There is only one local anesthetic capable of readily penetrating intact skin; this is the combination of 5% lidocaine and 5% prilocaine known as EMLA, an acronym for eutectic mixture of local anesthetics. It is a white, oily cream that is smeared over the target area and then covered with an occlusive dressing (such as Tegaderm); after 20-40 minutes, profound anesthesia of the superficial skin layers (to a depth of 5-6 mm) can be anticipated. Although the technique is useful for procedures such as tattoo removal or laser ablation of portwine stains, the area of skin treated should probably be modest. There are reports of facial procedures such as dermabrasion being performed after "facial anesthesia" effected by application of a form-fitting plastic mask slathered in EMLA, an approach that would seem to be time-consuming, expensive, and subject to the consequences of prilocaine toxicity.

LOCAL INFILTRATION: Anesthetic solutions such as bupivacaine or lidocaine are injected into the soft tissues surrounding a wound or surgical site; the technique is effective, for example, for the excision of small superficial cysts or lipomas, or for painless suturing of lacerations. It is not useful for large wounds.

INTRAVENOUS ANESTHESIA: The anesthetic solution is injected into a major vain draining an extremity. Commonly used for short surgical procedures on the arm; the limb is first squeezed free of blood (elastic bandage, then isolated (tourniquet) and the anesthetic (almost always lidocaine 0.5%) is injected into a distal vein. Excellent technique for surgeries such as contracture release or joint mobilizations.

PERIPHERAL NERVE BLOCK: A major nerve supplying a limb or specific area of the body is identified (anatomy, paresthesias, nerve stimulator) and a solution of local anesthetic is injected very close to, but not inside, the nerve yielding a sensory (and often motor) block dense enough for painless surgery. The block may last up to 24 hours depending on the amount and type of anesthetic agent used; or may be prolonged indefinitely by use of a continuous infusion of agent directed through a fine plastic catheter.

NEURAXIAL BLOCK: A term used to describe epidural and spinal analgesia in which small amounts of local anesthetic are injected or infused into the epidural space (yielding a segmental blockade of the nerves supplying a large territory) or into the subarachnoid space (yielding a spinal blockade of the lower half of the body).

Although it is completely acceptable for local, intravenous and peripheral blocks to be administered by non-anesthesiologists, neuraxial blocks must only be placed by specialists who have undergone intensive training both in the techniques of block placement and also in resuscitation and airway management.

There are relatively few types of surgery where regional anesthesia is absolutely indicated (as opposed to merely being an option) but certain surgeries lend themselves particular to regional techniques, and there are compelling reasons, sometimes, for either avoiding general anesthesia or, more commonly, for supplementing general anesthesia with some form of regional block. In general terms, the types of advantages to be expected from regional techniques are a reduction in overall stress of surgery, better postoperative pain control, decreased incidence of postoperative nausea and dysphoria, and, in many situations, improved wound healing.

Reduced surgical stress: Stress can sometimes be monitored by looking at changes in heart rate or blood pressure, or, in more sophisticated ways by monitoring cerebral blood flow or the release into the blood of specific markers of stress reactions such as cortisol. TCD studies show that cerebral blood flow through increases significantly for several minutes after skin incision in patients under apparently adequate general anesthesia (2 MAC isoflurane) and there is evidence, in children at least, that this effect is abolished or attenuated when there is effective concomitant epidural regional anesthesia. The relevance of these observations to aesthetic surgical procedures performed under regional anesthesia alone are that the same reductions in stress are present even when the patient is fully awake; decreased stress is almost always beneficial.

Reduced postoperative pain: Some procedures are particularly painful, for example many surgical procedures on the foot or knee. Patients who have this type of will need a high level of analgesia post-operatively, and - although this can be provided by simple techniques such as morphine injections, these tend to produce nausea, constipation, sleep disturbances and, sometimes, mood changes and dysphoria. By incorporating a regional technique such as sciatic or femoral nerve block into the anesthetic regimen all these complications can be reduced or eliminated; in addition, the period of awakening from general anesthesia (emergence) is typically much smoother, less stressful and more comfortable when all pain from the surgical site has been eliminated by a regional nerve block, rather than simply masked by systemic opioids.

Reduced postoperative infection: Inactive post-surgical patients lying in hospital beds are at significant risk for acquiring pneumonia. In general, opioids such as morphine cause respiratory depression and patients tend to breath less energetically than they should, exacerbating this risk. This is the reason why many post-trauma patients need routine respiratory therapy or incentive spirometry during convalescence. Reducing the amount of morphine needed generally reduces the incidence of respiratory depression and consequent pulmonary complications, and patients with good pain control provided by peripheral nerve blocks or epidural infusions require dramatically less morphine than they would otherwise.

The specific group of patients who have undergone painful chest or abdominal procedures performed, or who have had irritating drainage tubes placed represents a group at even greater risk of postoperative pneumonia. Painful chest wounds make it very difficult to cough breath deeply, and patients will often sit up in bed panting shallowly because it hurts to take proper breaths. This is a set-up for atalectasis, pulmonary infection and reduced oxygen supply; in many cases the appropriate use of regional techniques such as intercostal blocks can make a significant positive difference, and can even make the difference between a successful recovery or death in elderly or frail patients.

Improved healing: The body has a natural defense against blood loss after surgical incision and that is vasospasm, intense vasoconstriction causing arteries to clamp down in response to the stress of injury to reduce the amount of blood loss. Although this is beneficial acutely at the time of injury, it is generally unhelpful in the immediate postoperative period, and vasospasm or vasoconstriction is a feared complication of aesthetic surgical procedures involving rotational or translational flaps, starving the surgical wound of the blood needed for healing. One of the effects of regional nerve blocks using local anesthetics is sympathectomy, the elimination of vasoconstriction provoked by sympathetic responses to stress. For this reason, many surgeons request that regional blocks be used in patients undergoing re-implantation or reconstructive procedures in order to improve wound healing and to increase the chances of a successful graft.