The Veterinary Journal 200 (2014) 434–439
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The Veterinary Journal j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / t v j l
Ultrasound-guided anaesthetic blockade of the pelvic limb in calves Michela Re a, Javier Blanco-Murcia a, Alejandra Villaescusa Fernández a, Ignacio De Gaspar Simón b, Ignacio A. Gómez de Segura a,* a b
Department of Animal Medicine and Surgery, Veterinary Faculty, University Complutense, Avda, Puerta de Hierro s/n. 28040, Madrid, Spain Department of Anatomy and Embryology, Veterinary Faculty, University Complutense, Avda, Puerta de Hierro s/n. 28040, Madrid, Spain
A R T I C L E
I N F O
Article history: Accepted 11 April 2014 Keywords: Analgesia Sciatic-femoral nerve blockade Local regional anaesthesia Ultrasound Calf
A B S T R A C T
This study aimed to describe a suitable acoustic window to facilitate access to the sciatic and femoral nerves in calves and to study the effects of their blockade with local anaesthetics. The neuroanatomical and ultrasound (US) study was performed on the cadavers of 10 calves, and the effects of 2% lidocaine with epinephrine (0.2 mL/kg) were determined in five healthy calves. The sciatic nerve in the cadavers was easily visualised as a hyperechoic band distal to the femoral greater trochanter and caudal to the femoral shaft. The femoral nerve in the cadavers was not easily identified, and was visualised as a hyperechoic oval structure situated immediately medial to the psoas major muscle and lateral to the femoral artery. The sciatic nerve was stained by methylene blue, injected under US guidance, in 9/10 cases, and the femoral nerve was stained in 6/10 cases. Sciatic nerve blockade under US guidance produced adduction of the limb with metatarsophalangeal joint flexion, while the femoral nerve blockade produced reduced weight bearing. The sciatic nerve blockade produced a reduced response to the noxious stimulus, mainly in the phalanges, proximal and distal metatarsus, tarsus and tibia and, following the femoral nerve blockade, in the medial subarea of the femur. However, femoral nerve blockade produced a more variable degree of blockade. In conclusion, US -guided anaesthetic blockade of the sciatic nerve in calves may be considered for surgery in the distal pelvic limb, although further studies are necessary to determine its clinical application. © 2014 Elsevier Ltd. All rights reserved.
Introduction Loco-regional anaesthetic techniques are commonly employed in cattle under sedation to perform most common surgeries, potentially reducing the risks associated with general anaesthesia while providing adequate analgesia (Edmondson, 2008). When surgical procedures are required in the distal part of the pelvic limbs, local and regional anaesthesia can be performed using different techniques, such as ring blocks, intravenous regional anaesthesia, epidural anaesthesia, nerve block (Skarda, 1996) or general anaesthesia. Nerve block of the pelvic limbs usually involves the peroneal and tibial nerves (Thurmon and Ko, 1997), although this method is rarely used in clinical practice due to the difficulty of identifying the proper injection site for the local anaesthetic (Skarda, 1996). In people, combined anaesthetic block of the sciatic and femoral nerves has been shown to provide adequate analgesia of the legs (Enneking et al., 2005), and recent data support the usefulness of these techniques in dogs and cats (Campoy et al., 2010; Echeverry et al., 2010, 2012; Shilo et al., 2010; Haro et al., 2012). Blockade of the peripheral nerves can be improved through nerve stimulation
* Corresponding author. Tel.: +34 394 3858. E-mail address: [email protected] (I.A. Gómez de Segura). http://dx.doi.org/10.1016/j.tvjl.2014.04.010 1090-0233/© 2014 Elsevier Ltd. All rights reserved.
(Mahler and Adogwa, 2008; Rioja et al., 2012) and ultrasound (US) guidance (Campoy et al., 2010; Echeverry et al., 2010, 2012; Shilo et al., 2010; Costa-Farre et al., 2011). Both techniques are complementary. Peripheral nerve blockade should be based on the neuroanatomy of the species considered (Mahler and Adogwa, 2008). In calves, there are no studies describing the neuroanatomy of the sciatic and femoral nerves. The objective of the present study was to describe in cadavers an acoustic window that facilitated access to the sciatic and femoral nerves and to describe, in live calves the clinical application of blockade of these nerves produced by the administration of local anaesthetics under US guidance. Materials and methods All animal use was approved by the University Complutense Institutional Animal Care and Use Committee (CEA-UCM 100/2012, 14 June 2012).
Phase 1: Anatomical study of the sciatic and femoral nerves For the anatomical dissection of the sciatic and femoral nerves, cadavers of four calves (19 ± 9 days old, weighing 37 ± 5 kg) were used. For the sciatic nerve, a skin incision was made from the greater trochanter, caudal and distal to the crural region, to expose the lateral aspect of the pelvic limb. A transverse incision was made in the gluteobiceps muscle to expose the nerve. For the femoral nerve, the incision was
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Table 1 Maximum score and duration in minutes (in parentheses) obtained following sciatic nerve blockade in 10 pelvic limbs from five calves in the different subareas: lateral (L), dorsal (D), medial (M) and plantar (P) subareas of the phalanx, distal and proximal metatarsus and lateral, cranial (Cr), medial and caudal (Ca) subareas of the tibia and the tarsus and lateral subarea of the femur and the knee (0, positive normal response to stimuli; 1, diminished response to the stimulus; 2, negative response). Duration of 0 min indicates that the maximum score was achieved only at one time point. The number of limbs where a score of 2 was determined is shown in the last row. Animal – Limb
1 Left 1 Right 2 Left 2 Right 3 Left 3 Right 4 Left 4 Right 5 Left 5 Right Score = 2(n)
Phalanx
Proximal metatarsus
D
M
P
L
D
M
P
L
D
M
P
2 (70) 2 (20) 2 (0) 2 (70) 2 (80) 2 (80) 2 (80) 2 (70) 2 (40) 2 (60) 10
2 (70) 2 (0) 2 (0) 2 (0) 2 (80) 2 (80) 2 (80) 2 (70) 2 (40) 2 (60) 10
2 (70) 1 (30) 1 (80) 2 (50) 2 (80) 2 (80) 2 (80) 2 (80) 2 (30) 2 (0) 8
2 (30) 1 (0) 1 (80) 2 (40) 2 (80) 2 (60) 2 (80) 2 (70) 2 (30) 2 (60) 8
2 (20) 2 (0) 2 (0) 2 (40) 2 (70) 2 (40) 2 (80) 2 (70) 2 (40) 2 (70) 10
2 (80) 1 (70) 2 (0) 2 (0) 2 (50) 2 (40) 2 (80) 2 (70) 2 (40) 2 (70) 9
2 (20) 1 (30) 2 (0) 2 (40) 2 (50) 2 (80) 2 (80) 2 (80) 2 (30) 2 (70) 9
