The ScN and SN (sensory branch of the FN) are responsible for most of the sensory innervation of the pelvic limb in dogs.1 These nerves are frequently blocked to provide analgesia for surgical procedures involving the pelvic limb in dogs.2–4 Nevertheless, when more complete analgesic coverage of the pelvic limb is required, additional blockade of the ON and the LCFN is recommended.5,6
In recent years, ultrasonographic or NEL techniques have been increasingly used to perform PNBs.2,7,8 The use of these sophisticated techniques may optimize the needle position and improve the accuracy and safety of the nerve blockades.9–11 However, in developing countries, many veterinary practices lack the ancillary equipment necessary to perform these advanced PNB techniques.12 There are also clinical13,14 and technical3,4,12 conditions that could prevent the use of advanced neurolocation techniques, such as local presence of edema, underlying neuropathy, or blockade of nerves lacking motor supply (eg, the LCFN or SN). In these situations, PNBs achieved by the use of SALMs could be considered as an alternative to the application of advanced PNB techniques.12
The use of SALMs to achieve successful blockade of the FN, SN, and ScN in dogs has been reported.15,16 Descriptions of the use of NEL techniques to block the FN and ScN are also available.2,8,17 Finally, the use of ultrasound-guided techniques in dogs to block the ScN, FN, and ON have also been described.3,4,18–20 However, to the authors’ knowledge, the use of blind perineural injection techniques for ON or LCFN blockade by the sole use of SALMs in dogs has not been reported. In a previous study16 in dogs, a relatively effective approach to block the SN by the use of an SALM technique was developed. The objective of the study reported here was to evaluate the potential efficacy of blind perineural injection techniques to provide blockade of the SN, ON, and LCFN by assessing the distribution along those nerves of 3 injected volumes of a lidocaine-methylene blue solution in dog cadavers.
Materials and Methods
Animals
The study was conducted in 2 phases. In the first phase, 3 fresh intact canine cadavers were used to perform an anatomic examination of the target nerves to determine the optimal blind approaches. In the second phase, another 15 fresh intact canine cadavers were used to assess the efficacy of the blind perineural injection techniques. All the dogs were obtained from a local Zoonosis and Public Health Service and were euthanized for reasons unrelated to the objectives of the study. Euthanasia was performed by IV administration of an overdose of pentobarbitala (200 mg/kg). All of the dogs were adult nonchondrodystrophic dogs with a mean weight of 16.9 kg (range, 10.3 to 27.9 kg) and a mean body condition score of 3/5. This project was approved by the Bioethics Committee of our institution (Acta No. 2.3-409-2012). It was performed under the guidelines of the Colombian Animal Protection Law (Ley 84 de 1989).
Anatomic examination of SN, ON, and LCFN in dog cadavers (phase 1)
In each of the 3 cadavers, the left and right SNs, ONs, and LCFNs were dissected to examine their anatomic characteristics and determine the optimal approaches for perineural injection. For the SN and ON, a skin incision was made in the middle of the proximal portion of the thigh. Then, the skin was reflected cranially and caudally to expose the structures of interest. The SN was dissected in the femoral triangle with the femoral artery used as the reference feature. The ON was dissected with the pectineus and adductor muscles used as the reference features. The LCFN was approached by a medial celiotomy. Then, the viscera were removed to expose the psoas major and minor muscles, from where this nerve emerged. From this point, the LCFN was dissected until it reached the skin over the tuber coxae where it finally branched.
Assessment of the approaches for blind perineural injection of staining solution in the SN, ON, and LCFN in dog cadavers (phase 2)
Fifteen fresh dog cadavers were randomly assigned by the use of an online random number generator systemb to 1 of 3 experimental groups (5 dogs/group) to evaluate the spread of 3 volumes of staining solution (low volume, 0.1 mL/kg; medium volume, 0.2 mL/kg; or high volume, 0.3 mL/kg) along the SN, ON, and LCFN after blind perineural injection. For each cadaver in an experimental group, the same volume of staining solution was applied to each of the 3 studied nerves in the right and left pelvic limbs. The skin over each injection site was clipped of hair and cleaned. Results from phase 1 of the study were used to determine the blind perineural injection approaches to the target nerves.
Approach to the SN
The cadavers were positioned in dorsal recumbency with both pelvic limbs in maximum abduction until both femurs were at a 90° angle in relation to the vertebral column. The SN was accessed through a small triangular area limited cranially by the caudal portion of the sartorius muscle, dorsally by the abdominal wall, and caudally by the femoral artery. A small incision was made with a scalpel in the skin over this area, and the needle attached to a syringe was inserted perpendicular to the thigh. An LOR technique was used until a popping sensation was perceived as the needle crossed the fascial planes over the SN at a depth of approximately 1 cm. The staining solution was administered with the needle in this position (Figure 1).
