Vein pretreatment with magnesium sulfate to prevent pain on injection of propofol is not justified

A Comparative Study of Valsalva Maneuver, Lidocaine, and Valsalva Maneuvers with Administration of Lidocaine to Reduce the Pain Associated with Administration of Etomidate During General Anesthesia

Objectives

The purpose of this study is a comparison of Valsalva, lidocaine, and Valsalva with administration of lidocaine to reduce the pain associated with administration of etomidate.

Methods

The present study is a clinical trial study. The number of samples in each group was 30 and a total of 90 people were selected. This study was a clinical trial and the subjects were randomly divided into three groups: Group 1: Valsalva, 2: Lidocaine, 3: Valsalva and Lidocaine. Pain due to etomidate was rated on a VAS from 1 (painless) to 3 (worst imaginable pain) and their information was recorded. The collected information was entered into SPSS 22 and analyzed with appropriate statistical tests.

Results

A total of 90 subjects participated in the present study and were divided into 3 groups: Valsalva, lidocaine, and Valsalva with lidocaine. No significant difference was observed between demographic variables in the study groups. There was a significant relationship between severity of pain in the three groups. According to the results, the highest pain intensity was in the Valsalva group and the lowest pain intensity was in the Valsalva with lidocaine group.

Conclusions

Valsalva with lidocaine reduces the severity of pain caused by etomidate to a greater extent than other groups.

Reduction of extracellular sodium evokes nociceptive behaviors in the chicken via activation of TRPV1

Transient receptor potential vanilloid 1 (TRPV1), a non-selective cation channel, is mainly expressed in nociceptive primary sensory neurons. Sensitivity of TRPV1 to several stimuli is known to vary among species, specifically, the avian orthologue is nearly insensitive to capsaicin. Extracellular sodium ions ([Na⁺]_o) regulate TRPV1 activity in mammals, but their regulatory role on chicken TRPV1 (cTRPV1) is unknown. Here, we focused on the actions of capsaicin and low [Na⁺]_o on cTRPV1 activity. In chicken dorsal root ganglion (cDRG) neurons, capsaicin elicited [Ca²⁺]_i increases, but its effective concentration was much higher than those in mammals. Low [Na⁺]_o evoked [Ca²⁺]_i increases in cDRG neurons in a decreasing [Na⁺]_o-dependent manner and the complete removal of [Na⁺]_o (0Na) produced maximal effects. The population of 0Na-sensitive neurons was mostly overlapped with those of proton- and capsaicin-sensitive ones. Low [Na⁺]_o synergistically potentiated the capsaicin- and proton-induced TRPV1 activation in cDRG neurons. In HEK293 cells expressing cTRPV1 (cTRPV1-HEK), capsaicin elicited [Ca²⁺]_i increases with an EC₅₀ of 11.8 µM, and low [Na⁺]_o also did. Well-defined mammalian TRPV1 antagonists hardly suppressed cTRPV1 activation by low [Na⁺]_o. 0Na evoked outwardly rectified currents in cTRPV1-HEK. Mutagenesis analyses revealed a possible interaction of [Na⁺]_o with the proton-binding sites of cTRPV1. The administration of capsaicin and 0Na to chick eyes elicited pain-related behaviors. These results suggest that low [Na⁺]_o is capable of activating cTRPV1 in vitro, resulting in pain in vivo. Our data demonstrate that characterization of the cTRPV1 function is important to understand activation mechanisms of TRPV1.

Participation of peripheral TRPV1, TRPV4, TRPA1 and ASIC in a magnesium sulfate-induced local pain model in rat

