Administration of vecuronium, atracurium and pancuronium in divided doses: effect on onset and duration of action

The time to onset of neuromuscular block (as assessed by single twitch stimulation at 0.1 Hz) and the duration to 25% recovery of twitch height were measured after administration of vecuronium 0.1 mg kg-1, atracurium 0.5 mg kg-1 or pancuronium 0.1 mg kg-1, administered either as a single bolus or in divided doses, 10% being administered 4 min prior to the remaining 90%. The patients were anaesthetized with thiopentone, nitrous oxide in oxygen and i.v. fentanyl. There was no significant difference between the single- and divided-dose groups, either in the onset times (2.8 and 2.9 min for vecuronium, 2.7 and 2.4 min for atracurium and 3.3 min each for pancuronium for single- and divided-dose groups, respectively) or the duration to 25% recovery of twitch height (35 and 29 min for vecuronium, 45 and 39 min for atracurium and 87 and 93 min for pancuronium for single- and divided-dose groups, respectively).     

A comparison of remifentanil and fentanyl in patients undergoing carotid endarterectomy

BACKGROUND AND AIM: We investigated the haemodynamic stability and emergence characteristics of isoflurane/nitrous oxide anaesthesia supplemented with remifentanil or fentanyl in patients undergoing carotid endarterectomy. METHODS: Anaesthesia was induced with propofol (1-2 mg kg-1) and either remifentanil (0.5 microgram kg-1) or fentanyl (1 microgram kg-1), followed by an infusion of remifentanil (0.2 microgram kg-1 min-1) or fentanyl (2 micrograms kg-1 h-1). RESULTS: There were no significant differences between the groups in haemodynamic variables, postoperative pain, nausea or vomiting. After induction there was a significant decrease in mean arterial pressure for both groups (P < 0.001) and a decrease in heart rate (P = 0.001) in the remifentanil group. In both groups these haemodynamic changes continued during maintenance of anaesthesia (P < 0.05). The time to eye opening after surgery was significantly shorter with remifentanil compared with fentanyl (6.62 +/- 3.89 vs. 18.0 +/- 15.18 min, P = 0.015). CONCLUSION: Remifentanil appears to be a comparable opioid to fentanyl when supplementing isoflurane/nitrous oxide anaesthesia for carotid endarterectomy.     

Ketamine does not affect suxamethonium-induced neuromuscular blockade in man

The effect of ketamine on the onset time, the duration of action and the recovery characteristics of suxamethonium-induced neuromuscular blockade was examined in a double-blind randomized study comprising 30 patients anaesthetized with thiopentone, fentanyl, midazolam and nitrous oxide. The ulnar nerve was stimulated at the wrist using train-of-four stimulation (TOF; 0.2-ms duration, 2-Hz frequency every 10s), and the evoked twitch response was measured with a force-displacement transducer. After stabilization of the twitch recording, the patients in the ketamine group received ketamine 2 mg kg-1 i.v., followed by a ketamine infusion of 2 mg kg-1 h-1. The remaining patients served as controls and received equivalent volumes of isotonic saline. Suxamethonium I mg kg-1 was injected 2 min after the ketamine/placebo bolus dose. The onset time, recovery index, time to 90% recovery of the twitch height and the TOF ratio during recovery were similar in the two groups. Therefore, it is concluded that ketamine does not affect suxamethonium-induced neuromuscular blockade in man.     

Desflurane maintains intraocular pressure at an equivalent level to isoflurane and propofol during unstressed non-ophthalmic surgery

We have investigated the effects of desflurane compared with isoflurane and propofol on intraocular pressure (IOP) in 48 ASA I-II patients undergoing elective non-ophthalmic surgery. Anaesthesia was induced with thiopental 3-5 mg kg-1, fentanyl 2-4 micrograms kg-1 and vecuronium 0.1 mg kg-1. Patients were allocated randomly to receive propofol (n = 16) 4-8 mg kg-1 h-1, isoflurane (n = 16) or desflurane (n = 16) for maintenance of anaesthesia. Fentanyl was added if necessary. The lungs were ventilated with 70% nitrous oxide in oxygen. Arterial pressure, electrocardiography, heart rate and end-tidal carbon dioxide were measured throughout anaesthesia. IOP was measured before surgery, during maintenance and after emergence from anaesthesia with applanation tonometry by an ophthalmologist blinded to the anaesthetic technique. There was a significant decrease in IOP after induction of anaesthesia which did not differ between groups. Desflurane maintained IOP at an equivalent level to isoflurane and propofol.      

