Nerve Block Catheter Research Articles

Multilevel Continuous Intercostal Nerve Block Catheter: A Viable Alternative to Thoracic Epidural for Multiple Rib Fractures?

Multilevel Continuous Intercostal Nerve Block Catheter: A Viable Alternative to Thoracic Epidural for Multiple Rib Fractures?

In Reply

Drs. Slater and Lerner have reemphasized a critical point in our published case scenario1: Standard coagulation tests are inadequate in assessing adequacy of platelet function for epidural catheterization. Therefore, we recommended in our algorithm presented in figure 4 of our original report1 to use whole blood multiple electrode impedance aggregometry (Multiplate®; Roche Diagnostics, Mannheim, Germany) or whole blood turbidimetric aggregometry (VerifyNow®; Accumetrics, San Diego, CA) to support decision making in patients with antiplatelet therapy.1 Multiple electrode impedance aggregometry and VerifyNow® have been used to assess the efficacy of antiplatelet drugs and the dynamics of platelet function recovery after clopidogrel treatment—also under the scenario “risk–benefit analysis of neuraxial blockade.”2–7 Multiple electrode impedance aggregometry is as sensitive as light transmission aggregometry (Born aggregometry—the definitive standard of platelet function analysis) to detect platelet dysfunction,8,9 predict stent thrombosis and bleeding rates after coronary interventions,2,10 and can be used as a guide to support treatment of hemorrhagic patients undergoing cardiac surgery.11,12Please note that the value of thromboelastography or thromboelastometry in our case scenario relates to detection of trauma-induced coagulopathy with reduced clot firmness13 and hypercoagulability due to an acute phase reaction with high plasma fibrinogen concentrations, which we know occurs frequently after the acute phase of trauma-induced coagulopathy.14,15Dr. Flores suggests the use of multilevel continuous intercostal nerve block catheter in a patient with flail chest. Although the risk of epidural hematoma may be lower with intercostal nerve blocks compared with epidural analgesia, other risks such as pneumothorax/hematothorax and inadequate efficacy may limit its use under the condition described in our case scenario.We need to develop specific outcome-oriented clinical pathways in critical care medicine that do not exclusively take into account the data taken from elective surgical procedures in the operating room. In patients with flail chest presenting with traditional contraindications for neuraxial analgesia, careful risk–benefit analysis may indicate that epidural analgesia improves important outcome measures. We believe that thromboelastography or thromboelastometry and aggregometry (if available) are helpful instruments for decision support in such a case scenario.

The catheter-over-needle assembly offers greater stability and less leakage compared with the traditional counterpart in continuous interscalene nerve blocks: a randomized patient-blinded study

To the Editor, Continuous peripheral nerve blocks are susceptible to various complications, including leakage from the catheter insertion site which increases the risk of leakage of the bolus of injectate. This has the potential to disrupt the adhesive dressing and may further compromise the sterility of the surgical field if leakage occurs during the operation. Continuous interscalene brachial plexus blocks are commonly administered for pain control following shoulder and upper arm surgery. A prior study of complications of continuous interscalene analgesia showed a 9.3% incidence of leakage at the catheter site. We conducted a prospective randomized study to test the hypothesis that interscalene catheter-over-needle (CON) assemblies are clinically less prone to leakage at the insertion site compared with conventional catheterthrough-needle (CTN) counterparts. The primary outcome of the study was leakage from the catheter insertion site. Secondary outcomes were block performance time (the time from the initial skin puncture to first application of Tegaderm dressing) and pain scores in recovery and at 24 and 48 hr post-surgery. An 11-point visual analogue scale in which 0 indicated ‘‘no pain’’ and 10 indicated ‘‘worst pain imaginable’’ was used to record pain scores. The study was conducted from May 2012 to September 2012 at the University of Alberta Hospital. Following approval from the University of Alberta Health Research Ethics Board (January 2012) and informed written consent, adult patients admitted for shoulder surgery or surgery of the proximal humerus were randomly assigned using sealed envelopes to the CON (catheter-over-needle: study) or CTN (catheter-through-needle: control) group. Patients were blinded to the allocation, as was a member of the research team who collected follow-up data. Ultrasound-guided interscalene brachial plexus blocks using the CTN and CON methods were performed as previously described. All blocks were performed by staff regional anesthesiologists or by supervised regional anesthesia trainees. After insertion of the catheter, general anesthetic was administered to patients in both groups. A nerve block catheter remained in each of the patients in both groups throughout the operation and in the postoperative period with local anesthetic infusion with bolus dose for two to three days. Ten patients, six in the CON group and four in the CTN group, were approached and consented to participate in the trial. After the fourth CTN patient, the study was terminated at the request of our surgical colleagues (see below). None (0/6) of the CON patients experienced leakage around the catheter, and none required catheter remanipulation or fortification during the perioperative period (Table). Based on the ‘‘rule of three’’, the 95% confidence interval for the occurrence of leakage in CON patients was 0 to 0.5. In contrast, all CTN patients (4/4) experienced leakage around the perineural catheter during the perioperative period. One CTN catheter migrated out on postoperative day one, and two CTN catheters required fortification with gauze to address leakage. One CTN catheter was removed just before surgery due to excessive leakage; this case has been described previously. Following this case, the study had to be terminated earlier than anticipated at the surgeon’s request due to ClinicalTrials.gov Identifier: NCT01522053.

