A comparison of strength for two continuous peripheral nerve block catheter dressings

BACKGROUND

Despite the benefits of continuous peripheral nerve blocks, catheter dislodgment remains a major problem, especially in the ambulatory setting. However, catheter dressing techniques to prevent such dislodgment have not been studied rigorously. We designed this simulation study to test the strength of two commercially available catheter dressings.

METHODS

Using a cadaver model, we randomly assigned 20 trials to one of two dressing techniques applied to the lateral thigh: 1) clear adhesive dressing alone, or 2) clear adhesive dressing with an anchoring device. Using a digital luggage scale attached to a loop secured by the dressing, the same investigator applied steadily increasing force with a downward trajectory towards the floor until the dressing was removed or otherwise disrupted.

RESULTS

The weight, measured (median [10th-90th percentile]) at the time of dressing disruption or removal, was 1.5 kg (1.3-1.8 kg) with no anchoring device versus 4.9 kg (3.7-6.5 kg) when the dressing included an anchoring device (P < 0.001).

CONCLUSIONS

Based on this simulation study, using an anchoring device may help prevent perineural catheter dislodgement and therefore premature disruption of continuous nerve block analgesia.

An ultrasound-guided fascia iliaca catheter technique does not impair ambulatory ability within a clinical pathway for total hip arthroplasty

Background

Both neuraxial and peripheral regional analgesic techniques offer postoperative analgesia for total hip arthroplasty (THA) patients. While no single technique is preferred, quadriceps muscle weakness from peripheral nerve blocks may impede rehabilitation. We designed this study to compare postoperative ambulation outcome in THA patients who were treated with a new ultrasound-guided fascia iliaca catheter (FIC) technique or intrathecal morphine (ITM).

Methods

We reviewed the electronic health records of a sequential series of primary unilateral THA patients who were part of a standardized clinical pathway; apart from differences in regional analgesic technique, all other aspects of the pathway were the same. Our primary outcome was total ambulation distance (meters) combined for postoperative days 1 and 2. Secondary outcomes included daily opioid consumption (morphine milligram equivalents) and analgesic-related side effects. We examined the association between the primary outcome and analgesic technique by performing crude and adjusted ordinary least-squares linear regression. A P value < 0.05 was considered statistically-significant.

Results

The study analyzed the records of 179 patients (fascia iliaca, n = 106; intrathecal, n = 73). The primary outcome (total ambulation distance) did not differ between the groups (P = 0.08). Body mass index (BMI) was the only factor (β = -1.7 [95% CI -0.5 to -2.9], P < 0.01) associated with ambulation distance. Opioid consumption did not differ, while increased pruritus was seen in the intrathecal group (P < 0.01).

Conclusions

BMI affects postoperative ambulation outcome after hip arthroplasty, whereas the type of regional analgesic technique used does not. An ultrasound-guided FIC technique offers similar analgesia with fewer side effects when compared with ITM.

A Randomized Double-Blinded Trial on the Effects of Ultrasound Transducer Orientation on Teaching and Learning Ultrasound-Guided Regional Anesthesia

OBJECTIVES

Learning ultrasound-guided regional anesthesia skills, especially needle/ beam alignment, can be especially difficulty for trainees, who can often become frustrated. We hypothesized that teaching novices to orient the transducer and needle perpendicular to their shoulders will improve performance on a standardized task, compared to holding the transducer and needle parallel to the shoulders.

METHODS

This study compared the effects of transducer orientation on trainees' ability to complete a standardized ultrasound-guided nerve block simulation. The time to task completion and percentage of the attempt time without adequate needle visualization were measured. Participants were right-handed healthy adults with no previous ultrasound experience and were randomly assigned to training in either transducer and needle alignment in a coronal plane, parallel to the shoulders (parallel group) or transducer and needle alignment in a sagittal plane, perpendicular to the shoulders (perpendicular group). Participants used ultrasound to direct a needle to 3 targets in a standardized gelatin phantom and repeated this task 3 times. Their efforts were timed and evaluated by an assessor, who was blinded to group assignment.

RESULTS

Data were analyzed on 28 participants. The perpendicular group was able to complete the task more quickly (P < .001) and with a smaller proportion of time lost to inadequate needle visualization (P < .001).

CONCLUSIONS

Ultrasound-guided regional anesthesia trainees complete a standardized task more quickly and efficiently when instructed to hold the transducer and needle in an orientation perpendicular to their shoulders.

Use of a home positive airway pressure device during intraoperative monitored anesthesia care for outpatient surgery

Perioperative positive airway pressure (PAP) is recommended by the American Society of Anesthesiologists for patients with obstructive sleep apnea, but a readily available and personalized intraoperative delivery system does not exist. We present the successful use of a patient's own nasal PAP machine in the operating room during outpatient foot surgery which required addition of a straight adaptor for oxygen delivery and careful positioning of the gas sampling line to permit end-tidal carbox dioxide monitoring. Home PAP machines may provide a potential alternative to more invasive methods of airway management for patients with obstructive sleep apnea under moderate sedation.

Can bedside patient-reported numbness predict postoperative ambulation ability for total knee arthroplasty patients with nerve block catheters?

BACKGROUND

Adductor canal catheters offer advantages over femoral nerve catheters for knee replacement patients because they produce less quadriceps muscle weakness; however, applying adductor canal catheters in bedside clinical practice remains challenging. There is currently no patient-reported outcome that accurately predicts patients' physical function after knee replacement. The present study evaluates the validity of a relatively new patient-reported outcome, i.e., a numbness score obtained using a numeric rating scale, and assesses its predictive value on postoperative ambulation.

METHODS

We conducted a retrospective cohort study pooling data from two previously-published clinical trials using identical research methodologies. Both studies recruited patients undergoing knee replacement; one studied adductor canal catheters while the other studied femoral nerve catheters. Our primary outcome was patient-reported numbness scores on postoperative day 1. We also examined postoperative day 1 ambulation distance and its association with postoperative numbness using linear regression, adjusting for age, body mass index, and physical status.

