Onset and duration of action and hemodynamic effects of rocuronium bromide under balanced and volatile anesthesia.

The onset and duration of action, and hemodynamic effects of rocuronium bromide 0.6 or 0.9 mg kg-1 were studied in 4 groups of 10 patients each during anesthesia with nitrous oxide in oxygen and fentanyl or halothane. Neuromuscular block was monitored using mechanomyography and train-of-four (TOF) stimulation. The mean time to onset of complete neuromuscular block was 55 s with the 0.6 mg kg-1 dose during both anesthetic techniques. The times to recovery of T1 (first response in the TOF stimulation) to 25 and 90% of control and to the recovery of the TOF ratio to 0.7 were 36, 45 and 54 min respectively during narcotic anesthesia, and 35, 54 and 58 min during halothane anesthesia. Complete block with the 0.9 mg kg-1 dose occurred in 50, and 52 s respectively in the fentanyl and halothane groups. The recovery of T1 to 25% occurred in 49 and 52 min, to 90% in 66 and 71 min and to TOF ratio of 0.7 in 72 and 79 min respectively during balanced and halothane anesthesia. There were no significant changes in heart rate or mean arterial pressure during the 5 min following administration of either dose of rocuronium during balanced or halothane anesthesia. A separate group of 10 patients received 0.9 mg kg-1 of rocuronium during anesthesia with nitrous oxide, oxygen and isoflurane. Complete block occurred in an average time of 45 s in these patients with 25% recovery of T1 in 53 min.(ABSTRACT TRUNCATED AT 250 WORDS)

A serious and repeatable electrical hazard--compressed electrical cord and an operating table.

We describe a previously unreported hazard resulting from compression of an electrical cable by an operating theatre table. This resulted in a live wire contact to the operating table. Intermittent connection of the table to earth during a procedure resulted in triggering of a residual current device mitigating the effects of the hazard. The actual cause was not readily identified as the devices connecting the table to earth were considered most likely to be the source of the current. There was potential for significant injury to the patient and theatre staff which would have been diminished if staff had had a better understanding of the electrical safety equipment in use. We examine the underlying causes of the accident, discuss electrical safety and correct use of safety devices in the operating theatre, and propose guidelines for appropriate management.

The levering laryngoscope.

This is a report of a modification of the standard Macintosh laryngoscope blade to facilitate tracheal tube placement in cases of difficult visualisation of the larynx. The modification offers the unique advantage of a hinged blade tip, controlled by a lever on the handle of the laryngoscope which allows elevation of the epiglottis while decreasing the overall laryngoscopic elevation or levering movement required. It is an adaptation which can be applied to most laryngoscope blades, does not require any special training in its use and will prove useful for both routine intubations as well as those which may be difficult and associated with an anterior larynx.

A comparison of lignocaine with prilocaine in axillary brachial plexus anaesthesia.

Twenty patients received either lignocaine 1.5% with 1/200,000 adrenaline (group L), or prilocaine 1.5% plain (group P) as a brachial plexus block for surgery to the upper limb, in a randomised double-blind study. The two groups were comparable in age, weight and duration of surgery and there were no significant differences between the two groups with regard to onset, pattern or degree of sensory loss. The degree of motor loss was also comparable. The group L patients had a statistically significant longer duration of sensory loss than those in group P. All the blocks were performed using the same technique and provided complete surgical anaesthesia. Prilocaine 1.5% plain provides adequate sensory and motor blockade for brachial plexus anaesthesia and is a suitable agent for medium duration surgery to the upper limb.

Comparison of the effects of neostigmine and edrophonium on the duration of action of suxamethonium.

Rapid sequence induction of anaesthesia necessitating the use of suxamethonium may occasionally be needed soon after antagonism of neuromuscular block with anticholinesterase agents. The onset and duration of action of 1 mg kg-1 of suxamethonium was recorded in groups of 10 patients each, 5 or 10 min after the administration of edrophonium 1 mg kg-1 or neostigmine 40 micrograms kg-1 given for the antagonism of atracurium-induced neuromuscular block. Plasma cholinesterase activity was measured before, and 5 and 10 min after the administration of the anticholinesterases. A further 10 patients received suxamethonium 1 mg kg-1 without prior atracurium or anticholinesterase administration to serve as controls. The onset of action of suxamethonium was significantly prolonged when administered 5 min after both anticholinesterases, compared to the control group (P < 0.01). Recovery of suxamethonium block was delayed significantly after neostigmine, compared to both the edrophonium and the control groups (P < 0.05-0.001). Plasma cholinesterase activity was significantly reduced with the use of neostigmine but not with edrophonium (P < 0.001).

