Total intravenous anaesthesia with propofol,alfentanil, and oxygen-air: three different dosage schemes

Three different dosage schemes of propofol infusions combined with a fixed-rate alfentanil infusion were investigated in total intravenous anaesthesia. In 30 premedicated patients, divided at random into three groups, anaesthesia was induced with propofol 2 mg.kg-1 immediately followed by an alfentanil infusion 10 micrograms.kg-1.min-1 as a loading dose which was decreased after ten minutes to a maintenance dose of 1 microgram.kg-1.min-1. Vecuronium bromide 0.1 mg.kg-1 was used as the muscle relaxant. After induction of anaesthesia a propofol infusion 2 mg.kg-1.hr-1 was started in group A, 3 mg.kg-1.hr-1 in group B and 4 mg.kg-1 hr-1 in group C. At signs of light anaesthesia supplementary bolus doses of 20 mg propofol and 1 mg alfentanil were given. The patients' lungs were ventilated with air-oxygen (FIO2 0.35). The mean systolic and diastolic blood pressures showed no statistical significant differences between the three groups. A significant (P less than 0.01) decrease of the mean systolic and diastolic blood pressures was present after induction of anaesthesia and tracheal intubation. Recovery was uneventful in all but one patient, who had ventilatory depression that responded to naloxone (0.2 mg IV). Awareness did not occur in any patient. The only difference between the three groups was the higher number of supplementary bolus doses of propofol and alfentanil needed in group A (P less than 0.01). In total intravenous anaesthesia propofol 3 and 4 mg.kg-1.hr-1 as a maintenance dose combined with a two-step fixed-rate alfentanil infusion provided smooth anaesthesia and uneventful rapid recovery.     

Comparison of propofol and methohexital for dental and maxillofacial surgery

A prospective study has been undertaken to compare a new intravenous anaesthetic agent, propofol, to methohexitone in 40 ASA I or II patients aged between 18 and 50 years undergoing maxillo-facial surgery and divided into two groups. Intramuscular premedication was standardized for all patients. In group I, propofol 2 mg X kg-1 was injected over 1 min in a peripheral venous line with fentanyl 0.86 microgram X kg-1, followed by an infusion of propofol 5 mg X kg-1 X h-1 and fentanyl 3 micrograms X kg-1 X h-1. In group II, the fentanyl dosage was the same as in group I, whilst methohexitone 3 mg X kg-1 was given for induction and 4.5 mg X kg-1 X h-1 for maintenance of anaesthesia. The following were recorded during induction, maintenance and recovery; haemodynamic parameters using a non invasive method; respiratory parameters; quality of anaesthesia; side-effects. Statistical analysis was performed using the Student t test and qualitative analysis using the Schwartz comparison test at 2%. The following results were found: the quality of anaesthesia with propofol was superior to that of methohexitone during the three stages of anaesthesia. The duration of induction was similar in both groups, but the quality of induction (occurrence of more minor side-effects; p less than 0.05) and intubation was in favour of propofol (p less than 0.05). During maintenance, stability of anaesthesia and a lesser incidence of side-effects were again in favour of the propofol group, in which a slower rate was also found (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Electroencephalographic impact of propofol anesthesia

Two groups of patients were studied. In group A, propofol was used alone, given by repeat injections of 2.5 mg X kg-1 in 30 s, in 5 patients undergoing percutaneous thermocoagulation of the Vth cranial nerve. In group B, a series of 12 patients undergoing lumbar disc hernia surgery, propofol was given as a bolus of 2.5 mg X kg-1 in 60 s followed by an infusion of 7 to 12 mg X kg-1 X h-1 together with vecuronium and fentanyl. The EEG recording was carried out during the whole length of anaesthesia and for 1 h after its end. The recordings were all stereotyped, within five successive phases: the awake physiological pattern (phase 0) was desynchronized a mean 52 s after the start of the propofol injection; it was followed by an increase in amplitude of the alpha rhythm (phase I); within a mean of 132 s were seen phases II to V. Phase V corresponded to surgical anaesthesia and could be kept up by a rate of infusion of 9 mg X kg-1 X h-1 propofol. An increase in this rate gave rise to burst suppressions which lasted as much as 15 s or more, and disappeared very quickly when the infusion rate was slowed. After stopping the anaesthesia, the EEG phases were quickly reversed, V to 0: in a mean of 11.1 min, the EEG pattern had returned to the awake state (extremes 4.3 to 19 min).(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebrospinal fluid concentrations of propofol during anaesthesia in humans

