GYNECOLOGIC ANESTHESIA
• Many office procedures & selected transvaginal operations may be performed under local anesthesia, w/ or w/o sedation/analgesia
Examples: Loop electrosurgical excision procedures, 1st trimester dilation & curettage, hysteroscopy, endometrial ablation
Technique: Paracervical block or intracervical block
• Local anesthetic toxicity
Tox usually occurs following inadvertent intravascular injection
CNS effects typically precede CV effects
CNS: Prodrome of excitation, ringing in ears, perioral numbness, confusion; followed by convulsions; followed by coma
CV: Initial HTN, tachy; followed by HoTN, arrhythmias, cardiac arrest
Exception: Bupivacaine-cardiotoxicity predominates; prolonged Na+ channel blockage
Epi may be added to ↓ overall uptake & allow increased local effect.
Contraindications to use of epi exist. Cardiac: HTN, CHF, arrhythmias, MI. Other relative contraindications: Tricyclic antidepressant use, MAOI use, beta blockade, cocaine use, hyperthyroidism, asthma, diabetes
• Laparoscopic & prolonged gynecologic surgeries usually performed under GA
Laparoscopic procedures require complete relaxation of abdominal wall (ie, paralysis)
Std anesthesia techniques & precautions apply
Many laparoscopic procedures require prolonged Trendelenburg positioning for access to pelvis; in some pts, this may cause hemodynamic compromise, difficulty ventilating
• Transvaginal procedures & many abdominal procedures may be performed under neuraxial anesthesia/sedation, particularly if pt not candidate for GA due to medical comorbidities (though precludes use of paralytics)
Examples: Dilation & curettage/evacuation, operative hysteroscopy, vaginal hysterectomy or abdominal hysterectomy in pts not candidates for GA
• Both minilaparotomies & some laparoscopic procedures (most commonly sterilization) may be performed under sedation w/ local anesthesia only
PARENTERAL ANALGESIA IN OBSTETRICS
• All nonneuraxial methods provide only partial relief of labor pain.
May help laboring women cope w/ pain
Useful in cases of absolute contraindication to or pt refusal of neuraxial anesthesia
• Opioids act as opioid receptor agonists: Mu, kappa, delta
G-protein–coupled receptors → ↓ intracellular Ca → inhibition of release of pain neurotransmitters. Distributed through brain, terminal axons of spinal cord afferents
• Xfer across the placenta is rapid & signif; fetal effects may limit use
Drug xfer affected by prot binding capacity, size, ionization
In general, all local anesthetics & opioids transfuse freely across the placenta
Fetal acidosis results in ion trapping → fetal drug accum
• Side effects of systemic opioids
Maternal: Sedation, respiratory depression, N/V
Fetal: Decreased fetal HR variability during labor; pseudosinusoidal HR pattern, respiratory depression at birth. Use short-acting opioid w/ no active metabolites, if poss. Monit fetus continuously during administration of systemic opioids. Avoid administration shortly before deliv.
