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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.56 no.4 Campinas Set./Aug. 2006
The interaction between labor analgesia and its results. Assessment using the newborn´s weight and Apgar score*
Interacción entre la analgesia de parto y su resultado. Evaluación por el peso e índice e Apgar del recién nascido
Andrea Stolf Eberle, TSAI; Eliana Marisa Ganem, TSAII; Norma Sueli Pinheiro Módolo, TSAII; Rosa Beatriz AmorimIII; Giane NakamuraIV; Christiane D'Oliveira MarquesV; Yara Marcondes Machado Castiglia, TSAVI
do Programa de Pós-Graduação em Anestesiologia da FMB-UNESP
IIProfessora Adjunta Livre-Docente do Departamento de Anestesiologia da FMB-UNESP
IIIProfessora Assistente Doutora do Departamento de Anestesiologia FMB-UNESP
IVDoutora em Anestesiologia e Médica do Departamento de Anestesiologia da FMB-UNESP
VME do CET/SBA do Departamento de Anestesiologia da FMB-UNESP
VIProfessora Titular do Departamento de Anestesiologia da FMB-UNESP
OBJECTIVES: There are controversies regarding whether labor analgesia can
interfere with labor and the vitality of the newborn. The objective of this
study was the interaction between labor analgesia, using the continuous epidural
and combined spinal-epidural techniques with a small dose of local anesthetic,
and the type of delivery analyzing the newborn's weight and Apgar score.
METHODS: The results of 168 labor analgesias (from January 2002 to January 2003) were analyzed. They were divided in 4 groups: G1 (n = 58), continuous epidural and evolution to vaginal delivery; G2 (n = 69), combined spinal-epidural and evolution to vaginal delivery; G3 (n = 25), continuous epidural and evolution to cesarean; G4 (n = 16), combined spinal-epidural and evolution to cesarean. G1 received 0.125% ropivacaine (12 to 15 mL), G2 received subarachnoid 0.5% bupivacaine (0.5 to 1 mL) and sufentanil (10 mg). Epidural ropivacaine 0.5% for the vaginal delivery (8 mL) and for cesarean (20 mL). The patient's age, weight, height, body mass index (BMI), gestational age, number of prior pregnancies, and complications (arterial hypotension, bradycardia, and hypoxia) and the newborn's weight and Apgar score (at 1, 5, and 10 minutes) were evaluated.
RESULTS: The majority of pregnant women were primiparous and presented with a term pregnancy (one with gestational age of 28 weeks and none post-term pregnancy); weight, G2 < G4; and MBI, G2 £ G4. For the weight of the newborn, G1 < G3 and G2 < G4, and for the Apgar score at 1st minute, G1 > G3.
CONCLUSIONS: If the analysis focuses the newborn's weight and Apgar score, the techniques of analgesia, continuous epidural and combined spinal-epidural with small doses of local anesthetic, do not interfere with the result of the delivery.
Key Words: ANALGESIA, Labor; ANESTHETICS, Local; SURGERY, Obstetric: cesarean section.
Y OBJETIVOS: Existen controversias en cuanto a la posibilidad de que la
analgesia de parto interfiera en el trabajo de parto y en la vitalidad del recién
nacido. El objetivo de este estudio fue el de analizar la interacción
entre la analgesia del parto por las técnicas peridural continua y doble
bloqueo, con una pequeña dosis de anestésico local, y el tipo
de parto ocurrido, a través del análisis del peso e índice
de Apgar del recién nacido.
MÉTODO: Se analizaron, en estudios de prospección, los resultados de 168 analgesias de parto (de enero de 2002 a enero de 2003), divididas en 4 grupos: G1 (n = 58) peridural continua y evolución para parto vaginal; G2 (n = 69) doble bloqueo y evolución para parto vaginal; G3 (n = 25) peridural continua y evolución para cesárea; G4 (n = 16) doble bloqueo y evolución para cesárea. Para G1 se administró ropivacaína a 0,125% (12 a 15 mL), para G2, bupivacaína a 0,5% (0,5 a 1 mL), sufentanil (10 mg), por vía subaracnoidea. Se administró ropivacaína a 0,5%, por vía peridural, para el parto vaginal (8 mL) y para cesárea (20 mL). Se evaluaron la edad, el peso, la altura, el índice de masa corpórea (IMC), tiempo de gestación (TG), paridad y complicaciones (hipotensión arterial, bradicardia y hipoxia), y del RN, peso e índice de Apgar (1º, 5º y 10º min).
