The interest of 100 versus 200 Hz tetanic stimulations to quantify low levels of residual neuromuscular blockade with mechanomyography: a pilot study.

A more sensitive method than the train-of-four ratio seems required to detect low levels of residual neuromuscular blockade before tracheal extubation. The goal of the study was to determine the potential benefit of 5 s of 100 versus 200 Hz tetanic stimulation to quantify the residual block with mechanomyography in anesthetised patients. Twenty informed and consenting 18- to 80-year-old patients undergoing nose surgery were included. On the left hand, neuromuscular transmission was continuously monitored by acceleromyography. On the right side, a new mecanomyographic device (Isometric Thumb Force©) recorded the force of thumb adduction (N) developed during 5 s of 100- and 200 Hz tetanic stimulations of the ulnar nerve at three consecutive times: baseline before inducing the neuromuscular blockade, at the time of contralateral train-of-four ratio 0.9 recovery, and 3 min after additional sugammadex reversal. Tetanic Fade Ratios (TFR = F residual/F max) were compared between 100 and 200 Hz stimulations using Student's t test. At the time of TOF ratio 0.9 recovery, both 100 and 200 Hz TFR were significantly decreased compared to baseline (0.61 and 0.16 on average, respectively, p < 0.0001). The 200 Hz TFR was significantly lower than the 100 Hz TFR (p < 0.0001). There were no differences between baseline and post-reversal TFR. The 200 Hz TFR has the potential to better describe low levels of residual neuromuscular blockade than the TOF ratio and 100 Hz TFR and would benefit from further investigations. Retrospectively registered in the Australian and New Zealand Clinical Trials Registry ACTRN12619000273189.

100 Hz-5 s tetanic stimulation to illustrate the presence of "residual paralysis" co-existing with accelerometric 0.90 train-of-four ratio-A proof-of-concept study.

BACKGROUND: An acceleromyographic train-of-four (TOF) ratio of 0.90 at extubation does not prevent postoperative pulmonary complications in surgical patients receiving non-depolarising muscle relaxants. This recent observation suggests that a more selective neuromuscular transmission monitoring parameter is mandatory to detect more precisely any remaining residual paralysis. The aim of our proof-of-concept study was to evaluate, in patients receiving rocuronium, the degree of 100-Hz, 5-s tetanic fade present when the acceleromyographic TOF ratio has recovered to 0.90. METHODS: Twenty adult patients scheduled for surgery under general anaesthesia were included. Before anaesthesia induction, a TOF-Watch SX™ and a VISUAL-ITF© (a prototype monitor for recording isometric force) were positioned on both hands. After induction but before rocuronium injection, a 100-Hz, 5-s tetanus (TET0) was delivered to both ulnar nerves. Thereafter, TOF stimulations every 15 s were delivered to both arms until a TOF ratio > 0.90 was recorded; then, a 100-Hz, 5-s tetanus (TET1) was recorded on the VISUAL-ITF© monitor. The values of the tetanic parameters (force) recorded at TET0 and TET1 were compared using a Wilcoxon rank sum test. RESULTS: Compared to TET0, tetanic parameters of TET1 were significantly lower (median [range]): maximal force 36.4 [19.2-82.6] vs. 25.5 [5.0-42.4] Newton (p < 0.005); residual force 36.2 [18.2-82.0] vs. 5.5 [0.20-38.3] Newton (p < 0.0001) and residual force/maximal force ratio 0.98 [0.89-0.99] vs. 0.17 [0.03-0.90] (p < 0.0001). CONCLUSION: Our results confirm that even when the acceleromyographic TOF ratios have recovered to above 0.90, the contralateral 100-Hz, 5-s tetanic stimulus may show tetanic fade characteristic of residual neuromuscular block, and may help improve the safety of tracheal extubation.

Impact of an Original Methodological Tool on the Identification of Corrective and Preventive Actions After Root Cause Analysis of Adverse Events in Health Care Facilities: Results of a Randomized Controlled Trial.

OBJECTIVE: The aim of the study was to assess the effectiveness of a new methodological tool for the identification of corrective and preventive actions (CAPAs) after root cause analysis of health care-related adverse events. METHODS: From January to June 2010, we conducted a randomized controlled trial involving risk managers from 111 health care facilities of the Aquitaine Regional Center for Quality and Safety in Health Care (France). Fifty-six risk managers, randomly assigned to two groups (intervention and control), identified CAPAs in response to two sequentially presented adverse event scenarios. For the baseline measure, both groups used their usual adverse event management tools to identify CAPAs in each scenario. For the experimental measure, the control group continued using their usual tools, whereas the intervention group used a new tool involving a systemic approach for CAPA identification. The main outcome measure was the number of CAPAs the participants identified that matched a criterion standard established by eight experts. RESULTS: Baseline mean number of identified CAPAs did not differ between the two groups (P = 0.83). For the experimental measure, significantly more CAPAs (P = 0.001) were identified by the intervention group (mean [SD] = 4.6 [1.7]) than by the control group (mean [SD] = 2.8 [1.2]). CONCLUSIONS: For the two scenarios tested, more relevant CAPAs were identified with the new tool than with usual tools. Further research is needed to assess the effectiveness of the new tool for other types of adverse events and its impact on patient safety.

