Obstetric Issues for the Anesthesia Practitioner

Educational Objectives

The goal of this program is to improve the management of anesthesia for obstetric patients. After hearing and assimi­lating this program, the clinician will be better able to:

1.   List the main causes of maternal mortality associated with cesarean delivery.

2.   Describe methods for managing a difficult airway in an obstetric patient.

3.   Discuss guidelines for control of hemorrhage during deliveries.

4.   Assess complaints of leg pain or weakness in obstetric patients after delivery.

5.   Recognize the most common causes of neurologic deficits related to obstetric anesthesia and their incidences.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning committee to disclose relevant financial relationships within the past 12 months that might create any per­sonal conflicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the faculty and the planning committee reported nothing to disclose.

Acknowledgements

Dr. Camann spoke at the Postgraduate Symposium on Anesthesiology, held March 27-29, 2009, in Kansas City, KS, and sponsored by the University of Kansas Medical Center. Dr. Zakowski spoke at the Annual Meeting and Clinical Anesthe­sia Update, held May 15-17, 2009, in Monterey, CA, and sponsored by the California Society of Anesthesiologists. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

Obstetric Anesthesia Emergencies

William R. Camann, MD, Director of Obstetric Anesthesia, Brigham and Women’s Hospital, and Associate Professor of Anesthesia, Harvard Medical School, Boston, MA

Maternal mortality: causes related to cesarean delivery include complications of preeclampsia, amniotic fluid em­bolism, hemorrhage, and cardiac disease; more women with congenital heart disease now giving birth, leading to greater risk for cardiac complications during pregnancy; overall, maternal mortality relatively minor concern in United States; common causes in underdeveloped nations include hemorrhage, sepsis, unsafe abortion, and ob­structive labor

Difficult airway: main concern today in anesthesia-specific maternal mortality; solutions include better airway de­vices and screening methods, use of regional anesthesia in patients with perceived airway difficulties, and use of American Society of Anesthesiologists (ASA) Difficult Airway algorithm; inadequate training of residents  —  use of general anesthesia in obstetrics now so rare that residents may complete program without performing it

Airway management: need difficult airway cart in labor and delivery units; labor and delivery operating rooms at Brigham and Women’s Hospital display ASA Difficult Airway algorithm in rooms; simulator training recom­mended; prophylactic regional anesthesia  —  when patient with potential airway or other medical problem identi­fied before or early in labor, early (prophylactic) epidural recommended in case problem arises during labor; airway can change during labor; obstetricians should receive training in evaluation of airways, be able to under­stand anesthesiologists’ concerns, and anticipate problems; study demonstrated that obstetricians given such training more likely to recommend early epidural anesthesia in cases of perceived airway difficulties

Laryngeal mask airway (LMA): “wonderful” rescue device; speaker recommends use when indicated; in one study of >1000 elective cesarean deliveries performed under general anesthesia with LMA, success rate 99%, with no episodes of hypoxia, aspiration, regurgitation, laryngospasm, bronchospasm, or gastric insufflation

American College of Obstetricians and Gynecologists statement on anesthesia for emergency deliveries: pub­lished in 1992; remains valid today; states that “risk can be reduced by careful antepartum assessment, greater use of regional anesthesia when possible, and appropriate selection and preparation of patients for general anesthesia”; “obstetric care team should be alert to presence of risk factors”; for patients at risk, consideration should be given to the planned placement in early labor” of epidural catheter; “cesarean deliveries that are performed for non-reassur­ing fetal heart pattern do not necessarily preclude the use of regional anesthesia”

Team approach to hospital-based emergencies: promote whenever possible

“Condition O”: obstetric-specific rapid-response or code team for obstetric crises; indications include fetal distress, shoulder dystocia, maternal seizure, syncope, prolapsed umbilical cord, hemorrhage, and hypotension after epi­dural

Limitation of Good Samaritan defense: anesthesiologist used defense when sued for injury to neonate he helped to resuscitate; received remuneration only for mother’s care; Texas Supreme Court ruled defense does not apply to individuals at emergency scene remunerated for their services, even if actions in question not related to primary patient’s care

Hemorrhage: emergency recommendations from New York Hospital (Queens, NY) include guidelines for rapid emergency blood transfusion, and good communication among physicians, nurses, and blood bank; Brigham and Women’s Hospital has obstetric hemorrhage emergency pack available on demand from blood bank; other recommendations  —  monitor blood loss during labor, delivery, and early postpartum; do not delay transfusion for laboratory results; implement early aggressive care, even if mother seems hemodynamically stable; conduct reg­ular “hemorrhage drills” with all labor and delivery staff; provide continuing medical education

Recombinant factor VII: generally well tolerated; thrombosis most common side effect, but rare; 1.2-mg vial may cost $3600, so cost possible obstacle; not “magic bullet” (administering alone not enough; must replete other fac­tors [eg, fresh frozen plasma] as well)

