The key elements defi ning adequate consent (also see Chapter 13) are:
explanation of the procedure
•
explanation of risks, benefi ts and alternative options
•
answering any questions the patient may have
•
Cesarean delivery represents an occasion of great signifi cance to the parents, but sometimes generates considerable psychological stress.
Elements unique to cesarean delivery include having major surgery while fully alert and potentially consenting to major surgery while in severe pain or under great stress, with little time to refl ect on options. In urgent cases, consent is often given in a busy, noisy envi- ronment, when surrounded by a large number of unfamiliar staff, and while facing the possible loss of a child or serious personal risks.
General principles to note are:
Spending time obtaining informed consent establishes rapport and
•
may contribute to avoiding litigation should complications arise.
Most women want to maximize the information they receive about
•
anesthesia (and analgesia) and are not made more anxious by full disclosure of complications.
Obstetric Anesthesia81
The provision of information through pamphlets or other patient
•
education resources in the antenatal period, at anesthetic or preadmission clinics, improves opportunities for frank discussion at the time of surgery.
Providing an opportunity for the woman to ask questions is important.
•
The details of the discussion should be documented (consent forms
•
can be used as a checklist or aid).
Some of the difficulties facing the obstetric anesthesiologist in particular include:
The anesthesiologist is often expected to provide effective and safe
•
anesthesia within minutes of meeting the patient for the fi rst time.
However, in very few (only 20 % ) of unplanned cesarean deliveries was there no prior indication of the potential need for operative intervention.
The amount of time for informed discussion may be signifi cantly
•
constrained. Nevertheless, even in emergent situations, it is Table 4.1 Advantages and Disadvantages of Regional Anesthesia for Cesarean Delivery
Advantages Maternal safety
No airway management diffi culties with consequent risks of aspiration of
•
gastric content or hypoxic organ injury Less blood loss
•
Neonatal outcome
Immediate resuscitation at birth less likely to be required than after
•
general anesthesia
Desirable postoperative outcomes Less risk of nausea and vomiting
•
Delayed recovery of consciousness and drowsiness avoided
•
Early interaction with the newborn
•
Early resumption of oral intake
•
High quality analgesia achievable by several means
•
Consumer satisfaction
Presence of mother and father/support person at birth enhances birth
•
experience for parents
Early skin-to-skin contact improves maternal-infant bonding
•
Early attachment of infant to the breast
•
Disadvantages
Potential for hypotension, leading to maternal syncope, nausea or vomiting symptoms, and fetal compromise
Potential for post-dural puncture headache
Anesthesia cannot be established as quickly as general anesthesia
82Anesthesia for Cesarean Delivery
important to explain as much as possible about what is happening, while obtaining a brief history and performing a basic physical exam- ination of vital signs and the airway.
Always visit the woman postoperatively, to answer any questions
•
or concerns which may remain.
Consent for Regional Anesthesia
When obtaining consent for a regional anesthetic, the anesthesiologist has a valuable opportunity to establish rapport, assuage anxieties, and order drug therapy, if necessary.
The effects of regional anesthesia should be explained, and a treat-
•
ment plan agreed upon (Table 4.2 ).
The fear of pain during needle insertion or during surgery can be
•
minimized by empathetic reassurance. In rare instances, the applica- tion of topical local anesthetic cream, if time allows, may be helpful.
Although rarely necessary, the use of light sedation (intravenous
•
midazolam 1–2 mg, fentanyl 0.5–1 mcg/kg or remifentanil 0.1–0.25 mcg/kg) may be considered. These drugs are unlikely to affect neonatal outcomes, but should be timed to avoid maternal amnesic effects that detract from the birth experience.
Closed claims and similar studies indicate that litigation often results from maternal dissatisfaction with the management of pain during cesarean delivery, so it is critically important to explain common sensations. The patient should be aware that.
Pressure and stretching are normal parts of the experience.
•
Mild intraoperative pain is not uncommon (5
• % –20 % depending on
the situation).
More severe pain will not be ignored.
•
If pain leads to a complaint, the anesthesiologist should be able to demonstrate that they had taken reasonable steps to warn about it, and about conversion to general anesthesia. In addition,
The regional technique used must have been reasonable.
•
The block should have been tested and noted to be adequate prior
•
to surgery.
Pain should have been treated when it was reported.
•
The anesthesiologist should have provided follow-up and support.
