New Findings
What is the central question of this study?
Can physiological concentrations of metabolite combinations evoke sensations of fatigue and pain when injected into skeletal muscle? If so, ...what sensations are evoked?
What is the main finding and its importance?
Low concentrations of protons, lactate and ATP evoked sensations related to fatigue. Higher concentrations of these metabolites evoked pain. Single metabolites evoked no sensations. This suggests that the combination of an ASIC receptor and a purinergic P2X receptor is required for signalling fatigue and pain. The results also suggest that two types of sensory neurons encode metabolites; one detects low concentrations of metabolites and signals sensations of fatigue, whereas the other detects higher levels of metabolites and signals ache and hot.
The perception of fatigue is common in many disease states; however, the mechanisms of sensory muscle fatigue are not understood. In mice, rats and cats, muscle afferents signal metabolite production in skeletal muscle using a complex of ASIC, P2X and TRPV1 receptors. Endogenous muscle agonists for these receptors are combinations of protons, lactate and ATP. Here we applied physiological concentrations of these agonists to muscle interstitium in human subjects to determine whether this combination could activate sensations and, if so, to determine how the subjects described these sensations. Ten volunteers received infusions (0.2 ml over 30 s) containing protons, lactate and ATP under the fascia of a thumb muscle, abductor pollicis brevis. Infusion of individual metabolites at maximal amounts evoked no fatigue or pain. Metabolite combinations found in resting muscles (pH 7.4 + 300 nm ATP + 1 mm lactate) also evoked no sensation. The infusion of a metabolite combination found in muscle during moderate endurance exercise (pH 7.3 + 400 nm ATP + 5 mm lactate) produced significant fatigue sensations. Infusion of a metabolite combination associated with vigorous exercise (pH 7.2 + 500 nm ATP + 10 mm lactate) produced stronger sensations of fatigue and some ache. Higher levels of metabolites (as found with ischaemic exercise) caused more ache but no additional fatigue sensation. Thus, in a dose‐dependent manner, intramuscular infusion of combinations of protons, lactate and ATP leads to fatigue sensation and eventually pain, probably through activation of ASIC, P2X and TRPV1 receptors. This is the first demonstration in humans that metabolites normally produced by exercise act in combination to activate sensory neurons that signal sensations of fatigue and muscle pain.
Abstract Study objective The femoral, lateral femoral cutaneous, and obturator nerves (ONs) can reportedly be blocked using a single-injection deep to the fascia iliaca (FI) at the level of the ...inguinal ligament. Two commonly used methods (the FI compartment and 3-in-1 blocks) have produced inconsistent results with respect to local anesthetic distribution and effect on the ON. To date, no study of either method has been performed using advanced imaging techniques to document both needle placement and local anesthetic distribution. We report the outcome of a series of 3-in-1 and FI blocks performed using ultrasound to guide needle position and magnetic resonance imaging (MRI) to define local anesthetic distribution. Design Patients were prospectively studied, and images were interpreted using a randomized and blinded protocol. Setting The study was performed in the perioperative area of an academic orthopedic specialty hospital. Patients Ten patients (ASA 1-2) having anterior cruciate ligament reconstruction received either 3-in-1 or FI compartment blocks for postoperative analgesia using the surface landmarks described for these techniques. Interventions Ultrasound was used to position the injecting needle immediately deep to the FI. Local anesthetic distribution was studied using MRI. Measurements Patients were examined for motor and/or sensory function of the femoral, obturator, and lateral femoral cutaneous nerves. Magnetic resonance imaging was used to document the limits of injectate distribution. Main results Magnetic resonance imaging showed distribution of injectate over the surface of the iliacus and psoas muscles to the level of the retroperitoneum. No patient showed medial extension of injectate to the ON. At the level of the inguinal ligament, injectate extended laterally toward the anterior superior iliac spine and medially to the femoral vein. All patients had significant weakness with extension of the knee and sensory loss over the anterior, lateral, and medial thigh. No patient demonstrated decreased hip adductor strength. Conclusions Ultrasound and MRI show consistent superior extension of local anesthetic to the level of the retroperitoneum for both techniques. There was reliable clinical effect on the femoral and lateral femoral cutaneous nerves. However, none of the injections produced evidence of ON block either at the level of the retroperitoneum or the inguinal ligament.
