Remifentanil-induced pronociceptive effect and its prevention with pregabalin

Effects of opioid-sparing general anesthesia on postoperative nausea and vomiting in laparoscopic gynecological surgery

BACKGROUND

In this study, we aimed to investigate whether opioid-sparing anesthesia (OSA) reduces postoperative nausea and vomiting (PONV) in patients undergoing laparoscopic gynecological surgery.

METHODS

Adult patients undergoing elective laparoscopic gynecological surgery were randomly assigned to either the opioid-using anesthesia (OUA) or the OSA groups. In the OUA group, remifentanil was administered as an opioid during general anesthesia. In the OSA group, apart from a single dose of 5 μg/kg of alfentanil for tracheal intubation, no other opioids were used. In both groups, a multimodal intravenous non-opioid analgesic regimen was used preferentially in the post-anesthesia care unit (PACU). The primary outcome was the incidence of PONV, assessed by symptoms until the postoperative day 1.

RESULTS

A total of 120 patients were included in this study. The incidence of nausea in the PACU was significantly lower in the OSA group compared to in the OUA group (31.7% in the OSA group vs. 51.7% in the OUA group, P = 0.026). Pain scores and the incidence of opioid analgesic administration were lower in the OSA group during PACU stay, resulting in a significantly lower number of patients requiring rescue opioid analgesics (3.3% vs. 18.3%, P = 0.008). There were no significant differences in intraoperative vital signs, hemodynamic interventions, or duration of PACU and hospital stay between the two groups.

CONCLUSIONS

OSA significantly reduced postoperative nausea, pain scores, and the need for rescue analgesics in the PACU without increasing hemodynamic instability in patients undergoing laparoscopic gynecological surgery.

The analgesic efficacy of pregabalin versus placebo for septorhinoplasty: A meta-analysis

BACKGROUND

The analgesic efficacy of pregabalin supplementation for septorhinoplasty remains elusive. This meta-analysis was conducted to compare pregabalin supplementation with placebo for the postoperative pain control of septorhinoplasty.

METHODS

We systematically searched several databases including PubMed, EMbase, Web of Science, EBSCO and Cochrane library databases, and included randomized controlled trials (RCTs) regarding the effect of pregabalin supplementation versus placebo for pain control after septorhinoplasty. This meta-analysis was conducted by fixed or random-effect model based on the heterogeneity.

RESULTS

Seven RCTs were included in this meta-analysis. In comparison with control group for septorhinoplasty, pregabalin supplementation was associated with significantly decreased pain scores at 1 h (standard mean difference [SMD] = -1.45; 95% confidence interval [CI] = -2.43 to -0.47; P = .004), pain scores at 2 hours (SMD = -1.01; 95% CI = -1.83 to -0.20; P = .02), pain scores at 6 hours (SMD = -1.00; 95% CI = -1.47 to -0.54; P < .0001), number of rescue analgesics (odd ratio [OR] = 0.18; 95% CI = 0.08-0.39; P < .0001) and analgesic consumption (SMD = -2.78; 95% CI = -5.05 to -0.51; P = .02), but unraveled no obvious impact on the incidence of nausea and vomiting (OR = 0.55; 95% CI = 0.24-1.27; P = .16).

CONCLUSIONS

Pregabalin supplementation was effective to improve pain relief after septorhinoplasty.

Comparison of Single Target-Controlled Infusion Pump-Delivered Mixed Propofol and Remifentanil with Two Target-Controlled Infusion Pumps-Delivered Propofol and Remifentanil in Patients Undergoing Breast Cancer Surgery-A Prospective Study

