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Maternal temperature during labour using low-dose (ambulatory) epidural analgesia with bupivacaine and fentanyl
ORIGZNAL
ARTICLE
Maternal temperature during labour using low-dose (ambulatory) epidural analgesia with bupivacaine and fentanyl M. L. Thomas, S. M. Yentis, l? Barnes Mugill Dcp~rtment oj’A~wrsthrtic.s. Ck~lseo rend Wt~strm’rzstcr.Hospitcrl, London, UK SUMMARY Maternal temperature is known to increase during labour with conventional epidural analgesia mixtures. To date, the effect of newer low-dose (ambulatory) epidural concentrations on maternal temperature has not been studied. Twenty-six women in established labour received epidural analgesia with 0.1% bupivacaine and 2 j.tg/ml fentanyl. Tympanic membrane (core) temperature was measured every 30 min during labour. There was no significant overall rise in maternal temperature during labour with the use of an ambulatory epidural mixture. One patient exhibited an increase in temperature of O.S”C to 38°C after 720 min and another of l.l”C to 38.1”C after 630 min. We conclude that, whilst overall maternal temperature does not increase following low-dose epidural analgesia, individual increases may still occur after 10 h.
INTRODUCTION
ing ambulatory epidural analgesia in established labour were studied. The onset of labour was taken as cervical dilatation of 3 cm or more with effacement and regular contractions with or without membrane rupture. All mothers were preloaded intravenously with 500-1000 ml of Hartmann’s solution at room temperature. An epidural catheter was introduced at Ll-L4 and a segmental block was produced with 15 ml of 0.1 “/;I bupivacaine and 50 pg fentanyl. Top ups were 10 ml boluses of 0.1% bupivacaine with 2 pg/ml fentanyl as required. A midstream specimen of urine (MSU) and a high vaginal swab (HVS) were taken for bacterial culture at the start of the study period in each case, in order to exclude infection at these sites as a cause for any increase in maternal temperature. Maternal temperature was measured by non-invasive tympanic thermometer (First Temp GeniusO, Sherwood Medical’) every 30 min. Room temperature was also measured. Sample size was calculated from previous studies using power analysis with values for CI and B of 0.05 and 0.2 respectively. Temperature readings were analysed with Wilcoxon signed rank sum tests using the Bonferroni correction for repeated analysis.
Epidural analgesia in labour using concentrations of bupivacaine of 0.25% or above, with or without the addition of fentanyl, has been shown by several authors to be associated with increased maternal temperature during labour.‘-” The maximum increase typically occurs after 7 h and can be more than 1°C compared to pethidine controls.‘Current practice now commonly favours the use of low concentrations of local anaesthetic with opioid added in order to allow greater maternal mobility in labour and to improve maternal satisfaction.” No studies to date have examined the effect on maternal temperature in labour of an epidural mixture containing a concentration of bupivacaine lower than 0.25%. In this pilot study we measured maternal tympanic temperature in women receiving low-dose epidural analgesia in labour.
PATIENTS AND METHODS Ethics Committee approval and written informed consent were obtained. Twenty-eight healthy, apyrexial (less than 37.5”C) women with singleton pregnancies receiv-
RESULTS
M. L. Thomas, S. M. Yentis, P. Barnes, Anaesthetics. Chelsea and Westminster Road. London SW10 9NH. UK. Correspondence
Two women were excluded: one who had a temperature increase from 36.9”C to 38.1”C at delivery and a urinary tract infection confirmed by MSU and the second whose temperature increased from 35.6”C to 39.2”C after 6.5 h and whose HVS grew group B streptococcus.
