Routes and doses of lignocaine hydrochloride for analgesia of the velvet antler of stags

AIM: To evaluate the effectiveness of various routes of administration and doses of local anaesthetic to provide analgesia of the velvet antler of young stags. METHODS: In study 1, in which an electrical stimulus was used, 64 l-year-old male red and red X wapiti deer with velvet antler lo-30 cm long, were randomly allocated to one of ten treatments with four treatments/animal, and 23 or 24 antlers/treatment. Treatments delivered included three control groups, three local anaesthetic (2% lignocaine HCL) doses delivered by ring block (5, 10 or 15 ml per pedicle), and a high or low regional block with or without an auriculopalpebral nerve block (5 ml per site). An electrical stimulus was applied before and 1,2,4 and 8 minutes after local anaesthetic treatments and to controls, at an increasing voltage until a response was observed. The voltage and animal responses were recorded. In Study 2 the same seven local anaesthetic treatments (16-I 8 antlers/treatment) were evaluated using 58 of the stags from Study 1 when antlers were ready for removal, but a saw cut was used as the test stimulus. A test cut was applied to the antler I,2 and 4 minutes after application of local anaesthetic. If no response was observed, the antler was removed at that time. RESULTS: In Study 1, major dose and treatment effects were significantly different (p < 0.05) with the outcome variable being whether or not the deer responded. No stags given the high dose ring block responded to electrical stimulation 1 minute after treatment, one responded at 2 minutes, and none responded at 4 or 8 minutes. At least one animal responded after all other treatments at all time intervals. More deer responded after the low regional block than the high regional block, and there was a lower response rate when the auriculopalpebral nerves were anaesthetised. In Study 2, no deer responded 2 minutes after the medium dose ring block treatment. Three of 18 stags receiving the high dose ring block still responded after 2 minutes, and one responded after 4 minutes. Responses occurred to all other treatments at each time, with some deer requiring further administration of local anaesthetic before antler removal, even with the four minute waiting period. CONCLUSION: Ring blocks produced more consistent analgesia of the velvet antler than regional nerve blocks. The high dose ring block produced analgesia faster and more effectively than lower doses, and the regional nerve blocks were more effective when the auriculopalpebral nerve was blocked.     

Ultrasonographic guided block of the median nerve

Median nerve anaesthesia is sometimes indicated in the diagnosis of forelimb lameness in the horse in conjunction with the ulnar nerve block, but the localisation of the nerve to perform a precise deposition of the anaesthetic solution around and close to the nerve is difficult to achieve using the conventional blind technique. The objectives of this paper are to describe the ultrasonographic anatomy of the median nerve and the technique for performing an ultrasound-guided anaesthetic block of the nerve. The median nerve is imaged using a microconvex (or linear) probe in transverse section performed proximally to the chestnut on the medial aspect of the forearm. Distribution of the anaesthetic solution around the nerve is done by initially inserting the needle caudally and then cranially to the nerve and injecting 4–6 mL at each site. Control of the needle penetration avoids erroneous intravascular or intramuscular injections or sudden horse reaction. Ultrasound-guided injection has the potential to safely and accurately block the median nerve.     

The use of a nerve stimulation test to confirm sacrococcygeal epidural needle placement in cats

ObjectiveTo determine if a nerve stimulation test (NST) could act as a monitoring technique to confirm sacrococcygeal epidural needle placement in cats.Study designProspective experimental trial in a clinical setting.AnimalsTwenty-four adult cats, scheduled for a therapeutic procedure where epidural anesthesia was indicated.MethodsUnder general anesthesia, an insulated needle was inserted through the S₃-Cd₁ intervertebral space guided by the application of a fixed electrical current (0.7 mA) until a motor response was obtained. The NST was considered positive when the epidural nerve stimulation produced a motor response of the muscles of the tail, whereas it was considered negative when no motor response was evoked. In the NST positive cases, 0.3 mL kg⁻¹ of 0.5% bupivacaine was administrated before needle withdrawal. Ten minutes after injection, epidural blockade was confirmed by the loss of perineal (anal), and pelvic limbs reflexes (patellar and withdrawal).ResultsThe use of a fixed electrical stimulation current of 0.7 mA resulted in correct prediction of sacrococcygeal epidural injection, corroborated by post bupivacaine loss of perineal and pelvic limb reflexes, in 95.8% of the cases.Conclusion and clinical relevanceThis study demonstrates the feasibility of using, in a clinical setting, an electrical stimulation test as an objective and in real-time method to confirm sacrococcygeal epidural needle placement in cats.     