Total intravenous anesthesia (TIVA) with remifentanil and propofol (RP) is considered to be an ideal type of general anesthesia (GA) for pediatric and adult patients undergoing medical procedures. However, delivery of an RP mixture by target-controlled infusion (TCI) for GA in surgical procedures has not been described. We investigated the merit of this approach for breast cancer surgery. Eighty-four patients (n = 42 per group) were randomly allocated to propofol and remifentanil either delivered by separate TCI pumps (S group) or in an RP mixture by a single TCI pump (M group). Dosages were adjusted based on the bispectral index (BIS) and the analgesia nociception index (ANI). The primary outcomes were adequate anesthesia (BIS 40-60 and ANI 50-70, respectively), acceptable hemodynamic fluctuations (<30% of baseline) with less frequent TCI pump adjustments, bolus injections of anesthetics, and total consumption of anesthetics during the procedure. The secondary endpoints included time of emergence from anesthesia, patient satisfaction, postoperative pain, rescue with opioids, and adverse events. The characteristics of patients, hemodynamic parameters, BIS and ANI scores, duration of surgery, anesthesia, and emergence were not significantly different between groups. The adjustment frequency of TCI was significantly higher in the S group (3 (range 0-6) vs. 2 (0-6) times; p = 0.005). The total dosage of anesthetics, pain rating, patient satisfaction, need for opioids postoperatively, and incidence of adverse events were not significantly different. We have demonstrated that this RP mixture provided adequate hypnotic and analgesic effects under BIS and ANI monitoring in patients undergoing breast cancer surgery within 1 h.

Comparison of pregabalin with magnesium sulfate in the prevention of remifentanil-induced hyperalgesia in patients undergoing rhinoplasty: A randomized clinical trial

Objective

Remifentanil is usually used for controlled hypotension during rhinoplasty under general anesthesia (G/A). One of the complications of the remifentanil is postoperative hyperalgesia. In this study, we compare the effectiveness of pregabalin with that of Mg sulfate in postoperative remifentanil-induced hyperalgesia prevention.

Methods

In this prospective, randomized, double-blinded placebo-controlled trial, 105 patients who candidates rhinoplasty with G/A were enrolled and randomly allocated into three groups. Patients in group A received 300 mg pregabalin before anesthesia. They received physiologic saline infusion during the perioperative period. Those in group B received placebo capsules before anesthesia and intravenous Mg sulfate 30 mg/kg during the perioperative period. Those in group C received a placebo capsule before anesthesia and normal intravenous saline during the operation. Then, pain severity, sedation score, postoperative nausea and vomiting (PONV) were assessed and compared.

Results

In the Mg sulfate and placebo group, the mean numerical rating scale in the postoperative period was higher compared to the pregabalin group (p < .001). The mean total amount of morphine requirement, meanwhile the 24 h post-operation, was significantly decreased in the pregabalin group compared to the other groups (p < .001). Participants in the pregabalin group had less PONV compared to those in the pregabalin and placebo groups (p = .015).

Conclusions

In patients undergoing G/A with remifentanil for rhinoplasty, preoperative 300 mg pregabalin could effectively prevent not only remifentanil-induced hyperalgesia but also PONV.

Level of evidence

1b.

Effect of remifentanil on post-operative analgesic consumption in patients undergoing shoulder arthroplasty after interscalene brachial plexus block: a randomized controlled trial

PURPOSE

Remifentanil is useful in balanced anesthesia; however, there is concern regarding opioid-induced hyperalgesia. The effect of remifentanil on rebound pain, characterized by hyperalgesia after peripheral nerve block has rarely been studied. This study evaluated whether intraoperative remifentanil infusion may increase postoperative analgesic requirement in patients receiving preoperative interscalene brachial plexus block (IBP).

METHODS

Sixty-eight patients undergoing arthroscopic shoulder surgery under general anesthesia were randomly allocated to remifentanil (R) or control (C) group. Preoperative IBP with 0.5% ropivacaine 15 mL was performed in all patients. Intraoperative remifentanil was administered only in the R group. Postoperative pain was controlled using intravenous patient-controlled analgesia (IV-PCA) and rescue analgesics. The primary outcome was the dosage of fentanyl-nefopam IV-PCA infused over 24 h postoperatively. The secondary outcomes included the numeric rating scale (NRS) score recorded at 4-h intervals over 24 h, amount of rescue analgesics and total postoperative analgesics used over 24 h, occurrence of intraoperative hypotension, postoperative nausea and vomiting (PONV) and delirium.

RESULTS

The dosage of fentanyl-nefopam IV-PCA was significantly less in C group than R group for postoperative 24 h. Fentanyl 101 [63-158] (median [interquartile range]) µg was used in the C group, while fentanyl 161 [103-285] µg was used in the R group (median difference 64 µg, 95% CI 10-121 µg, P = 0.02). Nefopam 8.1 [5.0-12.6] mg was used in the C group, while nefopam 12.9 [8.2-22.8] mg was used in the R group (median difference 5.1 mg, 95% CI 0.8-9.7 mg, P = 0.02). The total analgesic consumption: the sum of PCA consumption and administered rescue analgesic dose, converted to morphine milligram equivalents, was higher in the R group than C group (median difference 10.9 mg, 95% CI 3.0-19.0 mg, P = 0.01). The average NRS score, the incidence of PONV and delirium, were similar in both groups. The incidence of intraoperative hypotension was higher in R group than C group (47.1% vs. 20.6%, P = 0.005).

