SECTION VIII. Obstetrics and Gynecology
A Assisted Reproductive Technologies
1. Procedure overview
Assisted reproductive technologies (ART) refers to all techniques used to retrieve and fertilize the human oocyte. In vitro fertilization (IVF) is the most common technique used to artificially fertilize the human oocyte.
The procedure is performed by initially stimulating maturation of the follicle with a gonadotropin-releasing hormone agonist which induces pituitary gland suppression and creates quiescent ovaries to prevent the production of a single dominant follicle. Follicle stimulating hormone (FSH) and human menopausal gonadotropin are then administered, which induces 10 to 15 ovarian follicles. The patient is then given human chorionic gonadotropin (HCG), which induces the follicle to then mature and move into the follicular fluid. The oocyte is retrieved transvaginally, transabdominally, or via laparoscopy with an ultrasonically guided probe 34 to 36 hours after HCG administration. All visible follicles are collected, washed, incubated for 4 to 6 hours in a culture medium, and examined microscopically. Most follicles contain only one oocyte. Fertilization occurs in the IVF laboratory. The oocyte is identified and has minimal exposure to ambient room temperature, room air, and especially any chemical odors. Sperm are washed and centrifuged. Fresh media is added next to the centrifuged sperm, and those sperm that swim to the media, which can number 50,000, are placed with the oocyte. Timing must be coordinated with proper maturation of the uterine endometrium. ART is found to increase the risk of multiple gestations. Also, it has been reported that atypical implantations of the fertilized ovum or zygote, such as abdominal, cervical, ovarian, or tubal pregnancy, occur more frequently with ART. Common ART techniques are listed in the following table.
Patients are assessed for antibodies to human immunodeficiency virus types 1 and 2 (HIV-1, HIV-2) and human T-cell lymphotropic virus type 1 (HTLV-1), hepatitis B antigen, and antibodies to hepatitis B and C. Patients are also tested for chlamydia, syphilis, gonorrhea, and cytomegalovirus. Smokers require twice as many attempts at successful IVF than nonsmokers, so smoking is extremely discouraged.
2. Anesthetic considerations
a) IVF is generally performed on patients who are American Society of Anesthesiologists (ASA) class 1 or 2 in their third or fourth decade of life.
b) Although IVF is a relatively simple procedure for the reproductive endocrinologist to perform, especially outside the operating room, IVF is an uncomfortable procedure and requires that patients do not move in order for the probe to be guided for retrieval and later reimplantation.
c) The vaginal wall must be pierced for the desired ovary to be accessed. Also, major blood vessels are present in the proximity of the ovaries, and their injury could lead to complications.
d) Anesthesia requirements vary with the individual needs of the patient and the reproductive endocrinologist. Multiple ART procedures may need to be performed until one of them is successful, so safe yet inexpensive anesthetic techniques are desirable.
e) Minimal sedation, moderate sedation/analgesia, regional intrathecal anesthesia, paracervical block, or general anesthesia can be administered to assist in making the procedure as comfortable and successful as possible.
f) Moderate sedation with analgesia is usually sufficient for most patients. None of the anesthetic procedures caused differences in reproductive outcome.
g) Anesthetic medications generally considered safe for use in anesthesia for ART are listed in the box at the top of p. 417. Anesthesia providers should consider using safe anesthetic techniques with quick onset and a short duration.
