Shortened Onset Time Research Articles

The effects of subtenon and intravenous dexmedetomidine on patients undergoing cataract surgery: A comparative randomized controlled double-blind study.

This prospective randomized study designed to evaluate the efficacy of dexmedetomidine either added to LA mixture or administered IV during subtenon block for cataract surgery. 75 patients, undergoing cataract surgery with subtenon anesthesia, were assigned randomly into three equal groups, Group I received subtenon bupivacaine 0.5% (1 ml) + lidocaine 2% (1 ml) + saline 0.9% (0.5 ml) and IV infusion of normal saline. Group II received subtenon bupivacaine 0.5% (1 ml) + lidocaine 2% (1 ml) + 0.5 μg/kg dexmedetomidine (0.5 ml) and IV infusion of normal saline. Group III received subtenon bupivacaine 0.5% (1 ml) + lidocaine 2% (1 ml) + saline 0.9% (0.5 μl) and IV infusion of 0.5 mg/kg dexmedetomidine over 10 min. before subtenon block. We recorded onset and duration of sensory and motor block, pain during subtenon injection, intraoperative hemodynamics, intraocular pressure, sedation and postoperative pain score. There was a significant decrease in the onset of action and an increase in the duration of sensory block in Group II. Pain during subtenon injection was significantly less in group III. Sedation Score was higher in Group III, while heart rate showed a significant reduction in the same group. The VAS was significantly decreased in group II. After the end of surgery, the intraocular pressure was significantly decreased in Groups II and III. Subtenon dexmedetomidine shortens onset time, prolongs sensory block durations and significantly decreases the postoperative pain score with hemodynamic stability, while, IV dexmedetomidine substantially reduces pain during subtenon block and produces intra-operative sedation.

Effects of Energy Drink and Alcohol Mixed with Energy Drink on Pentylenetetrazol-Induced Seizures in Rats.

Energy drink consumption is on an upswing with reportedly significant health problems associated with its consumption. Additionally, it is one of the most preferred products used in combination with alcohol. The present study aimed to investigate the effects of energy drink and alcohol mixed energy drink (AmED) on epileptic seizures. Adult female (250-350 g) Wistar rats were divided into five groups (n=8 for each group). Caffeine (3.43 mg/kg) was injected through the intraperitoneal (IP) route and alcohol (3.4 g/kg), energy drink (10.71 ml/kg), and AmED were given to the rats via intragastric intubation for 14 days. On the first, seventh, and fourteenth days of the experiment, pentylenetetrazole (PTZ) (60 mg/kg IP) was injected into the rats. The onset time and severity of seizures were evaluated immediately after PTZ. Both caffeine and energy drink caused a significant decrease in the onset time of the seizures. Energy drink showed a significantly shorter onset time than caffeine on the seventh (p=0.045) and fourteenth (p=0.048) day. Energy drink significantly increased the severity of PTZ-induced seizures (p s<0.01). Caffeine also produced significant increase in the severity of the seizures on the first (p=0.013) and fourteenth (p=0.047) day. Alcohol and AmED significantly shortened onset time of the seizures on the seventh (p=0.028 and p=0.016) and fourteenth day (p=0.039 and p=0.04), respectively. Both alcohol and AmED significantly decreased the severity of PTZ-induced seizures all observation intervals (p s<0.0001). Our results suggest that energy drink and AmED produced some significant unfavorable effects on PTZ-induced seizures. They may be dangerous in patient with epilepsy and individuals prone to seizure.

