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PRACTICE guidelines are systematically developed recommendations that assist the practitioner and patient in making decisions about health care. These recommendations may be adopted, modified, or rejected according to clinical needs and constraints.
Practice guidelines are not intended as standards or absolute requirements. The use of practice guidelines cannot guarantee any specific outcome. Practice guidelines are subject to periodic revision as warranted by the evolution of medical knowledge, technology, and practice. The guidelines provide basic recommendations that are supported by analysis of the current literature and by a synthesis of expert opinion, open forum commentary, and clinical feasibility data (Appendix).
A. Purpose of the Guidelines for Obstetrical Anesthesia
The purposes of these Guidelines are to enhance the quality of anesthesia care for obstetric patients, reduce the incidence and severity of anesthesia-related complications, and increase patient satisfaction.
B. Focus
The Guidelines focus on the anesthetic management of pregnant patients during labor, non-operative delivery, operative delivery, and selected aspects of postpartum care. The intended patient population includes, but is not limited to intrapartum and postpartum patients with uncomplicated pregnancies or with common obstetric problems. The Guidelines do not apply to patients undergoing surgery during pregnancy, gynecological patients or parturients with chronic medical disease (e.g., severe heart, renal or neurological disease).
C. Application
The Guidelines are intended for use by anesthesiologists. They also may serve as a resource for other anesthesia providers and health care professionals who advise or care for patients who will receive anesthesia care during labor, delivery and the immediate postpartum period.
D. Task Force Members and Consultants
The ASA appointed a Task Force of 11 members to review the published evidence and obtain consultant opinion from a representative body of anesthesiologists and obstetricians. The Task Force members consisted of anesthesiologists in both private and academic practices from various geographic areas of the United States.
The Task Force met its objective in a five-step process. First, original published research studies relevant to these issues were reviewed and analyzed. Second, Consultants from various geographic areas of the United States who practice or work in various settings (e.g., academic and private practice) were asked to participate in opinion surveys and review and comment on drafts of the Guidelines. Third, the Task Force held two open forums at major national meetings to solicit input from attendees on its draft recommendations. Fourth, all available information was used by the Task Force in developing the Guideline recommendations. Finally, the Consultants were surveyed to assess their opinions on the feasibility of implementing the Guidelines.
E. Availability and Strength of Evidence
Evidence-based guidelines are developed by a rigorous analytic process. To assist the reader, the Guidelines make use of several descriptive terms that are easier to understand than the technical terms and data that are used in the actual analyses. These descriptive terms are defined below:
The following terms describe the availability of scientific evidence in the literature.
Insufficient: There are too few published studies to investigate a relationship between a clinical intervention and clinical outcome.
Inconclusive: Published studies are available, but they cannot be used to assess the relationship between a clinical intervention and a clinical outcome because the studies either do not meet predefined criteria for content as defined in the “Focus of the Guidelines,” or do not meet research design or analytic standards.
Silent: There are no available studies in the literature that address a relationship of interest.
The following terms describe the strength of scientific data.
Supportive: There is sufficient quantitative information from adequately designed studies to describe a statistically significant relationship (p < 0.01) between a clinical intervention and a clinical outcome, using the technique of meta-analysis.
Suggestive: There is enough information from case reports and descriptive studies to provide a directional assessment of the relationship between a clinical intervention and a clinical outcome. This type of qualitative information does not permit a statistical assessment of significance.
Equivocal: Qualitative data have not provided a clear direction for clinical outcomes related to a clinical intervention and (1) there is unsufficient quantitative information or (2) aggregated comparative studies have found no quantitatively significant differences among groups or conditions.
The following terms describe survey responses from Consultants for any specified issue. Responses are weighted as agree =+1, undecided = 0 or disagree =-1.
Agree: The average weighted responses must be equal to or greater than +0.30 (on a scale of -1 to 1) to indicate agreement.
Equivocal: The average weighted responses must be between -0.30 and +0.30 (on a scale of -1 to 1) to indicate an equivocal response.
Disagree: The average weighted responses must be equal to or less than -0.30 (on a scale of -1 to 1) to indicate disagreement.
Guidelines
I. Perianesthetic Evaluation.
1. History and Physical Examination. The literature is silent regarding the relationship between anesthesia-related obstetric outcomes and the performance of a focused history and physical examination. However, there is suggestive data that a patient's medical history and/or findings from a physical exam may be related to anesthetic outcomes. The Consultants and Task Force agree that a focused history and physical examination may be associated with reduced maternal, fetal and neonatal complications. The Task Force agrees that the obstetric patient benefits from communication between the anesthesiologist and the obstetrician.
Recommendations: The anesthesiologist should do a focused history and physical examination when consulted to deliver anesthesia care. This should include a maternal health history, an anesthesia-related obstetric history, an airway examination, and a baseline blood pressure measurement. When a regional anesthetic is planned, the back should be examined. Recognition of significant anesthetic risk factors should encourage consultation with the obstetrician.