The concentration of propofol in and surrounding the human brain during propofol anaesthesia is unknown. We measured simultaneously the concentration of propofol in cerebrospinal fluid (CSF) from an indwelling intraventricular catheter and the concentration in arterial blood in five neurosurgical patients before, during induction (at 2.5 and 5 min) and during a maintenance propofol infusion (at 15 and 30 min). After induction of anaesthesia with propofol 2 mg kg-1, anaesthesia was maintained with an infusion of 8 mg kg-1 h-1 for 15 min and then reduced to 6 mg kg-1 h-1. The plasma concentration of propofol increased rapidly during induction and reached a plateau concentration of mean 2.24 (SD 0.66) micrograms ml-1 after 5 min. The concentration of propofol in CSF showed a slower increase during induction and remained almost constant at 35.5 (19.6) ng ml-1 at 15-30 min after induction. The CSF concentration of propofol that we measured was 1.6% of the plasma concentration and consistent with the high protein binding of the drug in plasma.      

Total intravenous anaesthesia with propofol or etomidate

In combination with fentanyl, propofol was compared with etomidate for total intravenous anaesthesia in 21 women (ASA Grades I-II) admitted for elective hysterectomy. They received either propofol (bolus 1.5 mg kg-1, infusion 9 mg kg-1 h-1 for 10 min thereafter 6 mg kg-1 h-1) or etomidate (bolus 0.10 mg kg-1, infusion 3 mg kg-1 h-1 reduced to 0.6 mg kg-1 h-1). Fentanyl 10 micrograms kg-1 was given for induction followed by an infusion of 30 micrograms kg-1 h-1 for 10 min reduced to 6 micrograms kg-1 h-1 for the first hour and successively reduced over time. Induction was smooth and maintenance easy to manage in both groups. There was no difference in time from end of infusion until extubation, but the time until the patients could report their date of birth was significantly shorter in the propofol group. Nausea and vomiting were more pronounced in the etomidate group, and mental side-effects were only seen after etomidate. After 3 months, more patients in the etomidate group complained of reduced power of concentration. We conclude that total intravenous anaesthesia with either propofol or etomidate is equally easy to manage, but in the recovery situation propofol was advantageous in time and quality.     

Effects of propofol and isoflurane on the neuromuscular block induced by atracurium]

Speed of onset, duration of action and recovery time for a bolus injection of atracurium were measured in two groups of patients. In group I anaesthesia considered of propofol, fentanyl, nitrous oxide and oxygen mixture. The induction dose of propofol was 2 mg/kg-1 followed by an infusion of 9.0 mg/kg-1/h-1 for first half hour and 4.5 mg/Kg-1/h-1 subsequently. In group II anaesthesia consisted of isoflurane, fentanyl, nitrous oxide and oxygen mixture. Isoflurane was given upon clinical needs. Speed of onset, duration of action, and recovery time for atracurium were measured in the two groups. No statistically significant differences between speed of onset and duration of action between the two groups were found. The recovery period from T1 = 10% to T1 = 70% twitch response was considerably longer with isoflurane (25 min +/- 6) than with propofol (18 min +/- 3) (p less than 0.01). Results obtained suggest that for adequate relaxation during tracheal intubation smaller doses of atracurium are not needed during isoflurane than propofol administration. Because of the longer recovery period of residual neuromuscular blockade during isoflurane anaesthesia decreasing doses of atracurium and careful monitoring of twitch depression tension are also suggested.     

Propofol vs thiopentone as anaesthetic agents for short operative procedures

In a randomized open study, 120 healthy female patients were included. For short gynaecological procedures they were anaesthetized with either propofol 2.5 mg X kg-1 (n = 60) or thiopentone 5 mg X kg-1 (n = 60) in combination with nitrous oxide/oxygen (67%/33%). Supplementary doses of propofol (10-20 mg) or thiopentone (25-50 mg) were given when necessary during the procedure. Induction characteristics for propofol and thiopentone 1 min after start of induction were similar. Propofol seemed to have a more depressant effect than thiopentone on the circulatory response to anaesthesia. Recovery times from the end of the operative procedure until the patients opened their eyes on command and were orientated were shorter in the propofol patients compared to the thiopentone patients. In the propofol group, patients recalled discomfort on injection more often than patients anaesthetized with thiopentone. Otherwise, the side-effects were similar in both groups. We conclude that propofol is similar to thiopentone in its anaesthetic qualities during induction and maintenance of short anaesthetic procedures. Propofol was associated with a more rapid emergence from anaesthesia than thiopentone.     

