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)     

Total intravenous anaesthesia with propofol or inhalational anaesthesia with isoflurane for major abdominal surgery: Recovery characteristics and postoperative oxygenation—an international multicentre study

Two hundred and ten adult patients undergoing open cholecystectomy, vagotomy or gastrectomy were included in a randomised multicentre study to compare postoperative nausea and vomiting, oxygen saturations for the first three postoperative nights, time to return of gastrointestinal function, mobilisation, and discharge from the hospital following induction and maintenance of anaesthesia with propofol and alfentanil or with thiopentone, nitrous oxide, isoflurane and alfentanil. Recovery from anaesthesia was significantly faster in the propofol group (mean (SD) times to eye opening and giving correct date of birth of 14.0 (SD 13.8) and 25.5 (SD 29.5) minutes, and 18.5 (SD 14.8) and 35.5 (SD 37.2) minutes in the propofol and isoflurane groups respectively). There was significantly less nausea in the propofol group (15.4%) than in the isoflurane group (33.7%) in the first two postoperative hours (p < 0.003) but not thereafter. There were no significant differences between the groups in any other recovery characteristics. The incidence of hypoxaemia (arterial oxygen saturation less than 93%) was close to 70% in both groups for the first three postoperative nights, indicating the need for oxygen therapy after major abdominal surgery.     

Anaesthesia for laparoscopy

This is a report about five anaesthetic techniques for laparoscopy. Propofol and etomidate were used for total intravenous anaesthesia. Propofol, etomidate and thiopentone were used as induction agents prior to inhalational anaesthesia with isoflurane and nitrous oxide. Fentanyl was used for analgesia. Induction with propofol and thiopentone was rapid. Etomidate induction was characterised by myoclonus. Maintenance was smooth with inhalational anaesthesia. Of the groups that received total intravenous anaesthesia, propofol provided stable anaesthesia but required extra bolus doses. Recovery was the most rapid following total intravenous anaesthesia with propofol. Postoperative side effects were much lower after propofol. No difference was observed between the groups with regard to changes in arterial blood pressure and heart rate.     

Patient maintained sedation for colonoscopy using a target controlled infusion of propofol

In this study, we evaluated safety and recovery using a patient maintained, target controlled infusion of propofol for sedation in 20 patients undergoing colonoscopy. Using a handset with a two-minute lockout interval, patients could make 0.2 micro g.ml(-1) increments to an initial target plasma concentration of 1 micro g.ml(-1) up to a maximum 4.5 micro g.ml(-1). Four patients became oversedated but required no airway or circulatory interventions. Subjects had a significant reduction in mean (SD) heart rate: 78.7 (15) vs. 69.8 (13.5) (p < 0.001) and in systolic blood pressure 121.1 (13.2) mmHg vs. 96.5 (8.6) mmHg (p < 0.001). Choice reaction time testing 15 min after colonoscopy showed a significant median (IQR [range]) rise of 162 (- 16, 383.3 [-199-859]) ms (p < 0.05). Six patients had faster reaction times postcolonoscopy. All patients denied unpleasant recall and were satisfied with the system. Although oversedation was a problem in this model, we conclude that patient maintained propofol sedation could be possible for colonoscopy.     

Ketamine as analgesic for total intravenous anaesthesia with propofol

A prospective study of 18 patients who underwent noncardiac surgery was performed to study the use of ketamine as an analgesic during total intravenous anaesthesia with propofol. A comparison was made with the combination propofol/fentanyl. The propofol/ketamine combination resulted in haemodynamically stable anaesthesia without the need for additional analgesics. Postoperative behaviour was normal in all patients and none of the patients reported dreaming during or after the operation. Propofol seems to be effective in eliminating side effects of a subanaesthetic dose of ketamine in humans. We recommend the propofol/ketamine combination for total intravenous anaesthesia for surgery when stable haemodynamics are required.     

