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PubMed2006

Is there an ideal approach for rapid-sequence induction in hypertensive patients?

STUDY OBJECTIVE: To compare 4 different anesthesia induction protocols, in a simulated model of rapid-sequence induction, in controlled hypertensive patients. DESIGN: Prospective, randomized, double-blind, clinical investigation. SETTING: Large metropolitan university hospital. PATIENTS: 120 ASA II-III adult hypertensive patients. INTERVENTIONS: Patients were allocated to 4 groups at random. After preoxygenation for 3 minutes, induction and tracheal intubation was performed in a 30 degrees head-up position. Thiopental (5-7 mg/kg) was the induction agent. Study groups were as follows: group LS (n = 30), lidocaine (1.5 mg/kg) and succinylcholine (1 mg/kg); group LR (n = 30), lidocaine (1.5 mg/kg) and rocuronium (1 mg/kg); group RS (n = 30), remifentanil (1 microg/kg) and succinylcholine (1 mg/kg); group RR (n = 30), remifentanil (1 microg/kg) and rocuronium (1 mg/kg). Patients were intubated 60 seconds after administration of muscle relaxant. MEASUREMENTS: Hemodynamic data were obtained before induction (baseline), after induction, at intubation, and at 1, 3, 5, and 10 minutes after intubation. More than 20% change in blood pressure and heart rate was considered significant. MAIN RESULTS: Systolic and mean arterial blood pressures at intubation and 1 and 3 minutes after intubation were higher in group LS compared with groups RS and RR (P < 0.01). Mean arterial blood pressure decreased after induction in groups LS, LR, and RR, but increased at intubation and 1 minute after intubation in groups LS and LR (P < 0.01). Mean arterial blood pressure was similar at all measurement intervals in group RS. The median area under the systolic, mean, and diastolic blood pressure time curves was higher in groups LS and LR compared with groups RS and RR (P < 0.05 and P < 0.01). CONCLUSIONS: Remifentanil is a better adjunct for attenuation of the response to laryngoscopy and intubation compared with lidocaine, whereas remifentanil-succinylcholine combination appears to be more beneficial in terms of hemodynamic stability in hypertensive patients.

Analgesics, Opioid↗
PubMed2000

Neuromuscular paralysis as a pharmacodynamic probe to assess organ function during liver transplantation.

Potential for assessing liver function during liver transplantation surgery by monitoring muscle paralysis from nondepolarizing neuromuscular blockers that are hepatically cleared is critically assessed. Rocuronium is strongly favored as a promising pharmacodynamic probe for predicting allograft liver function because it is predominantly eliminated via the liver and its putative metabolites are not active. Prolongation of recovery from rocuronium paralysis is closely correlated with allograft liver function postoperatively. Vecuronium, pancuronium, and perhaps pipecuronium may also prove to be useful probes, but the two former blockers have active metabolites. Further prospective studies are necessary with more precise measurement of neuromuscular function to confirm the predictive value of this method. Alterations in neuromuscular blocker plasma concentrations that are correlated with changes in liver function and either the dose required or the intensity or duration of paralysis needs to be demonstrated for this technique to be clinically useful.

Androstanols↗
PubMed1998

Neuromuscular blocking effects and train-of-four fade with cisatracurium: comparison with other nondepolarising relaxants.