2 (0) 2 (0) 2 (40) 2 (50) 2 (40) 2 (30) 2 (60) 2 (70) 2 (30) 2 (60) 10
2 (20) 2 (10) 1 (60) 2 (40) 2 (80) 2 (80) 2 (80) 2 (70) 2 (40) 2 (70) 9
2 (80) 2 (0) 2 (0) 2 (40) 2 (70) 2 (80) 2 (80) 2 (80) 2 (40) 2 (70) 10
1 (40) 2 (0) 2 (0) 2 (50) 1 (80) 1 (70) 1 (80) 1 (80) 1 (50) 1 (80) 3
2 (30) 1 (50) 2 (0) 2 (80) 2 (70) 2 (10) 2 (80) 2 (80) 2 (40) 2 (70) 9
Animal – Limb
1 Left 1 Right 2 Left 2 Right 3 Left 3 Right 4 Left 4 Right 5 Left 5 Right Score = 2(n)
Distal metatarsus
L
Tarsus
Tibia
Knee
Femur
L
Cr
M
Ca
L
Cr
M
Ca
L
L
2 (50) 2 (10) 2 (0) 2 (80) 2 (80) 2 (80) 2 (80) 2 (80) 2 (40) 2 (70) 10
2 (10) 1 (40) 1 (60) 2 (10) 2 (70) 2 (30) 2 (80) 2 (80) 2 (30) 2 (70) 8
1 (20) 1 (20) 1 (80) 2 (20) 1 (80) 1 (30) 2 (0) 1 (80) 2 (10) 2 (10) 4
2 (50) 2 (20) 2 (40) 2 (50) 2 (80) 2 (60) 2 (80) 2 (80) 2 (40) 2 (80) 10
2 (10) 1 (60) 1 (80) 2 (50) 2 (80) 2 (60) 2 (80) 2 (80) 2 (50) 2 (80) 8
1 (40) 1 (40) 1 (70) 1 (80) 1 (80) 1 (80) 1 (80) 1 (80) 2 (20) 1 (80) 1
0 2 (0) 1 (50) 2 (20) 1 (80) 1 (80) 2 (0) 1 (80) 2 (10) 1 (80) 4
2 (60) 2 (30) 2 (10) 2 (80) 2 (80) 2 (60) 2 (80) 2 (80) 2 (40) 2 (80) 10
0 1 (30) 1 (0) 0 0 0 1 (80) 0 1 (30) 1 (40) 0
0 1 (10) 1 (0) 0 0 0 1 (80) 0 1 (30) 1 (40) 0
made over the tensor fasciae latae muscle, and the muscle was resected to expose the ventral border of the major psoas muscle, where a short free segment of the femoral nerve was found to run towards the quadriceps muscle. One further cadaver was frozen (−20 °C for 8 days) and cryosectioned into 2.5 cm sections from the hip joint to the knee. Photographs were taken for comparison with the US images. Phase 2: Ultrasound-guided nerve blockade in cadavers For the US-guided nerve blockade both pelvic limbs from five fresh cadavers (aged 15 ± 8 days, weighing 38 ± 5 kg) were examined using a Logik Book XP (G&E Healthcare) with a 6–10 MHz linear transducer. The transducer was placed between the greater trochanter of the femur and the ischial tuberosity to visualise the sciatic nerve, and it was moved distally, following the path of the nerve, to obtain transverse images. To identify the femoral nerve, the transducer was placed ventral to the wing of the ilium and along the longitudinal axis of the femoral nerve and rotated 90° to obtain transverse sections. The depths at which the sciatic and femoral nerves were located were recorded. Finally, a suitable acoustic window was selected to perform the blockade of these nerves. The sciatic and femoral nerves (transverse sections) were then injected with 0.2 mL/kg of methylene blue using a 20G spinal needle (Becton Dickinson). The needle was inserted perpendicular to the nerves, with the direct observation of the advancement of the needle. Once the tip of the needle approached within 1 mm of the nerves, the dye was administered. The pelvic limbs were immediately dissected to macroscopically to verify the staining of the nerves and the length of the stain.
femoral nerve blockade was assessed using the weight-bearing capacity of the extremity. To evaluate analgesia, the nociceptive withdrawal response was assessed by applying pinpricks with a 21G needle as noxious stimulus. This was always done by the same investigator to minimise variation. The response was measured as follows: 0, positive normal response; 1, diminished response; 2, negative response. The nociceptive withdrawal response following sciatic and femoral nerve blockade was evaluated at seven anatomical areas shown in Tables 1 and 2. The nociceptive response was assessed at baseline and every 10 min for 90 min. However, in the last four limbs the response to the noxious stimulus was recorded until baseline values were restored.
Statistical analysis A descriptive statistical analysis of the quantitative variables was performed with the data expressed as means ± standard deviation or medians (range) where appropriate. The effects of local anaesthetic on the sciatic and femoral nerves in the different anatomical areas were analysed using the non-parametric Friedman test for related (repeated) samples with pairwise comparisons in order to compare each time point with the baseline value. All analyses were performed using SPSS 19.0 (IBM).
Results
Phase 3: Ultrasound-guided nerve blockade in live calves
Phase 1: Anatomical study and dissection of the sciatic and femoral nerves
For the US-guided nerve blockade, five calves (three Friesians and two crossbreds, aged 2.9 ± 1.4 months and weighing 86 ± 48 kg) were used. The left and right sciatic and femoral nerves were blocked unilaterally using the acoustic window defined in Phase 2. Nerves were blocked in a random order at 1-week intervals, so each calf was used four times. For 2 weeks before the start of the experiment, the calves were acclimated to the restraining device in a standing position with the head fixed (1 h daily). Food, but not water, was withheld overnight prior to blockade. Within 5 min of being put into the restraining device, the calves were sedated with 0.1 mg/kg IV xylazine (Xilagesic, Calier), the areas for US clipped and cleaned with alcohol, and acoustic gel applied. The sciatic and femoral nerves were then blocked with 0.2 mL/kg of a lidocaine (2%) and epinephrine (0.002%) mixture (Anesvet, Ovejero). A negative aspiration test was performed before injection. After the injection of the local anaesthetic, each calf received 0.01 mg/kg IV atipamezole (Antisedan, Pfizer) to reverse sedation (Iwamoto et al., 2012). Sciatic motor blockade was determined by assessing the ability of the animals to maintain a standing position, the presence of adduction of the affected extremity and the presence of flexion of the fetlock joint (metatarsophalangeal joint). The
The gross dissection of the sciatic nerve was performed easily in all cadavers. The nerve exited the pelvic cavity through the greater sciatic foramen continued caudally and then turned distally to pass deeper and caudally to the greater trochanter of the femur. Then, the nerve passed distally along the lateral surface of the thigh and deep to the biceps femoris, where the nerve was divided into two large branches: the tibial and the common peroneal nerves. Nerve branching was found to be more proximal in one cadaver than in the other three. The gross dissection of the femoral nerve was more difficult than the sciatic nerve due to the topography and length of this nerve, where a short free segment runs from the ventral border of the major psoas muscle to the quadriceps femoris muscle. The anatomical structures identified with ultrasonography and the corresponding anatomical sections are shown in Figs. 1 and 2.
