Top-up Injections Research Articles

A neural network for beam background decomposition in Belle II at SuperKEKB

We describe a neural network for predicting the background hit rate in the Belle II detector produced by the SuperKEKB electron–positron collider. The neural network, BGNet, learns to predict the individual contributions of different physical background sources, such as beam-gas scattering or continuous top-up injections into the collider, to Belle II sub-detector rates. The samples for learning are archived 1Hz time series of diagnostic variables from the SuperKEKB collider subsystems and measured hit rates of Belle II used as regression targets. We test the learned model by predicting detector hit rates on archived data from different run periods not used during training. We show that a feature attribution method can help interpret the source of changes in the background level over time.

New features of the MAX IV thermionic pre-injector

The MAX IV facility in Lund, Sweden consists of two storage rings for production of synchrotron radiation. The smaller 1.5GeV ring is presently under construction, while the larger 3GeV ring is being commissioned. Both rings will be operating with top-up injections from a full-energy injector. During injection, the electron beam is first delivered to the main injector from a thermionic pre-injector which consists of a thermionic RF gun, a chopper system, and an energy filter. In order to reduce losses of high-energy electrons along the injector and in the rings, the electron beam provided by the thermionic pre-injector should have the correct time structure and energy distribution. In this paper, the design of the MAX IV thermionic pre-injector with all its sub components is presented. The electron beam delivered by the pre-injector and its dependence on parameters such as optics, cathode temperature, and RF power are studied. Measurements are here compared with simulation results obtained by particle tracking and electromagnetic codes. The chopper system is described in detail, and different driving schemes that optimize the injection efficiency for the two storage rings are investigated. During operation, it was discovered that the structure of the beam delivered by the gun is affected by mode beating between the accelerating and a low-order mode. This mode beating is also studied in detail. Finally, initial measurements of the electron beam delivered to the 3GeV ring during commissioning are presented.

A Randomized Controlled Comparison of Epidural Analgesia and Combined Spinal-Epidural Analgesia in a Private Practice Setting

There has been no prospective evaluation of combined spinal-epidural (CSE) analgesia in a private practice setting and few studies have focused on pain relief during the second stage of labor and at delivery. In this randomized controlled trial, we compared verbal pain scores during the first and second stages of labor and at delivery in women receiving CSE or traditional epidural analgesia at a busy private maternity hospital. Healthy, term parturients received epidural or CSE analgesia for labor pain upon request. Epidural analgesia was initiated with 0.125% bupivacaine plus 2 μg/mL fentanyl, 15 mL; CSE analgesia was initiated with intrathecal plain bupivacaine 3.125 mg plus 5 μg fentanyl. Thereafter, patient-controlled epidural analgesia with 0.125% bupivacaine plus 2 μg/mL fentanyl was used for maintenance analgesia in both groups. The primary outcome was an assessment of "typical" pain, using a verbal rating pain score from 0 to 10, made at the end of the first stage of labor and shortly after delivery. Data from 398 epidural and 402 CSE subjects were analyzed. The typical verbal rating pain score during the first stage was lower in the CSE group (mean: 1.4 vs 1.9; P < 0.001; 99.5% confidence interval [CI] for difference: -0.92, -0.14). Pain scores during the second stage of labor (1.7 vs 1.9; P = 0.17; 99.5% CI for difference: -0.82, 0.28) and at delivery (2.0 vs 2.0; P = 0.77; 99.5% CI for difference: -0.73, 0.59) were the same between groups. Fewer patients received an epidural top-up dose in the CSE group (16.4% vs 25.6%; P = 0.002; 99.5% CI for difference: -17.0%, -1.0%). Epidural catheters were replaced in 1.2% CSE vs 2% in the epidural group (P = 0.39; 99.5% CI for difference: -3.3%, 1.8%). Compared with traditional epidural labor analgesia, CSE analgesia provided better first-stage analgesia despite fewer epidural top-up injections by an anesthesiologist.

Radiation safety impact for top-up operation at the NSRRC

Radiation safety impact for the upcoming top-up operation at the National Synchrotron Radiation Research Center (NSRRC) has been investigated with emphasis on the consequence of injection efficiency. Keeping the storage ring at high stored current by frequent injections, the top-up operation will inevitably increase the radiation dose compared with that in the present decay mode, especially when the injection efficiency is low. In addition, significantly high level of radiation could stream through the ratchet wall openings during top-up injections while shutters are open. Therefore, a series of radiation safety analyses including calculations and measurements have been carried out to assess the feasibility of this mode on the prospective radiation protection. The paper summarises the evaluation and the corresponding action plans for radiation safety.