Dexmedetomedine-As an Adjuvant to Epidural Analgesia: Comparison Between Different Doses

Background: Epidural analgesia offers superior pain relief and early mobilization, especially when a local anesthetic [LA] dose is combined with an adjuvant vs. an LA alone. Objective: The current study compares the analgesic and anesthetic efficiency of dexmedetomidine (1 and 2 μgkg-1) and levobupivacaine, as well as their respective side effects. Materials and methods: This study was conducted on a total of 60 ASA I-II patients aged between 20 and 70 years, who underwent elective lower limb operations. The patients that received 1 μgkg-1 dexmedetomidine plus levobupivacaine were assigned to Group 1 (n=30) and those that received 2 μgkg-1 dexmedetomidine plus levobupivacaine to Group 2 (n=30). Results: Group 2 showed a significantly shortened onset time of sensory block, time needed for maximum sensory level and prolonged duration of anesthesia. Postoperatively, the total dose of levobupivacaine used was significantly lower, patients experienced a higher level of sedation and postoperative analgesia. However, Bradycardia and hypotension were more pronounced in Group 2 patients. Conclusion: Dexmedetomedine 2 μgkg-1 as an adjuvant to epidural analgesia significantly prolonged the duration of anesthesia and provided excellent sedation and postoperative analgesia. Therefore, higher doses of epidural dexmedetomedine are recommended in long surgical operations to avoid delayed motor recovery, bradycardia and hypotension.

Dexmedetomidine versus fentanyl as adjuvant to epidural 0.5% levobupivacaine for transurethral prostate resection in elderly patients: a comparative evaluation

Background Regional anesthesia is the technique of choice for patients undergoing transurethral resection of the prostate (TURP), but anesthetic management of elderly patients is challenging due to compromised organ function. The present study aimed to evaluate the relative efficacy and safety of dexmedetomidine versus fentanyl in the enhancement of the quality and duration of epidural anesthesia with 0.5% levobupivacaine and hemodynamic stability during TURP in elderly patients. Patients and methods Sixty elderly consented patients were randomized into two equal groups of 30 patients each in a double-blind manner. They were given 15 ml of 0.5% levobupivacaine (75 mg) either with 1 ml (50 μg) dexmedetomidine (group LD) or with 1 ml (50 μg) fentanyl (group LF) using an epidural catheter. The primary endpoints were the onset and duration of sensory and motor blockade, duration of sensory analgesia, hemodynamic variability, respiratory adequacy, and any adverse effect. Results Demographic data were comparable in both groups. Onset of sensory and motor blockade was faster in patients of group LD than in patients of group LF, with a statistically significant difference ( P P Conclusion Dexmedetomidine as an adjuvant to epidural levobupivacaine for TURP has shortened onset time of anesthesia and prolonged duration of sensory analgesia. The surgical field vision was improved due to reduced bleeding.

Dexmedetomidine as an additive to local anesthetics compared with intravenous dexmedetomidine in peribulbar block for cataract surgery.

Background:No studies compared parenteral dexmedetomidine with its use as an adjuvant to ophthalmic block. We compared between adding dexmedetomidine to bupivacaine in peribulbar block and intravenous (IV) dexmedetomidine during peribulbar block for cataract surgery.Materials and Methods:A prospective, randomized, double-blind study on 90 patients for cataract surgery under peribulbar anesthesia. Study included three groups; all patients received 10 ml of peribulbar anesthesia and IV infusion of drugs as follows: Group I: Received a mixture of bupivacaine 0.5% (4.5 ml) + lidocaine 2% (4.5 ml) + normal saline (1 ml) + 150 IU hyaluronidase + IV infusion of normal saline, Group II: Received mixture of bupivacaine 0.5% (4.5 ml) + lidocaine 2% (4.5 ml) + dexmedetomidine 50 μg (1 ml) +150 IU hyaluronidase + IV infusion of normal saline and Group III: Received mixture of bupivacaine 0.5% (4.5 ml) + lidocaine 2% (4.5 ml) + normal saline (1 ml) +150 IU hyaluronidase + IV dexmedetomidine 1 μg/kg over 10 min; followed by 0.4 μg/kg/h IV infusion. We recorded onset, duration of block, Ramsay Sedation Score, intra-ocular pressure (IOP), hemodynamics, and adverse effects.Results:There was a significant decrease in the onset of action and increase in the duration of block in Group II as compared with the Group I and Group III. Mean Ramsay Sedation Score was higher in Group III. The IOP showed a significant decrease in Group II and Group III 10 min after injection (P < 0.01). Heart rate showed a significant decrease in Group III in comparison with the two other groups (P < 0.05). Only two patients in Group III developed bradycardia.Conclusion:Dexmedetomidine as an additive shortens onset time, prolong block durations and significantly decreases the IOP with minimal side effects. IV dexmedetomidine, in addition, produces intra-operative sedation with hemodynamic stability.

