What the Anesthesiologist Should Know before the Operative Procedure
Whether a neuraxial technique is the appropriate anesthetic choice for cesarean delivery will depend on the urgency of the procedure based on fetal or maternal issues, the presence of any significant maternal comorbidities or instability, and on occasion, whether a functioning labor epidural is already in place. When a cesarean delivery is elective, a neuraxial technique is preferred in the US and other developed countries by a wide margin.
The advantages of a neuraxial technique are avoidance of airway manipulation in a population with a 10-fold greater incidence of a difficult airway, less blood loss, an awake mother who can enjoy the birth of her child, and less fetal exposure to anesthetic agents.
Anesthesia-related maternal mortality from a neuraxial technique is a fraction of that with a general anesthetic by current data.
1. What is the urgency of the surgery?
The cesarean rate in the United States is 33% and climbing. Although many are electively performed for a variety of reasons, a significant percentage are urgently or emergently performed. Reasons vary greatly from a failure to progress in labor or failed induction, in which the fetus and mother are stable and movement back to the OR is controlled, to a placental abruption or terminal bradycardia that requires a rapid response.
What is the risk of delay in order to obtain additional preoperative information?
The ASA and American College of Obstetricians and Gynecologists (ACOG) issued a joint statement that non-elective cesarean delivery should be started within 30 minutes of being requested by the operating obstetrician. A newer version of this statement has been tempered recognizing that there is a difference in urgency levels that must be individualized, and rate of movement back to the OR should be dictated by resources, current activity, and preoperative diagnosis. Following adequate assessment of the situation, movement back should proceed as expeditiously as possible without compromising maternal or fetal safety. The 30 minute goal should be kept in mind but not doggedly adhered to under all conditions. Communication with the operating obstetrician is vital.
Emergent: If the mother is unstable because of bleeding, an embolus, or other life-threatening emergency, or the fetus has a category 3 tracing or other life-threatening event, the surgery should proceed as quickly as possible and certainly more quickly than 30 minutes.
Urgent: For non-emergent, non-elective procedures, teams should move as expeditiously as possible without compromising maternal or fetal safety and with 30 minutes as the goal. However, if more preparation time is necessary and the obstetrician is in agreement, taking extra time can be reasonable.
Elective: ACOG issued a statement in 2010 that no elective cesarean surgery should be performed before 39 weeks gestation without a clear medical or obstetrical indication. This was due to a significantly higher incidence of inadequate lung maturity in the newborn if delivered electively before 39 weeks.
2. Preoperative evaluation
Most patients for cesarean delivery have a benign medical history and require no more than what is recommended by the ASA Task Force for Obstetric Anesthesia in its published guidelines. Further evaluation should be dictated by history and exam.
i)A complete airway exam just prior to surgery is absolute. Obstetric patients have a ten-fold greater incidence of a difficult airway, especially for those coming to surgery after a failed or prolonged labor. The impact of labor, especially with use of the Valsalva maneuver during the second stage, can change a Mallampati (MP) 1 airway to a MP IV by the time surgery is called because of fluid shifts.
ii) Commonly ignored, the ASA task Force also recommends heart and lung exams on all patients, including parturients. A quick assessment of the spine can be made at the same time.
Despite some concerns, there is no evidence that the obstetric patient cannot make an informed decision while experiencing labor pain or coping with an urgent or emergency situation. Every parturient should go through the informed consent process unless the situation presents an immediate threat to the life of the mother or fetus. If the process is waived, documentation explaining why should be added to the record as soon as possible.
A large gauge IV such as an 18- or 16-gauge without a small bore tubing extension, such as the “pigtail,” is needed to allow for rapid fluid or blood administration, even in elective cases.
(1) Preloading with fluid prior to the initiation of neuraxial anesthesia is common but not obligatory. Rapid co-loading with crystalloid at the time of neuraxial placement is as effective as pre-loading. Although significant hypotension following a spinal anesthetic is a common complication, not all parturients suffer this and who will not is not predictable. Also, pre-hydration may abate the degree of hypotension but it has not been shown to prevent it. Regardless, this is readily corrected with more fluids and vasopressors, of which ephedrine, phenylephrine or a combination of both are preferred.
Unstable conditions warranting further evaluation may be categorized under obstetric or medical headings. In a true emergency, time may not allow further evaluation, but less acute situations may offer a brief window of opportunity. For units caring for high-risk parturients, a High-Risk Obstetric Anesthesia Consult service can be invaluable. Such services allow for patient evaluation prior to labor and a multidisciplinary plan developed that can be accessed by whoever is on the obstetric anesthesia service the day the patient arrives for delivery.
Obstetric-based conditions: Any hypertensive disorder of pregnancy, abnormal placental implantation, or subacute placental abruption are examples.
Medically unstable conditions: Uncorrected or uncompensated congenital cardiac defects or other cardiovascular diseases, evolving neurologic conditions, coagulopathies, evolving sepsis, abrupt changes in pulmonary, renal or hepatic function are medical examples.
Delaying surgery may be indicated if time is needed for completion of an on-going work-up for a maternal condition before electively proceeding and the fetus is stable. This should be for no more than a few days. Another acceptable albeit short-term delay is if the patient, who recently ate, has ruptured membranes but is not in labor and is scheduled to have an elective section. Time can be taken to allow for gastric emptying via time and pharmacologic means. However, the vast majority of non-elective cesarean deliveries cannot tolerate a lengthy delay and speed of movement to the OR should be decided on a case-by-case basis as dictated by maternal and fetal conditions, resources, and a conversation with the obstetrician.
3. What are the implications of co-existing disease on perioperative care?
This is not a discussion of the normal physiologic changes of pregnancy but of some of the more frequently encountered pre-existing diseases overlying normal pregnancy-induced changes. These conditions are identified during antenatal care, and patients are risk-stratified to appropriate facilities for management where members of the obstetric anesthesia department should be made aware and asked to consult on the patient antenatally as part of a multispeciality cohort.
b. Cardiovascular system:
Cardiac disease, either directly or indirectly, is a major contributor to maternal mortality and morbidity.
