Anesthesia for cesarean deliveryAuthorGilbert J Grant, MDSection EditorDavid L Hepner, MDDeputy EditorMarianna Crowley, MDDisclosures:Gilbert J Grant, MDNothing to disclose.David L Hepner, MDNothing to disclose.Marianna Crowley, MDEmployee of UpToDate, Inc.Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence.Conflict of interest policyAll topics are updated as new evidence becomes available and ourpeer review processis complete.Literature review current through:Feb 2015.|This topic last updated:Nov 21, 2014.INTRODUCTIONWhile regional anesthesia or general anesthesia are both acceptable for cesarean delivery [1], the use of general anesthesia has fallen dramatically in the past few decades and is now used in less than 5 percent of cesarean deliveries in the United States and United Kingdom [2].This topic reviews anesthetic issues specific to the planning and management of anesthesia for cesarean delivery. Management of anesthesia in pregnant patients and airway management of pregnant patients are discussed separately. (See"Management of the pregnant patient undergoing nonobstetric surgery"and"Airway management of the pregnant patient at delivery".)PLANNING THE ANESTHETIC APPROACHThe anesthetic plan for cesarean delivery must take into account the wellbeing of two patients: the mother and the fetus.Preanesthetic evaluationPlanning for anesthesia in pregnant patients must consider the physiologic changes of pregnancy and the status of the fetus. (See"Management of the pregnant patient undergoing nonobstetric surgery", section on 'Physiological changes related to pregnancy'.)The preanesthetic evaluation is similar to that for other preoperative patients, with a focus on assessment of the airway, lower back, and coexisting maternal medical conditions. It is reasonable to schedule a preadmission consultation with an anesthesiologist for patients at risk of complications during labor and delivery and those with procedure-related risks, even if they are not planning an anesthetic (table 1).Challenges and complications related to anesthesia are more common in obese parturients and include difficulty with monitoring, positioning, airway management, and neuraxial techniques [3]. Therefore, antepartum anesthesiology consultation is recommended. Scheduling the consultation in the early to mid third trimester is prudent in case of preterm delivery. (See"Preanesthesia medical evaluation of the obese patient"and"Anesthesia for the obese patient".)Laboratory testing is discussed separately. (See"Cesarean delivery: Preoperative issues", section on 'Laboratory testing'.)Rationale for neuraxial anesthesiaNeuraxial anesthesia is the most common anesthetic technique, used for over 95 percent of planned cesarean deliveries in the United States [4]. The preference for neuraxial techniques in most cases is based on a desire to avoid general anesthesia for delivery, because of:Perception that general anesthesia is less safe than neuraxial anesthesiaPassage of anesthetic drugs from the mother to the fetusDesire of parturients to remember the birth experienceIn patients with specific medical issues, such as predicted difficult airway or (rarely) malignant hyperthermia susceptibility, there are additional reasons to avoid general anesthesia. (See"Airway management of the pregnant patient at delivery", section on 'Management of the difficult airway'and"Susceptibility to malignant hyperthermia: Evaluation and management".)Although neuraxial anesthesia techniques are perceived to be safer for the mother than general anesthesia, the magnitude of benefit is unclear. The risk of anesthesia-related maternal mortality is extremely low in the United States. It is reported higher with general anesthesia than regional anesthesia (from 1991 to 2002: 6.5 versus 3.8 per million [5]); however, observational data may not fully account for confounders, such as greater use of general anesthesia in emergent and medically complicated cases. Anesthesiologists are using neuraxial techniques for urgent and emergent cesarean deliveries more often than in the past, and this has been associated with an increase in reports of regional anesthesia-related death, although overall anesthetic-related maternal mortality is decreasing.General anesthesia-associated maternal morbidities include airway-related complications (eg, aspiration of stomach contents, failed intubation). The consequences of airway problems may be severe, but the incidence is low (see"Airway management of the pregnant patient at delivery", section on 'Incidence and consequences of airway problems'). In addition, general anesthesia has been associated with a greater degree of maternal blood loss than neuraxial anesthesia in both a systematic review of randomized trials and a retrospective review of over 67,000 cesarean deliveries [1,6].Although passage of anesthetic drugs to the fetus may result in transient neonatal