Shearing of a Continuous Interscalene Catheter with Lancinating Symptoms After an Interscalene Block: A Case Report.

Placement of a continuous indwelling nerve block catheter is generally safe and effective for pain control in the outpatient setting1. As reported in several large series in the literature, catheter-related complications are rare1-3; however, neurologic injury is possible. We present a patient who experienced a unique complication after placement of an interscalene nerve catheter and successful postoperative anesthesia. The patient was informed that data concerning the case would be submitted for publication, and she provided consent. A healthy fifty-seven-year-old right-hand dominant woman (considered class-2 status by the American Society of Anesthesiologists) presented to our orthopaedic clinic with right shoulder pain. Five years previously, she had fallen from a standing height and had sustained a fracture of the proximal third of the humeral shaft, which had developed into a chronic atrophic nonunion with gross motion at the fracture site. She also had experienced weakness in the radial nerve distribution, suggesting partial nerve injury from the fracture. An interscalene approach to the brachial plexus was used for catheter placement to deliver continuous interscalene analgesia. This catheter was utilized to provide a longer duration of postoperative pain control than a single-shot interscalene block. An 18-gauge 50-mm Tuohy needle was advanced with use of nerve stimulator localization. Stimulation of the nerve was begun at 1.5 mA, and the stimulation progressed until the biceps contraction disappeared at 0.5 mA in order to accurately place the needle in close proximity to the nerves of the brachial plexus. A 19-gauge StimuCath (Arrow International, Reading, Pennsylvania) catheter (Fig. 1) was advanced 3 cm beyond the tip of the needle, and aspiration was negative for blood. There was no evidence of damage to the catheter before placement. A 40-mL combination bolus solution (30 mL of bupivacaine 0.5% with epinephrine, and 10 mL of …

Ultrasound‐guided approach to the paravertebral space for catheter insertion in infants and children

Paravertebral perineural blocks are used to prevent pain in the thoracoabdominal dermatomes. Traditionally, a landmark-based technique is used in children, while ultrasound-guided (UG) techniques are being employed in adult patients. To describe an UG technique for placement of thoracic paravertebral nerve block (TPVNB) catheters in pediatric patients. Retrospective chart review of a series of 22 pediatric patients' ages 6months to 17years with weights from 6.25kg to 135kg using a transverse in-plane technique. Catheters were placed both bilateral and unilateral for a variety of thoracic and abdominal procedures. A linear ultrasound transducer was used in all cases with frequency of oscillation and transducer length chosen based on individual patient characteristics of age, weight, and BMI. The median pain scores at 12, 24, 36, and 48h were 1.2 (interquartile range, 4.5), 0.84 (interquartile range 3.0), 1.6 (interquartile range 2.9), and 0.83 (interquartile range 1.74), respectively. The median dose of opioid expressed as morphine equivalents consumed during the first 24h after surgery was 0.14mg·kg(-1) (interquartile range, 0.78mg·kg(-1) ) and from 24 to 48h the median dose was 0.11mg·kg(-1) (interquartile range 0.44mg·kg(-1) ). No complications were noted, and catheters were left an average of 3days with a range of 1-5days with good pain relief. This technical description demonstrates the feasibility of placing PVNB catheters using a transverse in-line ultrasound-guided technique in a wide range of pediatric patients.