Neuromuscular blocking drugs exhibit different degrees of fade in response to train-of-four stimulation believed to represent their relative prejunctional effects. The present study was designed to compare the train-of-four fade after cisatracurium and compare this with other commonly used muscle relaxants. Train-of-four fade during onset and recovery of block were recorded after administration of cisatracurium 0.05 or 0.1 mg.kg-1, atracurium 0.5 mg.kg-1, vecuronium 0.08 mg.kg-1, mivacurium 0.15 mg.kg-1 or rocuronium 0.6 mg.kg-1 to patients anaesthetised with fentanyl, nitrous oxide and a propofol infusion. Neuromuscular monitoring was by stimulation of the ulnar nerve and recording the force of contraction of the adductor pollicis muscle. The onset and recovery of block were also measured. Train-of-four fade during onset of block was greater with the lower dose of cisatracurium compared with the higher dose of cisatracurium and all other relaxants. Train-of-four fade during recovery was similar. The median times (and ranges) for the onset of maximum block were 3.4 (2.1-5.6), 1.5 (1.2-2.3), 2.1 (1.2-2.6), 2.0 (1.5-2.7) and 1.0 (0.7-1.3) min for cisatracurium 0.1 mg.kg-1 and atracurium, mivacurium, vecuronium and rocuronium, respectively. The median times (and ranges) for the recovery of T1 to 25% of control and to a train-of-four ratio of 0.8 were 41 (21-50) and 65 (40-78); 43 (37-54) and 69 (58-79); 15 (11-20) and 25 (19-30); 31 (23-46) and 60 (45-117); and 33 (18-57) and 50 (28-76) min following cisatracurium, 0.1 mg.kg-1, atracurium, mivacurium, vecuronium and recuronium, respectively.

Adolescent↗
PubMed2006

The effect of bi-level positive airway pressure mechanical ventilation on gas exchange during general anaesthesia.

BACKGROUND: Atelectasis may occur and ventilation-perfusion mismatch may increase during general anaesthesia with neuromuscular paralysis and mechanical ventilation, though preservation of some intermittent muscle contraction might mitigate this process. There is still no ideal manoeuvre to minimize such mismatch or atelectasis. Bi-level positive airway pressure (BiPAP) ventilation adjusts to extra breaths and improves gas exchange during recovery of diaphragm function after neuromuscular paralysis. We hypothesize that BiPAP ventilation may limit the development of pulmonary shunt and may improve ventilation-perfusion mismatch when compared with standard IPPV, with or without PEEP when neuromuscular paralysis has been used during surgery. METHODS: Twenty ventilated patients either on BiPAP or IPPV with or without PEEP were studied randomly using the multiple inert gas elimination technique (MIGET) at 60 and 120 min after rocuronium at induction and after 60 min. Non-invasive cardiac output (NICO) monitoring and plasma concentrations of rocuronium were measured. We compared the data of MIGET, gas exchange, haemodynamic variables and pulmonary mechanics measurements between the different ventilatory modes. RESULTS: Intrapulmonary shunt (blood flow to V(A)/Q < 0.005) did not increase at 60 min of anaesthesia in any of the different ventilation modes compared with the shunt value before anaesthesia. Log standard deviation of perfusion increased in IPPV, with and without PEEP groups, compared with the baseline (P< 0.05) but did not increase in the BiPAP group. BiPAP ventilation generated a higher level of Pa(O2)than IPPV with or without PEEP (P<0.05). CONCLUSION: BiPAP ventilation was beneficial in decreasing ventilation-perfusion mismatch and improving oxygenation when compared with conventional IPPV (with or without PEEP).

Aged↗
PubMedDate not supplied

The detection and identification of quaternary nitrogen muscle relaxants in biological fluids and tissues by ion-trap LC-ESI-MS.

Quaternary nitrogen muscle relaxants pancuronium, rocuronium, vecuronium, gallamine, suxamethonium, mivacurium, and atracurium and its metabolites were extracted from whole blood and other biological fluids and tissues by using a solid-phase extraction procedure. The extracts were examined by using high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). The drugs were separated on a ODS column in a gradient of ammonium acetate buffer (pH 5.0) and acetonitrile. Full-scan mass spectra of the compounds showed molecular ions, and MS-MS spectra showed fragments typical of the particular compounds. LC-ESI-MS allowed an unequivocal differentiation of all muscle relaxants involved. The method was applied in a case of rocuronium and suxamethonium administration in a Caesarian section and in a case of intoxication by pancuronium injection. In both cases, the administered drugs could be detected and identified in the supplied samples.

Adult↗
PubMed1999

Molar potency is not predictive of the speed of onset of atracurium.

