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).     

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 less than 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 less than 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.     

The interpretation of train-of-four monitoring in intensive care: what about the muscle site and the current intensity?

OBJECTIVES: To investigate the effect of current intensity and choice of the stimulated muscle group on train-of-four (TOF) interpretation in the intensive care unit (ICU). DESIGN AND SETTING: Intervention study in a surgical intensive care unit. PATIENTS: 13 ventilated patients requiring prolonged muscle relaxation. MEASUREMENTS AND RESULTS: Prior to blockade TOF responses of left and right orbicularis oculi, adductor pollicis, and plantar flexors were recorded by setting the current intensity at 20, 40, 60, and 80 mA. The minimal current intensity (MCI) providing a supramaximal response was then identified for each muscle. Cisatracurium was then infused aiming to continuously observe a TOF at 2/4 on the left orbicularis oculi at 40 mA. The responses to TOF on all the muscle sites were further recorded at 40, 60, and 80 mA when the endpoint was reached for the first time, and after a 48-h infusion. After cessation of infusion the delay to observe 4/4 responses at TOF was recorded at each site at 40 mA or at MCI if MCI was above 40 mA. MCI did not differ between muscle groups. When the fixed endpoint was reached for the first time on left orbicularis oculi, the TOF response at 40 mA on right orbicularis oculi differed significantly. In contrast, no difference was observed between left and right sides at 40 mA at the other sites, nor at any sites at 60 and 80 mA. The TOF response on orbicularis oculi (left and right sides together) was different at 40 mA, compared to 60 and 80 mA. TOF responses at orbicularis oculi at 60 or 80 mA significantly differed from responses on adductor pollicis or plantar flexor, orbicularis oculi being less sensitive to cisatracurium than adductor pollicis or plantar flexor. After a 48-h infusion the same differences in sensitivities were observed between the muscle groups. At any current intensity the recovery was slower at adductor pollicis than at orbicularis oculi or plantar flexor. CONCLUSIONS: For a good TOF interpretation in the ICU the current intensity should be tested before onset of blockade. The orbicularis oculi is less sensitive to cisatracurium than adductor pollicis and plantar flexor both at onset and after a prolonged infusion. The recovery from relaxation is faster on orbicularis oculi and plantar flexor than on adductor pollicis.     

Nifedipine blocks ondansetron electrophysiological effects in rabbit purkinje fibers and decreases early after depolarization incidence

We hypothesized that a high concentration of nifedipine (1 μM), known to inhibit at least 75%of L-type Ca++ current, might counteract proarrhythmic dose-dependent effects of ondansetron (0.1 to 10 μM) in rabbit Purkinje fibers. Ondansetron is a 5-HT3 receptor antagonist commonly prescribed to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, and surgery but may increase the risk of developing prolongation of the QT interval of the electrocardiogram, which can lead to an abnormal and potentially fatal heart rhythm and recently raised FDA concerns and warnings. Neostigmine, a quaternary nitrogen agent that was also used clinically concomitant to antiemetics after anesthesia was further investigated dose-dependently (0.1 to 10 μM) and at fixed concentration (10 μM) with 0.1 to 10 μM ondansetron. The protocol included use-dependent (1 to 0.33 Hz) studies. APD durations, triangulation and early after depolarization (EAD) incidence were assessed. Ondansetron increased APD50, APD70 and APD90 (0.01 > p < 0.05) dose-dependently. APD90 averaged 102?1%of baseline to 302?49%dose-dependently (p < 0.001) and, at the highest dose, increased to 511?73%reverse use-dependently (p < 0.001). EAD were seen at top concentrations (33%) which were increased at lower rates (50%). Neostigmine induced reverse use-dependent APD changes (p < 0.05) but no EAD. In preparations treated by nifedipine and ondansetron, APD90 changes averaged 101?2%of baseline to 151?8%dose-dependently (p < 0.01) and to 193?13%reverse use-dependently (p < 0.05) and no EAD were seen. Thus nifedipine significantly shortened ondansetron-induced APD changes (p < 0.01), whereas neostigmine only slightly shortened ondansetron-induced APD changes (p < 0.05). There was a tendency for increased incidence of EAD (p < 0.06) in the ondansetron and neostigmine group vs. neostigmine alone. It is concluded that inhibition of L-type Ca++ current by high concentration nifedipine may counteract the ondansetron effects on APD changes.     