Photograph (A) and illustration (B) of the position of the needle for a perineural injection over the SN in a canine cadaver and photograph of a dissected cadaver after injection of 0.3 mL of staining solution/kg (C) in a study to evaluate the potential efficacy of blind perineural injection techniques to provide blockade of various nerves in dogs. The SN nerve was located by the use of SALMs and an LOR test. The cadaver was positioned in dorsal recumbency with both pelvic limbs in maximum abduction until both femurs were at a 90° angle in relation to the vertebral column. The SN was accessed through a small triangular area limited cranially by the caudal portion of the sartorius muscle, dorsally by the abdominal wall, and caudally by the femoral artery. A small incision was made with a scalpel in the skin over this area, and a needle attached to a syringe was inserted perpendicular to the thigh. An LOR technique was used until a popping sensation was perceived as the needle crossed the fascial planes over the SN at a depth of approximately 1 cm. The staining solution (1 of 3 volumes) was administered with the needle in this position. Following dissection, the distribution of the staining solution along the nerves was evaluated. Staining that extended ≥ 2 cm along the target nerves was considered to be compatible with an effective clinical nerve block. 1 = Femoral artery. 2 = Pectineus muscle. 3 = Penis. 4 = Femoral vein. 5 = SN. 6 = Caudal portion of the sartorius muscle. 7 = Muscular branch of the FN for the sartorius muscle. 8 = Muscular branch of the FN for the quadriceps femoris muscle. 9 = Iliopsoas muscle. 10 = Caudal abdominal nipple. Cd = Caudal. Dis = Distal. Prx = Proximal.
Citation: American Journal of Veterinary Research 78, 4; 10.2460/ajvr.78.4.412
Approach to the ON
The cadavers were placed in a position similar to that described for the SN injection. The depression between the adductor muscle and the pectineus muscle body was identified by digital palpation. The needle attached to a syringe was inserted at this depression area at an approximate angle of 30° in relation to the vertical plane of the table on which the cadaver was laid, and then directed proximally at a depth of approximately 3 cm. The staining solution was administered with the needle in this position (Figure 2).
Photograph (A) and illustration (B) of the position of the needle for a perineural injection over the ON in a canine cadaver and photograph of a dissected cadaver after injection of 0.3 mL of staining solution/kg (C) in a study to evaluate the potential efficacy of blind perineural injection techniques to provide blockade of various nerves in dogs. The cadaver was placed in a position similar to that described for the SN injection. The ON was located by the use of SALMs. The depression between the adductor muscle and the pectineus muscle body was identified by digital palpation. A needle attached to a syringe was inserted at this depression area at an approximate angle of 30° in relation to the vertical plane of the table on which the cadaver was laid, and then directed proximally at a depth of approximately 3 cm. The staining solution was administered with the needle in this position. Following dissection, the distribution of the staining solution along the nerves was evaluated. 1 = Pectineus muscle body. 2 = Adductor muscle. 3 = Inguinal nipple. 4 = ON. 5 = Muscular branches of the ON. 6 = Caudal abdominal nipple. Cr = Cranial. See Figure 1 for remainder of key.
Citation: American Journal of Veterinary Research 78, 4; 10.2460/ajvr.78.4.412
Approach to the LCFN
The cadavers were positioned in lateral recumbency with the pelvic limb to be injected uppermost. The end of the transverse process of the L7 vertebral body was located with the index finger of the investigator's nondominant hand, and then the needle attached to a syringe was inserted upwards through the skin to make contact with this transverse process. The needle was redirected laterally and then advanced distally 1.5 to 2 cm from the point where the needle made contact with the transverse process. The staining solution was administered with the needle in this position (Figure 3).