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Table 2 Maximum score and duration in minutes (in parentheses) obtained following femoral nerve blockade in 10 pelvic limbs from five calves in the different subareas: lateral (L), cranial (Cr) and medial (M) subareas of the femur and the knee, and lateral, cranial, medial and caudal (Ca) subareas of the tibia and the tarsus (0, positive normal response to stimuli; 1, diminished response to the stimulus; 2, negative response). Duration of 0 min indicates that the maximum score was achieved only at one time point. The number of limbs where a score of 2 was determined is shown in the last row. Animal – Limb
1 Left 1 Right 2 Left 2 Right 3 Left* 3 Right 4 Left* 4 Right* 5 Left* 5 Right Score = 2(n)
Femur
Knee
Tibia
Tarsus
L
Cr
M
L
Cr
M
L
Cr
M
Ca
L
Cr
M
Ca
0 0 0 0 1 (60) 0 0 1 (80) 1 (60) 1 (50) 0
0 0 0 0 1 (70) 0 1 (80) 1 (80) 1 (30) 1 (50) 0
2 (80) 1 (0) 1 (0) 1 (70) 2 (80) 0 2 (80) 2 (80) 2 (80) 1 (80) 5
0 0 2 (10) 1 (80) 1 (80) 0 2 (10) 1 (80) 1 (80) 1 (80) 2
1 (0) 1 (0) 2 (50) 1 (50) 1 (80) 2 (0) 1 (60) 1 (50) 1 (80) 1 (80) 2
2 (80) 1 (0) 1 (0) 0 2 (60) 0 2 (20) 2 (80) 2 (60) 2 (20) 6
0 0 0 1 (60) 1 (50) 0 1 (50) 1 (80) 1 (50) 1 (20) 0
0 1 (0) 0 1 (40) 2 (30) 0 2 (80) 2 (80) 2 (30) 2 (50) 5
1 (0) 0 0 1 (0) 2 (80) 0 2 (80) 2 (80) 2 (80) 1 (80) 4
0 0 0 2 (0) 1 (60) 0 1 (60) 1 (30) 1 (60) 1 (80) 1
0 0 0 1 (10) 1 (80) 0 1 (80) 1 (80) 0 1 (80) 0
0 0 0 1 (40) 2 (0) 0 2 (0) 1 (80) 2 (30) 2 (20) 3
0 0 0 1 (40) 2 (70) 0 2 (80) 2 (80) 2 (20) 1 (80) 4
0 0 0 2 (0) 1 (80) 0 1 (80) 1 (80) 1 (80) 1 (80) 1
* Animal fell to the ground.
Phase 2: Ultrasound-guided nerve blockade in cadavers The sciatic nerve was identified in all cases in a transverse plane, distal to the greater trochanter of the femur and caudal to the femoral shaft, as a hyperechoic band located at a depth of 3.2 ± 1.1 cm. The selected acoustic window was located slightly distal to the greater trochanter. Once the dye was administered, the spread of the liquid was observed as an anechoic space above the lateral part of the sciatic
nerve. The sciatic nerve was stained in nine pelvic limbs (mean length, 6.8 ± 3.3 cm). In one case, the sciatic nerve was not stained. The femoral nerve was not as easily identifiable as the sciatic nerve and was visualised in a cross plane as a hyperechoic oval structure situated medial to the psoas major muscle and lateral to the femoral artery (depth, 5.0 ± 1.7 cm). The dye injected under US guidance was observed as an anechoic space between the psoas major and iliacus muscles. Staining of the femoral nerve was successful in 6/10 cases
Fig. 1. (a) Position of the ultrasound transducer for the approach to the sciatic nerve blockade. (b) Anatomical section of the sciatic nerve at that level. (c) Corresponding transverse ultrasound image of the sciatic nerve. (d) Local anaesthetic administration spreading above the lateral surface of the sciatic nerve. (1) Sciatic nerve, (2) biceps femoris muscle, (3) semimembranosus muscle, (4) semitendinosus muscle, (5) femur, (6) local anaesthetic solution. Cr, cranial; Ca, caudal; M, medial; L, lateral.
M. Re et al./The Veterinary Journal 200 (2014) 434–439
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Fig. 2. (a) Position of the ultrasound transducer and needle for the approach to the femoral nerve blockade. (b) Anatomical section of the femoral nerve at that level. (c) Corresponding transverse ultrasound image of the femoral nerve. (d) Local anaesthetic administration surrounding the femoral nerve. (1) Psoas major muscle, (2) iliacus muscle, (3) gluteus accesorius muscle, (4) ilium, (5) local anaesthetic solution, the arrows show the N. femoralis. Cr, cranial; Ca, caudal; M, medial; L, lateral; V, ventral; D, dorsal.
(mean length, 7.8 ± 2.4 cm). The selected acoustic window for the femoral blockade was localised ventral to the wing and body of the ilium. Phase 3: Ultrasound-guided nerve blockade in calves In all cases, the sciatic nerve was easily identified, as in the cadavers, and the local anaesthetic spread above the lateral surface of the nerve. This blockade produced adduction of the limb and flexion of the fetlock joint, usually with weight bearing on this joint. No reduced response to the noxious stimulus was determined in the femur and knee areas. A lack of response to the noxious stimulus, with a median value of 2, was observed in the remaining anatomical areas with the exception of the cranial and medial subareas of the tibia, the medial subareas of the tarsus and proximal metatarsus (median = 1) (Fig. 3). Compared to the sciatic nerve, the femoral nerve of the calves was not easily identifiable. The local anaesthetic spread directly in an anechoic space between the psoas major and iliacus muscles. The femoral nerve blockade was characterised by reduced weight bearing of the limb, with the animals falling down in 40% of the experiments, at 1, 3, 10 and 15 min following the administration of the local anaesthetic. All calves which had a score of 2 in all medial subareas of the femur, knee, tibia and tarsus following femoral nerve blockade fell down. The animals were then placed in sternal recumbency. A reduced response to the noxious stimulus was observed only in
the medial subarea of the femur and the cranial subarea of the knee (Table 2). The maximum pain score (2) is shown in Tables 1 and 2 for the sciatic and femoral nerve blockade, respectively. The total duration of the blockade until full recovery lasted between 150 and 210 min in the four calves. No complications were observed during or for 24 h after the procedure.
Discussion Ultrasound guidance for the identification of the sciatic and femoral nerves in calves was found to be a relatively easy technique. Previous reports have described these techniques in dogs and cats, although limited information in calves have been available and this has mostly focused on the use of nerve blocks for diagnostic purposes (De Vlamynck et al., 2013). However, a US-guided brachial plexus block has been described in calves (Iwamoto et al., 2012), and the sciatic and femoral block using peripheral nerve stimulation has been described in goats and sheep (Adami et al., 2011; Wagner et al., 2011). The length of the sciatic nerve facilitates its approach at different locations, and three acoustic windows have been proposed in dogs, caudal to the sacrum at the level of the greater trochanter and in the distal third of the thigh (Echeverry et al., 2010; Shilo et al., 2010; Costa-Farre et al., 2011). In calves, the proximal third of the femur was selected for the blockade of this nerve because this area
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Fig. 3. Nociceptive response from five calves to a pinprick noxious stimulus in the phalanx, distal and proximal metatarsus, tarsus and tibia subareas following sciatic nerve blockade (0, positive normal response to stimuli; 1, diminished response to the stimulus; 2, negative response). Data are expressed as the median. Symbols indicate significant differences from baseline value within a defined anatomical subarea (P < 0.05).
