Pharmacologic Properties of Novel Local Anesthetic Agents in Anesthesia Practice

Beta-blocker carteolol and oxprenolol produce cutaneous analgesia in response to needle pinpricks in the rat

BACKGROUND

This present study was undertaken to determine whether beta-blockers produce the cutaneous analgesic effect, comparing them with the long-acting local anesthetic bupivacaine.

METHODS

Using a rat model of infiltrative cutaneous analgesia, the effect of 5 beta-blockers (oxprenolol, carteolol, butaxamine, metoprolol, and acebutolol) and bupivacaine was compared and eventually combined with epinephrine.

RESULTS

Among 5 beta-blockers, oxprenolol exhibited the most potent and the longest duration of cutaneous analgesia. In dose-response studies, the rank order of efficacy (ED₅₀ [50% effective dose]) was bupivacaine (0.40 [0.35-0.47] μmol) > oxprenolol (2.33 [2.06-2.64] μmol) > carteolol (4.86 [4.27-5.53] μmol) (p< 0.01). Carteolol provoked a longer duration of analgesia (p< 0.01) than oxprenolol or bupivacaine on an equipotent basis (ED₂₅, ED₅₀, and ED₇₅). Adding epinephrine 1:200,000 to drug preparations (carteolol, oxprenolol, and bupivacaine) at ED₉₅ had a peripheral action in prolonging the duration of action.

CONCLUSIONS

Oxprenolol and carteolol had greater potencies and longer durations of cutaneous analgesia than butaxamine, metoprolol, and acebutolol. Oxprenolol produced a similar duration of action when compared to bupivacaine, while carteolol had a greater duration of action than bupivacaine. Cutaneous analgesia of oxprenolol (or carteolol) plus adrenaline was greater than that of bupivacaine plus adrenaline.

Laparoscopic guided liposomal bupivacaine injection compared to transversus abdominus plane block for postoperative pain after robotic gynecologic oncology surgery

OBJECTIVE

The purpose of this study was to determine if laparoscopically guided transversus abdominis plane block (Lap-Tap) with liposomal bupivacaine provides superior postoperative pain control when compared to ultrasound-guided block (US-Tap) with liposomal bupivacaine at the time of robotic surgery for gynecology oncology patients.

METHODS

This was a prospective randomized controlled trial assigning patients to one of two cohorts: Cohort 1 consisted of US-Tap administered before the procedure using liposomal bupivacaine, Cohort 2 consisted of Lap-Tap administration with laparoscopic visualization using the medication above. Primary outcomes were pain scores and total opioid use in Oral Morphine Equivalents (OME) during the first 72 h after surgery. Secondary outcomes were postoperative pain satisfaction and oral narcotic requirements.

RESULTS

There was a significant increase in oral narcotic use in the first 24 h in the US-Tap cohort compared to the Lap-Tap cohort: Lap-Tap mean = 6.73 ± 8.22 OME versus US-Tap mean = 12.69 ± 12.94 p = 0.018 OME. The increase was equivalent to one additional Hydrocodone-Acetaminophen 7.5 mg/325 mg in the first 24 h after surgery. However, total oral narcotic use over the first 72 h was not significantly different between the two cohorts: Lap-Tap mean = 21.73 ± 19.83 OME, US-Tap mean = 32.50 ± 29.47, p = 0.062 OME. In addition, there was no significant difference in satisfaction or pain scores between the US-Tap and Lap-Tap groups at 24, 48, or 72-hours.

CONCLUSIONS

Lap-Taps are comparable to US-Tap for postoperative analgesia during the first 72-h after surgery when performing robotic-assisted gynecologic oncology surgery.

