Peripheral Nerve Blocks: A Color Atlas, 3rd Edition

24. General Considerations for Continuous Nerve Blocks

Jacques E. Chelly

In the past few years, continuous nerve blocks have enjoyed a significant surge of interest, especially for acute postoperative pain management following major orthopedic procedures (both inpatient and outpatient) in adults as well as in children. The present interest is based in part on several encouraging reports about the beneficial effects of these techniques on functional outcome and hospital length of stay. Furthermore, interest has been fueled by the increased number of indications for continuous lumbar plexus and femoral block, the development of new approaches related to the placement of sciatic perineural catheters (posterior popliteal, lateral, and gluteal approaches), the recent introductions of the insulated Tuohy needle, and new pumps especially designed for outpatient surgery. These techniques are very effective and provide a pain-free environment, especially when incorporated into a multimodal and multidisciplinary approach to postoperative pain management. To maximize functional outcome and shorter recovery, it is necessary to start prior to surgery and combine peripheral nerve blocks with cyclooxygenase (COX)-2 inhibitors, opioids, cryotherapy, appropriate immobilization, the least traumatic surgical techniques, and optimal sleep and nutrition after surgery.

The indications for continuous blocks for major inpatient orthopedic surgeries (which in the United States represent an average of 2 to 4 days of hospitalization), include major shoulder surgery; upper and lower extremity trauma; upper and lower extremity reimplantation; shoulder, elbow, hip, knee, and ankle arthroplasty; as well as prolonged upper and lower physical therapy.

The techniques applied vary with the indications. For major shoulder surgeries, most authors favor the use of continuous interscalene and (less frequently) supraclavicular continuous blocks. For major surgeries below the shoulder, infraclavicular, and axillary (including the Raj approach) continuous techniques have been demonstrated to be safe and effective. For major lower extremity surgeries, the techniques also vary according to the indications and the most prevalent nerve(s) involved in the postoperative pain. Thus, psoas compartment or lumbar plexus continuous blocks have been reported to be effective in patients undergoing hip surgery, whereas the use of continuous femoral blocks seems to be preferred for major knee surgery. Furthermore, for major ankle and foot surgeries, continuous sciatic nerve blocks using a subgluteal, lateral, and posterior popliteal approach are indicated.

Although several local anesthetic solutions have been advocated (including 1% procaine, 1% lidocaine, and 0.1%, 0.2%, 0.25%, and even 0.5% bupivacaine), it seems that 0.2% ropivacaine is becoming the local anesthetic of choice for these techniques. Compared with bupivacaine, ropivacaine is less toxic and provides a more preferential sensory block with less paresthesia. In addition, residual motor blocks may represent an important limitation to an optimum active mobilization and have been shown to be more frequent with bupivacaine than with ropivacaine. In the past few years, local anesthetic mixtures used for continuous nerve blocks have also included opioids such as morphine (0.03 mg/mL), fentanyl (2 mg/mL), diamorphine (0.02 mg/mL), sufentanil (0.1 mg/mL), and clonidine (1 mg/mL), but none of these drugs have been proven to be beneficial.

Until the introduction of electronic infusion pumps, continuous nerve blockades were performed using discontinuous perineural injections of various types of local anesthetic solutions in various concentrations and volumes. In the late 1970s, continuous infusion techniques were introduced and have now become the techniques of choice. In the past few years, however, the use of select patient-controlled techniques has generated particular attention. It has been shown that a patient-controlled bolus of 5 mL with a lockout period of 30 minutes or 5 mL/hour plus a 2 to 3 mL bolus and a lockout period of 20 to 30 minutes is as effective as 10 mL/hour after inpatient shoulder and knee surgery.

The constant search for increased efficiency and earlier discharge from the hospital coupled with present health care reimbursement issues led to a continuing increase in the number of orthopedic procedures being performed on an outpatient basis. In this environment, several authors have demonstrated that pain is the first cause of unscheduled rehospitalization and delayed discharge after ambulatory surgery, and that a significant number of patients experienced moderate to severe pain, despite the prescription of oral medication including opioids after surgery while being at home. Although the reasons for this situation are multifactorial, it is clear that ineffective or short-lasting pain treatment (including single peripheral nerve blocks and intraarticular injections of opioids or local anesthetics) represents an important contributing factor. To provide better postoperative pain control in an ambulatory environment, continuous perineural infusions of 0.2% ropivacaine have been used for several indications, including rotator cuff repair (interscalene continuous blocks) and hand surgery (axillary continuous blocks), anterior cruciate ligament (ACL) and patella repair (femoral continuous blocks), and major foot surgery (popliteal and lateral continuous sciatic blocks). In the past 2 years, several investigators have also reported the effectiveness and safety of continuous nerve blocks and subacromial infusion after ambulatory orthopedic surgery.

Catheter Placement for Continuous Regional Anesthesia

Some general guidelines for catheter placement that may be helpful are as follows:

1.   The placement of a perineural catheter needs to be performed in strict aseptic conditions, using sterile gloves, mask, sheets, etc., and appropriate disinfection of the skin.

2.   Although the level of sedation of the patient is similar for a single and a continuous nerve block, careful consideration should be given to an appropriate local anesthesia because the introducing needle or cannula is usually of a bigger gauge than the one used for a single block.

3.   The bevel of the introducing needle should be oriented along the same axis as the nerve. Then, the nerve should be approached at the least acute angle possible. In the case of an insulated Tuohy needle, the orientation of the bevel also depends on the direction the catheter should take.

4.   With the needle appropriately placed, inject an initial bolus of local anesthetic or saline to facilitate the introduction of the catheter by dilating the perineural compartment.

5.   Introduce the catheter firmly, but if it does not thread, do not force it and kink it. Instead, retrieve the catheter, and either lower the angle of the introducing needle or slightly change the orientation of the bevel of the introducing needle before reintroducing the catheter.

6.   The catheter is introduced 3 to 4 cm beyond the tip of the needle and the needle is withdrawn with a push-and-pull technique (the catheter being pushed while the needle is pulled).

7.   After the catheter has been successfully threaded, it is secured by removing the prep solution with sterile saline, swabbing the area with a clear adhesive, applying Steri-Strip (3M, St. Paul, MN), and then covering the catheter with a transparent dressing.

8.   To ensure catheter potency, inject an additional 3 to 5 mL of the anesthetic mixture.

9.   In most cases, the infusion of 0.2% ropivacaine is started postoperatively in the recovery room.

10.       The mode of infusion is either continuous (4 to 12 mL/hour, depending on the size of the patient and the expected pain the patient may experience) or postoperative patient-controlled regional analgesia (PCRA) with a basal infusion of 3 to 5 mL, bolus of 3 to 5 mL, and lockout period of 20 to 30 minutes.

11.       For patients being considered for a continuous nerve block at home, it is important to verify that (a) the patient is an appropriate candidate for ambulatory continuous nerve block, (b) proper patient education has been provided, not only regarding the technique but also regarding the infusion pump device, (c) discharge orders also include a set of written instructions related to side effects (local anesthetics and techniques) and contact information, and (d) follow-up is provided by a daily telephone call to verify that the patient is doing well, and after the end of the local anesthetic infusion that complete recovery of motor and sensory function has occurred. In the case of an incomplete recovery, a follow-up visit should be considered.