Ropivacaine 0.2% and lidocaine 0.5% for intravenous regional anesthesia in outpatient surgery.

BACKGROUND: A longer-acting local anesthetic agent, such as ropivacaine, may offer advantages over lidocaine for intravenous regional anesthesia. The objectives of this study were to evaluate whether the findings of volunteer investigations with intravenous regional anesthesia with ropivacaine (which have shown prolonged analgesia after release of the tourniquet) translates into improved pain control after surgery. METHODS: With Human Investigation Committee approval and a double-blind study design, 20 healthy patients with American Society of Anesthesiologists physical status I or II classification who were scheduled to undergo forearm and hand surgery were randomly assigned to administration of 40 ml of either 0.2% ropivacaine or 0.5% lidocaine for intravenous regional anesthesia. Evidence of central nervous system side effects, such as lightheadedness, tinnitus, and metallic taste, as well as cardiac arrhythmias, were evaluated and treated (if necessary) after local anesthetic administration, before and during surgery, and after release of the tourniquet until discharge from the postanesthesia care unit. Regression of sensory anesthesia in the nerve distributions of the forearm and hand was recorded. Verbal numerical pain scores were monitored and quantified until the patients were discharged to home from the postanesthesia care unit. Patient pain scores, side effect profiles, time to first oral intake, and total amount of oral analgesics were recorded 24 h postoperatively. RESULTS: Intravenous regional anesthesia with 0.2% ropivacaine and 0.5% lidocaine provided equivalent levels of surgical anesthesia. After release of the tourniquet, the first evidence for return of sensation in the distribution of the five peripheral nerves occurred later in the ropivacaine group (median, 20 min; range, 15-40 min) than in the lidocaine group (median, 1 min; range, 1-25 min). Verbal numerical pain scores were significantly lower at the time of admission, whereas during the remainder of the postanesthesia care unit stay and later at home, the difference in verbal numerical pain scores between the two groups was no longer statistically significant. CONCLUSIONS: Ropivacaine 0.2% may be an alternative to 0.5% lidocaine for intravenous regional anesthesia in the outpatient surgical setting. Longer-lasting analgesia in the immediate postoperative period may be due to a more profound and prolonged tissue binding effect of ropivacaine.

The traumatic airway: the anesthesiologist's role in the emergency room.

An approach to the airway is addressed in Table 1. A summary of induction/NMB agents and doses is given on Table 2; indications for the different agents are noted on Table 3. The central pharmacological issue is not that any one drug is universally preferred over another. Rather, it is key that one develop a thoughtful rationale for the drugs used, and a plan to get out of trouble if one is suddenly in the sinking situation of a patient with a difficult airway who cannot breathe on his or her own. The backup plan might involve the use of BVM ventilation, blind digital intubation, fiberoptic bronchoscope-aided intubation, retrograde techniques, light wand intubation, laryngeal mask airway techniques, posterior pharyngeal endotracheal tube placement ventilation, or a surgical airway. Most of these approaches are reviewed elsewhere.

Ziconotide, a new N-type calcium channel blocker, administered intrathecally for acute postoperative pain.

BACKGROUND AND OBJECTIVES: Voltage-sensitive calcium channel conductance is essential for the nervous system to signal a painful event. However, intrathecal administration of L-type calcium channel blockers does not provide analgesia. The present investigation was designed to assess the safety and analgesic efficacy of ziconotide, a new N-type calcium channel blocker, when administered intrathecally to patients with acute postoperative pain. METHODS: This randomized, double-blind, pilot study included patients undergoing elective total abdominal hysterectomy, radical prostatectomy, or total hip replacement. After intrathecal injection of local anesthetic and before surgical incision, a continuous intrathecal infusion of either placebo or 1 of 2 doses of ziconotide (0.7 microg/h or 7.0 microg/h) was started and continued for 48 to 72 hours postoperatively. Primary and secondary efficacy variables were the mean daily patient controlled analgesia (PCA) morphine equivalent consumption and visual analog pain intensity (VASPI) scores, respectively. RESULTS: Thirty patients received study drug; 26 were evaluable for efficacy. Mean daily PCA morphine equivalent consumption was less in patients receiving ziconotide than in placebo-treated patients, and the difference was statistically significant between 24 and 48 hours (P = .040). VASPI scores during the first 8 hours postoperatively were markedly lower in ziconotide-treated than in placebo-treated patients. In 4 of 6 patients receiving the high-dose of ziconotide (7 microg/h), adverse events, such as dizziness, blurred vision, nystagmus, and sedation contributed to study drug being discontinued after 24 hours. After ziconotide discontinuation, these symptoms resolved. CONCLUSIONS: Ziconotide showed analgesic activity, as shown by decreased PCA morphine equivalent consumption and lower VASPI scores. Because of a favorable trend of decreased morphine consumption with an acceptable side-effect profile in the low-dose ziconotide group, 0.7 microg/h may be closer to the ideal dose than 7 microg/h. Large-scale studies are required to clarify this issue.

Comparison of ropivacaine 0.2% and lidocaine 0.5% for intravenous regional anesthesia in volunteers.

