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Regional anesthesia in ambulatory surgery

From the Department of Anaesthesia, Ulleval University Hospital, N-0407 Oslo, Norway.

Address correspondence to: Dr. Johan Raeder, Anaesthesia Department, Ullevaal University Hospital, N-0407 Oslo, Norway. Phone: 011-47-22-11-9690; Fax: 011-47-22-11-9857; E-mail: johan.rader{at}ioks.uio.no

AMBULATORY surgery is characterized by procedures of low or intermediate duration and invasiveness; stable, elective patients and by high patient turnover. The principles of regional anesthesia, benefits and drawbacks, as well as a proper selection and performance of techniques must be discussed in this context.

Clinical benefits and drawbacks of regional anesthesia

These may be discussed in terms of safety, quality and economy:

Safety
Properly performed ambulatory anesthesia has a safety record of close to 100%, comparable with control groups of similar age not having surgery.¹ In the Closed Claims reports, regional anesthesia comes out favourably compared with general anesthesia. The latter is more often associated with serious circulatory or respiratory complications whereas regional anesthesia is associated with nerve injury.

However, major risks are specifically associated with regional techniques. An inadvertent iv injection or rapid absorption of a large dose of local anesthetic(s) may result in generalized convulsions and cardiac arrhythmia or arrest. With epidural or spinal anesthesia the physiologic changes associated with extended block of the sympathetic nervous system, may result in hypotension, bradycardia or cardiac arrest. Supraclavicular or intercostal blocks may result in pneumothorax. A prolonged postoperative spinal or epidural block will increase the risk of urinary retention and a prolonged paralysis of the lower body may increase the risk of pressure induced nerve injury. Postoperatively, rare cases of spinal hematoma or meningitis are reported.

Quality
In terms of quality, less initial postoperative pain is an important feature with regional anesthesia. There are also data to support that this initial pain relief also reduces pain after the block has weaned off. In a study by Dahl and co-workers² patients with epidural or spinal anesthesia had significantly less pain compared with general anesthesia for one to two hours after the block had weaned off. Both the absence of general anesthetic after-effects and the reduced need for opioids to relieve postoperative pain, result in less postoperative nausea or vomiting when regional anesthesia is used.³

With regional anesthesia, the patient has the option of choosing peroperative strategy. He or she may stay fully awake, watch the TV-screen during arthroscopy for example, and discuss with the surgeons as requested. If the patient specifically ask for this alternative, it is important not to use sedative drugs with a strong amnesic action, such as midazolam or propofol. Alternatives are listening to music on headphones, chatting with the anesthesiologist or having some sedation or continuous sleep.

Negative aspects of regional anesthesia include pain during injection of local anesthetics, occasional pain from the surgical site if the block is incomplete, and problems associated with eventual block failure.

Economy
Whereas modern anesthetic drugs for ambulatory general anesthesia may be expensive, the costs of drugs and equipment for regional anesthesia are generally low.³ Costs of postoperative medication for pain or nausea may also be reduced with regional anesthesia.

However, drug costs are only a minor part of the total costs associated with anesthesia, most expenses coming from use of labour and time in the highly dedicated operation theatre and recovery unit. A patient with regional anesthesia may be wheeled out directly of the operating room after the surgeon has finished; no emergence, extubation or re-establishment of airway and respiration have to take place. Except for epidural and spinal anesthesia, phase-I recovery may often be bypassed, adding further to the efficiency of postoperative care. A fully awake patient with no pain or nausea puts less workload on the recovery staff. The low rate of pain or nausea are specially important to achieve a rapid discharge from phase-I recovery or from the unit to home, after ambulatory care.

The negative aspects of costs with regional techniques may include extra preoperative time to establish a block and, for some blocks, to see if they are effective. In the case of spinal or epidural anesthesia, prolonged bed-occupancy postoperatively while waiting for the block to wear out may be a problem in terms of increased costs required for surveillance, and reduced turnover in the unit. If a patient is too heavily sedated during regional anesthesia, sedation may extend into the postoperative phase with reduced airway control, depressed respiration and delayed recovery; all add to increased postoperative costs.

