JNYSORA Volume 10 March 2009: Nerve Blocks For Postoperative Analgesia: Choices After Common Lower Extremity Procedures

This review will discuss the advantages and limitations of various nerve block techniques when used for postoperative pain management for several common surgical indications.

Introduction

Large proportion of patients undergoing surgery do not receive adequate postoperative analgesia. Postoperative pain is the leading cause of unplanned hospital admissions following ambulatory surgery and a major source of dissatisfaction with perioperative outcome. The estab-lishment of acute pain services in major institutions both in the United States and overseas has had a major impact on postoperative comfort and patient satisfaction. Most acute pain services primarily utilize patient controlled IV analgesia (PCA) and/or epidural infusion (PCEA), however advances in neuronal blockade offer an unprecedented range of effective and surgery-site specific analgesic options. Using long-acting local anesthetics, peripheral nerve blocks can be used to provide an excellent anesthesia and postoperative analgesia. Additionally, a catheter for continu-ous infusion of local anesthetics can be inserted perineurally to extend the analgesia beyond the duration of the single shot blocks. This review will discuss the advantages and limitations of various nerve block techniques when used for postoperative pain management for several common surgical indications.

Analgesia After Inguinal Hernia Surgery

Inguinal hernia repair, a very common outpatient procedure, is associated with a relatively high incidence of nausea and vomiting, urinary retention and postoperative pain. These problems often occur after general and spinal anesthesia and may lead to a intense postoperative discomfort and unplanned hospital admissions. However, Klein et al reported that excellent surgical anesthesia and postoperative analgesia in patients undergoing inguinal hernia repair can be obtained with thoracolumbar paravertebral blocks. Using 5 ml of 0.5 % bupivacaine (with 1:400 000 epinephrine) the authors obtained onset of anesthesia after 15-30 minutes and a long-lasting postoperative analgesia. The mean time to onset of discomfort and to first opioid request in their study were 14 hours and 22 hours, respectively.

Notably, this technique is easy to master and carries a relatively low risk of serious complications. With the patient in the sitting (or lateral decubitus position), the spinous processes beginning from T9 through L1 are identified. Needle insertion points are marked 2.5 cm lateral to the superior border of the spinous processes. After subcutaneous infiltration of local anesthetic a 10cm long 22G spinal needle (Quincke or Tuohy type), connected via an extension tubing to a syringe with local anesthetic, is inserted to contact the transverse process. Upon contacting the transverse process, the needle is “walked-off” the process and advanced 0.5 cm to 1 cm deeper to inject 5 ml of local anesthetic at each level (Figure 1). In our practice, we routinely use 0.75% ropivacaine with 1:300,000 epinephrine 5 ml/level for this indication. In most patients this suffices as a sole anesthetic/analgesic technique with complete analgesia typically extending over 10 hours postoperatively. This is in agreement with the study by Klein et al., where 65% of patients did not have incisional pain for 10 hours or longer although all patients had full return of sensation at 12 ± 6 hours.

Additional advantages of the paravertebral blocks include avoidance of general anesthesia, and long-lasting analgesia without affecting the ability to void or ambulate. While an epidural spread can occur in some patients, it is usually limited and short-lived.

Figure 1. Thoraco-lumbar paravertebral blocks is an excellent anesthesia technique in patients undergoing inguinal hernia surgery. Injections of 5 ml/ level of 0.5%-0.75% ropivacaine (T9-L1) results in long-lasting postoperative analgesia.

Figure 2. Continuous femoral or “three-in-one” nerve block can be used to treat pain after thigh and knee surgery. After initial injection of local anesthetic, an infusion of 8 ml/hr of 0.2% ropivacaine is initiated.

Analgesia After Hip Surgery

Lower extremity blocks have been traditionally of limited value both for surgical anesthesia and for postoperative analgesia in hip surgery. This is because of the complex innervation of the hip joint where sensory innervation of the hip comes from branches of both lumbar and sacral plexi. Thus it is not surprising that there are few reports that focus on using peripheral nerve blocks for this indication.

