[Non-specific histamine liberation and propofol]

[Use of Diprivan in allergic patient]

Propofol may be indicated in patients with a history of allergy provided some precautions are taken. At present, the only contra-indication for propofol are patients with a known allergy to muscle relaxants. Any anaphylactoid reaction has to be systematically reported (e.g. to the Drug Safety Department of Zeneca Pharma) and the patient tested according to the standard protocol, in order to further disclose the underlying mechanisms and evaluate the risk factors. Periodical analysis of notifications of adverse reactions will facilitate regular epidemiological studies and the update of the information on the drug for the anaesthetic community.

[Diprivan and electroconvulsive therapy]

Anaesthesia for Electroconvulsive Therapy (ECT) is characterized by short repeat anaesthetic procedures, performed outside an operating theatre. The efficacy of ECT relies upon the occurrence of tonoclonic convulsions. Propofol seems to be the intravenous induction agent of choice for ECT. Its pharmacokinetic properties ensure a rapid and deep anaesthesia, of short duration, with a minimum of side effects, and a rapid recovery of good quality, suitable for short repetitive procedures. As low doses of propofol are used, a rapid injection is required to obtain the hypnotic effect. These low doses also have the advantage of not affecting the convulsion threshold and therefore the efficacy of ECT. Clear upper airways and prevention of tongue biting are ensured by inserting a Guedel airway after loss of consciousness and before the electric shock. Intravenous administration of 10-20 micrograms.kg-1 atropine prevents from bradycardia, related to initial vagal stimulation induced by the electric shock. Its action is potentiated by the anticholinergic effect of tricyclic antidepressants. Its use is also justified when suxamethonium is given to prevent patient's movements and possible ECT-related trauma. Only suxamethonium is suitable for these procedures because of its pharmacokinetic properties (rapid onset and short duration of action). The suggested doses for this indication range from 0.5 to 1 mg.kg-1. When contraindicated, suxamethonium may be replaced by a benzodiazepine, in order to achieve an acceptable degree of muscle relaxation. There may then be an effect on the convulsion threshold.

Evaluation of histamine-releasing property of propofol in whole blood in vitro

We examined the property of emulsion form of propofol (ICI 35 868) to release histamine in whole blood in vitro. Heparinized whole blood from 10 healthy volunteers were incubated with medium and propofol at the final concentration of 0, 1, 10 and 100 microg.ml(-1). The concentration of histamine in supernatant fluid after incubation was measured by radioimmunoassay. Histamine release was expressed as the percentage of the concentration of histamine released into supernatant fluid relative to the total cellular histamine content, which was yielded by destroying cell components in the whole blood. Histamine release in the presence of propofol at the concentrations of 1, 10 and 100 microg.ml(-1) were almost the same as histamine release in the absence of propofol. We conclude that emulsion form of propofol has no property to release histamine in whole blood in vitro.

Plasma histamine levels during induction of anesthesia with propofol in dogs

We examined a property of emulsion formation of propofol (ICI 35868) to release histamine into circulating plasma in dogs. Plasma histamine was measured with radioimmunoassay before (baseline), and 1, 5 and 10 min after the administration of 15 mg.kg(-1) propofol. There were no significant differences between the plasma histamine levels at 1, 5 and 10 min after the administration of propofol and the baseline level. We conclude that the emulsion formation of propofol of 15 mg.kg(-1) does not release histamine during induction of anesthesia in dogs.

Basophil histamine release in atopic patients after in vitro provocation with thiopental, Diprivan and chlormethiazole

The degree of histamine release induced by three different anesthetic drugs was studied in vitro using basophil leukocytes from atopic patients (n = 11) and controls (n = 14). In all, eight dilutions (1/2 to 10(-5)) of Diprivan and its solvent Intralipid, thiopental and chlormethiazole in aqueous solution, were used. Histamine was released in four controls with weak dilutions (1/2 to 10(-5)) of Diprivan (n = 2) and thiopental (n = 2). The reaction with thiopental was greater than that with Diprivan. Five of the atopic subjects released histamine with one or more drug: thiopental and Diprivan four times each, Intralipid twice, and chlormethiazole once. Histamine release was greater in these patients than in controls, and occurred with dilutions ranging from 1/2 to 10(-2), except for one case. It is concluded that atopic patients release histamine with hypnotic anesthetic drugs more easily than normal subjects. In the clinical setting, where blood concentration of the drugs studied is equivalent to a dilution of less than 10(-3), they do not release much histamine. They may be used in atopic patients if the drugs are injected slowly.

