Philips Intellivue NMT module: precision and performance improvements to meet the clinical requirements of neuromuscular block management.

The variability or inaccuracy of acceleromyographic measurements could interfere with the interpretation of the train-of-four (TOF) ratio during neuromuscular block (NMB) recovery. This study evaluated the precision and performance of the Philips Intellivue NMT module (NMT) before (part 1) and after (part 2) several technical upgrades (i.e., firmware upgrade, new cable, and hand adapter) that were recently available. Two cohorts of 30 patients who were scheduled to undergo rhino/septoplasty under general anesthesia were included in the study. TOF ratios were recorded simultaneously every 15 s on both hands with the NMT and a TOF-Watch SX installed inside a SL TOF-Tube (TWX). Before rocuronium was administered and once final responses were stabilized, the average of the four successive measurements that determined the baselines and repeatability coefficients were compared using a z test. Simultaneous measurements were recorded at different NMB stages: onset, depth of NMB after intubation, when TWX recovered TOF count 2, TOF ratios 0.5 and 0.9, and when NMT recovered TOF ratio 0.9. The results were compared using a Student t test; p < 0.05 was considered significant. The NMT repeatability coefficients obtained in part 1 were significantly higher than with the TWX, they were significantly lower in part 2. Initially, the NMT significantly overestimated NMB recovery at every stage. Conversely, in the second part of the study, no difference reached statistical significance. With the recent upgrades and the new hand adapter, the NMT provided similar results compared with the TWX, Their implementation should be recommended in clinical practice.

Comparison of the TOF-Scan™ acceleromyograph to TOF-Watch SX™: Influence of calibration.

INTRODUCTION: Quantitative neuromuscular monitoring is now widely recommended during anesthesia using neuromuscular blocking agents to prevent postoperative residual paralysis and its related complications. We compared the TOF-Watch SX™ accelerometer requiring initial calibration to the TOF-Scan™, a new accelerometer with a preset stimulation intensity of 50mA not necessitating calibration. STUDY DESIGN: This pilot, prospective, observational study included adults undergoing general anesthesia with endotracheal intubation and muscle relaxation, having both arms free during surgery. Accelerometers were set up randomly on each arm. Anesthesia was started with remifentanil and propofol before an intubation dose of atracurium or rocuronium. Train of four stimulation was performed every 15s. Differences between measures were tested using Student's t-test and agreement assessed by Bland and Altman analysis. RESULTS: Thirty-two patients were included. During onset, a mean bias of -26seconds with a limit of agreement from -172 to +119seconds was observed between TOF-Watch SX™ and TOF-Scan™ to obtain 0 response to TOF. During recovery, TOF-Scan™ showed a significantly later recovery from 1 response to T4/T1>10%, but a bias of 0minute and limits of agreement from -4 to +4minutes for T4/T1>90% (NS). CONCLUSION: These results suggest a poor agreement between the calibrated TOF-Watch SX™ and the fix intensity TOF-Scan™ for onset and early recovery of relaxation (i.e. deep neuromuscular blockade) but a good agreement for recovery to TOF 90%. Data are not interchangeable between the devices, but both can be useful to detect residual paralysis.

Closed-loop anesthesia.

Automated anesthesia which may offer to the physician time to control hemodynamic and to supervise neurological outcome and which may offer to the patient safety and quality was until recently consider as a holy grail. But this field of research is now increasing in every component of general anesthesia (hypnosis, nociception, neuromuscular blockade) and literature describes some successful algorithms - single or multi closed-loop controller. The aim of these devices is to control a predefined target and to continuously titrate anesthetics whatever the patients' co morbidities and surgical events to reach this target. Literature contains many randomized trials comparing manual and automated anesthesia and shows feasibility and safety of this system. Automation could quickly concern other aspects of anesthesia as fluid management and this review proposes an overview of closed-loop systems in anesthesia.