2. Intrapartum Platelet Count. A platelet count may indicate the severity of a patient's pregnancy-induced hypertension. However, the literature is insufficient to assess the predictive value of a platelet count for anesthesia-related complications in either uncomplicated parturients or those with pregnancy-induced hypertension. The Consultants and Task Force both agree that a routine platelet count in the healthy parturient is not necessary. However, in the patient with pregnancy-induced hypertension, the Consultants and Task Force both agree that the use of a platelet count may reduce the risk of anesthesia-related complications.
Recommendations: A specific platelet count predictive of regional anesthetic complications has not been determined. The anesthesiologist's decision to order or require a platelet count should be individualized and based upon a patient's history, physical examination and clinical signs of a coagulopathy.
3. Blood Type and Screen. The literature is silent regarding whether obtaining a blood type and screen is associated with fewer maternal anesthetic complications. The Consultants and Task Force are equivocal regarding the routine use of a blood type and screen to reduce the risk of anesthesia-related complications.
Recommendations: The anesthesiologist's decision to order or require a blood type and screen or cross-match should be individualized and based on anticipated hemorrhagic complications (e.g., placenta previa in a patient with previous uterine surgery).
4. Perianesthetic Recording of the Fetal Heart Rate. The literature suggests that analgesic/anesthetic agents may influence the fetal heart rate pattern. There is insufficient literature to demonstrate that perianesthetic recording of the fetal heart rate prevents fetal complications. However, both the Task Force and Consultants agree that perianesthetic recording of the fetal heart rate reduces fetal and neonatal complications.
Recommendations: The fetal heart rate should be monitored by a qualified individual before and after administration of regional analgesia for labor. The Task Force recognizes that continuous electronic recording of the fetal heart rate may not be necessary in every clinical setting [1]and may not be possible during placement of a regional anesthetic.
II. Fasting in the Obstetric Patient.
1. Clear Liquids. Published evidence is insufficient regarding the relationship between fasting times for clear liquids and the risk of emesis/reflux or pulmonary aspiration during labor. The Task Force and Consultants agree that oral intake of clear liquids during labor improves maternal comfort and satisfaction. The Task Force and Consultants are equivocal whether oral intake of clear liquids increases maternal risk of pulmonary aspiration.
Recommendations: The oral intake of modest amounts of clear liquids may be allowed for uncomplicated laboring patients. Examples of clear liquids include, but are not limited to, water, fruit juices without pulp, carbonated beverages, clear tea, and black coffee. The volume of liquid ingested is less important than the type of liquid ingested. However, patients with additional risk factors of aspiration (e.g., morbid obesity, diabetes, difficult airway), or patients at increased risk for operative delivery (e.g., nonreassuring fetal heart rate pattern) may have further restrictions of oral intake, determined on a case-by-case basis.
2. Solids. A specific fasting time for solids that is predictive of maternal anesthetic complications has not been determined. There is insufficient published evidence to address the safety of any particular fasting period for solids for obstetric patients. The Consultants agree that a fasting period for solids of 8 hours or more is preferable for uncomplicated parturients undergoing elective cesarean delivery. The Task Force recognizes that in laboring patients the timing of delivery is uncertain; therefore compliance with a predetermined fasting period is not always possible. The Task Force supports a fasting period of at least 6 hours before elective cesarean delivery.
Recommendations: Solid foods should be avoided in laboring patients. The patient undergoing elective cesarean delivery should undergo a fasting period for solids consistent with the hospital's policy for nonobstetric patients undergoing elective surgery. Both the amount and type of food ingested must be considered when determining the timing of surgery.
III. Anesthesia Care for Labor and Vaginal Delivery
A. Overview of Recommendations. Anesthesia care is not necessary for all women for labor and/or delivery. For women who request pain relief for labor and/or delivery, there are many effective analgesic techniques available. Maternal request represents sufficient justification for pain relief, but the selected analgesia technique depends on the medical status of the patient, the progress of the labor, and the resources of the facility. When sufficient resources (e.g., anesthesia and nursing staff) are available, epidural catheter techniques should be one of the analgesic options offered. The primary goal is to provide adequate maternal analgesia with as little motor block as possible when regional analgesia is used for uncomplicated labor and/or vaginal delivery. This can be achieved by the administration of local anesthetic at low concentrations. The concentration of the local anesthetic may be further reduced by the addition of narcotics and still provide adequate analgesia.
B. Specific Recommendations.
1. Epidural anesthetics:
a. Epidural local anesthetics. The literature supports the use of single-bolus epidural local anesthetics for providing greater quality of analgesia compared to parenteral opioids. However, the literature indicates a reduced incidence of spontaneous vaginal delivery associated with single-bolus epidural local anesthetics. The literature is insufficient to indicate causation. Compared to single-injection spinal opioids the literature is equivocal regarding the analgesic efficacy of single-bolus epidural local anesthetics. The literature suggests that epidural local anesthetics compared to spinal opioids are associated with a lower incidence of pruritus. The literature is insufficient to compare the incidence of other side-effects.
b. Addition of opioids to epidural local anesthetics. The literature supports the use of epidural local anesthetics with opioids, when compared with equal concentrations of epidural local anesthetics without opioids for providing greater quality and duration of analgesia. The former is associated with reduced motor block and an increased likelihood of spontaneous delivery, possibly as a result of a reduced total dose of local anesthetic administered over time.##
The literature is equivocal regarding the analgesic efficacy of low concentrations of epidural local anesthetics with opioids compared to higher concentrations of epidural local anesthetics without opioids. The literature indicates that low concentrations of epidural local anesthetics with opioids compared to higher concentrations of epidural local anesthetics are associated with reduced motor block.
