Continuous Infusion Technique Research Articles

Successful Management of Opioid-refractory Pelvic Cancer Pain Using Continuous Local Anesthetic Infusion via a Tunneled Epidural

Opioid refractory pelvic cancer pain is common and difficult to manage, which often results in analgesic polypharmacy and escalating opioid doses, alongside the use of interventional techniques. However, up-titration of opioids often results in systemic side effects, and interventional procedures have limitations in their duration of action, efficacy, and risk of nerve damage. Therefore, intrathecal pumps have been utilized as a more permanent option for pain management. Their ability to deliver localized therapy using a variety of pharmacological agents makes it an attractive option for cancer pain management. However, they are limited by a need for careful titration, pump volume constraints, and risks of severe side effects. These limitations can be mitigated by targeting the epidural space instead, and we propose the use of a tunneled epidural catheter technique for continuous local anesthetic infusion in opioid-refractory pelvic and abdominal cancer pain. In this case report, we describe a patient with pelvic and abdominal cancer pain due to stage IV sigmoid adenocarcinoma with widespread metastases, who received adequate pain management from a continuous local anesthetic infusion through a tunneled lumbar epidural catheter. Throughout this patient’s hospital admission, their opioid requirements remained the same, and their pain remained well controlled on review in the community one month after discharge. This case demonstrated that epidural catheters with local anesthetic as the sole neuraxial analgesic agent over a short duration could potentially provide preventive analgesia. This case highlights that a local anesthetic tunneled epidural, without addition of neuraxial opioids, is an effective alternative to intrathecal pumps in managing complex cancer pain and has potential for preventive analgesia.

The Forces Associated with Bolus Injection and Continuous Infusion Techniques during Ultrasound-Targeted Nerve Contact: An Ex Vivo Study

Ultrasound-guided regional anaesthesia with real-time visualization of anatomical structures and needle trajectory has become the standard method for accurately achieving nerve block procedures. Nevertheless, ultrasound is particularly limited in accurately detecting the needle tip in tissues with complex echogenicity. Fat-filled circumneural fascial tissue provides a barrier to local anaesthetic diffusion. Injection during gentle needle nerve contact is more likely to spread under the circumneurium (halo sign). On the other hand, excessive force may cause hematoma or activate the piezo ion channels and intraneural calcium release. Therefore, it is vital to understand the mechanics of needle–tissue interaction for optimizing the procedural outcomes and patients’ safety. We hypothesised that continuous fluid infusion would reduce the needle force applied on the nerve compared to that of bolus injection. Thus, the primary objective of this study was to compare the forces associated with the bolus injection and continuous infusion techniques on the sciatic nerves of fresh lamb legs ex vivo. A needle combining pressure and force was inserted into six legs of lambs ex vivo using a motor stage at a constant velocity and imaged with a linear transducer. Saline injections were block randomised to bolus injection or infusion in the muscle upon gently touching and indenting of the epineurium at nine sites on six sciatic nerves at three angles (30°, 45° and 60°) in each location. The bolus was delivered over 6 s and infused for over 60 s. The result showed less force was generated during the infusion technique when gently touching the epineurium than that of the bolus technique, with p = 0.004, with significant differences observed at a 60° angle (0.49 N, p = 0.001). The injection pressure was also lower when light epineurium touches were applied (9.6 kPa, p = 0.02) and at 60° (8.9 kPa). The time to peak pressure varied across the insertion angles (p < 0.001), with the shortest time at 60° (6.53 s). This study explores future applications by emphasizing the significance of understanding needle–tissue interaction mechanics. This understanding is crucial for optimizing the procedural outcomes and enhancing patients’ safety in ultrasound-guided regional anaesthesia administration. Specifically, continuous infusion demonstrated a notable reduction in needle force compared to that of the bolus injection, especially during gentle epineurium contact.

Comparative evaluation of continuous infusion versus programmed intermittent bolus techniques in erector spinae plane block in modified radical mastectomy - A preliminary randomised controlled trial.