•
Dealing with a Patient Refusing Regional Anesthesia Many contraindications to regional anesthesia (Table 4.3 ) are relative.
In most instances, regional anesthesia will remain the anesthetic of choice. Despite this, some women will initially refuse regional
Obstetric Anesthesia83
anesthesia due to fear of pain either during block placement or during the surgery, or because of cultural unfamiliarity. In this situation -
Attempt to allay the patient’s concerns with compassionate but
•
realistic discussion, pointing out the advantages.
Respect the patient’s fi nal decision. Some women may have had a
•
distressing experience previously (for example, multiple failed attempts at insertion or severe pain during surgery) and will refuse any reasoned argument.
Regional Anesthesia for Nonelective Cesarean Delivery Cesarean deliveries can be classifi ed by their degree of urgency, and this classifi cation can be useful in determining an appropriate anesthetic
Table 4.2 Discussion Points at Consent for Regional Anesthesia
Advantages compared with general anesthesia
Enjoyment of the birth experience (including the father)
Fewer life-threatening complications (high-block, local anesthetic toxicity) Possibly lower mortality rate (extremely rare)
More alert neonate at birth Procedural events
Positioning and needle insertion Onset and testing of block Intraoperative positioning
Postoperative analgesic options (pros and cons, side effects) Post-block effects
Shaking
Nausea and vomiting Syncope Itch
Insertion site tenderness Intraoperative events
Abdominal stretching and pressure
Pain (incidence/location/timing/severity/treatment plan including conversion to general anesthesia)
Infrequent complications Post-dural puncture headache Rare complications
Neuraxial infection High block requiring intubation Neurological injury Extremely rare complications Death
84Anesthesia for Cesarean Delivery
(Table 4.3 ). For emergency or urgent cesarean delivery (Categories 1, 2 and 3), if a functioning epidural catheter is in place, it can be used to rapidly achieve a surgical anesthetic block (within 10–20 minutes), or spinal anesthesia can be established (within 10–20 minutes). General anesthesia is occasionally preferable, and may be mandated by failure of regional anesthesia or as the quickest means of anesthetizing the parturient (5–15 minutes) when there is life-threatening fetal compromise (Table 4.4 ).
In addition to the advantages of regional anesthesia noted above, a number of other factors have led to decreased use of general anesthesia. These include:
liberalization of the limits traditionally applied to defi ne when
•
regional anesthesia is safe
greater use of epidural analgesia during labor
•
better interdisciplinary communication, leading to earlier maternal
•
anesthetic assessment and preparation for operative delivery greater expertise in rapidly establishing safe regional anesthesia.
•
The American College of Obstetricians and Gynecologists (ACOG) suggests that when risk factors are identifi ed, “the obstetrician obtain antepartum consultation from an anesthesiologist” and that strategies such as early intravenous access and placement of an epidural or spinal
Table 4.3 Potential Contraindications to Regional Anesthesia
Infection risk
bacteremia and sepsis
• Infection
septic shock
•
local skin infection at insertion site
•
Severe immunocompromise in the presence of other risk factors Exacerbation of preexisting disease states
raised intracranial pressure
•
severe aortic stenosis
•
severe pulmonary hypertension
•
Maternal hypovolemia with cardiovascular instability obstetric or non-obstetric major hemorrhage
•
Vertebral canal hematoma risk severe thrombocytopenia
•
coagulopathy
•
anticoagulation
•
vertebral canal vascular pathology
•
Obstetric Anesthesia85
catheter be developed “to minimize the need for emergency induc- tion of general anesthesia in women in whom this would be especially hazardous”.
Consent for General Anesthesia
When obtaining consent for general anesthesia for cesarean delivery, a number of topics need to be discussed (Table 4.6 ). Place emphasis on:
Benefi ts and risks
•
Common events and symptoms
•
Preparation, and postoperative sequele
•
If the patient’s request for general anesthesia appears inadvisable, document in detail how her decision was reached.
Table 4.4 Categorization of Cesarean Delivery ∗
Category 1: Non-elective cesarean delivery because there is an immediate threat to the life of the mother or fetus
Category 2: Non-elective cesarean where delivery is indicated because of maternal or fetal compromise that is not immediately life-threatening Category 3: Non-elective cesarean where early delivery is needed but there is no maternal or fetal compromise
Category 4: Elective cesarean delivery scheduled at a time to suit the mother and the medical team
∗ Adopted by many hospitals based on Lucas DN, et al. J Royal Soc Med.