• Sedatives: Do not provide analgesia; typical use is for sleep/relaxation in latent labor
NEURAXIAL ANESTHESIA IN OBSTETRICS
• Most effective method for labor pain
• Also std for C/S, postpartum tubal ligations, urgent postpartum procedures whenever poss
• Indications for spinal/epidural anesthesia in labor
Maternal request
Anticipation of operative vaginal deliv or shoulder dystocia; breech extraction; high risk of C/S; Risk of hemorrhage; difficult intubation
Maternal condition where signif pain or stress would create medical risk (eg, sev respiratory or cardiac dz)
Maternal condition which could worsen & potentially limit use of neuraxial anesthesia later in labor course (eg, worsening thrombocytopenia or coagulopathy)
• Contraindications to spinal/epidural anesthesia in labor
Absolute: Maternal refusal, uncooperative pt; soft tissue infxn of site; uncorrected hypovolemia; uncorrected therapeutic anticoagulation; Lovenox w/i 24 h; certain spinal conditions (eg, ependymoma); sev thrombocytopenia (<50 K)
Relative: Certain spinal conditions (eg, discectomy, rod fusion); mod thrombocytopenia (<75 K); LP shunt, some neurologic dzs (ie, multiple sclerosis); fixed cardiac output conditions (ie, AS)
• Types of neuraxial blocks: Spinal, epidural, & CSE
Spinal:
Anesthetic/opioid delivered directly into spinal fluid w/ needle through dural puncture
Benefits: Rapid onset (2 min); 1/20 epidural dose used so less risk tox
Disadvantages: Limited duration (1–1.5 h)
Epidural:
Anesthetic/opioid delivered into epidural space via continuous infusion through catheter
Benefits: Ability to continuously infuse & adjust dosage as needed; pt controlled
Disadvantages: Slower onset (20 min), larger doses used (20× spinal doses)
CSE:
Meds delivered directly into spinal fluid, then catheter placed in epidural space
Benefit: Combination of rapid onset & ability to continuously infuse
Disadvantages: More technically challenging than epidural or spinal alone; increased risk of PDPH compared to spinal alone
Figure 4.1 Epidural block
LOCAL ANESTHETICS IN OBSTETRICS
• Indications for local anesthetics
Skin infiltration for episiotomies/assisted deliveries (nonemergent settings), laceration repair
Nerve blocks: Pudendal, paracervical (close proximity to large vessels → higher potential for tox)
Spinal & epidural anesthesia
• In an emergent setting where access to general anesthesia will be delayed, local anesthetics may be administered in large amts to perform C/S, followed by general anesthesia when available
Figure 4.2 Pudendal block
NONPHARMACOLOGIC ANALGESIA IN OBSTETRICS
• Advantages: Empowering, few side effects, may improve overall satisfaction w/ labor experience
• Disadvantages: Incomplete relief, pts may perceive eventual pharm rx as failure
• Evid: Many nonpharmacologic methods have not been well studied
GENERAL ANESTHESIA IN OBSTETRICS
• Rarely indicated for vaginal deliv except for emergent, unanticipated procedures (eg, breech extraction, internal version, shoulder dystocia)
• In US, 10% of C/S are performed under general anesthesia (Anesthesiology 2005;103:645)
Emergent (“crash”) C/Ss are the most common setting for general anesthesia
Other situations include nonemergent C/S in a pt w/ absolute contraindications to neuraxial anesthesia
Advantages: Rapid, complete anesthesia; ability to administer 100% oxygen
Disadvantages: Risk of difficult intubation; risk of aspiration; small risk of infant respiratory depression; anesthetics cause uterine atony, leading to more bld loss
• Other uses:
Uterine inversion: Obstetric emergency where body of uterus inverts following deliv
Nitric oxide or halogenated anesthetics relax uterus & facilitate replacement. Nitroglycerine may be given IV/sublingually if delay in general anesthesia is anticipated.
Can be considered in cases of retained placenta due to bandl’s ring or head entrapment for breech extraction; must balance w/ risk of uterine atony
POSTOPERATIVE PAIN MANAGEMENT
• Post C/S pain include visceral (uterus) & somatic pain (abdominal wall).
• Multimodal rx regimens
Goals: (1) Adequate pain control, (2) ↓ opioids to ↓ assoc side effects such as N/V, ileus, sedation, & effects on infant via secretion of active compounds into breast milk
• Oral pain meds – preferred mgmt once pt is tolerating PO
Opioids – carry above side effects
NSAIDs – important adjuvant therapy to reduce opioid exposure
Esp effective on visceral pain from uterine involution
Also available as 12 h IV formulation (ketorolac) for up to 4 doses postop
Breast-feeding: Opioids & NSAIDs considered generally compatible w/ breast-feeding
Exception: Meperidine – prolonged infant sedation by active metabolite normeperidine
• Postpartum bilateral tubal ligation:
Avoid long-acting intrathecal/epidural opioid/local anesthetic if goal is discharge soon after procedure. Infiltration of skin, fallopian tubes w/ local anesthetic shown to ↓ total analgesic use, ↑ time to analgesic use postoperatively. Sufentanil, bupivacaine, lidocaine all effective.