Setting targets for sedation with a target-controlled propofol infusion

We studied 30 unpremedicated patients undergoing muscle biopsy under femoral nerve block to determine sedation levels reached with a Diprifusor target-controlled propofol infusion, in order to establish the equivalent of the ED50 for different levels of depth of sedation. Infusion was started at 0.8 microg x ml(-1) and altered by increments of 0.1 microg x ml(-1) after equilibrium between target and calculated concentrations, until the desired level of sedation was reached. The ED50 target propofol concentrations for sedation at sedation levels 2 (drowsy), 3 (drowsy, responds to verbal stimulation) and 4 (responsive to physical stimulation only) were 1.0 microg x ml(-1), 1.6 microg x ml(-1) and 2.1 microg x ml(-1), respectively. At sedation level 3, several patients exhibited spontaneous movement, hindering surgery. Oxygen supplementation is recommended for sedation at level 4.     

Sensitivity to propofol in the elderly

Two studies were carried out on 609 fit, unpremedicated patients to assess the influence of patient age on the response to the rapidly-acting hindered phenol, propofol, which is being evaluated for induction of anaesthesia. In the first study, 1.25 mg/kg was injected over 20 seconds followed by 10-mg increments every 15 seconds until loss of verbal contact. This showed a great individual variation in response to the drug. A reduction in the 'induction' dose was found in elderly patients, which became marked around 60 years. In the second (340), doses ranging from 1.5-3.0 mg/kg in patients under 60 years and 1.25-2.25 mg/kg in those over 60 years were injected as a bolus over 20 seconds. Doses of 2.25-2.5 mg/kg were required to induce anaesthesia in patients under 60 years, whilst 1.5-1.75 mg/kg was adequate in those over 60 years. Side effects were more marked with the rapid injection and doses in excess of 1.75 mg/kg caused significant hypotension and apnoea in the elderly. These studies reveal marked sensitivity to propofol in the elderly with respect to both induction dose and acute toxicity.     

Conditions for laryngeal mask insertionA comparison of propofol versus sevoflurane with or without alfentanil

One hundred unpremedicated ASA 1 or 2 patients scheduled for elective surgery were divided equally into four groups and recruited into this prospective, randomised parallel groups study. Induction was with propofol 2.5 mg.kg-1 or vital-capacity breath induction with sevoflurane (> 7% in the inspiratory gas) in 65% nitrous oxide and oxygen, or gaseous induction with sevoflurane plus alfentanil 5 micrograms.kg-1 or propofol 2.5 mg.kg-1 and alfentanil 5 micrograms.kg-1. The conditions for laryngeal mask insertion were assessed and graded on a three-point scale using six variables. The overall condition for laryngeal mask insertion was assessed as excellent, satisfactory or poor on the basis of total score in each group. Excellent or satisfactory conditions were observed in 25 (100%) patients in the sevoflurane-alfentanil group, 22 (88%) in the propofol-alfentanil group and 16 (64%) patients each in the propofol and sevoflurane groups (p < 0.001). A sevoflurane-alfentanil combination provides better conditions for laryngeal mask insertion when compared with sevoflurane alone, or a propofol-alfentanil combination.     

Propofol infusion for sedation in outpatient oral surgery

An infusion of propofol was compared with intravenous boluses of diazepam as sedation for minor oral surgery under local anaesthesia in 12 healthy patients who had elective bilateral surgical extraction of lower third molars; the patients served as their own controls. Plasma catecholamine, vasopressin and cortisol concentrations were determined from repeated blood samples. The total administered dose of propofol was 3.93 (SD 1.34) mg/kg and of diazepam 0.28 (SD 0.07) mg/kg. No cardiovascular depression or airway problems occurred. Other side effects were also rare but some discomfort on injection was frequent with propofol. Recovery times were faster after propofol than after diazepam as assessed by the Maddox wing and visual analogue scales. Propofol also provided better amnesia compared to diazepam at the time of the extraction of the teeth. Eight of the 12 patients subjectively preferred propofol sedation. There was no hormonal stress response in either group.     