I. Congenital Heart Disease: The number of parturients with congenital heart disease has exploded because of palliative or definitive repairs undergone as children, but not all repairs tolerate the functional changes of pregnancy. A NYHA class 1 patient pre-pregnancy can decompensate to a class 3 or 4 during pregnancy, demonstrating that corrected and functioning anatomy in the non-pregnant state is not normal anatomy.
Neuraxial techniques can work well, even for severe defects, but knowledge of the original defect, any and all palliative or corrective procedures, pre-pregnant function, current studies and medications, and current status is vital to forming a plan.
The patient’s cardiologist should be consulted if the patient is not doing well or the lesion is complex.
II. Coronary artery disease or cardiac dysfunction – Parturients with significant cardiac disease are seen more frequently seen today in part because women are choosing to start their families at an older age and may be developing chronic cardiovascular conditions. The changes of pregnancy place a large demand on the heart, so any history suggestive of a significant change in functional status beyond that expected from pregnancy should be evaluated. Myocardial infarction, especially during pregnancy, or loss of left ventricular function is associated with high maternal mortality so a complete cardiac work-up is obligatory, as is a cardiac consultation.
III. Hypertensive Disease of Pregnancy: Although a full discussion is beyond the scope of this chapter, this entity is one of the leading causes of maternal morbidity and mortality. The degree of severity should be assessed by exam and laboratory results, and obstetric management choices (use of antihypertensives) and results should be noted. With very severe disease resulting in a significant thrombocytopenia or a complication such as hepatic rupture, neuraxial techniques may not be an option.
Perioperative risk reduction strategies
I. Any patient who achieves a term gestation without signs of decompensation does not need extra monitoring and is a good candidate for neuraxial anesthesia.
II. For those with a history of cardiac compromise or an event during pregnancy, more invasive monitoring such as an arterial line is warranted but central monitoring has not been found to be useful in guiding management. Some of the newer monitors that can report cardiac parameters off the arterial line trace may be helpful but have not been documented to be accurate in awake patients breathing spontaneously, as occurs in cesarean sections. Transthoracic echocardiography is a new technology that is gaining interest as a means to evaluate function.
III. Management goals are dictated by which cardiac condition is present. Primary concerns should include maintenance of fetoplacental perfusion as well as maternal coronary perfusion. Thus, avoidance of a rapid sympathectomy may be prudent, and an epidural technique or sequential CSE may be a better choice over a spinal.
IV. If magnesium sulfate is to be administered to prevent eclampsia, the bolus should not be given during the placement of a neuraxial technique. It should occur before or after. Notably, current preeclampsia recommendations state that magnesium sulphate should continue through the cesarean delivery if initiated prior to surgery.
Pregnant patients are prone to pulmonary edema because 1) hypoalbuminemia of pregnancy allows for leakage into the alveolar space, and 2) sensitivity of the endothelium to endotoxins can compromise the lining. A respiratory infection can induce pre-term labor (which may lead to a cesarean delivery) and medications to stop labor can induce pulmonary edema. Thus, patients should be evaluated prior to surgery and managed conservatively.
Other lung infections
URI, TB, influenza, pneumonia can all lead to significant maternal morbidity and exposure. Thus, the posted precautions should be observed to avoid spread.
Reactive airway disease (asthma)
Perioperative evaluation: Asthma follows a variable course during pregnancy but usually becomes less severe in the final 4 weeks of gestation. It is unusual that asthma or significant wheezing becomes an issue during cesarean delivery, but bronchodilators should be used if indicated. Although use of a neuraxial technique avoids the airway, airway function should be maximized prior to surgery.
Perioperative risk reduction strategies
These patients are most often already stabilized on their anti-asthma regimen prior to elective cesarean delivery and that should be continued. Even in a non-elective situation a neuraxial technique will allow for airway avoidance.
Chronic disease states are uncommon but associated with hypertension, preeclampsia, pre-term labor and fetal demise. Abnormal function may be due to an underlying disorder such as systemic lupus erythematosus.
A creatinine level at or above 1.0 mg/dL in a “normal” pregnancy should provoke a work-up as it indicates renal compromise. Any new finding of renal disease or change in a chronic renal state should be known by the obstetrician, aggressively evaluated and medically managed prior to presentation for delivery.
Review labs, especially the coagulation profile if the disease is associated with a coagulopathy.
Perioperative risk reduction
Avoid nephrotoxic antibiotics intraoperatively and NSAIDs for postoperative analgesia.
Gastric emptying is not delayed with pregnancy but does delay if labor is present and/or the patient is receiving opioids. Gestational esophageal reflux disease is very common.
Check NPO status. Current ASA intake guidelines hold for non-laboring patients having elective surgery.
2 hours for clear liquids.
6-8 hours for solids with the range dependent on the estimated fatty content of the meal.
For non-elective cases, a full stomach is likely so aspiration prophylaxis is usually administered before surgery.
Perioperative risk reduction
A Cochrane review of current evidence of the effectiveness of various agents noted 1) the available studies are of poor quality, and 2) current evidence supports the combination of H2 receptor antagonists and antacids as being more effective than either one alone or nothing at all. Proton pump inhibitors were not effective, and neither was metoclopramide, although that agent is commonly recommended.
Best support is for a H2 antagonist 30 minutes before and a non-particulate antacid closer to the procedure, if possible.
Acute fatty liver of pregnancy may occur in the third trimester and requires delivery as soon as possible, often in the form of a cesarean delivery.
Potentially fatal, acute hepatic failure is due to fatty infiltration of hepatocytes. The differential includes HELLP and preeclampsia. A thorough evaluation and review of the appropriate lab studies for dehydration (from N/V), renal and hepatic dysfunction and coagulopathy (DIC, thrombocytopenia) is a must as a neuraxial technique may prove contraindicated.