depression, in a 2012 Cochrane review of randomized trials of regional versus general anesthesia for cesarean for any indication, both approaches had similar neonatal outcomes (low Apgar scores, need for resuscitation) [1]. There is no strong evidence of long-term adverse effects on the child. (See'Neonatal effects'below.)Indications for general anesthesiaGeneral anesthesia is indicated for cesarean delivery if there is a contraindication to neuraxial anesthesia (eg, coagulopathy, profound maternal hypovolemia, and certain maternal medical conditions), urgency for the procedure due to fetal status, and patient refusal of neuraxial anesthesia.Factors that may lead the anesthesiologist to elect general anesthesia:Coagulopathy is a contraindication to neuraxial anesthesia, due to the risk of spinal epidural hematoma. Management of patients with coagulation abnormalities, and those on anti-thrombotic medication, is discussed separately. (See"Adverse effects of neuraxial analgesia and anesthesia for obstetrics", section on 'Neuraxial analgesia and low platelets'and"Neuraxial (spinal, epidural) anesthesia in the patient receiving anticoagulant or antiplatelet medication".)In patients with hypovolemia (eg, from acute hemorrhage) and certain cardiac pathologies (eg, aortic stenosis), neuraxial anesthesia and its accompanying sympathetic block and vasodilation may lead to severe maternal hypotension. While this can often be managed with fluid and vasopressors, or can be mitigated by slow dosing of an epidural, in extreme cases general anesthesia may be a more prudent choice. (See"Adverse effects of neuraxial analgesia and anesthesia for obstetrics"and'Fluid and hemodynamic management'below.)Urgent attainment of surgical anesthesia may be of critical importance to the wellbeing of the fetusand/ormother. The decision to use general rather than neuraxial anesthesia in an emergent situation should be made in conjunction with the obstetrical team.

Although most anesthesiologists agree that general anesthesia is the most reliable means of rapidly achieving operative anesthesia for cesarean, spinal anesthesia can often be achieved quickly and is increasingly being used in all but the most emergent situations. Spinal anesthesia has a more rapid onset of sensory and motor blockade than epidural anesthesia; however, if a functioning epidural catheter is in place (eg, for labor analgesia), it should be dosed with a rapid-acting local anesthetic. (See'Choosing a neuraxial technique'below.)Skin infection of the lower back, at the location of needle insertion, is a contraindication to placement of neuraxial anesthesia.Patient refusal of neuraxial anesthesia is most often due to fear of the needle and of backache (although unsubstantiated)and/orto worry about witnessing the operation [7,8].Planning postcesarean analgesiaA single dose of preservative-freemorphineorhydromorphoneadministered into the neuraxis may provide up to 24 hours of analgesia for patients receiving spinal or epidural anesthesia for cesarean delivery. An advantage of administering opioids via the neuraxial route is that they provide good pain control with minimal transfer of sedating medication in breast milk to the newborn. The most common side-effects of neuraxial opioids are pruritus, nausea, and vomiting. Respiratory depression is unlikely to occur in the postpartum period [9].To minimize the incidence of side effects, a spinalmorphinedose of 0.05 to 0.2 mg or an epidural morphine dose of 3 mg or less may be used. A dose of 100 mcg intrathecal morphine results in equivalent analgesia to 400 mcg, over 24 hours, with less pruritus [10,11]. The pain relief produced by 1.5 mg epidural morphine has been shown to be noninferior to 3 mg epidural morphine, with fewer side effects [12]. Neuraxialhydromorphoneis less hydrophilic than morphine, leading to a faster onset and a shorter duration of action [13]. In the Section Editors practice, an intrathecal dose of 50 to 100 mcg or an epidural dose of 1 mg of hydromorphone are utilized for post cesarean delivery analgesia. In hospitals where arrangements are in place to manage postpartum epidural catheters, patient-controlled epidural analgesia with opioid, dilute local anesthetic, andepinephrinemay be used to provide pain relief while minimizing unwanted side effects [14].Other options for treatment of postcesarean pain include patient-controlled IV opioid analgesia and oraland/orparenteral opioids. Multimodal analgesia allows for good pain relief with a reduction in opioid-related side effects; this should incorporate a nonsteroidal antiinflammatory drug (NSAID) (eg,ketorolac[30 mg IV every six hours], oribuprofenPO [600 mg four times a day or 800 mg three times a day],and/oracetaminophen1 gm IV or PO every six hours). (See"Cesarean delivery: Postoperative issues", section on 'Postoperative care'.).PATIENT PREPARATIONPreoperative fastingWe agree with the