M. Re et al./The Veterinary Journal 200 (2014) 434–439
of the nerve was easily accessed, and the nerve ran alone, away from any other major nerve or vessel. A shorter, although adequate, lateral pre-iliac acoustic window has been determined for the blockade of the femoral nerve, whereas the alternative approaches suggested for dogs, such as the inguinal, ventral suprainguinal, and femoral triangle approaches (Campoy et al., 2010; Echeverry et al., 2010, 2012) were not considered to be clinically suitable. In calves, the dorsal paralumbar approach has been proposed for the diagnosis and treatment of bovine spastic paralysis, although the femoral nerve could not be visualised and bony landmarks were used instead (De Vlamynck et al., 2013). The length of the nerve in contact with the local anaesthetic is a major factor that determines the success of the blockade. An in vitro study with human myelinated nerves suggested that the minimum length of contact between nerve and local anaesthetic necessary to produce an effective nerve blockade was 2–5 mm (Raymond et al., 1989). Similarly, in dogs, nerve staining ≥2 cm was considered evidence of an adequate blockade (Campoy et al., 2010). In the present study, the volume of dye used (0.2 mL/kg) was adequate to stain both nerves to a length of at least 2 cm. The anatomical areas innervated by the sciatic nerve were completely desensitised in 6/10 calf limbs, excluding the medial subareas of the proximal metatarsus, tarsus and the tibia, and the cranial subarea of the tibia. This differential effect might be related to a higher degree of blockade in the tibial nerve compared to the peroneal nerve as a consequence of the unequal distribution of the anaesthetic around the nerve. Onset of the nerve blockade was determined within 10 min of local anaesthetic administration with the maximum effect observed within 30 min. In most areas this maximum effect lasted up to 90 min after local anaesthetic administration, thus allowing between 40 and 80 min of analgesic effect depending on the anatomical area (Fig. 3). This duration is suitable for most surgical procedures in clinical practice in cattle, and should be suitable for surgery in the digital area, such as amputation or corn removal, fetlock, pastern and coffin joint lavage and debridement or wound suture. The identification of the femoral nerve was more difficult and gave variable results, producing desensitisation of the medial subarea of the femur and knee areas and the cranial subarea of the tibia in at least 50% of the limbs. The high proportion of calves falling after femoral nerve blockade may limit the clinical utility of the femoral block. Using local anaesthetics with fewer motor effects may overcome this problem. In calves, femoral blockade with procaine 4% (0.1 mL/kg) did not result in falling even though there was partial weight bearing (De Vlamynck et al., 2013). Lidocaine with epinephrine was chosen in our study due to its adequate duration of effect for most clinical procedures, safety, wide use in veterinary medicine, market availability and low cost. The addition of epinephrine increases the degree of blockade, prolongs analgesia and decreases toxicity by slowing systemic absorption (Skarda, 1996; Cuvillon et al., 2009). Although a baseline value was included, a potential limitation of our study may include the lack of a true control group that would allow comparisons at every time point. Additionally, sedation with xylazine, although antagonised with atipamezole, may have provided an analgesic effect biasing the results. However, the calves appeared to have fully recovered from the sedation and sedation is essential for performing the blockade under clinical conditions. Conclusion Ultrasound-guided anaesthetic blockade of the sciatic nerve in calves is a relatively simple and effective technique producing analgesia in the distal pelvic limbs. However, the femoral nerve was
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more difficult to identify, with local anaesthetic administration producing variable results. The anatomical areas that were anaesthetised following the blockade of both nerves support the suitability of this technique for surgery in the distal pelvic limb in cattle. However, clinical studies should determine the actual effectiveness of this technique and the minimum effective volume of the local anaesthetic or best drug selection. Conflict of interest statement None of the authors has any financial or personal relationships that could inappropriately influence the content of the paper. Acknowledgements The authors thank the clinical service of ruminants at the Veterinary Teaching Hospital of the Complutense University of Madrid for their support in the study. References Adami, C., Bergadano, A., Bruckmaier, R.M., Stoffel, M.H., Doherr, M.G., Spadavecchia, C., 2011. Sciatic-femoral nerve block with bupivacaine in goats undergoing elective stifle arthrotomy. The Veterinary Journal 188, 53–57. Campoy, L., Bezuidenhout, A.J., Gleed, R.D., Martin-Flores, M., Raw, R.M., Santare, C.L., Jay, A.R., Wang, A.L., 2010. Ultrasound-guided approach for axillary brachial plexus, femoral nerve, and sciatic nerve blocks in dogs. Veterinary Anaesthesia and Analgesia 37, 144–153. Costa-Farre, C., Blanch, X.S., Cruz, J.I., Franch, J., 2011. Ultrasound guidance for the performance of sciatic and saphenous nerve blocks in dogs. The Veterinary Journal 187, 221–224. Cuvillon, P., Nouvellon, E., Ripart, J., Boyer, J.C., Dehour, L., Mahamat, A., L’Hermite, J., Boisson, C., Vialles, N., Lefrant, J.Y., et al., 2009. A comparison of the pharmacodynamics and pharmacokinetics of bupivacaine, ropivacaine (with epinephrine) and their equal volume mixtures with lidocaine used for femoral and sciatic nerve blocks: A double-blind randomized study. Anesthesia and Analgesia 108, 641–649. De Vlamynck, C., Vlaminck, L., Hauspie, S., Saunders, J., Gasthuys, F., 2013. Ultrasoundguided femoral nerve block as a diagnostic aid in demonstrating quadriceps involvement in bovine spastic paresis. The Veterinary Journal 196, 451–455. Echeverry, D.F., Gil, F., Laredo, F., Ayala, M.D., Belda, E., Soler, M., Agut, A., 2010. Ultrasound-guided block of the sciatic and femoral nerves in dogs: A descriptive study. The Veterinary Journal 186, 210–215. Echeverry, D.F., Laredo, F.G., Gil, F., Belda, E., Soler, M., Agut, A., 2012. Ventral ultrasound-guided suprainguinal approach to block the femoral nerve in the dog. The Veterinary Journal 192, 333–337. Edmondson, M.A., 2008. Local and regional anesthesia in cattle. Veterinary Clinics of North America. Food Animal Practice 24, 211–226. Enneking, F.K., Chan, V., Greger, J., Hadzic, A., Lang, S.A., Horlocker, T.T., 2005. Lower-extremity peripheral nerve blockade: Essentials of our current understanding. Regional Anesthesia and Pain Medicine 30, 4–35. Haro, P., Laredo, F., Gil, F., Belda, E., Ayala, M.D., Soler, M., Agut, A., 2012. Ultrasoundguided block of the feline sciatic nerve. Journal of Feline Medicine and Surgery 14, 545–552. Iwamoto, J., Yamagishi, N., Sasaki, K., Kim, D., Devkota, B., Furuhama, K., 2012. A novel technique of ultrasound-guided brachial plexus block in calves. Research in Veterinary Science 93, 1467–1471. Mahler, S.P., Adogwa, A.O., 2008. Anatomical and experimental studies of brachial plexus, sciatic, and femoral nerve-location using peripheral nerve stimulation in the dog. Veterinary Anaesthesia and Analgesia 35, 80–89. Raymond, S.A., Steffensen, S.C., Gugino, L.D., Strichartz, G.R., 1989. The role of length of nerve exposed to local anesthetics in impulse blocking action. Anesthesia and Analgesia 68, 563–570. Rioja, E., Sinclair, M., Chalmers, H., Foster, R.A., Monteith, G., 2012. Comparison of three techniques for paravertebral brachial plexus blockade in dogs. Veterinary Anaesthesia and Analgesia 39, 190–200. Shilo, Y., Pascoe, P.J., Cissell, D., Johnson, E.G., Kass, P.H., Wisner, E.R., 2010. Ultrasoundguided nerve blocks of the pelvic limb in dogs. Veterinary Anaesthesia and Analgesia 37, 460–470. Skarda, R.T., 1996. Local and regional anesthesia in ruminants and swine. Veterinary Clinics of North America. Food Animal Practice 12, 579–626. Thurmon, J.C., Ko, J.C., 1997. Anesthesia and chemical restraint. In: Lameness in cattle, Second ed. W.B. Saunders Company, Philadelphia, pp. 41–55. Wagner, A.E., Mama, K.R., Ruehlman, D.L., Pelkey, S., Turner, A.S., 2011. Evaluation of effects of sciatic and femoral nerve blocks in sheep undergoing stifle surgery. Laboratory Animals 40, 114–118.