CONCLUSIONS

Remifentanil administration during arthroscopic shoulder surgery in patients undergoing preoperative IBP increased postoperative analgesic consumption.

Comparison of Intraoperative Infusion of Remifentanil Versus Fentanyl on Pain Management in Patients Undergoing Spine Surgery: A Double Blinded Randomized Clinical Trial

Background

Remifentanil is an ultra-short-acting opioid which facilitates hemodynamic management. However, there are concerns about postoperative Remifentanil hyperalgesia because of its potent fast onset and offset.

Objectives

The aim of this study was to determine visual analog scale (VAS), postoperative pain, and morphine used in two groups after spine surgery.

Methods

In this randomized clinical trial study, 60 patients aged 18 - 60 years old, according to the American Society of Anesthesiology (ASA) I - II, who underwent spinal canal stenosis or scoliosis surgery, were divided into two groups. In the control group, patients received 0.07 - 0.1 µg/kg/h intraoperative Fentanyl infusion, and in the intervention group 0.1 - 0.2 µg/kg/min remifentanil was infused during the surgery. Both groups received 15 mg/kg intravenous Acetaminophen 20 minutes before the end of the surgery. Postoperative pain score and morphine consumption were measured 6, 12, 24, and 48 hours after discharge from the post-anesthesia care unit (PACU).

Results

During the first 12 hours, VAS and morphine consumption were significantly higher in remifentanil group (P < 0.001). However, no significant difference was found between the two groups in morphine consumption 12 - 48 hours after surgery.

Conclusions

These findings suggest that Remifentanil infusion during surgery may increase postoperative pain. Also, VAS and morphine consumption were higher during the first 12 hours.

Effect of preoperative pregabalin on analgesia and interleukins after lumbotomy: prospective, randomized, comparative, double-blind study

Background

Pregabalin is an anticonvulsant and has been used for postoperative analgesia. This study aimed to assess the effect of a single preoperative dose of pregabalin for analgesia after nephrectomy.

Methods

The study was prospective, randomized, comparative, and double-blinded, conducted in 40 kidney transplant donors, between 18 and 60 years, American Society of Anesthesia physical status I or II. Epidural anesthesia was performed with 15 mL of 0.5% ropivacaine single shot and general anesthesia with 3 µg/kg of fentanyl, propofol, atracurium, and sevoflurane, and 50% of oxygen without nitrous oxide. Patients in group 1 were administered 300 mg of pregabalin and those in group 2 were administered placebo, in identical capsules, 1 hour prior to surgery. Postoperative analgesia was supplemented with tramadol. The following parameters were assessed: pain intensity after 6 and 24 hours; pain threshold, from the thenar and peri-incisional region, analgesic supplementation; ILs (IL6, IL8, and IL10) prior to surgery and after 6 and 24 hours.

Results

The pain intensity was lower with pregabalin after 24 hours (G1: 2.5±2.4, G2: 3.0±2.6). There was no difference in the sensitivity of the thenar and peri-incisional region after 6 and 24 hours; in the number of patients requiring supplementation (G1=15%, G2=45%); concentrations of IL-6, IL-8, and IL-10; and side effects (nausea, vomiting, dizziness, and pruritus).

Conclusion

Pregabalin in a single preoperative dose of 300 mg reduced pain intensity 24 hours after lumbotomy.

