Anesth Analg 2000;90:1241-1243
© 2000 International Anesthesia Research Society
CASE REPORTS
Obstetric Anesthesiology in the New Millennium
David J. Birnbach, MD
Department of Anesthesiology, St. Luke’s Roosevelt Hospital Center, Columbia University, New York, New York
Address correspondence and reprint requests to David J. Birnbach, MD, Department of Anesthesiology, St. Luke’s Roosevelt Hospital Center, 1000 Tenth Ave., New York, NY 10019.
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Introduction
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The past decade has seen major changes in the practice of obstetric anesthesiology, as evidenced by an improved understanding by anesthesiologists of the many disease entities seen in obstetric patients, as well as by the enhancements of new techniques and drugs. Recent advances in the practice of this specialty include the refinement of the combined spinal-epidural (CSE) technique for both labor analgesia and cesarean delivery, the use of continuous infusions of dilute solution of local anesthetics combined with opioids for labor analgesia, patient-controlled epidural analgesia (PCEA), the development of multi-orifice epidural catheters, the dramatic increase in the use of subarachnoid anesthesia for elective cesarean delivery, and the introduction of new amide local anesthetics. Because of the tremendous increase in the application of neuraxial techniques for labor analgesia and the increased use of spinal anesthesia, the administration of general anesthesia for cesarean delivery has dramatically decreased (1). In addition, a new philosophy of labor analgesia has evolved. Women in labor and their obstetricians are no longer seeking or expecting labor "anesthesia," but rather, "analgesia," and more women are requesting to ambulate while in labor. As our labor analgesia practice has changed, the debate regarding the influence of epidural analgesia on the course of labor has also evolved, with new studies suggesting that epidurals do not necessarily affect the rate of cesarean delivery (2,3).
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Labor Analgesia
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The past decade has brought about a global acceptance of the fact that labor results in severe pain for most women, and that there are now safe and effective means to reduce that pain. The ideal technique should dramatically reduce the pain of labor, while allowing the parturient to actively participate in the birthing experience. Today’s new techniques approach this laudable goal. Of all of the possible methods of pain relief now being used in labor, neuraxial blockade provides the most effective and least depressant analgesia.
Epidural analgesia provides excellent pain relief and the ability to extend the duration of the block to match the duration of labor, but its use in the past was sometimes problematic because of the potential for the development of motor block. The use of continuous infusions of dilute solutions of local anesthetics with opioids has overcome many of the problems associated with intermittent bolus techniques. This practice has allowed anesthesiologists to administer more dilute solutions of drug that provide satisfactory analgesia without appreciable motor block, and this has been associated with greater patient satisfaction (4). The advancements in spinal needle design have helped in the evolution of the CSE technique, which combines the advantages of spinal analgesia (speed of onset, lack of motor block) with the additional flexibility provided by the epidural catheter (5). The administration of spinal fentanyl or sufentanil produces immediate pain relief without motor block. Although 10 µg of intrathecal sufentanil is a safe and effective dose for labor analgesia (6), recent studies suggest that smaller doses (2.5–5 µg) when combined with bupivacaine produce adequate analgesia with fewer side effects (7,8). The use of PCEA has given some women a feeling of greater control of their birthing process (9). Multiorificed epidural catheters are now available and may improve epidural outcome and safety as a result of a greater likelihood of positive aspiration of an intravascular catheter (10) and by decreasing the number of failed blocks (11). Optimum insertion of the epidural catheter has also helped prevent failed blocks (12). These tangible benefits, and the growing discussion of labor analgesia in the lay press, have produced a near exponential increase in the use of neuraxial labor analgesia, to the point where most American parturients in labor are now receiving neuraxial analgesia (1).
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Anesthesia for Cesarean Delivery
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Pencil-point "atraumatic" spinal needles are now associated with an "inconsequential" incidence of spinal headache (13) and a high degree of success and have thus been an important factor in the resurgence of spinal and CSE techniques for cesarean delivery. Spinal has become the preferred method for elective cesarean delivery because of the simplicity of the technique and the speed of onset of a dense block. In addition, because such small doses of local anesthetic are needed, there is minimal transfer of the drug to the fetus and no risk of maternal systemic local anesthetic toxicity. Hypotension, despite left uterine displacement and IV hydration (14), continues to occur after spinal anesthesia and may produce nausea and vomiting, in addition to fetal acidosis. Recent evidence, however, suggests that using less spinal medication can achieve satisfactory anesthesia and reduce the incidence and severity of hypotension (15). If small-dose spinal is administered via a CSE technique, the epidural catheter can be used if supplementation of the block becomes necessary. Additionally, the prophylactic use of metoclopramide or acupressure may also decrease the incidence of hypotension-induced nausea and vomiting during cesarean delivery (16).
If a parturient who has a functioning epidural catheter for labor requires a cesarean delivery the labor epidural can be reinforced for operative use. The deaths caused by epidural 0.75% bupivacaine in the early 1980s (17), caused a change in practice, including the discontinuation of use of 0.75% bupivacaine in obstetric patients, the use of epidural test doses, and incremental dosing of epidural catheters. Recently, it has been suggested that because aspiration reliably detects most IV multiorifice epidural catheters, test doses are unnecessary (10). This view is somewhat controversial, however, and many anesthesiologists continue to prefer a formal epinephrine-containing test dose (18). Two new drugs have recently appeared on the horizon for increasing the safety of local anesthetics. Ropivacaine, a homolog of mepivacaine and bupivacaine, was the first single S isomer formulation to be marketed for clinical use. Recent studies suggest that it produces an epidural block that is indistinguishable from that of bupivacaine (19). Because the potency of ropivacaine has been reported to be less than that of bupivacaine (20), it may be that any benefits for reduced cardiotoxicity will come at the expense of efficacy. These potency issues must be resolved before the toxicity question can be answered. Levobupivacaine, the single levo isomer of bupivacaine, has recently received Food and Drug Administration approval, and is currently being investigated for clinical use in obstetrics. Its potential advantage is that it produces a differential block that appears to be equipotent to bupivacaine (21), but has a lower potential for cardiotoxicity (22).
The use of general anesthesia for cesarean delivery, although still necessary for some obstetric emergencies and the rare patient with a contraindication to regional anesthesia, has decreased dramatically. Recent evidence suggests that most maternal deaths caused by anesthesia occurred during general anesthesia for cesarean delivery. Regional anesthesia is not without risk, however, primarily because of the toxicity of local anesthetics and excessively high regional blocks. The incidence of these regional anesthesia-related deaths is decreasing, whereas the number of deaths caused by general anesthesia remains about the same (23).
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The Future
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The future of continuous spinal anesthesia (CSA) with microcatheters had a setback following the Food and Drug Administration withdrawal of these catheters in the early 1990s. However, an ongoing multi-institutional study evaluating the use of spinal microcatheters for labor has been reassuring (24). Because this study is still in progress, it is too early to draw conclusions regarding the future of CSA for labor. However, many are hopeful that the new millennium will see the return of CSA, using 21st century approaches to an old problem.
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Footnotes
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DJB is the Section Editor for Obstetric Anesthesiology.
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References
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Accepted for publication February 25, 2000.
This article has been cited by other articles:
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F. A. Chervenak, L. B. McCullough, and D. J. Birnbach
Ethics: An Essential Dimension of Clinical Obstetric Anesthesia
Anesth. Analg.,
May 1, 2003;
96(5):
1480 - 1485.
[Full Text]
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Introduction
Labor Analgesia