Magill Department of Hospital. 369 Fulham
to: Dr M. L. Thomas. 108
Maternal temperature with low-dose epidural analgesia Of the 26 remaining women, 24 were primiparous and 2 were multiparous. Eighteen had spontaneous rupture of membranes and 8 had artificial rupture. The times from onset of labour to delivery, from rupture of membranes to onset of epidural analgesia and from onset of epidural analgesia to delivery and the numbers of top-ups are given in the table. No other epidural drugs were given. No patients required boluses of more than 10 ml and no epidurals needed resiting. The mean (SD) starting room temperature was 24.3 (1.6)“C and the room temperature at delivery 24.2 (1.5)“C. None of the women left the room or bathed once the epidural was sited. The median and interquartile and total ranges for temperature readings are shown in the Figure. Although there appears to be a slight increase in temperature with time this was not significant. Power analysis reveals that 117 women would be required to show a temperature rise of the magnitude found (0.3”C) between time zero and 750 min, with 90% power. Two patients exhibited a sustained (at least two consecutive readings) pyrexia. In one, the temperature increased from 37.2”C to 38.1 “C after 720 min, and in the other, from 37°C to 37.9”C and 38.1”C for two consecutive readings at 600 and 630 min. Eight others had isolated readings of more than 37.5”C (median 37.6”C, range 37.6-37.8”C) but in all cases this fell below 37.5”C on successive readings. DISCUSSION
In our study, 0.1% epidural bupivacaine with fentanyl (2 pg/ml) was not associated with a significant rise in maternal temperature during labour. This is in contrast to the published work on higher concentrations of bupivacaine.‘.5 Although the numbers of women in this pilot study are small, the clinical significance of a 0.3”C rise in temperature is negligible, even were it to have reached statistical significance. Two patients in our study exhibited a sustained temperature increase, reaching 38.1 “C. Tn previous studies,? individual patients became pyrexial who did not receive epidural analgesia. We therefore feel it is not possible to blame epidural analgesia as a cause for the pyrexia in these two patients given the overall temperature changes in the present group and the mean increase of 1°C associated with epidural analgesia in previous studies. ‘m5
Table.
Duration
Time from Time from Time from Number of
of labour
and epidural
Tim(h)
Fig. Maternal temperature (“C) and number of subjects remaining in labour versus time from the onset of epidural analgesia to delivery. The box represents the interquartile range and the horizontal line the median. Vertical bars denote range.
In addition, these two temperature increases occurred after 600 and 720 min, whereas previous studies have demonstrated that epidural-associated pyrexia becomes apparent after 360420 min.lm5 Microbiological screening of these two patients and their babies revealed no infective cause for their pyrexia but does not exclude it. It would appear that if low-dose epidural analgesia does cause an increase in temperature, it is a much less marked effect than high-dose epidural ana’lgesia, although we did not have a control group for a number of logistical reasons. We could have used either an intramuscular pethidine analgesia group or a more conventional epidural analgesia mixture group as controls. However, the number of women requesting pethidine analgesia is so low in our unit that this group would have been too small to be used as unrandomized controls. Furthermore, pethidine tends to be used for labours of less than 7 h, which is less than the minimum time period we wished to study. We do not routinely offer conventional high-dose epidural analgesia in our unit since low-dose analgesia has been shown to be superior in many respects.8.9 Finally, the validity of a non-randomized control group would anyway be questionable. The absence of a significant change in maternal temperature with low-dose mixtures may reflect a difference in action on thermoreceptor pathways between highand low-dose bupivacaine plus or minus fentanyl. It has been elegantly shown that epidurdl bupivacaine produces differential block of non-painful somatosensory
details
onset of labour to delivery (h) rupture of membranes to epidural onset of epidural to delivery (h) top-ups
(h)
109
Median
Interquartile
15.5 9.5 IO 7
13.9-21.1 0.8-21.1 9.1 12.1 5 10
range
Total 5
range
21.4 8.3 31.0 4.8 22.9 3 I1
