Peripheral Nerve Blocks: A Color Atlas, 3rd Edition

1.Step-by-Step Approach to the Performance of Peripheral Nerve Blocks

Jacques E. Chelly

Evidence shows that peripheral nerve blocks performed in either awake or lightly sedated adult patients prior to or after surgery decrease the risk of complications associated with intraneural or intrathecal injections. Evidence also suggests that the use of peripheral nerve blocks for anesthesia reduces both operating room time and length of hospital stay (Table 1-1). Further, the use of peripheral nerve blocks for postoperative analgesia has also been shown to reduce length of hospital stay. Regardless of the timing of the performance of peripheral nerve blocks, the following 12 steps need to be considered:

1.   Obtain a complete and detailed history and physical examination of the patient, with special emphasis on history of coagulopathy, anticoagulant therapy, and sensory or motor nerve deficits, especially in the territory affected by the surgery and the block(s).

2.   Evaluate indications and determine the absence of contraindications for anesthesia and/or postoperative analgesia. The indications for peripheral nerve blocks include most upper and lower extremity surgery. In addition, thoracic, breast, urologic (e.g., nephrectomy, prostatectomy, cystectomy), and abdominal surgeries (e.g., liver resection, colectomy, pancreatectomy) and hernia repair (inguinal and umbilical) also benefit from the use of paravertebral blocks. These blocks have been demonstrated to be as effective as epidural. The contraindications to regional blocks are local (e.g., infection or trauma, possible preoperative nerve damage), surgical (e.g., nerve repair), related to the patient's condition (e.g., uncooperative or unwilling, presence of uncontrolled seizure disorder), and related to the surgeon's preference (unwilling to have his or her patients blocked). Coagulopathy and anticoagulation therapy at the time of the performance of the block, which are often cited as contraindications to peripheral nerve block anesthesia, should be considered a relative contraindication. Thus, most of the approaches are based on reaching a nerve superficially using a small gauge needle introduced into a groove and allowing compression in the area to be applied. Coagulopathy and anticoagulation therapy at the time of the performance of the block should be considered contraindications when the technique requires the needle to pass into muscular masses and when the nerve is located deep as in the case of a lumbar plexus, any paravertebral approaches, the classic posterior Labat approach to the sciatic nerve, or the anterior approach to the sciatic nerve. However, the use of thromboprophylaxis following surgery is not a contraindication to the performance of a peripheral nerve block prior to the initiation of the thromboprophylaxis.

Table 1-1. Benefits and Potential Risks of Peripheral Blocks


Potential Risks

During the performance of the block

Preemptive analgesia

Toxicity: cardiac, neurologic, allergic


Pain and hematoma at the puncture site

During surgery

Avoid general anesthesia

Discomfort, hemodynamic stability

Possible active mobilization of a joint by the patient at the request of the surgeon

Risk of block failure or incomplete block
Misevaluation of or changes in the surgical requirement

Postoperative period

Postoperative analgesia (several days with a continuous nerve block)

Theoretical increased risks of permanent or transient nerve damage

Reduced postoperative nausea and vomiting
Early discharge

3.   Establish which block(s) and approach and technique (i.e., neurostimulation, ultrasound, or combined) can best address the patient's needs by establishing the type of surgery being performed, and its approach and techniques. In addition, in the case of a block performed for postoperative analgesia, it is important to determine the expected duration of postoperative pain and the postoperative requirement for active vs. passive mobilization. These determinations help to differentiate between the need for a single and the need for a continuous block.

4.   Obtain an informed consent for the appropriate block by providing a detailed explanation of the respective risks and benefits of general and regional anesthesia techniques and the need for immediate or prolonged postoperative analgesia. In addition to the cited benefits of peripheral nerve blocks, the use of blocks is especially advantageous in patients with American Society of Anesthesiologists (ASA) III and IV status with compromised renal, pulmonary (depending on the block), and cardiac function. For patients to make an informed decision, it is essential for them to acknowledge that a peripheral nerve block may be associated with a toxic reaction to the administration of a local anesthetic solution, including seizure, cardiac arrhythmias (related to intravascular injection, increased sensitivity, or excessive concentrations of local anesthetic solutions), and transient or permanent nerve damage (e.g., acute pain during injection and paresthesia). The patient also needs to understand that although the risk of nerve damage is minimized by the use of a nerve stimulator or an ultrasound, nerve injury remains a possible complication. Finally, the patient needs to understand that choosing a peripheral nerve block for anesthesia does not mean that he or she must remain awake during the surgery. It should be made very clear that additional sedation is available.

