The influence of the H1 and H2 receptor antagonists, terfenadine and ranitidine on the hypotensive and gastric pH effects of the histamine releasing drugs, morphine and tubocurarine.

Morphine and tubocurarine may release histamine by direct mast cell degranulation which may result in systemic effects such as cutaneous flushing, local wheal and flare formation and hypotension. This randomised, double-blind study examined whether preoperative combined oral terfenadine (60 mg) and ranitidine (150 mg) attenuates the reduction in blood pressure and cutaneous flushing after the administration of tubocurarine and morphine in 60 patients undergoing elective gynaecological surgery. In addition, investigation was made of whether tubocurarine and morphine cause a significant decrease in gastric pH in comparison to the nonhistamine-releasing agents fentanyl and vecuronium. Patients were randomly assigned to one of three groups receiving either pre-operative terfenadine and ranitidine and intra-operative tubocurarine and morphine (group A); pre-operative placebo and intra-operative tubocurarine and morphine (group B); pre-operative placebo and intra-operative fentanyl and vecuronium (group C). Compared to group B, group A had less hypotension and tachycardia but no significant decrease in cutaneous flushing immediately following morphine and tubocurarine (p > 0.05). There were no significant differences in haemodynamic changes between the groups A and C. In those patients not pretreated with terfenadine and ranitidine (groups B and C), gastric pH decreased between 5 and 10 min following bolus administration of morphine and tubocurarine (group B), whereas patients receiving fentanyl and vecuronium (group C) had an increase in gastric pH. This suggests that histamine release following administration of morphine and tubocurarine is sufficient to increase gastric acidity.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of three ported cannulae available in New Zealand.

A comparison was made of the three 22-gauge ported intravenous cannulae available in New Zealand--Venflon 2, Vasofix Braunule and Insyte. All cannulae performed satisfactorily in terms of overall success of cannulation although significant differences were apparent in both clinical and laboratory performance. Anaesthetists' clinical preference was for Insyte and Venflon 2 brands, perceiving these to have greater ease of handling and better packaging. In a series of laboratory studies, Vasofix was found to have the highest flowrate, the fastest time to flashback and the lowest valve opening pressure. Insyte required the least force of penetration. Venflon 2 had the greatest margin of safety between pressure to inject through the port and pressure required to blow the syringe/port assembly apart. Potential problems were identified with the Insyte port valve mechanism.

A comparison of intravenous cannulae available in New Zealand.

This study examined physical and clinical features of eleven models of disposable intravenous cannulae available in New Zealand: Angiocath, Braunule, Insyte, Jelco, J.M.S., Medicut, Nipro, Quikcath, Surflo, Venflon and Wallace. Dimensions of external and internal diameter and wall thickness varied greatly among the models of the same gauge size. As a result, flow rates also varied greatly, but linearly with internal diameter. Anaesthetists were randomly given a range of 16 and 22 gauge cannulae for routine clinical use (forty of each model) and completed a questionnaire on features of cannula performance relating to success of cannulation, ease of insertion, ease of handling, kinking, and packaging. The results of this questionnaire are presented and discussed. The 22 gauge cannula tips were assessed microscopically for distortion after clinical use. Jelco cannulae were found to have the highest incidence of catheter tip distortion (54%).

Diazepam mixed micelle--comparison with diazepam in propylene glycol and midazolam.

A mixed micelle formulation of diazepam was compared with midazolam and diazepam in propylene glycol for evidence of venous intolerance following IV injection. The overall incidence of venous morbidity was 17% for diazepam mixed micelle, 26% for midazolam and 90% for diazepam in propylene glycol. Diazepam mixed micelle is suggested as a preferable alternative to the standard formulation.

Cutaneous sensitivity to atracurium and vecuronium in patients suffering anaphylactoid reactions to neuromuscular blockers.

Using an ordinal measure of cutaneous sensitivity to intradermal injections of atracurium and vecuronium, 40 nonreacting subjects were compared with a group of 24 patients previously suffering life-threatening anaphylactoid reactions to other muscle relaxants. Enhanced cutaneous sensitivity to vecuronium was found in three, and to atracurium in two of the previously reacting group. With the exception of those showing abnormal reactivity, no significant difference was found in the distribution of cutaneous sensitivity in the control and reacting group. A concentration of vecuronium 8.75 times that of atracurium was required to produce an equivalent intradermal wheal response.

Anaphylactoid reactions during anaesthesia. Seven years' experience of intradermal testing.

Sixty one patients who had suffered intra-operative anaphylactoid reactions were studied. Intradermal testing identified the causative agent in 84% of cases and, in 75% of these, muscle relaxants were responsible. Predisposing factors in patients sensitive to muscle relaxants were: female sex, previous allergy and atopy. The incidence of previous exposure was considerably higher than that reported in the literature. Pancuronium is suggested to be the least likely currently available agent to provoke a major anaphylactoid reaction.