Comparison of preemptive paracetamol, paracetamol-diclofenac & paracetamol-tramadol combination on postoperative pain after elective abdominal surgery under general anesthesia, Ethiopia: a randomized control trial study, 2018

Adequacy of Anesthesia Guidance for Combined General/Epidural Anesthesia in Patients Undergoing Open Abdominal Infrarenal Aortic Aneurysm Repair; Preliminary Report on Hemodynamic Stability and Pain Perception

Background/Objectives: Hemodynamic instability and inappropriate postoperative pain perception (IPPP) with their consequences constitute an anesthesiological challenge in patients undergoing primary elective open lumbar infrarenal aortic aneurysm repair (OLIAAR) under general anesthesia (GA), as suboptimal administration of intravenous rescue opioid analgesics (IROAs), whose titration is optimized by Adequacy of Anaesthesia (AoA) guidance, constitutes a risk of adverse events. Intravenous or thoracic epidural anesthesia (TEA) techniques of preventive analgesia have been added to GA to minimize these adverse events. Methods: Seventy-five patients undergoing OLIAAR were randomly assigned to receive TEA with 0.2% ropivacaine (RPV) with fentanyl (FNT) 2.5 μg/mL (RPV group) or 0.2% bupivacaine (BPV) with FNT 2.5 μg/mL (BPV group) or intravenous metamizole/tramadol (MT group). IROA using FNT during GA was administered under AoA guidance. Systemic morphine was administered as a rescue agent in all groups postoperatively in the case of IPPP, assessed using the Numeric Pain Rating Score > 3. The maximum score at admission and the minimum at discharge from the postoperative care unit to the Department of Vascular Surgery, perioperative hemodynamic stability, and demand for rescue opioid analgesia were analyzed. Results: Ultimately, 57 patients were analyzed. In 49% of patients undergoing OLIAAR, preventive analgesia did not prevent the incidence of IPPP, which was not statistically significant between groups. No case of acute postoperative pain perception was noted in the RPV group, but at the cost of statistically significant minimum mean arterial pressure values, reflecting hemodynamic instability, with clinical significance < 65mmHg. Demand for postoperative morphine was not statistically significantly different between groups, contrary to significantly lower doses of IROA using FNT in patients receiving TEA. Conclusions: AoA guidance for IROA administration with FNT blunted the preventive analgesia effect of TEA compared with intravenous MT that ensured proper perioperative hemodynamic stability along with adequate postoperative pain control with acceptable demand for postoperative morphine.

An Updated Review on the Metabolite (AM404)-Mediated Central Mechanism of Action of Paracetamol (Acetaminophen): Experimental Evidence and Potential Clinical Impact

Paracetamol remains the recommended first-line option for mild-to-moderate acute pain in general population and particularly in vulnerable populations. Despite its wide use, debate exists regarding the analgesic mechanism of action (MoA) of paracetamol. A growing body of evidence challenged the notion that paracetamol exerts its analgesic effect through cyclooxygenase (COX)-dependent inhibitory effect. It is now more evident that paracetamol analgesia has multiple pathways and is mediated by the formation of the bioactive AM404 metabolite in the central nervous system (CNS). AM404 is a potent activator of TRPV₁, a major contributor to neuronal response to pain in the brain and dorsal horn. In the periaqueductal grey, the bioactive metabolite AM404 activated the TRPV₁ channel-mGlu5 receptor-PLC-DAGL-CB1 receptor signaling cascade. The present article provides a comprehensive literature review of the centrally located, COX-independent, analgesic MoA of paracetamol and relates how the current experimental evidence can be translated into clinical practice. The evidence discussed in this review established paracetamol as a central, COX-independent, antinociceptive medication that has a distinct MoA from non-steroidal anti-inflammatory drugs (NSAIDs) and a more tolerable safety profile. With the establishment of the central MoA of paracetamol, we believe that paracetamol remains the preferred first-line option for mild-to-moderate acute pain for healthy adults, children, and patients with health concerns. However, safety concerns remain with the high dose of paracetamol due to the NAPQI-mediated liver necrosis. Centrally acting paracetamol/p-aminophenol derivatives could potentiate the analgesic effect of paracetamol without increasing the risk of hepatoxicity. Moreover, the specific central MoA of paracetamol allows its combination with other analgesics, including NSAIDs, with a different MoA. Future experiments to better explain the central actions of paracetamol could pave the way for discovering new central analgesics with a better benefit-to-risk ratio.

