Department of Anaesthesia, Northwick Park and St Marks NHS Trust, Watford Road, Harrow, Middlesex HA1 3AJ, UK*Corresponding author
Accepted for publication: October 31, 2000
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Br J Anaesth 2001; 86: 5679
Keywords: analgesia, obstetric; analgesic techniques, subarachnoid; analgesics opioid, diamorphine; analgesics opioid, fentanyl
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
Methods and results |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
After i.v. access had been secured, the epidural was sited at L2/3 or L3/4 with the patient sitting. Patients were allocated to one of two groups: group F received isobaric bupivacaine 2.5 mg plus fentanyl 25 µg, total volume 1.5 ml (n=32); group D received isobaric bupivacaine 2.5 mg plus diamorphine 250 µg, total volume 1.5 ml (n=30). The appropriate mixture was injected intrathecally through a 26 G Whitacre needle using a needle-through-needle technique. Cerebrospinal fluid aspirates were tested before and after injection, and the time of injection was noted. The attending midwife was unaware of the group allocation. Pulse, blood pressure and cardiotocograph recordings were carried out as normal.
The times to the first comfortable contraction (freedom from pain regardless of block height; t1) and to first top-up request (t2) were recorded by the midwife. Patients were told to inform their midwife as soon as the pain of contractions recurred. Maternal hypotension (systolic blood pressure less than 90 mm Hg or a reduction of more than 20 mm Hg from baseline or symptomatic), nausea, vomiting, pruritis and fetal bradycardia (less than 100 beats min1) were recorded and treated if necessary. Proprioception and lower limb power were assessed 30 min after injection using hallux positioning and modified Bromage scoring respectively. All patients were observed every 4 h for 24 h after treatment for evidence of respiratory depression. A respiratory rate greater than 9 b.p.m. was taken as adequate. All subsequent top-ups were opioid-free (0.2% ropivacaine 1015 ml) to avoid worsening any potential respiratory depression resulting from the intrathecal opioid.
The two groups were similar in terms of age, parity and induction and augmentation rates. Cervical dilation was similar in the two groups (group D, mean 4.0 cm, five patients >5 cm dilated; group F, mean 4.1 cm, seven patients >5 cm dilated). Two women were withdrawn from group D (one analgesic failure, one delivery) and one from group F (analgesic failure). Results from the remaining 59 patients were analysed using the t test, the 2 test, the MannWhitney U-test and the KruskalWallis test as appropriate. The results are summarized in Table 1. A P value less than 0.05 was taken as significant.
|
![]() |
Comments |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
The CSE is a technique commonly used to initiate labour analgesia. There is ongoing debate in the literature about whether the benefits offered by this approach to the labouring woman above those seen with a low-dose epidural outweigh the perceived small increase in risk associated with deliberate dural puncture.16 This argument has yet to be resolved, but it is clear that an increase in the duration of action of the initial dose results in less breakthrough pain during labour, a factor registered as important in studies of maternal satisfaction.7 The ultimate aim may be a single-intervention method of complete analgesia throughout childbirth, and our study indicates a possible step in the right direction. Decreasing the need for top-ups and associated medical/midwifery interventions may also result in a decrease in staff workload.
The dose of diamorphine used in this study was deliberately low because of worries regarding side-effects, principally pruritis and respiratory depression. Diamorphine was chosen in place of morphine because of its much higher oil/water partition coefficient (morphine 1.4, diamorphine 280, fentanyl 816).8 Doses of 500 µg diamorphine alone have been reported for intrathecal labour analgesia without respiratory depression occurring.9 Morphine has been reported to cause delayed respiratory depression and even apnoea with doses as low as 1 mg intrathecally,8 10 and thus, as a dose of 12 mg is reported to be necessary for significant benefit,10 11 it cannot be used reliably and safely in labour. Although we have found no evidence of respiratory depression with diamorphine 250 µg intrathecally, we have not proved conclusively that it will never occur. Care must always be taken in the post-delivery monitoring of these patients.
Recent studies have shown effective analgesia with doses of intrathecal opioid lower than those commonly used.12 It may be that the prolongation of action seen with diamorphine requires less than this 250 µg dose. It may also be that this extension of time to first top-up is increased with a higher intrathecal dose. It seems likely that we have detected an enhanced bupivacaine-sparing effect and that extension of this effect is dependent on local anaesthetic concentration at the effector site combined with improved or prolonged spinal opioid receptor stimulation. To what degree further extension of time to first top-up is possible remains to be elucidated, as does the minimum dose of diamorphine required to produce this effect.
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
2 Dresner M, Bamber J, Calow C, Freeman J, Charlton P. Comparison of low-dose epidural with combined spinalepidural analgesia for labour. Br J Anaesth 1999; 83: 75660
3 Nickells JS, Vaughan DJA, Lillywhite NK, Hasan M, Loughnan B, Robinson PN. Speed of onset of regional analgesia in labour: a comparison of the epidural and spinal routes. Anaesthesia 2000; 55: 1720[ISI][Medline]
4 Hepner DL, Gaiser RR, Cheek TG, Gutsche BB. Comparison of combined spinalepidural and low dose epidural for labour analgesia. Can J Anaesth 2000; 47: 2326
5 Price C, Lafreniere L, Brosnan C, Findley I. Regional analgesia in early active labour: combined spinal epidural vs. epidural. Anaesthesia 1998; 53: 9515[ISI][Medline]
6 Collis RE. Do the risks of combined spinalepidural analgesia in labour outweigh the benefits? Hosp Med 1998; 59: 38892[ISI][Medline]
7 Robinson PN, Salmon P, Yentis SM. Maternal satisfaction. Int J Obst Anesth 1998; 7: 327[ISI]
8 Westmore MD. Epidural opioids in obstetricsa review. Anesth Intensive Care 1990; 18: 292300[ISI][Medline]
9 Kestin IG, Madden AP, Mulvein JT, Goodman NW. Analgesia for labour and delivery using incremental diamorphine and bupivacaine via a 32 gauge intrathecal catheter. Br J Anaesth 1992; 8: 2447
10 Abouleish E. Apnoea associated with the intrathecal administration of morphine in obstetrics. Br J Anaesth 1988; 60: 5924[Abstract]
11 Leighton BL, De Simone C, Norris MC, Ben-David B. Intrathecal narcotics for labour revisited: the combination of fentanyl and morphine intrathecally provides rapid onset of profound, prolonged analgesia. Anesth Analg 1989; 69: 1225[ISI][Medline]
12 Lo WK, Chong JL, Chen LH. Combined spinal epidural for labour analgesiaduration, efficacy and side effects of adding sufentanil or fentanyl to bupivacaine intrathecally vs. plain bupivacaine. Singapore Med J 1999; 40: 63943[Medline]