[Non-specific histamine liberation and propofol]

The variations in blood pressure, heart rate and plasma histamine levels were monitored for 10 min in 40 patients at risk of releasing histamine after they had been given 2.5 mg X kg-1 propofol in oil emulsion (n = 20) or 7 mg X kg-1 thiopentone (n = 20). The measurements were carried out before anaesthesia, and 1, 2, 3, 5, 7 and 10 min after injecting the drug. All the patients were premedicated with a specific anti-H1 antagonist only (terfenadine). Histamine was measured by radio-immunology (Immunotech). Two patients from the propofol group and three from the thiopentone group showed minor signs, that may have been linked to a release of histamine. Blood pressure fell in both groups by about 20% (p less than 0.001) within the first minute, becoming stable afterwards. The heart rate did not change significantly. Plasma histamine levels did not change in either group, nor in those patients who had presented a local erythema. Propofol did not seem to induce non-specific histamine release when injected over a period of 60 s in patients at risk of doing so.

[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.

[Respiratory effects of propofol]

Like other general anaesthetics, propofol exerts a respiratory depressant effect. Apnoea is especially frequent during induction of anaesthesia by propofol; it differs from that caused by barbiturates by its longer duration. During continuous administration, propofol exerts the same effect on respiratory function as other general anaesthetics, with an increased respiratory rate, diminished tidal volume and hypercapnia.

[Comparative study of anesthesia and recovery with propofol and enflurane in cervical surgery]

The recovery times and the state of postoperative awakening were studied after anaesthesia with propofol or enflurane. The forty patients who were to undergo surgery for cold thyroid nodules were divided into two homogeneous groups which were similar in age, sex, weight and length of surgery. In one group, induction was carried out with propofol, fentanyl, pancuronium bromide, and maintained with 9 mg X kg-1 X h-1 propofol. In the other group, this was done with thiopentone, fentanyl, pancuronium bromide, followed by 0.8% enflurane. Repeat injections of fentanyl were given as required. The time between stopping giving the anaesthetic drug and eye opening was measured, as well as the performance in memorizing and sorting numbers; these two tests were carried out before and 2 h after surgery. The overall results did not show any differences between the two groups in recovery time or quality of awakening. In the propofol group, recovery time and quality were better than in the enflurane group if the patient was less than 50 years old or surgery lasted less than 100 min. In the propofol group, there were significant correlations between recovery time and age (r = 0.83), and between recovery time and duration of surgery (r = 0.87). The doses of this new product should therefore be modified according to the age of the patient and the length of surgery.

Comparative study of propofol-alfentanyl and ketamine-midazolam combinations]

The use of propofol alone or with alfentanil in the day-case anaesthesia for abortion was compared with that of ketamine with midazolam. Two hundred young women were assigned to two successive series of two groups each. The four groups were: group 1 (2 mg . kg-1 propofol only); group II (0.5 mg . kg-1 ketamine with 0.25 mg . kg-1 midazolam); group III (2 mg . kg-1 propofol with 4 micrograms . kg-1 alfentanil); group IV (1 mg . kg-1 ketamine with 0.1 mg . kg-1 midazolam). All the patients were premedicated one hour before anaesthesia with 0.25 mg . kg-1 midazolam orally. All the patients were asleep at the end of the propofol injection (60 s), and 10 to 15 s later for the ketamine-midazolam groups. The haemodynamic parameters did not vary much during induction with ketamine-midazolam. In the propofol groups, the heart rate remained steady, with an 8 to 12% fall in blood pressure. A fall of the mandible was seen in 40 and 84% of the patients in the propofol groups, with a short apnoea in 32 and 48% of these same patients. Clinical recovery was very quick, less than 12 min for all groups. The four psychomotor and sensory tests were carried out at the 30th min by 95% of the patients in the propofol groups, whereas only 50% of those in the ketamine-midazolam groups did so. Speed and quality were significantly better in the propofol groups. The most frequent adverse effect of propofol was pain during injection in 32 and 14% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