American College of Obstetricians and Gynecologists (ACOG) and the American Society of Anesthesiologists (ASA) recommendation that patients abstain from solid food for at least six hours prior to elective cesarean delivery (eight hours for fried or fatty foods) [15,16]. Clear liquids, which have a more rapid gastric transit time, may be ingested until two hours prior to surgery. The unpredictability of unplanned cesarean delivery makes it prudent that laboring women avoid solid food and restrict their oral intake to clear liquids.Reduction of gastric acidityIt is the acidity of gastric aspirate that makes it particularly injurious to the lungs (see"Aspiration pneumonia in adults", section on 'Pathophysiology'). When the risk of aspiration is felt to be high, drugs may be given to decrease the acidity and thus mitigate the pulmonary effects, although there is no high-quality evidence that any specific intervention improves clinical outcome [17]. We use the following regimen:Scheduled cesarean delivery under general anesthesia (not in labor) Intravenous (IV) histamine 2-receptor antagonist (H2 blocker) is administered at least 60 minutes prior to induction of anesthesia.H2 blockers (eg,ranitidine50 mg IV) require 40 to 60 minutes to decrease secretion of gastric acid and are sustained for eight hours, providing prophylaxis against aspiration pneumonitis upon extubation. In a 2014 Cochrane Review, H2 antagonists were associated with a reduced risk of intragastric pH 3.0 for approximately 30 minutes [20]. It has an unpleasant sour taste (that may itself lead to nausea [21]) and does not prevent continued acid production.Metoclopramide(10 mg IV, slowly) may shorten transit time and increase lower esophageal sphincter tone, and thus is sometimes used to decrease the risk of regurgitation. Some studies show a decrease in gastric volume when metoclopramide is administered preoperatively to various patient populations [22-25]. However, many anesthesiologists do not use it due to significant adverse reactions (eg, tardive dyskinesia, extrapyramidal symptoms) and lack of evidence of efficacy.Due to the low incidence of aspiration, and the difficulty in performing trials in pregnant women, these recommendations are based primarily on observational studies, physiology, and expert opinion. Although gastric emptying is not affected by pregnancy, and the risk of aspiration on induction of general anesthesia for cesarean is low (approximately 15 per 10,000 [26,27]), most experts still feel that these precautions are prudent.These precautions are not necessary prior to neuraxial anesthesia, as the risk of aspiration is minimal in conscious patients; however, patients with frequent reflux may obtain symptomatic relief from nonparticulate antacid, and administration of an IV H2 blocker and an oral nonparticulate antacid may be considered in patients considered at high risk of conversion to general anesthesia.Antibiotic prophylaxisTo reduce the risk of postoperative infection, a single IV dose of antibiotic should be administered preoperatively 60 minutes prior to skin incision, to all women undergoing cesarean delivery. (See"Cesarean delivery: Preoperative issues", section on 'Antibiotic prophylaxis'.)MANAGEMENT OF ANESTHESIAPhysiological changes related to pregnancy occur in virtually all organ systems and impact the management of anesthesia; these are discussed separately. (See"Management of the pregnant patient undergoing nonobstetric surgery", section on 'Physiological changes related to pregnancy'.)The parturient should be positioned supine with a 15 percent left lateral tilt to reduce aortocaval compression and cardiovascular compromise. Alternatively, a wedge may be placed under her right hip. (See"Cesarean delivery: Preoperative issues", section on 'Uterine displacement'.)Neuraxial anesthesiaNeuraxial anesthesia for cesarean delivery differs from analgesia for labor and vaginal delivery in two major ways:A more intense sensory and motor block is achieved by administering a higher concentration of local anesthetic. A more intense sensory block is needed because the nociceptive stimulus of surgery is more intense than the pain of labor; motor block is desirable to obtain abdominal muscle relaxation.The dermatomal block level required for cesarean delivery is higher than that required for labor analgesia. For cesarean delivery the anesthetic level must extend to at least the fourth thoracic dermatome to prevent nociceptive input from the peritoneal manipulation, whereas a sensory block to the 10th thoracic dermatome is sufficient for labor analgesia.Techniques, medications, and complications associated with neuraxial anesthesia are discussed separately. (See"Neuraxial analgesia and anesthesia for labor and delivery: Options"and"Neuraxial analgesia and anesthesia for labor and delivery: Drugs"and"Adverse effects of neuraxial analgesia and anesthesia for