Intravenous Regional Block (Bier Block)

Intravenous regional anesthesia was originally introduced by the German surgeon August K. G. Bier in 1908; thus the name, "Bier block". Dr. Bier described a complete anesthesia and motor paralysis after intravenous injection of prilocaine into a previously exsanguinated limb.

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Overview

Indications: Surgery on the wrist, hand and fingers. Local anesthetic: 15 mL of 2% lidocaine Complexity level: Basic

General considerations

Intravenous regional anesthesia was originally introduced by the German surgeon August K. G. Bier in 1908; thus the name, "Bier block". Dr. Bier described a complete anesthesia and motor paralysis after intravenous injection of prilocaine into a previously exsanguinated limb. The resultant anesthesia is produced by direct diffusion of the local anesthetic from the vessels into the nearby nerves. The technique was reintroduced into clinical practice using lidocaine as a local anesthetic in mid-1960s. Since its reintroduction, intravenous regional anesthesia is one of the most commonly used regional anesthesia techniques in the United States. Intravenous regional analgesia is best used for brief minor surgery (up to 1 hour) of the hand and forearm. Its use for longer surgical procedures is precluded by the appearance of the discomfort from the tourniquet, which limits the indications for its use. Some examples of suitable procedures include carpal tunnel release, tendon contracture release, and foreign body extraction. The main advantages of this technique are its simplicity and reliability. Its drawback is the lack of postoperative analgesia because the block quickly resolves after the release of the tourniquet. In this chapter, we describe the use of intravenous regional anesthesia for the upper extremity; identical principles with a larger volume of local anesthetic can be used for the lower extremity.

Regional anesthesia anatomy

Peripheral nerve endings of the extremities are nourished by small blood vessels. Injection of a local anesthetic solution into a venous system results in diffusion of the local anesthetic into the nerve endings with the consequent development of anesthesia. This holds true for as long as the concentration of the local anesthetic in the venous system remains relatively high. As it will be apparent in the technique description, it is imperative that before the injection, the venous system is exsanguinated to prevent dilution of local anesthetic

Distribution of anesthesia

Intravenous regional block results in anesthesia of the entire extremity below the level of the tourniquet. The duration of the anesthesia and analgesia are limited by the duration tourniquet.

Patient positioning

The patient is in the supine position with the arm to be blocked elevated to achieve passive exsanguination. This is a crucial step and care should be taken to allow 1-2 minutes for passive return of blood to the dependent levels. An intravenous line is started on the side opposite to be blocked before the block procedure.

Equipment

A standard regional anesthesia tray is prepared with the following equipment:

• 22-gauge intravenous catheter
• Flexible extension tubing
• 5" Esmarch bandage
• Double cuff tourniquet
• 20 mL syringes with local anesthetic
• Pressure source
• A double-cuff tourniquet with in-line valves

TIPS:

• A smaller gauge, IV catheter should be used to prevent oozing after the removal of the catheter (this often occurs even with most careful "exsanguination" procedure.
• Nearly all cuffs will have some small-volume leaks. Therefore, a constant-pressure gas source (e.g., automatically-controlled source of nitrogen) is necessary to allow for inflation of the cuff or automatic correction of any leaks.
• The pneumatic cuffs should be checked for air leak before applying on the extremity

Technique

A tourniquet is placed on the proximal arm of the extremity to be blocked. We use a "double cuff" to increase the reliability of the technique and help reduce the tourniquet pressure pain. Attention should be paid to generously wrapping the arm at the tourniquet site with a soft cloth to prevent discomfort on application of the tourniquet and skin bruising at the sites where the tourniquet may pinch the unprotected skin.

The tourniquet should be well secured and fastened to prevent its inadvertent slipping or opening with consequent loss of anesthesia and/or toxic reactions due to the access of the injected local anesthetic to the central circulation. Prior to proceeding, it is of utmost importance to check the functionality of the tourniquet by briefly inflating both tourniquet cuffs and squeezing the inflated cuffs and observing that there are no leaks and that the pressure raises with the squeezes.

TIPS:

• The use of a double tourniquet requires that the cuffs be narrower than the standard single cuffs (12-14 cm). Although the occlusion pressures with narrower cuffs have been suggested to be less reliable than that with a single cuff, this concern is more theoretical than practical.
• The tourniquet is typically placed on the arm. A forearm tourniquet has been proposed to reduce the total dose of local anesthetic and perhaps reduce the tourniquet discomfort, the upper arm tourniquet remains the most commonly used in our practice.

