Dara S. Breslin

Central nervous system toxicity following the administration of levobupivacaine for lumbar plexus block: A report of two cases.

Background and Objectives Central nervous system and cardiac toxicity following the administration of local anesthetics is a recognized complication of regional anesthesia. Levobupivacaine, the pure S(-) enantiomer of bupivacaine, was developed to improve the cardiac safety profile of bupivacaine. We describe 2 cases of grand mal seizures following accidental intravascular injection of levobupivacaine. Case Report Two patients presenting for elective orthopedic surgery of the lower limb underwent blockade of the lumbar plexus via the posterior approach. Immediately after the administration of levobupivacaine 0.5% with epinephrine 2.5 μg/mL, the patients developed grand mal seizures, despite negative aspiration for blood and no clinical signs of intravenous epinephrine administration. The seizures were successfully treated with sodium thiopental in addition to succinylcholine in 1 patient. Neither patient developed signs of cardiovascular toxicity. Both patients were treated preoperatively with β-adrenergic antagonist medications, which may have masked the cardiovascular signs of the unintentional intravascular administration of levobupivacaine with epinephrine. Conclusions Although levobupivacaine may have a safer cardiac toxicity profile than racemic bupivacaine, if adequate amounts of levobupivacaine reach the circulation, it will result in convulsions. Plasma concentrations sufficient to result in central nervous system toxicity did not produce manifestations of cardiac toxicity in these 2 patients.

A New Teaching Model for Resident Training in Regional Anesthesia

The adequacy of resident education in regional anesthesia is of national concern. A teaching model to improve resident training in regional anesthesia was instituted in the Anesthesiology Residency in 1996 at Duke University Health System. The key feature of the model was the use of a CA-3 resident in the preoperative area to perform regional anesthesia techniques. We assessed the success of the new model by comparing the data supplied by the Anesthesiology Residency to the Residency Review Committee for Anesthesiology for the training period July 1992–June 1995 (pre-model) and the training period July 1998–June 2001 (post-model). During the 3-yr training period, the pre-model CA-3 residents (n = 12) performed a cumulative total of 80 (58–105) peripheral nerve blocks (PNBs), 66 (59–74) spinal anesthetics, and 133 (127–142) epidural anesthetics. The CA-3 post-model residents (n = 10) performed 350 (237–408) PNBs, 107 (92–123) spinal anesthetics, and 233 (221–241) epidural anesthetics (P < 0.0001). All results are reported as median (interquartile range). We conclude that our new teaching model using our CA-3 residents as block residents in the preoperative area has increased their clinical exposure to PNBs.

A study of anesthetic drug utilization in different age groups

STUDY OBJECTIVE To determine anesthetic drug utilization in different age groups. DESIGN Retrospective, automated, intraoperative database study. SETTING Tertiary care medical center. MEASUREMENTS 30,842 noncardiac general anesthesia case records between January 1991 and July 1997 were studied. We investigated the effect of age on anesthetic requirements for fentanyl (F), midazolam (M), thiopental sodium (T), propofol (P), isoflurane (I), and nitrous oxide (N). Because drugs are not given in isolation we looked at the most common drug combinations, IFNTM, IFNPM, INFT, and PFNM. Regression analyses on log-transformed drug dosages were used to test the significance of age on individual requirements. RESULTS In each of the above anesthetic drug combinations, reduced doses of fentanyl, propofol, midazolam, thiopental, and isoflurane were used with increasing age. Fentanyl, propofol, thiopental, and isoflurane showed a 10%, 8%, 6%, and 4% reduction in dose per decade of age, respectively, from age of maximum dose to age 80 years. CONCLUSIONS In clinical practice, increasing age results in decreased anesthetic drug administration. The mechanism of this observation needs to be determined.

Severe phantom leg pain in an amputee after lumbar plexus block.

12. Capdevila X, Biboulet P, Morau D, Bernard N, Descholt J, Lopez S, d’Athis F. Continuous three-in-one blocks for postoperative pain control after lower limb orthopedic surgery: Where do catheters go? Anesth Analg 2002;94:1001-1006. 13. Ganapathy S, Wasserman RA, Watson JT, Bennet J, Armstrong K, Stockall C, Chess D, MacDonald C. Modified continuous femoral three-in-one block for postoperative pain control after total knee arthoplasty. Anesth Analg 1999;89: 1197-1202.Objectives: To describe the onset of phantom leg pain in an amputee with the performance of a lumbar plexus block and the subsequent alleviation after the performance of a sciatic nerve block. Case Report: A 72‐year‐old American Society of Anesthesiologists physical status III woman presented for left total hip arthroplasty. Her history was significant for a left below the knee amputation. Since the amputation she had suffered from intermittent phantom leg pain. A lumbar plexus block was performed for postoperative pain management. After the lumbar plexus block, the patient experienced severe pain radiating to the left phantom foot. Because of the severity of the phantom pain, a sciatic nerve block was performed. The phantom leg pain resolved within 5 minutes. The intraoperative care under general anesthesia was uneventful. After surgery the patient had continued blockade in both nerve distributions with excellent analgesia. Full recovery of the lumbar plexus and sciatic nerve function was present on the first postoperative day. Conclusion: The temporal relationship between the onset of the phantom leg pain and the lumbar plexus block suggests a causal relationship. In this case, it appears that ongoing peripheral input from the lumbar plexus may have been sufficient for the tonic inhibition of phantom pain in the sciatic distribution. The immediate reactivation of the phantom pain and its subsequent relief suggests dynamic processing of peripheral inputs by central neurons, which apparently is rapid and reversible in some cases of phantom pain.

