Cost Analysis and Financial Implications of a Peritoneal Surface Malignancy Program in the USA.

BACKGROUND: We aimed to describe the financial implications of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) in the USA. MATERIALS AND METHODS: We conducted a retrospective cost analysis of 100 CRS/HIPEC procedures to examine the impact of patient and procedural factors on hospital costs and reimbursement. A comparison of surgeons' work relative value units (wRVUs) between CRS/HIPEC and a representative sample of complex surgical oncology procedures was made to assess the physicians' compensation rate. Univariable and multivariable backward logistic regression was used to analyze the association between perioperative variables and high direct cost (HDCs). RESULTS: The median direct cost per CRS/HIPEC procedure was US $44,770. The median hospital reimbursement was US $43,066, while professional reimbursement was US $8608, resulting in a positive contribution margin of US $7493/procedure. However, the contribution margin significantly varied with the payer mix. Privately insured patients had a positive median contribution margin of US $23,033, whereas Medicare-insured patients had a negative contribution margin of US $13,034. Length of stay (LOS) had the most significant association with HDC, and major complications had the most significant association with LOS. Finally, CRS/HIPEC procedures generated a median of 13 wRVU/h, which is significantly lower than the wRVU/h generated by open pancreatoduodenectomies, open gastrectomies, and hepatectomies. However, higher operation complexity and multiple visceral resections help compensate for the relatively low wRVU/h. CONCLUSIONS: CRS/HIPEC is an expensive operation, and prolonged LOS has the most significant impact on the total cost of the procedure. High-quality care is essential to improve patient outcomes and maintain the economic sustainability of the procedure.

Guidelines for Perioperative Care in Bariatric Surgery: Enhanced Recovery After Surgery (ERAS) Society Recommendations: A 2021 Update.

BACKGROUND: This is the second updated Enhanced Recovery After Surgery (ERAS®) Society guideline, presenting a consensus for optimal perioperative care in bariatric surgery and providing recommendations for each ERAS item within the ERAS® protocol. METHODS: A principal literature search was performed utilizing the Pubmed, EMBASE, Cochrane databases and ClinicalTrials.gov through December 2020, with particular attention paid to meta-analyses, randomized controlled trials and large prospective cohort studies. Selected studies were examined, reviewed and graded according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. After critical appraisal of these studies, the group of authors reached consensus regarding recommendations. RESULTS: The quality of evidence for many ERAS interventions remains relatively low in a bariatric setting and evidence-based practices may need to be extrapolated from other surgeries. CONCLUSION: A comprehensive, updated evidence-based consensus was reached and is presented in this review by the ERAS® Society.

Teaching basic lung isolation skills on human anatomy simulator: attainment and retention of lung isolation skills.

BACKGROUND: Lung isolation skills, such as correct insertion of double lumen endobronchial tube and bronchial blocker, are essential in anesthesia training; however, how to teach novices these skills is underexplored. Our aims were to determine (1) if novices can be trained to a basic proficiency level of lung isolation skills, (2) whether video-didactic and simulation-based trainings are comparable in teaching lung isolation basic skills, and (3) whether novice learners' lung isolation skills decay over time without practice. METHODS: First, five board certified anesthesiologist with experience of more than 100 successful lung isolations were tested on Human Airway Anatomy Simulator (HAAS) to establish Expert proficiency skill level. Thirty senior medical students, who were naive to bronchoscopy and lung isolation techniques (Novice) were randomized to video-didactic and simulation-based trainings to learn lung isolation skills. Before and after training, Novices' performances were scored for correct placement using pass/fail scoring and a 5-point Global Rating Scale (GRS); and time of insertion was recorded. Fourteen novices were retested 2 months later to assess skill decay. RESULTS: Experts' and novices' double lumen endobronchial tube and bronchial blocker passing rates showed similar success rates after training (P >0.99). There were no differences between the video-didactic and simulation-based methods. Novices' time of insertion decayed within 2 months without practice. CONCLUSION: Novices could be trained to basic skill proficiency level of lung isolation. Video-didactic and simulation-based methods we utilized were found equally successful in training novices for lung isolation skills. Acquired skills partially decayed without practice.

Teaching basic fiberoptic intubation skills in a simulator: initial learning and skills decay.

