TRUNCAL BLOCKS

Technique - Intercostal Nerve Block (Lateral Approach)
Place the patient supine with hands clasped behind the head, to reveal the axillary fossa; prep the flank from the axilla to the costal margin then mark the mid-axillary line. Palpate ribs 2-7 and mark the points where each rib's lower margin intersects the mid-axillary line. Using a short, sharp bevel 25 gauge needle and 5 mL syringe filed with 2% lidocaine make a small skin wheal at each of the points identified (above); do this gently and stay superficial. Now, taking a 10 mL control syringe equipped with 3 cm short bevel 22 gauge needle identify the mid-point of the second rib in the axillary line by retracting the skin cephalad to position the skin wheal over the body of the rib. Stabilize the operative hand well, then gently insert the needle through the skin, keeping perpendicular to the skin surface in all planes, and touch the bone. Release skin traction and gently, very gently walk the needle tip caudad until it just drops over the inferior margin of the rib. Advance the needle tip a further 2-3 mm, aspirate to ensure that the tip is not intravenous or sub-pleural, then inject 2-3 mL 0.25% bupivacaine or 1% mepivacaine to suffuse the subcostal groove. Repeat this procedure for each dermatome to be blocked (typically T2-7).

Technique - Intercostal Nerve Block (Paravertebral Approach)
Place the patient prone on a relatively narrow padded surface (gurney, operating table) with arms loosely hanging at each side so as to rotate the scapulae laterally. Prepare the back over the thoracic midline then draw two paramedian lines to pass through the posterior angles of the ribs and medial to the medial margins of the scapulae. Palpate and mark the inferior edge of each rib then follow the general procedures noted above; first raising skin wheals at the intersections of the marking lines, displacing the wheals slightly cephalad, inserting the regional block needle (22 gauge, 3 cm, short bevel) at the wheal point then gently walking off the inferior margin of each rib as skin traction is released. Advance the needle a further 3-4 mm, aspirate for blood or air, inject agent adjacent to the subcostal groove (2-3 mL 0.25% bupivacaine or 1% mepivacaine).

There are several comments to make about these two approaches to breast anesthesia. Although not technically difficult to perform both blocks have certain inherent hazards; pneumothorax is a possibility if needle placement is too deep; systemic absorption of local anesthetic is relatively rapid from the subcostal route of injection and blood levels of bupivacaine can be significantly elevated some time (minutes) after placement of an extensive blockade. The approach is difficult in obese patients and is generally uncomfortable even for normal women with normal anatomy; for this reason it is common to provide relatively generous intravenous sedation. Midazolam/fentanyl combinations or propofol are likely to work well for most patients undergoing aesthetic surgery; there is less likely to be a role for droperidol or ketamine in this setting. However, the practitioner must be alert to the consequences of oversedation, particularly in the prone patient, and the usual array of anesthetic monitors must be applied and observed throughout. After placement of intercostal blocks there may be a subjective feeling of dyspnea because of elimination of sensory feedback from the intercostal structures; this is best treated with reassurance and explanation.

The anatomical distribution of the intercostal nerves suggests that the posterior, paravertebral technique is likely to block all branches of each nerve, whereas the mid-axillary, lateral technique may spare the anterior and posterior lateral cutaneous branches. Clinically this does not seem to be the case, presumably because there is significant spread of local anesthetic along the inferior margin of the rib in the subcostal groove. Even for surgical procedures limited to cutaneous tissues of the breast it may be necessary to supplement the basic breast block with either a superficial cervical plexus block (as described earlier) or, alternatively, a simple subcutaneous infiltration of local anesthetic along the infraclavicular margin and over the manubrium; this is because fibers from the cervical plexus provide sensory innervation to the upper chest wall and fibers from the contralateral intercostal nerves cross the midline. Again, to emphasize, the breast block is not appropriate for extensive surgery involving axillary structures or deep elements of the chest wall.