Selection of blocks

As a minimum, every anesthesiologist in ambulatory practice should master spinal anesthesia and some sort of arm block, preferably a brachial plexus block technique. The latter may be replaced by an iv regional technique if the training and frequency in brachial plexus blocks are very low. When performed regularly, a selection of other blocks may be added. The most useful in my experience will be: ankle block, interscalene (or parascalene) block, inguinal hernia block, femoral block, epidural block and caudal block in children. Depending of the case mix in the ambulatory unit, other blocks may also be useful: paracervical block, eye-blocks, isciadicus block, penis block and specific blocks of nerves in the distal upper extremity, fingers and toes.

Spinal anesthesia

Choice of needle and postspinal puncture headache (PSPH)
Ambulatory surgery patients are usually mobilized with little or no surgical sequelae after discharge. In this setting, a postspinal puncture headache (PSPH) lasting for days is unacceptable. The frequency of PSPH is related to age and the size of the lesion in the dura when the spinal needle is withdrawn. PSPH rapidly declines in incidence and severity in patients from 50 yr of age and older, but may still be a serious problem in a very few elderly patients. The size of the dural lesion is related to the size of the needle and the needle design. My choice is to use the 27 G pencil point needle with an introducer as my routine spinal needle for all ambulatory cases. With a difficult anatomy in an elderly patient, a 25 G or 22 G needle without introducer may sometimes be more easy to work with. If minor cost savings are an important issue, one may wish to use a 25 or 27 G Quincke needle in patients above the age of 50 yr.

With this approach, the incidence of mild PSPH should be in the 1–3% range and be acceptable as a minor postoperative problem. In some 0.5–1% of spinal anesthesias there will still be more severe headache, which may call for an epidural blood-patch. Thus, it is important to contact these patients the day after surgery for a standardized telephone follow-up including questions about headache.

Toxicity, side-effects
Whereas PSPH is related to needle size and design and not to drug characteristics, the opposite is the case for permanent nerve-tissue damage (PNTD) and transient neurologic symptoms (TNS), although nerve damage also may be caused by needle trauma. Backache has been related to both needle trauma and to chloroprocaine, or possibly to the solvent (EDTA) in chloroprocaine.⁴ PNTD and TNS are most frequently described with lidocaine, although both complications have also been reported after bupivacaine,⁵ TNS after mepivacaine⁵ and PNTD after chloroprocaine.⁶ Although lidocaine is involved in both TNS and PNTD, these seem to be two different issues, both pathophysiologically and clinically. TNS is benign, frequent and self-limited without neurologic symptoms or sequelae. The frequency with spinal lidocaine (0–40%) is independent on lidocaine baricity, concentration or dose. TNS is more frequent in the lithotomy position or when the hip-joint is frequently manipulated during anesthesia, as with knee-arthroscopy.⁷ PNTD is rare, but presents with neurologic symptoms and sometimes permanent paralyses. It is hardly never described with less than 100 mg lidocaine in solutions of less than 50 mg•ml^–1 concentration.⁸ Yet, with hyperbaric lidocaine, cases are reported with doses less than 100 mg.⁸ Whereas we do not know the pathophysiologic mechanism with TNS, there seems to be neurotoxicity involved with PNTD.

Choice of drugs

Lidocaine
Lidocaine is used frequently for short acting spinal anesthesia, due to its reliable effect lasting for one to three hours in a milligram-dose dependant fashion. A minimum concentration of 15 mg•ml^–1 seems to be necessary in order to provide good operating conditions (Liu, personal communication). For some procedures a dose of 40 mg may be adequate,⁹ but in most cases a dose of 50–70 mg would be more reliable. At our institution we use a 20- mg•ml^–1 hyperbaric solution. This will still be associated with TNS in some cases, but no cases of PNTD have been reported so far in the literature.

Bupivacaine
In small doses,¹⁰eventually combined with spinal adjuvants,¹¹ bupivacaine may have a short clinical duration of action, comparable to that of lidocaine. However, there are data indicating that the paralysing effects on detrusor muscles are prolonged, increasing the risk of unwarranted catheterization compared with lidocaine.¹² Ropivacaine may be a better alternative with a somewhat shorter and less intense motor block.