5.   Next, an intravenous access is secured and a nasal cannula is placed delivering O2 2 to 3 L/min. The patient's vital signs are established and monitored (blood pressure and pulse oximetry).

6.   After the patient is properly positioned, he or she may be given some sedation including midazolam IV (start with 0.5 mg i.v. in older patients and up to 2–3 mg in anxious healthy or young patients) and fentanyl 50 to 100 µg. The administration of these drugs should be titrated to the need of each individual patient. Midazolam is our drug of choice because of its relatively short half-life, lack of hemodynamic effects, and the availability of a specific antagonist (flumazenil) that can be administered immediately if necessary. It is important to recognize that most blocks can easily be performed with minimum sedation as long as a good local anesthesia is performed. In addition, not all patients are good candidates for blocks, especially those who are too anxious. In these patients, it is preferable to recommend general anesthesia and a postoperative analgesia not based on the use of a peripheral nerve block.

7.   Choose the proper local anesthetic mixture and concentration based on the desired onset time for the block, the expected duration of surgery, and the need for postoperative pain control, a need for a preferential sensory block.

8.   Perform the block:

a.   Position the patient correctly.

b.   Identify the appropriate landmarks; mark them and/or the area scanned with the ultrasound.

c.   After appropriate disinfection of the area, perform an appropriate local anesthesia, usually with 1% lidocaine. The depth of the local anesthesia depends on the depth of the nerve (very superficial for an interscalene block, more profound for an anterior sciatic or lumbar plexus block).

d.   Under strict aseptic conditions, introduce the insulated needle (connected to a nerve stimulator) or noninsulated needle (ultrasound); locate the nerve by advancing the needle slowly under vision (ultrasound) or by eliciting a specific motor response or an electrical paresthesia (neurostimulation) in the appropriate territory (sensory nerve).

e.   Adjust the position of the needle in the optimum position either under vision (ultrasound) or by maintaining the same motor response or paresthesia with a current less than 0.5 mA (neurostimulation). However, it is also important to confirm that the motor response disappears for a current less than 0.25 mA (which theoretically prevents too close proximity between the needle and the nerve).

f.    After appropriate positioning of the needle, and negative aspiration for blood, inject 1 to 2 mL of local anesthetic solution. In the case of neurostimulation, this injection should be associated with the disappearance of the elicited motor response. The current delivered by the nerve stimulator is then increased to 2 to 3 mA, which results in the reappearance of the specific motor response, confirming the appropriate positioning of the needle. In the case of ultrasound, this injection helps to verify that the needle is not intraneural. The rest of the local anesthetic solution is injected, confirming negative aspiration of blood every 5 mL.

9.   After the block is performed, evaluate the intensity of the motor and sensory block by asking the patient to perform specific movements. In addition, ice and pinprick may be used to evaluate the intensity of the sensory block, usually at 5-minute intervals. If after 30 minutes the sensory block is incomplete, consideration should be given to performing a complementary nerve block distal to the first approach.

10.       Before surgery, inform the surgeon of your evaluation and of the possible need for local anesthetic supplementation. Have the surgeon confirm your findings.

11.       Educate the patient on:

a.   what to do until complete recovery of motor and sensory function.

b.   how to manage postoperative pain including the use of oral medication.

c.   how to identify symptoms of local anesthetic toxicity and other relevant side effects and complications.

In the case of ambulatory surgery, it is most appropriate to discharge the patient with written and signed instructions (including a pager/telephone number that the patient can use) in case of questions or postsurgical problems.

12.       In the case of an ambulatory procedure, do a postoperative follow-up by telephone the next day. A second phone call made after the expected complete recovery to document the recovery process and to record the patient's comments, if any, is also recommended. If the patient complains of complications, he or she should be asked to return to the hospital for a complete evaluation.

Suggested Readings

Capdevila X, Pirat Ph, Bringuier S, et al, the French Study Group on Continuous Peripheral Nerve Blocks. Continuous peripheral nerve blocks in hospital wards after orthopedic surgery. A multicenter prospective analysis of the quality of postoperative analgesia and complications in 1,416 patients. Anesthesiology 2005;103:1035–1045.

Chelly JE, Greger J, Al-Samsam T, et al. Reduction of operating and recovery room times and overnight hospital stays with interscalene blocks as sole anesthetic technique for rotator cuff surgery. Minerva Anestesiol 2001;67:613–619.

