• Elyad Davidson, MD
• David J. Birnbach, MD

        I INTRODUCTION

In recent years, regional anesthesia techniques for surgery, obstetrics, and postoperative pain management have been used with increasing frequency.^1–3 The combined spinalepidural (CSE) technique, a comparatively new anesthetic technique, includes an initial subarachnoid injection followed by epidural catheter placement and administration of epidural medications. This allows for almost immediate relief of pain or induction of regional anesthesia by the rapid onset of the spinal drugs, and subsequent administration of medications for prolonged anesthesia. In addition postoperative analgesia via the epidural catheter can be delivered for extended periods.

        Clinical studies have demonstrated that the CSE technique provides excellent surgical conditions as quickly as the single-shot subarachnoid (SSS) block, and with advantages compared with the epidural block alone.^4–6 The introduction of CSE anesthesia offers benefits of both spinal and epidural anesthesia.

        Although the CSE technique has become increasingly popular over the past two decades, it is a more complex technique that requires comprehensive understanding of epidural and spinal physiology and pharmacology.

        This chapter discusses the technical aspects, advantages, potential complications, and limitations of the CSE technique for surgery and analgesia during labor.

        CLINICAL USE OF CSE ANESTHESIA

The results of a recent survey demonstrate wide variation in CSE use and practice among experienced anesthesiologists,⁷ reflecting concern over the frequency of CSE-related complications,^8,9 controversy over the technique,^10,11 and the potential for higher failure rates with CSE than with individual spinal or other anesthetic techniques.¹²

General Surgery

In the literature, the technique has been described for use in general, orthopedic, and trauma surgery of lower limb, as well as in urologic and gynecologic surgery. Clinical studies have demonstrated that the CSE technique provides excellent surgical conditions as quickly as with SSS block—conditions that are better than with epidural block alone.^4,13 With the CSE technique, surgical anesthesia is established rapidly, saving 15-20 min compared with epidural anesthesia. Furthermore, epidural catheterization provides the possibility of supplementing subarachnoid anesthesia, which may be insufficient when used alone. In a recent article it was also observed that various needles can be used in different combinations when performing CSE and may have different advantages and disadvantages for different patients and situations.¹⁴ This will be discussed later in the chapter.

Labor Analgesia

The CSE technique is widely used in obstetric practice to provide optimal analgesia for parturients. It offers effective, rapid-onset analgesia with minimal risk of toxicity or motor block.¹³ In addition, this technique provides the ability to prolong the duration of analgesia, as required, through the use of an epidural catheter. Furthermore, should an operative delivery become necessary, that same catheter can be used to provide operative anesthesia. The onset of spinal analgesia is almost immediate, and the duration is between 2 and 3 h, depending on which agent or agents are chosen. The duration of spinal analgesia, however, decreases when administered to a woman in advanced labor versus one in early labor.¹⁶ Patients may have greater satisfaction with CSE than with standard epidurals, perhaps because of a greater feeling of self-control.¹⁷ The original description of spinal labor analgesia involved sufentanil or fentanyl,¹⁸ but the addition of isobaric bupivacaine to the opioid produces a greater density of sensory blockade while still minimizing motor blockade.¹⁹ Originally, 25 meg of fentanyl or 10 meg of sufentanil was advocated, but more recent studies have suggested using smaller doses of opioid combined with a local anesthetic.²⁰ For example, many clinicians are now routinely use 5 meg of sufentanil or 15 meg of intrathecal fentanyl. Recent studies have suggested that ropivacaine and levobupivacaine can be substituted for intrathecal bupivacaine to provide labor analgesia.^21,22 The CSE technique has also made ambulation possible for many women receiving neuraxial analgesia, although ambulation may be possible with other techniques. In addition to the advantage of rapid onset of pain relief, the CSE technique may reduce the incidence of several potential problems associated with the conventional epidural technique, including incomplete (patchy) blockade, motor block, and poor sacral spread. Another potential advantage of the CSE technique is that, as suggested by preliminary study, it may be associated with a significant reduction in the duration of the first stage of labor in primiparous parturients.^23,24