Enhanced CO2 Storage and Sequestration in Deep Saline Aquifers by Nanoparticles: Commingled Disposal of Depleted Uranium and CO2

Geological storage of anthropogenic CO2 emissions in deep saline aquifers has recently received tremendous attention in the scientific literature. Injected buoyant CO2 accumulates at the top part of the aquifer under a sealing cap rock. Potential buoyant movement of CO2 has caused some concern that the high-pressure CO2 could breach the seal rock. However, CO2 will diffuse into the brine underneath and generate a slightly denser fluid that may induce instability and convective mixing. Onset times of instability and convective mixing performance depend on the physical properties of the rock and fluids, such as permeability and density contrast. We present the novel idea of adding nanoparticles (NPs) to injected CO2 to increase density contrast between the CO2-rich brine and the underlying resident brine and, consequently, decrease onset time of instability and increase convective mixing. The analyses show that 0.001 volume fraction of NPs added to the CO2 stream shortens onset time of mixing by approximately 80% and increases convective mixing by 50%. If it thus originally takes 5 years for the overlying CO2 to start convective mixing, by adding NPs, onset time of mixing reduces to 1 year, and after initiation of convective mixing, mixing improves by 50%. A reduction of the CO2 leakage risk ensues. In addition to other metallic NPs, use of processed depleted uranium oxide (DU) as the NPs is also proposed. DU-NPs are potentially stable and might be safely commingled with CO2 to store in saline aquifers.

Ultrasound-Guided Popliteal Block Shortens Onset Time Compared to Prebifurcation Sciatic Block

Ultrasound-Guided Popliteal Block Shortens Onset Time Compared to Prebifurcation Sciatic Block

Intravenous regional anesthesia using lidocaine and neostigmine for upper limb surgery

Study Objective To evaluate the effect of adding neostigmine to lidocaine in intravenous regional anesthesia (IVRA). Design Randomized, double-blinded study. Setting Tertiary-care academic medical institution. Patients 40 ASA physical status I and II patients scheduled for elective or emergency forearm and hand surgery. Intervention Patients were randomized to two groups of 20 patients each. In the control group, IVRA was established using 40 mL of 0.5% lidocaine with one mL of isotonic saline, while neostigmine group patients received 40 mL of 0.5% lidocaine with 0.5 mg neostigmine. Measurements Hemodynamic parameters, onset and recovery times of sensory and motor blocks, and quality of anesthesia achieved with IVRA were recorded. After tourniquet deflation, visual analog pain scores (VAS) were noted every 30 minutes in the first two hours, as were the time to first analgesic request and total analgesic requirement in the 24-hour postoperative period. Main Results In the first 24 hours after surgery, the neostigmine group had significantly lower VAS scores, longer time to first analgesic request, and reduced total analgesic requirement. Intraoperatively, the neostigmine group had significantly shorter sensory and motor block onset times and longer recovery times than the control group. No significant frequency of adverse effects was seen in either group. The quality of intraoperative anesthesia and frequency of tourniquet pain were similar in both groups. Conclusions The addition of neostigmine to lidocaine shortens onset time and improves postoperative analgesia in IVRA for upper limb surgery.

Ultrasound-Guided Popliteal Block Distal to Sciatic Nerve Bifurcation Shortens Onset Time

