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.

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.

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.