[Propofol versus methohexital in the surgery of the spinal canal]

The aim of this study was to compare the quality of postanaesthetic recovery after anaesthesia with methohexitone (M) or with propofol (P). Thirty patients undergoing spinal surgery were randomly assigned to either group. The induction dose was 2 mg . kg-1 for both M and P. Anaesthesia was maintained by continuous infusion. The rate was 0.15 mg . kg-1 . min-1 for P and 0.07 mg . kg-1 . min-1 for M. Analgesia was obtained with fentanyl with the same doses in both groups. The maintenance doses were subsequently decreased by 50 and 75% of the initial values. This work compared the quality induction and the criteria of recovery (Aldrete score, Newman test). In two patients in each group, sensory evoked potentials (SEP) were recorded to monitor neurological integrity. The quality of induction was similar in both groups. Awakening was significantly more rapid in group P. The SEP were much decreased in group P, whilst there were few changes in group M. Monitoring of medullar integrity is mandatory in spinal surgery, requiring a rapid recovery. This objective was obtained with shorter delays in patients anaesthetized with propofol than in those who had received methohexitone. However, the former, at the doses used, seemed to depress the SEP.

Computer applications in intravenous anaesthetic administration

The place of computerization in intravenous anaesthesia delivery: Although total intravenous anaesthesia may have advantages over inhalational anaesthesia in certain circumstances, it has drawbacks from the point of view of feedback control. The ideal agent is not available, although di-isopropylphenol holds promise. There is an undefinable end-point. Inadequate dosage produces the extremely unpleasant phenomenon of intra-operative awareness. Future developments, it seems, should include the development of suitable intravenous agents and transducers of anaesthetic depth, rather than increasingly complicated control systems. It is extremely unlikely that a computer will replace the anaesthetist in the foreseeable future. The anaesthetist is still required for, amongst other things, specifying the desired depth of anaesthesia and varying it during the operation, and for responding to unforeseen crises. It may be hoped that, by liberating the anaesthetist from those tasks which can be automated, more time can be devoted to patient monitoring and other aspects of anaesthetic care, thereby improving patient safety. There is an undoubted place for computerized delivery of anaesthesia in teaching (particularly teaching pharmacokinetic principles) and in research (for standardization of anaesthetic depth).

Comparison of propofol with methohexital for outpatient anesthesia

Propofol is an intravenous anesthetic currently available for clinical investigative use. The intraoperative and postoperative effects of propofol were compared to methohexital when used as an adjuvant to nitrous oxide for outpatient anesthesia. Sixty healthy young women were randomly assigned to receive either methohexital, 1.5 mg/kg intravenously (IV), or propofol, 2.5 mg/kg IV, for induction of anesthesia. Both drugs produced transient cardiovascular and respiratory depression after induction. Maintenance of anesthesia consisted of either methohexital, 6 +/- 2 mg/min, or propofol, 7 +/- 2 mg/min (mean +/- SD) by continuous infusion in combination with nitrous oxide, 70% in oxygen. Use of a propofol infusion was associated with lower blood pressures and heart rates during maintenance. Propofol was associated with fewer side effects (e.g., hiccoughing, nausea, and vomiting) intra- and postoperatively. Recovery times for awakening, orientation, and ambulation were consistently shorter with propofol. We conclude that propofol is a useful alternative to methohexital for induction and maintenance of outpatient anesthesia.

A comparison in men and women

The disposition kinetics of propofol have been determined in 12 patients (six female) receiving propofol 2.5 mg kg-1 for induction of anaesthesia, which was maintained with 67% nitrous oxide in oxygen and 1-1.5% halothane. Peripheral blood samples were collected at selected times up to 8 h after the injection of the drug, and whole blood propofol concentrations determined by HPLC with fluorescence detection. Drug concentration-time data were analysed by the non-linear regression program ELSFIT. This showed the data to be describable by a tri-exponential equation, corresponding to a three-compartment model. There were no differences in the derived kinetic indices for the male and female patients, with the exception of a greater Vdss:V gamma ratio in the males. The terminal half-life in the male patients was 262 min (SEM 44), and in the female patients 309 min (60). Vdss was 329 litre (67) and 313 litre (69) in male and female patients, respectively. The clearance in both groups was 1.8 litre min-1. Seven out of 12 patients showed significant secondary peaks in blood propofol concentration associated with recovery from anaesthesia.

