A comparative evaluation of intubating doses of atracurium,d-tubocurarine,pancuronium and vecuronium in children

To determine the onset and recovery times and haemodynamic effects of intubating doses of atracurium (0.4 mg.kg-1), d-tubocurarine (0.8 mg.kg-1), pancuronium (0.12 mg.kg-1), and vecuronium (0.07 mg.kg-1), sixty-seven children aged one to eight years were studied under halothane and nitrous oxide anaesthesia. The time to maximum twitch depression and the time to recovery to T1/Tc 25 per cent were recorded with an integrated evoked EMG recorder. The heart rate and systolic blood pressure were recorded for five minutes after drug administration and prior to intubation. There was no difference in onset times between drugs. The recovery time to T1/Tc 25 per cent following vecuronium (25.5 +/- 6.3 min) was shorter than following atracurium (37.5 +/- 7.0 min). Recovery times for d-tubocurarine and pancuronium were greater than sixty minutes. Elevation of heart rate occurred after administration of pancuronium (+29.8 per cent to +38.6 per cent) and d-tubocurarine (+31 per cent to +34.9 per cent), but no change was observed after atracurium or vecuronium. Elevation of blood pressure was greatest following pancuronium (+10.8 to +14.8 per cent). No significant change was observed following atracurium or vecuronium. A transient lowering of blood pressure (-9.3 per cent) occurred following d-tubocurarine.     

Clinical experience with atracurium during prolonged anaesthesia

The pharmacodynamic properties of repeated injections of atracurium were studied in twenty-two patients. A control group received narcotic-based anaesthesia while another group received the same narcotic-based anaesthesia subsequently modified by the addition of 0.5% isoflurane. The twitch response of the adductor pollicis muscle was recorded after train-of-four (TOF) stimulation of the ulnar nerve at the wrist. Duration of effect and recovery time were measured. A bolus dose of atracurium (0.5 mg/kg b.w.) was given for tracheal intubation and maintenance doses of 0.2 mg/kg b.w. were given during anaesthesia at a TOF ratio of 0.25. Mean duration of anaesthesia was 7.5 hours (range 3-19). In the control group mean duration of effect and mean recovery time remained unchanged (six doses studied). A noteworthy inter-individual variation was found. In the isoflurane group mean duration of effect increased from 36.1 (SD 6.3) minutes to 42.2 (SD 8.1) minutes (P less than 0.05) following the addition of isoflurane. Corresponding recovery times remained unchanged. We conclude that during repeated administration of atracurium during narcotic-based anaesthesia, each patient shows a constant interval between requirements for maintenance doses of atracurium of 0.2 mg/kg b.w. Addition of 0.5% isoflurane causes a moderate prolongation of the duration of effect, but recovery time remains unchanged.     

Equi-lasting doses of rocuronium, compared to mivacurium, result in improved neuromuscular blockade in patients undergoing gynecological laparoscopy

PURPOSE: To compare equi-lasting doses of a short-acting (mivacurium) to an intermediate-acting (rocuronium) neuromuscular relaxant, with regard to intubating conditions, efficacy, number of maintenance doses, hemodynamic alterations, adverse events and costs, in patients undergoing laparoscopic gynecological surgery. METHODS: Sixty patients were randomly allocated to receive either 0.2 mg*kg(-1) (3 x ED(95)) mivacurium or 0.5 mg*kg(-1) (1.7 x ED(95)) rocuronium, under propofol/fentanyl anesthesia. T1, first twitch of the train-of-four (TOF) and TOF ratio (T4:T1) were used to evaluate neuromuscular block using the Relaxometer(R) mechanomyograph. The trachea was intubated when T1 was maximally suppressed. Neuromuscular block was maintained at 25% T1 with equi-lasting doses of 0.075 mg*kg(-1) mivacurium or 0.15 mg*kg(-1) rocuronium. RESULTS: Mean (min) +/- SD mivacurium onset time (1.9 +/- 0.4) was longer than that of rocuronium (1.3 +/- 0.3). This did not yield a statistical difference in intubating conditions between the two groups. Interval 25-75% T1 recovery and time to 0.8 TOF recovery were prolonged following rocuronium (11.9 +/- 3.9, 52.6 +/- 15.5 respectively) compared to mivacurium (6.7 +/- 2.3, 39.2 +/- 8.1 respectively). More patients, 22/30, required mivacurium maintenance doses compared to 14/30 patients in the rocuronium group. Arterial blood pressure declined and 13/30 patients manifested erythema following mivacurium administration. The acquisition costs of rocuronium (6.93 Euro/patient) were 23% lower compared to mivacurium (8.96 Euro/patient). CONCLUSION: Equi-lasting doses of rocuronium resulted in favourable intubating conditions more rapidly, improved hemodynamic stability, required less frequent administration of maintenance doses and were not associated with erythema, compared to mivacurium.     

