Accidental Total Spinal Anesthesia
Definition:
➧ A syndrome of the central neurological blockade.
➧ It occurs when a volume of local anesthetic (LA) solution, intended for epidural anesthesia, enters the subarachnoid space and ascends to the cervical region.
Causes:
a) After a known dural tap:
➧ Accidental total spinal analgesia may occur in association with the original epidural after a known dural tap.
b) After a top-up dose:
➧ Following a top-up dose, as a result of accidental puncture of the dura by the epidural catheter.
➧ High spinal anesthesia has occurred after top-ups of epidural catheters.
➧ This is unlikely to result from catheter migration but may happen as a result of accidental puncture of the dura by the epidural catheter.
➧ If part of the catheter lies within the epidural space and part within the subarachnoid, with a slow injection of LA, the solution will emerge from the proximal holes, and with a rapid one from the more distal.
Presentation:
1-Unexpected rapid rise in the sensory level.
2-Numbness or weakness in the upper extremities.
3-There is severe hypotension and bradycardia secondary to blockade of the sympathetic outflow. Occasionally cardiac arrest occurs.
4-Rapidly increasing paralysis involves the respiratory muscles, due to phrenic nerve paralysis, resulting in apnea and hypoxia.
5-The pupils become dilated and consciousness is lost.
6-Cardiovascular collapse usually takes place immediately after the injection, although delays of up to 45 min. have been reported.
7-Deaths have occasionally been reported.
Duration:
➧ Apnea may vary from 20 min. to 6 h, unconsciousness from 25 min. to 4 h, while full recovery of sensation may take up to 9 h.
➧ The lengths of time vary with the agent, the dose, and the volume of LA given. Bupivacaine lasts longer than lidocaine.
Management:
a) Precautions:
1-A test dose of LA is recommended.
2-The injection of 3 ml of LA containing epinephrine 1:200 000, followed by an adequate pause to assess the effects, has been suggested.
3-It has been recommended that, if a dural puncture occurs during active labor when a cesarean section is required, then further attempts should not be made. Either a spinal or a general anesthetic should be employed as an alternative.
b) If Total Spinal a. occurs:
1-Call for help.
2-A non-pregnant patient should be turned supine, and the legs elevated to encourage venous return. The pregnant patient should be tilted in the lateral position to prevent aortocaval compression
3-The lungs should be inflated with oxygen
4-A tracheal tube can then be inserted. IPPV may have to be continued for up to 2 h, depending upon the LA and the volume used
5-Intravenous fluids should be infused rapidly
6-A vasopressor agent such as Ephedrine IV in 5–10 mg increments up to 30 mg is recommended. Epinephrine (adrenaline) 0.1–0.5 mg may occasionally be required but should preferably be avoided in patients in labor
7-Atropine for bradycardia, use epinephrine if the patient is unstable
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