obstetrics".)In healthy women with a reassuring fetal heart rate pattern, supplemental oxygen is not necessary [28]. Recommendations for women with obstructive sleep apnea are reviewed separately. (See"Intraoperative management of adults with obstructive sleep apnea".)Choosing a neuraxial techniqueCesarean delivery may be performed under epidural, spinal, or combined spinal-epidural (CSE) anesthesia. It is also possible to use continuous spinal anesthesia, which may be technically easier in select patient populations (eg, morbidly obese patients), but is an infrequent choice due to the significant risk of a postdural puncture headache. Spinal anesthesia is the quickest to place and has the most rapid onset; it is the most common type of anesthesia used for cesarean delivery. Epidural anesthesia is used when an epidural catheter (eg, for labor analgesia) has previously been placed, when there is an indication to establish the block slowly, or when surgery is anticipated to be prolonged. CSE is preferred by some practitioners as it combines the qualities of spinal anesthesia with the capability to prolong the block as needed.In obese patients, neuraxial anesthesia can be challenging due to difficulty in palpating landmarks and the patient's inability to assume an optimal position. Also, the catheter may become dislodged when the patient changes position [29]. Although neuraxial techniques are more likely to fail in obese compared to non-obese parturients, regional anesthetic techniques are usually safe and successful [30]. (See"Anesthesia for the obese patient".)Spinalanesthesia is relatively easy to perform, as it involves a distinct endpoint: namely, the emergence of cerebrospinal fluid from the hub of the spinal needle. Spinal anesthesia takes effect more quickly than epidural anesthesia; however, there is no ability to increase the duration of anesthesia when surgery is unexpectedly prolonged. Spinal anesthesia is indicated in situations where there is an urgency to deliver the fetus quickly and there is no epidural catheter in place.Epiduralanesthesia is slightly more time consuming to initiate and has a slower onset of action compared with spinal anesthesia, but has the advantage of being redosed to extend the duration of anesthesia, if needed. The slower onset may be of benefit in patients with relative hypovolemia or valvular disease (eg, aortic stenosis), as the clinician may more easily maintain an adequate blood pressure with fluidsand/orvasopressors during the onset of the sympathectomy.

Labor epidurals may be converted for operative anesthesia by injecting more concentrated local anesthetic; adequate anesthesia is achieved within a few minutes in almost all patients (97 percent) [31]. This usually requires less time than replacing the existing epidural with a spinal anesthetic; however, in some cases the redosed epidural results in inadequate anesthetic level for surgery. In a meta-analysis, risk factors for failed conversion of labor epidurals to operative anesthesia included an increasing number of clinician-administered boluses during labor, greater urgency for cesarean delivery, and a non-obstetric anesthesiologist providing care [32]. In urgent situations, with a marginally functioning catheter, the anesthesiologist may prefer to place a spinal rather than attempt the conversion. The dose of local anesthetic required for cesarean, for both spinal and epidural anesthesia, is lower in patients with prior neuraxial labor analgesia.CSEis a technique that combines the quick onset and reliability of spinal anesthesia with the ability to redose through the epidural catheter. Because it takes slightly longer to place than a standard spinal anesthetic, it is not typically used in situations where delivery is very urgent.A CSE technique may be preferable to a spinal technique in obese parturients to accommodate unexpectedly prolonged surgeries. Although single-shot spinal is generally faster to perform than CSE, this may not be the case in obese parturients, possibly because the epidural needle functions as an introducer for the less-rigid spinal needle along its relatively long course to the dura [33].Continuous spinal anesthesiais performed by introducing a catheter into the intrathecal space; this facilitates controlled anesthesia for as long as necessary. However, it is an infrequent choice due to the significant risk of a postdural puncture headache. Continuous spinal anesthesia is advantageous for cesarean delivery when epidural anesthesia is problematic, but neuraxial block is desirable. This includes technical difficulty with epidural placement (eg, morbid obesity), and anticipated inadequate epidural block due to poor distribution of local anesthetic (eg, patients with previous spinal surgery causing scarring in the epidural space). Continuous spinal may be preferable to single-shot spinal when slow onset of the sympathetic