Does the β-receptor antagonist esmolol have analgesic effects?: A randomised placebo-controlled cross-over study on healthy volunteers undergoing the cold pressor test

Remifentanil-induced hyperalgesia in healthy volunteers: a systematic review and meta-analysis of randomized controlled trials

ABSTRACT

Recent literature suggests that the withdrawal of remifentanil (RF) infusion can be associated with hyperalgesia in clinical and nonclinical settings. We performed a systematic review and a meta-analysis of randomized controlled trials with cross-over design, to assess the effect of discontinuing RF infusion on pain intensity and areas of hyperalgesia and allodynia in healthy volunteers. Nine studies were included. The intervention treatment consisted in RF infusion that was compared with placebo (saline solution). The primary outcome was pain intensity assessment at 30 ± 15 minutes after RF or placebo discontinuation, assessed by any pain scale and using any quantitative sensory testing. Moreover, postwithdrawal pain scores were compared with baseline scores in each treatment. Secondary outcomes included the areas (% of basal values) of hyperalgesia and allodynia. Subjects during RF treatment reported higher pain scores after discontinuation than during treatment with placebo [standardized mean difference (SMD): 0.50, 95% confidence interval (CI): 0.03-0.97; P = 0.04, I 2 = 71%]. A significant decrease in pain scores, compared with baseline values, was found in the placebo treatment (SMD: -0.87, 95% CI: -1.61 to -0.13; P = 0.02, I 2 = 87%), but not in the RF treatment (SMD: -0.28, 95% CI: -1.18 to 0.62; P = 0.54, I 2 = 91%). The area of hyperalgesia was larger after RF withdrawal (SMD: 0.55; 95% CI: 0.27-0.84; P = 0.001; I 2 = 0%). The area of allodynia did not vary between treatments. These findings suggest that the withdrawal of RF induces a mild but nonclinically relevant degree of hyperalgesia in HVs, likely linked to a reduced pain threshold.

Postoperative pain: a review of emerging therapeutic options

INTRODUCTION

Postoperative pain is often managed by opioid medications, even though they carry a risk of adverse effects such as vomiting, constipation, sedation, respiratory depression and physical dependence. Furthermore, opioid use in the healthcare setting has likely contributed to the epidemic. However, the mismanagement of postoperative pain can result in delayed recovery time, impaired physical function, increased risk of morbidity and mortality, chronic pain, and higher healthcare costs.

AREAS COVERED

This review explores emerging therapeutic options and strategies in the management of acute postoperative pain and focuses on opioid-sparing, multimodal analgesia. This includes regional anesthetic techniques, non opioid pharmacotherapy, novel opioids and non-pharmacologic therapy. We have also discussed examples of novel analgesics and formulations which have potential benefits in reducing postoperative pain and opioid use after surgery.

EXPERT OPINION

The development of novel regional anesthesia techniques allows for opioid minimization in increasing number of surgical procedures. This synergizes with the availability of novel non-opioid analgesic adjucts. In addition, several novel opioid drugs have been developed which may be pathway selective and associated with less adverse effect than conventional opioids.

Tilidine and dipyrone (metamizole) in cold pressor pain: A pooled analysis of efficacy, tolerability, and safety in healthy volunteers

The cold pressor test (CPT) is widely implemented and offers a simple, experimental acute pain model utilizing cold pain. Previous trials have frequently paired the CPT with opioids in order to investigate the mechanisms underlying pharmacological analgesia, due to their known analgesic efficacy. However, opioid side effects may lead to unblinding and raise concerns about the safety of the experimental setting. Despite the established clinical efficacy of dipyrone (metamizole), its efficacy, tolerability, and safety in cold pressor pain has not been systematically addressed to date. This pooled analysis included data of 260 healthy volunteers from three randomized, placebo‐controlled, double‐blind substudies using the CPT following a pre‐test‐post‐test‐design. These substudies allow for comparing a single dose of 800 mg dipyrone with two different doses of the opioid tilidine/naloxone (50/4 mg and 100/8 mg, respectively). Outcomes included pain intensity ratings, pain tolerance, medication‐attributed side effects, as well as changes of blood pressure and heart rate. We demonstrate that both opioid doses and dipyrone had a comparable, significant analgesic effect on cold pressor pain. However, dipyrone was associated with significantly less self‐reported adverse effects and these were not significantly different from those under placebo. These results indicate that the combination of dipyrone and the CPT provides a safe, tolerable, and effective experimental model for the study of pharmacological analgesia. In combination with a CPT, dipyrone may be useful as a positive control, or baseline medication for the study of analgesic modulation.

