Intravenous Regional Block (Bier Block)
- Indications: Surgery on the wrist, hand and fingers.
- Local anesthetic: 15 mL of 2% lidocaine
- Complexity level: Basic
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.
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.
- 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
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:
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.
- Inflate the distal cuff.
- Check the pressure in the distal cuff by squeezing the cuff and documenting the oscillations on the manometer.
- Deflate the proximal cuff.
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.
Systemic toxicity of local anesthetic -The risk mainly comes from an inadequate tourniquet application or equipment failure at the beginning of the procedure
-Every precaution should be undertaken to ensure that the tourniquet is reliable and the pressure is maintained
-Gradually release the tourniquet in two steps to prevent a massive "washout" of local anesthetic
-When the surgical procedure is completed, within 20 minutes after injection of local anesthetic, gradually release the tourniquet in several steps, with 2-minute intervals between deflations.
Hematoma -Use a small gauge IV catheter
-When the superficial veins are punctured during an unsuccessful attempt at placement of the IV catheter, apply firm pressure on the puncture site for 2-3 minutes. Failure to do so will invariably lead to venous bleeding during application of the Esmarch.
Engorgement of the extremity -Ensure that the tourniquet is fully functional and that the arterial pulse is absent
-This scenario may be more common in patients with arteriosclerosis; the calcifications in the arterial walls prevent effective function of the tourniquet; consequently, the arterial blood continues to enter the distal extremity while the venous blood is unable to escape, resulting in engorgement of the extremity and occasionally echimotic hemorrhage in the subcutaneous tissue.
Exchomoses and subcutaneous hemorrhage -The above principle applies.
-Assure that adequate padding is employed over the arm where the application of the tourniquet is planned.
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