Excessive remifentanil during total intravenous anesthesia is associated with increased risk of pain after robotic thyroid surgery

The widespread use of remifentanil during total intravenous anesthesia (TIVA) has raised concerns about the risk of postoperative remifentanil-associated pain. Although a recent meta-analysis suggests that remifentanil-associated pain is unlikely to occur in patients with TIVA because of the protective effect of co-administered propofol, the evidence is not conclusive. We retrospectively assessed 635 patients who received robotic thyroid surgery under TIVA to evaluate the risk of remifentanil-associated pain. Postoperative pain was evaluated using 11-point numeric rating scale (NRS). Time dependent Cox proportional hazards regression analysis was used to determine the risk factors of treatment-requiring pain (NRS > 4) during the first 48 postoperative hours. Postoperative pain rapidly decreased, and treatment-requiring pain remained in 12.8% (81 out of 635) of patients at 48 hours postoperatively. After adjusting for the time-dependent analgesic consumption, intraoperative use of remifentanil > 0.2 mcg/kg/min was a positive predictor of postoperative pain with a hazard ratio of 1.296 (95% C.I., 1.014–1.656, P = 0.039) during 48 hours after surgery. In conclusion, excessive use of remifentanil during TIVA was associated with increased risk of pain after robotic thyroid surgery. Prospective trials are required to confirm these results and determine whether decreasing remifentanil consumption below the threshold can reduce postoperative pain.

Why mu-opioid agonists have less analgesic efficacy in neuropathic pain?

Injury to peripheral nerves often leads to abnormal pain states (hyperalgesia, allodynia and spontaneous pain), which can remain long after the injury heals. Although opioid agonists remain the gold standard for the treatment of moderate to severe pain, they show reduced efficacy against neuropathic pain. In addition to analgesia, opioid use is also associated with hyperalgesia and analgesia tolerance, whose underlying mechanisms share some commonalities with nerve injury-induced hypersensitivity. Here, we reviewed up-to-day research exploring the contribution of mu-opioid receptor (MOR) on the pathophysiology of neuropathic pain and on analgesic opioid actions under these conditions. We focused on the specific contributions of MOR populations at peripheral, spinal and supraspinal level. Moreover, evidences of neuroplastic changes that may underlie the low efficacy of MOR agonists under neuropathic pain conditions are reviewed and discussed. Sensitization processes leading to pain hypersensitivity, molecular changes in signalling pathways triggered by MOR and glial activation are some of these mechanisms elicited by both nerve injury and opioid exposure. Nerve injury-induced pain hypersensitivity might be masking the initial analgesic effects of opioid agonists, and alternatively, sustained opioid treatment to individuals already suffering from neuropathic pain could aggravate their pathophysiological state. Finally, some combined therapies that can increase opioid analgesic effectiveness in neuropathic pain treatment are highlighted. SIGNIFICANCE: This review provides evidence of the low benefit of opioid monotherapy in neuropathic pain and analyses the reasons of this reduced effectiveness. Opioid agonists along with drugs targeted to block the sensitization processes induced by MOR stimulation might result in a better management of neuropathic pain.

Intraoperative electroacupuncture relieves remifentanil-induced postoperative hyperalgesia via inhibiting spinal glial activation in rats

Background Accumulating studies have suggested that remifentanil, the widely-used opioid analgesic in clinical anesthesia, can activate the pronociceptive systems and enhance postoperative pain. Glial cells are thought to be implicated in remifentanil-induced hyperalgesia. Electroacupuncture is a complementary therapy to relieve various pain conditions with few side effects, and glial cells may be involved in its antinociceptive effect. In this study, we investigated whether intraoperative electroacupuncture could relieve remifentanil-induced postoperative hyperalgesia by inhibiting the activation of spinal glial cells, the production of spinal proinflammatory cytokines, and the activation of spinal mitogen-activated protein kinases. Methods A rat model of remifentanil-induced postoperative hyperalgesia was used in this study. Electroacupuncture during surgery was conducted at bilateral Zusanli (ST36) acupoints. Behavior tests, including mechanical allodynia and thermal hyperalgesia, were performed at different time points. Astrocytic marker glial fibrillary acidic protein, microglial marker Iba1, proinflammatory cytokines, and phosphorylated mitogen-activated protein kinases in the spinal cord were detected by Western blot and/or immunofluorescence. Results Mechanical allodynia and thermal hyperalgesia were induced by both surgical incision and remifentanil infusion, and remifentanil infusion significantly exaggerated and prolonged incision-induced pronociceptive effects. Glial fibrillary acidic protein, Iba1, proinflammatory cytokines (interleukin-1β and tumor necrosis factor-α), and phosphorylated mitogen-activated protein kinases (p-p38, p-JNK, and p-ERK1/2) were upregulated after surgical incision, remifentanil infusion, and especially after their combination. Intraoperative electroacupuncture significantly attenuated incision- and/or remifentanil-induced pronociceptive effects, spinal glial activation, proinflammatory cytokine upregulation, and phosphorylated mitogen-activated protein kinase upregulation. Conclusions Our study suggests that remifentanil-induced postoperative hyperalgesia can be relieved by intraoperative electroacupuncture via inhibiting the activation of spinal glial cells, the upregulation of spinal proinflammatory cytokines, and the activation of spinal mitogen-activated protein kinases.