Comparison of train-of-four and posttetanic response as guides for endotracheal intubation in children

Study Objective: To evaluate and compare the predictive values of the absence of train-of-four (TOF) or Posttetanic response as guides for endotracheal intubation in children.

Design: Prospective controlled study in children.

Setting: Induction of anesthesia and endotracheal intubation at a university-affiliated hospital.

Patients: Thirty pediatric patients age 1 to 10 years, ASA physical status I, who were undergoing elective surgery were divided into two equal groups.

Interventions: Anesthesia was induced with halothane and maintained at 1% inspired concentration. Fifteen children were stimulated with the TOF (2 Hz for 2 seconds) technique and 15 with the twitch-tetanus-twitch sequence. All the patients received atracurium 0.4 mg/kg. Upon abolishment of the TOF or tetanus-twitch sequence, endotracheal intubation was performed and the conditions for intubation were evaluated.

Measurements and Main Results: In the group of Patients stimulated by the TOF technique, the neuromuscular response was ablated in 1.7 ± 0.1 minutes, a significantly shorter time than in those stimulated by the tetanus-twitch sequence (4.0 ± 0.4 minutes; p < 0.0001). Conditions for intubation did not differ between the two groups.

Conclusions: Good intubating conditions can generally be counted on when the TOF has disappeared; additional waiting for the disappearance of posttetanic response is unnecessary. The observation that the disappearance of the tetanus-twitch sequence is a good indicator of deep neuromuscular blockade during recovery from atracurium in children cannot be extrapolated to the induction period.     

Onset of the effect and intubation conditions following atracurium, verocuronium and suxamethonium

1. The onset of neuromuscular blockade following i.v. injection of atracurium 0.3, 0.4, or 0.5 mg/kg; vecuronium 0.08 or 0.1 mg/kg; and succinylcholine 1.0 mg/kg was studied in 205 adult patients during induction of anesthesia by means of the compound action potential (EMG) of the hypothenar muscle, which was indirectly stimulated via the ulnar nerve above the wrist, using the Datex Relaxograph. At the same time, the intubation conditions at 0.5, 1, 2, or 3 min after injection were assessed using a scoring system (Crul 1983) related to ease of laryngoscopy, movement of vocal cords and coughing, and reflex movements of the extremities. 2. Neuromuscular blockade and intubation conditions 2 min after administration of atracurium 0.3 mg/kg were 60 +/- 10% and 8.7 +/- 0.3; after 0.4 mg/kg 74 +/- 4% and 10.3 +/- 0.3; and after 0.5 mg/kg 86 +/- 5% and 11.8 +/- 0.2. After 0.08 mg/kg vecuronium 76 +/- 3% and 7.4 +/- 0.5 were recorded and after 0.1 mg/kg 85 +/- 6% and 10.5 +/- 0.4. Motor blockade 1 min after succinylcholine was 98 +/- 2% and intubation conditions scored 11.3 +/- 0.3. Relating intubation conditions to neuromuscular blockade yielded a close correlation and surprisingly good or very good intubation conditions (score more than 10) at a motor blockade of 80% (resp. 20% transmission). 3. Although succinylcholine is still the muscle relaxant with the most rapid onset of action, the new drug atracurium seems to satisfactorily facilitate tracheal intubation within an acceptably short time interval of 2 min after injection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atracurium during halothane anesthesia in humans

