Figure 49–1. The first step is nerve localization techniques identical to those with nonstimulating catheters. Shown here is the needle insertion for femoral nerve block.

Figure 49–2. Once the nerve is localized using stimulation with the needle, the needle is disconnected from the nerve stimulator and the motor response ceases. The stimulating catheter is now connected to the nerve stimulator and inserted through the needle, which brings back the motor response.

Figure 49–3. As the stimulating catheter is inserted through the needle, the exposed tip (arrow) of the catheter makes electrical contact with the inner metal lining of the needle and again enables stimulation with the needle until the tip of the catheter exits the needle.

        “The accurate placement of the tip of the needle and catheter is important to the success of the procedure… we adapted a previously described method of electrical localization of catheters to the purpose… by applying an electrical potential to the tip of the catheter byway of its stylet in the subarachnoid space. The same principle was used in localizing the tip of the needle in relation to the phrenic nerve in this study.”

        Indeed, early on nerve stimulation in nerve block was used to accurately place catheters for continuous blockade of a motor nerve—the phrenic nerve. Paradoxically, the nonstimulating catheter technique is often referred to as the “classical technique,” when in fact the stimulating technique was the technique that was described first.

        It was only decades later after the use of nerve stimulators for single-injection blocks of peripheral nerves became more popular that the technique of placing catheters for continuous peripheral nerve blocks by stimulating the nerve via both the needle and the catheter was “reinvented.”^{2, 8} In the 30 years after the first descriptions by Sarnoff and Sarnoff, the main focus in the development of continuous peripheral nerve blocks was on the upper extremity, and mainly to improve blood flow by sympathetic block for reimplantations of traumatic amputated parts of the upper limb. Most authors used variations of the axillary perivascular technique in the 1970s and 1980s.^9–12 For example, during the Angola Civil War in 1975 the present author, acting as anesthesiologist for the Number 1 Forward Surgical Unit, used a cut- down technique and under direct vision, placed central line catheters in the perivascular space to manage the pain due to severe battlefield injuries of the hand and arm.¹³ Of note, the main indication for continuous blocks in the 1970s and 1980s was to achieve sympathetic block and improve blood flow; at that time analgesia was considered merely, as an additional “bonus” and did not become the primary goal until the early 1990s.

        During the 1990s the emphasis shifted toward the use of continuous nerve blocks to manage acute postoperative pain. This was, among other factors, driven by the quest for cost-effective ambulatory surgery following the exponential escalation of health-care costs in the mid- to late 1980s. Because of the efficiency and relative safety of neuraxial nerve blocks, the lower extremity received little attention during the early development of the technique, and the main focus was on continuous blocks for the upper extremity.^14–17 During this era, only the nonstimulating catheter technique was used by most investigators in postoperative treatment of patients undergoing a variety of major surgical procedures on the upper and lower extremities. Francois Singelyn and coworkers¹⁸ were the first to demonstrate that continuous femoral nerve block in patients having total knee replacement provides superior pain control to intravenous morphine and epidural analgesia. This report was followed by others also documenting excellent analgesic potential, fewer complications, and faster rehabilitation with continuous nerve blocks.^{19, 20}

        The secondary failure of continuous nerve block catheters, however, represents a significant obstacle to the ability to reproduce results cited in these and other reports.^21–25 Ganapathy and coworkers²⁶ and Klein and colleagues²⁷ alerted practitioners to the importance of ensuring the functionality of the catheters before discharging patients home. Discharging patients from the hospital with continuous nerve blocks that malfunction after the primary block wears off can increase the costs of postoperative management if a patient has to be readmitted to the hospital to treat resulting acute pain.²⁷ It is for these reasons that the concept of the stimulating catheter (or the Sarnoff technique) was revisited in the mid- to late 1990s.^{2, 8}

        THE STIMULATING CATHETER TECHNIQUE

The technique described here is a general description of the stimulator technique applicable to most peripheral nerve blocks; the specifics of the techniques, however, vary somewhat for individual nerve block procedures. Figures 49-1 through 49-7 illustrate maneuvers specific to the stimulating catheter placement.

Stimulation Through the Needle

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Newer Amide Anesthetics & Sustained-Release Local Anesthetics1. Diagnosis & Management of Intraspinal, Epidural, & Peripheral Nerve Hematoma. Histology of Peripheral Nerves. Supraclavicular Brachial Plexus Block.