Visme et al. have compared combined the lumbar and sacral plexus block with spinal anesthesia for hip fracture surgery in elderly patients. While they concluded that the blocks can be used in hip surgery, the advantages of nerve blocks (less hypotension and unilateral block) were limited by the high percentage of failed (7%) and incomplete blocks (20%) in their study. Of note, the authors used the parasacral approach to the sciatic block in order to block the entire sciatic plexus in addition to the sciatic nerve. Unfortunately, the authors used lidocaine for nerve blocks, which resulted in a short duration of analgesia, comparable to that of spinal anesthesia. Nonetheless, an obvious advantage of nerve blocks is the ability of extend analgesia by a continuous infusion and/or intermittent boluses through an indwelling catheter.

While complete anesthesia of the hip using peripheral nerve blocks as sole anesthetic might not be easily achieved, the addition of the lumbar plexus block to a primary anesthetic may still be beneficial. For instance, Chudinov et al emphasized that lumbar plexus block alone is inadequate for hip surgery because the spread of local anesthetic is limited to the lumbar plexus. However, they achieved adequate pre and postoperative analgesia by continuous psoas compartment block in patients who underwent repair of the hip fractures. In another report, Stevens et al reported that the lumbar plexus block may significantly reduce perioperative pain and blood loss in patients undergoing total hip arthroplasty. In this study the intra and postoperative opioid requirements of patients in the block group was found to be significantly lower than in the control group.

Using a more distal approach, Singelyn et al have also recently reported the use of continuous femoral nerve block (“three-in-one” block) for pain management after total hip arthroplasty. The authors compared the continuous infusion of local anesthetic (0.125% bupivacaine with 1 µg/ml clonidine and 0.1 µg/ml sufentanyl) with two PCA only dosing regimens using the same solution. They reported that PCA boluses alone (5 ml/30 min) were associated with the smallest local anesthetic consumption, lowest VAS scores and the best patient satisfaction. Of note, in this study the authors obtained the blocks of the femoral and lateral femoral cutaneous nerves in well over two thirds of the patients, however obturator nerve blocks failed in many patients.

While the “three-in-one” block technique has an advantage of being superficial and easily accessible for blockade, the analgesia obtained in patients after hip surgery using these techniques is at best limited. Consequently, whenever indicated, we much prefer lumbar plexus or paravertebral blocks for analgesia after hip surgery.

Surgery on the Thigh Surgery

The lumbar plexus block, femoral block, sciatic block or their combination can be used to achieve complete anesthesia and excellent postoperative analgesia for surgery of the thigh. Common use for these techniques as a sole anesthetic or postoperative analgesia include thigh biopsy, long saphenous vein stripping, femur surgery, and surgery on the patella and quadriceps muscle tendon. In the last two indications, femoral block alone is an elegant anesthetic technique allowing prompt discharge home and analgesia for well over 12-16 hours when long acting local anesthetics are used.

The continuous femoral or 3-in-1 nerve blocks can be used successfully for postoperative pain relief after femoral shaft surgery. The continuous femoral nerve block technique is quite similar to single-shot femoral nerve blocks, except that a catheter is inserted after the injection and a continuous infusion is used to provide analgesia of the anterior thigh (Figure 2). The goal of the “three-in-one” technique however is to obtain blockade of the femoral, lateral cutaneous, and obturator nerves after a single injection of larger volume of local anesthetic. However, the ability to obtain block of the all three nerves using this technique has been a subject of a considerable controversy. Some authors have suggested that fascia iliaca block, where a double “pop” technique to enter the fascia iliaca 1.5 cm lateral to the artery, might result in higher success rate. This technique relies on both insertion of the catheter tip to L4 or L5 vertebrae and an adequate volume of local anesthetic. Unfortunately, up to 40% of catheters can fail to reach the desired position and it appears that lumbar plexus block is the technique of choice whenever anesthesia or analgesia of the entire thigh is sought.

Finally, it is interesting that the use of these blocks can provide analgesic benefits far beyond the duration of anesthesia. For instance, using a short acting local anesthetic, chloroprocaine 3% in the femoral nerve block for outpatients undergoing long saphenous vein striping surgery, Vloka et al reported significantly better postoperative analgesia and lower analgesic requirement in patients who received blocks compared to patients who had spinal anesthesia.

