Description and Evaluation of Dye and Contrast Media Distribution of Ultrasound-Guided Rectus Sheath Block in Cat Cadavers.

The rectus sheath block is an ultrasound-guided anaesthetic technique which aims to provide analgesia to the abdominal midline. This study aimed to assess the distribution of 0.4 mL kg-1 of a mixture of methylene blue and iopromide injected into each hemiabdomen in the internal rectus sheath in cat cadavers. We hypothesise that this technique would be feasible and would cover the rami ventrales of the last thoracic and the first lumbar spinal nerves. The study was divided into two phases. Phase 1 aimed to study the anatomical structures of the ventral abdominal wall (four cats were dissected). Phase 2 (ten cadavers) consisted of an ultrasound-guided injection of the mixture mentioned above and the assessment of its distribution by computed tomography and anatomical dissection. The results showed the staining of the cranioventral abdominal wall with a craniocaudal spread of four (three to eight) vertebral bodies. Methylene blue stained three (one to four) rami ventrales, affecting T10 (60%), T11 (100%), T12 (90%), T13 (50%) and L1 (5%). Based on these results, it could be stated that this technique could supply anaesthesia to the midline of the abdominal midline cranial to the umbilicus in clinical patients, but it may not be able to provide anaesthesia to the middle and caudal midline abdominal region.

Modified Ultrasound-Guided Dorsal Quadratus Lumborum Block in Cat Cadavers.

The quadratus lumborum (QL) block is an ultrasound-guided locoregional anesthesia technique which aims to provide analgesia to the abdomen. The main objective of this study was to assess a modified ultrasound-guided dorsal QL block in cat cadavers. For this purpose, a volume of 0.4 mL kg-1 of a mixture of iopromide and methylene blue was administered between the psoas minor muscle and the vertebral body (VB) of the first lumbar vertebra, and its distribution was assessed in thirteen cat cadavers. We hypothesized that this injection point would be feasible, offering a more cranial distribution of the injectate and a more consistent staining of the truncus sympathicus. The study was divided into two phases. Phase 1 consisted of an anatomical study (three cadavers were dissected). Phase 2 consisted of the ultrasound-guided administration of the injectate and the assessment of its distribution by computed tomography and anatomical dissection. The results showed a consistent distribution of contrast media within five (4-8) VBs from T10 to L5. Methylene blue stained three (2-6) rami ventrales, affecting T11 (10%), T12 (20%), T13 (60%), L1 (85%), L2 (95%) and L3 (65%). The truncus sympathicus was dyed in all cadavers with a spread of five (3-7) VBs. Finally, the splanchnicus major nerve was stained in all cadavers (100%). These results suggest that this technique could provide analgesia to the abdominal viscera and the abdominal wall, probably with the exception of the cranial aspects of the abdominal wall.

An Ultrasound-Guided Latero-Ventral Approach to Perform the Quadratus Lumborum Block in Dog Cadavers.

The QL block is a high-level locoregional anesthesia technique, which aims to provide analgesia to the abdomen. Several approaches of the QL block have been studied to find out which one allows a greater distribution of the injectate. The aim of this study is to compare the traditional interfascial QL block (IQL) with a new latero-ventral approach (LVQL). We hypothesize that this new approach could be safer and easier to perform, since the injectate is administered more superficially and further away from vital structures. Our second objective is to assess whether a higher volume of injectate (0.6 mL/kg) could reach the ventral branches of the last thoracic nerves, leading to a blockade of the cranial abdomen. Six thawed canine cadavers (12 hemiabdomens) were used for this purpose. Both approaches were performed in all cadavers. A combination of methylene blue/iopromide was administered to each hemiabdomen, randomly assigned to the LVQL or IQL. No differences were found regarding the ease of perform the LVQL with respect to IQL. The results show that both techniques reached the ventral branches from L1 to L3, although only the IQL consistently stained the sympathetic trunk (5/6 IQL vs. 1/6 LVQL). The use of a higher volume did not enhance a more cranial distribution of the injectate.

Ultrasonographic assessment of the renal size using a kidney length to vertebral body length ratio in cats.