Efficacy of Pregabalin in Acute Postoperative Pain Under Different Surgical Categories: A Meta-Analysis

The efficacy of pregabalin in acute postsurgical pain has been demonstrated in numerous studies; however, the analgesic efficacy and adverse effects of using pregabalin in various surgical procedures remain uncertain. We aim to assess the postsurgical analgesic efficacy and adverse events after pregabalin administration under different surgical categories using a systematic review and meta-analysis of randomized controlled trials.A search of the literature was performed between August 2014 to April 2015, using PubMed, Ovid via EMBASE, Google Scholar, and ClinicalTrials.gov with no limitation on publication year or language. Studies considered for inclusion were randomized controlled trials, reporting on relevant outcomes (2-, 24-hour pain scores, or 24 hour morphine-equivalent consumption) with treatment with perioperative pregabalin.Seventy-four studies were included. Pregabalin reduced pain scores at 2 hours in all categories: cardiothoracic (Hedge's g and 95%CI, -0.442 [-0.752 to -0.132], P = 0.005), ENT (Hedge g and 95%CI, -0.684 [-1.051 to -0.316], P < 0.0001), gynecologic (Hedge g, 95%CI, -0.792 [-1.235 to -0.350], P < 0.0001), laparoscopic cholecystectomy (Hedge g, 95%CI, -0.600 [-0.989 to -0.210], P = 0.003), orthopedic (Hedge g, 95%CI, -0.507 [-0.812 to -0.202], P = 0.001), spine (Hedge g, 95%CI, -0.972 [-1.537 to -0.407], P = 0.001), and miscellaneous procedures (Hedge g, 95%CI, -1.976 [-2.654 to -1.297], P < 0.0001). Pregabalin reduced 24-hour morphine consumption in gynecologic (Hedge g, 95%CI, -1.085 [-1.582 to -0.441], P = 0.001), laparoscopic cholecystectomy (Hedge g, 95%CI, -0.886 [-1.652 to -0.120], P = 0.023), orthopedic (Hedge g, 95%CI, -0.720 [-1.118 to -0.323], P < 0.0001), spine (Hedge g, 95%CI, -1.016 [-1.732 to -0.300], P = 0.005), and miscellaneous procedures (Hedge g, 95%CI, -1.329 [-2.286 to -0.372], P = 0.006). Pregabalin resulted in significant sedation in all surgical categories except ENT, laparoscopic cholecystectomy, and gynecologic procedures. Postoperative nausea and vomiting was only significant after pregabalin in miscellaneous procedures.Analgesic effects and incidence of adverse effects of using pregabalin are not equal in different surgical categories.

Evaluation of the effect of ketamine on remifentanil-induced hyperalgesia: a double-blind, randomized study

STUDY OBJECTIVE

Opioids are associated with hyperalgesia that can reduce their analgesic effect. The aim of this study was to determine whether the addition of ketamine reduces remifentanil-induced hyperalgesia; improves its analgesic effect; and alters interleukin 6 (IL-6), IL-8, and IL-10 levels.

DESIGN

This is a prospective, randomized, double-blind study.

SETTING

The setting is in a operating room and ward in a university hospital.

PATIENTS

There are 56 patients, aged ≥18 years, American Society of Anesthesiologists I or II, who underwent laparoscopic cholecystectomy.

INTERVENTIONS

Anesthesia was induced with remifentanil, 50% oxygen, and isoflurane. Patients randomized to group 1 received remifentanil (0.4 μg/kg per minute) and ketamine (5 μg/kg per minute), and patients randomized to group 2 received remifentanil (0.4 μg/kg per minute) and saline solution. Postoperative analgesia was achieved using morphine via patient-controlled analgesia.