Popliteal sciatic nerve block (SNB) in combination with saphenous nerve block provides anesthesia and analgesia for foot and ankle surgeries. Landmark-based and image-guided techniques, to date, aim at blocking the sciatic nerve proximal to its bifurcation. Sciatic nerve block is usually associated with a long onset time (30-60 mins). We hypothesized that SNB distal to its bifurcation (blocking its 2 main branches tibial and common peroneal nerves separately) is associated with a shorter onset time than blockade proximal to its bifurcation. Fifty patients scheduled for major elective foot or ankle surgery were randomly allocated to receive ultrasound-guided SNB 5 cm proximal to (group P) or 3 cm distal to (group D) its bifurcation in the popliteal fossa. Thirty milliliters of a standardized local anesthetic solution of equal volumes of 2% lidocaine and 0.5% bupivacaine with 1:200,000 epinephrine was used. Sensory and motor assessments were performed every 5 mins by a blinded observer until complete sensory and motor blockade developed in both tibial and common peroneal nerve territories. All patients in both groups developed a complete block. Patients in group D presented a 30% shorter onset of both sensory (21.4 [SD, 9.9] vs 31.4 [SD, 13.9] mins) (P = 0.005) and motor block (21.5 [SD, 11.3] vs 32.4 [SD, 14.9] mins) (P = 0.006) than patients in group P. Procedure time, procedure-related discomfort, and patient satisfaction were similar in both groups. Our data suggest that popliteal SNB distal to the bifurcation has a shorter onset time than SNB proximal to its bifurcation, and therefore, it may be a good option when a fast onset for a surgical block is required.

Ketamine, but not priming, improves intubating conditions during a propofol–rocuronium induction

Both ketamine and priming may shorten the onset time of rocuronium. This study investigates the effects of ketamine and priming as components of a propofol induction on intubating conditions and onset of neuromuscular block. This prospective randomized double-blind study was performed in 120 American Society of Anesthesiologists (ASA) I-II patients who were assigned to one of four groups of 30 patients each: control, priming, ketamine, and ketamine-priming. Ketamine 0.5 mg x kg(-1) or saline was given before priming and induction. Rocuronium 0.06 mg x kg(-1) or saline was injected 2 min before propofol 2.5 mg x kg(-1). This was followed by rocuronium 0.6 mg x kg(-1) or by rocuronium 0.54 mg x kg(-1) if priming was given. Intubation was performed one minute later. Intubating conditions were graded as excellent, good, or poor. Heart rate, noninvasive blood pressure, and train-of-four (TOF) response were monitored. Intubating conditions were graded excellent in 20% of the control group, 30% of the priming group, 47% of the ketamine group, and 57% of the ketamine-priming group. Analysis using forward stepwise regression indicated that ketamine improved intubating conditions (P = 0.001) but priming did not (P = 0.35). Time to reach a TOF count of zero was shortened by ketamine (P = 0.001) but not by priming (P = 0.94): 216 +/- 20 s in the control group, 212 +/- 27 s in the priming group, 162 +/- 18 s in the ketamine group, and 168 +/- 22 s in the ketamine-priming group. A low-dose ketamine used with a propofol-rocuronium induction improved intubating conditions and shortened onset time. Priming did not influence intubating conditions or onset time.

Twitch Potentiation Influences the Time Course of Twitch Depression in Muscle Relaxant Studies: A Pharmacokinetic-Pharmacodynamic Explanation

The time course of twitch depression following neuromuscular blocking agent (NMBA) administration is influenced by the duration of control neuromuscular monitoring (twitch stabilization). The physiological mechanism for this interaction is not known. During twitch stabilization twitch response often increases to a plateau, this is known as twitch potentiation or the staircase phenomenon. Since twitch potentiation contributes to the observed twitch response it may also influence the time course of twitch depression following NMBA administration. Our objective was to estimate the degree that twitch potentiation influences the time course of twitch depression following NMBA administration under conditions typical for muscle relaxation studies. We used previousy described pharmacokinetic-pharmacodynamic (PK-PD) and twitch potentiation models to simulate twitch data. Simulations consisted of twitch stabilization followed by a NMBA bolus dose and subsequent onset and recovery from muscle relaxation. Twitch data were analyzed for onset and recovery characteristics and the results compared to clinical muscle relaxation studies in existing literature. We found that twitch potentiation likely plays a minor role in shortened onset time and increased duration of twitch depression observed with long periods of twitch stabilization.

