Serum ropivacaine concentrations and systemic local anesthetic toxicity in trauma patients receiving long-term continuous peripheral nerve block catheters.

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

Advanced regional anesthesia morbidity and mortality grading system: regional anesthesia outcomes reporting (ROAR).

OBJECTIVE: A regional anesthesia complication grading system (regional anesthesia outcomes reporting [ROAR]) was developed and applied to 1,213 consecutive patients over a 14-month period. The goal of the project was the creation of a system to standardize complication reporting in the regional anesthesia literature. DESIGN: Patient demographics, status as a war casualty, regional block procedure-specific details, and complication grade were entered into an Internet-based, encrypted Department of Defense database. Regional anesthesia complications were later graded and subcategorized depending on what phase of the block the procedural adverse event took place. RESULTS: One thousand ninety-eight (90.5%) patients had neither regional anesthesia associated technical difficulties or more severe complications. Of a total of 147 cases with adverse events among 115 patients (1.3 per patient), the majority (63.3%, 93/147) were low-grade complications resulting in no significant morbidity. The most common complications resulting in patient morbidity were failed block requiring catheter removal and/or supplemental block (35.4%, 17/48). High grade complications represented only 4.1% (6/147) of all peri-procedural morbidity. These complications included pneumothorax requiring tube thoracostomy, transient laryngeal nerve dysfunction, and cancellation of planned operation after peripheral nerve block or catheter placement. CONCLUSIONS: The value of the ROAR system is that it identifies important issues in risk management in regional anesthesia, thereby providing opportunities for further investigation and clinical practice refinement. Furthermore, it provides for a common language when reporting outcomes in the regional anesthesia literature. Use of the ROAR system will provide consistency in outcomes reporting and facilitate comparisons between methods and procedures.

Utilidad de los anestésicos locales en anestesia regional / Local anesthetics for regional anesthesia: an update

La anestesia regional en el siglo XXI, específicamente el bloqueos nervioso periférico y el bloqueo continuo de nervios periféricos, siguen gozando de una popularidad sin precedentes. A pesar de este resurgimiento de la popularidad, la investigación de un anestésico local nuevo y de acción más prolongada e inyectable con mejor perfil de seguridad sigue siendo un objetivo distante y difícil de lograr. Se han creado pocos anestésicos locales nuevos para uso clínico desde comienzos de la década de 1970. Los esfuerzos por mejorar la eficacia, la duración y la seguridad de los anestésicos locales inyectables incluyen aditivos y la nueva tecnología de localización de la aguja. Cualquier explicación convincente de los anestésicos locales de uso frecuente utilizados en la anestesia regional debe incluir un resumen detallado de la toxicidad de los anestésicos locales que incluya prevención, detección y tratamiento. Se plantea un enfoque específico sobre la aparición reciente de intralipid como tratamiento de la cardiotoxicidad inducida por anestésicos locales. Esta revisión de los anestésicos locales examinará la farmacología básica, explorará las tendencias actuales en la práctica de la anestesia regional y describirá los adelantos recientes en el uso clínico de los anestésicos locales y sus aditivos.

Regional anesthesia in the 21st century, specifically peripheral nerve blocks (PNBs) and continuous peripheralnerve blocks (CPNBs), continues to enjoy unparalleled popularity. Despite this resurgence in popularity, thesearch for a new, longer-acting local anesthetic (LA) forinjection with an improved safety profile remains anelusive and distant goal. A paucity of new local anestheticshas been developed for clinical use since the early 1970’s.Efforts to improve the efficacy, duration, and safety ofinjected LAs include drug additives to LAs and new need lelocalization technology. Any cogent discussion of the common LAs used with regional anesthesia must includea thorough summary of LA toxicity to include prevention,detection, and treatment. A specific focus on the recentemergence of Intralipid as a treatment for local anestheticinducedcardiac toxicity will ensue. This LA review willexamine basic pharmacology, explore current trends in regional anesthesia practice, and describe recent developments in the clinical use of LA and additives.

Responding to challenges in modern combat casualty care: innovative use of advanced regional anesthesia.

BACKGROUND: The war in Iraq has resulted in a high incidence of severe extremity injury requiring multiple surgical procedures and extensive rehabilitation. We describe the use of advanced regional anesthesia to meet this significant medical challenge. METHODS: From March 2003 to December 2004, 4,100 casualties have been evacuated to Walter Reed Army Medical Center (WRAMC). Of 1,400 inpatients, 750 have been battle-injured with 500 having extremity injuries. Of these, 287 (57%) received surgical care incorporating regional anesthesia including single-injection peripheral nerve blocks and continuous peripheral and epidural infusion catheters. Wounding, surgical, anesthetic, and outcomes data have been prospectively collected. RESULTS: Over 900 operations (mean 4+/-2/patient) were performed on 287 casualties prior to arrival at WRAMC, and 634 operations (mean 2+/-1/patient) were performed at WRAMC. Thirty-five percent of this cohort was amputees. In the study group, 646 advanced regional anesthesia procedures, including 361 continuous peripheral nerve blocks (CPNBs), were performed with a mean catheter infusion time of 9 days (1-34). Catheter-related complications occurred in 11.9% of casualties and were technical or minor in nature. Catheter-related infection rate was 1.9%. In 126 casualties with indwelling CPNB catheters, a significant decrease in pain score over 7 days was apparent (mean 3.7+/-0.2 to 2.2+/-0.2, P<0.001). CONCLUSION: Advanced regional anesthetic techniques allowed for safe perioperative surgical anesthesia and analgesia in the management of the modern combat casualty.

Anaesthetic agents for advanced regional anaesthesia: a North American perspective.

Interest in the use of regional anaesthesia, particularly peripheral nerve blocks (PNBs) and continuous PNBs, has increased in recent years. Accompanying this resurgence in interest has been the development of new local anaesthetics and additives designed to enhance block duration and quality. This manuscript provides a literature-based review on accepted uses of local anaesthetics and adjuncts for a variety of regional anaesthesia techniques. A brief review of local anaesthetic pharmacodynamics describes the action of these drugs in preventing nerve depolarisation, thus blocking nerve impulses. Toxic adverse effects of local anaesthetics, specifically CNS and cardiac manifestations of excessive local anaesthetic blood concentrations and the direct neurotoxic properties of local anaesthetics, are discussed generally and specifically for many commonly used local anaesthetics. Clinically useful ester and amide local anaesthetics are evaluated individually in terms of their physical properties and toxic potential. How these properties impact on the clinical uses of each local anaesthetic is explored. Particular emphasis is placed on the long-acting local anaesthetic toxic potential of racemic bupivacaine compared with levobupivacaine and ropivacaine, which are both levorotatory stereoisomers. Guidelines for using ropivacaine and mepivacaine, based on the authors' experience using advanced regional anaesthesia in a busy practice, is provided. Finally, epinephrine (adrenaline), clonidine and other local anaesthetic additives and their rationale for use is covered along with other future possibilities.

Continuous peripheral nerve block for battlefield anesthesia and evacuation.

Peripheral nerve and continuous peripheral nerve block (CPNB) have the potential to be valuable techniques in combat anesthesia. We describe the first successful application of CPNB in the pain management and surgical management of a combat casualty as he was evacuated from the Iraqi battlefield to the United States.