Potent and long lasting antinociceptive effects after injection of low doses of a mu-opioid receptor agonist, fentanyl, into the brachial plexus sheath of the rat.

The effect of administering low doses (0.5-1.5 micrograms) of the mu-opioid receptor agonist fentanyl into the right brachial plexus sheath of the rat was examined using the vocalization threshold to paw pressure test. Both forepaws were tested in each rat. Fentanyl injected into the right brachial plexus sheath at 0.5-1.5 micrograms/kg produced a localized, dose-dependent, potent and long lasting antinociceptive effect, as gauged on the right forepaw. At the lower dose used (0.5 microgram/kg of fentanyl), the antinociceptive effect was restricted to the right forepaw and lasted for more than 2 h. Increasing doses of fentanyl (1 and 1.5 micrograms/kg) induced potent effects, lasting up to 5-6 h or even longer. In complete contrast, fentanyl administered i.v. at the dose of 1 microgram/kg had a very transient effect, only lasting up to 25 min. The results of injection of low doses of the opioid antagonist naloxone when administered either i.v. or locally into the paw, on the effect of fentanyl suggest the involvement of a peripheral site of action of the opioid. The present findings suggest that, as already observed in patients in clinical situations, low doses of opiates delivered using this administration route may provide prolonged regional analgesia, with the potential of avoiding centrally mediated side effects.

Ceftriaxone diffusion from blood to aqueous humour in man.

Ceftriaxone penetrates into the aqueous humour in man. The interaction of indomethacin on the disposition of ceftriaxone appeared to be time-dependent. Indomethacin delayed ceftriaxone penetration into, but enhanced its persistence in, the aqueous humour, permitting a period of antibioprophylaxis covering the required time for surgical treatment.

[Respiratory response to carbon dioxide after brachial plexus block with fentanyl and lidocaine]. / Réponse ventilatoire au dioxyde de carbonue après bloc axillaire avec fentanyl et lidocaïne.

Respiratory parameters, ventilatory response to carbon dioxide and quality of anaesthesia were studied in patients undergoing upper limb surgery under axillary blockade. Thirteen patients were randomly assigned to two groups, group A (n = 6), who were given 35 ml of 1.5% lidocaine with 1 in 200,000 of adrenaline, and group B (n = 7), who received 1 microgram.kg-1 of fentanyl with the same dose of lidocaine. Quality of the sympathetic, sensory and motor blocks were tested at 15 min (T1) and 45 min (T2) after the injection (T0). The other parameters measured at these three times, both with the patient in a half-sitting position breathing room air, and after a rebreathing test with CO2 through Read's circuit, were respiratory rate (FR), tidal volume (VT), minute ventilation (VE), and PetCO2. Fentanyl provided a better sensory and motor blockade at T1, without any difference in sympathetic blockade. The quality of the blocks was similar in both groups at T2. There were no significant differences in the respiratory parameters between the two groups. Moreover, there was no untoward effect due to fentanyl (nausea, pruritus). It is concluded that 1 microgram.kg-1 fentanyl added to a local anaesthetic solution may be useful, at least during the first hour of an axillary block, without any respiratory side-effects.

[Intranasal midazolam in pediatric ophthalmology]. / Midazolam intranasal en ophtalmologie pédiatrique.

Intranasal midazolam was tested in pediatric patients undergoing ophthalmological examination. 15 children aged 3.5 months to 10 years received 0.35-0.5 mg.kg-1 intranasal midazolam in association with a corneal anesthesia. The onset of sedation was rapid and permitted adequate ocular examination in all cases. In 8 of 15 cases where surgery followed immediately, the induction of inhalational anesthesia was easier. No local or general adverse reaction was noted. This non-invasive method of anesthesia may be compared to the intrarectal administration of midazolam, but the rapid onset of sedation and a cleaner route seem more suitable in surgical environment.

[Addition of fentanyl to adrenalinized lidocaine for the brachial plexus block]. / Adjonction de fentanyl à la lidocaïne adrénalinée pour le blocage du plexus brachial.

This study was designed to investigate the effects of fentanyl associated with lidocaïne in a solution used to perform axillary brachial plexus nerve block. Adrenergic, sensory and motor nerve blocks have been studied separately and compared to a control group receiving lidocaine without fentanyl. For each type of fibre, the degree of block was measured on, 2, 3, 4, 5 and 10 minutes after injection and the result were studied by variance analysis. Axillary nerve blocks were performed in two different hospitals by two anesthesiologists. After giving informed consent, the patients were randomly allocated in two groups receiving 30 ml 1.5% lidocaine with 1/200,000 epinephrine, with or without fentanyl 100 mu. There were no statistical differences between the two groups as far as adrenergic nerve block was concerned, whereas sensory and motor nerve blocks were significantly more important as soon as five minutes after injection and lasted longer when fentanyl was added to the solution. This enhancement of intensity and duration of sensory and motor nerve blocks when fentanyl is added allows a reduction of the quantity of lidocaine required, and shortens the delay between injection and complete blockade.

Midazolam and flumazenil in ophthalmology.

Midazolam's pharmacodynamic properties are used in ophthalmology in several indications: 1. to relieve anxiety and unwanted reactions during radial keratotomy in ambulatory patients; 2. to provide sedation and amnesia during cataract surgery using local anaesthesia, in combination with low doses of phenoperidine; 3. to induce general anaesthesia, combined with fentanyl and vecuronium, for intraocular surgery in the elderly; and 4. to decrease intraocular pressure. Flumazenil is not in routine use but is usually administered to antagonise the deleterious effects of midazolam on upper airway resistances and the respiration system and may be used to reverse "paradoxical", i.e. anxiogenic reactions to benzodiazepines in the elderly.