MEASUREMENTS

The measurements were postoperative pain intensity during 24 hours; morphine consumption; time to first morphine supplementation; hyperalgesia (using monofilaments and an algometer) and allodynia (using a soft brush) in the thenar eminence of the nondominant hand and in the periumbilical region 24 hours after surgery; extent of hyperalgesia using a 300-g monofilament near the periumbilical region 24 hours after surgery; and serum levels of IL-6, IL-8, and IL-10.

MAIN RESULTS

Groups were similar for baseline characteristics. There were no differences in pain intensity, time to first request of morphine, and total 24 hours dose of morphine between groups. There was a difference in hyperalgesia using monofilaments 24 hours after the surgery in the thenar eminence of the nondominant hand, with a better profile for the experimental group. However, there were no differences in hyperalgesia using an algometer, in allodynia using a soft brush; in extent of hyperalgesia; or in levels of IL-6, IL-8, and IL-10.

CONCLUSIONS

It was not possible to demonstrate that the addition of ketamine (5 μg/kg per minute) is effective in preventing or reducing remifentanil-induced postoperative hyperalgesia in laparoscopic cholecystectomy.

The analgesic effect of nefopam combined with low dose remifentanil in patients undergoing middle ear surgery under desflurane anesthesia: a randomized controlled trial

BACKGROUND

We investigated the effects of the combined administration of nefopam, a N-methyl-D-aspartate receptor antagonist and low dose remifentanil, on early postoperative pain and analgesic requirement.

METHODS

Fifty patients scheduled to undergo mastoidectomy and tympanoplasty were randomized to be given either nefopam 40 mg mixed with normal saline 100 ml (Group N) or an equal amount of normal saline (Group C) before anesthesia induction. Anesthesia was maintained with 5-6 vol% desflurane and remifentanil 0.05-0.15 µg/kg/min during the surgery. Postoperative pain was controlled by titration of ketorolac in the postanesthesia care unit (PACU) and ward. We evaluated the intraoperative remifentanil dose, recovery profiles, ketorolac demand in the PACU and ward, numeric rating scale (NRS) for pain at time intervals of every 10 min for 1 h in the PACU, 6, 12, 18 and 24 h in a ward, as well as the time to first analgesic requirement in the PACU and ward.

RESULTS

Ketorolac demand and NRS in the PACU were significantly lower in Group N than Group C (P = 0.002, P = 0.005, respectively). The time to first analgesic requirement in the PACU in Group N were significantly longer than Group C (P = 0.046). There were no significant differences in intraoperative remifentanil dose, ketorolac demand, NRS, and the time to first analgesic requirement in the ward between the groups.

CONCLUSIONS

Nefopam administration combined with low dose remifentanil infusion reduces pain and analgesic consumption during the immediate postoperative period in patients undergoing middle ear surgery under desflurane anesthesia.

Assessment of the effect of ketamine in combination with remifentanil on postoperative pain

BACKGROUND AND OBJECTIVES

The combination of ketamine and remifentanil seems to be associated with better analgesia and duration. The aim of this study was to evaluate whether a ketamine-remifentanil combination promotes improved postoperative analgesia.

METHODS

Prospective, randomized, double blind study of 40 patients undergoing video laparoscopic cholecystectomy. Anesthesia was performed with remifentanil, propofol, atracurium, and 50% oxygen. Group 1 (GI) patients received remifentanil (0.4 mcg.kg(-1).min(-1)) and ketamine (5 mcg.kg(-1).min(-1)) and Group 2 (G2) received remifentanil (0.4 mcg.kg(-1).min(-1)) and saline solution. Morphine 0.1mg.kg(-1) was administered at the end of the procedure, and postoperative pain was treated with morphine via PCA. We evaluated the severity of postoperative pain by a numerical scale from zero to 10 during 24 hours. We registered the time to the first analgesic supplementation, amount of morphine used in the first 24 hours, and adverse effects.

RESULTS

There was a decrease in pain severity between extubation and other times evaluated in G1 and G2. There was no significant difference in pain intensity between the groups. There was no difference between G1 (22±24.9 min) and G2 (21.5±28.1min) regarding time to first dose of morphine and dose supplement of morphine consumed in G1 (29±18.4mg) and G2 (25.1±13.3mg).

CONCLUSION

The combination of ketamine (5 mcg.kg(-1).min(-1)) and remifentanil (0.4mcg.kg(-1).min(-1)) for cholecystectomy did not alter the severity of postoperative pain, time to first analgesic supplementation or dose of morphine in 24hours.