Novel Local Anesthetics in Clinical Practice: Pharmacologic Considerations and Potential Roles for the Future

The treatment of pain, both acute and chronic, has been a focus of medicine for generations. Physicians have tried to develop novel ways to effectively manage pain in surgical and post-surgical settings. One intervention demonstrating efficacy is nerve blocks. Single-injection peripheral nerve blocks (PNBs) are usually preferred over continuous PNBs, since they are not associated with longer lengths of stay. The challenge of single injection PNBs is their length of duration, which at present is a major limitation. Novel preparations of local anesthetics have also been studied, and these new preparations could allow for extended duration of action of anesthetics. An emerging preparation of bupivacaine, exparel, uses a multivesicular liposomal delivery system which releases medication in a steady, controlled manner. Another extended-release local anesthetic, HTX-011, consists of a combination of bupivacaine and low-dose meloxicam. Tetrodotoxin, a naturally occurring reversible site 1 sodium channel toxin derived from pufferfish and shellfish, has shown the potential to block conduction of isolated nerves. Neosaxitoxin is a more potent reversible site 1 sodium channel toxin also found in shellfish that can also block nerve conduction. These novel formulations show great promise in terms of the ability to prolong the duration of single injection PNBs. This field is still currently in development, and more researchers will need to be done to ensure the efficacy and safety of these novel formulations. These formulations could be the future of pain management if ongoing research continues to prove positive effects and low side effect profiles.

From Poison to Promise: The Evolution of Tetrodotoxin and Its Potential as a Therapeutic

Tetrodotoxin (TTX) is a potent neurotoxin that was first identified in pufferfish but has since been isolated from an array of taxa that host TTX-producing bacteria. However, determining its origin, ecosystem roles, and biomedical applications has challenged researchers for decades. Recognized as a poison and for its lethal effects on humans when ingested, TTX is primarily a powerful sodium channel inhibitor that targets voltage-gated sodium channels, including six of the nine mammalian isoforms. Although lethal doses for humans range from 1.5-2.0 mg TTX (blood level 9 ng/mL), when it is administered at levels far below LD₅₀, TTX exhibits therapeutic properties, especially to treat cancer-related pain, neuropathic pain, and visceral pain. Furthermore, TTX can potentially treat a variety of medical ailments, including heroin and cocaine withdrawal symptoms, spinal cord injuries, brain trauma, and some kinds of tumors. Here, we (i) describe the perplexing evolution and ecology of tetrodotoxin, (ii) review its mechanisms and modes of action, and (iii) offer an overview of the numerous ways it may be applied as a therapeutic. There is much to be explored in these three areas, and we offer ideas for future research that combine evolutionary biology with therapeutics. The TTX system holds great promise as a therapeutic and understanding the origin and chemical ecology of TTX as a poison will only improve its general benefit to humanity.

"Shooting pain" in lumbar radiculopathy and trigeminal neuralgia, and ideas concerning its neural substrates

Patients with radicular low back pain (radicular LBP, sciatica) frequently describe their pain as "shooting" or "radiating." The dictionary meaning of these words implies rapid movement, and indeed, many sufferers report feeling pain moving rapidly from the lower back or buttock into the leg. But, others do not. Moreover, the sensation of movement is paradoxical; it is neither predicted nor accounted for by current ideas about the pathophysiology of radicular LBP. We have used a structured questionnaire to evaluate the sensory qualities associated with "shooting" and "radiating" in 155 patients, 98 with radicular LBP and 57 with trigeminal neuralgia, a second chronic pain condition in which shooting/radiating are experienced. Results indicated a spectrum of different sensations in different people. Although many sciatica patients reported rapid downward movement of their pain, even more reported downward expansion of the area of pain, some reported upward movement, and for some, there was no spatial dynamic at all. The velocity of movement or expansion was also variable. By cross-referencing sensations experienced in the sciatica and trigeminal neuralgia cohorts with known signal processing modes in the somatosensory system, we propose testable hypotheses concerning the pathophysiology of the various vectorial sensations reported, their direction and velocity, and the structures in which they are generated. Systematic evaluation of qualitative features of "shooting" and "radiating" pain at the time of diagnosis can shed light on the pain mechanism in the individual patient and perhaps contribute to a better therapeutic outcomes.

Antimalarial primaquine for skin infiltration analgesia in rats

OBJECTIVES

The purpose of this study was to estimate the ability of antimalarial medications to induce local infiltration analgesia.

METHODS

Using a rat model of skin infiltration anaesthesia, the effects of antimalarial medications (primaquine, chloroquine, hydroxychloroquine and amodiaquine) were compared with the application of lidocaine.