Ultrasonographic guided block of the tibial nerve

Tibial nerve anaesthesia is often utilised in the diagnostic evaluation of hindlimb lameness, but effective analgesia is sometimes difficult to achieve using a blind injection. The objectives of this paper are to describe the ultrasonographic anatomy of the caudomedial aspect of the superficial caudal crural compartment containing the tibial nerve and to describe a technique to perform an ultrasonographic guided block of this nerve. The tibial nerve is imaged by the use of a microconvex probe on a transverse section of the caudomedial part of the crus made approximately 8–10 cm proximal to the point of the hock. The needle is first inserted caudally to the probe, through the superficial caudal crural fascia, directed to the caudal aspect of the nerve where half of the volume of anaesthetic solution is injected (5–8 mL). A second injection is made similarly, cranial to the probe. Ultrasonographic guided injection of the tibial nerve increases accuracy of the nerve block by avoiding erroneous intravascular injections or injections under the deep caudal crural fascia that reduces diffusion of the anaesthetic solution. As deposit of anaesthetic solution can be done closer to the nerve, specificity of the block increases with quicker anaesthesia of the distal part of the limb. In addition, a smaller volume of anaesthetic solution (10–12 mL) can be used, thereby reducing the risk of proximal diffusion.     

Preliminary investigation of somatosensory evoked potentials in equine headshaking

The aim of this study was to develop a technique for recording electrical activity of the equine cerebral cortex following application of a noxious electrical stimulus to the maxillary branch of the trigeminal nerve in order to investigate trigeminal nerve neurophysiology in control and headshaking horses. Triphasic somatosensory evoked potentials (SEPs) were recorded using subcutaneous needle electrodes in four control and four headshaking horses under general anaesthesia. Dural electroencephalography electrodes were used to record SEPs in one further control and one further headshaking horse. Headshaking horses appeared to have decreased middle latency and inter-peak intervals following stimulation of the trigeminal nerve compared with control horses, supporting abnormal trigeminal nerve physiology in equine headshaking.     

The use of electrical stimulation to guide epidural and intrathecal needle advancement at the L5‐L6 intervertebral space in dogs

ObjectiveTo determine the minimal electrical threshold (MET) necessary to elicit appropriate muscle contraction when the tip of an insulated needle is positioned epidurally or intrathecally at the L_5-6 intervertebral space (phase-I) and to determine whether the application of a fixed electrical current during its advancement could indicate needle entry into the intrathecal space (phase-II) in dogs.Study designProspective, blinded study.AnimalsThirteen (phase-I) and seventeen (phase-II) dogs, scheduled for a surgical procedure where L_5-6 intrathecal administration was indicated.MethodsUnder general anesthesia, an insulated needle was first inserted into the L_5-6 epidural space and secondly into the intrathecal space and the MET necessary to obtain a muscular contraction of the pelvic limb or tail at each site was determined (phase-I). Under similar conditions, in dogs of phase-II an insulated needle was inserted through the L_5-6 intervertebral space guided by the use of a fixed electrical current (0.8 mA) until muscular contraction of the pelvic limb or tail was obtained. Intrathecal needle placement was confirmed by either free flow of cerebrospinal fluid (CSF) or myelography.ResultsThe current required to elicit a motor response was significantly lower (p < 0.0001) when the tip of the needle was in the intrathecal space (0.48 ± 0.10 mA) than when it was located epidurally (2.56 ± 0.57). The use of a fixed electrical stimulation current of 0.8 mA resulted in correct prediction of intrathecal injection, corroborated by either free flow of CSF (n = 12) or iohexol distribution pattern (n = 5), in 100% of the cases.Conclusion and clinical relevanceNerve stimulation may be employed as a tool to distinguish epidural from intrathecal insulated needle position at the L_5-6 intervertebral space in dogs. This study demonstrates the feasibility of using an electrical stimulation test to confirm intrathecal needle position in dogs.     