Cuff pressure of endotracheal tubes after changes in body position in critically ill patients treated with mechanical ventilation.

BACKGROUND: In order to avoid microaspiration and tracheal injury, the target for endotracheal tube cuff pressure is 20 to 30 cm H2O. OBJECTIVE: To assess the effect of changes in body position on cuff pressure in adult patients. METHODS: Twelve orally intubated and sedated patients received neuromuscular blockers and were positioned in a neutral starting position (backrest, head-of-bed elevation 30º, head in neutral position) with cuff pressure at 25 cm H2O. Then, 16 changes in position were performed: anteflexion head, hyperextension head, left and right lateral flexion of head, left and right rotation of the head, semirecumbent position (head-of-bed elevation 45°), recumbent position (head-of-bed elevation 10°), horizontal backrest, Trendelenburg position (10°), and left and right lateral positioning over 30°, 45°, and 90°. Once a patient was correctly positioned, cuff pressure was recorded during an end-expiratory ventilatory hold. The pressure observed was compared with the cuff pressure at the starting position. Values outside the target range (20-30 cm H2O) were considered clinically relevant. RESULTS: A total of 192 measurements were performed (12 subjects × 16 positions). A significant deviation in cuff pressure occurred with all 16 changes (P < .05). No pressures were less than the lower limit (20 cm H2O). Pressures were greater than the upper limit (30 cm H2O) in 40.6% of the measurements. In each position, the upper target limit was exceeded at least once. Within-patient variability was substantial (P = .02). CONCLUSION: Simple changes in patients' positioning can result in potentially harmful cuff pressures.

A technical description of a novel pharmacological anesthesia robot.

To control the three components of general anesthesia (hypnosis, analgesia, and neuromuscular blockade), an automated closed-loop, anesthesia-drug delivery system (McSleepy) was developed. Bispectral index was used as the control variable for hypnosis, the analgoscore for analgesia, and phonomyography for neuromuscular blockade. McSleepy can be used to control the induction, maintenance and emergence from general anesthesia. To do so, a large touch screen is used to provide a user friendly interface, permitting bidirectional communication: the user giving information about the different stages of anesthesia, and the system prompting the anesthesiologist to perform certain actions such as mask ventilation, intubation or waking-up the patient using audio clips with voice commands. Several safety features were implemented to provide a secure and reliable anesthesia. Preliminary results of 15 patients are presented in this paper. Evaluation of McSleepy was done through an assessment of its clinical performance and using Varvel's performance indices. The system was found to be clinically useful by providing good precision in drug administration and reliable results for the duration of a general anesthesia.

The efficacy of several neuromuscular monitoring modes at the P6 acupuncture point in preventing postoperative nausea and vomiting.

BACKGROUND: In this study, we tested the efficacy of several neuromuscular monitoring modes at the P6 acupuncture point for preventing postoperative nausea and vomiting (PONV). METHODS: In this prospective, double-blind, randomized, placebo-controlled trial, 264 women undergoing laparoscopic hysterectomy were evaluated for PONV. Neuromuscular blockade was monitored by acceleromyography with 1-Hz single twitch (ST) over the ulnar nerve (n = 54, control), and ST (n = 52), train-of-four (n = 53), double-burst stimulation (n = 53), or tetanus (n = 52) over the median nerve stimulating at the P6 acupuncture point. RESULTS: The incidence of PONV (P = 0.022), the number of requests for patient-controlled analgesia (P = 0.009), and total patient-controlled analgesia volume (P = 0.042) 6 hours after tetanic stimulation were significantly reduced in the treatment group compared with the control group. Overall, patients in the tetanus group were more satisfied with the management of PONV compared with patients in the control group. CONCLUSION: Tetanic stimulation applied to the P6 acupuncture point can reduce PONV after laparoscopic hysterectomy compared with ST stimulation of the ulnar nerve, resulting in a greater degree of patient satisfaction. None of the stimulations, ST, train-of-four, or double-burst, applied to the P6 acupuncture point significantly affected PONV.