Performance of acceleromyography with a short and light TOF-tube compared with mechanomyography: a clinical comparison.

BACKGROUND: Disturbances in the thumb's movement interfere with the functioning of acceleromyography in many clinical settings. The short and light (SL) train-of-four (TOF)-Tube is a new version of a rigid tubular device that was designed to protect the thumb from external disturbances during surgery, even when the hand is not accessible by the anaesthesiologist. OBJECTIVE: To compare the precision and performance of acceleromyography performed with the aid of the SL TOF-Tube (AMGTT) with standard isometric mechanomyography (MMG). DESIGN: Simultaneous arm-to-arm comparison of both methods in the same anaesthetised patient. SETTING: A monocentric study, performed from September 2007 to June 2008. PATIENTS: Nineteen ASA I to II patients scheduled to undergo lower limb orthopaedic surgery under general anaesthesia. INTERVENTION: Neuromuscular transmission monitoring during baseline, onset and spontaneous recovery of rocuronium-induced neuromuscular block. MAIN OUTCOME MEASURES: Initial baseline and repeatability coefficients were assessed during 10 consecutive measurements of the first twitch height (T1) and TOF T4/T1 ratio and compared using a z test. The spontaneous recoveries of defined blockade levels (onset, T1 25% of initial calibration and TOF ratio 0.9) were compared in terms of duration and intensity. Agreement between both techniques was assessed by the Bland-Altman method. RESULTS: The mean ±â€ŠSD control TOF ratios were 98 ±â€Š1% (MMG) and 103 ±â€Š2% (AMGTT). The repeatability coefficients were higher (P < 0.001) and the onset was longer (mean 0.44 min) (P < 0.001) when they were measured by AMGTT. The recoveries of T1 25% and TOF ratio 0.9 were not significantly different between the two methods, and the limits of agreement were in the usual range of contralateral comparisons (-19 and +24% for TOF ratio 0.9). CONCLUSION: Compared with mechanomyography, acceleromyography performed with the aid of an SL TOF-Tube offered acceptable precision and equivalent performance during neuromuscular block recovery.

Survey of muscle relaxant effects management with a kinemyographic-based data archiving system: a retrospective quantitative and contextual quality control approach.

In a retrospective quality control study of muscle relaxant management, we assessed unbiased files provided by an automatic archiving system using quantitative monitoring generated by a kinemyographic transducer and suggest improvements for a possible future design. 200 randomly selected files were double checked to collect the values of twitch height ratio (THr), train of four ratio (TOFr) and TOF count in four periods: references values acquisition (REF), maximal level of paralysis, paralysis maintenance, pre-tracheal extubation residual paralysis assessment (RPA). The parameter values were selected according to period-specific predefined rules. A quantitative quality control was based upon standardized cut-offs values. A contextual quality control was based upon the detection of "difficult-to-interpret" episodes. Results were expressed on a descriptive basis only. For the REF period, THrs and TOFrs were lacking in, respectively, 47 and 18 of the 200 recordings analysed. A starting TOFr above 0.90 existed in 119 files. Concomitant THrs and TOFrs >0.90 were evidenced 93 times. During RPA period, TOFr >0.90 was recorded on 82 occasions. The optimal combination of THr >0.80 and TOFr >0.90 was detected in 30 files only. Presence of "difficult to interpret" episodes started with 18 files for the REF period and increased to 42, 86 and 52 in the subsequent ones most of them probably related to the absence of initial calibration procedure. In the real life conditions, a near to optimal quality control is not always observable with the quantitative neuromuscular monitoring studied. To improve the NMT monitoring, the calibration of the sensor should be performed vigorously by the anaesthesia provider and the quality of this calibration must be displayed on the screen of the monitor.

Somatosensory evoked potentials as an objective assessment of the sensory median nerve blockade after infraclavicular block.

PURPOSE: Median nerve somatosensory evoked responses (MnSSER) alterations were compared to clinical tests (cold and pinprick) variations, in 20 ASA I adult patients following infraclavicular block obtained with 40 mL ropivacaine 0.5% to assess first, the difference of time course of the respective electrophysiological and clinical signs, and second, the objectivity and the reproducibility of MnSSER changes. CLINICAL FEATURES: Four MnSSER derivations (Erb's point; cutaneous projection of peripheral end of brachial plexus; posterior neck at C6 level, frontal and controlateral parietal scalp) were monitored and recorded for retrospective analysis. Continuous data acquisition were started before ropivacaine injection (baseline) and maintained for 30 min thereafter. Every three minutes after ropivacaine injection, cold and pinprick tests were performed in the hand median nerve cutaneous supply zone and were assessed using a sensory visual score (varying from 0-10). Data were compared using analysis of variance. Although MnSSER values were stable during baseline period, after ropivacaine administration, severe progressive amplitude depressions of selected MnSSER were detected in every patient. While clinical cold and pinprick tests became positive (score > 8) only 15.8 +/- 1.2 min and 20.1 +/- 1.8 min respectively after ropivacaine administration, the mean time to observe the earliest MnSSER 20% amplitude decrease at Erb's point derivation was reduced to 5.6 +/- 1.1 min (P < 0.01). CONCLUSION: Selected MnSSER amplitude reduction indicates objectively the onset of median nerve anesthesia following infraclavicular brachial plexus block before the appearance of clinical signs.