Efficacy of supplemental peripheral nerve blockade for hip fracture surgery: multiple treatment comparison

This study was designed to determine the most effective peripheral nerve block supplement to standard anesthesia management for hip fracture patients. We systematically reviewed randomized controlled trials (RCTs) published from 1990 to 2010 and conducted multiple treatment comparisons using direct and indirect evidence for two outcomes, i.e., acute pain intensity and delirium. We combined trials by type of injection (regardless of time of insertion during the perioperative phase, use of nerve block catheter, local anesthetic type, additives, or duration of treatment). Twenty-one RCTs comprising 1,422 participants were included. In most cases, the trials were conducted in Europe; they excluded patients with cognitive impairment, and they were unclear or at high risk of bias. The combination of obturator and lateral femoral cutaneous nerve blockade had the highest probability of being the most effective against acute postoperative pain. Fascia iliaca blockade had the highest probability of being the most effective against delirium. There was no difference in outcomes among other nerve blocks. Not all nerve blocks are equally effective in improving outcomes after hip fracture. Multiple treatment comparison, a tool to compare the effectiveness of multiple treatments simultaneously, provides useful guidance to anesthesia providers seeking effective treatment when faced with a body of RCTs wherein each investigates one treatment. More RCTs comparing multiple nerve blocks in hip fracture are needed.

Fluoroscopy Study of Peripheral Nerve Block Catheter Tip Movement?Its Clinical Implication in Guiding Catheter Adjustment

Background: Continuous peripheral nerve block catheter has been widely used clinically.A small percentage of catheters usually need adjustment after placement.However, there is no study on how to adjust catheter in the literature. Methods: Twelve fresh pork legs were randomly allocated into one of two groups, perineural catheter advanced 5 cm or less beyond needle tip (N=6), or more than 5 cm beyond needle tip (N=6). For both groups, ultrasound guided sciatic nerve block was performed with the “in-plane” approach.The anatomic landmarks and the locations of the sciatic nerve block equate to the Labat approach in humans. Thirty milliliter of normal saline was used to dissect the epineuron space before threading 20G soft non-stimulating catheter. The catheter was pulled back in onecentimeter increments at the level of the skin while the location of the tip of the catheter was identified by fluoroscopy after each centimeter pull back. The main outcome was the catheter tip movement. Results: The catheter tips advanced either cephalic or caudally without dominance trend, while most catheter tips located superficially to the needle tip (11 out of 12). In T 5 cm group, the catheter tip movement was initially 0.17 ± 0.11 cm per centimeter pull back, then increased to 0.25 ± 0.12 cm once the catheter tip was less than 5 cm beyond the initial depth of needle tip. Conclusions: We recommend that adjustment of the CPNC should base on the initial depth of the needle tip since the initial catheter tip movements among these over threaded catheters are very limited, and it would not be efficient in clinical practice to adjust peripheral nerve block catheter by pulling by centimeter increment.

Ultrasound‐Guided Continuous Superficial Peroneal Nerve Block below the Knee for the Treatment of Nerve Injury

(CRPS) describes a constellation of symptoms including pain, trophic changes, hyperesthesia, allodynia, and dysregulation of local blood flow often following trauma. It is often confined to the extremities. Treatment of this disorder consists of a variety of modalities including systemic pharmacotherapy, local anesthetic injections or infusions, psychological nonpharmacotherapy, physical rehabilitation, and surgical intervention. Chronic pain not related to CRPS can also be treated with similar interventions. Despite the array of available therapies, it can still be difficult to manage. We report a case of a 19-year-old patient diagnosed by her surgeon as having CRPS Type II, secondary to foot trauma, which was treated with a continuous infusion of local anesthetic at the superficial peroneal nerve (SPN). While placement of peripheral nerve block catheters to augment chronic pain therapy is not novel, the application of a perineural catheter at the SPN has not been previously described.