Ultrasonographic assessment of the renal size can provide useful clinical information, in combination with other ultrasonographic parameters. The aims of this study were to establish the agreement between the ultrasonographic and radiographic measurements of the kidneys (K) and vertebral bodies (L5 and L6), to establish an ultrasonographic measurement of kidney-to-vertebral body (L5 and L6) ratio to estimate the renal size in cats, and to assess the impact of age, body weight, sex, and gonadal status on the ultrasonographic measurements of the kidneys, vertebral bodies, and ratios. The vertebral bodies of L5 and L6 were chosen as they were easy to identify with ultrasonography (US) using the lumbosacral junction as a landmark, and they are not usually affected by vertebral anomalies. A total of 60 cats (19 intact males, 12 neutered males, 17 intact females, and 12 neutered females) were included in the study. The cats were divided into three age groups (<7 months, 7 months-7 years, and >7 years), two body weight categories (≤ 3.5 kg and >3.5 kg), and two sex and gonadal status groups (male and female, and intact and neutered, respectively). Measurements of the renal and vertebral body length were performed on the radiographic and ultrasonographic images. Two different ratios were obtained, namely, K/L5 and K/L6. There was no significant difference between the length of both kidneys and the length of the vertebral bodies of L5 and L6 on ultrasonographic or radiographic images. There was a good agreement between ultrasonographic and radiographic measurements of both kidneys and vertebral bodies. In conclusion, the kidney length to L6 length ratio obtained was 1.81 ± 0.20 (1.76-1.86), which was useful for evaluating the size of the feline kidney and was not influenced by the age, body weight, sex, or gonadal status.

Evaluation of High-Volume Injections Using a Modified Dorsal Quadratus Lumborum Block Approach in Canine Cadavers.

The quadratus lumborum (QL) block targets the fascial plane surrounding the QL muscle providing abdominal somatic and visceral analgesia. The extension of its analgesic effects is a subject of research, as it could not cover areas of the cranial abdomen in dogs. This study assesses in eight thawed canine cadavers, the distribution of high-volume injections (0.6 mL kg-1 of a mixture of methylene blue and iopromide) injected between the psoas minor muscle and the vertebral body of L1. Anatomical features of the area of interest were studied in two cadavers. In another six dogs, QL blocks were performed bilaterally under ultrasound-guidance. The distribution of contrast was evaluated by computed tomography (CT). Hypaxial abdominal muscles were dissected to visualize the dye spread (spinal nerves and sympathetic trunk) in 5 cadavers. The remaining cadaver was refrozen and cross-sectioned. CT studies showed a maximum distribution of contrast from T10 to L7. The methylene blue stained T13 (10%), L1 (100%), L2 (100%), L3 (100%), L4 (60%) and the sympathetic trunk T10 (10%), T11 (20%), T12 (30%), T13 (70%), L1 (80%), L2 (80%), L3 (60%) and L4 (30%). These findings may suggest that despite the high volume of injectate administered, this modified QL block could not produce somatic analgesia of the cranial abdomen, although it could provide visceral analgesia in dogs.

Short-Term Effects of Deliberate Subparaneural or Subepineural Injections With Saline Solution or Bupivacaine 0.75% in the Sciatic Nerve of Rabbits.