Adjuvants
Epinephrine may intensify and prolong the duration of spinal anesthesia, but it has been shown that the ability to void and discharge may be more delayed than the prolongation of anesthesia.¹³

Opioids are valuable adjuvants in order to decrease the dose of local anesthetic drug without prolonging recovery.¹⁴ However, it is important to limit the dose in order to avoid respiratory depression: 10–25 µg of fentanyl seem appropriate.¹⁴ Still, more than a 50% rate of pruritus may be encountered.¹⁴

Another approach to minimize the dose of spinal anesthetic is to have an epidural catheter in place for top-ups in those cases where a minimum dose turns out to be insufficient. Urmey et al. report the successful use of 40 mg lidocaine for spinal anesthesia lasting for one to 1.5 hr, combined with epidural catheter and top-ups when needed.⁹

Conclusion
Lidocaine is still my drug of choice when a short acting spinal anesthetic is needed. In a 2% solution and doses in the 40–70 mg range, no permanent nerve tissue damage have been reported. However, prilocaine should be tested more extensively in order to elucidate its role as less TNS provoking alternative to lidocaine. In very short cases or when rapid postoperative mobilisation is essential, the dose of lidocaine and thus the duration of anesthesia may be kept at a minimum with an adjuvant of 10 µg of fentanyl, iv or inhalational anesthetics or an epidural catheter as a rescue. Whereas TNS is a benign and self-limited condition, it may have an unacceptable high rate after lidocaine for procedures in the lithotomy position or after knee arthroscopy. In these cases a low dose of bupivacaine (e.g., 5–10 mg) may be an alternative, with the addition of fentanyl, but the risk of delayed discharge due to late voiding may be a problem. Ropivacaine 15–25 mg may be a better alternative.

Brachial plexus anesthesia¹⁵

Whereas the supraclavicular approach is discouraged in ambulatory practice due to the danger of pneumothorax, the axillary approach may be recommended for all procedures in the elbow, lower arm, hand or fingers. With a proper technique a tourniquet on the upper arm will also be well tolerated. The drawback with axillary block, as with all methods of brachial plexus block, is the occasional failure which, even in experienced hands, will occur with a 5–10% incidence. Further, the dose needed is at the limit of toxicity, and the risk of inadvertent iv injection or rapid vascular absorption is higher than with most other regional techniques. In order to minimize these problems, a dedicated regimen should be used for axillary plexus block. Due to the high failure rate, numerous alternative regimens exist.

My choice is to use lidocaine, mixing the two commercial solutions of 20 mg•ml^–1 with epinephrine 12.5 µg•ml^–1 (20 ml), with 10 mg•ml^–1 lidocaine plain (20 ml), adding 10 ml of saline, resulting in a total of 50 ml with lidocaine 12 mg•ml^–1 and epinephrine 5 µg•ml^–1. For an adult, all 50 ml will be injected as high in the axilla as possible, with a distal compression for two minutes afterwards with the arm adducted. Either a transarterial, double-paresthesia or nerve stimulator technique may be used.

Whereas an axillary block with lidocaine will provide surgical anesthesia within 15–30 min which lasts for two to four hours, an alternative is to mix 20 ml of bupivacaine 5 mg•ml^–1 instead of the lidocaine 10 mg•ml^–1 in the regimen described above. The onset of anesthesia will be about the same, but the block may last for eight to ten hours. This may be appropriate if intense postoperative pain is expected, but the patient must be instructed to use a sling and to be careful with his paralysed arm after discharge.

Interscalene block¹⁵

This block is appropriate for shoulder surgery, arthroscopy and upper arm surgery. The lower arm and hand are often not adequately anesthetized, especially the area innervated by the ulnar nerve. It is important to realize that this block almost invariably results in diaphragmatic hemiparesis and should be used with caution in patients with pulmonary disease who are dependent upon optimal diaphragmatic function. Some patients may also present a Horner syndrome with this block.

The drug mixture and equipment will be identical to that used during axillary block (see above), but the dose slightly lower, i.e., 30–35 ml.

