What Is the Role of a Periarticular Injection for Knee Arthroplasty Patients Receiving a Multimodal Analgesia Regimen Incorporating Adductor Canal and Infiltration Between the Popliteal Artery and Capsule of the Knee Blocks? A Randomized Blinded Placebo-Controlled Noninferiority Trial

BACKGROUND

Optimal analgesic protocols for total knee arthroplasty (TKA) patients remain controversial. Multimodal analgesia is advocated, often including peripheral nerve blocks and/or periarticular injections (PAIs). If 2 blocks (adductor canal block [ACB] plus infiltration between the popliteal artery and capsule of the knee [IPACK]) are used, also performing PAI may not be necessary. This noninferiority trial hypothesized that TKA patients with ACB + IPACK + saline PAI (sham infiltration) would have pain scores that were no worse than those of patients with ACB + IPACK + active PAI with local anesthetic.

METHODS

A multimodal analgesic protocol of spinal anesthesia, ACB and IPACK blocks, intraoperative ketamine and ketorolac, postoperative ketorolac followed by meloxicam, acetaminophen, duloxetine, and oral opioids was used. Patients undergoing primary unilateral TKA were randomized to receive either active PAI or control PAI. The active PAI included a deep injection, performed before cementation, of bupivacaine 0.25% with epinephrine, 30 mL; morphine; methylprednisolone; cefazolin; with normal saline to bring total volume to 64 mL. A superficial injection of 20 mL bupivacaine, 0.25%, was administered before closure. Control injections were normal saline injected with the same injection technique and volumes. The primary outcome was numeric rating scale pain with ambulation on postoperative day 1. A noninferiority margin of 1.0 was used.

RESULTS

Ninety-four patients were randomized. NRS pain with ambulation at POD1 in the ACB + IPACK + saline PAI group was not found to be noninferior to that of the ACB + IPACK + active PAI group (difference = 0.3, 95% confidence interval [CI], [-0.9 to 1.5], P = .120). Pain scores at rest did not differ significantly among groups. No significant difference was observed in opioid consumption between groups. Cumulative oral morphine equivalents through postoperative day 2 were 89 ± 40 mg (mean ± standard deviation), saline PAI, vs 73 ± 52, active PAI, P = .1. No significant differences were observed for worst pain, fraction of time in severe pain, pain interference, side-effects (nausea, drowsiness, itching, dizziness), quality of recovery, satisfaction, length of stay, chronic pain, and orthopedic outcomes.

CONCLUSIONS

For TKA patients given a comprehensive analgesic protocol, use of saline PAI did not demonstrate noninferiority compared to active PAI. Neither the primary nor any secondary outcomes demonstrated superiority for active PAI, however. As we cannot claim either technique to be better or worse, there remains flexibility for use of either technique.

Effect of Duloxetine on Opioid Use and Pain After Total Knee Arthroplasty: A Triple-Blinded Randomized Controlled Trial

BACKGROUND

Duloxetine, a serotonin-norepinephrine dual reuptake inhibitor, may improve analgesia after total knee arthroplasty (TKA). Previous studies had one primary outcome, did not consistently use multimodal analgesia, and used patient-controlled analgesia devices, potentially delaying discharge. We investigated whether duloxetine would reduce opioid consumption or pain with ambulation.

METHODS

A total of 160 patients received 60 mg duloxetine or placebo daily, starting from the day of surgery and continuing 14 days postoperatively. Patients received neuraxial anesthesia, peripheral nerve blocks, acetaminophen, nonsteroidal anti-inflammatory drugs, and oral opioids as needed. The dual primary outcomes were Numeric Rating Scale (NRS) scores with movement on postoperative days 1, 2, and 14, and cumulative opioid consumption surgery through postoperative day 14.

RESULTS

Duloxetine was noninferior to placebo for both primary outcomes and was superior to placebo for opioid consumption. Opioid consumption (mean ± SD) was 288 ± 226 mg OME [94, 385] vs 432 ± 374 [210, 540] (duloxetine vs placebo) P = .0039. Pain scores on POD14 were 4.2 ± 2.0 vs 4.8 ± 2.2 (duloxetine vs placebo) P = .018. Median satisfaction with pain management was 10 (8, 10) and 8 (7, 10) (duloxetine vs placebo) P = .046. Duloxetine reduced interference by pain with walking, normal work, and sleep.

CONCLUSION

The 29% reduction in opioid use corresponds to 17 fewer pills of oxycodone, 5 mg, and was achieved without increasing pain scores. Considering the ongoing opioid epidemic, duloxetine can be used to reduce opioid usage after knee arthroplasty in selected patients that can be appropriately monitored for potential side effects of the medication.

Midazolam-Induced Hiccups Reversed by Flumazenil: A Case Report

Hiccups are a common phenomenon experienced by many people and are usually short-lived with spontaneous resolution of symptoms. Certain anesthetic medications have been associated with the development of hiccups, though the underlying pathophysiology and reflex arcs remain poorly understood. We describe a patient who developed hiccups lasting 9 days following an orthopedic surgery and again developed hiccups during a subsequent surgery after only having received midazolam; flumazenil administration led to sustained cessation of his hiccup symptoms immediately.

A Comprehensive Enhanced Recovery Pathway for Rotator Cuff Surgery Reduces Pain, Opioid Use, and Side Effects

BACKGROUND

Patients often have moderate to severe pain after rotator cuff surgery, despite receiving analgesics and nerve blocks. There are many suggested ways to improve pain after rotator cuff surgery, but the effects of adopting a pathway that includes formal patient education, a long-acting nerve block, and extensive multimodal analgesia are unclear.

QUESTIONS/PURPOSES

(1) Does adoption of a clinical pathway incorporating patient education, a long-acting nerve block, and preemptive multimodal analgesia reduce the worst pain during the first 48 hours after surgery compared with current standard institutional practices? (2) Does adoption of the pathway reduce opioid use? (3) Does adoption of the pathway reduce side effects and improve patient-oriented outcomes?

