Benoit Plaud

Residual Paralysis in the PACU after a Single Intubating Dose of Nondepolarizing Muscle Relaxant with an Intermediate Duration of Action

Background Residual neuromuscular blockade remains a problem even after short surgical procedures. The train-of-four (TOF) ratio at the adductor pollicis required to avoid residual paralysis is now considered to be at least 0.9. The incidence of residual paralysis using this new threshold is not known, especially after a single intubating dose of intermediate-duration nondepolarizing relaxant. Therefore, the aim of the study was to determine the incidence of residual paralysis in the postanesthesia care unit after a single intubating dose of twice the ED95 of a nondepolarizing muscle relaxant with an intermediate duration of action. Methods Five hundred twenty-six patients were enrolled. They received a single dose of vecuronium, rocuronium, or atracurium to facilitate tracheal intubation and received no more relaxant thereafter. Neuromuscular blockade was not reversed at the end of the procedure. On arrival in the postanesthesia care unit, the TOF ratio was measured at the adductor pollicis, using acceleromyography. Head lift, tongue depressor test, and manual assessment of TOF and DBS fade were also performed. The time delay between the injection of muscle relaxant and quantitative measurement of neuromuscular blockade was calculated from computerized anesthetic records. Results The TOF ratios less than 0.7 and 0.9 were observed in 16% and 45% of the patients, respectively. Two hundred thirty-nine patients were tested 2 h or more after the administration of the muscle relaxant. Ten percent of these patients had a TOF ratio less than 0.7, and 37% had a TOF ratio less than 0.9. Clinical tests (head lift and tongue depressor) and manual assessment of fade showed a poor sensitivity (11–14%) to detect residual blockade (TOF < 0.9). Conclusion After a single dose of intermediate-duration muscle relaxant and no reversal, residual paralysis is common, even more than 2 h after the administration of muscle relaxant. Quantitative measurement of neuromuscular transmission is the only recommended method to diagnose residual block.

Vecuronium neuromuscular blockade at the diaphragm, the orbicularis oculi, and adductor pollicis muscles

To determine the relationship among diaphragm, orbicularis oculi, and adductor pollicis blockade, train-of-four stimulation was applied to the phrenic, facial, and ulnar nerves in 16 adult patients anesthetized with alfentanil-propofol-oxygen. Vecuronium 0.04 or 0.07 mg/kg was given. The response of the adductor pollicis was measured with a force transducer, and that of the other muscles by electromyography (EMG). No statistically significant differences were detected with either dose in the intensity of maximum blockade measured at the three muscles. With 0.04 mg/kg, the first response (T1) in the train-of-four was decreased (mean +/- SEM) 78 +/- 8, 62 +/- 11, and 84 +/- 3% for the diaphragm, orbicularis oculi, and adductor pollicis, respectively. Corresponding values after 0.07 mg/kg were 95 +/- 3, 82 +/- 11, and 95 +/- 2%, respectively. However, onset time was longer at the adductor pollicis than at the diaphragm, and the orbicularis oculi onset time approached that of the diaphragm. With 0.04 mg/kg, time to maximum diaphragmatic blockade was 2.9 +/- 0.3 min, compared with 3.7 +/- 0.6 min at the orbicularis oculi (no significant difference [NS]) and 6.6 +/- 0.4 min at the adductor pollicis (P less than 0.001). With vecuronium 0.07 mg/kg the values were 2.2 +/- 0.3, 3.4 +/- 0.5 (P = 0.024), and 6.3 +/- 0.6 (P less than 0.001), respectively. Time to 75% T1 recovery was similar at the diaphragm and the orbicularis oculi, but significantly longer at the adductor pollicis.(ABSTRACT TRUNCATED AT 250 WORDS)

Vecuronium neuromuscular blockade at the adductor muscles of the larynx and adductor pollicis