Perioperative risk reduction strategies
Take a little time to stabilize the patient before proceeding to surgery. The fetal status will usually allow for this, but this is a steadily deteriorating course so time is limited. If there are no signs of a coagulopathy, then a neuraxial technique can be used but typically this is not the case.
The most commonly encountered neurologic entities are radiating neuropathies from musculoskeletal changes of the lumbar spine, histories of seizures or migraines, and multiple sclerosis (MS). Serious chronic or evolving neurologic conditions should indicate that the patient is referred to a Level III obstetric practice if at all possible. Involvement of a neurologist knowledgeable in the changes of pregnancy and neurologic disease can greatly aid in management decisions.
New onset, evolving, or unstable neurologic changes are a contraindication to neuraxial anesthesia. Head trauma may also be a contraindication as epidural anesthesia can temporarily increase ICP, and spinal anesthesia can precipitate herniation of the brain stem if ICP is increased.
Most chronic situations are stable and some improve with pregnancy like migraine headaches. Diseases such as multiple sclerosis do not relapse because of anesthetic choice and are no longer contraindicated for neuraxial anesthesia (see below).
Careful history to document stability of the condition and neurologic exam documenting any sensorimotor changes. For radicular pain due to a lumbar neuropathy, document what position, if any, aggravates the condition and try to avoid that position during surgery.
Perioperative risk reduction strategies
For radicular pain, position in such a way as to not aggravate the neuropathy, if possible. Uterine displacement must be maintained until after delivery.
Pregnancy appears to have a protective effect on MS. Relapses are rare during pregnancy. Document current stability and note any current neurologic deficits. If there are any new or evolving neurologic changes, neuraxial technique should be abandoned.
Perioperative risk reduction strategies
Neither spinal nor epidural have been shown to be detrimental or provoke a relapse in a patient who is stable or in remission, although many feel better avoiding a spinal technique.
Anatomic variations include Chiari malformations, tethered cords, spina bifida and spinal diastematomyelias. Although successful neuraxial techniques have been described with some of these conditions, most practitioners prefer to avoid this approach and opt for a general technique instead.
Pregnancy produces an insulin-resistant state that exhibits an exaggerated response to a carbohydrate load. Gestational diabetes is common and usually controlled with diet, exercise and insulin if necessary. Whether with significant disease pre-pregnancy or gestational, patients are usually reasonably controlled before surgery. Diabetic ketoacidosis is a medical emergency that usually does not require delivery of the fetus.
Check the blood glucose level, evaluate for insulin use and most recent dose. To prevent neonatal hypoglycemia at delivery, a pre-delivery maternal glucose level of about 100 mg/dL is recommended.
Perioperative risk reduction strategy
Insulin requirements drop off quickly and dramatically after delivery. For those on an insulin infusion, discuss with the obstetrician whether the infusion should be stopped with delivery. Check glucose levels as soon as possible in recovery or intraoperatively if the procedure is prolonged.
Denying neuraxial anesthesia to patients with counts under 100,000 is not valid (refer to lab section for more information). Platelet function is as important as the count. Gestational thrombocytopenia occurs in 5% to 7% of pregnancies and platelets have normal function. Another less common condition but may be first diagnosed in pregnancy is immune (idiopathic) thrombocytopenic purpura (ITP). Thrombocytopenia is also associated with preeclampsia or HELLP.
Perioperative evaluation: Determine the diagnosis and whether platelet function is maintained. Thorough history for unusual bleeding (gingivitis causing gum bleeding with brushing is common in pregnancy). Check current platelet count and trends. Bleeding times are not considered a valid test.
Perioperative risk reduction strategies: Avoid neuraxial technique if platelet function is abnormal. Most are comfortable proceeding with a count of >70,000, and a growing number are comfortable with counts of 50,000 or above in the presence of normal function.
Most factor levels increase with pregnancy. Exceptions are XIII (decreases) and II & V (stable). (Factor XI is often described as decreasing but current evidence is that it likely is stable.) Von Willebrand’s disease (vWD) is the most commonly diagnosed inherited disorder but only type 1 has normal factor.
Perioperative evaluation: The diagnosis and factor levels are known by delivery time, often allowing for a neuraxial technique. Significant vWD type 1 can receive DDAVP (0.3 mcg/kg over 20-30 minutes) before proceeding and depending on the sub-type of type 2, replenishing with factor VIII or vWF concentrates is necessary. Same strategy for type 3. For surgery, the focus is on adequate factor VIII levels. Successful use of neuraxial techniques are routine for vWD type 1 managed this way and there are reports of neuraxial success with type 2 sub-sets.
Perioperative risk reduction strategies: For an elective cesarean delivery in a patient without an epidural, most prefer a spinal to reduce trauma (of which there is no evidence to support) and avoid catheter placement. The life of the factors is long enough that removal of an epidural catheter at the end of the surgery should not pose a risk.
Thrombogenesis is enhanced in pregnancy. Patients are generally already diagnosed with a thrombophilic disorder pre-pregnancy and removed from teratogenic medications (warfarin) to low molecular weight heparin (LMWH). If controlled on aspirin, this may be maintained until delivery.
Perioperative evaluation: Determine the diagnosis and last doses. Use of aspirin at 81 mg-325 mg/day is not a contraindication to neuraxial use. If on heparin for any length of time, check platelet levels (heparin-induced thrombocytopenia). Follow ASRA guidelines for placement timing for neuraxial management.