Single-shot erector spinae plane block (ESPB) provides excellent analgesia in mastectomy in the immediate post-operative period but is not sufficient to maintain for prolonged duration. This study compares the efficacy of programmed intermittent bolus (PIB) versus continuous infusion (CI) techniques after ESPB by placing a catheter for mastectomy. After ethical approval and patient consent, ESPB was performed at the T4 level in 50 patients with an initial bolus of 20 mL 0.375% ropivacaine and a catheter placed 30 min before surgery. In the postoperative period, they were randomised to Group I - intermittent bolus of 20 mL 0.2% ropivacaine every 4 h for 24 h and Group C - continuous infusion of 0.2% ropivacaine at 5 mL/h for 24 h. The primary outcome was the 24-h fentanyl consumption by patient-controlled analgesia device. Data was analysed using Stata 14.0. Group I patients had reduced post-operative fentanyl consumption {mean [standard deviation (SD)]: 166 (139.17) µg vs 332 (247.96) µg, P = 0.002} and lower median NRS scores (1 h: 3 vs 5), (2 h: 3 vs 5), (4 h: 3 vs 5), (6 h: 4 vs 5) with a higher mean (SD) Quality of Recovery-15 score {134.4 (8.53) vs 127 (12.89), P = 0.020} compared to Group C, respectively. The 24-h dermatomal sensory coverage was more comprehensive in Group I compared to Group C. The PIB technique after ESPB provides decreased postoperative opioid consumption, better post-operative analgesia and quality of recovery compared to the CI technique in patients undergoing mastectomy.

Erector spinae plane blocks: A narrative update.

The erector spinae plane block (ESPB) is perhaps one of the most interesting of the tissue plane blocks described recently. There has been an exponential increase in the number of publications for both adults and children over the past 5 years. Single-shot, intermittent bolus, and continuous infusion techniques have been used effectively. Both the efficacy and safety of the procedure are widely accepted, but the exact mechanism by which the local anesthetic spreads from the tip of the transverse process to block the dorsal and ventral rami of the spinal nerves is controversial and needs clarification. Anatomical differences in children, particularly in neonates and infants, may explain the spread in this age group. In most pediatric studies, erector spinae plane block was opioid sparing, and noninferiority was observed when compared with other regional techniques.

Dual erector spinae plane block for complex traumas of upper and lower limb: an opioid reduction strategy—a case series

BackgroundPatients with polytrauma (fractures of the humerus and the femur) require concurrent operative fixation. Pain originating from multiple operative sites leads to increasing doses of opioid-based analgesia, which has detrimental effects in the form of longer hospital stays, higher costs, and increased mortality.Case presentationIn twelve patients with humerus and femur fractures, a cervical erector spinae plane block (ESPB) at the level of T1 and a lumbar ESPB at the level of L2 were administered with a catheter and continuous infusion technique for postoperative analgesia. None of these patients required opioids in the postoperative period. The catheters were removed after 48 h.ConclusionsA dual ESPB can be used successfully in patients with multiple injuries by appropriately selecting the level of intervention, and opioid-sparing analgesia can be effectively delivered to these patients.

Effect of programmed intermittent epidural bolus protocol on physician-administered rescue boluses of labor analgesia

Background Prior studies have shown that programmed intermittent epidural bolus (PIEB) techniques, with or without patient-controlled epidural analgesia (PCEA) boluses, provide better pain relief, reduced motor block, and better patient satisfaction compared to continuous epidural infusion (CEI) techniques. We hypothesized that patients who had labor epidural analgesia (LEA) maintained with PIEB and PCEA would be less likely to receive a physician-administered rescue analgesia bolus compared to patients who had CEI and PCEA. Methods We searched our electronic medical record for patients who had CEI and PCEA from August 1, 2021 to December 31, 2021 and for patients who had PIEB and PCEA from August 2, 2022 to December 31, 2022. Results A total of 792 and 665 patients had maintenance of LEA with CEI/PCEA and PIEB/PCEA, respectively. A multivariate logistic regression was performed and, after adjusting for variables of interest, patients who had PIEB and PCEA were less likely to receive one or more physician-administered rescue analgesia boluses (odds ratio 0.504; 95% confidence interval 0.392, 0.649; P < 0.001) compared to patients who had CEI and PCEA. Conclusion PIEB/PCEA was associated with fewer physician-administered boluses of rescue analgesia compared to CEI/PCEA when used for LEA.