Infusion requirements and reversibility of rocuronium at the corrugator supercilii and adductor pollicis muscles.

BACKGROUND: The aim of this study is to compare the infusion rates required to maintain a constant neuromuscular block and the reversibility of rocuronium at the corrugator supercilii muscle (CSM) and the adductor pollicis muscle (APM). METHODS: We randomly allocated 30 female patients into two groups of 15 patients each to monitor neuromuscular block at either the CSM or the APM. After induction of anaesthesia and laryngeal mask insertion, contraction of the CSM to the facial nerve stimulation or that of the APM to the ulnar nerve stimulation was quantified using an acceleromyograph during 1.0-1.5% end-tidal sevoflurane anaesthesia. All the patients received a bolus of 1 mg/kg rocuronium. When the first twitch (T1) of train-of-four (TOF) recovered to 10% of the control, rocuronium infusion was commenced and maintained at T1 of 10% of the control at the CSM or APM for 120 min. Immediately after rocuronium infusion was discontinued, the time required for 0.04 mg/kg neostigmine-facilitated recovery to a TOF ratio of 0.9 was recorded. RESULTS: Rocuronium infusion dose after a lapse of 120 min was significantly larger in the CSM than in the APM [7.1 (2.3) vs. 4.7 (2.6) microg/kg/min; P=0.001]. The time for facilitated recovery was shorter in the CSM than in the APM [11.4 (3.8) vs. 16.2 (6.0) min; P=0.016]. CONCLUSION: A larger rocuronium infusion dose was required to maintain a constant neuromuscular block at the CSM. Neostigmine-mediated reversal was faster at the CSM.

Ultrasound-guided trigger point injections in the cervicothoracic musculature: a new and unreported technique.

BACKGROUND: Myofascial pain is defined as pain that originates from myofascial trigger points in skeletal muscle. It is prevalent in regional musculoskeletal pain syndromes, either alone or in combination with other pain generators. The myofascial pain syndrome is one of the largest groups of under diagnosed and under treated medical problems encountered in clinical practice. Trigger points are commonly seen in patients with myofascial pain which is responsible for localized pain in the affected muscles as well as referred pain patterns. Correct needle placement in a myofascial trigger point is vital to prevent complications and improve efficacy of the trigger point injection to help reduce or relieve myofascial pain. In obese patients, these injections may not reach the target tissue. In the cervicothoracic spine, a misguided or misplaced injection can result in a pneumothorax. Here, we describe an ultrasound-guided trigger point injection technique to avoid this potential pitfall. Office based ultrasound-guided injection techniques for musculoskeletal disorders have been described in the literature with regard to tendon, bursa, cystic, and joint pathologies. For the interventionalist, utilizing ultrasound yields multiple advantages technically and practically, including observation of needle placement in real-time, ability to perform dynamic studies, the possibility of diagnosing musculoskeletal pathologies, avoidance of radiation exposure, reduced overall cost, and portability of equipment within the office setting. To our knowledge, the use of ultrasound guidance in performing trigger point injection in the cervicothoracic area, particularly in obese patients, has not been previously reported. METHODS: A palpable trigger point in the cervicothoracic musculature was localized and marked by indenting the skin with the tip of a plastic needle cover. The skin was then sterile prepped. Then, using an ultrasound machine with sterile coupling gel and a sterile latex free transducer cover, the musculature in the cervicothoracic spine where the palpable trigger point was detected was visualized. Then utilizing direct live ultrasound guidance, a 25-gauge 1.5 inch needle connected to a 3 mL syringe was placed into the muscle at the exact location of the presumed trigger point. This guidance helps confirm needle placement in muscle tissue and not in an adipose tissue or any other non-musculature structure. RESULTS: The technique is simple to be performed by a pain management specialist who has ultrasound system training. CONCLUSION: Ultrasound-guided trigger point injections may help confirm proper needle placement within the cervicothoracic musculature. The use of ultrasound-guided trigger point injections in the cervicothoracic musculature may also reduce the potential for a pneumothorax by an improperly placed injection.

