Perspective Chapter: Epidural Administration – Various Advances in Techniques

Abstract

First described by Fidel Pages in 1921, epidural administration is a technique in which a medicine is injected into the epidural space has undergone various modifications and approaches in recent years. Epidural administration also involves the placement of a catheter into the epidural space, which may remain in place for the duration of the treatment. These advances have changed the face of clinical practice and improved the patient management. Modification to the approach of epidural administration has moved from the single-shot epidural administration to programmed injections. The use of these improved techniques has reduced complications associated with epidural administration and improved care. The administration of medication into this space has been considered as safe and effective for providing pain relief during childbirth and surgery. A review of these modes of administration will highlight the importance of each of the techniques.

1. Introduction

Epidural administration of medications has been used in many surgical and anesthetic managements of patients. It is currently mostly used for postoperative management in the regions of the body amenable to it [1]. It has a wide margin of safety in experienced hands. Beyond its use in postoperative pain management, it has been indicated in the administration of steroids, contrast agents and many others.

It is important to know that the positioning of the patients requiring epidural administration is determined by patient’s comfort, compliance and preference of the attending. Insertion of the needle is commonly performed in either sitting, or flexed lateral position, although the sitting position has higher rate of first pass insertion and shorter duration (skin puncture to correct needle placement time) [2].

This chapter will review the various methods epidural administration of agents into the epidural space can be achieved.

2. Methods of identifying epidural space

Epidural administration of pharmacologically active agents would be impossible without proper identification of the space. This is most frequent cause of failed epidural administration [3]. Patient positioning, the use of a midline or paramedian approach, and the method used for catheter fixation can all influence the success rate.

For epidural injection using the midline approach to be successful, the Tuohy needle would have to traverse the skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, and then into the epidural space. The epidural space is a potential space, the loss of resistance on a plunger is indicative of the entrance to the epidural space. Localization of the space is one of the major key steps in epidural administration. Many ingenious devices have been designed to improve the success of the puncture procedure and are based on the principle of loss of resistance within the epidural space.

3. Epidural space identification methods

1. Ogan’s slingshot epidural syringe: This simple device uses a rubber sling mounted on the plunger of the syringe which generates a head pressure on the plunger (Figure 1) [4].

   With a mounted Tuohy needle advancing into the epidural space, the plunger collapses as the needle gets into the epidural space. This device which depends on loss of resistance to air gives about 95-97% accuracy in identifying the epidural space.

2. Epidural balloon: This is also a device which depends on the negative pressure exhibited by the denting of the ligamentum flavum during penetration of the Tuohy needle (Figure 2).

   The balloon attached to plastic device collapses (or the air in the balloon is sucked in) as the needle enters into the epidural space.

3. Episure™ AutoDetect syringe: This is another epidural space localization device (Figure 3).

   This device works better when it is filled with normal saline and with an advancing mounted Tuohy needle into the space the plunger automatically loses resistance, which “provides an objective, visual confirmation that the epidural space has been identified.” Other devices used in the identifying the epidural space include the use of ultrasound guide [5], spring-loaded syringes, episure [6].

4. Epidrum©: This device depends on a low pressure loss of resistance to facilitate epidural space identification. The device is fixed between the syringe and needle and, filled with air to inflate its diaphragm. As the needle advances and gets into the epidural space, there will be a visible collapse of the diaphragm marking the endpoint of space identification. One great advantage of this device is that, it allows a slow advancement of the needle with both hands making a more accurate space identification possible (Figure 4).

   When inflated and connected to the Tuohy needle, Epidrum allows higher pressure changes due to the location of the epidural space to be differentiated from those due to smaller changes in the path through the different tissues of the patient [7].

