Spinal Anesthesia in Obstetrics -- New Concepts and Developments

William Camann, MD


November 26, 2003

In This Article


Spinal anesthesia was developed in the latter part of the last century when the German physicians Bier and Hildebrandt injected cocaine into their own cerebrospinal fluids. They experienced varying degrees of loss of sensation and the unpleasant side effect of "spinal headache," also known as postdural puncture headache (PDPH). Since then, spinal anesthesia has undergone periods of popularity and disfavor. Its use in obstetrics has been a blessing in many circumstances, but has created some problems in others. This brief review considers the current state-of-the-art of spinal anesthesia and its use in obstetric pain relief.

This technique, also known as CSE, combines the advantages of the long popular epidural anesthesia with the additional advantages of spinal injection. Technically, it involves placing a needle into the epidural space, followed by passage of another, small-gauge needle into the spinal space. Miniscule amounts of drug are needed to provide good effect when the spinal route is used. A small amount of drug (typically a combination of a local anesthetic such as bupivacaine and a narcotic such as fentanyl) is injected; then a flexible plastic catheter is inserted into the epidural space for additional drug injection.

The main advantage of CSE is the extremely rapid onset of pain relief when drugs are injected into the cerebrospinal fluid. Typically, laboring patients have full relief from contraction pain within 2-4 minutes after injection. Another advantage is that the small amount of drug generally results in little or no motor blockade of the lower extremities. The ability to retain motor power is of great benefit if the patient wishes to ambulate during labor. Moreover, the ability to push is retained if the block is administered in late stages of labor, which allows minimal interference with expulsive forces during the second stage of labor. The spinal injection is time-limited: most of these blocks will be effective for roughly 2 hours. The presence of the epidural catheter allows for further drug administration to extend the duration of the pain relief for as long as necessary during labor. The rapid onset of pain relief and the flexibility of the epidural catheter have made CSE a very popular choice in many obstetric units today. Maternal satisfaction is very high, and the additional cost of the technique is minimal.

CSE is not free of side effects. PDPH is a concern. However, the majority of these blocks are performed with very small-gauge needles; thus, the headache rate is generally < 1%. Opioid-induced pruritus and nausea are seen in roughly 20% to 40% of the patients, but these side effects are usually mild, well tolerated, and transient. More serious side effects such as respiratory depression are rare.


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