Cesarean Delivery

The CSE technique, first reported as an option for cesarean section in 1984,²⁵ has recently increased dramatically in popularity. The advantage of this technique is that it provides rapid onset of dense surgical anesthesia while allowing the ability to prolong the block with an epidural catheter. In addition, because the block can be supplemented at any time, the CSE technique allows the use of smaller doses of spinal local anesthetics, which may in turn reduce the incidence of high spinal block or prolonged hypotension.²⁶ Potential problems of the CSE technique for cesarean delivery include an inability to test the catheter, the possibility of a failed epidural catheter after spinal injection, and the risk of enhanced spread of previously injected spinal drug after use of the epidural catheter.²⁷

        ADVANTAGES OF CSE

Compared with Conventional Epidural or Subarachnoid Anesthesia

When CSE block was compared with either epidural or subarachnoid block for hip or knee arthroplasty, CSE anesthesia was found to be superior to epidural anesthesia. With the CSE technique, surgical anesthesia was rapidly established, saving 15-20 min compared with epidural anesthesia. Furthermore, the epidural catheter provided the possibility of supplementing insufficient subarachnoid anesthesia.⁴

        Patients who received the CSE technique had a more rapid onset of anesthesia and more intense motor blockade than those who received epidural anesthesia alone.

Clinical Pearls

CSE has been reported to decrease the failure rate and incidence of adverse events of neuraxial analgesia.²⁸ In a retrospective analysis of 19,259 deliveries (75% neuraxial labor analgesia rate), the overall failure rate with this technique was 12%. The patients had adequate analgesia from initial placement, but 6.8% of patients had subsequent inadequate analgesia during labor and required epidural catheter replacement. Ultimately, 98.8% of all patients received adequate analgesia, even though 1.5% of patients had one or more replacements. However, when compared with epidural analgesia alone for labor, the incidence of overall failure, accidental intravascular placement of epidural catheters, accidental dural punctures, inadequate epidural analgesia, and catheter replacements were shown to be significantly lower in patients receiving CSE analgesia.^15,28,29

        Norris and coworkers, and Eappen and colleagues reported that CSE has higher success rate than the conventional epidural technique.^15,28 This difference may be due to the option to confirm questionable epidural location by successful spinal injection.

        CSE enables low-dose spinal anesthesia for cesarean delivery.^30–34 When using SSS anesthesia for ambulatory surgery, many anesthesiologists tend to overdose because there is only one chance to ensure an effective spinal block. The presence of an epidural catheter as a “safety net” allows the anesthesiologist to use the lowest effective dose of local anesthetic. Urmey and coworkers used the CSE technique to investigate the appropriate dose of intrathecal isobaric lidocaine 2% for day-case arthroscopy.³⁵ The CSE technique provided excellent anesthesia for all 90 patients in his study. Patients receiving the smallest dose (40 mg) had a significantly shorter duration of anesthesia, which allowed quicker discharge than for the patients receiving 60 or 80 mg of intrathecal lidocaine.

        Norris suggested the use of a CSE technique with intrathecal sufentanil alone for outpatient shock-wave lithotripsy, reserving the use of epidural catheter for patients with inadequate analgesia.³⁶

        Epidural volume extension (EVE) and enhancement of a small-dose intrathecal block by epidural saline infusion has been demonstrated via a CSE technique.³⁷ The advantage of this EVE technique is that a small-dose spinal block may provide an adequate level of anesthesia while allowing faster motor recovery of the lower limbs. In a prospective, randomized, double-blind study, the EVE technique was compared with SSS anesthesia with respect to its sensory and motor block profile and hemodynamic stability. Sixty-two patients scheduled for elective cesarean delivery were randomized to receive either spinal anesthesia with hyperbaric 0.5% bupivacaine (9 mg) and fentanyl (10 meg) or CSE with intrathecal hyperbaric 0.5% bupivacaine (5 mg) with fentanyl (10 meg), followed by 0.9% saline (6.0 mL) through the epidural catheter 5 min later. Both groups were comparable in terms of demographic data and duration of surgery. In the comparison of sensory block, both groups had similar peak sensory block height and VAS pain scores. The hemodynamic profile and ephedrine dose required were comparable between the two groups. Patients in the EVE group, however, demonstrated significantly faster motor recovery to modified Bromage score of 0 (73 ± 33 min versus 136 ± 32 min; p < 0.05). CSE with EVE provided adequate anesthesia with only 55% of the bupivacaine dose and allowed faster motor recovery of the lower limbs.

