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Impact of morbid obesity on epidural anesthesia complications in labor

      Objective

      We sought to determine whether morbid obesity is associated with increased maternal hypotension or fetal heart rate (FHR) abnormalities after epidural anesthesia placement during labor.

      Study Design

      This was a retrospective cohort study of women undergoing epidural anesthesia during labor at term from April 2008 through July 2010.

      Results

      A total of 125 morbidly obese patients were matched for age and race with 125 normal-weight patients. Morbidly obese patients had more frequent persistent systolic (16% vs 4%, P = .003) and diastolic (49% vs 29%, P = .002) hypotension and more prolonged (16% vs 5%, P = .006) and late (26% vs 14%, P = .03) FHR decelerations. Increasing body mass index was associated with persistent systolic (odds ratio, 1.06; 95% confidence interval, 1.02–1.10) and diastolic (odds ratio, 1.04; 95% confidence interval, 1.01–1.06) hypotension after controlling for epidural bolus dose and hypertensive disorders.

      Conclusion

      Morbidly obese women have more hypotension and prolonged FHR decelerations following epidural anesthesia during labor at term.

      Key words

      Maternal hypotension is not uncommon with labor epidural anesthesia placement, complicating 5-17% of cases.
      • Paech M.J.
      • Godkin R.
      • Webster S.
      Complications of obstetric epidural analgesia and anesthesia: a prospective analysis of 10,995 cases.
      • Kinsella S.M.
      • Pirlet M.
      • Mills M.S.
      • et al.
      Randomized study of intravenous fluid preload before epidural analgesia during labor.
      Pregnancy increases maternal dependence on sympathetic vascular tone to maintain venous return and uteroplacental perfusion.
      • Assali N.S.
      • Prystowsky H.
      Studies on autonomic blockade, I: comparison between the effects of tetraethylammonium chloride (TEAC) and high selective spinal anesthesia on blood pressure of normal and toxemic pregnancy.
      • Tabash K.
      • Rudelstorfer R.
      • Nuwayhid B.
      • et al.
      Circulatory responses to hypovolemia in the pregnant and nonpregnant sheep after pharmacologic sympathectomy.
      Regional anesthesia-associated sympathectomy with resultant maternal hypotension decreases uteroplacental perfusion and is an important potential cause of intrapartum fetal heart rate (FHR) abnormalities and emergent cesarean delivery. Uncorrected maternal hypotension during regional anesthesia can cause decreased uteroplacental perfusion resulting in fetal and neonatal hypoxia and/or acidosis.
      • Ralston D.H.
      • Shnider S.M.
      The fetal and neonatal effects of regional anesthesia in obstetrics.
      Published data have demonstrated that pregnancy and obesity both decrease local anesthetic requirements during epidural anesthesia and may result in increased cephalad spread of epidural block.
      • Hodgkinson R.
      • Hussain F.J.
      Obesity and the cephalad spread of analgesia following epidural administration of bupivacaine for cesarean section.
      • Hodgkinson R.
      • Hussain F.J.
      Obesity, gravity, and spread of epidural anesthesia.
      • Panni M.K.
      • Columb M.O.
      Obese parturients have lower epidural local anesthetic requirements for analgesia in labor.
      However, the association between maternal obesity and epidural-associated hypotension is unknown. Our objective is to determine whether morbid obesity is associated with increased maternal hypotension or FHR abnormalities after epidural anesthesia placement during labor.
      For Editors' Commentary, see Table of Contents

