Practice Guidelines for Obstetrical
Anesthesia
A Report by the American Society of Anesthesiologists
Developed by the Task Force on Obstetrical Anesthesia
Joy L. Hawkins, M.D. (Chair)
Denver, Colorado |
Patricia A. Dailey, M.D.
Hillsborough, California |
James F. Arens, M.D.
Galveston, Texas |
Larry C. Gilstrap, M.D.
Houston, Texas |
Brenda A. Bucklin, M.D.
Omaha, Nebraska |
Stephen C. Grice, M.D.
Alpharetta, Georgia |
Robert A. Caplan, M.D.
Seattle, Washington |
Nancy E. Oriol, M.D.
Boston, Masachusetts |
David H. Chestnut, M.D.
Birmingham, Alabama |
Kathryn J. Zuspan, M.D.
Edina, Minnesota |
Richard T. Connis, Ph.D.
Woodinville, Washington |
|
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Introduction
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).
Purposes of the Guidelines
The purposes of these Guidelines are to enhance the quality
of anesthesia care for obstetric patients, reduce the incidence
and severity of anesthesiarelated complications, and increase
patient satisfaction.
Focus of the Guidelines
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).
Application of the Guidelines
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.
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 fivestep 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.
Availability and Strength of Evidence
Evidencebased 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 metaanalysis.
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 insufficient 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
anesthesiarelated 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 pregnancyinduced
hypertension. However, the literature is insufficient to assess
the predictive value of a platelet count for anesthesiarelated
complications in either uncomplicated parturients or those with
pregnancyinduced 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 anesthesiarelated
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 & 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 anesthesiarelated
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.,
morbidly obese, diabetic, difficult airway), or patients at increased
risk for operative delivery (e.g., non reassuring fetal heart
rate pattern) may have further restrictions of oral intake, determined
on a casebycase 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 prior to elective
cesarean delivery.
Recommendations:
Solid foods should be avoided in laboring patients. The patient
undergoing elective cesarean delivery should have a fasting period
for solids consistent with the hospital's policy for non-obstetric
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. The addition of opioids to epidural local anesthetics.
The literature supports that the use of epidural local anesthetics
with opioids, when compared with equal concentrations of
epidural local anesthetics without opioids, provides 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 an algesic 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, an 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.,
advanced labor).
Recommendations:
Spinal opioids with or without local anesthetics may be used
to provide effective, though 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.
There 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 anesthesia 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 inductiontodelivery
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.
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 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 post-delivery 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).
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 pregnancyrelated 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 routinely
use central invasive hemodynamic monitoring for severe preeclamptic
parturients.
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
References:
1. Guidelines for Perinatal Care, 4th Edition. American
Academy of Pediatrics and American College of Obstetricians and
Gynecologists, 1997, p 100-102.
2. Position on monitored anesthesia care. In ASA
Standards, Guidelines and Statements; American Society of Anesthesiologists
Publication: 20-21, October, 1997
3. Guidelines for cardiopulmonary resuscitation
and emergency cardiac care: Recommendations of the 1992 national
conference. JAMA 268(16):2249, 1992.
Table 1. Suggested Resources for Obstetric Hemorrhagic Emergencies*
- Large bore IV catheters.
- Fluid warmer.
- Forced air body warmer.
- Availability of blood bank resources.
- Equipment for infusing IV fluids and/or blood products rapidly.
Examples include (but are not limited to) hand squeezed fluid
chambers, hand inflated pressure bags, and automatic infusion
devices.
* IMPORTANT:
The items listed in this table represent suggestions. The items
should be customized to meet the specific needs, preferences,
and skills of the practitioner and health-care facility.
Table 2. Suggested Resources for Airway Management During
Initial Provision of Regional Anesthesia*
- Laryngoscope and assorted blades.
- Endotracheal tubes, with stylets.
- Oxygen source.
- Suction source with tubing and catheters.
- Self inflating bag and mask for positive pressure ventilation.
- Medications for blood pressure support, muscle relaxation,
and hypnosis.
* IMPORTANT:
The items listed in this table represent suggestions. The items
should be customized to meet the specific needs, preferences,
and skills of the practitioner and health-care facility.
Table 3. Suggested Contents of a Portable Unit
for Difficult Airway Management for Cesarean Section Rooms1,2
- Rigid laryngoscope blades and handles of alternate design
and size from those routinely used.3
- Endotracheal tubes of assorted size.
- Laryngeal mask airways of assorted sizes
- At least one device suitable for emergency nonsurgical airway
ventilation. Examples include (but are not limited to), retrograde
intubation equipment, a hollow jet ventilation stylet or cricothyrotomy
kit with or without a transtracheal jet ventilator, and the
esophageal-tracheal combitube.
- Endotracheal tube guides. Examples include (but are not limited
to) semirigid stylets with or without a hollow core for jet
ventilation, light wands, and forceps designed to manipulate
the distal portion of the endotracheal tube.
- Equipment suitable for emergency surgical airway access.
- Topical anesthetics and vasoconstrictors.
1 IMPORTANT:
The items listed in this table represent suggestions. The items
should be customized to meet the specific needs, preferences,
and skills of the practitioner and health-care facility.
2 Adapted from "Practice Guidelines for Management
of the Difficult Airway: A Report by the American Society of Anesthesiologists
Task Force on Management of the Difficult Airway. Anesthesiology
78:597-602, 1993."
3 The Task Force believes fiberoptic
intubation equipment should be readily available.
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) improves
maternal analgesia, but (b) increases maternal, fetal &
neonatal anesthetic complications.
6d. Epidural local anesthetics with opioids versus higher
concentrations of epidural local anesthetics without opioids:
(a) improves maternal analgesia, and (b) reduces 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, and (b) reduces maternal,
fetal & neonatal obstetric complications, and (c) improves
maternal satisfaction.
6l. Monitored/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 human 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 nonoverlapping 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 assure 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), linkage10a
(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-six percent
reported a safe fasting time (for solids) for uncomplicated vaginal
delivery of no less than 8 hours. Seventy-seven 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 56% (N = 83/147).
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
- 91%; 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
95%, cesarean anesthetic choices 100%, tubal ligation
96%, hemorrhagic emergencies 99%, airway emergencies
98%, 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.
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.
* No 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.
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