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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.57 no.1 Campinas Jan./Feb. 2007
Labor analgesia: a comparative study between combined spinal-epidural anesthesia versus continuous epidural anesthesia*
Analgesia de parto: estudio comparativo entre anestesia combinada raqui-peridural versus anestesia peridural continua
Carlos Alberto de Figueiredo Côrtes, TSAI; Cândido Amaral Sanchez, TSAI; Amaury Sanchez Oliveira, TSAII; Fernando Martinez SanchezIII
pelo CET/SBA Integrado de Campinas
IIResponsável pelo CET/SBA Integrado de Campinas
IIIME (2002-2003) do CET/SBA Integrado de Campinas
OBJECTIVES: Pain relief during labor is a permanent concern, aiming at the
maternal well being, decreasing the stress secondary to pain, and reducing its
consequences on the fetus. Several analgesia techniques can be used during labor.
The aim of this study was to compare continuous and combined epidural analgesia,
both of them using 0.25% bupivacaine with 50% enantiomeric excess and fentanyl.
METHODS: Forty pregnant women, in labor, with cervical dilation between 4 and 5 cm, were randomly divided in two groups. Group I received continuous epidural anesthesia. Group II received combined anesthesia. The following parameters were evaluated: anthropometric measurements, gestational age, cervical dilation, length of time between the blockade and absence of pain according to the visual analogic scale, ability to walk, length of time between analgesia and complete cervical dilation, duration of the expulsive phase, maternal hemodynamic parameters, and vitality of the newborn. Possible complications, such as respiratory depression, maternal hypotension, pruritus, nausea, and vomiting were also evaluated. The Student t test was used to compare the means and the Chi-square test was used to compare the number of pregnancies and type of labor.
RESULTS: There were no statistically significant differences between both groups regarding the length of time between the beginning of analgesia and complete cervical dilation, as well as regarding the duration of the expulsive phase, incidence of cesarean section related to the analgesia, maternal hemodynamic parameters, and vitality of the newborn.
CONCLUSIONS: Both techniques are effective and safe for labor analgesia, although the combined technique provided fast and immediate pain relief. Clinical studies with a larger number of patients are necessary to evaluate the differences in the incidence of cesarean sections.
Key Words: ANALGESIA, Obstetric: labor; ANESTHETICS, Local: 0.25% bupivacaine with 50% enantiomeric excess; ANALGESICS, Opioids: fentanyl; ANESTHETIC TECHNIQUES, regional: continuous epidural, combine spinal and epidural.
Y OBJETIVOS: El alivio del dolor en el trabajo de parto ha recibido una
atención constante objetivando el bienestar materno, disminuyendo el
estrés causado por el dolor y reduciendo las consecuencias de éste
sobre el concepto. Innumerables técnicas pueden ser utilizadas para la
analgesia de parto. Este trabajo tuvo como objetivo comparar la técnica
peridural continua con la combinada, ambas con el uso de bupivacaína
a 0,25% en exceso enantiomérico 50% y fentanil como agentes.
MÉTODO: Participaron del estudio 40 parturientes en trabajo de parto con dilatación cervical entre 4 y 5 cm que se repartieron en de los grupos iguales de forma aleatoria. El Grupo I recibió anestesia peridural continua. El Grupo II recibió anestesia combinada. Se evaluaron: medidas antropométricas, edad de embarazo, dilatación cervical, tiempo entre el bloqueo y la ausencia de dolor a través de la escala analógica visual, posibilidad de deambulación, tiempo entre el inicio de la analgesia y la dilatación cervical completa, duración del período expulsivo, parámetros hemodinámicos maternos y vital edad del recién nacido. Posibles complicaciones como depresión respiratoria, hipotensión arterial materna, prurito, náuseas y vómitos también fueron observados. Para la comparación de los promedios se utilizó el teste t de Student y para la paridad y tipo de parto se utilizó el teste del Qui-cuadrado.
RESULTADOS: No hubo diferencia estadística significativa entre los de los grupos con relación al tiempo entre el inicio de la analgesia y la dilatación cervical completa, como también con relación al tiempo de la duración del período expulsivo, incidencia de cesárea relacionada con la analgesia, parámetros hemodinámicos maternos y vital edad del recién nacido.
CONCLUSIONES: Las dos técnicas fueron eficaces y seguras para la analgesia del trabajo de parto, aunque la técnica combinada haya proporcionado un rápido e inmediato alivio del dolor. Estudios clínicos con mayor número de casos son necesarios para evaluar diferencia en la incidencia de cesarianas.
Pain relief during labor has been the focus of physicians aiming at maternal well being, decreasing pain related stress, and reducing the consequences of said stress on the fetus.