We previously showed that magnesium sulfate (MS) has systemic antinociceptive and local peripheral pronociceptive effects. The role of transient receptor potential (TRP) channels and acid-sensing ion channels (ASICs) in the mechanism of action of MS has not been investigated in detail. The aim of this study was to explore the participation of TRP channels in the pronociceptive action of MS in rats after its intraplantar injection. The paw withdrawal threshold (PWT) to mechanical stimuli was measured by the electronic von Frey test. Drugs that were tested were either co-administered with an isotonic pH-unadjusted or pH-adjusted solution of MS intraplantarily, or to the contralateral paw to exclude systemic effects. We found that the subcutaneous administration of both pH-adjusted (7.4) and pH-unadjusted (about 6.0) isotonic (6.2% w/v in water) solutions of MS induce the pain at the injection site. The pH-unadjusted MS solution-induced mechanical hyperalgesia decreased in a dose-dependent manner as a consequence of co-injection of capsazepine, a selective TRPV1 antagonist (20, 100 and 500pmol/paw), RN-1734, a selective TRPV4 antagonist (1.55, 3.1 and 6.2μmol/paw), HC-030031, a selective TRPA1 antagonist (5.6, 28.1 and 140nmol/paw), and amiloride hydrochloride, a non-selective ASIC inhibitor (0.83, 2.5 and 7.55μmol/paw). In pH-adjusted MS-induced hyperalgesia, the highest doses of TRPV1, TRPV4 and TRPA1 antagonists displayed effects that were, respectively, either similar, less pronounced or delayed in comparison to the effect induced by administration of the pH-unadjusted MS solution; the ASIC antagonist did not have any effect. These results suggest that the MS-induced local peripheral mechanical hyperalgesia is mediated via modulation of the activity of peripheral TRPV1, TRPV4, TRPA1 and ASICs. Specific local inhibition of TRP channels represents a novel approach to treating local injection-related pain.

Efficacy of different fluids preload on propofol injection pain: A randomized, controlled, double-blinded study

Injection pain of propofol remains a common clinical problem. Previous studies demonstrated that propofol injection pain was alleviated by applying nitroglycerin ointment to the skin of injection site, which inspires us to test whether venous vasodilation induced by fluid preload could alleviate the pain. Different types or volumes of fluid preload were compared. 200 ASA I-II adult patients were randomly assigned to five groups of 40 each. A 20 G cannula was established on the dorsum or wrist of the hand. When fluid preload given with Plasma-Lyte A 100 mL (P100 group), 250 mL (P250 group), 500 mL (P500 group), 0.9% saline 500 mL (N500 group) or Gelofusine 500 mL (G500 group) was completed within 30 min, respectively, Propofol (0.5 mg/kg, 1%) was injected at a rate of 0.5 mL/s. A blind investigator assessed the pain using a four-point scale. Incidence of pain in P100, P250, and P500 groups was 87.5%, 57.5% and 35%, respectively (P<0.05). The median pain intensity score was significantly lower in P500 group than that in P250 and P100 groups (P<0.05 and P<0.01, respectively). Comparison of the effect of different types of solution preload indicated that the highest incidence of pain was in N500 group (62.5%) (N500 vs. P500, P=0.014; N500 vs. G500, P=0.007). The median pain intensity score in N500 group was higher than that in P500 group (P<0.05) and G500 group (P<0.05). There was no significant difference between P500 and G500 groups. It is suggested that Plasma-Lyte A or Gelofusine preload with 500 mL before propofol injection is effective in alleviating propofol-induced pain.

Lidocaine for reducing propofol-induced pain on induction of anaesthesia in adults

BACKGROUND

Pain on propofol injection is an untoward effect and this condition can reduce patient satisfaction. Intravenous lidocaine injection has been commonly used to attenuate pain on propofol injection. Although many studies have reported that lidocaine was effective in reducing the incidence and severity of pain, nevertheless, no systematic review focusing on lidocaine for preventing high-intensity pain has been published.

OBJECTIVES

The objective of this review was to determine the efficacy and adverse effects of lidocaine in preventing high-intensity pain on propofol injection.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 10), Ovid MEDLINE (1950 To October 2014), Ovid EMBASE (1988 to October 2014), LILACS (1992 to October 2014) and searched reference lists of articles.We reran the search in November 2015. We found 11potential studies of interest, those studies were added to the list of 'Studies awaiting classification' and will be fully incorporated into the formal review findings when we update the review.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) using intravenous lidocaine injection as an intervention to decrease pain on propofol injection in adults. We excluded studies without a placebo or control group.

DATA COLLECTION AND ANALYSIS

We collected selected studies with relevant criteria. We identified risk of bias in five domains according to the following criteria: random sequence generation, allocation concealment, adequacy of blinding, completeness of outcome data and selective reporting. We performed meta-analysis by direct comparisons of intervention versus control. We estimated the summary odds ratios (ORs) and 95% confidence intervals using the random-effects Mantel-Haenszel method in RevMan 5.3. We used the I(2) statistic to assess statistical heterogeneity. We assessed overall quality of evidence using the GRADE approach.