Perioperative risk reduction strategies: Follow current ASRA guidelines if an epidural catheter is in use.
g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)
4. What are the patient's medications and how should they be managed in the perioperative period?
The vast majority of parturients are on pre-natal vitamins and folic acid. Even herbal supplements are usually stopped if used prior to pregnancy, although it is prudent to ask about their use. Obstetricians will usually discover what the patient is taking at the first antenatal visit and remove any herbals and potentially teratogenic medications.
h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
Most medications the patient is on preoperatively should be continued with the exception of anticoagulant medications.
i. What should be recommended with regard to continuation of medications taken chronically?
Antiplatelet: Low dose aspirin may be used during pregnancy to treat some conditions. It does not preclude the use of a neuraxial technique when taken on the day of surgery, although some obstetricians are stopping it prior to anticipated delivery.
Anticoagulants: Listed below are the only three drug classes seen in pregnancy. Management should follow current ASRA guidelines.
Heparin: Heparin is used to “bridge” the patient from another anticoagulant, such as a LMWH, to the postpartum period, so the time on it may be a few weeks. Timing for safe neuraxial placement depends on whether the patient is on prophylactic dosing or therapeutic dosing, and should follow ASRA guidelines. A PTT can be checked to assure adequate time off the heparin before neuraxial use.
LMWH: Patients are usually switched to heparin a couple weeks before surgery. However, they are often told that if they think they are going into labor, they should not take their next dose and come to their institution. Currently, patients on prophylactic doses can safely receive a neuraxial technique 10-12 hours after the last dose. Those on therapeutic doses must wait 24 hours.
Anti-Thrombin: Fondaparinox is the only drug used. The timing of withholding until neuraxial blockade can be safely administered has not been defined in the United States. European countries vary from 3-7 days, where used. Most in the United States suggest a waiting period of 3-5 days since the last dose but there is no hard evidence as to the ideal waiting period.
j. How to modify care for patients with known allergies
Whether or not a pregnant patient should undergo allergy testing is not clear. Many avoid it because of fears of an anaphylactic reaction leading to fetal compromise and maternal morbidity.
Obviously, all medications producing an allergic reaction should be avoided. On occasion, a parturient will complain of an opioid allergy or sensitivity that makes the use of any opioid unreasonable. Although intraoperative use of opioids can be avoided fairly easily, postoperative pain management is another issue. Such patients may benefit from a transversus abdominus plane (TAP) block and NSAIDs or acetaminophen. This should be discussed before the surgery if possible. The use of clonidine is another possibility.
k. Latex allergy – If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.
All neuraxial anesthesia kits used in the United States are latex-free. Many pharmacies now prepare and place anesthetic medications in latex-free syringes. If there is any question about the latex content of an item, that should be fully investigated and disclosed or replaced prior to an urgent situation where the need to know is now crucial.
l. Does the patient have any antibiotic allergies ? Common antibiotic allergies and alternative antibiotics
The current antibiotic protocol calls for 2-3 grams of cefazolin, based on BMI. If beta-lactam allergic, patients should get 600mg clindamycin administered over 10-20 minutes AND 1.5 mg/kg gentamicin administered over an hour.
m. Does the patient have a history of allergy to anesthesia?
Malignant hyperthermia (MH)
Documented: Neuraxial anesthesia techniques are ideal for a MH history:
Ensure MH cart available and protocol adheres to current therapy standards. These can be found at www.mhaus.org, the Malignant Hyperthermia National website.
Whether or not a pregnant patient should undergo allergy testing is not clear. Many avoid it because of fears of an anaphylactic reaction leading to fetal compromise and maternal morbidity.
Ester Class: If a patient claims a local anesthetic allergy, it is likely to this class as these metabolize to PABA – a known allergen.
Amide Class: Exceedingly rare but not unheard of, this needs clarification prior to delivery, ideally. If the patient is truly allergic, meperidine as the sole intrathecal agent has been used with good success.
Has local anesthetic properties
Must be preservative-free
5. What laboratory tests should be obtained and has everything been reviewed?
The ASA Task Force on Obstetric Anesthesia holds that there is no evidence that any particular test such as a platelet count or hematocrit is necessary for a healthy parturient undergoing a routine cesarean. Equally unnecessary is having a full type and crossmatch completed prior to surgery, but having a completed type and screen or blood sample in the blood bank is reasonable.
If the patient’s history warrants a platelet count, what is the lower limit that contraindicates a neuraxial block? The “100,000-rule” has no scientific basis, and it is now felt that 70,000 is safe, even though there is no evidence for that belief either. Increasing numbers of anesthesia providers are comfortable performing a neuraxial block in the presence of a count below 100,000 in a patient without a bleeding history, and some hold as safe a low of 50,000 in parturients with evidence of platelet dysfunction.
There are no established bedside tests that can be used to evaluate platelet function. The bleeding time of old is not considered valid. Increasingly, the platelet function analyzer (PFA) and the thromboelastogram (TEG) are considered to provide accurate information.
Whatever lab tests are ordered should be dictated by the patient’s medical or obstetric history. If tests are ordered, they should be checked prior to going back for an elective case. If there is a concern for a coagulopathy and the urgency of the case does not allow for testing and waiting for the results, then a neuraxial technique should be avoided.
Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
As this section deals solely with the use of neuraxial techniques for cesarean delivery, no other option will be discussed here. It should be noted that neuraxial techniques are the preferred anesthetic for cesarean delivery in the United States, Canada and many other developed countries.
Sedation is often not provided during cesarean sections because of concerns over fetal exposure pre-delivery. However, large doses would have to be administered to register an effect in the newborn. The use of midazolam can impair maternal memory of the delivery, and this may be very distressing to the mother. Thus, the potential for amnesia should be discussed before midazolam or other sedatives are administered. However, there are no contraindications or fetal concerns to preclude use of these agents if deemed helpful.
This is the preferred technique by many for cesarean delivery for those without a labor epidural in place.
Rapid onset with faster time to incision, especially beneficial in urgent or emergent situations when a well-functioning epidural catheter is not present.
Easy to perform with an obvious end point of CSF return.