PURPOSE: Generally, novices are taught fiberoptic intubation on patients by attending anesthesiologists; however, this approach raises patient safety concerns. Patient safety should improve if novice learners are trained for basic skills on simulators. In this educational study, we assessed the time and number of attempts required to train novices in fiberoptic bronchoscopy and fiberoptic intubation on simulators. Because decay in skills is inevitable, we also assessed fiberoptic bronchoscopy and fiberoptic intubation skill decay and the amount of effort required to regain fiberoptic bronchoscopy skill. METHODS: First, we established attempt- and duration-based quantitative norms for reaching skill proficiency for fiberoptic bronchoscopy and fiberoptic intubation by experienced anesthesiologists (n = 8) and prepared an 11-step checklist and a 5-point global rating scale for assessment. Novice learners (n = 15) were trained to reach the established skill proficiency in a Virtual Reality simulator for fiberoptic bronchoscopy skills and a Human Airway Anatomy Simulator for fiberoptic intubation skills. Two months later, novices were reassessed to determine decay in learned skills and the required time to retrain them to fiberoptic bronchoscopy proficiency level. RESULTS: Proficiency in fiberoptic bronchoscopy skill level was achieved with 11 ± 5 attempts and after 658 ± 351 s. After 2 months without practice, the time taken by the novices to successful fiberoptic bronchoscopy on the Virtual Reality simulator increased from 41 ± 8 to 68 ± 31 s (P = 0.0138). Time and attempts required to retrain them were 424 ± 230 s and 9.1 ± 4.6 attempts, respectively. CONCLUSION: Novices were successfully trained to proficiency skill level. Although fiberoptic bronchoscopy skills started to decay within 2 months, the re-training time was shorter.

Supplemental postoperative oxygen does not reduce surgical site infection and major healing-related complications from bariatric surgery in morbidly obese patients: a randomized, blinded trial.

BACKGROUND: Morbidly obese patients are at high risk for perioperative complications, including surgical site infections. Baseline arterial oxygenation is low in the morbidly obese, leading to low tissue oxygenation, which in turn is a primary determinant of infection risk. We therefore tested the hypothesis that extending intraoperative supplemental oxygen 12 to 16 hours into the postoperative period reduces the risk of surgical site infection and healing-related complications. METHODS: Morbidly obese patients having open or laparoscopic bariatric surgery were given 80% inspired oxygen intraoperatively. Postoperatively, patients were randomly assigned to either 2 L/min of oxygen via nasal cannula or approximately 80% supplemental inspired oxygen after tracheal extubation until the first postoperative morning. The risks of surgical site infection and of major healing-related complications were evaluated 60 days after surgery. RESULTS: In a preplanned interim analysis based on the initial 400 patients, the overall observed incidence of the collapsed composite of major complications was 13.3%; the observed incidence of components of the composite outcome ranged from 0% (peritonitis) to 8.5% (surgical wound infection). The estimated relative risk of any ≥1 major complications occurring within the first 60 days after surgery, adjusting for study site, was 0.94 (95% confidence interval, 0.52-1.68) (P = 0.80, Cochran-Mantel-Haenszel). The Executive Committee thus stopped the trial for futility. CONCLUSIONS: Supplemental postoperative oxygen does not reduce the risk of surgical site infection rate and healing-related postoperative complications in patients having gastric bypass surgery.

Preoperative Assessment of a Patient Undergoing Bariatric Surgery.

Over the past few decades, obesity rates in the United States have risen drastically, and with this, there has been a rising demand for bariatric surgery. As such, anesthesiologists need to be familiar with the challenges presented by patients seeking bariatric surgery. Obesity causes pathophysiologic changes which may affect decision-making during the management of these patients. Patients seeking bariatric surgery also have a long, prescribed preoperative course that offers anesthesiologists the opportunity to be involved earlier during the pre-surgical evaluation and optimization process.

An analysis of enhanced recovery pathways for bariatric surgery-preoperative fasting, carbohydrate loading, and aspiration risk: a position statement from the International Society for the Perioperative Care of Patients with Obesity.

Enhanced recovery pathways (ERPs) and recommendations have become widely accepted for metabolic and bariatric surgery, including recommendations for preoperative carbohydrate loading and duration of fasting status. There is still a lack of consensus regarding such protocols and the underlying issues of gastric emptying time, resting gastric volume and pH, and risk of aspiration in patients with severe obesity and in patients undergoing bariatric surgery. The goal of this position statement by the International Society for the Perioperative Care of Patients with Obesity (ISPCOP) is to provide an analysis of available data on preoperative fasting and loading with oral complex clear carbohydrate drinks as well its potential effects on perioperative risk of aspiration in the context of Enhanced Recovery Pathways for Metabolic and Bariatric Surgery (ERAMBS).

