Intravenous Regional Anesthesia

Indications and Contraindications

Indications for IVRA include any procedure on the arm or leg that requires operating anesthesia, muscle relaxation, or a bloodless field, such as reduction of fractures and dislocations, repair of major lacerations, removal of foreign bodies, débridement of burns, and drainage of infection ( Fig. 32.1 ). IVRA is commonly used for extremity surgery, such as carpal tunnel surgery or tendon repair. The procedure may be carried out on any patient of any age who is able to cooperate with the clinician.

The only absolute contraindications are allergy to the anesthetic agent and, possibly, uncontrolled hypertension. Relative contraindications include severe Raynaud's disease, Buerger's disease, or a crushed or already hypoxic extremity in which further transient ischemia would be detrimental. Homozygous sickle cell disease is a theoretical contraindication, but few data exist on the treatment of patients with this condition. IVRA is best used for procedures requiring no more than 60 to 90 minutes of tourniquet time. Continuous cardiac or blood pressure monitoring is not standard and not required unless extenuating circumstances prognosticate potential cardiovascular problems. An uncooperative patient may delay the procedure rather than contraindicate it. The judicious use of standard ED sedation may facilitate the use of IVRA in an anxious or transiently uncooperative patient.

Equipment

The equipment required for IVRA consists of the following:

• 1% lidocaine (Xylocaine), *

  * Commercial preparations with preservatives are commonly used. Lidocaine 0.5% is also available.

  without epinephrine , to be diluted to a 0.5% solution (Note: 1% lidocaine = 10 mg/mL; hence 1 mL of 1% lidocaine = 10 mg.)

• Clonidine, a parenteral opioid such as fentanyl, or ketorolac if used as additives

• Sterile saline solution as a diluent

• 50-mL syringe/18-gauge needle

• Pneumatic tourniquet (single or double cuff) such as the Zimmer A.T.S. 2000 Automatic Tourniquet System (Zimmer Inc., Bloomfield, CN) ( Fig. 32.2 ) (Note: Do not use a standard blood pressure cuff.)

  

• IV catheters (20- or 22-gauge) or a 21-gauge butterfly needle

• Elastic bandage/Webril padding

• 500 mL of 5% dextrose in water (D ₅ W) and IV extension tubing (optional)

Procedure

The procedure should be explained to the patient in advance. Premedication with midazolam (Versed), diazepam (Valium), or an opioid (e.g., morphine, fentanyl) may be helpful but need not be used routinely. The only painful portions of the procedure are establishment of the infusion catheter and exsanguination. The procedure should not be done on patients who are persistently uncooperative, intoxicated, or obtunded or who have had a previous reaction to a local anesthetic.

The patient need not be free of oral intake for a specific period before the procedure, but it is prudent to delay the procedure if the patient has just eaten a large meal. As a precaution, a suggested option is a large-bore catheter and an IV line with D ₅ W in the unaffected extremity. General resuscitation equipment, including suction, anticonvulsant drugs, bag-valve-mask (BVM) apparatus, and oxygen, should be available. Continuous cardiac and blood pressure monitoring is not routine but may be used as an option depending on the clinician's assessment of the potential for cardiovascular events.

While the patient is being prepared, keep the lidocaine solution ready, but withhold it until the injured extremity is exsanguinated and the cuff is in place and inflated, as discussed later. The standard dose of lidocaine for the arm is 3 mg/kg. Inject it as a 0.5% solution (1% lidocaine mixed with equal parts sterile saline in a 50-mL syringe). Hence, for a 70-kg patient, infuse 210 mg of lidocaine (21 mL of 1% lidocaine) mixed with 21 mL of saline for a total volume in the infusing syringe of 42 mL of 0.5% lidocaine. Farrell and coworkers described a procedure termed the minidose Bier block in which 1.5 mg/kg of lidocaine is used and reported a 95% success rate. This lower dose may decrease the incidence of central nervous system side effects and is more desirable in the ED setting. Additional lidocaine may be infused if the initial dose is inadequate. Do not use lidocaine with epinephrine. Plain lidocaine is also available as a 0.5% solution and can therefore be used directly to avoid diluting the stronger solution. Some prefer preservative-free lidocaine, but most clinicians use standard lidocaine with preservatives.

Apply a pneumatic tourniquet with cotton padding (to prevent ecchymosis) under the cuff proximal to the pathology. It is strongly advised that one not use a regular blood pressure cuff because these cuffs often leak or rupture and are not designed to withstand high pressure for any length of time. A specially designed portable double-cuff pneumatic system, such as that marketed by Zimmer Corporation, is ideal and preferred by the author.

Premix the anesthetic and saline solution in the syringe. Inflate the tourniquet and place a plastic catheter or a metal butterfly needle in a superficial vein as close to the pathologic site as possible, and securely tape it in place ( Fig. 32.3, step 1 ). It is usually desirable to use a vein on the dorsum of the hand, but importantly, the injection site should be at least 10 cm distal to the tourniquet to avoid injection of anesthetic proximal to or under the tourniquet. Keep the hub on the catheter to avoid backbleeding, or attach the syringe to the butterfly tubing. This catheter will be the route of injection of the anesthetic agent. Anesthesia from a fingertip-to-elbow direction seems to occur irrespective of the site of infusion of the anesthetic, but selecting an injection location near the site of pathology may provide more rapid anesthesia at a lower dosage.

Deflate the tourniquet used to obtain IV access, and exsanguinate the extremity so that when the anesthetic agent is injected, it will fill the drained vascular system. Exsanguination may be accomplished by either of two methods. Simple elevation of the extremity for a few minutes may be adequate, but wrapping the extremity in a distal-to-proximal direction with an elastic or Esmarch bandage, while being careful to not dislodge the infusion needle, significantly enhances exsanguination (see Fig. 32.3, step 2 ). Wrapping may be painful, so this step can be eliminated if it causes too much anxiety for the patient. If the wrapping procedure is not done, the extremity should be elevated for at least 3 minutes. During the wrapping procedure, take care to not dislodge or infiltrate the infusion catheter.