Background: Ultrasound (US)-guided techniques for peripheral nerve blockade have revealed that intraneural injections are relatively frequent and not necessarily associated with neurological deficits. Objectives: To evaluate the short-term effects of deliberate injections performed under direct vision in two different sites of the sciatic nerve (ScN). Material and Methods: Seventy-two New Zealand white rabbits randomly assigned to one of four experimental groups (n = 18) were employed. All procedures were conducted at a proximal femoral level where the ScN incorporates the common peroneal nerve and the tibial nerve (TN). Fixed volumes of 0.5 ml of saline solution (ES group) or bupivacaine 0.75% (EB group) were administered extrafascicularly inside the paraneurium of the ScN or intrafascicularly (IS and IB groups) under the epineurium of the TN. Cross-sectional area (CSA) and relative echogenicity (RE) of the entire ScN were determined by US before injections, after injections, and at 3 and 7 days. ScN samples were obtained for structural and ultrastructural histopathological studies. Proprioceptive, sensorial, and motor function were clinically evaluated on a daily basis. Results: The CSA of the ScN increased significantly immediately after injections when compared with pre-injection values in all groups (p < 0.05). The RE of the ScN decreased in relation to pre-injection values in all groups (p < 0.05). The CSA and RE of the ScN returned to normal values 7 days after injections in almost all groups. Injected nerves showed histological signs of mild perineural inflammation. Histopathological scores were not significantly different between groups (p > 0.05). The architecture of the ScN was preserved in all rabbits at 3 days and in 31/32 rabbits at 7 days. A focal area of damaged nerve fibers with degeneration of the axons and myelin sheath affecting the TN was observed in one rabbit of the IB group. Nerve function was not clinically impaired in any case. Conclusion: Despite the lack of severe nerve disruption observed in most rabbits, the evidence of a focal area of damaged nerve fibers in one rabbit injected intrafascicularly with bupivacaine confirms that intrafascicular injections should be avoided as they may increase the risk of nerve damage.

Pharmacokinetics and sedative effects of alfaxalone with or without dexmedetomidine in rabbits.

This study aimed to investigate the specific pharmacokinetic profile and effects of alfaxalone after intravenous (IV) and intramuscular (IM) administration to rabbits and evaluate the potential interaction with dexmedetomidine. The study design was a blinded, randomized crossover with a washout period of 2 weeks. Five New Zealand white rabbits were used. Each animal received single IV and IM injections of alfaxalone at a single dose of 5 mg/kg, and single IV and IM injections of alfaxalone (5 mg/kg) combined with dexmedetomidine (100 µg/kg) administered intramuscularly. Blood samples were collected at predetermined times and analysed by high-performance liquid chromatography. The plasma concentration-time curves were analysed by non-compartmental analysis. Sedation/anaesthesia scores were evaluated by a modified numerical rating scale. At pre-determined time points heart and respiratory rates were measured. Times to sternal recumbency and standing position during the recovery were recorded. Concentrations of alfaxalone alone were very similar (slighty smaller) to concentrations when alfaxalone was combined with dexmedetomidine, after both routes of administration. Dexmedetomidine enhanced and increase the duration of the sedative effects of alfaxalone. In conclusion, alfaxalone administered in rabbits provides rapid and smooth onset of sedation. After IV and IM injections of alfaxalone combined with dexmedetomidine, a longer MRT and a deeper and extended sedation have been obtained compared to alfaxalone alone. Consequently, alfaxalone alone or in combination with dexmedetomidine could be useful to achieve respectively moderate to deep sedation in rabbits.

Effects of midazolam before or after alfaxalone for co-induction of anaesthesia in healthy dogs.

OBJECTIVE: To study the effect of alternating the order of midazolam and alfaxalone administration on the incidence of behavioural changes, alfaxalone induction dose and some cardiorespiratory variables in healthy dogs. STUDY DESIGN: Prospective, randomized, controlled, clinical trial. ANIMALS: A total of 33 client-owned dogs undergoing elective procedures. METHODS: Following intramuscular acepromazine (0.02 mg kg-1) and morphine (0.4 mg kg-1) premedication, anaesthesia was induced intravenously (IV) with a co-induction of either midazolam (0.25 mg kg-1) prior to alfaxalone (0.5 mg kg-1; group MA), or alfaxalone followed by midazolam at identical doses (group AM). The control group (CA) was administered normal saline IV prior to alfaxalone administration. Additional alfaxalone (0.25 mg kg-1 increments) was administered as required in all groups until orotracheal intubation was possible. Changes in behaviour, quality of induction, ease of intubation and incidence of adverse events at induction were recorded. Heart rate (HR), respiratory rate (fR) and systolic arterial blood pressure (SAP) were measured before treatments (baseline values), 30 minutes after premedication and at 0, 2, 5 and 10 minutes postintubation. RESULTS: The incidence of excitement was higher in group MA compared with groups CA (p=0.005) and AM (p=0.013). The mean induction dose of alfaxalone was lower in group AM compared with group CA (p=0.003). Quality of induction and ease of intubation were similar among groups. Mean HR values decreased after premedication and increased after alfaxalone administration in all groups. Mean SAP values were similar between groups. The number of animals that required manual ventilation was higher in the MA group. CONCLUSIONS AND CLINICAL RELEVANCE: Despite a lower occurrence of adverse events at induction in group AM compared with group MA and a reduction of alfaxalone dose requirement in group AM compared with group CA, the use of an alfaxalone-midazolam co-induction does not seem to produce any cardiovascular or respiratory benefits in healthy dogs.