METHODS

From September 2018 to January 2020, 281 patients scheduled for arthroscopic ambulatory rotator cuff surgery were identified for this paired sequential prospective cohort study. Among patients in the control group, 177 were identified, 33% (58) were not eligible, for 11% (20) staff was not available, 56% (99) were approached, 16% (29) declined, 40% (70) enrolled, and 40% (70) were analyzed (2% [4] lost to follow-up for secondary outcomes after postoperative day 2). For patients in the pathway cohort, 104 were identified, 17% (18) were not eligible, for 11% (11) staff was not available, 72% (75) were approached, 5% (5) declined, 67% (70) enrolled, and 67% (70) were analyzed (3% [3] lost to follow-up for secondary outcomes after postoperative day 2). No patients were lost to follow-up for primary outcome; for secondary outcomes, four were lost in the control group and three in the pathway group after postoperative day 2 (p = 0.70). The initial 70 patients enrolled received routine care (control group), and in a subsequent cohort, 70 patients received care guided by a pathway (pathway group). Of the 205 eligible patients, 68% (140) were included in the analysis. This was not a study comparing two tightly defined protocols but rather a study to determine whether adoption of a pathway would alter patient outcomes. For this reason, we used a pragmatic (real-world) study design that did not specify how control patients would be treated, and it did not require that all pathway patients receive all components of the pathway. We developed the pathway in coordination with a group of surgeons and anesthesiologists who agreed to apply the pathway as much as was viewed practical for each individual patient. Patients in both groups received a brachial plexus nerve block with sedation. Major differences between the pathway and control groups were: detailed patient education regarding reasonable pain expectations with a goal of reducing opioid use (no formal educational presentation was given to the control), a long-acting nerve block using bupivacaine with dexamethasone (control patients often received shorter-acting local anesthetic without perineural dexamethasone), and preemptive multimodal analgesia including intraoperative ketamine, postoperative acetaminophen, NSAIDs, and gabapentin at bedtime, with opioids as needed (control patients received postoperative opioids but most did not get postoperative NSAIDS and no controls received gabapentin or separate prescriptions for acetaminophen). The primary outcome was the numerical rating scale (NRS) worst pain with movement 0 to 48 hours after block placement. The NRS pain score ranges from 0 (no pain) to 10 (worst pain possible). The minimum clinically important difference (MCID) [12] for NRS that was used for calculation of the study sample size was 1.3 [18], although some authors suggest 1 [13] or 2 [5] are appropriate; if we had used an MCID of 2, the sample size would have been smaller. Secondary outcomes included NRS pain scores at rest, daily opioid use (postoperative day 1, 2, 7, 14), block duration, patient-oriented pain questions (postoperative day 1, 2, 7, 14), and patient and physician adherence to pathway.

RESULTS

On postoperative day 1, pathway patients had lower worst pain with movement (3.3 ± 3.1) compared with control patients (5.6 ± 3.0, mean difference -2.7 [95% CI -3.7 to -1.7]; p < 0.001); lower scores were also seen for pain at rest (1.9 ± 2.3 versus 4.0 ± 2.9, mean difference -2.0 [95% CI -2.8 to -1.3]; p < 0.001). Cumulative postoperative opioid use (0-48 hours) was reduced (pathway oral morphine equivalent use was 23 ± 28 mg versus 44 ± 35 mg, mean difference 21 [95% CI 10 to 32]; p < 0.01). The greatest difference in opioid use was in the first 24 hours after surgery (pathway 7 ± 12 mg versus control 21 ± 21 mg, mean difference -14 [95% CI -19 to -10]; p < 0.01). On postoperative day 1, pathway patients had less interference with staying asleep compared with control patients (0.5 ± 1.6 versus 2.6 ± 3.3, mean difference -2.2 [95% CI -3.3 to -1.1]; p < 0.001); lower scores were also seen for interference with activities (0.9 ± 2.3 versus 1.9 ± 2.9, mean difference -1.1 [95% CI -2 to -0.1]; p = 0.03). Satisfaction with pain treatment on postoperative day 1 was higher among pathway patients compared with control patients (9.2 ± 1.7 versus 8.2 ± 2.5, mean difference 1.0 [95% CI 0.3 to 1.8]; p < 0.001). On postoperative day 2, pathway patients had lower nausea scores compared with control patients (0.3 ± 1.1 versus 1 ± 2.1, mean difference -0.7 [95% CI -1.2 to -0.1]; p = 0.02); lower scores were also seen for drowsiness on postoperative day 1 (1.7 ± 2.7 versus 2.6 ± 2.6, mean difference -0.9 [95% CI - 1.7 to -0.1]; p = 0.03).

CONCLUSION

Adoption of the pathway was associated with improvement in the primary outcome (pain with movement) that exceeded the MCID. Patients in the pathway group had improved patient-oriented outcomes and fewer side effects. This pathway uses multiple analgesic drugs, which may pose risks to elderly patients, in particular. Therefore, in evaluating whether to use this pathway, clinicians should weigh the effect sizes against the potential risks that may emerge with large scale use, consider the difficulties involved in adapting a pathway to local practice so that pathway will persist, and recognize that this study only enrolled patients among surgeons and the anesthesiologists that advocated for the pathway; results may have been different with less enthusiastic clinicians. This pathway, based on a long-lasting nerve block, multimodal analgesia, and patient education can be considered for adoption.

LEVEL OF EVIDENCE

Level II, therapeutic study.

The Feasibility of Outpatient Shoulder Arthroplasty: Risk Stratification and Predictive Probability Modeling

Whether shoulder arthroplasty can be performed on an outpatient basis depends on appropriate patient selection. The purpose of this study was to identify risk factors for adverse events (AEs) following shoulder arthroplasty and to generate predictive models to improve patient selection. This was a retrospective review of prospectively collected data using a single institution shoulder arthroplasty registry as well as the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, including subjects undergoing hemiarthroplasty, total shoulder arthroplasty (TSA), and reverse TSA. Predicted probability of suitability for same-day discharge was calculated from multivariable logistic models for different patient subgroups based on age, comorbidities, and Charlson/Deyo Index scores. A total of 2314 shoulders (2079 subjects) in the institutional registry met inclusion criteria for this study. Younger age, higher body mass index (BMI), male sex, and prior steroid injection were all significantly associated with suitability for discharge, whereas preoperative narcotic use, comorbidities (heart disease and anemia/other blood disease), and Charlson/Deyo Index score of 2 were associated with AEs that might prevent same-day discharge. Compared with TSA, reverse TSA was associated with less suitability for discharge (P=.01). On querying the ACS-NSQIP database, 15,254 patients were identified. Female sex, BMI less than 35 kg/m², American Society of Anesthesiologists class III/IV, preoperative anemia, functional dependence, low pre-operative albumin, and hemiarthroplasty were associated with unsuitability for discharge. Males 55 to 59 years old with no comorbidities nor history of narcotic use formed the lowest risk subgroup. Transfusion is the primary driver of AEs. Strategies to avoid this complication should be explored. Risk stratification will improve the ability to identify patients who can safely undergo outpatient shoulder arthroplasty. [Orthopedics. 2021;44(2):e215-e222.].

Intravenous vs Oral Acetaminophen as a Component of Multimodal Analgesia After Total Hip Arthroplasty: A Randomized, Blinded Trial

BACKGROUND

Multimodal analgesia including acetaminophen is increasingly popular for analgesia after total hip arthroplasty (THA). Intravenous (IV) administration of acetaminophen has pharmacokinetic benefits, but unclear clinical advantages. The authors hypothesized that IV acetaminophen would reduce pain with activity, opioid usage, or opioid-related side effects, compared to oral acetaminophen.