The first obstetric analgesia documented was performed by Simpson in 1847 using chloroform. From then on, several drugs and techniques have been used. Among them we can mention the inhalation of nitrous oxide, cyclopropane, or ether; intravenous agents, such as barbiturates and opioids; paracervical block, pudendal nerve block, and local anesthesia; spinal anesthesia for the expulsive phase; and continuous epidural anesthesia and combined anesthesia (spinal-epidural) 1.
The sensitive blockade of the efferent nerve fibers between T10 and L1 is necessary to achieve pain relief in the first phase of labor; this is not an extensive blockade and rarely produces hemodynamic changes, and can be achieved with both the continuous epidural and combined anesthesias 2.
The continuous epidural technique using 0.25% bupivacaine with 50% enatiomeric excess (S75-R25) associated with fentanyl provides for satisfactory analgesia, as long as adequate volumes and initial doses are used. There will be few hemodynamic consequences, as well as minimal motor blockade, which allow the patient to ambulate. The epidural catheter allows the administration of a maintenance dose, whenever necessary, or a perineal dose at the beginning of the expulsive phase 3.
Combined anesthesia is a recent option that is becoming increasingly more popular. It entails the subarachnoid administration of an opioid agonist to treat pain during the first stage of labor. An epidural catheter is introduced for the administration of a local anesthetic to relieve pain during the second phase of labor. The injection of opioids in the subarachnoid space does not produce motor blockade, regardless of the dose, because they exert their action on specific receptors in the Rexed laminae in the dorsal horn of the spinal cord, modulating pain without affecting the motor, autonomic, and proprioceptive pathways 1.
Ambulation does not seem to be related to a decrease in the duration of labor, but some studies have shown that the absence of ambulation increases the incidence of cesarean sections secondary to dystocia 4-6. Besides, ambulation would be related with decreased pain severity when these patients are compared with those who remain in bed 7.
The aim of this study was to compare two techniques of labor analgesia: continuous epidural versus combined anesthesia using, for both techniques, 0.25% bupivacaine with 50% enantiomeric excess (S75-R25) and fentanyl. The following parameters were evaluated: quality of analgesia, length of time to achieve analgesia, degree of motor blockade, capability to ambulate, spontaneous urination, duration of labor, possible maternal hemodynamic changes, and vitality of the newborn.
After approval by the Medical Ethics Committee of the Maternidade de Campinas and signing of the informed consent, a prospective, randomized study was undertaken with 40 pregnant women (nullipara and primipara), with cervical dilation of 4 to 5 cm, and a single fetus. Patients were divided in two equal groups:
- Group I (n=20) received continuous epidural anesthesia. Anesthesia was induced with 8 mL (20 mg) of 0.25% bupivacaine with 50% enantiomeric excess with epinephrine 1:200,000 associated with 100 µg of fentanyl. A maintenance dose of 4 mL of the same local anesthetic was administered whenever necessary. At the beginning of the expulsive phase, a perineal dose of 6 mL (15 mg) of the local anesthetic was administered.
- Group II (n=20) received combined anesthesia. Anesthesia was induced with the subarachnoid administration of 25 µg of fentanyl. A maintenance dose of 4 mL of 0.25% bupivacaine with 50% enantiomeric excess with epinephrine 1:200,000 was administered whenever necessary. At the beginning of the expulsive phase, a perineal dose of 6 mL of the local anesthetic was administered through the catheter into the epidural space.
Monitoring included electrocardiogram, pulse oxymeter, and non-invasive blood pressure. After venous cannulation with an 18G catheter, 10 mL.kg-1 of ringer's lactate was administered and a lumbar puncture was performed.
In Group I, lumbar puncture in the L3-L4 space was performed with a disposable 17G Tuohy needle after the skin was cleaned with alcoholic PVPI or chlorhexedine. The epidural space was located using the loss of resistance technique followed by the slow and fragmented administration of the local anesthetic and opioid for anesthetic induction. Afterwards, 2 to 3 cm of a 19G epidural catheter were introduced for the administration of a maintenance dose, if necessary, and the perineal dose.
In Group II, lumbar puncture in the L3-L4 space was done with a disposable 17G Tuohy needle after the skin was cleaned with alcoholic PVPI or chlorhexedine. The epidural space was identified with the loss of resistance technique. Spinal anesthesia, with the administration of 25 µg of fentanyl, was done after the introduction of a long 27G Whitacre needle through the epidural needle. Afterwards, 2 to 3 cm of a 19G catheter were introduced into the epidural space to administer the maintenance dose, if necessary, and the perineal dose.
Patients were placed on left lateral decubitus and, 20 minutes after the blockade, muscle strength was assessed asking the patient to raise the hip form the table, to raise and keep the lower limbs stretched for about 10 seconds, and to flex and extend the thighs and legs against the resistance exerted by the examiner. If motor blockade was absent, the patient was placed on the standing position and the Romberg test was performed. If there were no changes, the patient was encouraged to walk, with the anesthesiologist and/or nurse by her side for the first 50 meters.