Confirmation of epidural needle placement using nerve stimulation in dogs

Caudal epidural anesthesia is useful when anesthesia of the lumbar and sacral dermatomes is needed. Its success relies on the proper placement of the needle in the epidural space. However, accurate positioning of the needle can be difficult in certain patients (i.e.obesity). The purpose of this preliminary study was to document the use of nerve stimulation as a means of confirming accurate needle positioning in the epidural space prior to drug administration. Twenty large breed dogs undergoing hindlimb or perineal surgery were enrolled. Following induction of general anesthesia, patients were prepared for routine epidural drug administration. A 17 ga, 3.5” shielded Tuohy needle was used and was connected to a peripheral nerve stimulator set to deliver a current at 1 Hz, with a pulse width of 0.2 m sec. Initial current was set at 1.2 mA as the needle was advanced into position. Confirmation of epidural needle placement was confirmed when twitches were observed in the hindlimbs and/or tail. Current setting was then decreased incrementally by 0.2 mA until no further twitches were observed. Success of epidural drug placement was confirmed subjectively by motor blockade to the blocked dermatomes and clinical signs of balanced anesthesia (lack of sympathetic response to surgical stimulation while maintained at light plane of anesthesia). Lowest mean (range) current to elicit hindlimb twitches was 0.72 mA (0.4–1.0 mA). Lowest mean (range) current to elicit tail twitches was 0.58 mA (0.4–1.0 mA). Tail twitches were reliably lost at mean current of 0.37 mA (0.2–0.8). Epidural anesthesia was considered to be successful in 19/20 dogs. In only 9/20 dogs, needle placement would have been correct based on using ‘classic’ indicators alone (‘pop’ as enter epidural space, loss of resistance to injection). The results of this study suggest that nerve stimulation may be useful in confirming correct epidural needle placement prior to drug administration.     

Influence of electrical stimulation on regeneration of the radial nerve in dogs

The effects of biphasic electric fields on nerve regeneration that follows injury to the left radial nerve were studied in dogs by electromyography (EMG). Left and right radial nerves were crushed with a serrated haemostat. Stimulating electrodes were positioned proximally and distally to the site of the injury. The left nerves received rectangular, biphasic and current pulses (30 microA, 0.5 Hz) through the injury for two months. The right radial nerves were treated as controls and regenerated without electrical stimulation. EMG activities were recorded intramuscularly from the left and right musculus extensor digitalis communis (MEDC). Results obtained at the end of the two-month stimulation period showed a significant difference in EMG activity between the left (stimulated) and the right (non-stimulated) MEDC, suggesting that electrical treatment enhanced nerve regeneration.     

Nerve stimulator‐guided sciatic‐femoral nerve block in raptors undergoing surgical treatment of pododermatitis

