Anesthesiology

Carpal Tunnel Repair

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What the Anesthesiologist Should Know before the Operative Procedure

Carpal tunnel syndrome is a common hand disorder, which is caused by compression of the median nerve at the wrist. The consequent median nerve neuropathy causes pain, paresthesia, numbness, and weakness, which can be debilitating and can result in loss of work-productivity.

Surgical treatment for carpal tunnel syndrome is carpal tunnel release, which involves division of the flexor retinaculum (or transverse carpal ligament). It is the most common hand surgery performed in the United States, with estimated 500,000 performed per year.

The approaches to carpal tunnel release (CTR) surgery include the traditional open CTR, limited incision (or mini-open) CTR, and endoscopic CTR (single-port or two-port). The traditional CTR surgery is performed using a 4-6 cm longitudinal incision. The incision- related complications of this approach include scar tenderness, grip and pinch weakness, and pillar pain. This has led to attempts to reduce incision length.

The mini-open CTR approach is typically less than 2 cm, and is reported to reduce incision-related morbidity without reducing the success of the procedure. Similarly, the endoscopic approach, in which the transverse carpal ligament is divided from within the carpal tunnel, allows for smaller incisions and avoidance of potential incision-related complications.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Carpal tunnel release is an elective surgical procedure that is generally performed on an outpatient basis. Because this is an elective surgical procedure, it is imperative that the patient's co-morbidities are optimized prior to proceeding with the procedure.

2. Preoperative evaluation

Carpal tunnel syndrome is usually caused by work-related strain and repeated movements. The predisposing factors include obesity, diabetes, chronic arthritis, hypothyroidism, and pregnancy as well as certain sports activities such as baseball and weight training.

Preoperative evaluation should include assessment of the predisposing factors for carpal tunnel syndrome.

3. What are the implications of co-existing disease on perioperative care?

b. Cardiovascular system:

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c. Pulmonary:

N/A

d. Renal-GI:

N/A

e. Neurologic:

N/A

f. Endocrine:

N/A

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

N/A

4. What are the patient's medications and how should they be managed in the perioperative period?

N/A

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

N/A

i. What should be recommended with regard to continuation of medications taken chronically?

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j. How to modify care for patients with known allergies

N/A

k. Latex allergy - If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

N/A

l. Does the patient have any antibiotic allergies - Common antibiotic allergies and alternative antibiotics

N/A

m. Does the patient have a history of allergy to anesthesia?

N/A

5. What laboratory tests should be obtained and has everything been reviewed?

Preoperative laboratory tests should be based on the patient's comorbidities. There are no tests required specifically for the surgical procedure.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

An ideal anesthetic technique for CTR surgery should provide excellent surgical conditions that allow identification of critical anatomical structures such as the transverse carpal ligament and median nerve. In addition, if a tourniquet is used (to provide a bloodless field), the anesthetic technique should provide adequate analgesia for its tolerance. The anesthetic options for CTR surgery include local infiltration anesthesia, intravenous regional anesthesia (Bier block), peripheral nerve block (brachial plexus block or distal peripheral nerve block), and general anesthesia.

a. Regional anesthesia

Intravenous regional anesthesia (Bier block) is easy to perform and has rapid onset and a high success rate. In addition, it produces no residual motor blockade and allows early recovery and discharge home. The local anesthetic commonly used for intravenous regional anesthesia is lidocaine; however, other options include prilocaine, chloroprocaine, and articaine. The local anesthetic solution may be supplemented with drugs such as ketorolac, clonidine, and dexmedetomidine.

Limitations of the intravenous regional anesthesia technique include tourniquet pain, which can be minimized by using a double-cuff tourniquet. In addition, this technique does not provide postoperative analgesia. Major complications associated with this technique include local anesthetic toxicity, nerve injuries, and compartment syndrome.

Peripheral nerve blocks (brachial plexus block or distal nerve blocks) can be used to provide surgical anesthesia. Because peripheral nerve blocks provide prolonged pain relief they reduce analgesic requirements in the immediate postoperative period.

Potential disadvantages of peripheral nerve blocks include longer induction time and possible block failure that might increase operating room time. In addition, there may be prolonged motor blockade extending for several hours after surgery, which has a potential to produce injury to the hand.

Of note, single-shot techniques have a short duration of analgesia. Because it is difficult to anticipate the degree of pain at the time of discharge home, there might be greater pain after discharge. Furthermore, abrupt termination of the analgesic effect may lead to increased perception of pain after recovery from neural blockade. Therefore, single-shot peripheral nerve blocks should be supplemented with oral analgesics.

b. General anesthesia

An ideal general anesthetic should provide smooth and rapid induction, optimal operating conditions, and rapid recovery with minimal side effects. Use of shorter-acting intravenous anesthetics (e.g., propofol), inhaled anesthetic (i.e., desflurane and sevoflurane), and opioids (e.g., remifentanil) should provide optimal intraoperative conditions as well as allow rapid recovery from anesthesia.

Supralaryngeal devices (e.g., laryngeal mask airway) are increasingly used for peripheral and superficial elective surgical procedures. Compared with the tracheal tube, these devices do not require muscle relaxation and do not require laryngoscopy, and thus may prevent associated complications.

