[Respiratory response to carbon dioxide after brachial plexus block with fentanyl and lidocaine]

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.