UNLABELLED: A longer acting local anesthetic such as ropivacaine may offer advantages over lidocaine for IV regional anesthesia (IVRA). The objective of this investigation was to determine whether the use of ropivacaine improves the quality and duration of IVRA. In a randomized, double cross-over design, 10 volunteers received lidocaine 0.5% or ropivacaine 0.2% for IVRA of the upper extremity on two separate days with a standard double-cuff technique. Sensation to pinprick, response to tetanic stimuli, and tourniquet pain were assessed on a 0-10 verbal numeric score scale at 5-min intervals throughout the period of tourniquet inflation. Motor function was evaluated by grip strength. After release of the second (distal) cuff, pinprick sensation, motor strength, and systemic side effects were evaluated at 3, 10, and 30 min. No significant differences were observed for onset times of anesthesia and times to proximal (38 +/- 3 and 36 +/- 3 min) or distal (34 +/- 13 and 36 +/- 13 min) tourniquet release after the administration of ropivacaine and lidocaine, respectively. However, postdeflation hypoalgesia and motor blockade were prolonged with ropivacaine, and postdeflation light-headedness, tinnitus, and drowsiness were more prominent with lidocaine. We conclude that ropivacaine may be an alternative to lidocaine for IVRA. It may result in prolonged analgesia and fewer side effects after tourniquet release. IMPLICATIONS: In this study, volunteers received lidocaine 0.5% or ropivacaine 0.2% for IV regional anesthesia on two study days. Ropivacaine and lidocaine provided similar surgical conditions. However, after release of the distal tourniquet, prolonged sensory blockade and fewer central nervous system side effects were observed with ropivacaine.

A method for overcoming the ceiling effect of bounded pain scales.

OBJECTIVE: The Verbal Numerical Scale (VNS) for rating pain is bounded between 0 (= no pain) and 10 (= worst pain imaginable). We hypothesized that the limitations inherent to this boundary when rating extremely painful stimuli may be identified by integrating the VNS with an unbounded score such as magnitude estimation of relative change. METHODS: Volunteers received stimuli of increasing current via cutaneous electrodes until they rated >5 on the VNS scale. This stimulus, termed S, was arbitrarily assigned a magnitude estimate of 100%. Then, stimuli of varying currents were delivered; two were 10 mA and 20 mA higher than S (S(+10) and S(+20)), two were 1/2 of the current for the S stimulus (S(1/2)), and one was at the original current (Srepeat). The pain elicited by each stimulus was scored in proportion to the S stimulus. The extrapolated VNS score (VNSext) was determined by multiplying this magnitude estimate (%) by the VNS score for S. MAIN RESULTS: Seventy percent of the stimuli with higher intensity than S generated a VNSext score above 10. The mean magnitude estimations for S(+10) and S(+20) were 186% and 242%: they generated mean (median) VNSext values of 12.4 and 16.2, respectively (p = 0.019 for the difference between them by Wilcoxon signed rank test). CONCLUSIONS: The combined use of VNS and magnitude estimation confirmed that the ceiling of the bounded pain scale may significantly limit a patient's ability to describe a new pain stimulus. VNSext may provide a means of overcoming this limitation.

Prolonged use of a cook airway exchange catheter obviated the need for postoperative tracheostomy in an adult patient.

Catheters used to facilitate extubations of the known difficult airway are usually placed through an existing endotracheal tube (ETT), prior to its removal. We present a case in which a #11 Cook airway exchange catheter was placed adjacent to the ETT and left intratracheal for an extended period following removal of the ETT.

A prospective study of the safety of tracheal extubation using a pediatric airway exchange catheter for patients with a known difficult airway.

STUDY OBJECTIVE: To determine the usefulness of routinely inserting a hollow airway exchange catheter (jet stylet) prior to tracheal extubation of adult patients with risk factors for difficult tracheal intubation. DESIGN: Prospective, 1-year study of 40 consecutive patients undergoing mechanical ventilation who had one or more risk factors for difficult tracheal reintubation. SETTING: Surgical ICU of a tertiary university medical center. INTERVENTIONS: Study patients at risk for difficult tracheal reintubation were extubated using a No. 11 Cook airway exchange catheter (CAEC). Following tracheal extubation, the CAEC was secured, and humidified oxygen was insufflated through the central lumen (2 to 8 L/min) for a minimum of 4 h, during which oxyhemoglobin saturation (SpO2) and respiratory frequency were monitored. Stridor or other signs of respiratory difficulty were also assessed. The CAEC was removed when it became clinically apparent that the need for tracheal reintubation was unlikely. When patients failed to respond to tracheal extubation, the CAEC was used to facilitate reintubation of these difficult airways. RESULTS: Respiratory distress necessitating tracheal reintubation occurred in 3 of 40 patients (8%). One patient failed to respond to tracheal extubation twice. None of the patients developed oxyhemoglobin desaturation (SpO2 <90%) before or during tracheal reintubation. All four reintubations were accomplished during the first attempt using the CAEC as a stylet. The CAEC was kept in the trachea for a mean duration of 9.4 h. There were no adverse events documented. CONCLUSIONS: The No. 11 CAEC is a useful and effective tool for giving patients a trial of extubation. Administration of oxygen through the CAEC diminishes the potential for hypoxia while maintaining the ability to reintubate the trachea, especially when reintubation might prove challenging. Previous data suggest that the CAEC is rigid enough to facilitate tracheal reintubation in adults; this was confirmed in the three patients in our study who required tracheal reintubation. The risk of aspiration, barotrauma, or other airway trauma during prolonged placement of the CAEC appears to be low (zero incidence in 40 patients in this study), and use of the No. 11 CAEC appeared to be safe. Since oxygen can be delivered through the CAEC, it may provide a means to safely evaluate an airway during a trial of extubation, ie, a reversible extubation. Finally, oxygen administration through the CAEC may obviate the need for facemask or nasal cannula following tracheal extubation.