METHODS

In this double-blinded, randomized, controlled trial, 154 THA patients received either IV or oral acetaminophen as part of a comprehensive opioid-sparing multimodal analgesia strategy. Primary outcomes were pain with physical therapy on postoperative day (POD) 1, opioid side effects (POD 1), and cumulative opioid use.

RESULTS

There was no difference in opioid side effects, pain scores, or opioid use between the groups.

CONCLUSION

Patients in both groups had low pain scores, minimal opioid side effects, and limited opioid usage (corresponding to 6 doses of tramadol 100 mg over 3 days). This highlights multimodal analgesia as an effective method of pain control for THA.

Addition of Adductor Canal Block to Periarticular Injection for Total Knee Replacement: A Randomized Trial

BACKGROUND

Periarticular injection is a popular method to control postoperative pain after total knee replacement. An adductor canal block is a sensory block that can also help to alleviate pain after total knee replacement. We hypothesized that the combination of adductor canal block and periarticular injection would allow patients to reach discharge criteria 0.5 day faster than with periarticular injection alone.

METHODS

This prospective trial enrolled 56 patients to receive a periarticular injection and 55 patients to receive an adductor canal block and periarticular injection. Both groups received intraoperative neuraxial anesthesia and multiple different types of pharmaceutical analgesics. The primary outcome was time to reach discharge criteria. Secondary outcomes, collected on postoperative days 1 and 2, included numeric rating scale pain scores, the PAIN OUT questionnaire, opioid consumption, and opioid-related side effects.

RESULTS

There was no difference in time to reach discharge criteria between the groups with and without an adductor canal block. The Wilcoxon-Mann-Whitney odds ratio was 0.87 (95% confidence interval [CI], 0.55 to 1.33; p = 0.518). The median time to achieve discharge criteria (and interquartile range) was 25.8 hours (23.4 hours, 44.3 hours) in the adductor canal block and periarticular injection group compared with 26.4 hours (22.9 hours, 46.2 hours) in the periarticular injection group. Patients who received an adductor canal block and periarticular injection reported lower worst pain (difference in means, -1.4 [99% CI, -2.7 to 0]; adjusted p = 0.041) and more pain relief (difference in means, 12% [99% CI, 0% to 24%]; adjusted p = 0.048) at 24 hours after anesthesia. There was no difference in any other secondary outcome measure (e.g., opioid consumption, opioid-related side effects, numeric rating scale pain scores).

CONCLUSIONS

The time to meet the discharge criteria was not significantly different between the groups. In the adductor canal block and periarticular injection group, the patients had lower worst pain and greater pain relief at 24 hours after anesthesia. No difference was noted in any other secondary outcome measure (e.g., opioid consumption, opioid-related side effects, numeric rating scale pain scores).

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

What Pain Levels Do TSA Patients Experience When Given a Long-acting Nerve Block and Multimodal Analgesia?

BACKGROUND

The pain experience for total shoulder arthroplasty (TSA) patients in the first 2 weeks after surgery has not been well described. Many approaches to pain management have been used, with none emerging as clearly superior; it is important that any approach minimizes postoperative opioid use.

QUESTIONS/PURPOSES

(1) With a long-acting nerve block and comprehensive multimodal analgesia, what are the pain levels after TSA from day of surgery until postoperative day (POD) 14? (2) How many opioids do TSA patients take from the day of surgery until POD 14? (3) What are the PainOUT responses at POD 1 and POD 14, focusing on side effects from opioids usage?

METHODS

From January 27, 2017 to December 6, 2017, 154 TSA patients were identified as potentially eligible for this prospective, institutional review board-approved observational study. Of those, 46 patients (30%) were excluded (either because they were deemed not appropriate for the study, research staff were not available, patients were not eligible, or they declined to participate), and another six (4%) had incomplete followup data and could not be studied, leaving 102 patients (66%) for analysis here. Median preoperative pain with movement was 7 (interquartile range [IQR], 5-9) and 13 of 102 patients used preoperative opioids. All patients received a single-injection bupivacaine interscalene block with adjuvant clonidine, dexamethasone, and buprenorphine. Multimodal analgesia included acetaminophen, NSAIDs, and opioids. The primary outcome was the Numerical Rating Scale (NRS) pain score with movement on POD 14. The NRS pain score ranges from 0 (no pain) to 10 (worst pain possible). Secondary outcomes included NRS pain scores at rest and with movement (day of surgery, and PODs 1, 3, 7 and 14), daily analgesic use from day of surgery to POD 14 (both oral and intravenous), Opioid-Related Symptom Distress Scale (which assesses 12 symptoms ranging from 0 to 4, with 4 being the most distressing; the composite score is the mean of the 12 symptom-specific scores) on POD 1, and the PainOut questionnaire on POD 1 and POD 14. The PainOut questionnaire includes questions rating nausea, drowsiness, itching from 0 (none) to 10 (severe), as well as rating difficulty staying asleep from 0 (does not interfere) to 10 (completely interferes).

RESULTS

The median NRS pain scores with movement were 2 (IQR, 0-5) on POD 1, 5 (IQR, 3-6) on POD 3, and the pain score was 3 (IQR, 1-5) on POD 14. Median total opioid use (converted to oral morphine equivalents) was 16 mg (4-50 mg) for the first 24 hours, 30 mg (8-63 mg) for the third, and 0 mg (0-20 mg) by the eighth 24-hour period, while the most frequent number of activations of the intravenous patient-controlled analgesia device was 0. Median PainOut scores on POD 1 and POD 14 for sleep interference, nausea, drowsiness and itching were 0, and the median composite Opioid-Related Symptom Distress Scale score on day 1 was 0.3 (IQR, 0.1-0.5).

CONCLUSIONS

Clinicians using this protocol, which combines a long-acting, single-injection nerve block with multimodal analgesia, can inform TSA patients that their postoperative pain will likely be less than their preoperative pain, and that on average they will stop using opioids after 7 days. Future research could investigate what the individual components of this protocol contribute. Larger cohort studies or registries would document the incidence of rare complications. Randomized controlled trials could directly compare analgesic effectiveness and cost-benefits for this protocol versus alternative strategies, such as perineural catheters or liposomal bupivacaine. Perhaps most importantly, future studies could seek ways to further reduce peak pain and opioid usage on POD 2 and POD 3.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Enhanced recovery after surgery for primary hip and knee arthroplasty: a review of the evidence

Enhanced recovery after surgery (ERAS) protocols produce significant clinical and economic benefits in a range of surgical subspecialties. There is a long tradition of applying clinical pathways to the perioperative care of joint arthroplasty patients. Enhanced recovery after surgery represents the next step in the evolution of standardized care. To date, reports of full ERAS pathways for hip or knee arthroplasty are lacking. In this narrative review, we present the evidence base that can be usefully applied to constructing ERAS pathways for hip or knee arthroplasty. The history and rationale for applying ERAS to joint arthroplasty are explained. Evidence demonstrates improved outcomes after joint arthroplasty when a standardized approach to care is implemented. The efficacy of individual ERAS components in hip or knee replacement is considered, including preoperative education, intraoperative anaesthetic techniques, postoperative analgesia, and early mobilization after joint arthroplasty. Interventions lacking high-quality evidence are identified, together with recommendations for future research. Based on currently available evidence, we present a model ERAS pathway that can be applied to perioperative care of patients undergoing hip or knee arthroplasty.