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The Veterinary Journal j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / t v j l
Ultrasound-guided anaesthetic blockade of the pelvic limb in calves Michela Re a, Javier Blanco-Murcia a, Alejandra Villaescusa Fernández a, Ignacio De Gaspar Simón b, Ignacio A. Gómez de Segura a,* a b
Department of Animal Medicine and Surgery, Veterinary Faculty, University Complutense, Avda, Puerta de Hierro s/n. 28040, Madrid, Spain Department of Anatomy and Embryology, Veterinary Faculty, University Complutense, Avda, Puerta de Hierro s/n. 28040, Madrid, Spain
A R T I C L E
I N F O
Article history: Accepted 11 April 2014 Keywords: Analgesia Sciatic-femoral nerve blockade Local regional anaesthesia Ultrasound Calf
A B S T R A C T
This study aimed to describe a suitable acoustic window to facilitate access to the sciatic and femoral nerves in calves and to study the effects of their blockade with local anaesthetics. The neuroanatomical and ultrasound (US) study was performed on the cadavers of 10 calves, and the effects of 2% lidocaine with epinephrine (0.2 mL/kg) were determined in five healthy calves. The sciatic nerve in the cadavers was easily visualised as a hyperechoic band distal to the femoral greater trochanter and caudal to the femoral shaft. The femoral nerve in the cadavers was not easily identified, and was visualised as a hyperechoic oval structure situated immediately medial to the psoas major muscle and lateral to the femoral artery. The sciatic nerve was stained by methylene blue, injected under US guidance, in 9/10 cases, and the femoral nerve was stained in 6/10 cases. Sciatic nerve blockade under US guidance produced adduction of the limb with metatarsophalangeal joint flexion, while the femoral nerve blockade produced reduced weight bearing. The sciatic nerve blockade produced a reduced response to the noxious stimulus, mainly in the phalanges, proximal and distal metatarsus, tarsus and tibia and, following the femoral nerve blockade, in the medial subarea of the femur. However, femoral nerve blockade produced a more variable degree of blockade. In conclusion, US -guided anaesthetic blockade of the sciatic nerve in calves may be considered for surgery in the distal pelvic limb, although further studies are necessary to determine its clinical application. © 2014 Elsevier Ltd. All rights reserved.
Introduction Loco-regional anaesthetic techniques are commonly employed in cattle under sedation to perform most common surgeries, potentially reducing the risks associated with general anaesthesia while providing adequate analgesia (Edmondson, 2008). When surgical procedures are required in the distal part of the pelvic limbs, local and regional anaesthesia can be performed using different techniques, such as ring blocks, intravenous regional anaesthesia, epidural anaesthesia, nerve block (Skarda, 1996) or general anaesthesia. Nerve block of the pelvic limbs usually involves the peroneal and tibial nerves (Thurmon and Ko, 1997), although this method is rarely used in clinical practice due to the difficulty of identifying the proper injection site for the local anaesthetic (Skarda, 1996). In people, combined anaesthetic block of the sciatic and femoral nerves has been shown to provide adequate analgesia of the legs (Enneking et al., 2005), and recent data support the usefulness of these techniques in dogs and cats (Campoy et al., 2010; Echeverry et al., 2010, 2012; Shilo et al., 2010; Haro et al., 2012). Blockade of the peripheral nerves can be improved through nerve stimulation
* Corresponding author. Tel.: +34 394 3858. E-mail address: [email protected] (I.A. Gómez de Segura). http://dx.doi.org/10.1016/j.tvjl.2014.04.010 1090-0233/© 2014 Elsevier Ltd. All rights reserved.
(Mahler and Adogwa, 2008; Rioja et al., 2012) and ultrasound (US) guidance (Campoy et al., 2010; Echeverry et al., 2010, 2012; Shilo et al., 2010; Costa-Farre et al., 2011). Both techniques are complementary. Peripheral nerve blockade should be based on the neuroanatomy of the species considered (Mahler and Adogwa, 2008). In calves, there are no studies describing the neuroanatomy of the sciatic and femoral nerves. The objective of the present study was to describe in cadavers an acoustic window that facilitated access to the sciatic and femoral nerves and to describe, in live calves the clinical application of blockade of these nerves produced by the administration of local anaesthetics under US guidance. Materials and methods All animal use was approved by the University Complutense Institutional Animal Care and Use Committee (CEA-UCM 100/2012, 14 June 2012).
Phase 1: Anatomical study of the sciatic and femoral nerves For the anatomical dissection of the sciatic and femoral nerves, cadavers of four calves (19 ± 9 days old, weighing 37 ± 5 kg) were used. For the sciatic nerve, a skin incision was made from the greater trochanter, caudal and distal to the crural region, to expose the lateral aspect of the pelvic limb. A transverse incision was made in the gluteobiceps muscle to expose the nerve. For the femoral nerve, the incision was
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Table 1 Maximum score and duration in minutes (in parentheses) obtained following sciatic nerve blockade in 10 pelvic limbs from five calves in the different subareas: lateral (L), dorsal (D), medial (M) and plantar (P) subareas of the phalanx, distal and proximal metatarsus and lateral, cranial (Cr), medial and caudal (Ca) subareas of the tibia and the tarsus and lateral subarea of the femur and the knee (0, positive normal response to stimuli; 1, diminished response to the stimulus; 2, negative response). Duration of 0 min indicates that the maximum score was achieved only at one time point. The number of limbs where a score of 2 was determined is shown in the last row. Animal – Limb
1 Left 1 Right 2 Left 2 Right 3 Left 3 Right 4 Left 4 Right 5 Left 5 Right Score = 2(n)
Phalanx
Proximal metatarsus
D
M
P
L
D
M
P
L
D
M
P
2 (70) 2 (20) 2 (0) 2 (70) 2 (80) 2 (80) 2 (80) 2 (70) 2 (40) 2 (60) 10
2 (70) 2 (0) 2 (0) 2 (0) 2 (80) 2 (80) 2 (80) 2 (70) 2 (40) 2 (60) 10
2 (70) 1 (30) 1 (80) 2 (50) 2 (80) 2 (80) 2 (80) 2 (80) 2 (30) 2 (0) 8
2 (30) 1 (0) 1 (80) 2 (40) 2 (80) 2 (60) 2 (80) 2 (70) 2 (30) 2 (60) 8
2 (20) 2 (0) 2 (0) 2 (40) 2 (70) 2 (40) 2 (80) 2 (70) 2 (40) 2 (70) 10
2 (80) 1 (70) 2 (0) 2 (0) 2 (50) 2 (40) 2 (80) 2 (70) 2 (40) 2 (70) 9
2 (20) 1 (30) 2 (0) 2 (40) 2 (50) 2 (80) 2 (80) 2 (80) 2 (30) 2 (70) 9
2 (0) 2 (0) 2 (40) 2 (50) 2 (40) 2 (30) 2 (60) 2 (70) 2 (30) 2 (60) 10