Carbohydrate Loading and Aspiration Risk in Bariatric Patients: Safety in Preoperative Enhanced Recovery Protocols.

BACKGROUND: Enhanced recovery protocols have been developed to improve perioperative outcomes; however, there is ongoing concern for aspiration with recent oral intake in patients with obesity, who may be predisposed to impaired gastrointestinal motility and greater gastric volumes. We aim to study the safety of a 300-mL preoperative carbohydrate-loading drink preceding bariatric surgery. STUDY DESIGN: Data were collected prospectively from patients undergoing primary bariatric surgery. All bariatric patients at our institution are prescribed a proton pump inhibitor for 4 weeks before surgery and undergo a screening preoperative esophagogastroduodenoscopy (EGD) before surgery with a traditional 8-hour fast (NOCARB), followed by an intraoperative day-of-operation EGD with carbohydrate loading (CARB) 2 to 4 hours before incision. Gastric volumes and pH are measured after being endoscopically suctioned via direct visualization during both settings. RESULTS: We identified 203 patients: 94 patients (46.3%) in the CARB group and 109 patients (53.7%) in the NOCARB group. The patients were 82.3% female with a mean age of 42.8 years and average BMI of 41.7 kg/m 2 . There was no difference in gastric volume between NOCARB and CARB (17.0 vs 16.1 mL, p = 0.59). The NOCARB group had lower pH values than the CARB group (2.8 vs 3.8, p = 0.001). Subset analysis of 23 patients who had measurements on both screening and intraoperative EGD revealed lower gastric volumes in CARB patients (13.3 vs 18.3, p < 0.0001). CONCLUSIONS: When included in an enhanced recovery protocol, proton pump inhibitor use and preoperative carbohydrate loading 2 to 4 hours before bariatric surgery does not increase aspiration risk based on gastric volumes and pH and should be strongly considered in all eligible bariatric patients.

Teaching aseptic technique for central venous access under ultrasound guidance: a randomized trial comparing didactic training alone to didactic plus simulation-based training.

BACKGROUND: Our goal was to determine whether simulation combined with didactic training improves sterile technique during ultrasound (US)-guided central venous catheter (CVC) insertion compared with didactic training alone among novices. We hypothesized that novices who receive combined didactic and simulation-based training would perform similarly to experienced residents in aseptic technique, knowledge, and perception of comfort during US-guided CVC insertion on a simulator. METHODS: Seventy-two subjects were enrolled in a randomized, controlled trial of an educational intervention. Fifty-four novices were randomized into either the didactic group or the simulation combined with didactic group. Both groups received didactic training but the simulation combined with didactic group also received simulation-based CVC insertion training. Both groups were tested by demonstrating US-guided CVC insertion on a simulator. Aseptic technique was scored on 8 steps as "yes/no" and also using a 7-point Likert scale with 7 being "excellent technique" by a rater blinded to subject randomization. After initial testing, the didactic group was offered simulation-based training and retesting. Both groups also took a pre- and posttraining test of knowledge and rated their comfort with US and CVC insertion pre- and posttraining on a 5-point Likert scale. Subsequently, 18 experienced residents also took the test of knowledge, rated their comfort level, and were scored while performing aseptic US-guided CVC insertion using a simulator. RESULTS: The simulation combined with didactic group achieved a 167% (95% confidence interval [CI] 133%-167%) incremental increase in yes/no scores and 115% (CI 112%-127%) incremental increase in Likert scale ratings on aseptic technique compared with novices in the didactic group. Compared with experienced residents, simulation combined with didactic trained novices achieved an increase in aseptic scores with a 33.3% (CI 16.7%-50%) increase in yes/no ratings and a 20% (CI 13.3%-40%) increase in Likert scaled ratings, and scored 2.5-fold higher on the test of knowledge. There was a 3-fold increase in knowledge and 2-fold increase in comfort level among all novices (P < 0.001) after combined didactic and simulation-based training. CONCLUSION: Simulation combined with didactic training is superior to didactic training alone for acquisition of clinical skills such as US-guided CVC insertion. After combined didactic and simulation-based training, novices can outperform experienced residents in aseptic technique as well as in measurements of knowledge.