The Incidence of Complications Is Low Following Foot and Ankle Surgery for Which Peripheral Nerve Blocks Are Used for Postoperative Pain Management

BACKGROUND

The incidence of neurologic complications from foot and ankle surgery utilizing regional anesthesia is not well established.

QUESTIONS/PURPOSES

The purpose of this study was to prospectively determine the incidence of neurologic and peripheral nerve block (PNB) site complications on a busy foot and ankle service that utilizes ankle blocks (ABs) and popliteal blocks (POPs).

PATIENTS AND METHODS

This prospective observational study included patients undergoing foot and ankle surgery with ABs or POPs. Block choice was determined by surgeon's preference. Patients were assessed for complications during postoperative visits at 2, 6, and 12 weeks. The relation of each complication to the block was scored by a surgeon and anesthesiologist.

RESULTS

From October 2012 to October 2014, 2516 patients underwent 2704 surgeries. There were 195 complications (7.2%) considered neurologic or at the PNB site. The incidence of serious complications was 0.7%. A higher complication rate was reported for POPs (8.8%) than for ABs (2.5%). However, when analysis was limited to forefoot surgery, this difference was not significant. Dexamethasone use was associated with increased complications for POPs. Only 5 of the 195 total complications, and 2 of 20 serious complications, were deemed to have been likely caused by the block by both the surgeon and anesthesiologist reviewer.

CONCLUSIONS

The incidences of neurologic or block-related complications and serious complications were 7.2 and 0.7%, respectively, most without a clear surgical vs. nerve block etiology. The higher complication rate for POPs using perineural dexamethasone should be interpreted cautiously in light of the lack of randomization and likely confounders.

Unused Opioid Pills After Outpatient Shoulder Surgeries Given Current Perioperative Prescribing Habits

BACKGROUND

In the past 16 years, the number of prescription opioids sold in the United States, as well as deaths from prescription opioids, has nearly quadrupled. However, the overall amount of pain reported by patients has not changed significantly. Specific information about opioid prescriptions in the perioperative period is lacking. Of the studies that have been published, investigators have shown that the majority of patients have unused postoperative opioid pills. Moreover, patients appear to lack information about disposal of unused opioid pills.

PURPOSE

To compare the number of pills prescribed versus the numbers left unused after outpatient shoulder surgeries at an orthopaedic surgery institution.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

In this prospective, observational study, 100 patients (age >18 years) undergoing outpatient shoulder surgery (rotator cuff repair, labral repair, stabilization/Bankart repair, debridement) were enrolled. Follow-ups were conducted via surveys on postoperative days (PODs) 7, 14, 28, and 90. The primary outcome was the number of unused pills from the originally prescribed medication.

RESULTS

For all procedure types, the median (Q1, Q3) number of prescribed pills was 60 (40, 80). On POD 90, patients reported a median (Q1, Q3) of 13 (0, 32) unused pills; patients who underwent rotator cuff repairs had the lowest number of pills remaining (median [Q1, Q3], 0 [0, 16]), whereas patients who had stabilization/Bankart repairs had the highest number of unused pills (median [Q1, Q3], 37 [29, 50]). Patient satisfaction with pain management ranged from an average of 70% to 90%. Only 25 patients received instructions or education about opioid disposal.

CONCLUSION

Most outpatient shoulder surgery patients who underwent certain operations were prescribed more opioid analgesics than they consumed. Patient education regarding the disposal of opioids was lacking.

Buprenorphine, Clonidine, Dexamethasone, and Ropivacaine for Interscalene Nerve Blockade: A Prospective, Randomized, Blinded, Ropivacaine Dose-Response Study

OBJECTIVE

This study investigated interscalene block for shoulder arthroplasty with various ropivacaine concentrations in the presence of clonidine, dexamethasone, and buprenorphine. The goal was prolonged analgesia with minimal motor blockade.

DESIGN

Prospective, double-blind, randomized controlled trial.

SETTING

University-affiliated orthopedic hospital.

METHODS

Patients (20/group) received acetaminophen, ketorolac, pregabalin, opioids, and "Control"; interscalene block, 0.375% ropivacaine, intravenous additives (buprenorphine, clonidine, dexamethasone); "High Dose"; 0.375% ropivacaine, perineural additives; "Medium Dose"; 0.2% ropivacaine, perineural additives; and "Low Dose"; 0.1% ropivacaine, perineural additives.

RESULTS

Pain with movement at 24 hours was 4.9 ± 2.5 (mean ± standard deviation [SD]) (Control), 4.5 ± 3.0 (High Dose), 3.4 ± 1.8 (Medium Dose), 4.2 ± 2.4 (Low Dose). The difference between Medium Dose and Control was -1.5 (95% CI: -2.9, -0.1) (P = 0.040). Median time until need for opioids was 16.1 hours (Control) vs 23.7 hours (High Dose); hazard ratio 0.37 [95% CI: 0.17, 0.79]. High Dose had less pain with movement the morning after surgery, vs Control; 2.9 ± 2.5 vs 4.9 ± 2.7; P = 0.027. Pain with movement in the Post-Anesthesia Care Unit was higher in Low Dose, vs Control; 0.9 ± 1.4 vs 0 ± 0, P = 0.009. Low Dose had superior hand strength in the Post-Anesthesia Care Unit (mean ± SD of pre-operative strength: 44.0 ± 20.3%) compared to Control (27.5 ± 24.5%) (P = 0.031).

CONCLUSIONS

For maximum pain reduction, combining perineural additives with ropivacaine 0.375% or 0.2% is suggested. To minimize motor blockade, perineural additives can be combined with ropivacaine, 0.1%.

Pregabalin and pain after total knee arthroplasty: a double-blind, randomized, placebo-controlled, multidose trial

BACKGROUND

Pregabalin may reduce postoperative pain and opioid use. Higher doses may be more effective, but may cause sedation and confusion. This prospective, randomized, blinded, placebo-controlled study tested the hypothesis that pregabalin reduces pain at 2 weeks after total knee arthroplasty, but increases drowsiness and confusion.