KEY FINDINGS

At a dose of 3 μmol, primaquine and chloroquine displayed better potency (all P < 0.05) and greater duration (all P < 0.01) of cutaneous analgesia than lidocaine, whereas the other antimalarial medications showed a similar potency and duration of cutaneous analgesia when compared with lidocaine. When a dose of 3 μmol antimalarial medication was used, primaquine was the most potent and had the longest duration of action among four antimalarial medications. The relative potency ranking (ED50, 50% effective dose) has been found to be primaquine [2.10 (1.87 - 2.37) μmol] > lidocaine [6.27 (5.32 -7.39) μmol] (P < 0.01). Infiltration analgesia of skin with primaquine had a greater duration of action than did lidocaine on the equipotent (ED25, ED50, ED75) basis (P < 0.01).

CONCLUSIONS

Primaquine and chloroquine have greater potency and longer lasting skin analgesia when compared with lidocaine, while the other antimalarials display a similar potency in comparison with lidocaine.

Towards the advance of a novel iontophoretic patch for needle-free buccal anesthesia

The aim of this work was to develop a mucoadhesive iontophoretic patch for anesthetic delivery in the buccal epithelium. The patch was comprised of three different layers, namely i) drug release (0.64 cm²); ii) mucoadhesive (1.13 cm²); and iii) backing (1.13 cm²). Prilocaine and lidocaine hydrochlorides were used as model drugs (1:1 ratio, 12.5 mg per unit). An anode electrode (0.5 cm² spiral silver wire) was placed in between the drug release and mucoadhesive/backing layers to enable iontophoresis. Surface microscopy; mechanical and in vitro mucoadhesive properties; drug release kinetics and mechanism; and drug permeation through the porcine esophageal epithelium were assessed. Topographic analysis evidenced differences in the physical structures for the several layers. All layers presented suitable handling properties i.e., flexibility, elasticity and resistance. Both the release and mucoadhesive layers presented features of a soft and tough material, while the backing layer matched the characteristics of a hard and brittle material. A synergy between the drug release and mucoadhesive layers on the mucoadhesive force and work of adhesion of the tri-layered patch was observed. Passive drug release of both drugs fitted to First-order, Hixson-Crowell and Weibull kinetic models; and the release mechanism was attributed to anomalous transport. Iontophoresis remarkably enhanced the permeation of both drugs, but mainly prilocaine through the mucosa as evidenced by the permeability coefficient parameter (3.0-fold). The amount of these amino amide salts retained in the mucosa were also equally enhanced (4.7-fold), while the application of a tiny constant electric current (1 mA·cm^-2·h^-1) significantly decreased the lag time for lidocaine permeation by about 45%. In view of possible in vitro / in vivo correlations, the buccal iontophoretic patch displays a promising strategy for needle-free and patient-friendly local anesthesia in dentistry.

Epicardial Interventions: Impact of Liposomal Bupivacaine on Postprocedural Management (The EPI-LIBRE Study)

Background:

Electrophysiological procedures such as epicardial ventricular tachycardia ablation and Lariat left atrial appendage ligation that involve the epicardial space are typically associated with significant postoperative pain due to mechanical irritation and associated inflammation. There is an unmet need for an effective pain management strategy in this group of patients. We studied how this impacts patient comfort and duration of hospitalization and other associated comorbidities related to pericardial access.

Methods:

This is a multicenter retrospective study including 104 patients who underwent epicardial ventricular tachycardia ablation and Lariat left atrial appendage exclusion. We compared 53 patients who received postprocedural intrapericardial liposomal bupivacaine (LB)+oral colchicine (LB group) and 51 patients who received colchicine alone (non-LB group) between January 2015 and March 2018.

Results:

LB was associated with significant lowering of median pain scale at 6 hours (1.0 [0–2.0] versus 8.0 [6.0–8.0], P <0.001), 12 hours (1.0 [1.0–2.0] versus 6.0 [5.0–6.0], P <0.001), and up to 48 hours postprocedure. Incidence of acute severe pericarditis delayed pericardial effusion and gastrointestinal adverse effects were similar in both groups. Median length of stay was significantly lower in LB group (2.0 versus 3.0; adjusted linear coefficient −1 [CI −1.3 to −0.6], P <0.001). Subgroup analysis demonstrated similar favorable outcomes in both Lariat and epicardial ventricular tachycardia ablation groups.