functions with warmth perception being affected more than cold perception.“’ Such differential block may cause differences in central thermoregulation with less afferent warm neural transmission resulting in a greater perception of cold and thus inappropriate triggering of heat conservation reflexes and resultant pyrexia. It is reasonable to postulate that this effect is dose-related and may not be invoked to such an extent with lower concentration of bupivacaine. Opioids may have a direct action on thermoregulation. Certainly, morphine reduces neuronal discharge in the dorsal horn,” and opioids have a profound influence on central thermoregulatory mechanisms.” However, the addition of fentanyl to conventional concentrations of epidural bupivacaine seems to have no additional effect on maternal temperature.5 It has been proposed recently that epidural-associated pyrexia may be the result of central thermostat resetting rather than, or possibly in addition to, an alteration in afferent input.’ This effect may be less with lower doses of bupivacaine or with the addition of fentanyl. Another possibility for a reduced temperature effect is a difference in the volume of epidural solution used in the newer low-dose mixtures compared with the higher concentration and lower volumes used in the past. Previous work has shown that prewarming epidural solutions causes less shivering’? although whether shivering is a thermogenic response is disputed.14 It could be that higher volumes of cold solution administered epidurally cause a greater drop in core temperature, but the volumes used are still far smaller than that of the fluids administered intravenously; indeed the latter are used in larger volumes with higher-dose epidurals because of the greater incidence of hypotension in that group. Epidural analgesia is cited as a risk factor for the development of fever in labour and increases in maternal temperature are freely conveyed to the fetus.ls If low-dose epidural analgesia causes less increase in temperature than conventional mixtures, then the occurrence of maternal or fetal pyrexia during low-dose epidural analgesia is unlikely to be related to the epidural and thus infective causes need to be investigated. A controlled, randomized study is
not possible in our unit but this pilot suggests no significant rise in maternal temperature during low-dose epidural analgesia in labour. ACKNOWLEDGEMENTS
WC would like to thank Professor P. J. Steer for helpful comments, the staff of the delivery suite at Chelsea and Westminster Hospital for their support and Sherwood Medical for the loan of the tympanlc temperature probe.
REFERENCES
1.
2
3 4.
5.
6.
I. 8.
Mercier F .I. Benhamou D. Hyperthermia related to epidural analgesia during labor. International Journal of Obstetric Anesthesia 1997; 6: 19-24. Fusi L. Steer P J. Maresh M J. Beard R W. Maternal pyrexia associated with the use of epidural analgesia in labour. Lancet 1989: 1: 1250&1252. Herbst A, Wolner-Hanssen P, Ingermarsson I. Risk factors fol fever in labour. Obstet Gynecol 1995; 86: 790-794. Vinson D C. Thomas R. Kiser T. Association between epidural analgesia during labour and fever. J Fam Pratt 1993: 36: 617-622. Camann W R, Hortvet L A, Hughes N, Bader A M, Datta S. Maternal temperature regulation during extradural analgesia for labour. Br J Anaesth 1991; 67: 565-568. Murphy J D, Henderson K, Bowden M I, Lewis M, Cooper G M. Bupivacaine versus bupivacaine plus fentanyl for epidural analgesia: effect on maternal satisfaction. BMJ 1991: 302: 564-567. Edge G. Morgan M. The Genius infrared tympanic thermometer. Anaesthesia 1993; 48: 604-607. Reynolds F. Extradural opioids in labour. Br J Anaesth 1989; 63:251
9.
253.
Collis R E. Baxandall Kadim M Y, Morgan analgesia with ability
M L, Srikantharajah 1 D, Edge G, B M. Combined spinal epidural to walk throughout labour. Lancet 1993;
341:767-768.
10
Brennum J. Nielsen P T. Horn A, Arendt-Nielsen L, Secher N H. Quantitative sensory examination of epidurdl anaesthesia and analgesia in man; dose response effect of bupivacaine. Pain 1994; 56: 3 1S-326. II Kitahata L M, Kosaka Y, Taub A, Bonikos K. Hoffert M. Lamina specific suppression of dorsal horn unit activity by morphine sulfate. Anesthesiology 1974; 41: 3948. 12 Clark W G. Influence of opioids on central thermoregulatory mechanisms. Pharmacol Biochem Behav 1979; 10: 609-613. 13 Ponte J, Collett B J, Walmsey A. Anaesthetic temperature and shivering in epidural anaesthesia. Acta Anaesthesiol Stand 1986; 30: 5X4-587. 14. Buggy D, Gardiner J. The space blanket and shivering during extradural analgesia in labour. Acta Anaesthesiol Stand 1995; 39:551-553.
15
Macaulay and foetal
J H, Bond K, Steer P J. Epidural analgesia in labour hyperthermia. Obstet Gynecol 1992: 80: 665-668.