Anesthetic Medications Used for ART
Intrathecal
Bupivacaine
Lidocaine
Fentanyl
Morphine
Paracervical Block
Bupivacaine
Lidocaine
Mepivacaine
Intravenous Sedation or Total Intravenous Anesthesia
Fentanyl
Alfentanil
Remifentanil
Meperidine
Ketamine
Midazolam
Propofol
Inhalational Agents
Nitrous oxide
h) It should be noted that propofol, lidocaine, thipental, thiamylal, and alfentanil have been shown to accumulate in the follicular fluid.
i) Midazolam, when titrated in small doses to provide mild to moderated sedation and anxiolysis, has been shown to be safe, with no accumulation in follicular fluid or teratogenicity.
j) Ketamine (0.75 mg/kg) with midazolam (0.06 mg/kg) moderate sedation/analgesia has been safely used as an alternative to general anesthesia with isoflurane.
k) The literature has suggested the use of caution when using a potent inhaled agent (especially sevoflurane and desflurane) due to possible negative effects to ART outcomes.
l) Nonsteroidal antiinflammatory agents such as ibuprofen, indomethacin, ketoprofen, ketorolac, meloxicam, naproxen, or oxaprozin are avoided due to inhibition of prostaglandin synthesis and possible effects on embryo implantation.
m) Droperidol and metoclopramide have both been shown to induce rapid hyperprolactinemia and should be avoided. Low plasma prolactin levels are associated with higher incidences of pregnancy.
n) The common anesthetic agents that could cause potential problems with ART are listed below. The necessity for any medication given to the patient should be carefully considered, and the anesthetic technique should be kept simple and basic.
Common Anesthetic Agents That Could Cause Potential Problems with ART
Morphine
Sevoflurane
Desflurane
NSAIDS (e.g., ibuprofen, indomethacin, ketoprofen, ketorolac, meloxicam, naproxen, oxaprozin)
Droperidol
Metoclopramide
B Cesarean Section
1. Introduction
A cesarean section (C-section) is the surgical removal of a fetus through an abdominal/uterine incision. A low transverse incision is the most common; in an emergency, a rapid vertical midline incision may be used. Indications for a C-section are failure of labor to progress, previous C-section, fetal distress, malpresentation of the fetus or umbilical cord, placenta previa, and genital herpes or other local infections.
2. Perioperative assessment
a) In emergency cases, the time for assessment will be brief. Special attention should be paid to airway assessment because failed intubation is a major cause of maternal morbidity and mortality.
b) Key points regarding physiological changes in pregnancy
(1) Cardiac output increases mostly due to the increase in stroke volume, but also due to increase in heart rate.
(2) The greatest demand on the heart is immediately after delivery when cardiac output increases 180%.
(3) Blood volume is markedly increased and prepares the parturient for the blood loss associated with delivery.
(4) Plasma volume is increased to a greater extent than red blood cell volume, resulting in a dilutional anemia.
(5) Minute ventilation increases 45%, and this change is mostly due to the large increase in tidal volume.
(6) Oxygen consumption is markedly increased. Carbon dioxide production is similarly increased.
(7) Pregnant women have an increased sensitivity to local anesthetics, and a decreased MAC for all general anesthetics.
(8) Platelets, factor VII, and fibrinogen are increased.
(9) Intragastric pressure is increased in the last trimester which, in combination with increased acid volume, often results in heartburn.
(10) All pregnant women are at increased risk of aspiration due to the physiologic changes to the gastrointestinal system.
Musculoskeletal changes can result in a challenging neuraxial block.
3. Patient preparation
a) A nonparticulate antacid (such as sodium citrate, 30 mL) is routinely administered at most institutions, regardless of the anesthetic technique chosen. Sedation is best avoided. Benzodiazepines have been implicated as possible teratogens, and it is best to avoid maternal amnesia during childbirth.
b) Laboratory tests should include a type and screen, complete blood count, electrolytes, blood urea nitrogen, creatinine, glucose, prothrombin time, and partial thromboplastin time. In emergency C-sections, there may not be time to complete these tests.
4. Room preparation
a) Monitoring
(1) Standard
(2) If there is a history of pregnancy-induced hypertension, an arterial line is recommended.
(3) If there is severe preeclampsia, a central line is also recommended, with a pulmonary catheter in cases of hemodynamic instability.
b) Positioning: Supine with left lateral uterine displacement. This is accomplished by placing a wedge under the right hip. Failure to use left lateral uterine displacement can result in aortocaval compression.
c) Drugs and tabletop
(1) The tabletop should be set up for a general anesthetic.