Patient-controlled analgesia with and without background infusion. Analgesia assessed using the demand: delivery ratio.

Sixty adult patients following general surgical operation were treated with patient-controlled analgesia using morphine. Patients were allocated into three groups to receive: no background infusion, a 1 mg.h-1 or a 2 mg.h-1 background infusion. The other controls on the patient-controlled analgesia machine were set to allow a maximum dose of morphine of 6 mg.h-1 to each group. Analgesia was assessed after 4 and 24 h using a 100 mm horizontal visual analogue scale. The number of analgesic requests made by the patient and the number of those requests which resulted in successful deliveries was recorded. Patients who received a regimen including a background infusion had improved pain relief, particularly in the first 4 h of treatment (p < 0.05). Patients who received a background infusion of 2 mg.h-1 had an increased incidence of nausea (p < 0.05). A background infusion of 1 mg.h-1, with a 1 mg bolus dose and a 12 min lockout interval provided acceptable pain relief without excessive nausea. In all three groups the ratio of analgesic requests to successful deliveries correlated with the degree of pain reported by visual analogue score (p = 0.0001).

Recovery of mivacurium block with or without anticholinesterases following administration by continuous infusion.

Thirty patients received a bolus dose of 0.2 mg.kg-1 of mivacurium followed by an infusion during anaesthesia with thiopentone, fentanyl and halothane. Neuromuscular block was monitored using train-of-four stimulation and mechanomyography and the block maintained to keep the first response in the train-of-four (T1) at 10% of control. At the end of surgery the patients were randomly allocated to reversal with neostigmine or edrophonium or to spontaneous recovery. The mean dosage of mivacurium for maintaining the T1 at 10% was 5.7 micrograms.kg-1.min-1. There was a significant (r = -0.81, p < 0.001) negative correlation between time to recovery of T1 to 10% after the bolus dose and infusion rate. The times taken for T1 to reach 25, 75 and 90% of control and for the train-of-four ratio to reach 0.7 were significantly shorter (p < 0.05 to 0.001) with neostigmine and edrophonium compared to the spontaneously recovering group. The average (SD) times for attaining the train-of-four ratio of 0.7 were 7.0 (1.2), 6.8 (1.4) and 13.5 (2.3) min respectively for neostigmine, edrophonium and spontaneously recovering groups. There were no differences between endrophonium and neostigmine in any of the recovery times.

A comparison of the stress response to laryngoscopy. The Macintosh versus the McCoy blade.

The cardiovascular changes and catecholamine concentrations were compared in 20 patients before and after laryngoscopy with either the Macintosh or the McCoy laryngoscope blades. Following induction with fentanyl and thiopentone and muscle relaxation with vecuronium the vocal cords were visualised for 10 s with either the Macintosh or McCoy blade, chosen at random. Heart rate, arterial blood pressure and plasma noradrenaline and adrenaline concentrations were measured before, and at, laryngoscopy, and 1, 3 and 5 min later. There was a significant increase in both heart rate (33%) and arterial blood pressure (27%) after laryngoscopy using the Macintosh blade (p < 0.01). Use of the McCoy blade did not result in any significant change in either heart rate or arterial blood pressure. There was a slight increase (p > 0.05) in plasma noradrenaline concentrations using the Macintosh blade which persisted for 5 min after laryngoscopy. This was not observed with the McCoy blade. There was no change in plasma adrenaline concentrations with either blade during the 5 min after laryngoscopy when compared to the values before laryngoscopy. It is concluded that the stress response to laryngoscopy is less marked with the use of the McCoy blade and is probably due to a reduction in the force necessary to obtain a clear view of the larynx.

Accidental bronchial intubation. An analysis of AIMS incident reports from 1988 to 1994 inclusive.