Comparison of induction characteristics of four intravenous anaesthetic agents

The induction characteristics of thiopentone, etomidate and methohexitone have been compared to those of propofol (2,6 di-isopropyl phenol) in unpremedicated patients. Propofol 2.5 mg/kg caused significantly more hypotension, excitatory side effects and pain on injection at the dorsum of hand than thiopentone 5 mg/kg. However, with regard to the latter two sequelae, etomidate 0.3 mg/kg and methohexitone 1.5 mg/kg caused similar or more frequent upset. Propofol 2.0 mg/kg was equipotent with thiopentone 4.0 mg/kg in terms of successful induction of anaesthesia. Hypotension may contraindicate the use of propofol in the hypovolaemic or unfit patient.

I: Patients premedicated with morphine sulphate

The study was performed to determine the ED50 and ED95 of a continuous infusion of the emulsion formulation of propofol during 67% nitrous oxide anaesthesia in 57 patients premedicated with morphine sulphate 0.15 mg kg-1. Anaesthesia was induced with propofol 2 mg kg-1, and maintained before incision with a fixed-rate infusion of propofol to supplement nitrous oxide. The response to the first surgical incision, made at least 30 min after induction of anaesthesia, was observed. The ED50 was 53.5 micrograms kg-1 min-1 and the ED95 was 112.2 micrograms kg-1 min-1. At the time of the first surgical incision, the venous whole blood concentrations of propofol at the ED50 and ED95 infusion rates (EC50 and EC95) were 1.66 micrograms ml-1 and 3.39 micrograms ml-1, respectively. The satisfactory maintenance of anaesthesia provided by nitrous oxide supplemented with propofol was associated with haemodynamic stability and rapid, uncomplicated recovery.

Effects of propofol on cardiovascular dynamics, myocardial blood flow and myocardial metabolism in patients with coronary artery disease

The effects of propofol (emulsion formulation) on cardiovascular dynamics, myocardial blood flow and myocardial metabolism were studied in 12 patients scheduled for elective coronary artery bypass surgery. Measurements were performed with the patient awake, during steady-state maintenance anaesthesia with propofol 200 micrograms kg-1 min-1 at rest, and during sternotomy when the propofol was supplemented with fentanyl 10 micrograms kg-1. Propofol alone decreased mean arterial pressure and cardiac index; heart rate was increased. Myocardial blood flow and myocardial oxygen consumption were decreased by 26% and 31%, respectively. Myocardial lactate production was seen in one patient during this period. Surgical stimulation, under propofol-fentanyl anaesthesia, led to the return of arterial pressure and heart rate towards baseline; cardiac index decreased further. Myocardial blood flow and oxygen consumption increased such that they almost achieved their baseline values. Myocardial lactate production was seen in one patient. These results suggest that propofol may on occasions, lead to myocardial ischaemia in patients with coronary artery disease, but that it is able to block the sympathetic responses to surgical stimulation when combined with a suitable analgesic.

[Disoprivan for the induction and maintenance of short anesthesia]

Disoprivan (Propofol) was used for induction and maintenance of anaesthesia for short surgical procedures in non-premedicated and premedicated (0.5 mg atropine, 3 mg midazolam) patients. A dose of 130-150 mg Disoprivan was adequate for induction, and a dose of 72 and of 62 micrograms/kg body weight/min anaesthesia respectively, for maintenance, together with N2O/O2 2:1. The anaesthesia was characterized by an apnoea of 40-60 s duration, a decrease in arterial blood pressure of 20%, a slowing of heart rate in non-premedicated patients by 12 beats/min and a rapid and pleasant recovery with lack of emetic sequelae. Disoprivan is considered useful for this type of anaesthesia.