UNLABELLED: In an effort to determine the extent to which atracurium may represent an exception to the rule that molar potency predicts onset time, we studied the onset profile of atracurium after a dose selected to produce approximately 95% twitch depression. We compared these results with data obtained in a previous study after the administration of vecuronium, rocuronium, and cisatracurium. Eighteen ASA physical status I and II patients were studied. After the induction of anesthesia, tracheal intubation was accomplished without relaxants. The evoked electromyographic response to 0.10-Hz single stimuli was continuously recorded. After baseline stabilization, a single bolus of atracurium, averaging 0.21 mg/kg, was administered. If peak twitch depression did not fall within the range of 90%-98%, the patient was excluded. The time to 50% and 90% of peak effect was recorded. The time to 90% of maximal effect (192 +/- 23 s) was not different from that previously observed for vecuronium (201 +/- 20 s). The time to 50% of peak effect (110 +/- 15 s) was shorter (P < 0.05) after atracurium administration than after vecuronium (125 +/- 9 s). The onset times recorded for atracurium were slower than previously observed after rocuronium and more rapid than that which was seen after cisatracurium (P < 0.001). The observed onset profile of atracurium was considerably slower than anticipated, based on the drug's molar potency. The 95% effective dose (microM/kg) may not be a reliable predictor of a muscle relaxant's onset time, when the drug administered is a mixture isomers of varying potency. IMPLICATIONS: The speed of onset of atracurium is slower than predicted, based on its molar potency. Potency of a relaxant may not be a reliable predictor of its time to peak effect, when the drug administered is a mixture of isomers with widely different neuromuscular activities.

Adult↗
PubMed2000

Drug use inefficiency: a hidden source of wasted health care dollars.

UNLABELLED: A potential area for departmental savings is to minimize inefficient use of pharmaceuticals. We recorded drug waste data for multiple drugs for a fiscal year and surveyed providers' knowledge of departmental drug waste. Six large-cost or large-volume use drugs were chosen for study: thiopental, succinylcholine, rocuronium, atracurium, midazolam, and propofol. Amounts administered to patients were collected for one year by using a computerized anesthesia record keeper. Total drug distributed was the number of vials restocked by pharmacy for the year. An efficiency index, the percent administered to patients, was calculated for each drug. Drug administration to 25,481 patients was analyzed. Drug use efficiency indices were: atracurium 29%; thiopental, 31%; succinylcholine, 33%; propofol, 49%; midazolam, 53%; rocuronium, 61%. The total cost of unadministered study drugs was $165,667, 26% of the expenditure for all drugs. Most dollars wasted were for propofol, $80,863, and thiopental, $32,839. The reason most cited for drug waste was the disposal of full, or partially full, syringes. Drug wastage represents a significant portion of the entire anesthesia drug budget. Waste reduction strategies should allow a portion of the "avoidable" waste to be reduced. IMPLICATIONS: Unadministered drug amounts were measured for six study drugs over one fiscal year and found to be significant; the cost of unadministered drugs totaled $165,667. The reason most cited for waste was disposal of full, or partially full, syringes.

Androstanols↗
PubMed2001

Reexamined: the recommended endotracheal intubating dose for nondepolarizing neuromuscular blockers of rapid onset.

UNLABELLED: The results of any study of the relative importance of anesthetic depth versus intensity of neuromuscular block on conditions for endotracheal intubation can be manipulated by the investigator. Several independent factors, such as the depth of hypnosis induced, the interval between drug administration and laryngoscopy, the onset profile of the muscle relaxant, and the multiple of the 95% effective dose given, must be controlled. We attempted to design an induction sequence that provided good to excellent conditions for laryngoscopy and endotracheal intubation within 75-90 s of muscle relaxant administration with doses smaller than often suggested, while still administering only customary amounts of hypnotics and opioids. Alfentanil 12.5 microg/kg, propofol 2.0 mg/kg, and a test drug were administered rapidly. The test drugs were saline 0.05 mL/kg (n = 10), rapacuronium 1.0 or 1.2 mg/kg, or rocuronium 0.50 mg/kg (n = 30 each). Laryngoscopy was commenced 75 s after the test drug. Clinically acceptable conditions for intubation were achieved in all subjects after rocuronium or rapacuronium 1.2 mg/kg and in 28 of 30 patients after rapacuronium 1.0 mg/kg. In the Saline group, only 3 individuals achieved a good or excellent rating, and intubation was impossible in 2 of 10 individuals. For muscle relaxants of low potency, doses only 1.5 times the 95% effective dose can provide very satisfactory conditions for intubation if laryngoscopy is delayed to 75 s after drug administration. IMPLICATIONS: The dose of muscle relaxant usually recommended for facilitating tracheal intubation approximates at least two times the drug's effective dose (ED(95)). When the muscle relaxant in question has a rapid onset of action, this intubation dose may be decreased to 1.5 times the ED(95).