Photograph (A) and illustration (B) of the position of the needle for a perineural injection over the LCFN in a canine cadaver and photograph of a dissected cadaver after injection of 0.3 mL of staining solution/kg (C) in a study to evaluate the potential efficacy of blind perineural injection techniques to provide blockade of various nerves in dogs. The cadaver was positioned in lateral recumbency with the pelvic limb to be injected in an upward position. The end of the transverse process of the L7 vertebral body was located with the index finger of the investigator's nondominant hand (asterisk in panel A), and then the needle attached to a syringe was inserted upwards through the skin to make contact with this transverse process. The needle was redirected laterally and then advanced distally 1.5 to 2 cm from the point where the needle made contact with the transverse process. The staining solution was administered with the needle in this position. 1 = Iliac crest. 2 = Cranial portion of the sartorius muscle. 3 = LCFN. 4 = Abdominal wall. 5 = Deep circumflex iliac artery and vein. 6 = Epaxial muscles. 7 = Skin of the lateral thigh and caudal abdomen dissected and reflected distally and cranially. 8 = L7 transverse process; gray and blue syringes indicate the initial and final position of the needle, respectively. See Figures 1 and 2 for remainder of key.
Citation: American Journal of Veterinary Research 78, 4; 10.2460/ajvr.78.4.412
Perineural injection of staining solution and assessment of stain distribution in the SN, ON, and LCFN
For all perineural injections, the staining solution was a mixture of 2% lidocaine chlorhydratec and 2% methylene blued (50% vol/vol). The SN was injected by use of a short beveled needle.e The ON and the LCFN were injected by use of a conventional 21-gauge 1.5-inch hypodermic needle.f A negative aspiration test was conducted before administering the staining solution. Once the infiltration was completed, a gentle massage of the injection site was applied. On each cadaver, the left and right pelvic limbs were injected. Fifteen minutes after completing the injections, the target nerves and their branches were dissected to evaluate the distribution of the staining solution along the nerve length. We considered a length of nerve staining ≥ 2 cm to be consistent with successful nerve blockade (had an analgesic agent been injected).2,7 All the injections were performed by the same investigator (DFE) who had experience in performance of PNBs. The evaluation of the staining distribution along the target nerves was conducted by 2 investigators (JTP [15 nerves] and EFB [15 nerves]) who were blinded to the experimental group.
Results
In the first phase of the study, 3 dog cadavers with a mean weight of 15.7 kg were included. In the second phase of the study, dog cadavers were allocated to receive injections of a low, medium, or high volume of staining solution (5 dogs/group). These dogs had a mean body weight of 16.94 kg, 16.5 kg, and 17.3 kg in the low-, medium-, and high-volume groups, respectively. There was no difference (P = 0.794) in mean weight of the dogs among the experimental groups in phase 2.
Anatomic characteristics of the SN, ON, and LCFN
Dissection of the 3 cadavers (6 pelvic limbs) assigned to this phase of the study revealed similar findings in general. The SN was observed as a long thin cord. It originated from the FN where the FN emerged from the iliopsoas muscle, at the femoral triangle area. The SN extended distally along the cranial aspect of the femoral artery. The triangular area limited cranially by the caudal portion of the sartorius muscle, dorsally by the abdominal wall, and caudally by the femoral artery which was the more useful SALM to guide the SN injection. The FN, SN, and the muscular branches of the FN were covered at the femoral triangle area by 2 closely related fascial planes. The femoral fascia was the thinner and more external, whereas the iliac fascia was internal and considerably thicker. In all cadavers, a popping sensation was perceived as the needle advanced into these fascial planes, which allowed an LOR test to be conducted to estimate the depth of the injections. Abundant fatty tissue was observed under these fasciae and around the SN and the muscular branches of the FN, which were located, in general, at a depth of 1 cm from the skin at the injection site.
The ON was located at the iliopsoas muscle body and extended to the pelvis. Then, it passed through the cranial part of the obturator foramen. Once this nerve crossed the obturator foramen, a small nerve branch originating from the cranial aspect of the ON was identified in 3 out of 6 pelvic limbs. This branch was directed to the hip joint. The ON also provided branches for the external obturator, pectineus, gracilis, and adductor muscles (Figure 4). The depression located between the adductor and pectineus muscles was the most useful SALM to guide the ON injection. This depression was easily located in all cadavers.
Photograph of the gross anatomic features of the ON. 1 = ON. 2 = Articular branch of the ON for the hip joint. 3 = Pubis. 4 = Head of the femur. Lat = Lateral. Prx = Proximal.
Citation: American Journal of Veterinary Research 78, 4; 10.2460/ajvr.78.4.412
The LCFN was located between the psoas major and psoas minor muscles together with the deep circumflex iliac artery. This nerve passed ventrally to the end of the L7 transverse process, continuing to the ventral aspect of the abdominal wall between the internal abdominal oblique muscle and the external abdominal oblique muscle. The end of the transverse process of L7 was the most useful SALM to guide the LCFN injection. The terminal portion of the LCFN variably branched in the skin area close to the tuber coxae. A high number of individual variations in the number and distribution of these cutaneous branches were observed.