Cell salvage: traditionally contraindicated in obstetrics due to fears of amniotic fluid contamination; causative agents of amniotic fluid embolism still unidentified, but a-fetoprotein, tissue factor, and fetal squamous cells all removed during cell-salvage processing, and hundreds of reports now exist of safe obstetric use; incidence of amniotic fluid embolism between 1 and 8 in 80,000; still too early to conclude technique completely safe; conclusion  —  “jury is still out on cell salvage”; obstacles include setup and maintenance of equipment, availabil­ity, especially in rural areas, and safety

Interventional radiology: uterine artery embolization proven technique for controlling obstetric and gynecologic hemorrhage; use will increase as cesarean deliveries increase; abnormal placentation most common prenatal in­dication; other indications include lacerations, retained products of conception, atony, and rupture; formerly con­sidered last resort; many now advocate higher position in treatment algorithm; performing surgery first could make later embolization difficult or impossible; usually accomplished through femoral access; bilateral internal iliac angiography and catheterization done; more selective distal catheterization and embolization possible, based on location of bleeding; accomplished very quickly, even in unstable patients; complications  —  related to inser­tion of needles or catheters into large blood vessels; pelvic infection and ischemic phenomena; incidence low; controversy over whether uterine artery embolization increases risk for infertility or complicates future pregnan­cies; however, evidence suggests that subsequent pregnancies not jeopardized; practical concerns include qualifi­cations of radiology team; availability of team; availability of anesthesia equipment in radiology suite; ability of anesthesia personnel to accompany unstable patient to radiology; distance of radiology suite from labor and de­livery suite; timing of epidural (should be done before catheterization)

Neurologic Complications of Regional Anesthesia in Obstetrics

Mark I. Zakowski, MD, Chief, Section of    Obstetric Anesthesia, Department of Anesthesiology,    Cedars-Sinai Medical Center, Los Angeles, CA

Differential diagnosis for prolonged blockade after neuraxial anesthesia: do not assume prolonged drug effect; consider potential for neurotoxicity, trauma to peripheral nerve or spinal cord, or compression of spinal cord; also consider diminished spinal blood supply, neurologic disease, stress, or Guillain-Barré sydrome

Approach to patient: full history, detailed physical examination (PE), and laboratory tests (speaker recommends that anesthesiologist order tests); order neurology or neurosurgery consult when necessary

History: ask about previous back pain or numbness; pain or paresthesia during procedure; did patient experience period of full recovery? (rules out possibility of prolonged anesthetic effect); details of obstetric history and delivery (length of time patient pushed; position during second stage; instrumentation [forceps common cause of lumbosacral plexus injury]); baby’s weight (macrosomia possible risk factor); position of baby’s head

PE: should include full neurologic examination; speaker usually starts by putting pressure on spinous processes deep into epidural space; pain suggests epidural abscess; speaker also searches for knot in muscle; try to deter­mine whether lesion central or peripheral; muscle spasm could suggest strain or herniated disc; sacroiliac joint tenderness  —  unique to obstetrics; hormonal changes associated with pregnancy may cause joint to relax and tear; pressing sacroiliac joint very painful; not related to anesthesia; in chart, map out examination in detail

Laboratory tests: if infection suspected, order complete blood count and cerebrospinal fluid analysis; if epidural hematoma suspected, order computed tomography (CT) to check for spinal cord compression; CT also better when looking for intracranial blood (potential subarachnoid hemorrhage); magnetic resonance imaging pre­ferred when looking for infection

Electromyography (EMG): takes 2 to 3 wk for changes associated with nerve injury to become apparent; obtain baseline EMG within first week of symptoms; decreased amplitude associated with axonal loss; increased la­tency associated with demyelination

Evoked potentials: somatosensory evoked potentials (EPs) sensitive to cord compression (posterior spinal cord); motor EPs sensitive to anterior spinal cord issues

Obstetric-related deficits: postpartum complaints of neurologic dysfunction more likely to have obstetric rather than anesthetic cause; incidence of purely obstetric injury 2 to 5 in 10,000 births; risk factors include pro­longed labor (eg, second stage >3 hr); use of forceps; macrosomia (birth weight >9 lb); position of mother’s legs; position of baby’s head; if mother’s legs hyperflexed, rest them between pushes; over 60-yr period, inci­dence of permanent neurologic injury among women who received no obstetric anesthesia 2 to 5 in 10,000 births; fetal head position  —  occiput-anterior (OA) places less pressure on mother’s lumbosacral plexus than occiput-posterior (OP) or transverse position; L4-5 root particularly vulnerable to pressure and injury; femoral nerve injury most common serious injury speaker sees; symptoms include numbness in anterior thigh and weakness in quadriceps, possibly continuing down leg