Isoflurane and propofol for long-term sedation in the intensive care unit

Propofol and isoflurane have been reported recently to offer better sedation than alternative agents in patients who require long-term ventilation in the Intensive Care Unit. This is the first report of a direct comparison between propofol and isoflurane. Twenty-four patients predicted to require artificial ventilation for at least 48 h were entered into a randomised crossover study to monitor sedation quality and time to recovery from sedation. There were no significant differences between the two agents in either end-point, with over 95% optimal sedation achieved by the use of each drug. Few adverse events were noted. Technological advances in the administration of volatile agents as long-term sedatives in the Intensive Care Unit may facilitate their more widespread use.     

Comparison of propofol and methohexitone as anaesthetic agents for electroconvulsive therapy

Propofol was compared to methohexitone for induction of anaesthesia for electroconvulsive therapy. Seizures were significantly shorter after the use of propofol, in respect of both visible seizures and duration of cerebral electrical seizure activity. This suggests the possibility that additional treatments may be needed for the same clinical effect in psychiatric illness when propofol is used as the induction agent. Propofol was more effective than methohexitone at obtunding the hypertensive response to electroconvulsive therapy without causing significant hypotension.     

The effect of co-induction with midazolam upon recovery from propofol infusion anaesthesia

Forty-eight patients undergoing day-case anaesthesia were asked to complete pre- and postoperative tests of psychomotor function in order to study the influence of co-induction with midazolam in conjunction with propofol/alfentanil anaesthesia on postoperative psychomotor recovery. The study was placebo controlled and double blind with patients receiving either 0.03 mgkg⁻¹ of midazolam or saline 2 min before induction of anaesthesia with propofol and alfentanil. Patients who underwent co-induction with midazolam had significantly impaired concentration and rapidity of response but improved accuracy and vigilance when compared with those who received saline. The study confirmed that co-induction with a subanaesthetic dose of midazolam reduced the induction dose of propofol by up to 50%. We conclude that co-induction with midazolam reduces psychomotor recovery in the immediate postoperative phase following propofol infusion anaesthesia.     

Intravenous propofol anaesthesia using a computerised infusion system

Propofol offers many advantages as a total intravenous anaesthetic agent compared with other agents. However, considerable experience is necessary in order to give an uncomplicated anaesthetic. A mathematical model which describes the pharmacokinetic behaviour of the drug was incorporated into a computerised delivery system which enables the anaesthetist to achieve and maintain a target blood concentration of propofol and to manipulate this at will. The system was used to provide general anaesthesia for 33 healthy patients who underwent general surgery. A strong statistical relationship was found between measured blood propofol concentrations and the corresponding computer predictions (y = -0.50 + 1.36x). No significant differences in this relationship were found between patients who breathed spontaneously (y = -0.71x + 1.43x) and those who received intermittent positive pressure ventilation (y = -0.33 + 1.32x).     

The influence of isoflurane on a continuous infusion of mivacurium

Sixty surgical patients were studied to evaluate the neuromuscular effects of mivacurium 0.l5 mg.kg^-1 (2 × ED₉₅)for tracheal intubation. After intubation the patients were randomly allocated to receive alfentanil with either propofol (starting with 9mg.kg^-1 h^-1, reducing to 6mg.kg^-1 h^-1 after 20min) or isoflurane (0.5% end-tidal). In addition, all the patients were given a continuous infusion of mivacurium 10 μg.kg^-1 min^-1 after tracheal intubation which was adjusted to maintain 90% depression of T₁. Following mivacurium 0.15 mg.kg^-1 T₁ decreased below 25% in all but four patients. Mean (SD) percentage maximum block attainedwas 92.9% (12.5) after 309 (89)s. Tracheal intubation was completed 232 (155) s after administration of the relaxant and intubating conditions were graded as‘excellent’ or‘good’ in 56 patients. Although the mean (SD) mivacurium infusion rate for maintaining T₁ at 10% was higher in the propofol group, 4.8 (2.1) compared with 4.4 (2.0) μg.kg^-1 min^-1 in the isoflurane group, this was not significantly different (p > 0.05). The mean (SD) recovery index was prolonged in the isoflurane patients, 757 (508)s, compared to those receiving propofol, 466 (219)s (p < 0.05).