METHODS

Patients (30 per group) received capsules containing pregabalin (0, 50, 100, or 150 mg); two capsules before surgery, one capsule twice a day until postoperative day (POD) 14, one on POD15, and one on POD16. Multimodal analgesia included femoral nerve block, epidural analgesia, oxycodone-paracetamol, and meloxicam. The primary outcome was pain with flexion (POD14).

RESULTS

Pregabalin did not reduce pain at rest, with ambulation, or with flexion at 2 weeks (P=0.69, 0.23, and 0.90, respectively). Pregabalin increased POD1 drowsiness (34.5, 37.9, 55.2, and 58.6% in the 0, 50, 100, and 150 mg arms, respectively; P=0.030), but did not increase confusion (0, 3.5, 0, and 3.5%, respectively; P=0.75). Pregabalin had no effect on acute or chronic pain, opioid consumption, or analgesic side-effects. Pregabalin reduced POD14 patient satisfaction [1-10 scale, median (first quartile, third quartile): 9 (8, 10), 8 (7, 10), 8 (5, 9), and 8 (6, 9.3), respectively; P=0.023). Protocol compliance was 63% by POD14 (50.0, 70.0, 76.7, and 56.7% compliance, respectively), with no effect of dose on compliance. Per-protocol analysis of compliant patients showed no effect of pregabalin on pain scores.

CONCLUSIONS

Pregabalin had no beneficial effects, but increased sedation and decreased patient satisfaction. This study does not support routine perioperative pregabalin for total knee arthroplasty patients.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: http://www.clinicaltrials.gov/ct2/show/study/NCT01333956.

Patient-controlled epidural analgesia or multimodal pain regimen with periarticular injection after total hip arthroplasty: a randomized, double-blind, placebo-controlled study

BACKGROUND

The optimal postoperative analgesia after primary total hip arthroplasty remains in question. This randomized, double-blind, placebo-controlled study compared the use of patient-controlled epidural analgesia (PCEA) with use of a multimodal pain regimen including periarticular injection (PAI). We hypothesized that PAI would lead to earlier readiness for discharge, decreased opioid consumption, and lower pain scores.

METHODS

Forty-one patients received PAI, and forty-three patients received PCEA. Preoperatively, both groups were administered dexamethasone (6 mg, orally). The PAI group received a clonidine patch and sustained-release oxycodone (10 mg), while the PCEA group had placebo. Both groups received combined spinal-epidural anesthesia and used an epidural pain pump postoperatively; the PAI group had normal saline solution, while the PCEA group had bupivacaine and hydromorphone. The primary outcome, readiness for discharge, required the discontinuation of the epidural, a pain score of <4 (numeric rating scale) without parenteral narcotics, normal eating, minimal nausea, urination without a catheter, a dry surgical wound, no acute medical problems, and the ability to independently transfer and walk 12.2 m (40 ft).

RESULTS

The mean time to readiness for discharge (and standard deviation) was 2.4 ± 0.7 days (PAI) compared with 2.3 ± 0.8 days (PCEA) (p = 0.86). The mean length of stay was 3.0 ± 0.8 days (PAI) compared with 3.1 ± 0.7 days (PCEA) (p = 0.46). A significant mean difference in pain score of 0.74 with ambulation (p = 0.01; 95% confidence interval [CI], 0.18 to 1.31) and 0.80 during physical therapy (p = 0.03; 95% CI, 0.09 to 1.51) favored the PCEA group. The mean opioid consumption (oral morphine equivalents in milligrams) was significantly higher in the PAI group on postoperative day 0 (43 ± 21 compared with 28 ± 23; p = 0.002) and postoperative days 0 through 2 (136 ± 59 compared with 90 ± 79; p = 0.004). Opioid-Related Symptom Distress Scale (ORSDS) composite scores for severity and bothersomeness as well as scores for nausea, vomiting, and itchiness were significantly higher in the PCEA group (p < 0.05). Quality of Recovery-40 scores and patient satisfaction were similar.

CONCLUSIONS

PAI did not decrease the time to discharge and was associated with higher pain scores and greater opioid consumption but lower ORSDS scores compared with PCEA. The choice for analgesic regimen may depend on a particular patient's threshold for pain and the potential side effects.

Postoperative Analgesia with Saphenous Block Appears Equivalent to Femoral Nerve Block in ACL Reconstruction

BACKGROUND

Adequate pain control following anterior cruciate ligament reconstruction (ACL) often requires regional nerve block. The femoral nerve block (FNB) has been traditionally employed. Ultrasound application to regional nerve blocks allows for the use of alternatives such as the saphenous nerve block following ACL reconstruction.

QUESTIONS/PURPOSES

This study evaluated postoperative analgesia provided by the subsartorial saphenous nerve block (SSNB) compared to that provided by the traditional FNB for patients undergoing ACL reconstruction with patellar tendon (bone-tendon-bone (BTB)) autografts.

METHODS

A randomized, blinded, controlled clinical trial was conducted using 80 ASA I-III patients, ages 16-65, undergoing ACL reconstruction with BTB. The individuals assessing all outcome measures were blinded to the treatment group. Postoperatively, all patients received cryotherapy and parenteral hydromorphone to achieve numeric rating scale pain scores less than 4. At discharge, patients were given prescriptions for oral opioid analgesics and a scheduled NSAID. Patients were instructed to complete pain diaries and record oral opioid utilization. Patients were contacted on postoperative days (POD) 1 and 2 to ascertain the level of patient satisfaction with the analgesic regimen.

RESULTS

No differences between the two groups were found. Patient demographics and postoperative pain scores at rest were not different. In addition, there was no difference in opioid use, as measured in daily oral morphine equivalents between groups. A small but statistically significant report of higher patient satisfaction with the FNB was found on POD 1 but not on POD 2.

CONCLUSION

These data support our hypothesis that the SSNB provides similar and adequate postoperative analgesia when compared to the FNB, following arthroscopic ACL reconstruction with patellar tendon autograft.

A clinical pathway for total shoulder arthroplasty-a pilot study

BACKGROUND

Appropriate pain management after total shoulder arthroplasty (TSA) facilitates rehabilitation and may improve clinical outcomes.

QUESTIONS/PURPOSES

This prospective, observational study evaluated a multimodal analgesia clinical pathway for TSA.

METHODS

Ten TSA patients received an interscalene nerve block (25 cm(3) 0.375% ropivacaine) with intraoperative general anesthesia. Postoperative analgesia included regularly scheduled non-opioid analgesics (meloxicam, acetaminophen, and pregabalin) and opioids on demand (oral oxycodone and intravenous patient-controlled hydromorphone). Patients were evaluated twice daily to assess pain, anterior deltoid strength, handgrip strength, and sensory function.