Assessment of blind perineural injection techniques to simulate nerve blockade of the SN, ON, and LCFN
The proportions of limbs in each group in which an optimal spreading of staining solution along the target nerves was observed were determined (Table 1). The staining solution reached the SN and the muscular branches of the FN under the iliac fascia in all limbs (Figure 1). After perineural injection on the SN with the high volume of staining solution (0.3 mL/kg), the length of nerve staining was considered to be optimal in all 10 limbs. After perineural injection with the medium volume (0.2 mL/kg) or the high volume (0.3 mL/kg) of staining solution, the length of nerve staining along the muscular branches of the FN was considered to be optimal in all 10 limbs. The ON was stained under the femoral fascia and also between the interfascial planes of the pectineus and adductor muscles. After perineural injection with the medium volume (0.2 mL/kg) or the high volume (0.3 mL/kg) of staining solution, the solution diffused in a proximal direction and stained the main trunk of the ON in all the limbs, as well as its branches for the hip joint in those limbs where these branches were present (6/10 pelvic limbs); the solution also diffused distally and stained the muscular branches of the ON (Figure 2). The main trunk of the LCFN and most of its branches were stained between the skin and the external abdominal oblique muscle (Figure 3). After perineural injection of the medium volume or high volume of staining solution, the length of nerve staining along the LCFN was optimal in all 10 limbs.
Number of pelvic limbs with optimal distribution of stain along the SN, muscular branches of the FN, ON, and LCFN after blind perineural injection of 1 of 3 volumes (0.1 [low volume], 0.2 [medium volume], or 0.3 [high volume] mL/kg) of lidocaine-methylene blue solution in 15 dog cadavers (5 cadavers [10 pelvic limbs]/injection group).
| Volume of staining solution injected (mL/kg) | |||
|---|---|---|---|
| Nerve | 0.1 | 0.2 | 0.3 |
| SN | 7 | 9 | 10 |
| Muscular branches of the FN | 7 | 10 | 10 |
| ON | 9 | 10 | 10 |
| LCFN | 3 | 10 | 10 |
The SN and the muscular branches of the FN were located by the use of SALMs and an LOR test. The ON and LCFN were located by the use of SALMs. Following blind perineural administration of staining solution near the target nerves in both pelvic limbs of 15 cadavers, limbs were dissected to evaluate the distribution of the staining solution along the nerves. Staining that extended ≥ 2 cm along the target nerves was considered optimal and compatible with an effective clinical nerve block.
Discussion
The aim of the study reported here was to investigate the potential usefulness of blind perineural injection techniques as a means to provide nerve blockade of the SN, ON, and LCFN by assessing the distribution along those nerves of 3 volumes of an injected staining solution in dog cadavers. For the ON and LCFN, the blind approach was based solely on SALMs; for the SN, the approach was guided by SALMs and an LOR test. To the authors’ knowledge, these blind perineural injection techniques, as well as an estimate of their potential clinical efficacy, in these target nerves in dogs have not been described. Results from the present study indicated that these techniques can result in an optimal distribution of staining solution along the target nerves; from these data, it appears possible that these techniques could induce an adequate nerve blockade.
Nerve electrolocation and ultrasound-guided PNB techniques are increasingly used in veterinary anesthesia17,18,20 to improve the efficacy and safety of PNBs.11,21 This current trend could dissuade practitioners, particularly those in developing countries who have no access to NEL or ultrasonographic technology, from performing PNBs. Nevertheless, nerve blockade can be effectively and safely achieved by use of blind approaches.12 Moreover, there are some clinical circumstances where the use of a blind technique may be indicated. It has been reported that the large size of ultrasound probes could hamper ultrasound-guided techniques in small-sized dogs,3 and the presence of subcutaneous emphysema or edema may interfere with the ultrasound beam.14 It is also known that in humans with diabetes13 or neuropathy,22 the efficacy of NEL could be reduced. Finally, blind techniques can also be used to locate nerves lacking a motor supply, such as the SN and LCFN, where NEL techniques cannot be used.