The neuromuscular effects of atracurium were studied in 20 patients anesthetized with 0.8% end-tidal halothane. Neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle resulting from stimulation of the ulnar nerve. Four groups of five patients received single atracurium doses of 0.1, 0.15, 0.2, or 0.4 mg/kg, respectively. The block produced by 0.1 mg/kg was 25-72% and lasted 6-21 min. The block produced by 0.15 mg/kg was 69-93% and lasted 16-32 min. The blocks produced by 0.2 and 0.4 mg/kg were 95% or greater and lasted 42-84 min and 55-104 min, respectively. When indicated, intubation was easily performed in all patients receiving 0.2 and 0.4 mg/kg. The block could be readily antagonized by neostigmine and atropine. Changes in heart rate and blood pressure following atracurium administration averaged less than 5%.     

Atracurium for intubation in man

Atracurium is a new competitive neuromuscular blocking agent. We prospectively studied intubating conditions 2.5 minutes after atracurium doses of 0.4 or 0.5 mg/kg. For comparison, we evaluated conditions 1 minute after suxamethonium 1.0 mg/kg, there being 10 patients in each group. The same anaesthetist evaluated conditions during laryngoscopy and intubation in all patients. Intubating conditions were excellent in 33% of patients receiving atracurium 0.4 mg/kg and 60% of those receiving atracurium 0.5 mg/kg after 2.5 minutes; conditions were excellent in 80% of patients 1 minute after suxamethonium. The incidence of successful intubation on the first attempt was 67%, 90%, and 100%, respectively, in the three groups. Atracurium may be a suitable alternative to suxamethonium when speed of intubation is not critical.     

Priming with atracurium: improving intubating conditions with additional doses of thiopental

The effects of different intubating doses of atracurium on the time of onset, and the effect of an additional dose of thiopental on intubating conditions, were studied in 72 patients divided into six groups (n = 12 in each). Stratified sampling was used to obtain an even sex distribution. Groups I, III, and V (controls) received atracurium as a single bolus dose of 0.4, 0.5 or 0.6 mg/kg respectively. Groups II, IV, and VI received an initial (priming) dose of 0.05 mg/kg followed 3 min later by 0.35, 0.45, or 0.55 mg/kg respectively. The time of onset, that is the time from the intubating dose to complete suppression of the train-of-four (TOF) response, was significantly accelerated after administration of atracurium in divided doses. Increasing the intubating dose of atracurium after an initial 0.05 mg/kg from 0.35 to 0.55 mg/kg did not result in further significant acceleration of the onset time, but resulted in prolongation of the duration of neuromuscular blockade. When divided doses of atracurium were given, administration of 2 mg/kg thiopental (in addition to the 5 mg/kg used for induction) before the injection of the intubating dose resulted in improvement of intubating conditions as reflected by statistically significant changes in intubating scores. This result was probably due to the increase by thiopental in the depth of anesthesia. Therefore, when thiopental is given as supplement, the priming technique can be made to provide better conditions for tracheal intubation in less than 90 sec.     