RESULTS

Data from 94 subjects were included (femoral subjects, n = 46; adductor canal subjects, n = 48). Adductor canal patients reported decreased numbness (median [10(th)-90(th) percentiles]) compared to femoral patients (0 [0-5] vs. 4 [0-10], P = 0.001). Adductor canal patients also ambulated seven times further on postoperative day 1 relative to femoral patients. There was a significant association between postoperative day 1 total ambulation distance and numbness (Beta = -2.6; 95% CI: -4.5, -0.8, P = 0.01) with R(2) = 0.1.

CONCLUSIONS

Adductor canal catheters facilitate improved early ambulation and produce less patient-reported numbness after knee replacement, but the correlation between these two variables is weak.

Comparative Effectiveness of Two Ultrasound-Guided Regional Block Techniques for Surgical Anesthesia in Open Unilateral Inguinal Hernia Repair

Transversus abdominis plane (TAP) and ilioinguinal/iliohypogastric (II/IH) nerve blocks have been described as analgesic adjuncts for inguinal hernia repair, but the efficacy of these techniques in providing intraoperative anesthesia, either individually or together, is not known. We designed this retrospective cohort study to test the hypothesis that combining TAP and II/IH nerve blocks ("double TAP" technique) results in greater accordance between the preoperative anesthetic plan and actual anesthetic technique provided when compared to TAP alone. Based on this study, double TAP may be preferred for patients undergoing open inguinal hernia repair who wish to avoid general anesthesia.

Invasive Mechanical Ventilation in California Over 2000-2009: Implications for Emergency Medicine

INTRODUCTION

Patients who require invasive mechanical ventilation (IMV) often represent a sequence of care between the emergency department (ED) and intensive care unit (ICU). Despite being the most populous state, little information exists to define patterns of IMV use within the state of California.

METHODS

We examined data from the masked Patient Discharge Database of California's Office of Statewide Health Planning and Development from 2000-2009. Adult patients who received IMV during their stay were identified using the International Classification of Diseases 9th Revision and Clinical Modification procedure codes (96.70, 96.71, 96.72). Patients were divided into age strata (18-34 yr, 35-64 yr, and >65 yr). Using descriptive statistics and regression analyses, for IMV discharges during the study period, we quantified the number of ED vs. non-ED based admissions; changes in patient characteristics and clinical outcome; evaluated the marginal costs for IMV; determined predictors for prolonged acute mechanical ventilation (PAMV, i.e. IMV>96 hr); and projected the number of IMV discharges and ED-based admissions by year 2020.

RESULTS

There were 696,634 IMV discharges available for analysis. From 2000-2009, IMV discharges increased by 2.8%/year: n=60,933 (293/100,000 persons) in 2000 to n=79,868 (328/100,000 persons) in 2009. While ED-based admissions grew by 3.8%/year, non-ED-based admissions remained stable (0%). During 2000-2009, fastest growth was noted for 1) the 35-64 year age strata; 2) Hispanics; 3) patients with non-Medicare public insurance; and 4) patients requiring PAMV. Average total patient cost-adjusted charges per hospital discharge increased by 29% from 2000 (from $42,528 to $60,215 in 2014 dollars) along with increases in the number of patients discharged to home and skilled nursing facilities. Higher marginal costs were noted for younger patients (ages 18-34 yr), non-whites, and publicly insured patients. Some of the strongest predictors for PAMV were age 35-64 years (OR=1.12; 95% CI [1.09-1.14], p<0.05); non-Whites; and non-Medicare public insurance. Our models suggest that by 2020, IMV discharges will grow to n=153,153 (377 IMV discharges/100,000 persons) with 99,095 admitted through the ED.

CONCLUSION

Based on sustained growth over the past decade, by the year 2020, we project a further increase to 153,153 IMV discharges with 99,095 admitted through the ED. Given limited ICU bed capacities, ongoing increases in the number and type of IMV patients have the potential to adversely affect California EDs that often admit patients to ICUs.

Evaluation of a Standardized Program for Training Practicing Anesthesiologists in Ultrasound-Guided Regional Anesthesia Skills

OBJECTIVES

Practicing anesthesiologists have generally not received formal training in ultrasound-guided perineural catheter insertion. We designed this study to determine the efficacy of a standardized teaching program in this population.

METHODS

Anesthesiologists in practice for 10 years or more were recruited and enrolled to participate in a 1-day program: lectures and live-model ultrasound scanning (morning) and faculty-led iterative practice and mannequin-based simulation (afternoon). Participants were assessed and recorded while performing ultrasound-guided perineural catheter insertion at baseline, at midday (interval), and after the program (final). Videos were scored by 2 blinded reviewers using a composite tool and global rating scale. Participants were surveyed every 3 months for 1 year to report the number of procedures, efficacy of teaching methods, and implementation obstacles.

RESULTS

Thirty-two participants were enrolled and completed the program; 31 of 32 (97%) completed the 1-year follow-up. Final scores [median (10th-90th percentiles)] were 21.5 (14.5-28.0) of 30 points compared to 14.0 (9.0-20.0) at interval (P < .001 versus final) and 12.0 (8.5-17.5) at baseline (P < .001 versus final), with no difference between interval and baseline. The global rating scale showed an identical pattern. Twelve of 26 participants without previous experience performed at least 1 perineural catheter insertion after training (P < .001). However, there were no differences in the monthly average number of procedures or complications after the course when compared to baseline.

CONCLUSIONS

Practicing anesthesiologists without previous training in ultrasound-guided regional anesthesia can acquire perineural catheter insertion skills after a 1-day standardized course, but changing clinical practice remains a challenge.