[Use of propofol in 1350 anesthetized patients for electroconvulsive therapy]

Propofol was used for 1,350 sessions of electro-convulsive therapy (ECT). After 0.5 mg of intravenous atropine, patients received 1 to 1.5 mg.kg-1 bolus of propofol over a period of 20 seconds or less. This was convenient for loss of the eye-lash reflex. A bolus of 15 to 20 mg suxamethonium was given, in non allergic patients, to prevent trauma from the seizure. The patient was hyperventilated with pure oxygen through a facial mask. The electric shock was delivered bitemporally after a dental protection had been inserted. For each patient, the following data were noted: sex, use of tricyclic antidepressant drugs, atopy, amount of administered propofol and the effective intensity of the electric shock. The 99 patients were given 16.27 +/- 14 ECT sessions. Among them 26 took antidepressant drugs and 34 were atopic. There was no difference, except for weight, between the 25 men and 74 women. The mean dose of propofol was 1.37 +/- 0.3 mg.kg-1. The dose decreased with increasing age. There was no statistical relationship between the amount of propofol and intensity of the electric shock required to set off a seizure. The use of antidepressant drugs, and atopy did not influence the required amount of propofol. Speed of injection seemed to be the determining factor for narcosis with low doses of propofol. Hyperoxia and hypocapnia induced by hyperventilating with pure oxygen seemed to facilitate occurrence and duration of seizures. Although propofol has been said to reduce the length of seizures, there is controversy concerning the ECT efficacy criteria.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of the association propofol-alfentanil on bronchial resistances in asthmatic patients]

The bronchial resistances in 17 patients scheduled for ENT surgery were studied during general anaesthesia carried out with propofol and alfentanil. There were nine controls, all free from any allergic pathology. The other eight had bronchial hyperreactivity, with clinical asthma (one or two crises a month) treated with bronchodilators. Two had a complete Fernand-Widal syndrome, and the remaining six documented allergic asthma. All the patients were premedicated with hydroxyzine 2 mg.kg-1 orally on the eve of surgery, and two hours beforehand. Those patients who were on bronchodilators were given their drugs as usual with the premedication. Because bronchial resistances were measured with the patient breathing spontaneously (forced oscillation technique), induction was carried out in two steps, first with propofol 1.5 mg.kg-1, followed, two minutes later, by alfentanil 7 micrograms.kg-1. Once the bronchial resistances had been assessed the patient was given a further 2 mg.kg-1 dose of propofol, and alfentanil 40 micrograms.kg-1. The patient was then intubated, and anaesthesia maintained with propofol 9 mg.kg-1.h-1, and alfentanil 15 micrograms.kg-1 every fifteen minutes. In all, bronchial resistances were measured on the day before surgery, after premedication but before the patient had been given any anaesthetic drug, two minutes after the first injection of propofol, two minutes after the first injection of alfentanil, and after extubation. There were no significant differences between the two groups. Despite the small number of patients included in this study, it would seem that hydroxyzine, propofol and alfentanil may be used safely in patients with hyperreactive bronchi.

[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.

[Propofol versus propanidid for the conduction of suspension laryngoscopy]

Forty patients who where to undergo suspension laryngoscopy were randomly assigned to two groups, the first receiving 1 microgram . kg-1 fentanyl and a bolus of 2.5 mg . kg-1 propofol followed by 5 to 10 mg . kg-1 . h-1 propofol infusion, and the second 1 microgram . kg-1 fentanyl and 0.2 mg . kg-1 flunitrazepam with 8 mg . kg-1 propanidid in a bolus followed by 40 to 50 mg . kg-1 propanidid infusion. The following parameters were studied: length of apnoea, quality of anaesthesia, the time between stopping giving the anaesthetic and the moment when the patient opens the eyes, gives his name and date of birth, the heart rate, the systolic, diastolic and mean blood pressures, blood gases, before induction, during suspension and at stopping the infusion. Anaesthetic quality was the same for both protocols, and the variations of the haemodynamic parameters were very similar for both groups. Apnoea lasted twice as long with propofol as with the flunitrazepam-propanidid association (p less than 0.001), whereas recovery was twice as quick (p less than 0.001). This seemed to confirm that propofol is better indicated for this type of surgery than the previously used flunitrazepam-propanidid association.