Priming with vecuronium and atracurium--a comparison

Vecuronium (V) and atracurium (A) were compared in a randomised study in premedicated patients undergoing laparoscopy for gynecological pathology. Both groups contained ten patients. Anesthesia was induced with fentanyl (0.1 mg) and thiopentone (1 mg/kg initially and subsequently 4 mg/kg). A priming dose of vecuronium (20 micrograms/kg) or atracurium (100 micrograms/kg) was given one minute before the intubating dose (60 micrograms/kg for vecuronium and 300 micrograms/kg for atracurium). Ninety seconds thereafter intubation was performed. Maintenance of anesthesia consisted of isoflurane at an inspiratory concentration of 1% in a mixture of O2/N2O (50%/50%) with small supplements of fentanyl. Neuromuscular block was monitored with the Datex Relaxograph. Results show that neither drug offers major clinical advantages over the other: there is no difference in speed of onset (V:T190sec 14.6 +/- 4.3%; A:T190sec 23.5 +/- 6.5%; Mean +/- SEM) and duration of neuromuscular block (V:T150sec 34.2 +/- 3.5 min; A:T150sec 41.3 +/- 2.8 min; Mean +/- SEM) and intubation conditions are almost identical.     

Continuous infusion of atracurium in children

Atracurium infusion requirements were determined in 28 children anesthetized with N2O:O2 narcotic, N2O:O2 halothane (1% inspired), and N2O:O2 enflurane (2% inspired). When the patient was recovering from a bolus dose of 0.4 mg/kg atracurium, a continuous infusion of atracurium was started and the rate was adjusted to maintain 90-99% muscle twitch depression. Patients receiving enflurane anesthesia required atracurium at an infusion rate of 4.9 +/- 0.3 micrograms X kg-1 X min-1 which was a significantly lower rate (P = 0.0001) than those anesthetized with halothane (8.3 +/- 0.4 micrograms X kg-1 X min-1) or with N2O:O2 and narcotic (9.3 +/- 0.5 micrograms X kg-1 X min-1). At the onset of neuromuscular blockade, the twitch response disappeared faster after train-of-four stimulation repeated every 10 s than after single twitch rates of stimulation at 0.1 Hz. In children, during halothane anesthesia after 0.4 mg/kg atracurium, the response of the adductor of the thumb was ablated in 2.0 +/- 0.3 min with train-of-four stimulation, and in 3.7 +/- 0.4 min with single twitch stimulation. The authors recommend the use of a nerve stimulator during continuous infusion of atracurium because of the marked interpatient differences in infusion-rate requirements.     

Atracurium in clinical anaesthesia: effect of dosage on onset, duration and conditions for tracheal intubation

Conditions for tracheal intubation at 90 seconds, time to onset of maximum block and duration of clinical relaxation after five different doses of atracurium, which ranged from 0.4 to 1.0 mg/kg were studied in 200 adult patients who were anaesthetized with nitrous oxide, oxygen and halothane or fentanyl. The conditions for intubation improved significantly with increasing doses, and were acceptable in 55% patients with a 0.4 mg/kg dose and in about 90% of those who received the two higher doses. The time to onset of complete block was 257 seconds with 0.4 mg/kg and decreased progressively to 124 seconds with 1.0 mg/kg. The duration of clinical relaxation under fentanyl anaesthesia averaged 29 minutes with 0.4 mg/kg and increased in a dose-related manner to 57 minutes with 1.0 mg/kg: halothane anaesthesia produced only a marginal increase. There was no evidence of cumulation with up to six repeat doses of 0.125 mg/kg. The only side effect noticed was cutaneous flushing observed in 42% of patients. This was again dose dependent, being 18% with 0.4 mg/kg and increasing to 73% after 1.0 mg/kg. There was associated hypotension and bronchospasm in one patient.     