Adolescent↗
PubMed2002

The potency of new muscle relaxants on recombinant muscle-type acetylcholine receptors.

UNLABELLED: We studied the inhibition of fetal (gamma-nAChR) and adult (epsilon-nAChR) muscle-type nicotinic acetylcholine receptors by the two new nondepolarizing muscle relaxants (NDMRs) rocuronium and rapacuronium, the metabolite 3-desacetyl rapacuronium (Org 9488), and five other, longer-used NDMRs (pancuronium, vecuronium, mivacurium, d-tubocurarine, and gallamine). Receptors were expressed in Xenopus laevis oocytes by cytoplasmic injection of subunit complementary RNAs. Functional channels were activated with 10 microM acetylcholine, alone or in combination with various concentrations of the NDMRs. Currents were recorded with a whole-cell two-electrode voltage clamp technique. All NDMRs reversibly inhibited acetylcholine-activated currents in a dose-dependent fashion. Potencies of rapacuronium and Org 9488 were not statistically different at either gamma-nAChR (half-maximal response = 58.2 and 36.5 nM, respectively) or epsilon-nAChR (half-maximal response = 80.3 and 97.7 nM, respectively). The rank order of potencies at the epsilon-nAChR (pancuronium > vecuronium similar mivacurium > rocuronium similar d-tubocurarine > rapacuronium similar Org 9488 > gallamine) correlated highly with the clinical doses needed to produce 50% twitch depression at the adductor pollicis muscle in adults. Neuromuscular blockade by rapacuronium may be enhanced by its metabolite Org 9488. Different drug-receptor affinities of the tested NDMRs contribute to the differences in clinical dose requirements of these drugs needed to achieve appropriate muscle relaxation. IMPLICATIONS: Potencies of nondepolarizing muscle relaxants, studied at muscle nicotinic acetylcholine receptors expressed in a recombinant expression system, correlate highly with the clinical doses needed in adults to produce 50% twitch depression at the adductor pollicis muscle.

Acetylcholine↗
PubMed2002

A comparison between anterior and posterior monitoring of neuromuscular blockade at the diaphragm: both sites can be used interchangeably.

UNLABELLED: We present a novel site of monitoring neuromuscular blockade of the diaphragm at the patient's back. After the induction of anesthesia, 12 patients were orotracheally intubated. Two Ag/AgCl-electrodes were attached at the right seventh or eighth intercostal space between the midclavicular and anterior axillary line; two Ag/AgCl-electrodes were paravertebrally attached on the right side lateral to vertebrae T12-L1 or L1-2. Two Ag/AgCl-skin-electrodes were placed over the right thenar area for an electromyography recording of the adductor pollicis (AP) muscle, and two Ag/AgCl-skin-electrodes were used to stimulate the ulnar nerve. Onset and offset of neuromuscular blockade after rocuronium 0.6 mg/kg were determined, and significant differences between diaphragm and AP muscle and agreement between the two methods were determined. Mean maximum block was more than 96% at all sites. Lag time, onset 50, and onset time were not significantly different between the diaphragm and the AP. However, time to reach 25% of control twitch was significantly longer at the AP muscle than at the diaphragm (P < 0.001). The difference of the means and limits of agreement between the anterior and the posterior site of diaphragmatic monitoring were 0 +/- 11 s, 3 +/- 9 s, 0 +/- 19 s, and -2% +/- 5% for lag, onset 50, onset time, and peak effect, respectively, and -2 +/- 2 min for the time to reach 25% of control twitch of neuromuscular blockade. We conclude that anterior and posterior diaphragmatic monitoring can be used interchangeably to determine neuromuscular blockade after rocuronium. IMPLICATIONS: We present a novel site of monitoring neuromuscular blockade of the diaphragm at the patient's back, which shows good agreement with the conventional anterior site at the seventh or eighth intercostal space.