[Propofol in comparison with etomidate for the induction of anesthesia]

In the present study propofol and etomidate were compared with respect to the effects on the cardiovascular system and its side effects in 100 patients ASA grade I-IV. Anaesthesia was induced with 2.2 mg kg-1 body weight propofol. Supplemented with opioids and benzodiazepins the dose diminished to 1.8 mg kg-1 body weight (18.2%). In comparison with etomidate after propofol decrease in blood pressure was more marked, especially when supplemented with opioids and benzodiazepins but without supplementation these values ranged within acceptable limits. Following intubation blood pressure and heart rate after propofol increased only to the base line values contrary to etomidate. Following propofol administration smooth induction with very good ventilation was remarkable. Myocloni and anaphylactoid reactions were not seen. Pain on injection was frequent but thrombosis and phlebitis were not observed. There was a considerably lower incidence of postoperative nausea and vomiting compared with etomidate. The investigators concluded: propofol can be recommended for induction of anaesthesia as an alternative to etomidate.

Comparison with thiopentone

The ventilatory effects of induction of anaesthesia with either propofol 2.5 mg/kg or thiopentone 4.0 mg/kg have been observed in patients premedicated with either atropine alone or papaveretum and hyoscine. Induction of anaesthesia with propofol was accompanied by a greater degree of ventilatory depression which was of longer duration than following thiopentone. The effect was accentuated by the opioid premedication.

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 and alfentanil infusion. A comparison with methohexitone and alfentanil for major surgery

In 42 patients undergoing major surgery, anaesthesia was induced by intravenous alfentanil 10 micrograms/kg together with methohexitone 1.5 mg/kg or propofol 2 mg/kg. An infusion of six times these doses per hour was then started; the rate was varied subsequently as indicated by the monitoring of arterial blood pressure, heart rate, EEG and frontalis electromyogram. The mean duration of infusion was 76.7 minutes for propofol and 74.5 minutes for methohexitone and the infusion was stopped about 10 minutes before the end of surgery in each group. The induction dose differed, but the total dose requirement for the two drugs was similar. In every case, anaesthesia was satisfactory. Methohexitone caused a significant rise in mean pulse rate throughout anaesthesia (p less than 0.05, paired t-test). There was no change in mean pulse rate during propofol infusion. The dose of alfentanil used provided excellent control of autonomic reflexes, with negligible respiratory depression. Naloxone was not required. Propofol provided better anaesthesia than methohexitone, with fewer side effects (p less than 0.05, Chi squared test), easier control of the level of narcosis and faster recovery (p less than 0.001, t-test after log transformation).

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.

Anaesthesia with ICI 35,868 monitored by the cerebral function analysing monitor (CFAM)

Ten patients who received bolus doses of the cremophor formulation of ICI 35,868 were monitored using the Cerebral Function Analysing Monitor (CFAM). Visual inspection of the traces obtained showed an easily recognizable pattern which was associated with an increasing depth of anaesthesia. Statistical analysis showed a high correlation between venous blood levels of the drug and changes recorded by the CFAM, although there was marked inter-patient variation. It is suggested that this variation is due to the effect of a time-lag between changes in drug concentration in the brain and venous blood.

Intravenous anaesthesia for cystoscopy: a comparison of propofol or methohexitone with alfentanil

Sixty out-patients undergoing cystoscopy were allocated randomly into two groups. No premedication was given. Induction of anaesthesia was preceded by intravenous alfentanil 7 micrograms kg-1 given over 20 s, followed by methohexitone 1.5-2 mg kg-1 or propofol 2 mg kg-1, given over 20 s. Anaesthesia was maintained by increments of alfentanil, methohexitone or propofol, given as required.