No differences in the incidence of nausea, hypotension, duration of labor, or neonatal outcomes are found when epidural local anesthetics with opioids were compared to epidural local anesthetics without opioids. However, the literature indicates that the addition of opioids to epidural local anesthetics results in a higher incidence of pruritus. The literature is insufficient to determine the effects of epidural local anesthetics with opioids on other maternal outcomes (e.g., respiratory depression, urinary retention).
The Task Force and majority of Consultants are supportive of the case-by-case selection of an analgesic technique for labor. The subgroup of Consultants reporting a preferred technique, when all choices are available, selected an epidural local anesthetic technique. When a low concentration of epidural local anesthetic is used, the Consultants and Task Force agree that the addition of an opioid(s) improves analgesia and maternal satisfaction without increasing maternal, fetal or neonatal complications.
Recommendations: The selected analgesic/anesthetic technique should reflect patient needs and preferences, practitioner preferences or skills, and available resources. When an epidural local anesthetic is selected for labor and delivery, the addition of an opioid may allow the use of a lower concentration of local anesthetic and prolong the duration of analgesia. Appropriate resources for the treatment of complications related to epidural local anesthetics (e.g., hypotension, systemic toxicity, high spinal anesthesia) should be available. If opioids are added, treatments for related complications (e.g., pruritus, nausea, respiratory depression) should be available.
c. Continuous infusion epidural techniques (CIE) The literature indicates that effective analgesia can be maintained with a low concentration of local anesthetic with an epidural infusion technique. In addition, when an opioid is added to a local anesthetic infusion, an even lower concentration of local anesthetic provides effective analgesia. For example, comparable analgesia is found, with a reduced incidence of motor block, using bupivacaine infusion concentrations of less than 0.125% with an opioid compared to bupivacaine concentrations equal to 0.125% without an opioid.*** No comparative differences are noted for incidence of instrumental delivery.
The literature is equivocal regarding the relationship between different local anesthetic infusion regimens and the incidence of nausea or neonatal outcome. However, the literature suggests that local anesthetic infusions with opioids are associated with a higher incidence of pruritus.
The Task Force and Consultants agree that infusions using low concentrations of local anesthetics with or without opioids provide equivalent analgesia, reduced motor block, and improved maternal satisfaction when compared to higher concentrations of local anesthetic.
Recommendations: Adequate analgesia for uncomplicated labor and delivery should be provided with the secondary goal of producing as little motor block as possible. The lowest concentration of local anesthetic infusion that provides adequate maternal analgesia and satisfaction should be used. For example, and infusion concentration of bupivacaine equal to or greater than 0.25% is unnecessary for labor analgesia for most patients. The addition of an opioid(s) to a low concentration of local anesthetic may improve analgesia and minimize motor block. Resources for the treatment of potential complications should be available.
2. Spinal Opioids with or without Local Anesthetics. The literature suggests that spinal opioids with or without local anesthetics provide effective labor analgesia without significantly altering the incidence of neonatal complications. There is insufficient literature to compare spinal opioids with parenteral opioids. However, the Consultants and Task Force agree that spinal opioids provide improved maternal analgesia compared to parenteral opioids.
The literature is equivocal regarding analgesic efficacy of spinal opioids compared to epidural local anesthetics. The Consultants and Task Force agree that spinal opioids provide equivalent analgesia compared to epidural local anesthetics. The Task Force agrees that the rapid onset of analgesia provided by single-injection spinal techniques may be advantageous for selected patients (e.g., those in advanced labor).
Recommendations: Spinal opioids with or without local anesthetics may be used to provide effective, although time-limited, analgesia for labor. Resources for the treatment of potential complications (e.g., pruritus, nausea, hypotension, respiratory depression) should be available.
3. Combined spinal-epidural techniques. Although the literature suggests that combined spinal-epidural techniques (CSE) provide effective analgesia, the literature is insufficient to evaluate the analgesic efficacy of CSE compared to epidural local anesthetics. The literature indicates that use of CSE techniques with opioids when compared to epidural local anesthetics with or without opioids results in a higher incidence of pruritus and nausea. The Task Force and Consultants are equivocal regarding improved analgesia or maternal benefit of CSE versus epidural techniques. Although the literature is insufficient to evaluate fetal and neonatal outcomes of CSE techniques, the Task Force and Consultants agree that CSE does not increase the risk of fetal or neonatal complications.
