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.     

Propofol for intravenous sedation

This study investigated the properties of propofol when given by subanaesthetic infusion to provide sedation as an adjunct to spinal anaesthesia for lower limb surgery in 40 patients. Sedation, defined as sleep with preservation of eyelash reflex and purposeful reaction to verbal or mild physical stimulation, was satisfactorily achieved and maintained with minimal complications. The mean duration of infusion was 98 minutes and a mean infusion rate of 3.0 mg/kg/hour was required in patients over 65. This was significantly less (p less than 0.005) than the 4.1 mg/kg/hour required in younger patients. Recovery was impressively rapid; patients regained full consciousness approximately 4 minutes after the end of infusion, and were free from minor postoperative sequelae. Conversion to general anaesthesia was achieved in three patients where surgery encroached outside the analgesic field of the regional block, simply by increasing the infusion rate to approximately 10 mg/kg/hour.     

Anaesthesia for laparoscopy: alfentanil and fentanyl compared

A double blind comparison was made between alfentanil and fentanyl as analgesic components of anaesthesia. Sixty-six women undergoing laparoscopy received methohexitone, alcuronium, nitrous oxide and oxygen, with either alfentanil 0.75 mg or fentanyl 0.25 mg. Ten of the patients who received alfentanil and 1 patient who received fentanyl required supplementation of anaesthesia by enflurane. Recovery from anaesthesia was similar in the two groups of patients though the onset of spontaneous breathing occurred more quickly after alfentanil (P less than 0.002). The injection of fentanyl was followed by a fall in BP (P less than 0.05) and the mean minimum value for pulse rate occurring after fentanyl was slower than after alfentanil (P less than 0.05).     

Alfentanil used to supplement propofol infusions for oesophagoscopy and bronchoscopy

This randomised double-blinded study compared the cardiovascular stability and rate of recovery when propofol infusions with or without alfentanil were used to provide anaesthesia for rigid oesophagoscopy and (or) bronchoscopy. Forty-six patients were allocated randomly to receive either alfentanil 10 micrograms/kg or saline just before a rapid sequence induction with propofol. Suxamethonium 1 mg/kg was given and infusions of suxamethonium 10 mg/minute and propofol (10 mg/kg/hour for 10 minutes, 8 mg/kg/hour for 10 minutes and then 6 mg/kg/hour thereafter) were started. There were 23 patients in each group with no significant demographic differences between the groups. A significantly mean lower induction dose of propofol was needed in the alfentanil group (1.7 mg/kg compared to 2.2 mg/kg). Cardiovascular measurements were made on the ward pre-operatively, just before induction, just after induction, just after intubation, and at 3-minute intervals thereafter. Arterial pressure was significantly lower during the procedure in the patients who received alfentanil and there was a significant incidence of hypotension. There was no significant difference between the groups in respect of heart rate, with a significant increase in both groups just after intubation compared to the baseline values. Recovery from anaesthesia was assessed using the critical flicker fusion threshold. No differences were found between the groups and patients in both groups had returned to baseline values by 60 minutes. No patient had any recall of intra-operative events, and there were no other adverse effects of any significance.     

Intravenous anaesthesia with propofol and alfentanil. The influence of age and weight

Sixty healthy patients undergoing body surface surgery were anaesthetised with continuous infusions of propofol (200 micrograms/kg/minute) and alfentanil (0.25 microgram/kg/minute). Additional bolus doses of propofol (20 mg) were given if movement occurred. The incidence of patient movement in response to skin incision was significantly less in patients over 45 years of age than in those below 45 years (p less than 0.05). Maintenance dosage of propofol sufficient to abolish movement decreased with increasing age (p less than 0.001). Systolic blood pressure decreased in most patients over the first 10 minutes of anaesthesia and the magnitude of this decrease increased with age (p less than 0.0001). These parameters did not correlate strongly with body weight. Dose requirements of propofol are not the same for patients of all ages and strongly suggest that young and old patients should not be treated as a homogeneous group, either for investigative or clinical purposes.     

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).     

