Continuous three-in-one block is widely used for postoperative analgesia after proximal lower limb surgery, but location of the catheter has not been well addressed in the literature. We prospectively studied, in 100 patients, the characteristics of catheter threading under the iliac fascia and the correlations between catheter tip location and effective sensory and motor blockade of the three principal nerves of the lumbar plexus. Postoperatively, in conscious patients, 16 to 20 cm of a catheter was placed in the fascial sheath after femoral nerve location with a nerve stimulator. Contrast media (3 mL Iopamidol 390) was injected, and the catheter tip was located by means of an anteroposterior pelvic radiograph. An equal-volume mixture of 0.5% bupivacaine/2% lidocaine with epinephrine (30 mL) was injected through the catheter. Patient and catheter-insertion characteristics were noted. Thirty minutes after injection, sensory blockade was evaluated in the cutaneous territories of the lateral femoral cutaneous, femoral, and obturator nerves, along with motor blockade of the last two nerves. Pain scores at 30 min were also recorded. Seven block failures were noted. The tip of the catheter reached the lumbar plexus (Group 1) in 23% of the patients and lay deep to the medial (Group 2) or lateral (Group 3) part of the fascia iliaca in 33% and 37% of the patients, respectively. Demographic data and catheter threading characteristics were comparable among the groups. A three-in-one block was noted in 91% of Group 1 patients, but in only 52% and 27% of Group 2 and 3 patients, respectively (P < 0.05). Comparing Group 2 and 3 patients, sensory block was achieved in respectively 100% and 94% for the femoral nerve, 52% and 94% for the lateral femoral cutaneous nerve (P < 0.05), and 82% and 27% for the obturator nerve (P < 0.05). Visual analog scale pain scores on movement were significantly lower in Group 1 patients (P < 0.05). We conclude that during a continuous three-in-one block, the threaded catheter rarely reached the lumbar plexus. The quality of sensory and motor blockade and initial pain relief depend on the location of the catheter tip under the fascia iliaca.
Implications: The course of a continuous three-in-one block catheter is unpredictable. Only 23% of the catheters lie near the lumbar plexus. The success of sensory and motor blocks, as well as postoperative analgesia, depend on the position of the catheter under the fascia iliaca.