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Biomedical subjects

C Meistelman

Publications and source records attributed to C Meistelman.

At least 55 records · Page 3Linked to original sources
PubMed1993

The orbicularis oculi and the adductor pollicis muscles as monitors of atracurium block of laryngeal muscles.

The aim of this study was to determine whether atracurium-induced neuromuscular block at the laryngeal adductor muscles could be predicted by visual inspection of either adductor pollicis or orbicularis oculi responses. Twenty-one ASA Class I or II patients were anesthetized with propofol (2-2.5 mg/kg) and fentanyl (2-5 micrograms/kg). Tracheal intubation was performed without neuromuscular blocking drugs. Patients were assigned randomly to receive atracurium 0.3 or 0.5 mg/kg intravenously. Train-of-four stimulation was applied to the ulnar, facial, and recurrent laryngeal nerves. Laryngeal response was measured as the pressure change in the tracheal tube cuff positioned between the vocal cords. The response at the adductor pollicis and orbicularis oculi was evaluated visually by two observers who detected if and when block was complete. Twelve patients, including all those receiving 0.5 mg/kg, had complete orbicularis oculi block. The same patients, except one, also had 100% laryngeal block. Adductor pollicis response was abolished in the same 12 patients plus an additional 4 patients. In patients receiving atracurium 0.5 mg/kg, laryngeal and orbicularis oculi responses were abolished faster (mean +/- SD: 132 +/- 80 and 146 +/- 58 s, respectively) than the adductor pollicis muscle (243 +/- 55 s; P < 0.05). There was a significant correlation (r = 0.94; P < 0.001) between neuromuscular block onset time at the laryngeal adductor and orbicularis oculi muscles but not between laryngeal and thumb muscles. The authors conclude that, after injection of atracurium, laryngeal adductor and orbicularis oculi blocks have similar intensities and time courses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Rocuronium (ORG 9426) neuromuscular blockade at the adductor muscles of the larynx and adductor pollicis in humans.

The effects of rocuronium, 0.25 or 0.5 mg.kg-1, were measured simultaneously on the adductor muscles of the larynx and adductor pollicis in 14 adult patients. Anaesthesia was induced and maintained with propofol and fentanyl. Tracheal intubation was performed without muscle relaxants. The recurrent laryngeal and ulnar nerves were both stimulated supramaximally, at the notch of the thyroid cartilage and at the wrist respectively, using train-of-four stimulation. The laryngeal response was evaluated by measuring the pressure change in the cuff of a tracheal tube positioned between the vocal cords. Onset time, intensity of blockade and duration of action were less at the larynx than at the adductor pollicis. After rocuronium, 0.25 mg.kg-1, the onset time (interval between injection and maximal T1 blockade) was 1.6 +/- 0.1 min and 3.0 +/- 0.3 min (mean +/- SEM) at the laryngeal muscles and adductor pollicis, respectively (P less than 0.01 between muscles). Maximum blockade was 37 +/- 8% and 69 +/- 8%, respectively (P less than 0.05), and time to 90% T1 recovery was 7 +/- 1 min and 20 +/- 4 min, respectively (P less than 0.05). With 0.5 mg.kg-1, the onset time was also more rapid at the vocal cords (1.4 +/- 0.1 min) than at the adductor pollicis (2.4 +/- 0.2 min, P less than 0.001). Maximum blockade was 77 +/- 5% and 98 +/- 1%, respectively (P less than 0.01), and time to 90% T1 recovery was 22 +/- 3 min and 37 +/- 4 min, respectively (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

A kinetic-dynamic model to explain the relationship between high potency and slow onset time for neuromuscular blocking drugs.

To account for experimental data showing increased onset time with increased potency of neuromuscular blocking drugs, a pharmacokinetic-pharmacodynamic model is presented. It is characterized by a finite concentration of receptors (R) in the effect compartment. Transfer from central to effect compartment is linearly related to concentration gradient. A sigmoid Emax model is used to describe the relationship between receptor occupancy and effect. Plasma concentrations found in the literature are used. Differential equations are solved numerically for equipotent doses of drugs of different potencies. Because the density of receptors constitutes a significant drain of drug molecules for potent drugs, the model predicts an inverse relationship between speed of onset and potency. The concentration of receptors in the effect compartment R which best fits experimental data obtained in humans is 0.28 mumol/L. With this value of R, onset times are prolonged when the ED95 (dose for 95% blockade) is less than 0.1 mumol/kg. It is concluded that, in the development of a short-acting nondepolarizing neuromuscular blocking drug, agents having an ED95 of 0.1 mumol/kg or greater appear more promising.

Dose-Response Relationship, Drug↗
PubMed1991

Vecuronium is more potent in Montreal than in Paris.

