Francois Donati

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)

Onset of action of relaxants

ConclusionEven with the introduction of the priming technique, the time course of succinylcholine blockade is thus far unrivalled.54 Large doses may be administered to obtain profound relaxation without undue concern about recovery. However, many clinicians prefer the use of atracurium or vecuronium because of the side effects of succinylcholine. The induction technique must then allow for the longer onset time of the non-depolarizing blockers and the inadvisability of administering large doses for short duration procedures. Until a shorter acting non-depolarizer is available, anaesthetists will have to choose and base their decision on their own experience, the expected duration of the procedure, and most importantly, a good evaluation of the patient.

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.

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.

Tracheal resection and reconstruction

PurposeTo review the literature on tracheal and carinal resection and reconstruction, and to report the general approach to these patients, as well as the general guidelines for the safe administration of anesthesia. The airway management is extensively reviewed.SourceArticles obtained from a Medline search (1960 to October 1997; keywords: tracheal surgery, carinal surgery, airway management). Textbook literature including the bibliographies were also consulted.Principal FindingsBenign or malignant tracheal and carinal pathology causing obstruction can be managed in several ways but resection and reconstruction are the treatment of choice for most patients with tracheal stenosis or tumour. Surgery of the trachea is a special endeavour where the airway is shared by the surgeon and the anesthesiologist. The principal anesthetic consideration is ventilation and oxygenation in the face of an open airway. Ventilation can be managed in different ways, including manual oxygen jet ventilation, high frequency jet ventilation, distal tracheal intubation, spontaneous ventilation, and cardiopulmonary bypass.ConclusionThe management of anesthesia for tracheal surgery presents many challenges to the anesthesiologist. Knowledge of the various techniques for airway management is crucial. Meticulous planning and communication between the anesthesia and surgical teams are mandatory for the safe and successful outcome of surgery for patients undergoing this procedure.RésuméObjectifPasser en revue la documentation concernant la résection trachéale et carénale ainsi que leur reconstruction, et indiquer la conduite à tenir dans ce cas avec les patients, aussi bien que les directives générales pour l’administration sécuritaire de l’anesthésie. La gestion des voies respiratoires a fait l’objet d’un examen poussé.SourcesDes articles provenant d’une recherche dans Medline (1960 à octobre 1997; mots-clés: chirurgie de la trachée, chirurgie de la carène, gestion des voies respiratoires). Des monographies incluant les bibliographies ont aussi été consultées.Constatations principalesLa pathologie trachéale et carénale bénigne ou maligne causant de l’obstruction peut être traitée de différentes manières, mais la résection et la reconstruction sont le traitement de choix pour la plupart des patients atteints de sténose trachéale ou de tumeur. C’est une intervention spéciale où l’accès aux voies respiratoires est partagé par le chirurgien et l’anesthésiologiste. La considération anesthésique principale est la ventilation et l’oxygénation en présence de voies aériennes ouvertes. La ventilation jet manuelle avec de l’oxygène, la ventilation jet à haute fréquence, l’intubation trachéale distale, la ventilation spontanée et la circulation extracorporelle sont des variantes possibles de la ventilation dans ce cas.ConclusionLa gestion de l’anesthésie lors d’intervention à la trachée représente de nombreux défis pour l’anesthésiologiste. La connaissance des diverses techniques de gestion des voies respiratoires est primordiale. Une planification méticuleuse et une bonne communication entre les équipes d’anesthésie et de chirurgie sont obligatoires pour assurer la sécurité des patients et le succès de ce genre d’intervention.

Influence of extreme obesity on the body disposition and neuromuscular blocking effect of atracurium

The pharmacokinetics and pharmacodynamics of atracurium, a nondepolarizing neuromuscular blocking agent, were compared between morbidly obese patients and nonobese patients. Atracurium besylate (0.2 mg/kg) was administered intravenously as a bolus to patients who had received anesthesia. The force of contraction of the adductor pollicis was measured and plasma samples were collected for a 2‐hour period. The concentrations of atracurium and its major end product, laudanosine, were determined by use of a chromatographic method. The pharmacokinetic‐pharmacodynamic relationship was characterized by use of several models. No difference was observed between obese patients and nonobese patients in atracurium elimination half‐life (19.8 ± 0.7 versus 19.7 ± 0.7 minutes), volume of distribution at steady state (8.6 ± 0.7 versus 8.5 ± 0.7 L), and total clearance (444 ± 29 versus 404 ± 25 ml/min). However, if values were expressed on a total body weight basis, there was a difference between obese and nonobese patients in the volume of distribution at steady state (0.067 versus 0.141 L/kg) and total clearance (3.5 ± 0.2 versus 6.6 ± 0.5 ml/min/kg). Although atracurium concentrations were consistently higher in obese patients than in nonobese patients, there was no difference in the time of recovery from neuromuscular blockade between the two groups. Consequently, the median effective concentration was higher in obese than in nonobese patients (470 ± 46 versus 312 ± 33 ng/ml).