The ScN and the SN compose most of the sensory innervation of the pelvic limb in dogs.1 However, blockade of these nerves would not provide complete analgesic coverage of the pelvic limb. For this reason, the additional blockade of the ON and LCFN has been advocated to provide a complete analgesic coverage of the entire pelvic limb in dogs.5,6,21
Results of the present study indicated that the main anatomic features of the 3 evaluated nerves were similar to previous descriptions.1 In phase 1 of the present study, suitable approaches to access the target nerves were determined. It was also established that the fascial planes covering the SN at the femoral triangle facilitated more accurate location of this nerve by use of an LOR test. The LOR test relies on the loss-of-resistance sensation (a perceived pop or click) when fascial planes are crossed by a short beveled needle.12,23 A positive result of this test may improve the distribution of local anesthetic agents beneath the facial planes in which the SN is enclosed. An LOR test has been used in humans to block the FN at the level of the femoral triangle.23 However, those authors described a double pop sensation during the insertion of the needle in the fascial planes. This difference could be a consequence of anatomic differences in the fascial thickness at this site in humans and dogs. In humans, the FN is covered by the lata and iliac fascia, which are thick and also well separated12,23 allowing the feeling of 2 separate pops when the needle crosses them. However, in dogs, the femoral fascia is thin and is not always well separated from the iliac fascia.1 These facts could explain the single pop that was perceived during needle insertion in the present study.
The LOR test was found to be effective, and the perineural injections resulted in adequate distribution of staining solution along the SN and the muscular branches of the FN in at least 9 and more commonly 10 of the 10 limbs that received medium- or high-volume injections of staining solution. In a previous study16 performed in chondrodystrophoid and nonchondrodystrophoid dog cadavers (35 pelvic limbs), an efficacy of 83% (29/35 limbs) was reported when the SN was approached at the midlevel of the thigh by means of SALMs and an LOR test. Those authors16 concluded that the impossibility of obtaining a higher efficacy could be explained by individual and breed-related anatomic differences among the cadavers and also by the dehydration and rigidity of the specimens, which may have impaired the distribution of the injectate. The comparatively better results obtained in the present study could be related to the fact that only fresh cadavers from nonchondrodystrophoid dog breeds were used. This could have reduced the degree of anatomic variation among specimens and improved the degree of hydration of the fascial and nerve structures of interest. The volume of dye injected in the present study (0.3 mL/kg) was higher than that used in the previous study16 (0.13 mL/kg), which may have also contributed to improve the results. Additionally, the depth of the SN perineural injections was approximately 1 cm in all the limbs. In contrast, in a previous study,16 injections were made at different depths (3 to 5 cm), which could have resulted in inaccurate delivery of dye to this nerve.
For the SN assessments in the present study, the high volume of injectate (0.3 mL/kg) was identical to the volume administered with the guidance of an LOR test in humans to block the FN at the level of the femoral triangle.23 This volume was higher than the volumes of local anesthetics reported to block this nerve by ultrasound-guided techniques in dogs, namely 0.1 mL of lidocaine (2%)/kg4 and 0.2 mL of bupivacaine (0.5%)/kg.19 It has been described that the use of NEL and ultrasound-guided techniques to perform PNBs can greatly reduce the required volume of injectate to achieve a successful blockade.9 Nevertheless, the use of a high volume of local anesthetic in the vicinity of the target nerve is also associated with a higher success rate24 and a longer-lasting blockade.25,26
A potential clinical advantage of the SN blockade described in the present report, compared with other techniques,4,16,19,27 is the fact that additional blockade of the muscular branches of the FN can also be achieved. The additional blockade of these muscular branches may result in greater relaxation of the components of the quadriceps femoris muscle, which may facilitate maneuvers required to reduce fractures of the femoral shaft.23 However, it could delay the rapid return to ambulation. Early postoperative ambulation has been shown to improve the rehabilitation process of humans after knee surgeries.28
Blockade of the ON or LCFN is not usually performed in dogs undergoing surgical procedures involving the pelvic limb. One reason for this could be the lack of information regarding the sensory role of the ON in dogs.8 In the case of the LCFN, there are no published descriptions of suitable techniques to block this nerve effectively. The ON is considered a nerve with exclusive motor function.1 However, other authors have described sensory branches derived from this nerve in the stifle29,30 and hip joints31 in some dogs. In humans, the addition of ON blockade to FN blockade32 or dual FN and ScN33 blockade might improve the analgesic coverage during procedures related to the knee or hip joint. In dogs, incomplete analgesic coverage during stifle joint surgery may also result after dual FN and ScN blockade.g These findings support the hypothesis that analgesia provided by combined FN and ScN blockade could be insufficient for stifle joint surgical procedures in some dogs.20
