Robert Lennon

A Comprehensive Anesthesia Protocol That Emphasizes Peripheral Nerve Blockade for Total Knee and Total Hip Arthroplasty

R ecently, advances in radiographic imaging and surgical instrumentation have allowed experienced orthopaedic surgeons to perform total hip and total knee replacement surgery with surgical exposures that are less extensive than those associated with traditional techniques1,2. Commonly referred to as “minimally invasive total hip and total knee arthroplasty,” these techniques are now being touted as important surgical advancements. The introduction of minimally invasive total hip and total knee techniques has been accompanied by substantial concomitant changes in perioperative anesthetic techniques, rapid rehabilitation protocols, and changes in patient education and expectations. However, the specific contribution of each of these changes to observed improvements after contemporary total hip and total knee arthroplasty remains unclear. Tremendous strides in anesthesiology and perioperative pain management have been made with regard to the understanding of pain mechanisms and the importance of perioperative analgesia. The consequences of uncontrolled pain and medication-related side effects include the inability to actively participate in rehabilitation, delayed recovery, poor or suboptimal surgical outcome, prolonged hospitalization, and greater use of health-care resources3. Traditionally, the administration of intravenous opioids has been the mainstay for postoperative analgesia following total hip or total knee arthroplasty. However, parenteral opioids are commonly associated with inadequate pain relief, generalized sedation, and adverse side effects such as nausea, vomiting, gastrointestinal ileus, and pruritus. In response, some anesthesiologists have embraced the concept of “preemptive multimodal perioperative analgesia.” Preemptive analgesia involves the administration of analgesics prior to painful stimuli in order to prevent central sensitization and thus the amplification of pain4. Multimodal analgesia refers to the use of combined analgesic regimens for the treatment of postoperative pain. For example, low-dose opioids, local anesthetic infiltration, peripheral nerve blockade, nonsteroidal anti-inflammatory drugs, corticosteroids, clonidine, and cryotherapy all have been used in various combinations to manage postoperative …

Evaluation of a forced-air system for warming hypothermic postoperative patients.

Thirty adult surgical patients oral temperature ≤35.0°C were randomized into two groups. Group 1 patients were covered with cotton blankets warmed to 37.0°C, and group 2 patients were treated with a forced-air warming system. Mean oral temperature on admission to the recovery room was the same in both groups (34.3°C). Oral temperature and the presence or absence of shivering were recorded at 15-min intervals. After application of the selected warming method, patients in group 2 were warmer at all time intervals. Mean temperatures in the forced-air heating group and in group 1 were, respectively, 34.8°C and 34.3°C (P < 0.05) at 15 min; 35.0°C and 34.2°C (P < 0.01) at 30 min; 35.2°C and 34.5°C (P < 0.05) at 45 min; 35.8°C and 34.7°C (P < 0.001) at 60 min; 36.0°C and 35.0°C (P < 0.01) at 75 min; and 36.0°C and 35.0°C (P < 0.01) at 90 min. The incidence of shivering was significantly greater in group 1 at 15 and 45 min. In addition, time spent in the recovery room was significantly greater in group 1 than in group 2, 156.0 min versus 99.7 min (P < 0.003).

Evaluation of cisatracurium, a new neuromuscular blocking agent, for tracheal intubation