Less procedural discomfort than an epidural for the patient because of the more complete neural block.
Least absorption of medication into the maternal circulation so this has the least fetal exposure.
Time-limited, so be sure of surgical length.
Significant hypotension is common and can cause nausea, vomiting and a reduced uteroplacental circulation if not adequately treated
Postdural puncture headache (PDPH) can occur,
But rates are <1% due to improved technology in needle design
Rapid sympathectomy may not be tolerated in some cardiac conditions (e.g., stenotic or regurgitant valves)
Local anesthetic choice
This is the most commonly used.
Bupivacaine (0.75% or 0.5%): 7.5-15 mg
Lower doses may require more adjuvant medication support
10-12 mg is the most common dose with the broader range indicated above
Either hyperbaric or isobaric used, although many prefer hyperbaric
Ropivacaine is not approved for intrathecal dosing in the US
Lidocaine (5% or 2%): 60-75 mg
Greater transient neurologic symptoms (TNS) incidence over other local anesthetics makes this less desirable (see under Issues).
More limited duration than bupivacaine so surgical time is an issue
Opioids: Fentanyl (10-20 mcg) is most commonly used for intraoperative benefit, as it is too short-acting for postoperative pain management. Intraoperatively associated with more patient comfort. Also can prolong time to block regression. Sufentanil is more common for labor and not cesarean delivery and can cause a degree of sedation not seen with fentanyl. Preservative-free morphine at 100-200 mcg provides significant post-operative analgesia, and respiratory depression is exceptionally rare.
Common side effects are pruritus, nausea, and vomiting. Urinary retention is not an issue as patients have a catheter for 24 hours.
Epinephrine: Is used to prolong the duration of the anesthetic. The dose needed to provide this has not been established. It also improves the quality of the motor block
Lidocaine and Transient Neurologic Symptoms (TNS): Case reports suggest the use of hyperbaric lidocaine (5% usually) is associated with TNS. All local anesthetics have been reported to cause TNS but lidocaine does so at a relative risk of 7.3. Rates in pregnancy are reported as less than with the general population. Some institutions choose not to use it.
Management of Hypotension: A Cochrane review of the literature shows the following:
Preloading with crystalloid is common before spinals but co-loading with crystalloid is just as effective.
Colloids are more effective than crystalloids for the treatment of hypotension.
Prophylactic administration of ephedrine does not prevent hypotension, and neither does any other strategy.
Ephedrine and phenylephrine are equally effective pressors.
Continuous Spinals: The microcatheters may be gone for the moment but the technique is still used with current catheters. Usually this is due to an accidental dural puncture during an epidural placement and the epidural catheter is placed into the intrathecal space. New product designs may be available for ever more common use of this technique going forward.
Epidural – This is most commonly used when a labor epidural is in place and a cesarean delivery is needed. However, when tight hemodynamic control is important, this is the preferred technique.
Slower onset so less hemodynamic instability
Catheter allows for maintenance of anesthetic level despite length of surgery.
Allows for rapid conversion of a labor analgesic to a surgical anesthetic while moving to the operating area in emergent situations.
Less intense sensory block causes patients to complain about the sensation of “pulls and tugs”. This may lead to the use of more intravenous adjuvant medications to assist the patient through the surgery.
Less intense motor block than a spinal causing the surgeons to complain.
More fetal exposure as medication is absorbed from the maternal epidural space into her circulation and thus to the fetus. However, this tends to be clinically insignificant at commonly used doses.
Local Anesthetics: The volume given for cesarean delivery is 15-25 mL.
Bupivacaine (0.5%): slow onset and longest duration
0.75% is not available for epidural use, only spinal.
Lidocaine (2%, usually with epinephrine): intermediate in onset and duration. Speed of onset is improved significantly by adding sodium bicarbonate, 1 mL per 10 mL of lidocaine.
2-Chloroprocaine (3%): the only ester in common use fastest and least toxic if accidentally given intravascular. Shortest duration and is usually re-dosed by the clock, i.e. every 45 minutes.
Ropivacaine (0.75-1%): slow onset but less cardiotoxic than bupivacaine so available in a higher concentration
Opioids: The fentanyl dose is 50-100 mcg given preoperatively with the local anesthetic. This will not depress the fetus and should be given before delivery to improve the quality of the block. Preservative-free morphine is usually given for prolonged postoperative analgesia and the ED95 is 3.75 mg (usually 3-4 mg is given).
Epinephrine: Commonly used to reduce the absorption of local anesthetic from the epidural space and as a test dose to determine whether intravascular placement of the catheter has occurred (3 mL of 1:200,000). 15mcg should cause a tachycardia but is not thought to be reliable in a patient with pain. Also improves the motor quality of the block, but optimal dose for this use is unknown.
Sodium Bicarbonate: Used to speed the onset of action, primarily of lidocaine. Increases onset of lidocaine from 10 to 5 minutes.
Simultaneous administration of chloroprocaine and preservative-free morphine is generally avoided. Some indication that chloroprocaine interferes with the opioid action when given together, but the mechanism is unclear. Allowing the chloroprocaine time to absorb from the epidural space may improve the opioid effect but that may lead to a “window” of time between loss of sensory block from the chloroprocaine and onset of morphine for postoperative pain.
Choice of the best local anesthetic in the distressed fetus is often stated to be chloroprocaine. This is because early studies suggested there may be ion trapping of the amide local anesthetic, notably lidocaine, in an acidotic fetus leading to toxic levels. More recent studies suggest that carbonated lidocaine can convert a labor epidural to a surgical level almost as fast as chloroprocaine without signs of fetal effects. Use of lidocaine also removes concern over opioid effectiveness.
A slower onset of epidural blockade and sympathectomy can better preserve cardiac function if rapid preload or afterload reduction is a concern. The addition of sodium bicarbonate will speed the block onset and is associated with more hypotension.