Conclusions:

Addition of intrapericardial postprocedural LB to oral colchicine in patients undergoing epicardial access during ventricular tachycardia ablation or Lariat procedure is associated with significantly decreased numeric pain score up to 48 hours compared with colchicine alone. It is also associated with significantly shorter length of hospital stay without an increase in the risk of adverse events.

Dexamethasone and dexmedetomidine as adjuvants to local anesthetic mixture in intercostal nerve block for thoracoscopic pneumonectomy: a prospective randomized study

BACKGROUND AND OBJECTIVES

Perineural dexamethasone or dexmedetomidine prolongs the duration of single-injection peripheral nerve block when added to the local anesthetic solution. In a randomized, controlled, double-blinded study in patients undergoing thoracoscopic pneumonectomy, we tested the hypothesis that combined perineural dexamethasone and dexmedetomidine prolonged the duration of analgesia as compared with either perineural dexamethasone or perineural dexmedetomidine after intercostal nerve block (INB).

METHODS

Eighty patients were randomized to receive INB using 28 mL 0.5% ropivacaine, with 2 mL normal saline (R group), with 10 mg dexamethasone in 2 mL (RS group) or 1 µg/kg dexmedetomidine in 2 mL (RM group), or with 1 µg/kg dexmedetomidine and 10 mg dexamethasone in 2 mL (RSM group) administrated perineurally. The INB was performed by the surgeon under thoracoscopic direct vision; a total of six intercostal spaces were involved, each with an injection of 5 mL. The primary outcome was the duration of analgesia. Secondary outcomes included total postoperative fentanyl consumption, visual analog scale pain score and safety assessment (adverse effects).

RESULTS

The duration of analgesia in RSM (824.2±105.1 min) was longer than that in RS (611.5±133.0 min), RM (602.5±108.5 min) and R (440.0±109.6 min) (p<0.001). Total postoperative fentanyl consumption was lower in RSM (106.0±84.0 µg) compared with RS (243.0±175.2 µg), RM (237.0±98.7 µg) and R (369.0±134.2 µg) (p<0.001). No significant difference was observed in the incidences of adverse effects between the four groups.

CONCLUSION

The addition of combined perineural dexmedetomidine and dexamethasone to ropivacaine for INB seemed to be an attractive method for prolonged analgesia with almost no adverse effects.

TRIAL REGISTRATION NUMBER

ChiCTR-IOR-17012183.

Comparison of Intra-Socket Bupivacaine Administration Versus Oral Mefenamic Acid Capsule for Postoperative Pain Management Following Removal of Impacted Mandibular Third Molars

PURPOSE

Surgical removal of impacted third molar teeth is one of the most common surgical procedures performed in oral and maxillofacial surgery. Postoperative pain is a common and predictable occurrence after maxillofacial surgery.

MATERIALS AND METHODS

This randomized double-blind clinical trial was conducted with a crossover design in which each patient served as his or her own control. Forty-six patients with similar bilateral impacted lower third molars were selected. In each patient, the intervention and control sides of the mandible were randomly determined at the end of surgery. If the removed tooth was in the intervention side, then the patient would receive bupivacaine and a placebo of mefenamic acid. If the impacted tooth was in the control side, then the patient would receive a mefenamic acid capsule and a placebo of bupivacaine. Pain severity was assessed using a visual analog scale. Data were analyzed using paired-sample t test and a P value less than .05 was considered statistically significant.

RESULTS

Of 46 participants originally recruited, 43 were included in the present study. The mean postoperative pain score in patients who received bupivacaine was increased to a maximum 4 hours, with marked improvements after this time. The mean intensity of pain after administration of bupivacaine was lower than that of mefenamic acid capsules at different time points. Statistical analysis showed a relevant difference in pain intensity between the 2 study groups.