Surgical Site - Abdomen
Technique - Intercostal Nerve Block
Body contouring procedures such as abdominoplasty or belt lipectomy can be performed under regional anesthesia using a combination of local infiltration at wound margins and regional blockade provided by intercostal blocks. Although it is possible to carry out superficial surgery of the abdominal wall with this combination of anesthetic blockade, some form of systemic supplementation is frequently necessary. Again, this may take the form of bolus administration of modest amounts of midazolam and fentanyl, or may be provided with propofol or methohexital infusion. The approach to abdominal wall block is as described above, except that the dermatomes to be blocked will generally be T6-12. If abdominal wall relaxation is required then the intercostal injections should be made using 0.5% bupivacaine or 1.5-2% mepivacaine; if purely sensory anesthesia is required, 0.25% bupivacaine or 1% mepivacaine will suffice. The same caveats noted for breast block (above) apply to the abdominal block; in particular, it may be quite difficult to effect with obese patients (who may, paradoxically, represent a fairly significant proportion of candidates for abdominal contouring).

Technique - Liposuction
A common approach to removal of unwanted subcutaneous lipid stores; the most frequently treated areas in women are the abdomen, hips, thighs, knees, calves, ankles, and beneath the chin. In men the most commonly treated areas include the waist, the abdomen, breast and the neck/chin area. In many instances the technique can be performed without invoking general anesthesia, using an approach termed tumescent local anesthesia, involving subcutaneous infiltration of dilute lidocaine solution containing epinephrine - to produce subcutaneous swelling with profound local anesthesia and intense vasoconstriction - followed by aspiration of fat through small cannulae. Although the recommended doses of lidocaine are as high as 55 mg per kilogram of body weight, few safety data are available, and the technique has been criticized on the basis of this empirical protocol. Nevertheless, the general experience with tumescent liposuction is now very extensive and the few catastrophic complications reported seem to have been associated with inadequately monitored heavy sedation and/or general anesthesia. The possibility of lidocaine toxicity is real, given the very large absolute doses involved, but most of what is administered in the irrigating fluid is not absorbed. Note, however, that systemic toxicity involving high cerebral levels of lidocaine is the most frequent serious adverse outcome associated with its use and that toxic levels can rapidly be established with unintentional intravascular injection. Remember the sequential progression of symptoms of lidocaine toxicity which usually follow a predictable course: metallic taste - tongue numbness - dizziness - diploplia and visual halos - muscle spasm - unconsciousness - convulsions - coma - respiratory arrest - cardiac depression - anoxic brain damage/death. To emphasize again, an alert and communicative patient may be one of the best monitors of developing toxicity, and for this reason it is probably wise to restrict patients to minimal sedation during liposuction procedures. Although lidocaine is often considered relatively benign, all local anesthetics have similar toxic-therapeutic ratios with respect to CNS inhibition; lidocaine itself causes dizziness and visual changes at plasma concentrations around 5 mg/mL, convulsions at 10 mg/mL and respiratory arrest at 20 mg/mL. With tumescent liposuction techniques, it is difficult to predict precise blood levels of lidocaine from the clinical dosage used so a careful watch must be maintained for the early symptoms of toxicity. The local anesthetics do not themselves cause permanent CNS damage, but cerebral hypoxia during coma and decreased perfusion states is exacerbated by acidosis, hyperkalemia and hypoxemia generated by seizure activity. Therefore, if toxicity is noted stop administration of agent at once, provide supportive measures (airway maintenance, oxygen supplementation etc.) and treat seizures. Generally thiopental (2-4 mg/kg) or diazepam (0.1 mg/kg) will break seizure activity; if muscle spasm interferes with ventilation then succinylcholine (1 mg/kg) can be used, but this is not a trivial intervention and should not be undertaken unless endotracheal intubation could be performed immediately if ventilation remains problematic. Again, to emphasize, appropriate resuscitation equipment must be available at every location where regional anesthetics are administered, and appropriate monitors must be used for every case.