Effect of intravenous vasopressor on spread of spinal anaesthesia and fetal acid-base equilibrium.

BACKGROUND: We previously found rostral spread of spinal plain levobupivacaine to be less with prophylactic i.v. phenylephrine than with ephedrine during Caesarean delivery. This study investigated whether rostral spread of spinal hyperbaric bupivacaine is also less with phenylephrine than with ephedrine. METHODS: The study was randomized and double blind. It compared phenylephrine 100 microg ml-1 (phenylephrine group, n=27), and ephedrine 4.5 mg ml-1 (ephedrine group, n=27), given by infusion during spinal anaesthesia for Caesarean delivery. Block height was assessed to cold and light touch sensation at 15, 30, 60, and 90-min after the spinal injection of 2.8 ml of hyperbaric 0.5% w/v bupivacaine, combined with 0.4 ml diamorphine (1 mg ml-1). Umbilical blood gas values were monitored during the study. RESULTS: Block height was similar for both groups at all of the assessment times. Umbilical artery pH was higher with phenylephrine [median 7.32 (IQR 7.28-7.34)] than with ephedrine [7.20 (7.10-7.28)] (P<0.0001). There was a strong negative correlation between umbilical artery pH and spinal-delivery interval, but only with ephedrine: phenylephrine group, r2=0.09 (P=0.17), and ephedrine group, r2=0.53 (P<0.0001). Five-minute Apgar scores were higher with phenylephrine [10 (9-10)] than ephedrine [9 (9-9)] (P=0.009). CONCLUSIONS: In contrast to its effect on spinal plain levobupivacaine, we did not find rostral spread of spinal hyperbaric bupivacaine to be less with prophylactic phenylephrine than with ephedrine. We observed an unexpectedly high incidence of fetal acidosis with ephedrine and found evidence that longer spinal-delivery intervals increase the risk of fetal acidosis developing with ephedrine, but not phenylephrine.

Patient-controlled analgesia: epidural fentanyl and i.v. morphine compared after caesarean section.

We have compared patient-controlled epidural fentanyl (PCEF) and patient-controlled i.v. morphine (PCIM) after Caesarean section in 84 patients, in a randomized, double-blind study. All patients had an epidural and an i.v. patient-controlled analgesia (PCA) device, one of which delivered normal saline. Group PCEF received epidural fentanyl 20 micrograms with a 10-min lockout. Group PCIM received i.v. morphine 1 mg with a 5-min lockout. PCA use was lower for PCEF patients (P = 0.0007). The highest pain score recorded at rest for PCEF patients was median 20 (interquartile range 10-33) mm compared with 32 (14-52) mm for PCIM patients (P = 0.02). The highest pain score recorded on coughing was 31 (21-41) mm with PCEF compared with 56 (30-71) mm for PCIM (P = 0.001). There was less nausea (P = 0.02) and drowsiness (P = 0.0003) with PCEF. There was no difference in the overall incidence and severity of pruritus (P = 0.77). However, pruritus started earlier with PCEF.

Does intrathecal fentanyl produce acute cross-tolerance to i.v. morphine?

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 micrograms) (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 micrograms) 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.

Fluid absorption during laser ablation of the endometrium in the treatment of menorrhagia.

Twenty-six women participated in a two-part study to determine the magnitude of absorption of irrigating fluid during endometrial laser ablation (ELA), and the effect on this absorption of controlling the intra-uterine pressure (IUP) during ablation. Six women participated in the first part of the study in which IUP was uncontrolled during surgery. The mean fluid deficit was 2027 ml. In the second part of the study, 20 women were allocated randomly to two groups. In the first group (nine women), IUP was uncontrolled during surgery. The mean IUP was 100 mm Hg, mean maximum IUP 136 mm Hg and mean fluid deficit 1255 ml. In the second group (11 women), the IUP was controlled during surgery. The mean IUP was 66 mm Hg, mean maximum IUP 70 mm Hg, and there was no fluid deficit in any of the women. The study demonstrates that control of IUP during ELA was effective in preventing absorption of irrigating fluid.

Intrathecal diamorphine: a dose-response study.

A randomised double-blind study compared the dose-response relationship of intrathecal diamorphine (0, 0.25, 0.75, 1.5, and 2.5 mg) for postoperative pain relief, in 35 subjects who underwent total knee replacement surgery. Assessments commenced 2 h after the opioid injection and continued for 20 h. Pain, analgesic effect, supplementary analgesic requirements and adverse effects were noted. Intrathecal diamorphine was unable to delay the initial perception of discomfort. It was, however, capable of postponing the onset of severe pain requiring analgesic supplementation (control 5.25 h vs approximately 8 h: P less than 0.05). There was no significant difference in the quality of analgesia between the groups. Pruritus was the only undesirable feature unique to intrathecal diamorphine administration. Intrathecal diamorphine was safe and was not associated with clinically apparent respiratory depression. Its effects were inconsistent and its use was associated with irritating side effects. Possible explanations for the erratic behaviour of the diamorphine are discussed.