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tale: une étude pilote]
From the Department of Anesthesiology, University Hospitals Gasthuisberg, Katholieke Universiteit Leuven, Leuven, Belgium.
Address correspondence to: Dr. Marc Van de Velde, Director Obstetric Anesthesia and Extra Muros Anesthesia, Department of Anesthesiology, University Hospitals Gasthuisberg, Herestraat 49, B - 3000 Leuven, Belgium. Phone: 32 16 34 42 70; Fax: 32 16 34 42 45; E-mail: marc.vandevelde{at}uz.kuleuven.ac.be
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Abstract |
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Methods: Fifty patients requesting combined spinal epidural analgesia for labour pain relief were randomly assigned to receive intrathecal ropivacaine 3 mg, sufentanil 1.5 µg with or without clonidine 30 µg. Onset time and duration of analgesia, visual analogue scores for pain, blood pressure, ephedrine requirements, heart rate, incidence of nausea, pruritus and motor blockade, umbilical artery pH, fetal heart rate abnormalities and Apgar scores were noted and analyzed.
Results: Patients receiving spinal clonidine had significantly longer lasting analgesia compared to patients treated without clonidine (122 ± 56 min vs 90 ± 36 min, P < 0.05). Clonidine-treated patients experienced a more pronounced decrease in mean arterial pressure as compared to patients treated without clonidine (25 ± 10% vs 15 ± 12%, P < 0.05). The groups also differed in ephedrine requirement (4.91 mg vs 0.75 mg, P < 0.05), number of new onset fetal heart rate abnormalities (28% vs 0%, P < 0.05) and umbilical artery pH (7.219 ± 0.096 vs 7.289 ± 0.085, P < 0.05).
Conclusion: Intrathecal clonidine prolongs spinal analgesia with ropivacaine and sufentanil at the expense of maternal hypotension, worse fetal well being and worse neonatal umbilical artery pH. We do not recommend routine administration of spinal clonidine 30 µg to sufentanil and ropivacaine for labour pain relief.
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Introduction |
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Initial spinal analgesia is, however, of limited duration. Only 50% of women receiving a CSE during the late first stage of labour actually deliver during the spinal component of analgesia.5 Once spinal analgesia has worn off, epidural analgesia is required. Problems associated with the epidural catheter can occur, such as unilateral or patchy analgesia. The limited duration of initial spinal analgesia combined with problems associated with maintenance of epidural analgesia, have initiated the search for new combinations of analgesic drugs to prolong the duration of spinal analgesia without increasing side effects.
In recent years, clonidine, an 
-2 adrenoreceptor agonist has been used to prolong spinal anesthesia. Chiari et al. noted that spinal clonidine in doses between 100 and 200 µg produced effective analgesia but sedation and hypotension were common and often severe.6 Smaller doses of clonidine added to sufentanil alone successfully prolong analgesia but can induce hypotension especially if doses of 30 µg or more are used.7,8 D’Angelo et al.,9 Paech et al.10 and Sia11 examined the effects of clonidine added to intrathecally administered local anesthetics and opioids for labour analgesia. They could demonstrate a positive effect of clonidine on duration of spinal analgesia, although the difference did not reach statistical significance in the study by Paech et al.9–11 D’Angelo et al.9 did not observe more hypotension in clonidine treated patients. However, Sia11 and Paech et al.10 did. In 1998, Eisenach suggested that the intrathecal use of clonidine requires more investigation before it can routinely be used during spinal labour analgesia.12
We performed a double blind, randomized trial investigating the effects of CSE analgesia using intrathecal ropivacaine and sufentanil, with or without the addition of clonidine. We hypothesized that the addition of clonidine 30 µg would increase the total duration of spinal analgesia, without an effect on maternal hemodynamics or fetal outcome. The addition of clonidine to intrathecal ropivacaine and sufentanil has not been studied previously.