Recommendations: Combined spinal-epidural techniques may be used to provide rapid and effective analgesia for labor. Resources for the treatment of potential complications (e.g., pruritus, nausea, hypotension, respiratory depression) should be available.
4. Regional Analgesia and Progress of Labor. These is insufficient literature to indicate whether timing of analgesia related to cervical dilation affects labor and delivery outcomes. Both the Task Force and Consultants agree that cervical dilation at the time of epidural analgesia administration does not impact the outcome of labor.
The literature indicates that epidural analgesia may be used in a trial of labor for previous cesarean section patients without adversely affecting the incidence of vaginal delivery. However, randomized comparisons of epidural versus other specific anesthetic techniques were not found, and comparison groups were often confounded.
Recommendations: Cervical dilation is not a reliable means of determining when regional analgesia should be initiated. Regional analgesia should be administered on an individualized basis.
5. Monitored or Stand-by Anesthesia Care for Complicated Vaginal Delivery. Monitored anesthesia care refers to instances in which an anesthesiologist has been called upon to provide specific anesthesia services to a particular patient undergoing a planned procedure. [2]For these Guidelines, stand-by anesthesia care refers to the availability of the anesthesiologist in the facility, in the event of obstetric complications. The literature is silent regarding the subject of monitored or stand-by anesthesia care in obstetrics. However, the Task Force and Consultants agree that monitored or stand-by anesthesia care for complicated vaginal delivery reduces maternal, fetal, and neonatal complications.
Recommendations: Either monitored or stand-by anesthesia care, determined on a case-by-case basis for complicated vaginal delivery (e.g., breech presentation, twins, and trial of instrumental delivery), should be made available when requested by the obstetrician.
IV. Removal of Retained Placenta
1. Anesthetic Choices. The literature is insufficient to indicate whether a particular type of anesthetic is more effective than another for removal of retained placenta. The literature is also insufficient to assess the relationship between a particular type of anesthetic and maternal complications. The Task Force and Consultants agree that spinal or epidural anesthesia (i.e., regional anesthesia) is associated with reduced maternal complications and improved satisfaction when compared to general anesthesia or sedation/analgesia. The Task Force recognizes that circumstances may occur when general anesthesia or sedation/analgesia may be the more appropriate anesthetic choice (e.g., significant hemorrhage).
Recommendations: Regional anesthesia, general endotracheal anesthesia, or sedation/analgesia may be used for removal of retained placenta. Hemodynamic status should be assessed before giving regional anesthesia to a parturient who has experienced significant bleeding. In cases involving significant maternal hemorrhage, a general anesthetic may be preferable to initiating regional anesthesia. Sedation/analgesia should be titrated carefully due to the potential risk of pulmonary aspiration in the recently delivered parturient with an unprotected airway.
2. Nitroglycerin for Uterine Relaxation. The literature suggests and the Task Force and Consultants agree that the administration of nitroglycerin is effective for uterine relaxation during removal of retained placental tissue.
Recommendations: Nitroglycerin is an alternative to terbutaline sulfate or general endotracheal anesthesia with halogenated agents for uterine relaxation during removal of retained placental tissue. Initiating treatment with a low dose of nitroglycerin may relax the uterus sufficiently while minimizing potential complications (e.g., hypotension).
V. Anesthetic Choices for Cesarean Delivery
The literature suggests that spinal, epidural or CSE anesthetic techniques can be used effectively for cesarean delivery. When compared to regional techniques, the literature indicates that general anesthetics can be administered with shorter induction-to-delivery times. The literature is insufficient to determine the relative risk of maternal death associated with general anesthesia compared to other anesthetic techniques. However, the literature suggests that a greater number of maternal deaths occur when general anesthesia is administered. The literature indicates that a larger proportion of neonates in the general anesthesia groups, compared to those in the regional anesthesia groups, are assigned Apgar scores of less than 7 at one and five minutes. However, few studies have utilized randomized comparisons of general versus regional anesthesia, resulting in potential selection bias in the reporting of outcomes.
The literature suggests that maternal side effects associated with regional techniques may include hypotension, nausea, vomiting, pruritus and postdural puncture headache. The literature is insufficient to examine the comparative merits of various regional anesthetic techniques.
The Consultants agree that regional anesthesia can be administered with fewer maternal and neonatal complications and improved maternal satisfaction when compared to general anesthesia. The consultants are equivocal about the possibility of increased maternal complications when comparing spinal or epidural anesthesia with CSE techniques. They agree that neonatal complications are not increased with CSE techniques.
Recommendations: The decision to use a particular anesthetic technique should be individualized based on several factors. These include anesthetic, obstetric and/or fetal risk factors (e.g., elective versus emergency) and the preferences of the patient and anesthesiologist. Resources for the treatment of potential complications (e.g., airway management, inadequate analgesia, hypotension, pruritus, nausea) should be available.