Common peroneal nerve injury: often results from allowing woman to rest legs against bed rail while pushing, rather than using stirrups; rail should be padded with towel; classic symptom sensory loss in lateral calf down to webbed space between first and second toes, and motor problem such as foot drop or leg inversion; electro­diagnostic test results may be falsely negative due to variations in nerve anatomy; lateral femoral cutaneous nerve injury  —  sensory only; nerve may be compressed as it runs under lateral inguinal ligament; usually re­solves spontaneously within <6 wk

Femoral nerve injury: in mild cases, patient can walk but may have altered gait; compression due to leg hyper­flexion most common cause

Lumbosacral plexus injury: risk factors include first birth, shallow pelvis, cephalopelvic disproportion, and use of forceps; usually unilateral, but bilateral symptoms occur in 25% of cases; L4-5 nerve root usually affected; obturator nerve compressed less frequently

Other causes of nerve injury: spinal ischemia, anterior spinal artery syndrome (»15% of patients at risk; hall­marks include sudden onset, acute motor deficit, absence of pain and fever, and negative CT and white blood cell count), severe hypotension, and arteriovenous malformation (AVM) of spinal cord (rare); 20% of patients with spinal AVM also have cutaneous AVM at same level

Anesthesia-related deficits: incidence 1 in 10,000 to 100,000 births; include direct nerve trauma, severe hypotension or cardiac arrest, equipment problems, and adverse drug effects; speaker cautions against ignoring paresthesias (rec­ommends withdrawal of needle and recheck of anatomy); nerve may be injured from direct pressure; document all incidents; according to ASA closed claims data, 66% of patients with permanent neurologic injury had pares­thesia or pain on injection (may indicate intraneuronal injection)

Anatomic variations as cause of anesthetic injury: Tuffier’s line usually denotes L4 spinous process, but may be higher or lower; spinal cord usually ends at L1-2, but may be higher or lower

Timing of deficit: in French study of 103,000 regional anesthetics, all neurologic deficits appeared within 48 hr; deficits without paresthesia occurred mostly with spinal anesthesia; risk for neural injury or radiculopathy with spinal anesthesia 3 times greater than with epidural, especially when 5% lidocaine used

Pre-existing neurologic conditions: in study of 139 pregnant women with multiple sclerosis (MS), amyotrophic lat­eral sclerosis, or postpolio syndrome, no reports of new or worsening deficits after anesthesia; speaker counsels MS patients about lack of evidence that anesthesia will exacerbate condition, but cautions that MS variable; worsening of MS due to stress associated with delivery or surgery possible

Cardiac arrest: risk 2 to 7 times higher with spinal than epidural anesthesia; remain vigilant for severe hypotension (which could lead to cardiac arrest), and treat it aggressively; for bradycardia plus hypotension, administer ephedrine, phenylephrine (eg, Neosynephrine; however, >6-8 µg of phenylephrine may constrict uterine artery and cause fetal bradycardia), or atropine; if patient still hypotensive, consider 50 to 100 µg epinephrine; with proper recognition and prompt treatment, patient should recover

Mortality risk: latest data show risk 1.7 times greater with general vs regional anesthesia for cesarean delivery, or 1 per 1 million live births; if patient nervous, compare to mortality risk (>2 in 10,000) for licensed drivers

Suggested Reading

Auroy Y et al: Serious complications related to regional anesthesia: results of a prospective survey in France. Anesthesiology 87:479, 1997; Dyer RA, Piercy JL, Reed AR: The role of the anesthetist in the pre-eclamptic patient. Curr Opin Anaesthesiol 20:168, 2007; Gosman GG et al: Introduction of an obstetric-specific medical emergency team for obstetric crises: implemen­tation and experience. Am J Obstet Gynecol 198:367, 2008; Hebl JR et al: Neuraxial anesthesia and analgesia in patients with preexisting central nervous system disorders. Anesth Analg 103:223, 2006; Kuczkowsi KM: Labor pain and its management with the combined spinal-epidural analgesia: what does an obstetrician need to know? Arch Gynecol Obstet 275:183, 2007; Moore M et al: Selective arterial embolisation: a first line measure for obstetric haemorrhage? Int J Obstet Anesth 17:70, 2008; O’Rourke N et al: Cesarean delivery in the interventional radiology suite: a novel approach to obstetric hemostasis. Anesth Analg 104:1193, 2007; Percy, L: Texas courts review Good Samaritan defense. American Society of Anesthesiologists Newsletter 72:39, 2008; Pollard JB: Cardiac arrest during spinal anesthesia: common mechanisms and strategies for preven­tion. Anesth Analg 92:252, 2001; Shearer E: Occipitoposterior position in labor. Birth 33:169, 2006; Skupski DW et al: Im­proving hospital systems for the care of women with major obstetric hemorrhage. Obstet Gynecol 107:977, 2006.