Design and Implementation of a Perioperative Surgical Home at a Veterans Affairs Hospital

The innovative Perioperative Surgical Home model aims to optimize the outcomes of surgical patients by leveraging the expertise and leadership of physician anesthesiologists, but there is a paucity of practical examples to follow. Veterans Affairs health care, the largest integrated system in the United States, may be the ideal environment in which to explore this model. We present our experience implementing Perioperative Surgical Home at one tertiary care university-affiliated Veterans Affairs hospital. This process involved initiating consistent postoperative patient follow-up beyond the postanesthesia care unit, a focus on improving in-hospital acute pain management, creation of an accessible database to track outcomes, developing new clinical pathways, and recruiting additional staff. Today, our Perioperative Surgical Home facilitates communication between various services involved in the care of surgical patients, monitoring of patient outcomes, and continuous process improvement.

Simulation in teaching regional anesthesia: current perspectives

The emerging subspecialty of regional anesthesiology and acute pain medicine represents an opportunity to evaluate critically the current methods of teaching regional anesthesia techniques and the practice of acute pain medicine. To date, there have been a wide variety of simulation applications in this field, and efficacy has largely been assumed. However, a thorough review of the literature reveals that effective teaching strategies, including simulation, in regional anesthesiology and acute pain medicine are not established completely yet. Future research should be directed toward comparative-effectiveness of simulation versus other accepted teaching methods, exploring the combination of procedural training with realistic clinical scenarios, and the application of simulation-based teaching curricula to a wider range of learner, from the student to the practicing physician.

Continuous Versus Single-Injection Peripheral Nerve Blocks: A Prospective Cohort Study Comparing Procedural Time and Estimated Personnel Cost

Background and Objectives:

Continuous peripheral nerve blocks (CPNB) provide many additional benefits compared to single-injection peripheral nerve blocks (SPNB). However, the time and costs associated with CPNB provision have not been previously considered. The objective of this study was to compare the time required and estimated personnel costs associated with CPNB and SPNB.

Methods:

This IRB-exempt observational study involved provision of preoperative regional anesthesia procedures in a “block room” model by a dedicated team during routine clinical care. The primary outcome, the time to perform ultrasound-guided popliteal-sciatic blocks, was recorded prospectively. This time measurement was broken down into individual tasks: time to place monitors, prepare the equipment, scan and identify the target, perform the block, and clean up post-procedure. For peripheral nerve block catheters, time to insert, locate, and secure the catheter was also recorded. Cost estimates for physician time were determined using published national mean hourly wages.

Results:

Time measurements were recorded for 24 nerve block procedures (12 CPNB and 12 SPNB). The median (IQR; range) total time (seconds) taken to perform blocks was 1132 (1083-1290; 1060-1623) for CPNB versus 505 (409-589; 368-635) for SPNB (Table 1; p<0.001). The median (IQR) cost attributed to physician time during block performance was $35.20 ($33.66-$40.11) and $15.69 ($12.73-$18.32) for CPNB and SPNB, respectively.

Conclusion:

CPNB requires approximately 10 more minutes per procedure to perform when compared to SPNB. This additional time should be considered along with potential patient benefits and available resources when developing a regional anesthesia and acute pain medicine service.

Acute Pain Medicine in the United States: A Status Report

BACKGROUND

Consensus indicates that a comprehensive,multimodal, holistic approach is foundational to the practice of acute pain medicine (APM),but lack of uniform, evidence-based clinical pathways leads to undesirable variability throughout U. S. healthcare systems. Acute pain studies are inconsistently synthesized to guide educational programs. Advanced practice techniques involving regional anesthesia assume the presence of a physician-led, multidisciplinary acute pain service,which is often unavailable or inconsistently applied.This heterogeneity of educational and organizational standards may result in unnecessary patient pain and escalation of healthcare costs.

METHODS

A multidisciplinary panel was nominated through the APM Shared Interest Group of the American Academy of Pain Medicine. The panel met in Chicago, IL, in July 2014, to identify gaps and set priorities in APM research and education.

RESULTS

The panel identified three areas of critical need: 1) an open-source acute pain data registry and clinical support tool to inform clinical decision making and resource allocation and to enhance research efforts; 2) a strong professional APM identity as an accredited subspecialty; and 3) educational goals targeted toward third-party payers,hospital administrators, and other key stake holders to convey the importance of APM.

CONCLUSION

This report is the first step in a 3-year initiative aimed at creating conditions and incentives for the optimal provision of APM services to facilitate and enhance the quality of patient recovery after surgery, illness, or trauma. The ultimate goal is to reduce the conversion of acute pain to the debilitating disease of chronic pain.

A Randomized Controlled Trial Evaluating the See, Tilt, Align, and Rotate (STAR) Maneuver on Skill Acquisition for Simulated Ultrasound-Guided Interventional Procedures

OBJECTIVES

Achieving the best view of the needle and target anatomy when performing ultrasound-guided interventional procedures requires technical skill, which novices may find difficult to learn. We hypothesized that teaching novice performers to use 4 sequential steps (see, tilt, align, and rotate [STAR] method) to identify the needle under ultrasound guidance is more efficient than training with the commonly described probe movements of align, rotate, and tilt (ART).

METHODS

This study compared 2 instructional methods for transducer manipulation including alignment of a probe and needle by novices during a simulated ultrasound-guided nerve block. Right-handed volunteers between the ages of 18 and 55 years who had no previous ultrasound experience were recruited and randomized to 1 of 2 groups; one group was trained to troubleshoot misalignment with the ART method, and the other was trained with the new STAR maneuver. Participants performed the task, consisting of directing a needle in plane to 3 targets in a standardized gelatin phantom 3 times. The performance assessor and data analyst were blinded to group assignment.

RESULTS

Thirty-five participants were recruited. The STAR group was able to complete the task more quickly (P < .001) and visualized the needle in a greater proportion of the procedure time (P = .004) compared to the ART group. All STAR participants were able to complete the task, whereas 41% of ART participants abandoned the task (P = .003).

CONCLUSIONS

Novices are able to complete a simulated ultrasound-guided nerve block more quickly and efficiently when trained with the 4-step STAR maneuver compared to the ART method.