5. EpiFaith© syringe: EpiFaith is a relatively new device used in identifying the epidural space by loss of resistance technique. When the operator attaches the syringe to the Tuohy needle, the spring is held in place by the locking mechanism (where the yellow ring on the piston meets the blue plunger). The operator then pushes the syringe plunger forward to engage the spring. The operator can now advance the needle with two hands braced against the back. When the Tuohy needle tip enters the epidural space and there is a loss of resistance, the piston advances, and the yellow is visible. The piston moving forward, and the appearance of the yellow color are indicators of a loss of resistance [8] (Figure 5).

   It is a device that ensures the Touhy needles comes to an abrupt halt with the pressure change in the epidural space. EpiFaith is mechanically driven and reduces the risk of accidental dural puncture.

6. Acoustic puncture assist device: Failure in identifying the epidural space could be a great challenge to the attending Anesthetist. One way of correct identification is the use of Acoustic puncture assist device [9]. This method is designed to detect and signal by tone, the loss of resistance encountered during epidural procedure. The device records the pressure changes during epidural puncture of the ligamentum flavum. When in use, it provides an objective, visible pressure readings which again help in identifying the epidural space.

7. Fiber Bragg sensors: The mechanism of action of this device is characterized by periodic modulation of the refraction index along the axis of the fiber core. An abrupt relaxation of the fiber is observed as it passes from a thin and very hard tissue (like the ligament flavum) to a soft region (epidural space) signaling the entrance into the epidural space. This form of epidural space identification is still being researched in humans [10].

8. Ultrasound scan: Using either the linear or curved probe, the ultrasound can be used to guide the needle in identifying the epidural space. It is well known to provide a real time reliable information about the surrounding tissues when traversing to enter the epidural space. It has been associated with a high success rate.

   While most of the methods described earlier depend on loss of resistance to air (which could introduce air to cause patchy blocks), Evron et al. demonstrated the relevance of loss of resistance to lidocaine which could best be described as loss of resistance to fluid [11]. The advantage of Evron et al. technique added more value in which dilutional factor with saline is circumvented rather synergistic to other local anesthetics administered into the epidural space.

Figure 1.

Slingshot® epidural syringe.

Figure 2.

Epidural balloon – Vygon© UK.

Figure 3.

Episure™ syringe.

Figure 4.

Epidrum©.

Figure 5.

EpiFaith© syringe (drawing provided by flat medical Inc. (Taipei City, Taiwan)).

4. Methods of epidural administration

Various methods have been advanced in carrying out epidural administration in clinical practice. Each of these methods is unique in its own way. The purpose of epidural administration could be short term or long term; depending on the need of the patient or the purpose for which it is administered. Epidural administration of medications can be effected through:

1. Manual (bolus) injection

2. Delivered by a machine

   • Volumetric epidural infusion

   • Epidural syringe pump

There are ways in which the administration can be conducted:

1. Single bolus injection

2. Intermittent bolus injection

3. Continuous injection

4.1 Single shot epidural administration (SSEA)

Single shot epidural injections, involves injecting a single dose of a drug. It eliminates the risk associated with epidural infusion through an indwelling catheter, such as restricting mobility limited options for anticoagulant therapy, injections and also for steroid injections. It is frequently used in management of radiculopathies [12]. This technique does not require the retention of an epidural catheter. While single-shot epidural administration may be ideal in some settings, the incidence of complications has been argued to be the same with the use of continuous epidural with use of a catheter. However its application is well out of place in modern labor analgesia practice. It is quite difficult to accurately quantify and qualify the adequacy of sensory level of analgesia following a single-shot. The use of a single-shot is in favor of epidural administration of steroids for radicular pain and others [13].

4.2 Continuous epidural administration (CEA)

Continuous epidural administration can be carried out with the use of either a volumetric pump or syringe pump. Each of these devices works differently. While the volumetric pump allows a calculated dose of medication in an infusion bag to flow through the epidural catheter at a predetermined rate, the syringe pump delivers a calculated dose of medication through a syringe and catheter at predetermined rate to the patient. Continuous epidural infusions offer a safety advantage over intermittent epidural injections because peak and trough levels of the analgesic agent are avoided.