Long-Term Use of Nerve Block Catheters in Paediatric Patients with Cancer Related Pathologic Fractures

We report three cases of children with osteosarcoma and pathologic fractures treated with long-term continuous nerve blocks for preoperative pain control. One patient with a left distal femoral diaphysis fracture had a femoral continuous nerve block catheter for 41 days without complications. Another with a fractured left proximal femoral shaft had three femoral continuous nerve block catheters for 33, 26 and 22 days respectively. The third patient, whose right proximal humerus was fractured, had a brachial plexus continuous nerve block catheter for 36 days without complication. In our experience, prolonged use of continuous nerve block is safe and effective in children with pathologic fractures for preoperative pain control.

In Reply

References 2–6 of our colleagues' letter all involved epidural infusion,1–5with references 2–4 suggesting analgesia is improved using repeated bolus doses compared with a simple basal infusion. But all subjects had multi-orifice epidural catheters.1–3References 5 and 6 suggest that with the same infusion method, multi-orifice epidural catheters improve analgesia compared with single-orifice designs. But all had the same local anesthetic administration technique.4,5In other words, whereas for epidural infusions repeated boluses appear to improve analgesia compared with a simple basal infusion, all of these studies involved only multi-port catheters, and thus it remains unknown if using a single-orifice catheter would have resulted in different findings (the authors of those reports did not purport such a theory).1–3Therefore, we do not believe the data supports our colleagues' statement that a “better differential sensory-motor block” is “thought to be enhanced by multi-orifice flow.”However, even if our colleagues' speculation was correct for epidural infusion, local anesthetic pharmacodynamics varies considerably among various introduction modalities. For example, local anesthetic dose, as opposed to volume or concentration, appears to be the primary determinant of block effects during continuous femoral and posterior lumbar plexus nerve blocks.6,7In contrast, the effects are mixed for epidural local anesthetic infusions: total dose is the primary determinant of analgesia quality and dermatomal spread, whereas concentration is the primary determinant of motor block and sympathectomy/hypotension.8It is for this very reason that we undertook our investigation: data from the literature involving central nervous system infusions (unfortunately) cannot be directly applied to those of the peripheral nervous system, such as the continuous femoral nerve blocks (cFNB) of our study.9We therefore do not believe that the references cited in our colleagues' letter, or any published data, supports their supposition that for continuous peripheral nerve blocks “a multi-orifice catheter is required” to “maximize” benefits.Regarding continuous peripheral nerve blocks, there are two investigations involving popliteal-sciatic local anesthetic administration suggesting that repeated boluses improve analgesia compared with a basal infusion (our colleagues cited one of these two).10,11However, both of these studies involved single-orifice perineural catheters. Therefore, there are actually more investigations suggesting the superiority of repeated boluses that used single-orifice perineural catheters than there are studies (just one involving interscalene catheters) using a multiple-orifice design.12It appears that the references cited by our colleagues contradict their theory regarding the importance of multi-orifice catheters on bolus-versus -basal administration effects.10–12Regardless, dramatic pharmacodynamic differences exist even among various continuous peripheral nerve block catheter anatomic locations, and thus the results for popliteal-sciatic and interscalene catheters are not automatically applicable to cFNB.13Our colleagues' speculation that the results of our study might be different with a multi-orifice catheter may prove accurate in the future. However, given (1) our investigation's randomized, triple-masked, split-body study design using extremely precise sensory and motor outcome measures with established reliability and validity; (2) the lack of data suggesting that the number of catheter orifice(s) impact the success of bolus-versus -basal local anesthetic administration for the peripheral (or central) nervous system; and, (3) the dramatic, often opposite, differences in pharmacodynamics among various continuous peripheral nerve block catheter anatomic locations, we believe that our concluding statement is both accurate and warranted: “this study did not find evidence to support the hypothesis that varying the method of local anesthetic administration–basal infusion versus repeated bolus doses–influences cFNB effects to a clinically significant degree. Thus, it is doubtful that, when using a cFNB, varying the method of local anesthetic administration will provide an increased sensory-to-motor block ratio and minimize motor block and the risk of falling while optimizing cutaneous analgesia.”9