RESULTS

The nerve block lasted an average of 18 h. Patients had minimal pain after surgery; 0 (median score on a 0-10 scale) in the Post-Anesthesia Care Unit (PACU) but increased on postoperative day (POD) 1 to 2.3 (0.0, 3.8; median (25%, 75%)) at rest and 3.8 (2.1, 6.1) with movement. Half of the patients activated the patient-controlled analgesia four or fewer times in the first 24 h after surgery. Operative anterior deltoid strength was 0 in the PACU but returned to 68% by POD 1. Operative hand strength was 0 (median) in the PACU, but the third quartile (75%) had normalized strength 49% of preoperative value.

CONCLUSIONS

Patients did well with this multimodal analgesic protocol. Pain scores were low, half of the patients used little or no intravenous opiate, and some patients had good handgrip strength. Future research can focus on increasing duration of analgesia from the nerve block, minimizing motor block, lowering pain scores, and avoiding intravenous opioids.

Clinical outcomes in patients with pulmonary hypertension undergoing total hip arthroplasty

BACKGROUND

Pulmonary hypertension (PH) is regarded as a risk factor for perioperative complications in patients undergoing noncardiac surgery.

QUESTIONS/PURPOSES

The objective of this retrospective case-control study was to evaluate the adverse outcomes of pulmonary hypertension patients undergoing elective unilateral hip replacements.

METHODS

We performed a retrospective case-control study of total hip replacement patients with pulmonary hypertension (cases) and without pulmonary hypertension (control). From the years 2003 to 2008, we identified a total of 132 patients undergoing primary total hip replacements with a diagnosis of pulmonary hypertension (right ventricular systolic pressure >35). The primary outcome assessed was the incidence of adverse events that occurred during the postoperative hospital stay. Secondary outcomes studied included length of hospital stay, mortality, and ability to reach certain physical therapy milestones.

RESULTS

The PH group had significantly more adverse events than the control group. Nonlethal cardiac dysrhythmias comprised the most common adverse outcome among the PH group. Overall, the PH group had a morbidity rate of 34.7% while the control had a rate of 21%. The PH group had longer hospital stay (6.7 days vs. 5.9). Both groups had zero mortality during the hospital stay. The PH group had comparable rehabilitation recovery times than the control group.

CONCLUSION

This retrospective case-control study demonstrates that pulmonary hypertension patients undergoing total hip arthroplasty are more prone to adverse outcomes, especially cardiac dysrhythmias, and longer hospital stays.

Association of obesity with inflammation and pain after total hip arthroplasty

BACKGROUND

The prevalence of obesity is increasing, and obesity often leads to degenerative joint disease requiring total hip arthroplasty (THA). Obesity is a proinflammatory state associated with an increase in chronic, low-grade inflammatory response. As such, it may augment the postoperative inflammatory response, which has been associated with postoperative pain and complications.

QUESTIONS/PURPOSES

We determined whether severity of obesity was associated with (1) severity of inflammatory response, as measured by the in vivo circulating levels of cytokines and ex vivo functional reactivity of mononuclear blood cells, and (2) severity of pain, as measured by verbal pain scores and analgesic consumption, in the first 24 hours after THA.

METHODS

We studied 60 patients (20 normal weight, 20 overweight, 20 obese) undergoing elective primary unilateral THA in this prospective cross-sectional study. Blood samples were collected for C-reactive protein and cytokine levels, including IL-1β, IL-2, IL-6, IL-8, and tumor necrosis factor α (TNF-α), from patients before and 24 hours after surgery. Cytokine response of whole blood was evaluated ex vivo with or without two standard activators, phorbol-12-myristate-13-acetate and lipopolysaccharide, using standardized blood sample from patients at 24 hours. These standard immune activators are implicated in the inflammatory response to gram-negative infection, translocation of microbial products, pathophysiology of septic shock syndrome in human, and tumor promotion. Pain response was gauged using verbal pain scores (on a 0- to 10-point scale, where 0 = no pain and 10 = worst pain) at rest and with activity at 24 hours after surgery and analgesic consumption of volume of epidural analgesic solution for the first 24 hours after surgery.

RESULTS

No correlation was found between BMI and postoperative spontaneous circulating cytokine levels. However, after activation of blood leukocytes with lipopolysaccharide, there was a significant positive correlation between the BMI and IL-1β, IL-6, and TNF-α levels (r = 0.26-0.32; p = 0.03, p = 0.03, and p = 0.01, respectively), suggesting priming of the innate immune system in obesity and potential for excessive postoperative inflammatory response. Obesity was not associated with increased pain or analgesic consumption in the first 24 hours after surgery.

CONCLUSIONS

Obesity is associated with a proinflammatory state after THA as demonstrated by enhanced cytokine reactivity. Larger studies exploring the specific impact of obesity and inflammation on surgical outcomes, including pain, are warranted.

LEVEL OF EVIDENCE

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

Steroid modulation of cytokine release and desmosine levels in bilateral total knee replacement: a prospective, double-blind, randomized controlled trial

BACKGROUND

The perioperative inflammatory response as measured by elevated levels of interleukin-6 (IL-6) has been linked to acute respiratory distress syndrome, postoperative confusion, and fever. Because of the extent of surgery,patients undergoing bilateral total knee arthroplasty may be at high risk of complications. We had found a significant decrease in IL-6 in patients having bilateral total knee replacement who received two doses of 100 mg of hydrocortisone eight hours apart; however, by twenty-four hours, IL-6 levels were equal to those in the group that received a placebo. In the present study, we investigated whether the administration of three doses would reduce IL-6 levels at twenty-four hours and affect other outcomes such as desmosine level, a marker of lung injury.

METHODS

After institutional review board approval, a total of thirty-four patients (seventeen patients and seventeen control subjects) were enrolled in this double-blind, randomized, placebo-controlled study. Three doses of intravenous hydrocortisone (100 mg) or placebo were given eight hours apart. Urinary desmosine levels were obtained at baseline and at one and three days postoperatively. The level of IL-6 was measured at baseline and at six, ten, twenty-four, and forty-eight hours postoperatively. Pain scores, presence of fever, and functional outcomes were recorded.

RESULTS

The level of IL-6 increased in both groups, but was significantly higher in the control group, peaking at twenty-four hours (mean and standard deviation, 623.74 ± 610.35 pg/mL versus 148.13 ± 119.35 pg/mL; p = 0.006). Urinary desmosine levels significantly increased by twenty-four hours in the control group, but remained unchanged in the study group (134.75 ± 67.88 pmol/mg and 79.45 ± 46.30 pmol/mg, respectively; p = 0.006). Pain scores at twenty-four hours were significantly lower in the study group (1.4 ± 0.9 versus 2.4 ± 1.2; p = 0.01) as was the presence of fever (11.8%versus 47.1%; p = 0.03). Range of motion at the knee was significantly greater in the study group (81.6 ± 11.6 versus 70.6 ± 14.0 in the right knee [p = 0.02] and 81.4 ± 11.3 versus 73.4 ± 9.4 in the left knee [p = 0.03]).