Comparison of fentanyl and sufentanil in combination with bupivacaine for patient-controlled epidural analgesia during labor

Study Objective: To compare the efficacy of fentanyl plus bupivacaine with sufentanil plus bupivacaine for treatment of pain during labor and delivery using patient-controlled epidural analgesia (PCEA). Design: Prospective, double-blind, clinical investigation. Setting: University-affiliated hospital. Patients: 226 ASA physical status I and II laboring patients. Interventions: Patients were randomized to receive 0.125% bupivacaine with fentanyl (2 μg.ml -1 ) or 0.125% bupivacaine with sufentanil (0.25 μg.ml -1 ) through PCEA. Measurements: Maternal analgesia assessed by visual analog scale was recorded before epidural block, 1 and 3 hours after epidural block, at full cervical dilation, and at delivery. Motor blockade assessed by Bromage scale was recorded at delivery. Main results: Nine patients in group fentanyl, and 11 in group sufentanil were excluded from the study. Overall analgesia was good and no difference was observed between the two groups. Total boluses of 4 mL bupivacaine-opioid administered and the number of supplementary top-up injections of 5 mL 0.25% bupivacaine were similar in both groups. In group sufentanil, motor blockade and pruritus were significantly lower than in group fentanyl. Nausea was not recorded in any patients. Mode of delivery was similar in both groups, i.e., cesarean section, vacuum or forceps, or spontaneous vaginal delivery. No difference was observed in Apgar scores. Conclusions: Sufentanil is preferable to fentanyl during bupivacaine PCEA as there is less incidence of motor blockade and pruritus.

EARLY EXPERIENCE WITH SMALL VOLUME PERIURETHRAL POLYTETRAFLUOROETHYLENE FOR FEMALE STRESS URINARY INCONTINENCE

Injectable polytetrafluoroethylene paste has been used to treat female stress urinary incontinence. Since the substance is antigenically nonreactive we postulated that the reported morbidity may be due in part to the relatively large volumes injected. Therefore, we assessed the outcome of injecting small volumes of polytetrafluoroethylene with attention to the durability of success and morbidity. A total of 46 women with a median age of 73.8 years (range 26 to 88) with stress urinary incontinence were treated. The procedure was done on an outpatient basis using topical urethral lidocaine and periurethral lidocaine as anesthesia. A 20Fr urethroscope was used to inject polytetrafluoroethylene through an 18 gauge needle periurethrally. Patients were reinjected 1 to 3 months after initial injection if not cured (no incontinence or no pads). Continence was assessed by questionnaire from an interviewer not known to the patient. Subsequent top-up injections were given if required. Morbidity was monitored with clinical examination and imaging as required. Of the patients 14 (30.4%) were dry, 19 (41.3%) were improved and 13 (28.3%) had treatment failure at a mean of 17.9, 15. 9 and 9.1 months, respectively, after last injection. For cured and improved patients (71.7%) an average of 2 treatments were needed, for a total mean volume of 5.4 cc polytetrafluoroethylene. Using a Kaplan-Meier survival curve the probability of the 14 patients remaining dry without additional polytetrafluoroethylene was 90% at 1 and 60% at 2 years. Outcome was not affected by radiological type of incontinence (that is with or without hypermobility), age, pretreatment bladder instability or previous interventions. Periurethral injection of small volumes of polytetrafluoroethylene is effective and safe for treatment of female stress urinary incontinence. Early analysis shows that success is durable with minimal morbidity.