Comparative clinical studies of vecuronium, atracurium and pancuronium

The new relaxants vecuronium (Norcuron) and atracurium (Tracrium) have been compared with pancuronium (Pavulon) with respect to onset and duration of action and intubating conditions under clinical situations. A variant of the balanced anaesthesia technique with flunitrazepam, fentanyl and N2O/O2 was used. The following doses were considered equipotent (mg/kg body weight): vecuronium 0.07/0.10; atracurium 0.35/0.50; pancuronium 0.08/0.115. The degree of neuromuscular block was assessed in a semiquantitative manner, using the train of four. No difference between the three relaxants in onset of action was found. After the high doses, however, full paralysis developed 60 s earlier. The same is true of intubating conditions. Good or very good intubating conditions were obtained in the majority of cases 3 minutes after injection of the drug. Following the higher dose, good intubating conditions are achieved approximatively 1/2-1 min sooner. Both new relaxants allow for relatively rapid intubation without the inconvenience of a long duration of action. After a low initial dose the following time for recovery to 25% was noted (means +/- S.D., min): vecuronium 20.3 +/- 7.0; atracurium 28.0 +/- 3.1; pancuronium 53.3 +/- 14.8. The early recovery phase (from 5% to 25% recovery) was 6.1 +/- 2.4 after vecuronium, 8.3 +/- 1.7 after atracurium, 17.2 +/- 10.8 after pancuronium. There is a good correlation between our semiquantitative results, using the train of four, and quantitative recordings of muscle contractions reported in the literature. Both drugs show no cumulative effect after five repeated administrations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dose-response relationships for edrophonium and neostigmine antagonism of atracurium and cisatracurium- induced neuromuscular block

PURPOSE: To study the dose-response relationships for neostigmine and edrophonium during antagonism of neuromuscular block induced by atracurium and cisatracurium. METHODS: One hundred and twenty eight, ASA group 1 or 2 adults were given either 0.5 mg x kg(-1) atracurium or 0.1 mg x kg(-1) cisatracurium during fentanyl-thiopental-nitrous oxide-isoflurane anesthesia. The neuromuscular block was measured by an acceleration-responsive transducer. Responses were defined in terms of percent depression in the first twitch (T1) and train-of-four (TOF) response. When spontaneous recovery of first twitch height reached 10% of its initial control value, edrophonium (0.1, 0.2, 0.4, or 1 mg x kg(-1)) or neostigmine (0.005, 0.01, 0.02, or 0.05 mg x kg(-1)) was administered by random allocation. Neuromuscular function in another sixteen subjects was allowed to recover spontaneously. RESULTS: At five minutes, unlike edrophonium, neostigmine was equally effective against atracurium and cisatracurium with respect to T1 recovery. The neostigmine T1-ED50 was 10.3 +/- 1.06 (SEM) microg x kg(-1) after atracurium and 11.2 +/- 1.06) microg x kg(-1) after cisatracurium. The edrophonium ED50 was 157 +/- 1.07 microg x kg(-1) with atracurium and 47.4 +/- 1.07 microg x kg(-1) with cisatracurium, giving a neostigmine:edrophonium potency ratios of 15.2 +/- 1.7 and 4.2 +/- 0.41 (P < 0.001) for atracurium and cisatracurium, respectively. At 10 min neostigmine was 13 +/- 1.4 times as potent as edrophonium for achieving 50% TOF recovery after atracurium paralysis. After cisatracurium the potency ratio was 11.8 +/- 1.3 (NS). CONCLUSIONS: Although there were differences at five minutes, neostigmine:edrophonium potency ratios at 10 min, were similar in both relaxants studied.     

Rapid tracheal intubation with atracurium--a comparison of priming intervals

To determine the optimal interval between the administration of the priming dose and the intubating dose, atracurium was given to 44 patients either in a single dose of 0.5 mg X kg-1 or in an initial dose of 0.06 mg X kg-1 followed two, three or five minutes later with 0.44 mg X kg-1. When atracurium was given as a single bolus of 0.5 mg X kg-1 the time to 100 per cent twitch suppression (onset time) was 90.9 +/- 36 (mean +/- SD) seconds. When the priming interval was two minutes, the onset time of the intubating dose was 76.6 +/- 42.2 seconds (p = NS). But when the priming interval was three or five minutes, the onset times were 42.2 +/- 16.5 (p less than 0.01) and 52.6 +/- 28.8 (p less than 0.05) seconds respectively. Waiting for five minutes after the administration of the priming dose did not improve the intubating conditions. It is concluded that three minutes appears to be the optimal time interval for the administration of atracurium in divided doses. When a priming dose of atracurium is given three minutes before the intubating dose, it can provide an alternative to succinylcholine for rapid endotracheal intubation.     