        In another study, four different intrathecal doses of hyperbaric bupivacaine (2.5, 5, 7.5, and 10 mg) were compared in patients undergoing cesarean section under sequential CSE block, a technique that involves administration of a relatively small subarachnoid block that may be supplemented as needed by epidural local anesthetics. The authors demonstrated that 5 mg of intrathecal bupivacaine combined with an appropriate dose of epidural lidocaine provided adequate surgical analgesia while maintaining hemodynamic stability. Higher doses of intrathecal bupivacaine were associated with typical adverse effects of high subarachnoid block such as nausea, vomiting, and dyspnea.³⁸

CSE for High-Risk Patients

The sequential CSE technique may be particularly advantageous in high-risk patients, such as those with cardiac disease, when slower onset of sympathetic blockade is desirable.³⁹ Most spinal anesthetics are administered as a single-injection procedure and rapid onset of sympathetic blockade may result in abrupt, severe hypotension. Traditionally, high-risk patients are treated with slow epidural anesthesia, which requires much higher total dosages of local anesthetic than is the case with sequential CSE. With careful positioning of the patient prior to induction of subarachnoid anesthetic, and by allowing titration with small incremental epidural doses to the precise level of anesthesia desired, the sequential CSE technique may enhance the safety of the neuraxial block.

Clinical Pearls

In summary, CSE can reduce or eliminate many of the disadvantages of subarachnoid or epidural anesthesia alone while preserving their respective advantages. The CSE block offers the speed of onset, efficacy, and minimal toxicity of a subarachnoid block combined with the potential for improving an inadequate block or prolonging the duration of anesthesia with epidural supplements and extending the analgesia well into the postoperative period. Although the sequential CSE technique will take somewhat longer than the standard CSE technique, the use of minimal doses of local anesthetics has been shown to reduce the frequency and severity of hypotension when compared with epidural or spinal techniques.⁴⁰

        FUNCTIONAL ANATOMY RELATED TO CSE

When performing an epidural block, skin to epidural space distance (SED) and the posterior epidural space distance (PED) are measures that can help in reducing the inadvertent penetration of the dura and injury to neural structures.^41,42 The knowledge of these measures is also important in the success rate of epidural anesthesia. The PED, a measure of the epidural space depth, is particularly important with the CSE needle-through-needle (NTN) technique. Underestimation of this distance (short protrusion of the spinal needle through the epidural needle) will result in a higher incidence of spinal block failure. Any nonmidline approach also would increase the risk of not reaching the subarachnoid space because the dural sac has a triangular shape with the top pointing dorsally. Overestimation of PED will cause over protrusion of the spinal needle that may increase the risk of neural damage.⁴³ These distances have been measured using various methods,⁴⁴ including MRI, CT, and measurement of CSE tip-to-tip distance or the amount of protrusion of the spinal needle beyond the Tuohy needle. The SED distance is most commonly 4 cm (50%) and is 4-6 cm in 80% of the population according to detailed records of 3200 cases.⁴⁴ The width of the PED varies with vertebral level, being the widest in the midlumbar region (5-6 mm) and decreasing toward the cervical vertebral column. In the midthoracic region, it is 3-5 mm in the midline and narrows laterally. In the lower cervical region, it is only 1.5-2 mm in the midline.⁴⁵ These spaces also correlate with the weight-to-height ratio and BMI.⁴⁶ Based on these measures, the present design of spinal needle protrusion varies between 10 and 15 mm beyond the epidural needle.

Epidural Space & Ligament Flavum

The thickness of the ligamentum flavum, distance to dura, and skin-to-dura distance vary with the area of vertebral canal (Table 16-1).

        The two ligamenta flava are variably joined (fused) in the midline, and this fusion or lack of fusion of the ligamenta flavum occurs at different vertebral levels in individual patients. Lirk and coworkers investigated the incidence of midline gaps in the lumbar ligamentum flavum in embalmed cadavers.⁴⁷ Vertebral column specimens were obtained from 45 human cadavers. The gaps in the lumbar ligamentum flavum are most frequent between L1 and L2 (22.2%) but are rare below this level (L2 through L3 = 11.4%, L3 through L4 = 11.1%, L4 through L5 = 9.3%, L5 through SI = 0). Therefore, when using midline approach, one cannot rely on the ligamentum flavum to impede entering the epidural space in all patients.

    Data used, with permission, from Brown DL: Spinal, epidural, caudal anesthesia. In Miller RD (ed): Anesthesia, 6th ed. Churchill Livingstone, 2005, pp 1657.

