Motor-sparing peripheral nerve blocks for hip and knee surgery.

PURPOSE OF REVIEW: To summarize the recent literature describing and comparing novel motor-sparing peripheral nerve block techniques for hip and knee surgery. This topic is relevant because the number of patients undergoing same day discharge after hip and knee surgery is increasing. Preserving lower extremity muscle function is essential to facilitate early physical therapy for these patients. RECENT FINDINGS: Distal peripheral nerve blocks may allow for preserved quadriceps motor strength and comparable analgesia to traditional techniques. However, few studies in hip and knee populations include strength or function as primary outcomes. For hip surgeries, studies have failed to show analgesic differences between regional blocks and periarticular infiltration. Similarly for knee arthroplasty in the absence of periarticular infiltration, recent evidence suggests adding combinations of blocks (ACB plus iPACK or genicular nerve blocks) may balance pain control and early ambulation. SUMMARY: The use of motor-sparing peripheral nerve block techniques enables early ambulation, adequate pain control, and avoidance of opioid-related side effects facilitating outpatient/ambulatory lower extremity surgery. Further studies of these techniques for continuous peripheral nerve block catheters are needed to assess if extended blockade continues to provide motor-sparing and opioid-sparing benefits.

The Efficacy and Safety of Regional Nerve Blocks in Total Knee Arthroplasty: Systematic Review and Direct Meta-Analysis.

BACKGROUND: Regional nerve blocks are widely used in primary total knee arthroplasty (TKA) to reduce postoperative pain and opioid consumption. The purpose of our study was to evaluate the efficacy and safety of regional nerve blocks after TKA in support of the combined clinical practice guidelines of the American Association of Hip and Knee Surgeons, American Academy of Orthopaedic Surgeons, Hip Society, Knee Society, and American Society of Regional Anesthesia and Pain Management. METHODS: We searched MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials for studies published before March 24, 2020 on femoral nerve block, adductor canal block, and infiltration between Popliteal Artery and Capsule of Knee in primary TKA. All included studies underwent qualitative and quantitative homogeneity testing followed by a systematic review and direct comparison meta-analysis to assess the efficacy and safety of the regional nerve blocks compared to a control, local peri-articular anesthetic infiltration (PAI), or between regional nerve blocks. RESULTS: Critical appraisal of 1,673 publications yielded 56 publications representing the best available evidence for analysis. Femoral nerve and adductor canal blocks are effective at reducing postoperative pain and opioid consumption, but femoral nerve blocks are associated with quadriceps weakness. Use of a continuous compared to single shot adductor canal block can improve postoperative analgesia. No difference was noted between an adductor canal block or PAI regarding postoperative pain and opioid consumption, but the combination of both may be more effective. CONCLUSION: Single shot adductor canal block or PAI should be used to reduce postoperative pain and opioid consumption following TKA. Use of a continuous adductor canal block or a combination of single shot adductor canal block and PAI may improve postoperative analgesia in patients with concern of poor postoperative pain control.

The Efficacy and Safety of Regional Nerve Blocks in Total Hip Arthroplasty: Systematic Review and Direct Meta-Analysis.

BACKGROUND: Regional nerve blocks may be used as a component of a multimodal analgesic protocol to manage postoperative pain after primary total hip arthroplasty (THA). The purpose of our study was to evaluate the efficacy and safety of regional nerve blocks after THA in support of the combined clinical practice guidelines of the American Association of Hip and Knee Surgeons, American Academy of Orthopaedic Surgeons, Hip Society, Knee Society, and American Society of Regional Anesthesia and Pain Management. METHODS: We searched MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials for studies published prior to March 24, 2020 on fascia iliaca, lumbar plexus, and quadratus lumborum blocks in primary THA. All included studies underwent qualitative and quantitative homogeneity testing followed by a systematic review and direct comparison meta-analysis to assess the efficacy and safety of the regional nerve blocks. RESULTS: An initial critical appraisal of 3,382 publications yielded 11 publications representing the best available evidence for an analysis. Fascia iliaca, lumbar plexus, and quadratus lumborum blocks demonstrate the ability to reduce postoperative pain and opioid consumption. Among the available comparisons, no difference was noted between a regional nerve block or local periarticular anesthetic infiltration regarding postoperative pain and opioid consumption. CONCLUSION: Local periarticular anesthetic infiltration should be considered prior to a regional nerve block due to concerns over the safety and cost of regional nerve blocks. If a regional nerve block is used in primary THA, a fascia iliaca block is preferred over other blocks due to the differences in technical demands and risks associated with the alternative regional nerve blocks.