block is physiologically indicated (eg, cardiac disease) [34].DosingThe choice of local anesthetic for spinal or epidural anesthesia is based on the speed of onset, the quality of the block (density), and, for a spinal, the duration of action. If a patient has a partial (patchy) block from prior labor analgesia, or a failed attempt at a spinal or epidural block for cesarean (in which local anesthetic was injected but a satisfactory level was not achieved), the dose of anesthetic for a subsequent attempt at spinal or epidural anesthesia should be decreased to avoid ahigh/totalspinal. The safest approach is to perform a CSE with 25 to 50 percent of the usual dose of local anesthetic given intrathecally or an epidural anesthetic. The epidural catheter is then utilized to bring up the anesthetic level slowly.Spinal Onset of spinal anesthesia is similar for different local anesthetics, but duration differs (table 2);bupivacaineis most commonly used. Small doses of intrathecalfentanyl(eg, 15 mcg) may be used to prolong the duration of spinal anesthesia for cesarean [35].Epidural Two percentLidocainewithepinephrineis the most common anesthetic for cesarean.Sodium bicarbonatemay be added to speed its onset of action. For urgent cases, 3% 2-chloroprocaine with bicarbonate has the quickest onset. When bicarbonate is added to 2% lidocaine, the onset time for surgical anesthesia decreased from 9.7+/-1.6minutes to 5.2+/-1.5 minutes in one study [36], making it close to the onset of 2-chloroprocaine, but with a longer duration of action. Alternatives are 0.5%Bupivacaine, or 0.5%ropivacaine, but the onset is slower than with lidocaine [37]. The risk of cardiac toxicity has limited the popularity of bupivacaine; 0.5% ropivacaine may be less cardiotoxic. Specific doses and duration are presented in a table (table 3).Addingfentanylto local anesthetics may result in a significantly faster onset of the block [37]. When epidural fentanyl andmorphineare both given, the onset of analgesia from the morphine coincides with the offset of the fentanyl, resulting in good analgesia for 18 to 24 hours.CSE For CSE, options include either a standard spinal dose (eg,bupivacaine10 to 15 mg) or a lower dose, with the intent of dosing the epidural catheter to achieve an adequate block level. The epidural catheter should be aspirated and tested (eg, 3 mLlidocaine1.5% with 1:200,000epinephrine) prior to administration of epidural local anesthetics.Continuous spinal A reasonable choice for continuous spinal anesthesia is hyperbaric 0.75%bupivacaineadministered incrementally, starting with 3.75 mg. Isobaric 0.5% bupivacaine administered incrementally (starting with 5 mg and followed by 2 mg boluses as needed) is less often used.Fentanyl15 mcg orsufentanil5 mcg may be added.A detailed description of neuraxial anesthetic techniques, side effects, and complications can be found separately. (See"Neuraxial analgesia and anesthesia for labor and delivery: Options"and"Adverse effects of neuraxial analgesia and anesthesia for obstetrics"and"Neuraxial analgesia and anesthesia for labor and delivery: Drugs".)Inadequate blockAfter placement of the neuraxial anesthetic, the parturient is positioned supine, with left uterine displacement while awaiting development of an adequate block. If there is a sense of urgency, the skin is prepared for surgery, and surgical drapes placed while awaiting development of the block. If the leveland/orintensity of anesthetic block are insufficient to commence surgery, the options are:Wait. Generally the level of block to temperature sensation indicates the final sensory level. The level of a hyperbaricbupivacainespinal may be extended cephalad a few dermatomes by tilting the bed head-down, but this should be done with extreme caution, as this maneuver may cause an excessively high level.Inject additional local anesthetic. An epidural catheter may be redosed, or, if it is judged to have failed, a spinal may be placed. Performing a new epidural anesthetic is also a possibility, but the risk of cumulative local anesthetic causing systemic toxicity should be considered. If time is not an issue, a one- to two-hour delay would allow the local anesthetic in the initial epidural to be metabolized. A spinal placed in a patient with a partial neuraxial block should have a reduced dose to avoid an excessively high spinal block level. In patients with a partial (patchy) epidural, or with an inadequate spinal block, we decrease the dose of a subsequent spinal by approximately 50 percent, and are reticent to perform spinal anesthesia in this circumstance if the patient has an obvious difficult airway. In this situation, it is preferable to perform a CSE with a markedly reduced spinal dose (eg, 75 percent reduction of standard dose) and then use the epidural to increase the cephalad level of the block, if needed.Convert to general anesthesia.The decision on the best