A small IV intravenous catheter (e.g, 22-gauge) is introduced in the dorsum of the patient's hand of the arm to be anesthetized. The catheter should be firmly taped in place to prevent its dislodgment during the exsanguination with the Esmarch or the injection procedure. The arm is then elevated and at least for 1 minute to allow passive exsanguination, which occurs as the large veins are emptied into the more proximal circulation. Then, a 5" Esmarch is applied systematically from the finger tips to the distal cuff. The methodical application of the Esmarch requires an assistant to properly hold the arm in the upright position and some skill for proper application. The Esmarch should be always slightly stretched before applying the next turn-wrap around the extremity.

TIP: The proper and methodical application of the Esmarch and completeness of the exsangunation as the blood is being squeezed from the vascular beds into the proximal circulation are the most important steps to take to ensure a high success rate with this technique.

Once the Esmarch is applied, the following maneuvers are undertaken to complete the exsanguination of the extremity:

1. Inflate the distal cuff.
2. Inflate the proximal cuff.
3. Deflate the distal cuff.

The cuffs should be inflated to a pressure of 100 mm Hg above the systolic blood pressure, or at least 300 mm Hg. The Esmarch is then unwrapped and the extremity is checked for color (pale skin) and arterial occlusion (absence of the radial pulse).

TIP: Inadequate occlusion of the arterial blood flow by the tourniquets can result in venostasis and venous engorgement of the extremity, occasionally, this makes it difficult to operate.

The extremity is then lowered and the local anesthetic is slowly injected through the previously inserted IV catheter.

Choice of local anesthetic

Lidocaine is the most commonly used drug for intravenous regional anesthesia. Most authors recommend a larger volume of dilute solution of local anesthetic (e.g., 50 mL of 0.5% lidocaine). However, we prefer a smaller volume of a concentrated drug (e.g., 12-15 mL of 2% lidocaine) because the dilution and drawing of the drug in multiple syringes is time consuming and not necessary. In addition, smaller volumes are easier to inject and simpler to prepare.

Several other local anesthetic solutions and additives are reported to result in a slight prolongation of analgesia such as, bupivacaine 0.25%, ropivacaine 0.2%, meperidine, tramadol, ketorolac and clonidine. However, it is our opinion that the marginal potential improvements in analgesia with these medications or their adjuvants do not justify the compromise in safety and increase in complexity or side-effects of this otherwise very straightforward and safe technique.

Block Dynamics and Perioperative Management

The onset of anesthesia with this technique is within 5 minutes. The patient will typically report "pins and needles" in the extremity. However, this sign is almost always missed in our practice because we routinely administer small doses of midazolam (2-4 mg IV) to ensure the patient's comfort during the procedure. Most patients will invariably report pressure at the site of the tourniquet after 30-45 minutes; sometimes even earlier. When the discomfort becomes trouble-some and requires significant additional sedation and analgesics, the distal cuff over the anesthetized extremity is inflated and the proximal cuff is deflated. This provides immediate relief of discomfort due to the pressure from the proximal cuff. This maneuver will provide an additional 15-30 minutes of comfort. When tourniquet pain is first reported by the patient, the surgeon should be consulted for information on the expected time required to complete the surgery. The proximal tourniquet should not be released prematurely. The proper procedure for changing the tourniquet from the proximal to the distal cuff is as follows:

1. Inflate the distal cuff.
2. Check the pressure in the distal cuff by squeezing the cuff and documenting the oscillations on the manometer.
3. Deflate the proximal cuff.

TIP: It is important to properly label the proximal and distal cuffs and their respective valves to avoid deflation of the wrong cuff and the abrupt loss of anesthesia that would ensue or risk of local anesthetic toxicity.

Proper procedure of deflating the tourniquet at the end of surgery is also important to avoid the risk of local anesthetic toxicity when the procedure is completed within 45 minutes after the injection of local anesthetic. A two-stage deflation is suggested whereby the cuff is deflated for 10 seconds and reinflated for 1 minute before the final release. This practice allows for a more gradual "washout" of local anesthetic.

TIP: The release of the tourniquet will result in a rapid resolution of anesthesia and analgesia. The surgeon should be instructed to infiltrate local anesthetic before the release of the tourniquet to prevent a sudden, oncoming pain. When this is not possible, judicious doses of analgesic should be administered preemptively in anticipation of postoperative pain

Complications and How to Avoid Them

Complications of intravenous regional blocks are few and are mostly limited to systemic toxicity from the local anesthetic that is related to problems with the tourniquet.

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