Comparative effectiveness of infraclavicular and supraclavicular perineural catheters for ultrasound-guided through-the-catheter bolus anesthesia

OBJECTIVES

Using a through-the-needle local anesthetic bolus technique, ultrasound-guided infraclavicular perineural catheters have been shown to provide greater analgesia compared to supraclavicular catheters. A through-the-catheter bolus technique, which arguably "tests" the anesthetic efficacy of the catheter before initiating an infusion, has been validated for infraclavicular catheters but not supraclavicular catheters. This study investigated the through-the-catheter bolus technique for supraclavicular catheters and tested the hypothesis that infraclavicular catheters provide faster onset of brachial plexus anesthesia.

METHODS

Preoperatively, patients were randomly assigned to receive either a supraclavicular or an infraclavicular catheter using an ultrasound-guided nonstimulating catheter insertion technique with a mepivacaine bolus via the catheter and ropivacaine perineural infusion initiated postoperatively. The primary outcome was time to achieve complete sensory anesthesia in the ulnar and median nerve distributions. Secondary outcomes included procedural time, procedure-related pain and complications, and postoperative pain, opioid consumption, sleep disturbances, and motor weakness.

RESULTS

Fifty patients were enrolled in the study; all but 2 perineural catheters were successfully placed per protocol. Twenty-one of 24 (88%) and 24 of 24 (100%) patients in the supraclavicular and infraclavicular groups, respectively, achieved complete sensory anesthesia by 30 minutes (P= .088). There was no difference in the time to achieve complete sensory anesthesia. Supraclavicular patients reported more sleep disturbances postoperatively, but there were no statistically significant differences in other outcomes.

CONCLUSIONS

Both supraclavicular and infraclavicular perineural catheters using a through-the-catheter bolus technique provide effective brachial plexus anesthesia.

Developing a multidisciplinary fall reduction program for lower-extremity joint arthroplasty patients

With the anticipated increase in the number of total joint arthroplasty surgeries and associated fall risks, a fall reduction program can provide greater safety for patients in the postoperative period. Although further prospective studies are needed among total joint arthroplasty patients, there is sufficient evidence to show that a successful fall reduction program can be implemented. Common components to date have included a multidisciplinary team, multicomponent interventions specific to the risks associated with total knee and hip arthroplasty patients, education of patients and staff, and strategies to promote adherence to the program.

A pilot in vitro evaluation of the "air test" for perineural catheter tip localization by a novice regional anesthesiologist

The "air test" is used clinically to infer perineural catheter location and has been recently evaluated for use by experts. However, its utility for practitioners with less experience is unknown. We tested the hypothesis that the air test, when performed by a novice regional anesthesiologist, will improve assessment of perineural catheter tip position in a validated porcine-bovine model and determined the test's positive and negative predictive values, sensitivity, and specificity for a novice. In contrast to the results of the expert study, the air test did not improve the novice's assessment of perineural catheter tip location over chance.

A randomized comparison of proximal and distal ultrasound-guided adductor canal catheter insertion sites for knee arthroplasty

OBJECTIVES

Proximal and distal (mid-thigh) ultrasound-guided continuous adductor canal block techniques have been described but not yet compared, and infusion benefits or side effects may be determined by catheter location. We hypothesized that proximal placement will result in faster onset of saphenous nerve anesthesia, without additional motor block, compared to a distal technique.

METHODS

Preoperatively, patients receiving an ultrasound-guided nonstimulating adductor canal catheter for knee arthroplasty were randomly assigned to either proximal or distal insertion. A local anesthetic bolus was administered via the catheter after successful placement. The primary outcome was the time to achieve complete sensory anesthesia in the saphenous nerve distribution. Secondary outcomes included procedural time, procedure-related pain and complications, postoperative pain, opioid consumption, and motor weakness.

RESULTS

Proximal insertion (n = 23) took a median (10th-90th percentiles) of 12.0 (3.0-21.0) minutes versus 6.0 (3.0-21.0) minutes for distal insertion (n = 21; P= .106) to anesthetize the medial calf. Only 10 of 25 (40%) and 10 of 24 (42%) patients in the proximal and distal groups, respectively, developed anesthesia at both the medial calf and top of the patella (P= .978). Bolus-induced motor weakness occurred in 19 of 25 (76%) and 16 of 24 (67%) patients in the proximal and distal groups (P = .529). Ten of 24 patients (42%) in the distal group required intravenous morphine postoperatively, compared to 2 of 24 (8%) in the proximal group (P = .008), but there were no differences in other secondary outcomes.

CONCLUSIONS

Continuous adductor canal blocks can be performed reliably at both proximal and distal locations. The proximal approach may offer minor analgesic and logistic advantages without an increase in motor block.

A randomized clinical trial comparing the effectiveness of ultrasound guidance versus nerve stimulation for lateral popliteal-sciatic nerve blocks in obese patients

OBJECTIVES

Ultrasound guidance may decrease the procedural time for many peripheral nerve blocks compared to nerve stimulation, but these studies have generally excluded obese patients. This single-blinded randomized clinical trial was designed to compare procedural times and related outcomes for ultrasound- versus nerve stimulation-guided lateral popliteal-sciatic nerve blockade specifically in obese patients.

METHODS

With Institutional Review Board approval and informed consent, patients with a body mass index greater than 30 kg/m(2) who were scheduled for foot/ankle surgery and desiring a peripheral nerve block were offered enrollment. Study patients were randomly assigned to receive a lateral popliteal-sciatic nerve block under either ultrasound or nerve stimulation guidance. The patient and assessor were blinded to group assignment. The primary outcome was procedural time in seconds. Secondary outcomes included number of needle redirections, procedure-related pain, patient satisfaction with the block, success rate, sensory and motor onset times, block duration, and complication rates.

RESULTS

Twenty-four patients were enrolled and completed the study. All patients had successful nerve blocks. The mean procedural times (SD) were 577 (57) seconds under nerve stimulation and 206 (40) seconds with ultrasound guidance (P< .001; 95% confidence interval for difference, 329-412 seconds). Patients in the ultrasound group had fewer needle redirections and less procedure-related pain, required less opioids, and were more satisfied with their block procedures. There were no statistically significant differences in other outcomes.