Pain was evaluate by the visual analogic scale (VAS) and, if 20 minutes after the blockade the patient was still complaining of pain greater than 3, the maintenance dose was administered. In both groups the maintenance dose consisted of 4 mL of 0.25% bupivacaine with 50% enantiomeric excess. When the cervix was completely dilated, the perineal dose of 6 mL of 0.25% bupivacaine with 50% enantiomeric excess was administered.
The following data was evaluated: Anthropometric measurements: age, weight, height, gestational age, cervical dilation, length of time between the blockade and absence of pain according to the VAS scale; possibility of ambulation: assessed by the muscle strength of the legs and hip, and Romberg test; length of time between analgesia and complete cervical dilation, duration of the expulsive phase, heart rate, peripheral hemoglobin saturation, blood pressure, total amount of anesthetic used, Apgar index in the 1st and 5th minutes, and fetal heart rate and weight.
Possible complications, such as respiratory depression, maternal hypotension, pruritus, and nausea and vomiting were also evaluated.
Student t test was used to compare the following data: anthropometric measurements, gestational age, cervical dilation, length of time between blockade and absence of pain, length of time between analgesia and complete cervical dilation, duration of the expulsive phase, heart rate, peripheral hemoglobin saturation, blood pressure, amount of local anesthetic used, and Apgar index in the 1st and 5th minutes. The Chi-square test was used to compare the patient's parity and type of labor. A p < 0.05 was considered significant.
There were no differences between both groups regarding the anthropometrics data. Table I shows the values obtained, indicating that the groups were homogenous.
There were no statistically significant differences regarding parity and those results are shown in Table II.
Regarding gestational age, there were no statistically significant differences between the groups. The mean in group I was 39.58 ± 1.61 weeks and in Group II it was 39.60 ± 1.07 weeks (p = 0.96).
In this study, analgesia was performed when patients presented a cervical dilation between 4 and 5 cm. The mean cervical dilation for Group I was 4.70 ± 0.47 cm and in Group II it was 4.50 ± 0.51 cm. This difference was not statistically significant (p = 0.21).
At the beginning of the analgesia, pain evaluation (VAS) was similar in both groups (Group I = 7.70 ± 1.66 and in Group II = 7.20 ± 1.40). If we consider that pain equal or lower than 3 is bearable, there was a difference between both groups because 5 minutes after the analgesia the main pain score was 5.70 ± 2.20 in Group I and 0.95 ± 1.43 in Group II. Only 15 minutes after analgesia patients in Group I presented pain of 2.10 ± 2.05 and at 20 minutes, in this group, the level of pain was 1.40 ± 1.88 (Table III).
As for ambulation, after evaluating muscle strength and static balance by the Romberg test, every patient in both groups was able to walk without any problems, since there were no noticeable changes. The patients that needed to urinate had no difficulties.
There were no statistically significant differences regarding the length of time between analgesia and complete cervical dilation, and the duration of the expulsive phase. Table IV shows these results.
Cephalopelvic disproportion was the indication for the only cesarean section in Group I (Table V). There were four cesarean sections in Group II: one for cephalopelvic disproportion, one for breech presentation in a nulliparous patient, and two for sustained fetal bradycardia.
Figures 1, 2, 3, and 4 show that heart rate, oxygen saturation, and systolic and diastolic blood pressures remained within the normal range in both groups without statistically significant differences.
The dose of local anesthetic used demonstrated a statistically significant difference between both groups. Patients in Group I used more local anesthetic: 39 ± 5.28 mg. In Group II, the mean amount of local anesthetic used was 24.47 ± 9.70 mg. As for the maintenance dose, five patients in Group I required its administration while it was necessary in 10 patients in Group II. The perineal dose was administered in every patient who had a normal labor. Table VI shows these results.
Patients in this study did not present any of the possible side effects with the types of analgesia used.
There were no statistically significant differences regarding fetal heart rate, Apgar index, and weight, as can be seen in Table VII. Two patients in Group II had indications for urgent cesarean section due to sustained fetal bradycardia without maternal hypotension, which occurred 20 minutes after the combined technique was performed.
The results of this study indicate that there were no changes in hemodynamic parameters and hemoglobin saturation with both techniques.
Maternal hypotension, an important complication that could have affected especially those patients who received combined analgesia. In this technique, hypotension occurs in the first 15 minutes after administration of the opioid 8 and seems to be related to the sympathetic suppression caused by the fast pain relief secondary to the subarachnoid administration of the opioid 9. In this study, the two cesarean sections in Group II that were consequences of fetal bradycardia did not present with maternal hypotension and the indication for the surgery occurred 20 minutes after the analgesia was performed.