Delayed appearance of hypaesthesia and paralysis after femoral nerve block

We report on a female patient who underwent an arthroscopy of the right knee and was given a continuous femoral nerve block catheter. The postoperative course was initially unremarkable, but when postoperative mobilisation was commenced, 18 hours after removal of the catheter, the patient noticed paralysis and hypaesthesia. Examination confirmed the diagnosis of femoral nerve dysfunction. Colour duplex sonography of the femoral artery and computed tomography of the lumbar spine and pelvis yielded no pathological findings. Overnight the neurological deficits decreased without therapy and were finally no longer detectable. We speculate that during the administration of the local anaesthetic a depot formed, localised in the medial femoral intermuscular septa, which was leaked after first mobilisation. To our knowledge no similar case has been published up to now. We conclude that patients who are treated with a nerve block should be informed and physician should be aware that delayed neurological deficits are possible.

Continuous Peripheral Nerve Block Catheter Infections in Combat-related Injuries: A Case Report of Five Soldiers from Operation Enduring Freedom/Operation Iraqi Freedom

Case series. Military medical facility providing acute care for soldiers injured while fighting in the war in Iraq and Afghanistan. To report a series of infections related to use of continuous peripheral nerve catheters for postoperative pain control in the military polytraumatic setting. The analysis of the above infections includes similarities and differences in infection patterns and attempts to clarify possible risk factors for such infections to include duration of catheter placement, type of catheter, preprocedural antibiotics, and tunnel vs nontunneled catheters. The goal of this analysis is to assist in the development of protocols that may prevent future catheter infections. Clinical data were obtained from five previously healthy male soldiers receiving acute care at Brooke Army Medical Center using continuous peripheral nerve catheters for postoperative pain for multiple and frequent procedures. In a total of six catheter infections, two were noted to have superficial skin infections while four were shown to have deep tissue involvement confirmed by imaging studies. All patients were started on initial or additional antibiotics after catheter removal. Three catheter infections, all with stimulating catheters, required surgical irrigation and debridement in the operating room. Continuous peripheral nerve catheters are not without complications and risks including infection. Duration of catheter use was the most significant factor with the development of a catheter-related infection in our series. This series also highlights how stimulating and nonstimulating catheter infections may present differently, as stimulating catheters may have a greater tendency to present as deep space infections with minimal superficial findings.

Continuous Thoracic Paravertebral Nerve Block in a Working Anesthesia Resident—When Opioids are not an Option

Multiple unilateral rib fractures can cause significant pain and morbidity. Continuous nerve block catheters are often maintained while inpatient, and patients are discharged with oral analgesics. However, in many institutions, this dynamic is changing and patients are being managed effectively with outpatient catheters. A 45-year-old male was presented with fractured right ribs 6 through 9. The patient was an anesthesiology resident and was unable to perform his clinical duties. Single paravertebral nerve blocks were performed at right thoracic levels 6-9. At the T7 level, an indwelling catheter was placed. On post-injury day 18, he was able to discontinue the catheter and there were no associated complications. We report a unique case of a patient with multiple rib fractures who was not able to be exposed to potential side effects of opioids. The use of a continuous thoracic paravertebral nerve in an outpatient setting allowed a faster return to function with no adverse events.

Ultrasound-guided continuous suprascapular nerve block for adhesive capsulitis: one case and a short topical review

We present a case with an ultrasound-guided (USG) placement of a perineural catheter beneath the transverse scapular ligament in the scapular notch to provide a continuous block of the suprascapular nerve (SSN). The patient suffered from a severe and very painful adhesive capsulitis of the left shoulder secondary to an operation in the same shoulder conducted 20 weeks previously for impingement syndrome and a superior labral anterior-posterior tear. Following a new operation with capsular release, the placement of a continuous nerve block catheter subsequently allowed for nearly pain-free low impact passive and guided active mobilization by the performing physiotherapist for three consecutive weeks. This case and a short topical review on the use of SSN block in painful shoulder conditions highlight the possibility of a USG continuous nerve block of the SSN as sufficient pain management in the immediate post-operative period following capsular release of the shoulder. Findings in other painful shoulder conditions and suggestions for future studies are discussed in the text.