Brachial plexus block provides effective anesthesia and analgesia for upper extremity surgery but requires injection of large anesthetic volumes near major vascular structures. Moreover, the ...extensive motor and sensory loss produced by plexus block often exceeds the neural distribution needed for corresponding surgical procedures.High-resolution ultrasound facilitates selective nerve blocks at nearly every level of the upper extremity. We present fascial plane injection techniques for selective radial, median, and ulnar nerve blocks. These techniques can be used to match sensory distribution with specific surgical procedures. They are performed using low anesthetic volumes and without proximity to nerves or vascular structures. In this article, fresh cadaver dissections with corresponding ultrasound images are used to demonstrate stepwise fascial plane techniques for the radial, median, and ulnar nerves. These techniques are performed using familiar anatomic landmarks.Practical applications of these techniques are demonstrated for commonly performed procedures of the upper extremity. Corresponding injection volumes with duration of postoperative analgesia are presented. Selected injections are described for both surgical anesthesia and postoperative analgesia.Selective fascial plane injections can provide surgical anesthesia and postoperative analgesia in settings that might otherwise require much larger volumes of local anesthetic. These selective nerve blocks can match sensory loss with the anatomic pain distribution in each patient. Reliable techniques for selective nerve blocks of the upper extremity can expand the capabilities for ultrasound-guided regional anesthesia.
Background Interscalene brachial plexus block (ISBPB) provides excellent analgesia after rotator cuff surgery but is associated with diaphragm dysfunction. In this study, ISBPB with 20 mL of 0.125% ...or 0.25% bupivacaine were compared to assess the effect on diaphragm function, oxygen saturation, pain control, opioid requirements, and patient satisfaction. Materials and methods In this prospective, randomized, double-blind study, 30 adults undergoing outpatient arthroscopic rotator cuff repair were enrolled to receive ultrasound-guided interscalene brachial plexus catheter placement with 20 mL of 0.125% (n = 15) or 0.25% bupivacaine (n = 15). Diaphragm function and oxygen saturation were assessed before ISBPB placement and on discharge from the postanesthesia care unit. Postoperative pain scores, opioid requirements, and patient satisfaction were compared. Results Diaphragm function and oxygen saturation were superior in the low concentration group. Absent or paradoxic motion of the diaphragm was present in 78% of the 0.25% group compared with 21% of patients in the 0.125% group ( P = .008). Oxygen saturation decreased 4.3% in the 0.25% group compared with a decrease of 2.6% in the 0.125% group ( P = .04). Pain scores averaged 1 of 10 in the 0.25% group and 0 of 10 in the 0.125% group ( P = .02). Opioid requirements and patient satisfaction were not different between the two groups. Conclusions In this randomized, double-blind comparison of ISBPB performed with 20 mL of 0.125% or 0.25% bupivacaine, diaphragm function and oxygen saturation were superior in patients treated with more dilute bupivacaine. Furthermore, there were no clinically significant differences in pain scores, and no statistically significant differences in opioid requirements and patient satisfaction.
Purpose To determine whether patients with higher levels of preoperative psychological distress more frequently use a postoperative fascia iliaca nerve block for pain control after hip arthroscopy, ...and to determine whether a fascia iliaca nerve block is an effective adjunct to multimodal oral and intravenous analgesia after hip arthroscopy. Methods One hundred seven patients undergoing hip arthroscopy were prospectively enrolled. Before surgery, patients were administered the Distress Risk Assessment Method questionnaire to quantify their level of preoperative psychological distress. Postoperatively, patients with pain inadequately controlled by multimodal oral and intravenous analgesics could request and receive a fascia iliaca nerve block. Pain scores, opioid consumption, time in the post-anesthesia care unit (PACU), and postoperative complications were recorded for all patients. Results Patients with normal Distress Risk Assessment Method scores requested fascia iliaca nerve blocks approximately half as frequently (18 of 50 36%) as patients in the at-risk category (28 of 47 60%) or distressed category (7 of 10 70%) ( P = .02). Patients with high levels of distress also received 40% more intraoperative opioid than patients with normal scores ( P = .04). In the study population as a whole, patients who received a fascia iliaca nerve block (n = 53) had a higher initial visual analog scale (VAS) pain score in the PACU (7.2 ± 0.3 v 5.5 ± 0.4, P = .001) and showed greater improvement in the VAS pain score by PACU discharge (−4.3 ± 0.2 v −2.1 ± 0.3, P ≤ .0001) compared with patients who did not receive a block (n = 54). Conclusions Patients with higher levels of preoperative psychological distress more frequently requested a postoperative nerve block to achieve adequate pain control after hip arthroscopy. Patients receiving a block had greater improvement in VAS pain scores compared with patients managed with oral and intravenous analgesics alone. Level of Evidence Level IV, case series.
Background:
Opioid analgesics continue to be prescribed after ambulatory surgery despite untoward adverse effects, risk of overdose, and association with substance use disorder.
Purpose/Hypothesis:
...The purpose was to investigate the use of a novel system to provide scheduled and simultaneous dosing of acetaminophen, celecoxib, and pregabalin after anterior cruciate ligament reconstruction (ACLR). It was hypothesized that this system would markedly reduce pain and opioid use compared with existing best practice.
Study Design:
Randomized controlled trial; Level of evidence, 1.
