I. Problem: Failure to Place:
Cause:
1. Anatomic location difficult to find.
2. Flexible, small spinal needle bends away from dural sac (Chapter 59).
3. Inadequate needle length, especially when using introducer (Chapter 105).
Prevention:
1. Use longer or stiffer (larger) spinal needle.
2. Sitting posture may be helpful for anatomic localisation of the space.
Management:
1. Switch to epidural anesthesia (stiffer needle).
2. Switch to general anesthesia.
3. Local infiltration or pudendal block if vaginal delivery planned.
II. Problem: Inadequate anesthesia: missed segment, "hot spot".
Cause:
1. "Scarring" about nerve rootlets,
2. Poor distribution of local anesthetic, etc.
Prevention:
?Not preventable.
Management:
1. Use larger dose of local anesthetic and/or add narcotic to spinal anesthetic.
2. Have surgeon inject local anesthetic in area.
3. IV or inhalational analgesic supplementation.
4. If 1, 2, or 3 not adequate, go to general anesthesia.
III. Problem: Inadequate anesthesia: not dense enough or not high enough.
Cause:
1. Inadequate dose (mg) of local anesthetic (Chapter 78).
2. Inadequate volume (mls) of local anesthetic.
3. Inadequate spread, especially with hyperbaric solution (Figure 30.1).
4. Injection of local anesthetic partially in and out of dural sac (multicompartment block, Chapter 11).
5. Slow onset of block.
Prevention:
1. Use adequate dose of local anesthetic (bupivacaine 12 to 15mg; tetracaine 10 to 13mg; lidocaine 75 to 100mg).
2. Use adequate volume (1.5 to 3.5ml).
3. Advance spinal needle 1mm more after apparent puncture, rotate spinal needle 180-360 degrees to further assure tip and bevel within subarachnoid space (Figure E.1).
4. Adding narcotic to local anesthetic may help, but should not be relied upon for anesthesia (Chapter 61).
Management:
1. If incision not made and time allows, spinal may be repeated: use full dose.
2. If time since injection less than 12 minutes, upper level may be enhanced by having patient cough, especially if isobaric solution has been used.
3. It is usually necessary to use some head down tilt to achieve an adequate level with hyperbaric solutions (Chapter 30) (Figure 30.1).
4. If slow onset suspected, wait 3 minutes more if situation allows.
5. If incision made or emergency situation, supplement with IV and/or inhalation, or go to general anesthesia (dependent on degree of inadequacy of block).
IV. Problem: Inadequate duration:
Cause:
1. Surgery lasting longer than duration of local anesthetic action: May be due to surgical reasons, inadequate initial dose, or inappropriate choice of local anesthetic agent.
Prevention:
1. Select local anesthetic to provide 1.5 times expected length of procedure.
2. Consider addition of epinephrine or phenylephrine to spinal solution (Chapter 5), and/or
3. Consider addition of narcotic to spinal solution (may increase duration).
Management:
1. IV and/or inhalation supplementation if inadequacy mild.
2. General anesthesia if inadequacy moderate to severe and/or expected further duration unpredictable.