The differences between neuromuscular blockade of the adductor muscles of the vocal cords and the adductor pollicis were examined in 20 adult women anesthetized with fentanyl and propofol. Vecuronium 0.04 or 0.07 mg/kg was given as a single bolus by random allocation. The force of contraction of the adductor pollicis was recorded. Laryngeal response was measured as pressure changes in the cuff of the tracheal tube positioned between the vocal cords. Train-of-four stimulation was applied to the recurrent laryngeal nerve at the notch of the thyroid cartilage and to the ulnar nerve at the wrist. Neuromuscular blockade had a faster onset, was less intense, and recovered more rapidly at the vocal cords. With 0.04 mg/kg, maximum blockade of first twitch (T1) was 55 +/- 8 (mean +/- standard error of the mean [SEM]) and 88 +/- 4% at the vocal cords and the adductor pollicis, respectively (P = 0.006). Onset time was 3.3 +/- 0.1 and 5.7 +/- 0.2 min, respectively (P = 0.000001), and time to 90% T1 recovery was 11.3 +/- 1.6 and 26.1 +/- 1.8 min, respectively (P = 0.001). With 0.07 mg/kg, onset time was unchanged; maximum blockade was more intense, being 88 +/- 4 and 98 +/- 1%, respectively (P = 0.04 between muscles); and time to 90% T1 recovery was 23.3 +/- 1.8 min at the vocal cords versus 40.3 +/- 2.9 min at the adductor pollicis (P = 0.001). Approximately 1.73 times as much vecuronium was required at the larynx compared with the dose required at the adductor pollicis for the same intensity of blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Residual Paralysis after Emergence from Anesthesia

SEVERAL studies have documented that neuromuscular block often persists in the postanesthesia care unit (PACU), even with the administration of acetylcholinesterase inhibitors. The frequency of this phenomenon, which has been called “residual curarization,” “residual neuromuscular block,” “postoperative residual curarization,” or “residual paralysis,” ranges between 4 and 50% depending on the diagnostic criteria, the type of nondepolarizing neuromuscular blocking drug (NMBD), the administration of a reversal agent, and, to a lesser extent, the use of neuromuscular monitoring. The problem is obviously clinically relevant, because residual paralysis after emergence from anesthesia (henceforth referred to as residual paralysis) is associated with muscle weakness, oxygen desaturation, pulmonary collapse, and acute respiratory failure that could lead to severe permanent brain damage or death. Despite extensive documentation of such residual paralysis in the literature, awareness of its clinical consequences remains surprisingly limited, and the use of NMBDs, neuromuscular monitoring, and reversal agents are dictated more by tradition and local practices than by evidence-based medicine. Residual paralysis is associated with postoperative complications such as hypoxia, weakness, and respiratory failure. However, these complications may have many other causes so that the role of neuromuscular block is often unrecognized. Thus, it is important to manage neuromuscular block rationally and have a sound strategy to prevent, diagnose, and treat residual paralysis. This can be accomplished by adhering to simple and consistent guidelines not only before tracheal extubation but also throughout the surgical procedure. The data in the current literature on residual paralysis were obtained with acetylcholinesterase inhibitors as the only agents available to accelerate neuromuscular recovery. Reassessment of practice in this regard is relevant now that sugammadex, a selective binding agent, has become available in certain parts of the world.

Reversal of Rocuronium-induced Neuromuscular Blockade with Sugammadex in Pediatric and Adult Surgical Patients

Background:Sugammadex reverses neuromuscular blockade by chemical encapsulation of rocuronium. This phase IIIA study explored efficacy and safety of sugammadex in infants (28 days to 23 months), children (2–11 yr), adolescents (12–17 yr), and adults (18–65 yr). Methods:Anesthetized patients (American Society of Anesthesiologists class 1–2) received 0.6 mg/kg rocuronium and were randomized to receive sugammadex (0.5, 1.0, 2.0, or 4.0 mg/kg) or placebo at reappearance of T2. Neuromuscular monitoring was performed using acceleromyography. Primary endpoint was time from sugammadex/placebo administration to recovery of the train-of-four ratio to 0.9. Adverse events and electrocardiograms were recorded, and blood samples were collected for safety and determination of sugammadex and rocuronium plasma concentrations. Results:A dose-response relation was demonstrated in children (n = 22), adolescents (n = 28), and adults (n = 26), but not infants because of the small sample size (n = 8). After placebo, median recovery time of train-of-four to 0.9 was 21.0, 19.0, 23.4, and 28.5 min in infants, children, adolescents, and adults, respectively. After 2.0 mg/kg sugammadex train-of-four 0.9 was attained in 0.6, 1.2, 1.1, and 1.2 min, respectively. The sugammadex plasma concentrations were similar for the children, adolescent, and adult age groups across the dose range. Sugammadex was well tolerated: No reoccurrence of blockade, inadequate reversal, significant QT prolongation, or other abnormalities were observed. Conclusions:Sugammadex is a new reversal agent that rapidly, effectively, safely, and with similar recovery times reverses rocuronium-induced neuromuscular blockade in children, adolescents, adults, and the small number of infants studied.