way to deal with an inadequate block must consider clinical urgency and individual risks, and should also include a discussion with the obstetrician. If the interval from the sterile prep and drape of the abdomen to surgical incision is prolonged while waiting for an adequate anesthetic level, the fetal heart rate can be assessed with an external monitor placed in sterile sleeve.High levels of blockHigh thoracic levels of spinal or epidural blockade often lead to a subjective feeling of dyspnea. For most patients, reassurance that this is a normal sensation is sufficient. Assessing hand grip is a quick way to determine if the block involves the cervical roots. When a patient complains of difficulty breathing, adequacy of spontaneous ventilation and ability to protect the airway must be assessed; general anesthesia should be induced if they are compromised. (See'Induction'below.)HypotensionDense neuraxial blockade includes sympathetic block. Hypotension may be avoided with the use of IV fluidsand/orvasopressors. (See'Fluid and hemodynamic management'below.)Anxiety and painSome women may develop anxiety during cesarean delivery. This is first treated with verbal reassurance and then, if necessary, an anxiolytic such asmidazolam. Some patients prefer to avoid midazolam prior to delivery, as its amnestic properties may inhibit memory of the moment of birth.Pain may occur during cesarean delivery under neuraxial block, if the level of block is inadequate. If an epidural catheter is in place, additional anesthetic should be administered, ideally, 3% 2-chloroprocaine with bicarbonate or 2%lidocainewithepinephrineand bicarbonate. The obstetrician should be asked to cease operating, if possible, until the anesthetic takes effect. In the interim, small doses ofpropofol; opioids such asfentanylorremifentanil;midazolam; orketaminemay be used. A reasonable approach is midazolam (2 mg) followed by ketamine (10 mg starting dose titrated with incremental 10 mg doses to response), as it is unlikely to lead to respiratory depression. One must exercise extreme caution when administering these agents to parturients, as full stomach considerations apply. If deep levels of sedation are required, it is prudent to induce general endotracheal anesthesia with a rapid sequence induction to protect the airway.Nausea and vomitingNausea is a common complaint during cesarean delivery. It is often related to hypotension from the sympathetic block, in which case restoring the blood pressure (withphenylephrineorephedrine) should reverse the symptoms. It can also be caused by an insufficient block level, which can be treated by administering additional local anesthetic if an epidural catheter is in place. Uterine manipulation may also cause nausea and vomiting, especially if it is exteriorized, with its attendant peritoneal traction; this often resolves when the uterus is replaced. Nausea and vomiting is common after spinalmorphineadministration, but less likely following neuraxial administration of lipophilic opioids (eg,fentanyl,sufentanil). In one study, 31 percent of patients had both nausea and vomiting one hour after administration of only 60 mcg of spinal morphine [38].Nausea and vomiting as a result of neuraxial opioids may be treated withnaloxonein 40 to 100 mcg IV boluses, titrated every few minutes until the symptoms abate. If large doses of naloxone are needed, reversal of analgesia may occur, although this would be more problematic postoperatively, after the neuraxial local anesthetic block has dissipated. A mixed opioid agonist-antagonist, such asnalbuphine4 mg, may be used to avoid the problem of analgesia reversal, but this may cause sedation. An antiemetic such asondansetron4 mg may be indicated if a cause of nausea other than hypotension or inadequate block level is suspected.In a systematic review of randomized trials of interventions for preventing nausea and vomiting in women with neuraxial aesthesia for cesarean delivery, three interventions were effective: 5-HT3 antagonists (eg,ondansetron),dopamineantagonists (eg,metoclopramide), and small doses of sedatives (eg,propofol1mg/kg/hour)[39]. In another systematic review, prophylacticdexamethasoneled to decreased nausea and vomiting from spinalmorphine[40].PruritusNeuraxial opioids lead to pruritus in 60 to 100 percent ofpregnant/post-partumwomen [41]. This may resolve with small doses of intravenous opioid agonist-antagonists (eg,butorphanol1 mg, followed by 0.2mg/h[42]), or antagonists (eg,naloxone0.25 to 1mcg/kg/hrinfusion) [41].General anesthesiaWhether general anesthesia is planned, or induced emergently due to failed neuraxial anesthesia, the considerations and management are the same. The goal is to maintain hemodynamic and respiratory homeostasis for both parturient and fetus, and minimize time between induction and delivery. The patient is positioned and her abdomen prepared for surgery as she