      Materials and Methods

      In this retrospective cohort study, women who had undergone epidural anesthesia placement during labor from April 2008 through July 2010 at an academic tertiary care center were identified utilizing our computerized perinatal database. Women admitted for labor or induction who consented to epidural catheter placement and delivered at least 1 hour after epidural dosing were included. Women with multifetal deliveries, preterm deliveries, nonvertex presentations, major fetal anomalies, and those delivering within 1 hour of epidural dosing were all excluded.
      A total of 125 morbidly obese women with body mass index (BMI) ≥40 kg/m2 at delivery were matched for age and race to 125 normal-weight women with BMI ≤25 of kg/m2 (World Health Organization criteria). Individual patient charts, anesthesia records, and electronic fetal monitor (EFM) tracings were reviewed by a single investigator (L.K.V.). Tracing interpretation was performed in a masked fashion. Baseline maternal characteristics, epidural catheter placement information, hemodynamic parameters, and delivery outcomes were compared between groups.
      The primary outcome measure was the occurrence of maternal hypotension within 1 hour of epidural placement. The secondary outcome measure was the new onset of fetal heart tracing abnormalities within 1 hour of epidural placement.
      During this time period, women routinely received a 500-mL bolus of intravenous crystalloid for volume expansion prior to the procedure. Following epidural catheter placement and administration of a test dose, a bolus dose of 2-8 mL of a bupivacaine 0.125%, fentanyl 7.5 μg/mL, and epinephrine 5 μg/mL solution was administered. If the initial dose did not achieve satisfactory analgesia then additional anesthetic boluses were administered. The amount of epidural anesthetic bolus administered and the decision to administer any additional boluses were determined by the attending anesthesiologist, as was the decision to administer intravenous pressor support. Phenylephrine was the only pressor agent used.
      Baseline blood pressure was defined as the value recorded immediately prior to epidural catheter placement. Blood pressures were assessed in the supine position with a tilt. The lowest systolic and diastolic blood pressures recorded in 10-minute intervals for the first 30 minutes and at 15-minute intervals for the next 30 minutes were compared with baseline values. An optimal standard definition for obstetric anesthesia-related hypotension has not been established.
      • Dahlgren G.
      • Irestedt L.
      The definition of hypotension affects its incidence.
      We defined systolic and diastolic hypotension as a 20% decrease in systolic and a 20% decrease in diastolic blood pressure, respectively.
      • Klöhr S.
      • Roth R.
      • Hofmann T.
      • et al.
      Definitions of hypotension after spinal anesthesia for cesarean section: literature search and application to parturients.
      Although hypotension has been commonly defined by the systolic value in published studies, hypotension based on diastolic values is uncommonly evaluated. Because diastolic blood pressure maintains uteroplacental perfusion, diastolic hypotension could potentially have more clinical significance in this obstetric context and was therefore evaluated separately. Persistent hypotension was defined as at least a 20% decrease from baseline in 3 intervals during the first 60 minutes after epidural anesthetic bolus. We defined sustained hypotension as that occurring in all 5 measured intervals in the hour following epidural dosing. In an effort to be comprehensive we evaluated systolic and diastolic hypotension separately to determine which was more profoundly affected by epidural catheter dosing and which had a greater association with fetal heart tracing abnormalities.
      FHR tracings (EFM) for 60 minutes before and after epidural anesthetic bolus were classified according to the 2008 National Institute of Child Health and Human Development (NICHD) EFM guidelines.
      • Macones G.A.
      • Hankins G.D.V.
      • Spong C.Y.
      • et al.
      The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines.
      The preepidural and postepidural tracings were categorized as category I (normal), category II (indeterminate), or category III (abnormal) according to the published NICHD guidelines. Findings that were not present prior to epidural placement were considered new changes. New occurrence of decreased variability (minimal or absent), recurrent variable decelerations, recurrent late decelerations, and prolonged decelerations (>2 minutes) constituted “nonreassuring” tracings that would require an obstetric intervention. A nonreassuring tracing was defined as one that would require an obstetric intervention to either return to a category I tracing or necessitate delivery. Because prolonged and late decelerations are the anticipated tracing abnormalities with uteroplacental insufficiency after epidural-associated hypotension, these 2 findings were evaluated together as a composite variable.
      • Nielsen P.E.
      • Erickson J.R.
      • Ezzat I.A.
      • et al.
      Fetal heart rate changes after intrathecal sufentanil or epidural bupivacaine for labor analgesia: incidence and clinical significance.

      Wong CA, Scavones BM, Peaceman AM, et al. The risk of cesarean delivery with neuraxial analgesia given early versus late in labor. N Engl J Med 352;7:655-65.

      The occurrence of tachysystole in association with late or prolonged decelerations was also recorded.