ObjectiveTo describe the nerve stimulator-guided sciatic-femoral nerve block in raptors undergoing surgical treatment of pododermatitis.Study designProspective clinical trial.AnimalsFive captive raptors (Falco peregrinus) aged 6.7 ± 1.3 years.MethodsAnaesthesia was induced and maintained with isoflurane in oxygen. The sciatic-femoral nerve block was performed with 2% lidocaine (0.05 mL kg⁻¹ per nerve) as the sole intra-operative analgesic treatment. Intraoperative physiological variables were recorded every 10 minutes from endotracheal intubation until the end of anaesthesia. Assessment of intraoperative nociception was based on changes in physiological variables above baseline values, while evaluation of postoperative pain relied on species-specific behavioural indicators.ResultsThe sciatic-femoral nerve block was feasible in raptors and the motor responses following electrical stimulation of both nerves were consistent with those reported in mammalian species. During surgery no rescue analgesia was required. The anaesthesia plane was stable and cardiorespiratory variables did not increase significantly in response to surgical stimulation. Iatrogenic complications, namely nerve damage and local anaesthetic toxicity, did not occur. Recovery was smooth and uneventful. The duration (mean ± SD) of the analgesic effect provided by the nerve block was 130 ± 20 minutes.Conclusion and clinical relevanceThe sciatic-femoral nerve block as described in dogs and rabbits can be performed in raptors as well. Further clinical trials with a control groups are required to better investigate the analgesic efficacy and the safety of this technique in raptors.     

A new method for recording H-reflexes from the plantar muscles of dogs

H-reflexes were recorded consistently from the plantar muscles of pentobarbitone-anaesthetised dogs following supramaximal stimulation of the caudal cutaneous sural nerve (CCSN). As the amplitude, shape and latency of successive H-reflex potentials fluctuated from trial to trial, 16 consecutive sweeps were averaged to quantify the response. The averaged H-reflex had an amplitude of 1–6 ± 0–9 mV (mean ± SD] and a latency of 20 ± 2 ms. The CCSN-evoked H-reflex was recorded together with the CCSN-evoked compound muscle action potential (SurCMAP), which had a shorter latency (6 ± 1 ms) but comparable size (1–9 ± 1–3 mV). H-reflex afferents in the CCSN had overlapping but slightly higher electrical thresholds than plantar motoneurone axons. A ‘pure’ H-reflex could be obtained by injecting local anaesthetic below the site of nerve stimulation. Halothane/nitrous oxide anaesthesia substantially reduced the amplitude of H-reflex potentials in a reversible fashion.     

Electrically elicited blink reflex in horses with trigeminal and facial nerve blocks

OBJECTIVE: To reassess reference values for the components of the electrically induced blink reflex, document reference values for facial motor nerve conduction velocity, and demonstrate usefulness of the blink reflex as a diagnostic tool in peripheral facial and trigeminal nerve dysfunction in horses. ANIMALS: 10 healthy adult horses (8 males, 2 females) without neurologic abnormalities. PROCEDURE: Blink reflex tests were performed by electrical stimulation of the supraorbital nerve and facial (auriculopalpebral) nerve. Reflex and direct muscle-evoked potentials of the orbicularis oculi muscles were recorded from concentric needle electrodes inserted bilaterally in these muscles. Supraorbital and auriculopalpebral nerve blocks were performed by lidocaine hydrochloride injections. RESULTS: Supraorbital nerve stimulation elicited 2 or 3 ipsilateral and 1 contralateral reflex muscle potential in the orbicularis oculi muscles. Auriculopalpebral nerve stimulation elicited a direct and a reflex potential in the ipsilateral orbicularis oculi muscle. After left supraorbital nerve block, no responses could be elicited ipsilaterally or contralaterally upon stimulation of the blocked nerve, but bilateral responses were obtained upon stimulation of the right supraorbital nerve. After right auriculopalpebral nerve block, no responses were recorded from the right orbicularis oculi muscle upon stimulation of left or right supraorbital nerves. CONCLUSIONS AND CLINICAL RELEVANCE: Reference values for the components of the blink reflex and facial motor nerve conduction velocity will allow application of these tests to assist in the diagnosis of equine neurologic disorders involving the trigeminal and facial nerves, the brainstem, and the cranial end of the cervical segment of the spinal cord. This study reveals the usefulness of the blink reflex test in the diagnosis of peripheral trigeminal and facial nerve dysfunction in horses.     