2000;93:346–350.
Table 4.5 When to Consider General, Rather than Regional, Anesthesia
Category 1 cesarean delivery (immediate threat to the life of the fetus or mother)
After two attempts to establish regional anesthesia have failed Following eclampsia or other seizure or maternal collapse, when the mother is not fully alert, medically stable, or has focal neurological signs When intraoperative pain under regional anesthesia is severe or uncontrolled by other means
Cardiac disease when reduction in systemic or pulmonary vascular resistance may lead to a critical event
Cardiac or respiratory disease when the patient cannot tolerate the supine or semi-supine position
Respiratory disease when postoperative ventilation will be required An uncooperative patient
86Anesthesia for Cesarean Delivery
Explaining the Effects of Anesthesia on the Baby Factors Affecting Neonatal Outcome
Much of the evidence about neonatal outcome and its relation to the method of anesthesia is of poor quality and pertains only to elective delivery of healthy women and fetuses. At emergency cesarean delivery, neonatal acid base balance can be improved irrespective of the method of anesthesia.
Meta-analysis comparing regional and general anesthesia suggests that neonatal umbilical cord blood pH and base defi cit is:
worse with spinal anesthesia compared with general anesthesia
•
(although the magnitude of difference is small)
affected by the severity and duration of maternal hypotension and
•
the duration of the uterine incision to delivery interval Table 4.6 Discussion Points at Consent for General Anesthesia
Disadvantages compared with regional anesthesia
•
Missing the birth experience (including the father)
•
Greater risk of life-threatening complications (hypoxemia, aspiration,
•
anaphylaxis)
Possibly higher mortality rate (extremely rare)
•
Assisted ventilation of the neonate more likely
•
Procedural events
•
Monitoring
•
Aspiration prophylaxis
•
Preoxygenation
•
Cricoid pressure
•
Postoperative analgesia
•
Common postoperative sequelae
•
Coughing
•
Nausea and vomiting
•
Sore throat
•
Drowsiness
•
Infrequent complications
•
Dental injury
•
Awareness
•
Hypoxemia
•
Failed intubation
•
Rare complications
•
Aspiration
•
Extremely rare complications
•
Neurological injury
• Death
•
Obstetric Anesthesia87 possibly made worse by the arterial occlusion associated with inad-
•
equate pelvic tilt (indicating the lateral position may be preferable when establishing regional anesthesia).
Effects of Regional Anesthesia
Fetal and neonatal effects of local anesthetic or opioid are usually
•
undetectable.
Only a Venturi type face mask delivering at least 60
• % inspired
oxygen will improve fetal oxygenation, but this should be consid- ered if the fetus is thought to be hypoxemic.
The biochemical and metabolic condition of the healthy fetus is
•
unaffected by regional anesthesia, provided ephedrine and sustained or profound hypotension are avoided (Table 4.7 ).
Control of hypotension with ephedrine results in lower umbilical
•
artery pH and higher base defi cit than control with phenylephrine or metaraminol.
Table 4.7 Anesthesia and Neonatal Acid-Base Status at Elective Cesarean Delivery 1kPa = 7.5mmHg
General (n = 30)
Epidural (n = 30)
Spinal (n = 30) Maternal
pH 7.36 (0.04) a 7.44 (0.06) 7.42 (0.03) pO 2 (kPa) 30.80 (1.37) 31.73 (1.56) 32.10 (1.50) Base defi cit (mmol/l) 5.10 (1.82) 2.43 (2.13) 3.21 (1.79) Umbilical vein
pH 7.33 (0.05) 7.34 (0.04) 7.34 (0.05)
PO 2 5.80 (0.33) 5.67 (0.36) 5.92 (0.51) Base defi cit 4.00 (2.10) 4.80 (1.81) 4.78 (2.23) Umbilical artery
pH 7.28 (0.04) 7.29 (0.07) 7.28 (0.02)
PO 2 2.90 (0.19) 2.91 (0.23) 2.87 (0.23) Base defi cit 4.31 (1.79) 4.58 (1.99) 4.53 (2.01) Values are mean (SD). a P < 0.01 compared with other groups. Reprinted from the International Journal of Obstetric Anesthesia , Vol. 2. Mahajan J, et al.