(2) Set out a smaller endotracheal tube (6 to 6.5) as well (because of airway edema).
(3) Have ephedrine and oxytocin drawn up.
(4) Have difficult airway equipment available.
(5) Unless there is maternal hypoglycemia, avoid giving intravenous solutions with glucose because they may lead to neonatal hypoglycemia.
5. Perioperative management and anesthetic techniques
The guidelines for general anesthesia, spinal, and epidural are listed below.
a) General anesthesia for cesarean section
(1) Histamine 2-receptor antagonist or proton pump inhibitor and/or metroclopramide intravenously
(2) Clear antacid orally
(3) Left uterine displacement
(a) Application of monitors
(b) Denitrogenation (administration of 100% oxygen)
(c) Traditional 3 to 5 minutes versus 4 vital-capacity breaths
(4) Cricoid pressure
(5) Intravenous induction
(a) Thiobarbiturate, propofol, ketamine, or etomidate
(b) Succinylcholine (rocuronium or vecuronium if succinylcholine is contraindicated)
(6) Intubation with a 6.0- to 7.0-mm cuffed endotracheal tube
(7) Administration of 30% to 50% nitrous oxide in oxygen and a low concentration (e.g.,⅔ minimum alveolar concentration MAC) of a volatile halogenated agent.
(8) After delivery
(a) Increased concentration of nitrous oxide, with or without a low concentration of a volatile inhalation agent
(b) Opioid titrated as needed
(c) Intravenous hypnotic agent (e.g., benzodiazepine, barbiturate, propofol), if needed
(d) Muscle relaxant (e.g., succinylcholine boluses or infusion, vecuronium)
(9) Extubation awake with intact airway reflexes
b) Epidural anesthesia for cesarean section
(1) Metoclopramide 10 mg intravenously
(2) Clear antacid orally
(3) Intravascular volume replacement with Ringer’s lactate or normal saline (15 to 20 mL/kg)
(4) Application of monitors
(5) Supplemental oxygen by face mask or nasal prongs
(6) Epidural catheter at L2 to L3 or L3 to L4
(7) Left uterine displacement
(8) Test dose
(9) Therapeutic dose: 5-mL boluses of 2% lidocaine + 1:400,000 epinephrine. Alternatively, 5-mL boluses of 0.5% bupivacaine, 0.5% ropivacaine, or 3% 2-chloroprocaine (boluses of lidocaine or 2-chloroprocaine every 1 to 2 minutes, boluses of bupivacaine or ropivacaine every 2 to 5 minutes)
(10) Aggressive treatment of hypotension: Exaggerated left uterine displacement; intravenous fluids; ephedrine and/or low-dose phenylephrine
c) Spinal anesthesia for cesarean section
(1) Metoclopramide 10 mg intravenously
(2) Clear antacid orally
(3) Intravascular volume
(4) Replacement with Ringer s lactate or normal saline (15 to 20 mL/kg)
(5) Application of monitors
(6) Supplemental oxygen by face mask or nasal prongs
(7) Prophylactic intramuscular ephedrine (25 to 50 mg) in patients with a baseline systolic blood pressure of less than 105 mm Hg
(8) Lumbar puncture at L3 to L4
(a) Right lateral or sitting position
(b) 24- or 25-gauge Sprotte needle or 25- or 27-gauge Whitacre needle
(c) Bupivacaine 12 mg in 8.25% dextrose
(d) Morphine 0.1 to 0.25 mg for postoperative analgesia
(e) Left uterine displacement
(f) Aggressive treatment of hypotension
(i) Exaggerated left uterine displacement
(ii) Intravenous fluids
(iii) Ephedrine and/or low-dose phenylephrine
d) Tasks at delivery and postdelivery maintenance
(1) The length of time from uterine incision to delivery has been shown to correlate with the degree of neonatal acidosis. The interval should be recorded. An interval of 3 minutes seems to be the critical value; neonates delivered later than 3 minutes after uterine incision are more likely to be depressed.