Accidental bronchial intubation was examined in the first 3947 cases reported to the Australian Incident Monitoring Study and was found to have accounted for 154 (3.7%) of the total incidents reported. Most incidents were detected in the operating theatre (93.5%) and during maintenance of anaesthesia (77.9%), by unexplained oxygen desaturation alone (63.6%). Capnography remained normal or unremarkable during 88.5% of the episodes. One-third of cases were associated with head or neck surgery and possible flexion of the patient's head. A RAE tube was used in 20% of incidents, a greater frequency than occurred in the study overall. A third party was implicated in 36 (23.4%) of cases. Ninety per cent of cases were considered preventable. Major morbidity occurred in three cases and unplanned intensive care admission was required in a further five. Almost two-thirds (61.1%) of the incidents might have been avoided by the proposed markings on the tracheal tube. We conclude that when arterial desaturation occurs at any stage during anaesthesia the possibility of bronchial intubation must be considered. Asymmetrical ventilation may be difficult to detect clinically and in most cases there is no change in capnography.

Neuromuscular and haemodynamic effects of mivacurium in elderly and young adult patients.

We have studied the neuromuscular effects of mivacurium and changes in heart rate and arterial pressure in 40 elderly (aged 70 yr) and 20 young adult (aged 18-40 yr) patients anaesthetized with thiopentone, fentanyl, nitrous oxide in oxygen and halothane. Neuromuscular block was monitored by train-of-four (TOF) stimulation of the ulnar nerve and recording of the force of contraction of the adductor pollicis muscle using a force displacement transducer and a neuromuscular function analyser (Myograph 2000, Biometer Ltd). Twenty elderly and 10 young adults received single doses of mivacurium 0.15 mg kg-1 and spontaneous recovery was recorded. The other 20 elderly and 10 adults received the same dose but an infusion was started at T1 (first response in TOF) of 10% and the block maintained at this level. Haemodynamic effects were studied after administration of mivacurium over 15 or 5 s in elderly (n = 10 each) and over 5 s in adult (n = 10) patients. Onset of maximum block occurred at a mean time of 122 (SD 32) and 125 (49) s in elderly and young adults, respectively. Recovery of T1 to 25% occurred in 22.0 (5.7) and 17.2 (4.4) min, and T1 to 90% in 32.8 (6.9) and 24.4 (5.8) min in elderly and adult subjects, respectively. Recovery of the TOF ratio to 0.7 occurred in 32.8 (7.1) and 26.0 (15.0) min in the elderly and young subjects, respectively (all P < 0.05 between young and elderly).(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of the duration of control stimulation on the onset and recovery of neuromuscular block.

The onset of action of atracurium 450 micrograms/kg, mivacurium 160 micrograms/kg, and vecuronium 80 micrograms/kg was measured after train-of-four (TOF) stimulation had been applied for 1, 5, 10, 15, or 20 min in groups of 10 patients each during anesthesia with thiopental, nitrous oxide-oxygen, and fentanyl. TOF stimulation was applied to the ulnar nerve at 2 Hz every 12 s and the force of contraction of the adductor pollicis muscle recorded. There was a progressive and significant reduction in the time to onset of maximum block with increasing times of control stimulation with all three relaxants (P < 0.0001). The mean +/- SD times to onset of maximum block decreased from 224 +/- 103 to 73 +/- 28 s with atracurium, 239 +/- 81 to 101 +/- 33 s with vecuronium, and 198 +/- 72 to 106 +/- 23 s with mivacurium as the period of control stimulation increased from 1 to 20 min. The time to recovery of T1 (first response in the TOF stimulation) to 25% of control (duration of clinical relaxation) increased from 33 +/- 5.7 to 52 +/- 13.4 min with atracurium, 25 +/- 7.6 to 38 +/- 9.4 min with vecuronium, and 13 +/- 2.5 to 18 +/- 3.5 min with mivacurium with the period of control stimulation increasing from 1 to 20 min. The differences were significant for atracurium and vecuronium (P < 0.05-0.0001). We conclude that increasing periods of control stimulation are associated with decreasing time to onset of neuromuscular block with atracurium, vecuronium, and mivacurium at the adductor pollicis muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

A new device for measuring and recording the forces applied during laryngoscopy.