A prospective randomized double-blinded controlled study of ropivacaine 0.75% versus bupivacaine 0.5%–mepivacaine 2% for peribulbar anesthesia

Background and Objectives: Ropivacaine 1% has recently been used in clinical trials for peribulbar anesthesia. This study aims to compare the safety and the efficacy of ropivacaine 0.75% with that of a 1:1 mixture of bupivacaine 0.5% and mepivacaine 2% for peribulbar anesthesia. Methods: Two thousand patients undergoing peribulbar anesthesia for elective cataract phacoemulsification were prospectively studied over a 1-year period and randomly assigned to 1 of 2 groups according to the local anesthetic used. One thousand patients were administered peribulbar anesthesia with 9 mL of ropivacaine 0.75% plus 1 mL of hyaluronidase (group R), and 1,000 patients received peribulbar anesthesia with 4 mL of bupivacaine 0.5% plus 4 mL of mepivacaine 2% plus 1 mL of hyaluronidase plus 1 mL of sodium bicarbonate (group BM). Peribulbar anesthesia was always accomplished by the same physician by 2 injections of 5 mL each, with a 25-gauge 25-mm needle. Evaluation was performed by another physician blinded to the technique used and included assessment of pain on local anesthetic injection, ocular and eyelid akinesia, need for top-up injections, onset time and duration of anesthesia, intraoperative analgesia, duration of surgery, hemodynamic parameters, and incidence of perioperative complications. Results: A greater incidence of pain on injection was found in group BM (P < .001). No difference between the groups was found regarding the onset time and the duration of anesthesia. Perioperative analgesia was satisfactory in both groups with no significant difference. Patients in group R showed a reduced need for top-up injection and a better ocular akinesia at 8 and 10 minutes (P < .01). The akinesia of the eyelid was comparable in the 2 groups and complete in all cases at 8 minutes. Cardiac arrhythmias were more frequent in group BM (P < .01). Local complications did not differ between the groups. An increase in mean artierial blood pressure and heart rate was observed in both groups 1 minute after injection of local anesthetic. Conclusions: Peribulbar anesthesia with ropivacaine provided better ocular akinesia 8 to 10 minutes after block insertion than a bupivacaine-mepivacaine mixture, which reduced the need for top-up injections. Ropivacaine also caused less pain on injection. Reg Anesth Pain Med 2000;25:195-200.

Comparative evaluation of four different infusion rates of ropivacaine (2 mg/mL) for epidural labor analgesia

Background and Objectives. Previous studies have reported comparable efficacy for ropivacaine and bupivacaine when used for labor analgesia at concentrations of 2.5 mg/mL. In this multicenter study, we assessed ropivacaine at the commercially available concentration of 2 mg/mL (0.2%) for labor pain management. Methods. After Institutional Review Board approval and informed consent, 128 women at term were randomly assigned to receive ropivacaine at one of the four infusion rates via a lumbar epidural catheter. Analgesia was initiated with a 5-mL test dose, followed by injections of 5–15 mL of 2 mg/mL ropivacaine. The continuous infusion was then started at 4, 6, 8, or 10 mL/hour. Rescue analgesia was provided with 5-mL “top-up” injections as necessary to provide maternal comfort. Pain relief was assessed by using a visual analog pain scale (VAPS) and motor block was assessed by using a modified Bromage scale. Results. All infusion regimens effectively decreased VAPS, and most patients in all groups had minimal or no motor block at the end of the first stage of labor. Mean total number of the top-up injections required per patient were 3, 2, 1.5, and 1.4, respectively, in the 4, 6, 8, and 10-mL/hour groups ( P < .05, 4 mL/hour vs. all other groups). Despite receiving more total bolus dosages, the 4-mL/hour group had less motor block in the lower extremities ( P < .05). Apgar scores and neurological adaptive capacity scores were similar for all groups. Conclusions. The 2 mg/mL of ropivacaine produces satisfactory labor analgesia at epidural infusion rates of 4, 6, 8, and 10 mL/hour, provided supplemental bolus dosages are available. Clinically, a rate of 6 mL/hour may be the lowest effective rate that provides the best combination of pain relief, motor block, and rebolusing, although rates of 8 and 10 mL/hour produced similar results.

Injectable collagen for type 3 female stress incontinence: the first 50 Australian patients.