      Statistical analysis

      We note that a 5% incidence of hypotension has been found in the general population during epidural catheter placement for labor when intravenous preloading is performed.
      • Paech M.J.
      • Godkin R.
      • Webster S.
      Complications of obstetric epidural analgesia and anesthesia: a prospective analysis of 10,995 cases.
      • Zamora J.E.
      • Rosaeg O.P.
      • Lindsay M.P.
      • et al.
      Hemodynamic consequences and uterine contractions following 0.5 or 1.0 litre crystalloid infusion before obstetric epidural analgesia.
      A priori analysis demonstrated that to detect a 15% incidence of hypotension in morbidly obese women, at an alpha of 0.05 and a beta of 0.2, 100 women would be needed in each group. Statistical analyses were performed using commercially available software (SPSS, version 18.0; SPSS Inc, Chicago, IL). We evaluated differences between the groups using the Student t test for continuous variables, and the Mann-Whitney U test and Fisher's exact tests for categorical variables. We then performed multinomial logistic regressions for factors predictive of persistent systolic hypotension, persistent diastolic hypotension, and FHR abnormalities. Factors included in the models for persistent systolic and persistent diastolic hypotension were BMI, preeclampsia spectrum conditions, chronic hypertension, and epidural anesthetic bolus. Factors included in the model for FHR abnormalities were BMI, preeclampsia spectrum conditions, chronic hypertension, epidural anesthetic bolus, persistent systolic hypotension, and persistent diastolic hypotension. P < .05 was significant. This retrospective chart review was approved by the institutional review board at MetroHealth Medical Center, Cleveland, OH.