Caffeine supplementation as part of enhanced recovery after surgery pathways: a narrative review of the evidence and knowledge gaps.

Caffeine is used daily by 85% of United States adults and caffeine withdrawal is a major cause of perioperative headache. Studies have shown that caffeine supplementation in chronic caffeinators reduces the incidence of perioperative headache. This narrative review discusses the perioperative implications of caffeine withdrawal and outlines the benefits of and strategies of caffeine supplementation in the perioperative period. It is time to "wake up and smell the coffee" on integration of caffeine into established enhanced recovery after surgery protocols as a mechanism to consistently provide perioperative caffeine replacement.

RéSUMé: La caféine est utilisée quotidiennement par 85 % des adultes aux États-Unis, et le sevrage de la caféine constitue une cause majeure de céphalées périopératoires. Des études ont montré que la supplémentation en caféine chez les grands buveurs de café réduisait l'incidence des céphalées périopératoires. Ce compte rendu narratif discute des implications périopératoires du sevrage de la caféine et décrit les avantages et les stratégies de la supplémentation en caféine en période périopératoire. Il est temps de « se réveiller à l'odeur du café ¼ quant à l'intégration de la caféine dans les protocoles de récupération rapide après la chirurgie en tant que mécanisme pour procurer de façon systématique un subsitut périopératoire à la caféine.

Anaesthetic care of patients undergoing primary hip and knee arthroplasty: consensus recommendations from the International Consensus on Anaesthesia-Related Outcomes after Surgery group (ICAROS) based on a systematic review and meta-analysis.

BACKGROUND: Evidence-based international expert consensus regarding anaesthetic practice in hip/knee arthroplasty surgery is needed for improved healthcare outcomes. METHODS: The International Consensus on Anaesthesia-Related Outcomes after Surgery group (ICAROS) systematic review, including randomised controlled and observational studies comparing neuraxial to general anaesthesia regarding major complications, including mortality, cardiac, pulmonary, gastrointestinal, renal, genitourinary, thromboembolic, neurological, infectious, and bleeding complications. Medline, PubMed, Embase, and Cochrane Library including Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, NHS Economic Evaluation Database, from 1946 to May 17, 2018 were queried. Meta-analysis and Grading of Recommendations Assessment, Development and Evaluation approach was utilised to assess evidence quality and to develop recommendations. RESULTS: The analysis of 94 studies revealed that neuraxial anaesthesia was associated with lower odds or no difference in virtually all reported complications, except for urinary retention. Excerpt of complications for neuraxial vs general anaesthesia in hip/knee arthroplasty, respectively: mortality odds ratio (OR): 0.67, 95% confidence interval (CI): 0.57-0.80/OR: 0.83, 95% CI: 0.60-1.15; pulmonary OR: 0.65, 95% CI: 0.52-0.80/OR: 0.69, 95% CI: 0.58-0.81; acute renal failure OR: 0.69, 95% CI: 0.59-0.81/OR: 0.73, 95% CI: 0.65-0.82; deep venous thrombosis OR: 0.52, 95% CI: 0.42-0.65/OR: 0.77, 95% CI: 0.64-0.93; infections OR: 0.73, 95% CI: 0.67-0.79/OR: 0.80, 95% CI: 0.76-0.85; and blood transfusion OR: 0.85, 95% CI: 0.82-0.89/OR: 0.84, 95% CI: 0.82-0.87. CONCLUSIONS: Recommendation: primary neuraxial anaesthesia is preferred for knee arthroplasty, given several positive postoperative outcome benefits; evidence level: low, weak recommendation. RECOMMENDATION: neuraxial anaesthesia is recommended for hip arthroplasty given associated outcome benefits; evidence level: moderate-low, strong recommendation. Based on current evidence, the consensus group recommends neuraxial over general anaesthesia for hip/knee arthroplasty. TRIAL REGISTRY NUMBER: PROSPERO CRD42018099935.

A 3-arm randomized clinical trial comparing interscalene blockade techniques with local infiltration analgesia for total shoulder arthroplasty.