Monitoring the onset of neuromuscular block at the orbicularis oculi can predict good intubating conditions during atracurium-induced neuromuscular block.

This study was designed to assess whether monitoring the orbicularis oculi (OO) can predict good tracheal intubating conditions.Fifty patients, ASA grade I or II were studied. Anesthesia was induced with thiopental (5 mg/kg) and fentanyl (3 micro gram/kg). The ulnar and facial nerves were simultaneously stimulated using train-of-four (TOF) stimulations every 10 s. The responses of the adductor pollicis (AP) and the OO were estimated visually. Patients were randomly allocated to receive either atracurium 0.5 mg/kg (n = 30) or 0.3 mg/kg (n = 20). In each group, endotracheal intubation was performed randomly when the OO or the AP was completely blocked. If complete block was not obtained, intubation was performed 300 s after administration of atracurium. Intubating conditions were scored on a 1 to 4 scale. All intubations were performed by the same physician unaware of the dose and the muscular responses. After 0.5 mg/kg, both muscles were completely blocked in all patients. The average onset time (time from the injection of atracurium to the disappearance of all muscular responses after TOF) was shorter at the OO (2.35 +/- 0.12 min) than at the AP (3.59 +/- 0.15 min) (P < 0.001) (mean +/- SD). Endotracheal intubating conditions were comparable in both groups: good or excellent after 0.5 mg/kg. After 0.3 mg/kg, complete block was achieved only 2/20 at the OO and 12/20 at the AP. Intubating conditions were comparable in both groups: poor or inadequate, except in the two patients with complete OO block, for whom conditions were good. It is concluded that OO monitoring can predict good intubating conditions earlier than AP monitoring when using 0.5 mg/kg but not 0.3 mg/kg atracurium. (Anesth Analg 1995;80:360-3)

Antagonism of low degrees of atracurium-induced neuromuscular blockade: dose-effect relationship for neostigmine.

Background:Low degrees of residual paralysis (i.e., a train-of-four [TOF] ratio > 0.4) are relatively frequent, difficult to detect, and still potentially harmful. Unfortunately, the appropriate dose of anticholinesterase for this situation has not been determined. This may be of clinical interest because a high dose of neostigmine given at a shallow level of neuromuscular block may produce neuromuscular weakness. The purpose of this study was to investigate the dose–effect relationship of neostigmine to antagonize residual paralysis corresponding to a TOF ratio of 0.4 and 0.6. Methods:Recovery after 10, 20, 30 &mgr;g/kg neostigmine or placebo given at either 0.4 or 0.6 TOF ratio was assessed by acceleromyography in 120 patients undergoing intravenous anesthesia. Time to a 0.9 and 1.0 TOF ratio was measured, and the probability of successful reversal within 10 min after the respective neostigmine doses was calculated. In addition, the dose of neostigmine needed to achieve the recovery targets in 5 or 10 min was also determined. Results:When given at a TOF ratio of either 0.4 or 0.6, time to 0.9 and 1.0 TOF ratio was significantly shorter with any dose of neostigmine than without. The probability of successful reversal after 20 &mgr;g/kg neostigmine was 100% when a TOF ratio of 0.9 was the target; for a TOF ratio of 1.0, the probability was 93% and 67%, dependent on whether the dose of neostigmine was given at TOF ratio of 0.6 or 0.4, respectively. With a dose of 30 &mgr;g/kg, a TOF ratio of 1.0 is expected to be reached within approximately 5 min. Low doses of neostigmine are required to reach a TOF ratio of 0.9 or to accept an interval of 10 min. Conclusion:Reduced doses (10–30 &mgr;g/kg) of neostigmine are effective in antagonizing shallow atracurium block. For successful reversal within 10 min, as little as 20 &mgr;g/kg neostigmine may be sufficient. These dose recommendations are specific for atracurium and an intravenous anesthetic background.