      Results

      A total of 125 morbidly obese women met inclusion criteria and were matched by age and race with 125 normal-weight women. Both groups were similar in age, gestational age at delivery, race, insurance status, parity, and frequency of asthma (Table 1). Morbidly obese women had more frequent chronic hypertension, preeclampsia spectrum disorders (gestational hypertension, mild and severe preeclampsia, eclampsia), and diabetes (gestational and pregestational).
      TABLE 1Baseline characteristics by body mass index category
      CharacteristicsNormal weight n = 125Morbidly obese n = 125P value
      Age, y24 [21–31]25 [21–32].6
      Gestational age, wk39 [38–40]39 [38–40].6
      Nulliparity, %3544.2
      Prior vaginal deliveries1 [0–2]1 [0–2].4
      Race, %
       Black5058.3
       Hispanic1010
       White4032
      Insurance, %
       Public8484.1
       Private1616.1
      BMI, kg/m2
       Pregravid20 [18–21]41 [39–46]< .0001
       Delivery24 [23–25]45 [42–49]< .0001
      ASA score, U2 [2–2]2 [2–2].4
      Medical comorbidities, %
       Chronic hypertension418< .0001
       Preeclampsia spectrum1020.05
       Diabetes, pregestational05.03
       Diabetes, gestational210.006
       Asthma1015.3
      ASA, American Society of Anesthesiologists; BMI, body mass index.
      Data presented as percent or median [interquartile range].
      Vricella. Morbid obesity and epidural anesthetic complication for labor. Am J Obstet Gynecol 2011.
      Regarding delivery and anesthesia outcomes, morbidly obese women had more frequent labor induction, cesarean delivery, operative vaginal delivery, and emergent delivery for FHR abnormalities (Table 2). Rates of antepartum diagnosis of oligohydramnios and intrauterine growth restriction were similar in both groups. Apgar scores at 1 and 5 minutes were similar between groups. Infants born to morbidly obese women were heavier than those of normal-weight women (3380 ± 465 g vs 3132 ± 417 g, P < .0001).
      TABLE 2Delivery and anesthesia outcomes by body mass index category outcome
      OutcomeNormal weight n = 125Morbidly obese n = 125P value
      Induction, %2147< .0001
       Oligohydramnios106.3
       Intrauterine growth restriction30.1
      Delivery, %
       Spontaneous vaginal9372.0001
       Operative vaginal28.03
       Cesarean520.001
       Emergent (operative vaginal or cesarean)210.01
      Apgar score
       1 min9 [9–9]9 [9–9].9
       5 min9 [9–9]9 [9–9].9
      Infant weight, g3132 ± 4173380 ± 465< .0001
      Epidural catheter placement
       No. of attempts1 [1–1]1 [1–1].1
       Initial anesthetic bolus, mL4.7 ± 0.94.8 ± 1.0.5
       Total anesthetic bolus, 1 h, mL5.5 ± 1.95.3 ± 1.6.3
       Anesthesia levelT9 [T7–T10]T8 [T6–T9].1
      Phenylephrine
       Any dose, %914.3
       Total dose, μg345 ± 280702 ± 1058.2
      Baseline blood pressure, mm Hg
       Systolic125 ± 14130 ± 16.1
       Diastolic76 ± 1276 ± 121
      Data presented as mean ± SD, percent, or median [interquartile range].
      Vricella. Morbid obesity and epidural anesthetic complication for labor. Am J Obstet Gynecol 2011.
      Morbidly obese women had similar rates of initial successful epidural catheter placement and the groups were similar in initial and total epidural anesthetic bolus dose administered over the first hour. Morbidly obese women received more frequent and higher doses of intravenous pressor support with phenylephrine than normal-weight women; however the differences were not significant. Although morbidly obese women had more frequent chronic hypertension and preeclampsia spectrum disorders, baseline blood pressures taken immediately before epidural dosing were similar between groups.
      A single episode of postepidural hypotension occurred frequently in both morbidly obese and normal-weight groups (systolic hypotension: 44% vs 30%, P = .04; diastolic hypotension: 75% vs 66%, P = .2) (Figure). Persistent diastolic hypotension was more common than persistent systolic hypotension across both groups and persistent hypotension overall was more common in the morbidly obese group (systolic: 16% vs 4%, P = .003; diastolic: 49% vs 29%, P = .002). There was a 6-fold higher incidence of sustained diastolic hypotension among morbidly obese women; however the occurrence of sustained systolic hypotension was low across both groups and the difference among them was not significant (systolic: 2% vs 0%, P = .4; diastolic: 13% vs 2%, P = .003). Overall, diastolic hypotension occurred more frequently than systolic hypotension, and both systolic and diastolic hypotension were more prevalent among morbidly obese women compared with normal-weight controls.
      Figure thumbnail gr1
      FIGURESystolic and diastolic hypotension by BMI (kg/m2) category
      Hypotension was more common among morbidly obese patients than normal-weight patients. Diastolic hypotension was more common than systolic hypotension across groups.
      BMI, body mass index.
      Vricella. Morbid obesity and epidural anesthetic complication for labor. Am J Obstet Gynecol 2011.
      New findings of decreased long-term variability and mild, moderate, and severe variable decelerations were similar among BMI groups (Table 3). Morbidly obese women demonstrated new-onset late decelerations twice as frequently (26% vs 14%, P = .03) and new-onset prolonged decelerations 3 times more frequently (16% vs 5%, P = .006) than normal-weight women. Tachysystole-associated late or prolonged decelerations were more common among morbidly obese women (6% vs 1%, P = .04). Morbidly obese women were twice as likely to have a change from a category I tracing preepidural dosing to a category II tracing after epidural dosing (P = .02) and also more frequently developed a nonreassuring tracing than normal-weight women (36% vs 20%, P = .007).
      TABLE 3Postepidural anesthetic bolus fetal heart tracing changes by body mass index category
      Tracing changeNormal weight n = 125Morbidly obese n = 125P value
      Prolonged decelerations516.006
      Decreased variability561.0
      Late decelerations1426.03
      Nonreassuring tracing2036.007
      Variable decelerations
       Mild551.0
       Moderate511.1
       Severe221.0
      Late or prolonged decelerations1435< .0001
       Tachysystole-associated16.04
      Category I-II1630.02
      Data presented as percent.
      Vricella. Morbid obesity and epidural anesthetic complication for labor. Am J Obstet Gynecol 2011.
      Logistic regression analysis was performed to determine factors predictive of maternal hypotension and FHR abnormalities (Table 4). Each unit increase in BMI was associated with an increased risk of both persistent systolic and persistent diastolic hypotension after controlling for epidural bolus dose and hypertensive disorders. Epidural bolus dose was associated with persistent diastolic hypotension, but not persistent systolic hypotension. Increasing BMI, persistent systolic hypotension, and persistent diastolic hypotension were each associated with new onset of late or prolonged variable decelerations after controlling for hypertensive disorders and epidural anesthetic bolus dose.
      TABLE 4Logistic regression: factors associated with persistent hypotension and fetal heart tracing abnormalities
      FindingVariableCoefficientAdjusted OR95% CI
      Systolic hypotensionBMI, kg/m20.0061.061.02–1.10
      Diastolic hypotensionBMI, kg/m20.0021.041.01–1.06
      Volume anesthetic0.0481.331.00–1.77
      New-onset late or prolonged decelerationsBMI, kg/m20.0071.041.01–1.07
      Systolic hypotension0.0034.211.63–10.85
      Diastolic hypotension0.0022.801.46–5.34
      Controlled for chronic hypertension, preeclampsia spectrum disorders, and epidural anesthetic volume.
      BMI, body mass index; CI, confidence interval; OR, odds ratio.
      Vricella. Morbid obesity and epidural anesthetic complication for labor. Am J Obstet Gynecol 2011.