Ultrasound Guided Thoracic Paravertebral Block as an Analgesic Technique for Tracheoesophageal Fistula repair : A Case Report

Ultrasound has now become an eye of anaesthesiologist and has encouraged for its pervasive use. Its considerable use in the perioperative period for various invasive purposes has added an extra caution to prevent unforeseen complications over blind blocks. The ultrasound-guided thoracic paravertebral block provides excellent perioperative analgesia following thoracic surgery. It can be given as a single shot or a continuous infusion technique placing a catheter. Here the local anesthetic agent is deposited in the paravertebral space from where the spinal nerve emerges which are devoid of coverings and are sensitive to local anesthetics. Even a single-shot block provides analgesia of 4-6 dermatomal levels. The use of local anesthetics using ultrasound not only adds safety measures to minimize procedural complications but also reduces the perioperative requirement of opioids. It also helps in the reduction of postoperative pulmonary complications and early extubation following thoracic surgery. We report a case series where single-shot ultrasound-guided unilateral paravertebral blocks were used as an analgesic technique for the repair of tracheoesophageal fistula in neonates. After delivering anesthesia and confirming the correct placement of the endotracheal tube the neonate was kept on the left lateral position to undergo right thoracotomy and repair of fistula. Scanning at T4 level with a linear probe was done to identify the transverse process, pleura, costotransverse ligament, intercostal muscle, and the paravertebral space where the local anesthetic agent was deposited under aseptic precautions. Tenting of pleura was the endpoint for the completion of the block. The extensive use of various regional anesthetic technique has significantly improved the postoperative outcome of the patients along with adequate perioperative pain management.

Analgesic efficacy of continuous intravenous infusion of morphine in patients after hip and knee joint endoprosthetics: prospective study

Objectives of the study was to evaluate the possibility of using and the frequency of side effects of continuous intravenous morphine infusion for patients after arthroplasty of the lower limbs joints. Materials and methods. In the prospective study the results of treatment of 2 groups of patients were compared: after total knee arthroplasty (n = 52) and after total hip arthroplasty (n = 52). The rate of morphine administration in the total knee arthroplasty group ranged from 0.6 to 1.6 mg/hour, in the total knee arthroplasty group it was from 0.4 to 1.4 mg/hour. Continuous infusion of morphine was continued 24 hours after surgery. Indicators of systemic hemodynamics, gas exchange, pain and sedation were recorded. Results. The use of the technique of continuous intravenous infusion of morphine has shown the adequate level of anesthesia. An optimal balance between adequate analgesia, sedation and the absence of respiratory depression can only be achieved through a low rate of morphine administration. There was no significant difference in the incidence of complications and side effects (nausea, vomiting, acute urinary retention, delirium) in the groups with knee and hip arthroplasty. Conclusion. The technique provided, on the one hand, a good analgesic effect and sedation, but on the other hand, it was quite laborious and required careful monitoring of the parameters of the respiratory and cardiovascular systems. It is especially necessary to carefully monitor the indicators of vital functions in the evening and night hours.

Comparison of two different methods for labor analgesia depending on the mode of epidural infusion administration (continuous or intermittent)

Introduction: The use of a local anesthetic solution with opioids as a continuous epidural infusion administration during labor is controversial. It is considered to prolong the second stage of labor and to increase the total delivered dose of anesthetic, without improving the analgesia in comparison with the usage of the same solution in intermittent bolus doses, periodically. This study is designed to compare these two techniques. Materials and methods: In this study, 60 parturient women were included. Labor analgesia started with a single bolus dose of 10 mL ropivacaine 0.1% administered epidurally in both groups. Group A was, subsequently, given epidurally Ropivacaine 0.15% with Fentanyl 2 μgr/mL in continuous infusion with a rate of 10 mL/h throughout labor, while Group B was given the same dose per hour but in two bolus doses of 5 mL administered every 30 min. In both groups, we had the possibility of additional bolus doses of 5 mL of the same solution with a lock out interval of 20 min. The total dosage received, the duration of the 2nd stage of labor, the method of delivery (assisted or not, Cesarean section), the motor activity (using the Bromage scale) and the pain intensity (using the VAS 1–10, every 20 min) were evaluated. Results: No statistically significant differences were observed in the duration of labor (one way ANOVA), in the Bromage score and in the method of delivery between the two groups (x2 test). No differences were also observed in the recordings of pain intensity between the two groups (two-way ANOVA for repeated measurements), but in some specific instances Group A presented higher VAS score, although the total dosage of local anesthetic received was greater in this group compared to group B (180 mL vs. 162 mL, p = 0.04). Conclusions: The use of intermittent epidural bolus doses compared to a continuous infusion technique is associated with lower total consumption and periodically better pain management.

