Did you know that regional anesthesia evolved out of the process of garroting, or using a tourniquet to compress the nerve and restrict bloodflow?[1] With the advent of the hypodermic needle in 1853, physicians were able to administer local anesthesia by injecting morphine, then later cocaine and procaine, beneath the skin in order for the drug to reach the nerve.

In the early 20th century, August Karl Gustav Bier combined the injection and garroting techniques. He used a pair of tourniquets to stop bloodflow in a specific region in order to allow an injected anesthetic to infiltrate into the nerves of the region. "Bier's block" celebrated its 100th anniversary last year. Today, intravenous regional blocks are still used for short surgical procedures on extremities such as the hand, wrist and foot, although a cuff is generally used.[2] Find out how much you know about regional anesthesia by reading on and taking our quiz.

Peripheral nerve blocks
More commonly, anesthesia providers inject a local anesthetic — lidocaine, mepivacaine or bupivacaine — as close to a nerve, or group of nerves, as possible. The choice of local anesthetic often depends on the type and length of procedure. For example, lidocaine and mepivacaine are suitable for blocks that must last 2 to 4 hours, while bupivacaine can be used in longer procedures.[3]

Depending on the procedure, a single shot, double shot or continuous catheter of local anesthetic can be used. Until the early 1960s, 2 or more injections were commonly used for peripheral nerve blocks such as the axillary plexus block. Then a study by DeJong[4] reported that blocks could be successfully administered with a single, higher-volume shot of local anesthetic. This became the standard. However, practice began to swing the other way in the 1980s as studies by Vester-Andersen[5] reported that the incidence of block failure was still high with the higher concentration of anesthetic.

So what's most effective? A 2006 Cochrane Collaborative review of 12 studies with a total of 981 patients concluded that 3 or more shots provided better axillary plexus blocks than blocks performed with 1 or 2 injections.[6] (It should be noted that the review looked at studies in which the transarterial approach — passing the needle through the artery — and electrostimulation were used for guidance. No studies of procedures using ultrasound guidance were included.)

As for continuous catheters with peripheral nerve blocks, nearly 38% of the respondents to an Outpatient Surgery Magazine survey use them at least sometimes and about 52% use ultrasonic guidance. More than 87% use nerve stimulation or a combination of nerve stimulation and ultrasound, according to the survey.[7]

Proponents of ultrasound say it lets them better see the nerves, muscle and blood vessels as the needle advances. However, the cost of portable ultrasound devices ($24,000 to $50,000) has kept many surgical facilities from purchasing them.

Several studies have looked at the efficacy of ultrasonic guidance compared to nerve stimulation. In October a Cochrane review of 18 clinical trials with a total of 1,344 patients reported that ultrasound guidance had similar success rates — ranging from 72% to 99% — as nerve stimulators, which ranged from 58% to 93%. However, ultrasound improved the quality of the block, reduced insertion times by 2 to 5 minutes and reduced onset times by 4 to 14 minutes. The authors found no difference in the rate of complications between nerve stimulation and ultrasound.[8]

Blocks for the trunk and abdomen
Besides the extremities, regional anesthesia can be used for surgeries in the chest, abdomen and groin. For example, an intercostal nerve block is suited for intraoperative pain management for breast procedures and tumor excisions, and for post-op pain relief after a cholecystectomy.9 The anesthesia provider introduces the needle in the patient's back along the appropriate rib, using the bone to guide the needle toward the intercostal nerve. When the needle is properly placed, the anesthesia provider injects the local anesthetic.

Because the intercostal nerves are located close to the lungs, a pneumothorax (collapsed lung) is a rare but serious risk with these blocks. The incidence of a lung collapsing is 0.073% to 1.4% per nerve blocked.[10,11] Also, the anesthetic absorption rate is very high with these blocks because of the vascularity of the region. As a result, local anesthetic toxicity is another possible complication that warrants monitoring.[9]

Further down the trunk, the ilioinguinal and iliohypogastric nerves can be blocked for procedures to repair inguinal hernias. About 30% of these blocks fail because of the difficulty of locating the nerves by way of physical landmarks. Additionally, in small children the anesthesia provider needs to take caution not to puncture the colon, because of the proximity of the ilioinguinal and iliohypogastric nerves to the bowels.[12] Using ultrasound guidance appears to help with accuracy in placing the needle as close as possible to the nerve. An Austrian cadaver study showed that anesthesia providers were able to properly place the needle 95% of the time when using ultrasound.[13]

Femoral nerve blocks
The femoral nerve, as well as the lateral cutaneous nerve and the obturator nerve, can be blocked for surgery on the legs, including knee arthroscopy, joint replacement and vascular surgery. All 3 of these nerves can be blocked with a single injection, called a 3-in-1 block.