Effect of Intramuscular Tramadol on the Duration of Clinically Relevant Sciatic Nerve Blockade in Patients Undergoing Calcaneal Fracture Fixation: A Randomized Controlled Trial

BACKGROUND

Calcaneal fracture fixation can generate severe postoperative pain and analgesia can be supported by a sciatic nerve block. However, following resolution of the sensory blockade, rebound pain may ensue. The aim of this study was to assess whether an incidental finding of two patients with an extension of the sciatic nerve block beyond 24 h following 100 mg of intramuscular tramadol administration could be confirmed.

METHODS

Thirty-seven patients scheduled for a calcaneal intramedullary fixation (Calcanail^®) were randomly divided into two groups. The tramadol group (n = 19) received a sciatic nerve block with 20 mL of 0.25% bupivacaine and a concomitant dose of 100 mg of intramuscular tramadol, while the control group (n = 18) received an identical sciatic nerve block with concomitant injection of normal saline (placebo). All patients had a spinal anesthesia with light sedation for the procedure. The time to first analgesic request defined as appearance of any pain (NRS > 0) was assessed as the primary endpoint with a clinically relevant expected result of at least 50% elongation in sensory blockade.

RESULTS

The median time to first analgesic request from time of blockade in the tramadol group was 670 min compared with 578 min in the control group. The result was clinically not relevant and statistically not significant (p = 0.17). No statistical difference could be demonstrated in the time to first opioid request, although a trend for opioid sparing in the tramadol group could be seen. Total morphine consumption in the first 24 h was also statistically insignificant (the tramadol group 0.066 mg kg^-1 compared with 0.125 mg kg^-1 in the control group). In conclusion, intramuscular tramadol does not extend the duration of analgesia of a sciatic nerve block following a calcaneal fracture fixation beyond 2 h and an opioid sparing effect could not be demonstrated in this trial.

Synergistic interaction and activation of the opioid receptor-NO-cGMP-K+ channel pathway on peripheral antinociception induced by the α-Bisabolol-diclofenac combination

Introduction: The local peripheral combination of analgesic drugs with herbal derivatives may have beneficial effects. Information on the action mechanism of these interactions between drugs is scarce. Therefore, the main of the present study was to determine the pharmacological interaction and action mechanism of the combination α-Bisabolol and diclofenac. Methods: Rats were injected in the dorsal surface of the right hind paw with 1% formalin. Rats received subcutaneous injections in the dorsal surface of paw of vehicles or increasing doses of α-Bisabolol, diclofenac or their combination before formalin injection into the paw. Antinociception of the α-Bisabolol + diclofenac combination was evaluated with and without the local treatment of naloxone, metformin, NG-nitro-L-arginine methyl ester (L-NAME), 1H- (1,2,4)-oxadiazolo (4,2-a) quinoxalin-1-one (ODQ), glibenclamide, glipizide, 4-aminopyridine, tetraethylammonium, apamin, or charybdotoxin. Results: α-Bisabolol, diclofenac or α-Bisabolol-diclofenac combinations produced significant antinociception in the rat (p < 0.05). The experimental effective dose (ED) value of 109.2 µg/paw was different significantly of the theoretical effective dose (ED) of 245.7 µg/paw (synergism). Blockers significantly reverted the antinociception produced by the synergistic combination of α-Bisabolol and diclofenac. Discussion: Data showed a synergism of the α-Bisabolol-diclofenac combination and the activation of the opioid receptor-Nitric Oxide-cyclic GMP-K⁺ channels pathway and a biguanide-dependent mechanism in order to produce the potentiation of its peripheral antinociception in the formalin test.