Pharmacodynamics of high-dose vecuronium in children during balanced anesthesia.

To compare the speed of onset, intubating conditions, duration of action, and recovery from neuromuscular blockade with vecuronium to those with succinylcholine, 40 ASA physical status 1 or 2 children (ages 2-9 yr) were studied during N2O-O2-opioid anesthesia. Each child was randomly assigned to receive a bolus dose of one of the following muscle relaxants: succinylcholine 2.0 mg/kg (n = 10), vecuronium 0.1 mg/kg (n = 10), vecuronium 0.2 mg/kg (n = 10), or vecuronium 0.4 mg/kg (n = 10). The evoked electromyogram of the abductor digiti minimi to train-of-four stimulation was monitored. We found that with succinylcholine, the time to 95% twitch depression (speed of onset, mean +/- SD), 24 +/- 7 s, was significantly less than that with each dose of vecuronium: 0.1 mg/kg, 83 +/- 21 s; 0.2 mg/kg, 58 +/- 17 s; and 0.4 mg/kg, 39 +/- 11 s, respectively (P less than 0.05). The time to laryngoscopy and intubation did not differ significantly between succinylcholine (48 +/- 10 s) and vecuronium 0.4 mg/kg (57 +/- 13 s); however, both were significantly less than than with vecuronium 0.1 and 0.2 mg/kg (P less than 0.005). The intubating conditions were excellent in 100% of patients. The duration of action was least with succinylcholine (5.7 +/- 1.5 min) and increased with increasing doses of vecuronium: 0.1 mg/kg, 23.9 +/- 5.1 min; 0.2 mg/kg, 55.2 +/- 11.6 min; and 0.4 mg/kg, 74.6 +/- 9.9 min, respectively (P less than 0.001). The recovery index was most rapid with succinylcholine (1.6 +/- 0.4 min) and was slowest with vecuronium 0.4 mg/kg (22.6 +/- 2.1 min) (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Intubationsbedingungen nach Gabe von Atracurium und Vecuronium Bolusmethode vs. Primingtechnik

Prompted by the ongoing discussion of the pros and cons of using succinylcholine, this study was conducted to compare the responses to bolus injections of atracurium or vecuronium with those after sequential injection of these drugs (priming principle). We evaluated the earliest possible intubation times, intubating conditions, and the onset times (i.e. times from the end of injection to the maximum blockade) under conditions approaching real use as closely as possible. Methods. The randomized and double-blind study was carried out with 80 ASA risk class 1 and 2 patients. Approval of the institutional ethics committee was obtained, and each patient gave informed consent. Patients were randomly allocated to four study groups of 20 patients each. Isotonic saline was administered to those patients assigned to the atracurium or vecuronium bolus groups, whereas the patients assigned to the other two groups received a priming injection of either atracurium (0.05 mg/kg) or vecuronium (0.01 mg/kg). We observed the patients for signs of incipient muscular weakness before the induction of anaesthesia. Anaesthesia was induced with thiopental 3.5 min after the first injection (5 mg/kg and 50–100?mg before intubation). After a further 1 min during which adequate mask ventilatin with oxygen was assured, corresponding to a priming interval of 4.5?min, 0.5 mg/kg of atracurium or 0.1 mg/kg of vecuronium was administered to the patients in the bolus groups and 0.45 mg/kg of atracurium or 0.09 mg/kg of vecuronium as intubating doses to those in the priming groups. Intubation was attempted at 90, 120, 150 and 180?s thereafter. Intubating conditions were evaluated on the basis of laryngoscopy, vocal cord movement and coughing or bucking of the patients. Neuromuscular function was monitored via accelerometry at the adductor pollicis muscle (TOF stimulation of the ulnar nerve every 15?s). Results. The priming doses did not diminish the elicited twitches of the adductor pollicis muscle, but led to heavy eyelids and double vision in 35% of the atracurium patients and 47% of the vecuronium patients; these symptoms were well tolerated by the patients. At the time of intubation the adductor pollicis muscle was relaxed to approximately the same degree in all groups (mean±SD for the TOF ratios in the bolus groups was 0.46±0.37 for atracurium, 0.45±0.4 for vecuronium; in the priming groups 0.52±0.39 for atracurium, 0.53±0.36 for vecuronium). The administration of the relaxants in divided doses significantly shortened the intubating time after atracurium (100 vs 124?s) and improved the intubating conditions of vecuronium (good vs tolerable), but had no effect on the time course of the neuromuscular blockade (onset times in the bolus groups 224±84?s for atracurium and 209±64 s for vecuronium; in the priming groups 249±112?s for atracurium and 205±52 s for vecuronium). Conclusions. The priming technique presented here is clinically superior to the bolus method and therefore should be preferred in all elective cases and in those patients in whom succinylcholine is contraindicated.     