Sensitivity to atracurium in the lateral abdominal muscles]

OBJECTIVE: To study the effect of atracurium on the electromyographic activity of the lateral abdominal muscles and adductor pollicis in anaesthetized subjects. STUDY DESIGN: Prospective, comparative, open study. PATIENTS AND METHODS: Sixteen patients, ASA physical status 1 or 2, undergoing elective orthopaedic surgery under general anaesthesia were studied. Anaesthesia was induced with propofol/fentanyl and orotracheal intubation performed after glottic local anaesthesia without using muscle relaxant. Anaesthesia was maintained with isoflurane/nitrous oxide/oxygen and fentanyl reinjections. Supramaximal percutaneous stimulations in a simple twitch mode (0.1 Hz) were applied at the 9th-10th intercostal nerve on the posterior axillary line and at the ulnar nerve at the wrist. The electromyographic responses were registered using skin surface electrodes, placed on the D9-D10 dermatome in regard of the lateral abdominal muscles and of the thenar muscles. After a single bolus dose of atracurium 0.5 mg.kg-1, the following parameters were studied: the maximum effect (Emax), the time for obtaining Emax (Delay) and the recovery time of 5, 10, 25, 50, 75 and 100% of the control neuromuscular response (T5, T10, T25, T50, T75, T100). RESULTS: The dose of 0.5 mg.kg-1 of atracurium induced 100% block in both lateral abdominal muscles and adductor pollicis. Lateral abdominal muscles blockade had faster onset (136 +/- 4 s versus 205 +/- 29 s) and shorter recovery, T5, T10, T25, T50, T75 and T100 were significantly (p < 0.05) shorter than at the adductor pollicis. CONCLUSION: Lateral abdominal muscles blockade have faster onset and recovery than adductor pollicis.     

Comparison of propanidid with propofol for dental surgery of short or medium duration

The properties of propofol in emulsion given by continuous intravenous infusion to spontaneously breathing patients have been well studied. Thirty randomized voluntary premedicated patients undergoing dental extraction were anaesthetized with propofol (2.5 mg X kg-1 IVD, and 9 mg X kg-1 X h-1) or with propanidid (9 mg X kg-1 IVD, and 60 mg X kg-1 X h-1), supplemented with nitrous oxide in oxygen and fentanyl. Induction, maintenance and recovery times had the same characteristics. Highly significant differences occurred between the two groups regarding the increase in heart rate, apnoea and recovery time. This study showed that propofol was an eminently suitable agent for continuous intravenous anaesthesia in spontaneously breathing patients for dental surgery.     

Atracurium infusions in major ophthalmic surgery

Fifteen patients who were undergoing major ophthalmic surgery were anaesthetized using controlled ventilation with nitrous oxide, oxygen, midazolam and fentanyl after induction with thiopentone. Each was then given a bolus dose of 0.6 mg kg-1 atracurium followed immediately by an infusion of the drug at the rate of 0.6 mg kg-1 h-1, neuromuscular function being monitored throughout. Even slight movement can jeopardize the success of this type of surgery but good control of neuromuscular blockade was achieved without inhalational supplementation. The mean duration of the atracurium infusion was 118 min (range 30-247 min). The mean time from stopping the infusion to recovery of the first twitch of the train of four (TOF) to 20% was 25 min (range 11-44 min). Atropine (1.2 mg) and 5.0 mg neostigmine were then given in divided doses and a rapid and complete recovery was achieved. This technique can be used safely even in bad-risk patients but the infusion should be discontinued about 25 min before the end of surgery.     

Maintenance of anaesthesia with propofol--a comparative study of a stepdown infusion of propofol and a low dose infusion supplemented by incremental doses.

Forty-four patients, ASA Grade I or II, had anaesthesia induced with propofol at 100 mg min-1 followed by a maintenance rate of 6 mg kg-1 h-1 or a stepdown regimen of 10 mg kg-1 h-1 for 10 min, 8 mg kg-1 h-1 for the next 10 min and at 6 mg kg-1 h-1 thereafter. Anaesthesia was maintained with propofol infused using an Ohmeda 9000 pump supplemented by nitrous oxide and oxygen (2:1) in a Bain circuit with spontaneous ventilation. Incremental doses of 20 mg of propofol were given to both groups as clinically indicated to maintain anaesthesia. Both methods provided satisfactory maintenance of anaesthesia but significantly more incremental doses were required in the group receiving the steady rate infusion. However, a lower cumulative dose was required up to 30 min in this group but not by 40 min. A comparable fall in systolic and diastolic blood pressure and heart rate was seen in both groups. There was no difference in the recovery times between the groups and the total dose did not correlate with time to recovery.     