Results of the present study indicated that the technique used to simulate ON blockade with a medium (0.2 mL/kg) or high (0.3 mL/kg) volume of staining solution resulted in an adequate distribution of staining solution over the main trunk of the ON in all the assessed pelvic limbs as well as over its articular branches in the cases where these branches were present (6/10 pelvic limbs). The solution also diffused distally and stained the muscular branches of the ON. In phase 1 of the study, ON branches to the stifle region were identified in 3 of 6 pelvic limbs evaluated, similarly to a previous description.31
There are no available descriptions regarding the blockade of the ON as an individual nerve in dogs, to our knowledge. However, there are reports2,8,20 of its blockade as a part of a lumbar plexus block. In 17 canine cadavers, ultrasound-guided injection of a volume of 0.2 mL of staining solution/kg to simulate a lumbar plexus block made by a ventral suprainguinal approach resulted in optimal ON staining in all instances.20 Other authors34 achieved 90% efficacy of ON blockade after administering 0.1 mL of injectate/kg in the lumbar plexus with an ultrasound-guided lateral approach. However, a lower efficacy (75%) was reported after the administration of 0.1 mL of staining solution/kg in the lumbar plexus by use of a pre-iliac approach with NEL, as the ON was adequately stained in 3 of 4 cadaver limbs.8 In another study,2 the ON was found to be adequately stained in 6 of 7 (86%) pelvic limbs after injection of a higher volume (0.4 mL/kg) of staining solution. The optimal staining for the ON in the 3 experimental groups in the present study could be attributed to the accuracy of the blind approach used. This approach was developed specifically to reach the ON as the main target nerve. Therefore, this approach may have allowed optimal distribution of the injectate along the ON and its branches. Previous techniques used for ON blockade focus on the FN as the main target nerve, thereby relying on the posterior distribution of dye along the iliopsoas muscle to indirectly reach the ON.
The LCFN is a purely sensory nerve that innervates the skin of the lateral aspect of the thigh.1 In humans, LCFN blockade can be successfully used as the sole analgesic technique for muscle biopsy procedures and harvesting of split-thickness skin grafts in that body area.35,36 It can also contribute to analgesic coverage for hip joint or femur fracture repairs.37,38 There are other descriptions on the potential advantages of LCFN blockade in combination with FN blockade39 or ON blockade40 for procedures involving the hip joint and femur.38 Results of the present study in canine cadavers indicated that the blind perineural injection technique developed for LCFN blockade was potentially effective because the distribution of the medium and high volumes of staining solution was optimal in all pelvic limbs examined. Such nerve blockade may improve the analgesia of the dermatomes innervated by the LCFN, and a single injection technique could be an excellent alternative to a multiple-local-anesthetic-infiltration technique. In humans that have undergone lateral or anterolateral skin grafts, the immediate postoperative comfort provided by an LCFN blockade was greater than that provided by a multiple-local-anesthetic-infiltration technique.41 Furthermore, a single injection technique to block the LCFN may offer other advantages because it requires lower volumes of local anesthetics to achieve analgesia of a larger area and results in more rapid onset of action.42
In the present study, 3 blind perineural injection techniques were assessed with regard to potential efficacy for blockade of the SN, ON, and LCFN in dog cadavers. These approaches were based on SALMs and, for the SN, also an LOR test. Results indicated that these techniques have the potential to provide an inexpensive, affordable, and clinically effective method to achieve blockade of these nerves. However, because of the cadaveric nature of this study, further research is necessary to determine the analgesic efficacy of these techniques in live dogs in a clinical setting.
Acknowledgments
Preliminary results of this study were presented as an abstract at the Autumn Meeting of the Association of Veterinary Anesthetists, Vienna, Austria, March 2014, and were published as an abstract in Veterinary Anaesthesia and Analgesia 2015;42:A1-A40.
This research was funded by grants from the Central Research Office of the University of Tolima to Diego F. Echeverry-Bonilla (Project No. 370213). The authors thank Drs. Francisco Gil Cano (Murcia University, Spain) and Fabian Castañeda Herrera (Universidad del Tolima, Colombia) for their contributions to the anatomic components of the study.
ABBREVIATIONS
| FN | Femoral nerve |
| LCFN | Lateral cutaneous femoral nerve |
| LOR | Loss-of-resistance technique |
| NEL | Nerve electrolocation |
| ON | Obturator nerve |
| PNB | Peripheral nerve blockade |
| SALM | Superficial anatomic landmark |
| ScN | Sciatic nerve |
| SN | Saphenous nerve |
Footnotes
Euthanex, INVET, Bogotá, Colombia.
random.org, Randomness and Integrity Services Ltd, Dublin, Ireland. Available at: www.random.org. Accessed Dec 18, 2012.