RESULTADOS: La mayoría de las parturientes era primeriza, después de la 38ª semana de gestación (una TG de 28 semanas y ningún pos-datismo), con peso, G2 < G4, y IMC, G2 £ G4. Para el peso del RN, G1 < G3 y G2 < G4, y el Apgar del 1º min, G1 > G3.
CONCLUSIONES: Las técnicas de analgesia, peridural continua y doble bloqueo, con pequeñas dosis de anestésico local, no presentaron interacción con el resultado del parto, si el análisis está centrado en el peso y en el índice de Apgar del recién nacido.
Epidural analgesia for labor is safe, effective, and has gained much popularity in the last decades, replacing other methods, such as analgesia with inalational/anesthetics agents, general anesthesia, and paracervical blockade1. There are controversies as to whether this technique can interfere in the course of labor and in the vitality of the newborn. Several studies have demonstrated elevated rates of cesarean sections among patients who have received epidural analgesia2-4 while others were not able to prove it5-7.
A prospective study8 compared a group of pregnant women who received epidural analgesia with another group who received intravenous opioids in which the dose was controlled by the patients. It showed no difference in the rate of cesareans in both groups. A bias in the selection of the sample could be one of the explanations for that result pregnant women who present severe pain early in labor were more likely to receive epidural analgesia9,10.
Epidural analgesia with small doses of local anesthetics (0.125% ropivacaine or with a smaller concentration) is used to preserve muscular strength during the expulsive period, while reducing pain, promoting maternal satisfaction, and has little interference with the adaptive and neurological capabilities of the newborn11. However, except for the patient's own satisfaction, the clinical benefits of ambulation (due to a smaller motor blockade) in the progression and result of labor are debatable, and need to be further investigated. But there are no doubts that high concentrations (greater than 0.15%) of local anesthetics are undesirable due to the resulting motor blockade that interferes with the maternal efforts in expulsive phase12.
The combined spinal-epidural technique of labor analgesia, with subarachnoid local anesthetic and opioids after establishing the epidural access through the introduction of a catheter to be used during the expulsive phase, promoting deep analgesia is effective both in the first and in the second stages of labor12, is widely used nowadays. The motor blockade is also less intense, favoring maternal ambulation and the good development of labor.
The objective of this study was to investigate the relationship between analgesia for labor using the continuous epidural and combined spinal-epidural techniques, using small doses of local anesthetics, and the type of delivery. The study of this relationship was done analyzing the newborn's weight and Apgar score.
This prospective study was submitted to analysis, having being approved by the Ethics Committee on Clinical Research of the Faculdade de Medicina de Botucatu to be carried out by the Obstetrics Anesthesiology Service at University Hospital. Labor analgesia was done by the epidural technique with small doses of local anesthetic (10 to 15 mL of ropivacaine at a maximum concentration of 0.125%) or combined spinal-epidural administration of 0.5 hyperbaric bupivacaine (0.5 to 1 mL) and sufentanil (10 µg) during labor and the epidural administration of ropivacaine (maximum concentration of 0.125%) when the patient demanded due to recurring pain. 0.5% ropivacaine (8 and 20 mL, respectively) was used for the expulsive phase or the cesarean section. All pregnant women received intravenous hydration with Ringer's lactate before the blockade, being monitored with a sphygmomanometer, a cardioscope using the DII lead derivation, and pulse oxymeter.
The choice of technique was done at random and depended on the indication, for each case, of the team on call each 24-hour period. The entire anesthetic procedure was recorded in a database.
The results of 168 labors analgesia indicated by the University Obstetric team between January 2002 and January 2003 treated with the techniques described and performed by Anesthesiology Service were analyzed.
The types of labor analgesia, along with their results, were divided in 4 groups: G1 (58 pregnant, 34.5%) continuous epidural analgesia in patients who evolved to vaginal delivery; G2 (69 pregnant, 41.1%) combined spinal-epidural in patients who evolved to vaginal delivery; G3 (25 pregnant, 14.9%) continuous epidural analgesia in patients who underwent cesarean section; G4 (16 pregnant, 9.5%) combined spinal-epidural in patients who underwent cesarean section.
The following parameters related to the patient age, weight, height, body mass index (BMI), gestational age, and number of pregnancies and related to the newborn weight and Apgar score at 1, 5, and 10 minutes were analyzed.
The development of maternal bradycardia (cardiac frequency less than 50 bpm), hypotension (systolic blood pressure 30% smaller than the normal for the patient), and hypoxia (hemoglobin saturation below 90%) during labor analgesia were evaluated. The treatment of these occurrences was also assessed (displacement of the uterus to the left, increased infusion of Ringer's lactate, intravenous administration of fractioned doses of ephedrine and oxygen).