      Comment

      We found that morbidly obese women given similar bolus doses of epidural anesthetic had more frequent postepidural hypotension and related late or prolonged FHR decelerations than normal-weight controls. We also found that diastolic hypotension occurred more frequently among both BMI groups than systolic hypotension. Increasing BMI is associated with increased risk of persistent postepidural hypotension and subsequent late or prolonged variable decelerations. The incidence of persistent diastolic hypotension was positively related to the increasing epidural anesthetic dose.
      Our finding of a high overall incidence of epidural-related hypotension is not surprising as it is a well-documented consequence of regional anesthesia in pregnancy.
      • Assali N.S.
      • Prystowsky H.
      Studies on autonomic blockade, I: comparison between the effects of tetraethylammonium chloride (TEAC) and high selective spinal anesthesia on blood pressure of normal and toxemic pregnancy.
      • Tabash K.
      • Rudelstorfer R.
      • Nuwayhid B.
      • et al.
      Circulatory responses to hypovolemia in the pregnant and nonpregnant sheep after pharmacologic sympathectomy.
      In a term patient progressively dependent on the sympathetic nervous system for hemodynamic stability, pharmacologic sympathectomy can compromise venous return and uteroplacental perfusion.
      • Assali N.S.
      • Prystowsky H.
      Studies on autonomic blockade, I: comparison between the effects of tetraethylammonium chloride (TEAC) and high selective spinal anesthesia on blood pressure of normal and toxemic pregnancy.
      • Tabash K.
      • Rudelstorfer R.
      • Nuwayhid B.
      • et al.
      Circulatory responses to hypovolemia in the pregnant and nonpregnant sheep after pharmacologic sympathectomy.
      Our findings that diastolic blood pressures decreased more than systolic blood pressures is in keeping with prior studies documenting decreasing systemic vascular resistance during pregnancy that affects diastolic blood pressures to a greater extent.
      • Wilson M.
      • Morganti A.A.
      • Zervoudakis I.
      • et al.
      Blood pressure, the renin-aldosterone system and sex steroids throughout normal pregnancy.
      However, we found that both persistent systolic and diastolic hypotension were associated with the occurrence of late or prolonged variable decelerations. This finding suggests that although diastolic hypotension occurred more frequently than systolic, both contribute to maintaining uteroplacental perfusion to some extent.
      The cause of increased hypotension in morbidly obese women compared to normal-weight women is likely multifactorial; however we propose 2 possible mechanisms: anatomic distortion of the epidural space and inadequate volume preloading. The epidural space is smaller and epidural space pressures are higher in obese women at term due to increased density and engorgement of the epidural venous plexus exacerbated by increased vena cava compression from higher intraabdominal pressure.
      • Panni M.K.
      • Columb M.O.
      Obese parturients have lower epidural local anesthetic requirements for analgesia in labor.
      • Saravanakumar K.
      • Rao S.G.
      • Cooper G.M.
      Obesity and obstetric anesthesia.
      • Nguyen N.T.
      • Lee S.L.
      • Anderson T.J.
      • et al.
      Evaluation of intraabdominal pressure after open and laparoscopic gastric bypass.
      • Hirabayashi Y.
      • Matsuda I.
      • Inoue S.
      • et al.
      Spread of epidural analgesia following a constant pressure injection–an investigation of relationships between locus of injection, epidural pressure, and spread of analgesia.
      Magnetic resonance imaging studies have shown that obese women have decreased cerebrospinal fluid volume but have not shown a clear relationship between epidural space fat distribution and BMI.
      • Hogan Q.
      • Prost R.
      • Kulier A.
      • et al.
      Magnetic resonance imaging of cerebrospinal fluid volume and the influence of body habitus and abdominal pressure.
      • Wu H.T.
      • Schweitzer M.E.
      • Parker L.
      Is epidural fat associated with body habitus?.
      The idea that maternal obesity distorts the epidural space is supported by 2 studies by Hodgkinson and Hussain
      • Hodgkinson R.
      • Hussain F.J.
      Obesity and the cephalad spread of analgesia following epidural administration of bupivacaine for cesarean section.
      • Hodgkinson R.
      • Hussain F.J.
      Obesity, gravity, and spread of epidural anesthesia.
      that show that increasing BMI and weight increase the cephalad spread of epidural anesthesia, however Milligan et al
      • Milligan K.R.
      • Cramp P.
      • Schatz L.
      • et al.
      The effect of patient position and obesity on the spread of epidural analgesia.