MAIN RESULTS

We included 87 studies, 84 of which (10,460 participants) were eligible for quantitative analysis in the review. All participants, aged 13 years to 89 years, were American Society of Anesthesiologists (ASA) I-III patients undergoing elective surgery. Each study was conducted in a single centre in high- , middle- and low-income countries worldwide. According to the risk of bias assessment, all except five studies were identified as being of satisfactory methodological quality, allowing 84 studies to be combined in the meta-analysis. Five of the 84 studies were assessed as high risk of bias: one for participant and personnel blinding, one for incomplete outcome data, and three for other potential sources of bias.The overall incidence of pain and high-intensity pain following propofol injection in the control group were 64% (95% CI 60% to 67.9%) and 38.1% (95% CI 33.4% to 43.1%), respectively while those in the lidocaine group were 30.2% (95% CI 26.7% to 33.7%) and 11.8% (95% CI 9.7% to 13.8%). Both lidocaine admixture and pretreatment were effective in reducing pain on propofol injection (lidocaine admixture OR 0.19, 95% CI 0.15 to 0.25, 31 studies, 4927 participants, high-quality evidence; lidocaine pretreatment OR 0.13, 95% CI 0.10 to 0.18, 43 RCTs, 4028 participants, high-quality evidence). Similarly, lidocaine administration could considerably decrease the incidence of pain when premixed with the propofol (OR 0.19, 95% CI 0.15 to 0.24, 36 studies, 5628 participants, high-quality evidence) or pretreated prior to propofol injection (OR 0.14, 95% CI 0.11 to 0.18, 52 studies, 4832 participants, high-quality evidence). Adverse effects of lidocaine administration were rare. Thrombophlebitis was reported in only two studies (OR not estimated, low-quality evidence). No studies reported patient satisfaction.

AUTHORS' CONCLUSIONS

Overall, the quality of the evidence was high. Currently available data from RCTs are sufficient to confirm that both lidocaine admixture and pretreatment were effective in reducing pain on propofol injection. Furthermore, there were no significant differences of effect between the two techniques.

Magnesium sulfate with lidocaine for preventing propofol injection pain: a randomized, double-blind, placebo-controlled trial

PURPOSE

Propofol injection pain, despite various strategies, remains common and troublesome. This study aimed to test the hypothesis that pretreatment with the combination of intravenous lidocaine and magnesium would have an additive effect on reducing propofol injection pain.

METHODS

After institutional review board (IRB) approval and informed consent, we performed a prospective, double-blind, placebo-controlled, randomized trial. Subjects were randomly assigned to pretreatment with either lidocaine (50 mg), magnesium sulfate (0.25 mg), lidocaine (50 mg) plus magnesium sulfate (0.25 mg), or 0.9 % sodium chloride. Following pretreatment, propofol (50 mg) was administered, and subjects were questioned regarding injection site pain and observed for behavioral signs of pain.

RESULTS

Two hundred subjects were enrolled and 158 subjects (39 placebo, 38 lidocaine, 44 magnesium sulfate, and 37 lidocaine plus magnesium sulfate) received their assigned pretreatment intervention. Intergroup baseline characteristics were similar. The proportion of subjects reporting propofol injection pain was highest in those pretreated with magnesium sulfate (57 %), followed by those pretreated with placebo (46 %), lidocaine plus magnesium sulfate (41 %), and then lidocaine (29 %; p = 0.011). When adjusted for age, gender, diabetes mellitus, chronic pain, tobacco use, and selective-serotonin reuptake inhibitor use, the pain response scale scores were significantly reduced by lidocaine pretreatment compared to magnesium sulfate and placebo (p = 0.031 and p = 0.0003, respectively).

CONCLUSIONS

In this double-blind, placebo-controlled, randomized trial, the combination of intravenous magnesium sulfate and lidocaine offered no additional benefit for the relief of propofol injection pain compared to intravenous lidocaine alone. An improved, receptor-based understanding of the mechanism of propofol injection pain is still needed.

Paracetamol, ondansetron, granisetron, magnesium sulfate and lidocaine and reduced propofol injection pain

Background:

Propofol is a most widely used intravenous anesthetic drug. One of its most common complications is the pain upon injection; therefore, different methods, with various effects, have been proposed in order to alleviate the pain.