Propofol versus etomidate in short-time urologic surgery]

Thirty patients, scheduled for short urological surgical procedures and ranked ASA 1 or 2, were randomly assigned to two homogenous groups. In group P, they were given a 2 mg.kg-1 bolus of propofol and 10 micrograms.kg-1 of alfentanil, followed by a continuous infusion of propofol (5 mg.kg-1.h-1) and 5 micrograms.kg-1 doses of alfentanil. In group E, they were given a 0.3 mg.kg-1 bolus of etomidate, followed by an infusion (1.5 mg.kg-1.h-1). The doses of alfentanil were the same as in group P. Further doses of either propofol (0.5 mg.kg-1) or etomidate (0.2 mg.kg-1) were used should anaesthesia prove not to be deep enough. The patients were not intubated, and breathed spontaneously. Surgery lasted a mean of 18.3 +/- 11.8 min (group P) and 18.8 +/- 9.4 min (group E). The following parameters were studied: the amount of each agent required for maintenance of anaesthesia, the duration of apnoea at induction, the quality of anaesthesia and of muscle relaxation, adverse effects (coughing, trismus, restlessness, nausea, vomiting), the time required for recovery, and its quality. In group P, there was a 27% decrease in arterial pressure, without any tachycardia or hypoxia, together with a quick recovery of excellent quality. On the other hand, in group E, there was little or no haemodynamic alteration, but there often was a trismus at induction. Hypoxia also occurred during induction with etomidate, being severe enough in one case to require tracheal intubation and artificial ventilation. The reasons for this hypoxia seemed to be the apnoea and the trismus, which tends to hinder assisted ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of pre-induction glycopyrronium on the haemodynamic response of elderly patients to anaesthesia with propofol

This study investigated whether pretreatment with glycopyrronium can attenuate the hypotension caused by anaesthesia of the elderly with propofol. Twenty elderly patients (77.1 +/- 2.44 years, mean +/- SEM) of ASA physical status 2 or 3 scheduled for elective urological procedures were given glycopyrronium 0 (n = 10) or 5 micrograms.kg-1 (n = 10) in a randomised, double-blind manner, 5 min before induction of anaesthesia with propofol infused at 600 ml.h-1 (average induction dose 1.7 +/- 0.06 mg.kg-1, mean +/- SEM) followed by maintenance with a propofol infusion at 10 mg.kg-1.h-1. Although glycopyrronium significantly increased heart rate (p less than 0.01, ANOVA), the decrease in blood pressure 2 and 5 min after induction was similar in both groups. The study had a power of 80% to detect a 20 mmHg difference in systolic arterial pressure between treatment groups with p less than 0.05.     

The influence of esmolol on the dose of propofol required for induction of anaesthesia

Cardiac output may be an important determinant of the induction dose of intravenous anaesthetic. Esmolol is known to reduce cardiac output, and we examined its effect on the propofol dose required for induction of anaesthesia. The size of the effect seen with esmolol was compared with midazolam co-induction. Sixty patients were randomly allocated to placebo (saline), esmolol (1mg x kg(-1) bolus, followed by an infusion at 250 microg x kg(-1)min(-1)) or midazolam (0.04 mg x kg(-1)) groups. Induction of anaesthesia commenced 3 min following the administration of the study drug, using a Diprifusor set to achieve plasma propofol concentrations of 10 microg x ml(-1) at 5 min. The primary end point used was the propofol dose per kg at loss of response to command. The mean (SD) propofol dose for each group was 2.38 (0.48) mg x kg(-1) for placebo, 1.79 (0.36) mg x kg(-1) for esmolol and 1.34 (0.35) mg x kg(-1) for midazolam (all means significantly different; p < 0.0005). We found that predosing with esmolol reduces the propofol requirements for induction of anaesthesia by 25%.     

Rocuronium duration of action under sevoflurane, desflurane or propofol anaesthesia

