ANAESTHESIA FOR LARYNGOSCOPY: A TECHNIQUE USING THE NUFFIELD ANAESTHETIC VENTILATOR

An inflation catheter technique has been devised for providinggeneral anaesthesia during laryngoscopy using the control moduleof the Nuffield Anaesthetic Ventilator driven by 50% nitrousoxide in oxygen. The system is simple and reliable in use andensures adequate pulmonary ventilation. ^*Present address: The London Hospital, Whitechapel, London E118B.     

COMPARISON OF FOUR NARCOTIC ANALGESICS FOR EXTRADURAL ANALGESIA

The effectiveness of extradural injections of morphine sulphate6 mg, methadone 6 mg, pethidine 60 mg and fentanyl 60 µgin reheving pain after operation were compared in 24 patients.The average duration of pain relief following morphine was 12.3h; methadone 8 7 h, pethidine 6 6 h and fentanyl 5 7 h. Therewas no significant difference m the efficacy of the four drugs.There were no effects of clinical importance on heart rate,respiratory frequency or arterial pressure, but arterial systolicpressure decreased after morphine and pethidine. Pethidine alsocaused a statistically significant reduction in diastohc pressure.     

DOSE-EFFECT RELATIONSHIPS OF EXTRADURAL MORPHINE

The effectiveness of three different doses of extradural morphine(4,6 and 8 mg) in relieving post-operative pain was comparedin 24 patients. Although there was no significant differencein the efficacy of the three doses, increasing dosage increasedthe average duration of analgesia provided by the drug (4 mg–593min; 6 mg–722 min; 8 mg–885 min). All three dosesincreased the average peak expiratory flow rate, the greatestincreases bang seen at the higher dosages. Increasing dosagewas not accompanied by an increase in the occurrence of adverseeffects.     

EXPERIMENTAL COMPARISON OF EXTRADUPAL AND I.M. MORPHINE

Morphine sulphate 3 or 4 mg was administered to the extraduralspace in five volunteers. Morphine 10 or 15 mg i.m. was givenas control. Extradural administration resulted in an increaseof pain threshold in the legs but not in the forehead. Therewas no significant depression of carbon dioxide response ordeterioration of co-ordination or short-term memory. I.mn. morphinecaused an increase in forehead pain threshold, depression ofthe carbon dioxide response and some deterioration of cerebralfunction. Extradural morphine caused urinary retention in fourand inability to ejaculate in three of the subjects. The principalsite of action of extradural morphine appears to be regional,at spinal cord level, but it appears that autonomic functionas well as pain perception can be affected.     

Anaesthesia for bronchoscopy

The control module of the Nuffield (A-P) Anaesthetic Ventilator was found to be an efficient means of automatically controlling the ventilation of the lungs through a bronchoscope during a series of laboratory experiments. The relationships between lung characteristics (compliance and airway resistance) and the driving flow rate through various injectors on the final oxygen concentrations and tidal volumes delivered were determined. A 14 gauge injector provided the largest tidal volumes with the least entrainment of air.