Neuromuscular diagnosis in orthodontics: effects of TENS on the sagittal maxillo-mandibular relationship.

AIM: This study was conducted in order to assess the changes in the occlusal position of the mandible after ULF (Ultra Low Frequency)-TENS relaxing procedure in subjects in pubertal growth phase with diagnosed Angle Class II division 1 and mandibular dentoalveolar retrusion. MATERIALS AND METHODS: This study was performed on 19 patients (13 females, 6 males) with an Angle Class II division 1, aged between 10 and 15 years old (mean age 12.26, SD 1.32), characterised by mandible dentoalveolar retrusion and optimal vertical facial dimension, diagnosed by clinical and cephalometric evaluation. Diagnostic neuromuscular registrations were made for all subjects. The casts were mounted on articulator in habitual intercuspal position with a tooth-guided wax bite registration. Reference points were chosen at molar level. Subsequently the same casts were mounted in myocentric position and compared to the habitual intercuspal position, assessing the sagittal shift after TENS procedure. STATISTICS: Mean and standard deviation were calculated on the amount of shifting at the left molar reference point after TENS procedure. Analysis of variance (ANOVA), using STATA statistics package, was carried out in order to evaluate the influence of sex and age on the amount of molar shift. RESULTS: Nine subjects showed, in the sagittal plane, a forward mandibular shift in neuromuscular myocentric position compared to habitual intercuspal position. Six subjects showed no differences between habitual and myocentric position in the sagittal plane. Four individuals showed a backward mandible shift after TENS indicating worsening of the II molar class in the sagittal plane. CONCLUSION: This study suggests that TENS recorded occlusion in subjects with Class II division 1 with mandible dentoalveolar retrusion allows to visualise an unusual trend of growth. The advancements of the mandible were not taken into account. These results could offer new diagnosis and prognosis methods for Class II malocclusions.

Randomized prospective study comparing the laryngeal tube suction II with the ProSeal laryngeal mask airway in anesthetized and paralyzed patients.

BACKGROUND: The Laryngeal Tube Suction II (LTSII; VBM, Medizintechnik, Sulz, Germany) is a recent revision of the Laryngeal Tube Suction. This study compared insertion and ventilation profiles of the LTSII and the ProSeal Laryngeal Mask Airway (PLMA; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) in anesthetized and paralyzed patients. METHODS: One hundred adult male patients were randomly allocated to an LTSII or PLMArade mark group. The rate of successful insertion, insertion time, airway leak pressure at a cuff pressure of 60 cm H2O, tidal volume during pressure-controlled ventilation, incidence of gas leakage with cuff pressure reduced and with the shaft inclined, position of LTSII under fluoroscopic observation, and postoperative airway morbidity were determined. RESULTS: Insertion was successful in 37 and 48 of 50 patients with LTSII and PLMA, respectively (P = 0.002), with similar insertion times. Tidal volume was lower with LTSII than with PLMA. Median airway leak pressures of LTSII and PLMA were 16 and 21 cm H2O, respectively (P = 0.006). Gas leakage around the cuff was observed more frequently with LTSII than with PLMA when the cuff pressure was reduced or the shaft of the device inclined. The position of LTSII varied significantly and did not statistically correlate with patient height. Postoperative airway-related morbidity was not significantly different. Finally, tracheal misplacement of LTSII occurred in 5 of 50 patients (10%), but ventilation was possible in 4 of them, and misplacement was identified only after fluoroscopic examination was performed. CONCLUSION: Airway management with LTSII is inferior to that with PLMA.

Monitoring of neuromuscular blockade at the P6 acupuncture point reduces the incidence of postoperative nausea and vomiting.