Unusual presentation and complication of the prone position for spinal surgery

Patient positioning for operative procedures has long been associated with perioperative complications. We present a case report of shoulder dislocation, which occurred following positioning in the prone position, and was detected by axillary artery occlusion resulting in the loss of the radial artery blood pressure line waveform. We discuss the diagnosis and consequences of this complication.

Variability in determination of point of needle insertion in peripheral nerve blocks: A comparison of experienced and inexperienced anaesthetists

Accurate identification of surface landmarks is essential for the successful performance of peripheral nerve blocks. The variability between experienced and inexperienced practitioners in identifying anatomical landmarks has not been studied previously. Anaesthetists were asked to identify the point of needle insertion for posterior lumbar plexus and sciatic nerve blocks on a volunteer using a standard textbook description. The chosen point for needle insertion was described in terms of X and Y co‐ordinates, measured in millimetres, from a zero reference point marked on a volunteers back. Fifteen experienced and 22 inexperienced anaesthetists took part in the study. The lumbar plexus block mean [range] values for the X, Y co‐ordinates were 80 [62–108], 66 [46–86] and 92 [49–150], 62 [0–131] in the experienced and inexperienced groups, respectively. The sciatic nerve block X, Y co‐ordinates were 77 [62–99], 70 [49–89] and 68 [29–116], 62 [26–93] in the experienced and inexperienced groups, respectively. The variance for the point of needle insertion was significantly greater in the inexperienced group (p < 0.01) for both the lumbar plexus and sciatic nerve blocks. We conclude that with increasing experience, there is decreased variability in determining the point of needle insertion using anatomical landmarks.

Pharmacodynamic interactions between cisatracurium and rocuronium.

The onset and duration of maintenance doses of neuromuscular blocking drugs may be influenced by the original neuromuscular blocking drug used. We assessed the effect of the interaction between steroidal and benzo-isoquinolinium compounds on the clinical duration of maintenance doses of cisatracurium. Sixty adult patients undergoing anesthesia with isoflurane, nitrous oxide, and oxygen were randomized to receive the following: Group I = rocuronium 0.6 mg/kg followed by cisatracurium 0.03 mg/kg when the first twitch in the train-of-four (TOF) recovered to 25%, Group II = cisatracurium 0.15 mg/kg followed by cisatracurium 0.03 mg/kg, and Group III = rocuronium 0.6 mg/kg followed by rocuronium 0.15 mg/kg. Neuromuscular blockade was monitored using acceleromyography (TOF-Guard®, Boxtel, The Netherlands). The clinical duration (mean ± sd) of the first 2 maintenance doses was 41 ± 10, 31 ± 7‡, and 25 ± 8‡ min, and 39 ± 11, 30 ± 6†, 29 ± 9* min in Groups I–III, respectively (*P < 0.05, †P < 0.01, ‡P < 0.001; Group I versus II and III). Thus, the clinical duration of the first two maintenance doses of cisatracurium was prolonged when administered after rocuronium.

Identification of coracoid process for infraclavicular blocks.

12. Capdevila X, Biboulet P, Morau D, Bernard N, Descholt J, Lopez S, d’Athis F. Continuous three-in-one blocks for postoperative pain control after lower limb orthopedic surgery: Where do catheters go? Anesth Analg 2002;94:1001-1006. 13. Ganapathy S, Wasserman RA, Watson JT, Bennet J, Armstrong K, Stockall C, Chess D, MacDonald C. Modified continuous femoral three-in-one block for postoperative pain control after total knee arthoplasty. Anesth Analg 1999;89: 1197-1202.

Construct validity of a novel assessment tool for ultrasound-guided axillary brachial plexus block.

The purpose of this study was to examine the construct validity and reliability of a novel metrics‐based assessment tool, previously developed for ultrasound‐guided axillary brachial plexus block. Five expert and eight novice anaesthetists performed a total of 18 ultrasound‐guided axillary brachial plexus blocks on the same number of patients. A trained investigator video‐taped procedures according to a pre‐defined protocol. Two trained consultant anaesthetists independently scored the videos using the assessment tool. Compared with novices, experts completed more steps (mean 41.0 vs. 33.1, p = 0.001), had fewer procedural errors (2.8 vs. 7.9, p < 0.0001), had fewer critical errors (0.8 vs. 1.3, p = 0.030), and fewer total errors (3.5 vs. 9.1, p < 0.0001). The mean inter‐rater reliability for scoring of experts’ performance was 0.91, for novices’ performance was 0.84, and for all performance combined (n = 18) was 0.88. This assessment tool is valid, and discriminates reliably between expert and novice performance for placement of ultrasound‐guided axillary brachial plexus blocks.

Adjuncts to local anesthetics in peripheral nerve blockade.

The use of peripheral nerve blocks has increased greatly in recent years. Although peripheral nerve blockade has traditionally been carried out using local anesthetics (LA), many other pharmacologic products may also have the ability to prevent transmission along afferent nerve pathways. In addition to producing peripheral nerve blockade (PNB), a wide variety of adjunct agents have been used to influence the characteristics of the nerve block. Adjuncts may be used to provide neural blockade, quicken onset, prolong duration, or improve quality and success of the block. Some adjuvants may also be used to decrease systemic toxicity. This article will review the more commonly used adjuncts used in combination with local anesthetics to provide blockade of peripheral nerves in clinical practice.