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)     

Intravenous infusion of propofol for induction and maintenance of anaesthesia during endoscopic carbon dioxide laser ENT procedures with high frequency jet ventilation

Fourteen patients of ASA grades 1 3 were anaesthetised with continuous infusions of propofol and alfentanil for endoscopic carbon dioxide laser ENT microsurgery. Their lungs were ventilated with an oxygen-air mixture using a high frequency jet ventilator. Propofol was given at an initial rate of 120 μg/kg/minute for 10 minutes after a bolus dose of 2.6 mg/kg, and then at 80 fig μg/kg/minute. Alfentanil was given at a rate of 0.5 μg/kg/minute. Arterial pressure decreased significantly after the bolus dose. It increased significantly for a few minutes after laryngoscopy and returned to baseline values during maintenance of anaesthesia. Heart rate increased significantly during induction and until laryngoscopy was performed but it decreased below its initial value after 5 minutes of maintenance. Platelet count and the degree of aggregation did not change during infusion of propofol.     

The haemodynamic effects of bronchoscopy Comparison of propofol and thiopentone with and without alfentanil pretreatment

The haemodynamic response to bronchoscopy under general anaesthesia was investigated. Forty patients were allocated at random to receive either thiopentone or propofol; half the patients in each group received in addition 18 micrograms/kg of alfentanil one minute before induction of anaesthesia. The heart rate, noninvasive blood pressure and Holter ECG was monitored in all patients. Significant increases in heart rate (p less than 0.05), systolic and diastolic arterial pressures (p less than 0.01) occurred in the thiopentone only group, following bronchoscopy. Systolic and diastolic arterial pressure decreased in patients receiving thiopentone plus alfentanil, following induction of anaesthesia and laryngoscopy (p less than 0.05). No significant haemodynamic changes were seen in either of the groups which received propofol. ST segment changes on subsequent Holter analysis were seen in four patients, but there were no significant differences between the groups. Anaesthesia with propofol alone provides adequate haemodynamic stability for bronchoscopy and the addition is superfluous.     

Does obesity affect recovery?

One hundred and twenty unpremedicated patients, scheduled for minor gynaecological procedures, were randomly allocated to receive Althesin or methohexitone to supplement N2O and O2 anaesthesia. Patients were assessed as thin, medium or fat according to the degree of obesity as measured by skinfold calipers. The range of mean times for the patients to open their eyes was 3.1-4.0 minutes, to be orientated was 4.4-6.7 minutes and to perform a manipulative test was 27.7-32.1 minutes. No statistically significant differences were seen in these indices of recovery whether they received Althesin or methohexitone or whether they were thin, medium or fat. A paper and pencil test was also performed. Induction doses of the intravenous agent were calculated on a body weight basis and increments given only in response to movement. The mean total dose of Althesin was decreased from 1.33 mg total steroid/kg for thin patients to 1.06 mg total steroid/kg for fat patients (p less than 0.01). The mean total dose of methohexitone was decreased from 3.4 mg/kg for thin patients to 2.9 mg/kg for fat patients which was not significant.     

Comparison of etomidate and propofol for anaesthesia in microlaryngeal surgery

Propofol and etomidate were compared as hypnotics in total intravenous anaesthesia for microlaryngeal surgery combined with jet ventilation. Two groups of 15 patients were studied. In group 1, propofol 2.0 mg/kg was used for induction. For maintenance a continuous infusion of 12 mg/kg/hour was used for the first 10 minutes, followed by 9 mg/kg/hour for the next 10 minutes and 6 mg/kg/hour thereafter. In group 2, the induction dose of etomidate was 0.3 mg/kg followed by continuous infusion of 1.8 mg/kg/hour for 10 minutes, 1.5 mg/kg/hour for the next 10 minutes and 1.0 mg/kg/hour thereafter. Alfentanil was given for analgesia and suxamethonium for muscle relaxation. The propofol group showed better surgical conditions, more stable anaesthesia and better recovery according to the Steward score. Recovery times to opening eyes on command were comparable for both groups.     

Alfentanil in short procedures

Ninety patients, premedicated with temazepam 20 mg, undergoing suction termination of pregnancy, were studied. Forty patients received alfentanil (500 micrograms), and thirty halothane (1.5%) as supplements to either etomidate or methohexitone-nitrous oxide-oxygen anaesthesia. A further 20 patients received alfentanil 250 micrograms at induction of anaesthesia with methohexitone, followed by a further 250 micrograms immediately prior to the onset of surgery. Recovery was assessed by the time patients took to open eyes on command, to giving their correct date of birth, and to performing the 'p' deletion test. Satisfactory operating conditions were not obtained with the combination of etomidate and halothane. Faster recovery was seen in patients with either etomidate or methohexitone and receiving alfentanil (p less than 0.01) Testing by the 'p' deletion test showed impaired psychomotor performance at 30 minutes after cessation of anaesthesia in all groups compared with the pre-operative scores. Side effects leading to unsatisfactory anaesthesia were more frequent in patients who had received etomidate (p less than 0.01).     

