Jennifer J. Davis

Outpatient management of continuous peripheral nerve catheters placed using ultrasound guidance: an experience in 620 patients.

BACKGROUND: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. METHODS: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. RESULTS: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. CONCLUSIONS: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.

Improving Individual Measurement of Postoperative Pain: The Pain Trajectory

UNLABELLED The purpose of this study was to demonstrate a method for increasing the precision and information yield of postoperative pain assessment. We recorded pain intensity ratings over 6 days after surgery in 502 elective surgery patients and examined individual pain trajectories. A linear fit of an individual patients scores defines a trajectory with two features: (1) the intercept or initial pain intensity; and (2) the slope, or rate of pain resolution. Three pain trajectory patterns emerged from examination of the pain trajectory slopes. Most patients (63% of the sample) demonstrated a negative slope trajectory characterized by a decline in pain intensity over days after surgery. Other patients (25% of the sample) demonstrated a flat trajectory with no meaningful change over 6 days from pain they reported initially. A third patient group (12% of the sample) had a positive slope trajectory in which pain scores increased over 6 days after surgery. Measures derived from individual pain trajectories yielded much lower standard errors of measurement and therefore had better measurement precision than did conventional pain assessment methods. Pain trajectory measures proved sufficiently precise to characterize pain patterns reliably in individual patients. PERSPECTIVE Progress in acute pain management requires effective pain assessment. The acute pain trajectory quantifies rate of pain resolution as well as pain intensity. It affords more precise measurement than conventional pain assessment and can identify abnormal postoperative pain resolution.

A novel approach for assessing catheter position after ultrasound-guided placement of continuous interscalene block.

The increasing use of ultrasound has allowed anesthesiologists to perform nerve blocks with a high success rate and without nerve stimulation or eliciting a paresthesia. The ability to visualize peripheral nerve catheters using ultrasound is limited. We present a novel method to confirm the position of an interscalene catheter tip using injection of agitated contrast. The described technique is simple and allows timely assessment of catheter tip position.

Preoperative "fentanyl challenge" as a tool to estimate postoperative opioid dosing in chronic opioid-consuming patients.

When opioids are used for postoperative pain control, it is useful to define the dose-response relationship for analgesia and respiratory depression. We studied 20 chronically opioid-consuming patients having elective multilevel spine fusion. Preoperatively, each patient received a fentanyl infusion of 2 &mgr;g · kg−1 · min−1 until the respiratory rate was <5 breaths/min. Pharmacokinetic simulations were used to estimate the effect site concentration at the time of respiratory depression and to predict the patient-controlled analgesia settings that would provide an effect-site fentanyl concentration that was 30% of the concentration associated with respiratory depression. Postoperatively, patient-controlled analgesia settings were adjusted to achieve 2–3 demand doses per hour. At steady-state patient-controlled analgesia settings, arterial blood gases and plasma fentanyl levels were measured. Sixteen patients required no adjustment or one patient-controlled analgesia adjustment. The median arterial Pco2 level was 41 mm Hg and the interquartile range was 39–46 mm Hg. Plasma fentanyl levels demonstrated a significant correlation to the estimated effect-site concentration associated with respiratory depression determined during the preoperative fentanyl challenge. A preoperative fentanyl challenge used with pharmacokinetic simulations may be a useful tool to individualize the administration of analgesics to chronically opioid-consuming patients.

Ambulatory Anesthesia and Regional Catheters: When and How

Several clinical trials have demonstrated the superiority of continuous peripheral nerve block compared with traditional opioid-based analgesia. The ability to provide safe and effective continuous peripheral nerve block at home is an attractive alternative to opioid-based analgesia with its related side effects. In this article, the practical issues related to catheter use in the ambulatory setting are discussed. Techniques for catheter placement, infusion regimens, patient education, and complications are subject to many institutional preferences. In this review, special emphasis is placed on evidence-based techniques.

Three-times-daily subcutaneous unfractionated heparin and neuraxial anesthesia: a retrospective review of 928 cases.

Background and Objectives Subcutaneous (SC) unfractionated heparin (UFH) administered 3 times daily (TID) is widely used for venous thromboembolism prophylaxis in the perioperative period. There are no data in the literature regarding the incidence of adverse outcomes with neuraxial analgesia in the setting of this regimen. In this retrospective review, we report the incidence of untoward events related to anticoagulation with SC UFH TID in patients with indwelling epidural catheters. Methods We queried the electronic hospital databases to identify patients receiving thoracic epidural analgesia in conjunction with 5000 U UFH SC TID from July 2008 to October 2010. In this group, we identified the diagnoses of neuraxial hematoma, deep vein thrombosis, or pulmonary embolism and examined measured blood coagulation parameters. In addition, we determined the percentage of patients receiving concomitant therapy with ketorolac. Results We identified 928 patients who received thoracic epidural analgesia in conjunction with 5000 U UFH SC TID during this period. There were no cases of neuraxial bleeding. Seven patients had a diagnosed deep vein thrombosis or pulmonary embolism. Thirty-four percent (315/928) of patients received ketorolac. The measured activated thromboplastin time was more than 40 seconds (35 seconds being the upper limit of normal) in 115 patients (12%). Conclusions Given the rare incidence of neuraxial hematoma, statements regarding the appropriateness of epidural analgesia in the setting of TID SC UFH cannot be made from this limited sample size. At present, information regarding epidural hematoma in the setting of a TID SC UFH dosing regimen does not exist in the literature. Our study represents an initial step in the accumulation of data needed to prove or disprove the safety of this practice.