IV regional anesthesia

This technique is easy and administration is rapid. A double tourniquet is applied on the upper arm. Even with the use of a double tourniquet, there will be some discomfort from the tourniquet, limiting the recommended duration of the surgical procedure to a maximum of 45–60 min. The block is most successful with superficial procedures or procedures involving soft tissues whereas bones or joints may not be adequately anesthetized. Inadequate block may be seen with obese individuals and, of course, if for some reason the cuff is leaking.

Epidural anesthesia

Whereas spinal anesthesia is frequently used for day case anesthesia,³ epidural anesthesia has drawbacks: it is more time-consuming to administrate and there is a delay in onset of block.

However, there are situations where an epidural block may be appropriate. Some patients may have had bad previous experience with spinal headache or fear of this complication. Some female patients may have had good experience with epidural anesthesia previously during childbirth and request the same method again. Some surgical procedures may have an unpredictable or long duration, thus the flexibility of extra dosing through an epidural catheter may be important. Examples are knee arthroscopy which sometimes may turn out to extensive cruciate ligament repair or prolonged procedures for varicose veins or plastic surgery in the lower half of the body.¹⁶ In order to avoid delays I will use a slow (i.e., three to four minutes) injection of epidural lidocaine with no test dose, telling the scrub nurse to proceed while the block is settling.

Paracervical block

This is an easy block to perform with a rapid onset, within three to five minutes, and good anesthesia for uterine dilatation and curettage, and for hysteroscopy. It is an excellent alternative to general anesthesia in obese patients and patients with a minor upper airway infection. Usually it is most practical for the gynecologist to administer the block, using 10 ml of lidocaine 10 mg•ml^–1 with epinephrine on each side. There is a risk of iv injection in the highly vascularized uterine tissue and some patient discomfort may be present if the uterus is manipulated vigorously.

Inguinal hernia block

With appropriate technique this block provides excellent surgical and postoperative analgesia for hernia repair, simplifying anesthetic surveillance and postoperative care compared with either general anesthesia or spinal anesthesia. Using lidocaine 10 mg•ml^–1 a 4–5 ml dose should be administered twice, 1 cm medial to the anterior superior tubercle of the hip. Then a spinal needle should be used to infiltrate the skin area for the wound with another 10–15 ml. Then a blunt needle should be used 2 cm cephalad to the midpoint of the inguinal ligament, going deep subfascially and injecting a further 20–25 ml. The subfascial position is confirmed when a second click is felt as the blunt needle is advanced slowly into the layers, starting from the skin.

Ankle block

This is a very useful block for numerous procedures on the foot. As the block is somewhat painful, it may be advisable to give the patient a small dose of opioid (e.g., alfentanil 0.5 mg iv) before proceeding. My choice is to use a 22 G needle, first behind the medial malleous, behind the artery, searching for paresthesia down in the foot. Once paresthesia is found, I withdraw the needle 1 mm, aspirate and inject 5–7 ml of lidocaine 20 mg•ml^–1 with epinephrine. Then, I will change to a 10 ml syringe with lidocaine 10 mg•ml^–1 without epinephrine and inject 2 ml deep, medial to the extensor muscle of the big toe. Then I will use the needle from the same injection in a "fan" both medially and laterally, resulting in a semicircular subcutaneous cuff in front of the distal leg, proximal to the malleoli, injecting 8–12 ml of local anesthetic. The benefit of this technique is that the "fan" both relieves the pain of a distal tourniquet and provides analgesia in the dorsum of the foot.

If prolonged postoperative analgesia is desired for ten to 12 hr, lidocaine may be replaced with bupivacaine 2.5 or 5.0 mg•ml^–1 respectively.

Conclusion

Regional anesthesia is an attractive alternative for many ambulatory cases due to excellent postoperative pain relief and potential of speeding up the process from the OR to discharge. Regional anesthesia may be practised successfully in a busy ambulatory unit with a dedicated and simple regimen. For a more extensive discussion see Ræder J. Regional anaesthesia. In: Smith I (Ed.). Day Care Anaesthesia, London: BMJ Books, 2000: 97–126.

References

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