Delaunay L, Chelly JE. Blocks at the wrist provide effective anesthesia for carpal tunnel release. Can J Anaesth 2001;48:656–660.

Gebhard RE, Al-Samsam T, Greger J, et al. Distal nerve blocks at the wrist for outpatient carpal tunnel surgery offer intraoperative cardiovascular stability and reduce discharge time. Anesth Analg 2002;95:351–355.

Pavlin D, Chen C, Penaloza DA, et al. Pain as a factor complicating recovery and discharge after ambulatory surgery. Anesth Analg 2002;95:627–634.

Pavlin DJ, Rapp SE, Polissar NL, et al. Factors affecting discharge time in adult outpatients. Anesth Analg 1998;87:816–826.

Williams BA, Kentor M, Williams JW, et al. PACU bypass after outpatient knee surgery is associated with fewer unplanned admissions but more phase II nursing intervention. Anesthesiology 2002;97:981–988.

19. Antisocial Aspects of Hypnosis

Considerable controversy exists as to whether or not a hypnotized individual will commit an antisocial act following posthypnotic suggestions. The situational context in which a request is made to carry out an antisocial act is important. Orne and Evans demonstrated that nonhypnotized persons manifested the same antisocial behavior as hypnotized subjects.25 This indicates that the experimental control was recognized by the subjects as legitimate behavior. Many investigators believe it is possible,1,4,17,20,21,28,29,30,32 whereas others do not think the evidence warrants such assumptions.3,5,7,14,16,24,33 Kline denies the relationship,16 Orne stresses that the patient always has control,24 and Coe and associates emphasize that it is extremely difficult to perform a convincing study on antisocial behavior in a laboratory context.5 This view has been supported by others.2,8,24 Still other researchers take a position between the two camps.5,13,27 Most of the experiments to show that antisocial behavior can be induced have not been carefully structured; the experimental setting suffers from a “pseudoreality” situation. More recently, other experienced investigators have concluded that it is possible to tip the scales toward criminal impulses and get antisocial behavior.19 It has been posited that if a person harbors an antisocial impulse, he can act it out under hypnosis.5 Even though it may not be a coercive force, it may be a facilitating agent, and in the applied sense, it can be responsible for behavior.

Evans notes there has not been a single case of a crime committed “under the influence of hypnosis” in which there had not been a long-standing personal relationship between the victim and the accused.10 There is no concrete evidence that hypnosis per se enhances the degree of coercive control. Conn calls coercion through hypnosis a “myth” that belongs in the realm of demonology and folklore.6When a hypnotized person does antisocial things, it is not because the hypnotist has special powers, but because a folie à deux exists. Hypnosis can be used as an alibi, a rationalization, or a legitimation of behavior. Furthermore, since only a relatively few cases have been studied, more controlled clinical data is needed. Erickson, who believes that the possibilities for antisocial behavior are nonexistent, says that there are people “who will discount the theoretical possibility of hypnosis, yet will insistently attribute miraculous, effective, antisocial powers to even a single hypnotic suggestion.”7

Soldier volunteers in a military setting have performed antisocial acts through posthypnotic suggestions.29 It has been pointed out that such subjects were strongly motivated to act in this manner because of the “demand characteristics” of the situation; they intuitively or subliminally knew what the experimenter was trying to prove. They also felt that the hypnotist, usually a superior officer, would ensure the safety of all involved, irrespective of their actions.

In similar experiments, a college professor in a psychology class has asked a student to shoot a supposedly loaded gun. The student, on more than one occasion, pulled the trigger and thought he was “shooting” the professor. However, the subject recognized the surroundings and the professor's voice. No professor has handed a student a loaded gun and put a bullet-proof vest on himself and said, “Shoot me.” To evaluate the contradictory data that antisocial behavior can occur under hypnosis, one must consider many other factors such as motivation, roleplaying and exhibitionism, as well as the needs of the hypnotist.

There is a well-documented case in which a person ostensibly committed murder as well as other criminal acts at the behest of a hypnotist.9 This crime obviously was perpetrated because the subject, over a long interval, had developed a close emotional attachment to a mentally unbalanced hypnotist. In another case, a prisoner of war committed criminal acts through a posthypnotic suggestion.26 Judging from his relationship to the hypnotist and the nature of the subject's acts, however, it seems possible that the antisocial behavior could have been performed just as easily through strong persuasion without the use of hypnosis. The consensus of opinion is that the antisocial behavior induced in an unwilling subject is primarily dependent upon the hypnotist and the extent to which he participates in the act himself. The subject is but a part of the newly created, structured hypnotic relationship.15

Because only three documented cases of actual criminal behavior involving hypnotic suggestion have been reported in the last 25 years, Orne does not think that a cunning hypnotist could force another individual to do his criminal bidding purely by hypnotic suggestion.23 When a subject develops a strong personal attachment toward a hypnotist, as in the above-mentioned cases, it is not extraordinary for such a subject to become involved in an antisocial act which might benefit another individual. Orne concludes that “An explanation which purports to account for such behavior by singling out one aspect of the relationship, i.e., hypnosis, must be viewed with skepticism.”

