Epidural Analgesia

Jean Enthuse Sicard^[271] (1872–1929) and Fernand Cathelin^[272] (1873–1945) independently introduced cocaine through the sacral hiatus in 1901, becoming the first practitioners of caudal (epidural) anesthesia. Sicard was a neurologist and used the technique to treat sciatica and tabes, but Cathelin used the technique for surgical anesthesia. Arthur Läwen^[273] (1876–1958), a pupil of Heinrich Braun (1862–1934) and an early proponent of regional anesthesia, successfully used caudal anesthesia with large volumes of procaine for pelvic surgery. It soon became apparent that caudal anesthesia was sufficient for operations on the perineum, but the drug would have to be deposited into the epidural space at higher levels if the surgeon anticipated operating on the abdomen or thorax. Initial attempts to provide epidural anesthesia through needles placed at higher levels were unsuccessful. B. Heile^[274] published an extensive study of the epidural space in 1913, but the focus of his final report was on the treatment of neurologic conditions through epidural injections. His unique approach was to enter the epidural space through the intervertebral foramina (a technique that has recently been revived). Tuffier^[275] was aware of the need for entry at higher levels but was unable to perfect a reliable technique for lumbar or thoracic epidural injections.

In 1921, Fidel Pagés^[276] (1886–1923), a Spanish military surgeon, devised a technique to introduce epidural procaine at all levels of the neuraxis. His method was to use a blunt needle and then feel and hear the entry of the needle through the ligamentum flavum. His report of 43 cases of lumbar and thoracic epidural anesthetics represents a landmark article that went unnoticed because of its publication in an obscure medical journal. Pagés died in an automobile accident soon after his report on epidural analgesia, and no students at the time had learned his technique. Pagés had the idea to produce segmental anesthesia through epidural injections, avoiding some of the side effects of complete neuraxial block, which occurred after high subarachnoid administration of local anesthetics. He provided the anesthetics himself and then performed the operations, noting that much time was saved with the epidural technique compared with general anesthesia. Of the 43 cases, it appears that one subject received a total spinal anesthetic but survived after assisted ventilation.

Achille Mario Dogliotti^[277] (1897–1966) (see Fig. 1-11D ) described epidural injections of local anesthetics in 1931, apparently without prior knowledge of the work of Pagés. Dogliotti performed extensive studies to determine the spread of solutions within the epidural and paravertebral space after injection. His work launched one of the most valuable techniques in the modern practice of anesthesiology. An important innovation was Dogliotti's method of identification of the epidural space. His 1939 textbook illustrates the use of continuous pressure on the plunger of a saline-filled syringe as the needle is advanced through the ligamentous structures. In contrast to the methods of Corning and Pagés, the Dogliotti technique was reproducible and easily learned. Dogliotti also observed the extent and duration of analgesia after injection into various spinal interspaces.

Initial acceptance of epidural analgesia was slow to develop in North America, although it gained early acceptance in Europe and South America. A. Gutierrez of Argentina became an enthusiastic advocate for the epidural method and collected valuable data on a large series of successful epidural anesthetics. He also developed the "hanging drop" sign that is still used by some anesthesiologists to identify the epidural space.^[278] Dogliotti's anesthesia textbook^[279] was translated into English in 1939 and contained an extensive chapter on epidural analgesia. Textbooks by American authors several years later^{[197] [280]} contained only a short description of the technique, treating it as a novelty practiced only by those with special expertise. There were some early practitioners of epidural anesthesia in North America. Charles B. Odom of New Orleans published 285 cases of lumbar epidural anesthesia in 1936 and introduced the concept of a test dose to detect intrathecal injection.^[281] In Odom's series, there was one death attributed to the poor condition of the patient. John R. Harger and coworkers^[282] of Cook County Hospital in Chicago reported 1000 cases without a fatality using single injections of 45 to 50 mL of 2% procaine. Oral Crawford and colleagues^[283] reported more than 600 cases of thoracic epidural analgesia for thoracic surgery in 1951, with two deaths.