Knee surgery

Depending on the extent and type of surgery, the lumbar plexus block, femoral block, fascia iliaca blocks or the “three-in-one” technique can all be used to provide anesthesia and perioperative analgesia after knee surgery. In addition to being good alternatives to central neural blockade for patients who will be anticoagulated after surgery, these techniques provide unilateral analgesia with far fewer side-effects than epidural analgesia.

The femoral nerve block with 25 ml of either 0.25% or 0.5% bupivacaine (as part of a multi-modality analgesic regimen) provided better analgesia for the first 24 hours after outpatient arthroscopic anterior cruciate ligament repair then had spinal anesthesia. The requirements for analgesic therapy and pain scores were significantly lower in the group that received femoral block. The femoral block is especially appealing in outpatients because its use is associated with longer duration of analgesia and fewer complications than neuraxial anesthesia.

Pain after total knee replacement (TKR) is often difficult to control using only IV opioids. Allen et al performed femoral, combined femoral-sciatic and sham blocks in patients after total knee replacement and found that pain scores at rest and morphine consumption were significantly lower for at least 8 hours after transfer to the ward in the groups receiving peripheral nerve blocks. The addition of the sciatic nerve block to the femoral nerve block did not provide additional analgesic benefits. In contrast, Ganapathy et al and others found that blocking S1 as well as the femoral, lateral femoral cutaneous, and obturator nerve was beneficial in enhancing analgesia after TKR. McNamee et al compared postoperative analgesia provided by spinal anesthesia alone or in combination with femoral and sciatic blocks in 75 patients undergoing TKR, and concluded that these blocks were effective in providing prolonged postoperative analgesia following unilateral TKR without hindering postoperative mobilization.

Unfortunately, single-shot blocks eventually resolve by the morning after surgery, resulting in the return of pain. Thus, an ability to extend analgesia beyond the first 12-24 hours as well as the ability to re-bolus the catheter before physical therapy appear to have significant benefits. For instance, in a prospective, double-blind, randomized study, Singelyn and Gouverner suggested both the “3-in-1” block and epidural analgesia provided better pain control after total knee arthroplasty than IV PCA. The same authors have suggested that the PCA technique may reduce the local anesthetic consumption. In this study, boluses of 10ml of 0.125% bupivacaine with 1 mcg/ml of clonidine with a lockout of 60 minutes was found preferable to continuous infusion of the same solution at 5 ml/hr with smaller PCA boluses (2.5 ml/30 minutes). Similarly, using a “modified” femoral “three-in-one” block Ganapathy et al. achieved significantly better analgesia using 0.2% bupivacaine than a solution of 0.1% bupivacaine. Of note, the authors suggested that in order to achieve adequate analgesia after knee surgery, the tip of the catheter should lie at the level of the transverse processes of the L4 and L5 vertebra and an adequate volume and concentration of local anesthetic should be delivered to ensure blocking at least two nerve roots above and below the level of the catheter tip. However, with this technique aimed at inserting the needle under the fascia iliaca, where the nerve runs in the groove between iliacus and psoas muscles, only 40% of catheters were positioned successfully, as documented by the CT studies.

In addition to their value in managing postoperative pain after knee replacement, combined blocks of the lumbar and sacral plexii can be used as a sole anesthetic for the surgery. Our experience is that given adequate volume, the lumbar plexus block results in a very efficient surgical anesthesia in the distribution of the lumbar plexus. Consequently, these techniques are expected to provide more complete analgesia after surgery.

Foot and ankle surgery

Foot and ankle surgeries often result in severe postoperative pain that requires large doses of opioids and interfere with early mobilization. However, continuous sciatic or popliteal nerve blocks are very effective and relatively simple techniques which are far superior to parenteral opioids for pain control after lower extremity surgery.

A below knee amputation is a common procedure that invariably results in severe postoperative pain, significant psychological suffering, and a relatively high incidence of phantom limb pain. These patients present with multiple medical problems such as cardiovascular disease, uncontrolled diabetes mellitus, decreased pulmonary reserve, sepsis and systemic anticoagulation. It is this population of patients that is among the greatest beneficiaries of nerve blocks and a single shot or continuous sciatic or popliteal blocks present an ideal anesthetic/analgesic package in many clinical situations (Figure 3). Mansour’s sacral plexus block is an effective technique for continuous block. Souron et al reported the use of this technique to provide high quality postoperative analgesia after oncologic orthopedic surgery of the leg. In their series, adequate analgesia and low parenteral opioid requirement was almost universal in these patients.