Management of a failed conversion from a labor epidural to surgical anesthesia can force an intraoperative conversion to a general anesthetic. Multiple top-ups of an epidural during labor can predict a greater failure rate when converting to surgical anesthesia. Converting to a spinal anesthetic after dosing a poorly functioning labor epidural is associated with high spinal levels that may require airway management and pressor support. It is unknown how best to dose a spinal in this situation but one strategy is to consider a combined spinal-epidural technique with a lower initial spinal dose. Another strategy is to abandon the epidural all together and immediately proceed to spinal anesthesia. Under this scenario, high spinal complications have not been reported.
Combined Spinal-Epidural (CSE)
Combines the rapid onset of a spinal with the ability to dose an epidural catheter for long cases.
CSF in the spinal needle assures that the epidural needle is in the proper space, so the possibility of catheter failure is extremely small.
Less total drug is used than with an epidural alone.
Higher sensory levels are achieved than with single shot spinal if the epidural catheter is dosed soon after the dural puncture.
Longer time to place than a spinal so may not be an option in an emergent situation.
Postdural puncture headache can occur due to either needle, although the overall rate is lower with CSE and more on a par with an intrathecal injection.
The epidural catheter is untested going into the surgery
Possibly more hypotension can occur requiring more pressor use than with single shot spinal.
Adjuvant Medications: Are the same as noted above for each component (spinal and epidural)
Epidural volume expansion is the dosing of the epidural catheter soon after the intrathecal injection. The concept is that the injection of fluid into the epidural space will push the CSF upward leading to a higher spinal level. This has been demonstrated in studies showing a shorter time to maximal sensorimotor blockade, presumably from the epidural local anesthetic addition, and higher sensory level from the CSF displacement.
Sequential CSE: The concept is to administer a small spinal dose (5-7.5 mg bupivacaine with or without intended opioids) and then dose to T4 using the epidural catheter. This approach thus proves the placement of the epidural catheter before surgery begins but has also been shown to provide a more stable hemodynamic profile. This was shown to be an excellent technique for congenital cardiac conditions and stenotic valves. It could also prove useful in patients with a short stature such as achondroplastic dwarfism where determination of the proper intrathecal dose is difficult.
Contraindications for neuraxial techniques
Unstable hemodynamics (hemorrhage, hypovolemia)
Coagulopathies (DIC) or recent use of anticoagulants
Infection at the site
Evolving neurologic changes or increased ICP, excluding pseudotumor cerebri
Maternal refusal or inability to cooperate
Controversies/Issues: Although not absolutely contraindicated, the following conditions with disease examples should be reviewed for appropriateness on a case-by-case basis
Preexisting CNS disorders
Multiple Sclerosis: Although there is no indication that neuraxial techniques are harmful if the condition is stable, many are hesitant to inject intrathecally. Relapses are not associated with any type of anesthesia but may occur in the postpartum period due to other factors.
Preexisting peripheral neuropathy: The area of neuropathy should be documented and established that the condition is stable before proceeding.
Anatomic spinal variations (consultation with a neurosurgeon and review of earlier imaging are recommended prior to presentation to the labor floor)
Arnold-Chiari: Determine the type, dimensions and whether any previous surgery has occurred. Case reports have described successful neuraxial use but these cases should be approached cautiously.
Spina Bifida/Tethered Cord: Imaging studies are needed to determine whether or not a tethered cord is present. When present, the concern is for cord damage. Spina bifida occulta is the benign form found in about 20% of the population
Spinal diastematomyelias: These are spinal anomalies associated with split and tethered cords. Both injury and uneventful neuraxial placement have been described.
Previous corrective spinal surgery: A simple laminectomy generally leaves an epidural space in the nearby levels. However, in the case of more extensive surgery such as Harrington rods, a spinal approach for cesarean delivery is usually preferred over an epidural because extensive obliteration of the epidural space, scarring and lack of landmarks.
b. General anesthesia: Discussed in another section.
c. Monitored Anesthesia Care: Not an option
6. What is the author's preferred method of anesthesia technique and why?
What prophylactic antibiotics should be administered?
Recommendations are from the American College of Obstetricians and Gynecologists (ACOG) and are based on the SCIP protocols. 2012 recommendations are:
Choice: 2-3 grams of cefazolin intravenously. Dosing guidelines based on BMI are now 2 g for BMI below 100 kg, and 3 g for BMI of 120 kg or higher. The dose can be safely administered over 3-5 minutes.
If the patient is beta-lactam allergic, 600 mg of clindamycin and 1.5 mg/kg of gentamicin are the antibiotics of choice. Clindamycin should be administered over 10-20 minutes and gentamicin over 60 minutes.
Gentamicin dosing should be based on adjusted weight
Adjusted weight = IBW + 0.4(Actual BW – IBW)
Timing of administration: Administration before incision rather than after cord clamping is associated with a 50% decrease in endometritis but not necessarily wound site infection. All other factors are the same regardless of timing (maternal and neonatal outcomes)
ACOG recommends antibiotic administration completed within one hour pre-incision, whenever possible
In emergent situations, administer as soon as possible
What do I need to know about the surgical technique to optimize my anesthetic care?
Routine, elective sections with a Pfannenstiel incision should be completed within the time of a bupivacaine spinal
Consider a CSE or epidural for conditions that may increase the length of the procedure
History of multiple pelvic or abdominal procedures/infections
History of significant adhesions from a previous cesarean delivery
Surgical plans to extend the procedure (e.g., remove an ovarian cyst, hysterectomy for an accreta). Tubal ligations should not extend surgical time significantly
Concerns over an adherent placenta (placenta accreta).
Vertical incisions need a well-established level to at least T4 whereas pfannenstiel incisions may be tolerated at T6, especially if the uterus is not exteriorized.
What can I do intraoperatively to assist the surgeon and optimize patient care?