The relative potencies of thiopentone and propofol

The relative potencies of the intravenous anaesthetics propofol and thiopentone have been investigated by finding the dose necessary to produce unconsciousness in approximately 30%, 50% and 80% of patients. The estimated potency of propofol to thiopentone was 1:1.604 as obtained by the probit method of analysis which estimates the logarithm of the relative potency.

Incremental propofol for short procedures

Propofol was used to induce and maintain anaesthesia in patients undergoing minor gynaecological procedures. Quality of anaesthesia, the rate of recovery and the influence of different methods of premedication were assessed. Unpremedicated patients required a higher induction dose than those premedicated with either lorazepam or papaveretum and hyoscine, but maintenance dose requirements were comparable. Regardless of premedication, there were similar decreases in mean arterial pressure, although respiratory function recovered more rapidly in patients premedicated with lorazepam. No significant changes in heart rate were noted in any group. The overall incidence of pain on injection was 3.7% (lignocaine 0.5 mg added to each 9.5 mg of propofol) and a skin rash occurred in 6% of patients. All patients recovered rapidly and uneventfully.

Propofol in emulsion form: induction characteristics and venous sequelae

Propofol in a 1% emulsion was used to induce anaesthesia in 20 female patients premedicated with diazepam (10 mg). A dose of 2.5 mg kg-1 produced a rapid loss of consciousness and only minor excitatory effects. Discomfort during the injection was not severe. Cardiovascular changes included a fall in blood pressure similar to that which occurs with other induction agents, and a decrease in pulse rate. Apnoea occurred after each induction and in some patients (13) was prolonged (greater than 60 s). There were no venous sequelae, and patient acceptance was high. Propofol given in an emulsion to induce anaesthesia merits further study.

Comparison of propofol with methohexitone in the provision of anaesthesia for surgery under regional blockade

Propofol was compared with methohexitone for provision of light general anaesthesia in patients undergoing surgery under spinal analgesia. Intermittent bolus administration of both agents proved a feasible way of maintaining anaesthesia, a mean infusion rate of 0.13 mg kg-1 min-1 being required for propofol and 0.089 mg kg-1 min-1 for methohexitone. Propofol produced smoother anaesthesia with significantly fewer excitatory side effects and less pain on injection, but cardiovascular and respiratory depression occurred commonly. Recovery was rapid with both agents, but minor postoperative sequelae occurred more frequently after methohexitone.

Diprivan (ICI 35868, 2, 6, di-isoprophylphenol), a new intravenous anesthetic

Diprivan is a new anesthetic agent that is being tested in the United States after preliminary trials in Europe. Characteristic features include rapid induction and recovery, with cardiovascular and respiratory changes that are insignificant at the recommended dose. Lack of excitatory and emetic complications, along with absence of any toxic effects to date, have contributed to its consideration as an auspicious new agent.

Comparison of infusions of propofol and methohexitone to provide light general anaesthesia during surgery with regional blockade

General anaesthesia was induced with, and maintained by, an infusion of either propofol or methohexitone, in patients undergoing surgery with the aid of regional blockade. Both agents provided satisfactory and controllable anaesthesia. Complications were few with a similar incidence for the two drugs. Recovery from anaesthesia was significantly faster following propofol.

Assessment and modification of pain on induction with propofol (Diprivan)

Assessment of pain on injection of the emulsified formulation of di-isopropylphenol (propofol, 'Diprivan') was undertaken in 120 unpremedicated patients and comparison made with thiopentone. A high incidence of pain (37.5%) was found using dorsal hand veins, but use of forearm veins showed only a 2.5% incidence of pain. The use of intravenous lignocaine immediately before propofol injection only partially reduced the incidence of pain using dorsal hand veins (17.5%). A degree of cardiorespiratory depression accompanied induction but the incidence of other side effects was low.