2 (20) 2 (10) 1 (60) 2 (40) 2 (80) 2 (80) 2 (80) 2 (70) 2 (40) 2 (70) 9
2 (80) 2 (0) 2 (0) 2 (40) 2 (70) 2 (80) 2 (80) 2 (80) 2 (40) 2 (70) 10
1 (40) 2 (0) 2 (0) 2 (50) 1 (80) 1 (70) 1 (80) 1 (80) 1 (50) 1 (80) 3
2 (30) 1 (50) 2 (0) 2 (80) 2 (70) 2 (10) 2 (80) 2 (80) 2 (40) 2 (70) 9
Animal – Limb
1 Left 1 Right 2 Left 2 Right 3 Left 3 Right 4 Left 4 Right 5 Left 5 Right Score = 2(n)
Distal metatarsus
L
Tarsus
Tibia
Knee
Femur
L
Cr
M
Ca
L
Cr
M
Ca
L
L
2 (50) 2 (10) 2 (0) 2 (80) 2 (80) 2 (80) 2 (80) 2 (80) 2 (40) 2 (70) 10
2 (10) 1 (40) 1 (60) 2 (10) 2 (70) 2 (30) 2 (80) 2 (80) 2 (30) 2 (70) 8
1 (20) 1 (20) 1 (80) 2 (20) 1 (80) 1 (30) 2 (0) 1 (80) 2 (10) 2 (10) 4
2 (50) 2 (20) 2 (40) 2 (50) 2 (80) 2 (60) 2 (80) 2 (80) 2 (40) 2 (80) 10
2 (10) 1 (60) 1 (80) 2 (50) 2 (80) 2 (60) 2 (80) 2 (80) 2 (50) 2 (80) 8
1 (40) 1 (40) 1 (70) 1 (80) 1 (80) 1 (80) 1 (80) 1 (80) 2 (20) 1 (80) 1
0 2 (0) 1 (50) 2 (20) 1 (80) 1 (80) 2 (0) 1 (80) 2 (10) 1 (80) 4
2 (60) 2 (30) 2 (10) 2 (80) 2 (80) 2 (60) 2 (80) 2 (80) 2 (40) 2 (80) 10
0 1 (30) 1 (0) 0 0 0 1 (80) 0 1 (30) 1 (40) 0
0 1 (10) 1 (0) 0 0 0 1 (80) 0 1 (30) 1 (40) 0
made over the tensor fasciae latae muscle, and the muscle was resected to expose the ventral border of the major psoas muscle, where a short free segment of the femoral nerve was found to run towards the quadriceps muscle. One further cadaver was frozen (−20 °C for 8 days) and cryosectioned into 2.5 cm sections from the hip joint to the knee. Photographs were taken for comparison with the US images. Phase 2: Ultrasound-guided nerve blockade in cadavers For the US-guided nerve blockade both pelvic limbs from five fresh cadavers (aged 15 ± 8 days, weighing 38 ± 5 kg) were examined using a Logik Book XP (G&E Healthcare) with a 6–10 MHz linear transducer. The transducer was placed between the greater trochanter of the femur and the ischial tuberosity to visualise the sciatic nerve, and it was moved distally, following the path of the nerve, to obtain transverse images. To identify the femoral nerve, the transducer was placed ventral to the wing of the ilium and along the longitudinal axis of the femoral nerve and rotated 90° to obtain transverse sections. The depths at which the sciatic and femoral nerves were located were recorded. Finally, a suitable acoustic window was selected to perform the blockade of these nerves. The sciatic and femoral nerves (transverse sections) were then injected with 0.2 mL/kg of methylene blue using a 20G spinal needle (Becton Dickinson). The needle was inserted perpendicular to the nerves, with the direct observation of the advancement of the needle. Once the tip of the needle approached within 1 mm of the nerves, the dye was administered. The pelvic limbs were immediately dissected to macroscopically to verify the staining of the nerves and the length of the stain.
femoral nerve blockade was assessed using the weight-bearing capacity of the extremity. To evaluate analgesia, the nociceptive withdrawal response was assessed by applying pinpricks with a 21G needle as noxious stimulus. This was always done by the same investigator to minimise variation. The response was measured as follows: 0, positive normal response; 1, diminished response; 2, negative response. The nociceptive withdrawal response following sciatic and femoral nerve blockade was evaluated at seven anatomical areas shown in Tables 1 and 2. The nociceptive response was assessed at baseline and every 10 min for 90 min. However, in the last four limbs the response to the noxious stimulus was recorded until baseline values were restored.
Statistical analysis A descriptive statistical analysis of the quantitative variables was performed with the data expressed as means ± standard deviation or medians (range) where appropriate. The effects of local anaesthetic on the sciatic and femoral nerves in the different anatomical areas were analysed using the non-parametric Friedman test for related (repeated) samples with pairwise comparisons in order to compare each time point with the baseline value. All analyses were performed using SPSS 19.0 (IBM).
Results
Phase 3: Ultrasound-guided nerve blockade in live calves
Phase 1: Anatomical study and dissection of the sciatic and femoral nerves
For the US-guided nerve blockade, five calves (three Friesians and two crossbreds, aged 2.9 ± 1.4 months and weighing 86 ± 48 kg) were used. The left and right sciatic and femoral nerves were blocked unilaterally using the acoustic window defined in Phase 2. Nerves were blocked in a random order at 1-week intervals, so each calf was used four times. For 2 weeks before the start of the experiment, the calves were acclimated to the restraining device in a standing position with the head fixed (1 h daily). Food, but not water, was withheld overnight prior to blockade. Within 5 min of being put into the restraining device, the calves were sedated with 0.1 mg/kg IV xylazine (Xilagesic, Calier), the areas for US clipped and cleaned with alcohol, and acoustic gel applied. The sciatic and femoral nerves were then blocked with 0.2 mL/kg of a lidocaine (2%) and epinephrine (0.002%) mixture (Anesvet, Ovejero). A negative aspiration test was performed before injection. After the injection of the local anaesthetic, each calf received 0.01 mg/kg IV atipamezole (Antisedan, Pfizer) to reverse sedation (Iwamoto et al., 2012). Sciatic motor blockade was determined by assessing the ability of the animals to maintain a standing position, the presence of adduction of the affected extremity and the presence of flexion of the fetlock joint (metatarsophalangeal joint). The
The gross dissection of the sciatic nerve was performed easily in all cadavers. The nerve exited the pelvic cavity through the greater sciatic foramen continued caudally and then turned distally to pass deeper and caudally to the greater trochanter of the femur. Then, the nerve passed distally along the lateral surface of the thigh and deep to the biceps femoris, where the nerve was divided into two large branches: the tibial and the common peroneal nerves. Nerve branching was found to be more proximal in one cadaver than in the other three. The gross dissection of the femoral nerve was more difficult than the sciatic nerve due to the topography and length of this nerve, where a short free segment runs from the ventral border of the major psoas muscle to the quadriceps femoris muscle. The anatomical structures identified with ultrasonography and the corresponding anatomical sections are shown in Figs. 1 and 2.