VI. Postpartum Tubal Ligation
There is insufficient literature to evaluate the comparative benefits of local, spinal, epidural or general anesthesia for postpartum tubal ligation. Both the Task Force and Consultants agree that epidural, spinal and general anesthesia can be effectively provided without affecting maternal complications. Neither the Task Force nor the Consultants agree that local anesthetic techniques provide effective anesthesia, and they are equivocal regarding the impact of local anesthesia on maternal complications. Although the literature is insufficient, the Task Force and Consultants agree that a postpartum tubal ligation can be performed safely within eight hours of delivery in many patients.
Recommendations. Evaluation of the patient for postpartum tubal ligation should include assessment of hemodynamic status (e.g., blood loss) and consideration of anesthetic risks. The patient planning to have an elective postpartum tubal ligation within 8 hours of delivery should have no oral intake of solid foods during labor, and postpartum until the time of surgery. Both the timing of the procedure and the decision to use a particular anesthetic technique (i.e., regional versus general) should be individualized, based on anesthetic and/or obstetric risk factors and patient preferences. The anesthesiologist should be aware that an epidural catheter placed for labor may be more likely to fail with longer postdelivery time intervals. If a postpartum tubal ligation is to be done before the patient is discharged from the hospital, the procedure should not be attempted at a time when it might compromise other aspects of patient care in the labor and delivery area.
VII. Management of Complications
1. Resources for Management of Hemorrhagic Emergencies. The literature suggests that the availability of resources for hemorrhagic emergencies is associated with reduced maternal complications. The Task Force and Consultants agree that the availability of resources for managing hemorrhagic emergencies is associated with reduced maternal, fetal and neonatal complications.
Recommendations: Institutions providing obstetric care should have resources available to manage hemorrhagic emergencies (Table 1). In an emergency, the use of type-specific or O negative blood is acceptable in the parturient.
2. Equipment for Management of Airway Emergencies. The literature suggests, and the Task Force and Consultants agree that the availability of equipment for the management of airway emergencies is associated with reduced maternal complications.
Recommendations: Labor and delivery units should have equipment and personnel readily available to manage airway emergencies. Basic airway management equipment should be immediately available during the initial provision of regional analgesia (Table 2). In addition, portable equipment for difficult airway management should be readily available in the operative area of labor and delivery units (Table 3).
Table 3. Suggested Contents of a Portable Unit for Difficult Airway Management for Cesarean Section Rooms
3. Central Invasive Hemodynamic Monitoring. There is insufficient literature to indicate whether pulmonary artery catheterization is associated with improved maternal, fetal or neonatal outcomes in patients with pregnancy-related hypertensive disorders. The literature is silent regarding the management of obstetric patients with central venous catheterization alone. The literature suggests that pulmonary artery catheterization has been used safely in obstetric patients; however, the literature is insufficient to examine specific obstetric outcomes. The Task Force and Consultants agree that it is not necessary to use central invasive hemodynamic monitoring routinely for parturients with severe preeclampsia.
Recommendations: The decision to perform invasive hemodynamic monitoring should be individualized and based on clinical indications that include the patient's medical history and cardiovascular risk factors. The Task Force recognizes that not all practitioners have access to resources for utilization of central venous or pulmonary artery catheters in obstetric units.
4. Cardiopulmonary Resuscitation. The literature is insufficient to evaluate the efficacy of CPR in the obstetric patient during labor and delivery. The Task Force is supportive of the immediate availability of basic and advanced life-support equipment in the operative area of labor and delivery units.
Recommendations: Basic and advanced life-support equipment should be immediately available in the operative area of labor and delivery units. If cardiac arrest occurs during labor and delivery, standard resuscitative measures and procedures, including left uterine displacement, should be taken. In cases of cardiac arrest, the American Heart Association has stated the following:“Several authors now recommend that the decision to perform a perimortem cesarean section should be made rapidly, with delivery effected within 4 to 5 minutes of the arrest.”[3]
Appendix: Methods and Analyses.
The scientific assessment of these Guidelines was based on the following statements, or evidence linkages. These linkages represent directional statements about relationships between obstetrical anesthetic interventions and clinical outcomes.
I. Perianesthetic Evaluation
1. A directed history and physical examination reduces maternal, fetal & neonatal complications.
2a. A routine intrapartum platelet count reduces maternal anesthetic complications.
2b. For pregnancy-induced hypertension, an intrapartum platelet count reduces maternal anesthetic complications.
3. For all parturients, an intrapartum blood type & screen reduces maternal, fetal & neonatal complications.
4. Perianesthetic recording of the fetal heart rate reduces fetal & neonatal complications.
II. Fasting for Labor and Delivery
5a. Oral intake of clear liquids during labor improves patient comfort and satisfaction, and does not increase maternal complications.
5b. Oral intake of solids during labor increases maternal complications.
III. Anesthetic Choices for Labor and Delivery
6a. Epidural techniques versus parenteral opioids:(a) improve maternal analgesia, (b) decrease maternal anesthetic complications, and (c) decrease fetal and neonatal complications.
6b. Epidural techniques versus spinal techniques:(a) improve maternal analgesia and (b) decrease maternal anesthetic complications.
6c. Epidural local anesthetics with opioids versus equal concentrations of epidural local anesthetics without opioids:(a) improve maternal analgesia, but (b) increase maternal, fetal & neonatal anesthetic complications.