Accidental Subdural Injection of Ropivacaine

Accidental Subdural Injection of Ropivacaine

Using Stimulating Catheters for Continuous Sciatic Nerve Block Shortens Onset Time of Surgical Block and Minimizes Postoperative Consumption of Pain Medication After Halux Valgus Repair as Compared with Conventional Nonstimulating Catheters

We prospectively tested the hypothesis that the use of a stimulating catheter improves the efficacy of continuous posterior popliteal sciatic nerve block in 100 randomized patients scheduled for elective orthopedic foot surgery. After eliciting a sciatic mediated muscular twitch at < or = 0.5 mA nerve stimulation output, the perineural catheter was advanced 2-4 cm beyond the tip of the introducer either blindly (Group C; n = 50) or stimulating via the catheter (Group S; n = 50). A bolus dose of 25 mL of 1.5% mepivacaine was followed by a postoperative patient-controlled infusion of 0.2% ropivacaine (basal infusion: 3 mL/h; incremental dose: 5 mL; lockout time: 30 min). Propacetamol 2 g IV was administered every 8 h, and opioid rescue analgesia was available if required. Catheter placement required 7 +/- 2 min in Group S and 5 +/- 2 min in Group C (P = 0.056). A significantly shorter onset time of both sensory and motor blocks was noted in Group S. No difference in quality of pain relief at rest and during motion was reported between the groups. Median (range) local anesthetic consumption during the first 48 h after surgery was 239 mL (175-519 mL) and 322 mL (184-508 mL) in Groups S and C, respectively (P = 0.002). Rescue opioid analgesia was required by 12 (25%) and 28 (58%) patients in Groups S and C, respectively (P = 0.002). We conclude that the use of a stimulating catheter results in shorter onset time of posterior popliteal sciatic nerve block, similar pain relief with reduced postoperative consumption of local anesthetic solution, and less rescue opioid consumption. This prospective, randomized, blind investigation demonstrated that the use of a stimulating catheter for continuous posterior popliteal sciatic nerve block resulted in shorter onset time of sensory and motor blocks and less local anesthetic consumption and need for rescue pain medication after elective orthopedic foot surgery compared with blind catheter advancement.

The Hemodynamic Effects of Ephedrine on the Onset Time of Rocuronium in Pigs

Several studies have found a correlation between the onset time of muscle relaxants, cardiac index, and muscle blood flow. Ephedrine increases these hemodynamic variables and shortens onset time of rocuronium in humans. Our aim in this animal study was to determine the effect of ephedrine on the onset time of rocuronium, cardiac index, and muscle blood flow after administration of thiopental. At predefined measuring points, mean arterial blood pressure and cardiac index were measured invasively and onset time was determined mechanomyographically. Twenty-four pigs were randomly assigned to three groups. Group I received etomidate and subsequently rocuronium (2 x 95% effective dose). Instead of etomidate, Group II received thiopental. In Group III, ephedrine 100 mug/kg was given before thiopental; additionally, muscle blood flow was measured (fluorescent microspheres). Although there were differences in hemodynamics between Groups I and II, this was not reflected in different onset times of rocuronium. In Group III, ephedrine compensated the thiopental-induced decrease of mean arterial blood pressure, cardiac index, and muscle blood flow, but no significant shortening of onset time (Group I: 74 +/- 21 s; Group II: 71 +/- 24; Group III: 69 +/- 22 s) was found. Our results demonstrated that ephedrine-related increases in cardiac index and blood flow did not shorten onset time of rocuronium in healthy pigs.

Distinct roles of peroxynitrite and hydroxyl radical in triggering stunned myocardium-like impairment of cardiac myocytes in vitro.

