• Admir Hadzic, MD

        INTRODUCTION

As in other areas of medicine, anesthesiologists increasingly rely on more sophisticated equipment in regional anesthesia. The advanced technology used to accomplish and increase the success rate of regional anesthesia techniques requires thorough understanding of the equipment. One of the most important advances in regional anesthesia was the introduction of the portable peripheral nerve stimulator in the late 1970s and early 1980s.¹ Since that time, many improvements in nerve stimulators were made, as well as to the needle and catheter designs. Over the last decade, ultrasound also developed into a promising method for nerve localization.^1–3 As technology continues to evolve, it will likely assume a more significant role in regional anesthesia. Nevertheless, the performance of regional anesthesia techniques still requires proper set-up, careful preparation, detailed planning, and continuous monitoring to provide safe and effective patient care.

        INDUCTION & BLOCK ROOM

Clinical Pearls

        Regional anesthesia should be performed only in a designated area with the proper equipment (Figure 17-1). This area could be the operating room or a separate area within the surgical suite. Regardless of where the actual procedure is performed, adequate space, proper equipment, and careful monitoring are essential to ensure time-efficient and safe care of the patient undergoing the peripheral nerve block.^4–6 To facilitate the successful implementation of a nerve block, all supplies, drugs, and other equipment must be readily available in the room. The designated area must be large enough to enable proper monitoring and resuscitation of patients. And it should have proper lighting, suction, and equipment for oxygen administration and emergency airway management, including positive-pressure ventilation.

        MONITORING

Toxicity from an inadvertent intravascular injection or rapid absorption or channeling of local anesthetic into the systemic circulation is always a potential risk when administering local anesthetic for any regional block. Vigilant monitoring is crucial for diagnosing and managing any potential complications that arise during or after a regional anesthesia or analgesia procedure.^4,7 Every patient should have vascular access secured prior to performing the procedure.

Figure 17-1. An example of room/area with basic monitoring equipment.

Clinical Pearls

        The patient’s baseline level of consciousness, pulse oximetry, vital signs (blood pressure and heart rate), ECG, and respiratory rate should be monitored throughout the procedure. After completion of the block, all patients should be monitored for at least 30 min for any signs of local anesthetic toxicity. It is important to keep in mind that although a toxic reaction typically occurs during or immediately following the injection of local anesthetic, it can also occur due to absorption. In the latter scenario, signs and symptoms of toxicity become apparent after the serum levels of local anesthetic peak (typically, 20 min following the injection).

        Patients undergoing surgery under regional anesthesia should be cared for in the same way as patients having general anesthesia. Blood pressure, heart rate, respiratory rate, and ECG should be continuously monitored throughout the surgery. However, temperature monitoring is usually not necessary in minimally sedated and conversing patients.

        REGIONAL ANESTHESIA EQUIPMENT STORAGE CART

Clinical Pearls

        A well-stocked and maintained regional anesthesia cart is essential for providing effective, time-efficient, and safe regional anesthesia (Figure 17-2). The cart should be organized logically to include all commonly used equipment, supplies, and local anesthetics. Supplies needed include draping and skin disinfecting supplies, nerve stimulators, and resuscitation drugs and equipment.^4,6 An atlas and textbook of regional anesthesia are invaluable resources and can be included in the cart. Finally, the cart should be organized and stocked in such a way that most regional blocks can be performed efficiently and without interruption in the designated area.

Figure 17-2. An example of regional anesthesia equipment storage chart.

        EMERGENCY DRUGS & EQUIPMENT

Although adverse effects and complications from peripheral nerve blocks are relatively rare, in the case of an untoward reaction or complication, immediate and timely intervention is necessary to prevent adverse outcomes.^4,6,7 Thus, all emergency drugs and airway equipment should be readily available in a neatly organized designated drawer in the regional block cart. Emergency drugs should include atropine, epinephrine, phenylephrine, ephedrine, propofol, and suc- cinylcholine. In addition, laryngoscopic equipment with an assortment of commonly used blades, styletted endotracheal tubes and airways of various sizes, and a mask-valve ventilation device (Ambubag) with an oxygen source and a suction apparatus should be in the designated drawer.