PurposeThe primary objective of this study was a blinded, randomized comparison of the recommended intubating dose of atracurium (0.5 mg·kg−1) with an approximately equipotent dose of cisatracurium (0.1 mg·kg−1) during N20/02/propofol/ fentanyl anaesthesia.MethodsEighty ASA physical status 1 or 2 patients, 18–70 yr of age, within 30% of ideal body weight, scheduled for elective low to moderate risk, surgical procedures were studied. Adductor pollicis evoked twitch responses were measured with a Grass FT 10 force displacement transducer (Grass Instruments, Quincy, MA) and continuously recorded on a Gould multichannel polygraph (Gould Instrument Systems, Cleveland, OH) after induction of anaesthesia.ResultsIncreasing the initial dose of cisatracurium (from 0.1 to 0.15 and 0.2 mg·kg−1, decreased mean time of onset (from 4.6 to 3.4 and 2.8 min, respectively), and increased mean time of clinically effective duration (45 to 55 and 61 min, respectively). Recovery to a T4:T1 ratio of 0.7 occurred approximately seven minutes following administration of the reversal agent neostigmine for all treatment groups. Intubation conditions were good or excellent in over 90% of patients in all treatment groups (two minutes after approximately 2 x ED95 doses of cisatracurium or atracurium and 1.5 minutes after 3 × and 4 × ED95 doses of cisatracurium).ConclusionThe intubation results reported in this study together with the combination of predictable recovery from neuromuscular block and apparent haemodynamic stability make cisatracurium a potentially useful muscle relaxant in clinical practice.RésuméObjectifComparer aléatoirement et en aveugle la dose d’atracurium recommandée pour l’intubation (0,5 mg·kg−1) avec une dose approximative équipotente de cisatracurium (0,1 mg·kg−1) pendant une anesthésie associant N2O/O2/propofol/ fentanyl.MéthodesL’étude portait sur 84 patients ASA 1 et 2, âgés de 18 à 70 ans, dont le poids ne déviait pas de plus de 30% du poids idéal, programmés pour une chirurgie non urgente comportant un risque faible ou modéré. Le twitch évoqué à l’adducteur du pouce était mesuré après l’induction de l’anesthésie à l’aide d’un transducteur Grass FT 10 (Grass Instrument, Quincy, MA) et enregistré en continu sur un polygraphe Gould (Gould Instrument System, Cleveland, OH).RésultatsL’augmentation de la dose initiale de cisatracurium (de 0,1 à 0,15 et à 0,2 mg·kg−1) diminuait l’installation du bloc (respectivement de 4,6 à 2,8 min) et augmentait la durée moyenne d’efficacité clinique (respectivement de 45 à 55 et à 61 min). La récupération à 0,7 du rapport T4/T1 survenait environ sept minutes après l’administration de l’antagoniste néostigmine dans tous les groupes. Les conditions pour l’intubation étaient de bonnes à excellentes chez plus de 90% des patients de tous les groupes (deux minutes après des doses d’environ 2 × ED50 de cisatracurium ou d’atracurium et 1,5 min après 3 × et 4 × ED50 de cisatracurium).ConclusionLes résultats rapportés dans cette étude concernant l’intubation associés avec un récupération prévisible du bloc au cisatracurium et sa stabilité hémodynamique apparente montrent que le cisatracurium pourrait être un relaxant musculaire utile en clinique.

Brachial Plexus Anesthesia for Outpatient Surgical Procedures on an Upper Extremity

We retrospectively reviewed 543 brachial plexus blocks performed on 526 outpatients. Most (98%) of the blocks were performed by means of the axillary approach. Various techniques were used, including paresthesia, transarterial fixation, nerve stimulation, or a combination of techniques; a high success rate was achieved with each of them. Only 7% of the blocks were incomplete and thus necessitated either general anesthesia or block supplementation with thiopental sodium and nitrous oxide. No persistent neurologic deficit was ascribed to the anesthetic technique. This review indicates that brachial plexus block, especially with use of the axillary approach, is a safe and effective option for outpatient surgical procedures on an upper extremity.

Effect of partial neuromuscular blockade on intraoperative electromyography in patients undergoing resection of acoustic neuromas

