Abstract ID: A16
Abstract Title: New fenestrated needle for peripheral nerve block
Poster Type: Either
ABSTRACT BODY
Introduction
Existing techniques for femoral nerve (FN) or “3 in 1” block require the anesthesiologist to correctly position the needle tip into a tissue plane defined by the fascia iliaca (1). The correct depth for needle insertion is usually determined electrical stimulation or by eliciting a paresthesia of the FN (2, 3). Injection of sufficient volumes of local anesthetic into this fascial plane results in medial and lateral distribution of local anesthetic and subsequent blocking not only the FN, but also the lateral femoral cutaneous (LFC), and sensory portions of the obturator nerve (ON)(4).
This study evaluates the effectiveness of a new fenestrated needle for FN block that facilitates delivery of local anesthetic into the plane of the fascia iliaca without the use of a nerve stimulator or paresthesia. This 20G needle is 9cm in length and has an occluded tip. The distal 3cm have fenestrations at 1mm intervals on alternating sides of the needle (figure 1). During injection, local anesthetic enters fascial planes where resistance is low (figure 2).
Methods
After IRB approval and written informed consent, the needle was tested in 10 male volunteers. Needle insertion was 2cm lateral to the femoral artery and 1 cm inferior to the inguinal ligament. The needle was advanced in a transverse plane to a depth of 6cm in each patient. Careful aspiration was performed after which 15cc of 1% lidocaine containing 5mcg/ml of epinephrine and iopamidol were injected. Flouroscopy was performed in each patient to document the pattern of distribution of local anesthetic. Following injection, cold sensation in the distributions of the FN, LFC, and ON was assessed every 10 minutes. Motor strength was also assessed at 10 minute intervals on a scale of 0-5/5.
Results
The mean age of volunteers was 31 ± 9.7. The height and weight were 179 ± 3.6 cm and 91 ± 8.1 kg respectively. All ten volunteers had early loss of temperature sensation in the distributions of the FN and LFC. Nine patients had early loss of temperature sensation in the ON distribution. In one patient there was no sensory change in the ON. Fluoroscopy performed during and after injection revealed a planar distribution of local anesthetic (figure 3). Mean onset times for sensory loss in the FN, LFC, and ON were 10 ± 0, 19 ± 11, and 18 ± 10 minutes respectively. Onset of motor effect in the quadriceps muscle was at 18 ± 8.0 minutes with a maximal decrease to 1.8 ± 1.2/ 5. No motor effect was noted the adductor muscles (ON). The mean duration of block using lidocaine was 5.3 ± 0.9 hours.
Conclusion
The FN, LFC, and sensory portions of the ON are contained in a tissue plane defined by the fascia iliaca. This tissue plane offers low resistance to fluid distribution in comparison to surrounding dense tissue. A fenestrated needle traversing this plane can be used to deliver local anesthetic to this compartment and the nerves contained therein without electrical nerve stimulation or paresthesia. This technique consistently produced sensory and motor changes but not surgical block in the FN, LFC and ON.
References
1. Anesth Analg: 86:1039-44, 1998
2. Anesth Analg: 52:989-96, 1973
3. Anesth Analg: 69:705-13, 1989
4. Anesth Analg: 90:119-24, 2000
ATTACHED FILES
Reg Anesth Pain Med 2004; 29(2):A16