Effect of Preemptive Multimodal Analgesia Regimen on Post-operative Epidural Demand Boluses in Lower Limb Orthopaedic Surgeries

Introduction Excruciating pain is associated with lower limb orthopaedic surgeries involving femoral shaft fractures. Postoperative pain management is still ineffective in low-resource settings where the use of epidural and opioid-free analgesia is impractical. Literature is scarce with respect to the effect of a preemptive multimodal analgesia regimen on the requirement of postoperative epidural demand boluses. Hence, the present study aimed to evaluate the effect of pre-emptive multimodal analgesia in reducing the requirement of epidural demand boluses postoperatively, and to find out the time required to receive the first epidural bolus. Material and methods This double-blinded randomized control study included 48 subjects. Patients aged 18-60 years with lower limb fractures requiring surgery under combined spinal-epidural anesthesia were included. Patients were divided into two groups through random allocation. Group A: Preemptive multimodal group received intravenous paracetamol 1 g, IV diclofenac 75 mg diluted in 100ml NS, IV tramadol 50 mg diluted in 100ml NS and tab pregabalin 75 mg orally, 30 mins before surgery. Group B: Placebo group received 3 pints of 100ml NS IV and tab ranitidine 150 mg, 30 mins before surgery. Intraoperatively, combined spinal-epidural anaesthesia was administered taking all the aseptic precautions. Visual analogue scale (VAS) was recorded immediately on shifting to a postoperative room, and then at 1, 4, 8, 12, and 24 hr for both groups. Epidural boluses (10 ml of 0.125% bupivacaine with 2 μg/ml of fentanyl) were given whenever the patient's visual analogue scale was more than 4. The time at which the first epidural bolus was required by the patient was recorded. The total number of epidural boluses given over 24 hours based on VAS was recorded for both, the preemptive and placebo groups. If the patient still complained of pain, IV diclofenac 75 mg was given if the VAS was more than 4, while IV diclofenac 75 mg along with IV tramadol 50 mg was given if the VAS was more than 6. Patient satisfaction with anesthesia care, in general, was assessed 24 hrs postoperatively. Results A total of 48 subjects were included in the study. During the immediate-postoperative period, and at 8, 12 and 24 hr, the median VAS was significantly low in group A as compared to group B. A significant increase in the demand for epidural bolus immediate-postoperatively was observed in group B (70.83%) compared to group A (4.17%) (p-value of <0.001). At 8 hr, 12hr, and 24hr, patients in group A found a significantly less need for epidural boluses compared to Group B. The mean total number of epidural boluses taken in group A was significantly less compared to group B (1.79 ± 0.41 VS 3.33 ± 0.48, p-Value <0.001). In group A, all patients reported no requirement for diclofenac and tramadol. In group B, 8.33% required diclofenac 75 mg, while the remaining 91.66% had no requirement for diclofenac and tramadol. The difference in patient satisfaction with anaesthesia care in general between the two study groups was found to be significant with a p-value of 0.027. Patients in Group A were very satisfied compared with those in group B. Conclusions The study found that the pre-emptive multimodal analgesia group had better postoperative pain control because they required fewer epidural boluses and no extra analgesics postoperatively. This group was more satisfied with the anaesthesia care in general.

Paracetamol versus paracetamol/tramadol in postoperative intertrochanteric fracture: A noninferiority, randomized, controlled, double-blind study

BACKGROUND

One of the most common osteoporotic fractures among the elderly is hip fracture with tramadol frequently being prescribed for these patients. To decrease the risk of falling from tramadol, this study aimed to ascertain the effectiveness of paracetamol compared to paracetamol/tramadol for pain control following hip fixation surgery.