Treatment of Pain in Children after Limb-Sparing Surgery: An Institution's 26-Year Experience

A significant proportion of patients report long-term pain that is ≥5 on a 0-10 intensity scale after limb-sparing surgery for malignancies of the long bones. Patients experience several distinct types of pain after limb-sparing surgery which constitute a complex clinical entity. This retrospective study examined 26 years of experience in a pediatric institution (1981-2007) in pain management as long as 6 months after limb-sparing surgery and reviewed the historical evolution of pain interventions. One hundred fifty patients underwent 151 limb-salvage surgeries for bone cancer of the extremities in this series. Pain treatment increased progressively in complexity. Therapies included opioids, nonsteroidal antiinflammatory drugs, acetaminophen-opioid combinations, postoperative continuous epidural infusion, anticonvulsants and tricyclic antidepressants for neuropathic pain, local anesthetic wound catheters, and continuous peripheral nerve block catheters. Management of pain after limb-sparing surgery has evolved over the 26 years of this review. It currently relies on multiple “layers” of pharmacologic and nonpharmacologic strategies to address the complex mixed nociceptive and neuropathic mechanisms of pain in this patient population.

Serum Ropivacaine Concentrations and Systemic Local Anesthetic Toxicity in Trauma Patients Receiving Long-Term Continuous Peripheral Nerve Block Catheters

Ropivacaine is a long-acting local anesthetic used frequently for peripheral nerve blocks and continuous peripheral nerve block catheters. Combat trauma patients at Walter Reed Army Medical Center often receive continuous peripheral nerve block catheters as part of their pain regimen. These catheters remain in situ for several days to weeks. In this study, we evaluated the free ropivacaine drug levels over time in trauma patients by measuring the serum concentration of bound and unbound local anesthetic. The corresponding alpha(1)-acid glycoprotein concentration in patients with prolonged ropivacaine infusions was also measured. Fifteen patients were enrolled in the study; 2 patients were excluded because only a single ropivacaine level was obtained. Of the remaining 13 patients in the study, 2 had peripheral nerve catheters placed at the time of enrollment; the remaining 11 patients had catheters placed before enrollment. These patients were already receiving 0.2% ropivacaine infusions for a period of 18-126 h before the first assessment of local anesthetic level. Catheters infused 0.2% ropivacaine at a rate of 6-14 mL/h; catheter boluses were administered with 0.5% ropivacaine. Local anesthetic blood concentrations were scheduled to be measured on Days 1, 3, 5, 7, and 10 and every 3 days thereafter until all catheters were removed, although not all patients underwent each assessment. Specimens were assayed using high-performance liquid chromatography for total and free serum ropivacaine concentrations. Alpha(1)-acid glycoprotein was also measured. Thirteen patients remained in the study, for a total of 59 blood samples. The median number of days catheters remained in situ for the duration of acute pain therapy was 7 days (range: 6-27 days). The median number of days catheters remained in situ after enrollment into the study was 7 days (range: 4-25 days). The median number of blood samples collected per patient was 4 (range: 2-10 samples). Two patients had isolated increased concentrations of free ropivacaine into a previously identified toxic range with no obvious mitigating factors; both patients had received a 300-mg bolus of 0.5% ropivacaine approximately 24 h before that blood collection. The median ropivacaine concentration over the length of the study was 0.11 mg/L (range: undetectable to 0.63 mg/L). During the first week of the study, the median change in ropivacaine concentration per patient was 0.00 mg/L (range: -0.35 to 0.47 mg/L). Although 2 patients demonstrated isolated serum ropivacaine concentration spikes into a previously identified toxic range, continuous peripheral nerve block catheter management and local anesthetic doses as practiced at Walter Reed Army Medical Center did not result in clinically evident systemic ropivacaine toxicity. There was no correlation between free ropivacaine concentration and alpha(1)-acid glycoprotein concentration except in patients who had already been receiving ropivacaine infusions before entering the study. Despite this lack of correlation, the total duration of local anesthetic infusion did not seem to influence the free concentration of the drug.