Myocardial stunning is characterized by the impairment of excitation-contraction coupling via a decrease in myofilament Ca2+ responsiveness, thought to be triggered by hydroxyl radicals (*OH) generated upon reperfusion. Since peroxynitrite is also expected to be produced during reperfusion, we examined whether it can induce a stunned myocardium-like impairment of cardiac myocytes. Its effect on cultured cardiac myocytes was compared with that of hydrogen peroxide (H2O2), *OH source. Infusion of peroxynitrite (0.2 mM) induced a decrease in cell motion and a complete arrest in diastole at 2.9 +/- 0.3 min, which coincided with an elevation in [Ca2+]i. Arrest induced by infusion of H2O2 (10 mM) was not associated with an increase in [Ca2+]i. The ATP content was unaffected by peroxynitrite (control, 34.3 +/- 3.4: + peroxynitrite, 32.9 +/- 3.5 nmol/mg protein) and the cells remained viable. Sulfhydryl (SH) content was decreased by peroxynitrite, but not by H2O2. The membrane fluidity (a measure of peroxidation of the membrane lipids) was not affected by peroxynitrite, but was decreased by H2O2. Onset time of arrest was unaffected by deferoxamine (0.2 mM), but was delayed by DTT (10 mM) (from 2.9 +/- 0.3 to 19.2 +/- 1.6 min). Nitrotyrosine content was unchanged by peroxynitrite, and its augmentation with Fe3+/EDTA (1 mM) was not associated with a shortened onset time of arrest. The function of the Na+/Ca2+ exchanger was impaired by peroxynitrite, but not by H2O2. Peroxynitrite and H2O2 each induce arrest, but only the former increases [Ca2+]i. One of the mechanisms of the increase in [Ca2+]i is Na/Ca2+ exchanger dysfunction. The impairments were induced through SH oxidation by peroxynitrite, but through lipid peroxidation by H2O2. Myocardial stunning may be induced by both species in concert.

Nasal absorption kinetics of human growth hormone enhanced by acylcarnitines in rats

Pharmacokinetic analysis revealed that acylcarnitines enhanced overall nasal absorption of human growth hormone (HGH) in rats. Acylcarnitines dramatically shortened onset time, shortened absorption-duration time, and efficiently delivered HGH. HGH administered intranasally with acylcarnitines appeared in the blood within 0.28–2.7 min, far more rapidly than the 11.7 min after intranasal administration of HGH without acylcarnitines (CTL) or the 9.8 min after subcutaneous administration (SC). Absorption-duration times of HGH enhanced by acylcarnitines were in the range of 2.1–3.8 h, which are shorter than those of CTL (7.5 h) or SC (9.8 h). Among acylcarnitines at 1%, lauroylcarnitine chloride (LCC) showed the greatest absolute bioavailability (17.4%), which is 0.73 times the absolute bioavailability value for SC (22.1%). LCC enhancement reached a plateau at a concentration of 0.1%. This nasal absorption enhancement would be suitable for pulsatile administration. A single dose toxicity study also suggested that LCC had similar systemic safety to L-carnitine at a high dose of 100 mg/kg in mice. Further, the potential safety of LCC was ten times greater than palmitoylcarnitine chloride.

Bovine spongiform encephalopathy

Bovine spongiform encephalopathy

Inhibition of cellular antioxidants: a possible mechanism of toxic cell injury.

Cells that utilize molecular oxygen generate highly reactive oxygen-derived free radicals. Endogenous cellular oxidants inactivate oxidant free radicals and protect aerobic cells from oxidant injury. Glutathione, glutathione reductase, and superoxide dismutase are key components of this antioxidant defense. Inhibition of antioxidant components would be expected to result in cell injury. Using exposure to oxygen at high pressure to increase the level of oxidant free radicals, evidence is presented to support the hypothesis that inhibition of cellular antioxidants renders organisms more susceptible to oxygen toxicity. Diethyldithiocarbamate at doses of 250, 500 and 1000 mg/kg inhibited rat brain superoxide dismutase activity and shortened onset time to seizures in a dose-related manner in 4 ATA oxygen. Carmustine at doses of 12.5, 25 and 50 mg/kg inhibits glutathione reductase activity in rat brain in proportion to the dose. Time to onset of seizures of rats pretreated with carmustine prior to exposure to 4 ATA oxygen was shortened, and oxidized glutathione levels were increased in the cortex and subcortex. These data suggest that inhibition of antioxidant components results in organisms becoming more sensitive to oxygen toxicity. Compounds that inhibit cellular antioxidants may produce toxic cell injury by permitting intracellular oxidant free radicals to attack essential cell constituents.