Adult↗
PubMed1992

Iontophoretic study of speed of action of various muscle relaxants.

The speed of action of nondepolarizing muscle relaxants is inversely related to potency. The hypothesis that this effect occurs at the end plate was tested in a frog (Rana pipiens) cutaneous pectoris muscle preparation. Brief acetylcholine pulses (10-100 ms) were applied iontophoretically from a central barrel of a triple-barrelled microelectrode located near an end plate. Long pulses (10-200 s) of muscle relaxant (gallamine, rocuronium, d-tubocurarine, atracurium, vecuronium, pancuronium, and doxacurium) were applied from one of two other barrels. The responses were a voltage change at the end plate, measured with an intracellular electrode. To evaluate potency, intracellular voltage changes following iontophoretic acetylcholine pulses were measured after application of various concentrations of muscle relaxants. The following were the equilibrium dissociation constants, which represent concentration of relaxant for 50% inhibition of response (mean plus or minus standard deviation): gallamine, 4.56 +/- 0.44 microM (n = 5); rocuronium, 0.71 +/- 0.09 microM (n = 6); d-tubocurarine, 0.59 +/- 0.07 microM (n = 4); atracurium, 0.31 +/- 0.03 microM (n = 4); vecuronium, 0.23 +/- 0.02 microM (n = 5); pancuronium, 0.18 +/- 0.03 microM (n = 3); doxacurium, 0.11 +/- 0.03 microM (n = 5). Both onset and offset of effect of muscle relaxant proceeded with an exponential time course.(ABSTRACT TRUNCATED AT 250 WORDS)

Androstanols↗
PubMed2002

An isolated, antegrade, perfused, peroneal nerve anterior tibialis muscle model in the rat: a novel model developed to study the factors governing the time course of action of neuromuscular blocking agents.

BACKGROUND: A model of an antegrade, perfused, isolated rat peroneal nerve anterior tibial muscle was developed to study potentially important factors governing the time course of action of (nondepolarizing) neuromuscular blocking agents such as concentration, blood flow, and temperature. The model allows observation of the effects of selective changes in these factors. METHODS: The authors isolated the anterior tibial muscle and cannulated the anterior tibial artery and vein, providing a way for single-pass perfusion with blood from a donor rat. A force transducer was connected to the tibialis anterior muscle and a stimulator was connected to the tibial nerve. The influence of intrinsic potency (EC90) and muscle blood flow rate on the time course of pancuronium and rocuronium was investigated. RESULTS: The model remained stable for at least 4 h with respect to twitch height, muscle structure and function, and blood chemistry. Doubling the muscle-blood flow resulted in a significantly faster onset and offset for both pancuronium and rocuronium. Trebling the intrinsic potency (EC90) was not associated with significant changes in the time course of action of the relaxants. CONCLUSION: The authors developed and validated a model that allows us to study biophase kinetics of neuromuscular blocking agents in the anterior tibial muscle of the rat. In this model, muscle-blood flow rather than EC90 appears to predominantly determine the onset and offset time of nondepolarizing muscle relaxants.

Androstanols↗
PubMed1996

The influence of cold on the recovery of three neuromuscular blocking agents in man.

The Arrhenius hypothesis suggests that change in temperature has a less marked effect on the rate of physical processes than on biological reactions. We have investigated the process underlying recovery from neuromuscular block in man by studying the effect of cooling on the rate of recovery from depolarising and non-depolarising block. Vecuronium, rocuronium and decamethonium (C10) neuromuscular block were investigated using the isolated forearm technique on awake human volunteers. In these experiments, one arm was cooled whilst the other was used as control. Moderate hypothermia decreased the rate of recovery from all three agents, but this was significantly less marked with the depolarising drug. The mean Q10 (the anticipated change in rate of a reaction across of 10 degrees C temperature gradient) of the rate of recovery for vecuronium was 3.21, rocuronium 2.86 and decamethonium 1.29. This suggests a different process in the recovery of these two types of drug. According to the Arrhenius hypothesis this would suggest that the recovery from non-depolarising drugs is likely to involve a biochemical mechanism and that recovery from decamethonium is controlled by a physical process.

