60Pain Relief for Labor and Delivery
Obstetric Anesthesia61 Recommended Clinical Scenarios for Spinal Analgesia
Most often, the use of a continuous spinal technique for labor analge- sia is a consequence of diffi culty placing an epidural catheter, and the decision to use the catheter via the spinal route. Such scenarios might include:
Unintentional dural puncture in parturients that are nearing delivery
•
(multiparous women presenting in late phase labor).
Unintentional dural puncture during diffi cult placement (multiple
•
attempts in a morbidly obese patient or a patient with previous scoliosis surgery).
Unintentional dural puncture in a patient with an anticipated diffi -
•
cult airway.
Planned use of a continuous spinal technique can be useful in several clinical scenarios:
The patient with prior back surgery who desires regional analgesia
•
for labor, or anesthesia for surgical delivery. Even if an epidural catheter can be placed in such patients, the spread of local anes- thetic may be inadequate, resulting in an unacceptable block.
The patient considered likely to be extremely diffi cult or impossible
•
to intubate, secondary to deformity or airway anomaly. A planned continuous spinal anesthetic in these patients is a means of minimiz- ing the risk of losing the airway should emergent operative delivery be required.
Continuous spinal anesthesia can reduce the likelihood of a high spinal block from a one-shot spinal technique, by allowing for the careful titration of the anesthetic to a desired sensory dermatomal level.
In all cases the “spinal catheter” should be boldly marked to clearly stand out from a regular epidural catheter, properly documented on the anesthesia record, and all anesthesia providers in the labor suite should be personally notifi ed.
The potential for accidental administration of epidural doses into
•
the CSF or inaccurate dosing into the spinal catheter increases the available in the United States. As a consequence, relatively large gauge epidural catheters must be used for continuous spinal tech- niques and these catheters increase the likelihood of a post-dural puncture headache.
62Pain Relief for Labor and Delivery
likelihood of a high spinal block. A high spinal block in the uncon- trolled setting of a labor room potentially increases the risks of catastrophic loss of airway.
Recommended dosing regimens are outlined in Table 3.12 . Caution must be used when administering opioids, as repeat doses may increase the risk of respiratory depression. With the intermittent bolus technique, the catheter should be fl ushed after each injection with a 2 ml bolus, since the epidural catheter and fi lter may contain up to 1 ml of dead space.
Anesthesia for Vaginal Delivery
Vaginal Delivery
Pain during early labor is primarily visceral in nature, and nociceptive input enters the spinal cord at the T 10 –L 1 levels. As labor progresses, pain arises due to stimulation of spinal cord at S 2 –S 4 (the pudendal nerve). These dual pain pathways result in varying analgesic require- ments over the course of labor and during delivery. It is not uncom- mon for patients to experience increasing rectal pressure or perineal pain (sacral sparing) as labor progresses. The S 2 –S 4 nerve roots are relatively large, and may require higher concentrations of local anes- thetic to anesthetize than thoracic or lumbar nerve roots.
Table 3.12 Recommended Solutions for Maintenance of Spinal Catheter Analgesia
Technique Solution ∗ Labor
Analgesia:
Intermittent Bolus:
0.25 % Bupivacaine 1.75–2.5 mg + Fentanyl 15–20 mcg as needed (CSE doses every 1–2 hours)
Continuous Infusion:
0.05 % –0.125 % Bupivacaine + Fentanyl 2–5 mcg/ml @ 0.5–3.0 ml/hr and titrated to a T 10 block
Surgical Anesthesia:
Preservative free 0.5 % Bupivacaine 5.0 mg (1 ml) + Fentanyl 15 mcg for the initial dose followed by 0.5 ml boluses of 0.5 % bupivacaine (2.5 mg) every 5 min until the desired block height is obtained. Repeat the 0.5 ml bupivacaine dose as needed to maintain the desired block height
∗ The epidural catheter and fi lter has > 1 ml of dead space; therefore, a continuous spinal catheter should be fl ushed with 2 ml of saline after each bolus dose.
Obstetric Anesthesia63 Treatment for Breakthrough Pain during Labor
Administer 5–10 ml of epidural 0.125
• % –0.25 % bupivacaine with
fentanyl 25 mcg.
If ineffective, administer 5–10 ml of 2
• % lidocaine with fentanyl
25 mcg.
If discomfort persists, withdraw the epidural catheter so that 3–4 cm
•
remains within the epidural space and administer additional local anesthetic.
For vaginal delivery, perineal analgesia can usually be produced with
•
5–15 ml of either 2 % lidocaine or 2 % chloroprocaine (Table 3.13 ).
Forceps or Vacuum Assisted Delivery
Indications for assisted vaginal delivery include maternal exhaustion, cardiovascular or neurologic disorders that preclude maternal pushing, fetal distress, arrested rotation and abnormal fetal position.
Forceps deliveries are classifi ed as either outlet, low, mid, or high
•
depending on the relation of the fetal head to the introitus and ischial spines, although high forceps deliveries are almost never indicated.
Anesthetic requirements vary with the type of forceps delivery attempted. In general, higher fetal stations and rotation of the fetal head require more force by the obstetrician for delivery, which in turn increases the risk of fetal and maternal complications, as well as anesthetic requirements.
Anesthesia Requirements for Forceps or Vacuum Delivery
The dilute local anesthetic solutions used to provide labor analgesia are usually insuffi cient for forceps delivery. For outlet or low forceps, a dense T 10 sensory block will usually suffi ce.
Table 3.13 Recommended Epidural Local Anesthetics for Vaginal or Assisted Vaginal Delivery
Perineal (Sitting) Solution
Outlet Forceps
Mid Forceps
Initial Volume ∗
Agent % % % (ml)
Lidocaine 2 2 2 10–15
Chloroprocaine 2 2 3 10–15
Bupivacaine 0.25 0.25–0.5 0.5 10–15
∗ Volume should be varied to individual patient requirements. A dense T 10 sensory block is desirable for vaginal deliveries or low-risk assisted vaginal deliveries, while a dense T 6 sensory and motor block is desirable for a mid-forceps trial.
64Pain Relief for Labor and Delivery
Mid-forceps delivery with head rotation (mid-forceps trial) typically
•
requires a dense T 6 sensory block.
Mid-forceps trials can result in prolonged fetal bradycardia, requir-
•
ing cesarean section.
Consider attempting a mid-forceps trial in the operating room
•
prepared for an operative delivery (double set-up) rather than in the labor room.
3
• % chloroprocaine 15–20 ml should produce suffi cient anesthesia for the forceps trial, and for a lower abdominal incision should an emergent cesarean section be required.
Vacuum deliveries generally require anesthetic levels similar to those of low and outlet forceps.
Each patient should be evaluated individually, and the dose of local
•
anesthetic titrated to effect.