is preoxygenated. Immediately following induction and confirmation of a secure airway with end tidal carbon dioxide, the incision is made and delivery accomplished as efficiently as possible.InductionInduction of general anesthesia for cesarean delivery routinely involves thorough preoxygenation, rapid sequence induction with cricoid pressure, and endotracheal intubation; the basic sequence is the following:Preoxygenation with 100 percent oxygen is administered by tight-fitting face mask for three to five minutes. If there is insufficient time for this, the patient should take eight vital capacity breaths over 60 seconds. (See"Airway management of the pregnant patient at delivery", section on 'Preoxygenation'.)Preoxygenation is particularly important in obese pregnant women because they are more prone to severe hypoxemia and rapid desaturation after induction of general anesthesia. Time to 90 percent desaturation may be reduced to just 98 seconds in term parturients with very high body mass index (BMI, 50kg/m2or higher) compared to 292 seconds in non-obese pregnant women [43]. Preoxygenation may be more effective in the sitting or partial head-up position [44,45]. Rapid sequence induction is performed, immediately followed by endotracheal intubation. Typically, cricoid pressure is applied, and mask ventilation is avoided. However, some experts advocate avoiding cricoid pressure, or performing gentle bag-mask ventilation with peak airway pressures below 15 cm H2O [46,47]. (See"Airway management of the pregnant patient at delivery", section on 'Intubation'.)

The most common induction agents arepropofol(2 to 3mg/kg)andsuccinylcholine(1 to 1.5mg/kg),but alternatives includeetomidate(0.2 to 0.3mg/kg),ketamine(1 to 2mg/kg),and nondepolarizing neuromuscular blockers, depending on the clinical situation. (See"Management of the pregnant patient undergoing nonobstetric surgery", section on 'Induction'.)Proper placement of the endotracheal tube should be confirmed prior to incision.Airway managementManagement of the airway in pregnant women and management of the difficult airway are discussed in detail separately. (See"Management of the pregnant patient undergoing nonobstetric surgery", section on 'Induction of anesthesia'and"Airway management of the pregnant patient at delivery".)MaintenanceAnesthesia is usually maintained with inhalation agents (eg,sevoflurane,isoflurane), with or withoutnitrous oxide(N2O). A reasonable approach is to administer nitrous oxide (50 percent) and an inhalation anesthetic (eg, isoflurane, sevoflurane 0.5 minimum alveolar concentration [MAC]) until delivery. Nitrous oxide is often not used if there are fetal concerns, in which case higher concentrations of inhalation agents are necessary. After delivery, nitrous oxide may be increased to 70 percent and opioids are given, which may permit the inhalation agent to be decreased, as high concentrations can cause uterine atony.The optimal agent(s) and concentration(s) have not been determined. Considerations include:Adequate depth of anesthesia to prevent awareness with recall. MAC forisofluraneis decreased in pregnancy by about 30 percent [48-50]. Some experts advocate increasing N2O, especially when decreasing inhalation agent concentration after delivery, but the effects on awareness and recall are unclear [51,52]. (See'Awareness with recall'below.)Minimization of medication that transfers to the fetus prior to delivery. Opioids are often given after delivery. Opioids may be administered if needed prior to delivery, asnaloxonecan be used to reverse opioid effects in the neonate. It is important that pediatricians attending the birth are informed about medications the mother has received. Use ofpropofolfor maintenance is usually limited to patients with a medical reason to avoid inhalation anesthetics. Propofol does cross the placenta [53], but there is no evidence of neonatal effects when used for induction, and in small trials comparing propofol infusion to inhalation anesthetics for maintenance there were no differences in neonatal assessments [54,55]. However, in one series of 10 cesarean deliveries with propofol andremifentanilfor maintenance, neonatal depression occurred in six, and brief assisted mask ventilation was required [56].Minimization of inhalation anesthetics, which cause dose-dependent reduction in uterine tone and may lead to bleeding [57]. Doses as low as 0.5 MAC cause decreased contractility in vitro and may reduce the contractile effects of oxytocin [58-60].Appropriate oxygen concentration. Many anesthesiologists administer 100 percent oxygen prior to delivery of the fetus, especially in cases of nonreassuring fetal heart rate tracing. Increasing oxygen concentration to the parturient leads to increased fetal and neonatal oxygenation [61].The abdominal muscle relaxation provided by inhalation agents may obviate the need to redose a neuromuscular blocker