Androstanols↗
PubMed2005

Sepsis stage dependently and differentially attenuates the effects of nondepolarizing neuromuscular blockers on the rat diaphragm in vitro.

We investigated the effects of early and late sepsis on the actions of nondepolarizing neuromuscular blockers by using a rat sepsis model induced by cecal ligation and puncture. Isometric twitch tensions of nerve-hemidiaphragm preparations elicited by indirect (phrenic nerve) supramaximal stimulation at 0.1 Hz were evaluated. Rocuronium, pancuronium, and d-tubocurarine dose-dependently decreased the twitch tensions of the nonseptic, early septic, and late septic diaphragms (P < 0.01 each by analysis of variance [ANOVA]). Late sepsis shifted the concentration-twitch tension curves rightward from those of nonsepsis to larger degrees than did early sepsis, as indicated by increases in 50% inhibitory concentration (IC(50)) values (P < 0.01 each by ANOVA and P < 0.01 or 0.05 by the Scheffe F test). The standardized rightward shifts in early and late sepsis were largest for pancuronium, second largest for rocuronium, and smallest for d-tubocurarine (5.741, 2.979, and 1.660 times in late sepsis, respectively; P < 0.01 each by ANOVA and the Scheffe F test). Sepsis-induced increases in IC(50) values did not accompany the decreases in slopes. The results indicate that sepsis induces hyposensitivities to nondepolarizing neuromuscular blockers, the degree of which depends on the stage of sepsis and on the kind of neuromuscular blocker.

Androstanols↗
PubMed2005

Evaluation of a closed-loop muscle relaxation control system.

Automatic muscle relaxation control may reduce anesthesiologists' workload freeing them for other patient care requirements. In this report we describe a muscle relaxation controller designed for routine clinical application using rocuronium and the train-of-four count. A muscle relaxation monitor (TOF Watch SX) was connected to a laptop computer running a controller algorithm program that communicates with a syringe pump to form a closed-loop muscle relaxation system. The control algorithm uses proportional-integral and lookup table components and is designed to avoid the usability restrictions of existing controllers. The controller is optimized using an objective method to avoid the uncertainties of ''hand-crafted'' controller algorithms. Controller target was train-of-four count 1 or 2 and controller performance was evaluated in 15 patients. During 39 hours of closed-loop control, 96.1% of all twitches recorded were in the target range. Average rocuronium infusion rate was 0.36 mg.kg(-1).h(-1) (sd 0.18 mg.kg(-1).h(-1)). We show that the controller remains useful even in the presence of disturbances that can arise in routine clinical conditions. The muscle relaxation controller maintained the target train-of-four count values and may serve as a basis for the design of hardware and user interfaces for closed-loop muscle relaxation control in clinical conditions.

Aged↗
PubMed2005

Fade of pulmonary function during residual neuromuscular blockade.