Speak with the surgeon ahead of time to see if there are any concerns regarding the procedure. These can be acknowledged during the Sign In portion of the surgical pause.
Stay involved with the patient – they are generally NOT sedated
If sedation is requested by the patient, warn of the potential for impaired memory of the delivery if midazolam is used. Most patients will tolerate the procedure well if you keep them engaged.
Warn the patient of impending sensations (e.g., pressure from the delivery of the neonate). This will help keep the room calm and controlled, especially in the urgent or emergent situation.
What are the most common intraoperative complications and how can they be avoided/treated?
Hypotension: As addressed in “Spinal” section
Fluid preloading and co-loading are both effective
Colloid may be more effective than crystalloid, although crystalloid is still most commonly used
Ephedrine and phenylephrine are equally effective
Maternal tachycardia can be an issue with ephedrine, bradycardia with phenylephrine
Some evidence supports the use of infusions to provide better hemodynamic stability over boluses but this has not become routine practice.
There are no methods that can predict or prevent hypotension, so always be prepared to treat. The goal is to maintain the mother’s blood pressure within about 15% of her baseline, recalling that hypotension is defined as a 20% decline from an elevated baseline (hypertension) or a systolic pressure below 100 mmHg.
Prophylactic injections of ephedrine have not been shown to be effective
High neuraxial level or total spinal
In most cases of a high level due to intrathecal or epidural dosing where the patient is breathing but speech may be impaired
Provide reassurance and mask oxygen administration while evaluating the level
If breathing assistance is needed, consider intubation to prevent hypoventilation or aspiration.
Most cases are self-limited and resolve with delivery.
For a “total” spinal or severely impaired breathing, be sure to induce before intubation.
Intraoperative patient discomfort:
Use of neuraxial opioids has been shown to improve the quality of the block and diminish complaints
If a patient has a poorly functioning labor epidural and is now to have surgery, consider NOT using the epidural but performing a spinal technique instead, if conditions allow.
Intravenous opioids are safe at usual doses (50-100mcg), even before the time of delivery. Studies have shown minimal impact on the neonate.
Low-dose propofol, ketamine and midazolam have all been used to good effect if the surgery is completing. If this level of supplementation is needed at the beginning of the case after incision, consider conversion to a general anesthetic.
Do not delay conversion to general anesthesia if needed. Pain during surgery is a cause of malpractice claims.
Nausea/Vomiting: There are multiple reasons for nausea intraoperatively including hypotension, bleeding, medications given during the procedure, especially uterotonics, vagal stimulation and uterine exteriorization. Identifying the cause can direct therapy but many will give prophylactic agents such as metoclopramide 10 mg and/or ondasetron 4 mg.
Pruritus: This is commonly attributed to opioid administration and activation of the mu receptor, although this is not proven. Although self-limited, it can be very distressing to the patient.
Treatment includes administration of an opioid antagonist, opioid agonist/antagonist such as nalbuphine, seratonin antagonist such as ondansetron, or subhypnotic dose of propofol. A 5 mg dose of intravenous nalbuphine is generally effective.
Use of the antihistamine Benedryl is generally not effective as there is no evidence that the pruritus is histamine-induced.
Shivering: This is likely of a multifactorial etiology. Meperidine 12.5 to 25 mg IV has been shown to be the most consistently effective agent.
Oxytocin side effects: Cesarean delivery is the only situation when oxytocin is given rapidly
Oxytocin is one of 12 drugs that bear a “heightened risk of harm” categorization per the Institute for Safe Medication Practices (ISMP)
Side effects from rapid infusion are:
Arrhythmias and other EKG changes
Shortness of breath
Myocardial ischemia and maternal death have been reported with bolus tecniques.
Dosage considerations are based on the following evidence:
An IV infusion administration of 0.3 IU is the ED 90 for a cesarean procedure without prior labor
An IV infusion administration of 3 IU is the ED 90 for a cesarean procedure where labor has preceded the procedure (oxytocin receptors are down-regulated).
Current recommendations for administration are NOT to bolus rapidly, but to deliver as an IV infusion. Consider moving to a second line uterotonic such as methergine, carboprost or misoprostol, if uterine tone is not adequate at reasonable doses, especially for patients with risk factors for postpartum hemorrhage.
Postoperative issues are generally limited to pain management or temporary sensory changes. They may also include a post-dural puncture headache (PDPH) from the intrathecal injection or accidental epidural puncture
Unique to procedure
Patients may complain of prolonged sensory blockade or patchy areas postoperatively but these are usually self-limiting and only require reassurance.
A PDPH usually occurs 24 to 48 hours after the event. It is positional (worse with the upright position) because of the intracranial hypotension produced by the loss of CSF through the puncture site. Symptoms may also include tinnitus, neck stiffness, diplopia, nausea and vomiting. Conservative management can be a potent oral analgesic (not an NSAID), bed rest and plenty of fluids but these tend not to be effective. The only approach is an epidural blood patch at or just below the puncture site.
b. If the patient is intubated, are there any special criteria for extubation?
b. Postoperative management
What analgesic modalities can I implement?
With neuraxial techniques, preservative-free intrathecal or epidural morphine is the standard of care for postoperative analgesia. Fentanyl suffices for immediate postoperative effect and can “bridge” the patient if morphine administration is held until the post-operative period.
For intrathecal morphine administration, 100 mcg provides the same quality of analgesia as 200 mcg with a lower side effect profile if supplemented with NSAIDs or IV PCA.
The ED95 of epidural morphine is 3.75 mg (4 mg is more convenient).
If no spinal component was used and the epidural block was not satisfactory, consider not giving epidural morphine and use an IV-PCA modality or a transversus abdominus plane (TAP) block instead.
Access to adequate analgesics may be limited if the patient is placed on an epidural morphine protocol when the epidural functioned poorly intraoperatively.
Patients with a history of substance abuse may benefit from a TAP block and supplemental analgesics as necessary rather than neuraxial opioids that limit administration of those other analgesics.