BACKGROUND: The ideal analgesic modality for total shoulder arthroplasty (TSA) remains controversial. We hypothesized that a multimodal analgesic pathway incorporating continuous interscalene blockade (ISB) provides better analgesic efficacy than both single-injection ISB and local infiltration analgesia. METHODS: This single-center, parallel, unblinded, randomized clinical trial evaluated 129 adults undergoing primary TSA. Patients were allocated to single-injection ISB, continuous ISB, or local infiltration analgesia. The primary outcome was the Overall Benefit of Analgesia Score (range, 0 [best] to 28 [worst]) on postoperative day 1. Additional outcomes included pain scores, opioid consumption, quality of life, and postoperative complications in the first 24 hours, at 3 months, and at 1 year. RESULTS: We analyzed 125 patients (42 with single-injection ISB, 41 with continuous ISB, and 42 with local infiltration analgesia). The Overall Benefit of Analgesia Score was significantly improved in the continuous group (median [25th percentile, 75th percentile], 0 [0, 2]) compared with the single-injection group (2 [1, 4]; P = .002) and local infiltration analgesia group (3 [2, 4]; P < .001). Pain scores were significantly lower in the continuous group compared with the local infiltration analgesia group (P < .001 for all time points) and after 12 hours from ward arrival compared with the single-injection group (median [25th percentile, 75th percentile], 1.0 [0.0, 2.8] vs. 2.5 [0.0, 4.0]; P = .016). After postanesthesia recovery discharge, opioid consumption (oral morphine equivalents) was significantly lower in the continuous group (median [25th percentile, 75th percentile], 7.5 mg [0.0, 25.0 mg]) than in the local infiltration analgesia group (30 mg [15.0, 52.5 mg]; P < .001) and single-injection group (17.6 mg [7.5, 45.5 mg]; P = .010). No differences were found across groups for complications, 3-month outcomes, and 1-year outcomes. CONCLUSION: Continuous ISB provides superior analgesia compared with single-injection ISB and local infiltration analgesia in the first 24 hours after TSA.

Peripheral Nerve Blocks for Hip Fractures: A Cochrane Review.

BACKGROUND: This review focuses on the use of peripheral nerve blocks as preoperative analgesia, as postoperative analgesia, or as a supplement to general anesthesia for hip fracture surgery and tries to determine if they offer any benefit in terms of pain on movement at 30 minutes after block placement, acute confusional state, myocardial infarction/ischemia, pneumonia, mortality, time to first mobilization, and cost of analgesic. METHODS: Trials were identified by computerized searches of Cochrane Central Register of Controlled Trials (2016, Issue 8), MEDLINE (Ovid SP, 1966 to 2016 August week 1), Embase (Ovid SP, 1988 to 2016 August week 1), and the Cumulative Index to Nursing and Allied Health Literature (EBSCO, 1982 to 2016 August week 1), trials registers, and reference lists of relevant articles. Randomized controlled trials involving the use of nerve blocks as part of the care for hip fractures in adults aged 16 years and older were included. The quality of the studies was rated according to the Cochrane tool. Two authors independently extracted the data. The quality of evidence was judged according to the Grading of Recommendations, Assessment, Development, and Evaluations Working Group scale. RESULTS: Based on 8 trials with 373 participants, peripheral nerve blocks reduced pain on movement within 30 minutes of block placement: standardized mean difference, -1.41 (95% confidence interval [CI], -2.14 to -0.67; equivalent to -3.4 on a scale from 0 to 10; I statistic = 90%; high quality of evidence). The effect size was proportional to the concentration of local anesthetic used (P < .00001). Based on 7 trials with 676 participants, no difference was found in the risk of acute confusional state: risk ratio, 0.69 (95% CI, 0.38-1.27; I statistic = 48%; very low quality of evidence). Based on 3 trials with 131 participants, the risk for pneumonia was decreased: risk ratio, 0.41 (95% CI, 0.19-0.89; I statistic = 3%; number needed-to-treat for additional beneficial outcome, 7 [95% CI, 5-72]; moderate quality of evidence). No difference was found for the risk of myocardial ischemia or death within 6 months but the number of participants included was well below the optimum information size for these 2 outcomes. Based on 2 trials with 155 participants, peripheral nerve blocks also reduced the time to first mobilization after surgery: mean difference, -11.25 hours (95% CI, -14.34 to -8.15 hours; I statistic = 52%; moderate quality of evidence). From 1 trial with 75 participants, the cost of analgesic drugs when used as a single-shot block was lower: standardized mean difference, -3.48 (95% CI, -4.23 to -2.74; moderate quality of evidence). CONCLUSIONS: There is high-quality evidence that regional blockade reduces pain on movement within 30 minutes after block placement. There is moderate quality of evidence for a decreased risk of pneumonia, reduced time to first mobilization, and reduced cost of analgesic regimen (single-shot blocks).