METHOD

This was a noninferiority, double-blind, randomized, controlled trial at a tertiary care hospital. All patients were recruited between February 2020 and March 2022. Patients were randomly assigned to paracetamol alone (Group A) or paracetamol/tramadol (Group B). All patients in both groups followed the same protocol for the first two days after surgery. To ascertain differences in pain control between the two groups, different regimens were followed from postoperative days 3-5. Pain scores were assessed by a visual analog scale (VAS). All patients were asked to complete a satisfaction questionnaire on day 5.

RESULT

A total of 30 patients were randomly allocated into Group A (paracetamol alone) and 30 into Group B (paracetamol + tramadol). The mean pain score for Group A was 5.85 ± 0.52 and 5.35 ± 0.74 for Group B. Mean cumulative doses in Group A were 4.50 ± 1.33 and 4.06 ± 1.18 in Group B. Although the mean satisfaction with pain management was higher in Group B, this was not statistically significant.

CONCLUSION

VAS scores from Group A were slightly higher than Group B. Based on a 2.0-point noninferiority margin of pain, paracetamol alone was not inferior to paracetamol/tramadol in postoperative intertrochanteric fracture.

The Effects of Gabapentin on Post-Operative Pain and Anxiety, Morphine Consumption and Patient Satisfaction in Paediatric Patients Following the Ravitch Procedure-A Randomised, Double-Blind, Placebo-Controlled, Phase 4 Trial

The aim of the study was to investigate whether the use of pre- and postoperative gabapentin can decrease postoperative pain, morphine consumption, anxiety and side effects, as well as improve patient satisfaction. A total of 56 patients, 9−17 years of age, undergoing a modified Ravitch procedure, were randomised (allocation ratio 1:1) to receive multiple perioperative doses of gabapentin (preoperatively 15 mg/kg, postoperatively 7.5 mg/kg, two times per day for three days) or a placebo. All the patients received intravenous infusion of morphine, paracetamol and non-steroidal anti-inflammatory drugs. Metamizole was given as a “rescue drug”. The observation period included the day of surgery and three postoperative days. The primary outcomes were postoperative pain intensity (at rest, during deep breathing and coughing). Additional outcomes included the consumption of morphine, the total number of doses of metamizole, anxiety, postoperative side effects and patient satisfaction. Median average and maximal pain scores (on the day of surgery and on the second postoperative day) were significantly lower only in the gabapentin group at rest (p < 0.05). Compared to the placebo group, gabapentin treatment reduced the demand for morphine on the first postoperative day (median 0.016 vs. 0.019 mg/kg/h; p = 0.03) and the total number of metamizole doses (median 1 vs. 2 p = 0.04). Patient satisfaction was significantly greater in the gabapentin group (median 10 vs. 9; p = 0.018). Anxiety and postoperative side effects were similar in both groups (p > 0.05). Pre- and postoperative gabapentin administration as part of a multimodal analgesic regimen may decrease postoperative pain, opioid consumption and demand for a “rescue drug”, as well as improve patient satisfaction.

Endogenous opiates and behavior: 2020

This paper is the forty-third consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2020 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).

Paracetamol for multimodal analgesia

Pain and related disability remain a major social and therapeutic problem. Comorbidities and therapies increase drug interactions and side effects making pain management more compounded especially in the elderly who are the fastest-growing pain population. Multimodal analgesia consists of using two or more drugs and/or techniques that target different sites of pain, increasing the level of analgesia and decreasing adverse events from treatment. Paracetamol enhances multimodal analgesia in experimental and clinical pain states. Strong preclinical evidence supports that paracetamol has additive and synergistic interactions with anti-inflammatory, opioid and anti-neuropathic drugs in rodent models of nociceptive and neuropathic pain. Clinical studies in young and adult elderly patients confirm the utility of paracetamol in multimodal, non-opioid or opioid-sparing, therapies for the treatment of acute and chronic pain.