when the induction dose has worn off.Mechanical ventilation is adjusted to maintain the normal physiologic respiratory alkalosis of pregnancy, with an end-tidal carbon dioxide of about 30 mmHg. (See"Management of the pregnant patient undergoing nonobstetric surgery", section on 'Mechanical ventilation'.)EmergenceAt the end of surgery, the patient is awakened prior to extubation to ensure that airway reflexes are intact. Especially for obese patients, the head-up position is ideal to improve oxygenation and decrease work of breathing. (See"Airway management of the pregnant patient at delivery", section on 'Extubation'and"Anesthesia for the obese patient", section on 'Extubation'.)Awareness with recallHistorically, the incidence of recall of intraoperative awareness following cesarean delivery was as high as 26 percent [62], because low doses of anesthetics were used and current inhalation anesthetics were not yet available. With current techniques for general anesthesia for cesarean delivery, the risk of awareness with recall may be comparable to that of the general surgical patient [63], although some studies indicate increased risk [64].Midazolam(0.05 to 0.1mg/kg)may be used to minimize the risk of recall. (See"Awareness with recall following general anesthesia".)Fluid and hemodynamic managementInduction of both general and neuraxial anesthesia tends to reduce maternal blood pressure. Hypotension is usually transient at induction of general anesthesia, but of longer duration following placement of neuraxial anesthesia, as the neuraxial-induced sympathetic block causes vasodilation with pooling of blood in capacitance vessels. The onset of block is more rapid with spinal than epidural anesthesia; for this reason, significant hypotension occurs more commonly after spinal anesthesia than after epidural anesthesia.A practical strategy to minimize hypotension is to administer a rapid bolus of crystalloid at the time ofinduction/neuraxialplacement (co-load), possibly with a low-dosephenylephrineIV infusion. The benefit of prophylactic vasopressor infusion was shown in a 2014 systematic review in which administration of a prophylactic phenylephrine infusion to parturients having spinal anesthesia (with a fluid load) decreased the incidence of hypotension by about 60 percent before and after delivery (RR 0.36 and 0.37, respectively), as well as decreasing nausea and vomiting (RR 0.39); there were no differences in other maternal or fetal endpoints or outcomes [65]. There is no need to delay neuraxial placement to pre-load fluids, as co-loading fluids (either crystalloid or colloid) was as effective at minimizing hypotension as pre-loading colloid, and better than pre-loading crystalloid [66-68].Most anesthesiologists administer crystalloid rather than colloid solutions for cesarean delivery because they are less expensive and more readily available. Furthermore, the limited available data do not indicate an absolute benefit to colloids over crystalloids [67,69]. In fact, data in cardiac patients and critically ill non-obstetric patients show that resuscitation with hydroxyethyl colloids and albumin do not decrease mortality and are more likely to lead to renal injury [70-72].Glucose-free solutions should be used to prevent hyperinsulinemia in the fetus. Excessive placental glucose transfer can result in compensatory release of fetal insulin (fetal hyperinsulinemia) and neonatal hypoglycemia [73,74].Fetal oxygenation depends upon placental perfusion; thus, a decrease in maternal blood pressure can compromise fetal oxygenation, which can be manifested by changes in the fetal heart rate. (See"Nonstress test and contraction stress test", section on 'Cardiovascular response to hypoxemia'.)Vasopressor treatmentEitherphenylephrineorephedrineis an acceptable vasopressor in parturients [75-79]. Common doses for treatment of hypotension are ephedrine (5 to 10 mg IV boluses) and phenylephrine (50 to 100 mcg IV bolus, or 25 to 100mcg/minIV infusion), though rates of phenylephrine 75 to 100mcg/mintend to lead to more maternal hypertension [80]. A study demonstrated that prophylactic phenylephrine infusion following spinal anesthesia was associated with less nausea and vomiting and decreased need for physician intervention compared to phenylephrine bolus [81].The choice of therapy has often been guided by maternal heart rate.Phenylephrinemay be preferred when the maternal heart rate is relatively fast, since it tends to slow the heart rate. Conversely, in women with a low heart rate,ephedrinemay be preferable, as phenylephrine is more likely to produce maternal bradycardia [82]. Phenylephrine may also be preferable when the fetal heart rate has not been normal. In a systematic review of vasopressors for the management of hypotension after spinal anesthesia for elective cesarean delivery, ephedrine was associated with an increase in true fetal acidosis (pH