Comparative study between two ventral ultrasound-guided approaches to block the femoral nerve in the dog

1. Accuracy of two ventral approaches to block the femoral nerve in the Dog
Echeverry DF1, Laredo F2, Belda E2, Soler M2, Gil F2, Agut A2
Faculty of Veterinary Medicine and Zootechnic. Tolima University (Colombia)1 Veterinary Faculty. Murcia University (Spain)2
1. Objective: The femoral triangle
approach
To evaluate the accuracy of 2 (Fta) The ultrasonographic
ultrasound-guided approaches to locate characteristics of the
the femoral nerve (FN) in the dog The suprainguinal FN were also evaluated
approach
(SIa)
2. Materials & Methods:
The accuracy of the
nerve location was
confirmad by
N=5 nerve stimulation
Once the FN
Fta: Position of the transducer 0.2 mL kg-1 of
was located
(linear 13 MHz) and the needle. saline was injected
around the nerve
*
Sedation: medetomidine (10μg/kg) To evaluate
& butorphanol (0.25 mg/kg) IM 0.5 mA;2Hz;0.1 ms
Positive
The injectate
response
distribution
pattern
Extension of the stifle
SIa: Position of the transducer
(linear 13 MHz) and the needle.
*resting period beetwen treatments
8 days
3. Results:
ventral A ventral B
2 2
3
3 3
1
lateral lateral
Figure 1. (A) ultrasonographic image correspondig to the ventral FTa. (B) Ultrasonographic image
after the blocks. 1. femoral nerve; 2. femoral artery; 3. local anaesthetic.
ventral A ventral B
2 2
4
1 4
5
3 1
5
5
2
lateral lateral
Figure 2. (A) ultrasonographic image correspondig to the SIa. (B) Ultrasonographic image after the
blocks. 1. femoral nerve; 2. iliopsoas muscle; 3. ilion; 4. needle. 5. local anaesthetic surronding the FN.
Table1. Comparative study of the ultrasonographycal features beetwen the femoral triangle and suprainguinal approaches
Features Femoral triangle approach Suprainguinal approach
Size of the Acoustic window Small Wide
Visualization of the nerve during the blocks Scarce Adequate (permanent)
Visualization of the needle during procedure Scarce Adequate (permenent)
Distribution pattern of the injectate (saline) Irregular (in several planes under the femoral artery) Around of the femoral nerve (donnut sign)
Technical difficulty to perform the blocks High Low
Proximity to vascular structures Close to the femoral artery Far from vascular structures
Ultrasonographic appearence of the FN Hyperechoic triangular structure Hypoechoic oval to rounded structure
Accuracy of the approach to locate the femoral nerve 60% 100%
Use of the neurolocation to locate the target nerve 40% 0%
3. Conclussion:
The SIa seems to be an easier and more efficient technique to locate the FN in comparison to the FTa. The use of nervestimulation
as a complementary technique of nerve location appears to be essential when locating the FN by a FTa.
References:
1. Campoy L, Bezuidenhout AJ, Gleed RD, et al: Ultrasound-guided approach for axillary brachial plexus, femoral nerve, and sciatic nerve blocks in dogs. Vet Anaesth Analg 2010; 37(2):144-53.
2. Echeverry DF, Gil F, Laredo F, et al: Ultrasound-guided block of the sciatic and femoral nerves in dogs: a descriptive study. Vet J 2010; 186(2):210-5.