      found no relationship between obesity and cephalad spread. Obese women have been found to require lower epidural bupivacaine doses to achieve similar quality of analgesia to normal-weight women; supporting the idea that decreased epidural space volumes and increased epidural space pressures in obese women lead to higher concentration and greater cephalad spread of a given anesthetic dose.
      • Panni M.K.
      • Columb M.O.
      Obese parturients have lower epidural local anesthetic requirements for analgesia in labor.
      We propose that our finding of more frequent hypotension among morbidly obese women can be explained by similar mechanisms of reduced volume and increased pressure of the epidural space.
      Another plausible explanation for the increased incidence of hypotension in morbidly obese women is inadequate volume preloading related to greater circulating blood volumes. Morbidly obese women have a higher circulating blood volume and cardiac output of normal-weight women.
      • Alexander J.K.
      • Dennis D.W.
      • Smith W.G.
      • et al.
      Blood volume, cardiac output and systemic blood flow in extreme obesity.
      Volume preloading with 500-1000 mL of intravenous solutions has been shown to decrease the incidence of maternal hypotension following regional anesthesia placement and has become standard practice.
      • Zamora J.E.
      • Rosaeg O.P.
      • Lindsay M.P.
      • et al.
      Hemodynamic consequences and uterine contractions following 0.5 or 1.0 litre crystalloid infusion before obstetric epidural analgesia.
      In our study, women in both groups received a standard 500-mL crystalloid intravenous fluid bolus immediately before epidural dosing; this may have been inadequate for morbidly obese women with twice the circulating blood volumes compared to normal-weight women. It is likely that morbidly obese women require greater volumes of intravenous fluid to achieve adequate volume preloading prior to regional anesthesia placement.
      The findings of our study suggest that standard obstetric anesthesia practices with established safety profiles in normal-weight women could be inappropriate for morbidly obese women. Simple alterations to anesthesia protocols, including decreased anesthetic bolus doses and increased volume preloading, may achieve adequate pain control in morbidly obese women while decreasing the risk of maternal hypotension and resultant FHR abnormalities. In the morbidly obese obstetric population already known to be at increased risk for emergent cesarean delivery during which they are at greater risk for general anesthesia, failed intubation, and death, epidural-related hypotension has potentially severe consequences.
      • Hood D.D.
      • Dewan D.M.
      Anesthetic and obstetric outcomes in morbidly obese parturients.
      • Mhyre J.M.
      • Reisner M.N.
      • Polley L.K.
      • et al.
      A series of anesthesia-related maternal deaths in Michigan, 1985-2003.
      This study is limited by its retrospective nature. It is plausible that the actual volume of intravenous fluid preload administered could have differed from what was recorded. Variations in technique for measuring blood pressure have been shown to falsely elevate readings. However, techniques in epidural dosing and vital sign measurement after epidural are standardized, providing an intervention and measures that are objective and reproducible. The strengths of this study include the adequate sample size to measure the primary outcome and the effective matching maintaining similarity among groups.
      We failed to demonstrate significant differences in need for intravenous pressor support. However, the power to detect the demonstrated 30% increase in these outcomes was just 17% based on our sample size. Similarly, although morbidly obese women had more frequent emergent deliveries (operative vaginal and cesarean delivery), the study was not powered to detect a relationship between incidence of epidural-related maternal hypotension and emergent delivery. A larger study focusing on the incidence of profound maternal hypotension requiring intravenous pressor support would be needed to evaluate the incidence of emergent cesarean due to maternal hypotension with refractory fetal bradycardia.
      In summary, we found that morbidly obese women undergoing epidural anesthesia placement for labor had more hypotension and related FHR abnormalities than normal-weight women, and that diastolic blood pressure was more common than systolic hypotension. The optimal definition of epidural-related hypotension has not yet been determined. Further studies are needed to identify the most clinically significant definition of epidural-related hypotension in the obstetric population. Prospective studies are needed to determine if lower epidural anesthetic doses or greater volume preloading will achieve adequate analgesia in morbidly obese women with decreased risk of hypotension.

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