Age-dependent Bupivacaine-induced Muscle Toxicity during Continuous Peripheral Nerve Block in Rats

Regional blocks improve postoperative analgesia and postoperative rehabilitation in children and adult patients. Continuous peripheral nerve blocks have been proposed as safe and effective techniques for postoperative pain relief and chronic pain therapy, particularly in small children. Few clinical reports have described myotoxicity induced by bupivacaine in these young patients, in contrast with a larger number of observations in adults. Here, the authors addressed this issue by a comparative evaluation of bupivacaine-induced myotoxicity in young versus adult rats. Femoral nerve block catheters were inserted in male Wistar rats. Young (3-week-old) and adult (12-week-old) rats were randomly assigned to received seven injections (1 ml/kg) of 0.25% bupivacaine (n = 6 per experiment) or isotonic saline (n = 6 per experiment) at 8-h intervals. Rats were killed 8 h after the last injection. Psoas muscle adjacent to the femoral nerve was quickly dissected. Oxygen consumption rates were measured in saponin-skinned fibers, mitochondrial adenosine triphosphate synthesis rates were determined by bioluminescence, and citrate synthase activity was determined by spectrophotometry. Muscle ultrastructural damage was also examined and scored as normal, focal disruption, moderate disruption, or extreme disruption of the sarcomeres. Bupivacaine caused a reduction of mitochondrial adenosine triphosphate synthesis rate, a decrease of citrate synthase activity, and muscle ultrastructural damages. Young rats treated with bupivacaine showed more severe alterations of mitochondrial bioenergetics and muscle ultrastructure. These findings demonstrate that bupivacaine-induced myotoxicity can be explained by mitochondrial bioenergetics alterations, which are more severe in young rats.

Analysis of Common Reasons for Acute Pain Consultations in an Academic University Practice

The Acute Pain Service provides a variety of services to our hospital. They include management of epidural analgesia, continuous peripheral nerve block catheters, epidural blood patches, and consultations for management of uncontrolled pain. The purpose of this study was to identify common reasons for acute pain management consultations in an academic university practice.

Infectious Risk of Continuous Peripheral Nerve Blocks

Infectious Risk of Continuous Peripheral Nerve Blocks

Development of a technique for continuous perineural blockade of the palmar nerves in the distal equine thoracic limb

ObjectiveTo develop a technique for placing continuous peripheral nerve block (CPNB) catheters adjacent to palmar nerves in horses and to evaluate the effect of low-volume local anesthetic (LA) infusion on nociception in the distal equine thoracic limb. Study designIn vitro and in vivo laboratory investigation.Study material and animals Forty-two thoracic limbs from 22 equine cadavers and five horses. MethodsThoracic limb specimens were dissected to find landmarks for catheter insertion adjacent to medial and lateral palmar nerves. Based on the anatomy of the proximal metacarpus, a technique for placing palmar CPNB catheters was developed and the potential for catheter dislodgement studied in vitro by fluoroscopic visualization during passive carpal flexion and dye injection following simulated limb motion. The feasibility of CPNB catheter instrumentation in standing, sedated horses was tested in five animals, with ultrasound control. Electrical and mechanical stimulation thresholds and response latencies for hoof withdrawal responses (HWR) were determined following saline or LA infusion. ResultsMedial and lateral CPNB catheters were inserted percutaneously 2 and 4–5 cm, respectively, distal to the accessory carpal bone and advanced for ∼7 and 10 cm, respectively, to place the tip just proximal to the communicating branch of the nerves. Catheters were placed correctly in 88% and 85% of cadaver limbs. In the standing horses, LA infusion not only increased HWR thresholds and latencies to noxious mechanical or electrical stimulation but also caused vasodilation and limb swelling over time. ConclusionThe technique, developed in vitro, for placing and maintaining palmar CPNB catheters in the equine thoracic limb was successfully applied in vivo. Catheters were well tolerated but LA infusion may cause limb swelling, suggesting a need for further exploration of drug and infusion regimens. Clinical relevanceContinuous perineural LA infusion along palmar nerves may develop into an effective analgesic technique in horses suffering from lower limb pain.