A Three-arm Randomized Clinical Trial Comparing Continuous Femoral Plus Single-injection Sciatic Peripheral Nerve Blocks versus Periarticular Injection with Ropivacaine or Liposomal Bupivacaine for Patients Undergoing Total Knee Arthroplasty.

BACKGROUND: Multimodal analgesia is standard practice for total knee arthroplasty; however, the role of regional techniques in improved perioperative outcomes remains unknown. The authors hypothesized that peripheral nerve blockade would result in lower pain scores and opioid consumption than two competing periarticular injection solutions. METHODS: This three-arm, nonblinded trial randomized 165 adults undergoing unilateral primary total knee arthroplasty to receive (1) femoral catheter plus sciatic nerve blocks, (2) ropivacaine-based periarticular injection, or (3) liposomal bupivacaine-based periarticular injection. Primary outcome was maximal pain during postoperative day 1 (0 to 10, numerical pain rating scale) in intention-to-treat analysis. Additional outcomes included pain scores and opioid consumption for postoperative days 0 to 2 and 3 months. RESULTS: One hundred fifty-seven study patients received peripheral nerve block (n = 50), ropivacaine (n = 55), or liposomal bupivacaine (n = 52) and reported median maximal pain scores on postoperative day 1 of 3, 4, and 4.5 and on postoperative day 0 of 1, 4, and 5, respectively (average pain scores for postoperative day 0: 0.6, 1.7, and 2.4 and postoperative day 1: 2.5, 3.5, and 3.7). Postoperative day 1 median maximal pain scores were significantly lower for peripheral nerve blockade compared to liposomal bupivacaine-based periarticular injection (P = 0.016; Hodges-Lehmann median difference [95% CI] = -1 [-2 to 0]). After postanesthesia care unit discharge, postoperative day 0 median maximal and average pain scores were significantly lower for peripheral nerve block compared to both periarticular injections (ropivacaine: maximal -2 [-3 to -1]; P < 0.001; average -0.8 [-1.3 to -0.2]; P = 0.003; and liposomal bupivacaine: maximal -3 [-4 to -2]; P < 0.001; average -1.4 [-2.0 to -0.8]; P < 0.001). CONCLUSIONS: Ropivacaine-based periarticular injections provide pain control comparable on postoperative days 1 and 2 to a femoral catheter and single-injection sciatic nerve block. This study did not demonstrate an advantage of liposomal bupivacaine over ropivacaine in periarticular injections for total knee arthroplasty.

Epidural Local Anesthetics Versus Opioid-Based Analgesic Regimens for Postoperative Gastrointestinal Paralysis, Vomiting, and Pain After Abdominal Surgery: A Cochrane Review.

