Local anesthetics with prolonged periods of analgesic activity such as bupivicaine are being used to provide postoperative pain control in outpatient surgery. Nerve blocks can be used to provide anesthesia for more extensive surgical procedures to the extremities.
Digital nerve blocks can be done at the base of the fingers and toes by injecting proximal to the two dorsal and palmar/plantar nerves supplying each digit.
Brachial plexus block done by an interscalene, supraclavicular or axillary approach can provide anesthesia for the shoulder and hand.
Lower extremity blocks can be performed through injection of individual nerves including block of the femoral, sciatic, obturator and femoral lateral cutanous nerves or through a lumbar plexus block involving injection of anesthetic into the psoas muscle to block all of these nerves simultaneously.
Ankle block involves individual block of the five nerve branches innervating the foot.
Bier block. Intravenous regional anesthesia can be provided through a Bier block where local anesthetics are injected into the limb's circulation isolated from systemic perfusion by a tournequit. Care must be taken to avoid injection of anesthesia into the systemic circulation or directly into the nerve causing a neuropathy.
Spinal anesthesia is advantageous in patients requiring operations to the perineum and extremities in that it obviates the risk of aspiration and a difficult airway, allows for early identification of cardiac ischemic events and angina, and allows for detection of complications of urologic surgery such as bladder perforation and systemic absorption or irrigation solutions.
Despite these advantages spinal anesthesia has not shown a uniform reduction in cardiac ischemic events during surgery. Contraindications to spinal anesthesia include major coagulopathy and unstable neurologic disease.
Spinal anesthesia is produced by injecting anesthetics into the subarachnoid space at the L3-L4 level and the spinal level of anesthesia is determined by the dose of the drug administered. Other factors that can determine the level and number of spinal segments anesthetized include pregnancy, increased intra-abdominal pressure, positioning of the head of the patient, injection at higher spinal levels, rapid injection of the anesthetic and barbotage (a technique that promotes mixing of the CSF with the anesthetic).
Complications from spinal anesthesia arise from the loss of sympathetic tone and leakage of cerebrospinal fluid. The most immediate complication is a drop in blood pressure without a compensatory increase in heart rate and is seen most commonly in geriatric and pregnant patients. Hypotension is easily remedied by fluid bolus or ephedrine. Focal neurologic defecits following spinal anesthesia have also been reported but are minor and transient. Rarely patients can develop adhesive
arachnoiditis with nonspecific inflammation of the meninges and spinal cord resulting in paraplegia.
Spinal headache is a second complication produced by intracranial hypotension. Treatment of spinal headache includes fluid boluses, treatment with caffeine, or an injection of blood into the epidural space at the level of lumbar puncture known as an autologous blood patch.
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