CONCLUSION

The results of the present study showed that local administration of bupivacaine relieves postoperative pain after surgical removal of impacted third molar teeth.

A Comparative Study on Efficacy and Safety of Propofol versus Dexmedetomidine in Sleep Apnea Patients undergoing Drug-Induced Sleep Endoscopy: A CONSORT-Prospective, Randomized, Controlled Clinical Trial

The aim of this study is to compare the efficacy and safety of propofol with dexmedetomidine in patients with obstructive sleep apnea hypopnea syndrome (SAHS) undergoing drug-induced sleep endoscopy (DISE). The 88 patients diagnosed with SAHS in the Affiliated Hospital of Xuzhou Medical University were randomly allocated into 2 groups (n = 44). Patients in the group dexmedetomidine (group D) received continuous intravenous infusion of dexmedetomidine 1 μg/kg over 15 minutes before the endoscopy, and propofol 2 mg/kg was intravenously administrated in the group propofol (group P). Cardiopulmonary parameters of patients were recorded. The time to fall asleep, duration of endoscopic examination, the wakeup time of patients, the number of mask ventilations for patients, the satisfaction of patients and endoscopic performers, and false positive cases of SAHS of patients were compared between the two groups. Compared with group D, mean arterial pressure (MAP) and blood oxygen saturation (SPO₂) of patients in the P group were lower at the time point of T1 (P < 0.05), the duration of endoscopic examination and wakeup time of patients were obviously prolonged, the incidence of mask ventilation for patients and false positive cases of SAHS of patients was observably higher, and the satisfaction of endoscopic performers was markedly lower, but the time to fall asleep was significantly shortened (P < 0.05). Dexmedetomidine served as a novel sleep induced drug and can provide satisfactory conditions and be safely and effectively applied for endoscopy in patients with SAHS, without adverse hemodynamic effects.

Delivery systems of local anesthetics in bone surgery: are they efficient and safe?

Management of postoperative pain following bone surgery includes administration of local anesthetics (LAs). Smart delivery systems, including triggered systems, have been designed to provide a continuous release of LA in situ. However, these systems can provide a high level of LA locally. This review will examine the state-of-the-art regarding the LA delivery systems optimized for management of postoperative pain in bone surgery and will discuss the potential adverse effects of LAs on the overall pathways of bone healing, including the inflammation response phase, hemostasis phase, tissue repair phase and remodeling phase. There is a clinical need to document these effects and the potential impacts on the clinical outcome of the patient.

The Role of Transversus Abdominis Plane Blocks in Enhanced Recovery After Surgery Pathways for Open and Laparoscopic Colorectal Surgery

INTRODUCTION

The concepts of Enhanced Recovery After Surgery (ERAS^®) have steadily increased in usage, with benefits in patient outcomes and hospital length of stay. One important component of successful implementation of ERAS protocol is optimized pain control, via the multimodal approach, which includes neuraxial or regional anesthesia techniques and reduction of opioid use as the primary analgesic. Transversus abdominis plane (TAP) block is one such regional anesthesia technique, and it has been widely studied in abdominal surgery.

MATERIALS AND METHODS

We performed an extensive literature search in MEDLINE and PubMed. We review the benefits of TAP blocks for colorectal surgery, both laparoscopic and open. We organize the data by surgery type, by method of TAP block performance, and by a comparison of TAP block to alternative analgesic techniques or to placebo. We examine different endpoints, such as postoperative pain, analgesic use, return of bowel function, and length of stay.

RESULTS

The majority of studies examined TAP blocks in the context of laparoscopic colorectal surgery, with many, but not all, demonstrating significantly less use of postoperative opioids in comparison to placebo, wound infiltration, and standard postoperative patient-controlled analgesia with intravenous opioid administration. There is evidence that use of liposomal bupivacaine may be more effective than conventional long-acting local anesthetics. Noninferiority of TAP infusions has been demonstrated, compared with continuous thoracic epidural infusions.

CONCLUSION

TAP blocks are easily performed, cost-effective, and an opioid-sparing adjunct for laparoscopic colorectal surgery, with minimal procedure-related morbidity. The evidence is in concordance with several of the goals of ERAS pathways.