Objectives:

This study investigates the effects of paracetamol, ondansetron, granisetron, magnesium sulfate and lidocaine drugs on reducing the pain of propofol injection during anesthetic induction. Also, the hemodynamic changes will be analyzed.

Patients and Methods:

This is an interventional study containing 336 patients underwent elective orthopedic surgeries in Educational Hospitals of Mashhad University, using systematic sampling, the patients were divided into six groups. A 20-gauge needle was inserted into a venous vessel in the back of the hand and 100 cc of Ringer serum was injected into the vein, which was applied proximal to the injection site. Afterwards, paracetamol 2 mg/kg (group p), magnesium sulfate 2 mmol (group M), ondansetron 4 mg (group O), granisetron 2 mg (group G), lidocaine 40 mg (group L) and 5 cc saline (group S) were injected into the vessel, after 60 seconds, the tourniquet was opened. One quarter of the total dose of propofol (2.5 mg/kg) was injected with a flow rate of 4 mg/sec and then the injection pain was measured. Finally, the fentanyl (2 µg/kg), atracurium 0.5 mg/kg, and the remaining dose of propofol were injected and the vital signs were recorded before the administration of propofol and 1, 3, 5 and 10 minutes after the propofol injection.

Results:

The six groups did not significantly differ, regarding their gender, weight or age. Propofol injection pain was less in L and G groups, in comparison with the others (P ≤ 0.001). By analyzing the hemodynamic changes, it was observed that the least amount of change in mean arterial pressure was observed in the paracetamol group.

Conclusions:

The reduction of propofol injection pain was observed by using medications (in comparison with normal saline), but it was more significant in groups G and L. Moreover, Hypotension was higher in groups S and G and it was lessened in group P.

Intravenous lidocaine pretreatment with venous occlusion for reducing microemulsion propofol induced pain: Comparison of three doses of lidocaine

Objective

Pretreatment with intravenous 40 mg or 0.5 mg/kg lidocaine with venous occlusion is recommended to prevent pain following injection of lipid emulsion propofol. This approach is not sufficient to prevent pain from the injection of microemulsion propofol. The present study investigated whether a higher dose of lidocaine pretreatment with venous occlusion would be more effective for reducing pain following injection of microemulsion propofol compared with 40 mg lidocaine.

Methods

Patients undergoing elective surgery were randomly assigned to one of three groups: pretreatment with 40 mg (group L40), 60 mg (group L60) or 80 mg (group L80) lidocaine intravenously with venous occlusion, followed by injection with microemulsion propofol 1 min later. Pain was assessed on a four-point scale (severe, moderate, mild, none) based on physical responses to the injection.

Results

A total of 68 patients were included in the final analysis. Pain severity and incidence were significantly lower in patients in group L60 and L80 compared with patients in group L40. There were no statistically significant differences in pain incidence or severity between group L60 and group L80.

Conclusions

Pretreatment with 60 mg lidocaine intravenously with venous occlusion may be the most effective minimum dose for reducing injection pain following microemulsion propofol administration for induction of anaesthesia.

Single pretreatment of remifentanil may reduce pain after propofol and rocuronium injection in rapid sequence induction

Background

We designed this double-blind, placebo-controlled study to compare the efficacy of remifentanil in reducing the pain of both propofol and rocuronium injection during rapid-sequence induction.

Methods

Ninety-five patients, scheduled for elective surgery under general anesthesia, were divided into 3 groups: saline (Group S, n = 31), remifentanil 1 µg/kg (Group R, n = 32), and lidocaine 1.5 mg/kg (Group L, n = 32) were administered after tourniquet application. The occlusion was released after 1 min and 5 ml of 1% propofol was injected over 10 s. Pain on propofol injection was evaluated by a 10-point verbal numeric rating scale (VNRS). The rest of the induction dose of propofol and 1 mg/kg of rocuronium, were injected. Pain on rocuronium injection was evaluated by a four-point score (FPS).

Results

The VNRS of propofol injection was as follows: R (0.78) = L (1.34) < S (4.26). The incidence of withdrawal response due to rocuronium was as follows: R (6.3%) < L (53.1%) < S (83.9%). The FPS of rocuronium injection was as follows: R (0.81) < L (1.78) < S (2.93).