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Methods |
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Following iv hydration with 1000 mL of lactated Ringer’s solution, a CSE was performed at the L3–L4 interspace with the patient in the sitting position. The epidural space was located using the loss of resistance to saline technique with an 18-gauge Tuohy needle. Spinal puncture was performed using a 27-gauge pencil point needle. The spinal solution was given when spontaneous backflow of cerebrospinal fluid (CSF) occurred in the spinal needle and CSF could easily be aspirated. A 20-gauge epidural catheter was placed 5 cm in the epidural space. Intravascular or intraspinal placement of the catheter was checked by aspiration. No test dose was given. The catheter was secured and the patient was positioned in left lateral decubitus.
Patients were randomized to one of two study groups. Twenty-five patients received a spinal injection of ropivacaine 3 mg combined with sufentanil 1.5 µg dissolved in 2 mL saline (ROSU-group). Twenty-five patients received a spinal injection of 2 mL saline containing ropivacaine 3 mg, sufentanil 1.5 µg and clonidine 30 µg (CLON-group). Vials were prepared by the hospital pharmacist following a computer generated list. The vials were numbered with numbers 1 to 50 and stored in the refrigerator at the labour and delivery suite. Each number corresponded either to the CLON-group or the ROSU-group, based on the computer generated list. The midwife, assisting with the block, randomly took one vial out of storage and offered it to the anesthesiologist performing the CSE. Midwives, anesthesiologists and patients were blinded to the drugs used for spinal analgesia.
If spinal analgesia did not produce satisfactory pain relief within 15 min, additional epidural analgesia (ropivacaine 0.15% with 0.75 µg•mL–1 sufentanil, bolus of 5 mL) was given. Additional epidural top-ups were subsequently administered until satisfactory analgesia was achieved. However these patients were excluded from the study and their data were not used for further analysis. Satisfactory analgesia was defined as a VAS score for pain of less then 20 mm within 15 min following the intrathecal injection.
The first primary outcome variable was the duration of initial spinal analgesia. The duration of initial analgesia was defined as the time between the end of the spinal injection and the moment additional analgesia was requested by the patient. If the patients requested additional pain relief, patient-controlled epidural analgesia was initiated using a bolus of 4 mL with a lockout of 15 min. The epidural solution consisted of ropivacaine 0.15% and sufentanil 0.75 µg•mL–1.
The second primary outcome variable was the incidence of hypotension and the effect of spinal analgesia on maternal blood pressure. Hypotension was defined as a mean arterial pressure (MABP) decrease > 10%. Severe hypotension was defined as a decrease in MABP > 20%. We also recorded the lowest MABP following spinal analgesia and calculated the percentage decrease in arterial pressure.
Following initiation of analgesia, data were collected at regular time intervals until additional analgesia was requested. At this point the study stopped. The following data were collected: VAS for pain, block height, motor blockade, FHR, pruritus, nausea, maternal blood pressure, maternal heart rate (MHR) and the need for tocolytic drugs or ephedrine. Postpartum, maternal satisfaction was assessed using a VAS score (0 = totally unsatisfied, 100 = totally satisfied). Maternal side effects such as back pain, headache, etc., were recorded. Neonatal weight, Apgar scores and umbilical artery pH were recorded also.
Block height was tested using changes of sensory level to cold (ether). Motor block was quantified using the modified Bromage score (0 = no motor block, 1 = inability of straight leg raising, 2 = no knee flexion, 3 = no ankle or foot flexion). FHR and variations in FHR were monitored continuously using external cardiotocography and examined closely during a 15-min interval pre- and a 60-min post-puncture interval. FHR abnormalities considered were late decelerations (FHR < 100 beats•min–1 following a contraction) and/or bradycardia (FHR < 100 beats•min–1 for more than 90 sec). FHR abnormalities such as late decelerations, bradycardia or decreased variability were treated with oxygen, lateral decubitus and ephedrine if necessary.