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Table 2 Maximum score and duration in minutes (in parentheses) obtained following femoral nerve blockade in 10 pelvic limbs from five calves in the different subareas: lateral (L), cranial (Cr) and medial (M) subareas of the femur and the knee, and lateral, cranial, medial and caudal (Ca) subareas of the tibia and the tarsus (0, positive normal response to stimuli; 1, diminished response to the stimulus; 2, negative response). Duration of 0 min indicates that the maximum score was achieved only at one time point. The number of limbs where a score of 2 was determined is shown in the last row. Animal – Limb
1 Left 1 Right 2 Left 2 Right 3 Left* 3 Right 4 Left* 4 Right* 5 Left* 5 Right Score = 2(n)
Femur
Knee
Tibia
Tarsus
L
Cr
M
L
Cr
M
L
Cr
M
Ca
L
Cr
M
Ca
0 0 0 0 1 (60) 0 0 1 (80) 1 (60) 1 (50) 0
0 0 0 0 1 (70) 0 1 (80) 1 (80) 1 (30) 1 (50) 0
2 (80) 1 (0) 1 (0) 1 (70) 2 (80) 0 2 (80) 2 (80) 2 (80) 1 (80) 5
0 0 2 (10) 1 (80) 1 (80) 0 2 (10) 1 (80) 1 (80) 1 (80) 2
1 (0) 1 (0) 2 (50) 1 (50) 1 (80) 2 (0) 1 (60) 1 (50) 1 (80) 1 (80) 2
2 (80) 1 (0) 1 (0) 0 2 (60) 0 2 (20) 2 (80) 2 (60) 2 (20) 6
0 0 0 1 (60) 1 (50) 0 1 (50) 1 (80) 1 (50) 1 (20) 0
0 1 (0) 0 1 (40) 2 (30) 0 2 (80) 2 (80) 2 (30) 2 (50) 5
1 (0) 0 0 1 (0) 2 (80) 0 2 (80) 2 (80) 2 (80) 1 (80) 4
0 0 0 2 (0) 1 (60) 0 1 (60) 1 (30) 1 (60) 1 (80) 1
0 0 0 1 (10) 1 (80) 0 1 (80) 1 (80) 0 1 (80) 0
0 0 0 1 (40) 2 (0) 0 2 (0) 1 (80) 2 (30) 2 (20) 3
0 0 0 1 (40) 2 (70) 0 2 (80) 2 (80) 2 (20) 1 (80) 4
0 0 0 2 (0) 1 (80) 0 1 (80) 1 (80) 1 (80) 1 (80) 1
* Animal fell to the ground.
Phase 2: Ultrasound-guided nerve blockade in cadavers The sciatic nerve was identified in all cases in a transverse plane, distal to the greater trochanter of the femur and caudal to the femoral shaft, as a hyperechoic band located at a depth of 3.2 ± 1.1 cm. The selected acoustic window was located slightly distal to the greater trochanter. Once the dye was administered, the spread of the liquid was observed as an anechoic space above the lateral part of the sciatic
nerve. The sciatic nerve was stained in nine pelvic limbs (mean length, 6.8 ± 3.3 cm). In one case, the sciatic nerve was not stained. The femoral nerve was not as easily identifiable as the sciatic nerve and was visualised in a cross plane as a hyperechoic oval structure situated medial to the psoas major muscle and lateral to the femoral artery (depth, 5.0 ± 1.7 cm). The dye injected under US guidance was observed as an anechoic space between the psoas major and iliacus muscles. Staining of the femoral nerve was successful in 6/10 cases
Fig. 1. (a) Position of the ultrasound transducer for the approach to the sciatic nerve blockade. (b) Anatomical section of the sciatic nerve at that level. (c) Corresponding transverse ultrasound image of the sciatic nerve. (d) Local anaesthetic administration spreading above the lateral surface of the sciatic nerve. (1) Sciatic nerve, (2) biceps femoris muscle, (3) semimembranosus muscle, (4) semitendinosus muscle, (5) femur, (6) local anaesthetic solution. Cr, cranial; Ca, caudal; M, medial; L, lateral.
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Fig. 2. (a) Position of the ultrasound transducer and needle for the approach to the femoral nerve blockade. (b) Anatomical section of the femoral nerve at that level. (c) Corresponding transverse ultrasound image of the femoral nerve. (d) Local anaesthetic administration surrounding the femoral nerve. (1) Psoas major muscle, (2) iliacus muscle, (3) gluteus accesorius muscle, (4) ilium, (5) local anaesthetic solution, the arrows show the N. femoralis. Cr, cranial; Ca, caudal; M, medial; L, lateral; V, ventral; D, dorsal.
(mean length, 7.8 ± 2.4 cm). The selected acoustic window for the femoral blockade was localised ventral to the wing and body of the ilium. Phase 3: Ultrasound-guided nerve blockade in calves In all cases, the sciatic nerve was easily identified, as in the cadavers, and the local anaesthetic spread above the lateral surface of the nerve. This blockade produced adduction of the limb and flexion of the fetlock joint, usually with weight bearing on this joint. No reduced response to the noxious stimulus was determined in the femur and knee areas. A lack of response to the noxious stimulus, with a median value of 2, was observed in the remaining anatomical areas with the exception of the cranial and medial subareas of the tibia, the medial subareas of the tarsus and proximal metatarsus (median = 1) (Fig. 3). Compared to the sciatic nerve, the femoral nerve of the calves was not easily identifiable. The local anaesthetic spread directly in an anechoic space between the psoas major and iliacus muscles. The femoral nerve blockade was characterised by reduced weight bearing of the limb, with the animals falling down in 40% of the experiments, at 1, 3, 10 and 15 min following the administration of the local anaesthetic. All calves which had a score of 2 in all medial subareas of the femur, knee, tibia and tarsus following femoral nerve blockade fell down. The animals were then placed in sternal recumbency. A reduced response to the noxious stimulus was observed only in
the medial subarea of the femur and the cranial subarea of the knee (Table 2). The maximum pain score (2) is shown in Tables 1 and 2 for the sciatic and femoral nerve blockade, respectively. The total duration of the blockade until full recovery lasted between 150 and 210 min in the four calves. No complications were observed during or for 24 h after the procedure.
Discussion Ultrasound guidance for the identification of the sciatic and femoral nerves in calves was found to be a relatively easy technique. Previous reports have described these techniques in dogs and cats, although limited information in calves have been available and this has mostly focused on the use of nerve blocks for diagnostic purposes (De Vlamynck et al., 2013). However, a US-guided brachial plexus block has been described in calves (Iwamoto et al., 2012), and the sciatic and femoral block using peripheral nerve stimulation has been described in goats and sheep (Adami et al., 2011; Wagner et al., 2011). The length of the sciatic nerve facilitates its approach at different locations, and three acoustic windows have been proposed in dogs, caudal to the sacrum at the level of the greater trochanter and in the distal third of the thigh (Echeverry et al., 2010; Shilo et al., 2010; Costa-Farre et al., 2011). In calves, the proximal third of the femur was selected for the blockade of this nerve because this area
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Fig. 3. Nociceptive response from five calves to a pinprick noxious stimulus in the phalanx, distal and proximal metatarsus, tarsus and tibia subareas following sciatic nerve blockade (0, positive normal response to stimuli; 1, diminished response to the stimulus; 2, negative response). Data are expressed as the median. Symbols indicate significant differences from baseline value within a defined anatomical subarea (P < 0.05).