OBJECTIVES: A decrement in evoked muscle force with repetitive nerve stimulation (fade) suggests impaired neuromuscular transmission. We tested the hypothesis that fade of pulmonary function, ie, a decrease in values of FVC with the second spirometric maneuver compared to the first maneuver, occurs during impaired neuromuscular transmission. DESIGN: Prospective study. PARTICIPANTS: Six healthy male volunteers. INTERVENTIONS: A series of three consecutive spirometric maneuvers was performed every 5 min in six awake healthy volunteers before, during, and after partial paralysis evoked by rocuronium (0.01 mg/kg IV plus 2 to 8 microg/kg/min). MEASUREMENTS AND RESULTS: We measured FVC, FEV(1), forced inspiratory volume in 1 s (FIV(1)), peak expiratory flow (PEF), and peak inspiratory flow (PIF) by spirometry, and force of adductor pollicis muscle by mechanomyography (train-of-four [TOF] stimulation). A statistically significant fade (reduction of the second maneuver from the first maneuver) of FVC, FEV(1), FIV(1), PEF, and PIF was observed during neuromuscular blockade. With peak relaxation (TOF ratio, 0.5) fade amounted to medians of 10% (interquartile range [IQR], 9 to 23%), 7% (IQR, 2 to 16%), 31 (IQR, 19 to 47%), 9% (IQR, 3 to 24%), and 30% (IQR, 5 to 43%), respectively. A fade of >or= 10% was always associated with a clinically relevant (>or= 10%) FVC reduction from baseline (ie, FVC before rocuronium administration). However, FVC reduction from baseline was still present in 23% of measurements without a relevant FVC fade. CONCLUSIONS: A clinically relevant fall (fade) in FVC from the first to the second value during or after neuromuscular blockade suggests impaired pulmonary function and may be due to muscle paralysis. For this reason, the first (best) FVC value may overestimate pulmonary function and expose the patient to an unidentified risk.

Adult↗
PubMed1999

Transition time: a new parameter coinciding with fair intubating conditions.

With rocuronium optimal intubating conditions are earlier achieved than the adductor pollicis muscle onset time. Using the transition time we defined a better parameter for clinical relaxation. The onset of relaxation was determined in 20 patients. After a stable response was achieved with a 0.1 Hz single twitch stimulation 0.60 mg/kg rocuronium was injected. The three different stades during the onset of relaxation were determined. These are the lag time, transition time (transition between second and third phase) and onset time. Whether the transiton time corresponds with optimal intubating conditions was evaluated in 40 other patients. The median transition time was 67.4 (P25:52.5, P75:76.3) seconds with a corresponding relaxation of 76.2 (P25:81.4, P75:70.7)%. The intubating conditions were significantly better at a relaxation level corresponding with the transition time. We conclude that the transition time approximates the intubating time and corresponds with fair intubating conditions. This parameter can be preferred to define the moment with optimal intubating conditions.

Adolescent↗
PubMed1999

Visual estimation of onset time at the orbicularis oculi after five muscle relaxants: application to clinical monitoring of tracheal intubation.

UNLABELLED: The onset time of neuromuscular blockade at the adductor pollicis (AP) is different among neuromuscular blocking drugs, but these discrepancies had never been studied at the orbicularis oculi (OO). The purpose of this study was to verify if the differences in onset time observed at the AP still existed at the OO and to score the intubating conditions using monitoring at the OO after five muscle relaxants. The study included 172 adults aged 18-75 yr. Anesthesia was induced with fentanyl and propofol. Atracurium (0.5 mg/kg), mivacurium (0.20 mg/kg), rocuronium (0.6 mg/kg), succinylcholine (1.0 mg/kg), or vecuronium (0.08 mg/kg) was injected by random allocation. Time to complete disappearance of the response at the OO was assessed visually after train-of-four stimulation of the facial nerve. Laryngoscopy was then performed, and intubating conditions were determined on a scale of 1-4. Results were based on 150 patients. Onset time at the OO was (mean +/- SD): succinylcholine (57 +/- 17 s) < mivacurium (99 +/-19 s) = rocuronium (99 +/- 47 s) < atracurium (129 +/-33 s) = vecuronium (135 +/- 38 s) (P < 0.05). Overall intubating conditions were excellent (84%), good (14%), poor (1.3%), impossible (0.7%), and were similar among the five groups. We conclude that differences in onset time of muscle relaxants observed at the AP were also found at the OO. Visual estimation of the response at the OO correctly predicted good-to-excellent intubating conditions in more than 90% of cases for all the currently available muscle relaxants. IMPLICATIONS: Onset time of neuromuscular blockade, as estimated visually at the orbicularis oculi, depends on the muscle relaxants given. Regardless of the relaxant used, intubating conditions at loss of orbicularis oculi are acceptable.

Adolescent↗