Continuous variables were analyzed using analysis of variance and Scheffé’s post hoc test or unpaired t testing whenever appropriate. Categorical data were analyzed using Fisher’s exact test and Chi-square analysis. Data are presented as mean ± standard deviation, percent of group total or median with interquartile range. P < 0.05 was considered statistically significant.
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Results |
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). The duration of spinal analgesia was significantly longer in the CLON-group compared to the ROSU-group (P < 0.05). There were no differences in onset time of analgesia (Table II). VAS scores for pain were similar between the groups (Figure 1). Maternal satisfaction one hour and one day after delivery was high in both groups.
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). Percentage change in arterial pressure was more pronounced in the CLON-group compared to the ROSU-group (P < 0.05; Table IV). Eleven patients in the CLON-group had a reduction in MABP of more then 20%, compared to only five patients in the ROSU-group (P < 0.05). More ephedrine was used in CLON-group patients (P < 0.05; Table IV).
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. Umbilical artery pH was 7.289 ± 0.085 in the ROSU-group and 7.219 ± 0.096 in the CLON-group (P < 0.05). However, no differences in Apgar scores at one, five or ten minutes were observed. The number of children with umbilical artery pH < 7.2 was also identical in the two groups (Table III). No differences in outcome of labour were observed. The incidence of pruritus and nausea was similar in both groups. Motor block did not occur in any patient.
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Discussion |
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Considerable variation in the effect of clonidine on duration of labour analgesia has been observed in various studies. Methodological variations may explain why such differences have been observed. The timing of analgesia, the dose of local anesthetic and/or opioid, the type of opioid, the parity of patients and differences in patient education can all account for the observed variations.
Only four patients in the clonidine group delivered prior to epidural supplementation was required. This was similar to the patients treated without clonidine. Therefore, clonidine did not prolong analgesia beyond the need for epidural supplementation. Consequently, the observed differences in duration of spinal analgesia may be of little clinical benefit.
Unfortunately, our results demonstrate that spinal clonidine in a dose of 30 µg significantly influences maternal hemodynamics. Hypotension occurred more often and more ephedrine was required to restore maternal arterial pressure. This is in agreement with Sia11 and Paech et al.10 who also noted that the combination of clonidine, bupivacaine and sufentanil has important effects on maternal hemodynamics. D’Angelo et al.9 and Owen et al.,14 however, did not note a significant increase in the incidence and severity of hypotension. Actually, this may have been the result of a small sample size, as they reported an increase in the incidence of hypotension, but the difference failed to reach statistical significance.
Apgar scores were unaffected by clonidine treatment in the studies by Sia,11 D’Angelo et al.9 and Paech et al.10 Our results confirm these findings. However Apgar scores are a relatively crude measure of neonatal outcome and intrapartum hypoxia. In contrast to these studies, we also report on FHR changes following CSE and on umbilical artery blood gases. More new onset FHR abnormalities developed following CSE. Importantly, neonates from clonidine-treated patients had significantly lower umbilical artery pH values compared to patients treated with plain ropivacaine and sufentanil. Previous investigations, studying the combination of intrathecal local anesthetic, opioid and clonidine failed to report such findings.9–11 We cannot conclusively establish a causal relationship between the addition of clonidine to the spinal anesthetic and worse neonatal outcome. However we could not identify any other factors associated with low umbilical artery pH values in our trial. No correlation existed between low umbilical artery pH and parity, duration of labour, FHR abnormalities prior to initiation of analgesia, maternal co-existing disease, maternal fever, etc. We therefore assume that maternal hypotension due to spinal clonidine could be involved in worse neonatal outcome as compared to patients not treated with spinal clonidine.