ARTICLE
Maternal temperature during labour using low-dose (ambulatory) epidural analgesia with bupivacaine and fentanyl M. L. Thomas, S. M. Yentis, l? Barnes Mugill Dcp~rtment oj’A~wrsthrtic.s. Ck~lseo rend Wt~strm’rzstcr.Hospitcrl, London, UK SUMMARY Maternal temperature is known to increase during labour with conventional epidural analgesia mixtures. To date, the effect of newer low-dose (ambulatory) epidural concentrations on maternal temperature has not been studied. Twenty-six women in established labour received epidural analgesia with 0.1% bupivacaine and 2 j.tg/ml fentanyl. Tympanic membrane (core) temperature was measured every 30 min during labour. There was no significant overall rise in maternal temperature during labour with the use of an ambulatory epidural mixture. One patient exhibited an increase in temperature of O.S”C to 38°C after 720 min and another of l.l”C to 38.1”C after 630 min. We conclude that, whilst overall maternal temperature does not increase following low-dose epidural analgesia, individual increases may still occur after 10 h.
INTRODUCTION
ing ambulatory epidural analgesia in established labour were studied. The onset of labour was taken as cervical dilatation of 3 cm or more with effacement and regular contractions with or without membrane rupture. All mothers were preloaded intravenously with 500-1000 ml of Hartmann’s solution at room temperature. An epidural catheter was introduced at Ll-L4 and a segmental block was produced with 15 ml of 0.1 “/;I bupivacaine and 50 pg fentanyl. Top ups were 10 ml boluses of 0.1% bupivacaine with 2 pg/ml fentanyl as required. A midstream specimen of urine (MSU) and a high vaginal swab (HVS) were taken for bacterial culture at the start of the study period in each case, in order to exclude infection at these sites as a cause for any increase in maternal temperature. Maternal temperature was measured by non-invasive tympanic thermometer (First Temp GeniusO, Sherwood Medical’) every 30 min. Room temperature was also measured. Sample size was calculated from previous studies using power analysis with values for CI and B of 0.05 and 0.2 respectively. Temperature readings were analysed with Wilcoxon signed rank sum tests using the Bonferroni correction for repeated analysis.
Epidural analgesia in labour using concentrations of bupivacaine of 0.25% or above, with or without the addition of fentanyl, has been shown by several authors to be associated with increased maternal temperature during labour.‘-” The maximum increase typically occurs after 7 h and can be more than 1°C compared to pethidine controls.‘Current practice now commonly favours the use of low concentrations of local anaesthetic with opioid added in order to allow greater maternal mobility in labour and to improve maternal satisfaction.” No studies to date have examined the effect on maternal temperature in labour of an epidural mixture containing a concentration of bupivacaine lower than 0.25%. In this pilot study we measured maternal tympanic temperature in women receiving low-dose epidural analgesia in labour.
PATIENTS AND METHODS Ethics Committee approval and written informed consent were obtained. Twenty-eight healthy, apyrexial (less than 37.5”C) women with singleton pregnancies receiv-
RESULTS
M. L. Thomas, S. M. Yentis, P. Barnes, Anaesthetics. Chelsea and Westminster Road. London SW10 9NH. UK. Correspondence
Two women were excluded: one who had a temperature increase from 36.9”C to 38.1”C at delivery and a urinary tract infection confirmed by MSU and the second whose temperature increased from 35.6”C to 39.2”C after 6.5 h and whose HVS grew group B streptococcus.