        TECHNIQUE

A number of recent reviews have discussed the technical factors related to performance and success of CSE.^48–50

        Although CSE is considered a new technique, Soresi in 1937 described the intentional injection of anesthetic agents outside and within the subarachnoid space.⁵¹ Somewhat different from current practice, Soresi intentionally used a single needle. He first injected some local anesthetic into the epidural space and then advanced the needle and injected the rest of the medication to cause a subarachnoid block. Although this technique included both spinal and epidural anesthesia, no catheter was used. In 1979 Curelaru⁵² reported the first CSE with an introduction of an epidural catheter through a Tuohy needle. Catheter insertion was followed by a test dose and then a traditional dural puncture, which was performed at a different interspace using a 26-gauge spinal needle. That same year, Brownridge suggested the use of CSE for obstetrics. He described successful use of CSE for elective cesarean section in 1981.^53,54 In 1982, the needle-through-needle (NTN) CSE technique was first described independently by Coates⁵⁵ and Mumtaz and colleagues,⁵⁶ and its use in obstetric practice was first published in 1984 by Carrie and O’Sullivan.⁵⁷

        Several approaches for initiation of CSE have been described in the recent literature.

Needle-Through-Needle Technique

In contrast to Serosi’s description of CSE, in which a single needle was introduced into the epidural space and then advanced into the subarachnoid space, the needle-through- needle (NTN) technique includes use of separate epidural and spinal needles.

Figure 16-1. Epidural needle is placed in the epidural space indentically to the technique in epidural anesthesia.

        The epidural space is penetrated with a conventional epidural needle and technique, and then a long spinal needle is passed through the epidural needle until CSF appears in the hub of the spinal needle. Drug is administered into the subarachnoid space, the spinal needle is removed, and an epidural catheter is inserted into the epidural space (Figures 16-1 through 16-7). Although several different CSE techniques are used in clinical practice (including the two needle, two interspace technique), NTN is the most widely used CSE technique in the US.

Separate Needle Technique

CSE may be performed using two separate needles (separate needle technique; SNT), with spinal block and epidural catheter placement at either a single^58,59 or two different interspaces.^60–62 If the epidural catheter is placed first, proper placement can be tested before administration of spinal medications, potentially decreasing the risk of inadvertent intravascular or intrathecal catheter migration. Placing the epidural catheter first may also reduce the risk of neural damage, which may occur when the catheter is inserted after subarachnoid block, since paresthesia and other warning signs of improper needle placement may be absent after administration of spinal medications. However, there is also a risk of striking the epidural catheter with the spinal needle.^63–65 Some authors consider this to be a purely hypothetical risk and have demonstrated that it is not possible to perforate an epidural catheter with commonly used spinal needles.^66,67

Figure 16-2. Entry of the needle into the epidural space is recognized by a sudden loss of resistance to injection of air.

Figure 16-3. A small-bore spinal needle is placed through the epidural needle until CSF appears at the hub of the needle, indicating successful entrance of the spinal needle into the subarachnoid space. Typically, a loss of resistance is felt as the needle makes a slight bend to exit through the curved tip of the epidural needle and another as the spinal needle pierces the dura and enters the subarachnoid space.

Cook⁶⁸ recently reported a series of 201 consecutive CSEs performed with a novel separate-needle technique. The study was designed to avoid potential and actual problems associated with the CSE technique. Cook placed the spinal needle in the subarachnoid space and then replaced the spinal needle stylet to stop the CSF leak. He next placed the epidural catheter through a different interspace and returned to the spinal needle to inject the subarachnoid drug, thus avoiding epidural catheter insertion in an anesthetized patient. This method of CSE anesthesia, though more work, may be associated with high success and low complication rates.

Figure 16-4. CSF appears in the hub of the spinal needle, indicating the subarachnoid placement of its tip.

Figure 16-5. A desired dose of local anesthetic with or without additives is injected through the spinal needle.

Regardless of which component is performed first, the major disadvantage of the two-needle/two-interspace technique is that it takes longer to perform and requires two separate injections.

Comparison of Techniques

Comparison of NTN & SNT CSE Techniques

The SNT technique has a few theoretical advantages over the NTN technique. It enables placement of the epidural catheter prior to initiation of the spinal block. The SNT may thus theoretically reduce the risk for neurologic injury, since paresthesia and other symptoms are not masked. Since the epidural catheter is placed early, problems that may occur due to delayed catheter placement (technical problems) after the injection of a hyperbaric spinal solution (such as unilateral, sacral, or low lumbar regional neuraxial block) are avoided.^69–71

Figure 16-6. A flexible catheter is placed through the epidural needle and left about 5 cm in the epidural space.