We are aware that, as in previous studies, the present trial suffers from the limited number of patients recruited and randomized. Based on a 30-min difference in duration of analgesia (as determined in our trial), post hoc power analysis reveals a power of 0.65 if data from all 50 scheduled patients (25 in each group) could have been used for data analysis. Since data from only 38 patients were used for the final analysis, the power of the study is 0.50. This pilot trial was designed to evaluate the effectiveness and safety of intrathecal clonidine in our patient population and in our practice before embarking on a more extensive trial including a statistically useful number of patients. In order to reach a power of 0.90, 48 patients completing the trial would be required in each group. This would mean, based on our dropout rate of 24%, that we should include approximately 125 patients. Our preliminary results provide no solid basis to perform such a trial since significantly more maternal hypotension and worse fetal outcome was associated with the use of clonidine. Furthermore, we question the clinical importance of a 30-min increase in duration of initial spinal analgesia.
We conclude that intrathecal clonidine 30 µg prolongs analgesia provided by a ropivacaine and sufentanil mixture. We question the clinical significance of the observed 30-min extension of spinal analgesia. We feel it is justified to warn against the routine use of intrathecal clonidine since maternal hypotension, signs of intrapartum hypoxia and acidosis and worse neonatal outcomes were observed following its use. We do not recommend the routine addition of intrathecal clonidine 30 µg to sufentanil 1.5 µg and ropivacaine 3 mg for pain relief during labour.
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Footnotes |
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References |
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2 Norris MC, Grieco WM, Borkowski M, et al. Complications of labor analgesia: epidural versus combined spinal epidural techniques. Anesth Analg 1994; 79: 529–37.
3 Landau R. Combined spinal-epidural analgesia for labor: breakthrough or unjustified invasion? Sem Perinatol 2002; 26: 109–21.
4 Van De Velde M, Mignolet K, Vandermeersch E, Van Assche A. Prospective, randomized comparison of epidural and combined spinal epidural analgesia during labor. Acta Anaesthesiol Belg 1999; 50: 129–36.[Medline]
5 Viscomi CM, Rathmell JP, Pace NL. Duration of intrathecal labor analgesia: early versus advance labor. Anesth Analg 1997; 84: 1108–12.[Abstract]
6 Chiari A, Lorber C, Eisenach JC, et al. Analgesic and hemodynamic effects of intrathecal clonidine as the sole analgesic agent during first stage of labor. A dose-response study. Anesthesiology 1999; 91: 388–96.[Medline]
7 Mercier FJ, Dounas M, Bouaziz H, et al. The effect of adding a minidose of clonidine to intrathecal sufentanyl for labor analgesia. Anesthesiology 1998; 89: 594–601.[Medline]
8 Gautier PE, De Kock M, Fanard L, Van Steenberge A, Hody JL. Intrathecal clonidine combined with sufentanyl for labor analgesia. Anesthesiology 1998; 88: 651–6.[Medline]
9 D’Angelo R, Evans E, Dean LA, Gaver R, Eisenach JC. Spinal clonidine prolongs labor analgesia from spinal sufentanyl and bupivacaine. Anesth Analg 1999; 88: 573–6.
10 Paech MJ, Banks SL, Gurrin LC, Yeo ST, Pavy TJ. A randomized, double-blinded trial of subarachnoid bupivacaine and fentanyl, with or without clonidine, for combined spinal/epidural analgesia during labor. Anesth Analg 2002; 95: 1396–401.
11 Sia AT. Optimal dose of intrathecal clonidine added to sufentanil plus bupivacaine for labour analgesia. Can J Anesth 2000; 47: 875–80.
12 Eisenach JC. Additives for epidural analgesia for labor: why bother? (Editorial). Reg Anesth Pain Med 1998; 23: 531–2.[Medline]
13 Landau R, Schiffer E, Morales M, Savoldelli G, Kern C. The dose-sparing effect of clonidine added to ropivacaine for labor epidural analgesia. Anesth Analg 2002; 95: 728–34.
14 Owen MD, Ozsarac O, Sahin S, Uckunkaya N, Kaplan N, Magunaci I. Low-dose clonidine and neostigmine prolong the duration of intrathecal bupivacaine-fentanyl for labor analgesia. Anesthesiology 2000; 92: 361–6.[Medline]
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