6d. Epidural local anesthetics with opioids versus higher concentrations of epidural local anesthetics without opioids:(a) improve maternal analgesia, and (b) reduce maternal, fetal & neonatal anesthetic complications.
6e. Epidural infusion of lower concentrations of local anesthetics with opioids (i.e., bupivacaine concentrations less than 0.125% with opioids versus concentrations equal to 0.125%):(a) provides equivalent maternal analgesia, (b) reduces maternal motor block, but (c) increases opioid-related maternal anesthetic complications.
6f. Epidural infusion of lower concentrations of local anesthetics with opioids (i.e., bupivacaine concentrations less than 0.25% with opioids versus bupivacaine equal to or greater than 0.25%):(a) provides equivalent maternal analgesia, (b) reduces maternal motor block, but (c) increases opioid-related maternal anesthetic complications.
6g. Spinal opioids (with or without local anesthetic) versus parenteral opioids:(a) improve maternal analgesia, (b) reduce maternal, fetal & neonatal anesthetic complications, and (c) improve maternal satisfaction.
6h. Combined spinal-epidural techniques versus epidural local anesthetics:(a) improve maternal analgesia, but (b) increase maternal, fetal & neonatal anesthetic complications.
6i. Administering epidural analgesia at cervical dilatations of 3 to 5 centimeters (versus <3 cm)(a) improves maternal analgesia, (b) reduces maternal, fetal & neonatal obstetric complications, and (c) improves maternal satisfaction.
6j. Administering epidural analgesia at cervical dilatations of 3 to 5 centimeters (versus >5 cm)(a) improves maternal analgesia, (b) reduces maternal, fetal & neonatal anesthetic complications, and (c) improves maternal satisfaction.
6k. Epidural techniques for trial of labor patients:(a) reduces the incidence of cesarean delivery, (b) reduces maternal, fetal & neonatal obstetric complications, and (c) improves maternal satisfaction.
6l. Monitored or stand-by anesthesia care for complicated vaginal delivery reduces maternal, fetal & neonatal complications.
IV. Removal of Retained Placenta
7. Regional anesthesia [versus general anesthesia or sedation] for pain management during removal of retained placenta reduces maternal anesthetic complications and improves patient satisfaction.
8. Administration of nitroglycerin for uterine relaxation improves success at removing retained placenta.
V. Anesthetic Choices for Cesarean Delivery
9a. Spinal anesthesia for cesarean section provides maternal comfort & satisfaction without clinically significant maternal, fetal & neonatal anesthetic complications.
9b. Epidural anesthesia for cesarean section provides maternal comfort & satisfaction without clinically significant maternal, fetal & neonatal anesthetic complications.
9c. General anesthesia for cesarean section provides maternal comfort & satisfaction without clinically significant maternal, fetal & neonatal anesthetic complications.
9d. Combined spinal-epidural techniques versus epidural or spinal techniques alone for cesarean section provide maternal comfort & satisfaction without clinically significant maternal, fetal & neonatal anesthetic complications.
VI. Postpartum Tubal Ligation
10a. Local anesthesia for postpartum tubal ligation without preexisting anesthesia (a) improves maternal analgesia, (b) reduces maternal anesthetic complications, and (c) improves maternal satisfaction.
10b. Spinal anesthesia for postpartum tubal ligation without preexisting anesthesia (a) improves maternal analgesia, (b) reduces maternal anesthetic complications, and (c) improves maternal satisfaction.
10c. Epidural anesthesia for postpartum tubal ligation without preexisting anesthesia (a) improves maternal analgesia, (b) reduces maternal anesthetic complications, and (c) improves maternal satisfaction.
10d. General anesthesia for postpartum tubal ligation without preexisting anesthesia (a) improves maternal analgesia, (b) reduces maternal anesthetic complications, and (c) improves maternal satisfaction.
11. A postpartum tubal ligation [i.e., within 8 hours of delivery]:(a) does not increase maternal anesthetic complications, (b) improves patient satisfaction, and (c) improves cost/efficiency.
VII. Management of Complications
12. Availability of resources for management of hemorrhagic emergencies reduces maternal, fetal & neonatal anesthetic complications.
13. Availability of equipment for management of airway emergencies reduces maternal, fetal & neonatal anesthetic complications.
14. Peripartum invasive hemodynamic monitoring for preeclamptic patients reduces maternal, fetal & neonatal anesthetic and obstetric complications.
15. Immediate availability of basic and advanced life-support equipment in the operative area of labor and delivery units reduces maternal, fetal & neonatal complications.
Scientific evidence was derived from aggregated research literature with meta-analyses utilized when appropriate, and from surveys, open presentations and other consensus-oriented activities. For purposes of literature aggregation, potentially relevant clinical studies were identified via electronic and manual searches of the literature. The electronic search covered a 33-year period from 1966 through 1998. The manual search covered a 59-year period of time from 1940 through 1998. Over 4000 citations were initially identified, yielding a total of 2347 non-overlapping articles that addressed topics related to the 33 evidence linkages. Following review of the articles, 1819 studies did not provide direct evidence, and were subsequently eliminated. A total of 528 articles (from 57 journals) contained direct linkage-related evidence.