Figure 16-7. Epidural catheter is checked by the aspiration test to rule out its inadvertent intravascular (appearance of blood in the catheter) or intrathecal (appearance of CSF) placement.

        Several studies have compared NTN and SNT techniques.^72–75 Some have reported better success and lower failure rates with the SNT. However, these studies also report greater patient acceptance and less discomfort with the NTN technique. A recent prospective randomized study⁷⁶ compared the outcomes and techniques of NTN and SNT (double space) CSE in 200 patients receiving elective cesarean section. A successful block to the T5 level with the double-space and the NTN techniques were 80 vs 54, with an odds ratio of 0.29. SNT had a greater success rate than the NTN technique; the T5 dermatome was reached with fewer corrective manipulations (epidural augmentation or repeated blocks). Failure to enter the intrathecal space once the epidural space had been located occurred in 29 patients in the NTN group. Time to readiness for surgery was slightly increased with SNT ( 15 min with SNT vs 12.9 min with NTN).

Techniques to Improve Success & Safety of CSE

The success of CSE block depends heavily on accurate cannulation of the epidural space. The identification of the epidural space is traditionally achieved by a blind loss of resistance. With the blind handling of the needles, in which the feedback to the operator is merely tactile, deviation of the axis of the needle trajectory may occur. Because of the triangular form of the dural sac, deviation from the midline of the spinal needle will cause the operator to miss the dural sac, leading to spinal component failure or unsuccessful dural puncture. Complications such as paresthesia, postdural puncture headache (PDPH) are also associated with the puncture technique.

        Grau and coworkers performed real-time ultrasonic scanning of the lumbar spine to provide accurate reading of the location of the needle tip and to facilitate the performance of CSE anesthesia.⁷⁷ Their aim was to establish a less-invasive method to monitor the advancement of the needle in real time.

        Thirty parturient patients scheduled for cesarean section were randomized to three equal groups. Ten control patients received conventional CSE anesthesia. Ten received ultrasonic scans by an offline technique. The remaining 10 received online imaging of the lumbar region during puncture. The Tuohy needle was inserted using the midline approach in all three groups. In the control group, CSE was performed using the single-space NTN technique with the standard loss of resistance to saline method.

        In the offline group, ultrasound images were taken just before the puncture to improve needle trajectory. In the online group, ultrasonic images were taken to monitor and identify needle trajectory in real time.

        They reported that in both ultrasound groups, a significant reduction in the number of necessary puncture attempts was found (p < 0.036); the number of interspaces necessary for puncture was reduced (p < 0.036); the number of spinal needle manipulations was significantly reduced (p < 0.036). dural tenting was observed in 9 out of 10 in the online group (tenting length 2.4 mm). Asymmetric block was observed in 10% of those in the control group, but not in any of those in the ultrasound groups.

        The authors concluded that the use of ultrasound imaging was obviously helpful in finding the ideal needle trajectory and to improve puncture conditions by demonstration of the relevant anatomy.

        In the CSE NTN technique, there is no practical test to confirm correct epidural catheter placement. Tsui and colleagues proposed the use of nerve stimulators to confirm the proper placement of epidural catheter.⁷⁸ They studied 39 obstetric patients in labor who received epidural catheters (not CSE) for analgesia. A low-current (1-10 mA) electrical stimulation was used to confirm the correct placement of epidural catheter (19-gauge Arrow Flextip Plus). A positive motor response (truncal or limb) indicated that the catheter was in the epidural space. They reported that the sensitivity and specificity of this test was 100% and 100%, respectively, with 38 true-positive tests and 1 true-negative test. A case of intravascular epidural catheter migration was detected using this new test and was subsequently confirmed by a positive epinephrine test. If the motor response only occurs with larger currents (>10 mA) or does not respond at all (before receiving any local anesthetics), the catheter is outside the epidural space. If a positive response occurs at an unusually low milliamperage (<1 mA), intrathecal placement is likely. More detail on the electrical stimulation can be found in Chapter 5 (Electrophysiology of Nerve Stimulation).