Assessment of the effect of ketamine in combination with remifentanil on postoperative pain

BACKGROUND AND OBJECTIVES

The combination of ketamine and remifentanil seems to be associated with better analgesia and duration. The aim of this study was to evaluate whether a ketamine- remifentanil combination promotes improved postoperative analgesia.

METHODS

Prospective, randomized, double blind study of 40 patients undergoing video laparoscopic cholecystectomy. Anesthesia was performed with remifentanil, propofol, atracurium, and 50% oxygen. Group 1 (GI) patients received remifentanil (0.4 mcg.kg(-1).min(-1)) and ketamine (5 mcg.kg(-1).min(-1)) and Group 2 (G2) received remifentanil (0.4 mcg.kg(-1).min(-1)) and saline solution. Morphine 0.1 mg.kg(-1) was administered at the end of the procedure, and postoperative pain was treated with morphine via PCA. We evaluated the severity of postoperative pain by a numerical scale from zero to 10 during 24 hours. We registered the time to the first analgesic supplementation, amount of morphine used in the first 24 hours, and adverse effects.

RESULTS

There was a decrease in pain severity between extubation and other times evaluated in G1 and G2. There was no significant difference in pain intensity between the groups. There was no difference between G1 (22 ± 24.9 min) and G2 (21.5 ± 28.1 min) regarding time to first dose of morphine and dose supplement of morphine consumed in G1 (29 ± 18.4 mg) and G2 (25.1 ± 13.3 mg).

CONCLUSION

The combination of ketamine (5 mcg.kg(-1).min(-1)) and remifentanil (0.4 mcg.kg(-1).min(-1)) for cholecystectomy did not alter the severity of postoperative pain, time to first analgesic supplementation or dose of morphine in 24 hours.

Pain management for the cancer patient - current practice and future developments

Anaesthesiologists will be asked to provide pain management for cancer patients in the absence of more specialised services, when interventional techniques are indicated and in the postoperative period. In all these settings, the complexity of cancer pain and its psychosocial connotations need to be considered to provide appropriate and holistic care. Principles of systemic pain management, effective in most patients, continue to follow established guidelines; identification of neuropathic pain and its appropriate treatment is important here. Interventional pain relief is required in a minority of cancer patients, but it should be considered when appropriate and then done with best available expertise. Neurolytic procedures have lost importance here over the years. Postoperative pain management should be multimodal with consideration of regional techniques when applicable. In managing postoperative pain in cancer patients, opioid tolerance needs to be addressed to avoid withdrawal and poor analgesia. Preventive techniques aiming to reduce chronic postoperative pain should be considered.

Effect of oral pregabalin on opioid-induced hyperalgesia in patients undergoing laparo-endoscopic single-site urologic surgery

Background

Pregabalin is an antiepileptic drug that is effective for treating postoperative pain, neuropathic pain, anxiety, and hemodynamic instability. The aim of this study was to investigate the effect of a single preoperative dose of pregabalin in patients with opioid-induced hyperalgesia (OIH).

Methods

Ninety ASA I-II patients undergoing laparoendoscopic single-site urologic surgery were randomly assigned to one of the following three groups that received either pregabalin or placebo 1 h before anesthesia and an intraoperative remifentanil infusion. Group plL received placebo and 0.05 µg/kg/min remifentanil, group plH received placebo and 0.3 µg/kg/min remifentanil, and group prH received 300 mg pregabalin plus 0.3 µg/kg/min remifentanil. The primary endpoint was pain intensity upon movement 1, 6, 12, and 24 h after surgery. Secondary endpoints were the area of hyperalgesia and mechanical hyperalgesia threshold 24 h after surgery, time to first postoperative analgesic requirement, and cumulative postoperative volume of morphine administered via a patient-controlled analgesia (PCA) pump over 24 h.

Results

The time to first postoperative analgesic requirement in group plH was significantly shorter than that in group plL. The injected PCA volume was significantly greater in group plH than that in the other two groups. Postoperative pain intensity in group plH was significantly greater than that in the other two groups at 6, 12, and 24 h after surgery. The mechanical hyperalgesia threshold and the area of hyperalgesia around the surgical incision 24 h after surgery in group plH differed significantly from those in the other two groups, which were not significantly different. Adverse effects were comparable among groups.