A simple approach to the sciatic nerve that does not require geometric calculations or multiple landmarks.

BACKGROUND: Blockade of the sciatic nerve is necessary for complete analgesia of the lower extremity using peripheral nerve blocks. We identified the sciatic nerve in relation to the ischial tuberosity in fresh cadaver dissections as well as in patients to compare sciatic nerve blockade using the conventional approach versus our experimental approach. Specifically, we tested the hypothesis that in patients in the prone position, our novel approach (changing the point of needle insertion to 3 cm lateral from the ischial tuberosity) requires fewer needle passes and less time. METHODS: The location of the sciatic nerve in relation to the ischial tuberosity was identified in 20 cadavers; this information was used to devise an alternative approach to the sciatic nerve. In a randomized, controlled, crossover patient study, we compared a prone subgluteal approach (conventional approach, n = 19) with an experimental approach with the insertion point 3 cm lateral to the midpoint of ischial tuberosity with patients in prone position (n = 20). We recorded the number of passes and the time taken to obtain an initial sciatic nerve twitch at a current of 1.5 mA and a twitch at <0.5 mA. RESULTS: The sciatic nerve averaged 2.8 +/- 0.4 cm from the midpoint of ischial tuberosity in cadavers in prone position. When needles were inserted from surface landmarks, those inserted through the experimental insertion point consistently transected the sciatic nerve. In contrast, needles inserted through the conventional approach were 2.27 +/- 0.47 cm lateral to the sciatic nerve. Clinically, our experimental approach required fewer passes to obtain a sciatic nerve twitch than the conventional approach. We were unable to obtain a twitch in 55% of patients with the conventional approach and converted them to the experimental approach. In patients originally assigned to the experimental approach and those switched to the experimental approach after failure with the conventional approach, we obtained the first sciatic nerve twitch in 1 pass in 45% of the patients and in 3 passes in 85%. CONCLUSIONS: We describe a landmark that is more effective for identifying the location of the sciatic nerve than that used for the prone subgluteal approach.

Preventing Nausea and Vomiting After Bariatric Surgery: Is the Apfel Risk Prediction Score Enough to Guide Prophylaxis?

Postoperative nausea and vomiting (PONV) is a frequent side effect in patients undergoing bariatric procedures. The simplified Apfel score is an attractive and frequently used tool to assess PONV risk in the general surgical population. Despite applying the recommendations based on the Apfel risk prediction score, several studies show that up to 82% of patients undergoing metabolic and bariatric surgery suffer from PONV in the PACU. A combination of multiple antiemetic drugs of different pharmacologic classes targeting a variety of receptors in addition to an intraoperative opioid-free TIVA technique should be considered in high-risk patients.

Guidelines for Perioperative Care in Cytoreductive Surgery (CRS) with or without hyperthermic IntraPEritoneal chemotherapy (HIPEC): Enhanced Recovery After Surgery (ERAS®) Society Recommendations - Part II: Postoperative management and special considerations.

BACKGROUND: Enhanced recovery after surgery (ERAS) pathways have been shown to considerably reduce complications, length of stay and costs after most of surgical procedures by standardised application of best evidence-based perioperative care. The aim was to elaborate dedicated recommendations for cytoreductive surgery (CRS) ± hyperthermic intraperitoneal chemotherapy (HIPEC) in a two-part series of guidelines based on expert consensus. The present part II of the guidelines highlights postoperative management and special considerations. METHODS: The core group assembled a multidisciplinary panel of 24 experts involved in peritoneal surface malignancy surgery representing the fields of general surgery (n = 12), gynaecological surgery (n = 6), and anaesthesia (n = 6). Experts systematically reviewed and summarized the available evidence on 72 identified perioperative care items, following the GRADE (grading of recommendations, assessment, development, evaluation) system. Final consensus (defined as ≥50%, or ≥70% of weak/strong recommendations combined) was reached by a standardised 2-round Delphi process, regarding the strength of recommendations. RESULTS: Response rates were 100% for both Delphi rounds. Quality of evidence was evaluated high, moderate low and very low, for 15 (21%), 26 (36%), 29 (40%) and 2 items, respectively. Consensus was reached for 71/72(98.6%) items. Strong recommendations were defined for 37 items. No consensus could be reached regarding the preemptive use of fresh frozen plasma. CONCLUSION: The present ERAS recommendations for CRS ± HIPEC are based on a standardised expert consensus process providing clinicians with valuable guidance. There is an urgent need to produce high quality studies for CRS ± HIPEC and to prospectively evaluate recommendations in clinical practice.