BACKGROUND: Electrical stimulation of the P6 acupuncture point reduces the incidence of postoperative nausea and vomiting (PONV). Neuromuscular blockade during general anesthesia can be monitored with electrical peripheral nerve stimulation at the wrist. The authors tested the effect of neuromuscular monitoring over the P6 acupuncture point on the reduction of PONV. METHODS: In this prospective, double-blinded, randomized control trial, the authors investigated, with institutional review board approval and informed consent, 220 women undergoing elective laparoscopic surgery anesthetized with fentanyl, sevoflurane, and rocuronium. During anesthesia, neuromuscular blockade was monitored by a conventional nerve stimulator at a frequency of 1 Hz over the ulnar nerve (n = 110, control group) or over the median nerve (n = 110, P6 group) stimulating at the P6 acupuncture point at the same time. The authors evaluated the incidence of nausea and vomiting during the first 24 h. RESULTS: No differences in demographic and morphometric data were found between both groups. The 24-h incidence of PONV was 45% in the P6 acupuncture group versus 61% in the control group (P = 0.022). Nausea decreased from 56% in the control group to 40% in the P6 group (P = 0.022), but emesis decreased only from 28% to 23% (P = 0.439). Nausea decreased substantially during the first 6 h of the observation period (P = 0.009). Fewer subjects in the acupuncture group required ondansetron as rescue therapy (27% vs. 39%; P = 0.086). CONCLUSION: Intraoperative P6 acupuncture point stimulation with a conventional nerve stimulator during surgery significantly reduced the incidence of PONV over 24 h. The efficacy of P6 stimulation is similar to that of commonly used antiemetic drugs in the prevention of PONV.

Model-based control of neuromuscular block using mivacurium: design and clinical verification.

BACKGROUND: Short-acting agents for neuromuscular block (NMB) require frequent dosing adjustments for individual patient's needs. In this study, we verified a new closed-loop controller for mivacurium dosing in clinical trials. METHODS: Fifteen patients were studied. T1% measured with electromyography was used as input signal for the model-based controller. After induction of propofol/opiate anaesthesia, stabilization of baseline electromyography signal was awaited and a bolus of 0.3 mg kg-1 mivacurium was then administered to facilitate endotracheal intubation. Closed-loop infusion was started thereafter, targeting a neuromuscular block of 90%. Setpoint deviation, the number of manual interventions and surgeon's complaints were recorded. Drug use and its variability between and within patients were evaluated. RESULTS: Median time of closed-loop control for the 11 patients included in the data processing was 135 [89-336] min (median [range]). Four patients had to be excluded because of sensor problems. Mean absolute deviation from setpoint was 1.8 +/- 0.9 T1%. Neither manual interventions nor complaints from the surgeons were recorded. Mean necessary mivacurium infusion rate was 7.0 +/- 2.2 microg kg-1 min-1. Intrapatient variability of mean infusion rates over 30-min interval showed high differences up to a factor of 1.8 between highest and lowest requirement in the same patient. CONCLUSIONS: Neuromuscular block can precisely be controlled with mivacurium using our model-based controller. The amount of mivacurium needed to maintain T1% at defined constant levels differed largely between and within patients. Closed-loop control seems therefore advantageous to automatically maintain neuromuscular block at constant levels.

The cuff method: a pilot study of a new method of monitoring neuromuscular function.