Total intravenous anaesthesia for direct laryngoscopy: propofol infusion compared to thiopentone combined with midazolam and methohexitone infusion

Total intravenous anaesthesia for direct laryngoscopy was investigated in 40 patients, randomized into four groups of 10 patients each. First, propofol infusion was compared to thiopentone combined with midazolam. Next, a comparison of propofol infusion with methohexitone infusion was undertaken. The propofol group showed significantly lower peroperative blood pressure compared to the thiopentone/midazolam group. The second propofol group required significantly less alfentanil to stabilize the blood pressure, compared to the methohexitone group. Completeness of recovery, assessed by means of a coin counting test, was faster in the propofol group compared to the thiopentone/midazolam group, while no difference could be demonstrated between the second propofol group and the methohexitone group. It is concluded that propofol seems to be superior to both thiopentone/midazolam and methohexitone with respect to the stability of peroperative blood pressure. Concerning recovery, propofol is superior to thiopentone/midazolam, but offers no advantage over methohexitone.     

Muscular rigidity caused by alfentanil: prevention

We studied three groups of 30 patients each, undergoing minor orthopaedic surgery, anaesthetized with alfentanil (30 micrograms/kg bolus followed by an infusion of 0.3 micrograms/kg/min), thiopental 3 mg/kg and 70% N2O via facial mask. Patients in group I were treated, three minutes before induction, with vecuronium 0.02 mg/kg i.v., while those in group II were premedicated with diazepam 0.15 mg/kg i.m. 30-45 minutes before induction. Group III served as control. Muscular rigidity was evaluated clinically with a subjective score based on a scale of 0 (no rigidity) to 3 (severe rigidity). Diazepam did not give significant protection from muscular rigidity. Vecuronium administration did not significantly reduced the number of patients who became rigid, but significantly decreased the incidence of severe rigidity (p less than 0.005), the mean rigidity score (p less than 0.05) and the incidence of rigidity at the induction of anaesthesia (p less than 0.0005). We also observed a progressively increasing incidence of rigidity with increasing age (not significantly) and body weight (p less than 0.05 total rigidity, p less than 0.01 severe rigidity).     

Propofol combined with nitrous oxide-oxygen for induction and maintenance of anaesthesia

After a bolus of 2 mg/kg, propofol was given by continuous infusion (150 micrograms/kg/minute for 30 minutes and then 100 micrograms/kg/minute) supplemented with nitrous oxide for anaesthesia during ear surgery in 12 patients. Cardiovascular changes were not significant except for a decrease in heart rate after 60 minutes. Acid-base balance was unaffected by the amount of fatty emulsion. Cortisol levels showed a nonsignificant decrease during the prolonged administration of propofol but had recovered completely by one hour following anaesthesia. Mean blood concentrations of propofol were 10.5 micrograms/ml (SEM 1.2) at the onset of unconsciousness, between 3.4 and 4.5 micrograms/ml during continuous infusion and 2.9 micrograms/ml (SEM 0.3) on awakening. Patients opened their eyes 6 minutes (SEM 1) after discontinuation of the infusion, and were responsive at 7.5 minutes (SEM 0.5), which suggests that propofol infusion can be used safely for surgery of 2 hours' duration.     

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.     

Alfentanil v. isoflurane for outpatient arthroscopy

Alfentanil by continuous intravenous infusion and isoflurane have been compared as anaesthetic agents for outpatient arthroscopy. In 42 patients, divided at random into two groups, anaesthesia was induced with methohexitone and vecuronium bromide, and, after intubation, maintained with nitrous oxide 66% in oxygen combined with alfentanil or isoflurane. Alfentanil was given before intubation (1 mg), as a loading dose before starting surgery (50 micrograms kg-1) and by a continuous infusion at a rate of 1 microgram kg-1 min-1. Isoflurane was given in a concentration of 0.9% as a maintenance dose. Awakening from anaesthesia was more rapid with alfentanil than with isoflurane. Recovery tests were applied in the recovery room. Both anaesthetic techniques provided satisfactory anaesthesia and rapid recovery. All patients but one were content with the anaesthesia. The patients who received isoflurane scored better in the recovery tests in the first 3 h, but after 3 h there was no difference between the groups. The alfentanil group showed a higher incidence of nausea and/or vomiting: 45% compared to 14% in the isoflurane group.     