Anaesthetic technique for elective caesarean section and neurobehavioural status of newborns, 89–93, Copyright (1996), with permission from Elsevier.
88Anesthesia for Cesarean Delivery
Uncorrected hypotension may cause subtle neurobehavioral
•
changes in infant responsiveness and sucking.
Effects of General Anesthesia
Fetal drug exposure is limited by factors regulating placental
• transfer.
Fetal oxygenation is improved by giving the woman 100
• % inspired
oxygen, but no improvement in neonatal clinical outcome has been shown.
The sedative effects of the inhalational anesthetics and the respira-
•
tory depressant effects of opioid may be evident at birth, especially after a prolonged induction to delivery interval ( > 15 minutes).
A person experienced in neonatal resuscitation should be availa-
•
ble, because active resuscitation is more likely to be necessary (although usually confined to assistance in establishing first breaths).
In cesarean delivery for fetal compromise, lower Apgar scores
•
and neonatal intubation may be more likely than after regional anesthesia (Figure 4.1 ).
Percentage
100
80
60
40
20
0
Epidural General Spinal
1 min score
Epidural General Spinal
5 min score Apgar 1–4
Apgar 5–7 Apgar 8–10
Figure 4.1 Infl uence of anesthetic technique on neonatal condition after urgent cesarean section for fetal distress. Data derived from Marx, G.F., et al.
(1984) Fetal-neonatal status following cesarean section for fetal distress.
Br J Anaesth. 56:1011. Reprinted with permission from Reisner LS and Lin D, Anesthesia for cesarean section. In: Chestnut DH, Obstetric Anesthesia 2 nd ed.
1999, Elsevier.
Obstetric Anesthesia89
Patient Preparation
Preoperative Assessment
Ideally, a thorough pre-anesthesia assessment should be completed, including:
Patient characteristics (age, weight, fasting status).
•
Past medical and surgical history.
•
Systems review, medications and allergies.
•
Physical examination focusing on the cardiovascular and respiratory
•
systems, and the relevant airway investigations and imaging.
Additional elements related to pregnancy and cesarean delivery.
•
(Table 4.8 ) Fasting
The American Society of Anesthesiologist’s (ASA) practice guidelines recommend a fasting interval of at least 6 hours for solids prior to elective cesarean delivery.
In laboring women, oral intake should be limited to clear fl uids
•
alone, due to diffi culty predicting which women are at risk of surgical delivery.
In many cases, the urgency of delivery will take precedence over
•
fasting status. In parturients who have not been “nil per oris” (NPO),
Table 4.8 Pre-Anesthesia Assessment Related to Pregnancy and Cesarean Delivery
Past obstetric history Current obstetric history Indication for cesarean delivery Gestational age
Pregnancy-related diseases and disorders and their management Presence of ruptured membranes or labor
Fetal status during pregnancy and current fetal status Relevant surface landmarks, especially vertebral column Relevant investigations and laboratory tests
Hemoglobin concentration / hematocrit Platelet count
Blood group and hold or blood crossmatch Relevant imaging
Placental location Spinal anatomy
90Anesthesia for Cesarean Delivery
regional anesthesia is preferable in terms of avoiding the risk of aspi- ration.
Preoperative Optimization
Preoperative optimization is an important goal, irrespective of the urgency of delivery. Recent data from the CEMACH database noted the failure of staff to recognize the severity of maternal illness.
Undiagnosed or inadequately treated sepsis and cardiac failure are examples of conditions in which induction of anesthesia may precipi- tate a fatal event.
The timing of delivery in critically ill pregnant women requires careful consideration, preferably decided by a multidisciplinary team including obstetricians, obstetric physicians, neonatologists and anesthesiologists. Even if delivery appears mandated by an imme- diate threat to the life of the fetus, intrauterine resuscitation (see Chapter 15) may improve the fetal condition signifi cantly and gain preparation time. The life of the mother must always take priority over that of the fetus.
Airway Assessment
Diffi cult intubation (incidence 1 in 30–60) or failed intubation (inci- dence 1 in 250–1500) leading to hypoxemia, aspiration, and cardiac arrest, represents the most common fatal complication of obstetric anesthesia in developed countries (fatal complications of regional block are very rare except in developing countries).
Although difficulties may arise unexpectedly, in many cases good airway assessment will be predictive and critical to manage- ment planning. A high false positive rate (low specifi city) is not an issue, and a diffi cult airway cart should be available in all units, prefer- ably housed beside the operating table when general anesthesia is induced.