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of the nerve was easily accessed, and the nerve ran alone, away from any other major nerve or vessel. A shorter, although adequate, lateral pre-iliac acoustic window has been determined for the blockade of the femoral nerve, whereas the alternative approaches suggested for dogs, such as the inguinal, ventral suprainguinal, and femoral triangle approaches (Campoy et al., 2010; Echeverry et al., 2010, 2012) were not considered to be clinically suitable. In calves, the dorsal paralumbar approach has been proposed for the diagnosis and treatment of bovine spastic paralysis, although the femoral nerve could not be visualised and bony landmarks were used instead (De Vlamynck et al., 2013). The length of the nerve in contact with the local anaesthetic is a major factor that determines the success of the blockade. An in vitro study with human myelinated nerves suggested that the minimum length of contact between nerve and local anaesthetic necessary to produce an effective nerve blockade was 2–5 mm (Raymond et al., 1989). Similarly, in dogs, nerve staining ≥2 cm was considered evidence of an adequate blockade (Campoy et al., 2010). In the present study, the volume of dye used (0.2 mL/kg) was adequate to stain both nerves to a length of at least 2 cm. The anatomical areas innervated by the sciatic nerve were completely desensitised in 6/10 calf limbs, excluding the medial subareas of the proximal metatarsus, tarsus and the tibia, and the cranial subarea of the tibia. This differential effect might be related to a higher degree of blockade in the tibial nerve compared to the peroneal nerve as a consequence of the unequal distribution of the anaesthetic around the nerve. Onset of the nerve blockade was determined within 10 min of local anaesthetic administration with the maximum effect observed within 30 min. In most areas this maximum effect lasted up to 90 min after local anaesthetic administration, thus allowing between 40 and 80 min of analgesic effect depending on the anatomical area (Fig. 3). This duration is suitable for most surgical procedures in clinical practice in cattle, and should be suitable for surgery in the digital area, such as amputation or corn removal, fetlock, pastern and coffin joint lavage and debridement or wound suture. The identification of the femoral nerve was more difficult and gave variable results, producing desensitisation of the medial subarea of the femur and knee areas and the cranial subarea of the tibia in at least 50% of the limbs. The high proportion of calves falling after femoral nerve blockade may limit the clinical utility of the femoral block. Using local anaesthetics with fewer motor effects may overcome this problem. In calves, femoral blockade with procaine 4% (0.1 mL/kg) did not result in falling even though there was partial weight bearing (De Vlamynck et al., 2013). Lidocaine with epinephrine was chosen in our study due to its adequate duration of effect for most clinical procedures, safety, wide use in veterinary medicine, market availability and low cost. The addition of epinephrine increases the degree of blockade, prolongs analgesia and decreases toxicity by slowing systemic absorption (Skarda, 1996; Cuvillon et al., 2009). Although a baseline value was included, a potential limitation of our study may include the lack of a true control group that would allow comparisons at every time point. Additionally, sedation with xylazine, although antagonised with atipamezole, may have provided an analgesic effect biasing the results. However, the calves appeared to have fully recovered from the sedation and sedation is essential for performing the blockade under clinical conditions. Conclusion Ultrasound-guided anaesthetic blockade of the sciatic nerve in calves is a relatively simple and effective technique producing analgesia in the distal pelvic limbs. However, the femoral nerve was
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more difficult to identify, with local anaesthetic administration producing variable results. The anatomical areas that were anaesthetised following the blockade of both nerves support the suitability of this technique for surgery in the distal pelvic limb in cattle. However, clinical studies should determine the actual effectiveness of this technique and the minimum effective volume of the local anaesthetic or best drug selection. Conflict of interest statement None of the authors has any financial or personal relationships that could inappropriately influence the content of the paper. Acknowledgements The authors thank the clinical service of ruminants at the Veterinary Teaching Hospital of the Complutense University of Madrid for their support in the study. References Adami, C., Bergadano, A., Bruckmaier, R.M., Stoffel, M.H., Doherr, M.G., Spadavecchia, C., 2011. Sciatic-femoral nerve block with bupivacaine in goats undergoing elective stifle arthrotomy. The Veterinary Journal 188, 53–57. Campoy, L., Bezuidenhout, A.J., Gleed, R.D., Martin-Flores, M., Raw, R.M., Santare, C.L., Jay, A.R., Wang, A.L., 2010. Ultrasound-guided approach for axillary brachial plexus, femoral nerve, and sciatic nerve blocks in dogs. Veterinary Anaesthesia and Analgesia 37, 144–153. Costa-Farre, C., Blanch, X.S., Cruz, J.I., Franch, J., 2011. Ultrasound guidance for the performance of sciatic and saphenous nerve blocks in dogs. The Veterinary Journal 187, 221–224. Cuvillon, P., Nouvellon, E., Ripart, J., Boyer, J.C., Dehour, L., Mahamat, A., L’Hermite, J., Boisson, C., Vialles, N., Lefrant, J.Y., et al., 2009. A comparison of the pharmacodynamics and pharmacokinetics of bupivacaine, ropivacaine (with epinephrine) and their equal volume mixtures with lidocaine used for femoral and sciatic nerve blocks: A double-blind randomized study. Anesthesia and Analgesia 108, 641–649. De Vlamynck, C., Vlaminck, L., Hauspie, S., Saunders, J., Gasthuys, F., 2013. Ultrasoundguided femoral nerve block as a diagnostic aid in demonstrating quadriceps involvement in bovine spastic paresis. The Veterinary Journal 196, 451–455. Echeverry, D.F., Gil, F., Laredo, F., Ayala, M.D., Belda, E., Soler, M., Agut, A., 2010. Ultrasound-guided block of the sciatic and femoral nerves in dogs: A descriptive study. The Veterinary Journal 186, 210–215. Echeverry, D.F., Laredo, F.G., Gil, F., Belda, E., Soler, M., Agut, A., 2012. Ventral ultrasound-guided suprainguinal approach to block the femoral nerve in the dog. The Veterinary Journal 192, 333–337. Edmondson, M.A., 2008. Local and regional anesthesia in cattle. Veterinary Clinics of North America. Food Animal Practice 24, 211–226. Enneking, F.K., Chan, V., Greger, J., Hadzic, A., Lang, S.A., Horlocker, T.T., 2005. Lower-extremity peripheral nerve blockade: Essentials of our current understanding. Regional Anesthesia and Pain Medicine 30, 4–35. Haro, P., Laredo, F., Gil, F., Belda, E., Ayala, M.D., Soler, M., Agut, A., 2012. Ultrasoundguided block of the feline sciatic nerve. Journal of Feline Medicine and Surgery 14, 545–552. Iwamoto, J., Yamagishi, N., Sasaki, K., Kim, D., Devkota, B., Furuhama, K., 2012. A novel technique of ultrasound-guided brachial plexus block in calves. Research in Veterinary Science 93, 1467–1471. Mahler, S.P., Adogwa, A.O., 2008. Anatomical and experimental studies of brachial plexus, sciatic, and femoral nerve-location using peripheral nerve stimulation in the dog. Veterinary Anaesthesia and Analgesia 35, 80–89. Raymond, S.A., Steffensen, S.C., Gugino, L.D., Strichartz, G.R., 1989. The role of length of nerve exposed to local anesthetics in impulse blocking action. Anesthesia and Analgesia 68, 563–570. Rioja, E., Sinclair, M., Chalmers, H., Foster, R.A., Monteith, G., 2012. Comparison of three techniques for paravertebral brachial plexus blockade in dogs. Veterinary Anaesthesia and Analgesia 39, 190–200. Shilo, Y., Pascoe, P.J., Cissell, D., Johnson, E.G., Kass, P.H., Wisner, E.R., 2010. Ultrasoundguided nerve blocks of the pelvic limb in dogs. Veterinary Anaesthesia and Analgesia 37, 460–470. Skarda, R.T., 1996. Local and regional anesthesia in ruminants and swine. Veterinary Clinics of North America. Food Animal Practice 12, 579–626. Thurmon, J.C., Ko, J.C., 1997. Anesthesia and chemical restraint. In: Lameness in cattle, Second ed. W.B. Saunders Company, Philadelphia, pp. 41–55. Wagner, A.E., Mama, K.R., Ruehlman, D.L., Pelkey, S., Turner, A.S., 2011. Evaluation of effects of sciatic and femoral nerve blocks in sheep undergoing stifle surgery. Laboratory Animals 40, 114–118.