This study was undertaken to compare the potency of vecuronium in patients anaesthetized in Montreal or Paris. Anaesthesia was induced with thiopentone and maintained with N2O, and intermittent boluses of thiopentone and fentanyl in 18 patients in Paris and 19 in Montreal. Neuromuscular blockade was measured using train-of-four stimulation of the ulnar nerve. The force of contraction of the adductor pollicis muscle was measured. Single doses of vecuronium, 20, 30, or 40 micrograms.kg-1 were given by random allocation. Dose response curves were constructed by obtaining the linear regression of the logit of the first response (T1) neuromuscular blockade versus log dose. The patients in Paris required 27% more vecuronium (95% confidence limits 5-53%; P = 0.01) for the same intensity of blockade. In Montreal, the ED50 and ED90 (+/- SEE for the mean) values were 26.0 +/- 1.4 and 44.2 +/- 2.5 micrograms.kg-1 compared with 33.0 +/- 3.3 and 71.9 +/- 7.2 micrograms.kg-1 in Paris respectively. The patients were comparable with respect to age, sex, height and weight. These results confirm, for vecuronium, the transatlantic difference in potency of neuromuscular blocking drugs which was previously observed with d-tubocurarine between London and New York.

Adult↗
PubMed1991

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.

Anesthesia↗
PubMed1991

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)

Female↗
PubMed1991

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.

Adolescent↗
PubMed1990

Carbon dioxide monitoring during high frequency jet ventilation for direct laryngoscopy.

To improve ventilation monitoring during direct laryngoscopy, we have developed a high frequency jet ventilator which allows the aspiration of tracheal gas for carbon dioxide analysis (PtCO2) through the injector after stopping the ventilator. In 41 patients undergoing direct laryngoscopy, PaCO2 and PtCO2 were measured simultaneously during high frequency jet ventilation under general anaesthesia. PtCO2 and PaCO2 correlated significantly (r = 0.88), but PtCO2 underestimated PaCO2 by 0.84 (SD 0.72) kPa. The arterial to tracheal PCO2 difference was influenced by airway obstruction.

Anesthesia, General↗
PubMed1990

Effects of age on plasma protein binding of sufentanil.

The plasma protein binding of sufentanil has been studied in newborns, infants (0.5 +/- 0.3 yr), children (6.8 +/- 3.0 yr), and adults (39.5 +/- 9.0 yr). Binding of sufentanil was determined in vitro by equilibrium dialysis, and radioactive tritiated sufentanil was used for the determination of drug concentrations in plasma and buffer. The free fraction of sufentanil was significantly higher in the newborn (19.5 +/- 2.7%; P less than 0.01) than in the other age groups. The free fraction was also significantly higher in infants (11.5 +/- 3.2%; P less than 0.01) than in children (8.1 +/- 1.4%) or in adults (7.8 +/- 1.5%) but did not differ significantly between children and adults. The free fraction of sufentanil was strongly correlated with the alpha 1-acid glycoprotein plasma concentration (r = -0.73; P less than 0.001) whereas it was weakly correlated with albumin plasma concentration (r = -0.35; P less than 0.05). These data suggest that the lower concentration of alpha 1-acid glycoprotein in newborns and infants probably accounts for the decrease in protein binding of sufentanil in these age groups when compared with that in older children or adults. The increased free fraction in the neonate might contribute to the enhanced effects of lipophilic opioids in the neonate.

Adult↗
PubMed1990

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)

Diaphragm↗
PubMed1989

Recovery from vecuronium neuromuscular blockade following neostigmine administration in infants, children, and adults during halothane anesthesia.

To determine whether neostigmine had different effects in pediatric patients during vecuronium neuromuscular blockade, the rate of recovery following neostigmine administration was compared in infants (n = 8), children (n = 10), and adults (n = 10) during nitrous oxide-halothane anesthesia. After induction of anesthesia, patients received 100 micrograms/kg of vecuronium. The EMG response of the adductor pollicis was monitored after train-of-four (TOF) stimulation of the ulnar nerve every 20 s. When the first twitch of TOF spontaneously recovered to 10% of control value, neostigmine was injected (40 micrograms/kg in adults, 30 micrograms/kg in infants and children). During the first few minutes following neostigmine administration, no differences were observed between the three groups. After the 8 min, recovery was more rapid in children than in infants and adults up to and including the 15th min. Ten minutes after neostigmine administration, the first twitch (mean +/- SD) reached 97 +/- 3%, 99 +/- 2%, and 97 +/- 5% of control value in infants, children, and adults, respectively; TOF ratio was greater in children (0.96 +/- 0.03) than in either adults (0.82 +/- 0.17) or in infants (0.83 +/- 0.14) (P less than 0.05). During the first minutes after neostigmine administration, the lack of difference in TOF recovery in the three groups suggests that neostigmine is the main factor of recovery. In contrast, the more complete recovery after the eighth minute in children could be due to the faster rate of spontaneous recovery from vecuronium induced neuromuscular blockade in children.

Adult↗