Esmolol Infusion Reduces Blood Loss and Opiate Consumption during Fertility Preserving Myomectomy

Objectives

The objective of this study is to evaluate the effect of esmolol-induced hypotensive anesthesia (EIHA) on intra-operative (IO) bleeding during open myomectomy.

Patients and Methods

Eighty-eight women were randomly divided into the study group received EIHA without uterine tourniquet and control group who received normotensive anesthesia with uterine tourniquet. EIHA was provided as priming dose of esmolol (0.5 mg.kg^-1) before the induction of anesthesia and esmolol infusion (0.05-0.3 mg.kg^-1.min^-1) to maintain mean arterial pressure at 60-70 mmHg that was stopped on completion of myomectomy. Fentanyl was used as IO analgesia (loading dose: 1.0 μg.kg^-1 then infusion of 0.2-0.4 μg.kg^-1.h^-1). All patients received 6% hydroxyethyl starch (HES; initially, 3 mL.kg^-1 over 5-10 minutes and supplemental doses according to requirements) and Lactated Ringer's solution (LR; 5 mL.kg^-1.h^-1). Trigger for blood transfusion was hemoglobin concentration (HBC) <7 g.dL^-1. Study outcomes included the extent of postoperative (PO) HBC deficit in relation to preoperative HBC, frequency of tourniquet application for the study patients, and total fentanyl consumption.

Results

EIHA significantly reduced blood pressure measures since laryngoscopy and tracheal intubation till the end of surgery in the study group compared to control group. Eight study patients (18.9%) required tourniquet application for control of bleeding; however, amount of IO blood loss; total field visibility score and PO HBC deficit were non significantly lower in the study group. EIHA allowed significant reduction of the IO amount of LR and additional amounts of HES infusions. Study patients group consumed significantly lower IO fentanyl doses with significantly longer duration till the 1^st PO request and the number of additional fentanyl, and lower numeric rating scale scores in study group compared to controls.

Conclusion

Open myomectomy under EIHA is feasible and safe and allows fertility-sparing with minimal risk of blood transfusion. The applied procedure of EIHA allowed blunting of pressor reflexes secondary to LIT, surgical stresses and extubation, and allowed reduction of IO and PO opioid doses.

Comparison of Metoprolol and Tramadol with Remifentanil in Endoscopic Sinus Surgery: A Randomised Controlled Trial

Objective

Controlled hypotension is commonly induced during functional endoscopic sinus surgery to limit mucosal bleeding. This may be detrimental to elderly patients and patients with arterial stenosis. The aim of this pilot study was to determine if a normotensive anaesthetic technique with sufficient analgesia and without profound vasodilation may reduce intraoperative bleeding and incidence of adverse haemodynamic effects associated with vasodilation and variable rate continuous infusions.

Methods

In this double-blind randomised controlled trial in a tertiary care centre, a total of 88 patients were randomised to receive intravenously either 0.1 mg kg^-1 metoprolol and 1 mg kg^-1 tramadol following anaesthesia induction (MT group) or a bolus dose of 0.5 μg kg^-1 remifentanil following anaesthesia induction, followed by 0.25-0.5 μg kg^-1 min^-1 remifentanil infusion (R group). The primary outcome was quality of surgical field and incidence of adverse haemodynamic effects. The secondary outcomes were time to achieve intraoperative bleeding score <3, bleeding rate and changes in cerebral regional oximetry.

Results

A total of 105 patients were recruited, in which 88 were randomised. The median intraoperative bleeding score was similar (1, interquartile range: 1-1, p=0.69). The mean bleeding rate was lower in the MT group, although the difference was not significant (p=0.052, 95% CI 0 to 8.8). Hypotension, bradycardia and cerebral desaturation in the MT group were not observed compared to hypotension in 3 (7%), bradycardia in 18 (41%) and cerebral desaturation in 2 (5%) patients in the R group (p=0.241, p<0.001, p=0.474, respectively).

Conclusion

Providing sufficient analgesia and eliminating stress response can provide stable heart rate and good surgical field with no need for additional hypotension. This normotensive technique may be useful in patients with stenotic arteries or ischaemic organ diseases.