Variance Analysis with determination of F and p were used for the maternal variables (age, weight, height, BMI, and number of pregnancies) and the newborn's weight. The mean and standard deviation were studied to indicate a central tendency and variability, respectively, in each group. The mean and percentiles P25 and P75 were used for the Apgar score (at 1, 5, and 10 minutes) of each group. Comparisons among the groups were done by the Kruskal-Wallis non-parametric test to determine p. Values of p < 0.05 were considered significant. Values of 0.5 < p < 0.10 were considered a significant tendency13.
The newborns' weight and Apgar scores were also analyzed to determine the effects of each type of delivery in each analgesia, i. e., for vaginal delivery or cesarean the mean weights and Apgar scores after epidural combined spinal-epidural analgesia. The same was done to determine the effects of analgesia in each type of delivery, that is, for each technique, epidural or combined spinal-epidural, the mean weight and the mean Apgar scores obtained in each type of delivery, vaginal delivery or cesarean, were evaluated13.
The labors studied did not present fetal malformations. Six patients in the G1 group were in their second pregnancy; four of those had vaginal deliveries in the first pregnancy and two had cesareans. The other women were primiparous (90%). All patients in the G2 group were primiparous (100%). In G3, five patients were in their second pregnancy and just one had had a cesarean in the first pregnancy. Hence, 80% were primiparous. In G4, just one patient had had a cesarean in the first pregnancy and 94% were primiparous.
Statistical analysis showed that there were no differences in the groups regarding maternal age and height, and gestational age. In G1, one patient was in the 28th week and one in the 35th week. In G2 six patients were in the 35th week. In G3 one patient was in the 34th week. The other patients were at term and no patient was post-term. Regarding maternal weight, there was a tendency for G2 < G4 while G1 = G3 and intermediate between the other two groups. The BMI of the patients in G2 < G4, which presented a significant difference, and G1 = G3 were intermediates between the other two groups (Table I).
Bradycardia and hypoxia were not observed in any patient in the four groups. One patient in G1, four in G3, and three in G4 presented hypotension, which was successfully treated displacing the uterus to the left, increasing the rate of infusion of Ringer's lactate, and with small doses of ephedrine (10 mg).
Table II shows the mean and the standard deviation of the newborns' weights in the four groups. There was no interaction between the two techniques of analgesia for labor and both types of delivery. Statistical analysis demonstrated that with both epidural and combined spinal-epidural the weights were G1 < G3 and G2 < G4, showing that the weights of the newborns delivered through the vagina were smaller than those born through cesarean section.
To determine the effects of the type of analgesia on each type of delivery, statistical analysis showed that, on both vaginal delivery and cesarean section, the newborns' weights were G1 = G2 and G3 = G4, i.e., the weight of the newborns whose mothers received epidural analgesia were equal to those whose mothers received combined spinal-epidural .
The statistical analysis of the Apgar score (Table III) showed that it was the same at 1, 5, and 10 minutes for both vaginal delivery and cesarean section regardless of the type of analgesia (G1 = G2 and G = G4). However, the Apgar score at 1 minute was significantly higher in newborns delivered by the vagina and whose mothers received epidural analgesia (G1 > G3). The Apgar scores at 5 and 10 minutes were equal for G1 and G3.
Table I shows that the only statistically significant difference in the population studied was in the BMI the pregnant who were treated with combined spinal-epidural, G2 and G4, had a BMI significantly higher, but those who evolved for vaginal delivery (G2) had a smaller BMI. However, the mean of the sample was overweight. Hess et al.9 observed that women with higher BMI were more likely to undergo cesarean section when they studied the relationship between labor result and severe pain.
On the other hand, if only the BMI of the pregnant women in this study is analyzed, the fetus may be the one variable to influence the type of delivery. Thus, the BMI of the mothers in G1 was equal to that of the mothers in G3, but the Apgar score of the newborns in G1 (mothers who evolved to vaginal delivery) at 1 minute was better than that of the ones in G3 (mothers who had cesareans sections) (Table II).
The results on table II demonstrate that the babies delivered by the vaginal route were smaller than those born by cesarean section, regardless of the type of analgesia administered (epidural or combined spinal-epidural). The mean weight of the newborns in the vaginal delivery group was 300 g smaller than those delivered by cesarean section. Based on these results, one can assume that the weight, but not the type of analgesia administered, would have influenced the type of delivery.
A study involving 112 women whose labor was induced evaluated the effects of epidural analgesia on the duration of labor and on the maternal-fetal outcome14. There was a marked reduction of complications during the intralabor period, but there was no influence on the number of cesareans sections performed and in the Apgar score of the newborns, despite de fact that the duration of labor was increased. However, another local anesthetic, bupivacaine, was used, which provided for greater motor blockade than ropivacaine, and higher doses and concentrations than those recommended in our study were administered, which could explain those results.