The corrugator supercilii, not the orbicularis oculi, reflects rocuronium neuromuscular blockade at the laryngeal adductor muscles.

BackgroundSome studies suggest that the orbicularis oculi is resistant to neuromuscular blocking drugs and behaves like laryngeal muscles. Others report little or no difference between the orbicularis oculi and the adductor pollicis. These discrepancies could be related to the exact site of recording. The purpose of this study was to compare two monitoring sites around the eye with the adductor pollicis and the laryngeal adductor muscles. MethodsAfter institutional approval and informed consent, the evoked response to train-of-four stimulation was measured in 12 patients by acceleromyography at the thumb (adductor pollicis), the eyelid (orbicularis oculi), and the superciliary arch (corrugator supercilii) after 0.5 mg/kg rocuronium during propofol–fentanyl–nitrous oxide anesthesia. In 12 other patients, laryngeal adductor neuromuscular blockade was assessed via the cuff of the tracheal tube and compared with the adductor pollicis and the corrugator supercilii after 0.6 mg/kg rocuronium. ResultsAfter 0.5 mg/kg, maximum blockade (%T1, mean ± SD) was less at the corrugator supercilii (80 ± 20%) than at the adductor pollicis (100 ± 1%) and the orbicularis oculi (93 ± 8%) (P < 0.01). Clinical duration (25%T1) was shorter at the corrugator supercilii (12 ± 7 min) than at the adductor pollicis (25 ± 4 min) and orbicularis oculi (24 ± 10 min) (P < 0.01). After 0.6 mg/kg, maximum blockade was similar at the corrugator supercilii (88 ± 8%) and the laryngeal adductor muscles (89 ± 11%). Clinical duration at the corrugator supercilii and the laryngeal adductors was 17 ± 7 and 17 ± 10 min, respectively. ConclusionsMuscles around the eye vary in their response to rocuronium. The response of the superciliary arch (corrugator supercilii) reflects blockade of laryngeal adductor muscles. However, the eyelid (orbicularis oculi) and thumb (adductor pollicis) have similar sensitivities.

Complications and fiberoptic assessment of size 1 laryngeal mask airway.

In pediatric practice, complications due to the laryngeal mask airway (LMA) have been studied with size 2 LMA, but not with size 1 LMA. We, therefore, compared prospectively the complications induced by LMA size 1 and 2 in 141 children aged 21 days to 11 yr. Intraoperative and lowest SpO2 values after removal of LMA were recorded. The following complications were recorded: cough, laryngospasm, bronchospasm, apnea, and airway obstruction. In 14 patients in the size 1 LMA group and 26 patients in the size 2 LMA group, pharyngolaryngeal structures were checked with fiberoptic examination. The number of attempts, complications, intraoperative SpO2, and lowest SpO2 values were similar when using size 1 and size 2 LMA. Fiberoptic examination of size 1 LMA showed a high incidence of impinging of the epiglottis in the LMA bars without airway obstruction. In conclusion, there was no difference in the complication rate between the two pediatric sizes of LMA when used in pediatric patients.

Perioperative Use of Dobutamine in Cardiac Surgery and Adverse Cardiac Outcome : Propensity-adjusted Analyses