CONCLUSIONS

Hydrocortisone (100 mg) given over three doses, each eight hours apart, decreased and maintained a lower degree of inflammation with bilateral total knee replacement as measured by IL-6 level. Corticosteroids decreased the prevalence of fever, lowered visual analog pain scores, and improved knee motion. The significantly lower values of desmosine in the study group suggest that this treatment may be protective against lung injury.

Postoperative delirium in elderly patients after elective hip or knee arthroplasty performed under regional anesthesia

Delirium is a major adverse postoperative event in elderly patients. Incidence rates of postoperative delirium are difficult to determine. Because of the accuracy, brevity, and ease of use by clinical interviewers, the Confusion Assessment Method (CAM) has become widely used. This study used the CAM to determine the rate of postoperative delirium in patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA) procedures under regional anesthesia. Following Institutional Review Board approval, a prospective study of 20 patients per group ages 70 and above undergoing unilateral THA or TKA was initiated. Both groups received a combined spinal-epidural, postoperative patient-controlled epidural anesthesia, and postoperative oral opioids. Patient interviews occurred five times: once preoperatively and two times each on postoperative days 1 and 2. Only two patients were assessed as delirious according to the CAM method (one in each group; 5%). Patient assessment by other clinicians indicated that five additional patients experienced acute change in mental status; however, these patients were not delirious at the times of the study interviews. The rate of delirium in the elderly after arthroplasty performed under regional anesthesia is very low. Reasons for this include patient selection criteria and anesthesia type. The study excluded patients with several proposed risk factors for postoperative delirium: prior history of dementia, history of mental illness, and use of benzodiazepines. The use of regional anesthesia may have also reduced the occurrence of postoperative delirium.

Clonidine and analgesic duration after popliteal fossa nerve blockade: randomized, double-blind, placebo-controlled study

BACKGROUND

We tested the hypothesis that 100 microg clonidine added to 0.375% bupivacaine would prolong the duration of analgesia from popliteal fossa nerve blockade.

METHODS

Ninety-nine patients scheduled for hospital admission after foot or ankle surgery entered this randomized, double-blind, placebo-controlled trial. Patients received a popliteal fossa block (nerve stimulator technique, via the posterior approach) using 30 mL 0.375% bupivacaine, with epinephrine. Patients were randomized to receive no clonidine, 100 microg clonidine IM, or 100 microg clonidine with bupivacaine for the popliteal block. Patients also received a combined spinal-epidural anesthetic, a saphenous nerve block, and postoperative IV patient-controlled analgesia. The primary outcome was patient-reported duration of analgesia.

RESULTS

Duration of analgesia was statistically longer in the block clonidine group (18 +/- 6 h for clonidine with bupivacaine vs 14 +/- 7 h for IM clonidine and 15 +/- 7 h for control, P = 0.016 for control vs clonidine with bupivacaine). Pain scores, analgesic use, and side effects attributable to pain management were similar among groups.

CONCLUSIONS

Clonidine significantly prolongs the analgesic duration after popliteal fossa nerve blockade with bupivacaine.

Nerve Localization Techniques for Interscalene Brachial Plexus Blockade: A Prospective, Randomized Comparison of Mechanical Paresthesia Versus Electrical Stimulation

Postoperative neurologic symptoms (PONS) are relatively common after upper extremity orthopedic surgery performed under peripheral neural blockade. In this study, we prospectively compared the incidence of PONS after shoulder surgery under interscalene (IS) block using the electrical stimulation (ES) or mechanical paresthesia (MP) techniques of nerve localization. For patients randomized to the MP group, a 1-in, 23-g long-beveled needle was placed into the IS groove to elicit a paresthesia to the shoulder, arm, elbow, wrist, or hand. For patients randomized to the ES group, a 5-cm, 22-g short-beveled insulated needle was placed into the IS groove to elicit a motor response including flexion or extension of the elbow, wrist, or fingers or deltoid muscle stimulation at a current between 0.2 and 0.5 mA. Each IS block was performed with 50-60 mL of 1.5% mepivacaine containing 1:300,000 epinephrine and 0.1meq/L sodium bicarbonate. Two-hundred-eighteen patients were randomized between the two groups. One patient was lost to follow-up. Twenty-five patients (23%) in the ES group experienced paresthesia during needle insertion. The incidence of PONS using the ES technique was 10.1% (11/109), whereas the incidence with the MP technique was 9.3% (10/108) (not significant). The PONS lasted a median duration of 2 mo, and symptoms in all patients resolved within 12 mo. The success rate, onset time, and patient satisfaction were also comparable between groups. We conclude that the choice of nerve localization technique can be made based on the patient's and anesthesiologist's comfort and preferences and not on concern for the development of PONS.

A preadmission telephone call to initiate the consent process for clinical anesthesia research

Consent for a clinical anesthesia research trial is frequently sought in hospital on the day of surgery. This time is often associated with increased anxiety, diminished privacy, and limited opportunity for reflection. Our objective was to determine whether a preadmission telephone call on the day before surgery resulted in greater satisfaction compared to the traditional practice of initiating the consent process on the day of surgery. We randomized 124 patients eligible for participation in a minimal-risk clinical anesthesia trial to receive either a preadmission telephone call on the day before surgery to initiate consent (Telephone group; n = 62), or no telephone call (Control group; n = 62). In the Telephone group, 21 patients (33.9%) were successfully contacted by telephone, whereas 41 patients (66.1%) were not contacted. Both the Telephone and Control groups reported similar understanding regarding the purpose of the trial. Both groups similarly agreed that the time and setting of recruitment and consent were appropriate. Patients in both groups reported having enough time to consider their participation in the trial. Few patients in either group reported feeling anxious at the time of consent or pressured to participate in the trial. Finally, patients in both groups were equally satisfied with the consent process.

IMPLICATIONS

A preadmission telephone call on the day before surgery to initiate the consent process for a minimal-risk clinical anesthesia research trial does not improve satisfaction among consenting patients compared to initiating consent in hospital on the day of surgery, and can be an impractical method to initiate the consent process.