Roxicaína, Ropsohn Therapeutics Ltda, Bogotá, Colombia.
Methylene blue powder, Disproalquímicos SA, Bogotá, Colombia.
Stimuplex D, 55 mm, 22 gauge, 21 gauge × 1 1/2”, Medical SA, Melsungen, Germany.
Hypodermic needle, Alfasafe Health Care Products, Bogotá, Colombia.
Campoy L, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY: personal communication, 2015.
References
1. Evans H, de Lahunta A. The spinal nerves. In: Evans H, de Lahunta A, eds. Miller's anatomy of the dog. 4th ed. St Louis: Elsevier-Saunders Co, 2013; 636–656.
2. Campoy L, Martin-Flores M, Looney AL, et al. Distribution of a lidocaine-methylene blue solution staining in brachial plexus, lumbar plexus and sciatic nerve blocks in the dog. Vet Anaesth Analg 2008; 35: 348–354.
3. 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: 210–215.
4. Costa-Farré C, Blanch XS, Cruz JI, et al. Ultrasound guidance for the performance of sciatic and saphenous nerve blocks in dogs. Vet J 2011; 187: 221–224.
5. Murray JM, Derbyshire S, Shields MO. Lower limb blocks. Anaesthesia 2010; 65: 57–66.
6. Sakura S, Hara K, Ota J, et al. Ultrasound-guided peripheral nerve blocks for anterior cruciate ligament reconstruction: effect of obturator nerve block during and after surgery. J Anesth 2010; 24: 411–417.
7. Echeverry DF, Laredo FG, Gil F, et al. Ventral ultrasound-guided suprainguinal approach to block the femoral nerve in the dog. Vet J 2012; 192: 333–337.
8. Portela DA, Otero PE, Briganti A, et al. Femoral nerve block: a novel psoas compartment lateral pre-iliac approach in dogs. Vet Anaesth Analg 2013; 40: 194–204.
9. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anaesthesia. Br J Anaesth 2005; 94: 7–17.
10. Abrahams MS, Aziz MF, Fu RF, et al. Ultrasound guidance compared with electrical neurostimulation for peripheral nerve block: a systematic review and meta-analysis of randomised controlled trials. Br J Anaesth 2009; 102: 408–417.
11. Gelfand HJ, Ouanes JP, Lesley MR, et al. Analgesic efficacy of ultrasound-guided regional anesthesia: a meta-analysis. J Clin Anesth 2011; 23: 90–96.
12. Singh SK, Kuruba SM. The loss of resistance nerve blocks. ISRN Anesthesiol. Article ID 2011; 2011: 421505.
13. Sites BD, Gallagher J, Sparks M. Ultrasound-guided popliteal block demonstrates an atypical motor response to nerve stimulation in 2 patients with diabetes mellitus. Reg Anesth Pain Med 2003; 28: 479–482.
14. Saranteas T, Karakitsos D, Alevizou A, et al. Limitations and technical considerations of ultrasound-guided peripheral nerve blocks: edema and subcutaneous air. Reg Anesth Pain Med 2008; 33: 353–356.
15. Mihelic D, Zobundzija M, Brkic A, et al. Anatomical possibilities of access to and blockade of m. femoralis in the dog. Vet Med (Praha) 1995; 40: 283–287.
16. Rasmussen LM, Lipowitz AJ, Graham LF. Development and verification of saphenous, tibial and common peroneal nerve block techniques for analgesia below the thigh in the nonchondrodystrophoid dog. Vet Anaesth Analg 2006; 33: 36–48.
17. Mahler SP, Adogwa AO. Anatomical and experimental studies of brachial plexus, sciatic, and femoral nerve-location using peripheral nerve stimulation in the dog. Vet Anaesth Analg 2008; 35: 80–89.
18. 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: 144–153.
19. Shilo Y, Pascoe PJ, Cissell D, et al. Ultrasound-guided nerve blocks of the pelvic limb in dogs. Vet Anaesth Analg 2010; 37: 460–470.
20. Echeverry DF, Laredo FG, Gil F, et al. Ultrasound guided ‘two-in-one’ femoral and obturator nerve block in the dog: an anatomical study. Vet Anaesth Analg 2012; 39: 611–617.
21. Gurney MA, Leece EA. Analgesia for pelvic limb surgery. A review of peripheral nerve blocks and the extradural technique. Vet Anaesth Analg 2014; 41: 445–458.
22. Minville V, Zetlaoui PJ, Fessnmeyer C, et al. Ultrasound-guidance for difficult lateral popliteal catheter insertion in a patient with peripheral vascular disease. Reg Anesth Pain Med 2004; 29: 368–370.
