaline, serotonin, gamma-aminobutyric acid (GABA), and glycine in parturients with labor pain compared to those without labor pain.

Methods

One hundred term uncomplicated pregnant women receiving spinal anesthesia for cesarean section were enrolled in this prospective cross-sectional study. CSF noradrenaline, serotonin, GABA, and glycine levels were analyzed by enzyme-linked immunosorbent assay. Labor pain score was assessed by numerical rating scale.

Results

Median CSF serotonin concentration in parturients with labor pain was significantly lower than in those without pain (p < 0.001). Median CSF glycine level in the labor pain group was significantly higher than in the control group (p < 0.001). There were no significant differences in median CSF level of noradrenaline or GABA between parturients with and without labor pain. Subsequent analysis showed labor pain scores to be negatively correlated with CSF serotonin (r = −0.217, p = 0.04) but positively correlated with CSF glycine (r = 0.415, p < 0.001).

Conclusion

CSF serotonin and glycine were significantly correlated with labor pain scores. These findings suggest that the serotonergic and glycinergic systems may play a role in spinal modulation of visceral pain.

Perioperative pain management in fast-track knee arthroplasty

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Is pregabalin effective and safe in total knee arthroplasty? A PRISMA-compliant meta-analysis of randomized-controlled trials

BACKGROUND

Pain management after total knee arthroplasty (TKA) varies and has been investigated for years. Pregabalin as an anticonvulsant agent that selectively affects the nociceptive process has been used for pain relief after operation. This meta-analysis was conducted to examine the evidence of pregabalin in TKA.

METHODS

Systematic searches of all related literatures were conducted using the following databases: MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials. Only randomized-controlled trials (RCTs) for TKA were included. The postoperative narcotic requirements, visual analog scale scores, knee flexion range, and relative risk of incidence rate of adverse effects in the pregabalin group versus placebo group were extracted throughout the study.

RESULTS

Seven placebo-controlled RCTs met the inclusion criteria. The use of pregabalin significantly decrease the postoperative total morphine consumption (P < .05) and increase the passive knee flexion range (P < .05). Compared with the control group, the incidence of some side effects (nausea, vomiting, pruritus, and constipation) was less in the pregabalin group (P < .05).

CONCLUSIONS

The administration of pregabalin is not only efficacious in the reduction of narcotic requirements and incidence of some adverse effect, but also workable for the improvement of passive knee flexion range after TKA.

A Meta-Analysis on the Use of Gabapentinoids for the Treatment of Acute Postoperative Pain Following Total Knee Arthroplasty

BACKGROUND

Total knee arthroplasty is a painful procedure, with approximately half of patients reporting severe pain during the early postoperative period. Gabapentinoids are used as an adjunct for the management of acute pain in approximately half of enhanced recovery programs. We performed a meta-analysis to assess the effectiveness and safety of gabapentinoids for the treatment of acute postoperative pain following total knee arthroplasty.

METHODS

Randomized controlled trials of patients undergoing elective primary total knee arthroplasty that compared the use of the gabapentinoid class of drugs (gabapentin [Neurontin; Pfizer]) or pregabalin [Lyrica; Pfizer]) with that of placebo were retrieved, with 12 studies meeting inclusion criteria. The primary outcome was pain intensity with activity at 48 hours following the surgical procedure. The secondary outcomes included pain intensity at other time points, opioid consumption, knee function, incidence of chronic pain, and adverse events.