        PREMEDICATION

Sedation and analgesia is used commonly when preparing patients for regional anesthesia. Particular attention should be paid to the dosage and titration of these drugs in order to obtain the maximum benefit with minimal side effects, especially in elderly patients.⁸ Ideally, sedatives should be short- acting, easy to administer, and have a low side effect profile and a high safety margin. Effective sedation can be achieved with propofol, midazolam, fentanyl, remifentanil, or a combination of these drugs. The dosages of sedative and analgesic agents are titrated to achieve a level of sedation appropriate for a specific nerve block procedure and patient characteristics (Table 17-1).

        SPECIALTY TRAYS

A commercially or institutionally prepared nerve block tray is useful for an efficient and successful nerve block. Ideally, such trays should be customized to contain all necessary equipment to perform the intended regional anesthesia procedure without interruption.^4–6,9 In practice, however, it is difficult to have a single set-up containing all desirable items, particularly with the extensive assortment of needles and catheters available. Instead, a basic regional anesthesia set-up that is suitable for most nerve blocks can be prepared or obtained commercially (Figure 17-3). Such a set-up should include items for sterile skin preparation and draping and needles and syringes for skin infiltration. The specific needle/catheter should then be selected and simply added to the tray for a specific block. Inclusion of a marking pen and ruler is helpful for outlining the patient’s anatomy prior to performing the procedure. With proper preparation, the anesthesiologist can focus on performing the entire procedure without distraction.

Figure 17-3. An example of a commercially available basic regional anesthesia tray.

        REGIONAL BLOCK NEEDLES

Clinical Pearls

        A wide variety of needles are available for peripheral nerve blocks. Depending on the block performed, the preference of the clinician, and the size of the patient, needles are chosen based on tip design, length, gauge, and the absence or presence of insulation.^4,6,7,9,10 Most anesthesiologists, however, now commonly use insulated needles for better block precision (see Chapter 5, Electrophysiology of Nerve Stimulation).

Needle Tip Design

Nerve injury following local anesthetic injection usually occurs from one of three mechanisms.^10,11 The first mechanism is from direct trauma to the nerve by the advancing needle. The second is from mechanical neural damage or ischemia to the nerve from a high-pressure intraneural injection of local anesthetic. Finally, nerve injury can occur as a result of a combination of the previous two mechanisms, with the possibility of toxic effects occurring from the local anesthetic or its preservative.

        Currently, there is lack of clear evidence to suggest unequivocally that needle design is a significant factor in nerve injury; however, most expert anesthesiologists believe that pencil-point or short, blunt-bevel needle designs are less likely to cause injuries during nerve blockade. Intuitively, needles with short, blunt bevels or pencil points are much less likely to penetrate or cut nerves during needle advancement than are long- (cutting) bevel needles. Blunted, Tuohy-tip design needles recently were used with success for continuous peripheral nerve blocks.^12,13 The design of the needle tip can have a direct effect on an anesthesiologist’s ability to appreciate the various tissue planes as it passes through them. Blunt, short-bevel, and Tuohy needles offer more resistance and thus give a better feel (with some techniques) as the needle traverses tissue layers than do sharper, long-bevel needles. In an in vitro study, anesthesiologists preferred needles that offered moderate resistance and enhanced feel with the tissue penetration.¹⁴ For a single-shot deep nerve or major plexus nerve block, most experts use short- and blunt-beveled needles with or without insulation (Figures 17-4 and 17-5). On the other hand, sharp and smaller gauge needles (eg, 25- and 26-gauge) are often used for transarterial axillary, superficial, and field blocks. If a block does not require nerve stimulation (eg, a paravertebral block), a 22-gauge, uninsulated Tuohy needle or Quincke spinal needle can be used. In the case of continuous blocks, short-bevel and Tuohy-style tips are used most commonly.

Figure 17-4. Various uninsulated single-shot needle tips. Top to bottom: Quincke, short-beveled, Tuohy.

Needle Length

The appropriate length of a needle must be selected based on the block performed and the size of the patient. A needle that is too short will not reach its targeted depth. In contrast, excessively long needles carry a higher risk of causing serious complications, not only because they are more difficult to manipulate but also because they tend to be inserted too deeply. The recommended needle lengths provided in this chapter are based on the authors’ practice⁴ and should be regarded as general guides only (Table 17-2).

Figure 17-5. Various insulated single-shot needle designs. Top to bottom: Sprotte, Quincke, short-beveled.

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. Cervical Plexus Block.