Figure 3. Continuous sciatic nerve block is an excellent analgesia technique in patients after extensive foot surgery or lower extremity amputations. After obtaining twitches of the foot, the catheter is inserted 3-5 cm beyond the needle tip and secured to the skin.

Of particular interest is that analgesia with lower extremity blocks lasts significantly longer than do ankle blocks even with the single-shot techniques. For instance, McLeod et al found that the lateral popliteal block with 0.5% bupivacaine lasted 18 hours as compared to the ankle blocks – 6.2 hours. The popliteal fossa block also can be used as an analgesic technique in children. In a study of the efficacy of the popliteal block (0.75ml/kg of 0.2% ropivacaine) after foot and ankle surgery. Nineteen of 20 children required no analgesic agents during the first postoperative 8 hours (range 8 to 12 hours). Blocking the sciatic nerve in the popliteal fossa is an excellent choice for foot and ankle surgery. When used as a sole technique in outpatients, it provides anesthesia and postoperative analgesia, allows the use of a calf tourniquet and does not cause systemic complications seen with the neuroaxial blockade. It should be noted that block requires a larger volume ( 40-50 ml ) of local anesthetic for blockade of both divisions of the sciatic nerve.

The tibial nerve block can also be used to treat postoperative pain with in patients undergoing hallux valgus surgery. This can be combined with a perineural catheter infusion of the tibial nerve using 0.25% bupivacaine at a rate of 2.5 ml/hr. Using this technique, Levecque et al achieved excellent analgesia with none of the postoperative pain scores above 1 on the visual analogue scale (VAS) at 4, 8, 12, 24, 36 and 48 hours. Similarly, the ankle block is safe, simple to perform, and almost uniformly successful for various foot surgery.

Ambulatory Surgery

Ambulatory surgery continues to grow and currently constitutes over 70% of all elective surgery performed in the United States. One of the main limiting criteria for performing ambulatory surgery is postoperative pain. As we continue the transition to even more ambulatory and early discharge procedures, expanding our analgesic options for patients in the outpatient settings is a necessity. Single shot peripheral nerve blocks can also be especially useful in this setting. While the duration of the block is limited to the type and duration of action of local anesthetic used, analgesia typically extends the expected duration of the blockade. Until recently, the use of continuous regional analgesia had been restricted to inpatient care, requiring rather impractical infusion pumps and a hospital stay. However, recent developments of better needles for continuous peripheral nerve blocks and portable battery-powered infusion pumps have facilitated the introduction of these techniques in outpatients in several medical centers. While there is little literature on the safety and efficacy of continuous infusion of local anesthetics in patient homes, recent reports suggest that these methods of analgesia can be used with a high level of patient satisfaction. These techniques however, do require a substantial level of expertise, good patient education and close followup. Given these limitations, wider implementation of these pain management techniques in outpatients remains a subject of debate. Alternatively , peripheral nerve block catheters can be used to simply “top-up” the block with a long acting local anesthetic just prior to patient discharge.

Summary

Despite our increasing understanding of and interest in pain mechanisms and pain management, a large number of patients continue to experience unacceptable pain after surgery. The ability to interrupt pain pathways at multiple anatomic levels and to provide an excellent operating conditions without over sedation or obtundation, makes peripheral nerve blocks ideally suited for surgery and postoperative analgesia. When long-acting local anesthetics are used, peripheral nerve blocks can be used to provide excellent anesthesia and postoperative analgesia in patients undergoing a wide variety of surgical procedures. Additionally, a catheter for continuous infusion of local anesthetics can be inserted perineurally to extend the analgesia beyond the duration of the single shot blocks. As long acting, depot local anesthetics become available in the near future, peripheral nerve blocks will likely play a crucial role in routine postoperative pain management in the majority of patients undergoing surgical procedures

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