On the biopotency and site of action of drugs affecting endocrine tissues with special reference to the anti-steroidogenic effect of anaesthetic agents

Dispersed guinea-pig adrenal cells or mouse Leydig cells were stimulated with a saturating dose of adrenocorticotrophin (ACTH, 50 ng/1) or luteinizing hormone (LH, 5IU/1), respectively. The incubations were performed in the presence of increasing concentrations (10(-9) - 5 X 10(-4)mol/l) of the anaesthetic agents propofol, thiopentone and etomidate. At the end of this stimulation period, cortisol (from the adrenal preparation) or testosterone (from the Leydig cell culture) were assayed by radioimmunoassay. Propofol, thiopentone and etomidate all inhibited ACTH-stimulated cortisol secretion in a dose-related fashion. Similar inhibition of LH-stimulated testosterone output was found with propofol and thiopentone whereas etomidate was without effect at any concentration employed, an observation in accordance with its known site of action, 11 beta-hydroxylase, an enzyme which is not involved in the biosynthesis of testosterone. The concentration (mumol/l) of anaesthetics which gave 50% inhibition (ED50) of ACTH-stimulated cortisol secretion was 0.1 +/- 0.002 (n = 7), 160 +/- 18 (n = 3) and 170 +/- 18 (n = 3) (mean +/- s.e.m.) for etomidate, thiopentone and propofol, respectively. The corresponding values for the LH stimulated testosterone output from the Leydig cell preparations were 186 (thiopentone) and 180 (propofol) mumol/l. In a separate series of experiments adrenal cells were stimulated with (a) the cortisol precursor steroids (all at 10(-5)mol/l) pregnenolone, 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone and 11-deoxycortisol, (b) dibutyryl cAMP (10(-3)mol/l) or (c) ACTH (100 ng/l) in the presence and absence of either etomidate (5 X 10(-5)mol/l), propofol (2.5 X 10(-4)mol/l) or thiopentone (5 X 10(-4)mol/l). All the stimulators increased cortisol production by > 7-fold over that seen in their absence. Propofol depressed ACTH and dibutyryl cAMP induced cortisol output by > 60% (P < 0.05) but was without effect when the steroid precursors were used, suggestive of an inhibition between the sequence involving ACTH binding -> pregnenolone production. In contrast, etomidate and thiopentone reduced cortisol secretion by > 40% (P < 0.05) regardless of the stimulator used, indicating that at least one site of action was at the level of the final enzymic step of cortisol synthesis, i.e. 11beta-hydroxylase.

Comparison of propofol and thiopentone for induction of anaesthesia in premedicated patients

Thirty premedicated ASA I or II patients scheduled for minor gynaecological surgery, were randomly allocated to receive either 1.5 mg/kg or 2 mg/kg propofol of the new emulsion formulation, or 4 mg/kg thiopentone, given over 20 seconds. Anaesthesia was successfully induced in all 30 patients. The mean (SEM) induction times were for propofol 1.5 mg/kg 33.3(3.2) seconds, for 2 mg/kg 30.5(2.7) seconds and for thiopentone 34.6(2.7) seconds. The incidence of apnoea greater than 10 seconds, was respectively 60, 80 and 80%, and the mean duration of apnoea 30.8(5.3), 37.1(5.0) and 23.7(5.0) seconds. The mean systolic blood pressure decreased after propofol 1.5 mg/kg by 16.0 mmHg, after 2 mg/kg by 18.6 mmHg, and increased after thiopentone by 1 mmHg, 2 minutes after injection. Heart rate increased significantly 2 minutes after thiopentone by an average of 15.1 beats/minute, but not after propofol. Pain was not reported during or after the injection. No major adverse reactions occurred at induction or during maintenance of anaesthesia with an inhalation agent. One patient who received 2 mg/kg propofol and isoflurane vomited for 24 hours. The recovery of anaesthesia after propofol induction, was quicker than after thiopentone.