Background:Catecholamines, mainly dobutamine, are often administered without institutional guidelines or prespecified algorithms in cardiac surgery. The current study assessed the consequences on clinical outcome of catecholamines simply based on the clinical judgment of the anesthesiologists after cardiopulmonary bypass in adult cardiac surgery. Methods:Consecutive patients were enrolled in a nonrandomized cohort study. Factors associated with perioperative use of catecholamines and with outcomes were recorded prospectively to conduct bias adjustment, including propensity scores. Major cardiac morbidity (i.e., ventricular arrhythmia, use of an intraaortic balloon pump and postoperative myocardial infarction) and all-cause intrahospital mortality were the primary and secondary endpoints, respectively. Results are expressed as odds ratio (OR) [95% confidence interval]. Results:During the study, 84 of 657 patients (13%) received catecholamines, most often dobutamine (76 of 84, 90%). A higher incidence of both major cardiac morbidity (30 vs. 9%; P < 0.001; OR, 4.2 [2.5–7.3]) and all-cause intrahospital mortality (8 vs. 1%; P < 0.001; OR, 12.9 [3.7–45.2]) was observed in the catecholamine group compared with the control group. After adjusting for channeling bias and confounding factors, catecholamine administration remained significantly associated with major cardiac morbidity after propensity score stratification (OR, 2.1 [1.0–4.4]; P < 0.05), propensity score covariance analysis (OR, 2.3 [1.0–5.0]; P < 0.05), marginal structural models (OR, 1.8 [1.3–2.5]; P < 0.001), and propensity score matching (OR, 3.0 [1.2–7.3]; P < 0.02), but not with all-cause intrahospital mortality. Conclusions:These results suggest that dobutamine should only be administered when the benefit is judged to outweigh the risks.

Neuromuscular effects of succinylcholine on the vocal cords and adductor pollicis muscles.

To quantify the effects of succinylcholine at the laryngeal adductor muscles and the adductor pollicis, 17 adult patients were studied during propofol-fentanyl anesthesia. Train-of-four stimulation was applied to the ulnar nerve at the wrist and the recurrent laryngeal nerve at the notch of the thyroid cartilage. Laryngeal response was measured as pressure changes in the cuff of the tracheal tube positioned between the vocal cords. The force of contraction of the laryngeal adductor muscles and of the adductor pollicis were compared after administration of 0.25 or 0.5 mg/kg of succinylcholine. With 0.25 mg/kg, maximum blockade of first twitch (T1) was 66% ± 10% (mean ± SEM) and 45% ± 13% at the vocal cords and the adductor pollicis, respectively (P < 0.01). After 0.5 mg/kg, maximum blockade at the vocal cords (93% ± 2%) and the adductor pollicis (84% ± 6%) did not differ significantly. For both doses, time to maximal blockade was shorter for the vocal cords (0.9 ± 0.1 min) than for the adductor pollicis (1.7 ± 0.2 min; P < 0.01). Time to 90% recovery of T1 after a bolus of 0.5 mg/kg was similar at the vocal cords (4.3 ± 0.5 min) and the adductor pollicis (5.2 ± 0.8 min) (NS). The ED50 was less at the laryngeal adductors (0.170 mg/kg) than at the adductor pollicis (0.278 mg/kg). It is concluded that, in adults, succinylcholine-induced blockade is more rapid and more intense at the laryngeal muscles than at the adductor pollicis.

A Method to Measure Elicited Contraction of Laryngeal Adductor Muscles during Anesthesia

The recurrent laryngeal nerve was stimulated with surface electrodes to produce vocal cord adduction, and the response was measured as pressure changes in the inflatable cuff of a tracheal tube positioned between the vocal cords. To test the linearity of the system, a model of the larynx consisting of a syringe barrel was constructed, and weights were applied to two bands of tissue simulating the vocal cords. Tests on Mallinckrodt size-7.5 tubes showed that the pressure increase produced by a given force was independent of baseline pressure in the range 10-30 mmHg. In addition, the pressure inside the inflatable cuff was linear with increasing weight (or force) for a baseline pressure of 10 mmHg. Thirty ASA physical status 1 or 2 adults were anesthetized with propofol and fentanyl. Tracheal intubation was performed in the absence of muscle relaxants, and the inflatable cuff of the tracheal tube was positioned between the vocal cords. Pressure inside the cuff was measured with an air-filled transducer. Stimulation was produced at different sites along the course of the recurrent laryngeal nerve. A surface electrode placed over the notch of the thyroid cartilage produced consistent adduction of the cords, measured as an increase of 8.9 +/- 5.1 mmHg (mean +/- standard deviation [SD]) in the cuff pressure. Neuromuscular blocking drugs produced train-of-four fade, and large doses abolished the response completely, ruling out direct muscle stimulation. It is concluded that this assembly can provide useful information on intrinsic laryngeal muscle function.