Guidelines for Perioperative Care in Cytoreductive Surgery (CRS) with or without hyperthermic IntraPEritoneal chemotherapy (HIPEC): Enhanced recovery after surgery (ERAS®) Society Recommendations - Part I: Preoperative and intraoperative management.

BACKGROUND: Enhanced recovery after surgery (ERAS) pathways have been shown to considerably reduce complications, length of stay and costs after most of surgical procedures by standardised application of best evidence-based perioperative care. The aim was to elaborate dedicated recommendations for cytoreductive surgery (CRS) ± hyperthermic intraperitoneal chemotherapy (HIPEC) in a two-part series of guidelines based on expert consensus. The present part I of the guidelines highlights preoperative and intraoperative management. METHODS: The core group assembled a multidisciplinary panel of 24 experts involved in peritoneal surface malignancy surgery representing the fields of general surgery (n = 12), gynaecological surgery (n = 6), and anaesthesia (n = 6). Experts systematically reviewed and summarized the available evidence on 72 identified perioperative care items, following the GRADE (grading of recommendations, assessment, development, evaluation) system. Final consensus (defined as ≥50%, or ≥70% of weak/strong recommendations combined) was reached by a standardised 2-round Delphi process, regarding the strength of recommendations. RESULTS: Response rates were 100% for both Delphi rounds. Quality of evidence was evaluated high, moderate low and very low, for 15 (21%), 26 (36%), 29 (40%) and 2 items, respectively. Consensus was reached for 71/72(98.6%) items. Strong recommendations were defined for 37 items, No consensus could be reached regarding the preemptive use of fresh frozen plasma. CONCLUSION: The present ERAS recommendations for CRS±HIPEC are based on a standardised expert consensus process providing clinicians with valuable guidance. There is an urgent need to produce high quality studies for CRS±HIPEC and to prospectively evaluate recommendations in clinical practice.

Suppression of shivering during hypothermia using a novel drug combination in healthy volunteers.

BACKGROUND: Hypothermia may be beneficial in stroke victims; however, it provokes vigorous shivering. Buspirone and dexmedetomidine each linearly reduce the shivering threshold with minimal sedation and no respiratory depression. This study tested the hypotheses that the combination of buspirone and dexmedetomidine would (1) synergistically reduce the shivering threshold, (2) synergistically reduce the gain and maximum intensity of shivering, and (3) produce sufficient inhibition to permit cooling to 34 degrees C without excessive hypotension or sedation. METHODS: Eight healthy men were randomly assigned on 4 days to (1) no drug, (2) buspirone (60 mg orally), (3) dexmedetomidine (intravenous infusion to target plasma concentration of 0.6 ng/ml), or (4) combination of buspirone and dexmedetomidine at same doses. Lactated Ringer's solution (approximately 3 degrees C) was infused intravenously to decrease tympanic membrane temperature by 1.5 degrees C/h. Shivering threshold was defined as an increase in oxygen consumption greater than 20%. Sedation was evaluated using the Observer's Assessment of Sedation/Alertness scale. RESULTS: Mean arterial pressure and heart rate were slightly lower on dexmedetomidine and combination days. Likewise, the level of sedation was statistically different on these 2 days but clinically unimportant. Buspirone reduced the shivering threshold from 36.6 degrees C +/- 0.4 degrees C to 35.9 degrees C +/- 0.4 degrees C, dexmedetomidine reduced it to 34.7 degrees C +/- 0.5 degrees C, and the combination to 34.1 +/- 0.4 degrees C. The interaction effect of 0.04 degrees C was not significant. The gain of shivering and maximum shivering intensity were similar on each day. CONCLUSIONS: The combination of buspirone and dexmedetomidine additively reduced the shivering threshold. Thus, supplementing dexmedetomidine with buspirone blocks shivering and causes only minimal sedation.

Neuromuscular block differentially affects immobility and cortical activation at near-minimum alveolar concentration anesthesia.