Assessment of the potential efficacy of blind perineural injection techniques for blockade of the saphenous, obturator, and lateral cutaneous femoral nerves in dog cadavers.

OBJECTIVE To evaluate the potential efficacy of blind perineural injection techniques to provide nerve blockade of the saphenous, obturator, and lateral cutaneous femoral nerves by assessing the distribution along those nerves of 3 volumes of an injected staining solution in dog cadavers. ANIMALS 18 canine cadavers. PROCEDURES The anatomic characteristics of the target nerves were evaluated by dissection in 3 cadavers. The saphenous nerve was located by the use of superficial anatomic landmarks and a loss-of-resistance test. The obturator and lateral cutaneous femoral nerves were located by the use of superficial anatomic landmarks. Following perineural administration of 3 volumes (0.1, 0.2, and 0.3 mL/kg) of staining solution near the target nerves in 15 cadavers, 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. RESULTS In all cadavers, nerves were appropriately stained by the blind techniques used here. The staining distribution along the nerves was considered to be optimal after perineural injection of 0.2 mL of staining solution/kg in the obturator and lateral cutaneous femoral nerves and 0.3 mL of staining solution/kg in the saphenous nerve. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the evaluated blind perineural injection techniques may be an inexpensive, safe, and clinically effective method to block the saphenous, obturator, and lateral cutaneous femoral nerves in dogs.

Evaluation of an ultrasound-guided technique for axillary brachial plexus blockade in cats.

Objectives The aim of this study was to evaluate and refine an ultrasound (US)-guided technique to block the brachial plexus (BP) at the level of the axillary space in live cats. Methods Eight adult experimental cats were enrolled into the study. The animals were sedated and positioned in dorsal recumbency with the limb to be blocked abducted 90º. The US transducer was placed in the axillary region and a non-traumatic peripheral nerve block needle was inserted in-plane with respect to the transducer, medial to the BP up to the level of the axillary artery. Lidocaine 1% (0.4 ml/kg) was injected as the needle was being progressively withdrawn in a caudal-to-cranial direction. The efficacy of the block was confirmed by evaluation of the motor and sensory functions of the blocked forelimb. Motor blockade was assessed observing the position of the blocked leg on standing and walking patterns. Sensory blockade was evaluated by the stimulation of mechanical nociceptors in the dermatomes supplied by the four major sensory nerves of the distal thoracic limb. Results The BP was successfully located by US in all cases. The achieved BP block was complete in six cats (75%) and partial in the remaining two cats (25%). All animals recovered uneventfully from the sedation and the BP blocks. Conclusions and relevance The US-guided block at the axillary space evaluated in this study is a feasible, reproducible and safe technique to block the BP plexus in experimental live cats.

Clinical efficacy and cardiorespiratory effects of intramuscular administration of alfaxalone alone or in combination with dexmedetomidine in cats.