Atracurium infusion in total intravenous anesthesia

The neuromuscular blocking effect of atracurium given as a bolus dose (0.5 mg X kg-1) followed by a maintenance infusion was studied during two different anesthetic techniques. It has been reported that benzodiazepines interact with non-depolarising neuromuscular blockers. In this study no difference was found in the effect of atracurium given with conventional fentanyl/nitrous oxide anesthesia when compared to total intravenous anesthesia using midazolam/alfentanil. More than 90% twitch depression was achieved after 123 and 137 s, respectively. Recovery time to 10% twitch height following the bolus dose was around 32 min. The dosage range for atracurium given by infusion (0.29-0.44 mg X kg-1 X h-1) was confirmed.     

Recovery characteristics using isoflurane or propofol for maintenance of anaesthesia: a double-blind controlled trial

We studied 114 female patients (ASA 1 or 2) who were within 20% of ideal body weight and who were scheduled to undergo gynaecological laparoscopy which required supplementation with an opioid (groups IA and PA), or dental procedures which did not require opioid supplementation (groups IO and PO). A computerised package of psychomotor tests was performed before surgery. Anaesthesia was induced with propofol 2.5 mg.kg-1 and all patients received atracurium 0.3 mg.kg-1 and 67% nitrous oxide in oxygen. Patients in group IA received isoflurane 1% (inspired), and alfentanil 10 micrograms.kg-1 as a bolus and 10 micrograms.kg-1.h-1 as an infusion. Patients in group PA received propofol 9 mg.kg-1.h-1 as an infusion, decreasing to 6 mg.kg-1.h-1 after 15 min, together with alfentanil 10 micrograms.kg-1.h-1. Patients in groups IO and PO received isoflurane and propofol in the regimens described for groups IA and PA, but without alfentanil. Recovery was assessed by a blinded observer who recorded times to awakening (eye opening) and orientation (giving date of birth), and who repeated the psychomotor tests at 1, 3 and 5 h. Linear analogue scales of mood, nausea and pain were obtained and other side effects were noted in the succeeding 48 h. A matched control group of 25 females (who were not anaesthetised) underwent psychomotor testing on four occasions in order to assess the 'learning effect' of repeated recovery testing. The analysis of recovery tests did not assume a normal distribution.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recovery and discharge of patients after long propofol infusion vs isoflurane anaesthesia for ambulatory surgery

Fifty unpremedicated patients scheduled for outpatient restorative dentistry and/or oral surgery lasting 2 to 4 h were anaesthetized with either propofol infusion or isoflurane inhalation. Before induction of anaesthesia with propofol (2.5 mg.kg-1), all patients were given 75 mg of diclofenac and 0.01 mg.kg-1 vecuronium intravenously. Intubation was facilitated with suxamethonium (1.5 mg.kg-1) and anaesthesia was maintained in random order either with propofol infusion (12 mg.kg-1.h-1 for the first 20 min, 9 mg.kg-1.h-1 for the next 20 min, and 6 mg.kg-1.h-1 for the rest of the anaesthesia) or with isoflurane (inspired concentration 1-2.5%), both with nitrous oxide and oxygen (30%). The patients breathed spontaneously using a non-rebreathing circuit. Patients given propofol infusion became re-orientated faster (11.0 +/- 5.5 min vs. 16.5 +/- 7.5 min; P less than 0.01) and at 30 min walked along a straight line better (P less than 0.01). At 60 min, none of the propofol patients displayed an unsteady gait, whereas 11 of the 25 isoflurane patients did (P less than 0.001). None of the patients receiving propofol had emesis at the clinic, compared with 10 of the 25 patients receiving isoflurane (P less than 0.001). The overall incidence of emesis was 2 of 25 and 14 of 25 in the propofol and isoflurane groups, respectively (P less than 0.01). Patients receiving propofol were discharged home earlier than patients receiving isoflurane (80 +/- 14 min and 102 +/- 32 min, respectively; P less than 0.01). It is concluded that propofol allows early discharge of patients, even after long anaesthesias.     