Intraoperative electromyographic monitoring of the facial nerve during acoustic neuroma excision provides early detection of nerve injury and improved outcome. To determine whether a useful level of peripheral neuromuscular blockade could be achieved without compromise of facial electromyographic monitoring, we studied 10 patients undergoing resection of acoustic neuroma. Facial nerve monitoring was accomplished by placement of wire electrodes in the orbicularis oris, orbicularis occuli, and mentalis muscles. Peripheral neuromuscular blockade was assessed by recording unprocessed hypothenar compound muscle action potentials (CMAPs). After induction of anesthesia, an infusion of atracurium (1.0 micrograms.kg-1.min-1) accompanied by a bolus dose of 50 micrograms/kg was administered. The infusion was then increased in increments of 0.5 micrograms.kg-1.min-1 until a 50% reduction in hypothenar single-twitch CMAP was obtained. Facial nerve function was continuously monitored by comparison of facial CMAPs produced by stimulation of the nerve proximal and distal to the tumor bed. The mean (+/- SD) infusion rate of atracurium was 2.55 +/- 0.75 micrograms.kg-1.min-1. Decrements in facial nerve CMAPs were detected in 6 of 10 patients, and all demonstrated moderate to severe facial nerve dysfunction. In no patient was an unexpected deficit present postoperatively. Moderate degrees of peripheral neuromuscular blockade can be achieved without compromising facial nerve electromyographic monitoring.

The Effects of Intraoperative Blood Salvage and Induced Hypotension on Transfusion Requirements During Spinal Surgical Procedures

Spinal surgical procedures, such as placement of Harrington rods for correction of scoliosis, are associated with considerable perioperative blood loss and, hence, with the risks associated with homologous blood transfusions. To test the hypothesis that intraoperative autologous blood transfusions could decrease the amount of homologous blood needed in such operations, we conducted a two-part study: (1) a retrospective review of 142 patients in whom blood salvage was not used and (2) a prospective review of 28 patients who received autologous transfusions. Intraoperative autologous transfusion reduced the amount of homologous blood required by more than 50% (5.1 versus 2.0 units; P less than 0.001). The total amount of homologous blood required during the hospital stay was also significantly reduced by intraoperative autologous transfusion (6.0 versus 3.4 units; P less than 0.001). Induced hypotension in 81 of the 142 patients who did not receive autologous transfusions did not decrease the homologous blood transfusion requirements from those needed by the normotensive patients. We conclude that intraoperative autologous transfusion significantly reduces the need for homologous blood products in patients who undergo spinal surgical procedures. Induced hypotension, which did not affect transfusion requirements in our study, should be further evaluated in a blinded, prospective study.

Combined H1 and H2 receptor blockade attenuates the cardiovascular effects of high-dose atracurium for rapid sequence endotracheal intubation

Large doses of atracurium (1.5 mg/kg) (six times the ED95) can result in significant histamine release, resulting in systemic hypotension. The efficacy of histamine receptor blockade in attenuating atracurium induced hypotension was therefore studied. Four groups of seven patients each were studied: group I, control; group II, H1 blockade (1 mg/kg diphenhydramine); group III, H2 blockade (cimetidine 4 mg/kg); and group IV, H1 and H2 blockade (diphenhydramine 1 mg/kg and cimetidine 4 mg/kg). All patients were anesthetized with an intravenous narcotic-nitrous oxide technique and then given 1.5 mg/kg atracurium. In group I, mean arterial pressure (MAP) decreased 30 mm Hg after 2 minutes and remained 25 mm Hg below baseline at 3 minutes, a change significantly greater than that in group IV, in which MAP decreased 8 and 7 mm Hg, respectively. H1 receptor blockade was associated with no significant attenuation of changes in MAP. H2 receptor blockade alone was associated with significant decreases in MAP, possibly secondary to enhanced release of histamine via an antagonist effect on recently described H3 receptors. Plasma histamine levels increased significantly 2 minutes after atracurium administration and correlated with hemodynamic changes. It is concluded that combined H1 and H2 receptor blockade attenuates cardiovascular effects associated with large doses of atracurium in humans. Histamine-releasing agents may be contraindicated in patients subject to chronic H2 receptor blockade.