(2) After the umbilical cord has been clamped, the anesthesia provider’s options for anesthetic maintenance increase, because the administered drugs will no longer reach the baby. If adequate uterine contraction is achieved with oxytocin, there is no reason why the use of an inhalation anesthetic cannot be continued.
(3) A low-dose inhalation agent (up to 1 MAC), with or without nitrous oxide, and either fentanyl or sufentanil work well. The obstetrician also may want an antibiotic to be given. If uterine tone does not allow the use of an inhalation agent, an opioid technique is useful.
(4) When opioids are used, nitrous oxide is usually needed. If nitrous oxide is not used, the anesthesia provider may consider giving a small dose of midazolam for amnesia. Opioid administration should be customized to the circumstances. One option is giving up to 5 mcg of fentanyl per kilogram or 0.5 mcg of sufentanil per kilogram, adjusting the dose according to the expected duration of the case and the patient’s response. Another opioid choice is morphine 10 mg intravenously and 10 mg intramuscularly.
(5) After the placenta has been delivered, oxytocin should be given immediately unless the obstetrician’s plan for uterine contraction calls for the use of another agent.
(a) The half-life of oxytocin varies from 4 to 17 minutes. It is metabolized by liver, kidney, and plasma enzyme pathways in the parturient.
(b) Commercially available preparations of oxytocin contain a preservative that causes systolic and especially diastolic hypotension, flushing, and tachycardia when infused at high doses.
(c) The amount of oxytocin added to the IV solution should be tailored to the volume of solution remaining in the bag, the flow rate of the IV, and the patient’s condition. If the IV bag is nearly empty or if IV solution is being administered rapidly, less oxytocin should be added to the bag.
(d) In general, the obstetrician is likely to desire the administration of 30 to 40 units of oxytocin over the first hour postpartum.
(e) If an unusually large blood loss results in hypotension, and if fluid resuscitation is needed, it may be helpful to infuse the oxytocin at an appropriate rate and to start a second IV line for administering fluid volume at a rapid rate.
(f) If the solution with the added oxytocin is infused fast enough to replace volume, then it is likely that the high dose of oxytocin may cause further hypotension.
(6) If oxytocin does not adequately stimulate uterine contraction, the next drug used is usually an ergot alkaloid (Methergine, Ergotrate).
(a) Because of their potent vascular effects, ergot alkaloids are not administered intravenously. Ergot alkaloids normally cause an increase in blood pressure, central venous pressure, and pulmonary capillary wedge pressure.
(b) IV administration may result in arterial and venous constriction, coronary artery constriction, severe hypertension, cerebral bleeding, headache, nausea, and vomiting.
(c) An intramuscular dose of 0.2 mg is commonly administered for stimulating uterine contractions.
(d) In some cases, the obstetrician may choose to administer oxytocin or ergotamine directly into the uterine muscle to maximize effect.
(e) Ergot alkaloids are metabolized and eliminated chiefly by the liver. The plasma half-life is approximately 2 hours, but uterine effects last much longer.
(f) Ergot alkaloids potentiate sympathomimetics, especially α-agonists (including ephedrine). Severe hypertension, cerebrovascular accidents, and retinal detachment have occurred when the two drugs were used simultaneously. These effects may persist even when the vasopressor is given well after the last dose of methylergonovine maleate.
(7) When the uterus does not contract well despite the use of oxytocin and ergot alkaloids, prostaglandin F 2a (hemabate; 250 mcg) is administered either intramuscularly or directly into the uterine muscle.
(a) Prostaglandins are potent stimulators of uterine contractions. The contractions induced by prostaglandins are strong and painful.