RESULTS

No difference in pain score at 12, 24, 48, or 72 hours following the surgical procedure was seen between gabapentin and placebo. Although pregabalin was associated with reduced pain scores at 24 and 48 hours, this corresponded to a reduction of 0.5 point (95% confidence interval, 0 to 1.0 point) at 24 hours and 0.3 point (95% confidence interval, 0 to 0.6 point) at 48 hours on an 11-point numeric rating scale, which was assessed as not clinically important. Overall, no clinically relevant reduction in pain scores was associated with the use of gabapentinoids. Likewise, gabapentinoids were associated with a small, but not clinically important, reduction in cumulative opioid consumption at 48 hours (mean difference, -23.2 mg [95% confidence interval, -40.9 to -5.4 mg]). There was no difference in knee flexion at 48 hours (p = 0.63) or in the incidence of chronic pain at 3 months (p = 0.31) or 6 months (p = 0.54) associated with the use of gabapentinoids. Although gabapentinoids were associated with a significant reduction in the incidence of nausea (risk ratio, 0.7 [95% confidence interval, 0.6 to 0.9]; p < 0.001), pregabalin was also associated with a significant, clinically relevant increase in the risk of sedation (risk ratio, 1.4 [95% confidence interval, 1.1 to 1.9]; p = 0.02).

CONCLUSIONS

On the basis of this meta-analysis, we found no evidence to support the routine use of gabapentinoids in the management of acute pain following total knee arthroplasty.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Plasma substance P concentrations in patients undergoing general anesthesia: an objective marker associated with postoperative nausea and vomiting

Background

This study investigated plasma concentrations of substance P (SP) in patients undergoing general anesthesia (GA) and postoperative nausea and vomiting (PONV). This prospective, observational, cohort study included 23 patients who underwent scheduled surgery under general anesthesia. Blood was collected from the radial artery at predetermined time points (15-30 mins prior anesthesia, 15-30 mins after surgery/GA, and 24 h after surgery). PONV, SP concentrations, risk factors, and analgesics used were measured.

Findings

Nine of 23 patients experienced PONV. In patients without PONV, SP concentrations significantly decreased (P < 0.0001) at the end of surgery/GA, compared to baseline, and recovered at 24 h after surgery/GA (452.9 ± 146.2 vs. 666.9 ± 176.5 vs. 580.7 ± 168.6 pg/mL, respectively), whereas SP levels were unchanged during surgery/GA and increased at 24 hours after surgery (P = 0.020) in patients with PONV (726.1 ± 167.8 vs. 655.8 ± 168.0 vs. 779.7 ± 220.7 pg/mL, respectively).

Conclusions

These finding suggest that SP levels may be utilized as an objective marker for PONV.

Perioperative use of pregabalin for acute pain-a systematic review and meta-analysis

Evidence supporting postoperative pain management using pregabalin as an adjunct intervention across various surgical pain models is lacking. The objective of this systematic review was to evaluate "model-specific" comparative effectiveness and harms of pregabalin following a previously published systematic review protocol. MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were searched from inception through August 2013. Data were screened and single extraction with independent verification and dual risk of bias assessment was performed. Quality of evidence (QoE) was rated using the GRADE approach. Primary outcomes were pain relief at rest and on movement and reduction in postoperative analgesic consumption. A total of 1423 records were screened, and 43 studies were included. Perioperative pregabalin resulted in: 16% (95% confidence interval [CI], 9%-21%) reduction in analgesic consumption (moderate QoE, 24 trials) and a small reduction in the magnitude of pain in surgeries associated with pronociceptive pain. Per 1000 patients, 10 more will experience blurred vision (95% CI, 5-20 more; moderate QoE, 17 trials) and 41 more sedation (95% CI, 13-77 more, 17 trials). To prevent 1 case of perioperative nausea and vomiting, the number needed to treat is 11 (95% CI: 7-28, 25 trials). Inadequate evidence addressed outcomes of enhanced recovery and serious harms. Pregabalin analgesic effectiveness is largely restricted to surgical procedures associated with pronociceptive mechanisms. The clinical significance of observed pregabalin benefits must be weighed against the uncertainties about serious harms and enhanced recovery to inform the careful selection of surgical patients. Recommendations for future research are proposed.