At the same time, many anesthesia providers use a multimodal approach to post-op pain control with orthopedic procedures. More than 71% of the respondents to the Outpatient Surgery Magazine survey said they use multimodal therapy. Sending patients home with a continuous catheter is another option, although less popular among survey respondents. Two-thirds (66%) of the respondents said they never send patients home with a pain pump.

One reason is that sometimes the femoral block can work too well when the patient is at home with a continuous catheter. Following case studies of 4 patients who fell and hurt themselves when they first tried to walk, a group of British researchers have recommended that a patient make sure he can feel a light touch and vibration on his leg to confirm that the anesthesia has indeed worn off before ambulating.[14]

Blocks for eye surgery
More than half of cataract surgeons use regional anesthesia during extraction procedures. About 26% use a retrobulbar block and 24% use a peribulbar block, according to an AAAHC Institute survey.[15] However, topical anesthesia continues to grow in popularity because of its simplicity. Today about 42% use it, according to the survey conducted in 2008 among 77 surgical facilities.

In 1936 W.S. Atkinson developed the technique for a retrobulbar block, which became the primary ocular regional block[16] used for cataract surgery. To establish a retrobulbar block, the anesthesia provider injects a local anesthetic, such as lidocaine, xylocaine or bupivacaine, into the space behind the eye containing the optic nerve and muscles that control eye movement.

Retrobulbar blocks generally don't require much local anesthetic to paralyze the eye. For the same reason, the anesthetic usually doesn't reach the facial nerve that controls the squinting process. Many anesthesia providers also administer a facial nerve block that prevents squinting and allows for placement of the lid speculum.

Retrobulbar hemorrhaging is the most common complication during a retrobulbar block, occurring 1% to 3% of the time.[17] Another complication of concern during the administration of this block is post-retrobulbar apnea syndrome. This can occur when the local anesthetic is mistakenly injected into the optic nerve sheath, then spreads into the cerebrospinal fluid and the mid-brain. Depending on how much of the drug reaches the brain, the anesthetic can cause unconsciousness and apnea, which would require intubation and ventilation.[18]

In the 1980s, Atkinson's technique was adapted by Davis and Mandel[19] to create the peribulbar block. Some anesthesia providers consider a peribulbar block to be theoretically safer than a retrobulbar block because:

• it uses a shorter needle (5¼ 8 inch to 11¼ 4 inches);
• you don't have to insert a needle blindly into the space behind the eye; and
• the needle is farther from the globe of the eye and the brain.

In a peribulbar block, the local anesthetic is deposited outside the muscle cone. This means that there's less risk of perforation of the globe or injection of local anesthetic into blood vessels or the optic nerve. Peribul-bar blocks require more anesthetic and often need more time to take effect. At the same time, the large dose of anesthetic infiltrates to the facial nerve so that a facial nerve block is not necessary.[20]

As peribulbar blocks have become more popular, a debate has developed surrounding which technique — retrobulbar or peribulbar — is more effective and safer. A Cochrane Collaborative review of clinical trials with a total of 1,438 patients comparing peribulbar and retrobulbar blocks for cataract surgery found no difference in pain control, rate of akinesia or severe complications between the techniques. The researchers reported that peribulbar blocks caused slightly more conjunctival chemosis than retrobulbar blocks and sometimes required an additional injection[.21]

Time of rediscovery
As the evidence and positive experience pile up, anesthesia providers will find new applications for regional anesthesia. Essentially, wherever there's a nerve, it can be blocked.

Answers
1. b; 2. c; 3. b; 4. a; 5. b, c and d; 6. b; 7. d; 8. d