A comparison of the induction characteristics of thiopentone and propofol (2,6-di-isopropyl phenol)

A study has been undertaken to compare the induction characteristics of the new intravenous anaesthetic agent 2,6 di-isopropyl phenol, newly prepared in a lipid emulsion (propofol) with those of thiopentone. Despite a significantly higher incidence of pain on injection and spontaneous movement, the new agent was felt to perform comparably to thiopentone as an induction agent. Unfortunately, propofol caused decreases in blood pressure which were significantly greater than those seen after thiopentone. This feature may prove to be a considerable hurdle to the general acceptance of propofol.

Total intravenous anaesthesia in the horse with propofol

The use of propofol, solubilised in a non-ionic emulsifying agent, for the induction and maintenance of anaesthesia in experimental ponies was assessed. Pilot studies revealed that premedication with xylazine (0.5 mg/kg bodyweight [bwt]) intravenously (iv) followed by propofol (2.0 mg/kg bwt) iv provided a satisfactory smooth induction. Two infusion rates (0.15 mg/kg bwt/min and 0.2 mg/kg bwt/min) were compared for maintenance of anaesthesia. An infusion rate of 0.2 mg/kg/min produced adequate anaesthesia in these ponies. Cardiovascular changes included a decrease in arterial pressure and cardiac output during maintenance. Respiratory depression was manifested by a decrease in rate and an increase in arterial carbon dioxide tension. Recovery after 1 h anaesthesia was rapid and smooth. In conclusion, induction and maintenance of anaesthesia with propofol in premedicated ponies proved a satisfactory technique.

Comparison of the new emulsion formulation of propofol with methohexitone and thiopentone for induction of anaesthesia in day cases

The new emulsion formulation of di-isopropyl phenol (propofol) was compared with methohexitone and thiopentone for induction of anaesthesia in day cases. Propofol produced significantly smoother induction of anaesthesia, but caused more cardiovascular and respiratory depression. Pain on injection was significantly less than with methohexitone. Post-anaesthetic recovery was superior with propofol, with virtual absence of side effects, and rapid recovery with little impairment of psychomotor function 30 min after anaesthesia.

Short communication

Pain on injection of three anaesthetic induction agents, thiopentone, methohexitone and propofol (diisopropyl phenol), administered into a vein on the dorsum of the hand or wrist, was studied in 32 premedicated patients undergoing elective surgery. The pain was rated as none, mild or severe. A 1% emulsion formulation of propofol (ICI 35 868) (2 mg kg-1) and methohexitone (2 mg kg-1) induced pain significantly more often, in 100% and 80% of patients, respectively, than thiopentone (4 mg kg-1), 0%. The pain was rated as severe more often in patients receiving propofol (67%, P less than 0.01 vs thiopentone) than in those anaesthetized with methohexitone (20%) or thiopentone (0%). It is concluded that the fat emulsion form of propofol, when injected into a peripheral vein, frequently induces severe pain.

Comparison of the effects of thiopentone and propofol

The haemodynamic changes following induction of anaesthesia with equipotent doses of propofol and thiopentone have been compared. Propofol caused a significant fall in arterial blood pressure and total peripheral resistance, with a slight fall in cardiac output. There were no changes in heart rate. Apart from an initial, but statistically insignificant increase in heart rate, similar changes were produced by thiopentone, but to a lesser degree. It is concluded that induction of anaesthesia with propofol results in acceptable haemodynamic changes, but that the agent is more depressant to the cardiovascular system than thiopentone.

Use of an emulsion of ICI 35868 (propofol) for the induction and maintenance of anaesthesia