These devices are well tolerated at lower concentrations of inhaled anesthetics and, therefore, may allow titration of anesthetic to surgical stimulus rather than airway device tolerance. With the patient breathing spontaneously, opioid requirements can be based upon respiratory rate, while sedative-hypnotic anesthetics may be titrated using a brain function monitor or recommended end-tidal concentrations of inhaled anesthetics known to prevent awareness. Overall, this approach may allow earlier emergence from anesthesia and improve perioperative efficiency. The supralaryngeal devices should be avoided in patients with laryngeal pathology or those with significantly reduced lung compliance, as well as in patients at high risk of regurgitation or aspiration.

Maintenance of anesthesia could be with propofol infusion (total intravenous anesthesia) or inhaled anesthetic. Inhaled anesthetics exert some neuromuscular blocking effects, which may reduce the need for muscle relaxants and reduce the potential for postoperative residual paralysis. Inhaled anesthesia techniques allow an earlier emergence from anesthesia, but this does not translate into earlier time to discharge home.

The use of nitrous oxide remains controversial. However, its benefits (i.e., analgesia and reduced requirements for sedative-hypnotics) may outweigh the potential side effects (i.e., increased postoperative nausea and vomiting and pressure effects through expansion of closed spaces). Use of propofol for induction of anesthesia and antiemetic prophylaxis (both of which are highly beneficial in ambulatory anesthesia), negate the emetic effects of nitrous oxide. A recent review suggested that nitrous oxide improves quality of general anesthesia and facilitates recovery with minimal side effects. Overall, there is no convincing reason to avoid nitrous oxide.

Compared with regional anesthesia, general anesthesia is associated with delayed recovery and higher incidence of postoperative pain, nausea, and vomiting. Patients receiving general anesthesia should receive wound infiltration with a long-acting local anesthetic for postoperative pain relief.

c. Monitored anesthesia care

Local anesthetic wound infiltration techniques are simple to administer and allow expeditious onset of surgery as well as provide excellent surgical pain relief and overall, facilitate recovery and discharge home. In addition, local anesthetic techniques provide excellent postoperative analgesia that outlasts the duration of action of the local anesthetic, and thus should reduce postoperative opioid requirements and opioid-related side effects.

The local anesthetic techniques are well suited for carpel tunnel release surgery performed without a tourniquet. In this case, local anesthetic is combined with epinephrine to reduce intraoperative bleeding.

Local anesthetic techniques do not control tourniquet pain. A forearm tourniquet, which is efficacious in preventing surgical bleeding, could be used as it is well tolerated by an 'awake' patient undergoing short surgical procedure such as carpel tunnel release.

Of note, local anesthetic infiltration techniques may not be suitable for patients requiring excessive manipulation of the median nerve (e.g., epineurectomy and internal neurolysis) and flexor tenosynovectomy.

6. What is the author's preferred method of anesthesia technique and why?

The preferred technique for most CTR procedures is local infiltration anesthesia supplemented with intravenous sedation/analgesia.

If general anesthesia is required, optimal technique includes induction of anesthesia with propofol and maintenance with nitrous oxide in 50% oxygen and a shorter-acting inhaled anesthetic (i.e., desflurane or sevoflurane) titrated to a brain function monitor. The airway is secured using a supralaryngeal device (assuming there are no contraindications). Intraoperative analgesia could be provided with local anesthetic wound infiltration and/or a low-dose opioid such as fentanyl. Prophylactic antiemetics could include dexamethasone 4 mg after induction of anesthesia and ondansetron 4 mg given at the end of surgery. in addition, if the patient did not receive oral NSAIDs or COX-2 specific inhibitors prior to surgery, ketorolac 30 mg IV is administered at the end of surgery.

Peripheral nerve blocks are generally used because adequate pain relief can be achieved with wound infiltration with local anesthetic and oral non-opioid analgesics (e.g., NSAIDs and COX-2 specific inhibitors and acetaminophen).

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

N/A

c. Postoperative management

Prophylactic analgesia may include nonsteroidal anti-inflammatory drugs (NSAIDs) or cycloxygenase-2 (COX-2) specific inhibitors combined with acetaminophen initiated prior to surgery. In addition, wound infiltration should further improve pain relief and reduce the need for opioids.

After discharge home, pain should be treated with a combination of acetaminophen and NSAIDs or COX-2 specific inhibitors, which is more effective than either drug alone. Regular dosing with analgesic medications provides superior analgesia as this prevents the pain from becoming severe and decreases the incidence of breakthrough pain. Opioid analgesics may be added to this regimen if necessary. Of note, analgesics should be continued until wound healing has occurred.

What's the Evidence?

Ono, S, Clapham, PJ, Chung, KC. "Optimal management of carpal tunnel syndrome". Intern J Gen Med. vol. 3. 2010. pp. 255-61.

Shores, JT, Lee, WP. "An evidence-based approach to carpal tunnel syndrome". Plat Reconstr Surg. vol. 126. 2010. pp. 2196-204.

Keith, MW, Masear, V, Chung, KC. "American Academy of Orthopaedic Surgeons Clinical Practice Guideline on diagnosis of carpal tunnel syndrome". J Bone Joint Surg Am. vol. 91. 2009. pp. 2478-9.

Sunha, A, Chan, V, Dimitri, J, Anastakis, DJ. "Anesthesia for carpal tunnel release". Can J Anaesth. vol. 50. 2003. pp. 323-7.

Brown, AR. "Anaesthesia for procedures of the hand and elbow". Best Prac Res Clin Anaesthesiol. vol. 16. 2002. pp. 227-46.

Guay, J. "Adverse events associated with intravenous regional anesthesia (Bier block): a systematic review of complications". J Clin Anesth. 2009. pp. 585-94.

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