23. Khoo ST, Brown TC. Femoral nerve block-the anatomical basis for a single injection technique. Anaesth Intensive Care 1983; 11: 40–42.
24. Vester-Andersen T, Christiansen C, Sorensen M, et al. Perivascular axillary block II: influence of injected volume of local anaesthetic on neural blockade. Acta Anaesthesiol Scand 1983; 27: 95–98.
25. Ilfeld BM, Loland VJ, Gerancher JC, et al. The effects of varying local anesthetic concentration and volume on continuous popliteal sciatic nerve blocks: a dual-center, randomized, controlled study. Anaesth Analg 2008; 107: 701–707.
26. Fredrickson MJ, Abeysekera A, White R. Randomized study of the effect of local anesthetic volume and concentration on the duration of peripheral nerve blockade. Reg Anesth Pain Med 2012; 37: 495–501.
27. Rasmussen LM, Lipowitz AJ, Graham LF. Controlled, clinical trial assessing saphenous, tibial and common peroneal nerve blocks for the control of perioperative pain following femoro-tibial joint surgery in the nonchondrodystrophoid dog. Vet Anaesth Analg 2006; 33: 49–61.
28. Osses CH. Bloqueos regionales continuos en anestesiología pediátrica. Bol El Dolor 2005; 14: 8–12.
29. O'Connor BL, Woodbury P. The primary articular nerves to the dog knee. J Anat 1982; 134: 563–572.
30. Budras KD, McCarthy PH, Fricke W, et al. Pelvic limb. In: Budras KD, McCarthy PH, Fricke W, et al, eds. Anatomy of the dog. 5th ed. Hannover, Germany: Ed SchlüterscheVerlagsgesellschaft mbH & Co, 2007; 76–82.
31. Huang CH, Hou SM, Yeh LS. The innervation of canine hip joint capsule: an anatomic study. Anat Histol Embryol 2013; 42: 425–431.
32. Macalou D, Trueck S, Meuret P, et al. Postoperative analgesia after total knee replacement: the effect of an obturator nerve block added to the femoral 3-in-1 nerve block. Anesth Analg 2004; 99: 251–254.
33. McNamee DA, Parks L, Milligan KR. Post-operative analgesia following total knee replacement: an evaluation of the addition of an obturator nerve block to combined femoral and sciatic nerve block. Acta Anaesthesiol Scand 2002; 46: 95–99.
34. Graff SM, Wilson DV, Guiot LP, et al. Comparison of three ultrasound-guided approaches to the lumbar plexus in dogs: a cadaveric study. Vet Anaesth Analg 2015; 42: 394–404.
35. Maccani RM, Wedel DJ, Melton A, et al. Femoral and lateral femoral cutaneous nerve block for muscle biopsies in children. Paediatr Anaesth 1995; 5: 223–227.
36. Karacalar A, Karacalar S, Uckunkaya N, et al. Combined use of axillary block and lateral femoral cutaneous nerve block in upper-extremity injuries requiring large skin grafts. J Hand Surg Am 1998; 23: 1100–1105.
37. Jones SF, White A. Analgesia following femoral neck surgery. Lateral cutaneous nerve block as an alternative to narcotics in the elderly. Anaesthesia 1985; 40: 682–685.
38. Miller BR. Combined ultrasound-guided femoral and lateral femoral cutaneous nerve blocks in pediatric patients requiring surgical repair of femur fractures. Paediatr Anaesth 2011; 21: 1163–1164.
39. Vandebroek A, Vertommen M, Huyghe M, et al. Ultrasound guided femoral nerve block and lateral femoral cutaneous nerve block for postoperative pain control after primary hip arthroplasty: a retrospective study. Acta Anaesthesiol Belg 2014; 65: 39–44.
40. Rashiq S, Vandermeer B, Abou-Setta AM, et al. Efficacy of supplemental peripheral nerve blockade for hip fracture surgery: multiple treatment comparison. Can J Anaesth 2013; 60: 230–243.
41. Shank ES, Martyn JA, Donelan MB, et al. Ultrasound-guided regional anesthesia for pediatric burn reconstructive surgery: a prospective study. J Burn Care Res 2016; 37: e213–e217.
42. Kiliçaslan A, Erol A, Topal A, et al. Combined use of ultrasound guided infraclavicular block and lateral femoral cutaneous nerve block in upper extremity reconstruction requiring large skin graft: case report. Agri 2013; 25: 133–136.