2,6-Diisopropyl phenol in a fat emulsion formulation (propofol) has been used to supplement 67% nitrous oxide in oxygen anaesthesia in 20 patients premedicated with morphine 0.15 mg kg-1 and atropine 0.6 mg, and undergoing body surface surgery. Following an induction dose of propofol 2.5 mg kg-1, the mean maintenance dose was 73.4 micrograms kg-1 min-1. When compared with 10 patients receiving Althesin to supplement nitrous oxide in oxygen in a similar manner, recovery was considerably faster following propofol. The only major side-effect associated with the use of propofol was pain on injection in nine out of 20 patients. When the patients receiving propofol were compared with a second control group (n = 11) in whom anaesthesia was induced with thiopentone 4 mg kg-1 and maintained with 1% halothane and nitrous oxide in oxygen, the former group showed a significant (P less than 0.01) decrease in the plasma cortisol concentration 30 min after the induction of anaesthesia. However, by 3 h after induction, the cortisol concentration in both groups was not significantly different from the baseline (preinduction) value. The mechanism of this decrease is not known. Investigation of the influence of the fat emulsion on blood coagulation and fibrinolysis revealed no differences when compared with patients receiving Althesin.

Comparison of ICI 35868, etomidate and methohexitone for day-case anaesthesia

The anaesthetic properties and side-effects of propofol 1.5 mg kg-1, etomidate 0.2 mg kg-1, and methohexitone 1.5 mg kg-1 were compared in 71 healthy female patients undergoing short gynaecological procedures. Propofol proved to be a safe and effective agent for induction and maintenance of anaesthesia and was associated with a lower incidence of side-effects than either etomidate or methohexitone.

Effect of speed of injection on induction of anaesthesia using propofol

Sixty unpremedicated patients (30 male) were randomly allocated to three groups. They received an induction dose of propofol 2 mg kg-1 over 5, 20 or 60 s to a forearm vein. Anaesthesia was maintained with conventional inhalation anaesthetic agents. Anaesthesia was induced satisfactorily in all 20 of the patients in the 5-s group, in 19 of the patients in the 20-s group and in 18 of the patients in the 60-s group. The rate of injection had a significant influence on induction time. Mean induction time increased from 21.5 to 34.7 and 50.5 s, when injection time was increased from 5 to 20 to 60 s, respectively. Similar induction times were found in male and female patients. There was no significant difference between the groups, in depth of anaesthesia obtained--as assessed by the eyelash reflex. Mean arterial pressure decreased to the same extent in all three groups. Two minutes after induction, mean systolic arterial pressure was reduced by 15.1, 13.5 and 19.3 mm Hg in the 5-, 20- and 60-s groups, respectively, and mean diastolic arterial pressure by 10.3, 13.2 and 13.7 mm Hg. Heart rate changes were insignificant. Apnoea of more than 10 s duration was seen frequently in all three groups, but the results suggest that the incidence was not influenced by the rate of injection. Three patients experienced mild pain at the time of injection. No major adverse reactions occurred during or after anaesthesia.

Comparison of the effects of etomidate, thiopentone and propofol on cortisol synthesis

The inhibitory effects of etomidate, thiopentone and propofol on basal and ACTH-stimulated cortisol synthesis by isolated bovine adrenocortical cells have been examined. Concentrations required for 50% inhibition of ACTH-stimulated cortisol output were 1.1 X 10(-4) mol litre-1 for propofol, 3 X 10(-5) mol litre-1 for thiopentone and 4.6 X 10(-1) mol litre-1 for etomidate. At concentrations likely to be achieved during anaesthesia, etomidate would block cortisol output by isolated cells, thiopentone might slightly reduce output and propofol would be unlikely to alter cortisol synthesis significantly.

Effect of propofol, thiopentone and etomidate on adrenal steroidogenesis in vitro

The i.v. anaesthetic agents propofol, thiopentone and etomidate inhibited ACTH-stimulated production of cortisol by guineapig dispersed adrenal cells in a dose-related manner. For two of the drugs, propofol and thiopentone, inhibition occurred over a similar concentration range: 2 X 10(-5) - 5 X 10(-4) mol litre-1. With etomidate, inhibition occurred over a much lower concentration range (5 X 10(-8) - 5 X 10(-6) mol litre-1). The concentrations of anaesthetic which induced 50% inhibition of cortisol secretion were propofol 1.7 X 10(-4), thiopentone 1.6 X 10(-4), and etomidate 1.0 X 10(-7) mol litre-1.