One major limitation of the neuraxial techniques was the short duration of procaine. Bier experimented with the addition of rubber and latex to the spinal anesthetic solution in an attempt to prolong the block duration.^[253] These ideas were not expanded on because of complications or lack of effect. To deal with the same problem, William Lemmon^[284] used a 17-gauge, malleable, silver needle that was connected through a hole in the operating room table to rubber tubing and a syringe. Injections could then be made at intervals to maintain the spinal block for several hours. Edward Tuohy^[285] used a ureteral catheter threaded through a large Huber-tipped spinal needle to provide continuous spinal anesthesia. The Tuohy needle was a simple modification of the Huber needle and was used by him to thread the catheter into the subarachnoid space. Beginning in 1947, Manuel Martinez Curbelo^[286] of Havana, Cuba used the Tuohy needle and a small ureteral catheter to provide continuous lumbar epidural analgesia. He reported 59 successful

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Caudal anesthesia had a resurgence in popularity after the report by Edwards and Hingson^[287] in 1942 that analgesia for labor and delivery could be achieved with caudal injections of tetracaine through a malleable needle left in situ within the sacral canal. Their report was widely publicized, and within months the technique was adopted by several hospitals. Although for many years caudal epidural injections were used for obstetric analgesia, it became apparent that the lumbar approach to the epidural space was more consistent, and it eventually replaced the caudal approach.

Beginning in 1960, coincident with its rising popularity in obstetric anesthesia, the epidural method was taken up by several practitioners in North America. Philip Bromage and John Bonica performed several studies on epidural dose-response relationships and the hemodynamic changes that followed initiation of the block. Textbooks soon followed that introduced epidural analgesia into the operating room. ^{[288] [289] [290]} Although Dogliotti thought general anesthesia was contraindicated after initiation of epidural block, Bromage, and later Michael Cousins,^[291] discussed the advantages of providing general anesthesia during prolonged surgery with epidural analgesia extending throughout the surgical procedure and into the postoperative period. Although lumbar epidurals were widely used for postoperative pain relief, problems with ambulation and inadequate analgesia led to the current practice of placing epidural catheters between the appropriate interspaces to provide selective antinociception along the surgical incision site.

A report in 1979 by J. Wang^[292] demonstrated long-lasting analgesia from intrathecal administration of morphine in eight patients with cancer pain. This clinical study had firm groundwork from prior basic studies on the spinal effects of opioids in animals. In 1976, Yaksh^[293] had reported that intrathecal morphine produced spinal analgesia in rats. Duggan and associates^[294] demonstrated evidence of spinal analgesia after iontophoretic application of morphine into the dorsal horn region of the spinal cords of animals. Autoradiographic studies demonstrated a high density of opioid receptors in the substantia gelatinosa of the spinal cord.^[295]

The use of spinal opioids spread rapidly after the initial report by Wang.^[292] Samii and colleagues^[296] confirmed that selective opioid spinal analgesia occurs in humans. Cousins^[297] noticed that 1 to 2 mg of intrathecal morphine injected into the thoracic intrathecal region relieved the pain of breast or lung cancer for more than 24 hours. Behar ^[298] reported epidural opioid therapy in 1979. The explosive interest in neuraxial opioids that followed these reports was equal to the enthusiasm after the initial report of cocaine spinal anesthesia. The use of epidural catheters to provide long-lasting pain relief after surgery led to the formation of acute pain services.^[299] With special attention to drug concentrations and rates of infusion, patients were able to recuperate without pain and ambulate on the first postoperative day, even after extensive thoracic, abdominal, and orthopedic operations. The special advantage of epidural opioids was the synergistic effect they exhibited with local anesthetics, allowing a marked decrease in the dose of both drugs to achieve the same level of analgesia.^[300]