A comparison of train-of-four monitoring: Mechanomyography at the thumb vs acceleromyographyat the big toe

BACKGROUND: It is not known if the information on neuromuscular function obtained from the hand is interchangeable with that of the foot. In the present study the agreement of thumb mechanomyography with acceleromyography of the big toe was studied. METHODS: Ten healthy patients scheduled for oral surgery were studied. Anaesthesia was induced with fentanyl 2 micrograms kg-1 and propofol 2 mg kg-1, and maintained with propofol 100-175 micrograms kg-1 min-1, nitrous oxide 60-70%, and fentanyl 1-2 micrograms kg-1 h-1. Vecuronium 0.1 mg kg-1 was used for muscle relaxation. Mechanomyography (MMG) of the thumb (Myograph 2000) and acceleromyography (AMG) of the big toe (TOF-Guard) were recorded simultaneously in all patients, and onset, period of no-twitch response, duration of action, and spontaneous recovery time obtained from both muscle groups. The agreement between methods was tested by calculation of bias and limits of agreement. RESULTS: The onset time and duration of action were significantly shorter (87 s vs 154 s, and 35 min vs 38 min, respectively), and the spontaneous recovery time significantly longer in the thumb than in the big toe (32 min vs 19 min). Period of no-twitch response was not significantly different in the two muscle groups. Limits of agreement (thumb big toe) were -21 to -113 s, -7 to 1 min, and -9 to 35 min, for onset time, duration of action, and spontaneous recovery time, respectively. CONCLUSIONS: We conclude that clinically acceptable agreement between thumb mechanomyography and big toe acceleromyography was found for the period of no-twitch response, suggesting that the timing of supplemental doses of vecuronium can be guided by AMG at the big toe. However, the spontaneous recovery time agreement (to TOF ratio = 0.75) between the thumb and the big toe was poor.     

Effect of milrinone on vecuronium-induced neuromuscular block

We examined the effect of milrinone, a phosphodiesterase III inhibitor, on neuromuscular block induced by vecuronium. Thirty adult patients were randomly assigned to one of two equal groups: the milrinone group and the control group. Subjects in the milrinone group received an intravenous loading dose of milrinone 5 microg x kg-1x min-1 for 10 min, followed by an infusion at a rate of 0.5 microg x kg-1x min-1. Subjects in the control group received normal saline at a rate of 0.1 ml x kg-1 x h-1. Thirty minutes after the beginning of the infusion of milrinone, anaesthesia was induced with intravenous thiopental 4 mg x kg-1 and fentanyl 2 microg x kg-1, and was maintained with isoflurane in oxygen and nitrous oxide. Neuromuscular blockade was monitored electromyographically at the adductor pollicis muscle. The times from the administration of vecuronium 0.1 mg.kg-1 to the onset of neuromuscular block and the return of the first, second, third, and fourth response of the train-of-four were compared between the two groups. Times to the recovery of the ratio of the first twitch to the control twitch to 25%, 50% and 75%, and times to the recovery of train-of-four ratio to 25%, 50% and 75% were also compared between the two groups. The onset of neuromuscular block in the milrinone group was significantly slower than in the control group. The times to the returns of the four twitches of the train-of-four, times to recovery of the ratio of the first twitch to the control twitch to 25% and 50%, and the times to the recovery of the train-of-four ratio to 25% and 50% were significantly shorter in the milrinone group than in the control group. We conclude that milrinone delays the onset of neuromuscular blockade but hastens its recovery in anaesthetised patients receiving vecuronium.     

Effects of propofol, propofol-nitrous oxide and midazolam on cortical somatosensory evoked potentials during sufentanil anaesthesia for major spinal surgery

