Letter to the Editor: In Response
We appreciate Dr. Colclough's thoughtful letter about our paper comparing spinal and epidural anesthesia for cesarean section. However, we disagree with him on several of the issues he raises. Our data and that of other investigators (cited in our paper) demonstrate that spinal anesthesia for cesarean section is faster to perform and has fewer complications, and that patients may experience less discomfort intraoperatively.
Dr. Colclough states that many anesthesiologists can place a needle in the epidural space more quickly than they can place a small-gauge spinal needle into the cerebrospinal fluid. We doubt this is the case and are unaware of any research supporting this statement. However, even if an epidural needle can be properly positioned faster than a spinal needle, the rest of the spinal anesthetic procedure can be performed much more quickly. The mechanics of performing a safe epidural block (even when the initial dose is administered through the needle) include giving a test dose, waiting 3 to 4 min to observe the patient before further dosing, fractionating the local anesthetic dose over several minutes, and then threading the catheter. Administering a bolus of even a relatively nontoxic local anesthetic such as chloroprocaine is inappropriate, except in extreme emergencies. Furthermore, in our experience, 20 mL of chloroprocaine does not always produce an adequate block, necessitating further dosing and delay. We agree with Dr. Colclough that continuous epidural anesthesia is inherently more versatile than spinal anesthesia, but believe that the "one-shot" epidural technique he describes lacks versatility until the catheter has been tested and confirmed to be correctly sited. This would require injection of a second test dose via the catheter, causing additional delay.
Perhaps the most compelling argument favoring spinal anesthesia is the decreased incidence of potential complications. When giving local anesthetics into the epidural space, drug may be injected into either the intravascular or intrathecal space with disastrous results. Even when correctly deposited in the epidural space, maldistribution of drug may leave some nerve roots unblocked, causing a failed block.
In summary, we believe our data support our conclusions. The increasing use of spinal anesthesia for cesarean section in major obstetric centers throughout the world similarly reflects the experience that failure and complications occur less frequently than with epidural anesthesia. We encourage others to critically review their practice. We especially invite practitioners in nonteaching centers to conduct similar studies to see whether the trends we report hold true in the general community.
Edward T. Riley, MD
Sheila E. Cohen, MB, ChB
Alex Macario, MD
Emily F. Ratner, MD
Department of Anesthesia, Stanford University School of Medicine, Stanford, CA 94305-5117