Very limited air elimination capability of the level 1 fluid warmer.

STUDY OBJECTIVE: To determine the volume of air in 1000-ml crystalloid bags before and after connection to an infusion set; and to determine the volume of air that is not eliminated by the air eliminator in the Level 1 fluid warming device (Level 1 Technologies, Inc., Rockland, MA) when air boluses of different volumes enter into the fluid warming set. DESIGN: Prospective analysis and laboratory investigation. SETTING: Operating room (OR) and research laboratory of a university hospital. INTERVENTIONS: Air was aspirated from 200 collapsible, 1000-ml crystalloid bags: 100 before being connected to an infusion set and 100 after being connected to a patient in the OR. A roller pump from a cardiopulmonary bypass machine was connected to a Level 1 D-300 fluid administration set to maintain a continuous flow of normal saline through its air eliminator at a flow that approximated gravity or two thirds maximal flow, which is the rate achieved when fluid is pressurized to 300 mmHg throughout the system. Different volumes of air were administered and the air that passed through the air eliminator was measured. MEASUREMENTS AND MAIN RESULTS: Nonspiked bags contained 56.2 +/- 4 ml (mean +/- SD) of air (range 43-66 ml), and spiked bags contained 61.2 +/- 13 ml of air (range 4-102 ml), a significant difference (p < 0.0001). The amount of air passing through the air eliminator differed significantly at gravity and at two thirds maximal flow with boluses of 5, 10, 20, and 30 ml of air (p < 0.0001), but not with the 60 ml bolus of air. The amount of air passing through the eliminator also differed significantly (p < 0.0001) between boluses of different sizes at each flow rate. At the higher flow rate, even small boluses of air were not reliably eliminated; up to 56% of a 5 ml air bolus passed through the eliminator. CONCLUSION: Air must be rigorously eliminated from all fluid containers because of the limited air elimination capability of the Level 1 air eliminator.

Thrombolytic therapy for treatment of pulmonary embolism in the postoperative period: case report and review of the literature.

A patient with morbid obesity and insulin-dependent diabetes was admitted to the surgical intensive care unit, four days status postsurgical repair of an umbilical hernia. A pulmonary embolus (PE) was diagnosed by ventilation/perfusion scan and confirmed by transthoracic echocardiogram. A right ventricular ejection fraction/volumetric/oximetry pulmonary artery catheter revealed a very low ejection fraction and cardiac index. Systemic urokinase therapy was initiated and the patient improved considerably over the ensuing 12 hours. Anesthesiologists must be able to diagnose the signs and symptoms of PE and should be familiar with treatment modalities to reverse right ventricular dysfunction. Review of the literature regarding thrombolytic therapy in the perioperative period indicates potential benefit in select patients.

[Anesthesia simulators and training devices]. / Anästhesiesimulatoren und Trainingsgeräte.

Simulators and training devices are used extensively by educators in 'high-tech' occupations, especially those requiring an understanding of complex systems and co-ordinated psychomotor skills. Because of advances in computer technology, anaesthetised patients can now be realistically simulated. This paper describes several training devices and a simulator currently being employed in the training of anaesthesia personnel at the University of Florida. This Gainesville Anesthesia Simulator (GAS) comprises a patient mannequin, anaesthesia gas machine, and a full set of normally operating monitoring instruments. The patient can spontaneously breathe, has audible heart and breath sounds, and palpable pulses. The mannequin contains a sophisticated lung model that consumes and eliminates gas according to physiological principles. Interconnected computers controlling the physical signs of the mannequin enable the presentation of a multitude of clinical signs. In addition, the anaesthesia machine, which is functionally intact, has hidden fault activators to challenge the user to correct equipment malfunctions. Concealed sensors monitor the users' actions and responses. A robust data acquisition and control system and a user-friendly scripting language for programming simulation scenarios are key features of GAS and make this system applicable for the training of both the beginning resident and the experienced practitioner. GAS enhances clinical education in anaesthesia by providing a non-threatening environment that fosters learning by doing. Exercises with the simulator are supported by sessions on a number of training devices. These present theoretical and practical interactive courses on the anaesthesia machine and on monitors. An extensive system, for example, introduces the student to the physics and clinical application of transoesophageal echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)