Summary Minimum alveolar concentration (MAC) for halothane was measured before and after administration of intravenous butorphanol (0.022 and 0.044 mg/kg in bodyweight in nine yearling Shetland ponies. Arterial blood pressure, heart rate, respiratory rate, expired CO2 and rectal temperature was also measured. Even though mean MAC values decreased 10 and 9 per cent after the low and high doses respectively, they were not statistically different from those measured prior to butorphanol. Halothane MAC values increased after butorphanol in two ponies, both animals increasing locomotor activity and demonstrating apparent central nervous system stimulation. No significant differences were seen in any variable measured after butorphanol administration.

We have examined the hypothesis that intrathecal fentanyl at operation can increase postoperative i.v. morphine requirements. We studied 60 patients undergoing Caesarean section. All received intrathecal 0.5% plain bupivacaine 2 ml combined with either fentanyl 0.5 ml (25 g) (group F) (n:30) or normal saline 0.5 ml (group S) (n:30). In addition, 10 ml of an extradural solution (fentanyl 1 ml (50 g) combined with 0.5% bupivacaine 9 ml) was administered after delivery. Extradural solution was only given before delivery if the intrathecal injection failed to produce a block above T6 or the patient required further analgesia. Postoperative analgesia was provided with i.v. morphine patient-controlled analgesia. At operation, intrathecal fentanyl reduced the need to administer extradural solution before delivery, increased the anaesthetist's satisfaction with analgesia and reduced nausea, but increased pruritus. Up to 6 h after delivery there was no difference in postoperative morphine requirements or pain scores. Between 6 h and 23 h there was a 63% increase in morphine requirements in group F. We consider the most likely explanation for this finding to be that intrathecal fentanyl induced acute spinal opioid tolerance.

In this randomized, double-blind study of 60 patients, we have assessed the analgesic efficacy of extradural bupivacaine and extradural fentanyl, either alone or in combination, after Caesarean section. Patients received 0.1% bupivacaine (group B), fentanyl 4 micrograms ml-1 (group F) or 0.05% bupivacaine combined with fentanyl 2 micrograms ml-1 (group BF) by patient-controlled extradural analgesia (PCEA). Adding fentanyl to bupivacaine reduced the dose of bupivacaine by up to 68%, improved analgesia at rest and decreased PCEA use. Motor and sensory block were decreased, but there was more pruritus. Overall patient satisfaction was increased. Adding bupivacaine to fentanyl reduced the dose of fentanyl by up to 57% without altering pain scores or PCEA use. Sensory block increased but pruritus did not decrease. Bupivacaine 0.05% produced clinically significant leg weakness in three patients. Overall patient satisfaction was not altered. There was a significant additive analgesic effect between 0.05% bupivacaine and fentanyl but no clinical benefit was demonstrated from using the combination compared with fentanyl alone for this group of postoperative patients.

SummaryThe changes in intra-ocular pressure associated with two dgferent anaesthetic induction and tracheal intubation techniques were conipared (n = 30). After pre-oxygenation, Group A received thiopentone ( 5 mglkg) followed by suxamethonium (1.5 Patients with penetrating eye injuries may present for surgery with a potential full stomach and in this situation many anaesthetists would choose a rapid sequence induction. Suxamethonium remains the relaxant of choice for this technique, but its use is accompanied by an increase in intra-ocular pressure (IOP).1-3 A number of studies4~~' have invcstigatcd the substitution of atracurium or vecuronium for suxamethonium. However, this has not eliminated increases in IOP above baseline value^^'^ and is associated with othcr disadvantages. These are an increased delay in obtaining full r e l a x a t i~n ;~~~~~ suboptimal intubating condition^;^-' ' administration of thc relaxant 20-30 seconds before induction,'-' and a lowered safety margin in railed intubation. One previous paper only'2 has conipared the IOP changes when suxamethonium or atracurium was used for rapid sequence induction. The authors contined their conclusions to the suitability of atracurium in rapid sequence induction but there was evidence that suxamethonium could be associated with only minimal elevations in IOP. Our study thereforc furthcr invcstigatcs thc changes in IOP when thiopentone and suxamethonium or thiopentone and atracurium are used for induction and intubation. MethodsThirty patients in ASA groups 1 or 2 and aged 16-65, who required tracheal intubation for nonophthalmic surgery were included in the study; all gave informed consent which had ethics committee approval. Hypertensive patients and those with known ocular discasc wcrc cxcludcd. Premcdication was with papaveretum 0.3 mgikg and hyoscine 0.06 nigikg intramuscularly one hour bcforc anacsthesia. Baseline IOP, arterial blood pressure and pulse were recorded on arrival in the anaesthetic room. Baseline IOP was measured in the right eye with the patient supine, using a Perkins hand-held applanation t~n o m e t e r . '~ All readings were taken after the topical instillation of lignocaine and flourescein eye drops and performed by one of the authors (L.L.), who was unaware of the anaesthetic agents used. All patients were pre-oxygenated for 2 minutes before induction and allocated randomly to one of two groups.