Magill Department of Hospital. 369 Fulham
to: Dr M. L. Thomas. 108
Maternal temperature with low-dose epidural analgesia Of the 26 remaining women, 24 were primiparous and 2 were multiparous. Eighteen had spontaneous rupture of membranes and 8 had artificial rupture. The times from onset of labour to delivery, from rupture of membranes to onset of epidural analgesia and from onset of epidural analgesia to delivery and the numbers of top-ups are given in the table. No other epidural drugs were given. No patients required boluses of more than 10 ml and no epidurals needed resiting. The mean (SD) starting room temperature was 24.3 (1.6)“C and the room temperature at delivery 24.2 (1.5)“C. None of the women left the room or bathed once the epidural was sited. The median and interquartile and total ranges for temperature readings are shown in the Figure. Although there appears to be a slight increase in temperature with time this was not significant. Power analysis reveals that 117 women would be required to show a temperature rise of the magnitude found (0.3”C) between time zero and 750 min, with 90% power. Two patients exhibited a sustained (at least two consecutive readings) pyrexia. In one, the temperature increased from 37.2”C to 38.1 “C after 720 min, and in the other, from 37°C to 37.9”C and 38.1”C for two consecutive readings at 600 and 630 min. Eight others had isolated readings of more than 37.5”C (median 37.6”C, range 37.6-37.8”C) but in all cases this fell below 37.5”C on successive readings. DISCUSSION
In our study, 0.1% epidural bupivacaine with fentanyl (2 pg/ml) was not associated with a significant rise in maternal temperature during labour. This is in contrast to the published work on higher concentrations of bupivacaine.‘.5 Although the numbers of women in this pilot study are small, the clinical significance of a 0.3”C rise in temperature is negligible, even were it to have reached statistical significance. Two patients in our study exhibited a sustained temperature increase, reaching 38.1 “C. Tn previous studies,? individual patients became pyrexial who did not receive epidural analgesia. We therefore feel it is not possible to blame epidural analgesia as a cause for the pyrexia in these two patients given the overall temperature changes in the present group and the mean increase of 1°C associated with epidural analgesia in previous studies. ‘m5
Table.
Duration
Time from Time from Time from Number of
of labour
and epidural
Tim(h)
Fig. Maternal temperature (“C) and number of subjects remaining in labour versus time from the onset of epidural analgesia to delivery. The box represents the interquartile range and the horizontal line the median. Vertical bars denote range.
In addition, these two temperature increases occurred after 600 and 720 min, whereas previous studies have demonstrated that epidural-associated pyrexia becomes apparent after 360420 min.lm5 Microbiological screening of these two patients and their babies revealed no infective cause for their pyrexia but does not exclude it. It would appear that if low-dose epidural analgesia does cause an increase in temperature, it is a much less marked effect than high-dose epidural ana’lgesia, although we did not have a control group for a number of logistical reasons. We could have used either an intramuscular pethidine analgesia group or a more conventional epidural analgesia mixture group as controls. However, the number of women requesting pethidine analgesia is so low in our unit that this group would have been too small to be used as unrandomized controls. Furthermore, pethidine tends to be used for labours of less than 7 h, which is less than the minimum time period we wished to study. We do not routinely offer conventional high-dose epidural analgesia in our unit since low-dose analgesia has been shown to be superior in many respects.8.9 Finally, the validity of a non-randomized control group would anyway be questionable. The absence of a significant change in maternal temperature with low-dose mixtures may reflect a difference in action on thermoreceptor pathways between highand low-dose bupivacaine plus or minus fentanyl. It has been elegantly shown that epidurdl bupivacaine produces differential block of non-painful somatosensory
details
onset of labour to delivery (h) rupture of membranes to epidural onset of epidural to delivery (h) top-ups
(h)
109
Median
Interquartile
15.5 9.5 IO 7
13.9-21.1 0.8-21.1 9.1 12.1 5 10
range
Total 5
range
21.4 8.3 31.0 4.8 22.9 3 I1