Recording of cortical somatosensory evoked potentials (CSEP) enables monitoring of spinal cord function. We studied the effects of propofol, propofol-nitrous oxide or midazolam during sufentanil anaesthesia on CSEP monitoring during major spinal surgery. Thirty patients with normal preoperative CSEP were allocated randomly to one of the following anaesthesia regimens: propofol (2.5 mg kg-1 followed by 10-6 mg kg-1 h-1) with or without nitrous oxide, or midazolam (0.3 mg kg-1 followed by 0.15 mg kg-1 h-1) combined with sufentanil 0.5 microgram kg- 1 h-1 in the propofol and midazolam groups, or 0.25 microgram kg-1 h-1 in the propofol-nitrous oxide group. CSEP were elicited by alternate right and left tibial posterior nerve stimulation and recorded before and after induction (15 min, 1, 2 and 3 h), and during skin closure. CSEP latencies were not significantly modified in the three groups. CSEP amplitude decreased significantly in the propofol-nitrous oxide group (from mean 2.0 (SEM 0.3) to 0.6 (0.1) microV; P < 0.05) but not in the propofol (from 1.8 (0.6) to 2.2 (0.3) microV) or midazolam (1.7 (0.5) to 1.6 (0.5) microV) groups. The time to the first postoperative voluntary motor response (recovery) delay was significantly greater in the midazolam group (115 (19) min) compared with the propofol and propofol-nitrous oxide groups (43 (8) and 41 (3) min, respectively). Consequently, the use of propofol without nitrous oxide can be recommended during spinal surgery when CSEP monitoring is required.      

Atracurium versus vecuronium: a comparison of recovery in outpatient arthroscopy

Atracurium 0.5 mg.kg-1 and vecuronium 0.1 mg.kg-1 were compared as neuromuscular relaxants for outpatient arthroscopy of the knee under general anaesthesia. In 40 unpremedicated patients divided at random into two groups, anaesthesia was induced with methohexitone, atracurium (Group A) or vecuronium (Group B), three per cent isoflurane prior to intubation and 0.9 per cent during maintenance with nitrous oxide 66 per cent in oxygen. Neuromuscular function was recorded by a Datex Relaxograph. Recovery was assessed by the time the patients took to open their eyes, to be able to answer five questions correctly, the time to recovery of ocular balance (Maddox Wing test) and by comparing pre- and postoperative performance of a paper and pencil test (the p-deletion test). Recovery tests showed no significant differences between groups. After three hours all the patients were fit for discharge. The patients were interviewed one month after the procedure. All were satisfied with their anaesthetic. "Full recovery" took 1.5 days with a range of 1 h-7 days. The only significant difference (p less than 0.01) between the groups was the need for pharmacological reversal of residual paralysis. In a procedure with a mean duration of 45.6 minutes, and using isoflurane, all but one patient (95 per cent) in the atracurium group required neostigmine versus nine patients in the vecuronium group (45 per cent).     

Comparison of propofol and antagonised midazolam anaesthesia for day-case surgery

A technique of midazolam/fentanyl/isoflurane/nitrous oxide anaesthesia, in which the benzodiazepine was antagonised by the specific antagonist, flumazenil, was compared with propofol/fentanyl/nitrous oxide anaesthesia for minor outpatient urological surgery. No significant difference was found in the overall ease of anaesthesia; however, using subjective (linear analogue sedation scales) and objective (letter deletion and simple reflex time) tests, recovery was found to be significantly slower for the antagonised midazolam group. For both groups, the most frequent intraoperative problem was patient movement in response to surgical stimulation and, postoperatively, headache. The midazolam group displayed the greatest degree of residual sedation at the 4-hour time of discharge and on arrival home a significantly larger number of patients in the midazolam group slept for a period. It is likely that the dose of flumazenil chosen (1 mg) was inadequate to completely antagonise the dose of midazolam (mean 17 mg) for the full duration of recovery.     

Neuromuscular and cardiovascular effects of mivacurium chloride in surgical patients receiving nitrous oxide-narcotic or nitrous oxide-isoflurane anaesthesia