The optimal priming dose for atracurium

To determine the optimal priming dose for administration in divided doses, atracurium was given to 77 patients either in a single dose of 0.5 mg X kg-1 or in an initial dose of 0.04, 0.05, 0.06, 0.07, 0.08 or 0.09 mg X kg-1, followed three minutes later by the remainder of the 0.5 mg X kg-1 dose. Patients were anaesthetized throughout the study. When atracurium was given as a single bolus of 0.5 mg X kg-1, the mean time to complete neuromuscular block was 141.5 seconds. Administration in divided doses accelerated the onset time (p less than 0.01), that is the time from the intubating dose to the complete suppression of train-of-four (TOF) response. The TOF ratio decreased slightly but statistically significantly following the priming doses. When the priming dose was 0.05 mg X kg-1, the mean onset time was 70.9 seconds and priming with larger doses did not add any further advantage. It is concluded that 0.05 mg X kg-1 appears to be the optimal priming dose for the administration of atracurium in divided doses. When 0.05 mg X kg-1 is given three minutes before the intubating dose, tracheal intubation can be accomplished in less than 90 seconds.     

A dose-ranging study of rapacuronium in pediatric patients

BACKGROUND: The aim of this study was to determine the dose or doses of the new rapid-onset, short-acting, neuromuscular blocking drug rapacuronium that would provide satisfactory conditions for tracheal intubation at 60 s in infants and children. METHODS: Sixty-five infants (< 1 yr), 51 younger children (1-6 yr), and 49 older children (7-12 yr) were studied. Anesthesia was induced with thiopental-nitrous oxide-oxygen. Tracheal intubation was attempted 60 s after administration of one of five doses of rapacuronium (0.5, 1.0, 1.5, 2.0, or 2.5 mg/kg) and intubating conditions were assessed using a four-point scale. Following tracheal intubation, anesthesia was maintained with nitrous oxide-oxygen and alfentanil (12.5-50 microg/kg) as necessary. Neuromuscular transmission was monitored in an uncalibrated fashion using an acceleromyograph. RESULTS: Intubating conditions were good or excellent at 60 s in all infants after doses of 1.5 mg/kg or more and in all younger and older children after doses of 2.0 mg/kg or more. The duration of action of rapacuronium was dose- and age-dependent. Mean times to reappearance of the third twitch of the train-of-four (TOF; T3) were less than 10 min in infants at doses of 1.5 mg/kg or less and in younger and older children at doses of 2.0 mg/kg or less. Recovery of T3 after 1.0-2.0 mg/kg rapacuronium was significantly slower in infants compared with younger (P = 0.001) and older (P = 0.02) children. Five adverse experiences were related to rapacuronium administration: Bronchospasm (two instances), tachycardia (one instance), and increased salivation (two instances). None were serious. CONCLUSIONS: Doses of 1.5 and 2.0 mg/kg rapacuronium can produce satisfactory intubating conditions at 60 s in anesthetized infants and children, respectively, and are associated with a short duration of action.     