OBJECTIVE: To investigate the sedative, anaesthetic and cardiorespiratory effects of intramuscular (IM) administration of alfaxalone alone or in combination with dexmedetomidine in cats. STUDY DESIGN: Blinded, randomized crossover study with a washout period of 15 days. ANIMALS: Seven adult cats, weighing 3.5 ± 0.7 kg. METHODS: Cats were assigned randomly to each of three treatments: A5 (alfaxalone 5 mg kg(-1) ), D20 A5 (dexmedetomidine 20 µg kg(-1) and alfaxalone 5 mg kg(-1) ) and D40 A5 (dexmedetomidine 40 µg kg(-1) and alfaxalone 5 mg kg(-1) ). Drugs were administered IM into the epaxial muscles. Sedation or anaesthesia scores were evaluated by a modified numerical rating scale. Times to extubation, head-lift, sternal recumbency and standing were recorded. Heart and respiratory rates, systolic arterial pressure, arterial oxygen saturation of haemoglobin, end-tidal carbon dioxide tension and rectal temperature were measured at 5, 10, 15, 20, 30, 45, 60, 90, 120 and 150 minutes after drug administration. Adverse events were recorded. Data were analysed by one-way anova with Tukey's post-hoc test for parametric values and, for non-normally distributed parameters, a Kruskal-Wallis test and Mann-Whitney U-test for two independent samples (p < 0.05). RESULTS: Sedation scores were significantly different among the treatments. Cats in A5 were deeply sedated, whereas cats administered dexmedetomidine were anaesthetized. The onset of action and the duration of anaesthesia were related to the dose of dexmedetomidine. Cardiorespiratory parameters remained stable in the A5 group. Lower heart rates, higher systolic blood pressures and occasional low pulse oximetry readings were observed in the dexmedetomidine groups. A limited number of adverse events (hyperkinesia, emesis) occurred during recovery. CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone administered IM induced sedation in cats. The addition of dexmedetomidine to alfaxalone induced general anaesthesia with a mild decrease in the heart rate and arterial oxygen saturation of haemoglobin.

Comparison of two techniques for ultrasound-guided axillary brachial plexus blockade in cats.

Axillary blockade of the brachial plexus (BP) is advocated in humans and dogs for surgical procedures carried out on the foot, carpus and elbow as it provides complete analgesia distally from above the elbow joint. The aim of this study was to develop an ultrasound (US)-guided approach to block the BP in cats. Two groups of 12 feline cadavers each were used to compare two different techniques to block the BP at the axillary level. The reliability of the techniques was assessed by anatomical and computed tomography (CT) studies. Cadavers of the first group were positioned in dorsal recumbency with the forelimb to be blocked adducted (thoracic limbs flexed and orientated caudally) (FAD technique). The second group was positioned in dorsal recumbency with the forelimb abducted 90° (FAB technique). The accuracy of the techniques was determined by US after injecting 1 ml blue ink along the BP nerves, and by CT after injecting 1 ml of an iodinated contrast medium. The anatomical and CT studies confirmed the accuracy of the US location of the BP nerves. Staining of the axillaris, musculocutaneous, radialis, medianus and ulnaris nerves was observed in 100% of cats using the FAB technique and in 66% of the cats using the FAD technique. Rate of complications was higher in the FAD technique. In conclusion, a US-guided axillary approach to the BP by the use of a FAB technique is a safe and feasible procedure to block the BP in the cat. Further studies are needed to ascertain whether the technique can be applied in a clinical setting.

Ultrasound-guided administration of lidocaine into the sciatic nerve in a porcine model: correlation between the ultrasonographic evolution of the lesions, locomotor function and histological findings.

Intraneural puncture of local anaesthetics has been associated with permanent or transitory nerve injury. The use of ultrasound (US)-guided techniques for the blockade of peripheral nerves has revealed that intraneural puncture is a relatively common complication, which is not frequently associated with neurological deficits. In this study, 2.5 mL of lidocaine were administered using US-guidance into the sciatic nerve (ScN) of 12 piglets. The punctured nerves were sequentially evaluated by US (cross sectional area and relative echogenicity) before and immediately after the injections, and then at 1, 2, 4, 7 and 14 days. At these times, animals were euthanased two by two at each time point, and ScN samples were removed for histological examination. Cross sectional area and relative echogenicity values were statistically different immediately after the injections, returning to pre-puncture values within 4 days. The inflammatory process observed by histopathology showed a similar trend indicating that the integrity of the perineurium was maintained. Locomotor deficits were not observed. The increase in size of the ScN produced by the injection of lidocaine intraneurally did not induce motor deficits in piglets in the current study.

