Continuous peripheral nerve blocks allow the maintenance of analgesia either by repeated injections or by continuous infusion of local anesthetics. Most of the studies on the use of this technique are in the postoperative setting rather than in the setting of trauma. The advantages of this technique in trauma, however, are quite obvious. With a catheter in place, the duration of the analgesia or anesthesia can be extended, and the concentration of the local anesthetic can be changed to provide sympathetic block, sensory block, or motor block with muscle relaxation, as desired.
Winnie popularized the concept of a fascial covering of the brachial plexus from its roots emerging from the intervertebral foramina to the level of nerves at the axilla. He equated a continuous axillary brachial block to a continuous caudal block, a continuous subclavian perivascular block to a continuous lumbar epidural block, and a continuous interscalene block to a continuous thoracic or cervical epidural block.™ As previously stated, this chapter does not go into the details of the techniques but rather provides only general comments.
Placement of a catheter in the axilla is easy and free of serious complications. However, axillary catheters have the highest rate of accidental displacement secondary to movement of the upper extremity, and suturing may be required. The presence of moisture and hair in the axilla makes it difficult to maintain a sterile environment, and infections are possible. In one study, however, axillary catheters were left in place for a mean of 11.5 days, and cultures of the catheter tips were positive only in those that were left in place longer than 4 days.™ None had signs or symptoms of local or systemic infection.
An infraclavicular catheter is less likely to be dislodged, and catheters have been left in place for 3 weeks.12" The infraclavicular technique is ideal for patients who cannot abduct the upper arm. A subclavian perivascular catheter also moves very little with movements of the head and neck because it lies flat against the patient's neck. Blockade of the brachial plexus at this level involves the trunks and can be achieved with a smaller volume of local anesthetic. Possible complications of the subclavian perivascular technique include pneumothorax and injection into the vertebral artery. Interscalene catheters are difficult to immobilize and easily dislodged by movements of the head and neck because the catheter emerges from the skin at a right angle to the head and neck.1™ Suturing the catheter has been recommended.1™ Hemidiaphragmatic paralysis is common with this technique.
The local anesthetic can be administered continuously, or injections may be given intermittently. There appears to be no difference in the sensory or motor blockade characteristics between these two techniques, although higher plasma concentrations were noted with continuous infusion.12" Bupivacaine is the most commonly used local anesthetic, and the 0.25% concentration is the most commonly used concentration. The use of 0.125% concentration is recommended when assessment of motor function is required. Winnie discouraged the use of adjuvants such as bicarbonate or alpha-agonists because these adjuncts only complicate the pharmacologic management of the trauma patient.1203
Continuous plexus blocks of the lower extremity can be achieved with the inguinal paravascular lumbar plexus block, "3-in-1" block, lumbosacral plexus block, psoas compartment block, and continuous sciatic nerve block. With the 3-in-1 block, the "intracath technique" is recommended.1™ With this technique, a catheter can be inserted through the initial catheter and inserted as far as desired. Contraction of the quadriceps muscles from the nerve stimulator is seen with the 3-in-1 block. In patients with fracture of the femur, this painful muscle contraction should be minimized during the nerve stimulation. Studies have shown that the efficacy of the continuous lumbar plexus block via the 3-in-1 technique1203 1203 is as effective as continuous epidural morphine, with less incidence of pruritus, nausea, vomiting, and urinary retention.»3 The use of 0.125% bupivacaine appears to be as effective as 0.25% bupivacaine. 28 Blockade of the lumbar plexus, however, does not provide analgesia to areas innervated by the sciatic nerve.
Continuous lumbosacral plexus block has been achieved with the use of a Tuohy needle and an epidural catheter.2" A continuous sciatic nerve block has been described, whereby the catheter is placed near the sciatic nerve after its exit from the greater sciatic foramen.'213 A combination of the continuous parasacral sciatic nerve block and the lumbar plexus block has also been described.1213 There is less experience with these techniques compared with the "3-in-1" approach to the lumbar plexus.
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