The explanations that characterize virtually all the experimental studies on antisocial behavior to date have been summarized as follows: The subjects believed that protective measures had been taken, since they knew it was only an experiment; they trusted the hypnotist either because they had confidence in him or because there were legitimate reasons for the hypnotist's requests; or the subjects had latent criminal tendencies. After studying all the available data, it is concluded that “hypnosis alone is incapable of causing antisocial behavior; that criminal behavior can be induced only if perceptual alterations are produced so that the act is not considered antisocial.31 After an extensive review of the pros and cons of whether or not an antisocial act can be committed through hypnosis, Conn answers with an emphatic No!6


Considering the thousands of people hypnotized daily by entertainers, there are remarkably few documented cases of harm. The author, however, is unalterably opposed to the entertainer-hypnotist's using hypnosis in any manner. Irrespective of his technical proficiency in inducing hypnosis, he does not know the emotional makeup of the person he is hypnotizing. Without this knowledge, he invites trouble for himself and his subject. Often the person hypnotized by the entertainer may have an emotional upset after he suffers embarrassment while on the stage. Frequently, some members of the audience will be hypnotized inadvertently. However, these are only temporary reactions.

Stage hypnotists supposedly have induced depressive reactions in some subjects. However, in most instances they failed to remove the suggestions which upset the subject. Typical is the following: “You will cry and feel sad because your husband is very sick.” Inexperienced entertainer-hypnotists also fail to recognize that some subjects will overreact physiologically to psychological suggestions. If, for instance, a deeply hypnotized subject is asked to imagine that he is hanging from a 10-story window ledge, and that his strength is ebbing, it is possible that he could easily develop a cardiac collapse if he has a bad heart. Entertainers are going to give medical hypnosis a “black eye” until pending legislation prohibits them from using it for amusement purposes. The various bills in the state legislatures for these purposes have been reviewed. Harding contends that hypnosis is damaging not only to hypnotized subjects, but also to the audience.11 The amateur operator often may encounter violent hysteric outbursts which he is poorly equipped to handle. Naturally, when this occurs, the hypnosis should be terminated immediately. Prompt removal of the subject from the stage, together with strong reassurance, will invariably remedy this difficulty. Heavy sedation may be necessary for those who overreact.

Age regression in the hands of the inept hypnotist is potentially the most dangerous of all hypnotic phenomena; here, deeply buried traumatic memories can erupt and result in panic reactions. If the resulting acting-out behavior is not handled properly, or if the regression cannot be removed, the hypnotist can identify with someone that the subject liked at an earlier age level. In the role of a benevolent surrogate figure, he can request the subject to return to his present chronologic age. It should be suggested that the subject will feel none the worse for his experience after dehypnotization.

Entertainer-hypnotists are not familiar with such technics, nor are they competent to handle conflictual material as it emerges. Therefore, the entertainer has no right to meddle with raw human emotions. Then, too, there are many amateur hypnotists and a few entertainer-hypnotists who treat a wide variety of medical conditions in which hypnosis is not indicated. Their inability to make a diagnosis can cause delay in effective medical assistance.

For over 40 years, the author has requested the American Medical Association and the federal authorities to ban hypnosis by the stage hypnotist because, as long as it is identified with entertainment, professional men will hesitate to employ hypnotherapy. This is particularly true where the physician must practice medicine according to the dictates of public policy.

Unfortunately, irrational prejudices about hypnosis are still held by the layman. It is sincerely hoped that healthier public attitudes toward hypnosis and appropriate legislation will eventually make it an exclusive medical tool. Yet it is regrettable that many serious-minded scientists who use hypnotherapy have to fight a two-front war—on the one hand, against the mountebanks who are promising quick cures with hypnosis and, on the other, against those colleagues who utterly disbelieve in its utility.


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8. _____________: Observations concerning alterations in hypnosis of visual perceptions. Am. J. Clin. Hypn., 5:131, 1962.

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