(b) Nausea, vomiting, and diarrhea are frequent side effects. In addition to causing uterine contractions, prostaglandins may cause hypotension by relaxing vascular smooth muscle; however, cases of severe hypertension after prostaglandin administration have also been reported.
(c) Prostaglandins may cause a recalcitrant uterus to contract and stop bleeding. If they do not, the surgeon is likely to extend the procedure and include hysterectomy, for which the anesthesia provider must be prepared.
e) Emergence from anesthesia
(1) Even with the administration of metoclopramide, the parturient often has a large volume of gastric contents. Suctioning of the stomach with an orogastric tube while the patient is anesthetized decreases the incidence of vomiting after awake extubation.
(2) Before extubation, the anesthesia provider should verify full recovery of neuromuscular function. Because cesarean section is usually a brief procedure involving fairly limited exposure to anesthetic, emergence is often quick. Advance preparation limits patient discomfort before extubation.
C Dilatation and Curettage
1. Introduction
Dilatation and curettage (D & C) involves dilation of the cervix and scraping of the endometrial lining of the uterus. The procedure is done to diagnose and treat uterine bleeding, cervical lesions, or stenosis. D & Cs are also used to complete an incomplete or missed abortion and are then boarded as suction D & Cs with the gestational week.
2. Preoperative assessment and patient preparation
a) History and physical examination: Assess for any cardiac, respiratory, neurologic, or renal abnormalities. Assess for a history of hiatal hernia or reflux; if a suction D & C, assess the gestational week; if greater than 16 weeks, consider the patient to have a full stomach.
b) Patient preparation
(1) Laboratory tests: Human chorionic gonadotropin, urinalysis, complete blood count
(2) Medications: Evaluation of any medications the patient is taking
(3) Intravenous therapy: One 18-gauge peripheral intravenous line
3. Room preparation
a) Monitoring equipment: Standard
b) Additional equipment: Bair Hugger
4. Perianesthetic management
a) Drugs: Anxiolytic agents (midazolam [Versed], 0.01 to 0.02 mg/kg), narcotics (fentanyl, 1 to 2 mcg/kg), oxytocin (Pitocin) for suction D & Cs, and induction agents (propofol, 2.5 mg/kg, or thiopental [Pentothal] 4 mg/kg) can be used.
b) This procedure can be done either with a short-acting spinal or saddle block with lidocaine, 7.5 to 10 mg, as a general anesthetic by mask, laryngeal mask airway, or with an endotracheal tube with inhalation agent/nitrous oxide or with heavy sedation (midazolam [Versed], fentanyl, and propofol).
c) Postoperatively, assess for bleeding, nausea, and cramping. Treat with narcotics, nonsteroidal antiinflammatory drugs, and antiemetics.
D Gynecologic Laparoscopy
1. Introduction
Laparoscopy is a common endoscopic technique in gynecologic procedures. It is frequently used to diagnose or treat pelvic conditions that may include sterilization, adhesions, pain, endometriosis, ectopic pregnancies, ovarian cysts and tumors, infertility, and vaginal hysterectomy. A pneumoperitoneum is achieved by insertion of a trocar and insufflation of carbon dioxide.
2. Preoperative assessment and patient preparation
a) History and physical examination: As indicated by the patient’s history and medical condition
b) Patient preparation
(1) Laboratory tests: Complete blood count and other tests as indicated
(2) Diagnostic tests: Pregnancy testing and as indicated
(3) Preoperative medications: As indicated
(4) Intravenous therapy: One or two 16- to 18-gauge intravenous catheters
3. Room preparation
a) Monitoring equipment: Standard
b) Additional equipment: Fluid warmer and Bair Hugger; other equipment as needed
c) Drugs
(1) Anesthetic and adjunct agents and antibiotics are used.
(2) Intravenous fluids: Depends on the procedure performed; calculate as indicated. Estimated blood loss is less than 50 to 100 mL.
(3) Blood: Type and screen.
(4) The tabletop is standard.