BACKGROUND AND OBJECTIVE: We conducted a prospective randomized study to evaluate whether the duration of action of a single bolus dose of rocuronium is influenced by maintenance of anaesthesia with sevoflurane, desflurane or propofol infusion. METHODS: Fifty-seven ASA I-II patients undergoing elective abdominal surgery were enrolled in this study. Anaesthesia was induced with thiopental 3-5 mg kg(-1) or propofol 2.5 mg kg(-1) and fentanyl 5 microg kg(-1) and tracheal intubation was facilitated with rocuronium 0.9 mg kg(-1). Thereafter patients were randomly allocated to three different groups to receive sevoflurane, desflurane or propofol for maintenance of anaesthesia. Recovery of neuromuscular function was monitored by single twitch stimulation of the ulnar nerve and by recording the adductor pollicis response using accelerometry. Intergroup recovery times to 5% of control value of single twitch were analysed using analysis of variance with Bonferroni correction. RESULTS: The mean (95% confidence interval) recovery time to 5% of control value of single twitch during desflurane anaesthesia was 90.18 (86.11-94.25) min. Significantly shorter recovery times were observed during sevoflurane or propofol anaesthesia, 58.86 (54.73-62.99) min and 51.11 (45.47-56.74) min, respectively (P < 0.001). There were also significant differences in the recovery time between groups receiving desflurane vs. sevoflurane (P < 0.001) and desflurane vs. propofol (P < 0.001). CONCLUSIONS: Desflurane anaesthesia significantly prolongs the duration of action of rocuronium at 0.9 mg kg(-1) single bolus dose, compared to sevoflurane or propofol anaesthesia maintenance regimens.     

Total intravenous anaesthesia using propofol infusion--50 consecutive cases

Fifty consecutive patients in the authors' practice were anaesthetised with a total intravenous technique using propofol infusion, fentanyl, vecuronium and oxygen in air. Patients were predominantly elderly and undergoing major upper gastrointestinal surgery for a mean duration of 133 minutes (range 20 minutes to 7 hours). Twenty-one patients had significant concomitant medical illness. Propofol was found to give a rapid, smooth induction with wide variation in dose requirement (0.5 to 2.9 mg/kg). There was a mean systolic blood pressure fall of 27% from preoperative values, greatest in elderly patients. Depth of anaesthesia was readily adjusted by alteration in infusion rate according to standard clinical criteria. The dose of propofol required for maintenance was highly variable (range 2-15 mg/kg/hr in the first hour). Three patients reported dreaming and two of these had shown signs of light anaesthesia. Recovery was rapid, with few side-effects, and a mean time to open eyes on command of 8.5 minutes from the end of infusion. Propofol was considered to be a satisfactory intravenous agent for the induction and maintenance of anaesthesia in the majority of patients studied. The most significant problem was hypotension following the induction dose.     

Recovery after anesthesia with propofol in otorhinolaryngologic surgery of brief duration

This study was designed to assess recovery from total intravenous anaesthesia with propofol for short ENT procedures. Twenty-six patients (ASA I and II) were assigned to two groups of thirteen: one breathed air (Laser laryngeal microsurgery), the second N2O-O2 (FIO2 : 0.5) (various ENT procedures). The induction sequence was exactly the same for both groups: oral premedication with 10 mg diazepam one hour before surgery, I mg pancuronium bromide, 2 micrograms X kg-1 fentanyl, denitrogenation within 3 min, after which propofol was delivered (2.5 mg X kg-1). When the eye-lash reflex had disappeared (time recorded), 1.5 mg X kg-1 suxamethonium was given and laryngotracheal intubation carried out. A continuous infusion of propofol (9 mg X kg-1 X h-1) was started. Surgery began 5 +/- 2 min after the start of propofol infusion. The durations of anaesthesia, surgery and propofol infusion were similar in both groups. To have good surgical conditions, it was necessary to give repeated doses of propofol for 15 patients. Thus, the total dose of propofol was significatively different between the two groups: 24.5 +/- 6.7 mg X kg-1 X h-1 in group "air" versus 16 +/- 3.6 mg X kg-1 X h-1 in group "N2O-O2" (p less than 0.001). Extubation occurred within 16 +/- 8 min in group "air", being more rapid in group "N2O-O2" (11 +/- 9 min; no significant difference). Recovery was assessed with two psychomotor tests: choice reaction time (CRT) and tracing test (TT).(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of different doses of remifentanil on the cardiovascular response to laryngoscopy and tracheal intubation