BACKGROUND: The aim of this review was to compare the effects of postoperative epidural analgesia with local anesthetics to postoperative systemic or epidural opioids in terms of return of gastrointestinal transit, postoperative pain control, postoperative vomiting, incidence of gastrointestinal anastomotic leak, hospital length of stay, and cost after abdominal surgery. METHODS: Trials were identified by computerized searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 12), Medical Literature Analysis and Retrieval System Online (MEDLINE) (from 1950 to December, 2014) and Excerpta Medica dataBASE (EMBASE) (from 1974 to December 2014) and by checking the reference lists of trials retained. We included parallel randomized controlled trials comparing the effects of postoperative epidural local anesthetic with regimens based on systemic or epidural opioids. The quality of the studies was rated according to the Cochrane tool. Two authors independently extracted data. We judged the quality of evidence according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) working group scale. RESULTS: Based on 22 trials including 1138 participants, an epidural containing a local anesthetic will decrease the time required for return of gastrointestinal transit as measured by time required to observe the first flatus after an abdominal surgery standardized mean difference (SMD) -1.28 (95% confidence interval [CI], -1.71 to -0.86; high quality of evidence; equivalent to 17.5 hours). The effect is proportional to the concentration of local anesthetic used. Based on 28 trials including 1559 participants, we also found a decrease in time to first feces (stool): SMD -0.67 (95% CI, -0.86 to -0.47; low quality of evidence; equivalent to 22 hours). Based on 35 trials including 2731 participants, pain on movement at 24 hours after surgery is also reduced: SMD -0.89 (95% CI, -1.08 to -0.70; moderate quality of evidence; equivalent to 2.5 on a scale from 0 to 10). Based on 22 trials including 1154 participants, we did not find a difference in the incidence of vomiting within 24 hours: risk ratio 0.84 (95% CI, 0.57-1.23); low quality of evidence. Based on 17 trials including 848 participants we did not find a difference in the incidence of gastrointestinal anastomotic leak: risk ratio 0.74 (95% CI, 0.41-1.32; low quality of evidence). Based on 30 trials including 2598 participants, epidural analgesia reduces length of hospital stay for an open surgery: SMD -0.20 (95% CI, -0.35 to -0.04; very low quality of evidence; equivalent to 1 day). Data on cost were very limited. CONCLUSIONS: An epidural containing a local anesthetic, with or without the addition of an opioid, accelerates the return of the gastrointestinal transit (high quality of evidence). An epidural containing a local anesthetic with an opioid decreases pain after an abdominal surgery (moderate quality of evidence). An epidural containing a local anesthetic does not affect the incidence of vomiting or anastomotic leak (low quality of evidence). For an open surgery, an epidural containing a local anesthetic would reduce the length of hospital stay (very low quality of evidence).

The Impact of Anesthetic Management on Surgical Site Infections in Patients Undergoing Total Knee or Total Hip Arthroplasty.

BACKGROUND: Surgical site infection (SSI) is one of the most challenging and costly complications associated with total joint arthroplasty. Our primary aim in this case-controlled trial was to compare the risk of SSI within a year of surgery for patients undergoing primary total knee arthroplasty (TKA) or total hip arthroplasty (THA) and revision TKA or THA under general anesthesia versus neuraxial anesthesia. Our secondary aim was to determine which patient, anesthetic, and surgical variables influence the risk of SSI. We hypothesized that patients who undergo neuraxial anesthesia may have a lesser risk of SSI compared with those who had a general anesthetic. METHODS: We conducted a retrospective, case-control study of patients undergoing primary or revision TKA and THA between January 1, 1998, and December 31, 2008, who subsequently were diagnosed with an SSI. The cases were matched 1:2 with controls based on type of joint replacement (TKA versus THA), type of procedure (primary, bilateral, revision), sex, date of surgery (within 1 year), ASA physical status (I and II versus III, IV, and V), and operative time (<3 vs >3 hours). RESULTS: During the 11-year period, 202 SSIs were identified. Of the infections identified, 115 (57%) occurred within the first 30 days and 87 (43%) occurred between 31 and 365 days. From both univariate and multivariable analyses, no significant association was found between the use of central neuraxial anesthesia and the postoperative infection (univariate odds ratio [OR] = 0.92; 95% confidence interval [CI], 0.63-1.34; P = 0.651; multivariable OR = 1.10; 95% CI, 0.72-1.69; P = 0.664). The use of peripheral nerve block also was not found to influence the risk of postoperative infection (univariate OR = 1.41; 95% CI, 0.84-2.37; P = 0.193; multivariable OR = 1.35; 95% CI, 0.75-2.44; P = 0.312). The factors that were found to be associated with postoperative infection in multivariable analysis included current smoking (OR = 5.10; 95% CI, 2.30-11.33) and higher body mass index (BMI) (OR = 2.68; 95% CI, 1.42-5.06 for BMI ≥ 35 kg/m compared with those with BMI < 25 kg/m). CONCLUSIONS: Recent studies using large databases have concluded that the use of neuraxial compared with general anesthesia is associated with a decreased incidence of SSI in patients undergoing total joint arthroplasty. In this retrospective, case-controlled study, we found no difference in the incidence of SSI in patients undergoing total joint arthroplasty under general versus neuraxial anesthesia. We also concluded that the use of peripheral nerve blocks does not influence the incidence of SSI. Increasing BMI and current smoking were found to significantly increase the incidence of SSI in patients undergoing lower extremity total joint arthroplasty.