A comparison of alfentanil requirements in European and Asian patients during general anaesthesia

Alfentanil requirements were compared in thirty-six Asian and forty-three European patients during general anaesthesia with muscle relaxants. Alfentanil infusion at 5 micrograms/kg/min was started immediately after induction with thiopentone and alcuronium. The infusion rate was reduced to 0.5 microgram/kg/min after ten minutes. An incremental dose of 5 micrograms/kg/min for five minutes was given on each occasion when anaesthesia was clinically judged to be inadequate. Recovery parameters were recorded. Pharmacokinetics were also studied in five Europeans, four Chinese and four Nepalese. The dosage of alfentanil required was comparable in both Asian and European patients, but recovery was slower in the Asian patients. The elimination half-life in the Chinese and the Nepalese were both significantly shorter than that of the Europeans (P less than 0.05), but at the time of recovery of spontaneous ventilation, the mean plasma concentrations were not significantly different.     

Effects of dose and concentration of rectal methohexitone for induction of anaesthesia in children

To investigate the effect of dose and concentration of rectal methohexitone for induction of anaesthesia, 60 children (ASA physical status 1 or 2) undergoing outpatient surgery were studied. Each child was randomly assigned to receive one of three rectal solutions (each containing atropine 0.02 mg X kg-1): Group A - ten per cent methohexitone, 25 mg X kg-1 (n = 20); Group B - ten per cent methohexitone, 15 mg X kg-1 (n = 20); or Group C - one per cent methohexitone, 15 mg X kg-1 (n = 20). After induction of anaesthesia, or a maximum period of 20 minutes following rectal administration of methohexitone, halothane, nitrous oxide, and oxygen were administered by mask. The time to induction of anaesthesia, complications, postanaesthetic recovery scores, and recovery time did not differ significantly among the three groups. The incidence of failed inductions did not differ significantly between Group A (zero per cent) and Group C (ten per cent) but both were significantly less than Group B (45 per cent) (p less than 0.05). Heart rate increased significantly between 10 and 30 minutes after rectal administration of methohexitone and atropine. The authors conclude that ten per cent rectal methohexitone 25 mg X kg-1 and one per cent rectal methohexitone 15 mg X kg-1 are equally effective for induction of anaesthesia in children and both are significantly more effective than ten per cent methohexitone 15 mg X kg-1.     

Effect of methohexitone and propofol with or without alfentanil on seizure duration and recovery in electroconvulsive therapy

We have studied the effects of methohexitone and propofol with and without alfentanil on seizure duration and recovery in this observer- blinded, prospective, randomized, crossover study involving 24 patients undergoing electroconvulsive therapy (ECT). Each patient had four treatment sessions, and received the following four i.v. regimens in random order: methohexitone 0.75 mg kg-1, methohexitone 0.50 mg kg-1 and alfentanil 10 micrograms kg-1, propofol 0.75 mg kg-1, propofol 0.50 mg kg-1 and alfentanil 10 micrograms kg-1. Additional methohexitone or propofol was given as needed in 10-20-mg increments until loss of consciousness. Suxamethonium 1.0 mg kg-1 i.v. was given for muscular paralysis. Mean motor and EEG seizure durations were longer with methohexitone-alfentanil (44.7 (SD 15.0) and 70.5 (29.7) s) than with methohexitone (37.6 (12.6) and 52.6 (15.3) s) and similarly, seizures were longer with propofol-alfentanil (36.8 (15.2) and 54.5 (20.9) s) than with propofol alone (27.2 (11.9) and 39.2 (3.9) s). Seizures were longest with methohexitone-alfentanil and shortest with propofol. Recovery time was statistically shorter in patients receiving propofol compared with methohexitone-alfentanil and methohexitone alone. Alfentanil with a reduced dose of methohexitone or propofol provided unconsciousness and increased seizure duration in patients undergoing ECT. We conclude that the combination of methohexitone with alfentanil is a good regimen for ECT, especially for patients with short seizure duration.