functions with warmth perception being affected more than cold perception.“’ Such differential block may cause differences in central thermoregulation with less afferent warm neural transmission resulting in a greater perception of cold and thus inappropriate triggering of heat conservation reflexes and resultant pyrexia. It is reasonable to postulate that this effect is dose-related and may not be invoked to such an extent with lower concentration of bupivacaine. Opioids may have a direct action on thermoregulation. Certainly, morphine reduces neuronal discharge in the dorsal horn,” and opioids have a profound influence on central thermoregulatory mechanisms.” However, the addition of fentanyl to conventional concentrations of epidural bupivacaine seems to have no additional effect on maternal temperature.5 It has been proposed recently that epidural-associated pyrexia may be the result of central thermostat resetting rather than, or possibly in addition to, an alteration in afferent input.’ This effect may be less with lower doses of bupivacaine or with the addition of fentanyl. Another possibility for a reduced temperature effect is a difference in the volume of epidural solution used in the newer low-dose mixtures compared with the higher concentration and lower volumes used in the past. Previous work has shown that prewarming epidural solutions causes less shivering’? although whether shivering is a thermogenic response is disputed.14 It could be that higher volumes of cold solution administered epidurally cause a greater drop in core temperature, but the volumes used are still far smaller than that of the fluids administered intravenously; indeed the latter are used in larger volumes with higher-dose epidurals because of the greater incidence of hypotension in that group. Epidural analgesia is cited as a risk factor for the development of fever in labour and increases in maternal temperature are freely conveyed to the fetus.ls If low-dose epidural analgesia causes less increase in temperature than conventional mixtures, then the occurrence of maternal or fetal pyrexia during low-dose epidural analgesia is unlikely to be related to the epidural and thus infective causes need to be investigated. A controlled, randomized study is
not possible in our unit but this pilot suggests no significant rise in maternal temperature during low-dose epidural analgesia in labour. ACKNOWLEDGEMENTS
WC would like to thank Professor P. J. Steer for helpful comments, the staff of the delivery suite at Chelsea and Westminster Hospital for their support and Sherwood Medical for the loan of the tympanlc temperature probe.
REFERENCES
1.
2
3 4.
5.
6.
I. 8.
Mercier F .I. Benhamou D. Hyperthermia related to epidural analgesia during labor. International Journal of Obstetric Anesthesia 1997; 6: 19-24. Fusi L. Steer P J. Maresh M J. Beard R W. Maternal pyrexia associated with the use of epidural analgesia in labour. Lancet 1989: 1: 1250&1252. Herbst A, Wolner-Hanssen P, Ingermarsson I. Risk factors fol fever in labour. Obstet Gynecol 1995; 86: 790-794. Vinson D C. Thomas R. Kiser T. Association between epidural analgesia during labour and fever. J Fam Pratt 1993: 36: 617-622. Camann W R, Hortvet L A, Hughes N, Bader A M, Datta S. Maternal temperature regulation during extradural analgesia for labour. Br J Anaesth 1991; 67: 565-568. Murphy J D, Henderson K, Bowden M I, Lewis M, Cooper G M. Bupivacaine versus bupivacaine plus fentanyl for epidural analgesia: effect on maternal satisfaction. BMJ 1991: 302: 564-567. Edge G. Morgan M. The Genius infrared tympanic thermometer. Anaesthesia 1993; 48: 604-607. Reynolds F. Extradural opioids in labour. Br J Anaesth 1989; 63:251
9.
253.
Collis R E. Baxandall Kadim M Y, Morgan analgesia with ability
M L, Srikantharajah 1 D, Edge G, B M. Combined spinal epidural to walk throughout labour. Lancet 1993;
341:767-768.
10
Brennum J. Nielsen P T. Horn A, Arendt-Nielsen L, Secher N H. Quantitative sensory examination of epidurdl anaesthesia and analgesia in man; dose response effect of bupivacaine. Pain 1994; 56: 3 1S-326. II Kitahata L M, Kosaka Y, Taub A, Bonikos K. Hoffert M. Lamina specific suppression of dorsal horn unit activity by morphine sulfate. Anesthesiology 1974; 41: 3948. 12 Clark W G. Influence of opioids on central thermoregulatory mechanisms. Pharmacol Biochem Behav 1979; 10: 609-613. 13 Ponte J, Collett B J, Walmsey A. Anaesthetic temperature and shivering in epidural anaesthesia. Acta Anaesthesiol Stand 1986; 30: 5X4-587. 14. Buggy D, Gardiner J. The space blanket and shivering during extradural analgesia in labour. Acta Anaesthesiol Stand 1995; 39:551-553.
15
Macaulay and foetal
J H, Bond K, Steer P J. Epidural analgesia in labour hyperthermia. Obstet Gynecol 1992: 80: 665-668.