Fall-prevention strategies and patient characteristics that impact fall rates after total knee arthroplasty.

BACKGROUND: Fall prevention has emerged as a national quality metric, a focus for The Joint Commission, because falls after orthopedic surgery can result in serious injury. In this study, we examined patient characteristics and effects of fall-prevention strategies on the incidence of postoperative falls in patients undergoing total knee arthroplasty. METHODS: We reviewed electronic records of all patients who fell after total knee arthroplasty between 2003 and 2012 (10 years). Patient demographics, including age, sex, and body mass index, were analyzed. The impact of various fall-prevention efforts, including provider and patient education, Hendrich II Fall Risk Model, fall-alert signs, and the use of patient lifts on the incidence of falls, also was studied. RESULTS: Between January 2, 2003, and December 31, 2012 (10 years), 15,189 total knee arthroplasties were performed at Methodist Hospital, Mayo Clinic Rochester, MN. The overall fall rate was 15.3 per 1000 patients (95% confidence interval [CI]: 13.4-17.4). The rate varied significantly (P < 0.001) during the 10-year period with an initial increase followed by a gradual decrease after the initiation of the fall-prevention strategies. From multivariable analysis adjusting for the temporal trends over time, the odds of falling were found to increase with older age (odds ratio = 1.7 and 2.0 for those 70-79 and ≥80 compared with those 60-69 years of age; P < 0.001) and were lower for patients undergoing revision compared with primary total knee arthroplasties (odds ratio = 0.6, P = 0.006). There was no statistically significant difference in fall rates by sex or body mass index. Most patient falls (72%; 95% CI: 66%-78%) occurred within their own rooms. Elimination-related falls (those that occurred while in the bathroom, while going to and from the bathroom, or while using a bedside commode) comprised a majority (59%; 95% CI: 53%-65%) of the falls. Most patients who fell were not considered high risk according to the Hendrich II Fall Risk Model. Twenty-three percent of falls were associated with morbidity, including 7 return visits to the operating room and 2 new fractures. CONCLUSIONS: Our data demonstrate a reduction in fall incidence coinciding with the implementation of a multi-intervention fall-prevention strategy. Despite prevention efforts, patients of advanced age, elimination-related activities, and patients in the intermediate phase (late postoperative day 1 through day 3) of recovery continue to have a high risk for falling. Therefore, fall-prevention strategies should continue to provide education to all patients (especially elderly patients) and reinforce practices that will monitor patients within their hospital rooms.

A single center descriptive study of local anesthetic dose in knee arthroplasty: Was there evidence of local anesthetic systemic toxicity?

STUDY OBJECTIVE: Describe dosing of local anesthetic when both a periarticular injection (PAI) and peripheral nerve block (PNB) are utilized for knee arthroplasty analgesia, and compare the dosing of local to suggested maximum dosing, and look for evidence of local anesthetic systemic toxicity (LAST). DESIGN: A single center retrospective cohort study between May 2018 and November 2022. SETTING: A major academic hospital. PATIENTS: Patients who had both a PAI and PNB while undergoing primary, revision, total, partial, unilateral, or bilateral knee arthroplasty. INTERVENTIONS: None. MEASUREMENTS: Calculate the dose of local anesthetic given via PAI, PNB, and both routes combined as based on lean body weight and compare that to the suggested maximum dosing. Look for medications, clinical interventions, and critical event notes suggestive of a LAST event. MAIN RESULTS: There were 4527 knee arthroplasties where both a PAI and PNB were performed during the study period. When combining PAI and PNB doses, >75% of patients received more than the suggested maximum dose of 3 mg/kg lean body weight. The median local anesthetic dosing over the study period, 4.4 mg/kg (IQR 3.5,5.9), was 147% of the suggested maximum dose (IQR 117,197). There was no conclusive evidence of LAST among any of the patients in the study. CONCLUSIONS: Over the course of our study, we had 4527 knee arthroplasties with a median PAI and PNB local anesthetic dose that was 147% of the suggested maximum without any clear clinical evidence of a LAST event.