A Computer-Controlled, Closed-Loop Infusion System for Infusing Muscle Relaxants: Its Use During Motor-Evoked Potential Monitoring

A microcomputer-controlled closed-loop infusion system (MCCLIS) has been developed that provides stable intraoperative levels of partial neuromuscular blockade. Complete neuromuscular blockade interferes with intraoperative motor-evoked potential (MEP) monitoring used for patients undergoing surgical procedures that place them at risk for spinal cord ischemia. Nine patients were studied during which the MCCLIS maintained stable levels of partial neuromuscular blockade and allowed transcranial magnetic motor-evoked potential (TcM-MEP) monitoring during thoracoabdominal aortic aneurysmectomy. The use of TcM-MEP for monitoring intraoperative spinal cord function was balanced against surgical considerations for muscle relaxation with 80% to 90% neuromuscular blockade fulfilling each requirement. Intraoperative adjustment of partial neuromuscular blockade to facilitate TcM-MEP monitoring was also possible with the MCCLIS. The MCCLIS should allow for further investigation into the sensitivity, specificity, and predictability of TcM-MEP monitoring for any patient at risk for intraoperative spinal cord ischemia including those undergoing thoracoabdominal aortic aneurysmectomy.

A Versatile, Computer-Controlled, Closed-Loop System for Continuous Infusion of Muscle Relaxants

A computer-controlled, closed-loop system for continuous infusion of muscle relaxants that allows the operator to choose either atracurium besylate or vecuronium bromide to provide any desired target level of neuromuscular blockade is described. This new system offers certain advantages over computer-controlled systems described previously for continuous infusion of muscle relaxants—that is, the option to choose either of two muscle relaxants to be infused and the inclusion of monitors to provide feedback about the dosage needed to produce a target level of neuromuscular blockade. The clinical performance of this system was tested in 36 patients who were 18 to 65 years old, were classified in American Society of Anesthesiologists physical status 1 or 2, and were undergoing elective orthopedic, abdominal, or thoracic procedures. In all patients, the control algorithm rapidly induced the target level of neuromuscular blockade and maintained that level of blockade at steady state with minimal oscillation. We conclude that the automatic feedback control system described can induce and precisely maintain any predetermined target level of neuromuscular blockade.

Doxacurium chloride for neuromuscular blockade before tracheal intubation and surgery during nitrous oxide-oxygen-narcotic enflurane anesthesia

The neuromuscular effects of doxacurium (BW A938W were studied in 36 patients, divided into four groups of 9 patients each, given doxacurium either 50 fig/kg (2 × ED95) 5 or 4 minutes or 80 μg/kg (3 × ED95) 4 or 3 minutes before tracheal intubation. Adequate neuromuscular relaxation permitted successful intubation at 5 minutes for doxacurium 50 μg/kg and at 4 minutes for 80 μg/kg. Time to 90% blockade was 5.4 ± 1.5 minutes for doxacurium 50 μg/kg and 3.5 ± 1.2 minutes for 80 μg/kg. Time to 25% spontaneous recovery was 84.7 ± 54.3 minutes for doxacurium 50 μg/kg and 164.4 ± 85.2 minutes for 80 μg/ kg. Either neostigmine 45 tiglkg, neostigmine 60 μg/kg, or edrophonium 1000 μg/kg was given for reversal when T1 had spontaneously recovered to 25% of baseline level, T1 being the first response to repetitive train-of-four (TOF) stimuli (2 Hz for 2 seconds at 10-second intervals) expressed as percent of baseline level. The T4:T1 ratio is the amplitude of the fourth twitch relative to the first twitch in a TOF stimulus expressed as a ratio. Tl rapidly achieved 90% of baseline in 5–10 minutes after reversal of neuromuscular blockade. In contrast, the T4:T1 ratio lagged, recovering to a mean of 0.6 at 20 minutes when T1 was over 90% of baseline. Recovery patterns were not statistically significantly different (unpaired t-test) among the three reversal regimens. Therefore, the reversal data were pooled. No clinically significant hemodynamic effects occurred in any group. The authors conclude that doxacurium is a long-acting muscle relaxant that provides excellent intubating conditions within 5 minutes with 50 uglkg and within 4 minutes with 80 fig/kg. Neuromuscular blockade lasts approximately 85 and 164 minutes, respectively. The neuromuscular blockade is pharmacologically readily reversible.