With the extremity still elevated or wrapped, inflate the tourniquet to 250 mm Hg (or 100 mm Hg above systolic pressure). Place the arm by the patient's side, and remove the elastic exsanguination bandage (see Fig. 32.3, steps 3 to 5 ). In a child, inflate the tourniquet to 50 mm Hg above systolic pressure. In elderly obese patients with calcified peripheral vessels, arterial occlusion may not be achieved safely. In the leg, cuff pressure of 300 mm Hg or approximately twice the systolic pressure measured in the arms is suggested.

With the tourniquet now inflated, slowly inject the 0.5% lidocaine solution into the infusion catheter at the calculated dose (see Fig. 32.3, step 6 ). Note that the solution is placed in the arm in which the circulation is blocked, not in the precautionary keep-open IV line on the unaffected side. At this point, blotchy areas of erythema may appear on the skin. This is not an adverse reaction to the anesthetic agent but merely the result of residual blood being displaced from the vascular compartment, and it heralds success of the procedure.

In 3 to 5 minutes, the patient will experience paresthesia or warmth beginning in the fingertips and traveling proximally, with final anesthesia occurring above the elbow, to the level of the tourniquet. Complete anesthesia ensues in 10 to 20 minutes, followed by muscle relaxation. Note that adequate analgesia may exist even if the patient can still sense touch and position and has some motor function. If the “minidose” technique (initial dose of 1.5 mg/kg of lidocaine) does not provide adequate anesthesia, infuse an additional 0.5 to 1 mg/kg of diluted lidocaine at this time. As an example, for a 70-kg patient, an additional 0.5 mg/kg of lidocaine equals 35 mg lidocaine (3.5 mL of 1% lidocaine), and when the 1% lidocaine is diluted equally with saline, the final volume of the additional 0.5% lidocaine is 7 mL. Additional lidocaine was required in 7% of cases in one series in which the minidose regimen was used. The clinician should be patient, however, and wait a full 15 minutes before infusing additional lidocaine. Alternatively, if analgesia is slow or inadequate, an extra 10 to 20 mL of saline solution may be injected to supplement the total volume of solution to enhance the effect. Do not exceed a 3-mg/kg total dose of lidocaine. For obese patients, a maximum of 300 mg of lidocaine is suggested for the arm and no more than 400 mg for the leg. Data for very obese patients do not exist. Next, withdraw the infusing needle and tightly tape the puncture site to prevent extravasation of the anesthetic agent. Perform the surgical procedure or manipulation, including postreduction x-ray films and casting or bandaging (see Fig. 32.3, step 7 ).

On completion of the procedure, deflation of the tourniquet may be cycled to prevent a bolus effect of any lidocaine that may remain in the intravascular compartment. Deflate the cuff for 5 seconds and reinflate it for 1 to 2 minutes. Repeat this action two or three times. This is probably required only if the cuff has been inflated for less than 30 minutes. A single deflation is often performed if the cuff has been inflated for longer than this time.

If the tourniquet has been in place for less than 30 minutes, an increase in transient lidocaine-related side effects may be seen if cycled deflation has not been used because adequate tissue fixation of the lidocaine has probably not occurred. This may result in a higher peak plasma lidocaine level, with increased side effects. If the surgical procedure is completed rapidly and the 3-mg/kg limit of lidocaine has been infused, the tourniquet should remain inflated until 20 to 30 minutes has elapsed, and only then should it be deflated via the cycling technique. It is reasonable to use a 20-minute cutoff if the minidose technique is used or a total of 200 mg or less of lidocaine has been administered because this dose is equal to a commonly administered antiarrhythmic IV bolus.

Sensation returns quickly when the tourniquet is removed, and in 5 to 10 minutes the extremity returns to its pre-anesthetic level of sensation and function. Many patients describe a transient intense tingling sensation after cuff deflation. If the procedure takes longer than 20 or 30 minutes, many patients complain of pain from the tourniquet because it is not inflated over an anesthetized area. Use of a double-cuff tourniquet may alleviate the problem of pain under the cuff. A wide tourniquet cuff (14 cm) is less painful than a narrow tourniquet (7 cm) when the cuff is inflated 10 mm Hg above loss of the arterial pulse. The reason for pain under the tourniquet is unknown, but this can be a limiting factor because most patients begin to feel significant discomfort after 30 minutes if only a single cuff is used. Tourniquet pain can be significantly reduced and tourniquet time extended by adding ketorolac to the lidocaine anesthetic (see later).

In the preferred double-cuff system, two separate tourniquets are placed side by side on the extremity. One is termed the proximal cuff and the other the distal cuff . The proximal cuff is inflated at the beginning of the procedure, and anesthesia is obtained under the deflated distal cuff. When the patient begins to feel pain under the proximal cuff, the distal cuff is first inflated over an already anesthetized area, and the pain-producing proximal cuff is then deflated. One must be certain to inflate the distal cuff before the proximal cuff is released; otherwise, the anesthetic will rapidly diffuse into the general circulation.

After 45 to 60 minutes of observation, the patient may be discharged ( Box 32.1 ). Observation time depends on the use of other medications, procedural difficulties, and overall assessment of the patient. There are no standard or specific postprocedure instructions, but precautions similar to those given for conscious sedation are reasonable. Driving is best prohibited for 6 to 8 hours, and the patient should leave with a responsible adult. Delayed complications from lidocaine have not been reported.