The etiology of fetal bradycardia is not well known, but it seems to be related to the fast reduction of the pain caused by uterine contractions, which reduces maternal plasma concentration of b-endorphins 10 and epinephrine 11. A sudden plasma imbalance of epinephrine/norepinephrine may result in uterine hypotonus and/or arterial spasm and the consequent decrease in uterine-placental blood flow 12. When this bradycardia is severe, it is an indication for cesarean section. Fetal bradycardia can occur with the combined technique as well as with the continuous epidural. But in the combined technique, there is an immediate and marked cessation of the pain secondary to uterine contractions after the subarachnoid administration of an opioid, and the incidence of fetal bradycardia is higher 5,9,12.
There were no cases of motor blockade in both groups that would hinder ambulation. It is considered ambulation when the patient walks for at least 5 minutes in one hour 13-16. Although there is controversy on the role of ambulation on decreasing the duration of labor, it gives the patient a feeling of freedom and self-control, since she is not restricted to the birth table 6. Besides, the amount of anesthetic and ocitocine are reduced when the patient is able to walk. There seems to be an "analgesic effect" associated with ambulation; the perception of pain may be affected when one is standing up or walking due to the possible reduction in traction and pressure on the roots of the lumbosacral plexus and the pelvic muscles during uterine contractions 5,6.
Subarachnoid fentanyl or sufentanyl in combined anesthesia allows for the immediate relief of the pain caused by uterine contractions without motor blockade of the lower limbs. This is one of the greatest advantages of this technique, as demonstrated by the results in Group II 4,14,17,18. However, due its relatively short duration, of approximately 90 minutes, the dose of subarachnoid opioid is not enough for the entire period of cervical dilation and, therefore, the epidural administration of maintenance doses of the local anesthetic is necessary 9,17,19. Patients in Group I also experienced a marked reduction in pain at the 5-minute mark, but the groups were similar only at the 15-minute mark, which was deemed satisfactory if the total duration of labor and the time of analgesia until delivery are taken into consideration. In this study, only 5 patients in Group I needed a maintenance dose against 10 patients in Group II.
Craig et al. 17 defined the maximum dose of 25 µg of fentanyl that can be used with a minimal incidence of side effects. A dose of 10 µg of fentanyl provides a longer duration of analgesia, approximately 102.4 ± 49.8 20. However, this dose has been linked with complications, such as high levels of analgesia reaching areas innervated by the trigeminal nerve 21, pruritus, nausea, vomiting, and respiratory deppression 20. In this study, these complications and maternal hypotension were not present. The subarachnoid administration of morphine or meperidine is not indicated for labor analgesia, because there is an increased incidence of side effects, such as maternal hypotension, pruritus, nausea, vomiting, respiratory depression, and fetal bradycardia 9,17. Subarachnoid clonidine is not advisable either for obstetric analgesia because it also causes maternal hypotension and fetal bradycardia 22.
Even though the beginning of analgesia is delayed with continuous epidural anesthesia, maternal hypotension and fetal bradycardia are not as frequent as with the combined technique 5,9,12. Moreover, the need for maintenance dose, besides the perineal dose, was reduced.
The elevated incidence of forceps labor was related to the obstetric procedures of the hospital where the study was conducted and not to analgesic interference with the evolution of the second phase of labor. According the Chestnut et al., the early administration of epidural analgesia does not increase the use of forceps 8.
According to Vallejo et al 16, who obtained an incidence of 19% of cesarean sections, continuous epidural anesthesia is the most effective technique for labor analgesia because it does not increase the incidence of cesarean sections, as reported in the literature. In this study, continuous epidural anesthesia did not increase the number of cesarean sections, and its incidence was of only 5% versus 20% in the combined technique.
One important advantage of the continuous epidural anesthesia is that the dura mater is not perforated, which would breach the integrity of the protective barrier of the central nervous system, posing a greater risk of disseminating infectious agents and, consequently, bacterial meningitis, as reported in the literature 14,23.
In both groups, 0.25% bupivacaine with 50% enantiomeric excess was the local anesthetic used. Although the doses were low and hardly toxic, in the cases that needed further administration of analgesics for the cesarean sections, there was a summation of doses; therefore, the least toxic and safer local anesthetic should be used.
We concluded that although the combined technique provided fast and immediate relief of pain, both techniques were effective and safe for labor analgesia.
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Dr. Carlos Alberto Figueiredo Côrtes
Av. Orosimbo Maia, 165 3º andar
13023-910 Campinas, SP
Submitted em 06
de abril de 2006
Accepted para publicação em 29 de setembro de 2006
* Received from do Hospital e Maternidade de Campinas, CET/SBA Integrado de Campinas, Campinas, SP