Effects of altering the sequence of midazolam and propofol during co-induction of anaesthesia.

OBJECTIVE: To assess the effects of varying the sequence of midazolam and propofol administration on the quality of induction, cardiorespiratory parameters and propofol requirements in dogs. STUDY DESIGN: Randomized, controlled, clinical study. ANIMALS: Thirty-three client owned dogs (ASA I-III, 0.5-10 years, 5-30 kg). METHODS: Dogs were premedicated with acepromazine (0.02 mg kg(-1) ) and morphine (0.4 mg kg(-1) ) intramuscularly. After 30 minutes, group midazolam-propofol (MP) received midazolam (0.25 mg kg(-1) ) intravenously (IV) before propofol (1 mg kg(-1) ) IV, group propofol-midazolam (PM) received propofol before midazolam IV at the same doses, and control group (CP) received saline IV, instead of midazolam, before propofol. Supplementary boluses of propofol (0.5 mg kg(-1) ) were administered to effect to all groups until orotracheal intubation was completed. Behaviour after midazolam administration, quality of sedation and induction, and ease of intubation were scored. Heart rate (HR), respiratory rate, and systolic arterial blood pressure were recorded before premedication, post-premedication, after midazolam or saline administration, and at 0, 2, 5, and 10 minutes post-intubation. End-tidal CO2 and arterial oxygen haemoglobin saturation were recorded at 2, 5 and 10 minutes post-intubation. RESULTS: Quality of sedation and induction, and ease of intubation were similar in all groups. Incidence of excitement was higher in the MP compared to CP (p = 0.014) and PM (p = 0.026) groups. Propofol requirements were decreased in MP and PM groups with respect to CP (p < 0.001), and in PM compared to MP (p = 0.022). The HR decreased after premedication in all groups, and increased after midazolam and subsequent times in MP (p = 0.019) and PM (p = 0.001) groups. Incidence of apnoea and paddling was higher in CP (p = 0.005) and MP (p = 0.031) groups than in PM. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of midazolam before propofol reduced propofol requirements although caused mild excitement in some dogs. Administration of propofol before midazolam resulted in less excitatory phenomena and greater reduction of propofol requirements.

Imaging diagnosis-infiltrative lipoma causing spinal cord and lumbar nerve root compression in a dog.

A 12-year-old, male, fox terrier dog presented with an abnormal gait of the left pelvic limb. Computed tomography revealed a large, homogeneous, hypoattenuating, noncontrast enhancing mass within the left epaxial muscles that invaded the L5-6 vertebral canal and caused spinal cord compression. Imaging findings were consistent with an infiltrative lipoma. The mass was removed and a left hemilaminectomy was performed in the affected area. Histopathology confirmed the mass to be an infiltrative lipoma. The dog recovered and regained neurologic function within 2 weeks. Computed tomography assisted preoperative planning by characterizing the shape, size, and location of the mass.

Correlative ultrasound anatomy of the feline brachial plexus and major nerves of the thoracic limb.

Brachial plexus avulsions commonly occur in cats due to traumatic injuries involving the shoulder. Ultrasound may be an effective method for detecting injured nerves. Additional applications may include characterization of brachial plexus neoplasms and guidance of anesthetic nerve blocks. Aims of this study were to describe ultrasonographic approaches and the normal appearance of this plexus and other major nerves of the thoracic limb in cats. Eight feline cadavers were used to determine anatomic landmarks, obtain cross-sectional anatomic images of the target nerves, and compare these with ultrasound images. An ultrasonographic study was performed in five fresh feline cadavers to assess the brachial plexus and its major components at the levels of the axilla and proximal, middle and distal (lateral and medial approaches) humeral regions. Five healthy adult cats were recruited for an in vivo ultrasonographic study using the same protocol described for the cadaver ultrasonographic study. The roots of the brachial plexus appeared as a cluster of small, round hypoechoic structures surrounded by a hyperechoic rim in the axillary approach. The radialis, medianus, and ulnaris nerves were individually visualized on proximal and middle humeral approaches. The medianus and ulnaris nerves were easily identified on the medial aspect of the humerus in the distal approach. The superficial branch of radialis nerve was seen on the lateral aspect of the distal humerus approach. The nerves appeared as oval-to-round hypoechogenic structures with a hyperechogenic rim. Future studies are needed to compare findings from this study with those in cats with confirmed brachial plexus injuries or other lesions.