A background for the management of osteoarthritic knee pain

Knee osteoarthritis (KOA) is the most common degenerative arthritis and is treated by a wide range of practitioners. Treatment planning requires knowledge of the knee joint components and the influence of systemic and environmental factors. The treatment of KOA has changed little in 50 years. We are entering a new stage where KOA is now being viewed as an organ in failure. Neurotransmission of pain is both peripheral and central. Medical treatment can influence both pathways. Current guidelines for treatment have more rigid criteria based on the literature. In the future, the use of genetic-based biomarkers, clinical patterns of response and imaging characteristics will likely create subgroups of individuals who could benefit from improved designer therapies.

Human cerebrospinal fluid increases the excitability of pyramidal neurons in the in vitro brain slice

KEY POINTS

The cerebrospinal fluid contains numerous neuromodulators at ambient levels but whether, and how, they affect the activity of central neurons is unknown. This study provides experimental evidence that human cerebrospinal fluid (hCSF) increases the excitability of hippocampal and neocortical pyramidal neurons. Hippocampal CA1 pyramidal neurons in hCSF displayed lowered firing thresholds, depolarized resting membrane potentials and reduced input resistance, mimicking properties of pyramidal neurons recorded in vivo. The excitability-increasing effect of hCSF on CA1 pyramidal neurons was entirely occluded by intracellular application of GTPγS, suggesting that neuromodulatory effects were mediated by G-protein coupled receptors. These results indicate that the CSF promotes spontaneous excitatory neuronal activity, and may help to explain observed differences in the activity of pyramidal neurons recorded in vivo and in vitro. The composition of brain extracellular fluid is shaped by a continuous exchange of substances between the cerebrospinal fluid (CSF) and interstitial fluid. The CSF is known to contain a wide range of endogenous neuromodulatory substances, but their collective influence on neuronal activity has been poorly investigated. We show here that replacing artificial CSF (aCSF), routinely used for perfusion of brain slices in vitro, with human CSF (hCSF) powerfully boosts spontaneous firing of CA1, CA3 and layer 5 pyramidal neurons in the rat brain slice. CA1 pyramidal neurons in hCSF display lowered firing thresholds, more depolarized resting membrane potentials and reduced input resistance, mimicking properties of pyramidal neurons recorded in vivo. The increased excitability of CA1 pyramidal neurons was completely occluded by intracellular application of GTPγS, suggesting that endogenous neuromodulators in hCSF act on G-protein coupled receptors to enhance excitability. We found no increase in spontaneous inhibitory synaptic transmission by hCSF, indicating a differential effect on glutamatergic and GABAergic neurons. Our findings highlight a previously unknown function of the CSF in promoting spontaneous excitatory activity, and may help to explain differences observed in the activity of pyramidal neurons recorded in vivo and in vitro.

Pain after knee arthroplasty: an unresolved issue

PURPOSE

Despite the recent advances in the understanding of pain mechanisms and the introduction of new drugs and new techniques in the postoperative management, pain after total knee arthroplasty (TKA) is still an unresolved issue. It affects the quality of life and rehabilitation of an important percentage of patients undergoing TKA. The aim of this narrative review was to give an overview on pain mechanisms and multimodal pain management.

METHODS

A review of all peer-reviewed articles on pain after knee arthroplasty was performed by two reviewers. Recent articles on incisional pain mechanisms were included because of their importance in the understanding of postsurgical pain. Search was performed in Pubmed, Cochrane and Google Scholar data bases.

RESULTS

Postsurgical pain mechanisms are based on both local and systemic inflammatory reactions. Peri-operative pain management starts with the anaesthetic technique and resides on a multimodal analgesia regimen. New concepts, drugs and techniques have shown their efficacy in reducing the severity of acute postoperative pain and the risk of developing chronic pain after TKA.

CONCLUSION

This narrative review offers a clear overview of pain mechanism after knee arthroplasty and an understanding on how multimodal pain management can reduce the intensity and duration of pain after knee arthroplasty.