CONCLUSIONS

The results of this study show that, for obese patients undergoing lateral popliteal-sciatic nerve blocks, ultrasound guidance reduces the procedural time and procedure-related pain and increases patient satisfaction compared to nerve stimulation while providing similar block characteristics.

Effectiveness of preoperative beta-blockade on intra-operative heart rate in vascular surgery cases conducted under regional or local anesthesia

BACKGROUND

Preoperative β-blockade has been posited to result in better outcomes for vascular surgery patients by attenuating acute hemodynamic changes associated with stress. However, the incremental effectiveness, if any, of β-blocker usage in blunting heart rate responsiveness for vascular surgery patients who avoid general anesthesia remains unknown.

METHODS

We reviewed an existing database and identified 213 consecutive vascular surgery cases from 2005-2011 conducted without general anesthesia (i.e., under monitored anesthesia care or regional anesthesia) at a tertiary care Veterans Administration medical center and categorized patients based on presence or absence of preoperative β-blocker prescription. For this series of patients, with the primary outcome of maximum heart rate during the interval between operating room entry to surgical incision, we examined the association of maximal heart rate and preoperative β-blocker usage by performing crude and multivariate linear regression, adjusting for relevant patient factors.

RESULTS

Of 213 eligible cases, 137 were prescribed preoperative β-blockers, and 76 were not. The two groups were comparable across baseline patient factors and intraoperative medication doses. The β-blocker group experienced lower maximal heart rates during the period of evaluation compared to the non-β-blocker group (85 ± 22 bpm vs. 98 ± 36 bpm, respectively; p = 0.002). Adjusted linear regression confirmed a statistically-significant association between lower maximal heart rate and the use of β-blockers (Beta = -11.5; 95% CI [-3.7, -19.3] p = 0.004).

CONCLUSIONS

The addition of preoperative β-blockers, even when general anesthesia is avoided, may be beneficial in further attenuating stress-induced hemodynamic changes for vascular surgery patients.

Continuous adductor canal blocks are superior to continuous femoral nerve blocks in promoting early ambulation after TKA

BACKGROUND

Femoral continuous peripheral nerve blocks (CPNBs) provide effective analgesia after TKA but have been associated with quadriceps weakness and delayed ambulation. A promising alternative is adductor canal CPNB that delivers a primarily sensory blockade; however, the differential effects of these two techniques on functional outcomes after TKA are not well established.

QUESTIONS/PURPOSES

We determined whether, after TKA, patients with adductor canal CPNB versus patients with femoral CPNB demonstrated (1) greater total ambulation distance on Postoperative Day (POD) 1 and 2 and (2) decreased daily opioid consumption, pain scores, and hospital length of stay.

METHODS

Between October 2011 and October 2012, 180 patients underwent primary TKA at our practice site, of whom 93% (n = 168) had CPNBs. In this sequential series, the first 102 patients had femoral CPNBs, and the next 66 had adductor canal CPNBs. The change resulted from a modification to our clinical pathway, which involved only a change to the block. An evaluator not involved in the patients' care reviewed their medical records to record the parameters noted above.

RESULTS

Ambulation distances were higher in the adductor canal group than in the femoral group on POD 1 (median [10(th)-90(th) percentiles]: 37 m [0-90 m] versus 6 m [0-51 m]; p < 0.001) and POD 2 (60 m [0-120 m] versus 21 m [0-78 m]; p = 0.003). Adjusted linear regression confirmed the association between adductor canal catheter use and ambulation distance on POD 1 (B = 23; 95% CI = 14-33; p < 0.001) and POD 2 (B = 19; 95% CI = 5-33; p = 0.008). Pain scores, daily opioid consumption, and hospital length of stay were similar between groups.

CONCLUSIONS

Adductor canal CPNB may promote greater early postoperative ambulation compared to femoral CPNB after TKA without a reduction in analgesia. Future randomized studies are needed to validate our major findings.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Application of echogenic technology for catheters used in ultrasound-guided continuous peripheral nerve blocks

Limited data exist regarding the echogenicity of perineural catheters, but visualization is crucial to ensure accurate placement and efficacy of the subsequent local anesthetic infusion. The objective of this study was to determine the comparative echogenicity of various regional anesthesia catheters. In an in vitro porcine-bovine model, we compared the echogenic qualities of 3 commercially available regional anesthesia catheters and 1 catheter under development to optimize echogenicity. Outcomes included visual echogenicity ranking, image quality, and scanning time, as assessed by 2 blinded investigators. The experimental catheter was found to be more echogenic than 2 of the 3 comparators.

Association of age and packed red blood cell transfusion to 1-year survival--an observational study of ICU patients

OBJECTIVES

To compare the 1-year survival for different age strata of intensive care unit (ICU) patients after receipt of packed red blood cell (PRBC) transfusions.

BACKGROUND

Despite guidelines documenting risks of PRBC transfusion and data showing that increasing age is associated with ICU mortality, little data exist on whether age alters the transfusion-related risk of decreased survival.

METHODS

We retrospectively examined data on 2393 consecutive male ICU patients admitted to a tertiary-care hospital from 2003 to 2009 in age strata: 21-50, 51-60, 61-70, 71-80 and >80 years. We calculated Cox regression models to determine the modifying effect of age on the impact of PRBC transfusion on 1-year survival by using interaction terms between receipt of transfusion and age strata, controlling for type of admission and Charlson co-morbidity indices. We also examined the distribution of admission haematocrit and whether transfusion rates differed by age strata.

RESULTS

All age strata experienced statistically similar risks of decreased 1-year survival after receipt of PRBC transfusions. However, patients age >80 were more likely than younger cohorts to have haematocrits of 25-30% at admission and were transfused at approximately twice the rate of each of the younger age strata.

DISCUSSION

We found no significant interaction between receipt of red cell transfusion and age, as variables, and survival at 1 year as an outcome.