The effects of acute isovolemic hemodilution on oxygenation during one-lung ventilation.

Data on the effects of isovolemic hemodilution (IH) on oxygenation during one-lung ventilation (OLV) are lacking. We studied 47 patients with hemoglobin >14 g/dL who were scheduled for lung surgery (17 with normal lung function [group NL], 17 with chronic obstructive pulmonary disease [COPD] [group COPD], and 13 with COPD as control for time/anesthesia effects [group CTRL]). Anesthesia was standardized. The tracheas were intubated with a double-lumen tube. Ventilatory settings and fraction of inspired oxygen remained constant. The study was performed with patients in the supine position before surgery. OLV was initiated for 15 min. Two-lung ventilation was reinstituted, and IH was performed (500 mL); an identical volume of hydroxyethyl starch was administered. Subsequently, OLV was again performed for 15 min. In group CTRL, the same sequences of OLV were performed without IH. At the end of each period of OLV, pulmonary mechanics and blood gases were recorded. Data were analyzed by analysis of variance (mean +/- sd). In group NL and group CTRL, the arterial oxygen partial pressure remained constant, whereas it decreased in group COPD from 119 +/- 21 mm Hg before IH to 86 +/- 16 mm Hg after IH (P <0.01). Mild IH impairs gas exchange during OLV in COPD patients, but not in patients with normal lung function.

Does aprotinin influence the inflammatory response to cardiopulmonary bypass in patients?

OBJECTIVES: Aprotinin has been shown to have anti-inflammatory properties, but its effects on the inflammatory reaction to cardiopulmonary bypass remain controversial. This prospective, randomized, double-blind study evaluated the influence of aprotinin on various blood markers of inflammation during and after cardiopulmonary bypass. METHODS: Sixty male patients underwent coronary artery bypass grafting. The patients were randomized into 3 groups: a placebo group, a second group receiving 2,000,000 KIU of aprotinin followed by an infusion of 500,000 KIU/h and 2,000,000 KIU in the pump prime, and a third group receiving half this dosage. Measurements of tumor necrosis factor, interleukin 6, interleukin 8, interleukin 10, endotoxin, histamine, complement factors, prekallikrein, and prostaglandin D(2) were obtained at baseline, 30 minutes after study drug loading, 10 minutes after the beginning of cardiopulmonary bypass, before the end of bypass, 4 hours after bypass, and on the first and second postoperative days. RESULTS: Aprotinin had no significant effect on any of these parameters. As expected, aprotinin reduced early blood loss in both treated groups. CONCLUSIONS: These results indicate that aprotinin at doses currently used to reduce blood loss has no significant influence on the systemic inflammatory response during moderate hypothermic cardiopulmonary bypass in human subjects, as assessed by the mediators measured in this study.

Sciatic nerve blockade in the supine position: a novel approach.

PURPOSE: Sciatic nerve block is useful for surgery below the knee both intra- and postoperatively. Several techniques to insert a catheter at the knee level or higher have been described but need mobilization (lateral decubitus) of the patient. We describe novel landmarks, using a high lateral approach, to block the sciatic nerve without moving the patient. CLINICAL FEATURES: One hundred seven ASA I, II and III ASA patients scheduled for major foot or ankle surgery were studied prospectively. With patients awake and lying in the supine position, the catheter was introduced along novel landmarks in the peri-nervous adipose space using specifically designed material and nerve stimulation (< 0.5 mA). After a negative test dose (1% lidocaine with 1/200.000 epinephrine), 10 mL of 0.5% bupivacaine and 10 mL of 2% lidocaine were injected. Thirty minutes after performance of the block, the cutaneous and dermatomal sensory blockade were assessed using cold and pinprick tests while motor block was assessed using a modified Bromage scale. Complications and incidents were recorded. The tibial and superficial peroneal nerve were always blocked, while the deep peroneal and postero-femoral cutaneous nerves were blocked in only 97% and 83% of the patients, respectively. Anesthesia, was always present in the dermatome L5 and in the S1 dermatome in 98% of the patients. No major incidents or complications were noted. Three catheters could not be inserted and the anesthestic solution was injected through the needle. CONCLUSION: The lateral technique for sciatic nerve anesthesia and catheter insertion allows patients to remain in the supine position for performance of the block and catheter insertion, and results in a high rate of homogeneous anesthesia and a low incidence of side effects.

Lumbar plexus posterior approach: a catheter placement description using electrical nerve stimulation.

IMPLICATIONS: The authors describe a modified technique of posterior approach to the lumbar plexus in the psoas compartment which allows nerve stimulation for the location of the plexus and catheter placement for extended-duration surgery and postoperative patient-controlled regional analgesia. A frequent incidence of total lumbar plexus block was observed.