We have compared three bolus and infusion regimens of remifentanil on the cardiovascular response to laryngoscopy and orotracheal intubation in three groups of 20 ASA I-II female patients, in a randomized, double- blind study. Patients in group 1 received glycopyrolate 200 micrograms i.v. followed by a bolus dose of remifentanil 1 microgram kg-1 over 30 s and an infusion of remifentanil at a rate of 0.5 microgram kg-1 min- 1. The other patients received remifentanil 0.5 microgram kg-1 over 30 s and an infusion of 0.25 microgram kg-1 min-1 with (group 2) or without (group 3) pretreatment with glycopyrrolate 200 micrograms. All patients then received a sleep dose of propofol, rocuronium 0.6 mg kg-1 and 1% isoflurane with 67% nitrous oxide in oxygen. Laryngoscopy and tracheal intubation were performed 3 min later. Heart rate and arterial pressure were recorded at 1-min intervals from before induction of anaesthesia until 5 min after intubation. Baseline heart rate was similar in all groups, but decreased in group 3 (no glycopyrrolate) after induction and remained significantly lower after intubation compared with the other groups (P < 0.05). Heart rate and arterial pressure increased slightly after intubation in each group but there were no significant differences in mean arterial pressure between groups at any time. The incidence of bradycardia (one patient in group 2) and hypotension (two patients in groups 1 and 2 and three patients in group 3) was low.      

Use of propofol in anesthesia in cardiac surgery. Preliminary results

Nine patients, all NYHA class III and IV, who were to undergo surgery with cardiopulmonary bypass, were divided into two groups. All nine were premedicated with 2 mg flunitrazepam orally 90 min before surgery. Group A consisted in five men, mean age 53 years (extremes: 43 and 73), with no significant difference in weight and body surface area, who were to undergo aortic valve replacement (2), mitral valve replacement (2), and aortic and mitral valve replacement (1). They were given 1.5 mg X kg-1 propofol as a bolus at induction, followed by an infusion of 50 micrograms X kg-1 X min-1 propofol. Group B consisted in four patients, two men and two women, mean age 60 years (extremes: 49 and 76), with no significant difference in weight and body surface area, who were to undergo aortic valve replacement (3) and corrective surgery for left ventricular aneurysm (1). They were given 2 mg X kg-1 propofol as a bolus at induction, followed by an infusion of 100 micrograms X kg-1 X min-1 propofol. All the patients were intubated after 0.1 mg X kg-1 pancuronium; they were given 10 micrograms X kg-1 before intubation and 10 micrograms X kg-1 before skin incision. Repeat doses of fentanyl and pancuronium were given as required. The haemodynamic parameters studied were: heart rate, systolic, diastolic and mean blood pressures, central venous pressure, mean pulmonary pressure, wedge pressure, and cardiac output measured by thermodilution. The following indices were calculated: cardiac index, systolic index, right and left systolic work indices, and pulmonary and systemic vascular resistances.(ABSTRACT TRUNCATED AT 250 WORDS)     

Propofol emulsion for induction and maintenance of anaesthesia. A combined technique of general and regional anaesthesia

To provide general anaesthesia with endotracheal intubation during regional blockades, three dose regimens of propofol emulsion were studied: induction 2 mg kg-1, infusion rate 9 mg kg-1 h-1 (Group 1); induction 2.5 mg kg-1, infusion rate 12 mg kg-1 h-1 (Group 2); induction 2.5 mg kg-1, infusion rate 9 mg kg-1 (Group 3). Each group comprised 10 healthy (ASA class 1 or 2) unpremedicated patients. The induction times measured from the start of injection until counting ceased (+/- 50 s) and until eye-lash reflex disappeared (+/- 80 s) showed no statistical differences between groups. In five patients in Group 1 and one patient in each of Groups 2 and 3 the induction dose was too low for intubation. Pain on injection was seen in 13 cases (mild 6, moderate 6 and severe 1). Cough accompanied by hypersalivation was the most important side-effect. Recovery times varied widely and showed no statistical differences. Answering simple questions was possible after 14 min in Group 1, 23 min in Group 2 and 19 min in Group 3. Apart from a short period of euphoria, recovery was uneventful. There was no tendency to fall asleep again. None of the combinations of induction doses and infusion rates provided good anaesthesia conditions for an acceptable number of patients.     

Effects of propofol on intraocular pressure in surgery of strabismus in children

Propofol was assessed for eye surgery in 20 children. ASA group I or II, 2-14 year-old, randomly assigned to 2 equal groups. Premedication, analgesia and muscle paralysis were similar in both groups. Group P patients were given an induction dose of 4 mg.kg-1 propofol, followed by an infusion of 15 mg.kg-1.h-1 for the first half hour, and then 10 mg.kg-1.h-1 to maintain anaesthesia. Group C patients were given 10 mg.kg-1 thiopentone for induction and halothane for maintenance. The quality of anaesthesia was assessed by monitoring adverse effects, heart rate, blood pressure, the length of anaesthesia, the delay of the first spontaneous breath and eye opening, and extubation. Intraocular pressure was measured before and 3 min after intubation, and 5 min after extubation. The quality of anaesthetic induction and maintenance were very similar in both groups. Pain occurred more frequently at the injection site with propofol (p less than 0.01). Children in group P recovered more quickly, and extubation was possible much earlier in this group (p less than 0.05). However, restlessness was significantly more frequent in group P (n = 9) than in group C (n = 1) (p less than 0.01). Systolic, diastolic blood pressure and heart rate were significantly lower in group P (p less than 0.05; 0.001; 0.001 respectively). No significant decrease in intraocular pressure in both groups was observed. The use of propofol for eye surgery in children is acceptable, despite some restlessness during recovery.     