French survey of neuromuscular relaxant use in anaesthetic practice in adults

Guidelines about the use of neuromuscular blocking agents based on a national consensus conference have been published in 2000. A survey was carried out to assess adherence to these guidelines. An online questionnaire was designed from the different guidelines concerning the use of muscle relaxant for tracheal intubation and surgery, monitoring and antagonism of neuromuscular blockade. In addition, question about the knowledge of the pharmacodynamics of neuromuscular blocking agents were asked. Analysis concerned 1230 answers from senior anaesthetists. Tracheal intubation is facilitated by the use of a competitive agent or by succinylcholine by 58 and 8% of responders respectively. Atracurium and cisatracurium were most frequently used (49 and 44%, respectively). The duration of effect of an intubating dose of atracurium, vecuronium or rocuronium was estimated equal or below 60 min by more than half of responders, whereas that of cisatracurium was longer. Fifty-two or 74% of responders used neuromuscular monitoring, whether a single or repeated dose of muscle relaxant was administered. Antagonism of neuromuscular blockade was systematic, frequent, and episodic or excluded by 6, 26, 55 and 13% of responders, respectively. Monitoring and antagonism of neuromuscular blockade are underused despite the guidelines. Underestimation of the risk of postoperative residual curarization is linked to the underestimation of the duration of competitive neuromuscular blocking agents.     

Enquête sur l’évaluation et la prise en charge nutritionnelle des patients adultes cirrhotiques candidats à une transplantation hépatique

Objective

The European Society for Clinical Nutrition and Metabolism (EPSEN) guidelines on nutrition for liver disease patients has been recently updated. The aim of our study was to evaluate perioperative nutrition in cirrhotic patients waiting for liver transplantation (LT).

Study design

Prospective electronic survey. A standardized questionnaire was sent to the anaesthesiologist of the 18 French adult LT centers. The questionnaire had closed-ended questions to evaluate nutritional practices in cirrhotic patients waiting for a LT.

Results

The response rate was 100%. Nutritional status of the cirrhotic patients waiting for LT was assessed by anaesthesiologists (12 centres) and/or hepatologists (11 centres) and more rarely by nutrition physician, dietetics or liver surgeons. Body mass index (13 centres), weight loss (10 centres), albuminemia (10 centres) were the most frequent items used to assess the nutritional status. Before LT, preoperative oral intakes were administered in undernourished patients in only 55% of the cases. Postoperatively, nutritional support was administered between day 1 and 3 after LT.

Conclusion

Perioperative nutritional practices in cirrhotic patients waiting for LT are heterogeneous between centers, especially about nutrition assessment. Most of the centres did not follow the actual guidelines.     

Temporal Relation between Acoustic and Force Responses at the Adductor Pollicis during Nondepolarizing Neuromuscular Block

Background: Contracting muscle emits sounds. The purpose of this study was to compare the time course of muscular paralysis at the adductor pollicis muscle (AP) with use of acoustic myography and mechanomyography.

Methods: Thirteen elective surgery patients, American Society of Anesthesiologists physical status I, received rocuronium (0.6 mg/kg intravenously) as a bolus dose during general anesthesia. Force of AP was measured with use of a strain gauge, and sounds were recorded simultaneously with use of a small condenser microphone fixed on the palmar surface of the hand over the AP. Supramaximal stimulation was applied to the ulnar nerve at 0.1 Hz for 45-60 min. In seven patients, the response to train-of-four stimulation was also recorded during recovery.

Results: Force and sounds both were equally sensitive in measuring maximum block. The relation between sound and force was curvilinear, with good agreement near 0 and 100% and acoustic response exceeding mechanical response at intermediate levels of block. The acoustic signal had a slower onset and a faster recovery than the force response. The fade response of sound to train-of-four stimulation also recovered faster than that of force.