Methods:
Included were 100 patients scheduled for elective, primary ACLR using allograft or hamstring tendon autograft. Selection criteria included age between 18 and 65 years and weight between 65 and 120 kg. Exclusion criteria were a known allergy to any drug used in the study or the use of opioid analgesics before surgery. Patients in the intervention group received a blister pack with scheduled, simultaneous doses of acetaminophen, celecoxib, and pregabalin; patients were also given oxycodone 5 mg as needed for breakthrough pain. Patients in the control group were prescribed ibuprofen and oxycodone 5 mg/acetaminophen 325 mg as needed for pain. The primary outcome measure was pain. Secondary outcomes were nausea, itching, and daily oxycodone use. Patients were asked to quantify their average pain at rest, nausea, and itching on an 11-point verbal scale (from 0 to 10). These data were recorded for 6 days during daily telephone contacts with patients after hospital discharge.
Results:
Cumulative results for 6 days showed significantly lower values in the intervention group compared with the control group for pain (median interquartile range, 28 14-35 vs 35 28-41, respectively; P = .009) and oxycodone use (median interquartile range number of tablets, 0 0-2 vs 8 1.25-16, respectively; P < .001). Based on these data, the upper tolerance limits for the number of oxycodone tablets required by 90% of patients in the intervention and control groups were 8 tablets and 30 tablets, respectively. Cumulative results for nausea and itching were also significantly lower for the intervention group. Most patients in the intervention group used no opioids during recovery.
Conclusion:
Simultaneous dosing of 3 nonopioid analgesics resulted in reduced postoperative pain and markedly lower opioid use.
Registration:
NCT04015908 (ClinicalTrials.gov identifier).
Continuous peripheral nerve block (CPNB) is an optimal choice for analgesia after orthopedic procedures, but is not commonly used in outpatients because of concern regarding the possibility of ...catheter-related complications. In addition, it may be difficult to provide adequate patient access to physicians in this setting. We present 620 outpatients who were treated with CPNB using an established protocol.
All catheters were placed using direct ultrasound visualization. These patients received extensive oral and written preoperative instruction and were provided continuous telephone access to the anesthesiologist during the postoperative period. All patients were also contacted at home by telephone on the first postoperative day. In addition, each patient was seen and examined by the surgeon within 2 wk of hospital discharge.
Of the 620 patients, there were 190 interscalene (brachial plexus), 206 fascia iliaca (femoral nerve), and 224 popliteal fossa (sciatic nerve) catheters. Two patients (0.3%) had complications related to the nerve block. In both of these patients, the symptoms resolved within 6 wk of surgery. Twenty-six patients (4.2%) required postoperative interventions by the anesthesiologist. One patient returned to the hospital for catheter removal.
In this large series of outpatients treated with CPNB, there were surprisingly few interventions requiring an anesthesiologist. Likewise, patients were able to manage and remove their catheters at home without additional follow-up. This suggests that with adequate instruction and telephone access to health care providers, patients are comfortable with managing and removing CPNB catheters at home.
Background
Continuous femoral nerve block has been shown to decrease opioid use, improve postoperative pain scores, and decrease length of stay. However, several studies have raised the concern that ...continuous femoral nerve block may delay patient ambulation and increase the risk of falls during the postoperative period.
Questions/purposes
This study sought to determine whether continuous femoral nerve block with a single-shot sciatic block prevented early ambulation after total knee arthroplasty (TKA) and whether the technique was associated with adverse effects.
Methods
Between January 2011 and January 2013, 77 consecutive patients undergoing primary TKAs at an orthopaedic specialty hospital received a continuous femoral nerve block for perioperative analgesia. The femoral block was placed preoperatively with an initial bolus and 76 (99%) patients received a single-shot sciatic nerve block performed at the same time. Fifty-eight percent (n = 45) received an initial bolus of 0.125% bupivacaine and 42% (n = 32) received 0.25% bupivacaine. All 77 patients received 0.125% bupivacaine infusion postoperatively with the continuous femoral nerve block. All patients were provided a knee immobilizer that was worn while they were out of bed and was used until 24 hours after removal of the block. All patients also used a front-wheeled walker to assist with ambulation. All 77 patients had complete records for assessing the end points of interest in this retrospective case series, including distance ambulated each day and whether in-hospital complications could be attributed to the patients’ nerve blocks.
Results
Thirty-five patients (45%) ambulated for a mean distance of 19 ± 22 feet on the day of surgery. On postoperative Days 1 and 2, all 77 patients successfully ambulated a mean of 160 ± 112 and 205 ± 123 feet, respectively. Forty-eight patients (62%) had documentation of ascending/descending stairs during their hospital stay. No patient fell during the postoperative period, required return to the operating room, or readmission within 90 days of surgery. One patient experienced a transient foot drop related to the sciatic nerve block, which resolved by postoperative Day 1.
Conclusions
Continuous femoral nerve block with dilute bupivacaine (0.125%) can be successfully used after TKA without preventing early ambulation. By taking active steps to prevent in-hospital falls, including the use of a knee immobilizer for ambulation while the block is in effect, patients can benefit from the analgesia provided by the block and still ambulate early after TKA.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
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