The effects of femoral nerve blockade in conjunction with epidural analgesia after total knee arthroplasty

Either epidural analgesia or femoral nerve blockade improves analgesia and rehabilitation after total knee arthroplasty. No study has evaluated the combination of femoral nerve blockade and epidural analgesia. In this prospective, randomized, blinded study we investigated combining femoral nerve blockade with epidural analgesia. Forty-one patients received a single-injection femoral nerve block with 0.375% bupivacaine and 5 microg/mL epinephrine; 39 patients served as controls. All patients received combined spinal-epidural anesthesia and patient-controlled epidural analgesia with 0.06% bupivacaine and 10 microg/mL hydromorphone. Average duration of epidural analgesia was 2 days. All patients received the same standardized physical therapy intervention. Median visual analog scale (VAS) scores with physical therapy were significantly lower for 2 days among patients who received a femoral nerve block versus controls: 3 versus 4 (day 1), 2.5 versus 4 (day 2); P < 0.05. Median VAS pain scores at rest were 0 in both groups on days 1 and 2. Flexion range of motion was improved on postoperative day 2 (70 degrees versus 63 degrees ; P < 0.05). No peripheral neuropathies occurred. We conclude that the addition of femoral nerve blockade to epidural analgesia significantly improved analgesia for the first 2 days after total knee arthroplasty.

The Incidence of Transient Neurologic Symptoms After Spinal Anesthesia with Mepivacaine

We prospectively evaluated 1273 patients who received spinal (or combined spinal-epidural [CSE]) anesthesia with 1.5% mepivacaine (plain, no glucose) for ambulatory surgery. We hypothesized that analysis of a large series of patients would confirm previous findings that isobaric 1.5% mepivacaine is not frequently associated with transient neurologic symptoms (TNS). Patients were contacted twice after the anesthetic, at days 1-4 and days 6-9. One-thousand-two-hundred-ten patients were successfully contacted postoperatively (95% follow-up rate). None of the patients had permanent neurologic sequelae from the anesthetic. None of the 372 CSE anesthetics was inadequate for surgery. Fourteen of 838 (1.7%) of the spinal anesthetics were inadequate. TNS, defined as the new onset of back pain that radiated bilaterally to buttocks or distally, occurred in 78 patients (6.4%; 95% confidence intervals 5.1%-8%). The mean age of patients who developed TNS (48 +/- 14 yr) was older than that of patients without TNS (41 +/- 16 yr) (P < 0.001). TNS was not influenced by gender or intraoperative position. The frequent success rate and infrequent rates of complications such as TNS and postdural puncture headache suggest that spinal anesthesia with mepivacaine is likely to be a safe and effective anesthetic for ambulatory patients.

Ketamine stimulates secretion of beta-endorphin from a mouse pituitary cell line

BACKGROUND AND OBJECTIVES

beta-endorphin is an endogenous opioid that mediates pain-induced analgesia. Propofol inhibits in vitro secretion of beta-endorphin from a mouse pituitary cell line (AtT-20). We hypothesized that ketamine would also alter secretion of beta-endorphin.

METHODS

AtT-20 cells were exposed to the intravenous anesthetic ketamine (10 to 40 micromol/L). Secretion of beta-endorphin was determined by enzyme-linked immunosorbent assay. Long-term effects were determined by exposing the cells to ketamine, allowing the cells to recover overnight, then stimulating the secretion of beta-endorphin. AtT-20 cells were stimulated with secretagogues to induce secretion of beta-endorphin. The effect of ketamine on stimulated secretion was determined. Cultures of AtT-20 cells were grown for 5 days in the presence of ketamine. Cell numbers were determined on each day.

RESULTS

Ketamine increased secretion of beta-endorphin to levels that were up to 3 times greater than baseline secretion. Stimulation of beta-endorphin secretion by ketamine persisted into the subsequent day. Ketamine caused increased secretion from cells stimulated with secretagogues. Ketamine was not toxic to these cells; AtT-20 cells grew normally for 5 days in the presence of up to 40 micromol/L ketamine.

CONCLUSIONS

Clinically relevant concentrations of ketamine stimulated both immediate and delayed secretion of beta-endorphin. This suggests that the prolonged analgesia observed in some clinical situations with ketamine could be in part caused by increased release of an endogenous opioid.

Inhibition of regulated neuropeptide secretion from mouse pituitary cells by propofol

Neuropeptides modulate neuronal responses to stimuli. Secretion of neuropeptides is a potential site for anesthetic action. This paper examines the hypothesis that propofol alters the secretion of beta-endorphin. Cultures of a mouse pituitary cell line (AtT-20) were exposed to propofol in vitro, then induced to secrete beta-endorphin. Secretion was measured by immunoassay. Propofol caused statistically significant inhibition of secretion. Secretion stimulated by phorbol ester was inhibited by propofol with a calculated 50% inhibitory concentration (IC50) value of 48 microM. The propofol IC50 values for secretion stimulated by other secretagogs were 47 microM (barium), 42 microM (Bay K 8644, a calcium channel agonist), and 28 microM (a cyclic adenosine monophosphate [cAMP] analog). AtT-20 cells recovered their ability to secrete beta-endorphin upon removal of the propofol, which demonstrated that they were not damaged permanently by propofol. The effect was relatively specific to neuropeptide secretion, as AtT-20 cells grew normally for 5 days in the presence of 10 or 80 microM propofol. The finding suggests that propofol inhibited a site in neuropeptide exocytosis common to the three studied pathways of secretion.

Yeast signal peptidase contains a glycoprotein and the Sec11 gene product

Partially purified yeast microsomal signal peptidase appears to be a complex of four polypeptides of 13, 18, 20, and 25 kDa. The 18-kDa chain is the product of the Sec11 gene, which is necessary for signal peptidase activity. The 25-kDa subunit is a glycoprotein that binds Con A. Two related methods for purification of the enzyme are presented; the first includes removal of peripheral membrane proteins from microsomes by alkali extraction, solubilization of the enzyme by nonionic detergent and high salt, and four different chromatographic procedures. An alternative method was developed based on lectin-affinity chromatography.

Solubilization and characterization of yeast signal peptidase

An efficient post-translational assay for solubilized yeast signal peptidase has been developed. The enzyme can be solubilized in nonionic detergent (0.5% Nikkol) without added salt, but salt increased the efficiency of solubilization. Radiosequencing of the cleaved substrate revealed that the enzyme removed the signal peptide. The substrate (prepro-alpha-factor) must be pretreated with sodium dodecyl sulfate to be cleaved. The enzyme displays a broad, alkaline pH optimum, retaining activity at pH 12. Moderately high temperatures (35 degrees C), excess detergent (greater than 0.5% Nikkol), or high salt (greater than 300 mM KOAc) will inactivate the enzyme. Phosphatidylcholine is necessary for optimal activity. The optimal ratio of Nikkol:lipid:sodium dodecyl sulfate is 6.4:2.2:1. The membrane association of yeast signal peptidase is resistant to carbonate extraction, indicating that it is an integral membrane protein.