Combination of epidural bupivacaine and fentanyl for labour analgesia: An observational longitudnal study

Labour is a physiological process which is associated with most severe pain. Goal of labour analgesia should be to ensure painless labour without any side effect. Various methods have been used to alleviate pain during labour but the only consistently effective method is lumbar epidural analgesia. Since higher doses of local anaesthetics cause undesirable effects like motor block and hemodynamic changes, adjuvants like opioids are used.The present study evaluates the clinical effectiveness of continuous lumbar epidural for vaginal delivery using 0.0625% bupivacaine with 2.5 mcg/ml of fentanyl. 91 patients admitted to Lalladed hospital govt medical college Srinagar for vaginal delivery and who were in active labour were given first loading dose of 10ml 0.25% plain bupivacaine via epidural catheter followed by continuous epidural infusion of 0.0625% bupivacaine with 2.5 mcg/ml fentanyl @ 12ml/hr. the parturients were assessed for onset and duration of analgesia, hemodynamics, sensory block, mode of delivery, and APGAR(neonatal outcome). Onset of analgesia was significantly faster(10 min). The duration of analgesia was also longer. There were no significant hemodynamic changes. No motor block was seen. 1 min and 5 min APGAR scores were comparable. It was concluded that epidural labour analgesia with low dose bupivacaine (0.0625%) with fentanyl (2.5mcg/ml) given through continuous infusion technique provides good pain relief to the parturient in labour with increased maternal satisfaction without significant maternal or fetal side effects.

Intermittent bolus versus continuous infusion techniques for local anesthetic delivery in peripheral and truncal nerve analgesia: the current state of evidence

Manually delivered intermittent bolus (MIB) and programmable intermittent bolus (PIB), alternatives to continuous infusion (CI), involve administering a set volume of solution at a set interval of time. The benefits of intermittent bolus techniques in truncal and peripheral nerve blockade (TPNB) are unclear, and studies have largely demonstrated conflicting results. Using MEDLINE, Embase, Google Scholar, and the Cochrane Library, we conducted an evidenced-based review of published randomized controlled trials comparing intermittent bolus and CI methods in TPNB. In total, 13 randomized controlled trials were identified and evaluated. Outcomes data addressed in these studies included assessments of pain, opioid and local anesthetic consumption, patient satisfaction, adverse events, and physical therapy metrics. The overall quality of current evidence was found to be low given the small sample sizes, heterogeneity of data, and the variations in intermittent bolus techniques between studies. At this time, we found limited supportive data to endorse MIB or PIB over CI in TPNB. While unable to provide data-driven conclusions for local anesthetic delivery methods at this time, we propose that future studies and quantitative analysis between techniques should be on an anatomic, site-specific basis, with greater focus on evaluation of opioid use, adverse events, patient satisfaction, and rehabilitative metrics.

A randomized, controlled trial of comparison of a continuous femoral nerve block (CFNB) and continuous epidural infusion (CEI) using 0.2% ropivacaine for postoperative analgesia and knee rehabilitation after total knee arthroplasty (TKA)

Background and Aims:Postoperative pain relief following total knee arthroplasty (TKA) is a major concern as it will help to achieve an effective functional outcome. The present study was conducted to compare continuous femoral nerve block (CFNB) and continuous epidural infusion (CEI) techniques using ropivacaine.Material and Methods:Forty patients were randomly allocated into group F and group E to receive 0.2% ropivacaine through femoral catheter or epidural catheter respectively. An infusion was started @6 ml/h post-operatively when VAS was ≥4. The dose was titrated to keep VAS <4 (with minimum rate 2 ml/h and maximum rate 10 ml/h). If VAS ≥4 occurred despite maximum rate of infusion, a rescue analgesic was given. Primary objectives were to compare visual analogue score (VAS), rehabilitation indices, and rescue analgesic requirement. Secondary objectives were to assess patient and surgeon's satisfaction score, motor blockade, and complications if any.Results:The mean VAS score, rehabilitation goals, rescue analgesic requirement, and patient's and surgeon's mean satisfaction scores were comparable in both the groups. Motor blockade was not seen and though the number of side effects were more in group E, they did not achieve statistical or clinical significance.Conclusion:CFNB can be used as an alternative, effective postoperative analgesic technique for TKA.

Modulation of sympathetic vasoconstriction is critical for the effects of sleep on arterial pressure in mice.