Getting the best value for consumable supplies in regional anesthesia.

A recent Congressional Budget Office report revealed that each year, over 16% of the gross domestic product for the United States is spent on healthcare. This percentage exceeds that spent in other industrialized countries by a considerable margin. One of the largest factors driving spending growth in healthcare is the greatly expanded technology in medical science. Regional anesthesia (RA), like many other disciplines, has been the beneficiary of numerous advances in devices and techniques. The focus of this article will be to review a number of RA practices with a focus on cost minimization and, when data are available, cost effectiveness. Clinical outcomes and comparative costs for consumable supplies will be presented. To provide a pragmatic view of these expenses, the projected annual cost of supplies at ‘‘high volume’’ centers, that is, those performing approximately 1000 procedures per year, will also be presented.

Evaluation of a New Needle Guidance System for Ultrasound: Results of a Prospective, Randomized, Blinded Study.

Background and Objectives Accurate needle control during ultrasound (US)-guided nerve blocks may be an elusive goal for the anesthesiologist. Despite modifications to increase echogenicity, needle visibility still requires precise alignment within the transducer beam. In this study, we evaluated a magnetically guided ultrasound (MGU) system that produces a real-time, graphic display of the needle position and trajectory that is independent of the US beam. Methods The MGU system was compared with echogenic needles and conventional ultrasound (CU) by anesthesiologists with and without prior experience performing US-guided nerve blocks. Participants were asked to perform tasks to quantify accuracy with respect to needle direction (directional accuracy) and needle tip position (positional accuracy). These evaluations were performed in a porcine tissue model. Results Regarding directional accuracy, inexperienced subjects were able to contact a target capsule with a single needle pass during both in-plane (IP) and out-of-plane (OOP) approaches using the magnetic guidance system. By contrast, using CU, subjects required redirection 3.8 ± 2.4 (P = 0.02), and 4.5 ± 3.9 (P = 0.04) times, respectively, for IP and OOP approaches. Experienced subjects contacted the target capsule with a single pass for both IP and OOP approaches when using the magnetic guidance system. With CU, experienced subjects were able to contact the target with a single pass using an IP approach but required redirection 3.4 ± 2.8 (P = 0.046) times during OOP approaches. Positional accuracy was also superior for both inexperienced (P = 0.04) and experienced (P = 0.02) users during an OOP approach. Conclusions In a tissue model, the MGU system improved control of needle trajectory and needle tip position for both inexperienced and experienced subjects.

Ultrasound-guided regional anesthesia: why can't we all just stay away from the nerve?

To the Editor:—I read, with interest, the case report describing a brachial plexopathy after an ultrasound-guided interscalene block in a patient with multiple sclerosis and the accompanying editorial and would like to make an observation not mentioned in either. Interscalene blocks have been performed using either mechanical paresthesia or electrical nerve stimulation, for decades, with success rates reported to be 94–99%. In both of these techniques, the entire dose of local anesthetic is injected upon eliciting the initial desired response. These true single-injection techniques occur at the first nerve root, and likely the most superficial one, encountered. Perlas et al. used real-time ultrasound to quantify the sensitivity of both paresthesia and motor nerve stimulation techniques. A 22-gauge insulated needle was in the axilla of 103 patients, and after visualizing direct needle–nerve contact, the patients were asked whether they felt any paresthesia. The nerve stimulator was then turned on, and a motor response was sought at 0.5 mA or less. The authors concluded that there are a significant number of false-negative responses (direct needle–nerve contact not resulting in paresthesia or motor response) with these traditional methods of localization. This study showed that direct ultrasound visualization does not prevent intimate needle–nerve contact. Although Koff et al. note that their needle “was not seen to penetrate the epineurium by [their] ultrasound image” after the first injection at C5, one must wonder how that initial volume of injection altered the ability to discern the needle–nerve relation of the three subsequent injections/maneuvers used to complete the block. One of the many questions that needs to be addressed, as we continue to promote the benefits of ultrasound for peripheral nerve blocks, is whether there are any advantages to repositioning a needle multiple times to be able to visualize local anesthetic spread around each of the nerve roots, because our historic success rates imply that this occurs adequately, with the initial injection. That is, does this practice of diving for individual and deeper nerve roots actually increase the risk to patients? The enemy of very good may prove to be better.

Local anesthetic injection deep to the fascia iliaca at the level of the inguinal ligament: the pattern of distribution and effects on the obturator nerve

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.