In characterising the forces exerted during laryngoscopy it is accepted that the significant force component is that which is parallel to the axis of the laryngoscope handle. This paper describes a new method of evaluating the forces exerted at laryngoscopy. A laryngoscope handle has been redesigned, incorporating a force-displacement transducer on the handle at the end opposite to where the blade is attached. The device is designed specifically to sense the axial component of force. The blade attachment block has been detached from the sleeve and connected to a steel shaft which forms the new battery compartment. This allows the axial force exerted at the blade during laryngoscopy to be transmitted along this shaft to the sensing transducer. Linear ball bearings have been introduced between the new shaft and the handle sleeve (outer casing). The rolling friction has been reduced to less than 0.1% by diamond-lapping the precision ground surface-hardened rod to produce a mirror finish. Thus, the force transmitted to the transducer is essentially constant regardless of where the load is applied along the blade. The output from the system is directly downloaded to a laptop computer and the data analysed almost instantaneously to determine the duration of laryngoscopy, the peak forces applied, the mean force with its standard deviation and graphic display of the data. Provision has been made for data entry checks, recording patient details and study data, and creating a data base for the storage and retrieval of the study details.

Administration of rocuronium (Org 9426) by continuous infusion and its reversibility with anticholinesterases.

The use of rocuronium (Org 9426) as a single bolus followed by an infusion was assessed in 50 patients under anaesthesia with nitrous oxide-oxygen and halothane. Neuromuscular block was monitored using train-of-four stimulation and recording the force of contraction of the adductor pollicis muscle. Rocuronium was administered in an initial bolus dose of 0.45 mg.kg-1 followed by an infusion adjusted manually to maintain the T1, the first response in the train-of-four, at 10% of control. Following cessation of rocuronium infusion the patients were either allowed to recover spontaneously (n = 10) or were given neostigmine 50 micrograms.kg-1 or edrophonium 1 mg.kg-1 at 10 or 25% recovery of the T1 (n = 10 for each group). Adequate antagonism was defined as attaining a sustained train-of-four ratio of 0.7. Rocuronium requirements showed marked variation among individual patients but were relatively constant in individual patients. The mean (SD) time to attain stable infusion rates was 17.4 (10.9) min. The mean (SD) requirement of rocuronium for steady state 90% block of T1 was 572 (190) micrograms.kg-1.h-1 (range 242-1104 micrograms.kg-1.h-1). The mean (SD) time to attain a train-of-four ratio of 0.7 in the group allowed to recover spontaneously was 36.1 (7.3) min. This interval was 7.5 (1.9), 9.3 (7.0), 4.6 (1.9) and 1.9 (0.9) min respectively in the groups receiving neostigmine at T1 of 10%, edrophonium at T1 of 10%, neostigmine at T1 of 25% and edrophonium at T1 of 25%. The antagonism was significantly faster in those reversed at 25% (p < 0.05). Three patients in the group receiving edrophonium at T1 of 10% and one in the group receiving neostigmine at T1 of 25% failed to attain a train-of-four ratio of 0.7. It is concluded that rocuronium can be administered as a continuous infusion for stable neuromuscular block. Neostigmine may be a more reliable antagonist of deep block, whereas edrophonium is advantageous when there is a greater spontaneous recovery.

Dose-responses for edrophonium during antagonism of vecuronium block in young and older adult patients.

The dose-response relationship for edrophonium during antagonism of vecuronium-induced neuromuscular blockade was studied in two groups of adult patients of mean (SD) age 35 (10.0) years (n = 42) and 77 (5.4) years (n = 42) respectively. Neuromuscular block was monitored by recording the force of contraction of the adductor pollicis muscle following train-of-four stimulation. Six patients in each age group received 0.1, 0.3, 0.5, 0.7, 1.0, or 1.5 mg.kg-1 of edrophonium, or normal saline at 10% recovery of T1 (first response in the train-of-four) after a single dose of vecuronium 0.08 mg.kg-1. The train-of-four ratios were recorded continuously over the next 10 min and the values at 1 min intervals from 5 min onwards were used to construct the dose-response curves. The dose-response curves showed no significant difference between the two age groups except at 10 min. The estimated dose of edrophonium required for attaining a train-of-four ratio of 0.7 at 10 min was 0.9 and 1.3 mg.kg-1 in the younger and older groups, respectively (p < 0.05).