While values of arterial pressure during sleep are predictive of cardiovascular risk, the autonomic mechanisms underlying the cardiovascular effects of sleep remain poorly understood. Here, we assess the autonomic mechanisms of the cardiovascular effects of sleep in C57Bl/6J mice, taking advantage of a novel technique for continuous intraperitoneal infusion of autonomic blockers. Our results indicate that non-REM sleep decreases arterial pressure by decreasing sympathetic vasoconstriction, decreases heart rate by balancing parasympathetic activation and sympathetic withdrawal, and increases cardiac baroreflex sensitivity mainly by increasing fluctuations in parasympathetic activity. Our results also indicate that REM sleep increases arterial pressure by increasing sympathetic activity to the heart and blood vessels, and increases heart rate, at least in part, by increasing cardiac sympathetic activity. These results provide a framework for generating and testing hypotheses on cardiovascular derangements during sleep in mouse models and human patients. The values of arterial pressure (AP) during sleep predict cardiovascular risk. Sleep exerts similar effects on cardiovascular control in human subjects and mice. We aimed to determine the underlying autonomic mechanisms in 12 C57Bl/6J mice with a novel technique of intraperitoneal infusion of autonomic blockers, while monitoring the electroencephalogram, electromyogram, AP and heart period (HP, i.e. 1/heart rate). In different sessions, we administered atropine methyl nitrate, atenolol and prazosin to block muscarinic cholinergic, β1 -adrenergic and α1 -adrenergic receptors, respectively, and compared each drug infusion with a matched vehicle infusion. The decrease in AP from wakefulness to non-rapid-eye-movement sleep (N) was abolished by prazosin but was not significantly affected by atropine and atenolol, which, however, blunted the accompanying increase in HP to a similar extent. On passing from N to rapid-eye-movement sleep (R), the increase in AP was significantly blunted by prazosin and atenolol, whereas the accompanying decrease in HP was blunted by atropine and abolished by atenolol. Cardiac baroreflex sensitivity (cBRS, sequence technique) was dramatically decreased by atropine and slightly increased by prazosin. These data indicate that in C57Bl/6J mice, N decreases mean AP by decreasing sympathetic vasoconstriction, increases HP by balancing parasympathetic activation and sympathetic withdrawal, and increases cBRS mainly by increasing fluctuations in parasympathetic activity. R increases mean AP by increasing sympathetic vasoconstriction and cardiac sympathetic activity, which also explains, at least in part, the concomitant decrease in HP. These data represent the first comprehensive assessment of the autonomic mechanisms of cardiovascular control during sleep in mice.

Vecuronium Requirement By Continuous Infusion Technique In Adult Patients During Fentanyl Nitrous Oxide – Oxygen Anesthesia.

Vecuronium Requirement By Continuous Infusion Technique In Adult Patients During Fentanyl Nitrous Oxide – Oxygen Anesthesia.

Epidural Catheter Design

Epidural catheters have evolved during the past several decades, as clinicians and manufacturers have sought to influence the quality of analgesia and anesthesia and reduce the incidence of catheter-related complications. This evolution has allowed a transformation from single-shot to continuous-infusion techniques and resulted in easier passage into the epidural space, more extensive medication distribution, and ultimately, improved patient satisfaction. Particular catheter features, including the materials used, tip design, and orifice number and arrangement, have been associated with specific outcomes and provide direction for future development.

Epidural Catheter Design

Epidural catheters have evolved during the past several decades, as clinicians and manufacturers have sought to influence the quality of analgesia and anesthesia and reduce the incidence of catheter-related complications. This evolution has allowed a transformation from single-shot to continuous-infusion techniques and resulted in easier passage into the epidural space, more extensive medication distribution, and ultimately, improved patient satisfaction. Particular catheter features, including the materials used, tip design, and orifice number and arrangement, have been associated with specific outcomes and provide direction for future development.

Efficacy of Continuous Regional Arterial Infusion With Low-Molecular-Weight Heparin for Severe Acute Pancreatitis in a Porcine Model