Conclusions

Pretreatment with a bolus of remifentanil was effective in simultaneously reducing injection pain of propofol and rocuronium. In addition, remifentanil pretreatment was more effective in suppression of withdrawal response by rocuronium than lidocaine.

Evaluation of dose effects of magnesium sulfate on rocuronium injection pain and hemodynamic changes by laryngoscopy and endotracheal intubation

Background

Rocuronium produces injection pain in 50-80% of treated patients. Therefore, a variety of pretreatments have been attempted to reduce this issue. We evaluated the efficacy of 3 different doses of magnesium on the rocuronium injection pain and following hemodynamic changes by laryngoscopy and tracheal intubation (LTI).

Methods

Two hundreds patients, ASA I and II, undergoing general anesthesia for elective surgery were randomly divided to 4 groups: group 1, 2, 3, 4 received saline 5 ml, magnesium 5, 10 and 20 mg/kg prior to 0.6 mg/kg of rocuronium, respectively. Then, group 1 only was treated with esmolol (20 mg) before LTI. Pain intensity with rocuronium injection was assessed using a four-point scale according to patient's movement. Cardiovascular responses at baseline, after induction, 1 minutes after LTI were determined.

Results

Compared to saline, 10 and 20 mg/kg of magnesium significantly reduced the incidence of overall movement after rocuronium injection (34% and 36% in group 3 and 4, respectively vs. 76% in the group 1) (P < 0.0001). Generalized movement was seen in 4% of patients in groups 3 and 4, respectively. Compared to baseline values, diastolic blood pressure (DBP) immediately after LTI significantly increased within groups 1 and 2 (P < 0.001), but not within groups 3 and 4.

Conclusions

Magnesium (10 and 20 mg/kg) prior to rocuronium was effective in attenuating rocuronium associated injection pain and cardiovascular changes by LTI.

Modulation of the cold-activated cation channel TRPM8 by surface charge screening

TRPM8, a cation channel activated by cold and by cooling agents such as menthol and icilin, is critically involved in somatosensory cold sensation. Ion fluxes through TRPM8 are highly sensitive to changes in extracellular Ca(2+) and pH, but the mechanisms underlying this type of modulation are poorly understood. Here we provide evidence that inhibition of TRPM8 currents by extracellular divalent cations and protons is due to surface charge screening. We demonstrate that increasing concentrations of divalent cations or protons cause parallel shifts of the voltage dependence of TRPM8 activation towards positive potentials. These shifts were interpreted using the Gouy-Chapman-Stern theory, yielding an estimate for the density of fixed negative surface charge between 0.0098 and 0.0126 equivalent charges per A(2). These results represent the first description of the effects of surface charge screening on a TRP channel and provide a straightforward explanation for the known effects of extracellular Ca(2+) on cold-sensitive neurons.

Evaluation of the efficacy of magnesium sulphate as an adjuvant to lignocaine for intravenous regional anaesthesia for upper limb surgery

Several additives have been combined with local anaesthetics for intravenous regional anaesthesia to improve block quality, analgesia and to decrease tourniquet pain. Magnesium sulphate is one potential additive. This prospective, randomised, double-blinded study was conducted in 30 ASA physical status I or II patients undergoing upper limb surgery under tourniquet. In group L, patients received intravenous regional anaesthesia with lignocaine alone (9 ml of 2% lignocaine diluted with normal saline to total volume of 36 ml). Patients in group M received intravenous regional anaesthesia with lignocaine plus magnesium sulphate (6 ml of 25% magnesium sulphate plus 9 ml of 2% lignocaine diluted with normal saline to total volume of 36 ml). Assessment was by observing the response to injection of drug; sensory and motor block and tourniquet pain. The mean time of onset of sensory block was 12.40 and 3.47 minutes in groups L and M respectively (P < 0.001). The average times of onset of motor block in groups L and M were 17 and six minutes respectively (P < 0.001). Of the patients in group M, 66.7% reported moderate to severe pain while the drug was being injected, compared to 20% in group L (P=0.011). There was a statistically significant difference in visual analogue scale for tourniquet pain at 10 and 30 minutes after tourniquet inflation (lower in group M). These findings indicate that magnesium sulphate added as an adjuvant to lignocaine hastens the onset of sensory and motor block and decreases tourniquet pain. However there is increased incidence of transient pain on injection if magnesium sulphate is added.