Airway assessment should be routine and performed at patient admission or as early as possible in labor. Ideally there are hospital- based systems of referral to the anesthesiology department of women of known or suspected high risk of airway diffi culty.
Risk Factors for a Diffi cult Airway
Risk factors must be sought and a comprehensive evaluation performed (Table 4.9 and Figure 4.2 ). Review of documentation of previous airway management is valuable, but unless reasonably contemporane- ous it may not refl ect the patient’s current condition.
Obstetric Anesthesia91 Table 4.9 Indicators of Potential Diffi culty with the Airway History
Previous anesthesia and airway management details (known diffi culty)
•
Breath sounds (stridor associated with airway infection or severe
•
preeclampsia) Examination and Tests
Morbid obesity (associated with diffi cult ventilation and
•
intubation)
Limited cervical spine or atlanto-occipital joint extension (including
•
due to large hair knots or buns) Short neck (thyromental distance < 6 cm)
•
Reduced laryngoscope access (e.g., anterior neck mass or large breasts)
•
Small oral cavity or large tongue (Grade 3 or 4 Mallampati view)
•
Temporomandibular joint dysfunction or reduced mouth opening
•
(inter-incisor distance < 3 cm)
Prominent upper incisors (inability to protrude lower teeth past upper
•
teeth or to bite upper lip) Receding mandible
•
Height to thyromental distance ratio
• > 21
Poor dentition (missing, loose, or prosthetic teeth)
•
Oral pathology
•
Most individual tests show poor specifi city and positive predictive value.
Combinations (e.g., Mallampati test and upper-lip bite test) are more accurate, and multiple factors multiply the relative risk of diffi cult airway management.
Class I
Class I Class II Class III Class IV
Class II Class III Class IV
Figure 4.2 Airway assessment. Upper panel: classifi cation of view of the pharyngeal structures during airway assessment. Lower panel: Classifi cation of direct laryngoscopic view. Upper panel modifi ed from Mallampati SR, et al. A clinical sign to predict diffi cult intubation: a prospective study. Can Anaesth Soc J. 1985; 32: 429-434. Lower panel modifi ed from Comarck RS and Lehane J.
Diffi cult intubation in obstetrics. Anaesthesia 1994; 39: 1105-1111. Reprinted with permission from Samsoon GLT and Yount JRB. Diffi cult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 488.
92Anesthesia for Cesarean Delivery
Airway management plans are best based on established algorithms, such as those endorsed by the ASA, with appropriate modifi cations for the obstetric population. Such plans include:
Avoiding nasal instrumentation if possible because of the risk of
•
epistaxis (due to increased vascularity and edema of the nasal mucosa).
Early placement of an epidural catheter during labor in women at
•
increased risk of diffi cult airway management (e.g., morbidly obese, known or suspected diffi cult intubation). This allows for rapid induction of surgical anesthesia if necessary.
Repeat airway assessment in laboring women to exclude changes
•
within the airway (e.g., mucosal or tongue swelling or laryngeal edema due to deteriorating preeclampsia).
Use of awake fiberoptic intubation when general anesthesia
•
appears necessary in a woman at high risk of difficult airway management.
If difficulty is anticipated the anesthesiologist should be familiar with and have prepared a range of equipment for intubation, aids to intubation, and both supraglottic and transtracheal airway devices.
The patient should be warned about possible dental and soft tissue injury. Experienced assistants are essential.
Minimization of Aortocaval Compression Physiology
Once the gravid uterus rises from within the pelvis (at approximately 20 weeks gestation) it may obstruct the inferior vena cava and/or the aorta (usually just below the bifurcation of the iliac arteries) when the woman lies supine.
At term, imaging shows that 90
• % of women lying supine have
partial or complete inferior vena caval obstruction (with diversion of venous fl ow via the azygous system) and 10 % –15 % become symptomatic (syncope, nausea) due to reduced cerebral perfusion.
Aortic obstruction and impaired placental fl ow may be silent but
•
cause fetal hypoxemia and acidosis.
These effects are exaggerated by anesthesia, due to venous pooling,
•
reduction in blood pressure, impaired compensatory vasoconstric- tion, and reduced cardiac output.
In combination with other events, the hemodynamic disturbance of aortocaval compression has contributed to case fatalities.