4. Perioperative management and anesthetic technique
General anesthesia is preferred.
a) Induction: Standard, as indicated
b) Maintenance: Inhalational agent/oxygen/opioid and nondepolarizing agent as indicated; antiemetics possible
c) Position: Lithotomy; Trendelenburg to improve pelvic exposure
d) Emergence: Standard
5. Postoperative implications
Complications include nausea, vomiting, and anemia.
E Hysterectomy: Vaginal or Total Abdominal
1. Introduction
Hysterectomy is commonly performed to treat uncontrolled uterine bleeding, dysmenorrhea, uterine myoma, gynecologic cancer, adhesions, endometriosis, and pelvic relaxation syndrome. Frequently, laparoscopy is used; for ovarian cancer prophylaxis, a bilateral salpingo-oophorectomy may be performed as well.
2. Preoperative assessment
a) History and physical examination: As indicated by the patient’s history and medical condition
b) Patient preparation
(1) Laboratory tests: These are as indicated by the patient’s history and medical condition.
(2) Diagnostic tests: These are as indicated by the patient’s history and medical condition.
(3) Preoperative medications: Anxiolytics are given as indicated; consider prophylaxis for postoperative nausea and vomiting.
(4) Intravenous therapy: Two 16- to 18-gauge intravenous lines are used; consider a central line and/or an arterial line if the procedure is radical.
(5) An epidural catheter may be placed for intraoperative or postoperative pain relief.
3. Room preparation
a) Monitoring equipment is standard.
b) Consider an arterial line and central venous pressure catheter if large blood loss is expected.
c) Additional equipment includes a fluid warmer and Bair Hugger.
d) Drugs
(1) Anesthetic and adjunct agents and antibiotics are used.
(2) Intravenous fluids: For vaginal hysterectomy, calculate for moderate blood loss; crystalloids at 4 to 6 mL/kg/hr. Estimated blood loss is 750 to 1000 mL. For abdominal hysterectomy, calculate for a moderate to large blood loss; crystalloids at 6 to 10 mL/kg/hour. Estimated blood loss is 1000 to 1500 mL.
(3) Blood: Type and crossmatch for 2 to 4 units of packed red blood cells.
(4) The tabletop is standard.
4. Perioperative management and anesthetic technique
General or regional anesthesia is used, with a subarachnoid block or epidural with a sensory level of anesthesia of T6 to T8.
a) Induction: Standard, with the choice as indicated
b) Maintenance
(1) General anesthesia: Inhalational agent/oxygen/opioid/anxiolytic and nondepolarizing muscle relaxant
(2) Regional: Local anesthetic of choice; supplemental anxiolytic and sedation
(3) Position: Abdominal, supine; vaginal, lithotomy
c) Emergence: Standard
5. Postoperative implications
a) Complications: Nausea, vomiting, anemia
b) Pain management: Patient-controlled analgesia; epidural opiates or an epidural local anesthetic such as 0.125% or 0.25% bupivacaine (Marcaine), with fentanyl, 1 mcg/mL at an infusion of 8 to 10 mL/hr.
F Loop Electrosurgical Excision Procedure
1. Introduction
The loop electrosurgical excision procedure is performed for the diagnosis and treatment of cervical intraepithelial neoplasia. This form of electrosurgery uses a loop electrode for excision and fulguration to prevent cervical bleeding. Other types of therapy that may be used to ablate cervical lesions are cryosurgery and carbon dioxide laser surgery.
2. Preoperative assessment and patient preparation
a) History and physical examination: As indicated by the patient’s history and medical condition
b) Patient preparation
(1) Laboratory tests: Pregnancy test, hemoglobin and hematocrit, urinalysis
(2) Preoperative medications: Anxiolytics possible if the patient is not pregnant (e.g., midazolam, 0.01 to 0.02 mg/kg)
(3) Intravenous therapy: One 18-gauge intravenous catheter