Treating intractable phantom limb pain with ambulatory continuous peripheral nerve blocks: a pilot study

BACKGROUND

There is currently no reliable treatment for phantom limb pain (PLP). Chronic PLP and associated cortical abnormalities may be maintained from abnormal peripheral input, raising the possibility that a continuous peripheral nerve block (CPNB) of extended duration may permanently reorganize cortical pain mapping, thus providing lasting relief.

METHODS

Three men with below-the-knee (2) or -elbow (1) amputations and intractable PLP received femoral/sciatic or infraclavicular perineural catheter(s), respectively. Subjects were randomized in a double-masked fashion to receive perineural ropivacaine (0.5%) or normal saline for over 6 days as outpatients using portable electronic infusion pumps. Four months later, subjects returned for repeated perineural catheter insertion and received an ambulatory infusion with the alternate solution ("crossover"). Subjects were followed for up to 1 year.

RESULTS

By chance, all three subjects received saline during their initial infusion and reported little change in their PLP. One subject did not receive crossover treatment, but the remaining two subjects reported complete resolution of their PLP during and immediately following treatment with ropivacaine. One subject experienced no PLP recurrence through the 52-week follow-up period and the other reported mild PLP occurring once each week of just a small fraction of his original pain (pretreatment: continuous PLP rated 10/10; posttreatment: no PLP at baseline with average of one PLP episode each week rated 2/10) for 12 weeks (lost to follow-up thereafter).

CONCLUSIONS

A prolonged ambulatory CPNB may be a reliable treatment for intractable PLP. The results of this pilot study suggest that a large, randomized clinical trial is warranted.

Choice of loco-regional anesthetic technique affects operating room efficiency for carpal tunnel release

Intravenous regional anesthesia (Bier block) is indicated for minor procedures such as carpal tunnel release but must be performed in the operating room. We hypothesize that preoperative peripheral nerve blocks decrease anesthesia-controlled time compared to Bier block for carpal tunnel release. With IRB approval, we reviewed surgical case data from a tertiary care university hospital outpatient surgery center for 1 year. Unilateral carpal tunnel release cases were grouped by anesthetic technique: (1) preoperative nerve blocks, or (2) Bier block. The primary outcome was anesthesia-controlled time (minutes). Secondary outcomes included surgical time and time for nerve block performance in minutes, when applicable. Eighty-nine cases met criteria for analysis (40 nerve block and 49 Bier block). Anesthesia-controlled time [median (10th-90th percentiles)] was shorter for the nerve block group compared to Bier block [11 (6-18) vs. 13 (9-20) min, respectively; p = 0.02). Surgical time was also shorter for the nerve block group vs. the Bier block group [13 (8-21) and 17 (10-29) min, respectively; p < 0.01), but nerve blocks took 10 (5-28) min to perform. Ultrasound-guided nerve blocks performed preoperatively reduce anesthesia-controlled time compared to Bier block and may be a useful anesthetic modality in some practice environments.

An in vitro study to evaluate the utility of the "air test" to infer perineural catheter tip location

Injection of air under ultrasound guidance via a perineural catheter after insertion ("air test") has been described as a means to infer placement accuracy, yet this test has never been rigorously evaluated. We tested the hypothesis that the air test predicts accurate catheter location greater than chance and determined the test's sensitivity, specificity, and positive and negative predictive values using a porcine-bovine model and blinded expert in ultrasound-guided regional anesthesia. The air test improved the expert clinician's assessment of catheter tip position compared to chance, but there was no difference when compared to direct visualization of the catheter without air injection.

A randomized comparison of long-and short-axis imaging for in-plane ultrasound-guided femoral perineural catheter insertion

OBJECTIVES

Continuous femoral nerve blocks provide effective analgesia after knee arthroplasty, and infusion effects depend on reliable catheter location. Ultrasound-guided perineural catheter insertion using a short-axis in-plane technique has been validated, but the optimal catheter location relative to target nerve and placement orientation remain unknown. We hypothesized that a long-axis in-plane technique for femoral perineural catheter insertion results in faster onset of sensory anesthesia compared to a short-axis in-plane technique.

METHODS

Preoperatively, patients receiving an ultrasound-guided nonstimulating femoral perineural catheter for knee surgery were randomly assigned to either the long-axis in-plane or short-axis in-plane technique. A local anesthetic was administered via the catheter after successful insertion. The primary outcome was the time to achieve complete sensory anesthesia. Secondary outcomes included the procedural time, the onset time of the motor block, pain and muscle weakness reported on postoperative day 1, and procedure-related complications.

RESULTS

The short-axis group (n = 23) took a median (10th-90th percentiles) of 9.0 (6.0-20.4) minutes compared to 6.0 (3.0-14.4) minutes for the long-axis group (n = 23; P = .044) to achieve complete sensory anesthesia. Short-axis procedures took 5.0 (4.0-7.8) minutes to perform compared to 9.0 (7.0-14.8) minutes for long-axis procedures (P < .001). In the short-axis group, 19 of 23 (83%) achieved a complete motor block within the testing period compared to 18 of 23 (78%) in the long-axis group (P = .813); short-axis procedures took 12.0 (6.0-15.0) minutes versus 15.0 (5.1-27.9) minutes for long-axis procedures (P = .048). There were no statistically significant differences in other secondary outcomes.

CONCLUSIONS

Long-axis in-plane femoral perineural catheters result in a slightly faster onset of sensory anesthesia, but placement takes longer to perform without other clinical advantages.

Preliminary study of ergonomic behavior during simulated ultrasound-guided regional anesthesia using a head-mounted display

A head-mounted display provides continuous real-time imaging within the practitioner's visual field. We evaluated the feasibility of using head-mounted display technology to improve ergonomics in ultrasound-guided regional anesthesia in a simulated environment. Two anesthesiologists performed an equal number of ultrasound-guided popliteal-sciatic nerve blocks using the head-mounted display on a porcine hindquarter, and an independent observer assessed each practitioner's ergonomics (eg, head turning, arching, eye movements, and needle manipulation) and the overall block quality based on the injectate spread around the target nerve for each procedure. Both practitioners performed their procedures without directly viewing the ultrasound monitor, and neither practitioner showed poor ergonomic behavior. Head-mounted display technology may offer potential advantages during ultrasound-guided regional anesthesia.