Administration of heparin or its derivatives has been proved to be beneficial in the treatment of severe acute pancreatitis (SAP). However, drugs administered by conventional intravenous way are difficult to reach the pancreatic tissue and may cause bleeding complications due to coagulation and microcirculatory disturbance following initiation of SAP. In this study, we aimed to assess the effects of low-molecular-weight heparin (LMWH) administered with continuous regional arterial infusion (CRAI) technique in a porcine model of SAP. Following baseline measurements, 18 animals were divided into three groups: CRAI group (LMWH infused through placed arterial catheter), venous group (LMWH infused through central venous catheter), and SAP control group. We used retrograde intraductal infusion of sodium taurocholate to induce SAP. Global hemodynamic profiles, urine output, systemic oxygenation, and inflammatory and serum biochemical parameters of the animals were studied. At the end of the experiment, histological examination of pancreas, intestine, and lung was performed. Continuous regional arterial infusion with LMWH remarkably stabilized hemodynamic profiles, improved systemic oxygenation and peripheral perfusion, alleviated histological injury of pancreas (especially for the necrosis scale), and downregulated inflammatory response when compared with the other two groups. Moreover, serum D-dimer level also decreased most significantly in the CRAI group (474 ± 144 vs. 664 ± 155 µg/L in the venous group and 945 ± 351 µg/L in the controls at the end), partly indicating ameliorated coagulation disorders in the study group. No bleeding complication was observed in the CRAI group, whereas two animals in the venous group presented gastrointestinal hemorrhage. Continuous regional arterial infusion with LMWH exhibits strong therapeutic effects in the course of SAP with great safety. Human studies using this novel therapy are required to assess these potential benefits in the clinical setting.

Safety of liposome extended-release bupivacaine for postoperative pain control.

Background: Ideal postoperative pain management requires a multidisciplinary approach in combination with a variety of dosage regimens. Approximately 21–30% of patients experience moderate to severe pain in the postoperative period, which may have a significant impact on recovery rate, standard of living, psychological health, and postoperative complications.Objective: Analysis of the incidence and characterization of reported adverse effects with DepoFoam bupivacaine compared to conventional bupivacaine or placebo.Methods: A systematic review of prospective studies on the use of DepoFoam versus bupivacaine or placebo was performed in order to answer the clinically relevant question: is DepoFoam a safer formulation in place of bupivacaine single injection or continuous local infusion techniques for postoperative pain management? Inclusion criteria required randomized, controlled, double-blind trials in patients 18 years old or older, single dose used for postoperative pain control, and a primary procedure performed.Results: Six studies fitted the inclusion criteria for analysis, DepoFoam bupivacaine used in therapeutic doses was well-tolerated, had a higher safety margin, and showed a favorable safety profile compared to bupivacaine and control groups.Conclusion: Extended drug delivery system DepoFoam bupivacaine is a promising drug formulation that may significantly improve postoperative care and pain control in surgical patients.

How do I do it: Continuous local anesthetic infusion for children with spinal dysraphism undergoing major reconstruction of the lower urinary tract

Postoperative pain control is a fundamental aspect of contemporary pediatric surgery. While many options for analgesia are available to the general patient population, choices are limited for individuals with spinal dysraphism who undergo major urologic procedures. Continuous infusion of local anesthetics has been shown to improve postoperative pain scores and decreases the need for systemic analgesia. We present our technique for continuous local anesthetic infusion utilizing readily available equipment with limited additional cost.

The efficacy of automated intermittent boluses for continuous femoral nerve block: a prospective, randomized comparison to continuous infusions

Study ObjectiveTo determine whether an automated intermittent bolus technique provides enhanced analgesia compared with a continuous infusion for femoral nerve block. DesignProspective, single-blinded, randomized controlled trial (ClinicalTrials.gov Identifier: NCT01226927). SettingPerioperative areas and orthopedic surgical ward of a university hospital. Patients45 ASA physical status 1, 2, and 3 patients undergoing unilateral primary total knee arthroplasty. InterventionsAll patients received single-injection sciatic and femoral nerve blocks plus femoral nerve catheter placement for postoperative analgesia. Patients were randomly assigned to an automated intermittent bolus (5 mL every 30 min with 0.1 mL/hr basal rate) or a continuous infusion (10.1 mL/hr) delivery method of 0.2% ropivacaine. MeasurementsConsumption of intravenous patient-controlled analgesia (IV-PCA) and visual analog scale (VAS) pain scores were assessed postoperatively at set intervals until the morning of postoperative day (POD) 2. Main ResultsThe mean (SEM) cumulative IV-PCA dose (mg of hydromorphone) for the 36-hour postoperative interval measured was 12.9 ± 2.32 in the continuous infusion rate group (n = 20) and 7.8 ± 1.02 in the intermittent bolus group [n = 21, t(39) = 2.04, P = 0.048; a 39 ± 14% difference in total usage]. Pain scores were statistically significantly lower in the intermittent bolus group in the afternoon of POD 1 (t(39) = 2.47, P = 0.018), but were otherwise similar. ConclusionsAn automated intermittent bolus infusion technique for femoral nerve catheters is associated with clinically and statistically significantly less IV-PCA use (ie, an opioid-sparing effect) than a continuous infusion technique.