Adjuvant medications such as an NSAID (e.g., ketorolac) or acetaminophin are commonly ordered for incisional pain that may not be covered by the morphine.
What's the Evidence?
“American Society of Anesthesiologists Task Force on Obstetric Anesthesia. Practice Guidelines for Obstetric Anesthesia. An updated report by the American Society for Anesthesiologists Task Force on Obstetric Anesthesia. “. Anesthesiology. vol. 106. 2007. pp. 843-63. (These are the practice guidelines as written and agreed upon by a panel of experts on obstetric anesthesia. This is a comprehensive article covering all aspects care during the perioperative period as well as some emergency situations.)
INTRAOPERATIVE MANAGEMENT: NEURAXIAL ANESTHESIA AND IMPLICATIONS OF PREEXISTING DISEASE
Horlocker, TT, Wedel, DJ, Rowlingson, JC. “Regional anesthesia in the patient receiving antithrombotic and thrombolytic therapy. American Society of Regional Anesthesia and Pain Medicine Evidence-Based Guidelines (3rd Edition)”. Reg Anesth Pain Med.. vol. 35. 2010. pp. 64-101. This covers the contraindications for neuraxial anesthesia as well as the guidelines over when and whether to administer, and the timing of reestablishing coagulation after a neuraxial block.)
Paranjothy, S, Griffiths, JD, Broughton, HK. “Interventions at caesarean section for reducing the risk of aspiration pneumonitis”. Cochrane Database Syst Rev. 2010. pp. CD 004943Presents the current evidence for and against the effectiveness and use of various agents that are commonly used.)
AUTHOR'S PREFERRED METHOD
Cyna, AM, Andrew, M, Emmett, RS. “Techniques for preventing hypotension during spinal anaesthesia for caesarean section”. Cochrane Database Syst Rev. 2006. pp. CD002251(Presentation of current evidence on incidence and management of hypotension following spinal anesthesia.)
WHAT THE ANESTHESIOLOGIST SHOULD KNOW
Douglas, MJ, Halpern, SH, Douglas, MJ. “The use of neuraxial anesthesia in parturients with thrombocytopenia: what is an adequate platelet count?”. Evidence-based obstetric anesthesia. 2005. pp. 165-77. (Debunks the myth of the "100,000 platelet count" as the de facto limit for safe neuraxial administration. Presents a wealth of evidence-based information and recommendations supported by the evidence.)
“The incidence of transient radicular irritation after spinal anesthesia in obstetric patients”. Reg Anesth Pain Med . vol. 24. 1999. pp. 55-8. (A nice review of this local anesthetic complication following intrathecal administration.)
INTRAOPERATIVE MANAGEMENT, NEURAXIAL ANESTHESIA
Ginosaur, Y, Mirikatani, E, Drover, DR, Cohen, SE, Riley, ET. “ED50 and ED95 of intrathecal hyperbaric bupivacaine coadministered with opioids for cesarean delivery”. Anesthesiology. vol. 100. 2004. pp. 676-82. (Nice study determining the "best" dose of bupivacaine for intrathecal administration when combined with opioids; the most commonly used method in the U.S.)
WHAT THE ANESTHESIOLOGIST SHOULD KNOW
Camann, WR, Bader, AM. “Spinal anesthesia for cesarean delivery with meperidine as the sole agent”. Int J Obstet Anesth. vol. 1. 1992. pp. 156-8. (A discussion and case report of the use of intrathecal meperidine as the sole anesthetic agent for cesarean delivery.)
WHAT IS THE PREFERRED TECHNIQUE: POSTOPERATIVE MANGEMENT?
Palmer, CM, Nogami, WM, VanMaren, G, Alves, DM. “Postcesarean epidural morphine: a dose-response study”. Anesthesiology. vol. 90. 2000. pp. 887-91. (Covers the ED95 for intrathecal and epidural morphine dosing.)
WHAT IS THE PREFERRED TECHNIQUE? COMMON INTRAOPERATIVE SIDE EFFECTS
Tsen, LC, Balki, M. “Oxytocin protocols during cesarean delivery: time to acknowledge the risk/benefit ratio?”. Int J Obstet Anesth. vol. 19. 2010. pp. 243-5. (Excellent editorial attached to another study discussing the ED95 of oxytocin dosing. Reviews the side effects and dangers of oxytocin overdosing and suggests a more rational dosing regimen.)
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- What the Anesthesiologist Should Know before the Operative Procedure
- 1. What is the urgency of the surgery?
- What is the risk of delay in order to obtain additional preoperative information?
- 2. Preoperative evaluation
- 3. What are the implications of co-existing disease on perioperative care?
- b. Cardiovascular system:
- c. Pulmonary:
- d. Renal-GI:
- e. Neurologic:
- f. Endocrine:
- g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)
- 4. What are the patient's medications and how should they be managed in the perioperative period?
- h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
- i. What should be recommended with regard to continuation of medications taken chronically?
- j. How to modify care for patients with known allergies
- k. Latex allergy - If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.
- l. Does the patient have any antibiotic allergies ? Common antibiotic allergies and alternative antibiotics
- m. Does the patient have a history of allergy to anesthesia?
- 5. What laboratory tests should be obtained and has everything been reviewed?
- Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
- b. General anesthesia: Discussed in another section.
- c. Monitored Anesthesia Care: Not an option
- 6. What is the author's preferred method of anesthesia technique and why?
- What prophylactic antibiotics should be administered?
- What do I need to know about the surgical technique to optimize my anesthetic care?
- What can I do intraoperatively to assist the surgeon and optimize patient care?
- What are the most common intraoperative complications and how can they be avoided/treated?
- Postoperative issues
- a. Neurologic:
- b. If the patient is intubated, are there any special criteria for extubation?
- b. Postoperative management
- What's the Evidence?