        The electrical stimulation test may not be applicable when the CSE technique is used for surgery in which anesthetic doses oflocal anesthetics are administered intrathecally prior to the placement of the epidural catheter. When using the CSE technique for labor analgesia, this test may be utilized as a simple and practical method for determining the epidural catheter placement. The standard test dose (3 mL of 1.5% lidocaine with 1:200,000 epinephrine) may help to identify vascular and intrathecal placement, but it does not verify appropriate epidural placement or function.

        PHARMACOLOGIC CHOICES FOR CSE

Sufentanil and fentanyl, with or without local anesthetics, are most often administered intrathecally to provide analgesia for the laboring woman receiving CSE. The usual dosage of sufentanil is 2.5-10 meg; however, most practitioners are now using 2.5 or 5 meg. The ED₅₀ and ED₉₅ for laboring patients were found to be 2.6 meg and 8.9 meg, respectively.⁷⁹ The doses of fentanyl used are typically 10-25 meg. The median effective dose (ED50) and the effective dose for 95% of patients (ED95) for laboring patients has been reported to be

5.5 and 17.4 meg, respectively.⁸⁰ Although the original studies used much higher doses of intrathecal opioids (10 meg sufentanil and 25-50 meg of fentanyl), subsequent studies have suggested the use of smaller doses, with reduced side effects and similar analgesic effect.⁸¹

        Morphine, a highly ionized, water-soluble opioid, produces analgesia of long duration, but with a slow onset (approximately 60 min between injection and onset). In addition it may be associated with an unacceptably high incidence of side effects such as nausea, vomiting, and pruritus, as well as the potential for delayed respiratory depression. These side effects, coupled with the slow onset of pain relief, limit the usefulness of intrathecal morphine for labor analgesia. Intrathecal meperidine (10 mg) may provide reliable analgesia in advanced labor,⁸² but has been associated with a high incidence of nausea, vomiting, hypotension, and ephedrine requirement. In addition, it is the only opioid that has intrinsic local anesthetic properties at clinically used doses,⁸² by blocking nerve conduction at the proximal end of the dorsal root⁸³ by a mechanism other than sodium channel blockade.⁸⁴ This nerve conduction blockade is not naloxone reversible.⁸³

Clinical Pearls

In many patients, a single intrathecal injection of a lipidsoluble opioid is insufficient to produce analgesia for the entire duration of labor.

        When the second stage of labor is imminent, the subarachnoid administration of local anesthetic plus opioid should be considered to achieve a greater depth of pain relief. The combination of 2.5 to 5 meg sufentanil plus 2.5 mg bupivacaine provides rapid analgesia without motor block, alleviates the pain of the second stage of labor, and lasts longer than sufentanil alone.⁸⁵ Although the original reports⁸⁶ recommended the use of 10 meg of sufentanil, Sia and colleagues showed that adequate relief of labor pain could be safely provided by administering half that dose of intrathecal sufentanil plus bupivacaine.⁸⁷

        New studies⁸⁸ have attempted to determine the ED₅₀ for intrathecal bupivacaine, defined as the minimum local anesthetic dose (MLAD) and then use this to asses the effect of different doses of fentanyl. The MLAD of intrathecal bupivacaine has been found to be 1.99 mg, and the addition of 5 meg of intrathecal fentanyl offered a similarly significant sparing effect to 15 or 25 meg of fentanyl, resulting in less pruritus but with a shortening of duration of action.

        Levin and coworkers compared a standard dose of intrathecal bupivacaine with sufentanil for CSE analgesia using two doses of ropivacaine (2 and 4 mg) with sufentanil and concluded that both local anesthetics provided similar duration of labor analgesia with equivalent side effects.⁸⁹ In addition, a recently published pilot study showed that intrathecal ropivacaine with or without sufentanil also provides effective analgesia and does not impair motor strength, which might facilitate ambulation during labor.⁹⁰

        COMPLICATIONS & CONCERNS OF CSE TECHNIQUE

Failure of the Spinal Component

The most common method of performing a CSE is the single-interspace NTN technique. In earlier reports, failure to achieve a spinal block with this technique has been reported in 10 to 15% of cases in the past.^91,92 However, more recent reports have demonstrated failure rates in the range of 2 to 5%.^93–95

Clinical Pearls

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Stimulating Catheters. Ultrasound-Assisted Nerve Blocks in Adults. Cutaneous Blocks for the Upper Extremity. Supraclavicular Brachial Plexus Block.