Vascular surgery patients prescribed preoperative β-blockers experienced a decrease in the maximal heart rate observed during induction of general anesthesia

OBJECTIVE

To investigate the association of preoperative β-blocker usage and maximal heart rates observed during the induction of general anesthesia.

DESIGN

Retrospective descriptive, univariate, and multivariate analyses of electronic hospital and anesthesia medical records.

SETTING

A tertiary-care medical center within the Veterans Health Administration.

PARTICIPANTS

Consecutive adult elective and emergent patients presenting for vascular surgery during calendar years 2005 to 2011.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 430 eligible cases, 218 were prescribed β-blockers, and 212 were not taking β-blockers. The two groups were comparable across baseline patient factors (ie, demographic, morphometric, surgical duration, and surgical procedures) and induction medication doses. The β-blocker group experienced a lower maximal heart rate during the induction of general anesthesia compared with the non-β-blocker group (105 ± 41 beats/min v 115 ± 45 beats/min, respectively; p < 0.01). Adjusted linear regression found a statistically significant association between lower maximal heart rate and the use of β-blockers (β = -11.1 beats/min, p < 0.01). There was no difference between groups in total intraoperative β-blocker administration.

CONCLUSIONS

Preoperative β-blockade of vascular surgery patients undergoing general anesthesia is associated with a lower maximal heart rate during anesthetic induction. There may be potential benefits in administering β-blockers to reduce physiologic stress in this surgical population at risk for perioperative cardiac morbidity. Future research should further explore intraoperative hemodynamic effects in light of existing practice guidelines for optimal medication selection, dosage, and heart rate control.

Continuous femoral nerve blocks: varying local anesthetic delivery method (bolus versus basal) to minimize quadriceps motor block while maintaining sensory block

BACKGROUND

Whether the method of local anesthetic administration for continuous femoral nerve blocks--basal infusion versus repeated hourly bolus doses--influences block effects remains unknown.

METHODS

Bilateral femoral perineural catheters were inserted in volunteers (n = 11). Ropivacaine 0.1% was concurrently administered through both catheters: a 6-h continuous 5 ml/h basal infusion on one side and 6 hourly bolus doses on the contralateral side. The primary endpoint was the maximum voluntary isometric contraction (MVIC) of the quadriceps femoris muscle at hour 6. Secondary endpoints included quadriceps MVIC at other time points, hip adductor MVIC, and cutaneous sensation 2 cm medial to the distal quadriceps tendon in the 22 h after initiation of local anesthetic administration.

RESULTS

Quadriceps MVIC for limbs receiving 0.1% ropivacaine as a basal infusion declined by a mean (SD) of 84% (19) compared with 83% (24) for those receiving 0.1% ropivacaine as repeated bolus doses between baseline and hour 6 (paired t test P = 0.91). Intrasubject comparisons (left vs. right) also reflected a lack of difference: the mean basal-bolus difference in quadriceps MVIC at hour 6 was -1.1% (95% CI -22.0-19.8%). The similarity did not reach the a priori threshold for concluding equivalence, which was the 95% CI decreasing within ± 20%. There were similar minimal differences in the secondary endpoints during local anesthetic administration.

CONCLUSIONS

This study did not find evidence to support the hypothesis that varying the method of local anesthetic administration--basal infusion versus repeated bolus doses--influences continuous femoral nerve block effects to a clinically significant degree.

Comparison of procedural times for ultrasound-guided perineural catheter insertion in obese and nonobese patients

OBJECTIVES

Perineural catheter insertion with ultrasound guidance alone has been described, but it remains unknown whether this new technique results in the same procedural time and success rate for obese and nonobese patients. We therefore tested the hypothesis that obese patients require more time for perineural catheter insertion compared to nonobese patients despite using ultrasound.

METHODS

Data from 5 previously published randomized clinical trials comparing ultrasound- and stimulation-guided perineural catheter insertion techniques were reviewed, and patients who received ultrasound-guided catheters were divided into 2 groups: obese (body mass index ≥30 kg/m(2)) and nonobese (body mass index <30 kg/m(2)). A standardized ultrasound-guided nonstimulating catheter technique was used with mepivacaine, 1.5% (40 mL), as the initial bolus via the placement needle for the primary surgical nerve block. The primary outcome was the procedural time for perineural catheter insertion. Secondary outcomes included block efficacy, procedure-related pain, fluid leakage, vascular puncture, and catheter dislodgment.

RESULTS

A sample of 120 patients was identified: 51 obese and 69 nonobese. All obese patients had successful catheter placement compared to 68 of 69 (98%) nonobese patients (P = .388). The time for perineural catheter insertion [median (10th-90th percentiles)] was 7 (4-12) minutes for obese patients versus 7 (4-15) minutes for nonobese patients (P = .732). There were no statistically significant differences in other secondary outcomes.

CONCLUSIONS

On the basis of this retrospective analysis, perineural catheter insertion is not prolonged in obese patients compared to nonobese patients when an ultrasound-guided technique is used. However, these results are only suggestive and require confirmation through prospective study.

Regional anaesthesia in the obese patient: lost landmarks and evolving ultrasound guidance

Obesity is associated with a number of anaesthetic-related risks. Regional anaesthesia offers many potential advantages for the obese surgical patient. Advantages include a reduction in systemic opioid requirements and their associated side effects, and possible avoidance of general anaesthesia in select circumstances, with a lower rate of complications. Historically, performing regional anaesthesia procedures in the obese has presented challenges due to difficulty in identifying surface landmarks and availability of appropriate equipment. Ultrasound guidance may aid the regional anaesthesia practitioner with direct visualisation of underlying anatomic structures and real-time needle direction. Further research is needed to determine optimal regional anaesthesia techniques, local anaesthetic dosage and perioperative outcomes in obese patients.