BACKGROUND: A new method of monitoring neuromuscular blockade based on a modified blood pressure cuff that incorporates stimulating electrodes was compared with mechanomyography (MMG) ('gold standard'). METHODS: Forty adults and 20 children (ASA I-II) underwent neuromuscular blockade monitoring on the contralateral arms and on the same arm using the new cuff method and MMG. Only train-of-four (TOF) ratios > 0.1 and T(1) heights > 0 were studied. Supramaximal stimulation was also assessed. A device based on a PC with an analogue-to-digital conversion card was used to control and synchronize MMG and the cuff method. The agreement between both methods was assessed using the statistical method of Bland and Altman. RESULTS: When TOF ratios were >0.7, the bias between the two methods was -0.04 with the limits of agreement ranging from -0.21 to -0.12 (95% CI -0.06 to -0.02). The T(1) > 0 heights bias was -0.01 with the limits of agreement ranging from -0.26 to 0.24 (95% CI -0.02 to -0.003). The sensitivity of the cuff method was 88%, with a specificity of 85% and an accuracy of 86%. CONCLUSION: This pilot study indicates that the cuff method could be useful to monitor neuromuscular blockade according to the bias and limits of agreement compared with MMG, particularly when the degree of blockade was evaluated by TOF ratios > 0.7. The new cuff method is easy and simple to use. However, further studies in a larger number of patients are necessary to confirm these favourable preliminary results.

Simultaneous determination of neuromuscular blockade at the adducting and abducting laryngeal muscles using phonomyography.

UNLABELLED: Phonomyography (PMG) is a new method for measuring neuromuscular blockade (NMB) at the larynx. In this study, we used PMG to compare NMB at the posterior cricoarytenoid (PCA) and the lateral cricoarytenoid muscle (LCA) in humans. Twelve patients were included in this study. Endotracheal intubation was performed without aid of neuromuscular blocking drugs. One small condenser microphone was inserted beside the vocal cords into the muscular process at the base of the arytenoid cartilage to record acoustic responses of the LCA (vocal cord adduction), and a second microphone was placed behind the larynx to measure NMB of the PCA (vocal cord abduction). Stimulation of the recurrent laryngeal nerve was performed using superficial electrodes placed at the neck (midline between jugular notch and cricoid cartilage) using train-of-four (TOF) stimulation every 12 s. After supramaximal stimulation, mivacurium 0.1 mg/kg was injected and onset, peak effect, and offset of NMB measured and compared using t-test (P < 0.05). The data are presented as mean (SD). Peak effect, onset time, and early recovery to 25% of control twitch height were not significantly different between PCA and LCA at 86% (13) versus 78% (16), 2.3 min (0.45) versus 2.3 min (1.0), and 9.55 min (3.05) versus 8.5 min (4.7), respectively. However, recovery to 75%, 90% of control twitch height, and recovery to a TOF ratio of 0.8 were significantly longer at the PCA than at the LCA at 14 min (4) versus 11 min (5), 17 min (5) versus 11.8 min (5.6), and 17.5 min (5.6) versus 12.3 min (5.5), respectively. The authors conclude that recovery of NMB at the PCA takes longer than at the LCA in humans after mivacurium. IMPLICATIONS: After neuromuscular blockade in humans, the recovery of the ability to open the vocal cords takes longer than the ability to close the vocal cords.

[The syringe pump as actuator--a practical application problem of feedback control systems]. / Die Spritzenpumpe als Stellglied--Ein Problem im praktischen Einsatz regelkreisgesteuerter Systeme.

Based on a computer simulation programme, the accuracy of the Graseby 3400 syringe pump was tested for its use in a feedback control system of the neuromuscular block. Firstly, a calculation of errors to determine the difference between the target and actual flow rates was carried out. Next, the characteristic curves of the syringe pump were determined under different flow and sampling rates to correct the application software of the feedback controller with a view to obtaining the correct flow rates online. It was discovered that, particularly with short 12 s sampling rates, dose-dependent errors of almost 100% were provable. Therefore, the application of a robust controller and integration of the characteristic curves at the outlet of the controller software are required. For the adoption of syringe pumps in medical feedback control systems, definite determination of the actual infusion quantity using an exact calculation of errors is required. Especially in cases of short sampling rates in combination with low infusion quantities, the syringe pump comes almost to a standstill, which results in extreme differences between target and actual flow rates.