Continuous epidural analgesia is commonly used for labor analgesia, postoperative pain control after thoracic, abdominal, lower extremity, and rarely, upper extremity surgeries. An infusion pump can be used to carry out epidural administration of medications. This device is commonly used in areas such as obstetrics to deliver medications (e.g., bupivacaine or other controlled substances) for maintenance of analgesia during labor.

4.2.1 Infusion or volumetric pump

This plays an important role in postoperative pain relief. It requires repeated injections or continuous infusion of local anesthetic solutions, using a volumetric pump, capable of delivering continuous and very specific amounts of fluid at either a slow or fast rate, with the presence of an indwelling catheter. The initial dose establishes the extent of analgesia and continuous infusion preserves it. It is associated with the risk of misplacing the catheter and infection [14]. However, a primary safety concern with epidural volumetric infusion pump is the risk of delivery through an incorrect route of administration, which can happen when epidural infusions are mixed with intravenous infusions. Infusing medications intended for epidural delivery through intravenous sites or vice versa can be detrimental (Figure 6).

Figure 6.

A volumetric pump - Infusomat® P (B Braun).

4.2.2 Syringe pump

The syringe pump can be used to deliver a calculated dose and rate of a medication into the epidural space through an epidural catheter (Figure 7).

Figure 7.

P2000 syringe pump (IVAC®).

The pump maintains a steady stream of flow of the medication administered without the patient’s input.

4.3 Combine spinal epidural administration (CSEA)

Epidural administration can be achieved through the use of a combined spinal epidural technique. The epidural component of this procedure is through the placement of catheter into the epidural space [15]. The medications to be administered can be done through the use of an infusion (volumetric) or syringe pump.

4.4 Patient controlled epidural administration (PCEA)

The patient-controlled epidural analgesia (PCEA) technique has been recently set up as a preferred mode of epidural drug delivery and used widely. The development of PCEA allows patients to superimpose a limited volume of bolus dosing on an already established continuous infusion (Figure 8).

Figure 8.

Patient-controlled syringe pump SP-14S (aitecs©).

It has been found that patients with PCEA require less local anesthetic than patients with continuous epidural administration, to achieve a similar quality of epidural analgesia [16]. To forestall overdosing, the patient controlled pump is incorporated with a lockout mechanism which prevents repeated self-dosing within a given time interval.

4.5 Computer integrated patient-controlled epidural injection (CIPCEA)

Computer-integrated patient-controlled epidural analgesia (CIPCEA) is a novel epidural delivery system programmed to analyze the pharmacologic agent use across the last hour and adjusts the background infusion rate according to an algorithm [17] (Figure 9).

Figure 9.

Computer integrated patient controlled epidural pump (first generation computer integrated infusion pump set-up using an IBM Thinkpad laptop (IBM, USA) connected to a modified syringe pump (IVAC P700, Alaris, UK).

This novel method of epidural drug injection automatically adjusts the injection rates based on the patients need for analgesia [18]. When compared with the conventional patient controlled injection, there was more patient satisfaction and less local anesthesia use in the CIPCEI group [18].

4.6 Programmed intermittent bolus epidural injection (PIEBA)

Programmed intermittent epidural bolus (PIEB) is a new way of injecting local anesthetic agents into the epidural space through an epidural catheter at fixed time intervals [19].

This is an automated method of administering boluses of local anesthetic solution into the epidural space at fixed time intervals. It has been described as a method that works perfectly well with patient-controlled epidural administration (PCEA) [16].The combination of methods prolongs the duration of analgesia, reduces motor block, lowers incidence of breakthrough pain, and reduces local anesthetic consumption compared to continuous epidural injection [20]. However, it remains unclear what is the optimal PIEBA dosing regimen.

5. Conclusion

Epidural administration is a valuable tool in clinical practice. It has been used in various management or treatment of pain such as postoperative, labor analgesia, steroid administration, injection of platelet-rich plasma concentrate and other needs in clinical medicine. More researches are still on in exploring other ways the epidural space can be beneficial in clinical practice.