Conclusions

High-dose remifentanil induced hyperalgesia, including increased pain intensity, increased area of hyperalgesia, and decreased mechanical hyperalgesia threshold. These effects were attenuated by oral administration of a single preoperative dose of pregabalin (300 mg) in patients undergoing laparo-endoscopic single-site urologic surgery.

Acute pain management in the opioid-tolerant patient

SUMMARY Opioid use is increasing worldwide leading to an increasing number of opioid-tolerant patients requiring acute pain management after surgery, trauma and acute diseases. Provision of analgesia in opioid-tolerant patients is complex due to the pharmacological effects of long-term opioid exposure, but also due to pre-existing pain states, comorbidities and psychosocial issues. Acute pain management in these patients is governed by the principles of provision of good analgesia, avoidance of withdrawal and organized discharge. Pain relief needs to be achieved by the use of multimodal analgesia, including regional anesthetic techniques and, if needed, opioids in increased doses. Withdrawal is best prevented by ongoing opioid substitution at previously established doses. Discharge planning requires multidisciplinary input and good communication with all healthcare providers involved.

Effect of timing of morphine administration during propofol - remifentanil anesthesia on the requirements of post-operative analgesia

Background

An important concern of intra-operative infusion of remifentanil is the possible development of acute opioid tolerance, which manifests as an increased postoperative analgesia requirement. We have examined the effect of the timing of intra operative morphine administration on the need for morphine consumption for pain control during the first 24 hours after operation.

Methods

Sixty adult patients scheduled for elective open unilateral nephrolithotomy surgery were recruited for this prospective randomized double-blind study. Anesthesia was induced with 0.03 mg/kg midazolam, 1 µg/kg remifentanil, and 1.5-2 mg/kg propofol. Anesthesia was maintained with 100 µg/kg/min propofol, and 0.25 µg/kg/min remifentanil. Both groups received 0.1 mg/kg morphine intravenously at 2 different times; in the first group (group E) immediately after intubation and in the second group (group L) 20-30 min before the anticipated end of operation.

Results

There was no difference in pain scores at awakening, the amount of morphine given to the 2 groups for pain control, or the time to discharge from PACU between the 2 groups. The pain scores at admission to ward and at every 4 hours thereafter, until 24 hours, were not significantly different between the 2 groups. The cumulative amount of the first 24 hours morphine consumption in the ward in E group was 28.2 ± 20.1 mg and 26.5 ± 15 mg in L group, respectively (P = 0.71).

Conclusions

Early intra-operative administration of morphine compared to that of morphine in the end of surgery did not affect postoperative morphine consumption and pain scores during the first 24 hours after surgery for open nephrolithotomy. Newer pharmacologic interventions for prevention of acute tolerance of opioids seems rational (Clinical trial registration No. ACTRN: 12609000570280).

Postoperative pain trajectories in chronic pain patients undergoing surgery: the effects of chronic opioid pharmacotherapy on acute pain

For 2 weeks following surgery, 55 patients with preexisting chronic pain (CP) reported daily postoperative pain with movement and at rest. Of these, 30 CP patients used opioid pharmacotherapy for CP management and 25 did not. We modeled pain resolution in each patient using a linear fit so that each patient yielded 2 scores for each pain rating: 1) an intercept, or initial level of pain, immediately after surgery; and 2) a slope, or rate of pain resolution. The patients not using opioid pharmacotherapy had a mean pain with movement intercept of 5.4 and a slope of -.20, while the patients using opioid pharmacotherapy had a significantly higher mean intercept of 7.68 (P = .001) and a slope of -.21, sustaining higher pain levels over days. The opioid pharmacotherapy patients had the same rate of pain resolution as the other CP patients, and both groups resolved their pain more slowly than normal surgery patients. Preexisting CP may predispose a patient undergoing surgery to a slower rate of postoperative pain resolution. Chronic pain patients who use opioids share this predisposition but in addition, they are at risk for markedly higher postoperative pain across the entire pain resolution trajectory.

PERSPECTIVE

This is an observational rather than a randomized controlled study, and as such is less definitive. Nonetheless, these findings are consistent with those of animal studies showing that prolonged exposure to opioids can produce opioid-induced hyperalgesia. Patients with opioid pharmacotherapy for chronic pain who undergo surgery merit special attention for acute pain management.