To assess the safety, efficacy and durability of injectable glutaraldehyde cross-linked (GAX) collagen in the treatment of type 3 female stress incontinence. A prospective study of incontinent women attending a private practice for clinical and urodynamic assessment. Fifty women who had had an average of 1.8 previous operations for stress urinary incontinence took part in the study. Each had been diagnosed as having type 3 genuine stress incontinence (poor or nonfunctioning urethral sphincter mechanism in the presence of a bladder neck which is well supported, usually by scar tissue from previous surgery). Subject to a negative skin test for allergy, each patient underwent the implantation of GAX collagen (Contigen), a biocompatible product causing no foreign body reaction. The implant was performed by a short day-only procedure involving cystoscopically controlled periurethral (71%) or transurethral (29%) injection of Contigen. The aim was to achieve closure of the urethra at the bladder neck and increase resistance to urine loss. Top-up injections were used as required. The follow-up period ranged from one to 21 months (mean, 11 months). Of these first 50 female patients, 41 (82%) were successfully treated. Twenty-one (42%) were no longer incontinent; 20 (40%) desired no further treatment because their condition was improved; seven (14%) did not respond to treatment and two patients were awaiting top-up injections. The average number of injections given was 1.9 and the average volume injected was 14.4 mL. There were no allergic reactions or infections. Side effects were temporary and of a minor nature. Injectable GAX collagen appears to be a safe and effective treatment for type 3 stress urinary incontinence. Its durability awaits further follow-up.

CONTINUOUS EXTRADURAL ANALGESIA IN LABOUR: Comparison Between “On Demand” and Regular “Top-up” Injections

In a prospective comparative study 240 patients received extradural bupivacaine, either by regular timed injections or "on demand", for pain relief during the first stage of labour. Three concentrations of bupivacaine were used (0.5%, 0.375% and 0.25%). Quality and continuity of analgesia, motor blockade, spread of sensory blockade, cardiovascular changes, fetal outcome and maternal sequelae were recorded. Overall, the analgesia provided by regular top-up injections was superior to the on demand technique, especially when 0.375% bupivacaine was used. This improved analgesia was achieved without causing an increased incidence of operative deliveries or deleterious sequelae, with respect to the mother or the neonate.

Continuous infusion epidural analgesia in obstetrics

Summary The effects of 0.08% (Group A) and0.25% (Group B) solutions of bupivacaine were compared in a random manner, to assess continuous pump infusion epidural analgesia in labour. Both solutions were infused at a dose rate of 20 mg bupivacaine/hour. The results in all the mothers who had received infusions lasting more than 4 hours were studied. There were 25 11 Group A and 28 in Group B. Any treatment during the infusion epidural for inadequate analgesia, hypotension, etc., was recorded as an intervention. The mean of the intervention-free intervals n>as significantly greater in Group A than in Group B. and significantly fewer top-up injections were required in Group.4. The results show that the administration of a 0.08% solution of bupivacaine into the epidural space by continuous pump infusion is more labour saving than the infusion of a 0.25% solution. The concept that a greater volume infusion rate maintains a more extended liquid sleeve of local anaesthetic in the epidural space is supported.

Continuous infusion epidural analgesia in obstetrics

Summary The effects of 0.08% (Group A) and0.25% (Group B) solutions of bupivacaine were compared in a random manner, to assess continuous pump infusion epidural analgesia in labour. Both solutions were infused at a dose rate of 20 mg bupivacaine/hour. The results in all the mothers who had received infusions lasting more than 4 hours were studied. There were 25 11 Group A and 28 in Group B. Any treatment during the infusion epidural for inadequate analgesia, hypotension, etc., was recorded as an intervention. The mean of the intervention-free intervals n>as significantly greater in Group A than in Group B. and significantly fewer top-up injections were required in Group.4. The results show that the administration of a 0.08% solution of bupivacaine into the epidural space by continuous pump infusion is more labour saving than the infusion of a 0.25% solution. The concept that a greater volume infusion rate maintains a more extended liquid sleeve of local anaesthetic in the epidural space is supported.

Plasma concentrations of lidocaine and its principal metabolites during intermittent epidural anesthesia.

