[Total spinal block after posterior lumbar plexus blockade: case report.]

Lumbar plexus blockade can be very useful in surgical procedures of the hip, thigh, and knee, but it should be performed by an experienced anesthesiologist due to potential complications. The current report presents a case of total spinal block after posterior lumbar plexus blockade and discusses the possible pathophysiological mechanisms.

Male patient, 34 years old, 97 kg, physical status ASA I, scheduled for total hip arthroplasty. After general anesthesia, a right posterior lumbar plexus blockade was performed with the adjunct of a peripheral nerve stimulator. The needle was introduced to a depth of 8 cm, perpendicular to the skin, 4 cm from the mid line, on a line perpendicular to the spinal process of L4. After identification of a motor response from the quadriceps, the intensity of the current was reduced to 0.35 mA and 0.5% ropivacaine (39 mL) was administered. During the injection, there were intermittent contractions of the quadriceps. After the block, the patient presented apnea, hypotension, and both pupils were dilated. At the end of the surgery, the patient presented motor block of the lower extremities, which reversed only nine hours after the block. In the postoperative period, the patient complained of severe pain; he was discharged 12 days after the surgery without motor or sensitive deficits.

To identify the psoas compartment, where the lumbar plexus blockade is located, the intensity of the current must be between 0.5 and 1 mA. Motor response with low current indicates that the needle may be inside the sheath that surrounds the nervous root and extends to the epidural and subarachnoid spaces, to where the anesthetic solution might spread. Despite the wide safety margin of the procedure, the anesthesiologist must have keen anatomy knowledge, training on the technique, and be constantly alert to perform a lumbar plexus blockade.