Efficacy of intravenous acetaminophen and lidocaine on propofol injection pain

BACKGROUND

Different methods and propofol formulations have been used to decrease propofol injection pain, but it remains an unresolved problem. We aimed to investigate the effect of i.v. acetaminophen pretreatment on the propofol injection pain.

METHODS

One hundred and fifty ASA I-II patients undergoing general anaesthesia were randomly allocated into three groups. A 20-gauge catheter was inserted into a superficial radial vein of the left hand, and after the occlusion of venous drainage, Groups I, II, and III were pretreated with 40 mg of lidocaine in saline, 50 mg of i.v. acetaminophen, and 5 ml of saline, respectively. The occlusion was released after 2 min and one-fourth of the total propofol dose was injected into the vein over a period of 5 s. During the injection of both pretreatment solution and propofol, patients' pain was assessed and recorded as 0-3, corresponding to no, mild, moderate or severe pain, respectively. Chi2 and Kruskal-Wallis tests were used for the statistical analysis. For all analyses, differences were considered to be significant at P<0.05.

RESULTS

Patient characteristics were similar among the groups. Incidence of pain on injection of propofol in control, i.v. acetaminophen, and lidocaine groups was 64%, 22% and 8%, respectively (P<0.05).

CONCLUSIONS

Pretreatment with i.v. acetaminophen seems to be effective in attenuating pain during i.v. injection of propofol.

Comparison of diphenhydramine and lidocaine for prevention of pain after injection of propofol

BACKGROUND AND OBJECTIVE

Pain on injection is still a problem with propofol. The purpose of the study was to compare the effectiveness of diphenhydramine and lidocaine on pain caused by propofol at the site of injection.

METHODS

One hundred and eighty ASA I-II adults undergoing elective surgery were randomly assigned into three groups of 60 each. Group I (placebo) received 2 mL normal saline, Group II received 2 mL (40 mg) 2% lidocaine and Group III received 2 mL (20 mg) diphenhydramine intravenously (i.v.) during a 1-min venous occlusion, followed by propofol into a cephalic forearm vein of the antecubital fossa. Pain assessment was made immediately after propofol injection.

RESULTS

In the placebo group 25 (41.7%) patients experienced pain during propofol injection as compared to 2 (3.3%) and 3 (5.0%) in the lidocaine and diphenhydramine groups, respectively. The prevalence of pain and pain score were significantly less in both the lidocaine and diphenhydramine groups than in the placebo group (P = 0.00). No difference was found between the diphenhydramine and lidocaine groups (P = 0.60).

CONCLUSION

Previous injection of diphenhydramine with venous occlusion can be considered as an alternative to lidocaine for reducing the prevalence of pain caused by injection of propofol into peripheral veins.

Extracellular cations sensitize and gate capsaicin receptor TRPV1 modulating pain signaling

Transient receptor potential (TRP) channels detect diverse sensory stimuli, including alterations in osmolarity. However, a molecular detector of noxious hypertonic stimuli has not yet been identified. We show here that acute pain-related behavior evoked by elevated ionic strength is abolished in TRP vanilloid subtype 1 (TRPV1)-null mice and inhibited by iodoresiniferatoxin, a potent TRPV1 antagonist. Electrophysiological recordings demonstrate a novel form of ion channel modulation by which extracellular Na+, Mg2+, and Ca2+ ions sensitize and activate the capsaicin receptor, TRPV1. At room temperature, increasing extracellular Mg2+ (from 1 to 5 mM) or Na+ (+50 mM) increased ligand-activated currents up to fourfold, and 10 mM Mg2+ reduced the EC50 for activation by capsaicin from 890 to 450 nM. Moreover, concentrations of divalent cations >10 mM directly gate the receptor. These effects occur via electrostatic interactions with two glutamates (E600 and E648) formerly identified as proton-binding residues. Furthermore, phospholipase C-mediated signaling enhances the effects of cations, and physiological concentrations of cations contribute to the bradykinin-evoked activation of TRPV1 and the sensitization of the receptor to heat. Thus, the modulation of TRPV1 by cationic strength may contribute to inflammatory pain signaling.