The neuromuscular and cardiovascular effects of mivacurium chloride were studied during nitrous oxide-oxygen narcotic (fentanyl) (n = 90) and nitrous oxide-oxygen isoflurane (ISO) anaesthesia (n = 45). In addition, a separate group (n = 9) received succinylcholine during fentanyl anaesthesia to compare its neuromuscular effects with mivacurium. Mivacurium was initially administered as a single bolus in doses from 0.03 mg.kg-1 to 0.25 mg.kg-1 to study the dose-response relationships, as well as the cardiovascular effects of mivacurium. Neuromuscular block (NMB) was measured by recording the twitch response of the adductor pollicis muscle following ulnar nerve stimulation (0.15 Hz, 0.2 ms supramaximal voltage). The ED95 values for mivacurium were estimated to be 0.073 mg.kg-1 and 0.053 mg.kg-1 in the fentanyl and ISO groups respectively. The duration of block (time from injection to 95 per cent recovery) for a dose of 0.05 mg.kg-1 mivacurium was 15.3 +/- 1.0 min and 21.5 +/- 1.3 min for fentanyl and ISO anaesthesia, respectively. The recovery index (25-75 per cent) between initial bolus dose (6.1 +/- 0.5 min), repeat bolus doses (7.6 +/- 0.6 min), mivacurium infusion (6.7 +/- 0.7 min) and succinylcholine infusion (6.8 +/- 1.8 min) were not significantly different. There was minimal change in mean arterial pressure (MAP) or heart rate (HR) following bolus doses of mivacurium up to 0.15 mg.kg-1. Bolus administration of 0.20 mg.kg-1 or 0.25 mg.kg-1 of mivacurium decreased MAP from 78.2 +/- 2.5 to 64.0 +/- 3.2 mmHg (range 12-59 per cent of control) (P less than 0.05). The same doses when administered slowly over 30 sec produced minimal change in MAP or HR.     

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.     

Atracurium with halothane and isoflurane in pediatric anesthesia

The study was carried out to assess the effects of atracurium neuromuscular blockade in children anaesthetized with N2O:O2: halothane vs N2O:O2: isoflurane. Thirty-two ASA I-II children, age 1-13 yr, undergoing elective surgery, were divided into two groups according to age and the mode of anaesthesia induction. Anaesthesia was induced in the younger children (group 1: 1-6 yr) with nitrous oxide and inspired halothane or isoflurane in oxygen via a face mask. Intravenous thiopental (6-7 mg/kg-1) was used to induce anaesthesia in older children (group 2: 7-13 yr). Each group of patients was randomly allocated to two groups each receiving halothane (group A: n = 8) or isoflurane (group I: n = 8). Halothane 0.8% end-tidal and isoflurane 1% end-tidal as anaesthesia maintenance. A bolus dose of atracurium 0.35 mg/kg-1 was administered. Premedication consisted of oral flunitrazepam (0.04 mg/kg-1) and bellafoline (0.02 mg/kg-1). Heart rate (by electrocardiography), arterial pressure (by auscultation) were monitored. Then end-expired carbon dioxide concentration was maintained at 30-40 mmHg. Neuromuscular transmission was evaluated by response to indirect stimulation (TOF) of the ulnar nerve at the wrist via surface electrodes. Conditions for endotracheal intubation were excellent in 25 of the children, good in 6 and poor in 1. The intubation was carried out within 112 s (group 1A), 130 s (group 1 I), 112 s (group 2A) and 135 s (group 2 I) following the administration of atracurium. The maximum twitch depression was recorded in the isoflurane groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Potency and time course of action of rocuronium during desflurane and isoflurane anaesthesia

We have studied the potency and onset and duration of action of rocuronium in patients anaesthetized with 1 MAC of desflurane or isoflurane (in 66% nitrous oxide). Potency was estimated using the single bolus dose technique. Neuromuscular block was measured by stimulation of the ulnar nerve and recording the force of contraction of the adductor pollicis muscle. The ED50 and ED95 of rocuronium were estimated as 138 (95% confidence limits 117-162) micrograms kg-1 and 281 (241-328) micrograms kg-1, and 126 (105-151) micrograms kg-1 and 283 (236-339) micrograms kg-1 during desflurane and isoflurane anaesthesia, respectively. The mean times to onset of maximum block after rocuronium 0.6 mg kg-1 were 1.0 (SD 0.10) min and 1.1 (0.15) min, respectively, during anaesthesia with desflurane and isoflurane. The respective times to recovery of T1 (the first response in the train-of- four (TOF) stimulation) to 25% and 90% were 36 (8.3) min and 54 (15.4) min during desflurane anaesthesia and 31 (8.2) min and 45 (12.7) min during isoflurane anaesthesia. The times to recovery of the TOF ratio to 0.7 were 66 (13.4) min and 52 (16.3) min and the 25-75% recovery indices 14 (5.3) min and 10 (3.2) min, respectively, in the desflurane and isoflurane groups. There were no differences in the estimated potency or onset of action of rocuronium during desflurane and isoflurane anaesthesia. However, duration of action tended to be longer curing desflurane anaesthesia although only the differences in times to TOF ratio of 0.7 and the recovery indices were close to being significantly different (P = 0.0503 and 0.0560).