Plasma concentration-time courses of lidocaine and its principal metabolites (monoethylglycinexylidide, MEGX, and glycinexylidide, GX) were studied during intermittent epidural injections of lidocaine HCl in eight female patients (ASA status 1). The initial dose (320-400 mg without epinephrine) followed by top-up injections of about 60% of the mean initial dose every 35-55 min resulted in a plasma accumulation of lidocaine: the peak concentration increased from 2.30 +/- 0.46 (mean +/- SD) microgram/ml following the first injection and 3.34 +/- 0.76 microgram/ml after the second, to 4.11 +/- 0.72 microgram/ml following the third. The maximum concentrations of MEGX and GX were 0.66 +/- 0.22 and 0.28 +/- 0.08 microgram/ml, respectively. A pharmacokinetic model could successfully fit the entire plasma concentration-time profile of lidocaine during repeated epidural injections (r2 = 0.886 to 0.983). Such pharmacokinetic variables as elimination half-life (t1/2, 2.33 +/- 0.43 h), apparent volume of distribution divided by bioavailability (Vd/F, 2.51 +/- 0.61 l/kg), and clearance divided by bioavailability (Cl/F, 11.65 +/- 1.21 ml X kg-1 X min-1) obtained from the female patients were in reasonable agreement with those reported from healthy females receiving the intravenous lidocaine HCl. A computer-aided simulation generated from using the mean kinetic data in a 50-kg woman predicted that plasma lidocaine concentration would reach the postulated toxic range (approximately equal to 6 microgram/ml) after the fourth supplementary dose under a similar dosing scheme as performed in this study. In conclusion, an accumulation of lidocaine in plasma occurs during a usual intermittent epidural dosing.(ABSTRACT TRUNCATED AT 250 WORDS)

EXTRADURAL ANALGESIA: THE INFLUENCE OF VOLUME AND CONCENTRATION OF BUPIVACAINE ON THE MODE OF DELIVERY, ANALGESIC EFFICACY AND MOTOR BLOCK

Five hundred and seventeen women in labour receiving extradural analgesia, using bupivacaine plain solution, were randomly allocated to one of three groups. Group A received 6-8ml of 0.5% solution, group B 10-14ml of 0.25% solution, and group C 6-8 ml of 0.25% solution. Spontaneous delivery occurred in 31.7% of patients in group A, 38.7% in group B and 53% in group C (P less than 0.001). The percentage of rotational forceps, ventouse and Caesarean section deliveries was similar in the three groups. Analgesia was most effective in group A, and at least in group C, both during labour and at delivery, although assessment by linear analogue score suggested that the differences between the three groups were slight. Motor block was most frequent and rapidly progressive in groups A, but was progressive in all groups, and after five or more top-up injections, was similar in the three groups. Difficulties with micturition following delivery were significantly more common in group A.

OBSERVED AND PREDICTED ACCUMULATION OF LOCAL ANAESTHETIC AGENTS DURING CONTINUOUS EXTRADURAL ANALGESIA

After lumbar extradural injections of ligocaine or etidocaine for surgical anaesthesia further accumulation in the plasma was minimal following top-up injections for pain relief after operation. The dose regimens were: 20 ml of 2% plain lignocaine HCl solution for surgical anaesthesia followed by 10 ml every 1 h until 4 h, and 20 ml of 1% plain etidocaine HCl solution for surgical anaesthesia followed by 10 ml every 2 h until 8 h. Plasma drug concentrations measured after initial doses were used to predict those following successive doses. Agreement between predicted and experimental values was good and further projections were made concerning the local accumulation of etidocaine.

Epidural Anaesthesia-Still a Cinderella?

Method Approach to the epidural spade was made with the patient' in the left lateral position,awake but premedicated. Skin and supra-spinous ligament wereinfiltrated with 1 per cent lignocaine, a Size introducer was used to penetrate the skin and supra-spinous ligament. and a Tuohy needle inserted. The epidural space was identified by the loss of resistance method using air as vehicle. An epidural catheter was passed and directed cephelad for 2-3 cm. The needle was', removed and the catheter strapped to a shoulder. The patient then moved into the supine position and a test dose of 40 mg of'2 per cent lignocaine was injected. A vein was cannulated and basal readings of blood pressure and pulse rate were taken. The patient was then asked whether there were pins and needles in the legs and was asked to move the toes. After a negative response the definitive injection of analgesic was made and the trolley tilted as indicated. In general no' tilt was applied to patients for limb surgery, 5_lO° Trendelenberg to those for lower and lO-ISO to tliose for upper abdominal surgery. When a thoracic epidural was performea the patient was tilted into 15° of reverse Trendelenberg. Pulse rate and blood pressure were recorded at five minute intervals until the end of the surgical procedure. The level of analgesia was determined with a pin just prior to induction' of general anaesthesia. The catheter was left in situ at the end of operation and further injections, usually of 20 ml of 0.25 per cent bupivacaine, were made as indicated. The catheter was removed after 48 hours, or earlier if it had not been used for 12 hours. Like Bevan and Austin the writer has' trained the nursing staff of Recovery ward to give the post-operative top-up injections and has left the timing of injections to their discretjon.