A directional result for each study was initially determined by classifying the outcome as either supporting a linkage, refuting a linkage, or neutral. The results were then summarized to obtain a directional assessment of support for each linkage. The literature relating to 8 evidence linkages contained enough studies with well-defined experimental designs and statistical information to conduct formal meta-analyses. These eight linkages were: linkage 6a [epidural versus parenteral techniques for labor], 6b [epidural versus single-shot spinal techniques for labor], 6c [epidural local anesthetics with opioids versus equal dosages of local anesthetics without opioids], 6d [epidural local anesthetics with opioids versus higher concentrations of local anesthetics without opioids], 6e [epidural infusion of local anesthetic (bupivacaine) concentrations of less than 0.125% versus concentrations equal to 0.125%], 6h [combined spinal-epidural techniques versus epidural local anesthetics for labor], 6k [epidural anesthesia for trial of labor], and 9c [general anesthesia versus epidural or spinal anesthesia for cesarean delivery].
Combined probability tests were applied to continuous data, and an odds-ratio procedure was applied to dichotomous study results. Two combined probability tests were employed as follows:(1) The Fisher Combined Test, producing chi-square values based on logarithmic transformations of the reported p-values from the independent studies, and (2) the Stouffer Combined Test, providing weighted representation of the studies by weighting each of the standard normal deviates by the size of the sample. An odds-ratio procedure based on the Mantel-Haenszel method for combining study results using 2 x 2 tables was used with outcome frequency information. An acceptable significance level was set at p < 0.01 (one-tailed) and effect size estimates were calculated. Interobserver agreement was established through assessment of interrater reliability testing. Tests for heterogeneity of the independent samples were conducted to ensure consistency among the study results. To control for potential publishing bias, a “fail-safe N” value was calculated for each combined probability test. No search for unpublished studies was conducted, and no reliability tests for locating research results were done.
Meta-analytic results are reported in Table 4. To be considered acceptable evidence, both the Fisher and weighted Stouffer combined test results must agree. Significant combined test values were found for:(1) analgesic efficacy - linkages 6a (epidural versus parenteral techniques for labor) and 6c (epidural local anesthetics with opioids versus equal dosages of local anesthetics without opioids);(2) duration of analgesia - linkage 6c (epidural local anesthetics with versus without opioids), and (3) incision-to-delivery time - linkage 9c (general anesthesia versus epidural or spinal anesthesia for cesarean delivery). Weighted effect size values for these linkages ranged from r = 0.13 to r = 0.41, representing small-to-moderate effect size estimates.
To be considered acceptable evidence, combined test results must agree with Mantel-Haenszel odds-ratios when both types of data are assessed. Odds ratios were significant for the following outcomes:(1) analgesic efficacy - linkage 6c (epidural local anesthetics with opioids versus equal dosages of local anesthetics without opioids);(2) mode of delivery - linkage 6a (epidural versus parenteral techniques for labor);(3) motor block; linkage 6c (epidural local anesthetics with opioids versus equal dosages of local anesthetics without opioids), 6d (epidural local anesthetics with opioids versus higher concentrations of local anesthetics without opioids), and 6e (epidural infusion of local anesthetic concentrations of less than 0.125% versus concentrations equal to 0.125%);(4) pruritus - linkage 6c (epidural local anesthetics with opioids versus equal dosages of local anesthetics without opioids), 6d (epidural local anesthetics with opioids versus higher concentrations of local anesthetics without opioids) and 6h (combined spinal-epidural techniques versus epidural local anesthetics for labor);(5) nausea - 6h (combined spinal-epidural techniques versus epidural local anesthetics for labor;(6) Apgar scores at 1-minute - linkage 6a (epidural versus parenteral techniques for labor), and linkage 9c (general anesthesia versus epidural or spinal anesthesia for cesarean delivery), and (7) Apgar scores at 5-minutes - linkage 9c (general anesthesia versus epidural or spinal anesthesia for cesarean delivery).
For the findings noted above, tests for heterogeneity of statistical tests and effect size were nonsignificant for the following outcomes and linkages:(1) analgesic efficacy - linkage 6c;(2) mode of delivery - linkage 6a;(3) motor block - linkages 6c, 6d, and 6e;(4) pruritus - linkages 6c and 6d;(5) nausea - linkage 6h;(6) Apgar scores at 1-minute - linkage 6a; and (7) Apgar scores at 5-minutes - linkage 9c. These findings indicate that the pooled studies provided common estimates of significance and population effect sizes.