BACKGROUND: Anesthesia-induced immobility and cortical suppression are governed by anatomically separate, but interacting, areas of the central nervous system. Consequently, larger volatile anesthetic concentrations are required to suppress cortical activation than to abolish movement in response to noxious stimulation. We examined the effect of decreased afferent input, as produced by neuromuscular block (NMB), on immobility and cortical activation, as measured by bispectral index (BIS) of the electrocardiogram, in the presence of noxious stimulation during approximately minimum alveolar concentrations (MACs) of desflurane anesthesia. METHODS: The effect of NMB on the median effective end-tidal concentration of desflurane (EtDes(50), or MAC(tetanus)) for immobility was estimated using the up-and-down method and isolated forearm technique in 24 healthy volunteers. Each volunteer sequentially received saline, mivacurium, and succinylcholine in a randomized order, while EtDes concentration during each of the treatments was determined based on the movement response of the previous volunteer on the same treatment. Nonlinear mixed-effects modeling was used to evaluate the effect of NMB on BIS versus EtDes concentration relationship at baseline and after noxious stimulation, while the frontal electromyogram (EMG(BIS)) effect on BIS was also modeled as a covariate. Cardiovascular responses to noxious stimulation were compared across treatments. RESULTS: Succinylcholine and mivacurium significantly reduced MAC(tetanus) (95% confidence interval) from 5.00% (4.85%-5.13%), during saline, to 4.05% (3.81%-4.29%) and 3.84% (3.60%-4.08%), respectively. Noxious stimulation significantly, although minimally, increased BIS response during all treatments. Succinylcholine increased BIS independently of an effect on EMG(BIS). Succinylcholine administration increased cardiovascular activity. Interestingly, although cardiovascular reaction to the noxious event was ablated by mivacurium, cortical response, as determined by BIS, was retained. CONCLUSIONS: Both succinylcholine and mivacurium enhanced immobility during near-MAC anesthesia. All treatments were associated with a small, although significant, BIS increase in response to noxious stimulation, whereas succinylcholine increased BIS independently of noxious stimulation or EMG(BIS). Mivacurium suppressed autonomic response to a noxious event.

The effects of local anesthetic concentration and dose on continuous infraclavicular nerve blocks: a multicenter, randomized, observer-masked, controlled study.

BACKGROUND: It remains unclear whether local anesthetic concentration or total drug dose is the primary determinant of continuous peripheral nerve block effects. The only previous investigation, involving continuous popliteal-sciatic nerve blocks, specifically addressing this issue reported that insensate limbs were far more common with higher volumes of relatively dilute ropivacaine compared with lower volumes of relatively concentrated ropivacaine. However, it remains unknown if this relationship is specific to the sciatic nerve in the popliteal fossa or whether it varies depending on anatomic location. We therefore tested the null hypothesis that providing ropivacaine at different concentrations and rates, but at an equal total basal dose, produces comparable effects when used in a continuous infraclavicular brachial plexus block. METHODS: Preoperatively, an infraclavicular catheter was inserted using the coracoid approach in patients undergoing moderately painful orthopedic surgery distal to the elbow. Patients were randomly assigned to receive a postoperative perineural ropivacaine infusion of either 0.2% (basal 8 mL/h, bolus 4 mL) or 0.4% (basal 4 mL/h, bolus 2 mL) through the second postoperative day. Both groups, therefore, received 16 mg of ropivacaine each hour with a possible addition of 8 mg every 30 min via a patient-controlled bolus dose. Our primary end point was the incidence of an insensate limb during the 24-h period beginning the morning after surgery. Secondary end points included analgesia and patient satisfaction. RESULTS: Patients given 0.4% ropivacaine (n = 27) experienced an insensate limb, a mean (sd) of 1.8 (1.6) times, compared with 0.6 (0.9) times for subjects receiving 0.2% ropivacaine (n = 23; estimated difference = 1.2 episodes, 95% confidence interval, 0.5-1.9 episodes; P = 0.001). Satisfaction with postoperative analgesia (scale 0-10, 10 = highest) was scored a median (25th-75th percentiles) of 10.0 (8.0-10.0) in Group 0.2% and 7.0 (5.3-8.9) in Group 0.4% (P = 0.018). Analgesia was similar in each group. CONCLUSIONS: For continuous infraclavicular nerve blocks, local anesthetic concentration and volume influence perineural infusion effects in addition to the total mass of local anesthetic administered. Insensate limbs were far more common with smaller volumes of relatively concentrated ropivacaine. This is the opposite of the relationship previously reported for continuous popliteal-sciatic nerve blocks. The interaction between local anesthetic concentration and volume is thus complex and varies among catheter locations.