Ultrasound-guided 'two-in-one' femoral and obturator nerve block in the dog: an anatomical study.

OBJECTIVE: To evaluate the dye extent and distribution at the lumbar plexus (LP) of three volumes of local anaesthetic-methylene-blue solution administered close to the femoral nerve (FN) by the use of a ventral ultrasound (US)-guided suprainguinal approach (SIA). STUDY DESIGN: Prospective experimental trial. ANIMALS: Twenty mongrel canine cadavers weighing 17.7 ± 3.8 kg (mean ± SD). METHODS: The left and right LP of two cadavers were dissected to identify the FN, obturator nerve (ON) and lateral femoral cutaneous nerve (LFCN). The extent and distribution of dye at the LP of each of three volumes of injectate of 0.2, 0.4 and 0.6 mL kg(-1) administered close to the FN by a ventral US-guided SIA then were studied in a further 18 dog cadavers (n = 6 per group). Staining of ≥2 cm along the target nerves was indicative of sufficient spread to produce a nerve block. RESULTS: The ventral US-guided SIA allowed the observation of the FN within the iliopsoas muscle (IPM) in a total of 17 cadavers. The assessment of the dye extent and distribution revealed a similar pattern regardless of the injected volume. From the injection site, the spreading of injectate occurred in cranial, lateral and caudal directions. The FN and ON were effectively stained in all the cases. The LFCN was not effectively stained in any case. CONCLUSIONS AND CLINICAL RELEVANCE: A volume of 0.2 mL kg(-1) administered close to the FN by a ventral US-guided SIA produced a sufficient distribution of the injectate within the IPM to produce effective staining of the FN and ON. This US-guided technique may be an appropriate alternative to previously reported techniques based on electrolocation to block the FN and ON in the dog.

The effects of atracurium on bispectral index (BIS) values in dogs anaesthetized with isoflurane.

Balanced anaesthesia techniques employ specific drugs in addition to general anaesthetics. The potential effect of some of these drugs on the bispectral index (BIS) remains unclear. BIS seems to be unaffected by the administration of neuromuscular blockers while opioids may block nociceptive-induced BIS increases in anaesthetized humans. In this study, the effect of a single dose of atracurium on BIS values was assessed in dogs premedicated with morphine and anaesthetized with isoflurane (1 MAC). Fifteen female dogs undergoing elective ovariohysterectomy were employed. BIS values were recorded before and after the administration of atracurium. These values were then recorded again once the animals were surgically stimulated. The end tidal isoflurane concentration, cardiovascular and respiratory parameters were recorded through the study. Results show that the mean (±SD) BIS values decreased slightly, but significantly (P=0.033) from 67±8.42 to 65±5.84 after the administration of atracurium. Despite significant increase in heart rate and arterial pressure during the surgical phase, the mean BIS values were not modified by ovariohysterectomy. Atracurium appeared to have minimal clinical effect on the BIS in anaesthetized dogs.

Ventral ultrasound-guided suprainguinal approach to block the femoral nerve in the dog.

This prospective study assessed a ventral ultrasound-guided suprainguinal approach to block the femoral nerve (FN) in dogs. The anatomical features of the FN were evaluated in four canine cadavers. In another five cadavers, the FN was located by ultrasound-guidance and the accuracy of this technique was evaluated by injection of black ink and posterior evaluation of the degree of staining of the nerves. In five live dogs, the FN was blocked with 2% lidocaine. The distribution of lidocaine around the nerve and the presence of motor deficit were evaluated. The FN was easily located and accurately blocked in all cases. This new ultrasound-guided approach was reliable for blocking the FN and might be a suitable alternative to the traditional approaches described to block the FN in the dog.