Effect of remifentanil on the haemodynamic response to orotracheal intubation

We have examined the effect of remifentanil on the haemodynamic response to orotracheal intubation in a randomized, double-blind study. We studied 40 patients allocated to one of four groups of 10 each, to receive the following immediately before induction of anaesthesia: remifentanil 1 microgram kg-1 bolus over 30 s, followed by an infusion of 0.5 microgram kg-1 min-1; saline placebo only; glycopyrrolate 200 micrograms and remifentanil 1 microgram kg-1 bolus over 30 s, followed by an infusion of 0.5 microgram kg-1 min-1; or glycopyrrolate 200 micrograms only. Anaesthesia was induced with propofol, vecuronium and 1% isoflurane with 66% nitrous oxide in oxygen. The trachea was intubated under direct laryngoscopy 3 min after induction of anaesthesia. Arterial pressure and heart rate were measured non- invasively, immediately before induction of anaesthesia and then at 1- min intervals. Remifentanil was found to effectively attenuate the pressor response to intubation (P < 0.05 for the increase in mean arterial pressure; P < 0.01 for the increase in heart rate). In the absence of a concurrent vagolytic agent, remifentanil was associated with bradycardia or hypotension, or both, in five of 10 patients, compared with one patient who received remifentanil and glycopyrrolate.      

Propofol auto-co-induction as an alternative to midazolam co-induction for ambulatory surgery

We propose the use of an intravenous propofol/propofol auto-co-induction technique as an alternative to propofol/midazolam for induction of anaesthesia. We have studied 54 unpremedicated ASA 1 or 2 patients undergoing day-stay anaesthesia for minor orthopaedic surgery. All received 10 micrograms.kg-1 or alfentanil before induction, followed by either midazolam 0.05 mg.kg-1, propofol 0.4 mg.kg-1 or saline, and 2 min later, a propofol infusion at a rate of 50 mg.kg-1.h-1 until loss of eyelash reflex. We compared pre- and postinduction haemodynamic changes, complications at insertion of a laryngeal mask airway and recovery from anaesthesia in the three groups. Both co-induction techniques showed less postinduction hypotension and significant reduction of the total induction dose of propofol when compared to the control group. In the propofol/propofol group there was a decreased incidence of apnoea during induction of anaesthesia. These patients were discharged from hospital 2 h after the end of anaesthesia whereas patients in the midazolam/propofol group were discharged after 2 1/2 h (p < 0.001).     

Prediction of the maintenance dose of vecuronium for continuous infusion]

The purpose of this study is to examine how to predict the optimal maintenance dose of vecuronium for continuous infusion, knowing the recovery time from the block induced by the first bolus injection. All patients studied were undergoing surgical procedures and were anesthetized using thiopental, vecuronium, 50% nitrous oxide and 2% enflurane in oxygen. Mechanical twitch responses of adductor pollicis muscle caused by the stimulation of the ulnar nerve supramaximally were monitored. Vecuronium concentrations in the plasma were measured using high performance liquid chromatography. The experiments consisted of two phases. Phase 1.: To demonstrate the relationship between the recovery time (T0-T25) and the maintenance dose. Thirty patients were studied in this phase. A bolus injection was given as the first dose (1.5 mg.kg-1). During the recovery from the first block, recovery time (T1) was measured and the second dose (2 mg) was injected at the T25 (25% control twitch height). After waiting the recovery until the T25, the third dose (2 mg) was injected. The duration (T2) (min) between the second and the third injection was measured. The maintenance dose-recovery time curve was obtained. Y = 52.70.exp (-17.50 X) + 1224.53.exp (-224.27X), X = recovery time (min), Y = maintenance dose (mg.hr-1). Phase 2.: Thirty patients were studied in this phase. Patients received infusions after the bolus injection. The infusion rates were obtained from the maintenance dose-recovery time curve.(ABSTRACT TRUNCATED AT 250 WORDS)