Kampe et al.15 established the cardiovascular effects on the mother and on the fetus of pregnant women who received epidural analgesia with 0.75% ropivacaine and 0.5% bupivacaine for elective cesarean section. Maternal BMI was the parameter that had greater influence on the umbilical arterial pH. The authors believed that mothers with elevated BMI were more likely to give birth to babies with lower pH because the aortal-cava compression by the uterus should be greater due to the amount of fatty tissue present or because the uterine incision could be made in a more advanced stage for technical reasons.
There are several causes of depression at birth. Biochemical indicators, which demonstrate the presence of fetal acidosis, measure the most specific evidences of intra-uterus hypoxia. On the other hand, the Apgar score, even though it is not a specific indicator, evaluates the effects on the newborn16 that cannot be obtained with biochemical measurements. In our study there were no cases of fetal malformation and just one case of delivery in the 28th week in G1, the most apparent causes of depression at birth.
An analysis of 1,000,000 births at term in Sweden16 indicated a strong influence of the newborns' weight and gestational age on the resulting low Apgar score. Low birth weight is a known risk factor for fetal compromise and a typical result of chronic placental insufficiency17; meanwhile, macrosomia did not stir the same interest. However, the authors discovered that weight deviation, in either direction, at birth presented a similar risk for a low Apgar score at 5 minutes. On the other hand, they indicated that fetal compromise on post-term pregnancies had already been reported18 and their results are in accordance with those previous reports the risk was obvious in 41-week pregnancies and markedly increased in 43-week pregnancies. Newborns were not always exposed to epidural analgesia, but the authors believed that this factor predisposes to an increased risk of low Apgar scores at birth. But they did not report which drugs were used for analgesia.
The low Apgar score is frequently used as a synonym of neonatal asphyxia. Low scores at 1st minute are often caused by temporary depression, while low scores at 5 and 10 minutes indicate the presence of clinically important complications, indicating that the newborn did not respond well to the resuscitation maneuvers. The newborns studied presented good Apgar scores at 1st minute. Those born under the effects of epidural analgesia presented higher scores with vaginal deliveries leading to the assumption that other problems unrelated to the technique of analgesia probably influenced the type of delivery.
A study12 compared epidural bupivacaine and ropivacaine, both at 0.08% and associated with fentanil 2 mg.mL-1, for labor analgesia and observed that the evolution of the cervical dilation in pregnant women was 1.12 cm.h-1 and 1.18 cm.h-1, respectively. The capacity to ambulate was preserved in all pregnant women in the ropivacaine group versus 75% in the bupivacaine group. Neither group had Apgar scores at 5 minutes smaller than 7. The authors also did not observe changes in maternal hemodynamics and concluded that labor analgesia, used in the way they designed, did not affect the development of the study. They believed, however, that the impact in ambulation and the method of analgesia used (low concentration of local anesthetic and association to fentanil) needed to be further investigated.
Regarding higher concentrations of local anesthetics, which cause hemodynamic changes, Kampe et al.15 considered that, if maternal arterial blood pressure and cardiac frequency are clinically acceptable, i.e., within normal limits, they do not influence birth. Therefore, by anesthetizing pregnant women undergoing elective cesarean sections with epidural 0.5% bupivacaine or 0.75% ropivacaine, they observed greater reduction in cardiac frequency in those women who received ropivacaine but there were no differences between both groups regarding motor blockade, level of sensitive blockade, umbilical cord blood pH, and Apgar score.
It is important to remember that uterine activity decreases, especially the intensity of its contractions, and labor is prolonged when analgesia is complicated by maternal arterial hypotension (due to aortal-cava compression). Most pregnant women in this study did not present hypotension, and when it occurred it was corrected promptly14.
To finish, it can be said that both techniques of analgesia studied, continuous epidural and combined spinal-epidural with small doses of local anesthetics, did not influence the type of delivery, if the analysis of that interaction focuses on newborn weight and Apgar score. However, other studies are necessary in order to reach a consensus on this matter.
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Dra. Yara Marcondes Machado Castiglia
Depto. de Anestesiologia da FMB-UNESP
18718-970 Botucatu, SP.
Submitted for publication
11 de outubro de 2005
Accepted for publication 3 de abril de 2006
* Received from CET/SBA do Departamento de Anestesiologia da Faculdade de Medicina de Botucatu da Universidade Estadual de São Paulo (FMB-UNESP), Botucatu, SP.