Duration of stabilization of control responses affects the onset and duration of action of rocuronium but not suxamethonium.

The effect of the duration of stabilization of control responses on the onset and duration of clinical relaxation of suxamethonium 1 mg kg-1 and rocuronium 0.6 mg kg-1 were investigated in 90 patients. The control responses were allowed to stabilize for 1, 5, 10, 15 or 20 min prior to administration of rocuronium and for 1, 5, 10 or 15 min prior to suxamethonium. The mean onset time for rocuronium decreased from 150 to 46 s as the duration of stabilization increased from 1 to 20 min (P < 0.001) although the maximal effect was observed within the first 5 min. The average duration of clinical relaxation also increased from 25 to 40 min (P < 0.001). No effect was observed for either variable in the case of suxamethonium.

A comparison of the forces exerted during laryngoscopy. The Macintosh versus the McCoy blade.

The forces exerted at laryngoscopy with the McCoy and Macintosh blades have been compared in 40 patients. The variables measured were the duration of laryngoscopy, the three maximally-applied forces and the mean force. The mean (SD) forces recorded were 18.9 (7.82) and 10.1 (5.33) N, respectively, with the Macintosh and the McCoy blades (p < 0.001) with a similar duration of laryngoscopy. There was a significant positive correlation between the mean force and patients' weight, height and body mass index for the Macintosh blade but only for weight and height for the McCoy blade. It is concluded that the use of the McCoy blade results in significantly less force being applied during laryngoscopy. This may be the reason for the reduction in the stress response reported previously with the use of the McCoy blade.

Antagonism of mivacurium block with edrophonium from various degrees of spontaneous recovery.

Seventy adult patients received mivacurium 0.15 mg kg-1 during anaesthesia with thiopentone, nitrous oxide and 0.5% halothane. Neuromuscular block was monitored using mechanomyography and train-of-four stimulation. Edrophonium 0.75 mg kg-1 was administered 5 or 10 min after mivacurium, or when the first response in the TOF (T1) had recovered to 5, 10, 25 or 50% of control in groups of 10 patients each. A control group was allowed to recover spontaneously. The mean time taken from administration of mivacurium to attaining a TOF ratio of 0.7 was between 19.3 and 24.9 min in the groups given edrophonium, regardless of the time of administration, compared with 26.7 min in the spontaneous recovery group. The differences, however, were not significant among the groups showing little advantage in antagonizing mivacurium block.

Pharmacokinetics of rocuronium after bolus and continuous infusion during halothane anaesthesia.

We have studied the pharmacokinetics of a single bolus of rocuronium (Org 9426), followed by an infusion, in eight patients during anaesthesia with halothane and nitrous oxide in oxygen. Neuromuscular block was monitored using train-of-four (TOF) stimulation and recording the force of contraction of the adductor pollicis muscle. Rocuronium was administered as an initial bolus dose of 0.45 mg kg-1 followed by an infusion adjusted manually to maintain T1 (first response in the TOF) at 10% of control. Mean onset time and time to recovery of T1 to 10% were 72 (SD 19.6) s and 27 (9.6) min, respectively. The infusion rates were stable in 19.8 (6.5) min. The mean requirement for rocuronium for steady state 90% block of T1 was 528 (163.3) micrograms kg-1 h-1. After cessation of surgery the infusion was stopped and patients were allowed to recover spontaneously. The times to attain a T1 of 90% and a TOF ratio of 0.7 were 31 (11.7) min and 36 (7.3) min, respectively. Blood samples were collected for 390 min after cessation of infusion and concentrations of rocuronium and its putative metabolites measured using HPLC. A two-exponential equation was used to describe the pharmacokinetic data. The rate of clearance, mean residence time and volume of distribution at steady state were 3.3 (0.77) ml kg-1 min-1, 67.2 (18.8) min and 212.5 (40.1) ml kg-1, respectively. The distribution (T1/2 alpha) and elimination (T1/2 beta) half-lives were 7.5 (3.33) min and 85.6 (18.4) min, respectively. These values were not significantly different from previously published data for a single bolus dose of rocuronium.