For the findings noted above, tests for heterogeneity of statistical tests were significant for the following outcomes and linkages:(1) analgesic efficacy - linkage 6a;(2) Apgar scores at 1-minute - linkage 9c;(3) Apgar scores at 5-minutes - linkage 9c, and (4) incision-to-delivery time - linkage 9c. Tests for heterogeneity of effect size were significant for the following outcomes and linkages:
(1) analgesic efficacy - linkage 6a;(2) duration of analgesia - linkage 6c;(3) pruritus - linkage 6h;(3) Apgar scores at 1-minute - linkage 9c; and (4) incision-to-delivery time - linkage 9c. For analgesic efficacy, the heterogeneous findings for linkage 6a may reflect the differential influence of the various statistical tests combined with a small number of studies used in the analysis. For pruritus, variability in the reported odds ratios may reflect the varying use of opioids in the epidural local anesthetic groups, in contrast with consistent opioid use in the CSE groups, and further analysis may need to control for opioid use in both groups. For incision-to-delivery times and Apgar scores at 1-minute, variability in statistical tests and effect sizes may be the result of nonrandomized comparisons in these meta-analyses. Due to the small number of studies included in these meta-analyses, examination of the analyses for moderator variables could not be conducted.
Agreement among Task Force members and two methodologists was established by interrater reliability testing. Agreement levels using a Kappa statistic for two-rater agreement pairs were as follows:(1) type of study design, k = 0.79 to 0.83;(2) type of analysis, k = 0.57 to 0.73;(3) evidence linkage assignment, k = 0.65 to 0.93; and (4) literature inclusion for database, k = 0.54 to 1.00. Three-rater chance-corrected agreement values were:(1) design, Sav = 0.80, Var (Sav)= 0.004;(2) analysis, Sav = 0.64, Var (Sav)= 0.008;(3) linkage identification, Sav = 0.76, Var (Sav)= 0.004;(4) literature database inclusion, Sav = 0.65, Var (Sav)= 0.040. These values represent moderate to high levels of agreement.
The findings of the literature analyses were supplemented by the opinions of Task Force members as well as by surveys of the opinions of a panel of Consultants as described in the text of the Guidelines. The rate of return was 78%(N = 114/147). The percentage of Consultants supporting each linkage is reported in Table 5. Consultants were supportive (i.e., they agreed that the specified linkage improved analgesia, reduced the risk of adverse outcomes or improved maternal satisfaction) of the following linkages: linkage 1 (history and physical exam), linkage 4 (recording of fetal heart rate), linkage 6c/d (epidural local anesthetics with versus without opioids), linkage 6l (monitored/stand-by anesthesia care), linkage 7 (regional anesthesia for retained placenta), linkage 8 (nitroglycerin for retained placenta), linkage 9a (spinal anesthesia for cesarean delivery), linkage 9b (epidural anesthesia for cesarean delivery), linkage 10b (spinal anesthesia for PPTL), linkage 10c (epidural anesthesia for PPTL), linkage 11 (immediate postpartum tubal ligation), linkage 12 (availability of hemorrhagic resources), and linkage 13 (availability of airway resources). Consultants were not supportive of linkage 9c (general anesthesia for cesarean delivery), linkage 10a (local anesthesia for PPTL), 10d (general anesthesia for PPTL), and linkage 14 (invasive hemodynamic monitoring). Consultants believed that all of the linkages were important issues for the Guidelines to address.
Seventy-six percent of the responding Consultants indicated that fasting times for solids should be determined either on a case-by-case basis or by institutional protocol. Fifty-five percent reported a safe fasting time (for solids) for uncomplicated vaginal delivery of no less than 8 hours. Seventy-six percent indicated a safe fasting time (for solids) for elective cesarean delivery of no less than 8 hours.
The Consultants were asked to indicate which, if any, of the evidence linkages would change their clinical practices if the Guidelines were instituted. The rate of return was 59%(N = 86/147). The percent of responding Consultants expecting no change associated with each linkage were as follows: history and physical exam - 98%; routine platelet count - 96%; blood type and screen - 96%; fetal heart rate recording - 98%; oral intake of liquids - 92%; oral intake of solids - 95%; epidural local anesthetics for labor - 100%; epidural infusion for labor - 100%, spinal opioids for labor - 98%, CSE for labor - 98%, cervical dilation - 98%, monitored/stand-by anesthesia care - 100%, retained placenta analgesia - 99%, nitroglycerin for retained placenta - 94%, cesarean anesthetic choices - 100%, tubal ligation - 96%, hemorrhagic emergencies - 99%, airway emergencies - 96%, hemodynamic monitoring - 99%, and CPR - 99%. Ninety-eight percent of the respondents indicated that the Guidelines would have no effect on the amount of time spent on a typical case. [dagger][dagger][dagger]
## No meta-analytic differences in the likelihood of spontaneous delivery were found when studies using morphine or meperidine were added to studies using only fentanyl or sufentanil.
*** References to bupivacaine are included for illustrative purposes only, and because bupivacaine is the most extensively studied local anesthetic for CIE. The Task Force recognizes that other local anesthetic agents are equally appropriate for CIE.
[dagger][dagger][dagger] Readers with special interest in the statistical analyses used in establishing these Guidelines can receive further information by writing to the American Society of Anesthesiologists: 520 North Northwest Highway, Park Ridge, Illinois 60068-2573.