Intubating conditions after pipecuronium bromide: the influence of dose and time.

STUDY OBJECTIVE: To determine the intubating conditions following the administration of pipecuronium bromide in doses of two (0.07 mg/kg) or three (0.1 mg/kg) times ED95 (average dose that gives 95% block of the first twitch). DESIGN: To compare intubating conditions at 11/2 and 21/2 minutes in 41 patients receiving balanced anesthesia. SETTING: Surgical patients at Thomas Jefferson University Hospital. PATIENTS: Forty-one patients undergoing surgical procedure who received general anesthesia. INTERVENTIONS: After obtaining a stable baseline of train-of-four (TOF), 41 patients randomly received either 0.07 mg/kg or 0.1 mg/kg of pipecuronium as a single intravenous (IV) bolus dose, and the trachea was intubated either at 11/2 or 21/2 minutes. MEASUREMENTS AND MAIN RESULTS: Intubating conditions at 21/2 minutes appeared significantly better than those at 11/2 minutes, regardless of the pipecuronium dose. The mean time for T1 (first twitch of TOF) to reach 50% and 90% suppression was 1.36 +/- 0.51 minutes and 2.29 +/- 0.8 minutes, respectively, for the 0.07 mg/kg dose and 1.07 +/- 0.27 minutes and 1.72 +/- 0.45 minutes, respectively, for the 0.1 mg/kg dose. This did not make a significant difference in intubating conditions at either time. The time to 25% recovery of T1 was 68.2 +/- 22 minutes for the 0.07 mg/kg dose and 121.5 +/- 49 minutes for the 0.1 mg/kg dose. In patients who had spontaneous recovery of T1 to between 10% and 25% of control, administration of neostigmine or edrophonium resulted in identical recovery in 10 minutes. However, in patients with less than 10% spontaneous recovery of T1, neostigmine appeared to be superior to edrophonium. CONCLUSION: Pipecuronium has a relatively rapid onset. The trachea could be intubated successfully in 11/2 minutes with a dose of either 0.07 mg/kg or 0.1 mg/kg. If the clinical situation requires perfect relaxation with no movement or bucking, we recommend waiting at least 21/2 minutes.     

Facilitation of rapid endotracheal intubations with divided doses of nondepolarizing neuromuscular blocking drugs

The authors sought to determine whether prior administration of a small, subparalyzing dose of nondepolarizing muscle relaxant would shorten the onset time of an intubating dose of muscle relaxant. Initially, in 60 anesthetized patients, twitch response of adductor pollicis to ulnar nerve stimulation was studied after a small dose of pancuronium 0.015 mg . kg-1, metocurine 0.03 mg . kg-1, or d-tubocurarine 0.04 mg . kg-1, followed 3 min later by pancuronium 0.08 mg . kg-1 or atracurium 0.4 mg . kg-1 administered iv. After 60 s, the minimum neuromuscular block, in all patients was 79.0 +/- 5.0%. A 95% depression or twitch tension occurred between 59.1 +/- 5.3 and 86.1 +/- 5.9 s. In another 60 patients, intubating conditions under similar regimen were studied, except the small dose of muscle relaxant was given immediately prior to induction of anesthesia. At the end of 60 s, good to excellent intubating conditions were present in 100% of the patients following the second dose of pancuronium and in 83% of the patients following atracurium. In 17% of the patients, after atracurium intubating conditions were fair. When nondepolarizing neuromuscular blocking drugs are administered in divided doses, neuromuscular blockade adequate for endotracheal intubation is achieved in less than 90 s. This facilitates rapid endotracheal intubation in a time comparable to using succinylcholine, without undesirable effects of the depolarizing neuromuscular blocking drugs.