Continuous femoral versus posterior lumbar plexus nerve blocks for analgesia after hip arthroplasty: a randomized, controlled study

BACKGROUND

Hip arthroplasty frequently requires potent postoperative analgesia, often provided with an epidural or posterior lumbar plexus local anesthetic infusion. However, American Society of Regional Anesthesia guidelines now recommend against epidural and continuous posterior lumbar plexus blocks during administration of various perioperative anticoagulants often administered after hip arthroplasty. A continuous femoral nerve block is a possible analgesic alternative, but whether it provides comparable analgesia to a continuous posterior lumbar plexus block after hip arthroplasty remains unclear. We therefore tested the hypothesis that differing the catheter insertion site (femoral versus posterior lumbar plexus) after hip arthroplasty has no impact on postoperative analgesia.

METHODS

Preoperatively, subjects undergoing hip arthroplasty were randomly assigned to receive either a femoral or a posterior lumbar plexus stimulating catheter inserted 5 to 15 cm or 0 to 1 cm past the needle tip, respectively. Postoperatively, patients received perineural ropivacaine, 0.2% (basal 6 mL/hr, bolus 4 mL, 30-minute lockout) for at least 2 days. The primary end point was the average daily pain scores as measured with a numeric rating scale (0-10) recorded in the 24-hour period beginning at 07:30 the morning after surgery, excluding twice-daily physical therapy sessions. Secondary end points included pain during physical therapy, ambulatory distance, and supplemental analgesic requirements during the same 24-hour period, as well as satisfaction with analgesia during hospitalization.

RESULTS

The mean (SD) pain scores for subjects receiving a femoral infusion (n = 25) were 3.6 (1.8) versus 3.5 (1.8) for patients receiving a posterior lumbar plexus infusion (n = 22), resulting in a group difference of 0.1 (95% confidence interval -0.9 to 1.2; P = 0.78). Because the confidence interval was within a prespecified -1.6 to 1.6 range, we conclude that the effect of the 2 analgesic techniques on postoperative pain was equivalent. Similarly, we detected no differences between the 2 treatments with respect to the secondary end points, with one exception: subjects with a femoral catheter ambulated a median (10th-90th percentiles) 2 (0-17) m the morning after surgery, in comparison with 11 (0-31) m for subjects with a posterior lumbar plexus catheter (data nonparametric; P = 0.02).

CONCLUSIONS

After hip arthroplasty, a continuous femoral nerve block is an acceptable analgesic alternative to a continuous posterior lumbar plexus block when using a stimulating perineural catheter. However, early ambulatory ability suffers with a femoral infusion.

Preliminary experience with a novel ultrasound-guided supraclavicular perineural catheter insertion technique for perioperative analgesia of the upper extremity

OBJECTIVE

Brachial plexus perineural catheters provide specific analgesia for upper extremity surgery. Although single-injection ultrasound-guided supraclavicular blocks have been described, little is known about the efficacy of perineural catheters inserted using this approach. We present our experience with ultrasound-guided supraclavicular perineural catheters for distal upper extremity surgery.

METHODS

In this case series, 10 patients who underwent upper extremity surgery for orthopedic trauma at a tertiary care university hospital received a supraclavicular brachial plexus perineural catheter for postoperative pain management. In all patients, a nonstimulating catheter was inserted using an ultrasound-guided technique with the catheter tip remaining under direct vision until placement needle withdrawal. Postoperatively, a perineural ropivacaine, 0.2%, infusion was administered at a basal rate of 6 mL/h with a patient-controlled bolus of 4 mL and a lockout interval of 30 minutes.

RESULTS

Of the 10 patients, all had successful perineural catheter placement. Patients required a median (range) of 0 (0-100) μg of fentanyl for catheter insertion analgesia. There were no vascular punctures or other direct procedure-related complications. Catheters were maintained for a median (range) of 4 (2-5) days in both hospitalized and ambulatory patients. Median (range) pain scores on postoperative days 1 and 2 were 5 (0-7) and 4 (3-6), respectively, on a numeric rating scale. Three patients' catheters were removed by patient request or dislodged on postoperative day 1.

CONCLUSIONS

Supraclavicular brachial plexus perineural catheter insertion using ultrasound guidance is feasible and deserves further study with a randomized controlled trial comparing this relatively new technique with more established approaches.

A multicenter, randomized, triple-masked, placebo-controlled trial of the effect of ambulatory continuous femoral nerve blocks on discharge-readiness following total knee arthroplasty in patients on general orthopaedic wards

A continuous femoral nerve block (cFNB) involves the percutaneous insertion of a catheter adjacent to the femoral nerve, followed by a local anesthetic infusion, improving analgesia following total knee arthroplasty (TKA). Portable infusion pumps allow infusion continuation following hospital discharge, raising the possibility of decreasing hospitalization duration. We therefore used a multicenter, randomized, triple-masked, placebo-controlled study design to test the primary hypothesis that a 4-day ambulatory cFNB decreases the time until each of three predefined readiness-for-discharge criteria (adequate analgesia, independence from intravenous opioids, and ambulation 30m) are met following TKA compared with an overnight inpatient-only cFNB. Preoperatively, all patients received a cFNB with perineural ropivacaine 0.2% from surgery until the following morning, at which time they were randomized to either continue perineural ropivacaine (n=39) or switch to normal saline (n=38). Patients were discharged with their cFNB and portable infusion pump as early as postoperative day 3. Patients who were given 4 days of perineural ropivacaine attained all three criteria in a median (25th-75th percentiles) of 47 (29-69)h, compared with 62 (45-79)h for those of the control group (Estimated ratio=0.80, 95% confidence interval: 0.66-1.00; p=0.028). Compared with controls, patients randomized to ropivacaine met the discharge criterion for analgesia in 20 (0-38) versus 38 (15-64)h (p=0.009), and intravenous opioid independence in 21 (0-37) versus 33 (11-50)h (p=0.061). We conclude that a 4-day ambulatory cFNB decreases the time to reach three important discharge criteria by an estimated 20% following TKA compared with an overnight cFNB, primarily by improving analgesia.