Peripheral nerve stimulation under ultrasonographic control to determine the needle‐to‐nerve relationship

ObjectiveTo determine the needle‐to‐nerve distances during electrical nerve location in dogs at different currents and pulse duration using a peripheral nerve stimulator (PNS) under ultrasound control (US), and the minimal electrical thresholds (MET) necessary to obtain a motor response (MR) after achieving needle‐to‐nerve contact.Study designProspective in vivo experimental trial in a clinical settingAnimalsThirty dogs, scheduled for locoregional anaesthesia of the sciatic nerve.MethodsNeedle‐to‐nerve distance was measured ultrasonographically after obtaining the MR of sciatic nerve with 2, 1 and 0.5 mA and pulse duration 0.1 ms (NS0.1). Thereafter the needle was placed in contact with the nerve and MET was determined. The procedure was repeated with 0.3 ms (NS0.3). Finally the needle was reintroduced to contact the sciatic nerve guided only by US, thus MET‐US was determined. Data were analysed using Kruskal–Wallis or Mann–Whitney tests.ResultsNeedle‐to‐nerve distances were greater when MR was obtained with 2 mA than with 1 and 0.5 mA at 0.1 and 0.3 ms. No significant differences were observed between the needle‐to‐nerve distances using 0.1 or 0.3 ms.The MET [median (range)] was 0.4 (0.18–1.3) mA in NS0.1, 0.32 (0.12–0.8) mA in NS0.3; while MET‐US was 0.7 (0.32–1.5) mA. When the needle contacted the nerve, the MR achieved with currents below 0.3 mA was obtained in 17.2, 40 and 0% of cases using NS0.1, NS0.3 and US respectively.Conclusions and clinical relevanceThe electrical current necessary to obtain a MR decreased as the needle moved towards the nerve. However when the needle tip contacted the nerve, an MR with low current intensity could not be obtained. Thus the absence of motor response at currents below 0.3 mA cannot rule out needle‐epineurium contact. When ultrasound is combined with PNS, it is more important to assess the correct needle position than searching for an MR at low currents.     

Transcranial magnetic stimulation of the motor cortex and percutaneous magnetic stimulation of the peripheral nervous structures in the dog

The motor cortex was transcranially and peripheral nervous structures (motor roots, plexus, peripheral nerves) were percutaneously stimulated by magnetic pulses in awake dogs and in dogs awaking from general anesthesia. The compound muscle action potentials were recorded by surface or needle electrodes. The central motor conduction time as an information about central motor tracts was obtained by subtracting the peripheral latency from the corticomuscular latency. The peripheral latency was assessed by high voltage electrical and magnetic stimulation of motor roots and by the F-wave technique. The motor conduction velocity of the tibial nerve was measured by percutaneous magnetic and by electrical stimulation and the resulting values were compared.     

Electrophysiologic studies of the facial reflexes of the dog

Reflexes associated with the trigeminal and facial nerves were investigated electromyographically in 14 barbiturate-anesthetized dogs. Using subcutaneous needle electrodes, electrical stimulation of the infraorbital, frontal, and zygomaticofacial branches of the trigeminal nerve produced reflex contractions of the ipsilateral orbicularis oculi muscle. Cutaneous and subcutaneous electrical stimulation of the internal auricular branches of the facial nerve also produced reflex contractions of the ipsilateral orbicularis oculi muscle. After sectioning of this branch between the vagus and facial nerves, electrical stimulation of the proximal portion of the auricular branch of the vagus nerve produced reflex contractions of the ipsilateral orbicularis oculi muscle. After sectioning of the auricular branch of the vagus nerve; electrical stimulation of the proximal portion of the caudal and middle internal auricular nerves did not produce reflex contractions of the ipsilateral orbicularis oculi muscle. Subcutaneous electrical stimulation of the palpebral nerve produced reflex contractions and direct-evoked muscle activity of the orbicularis oculi muscle. Subcutaneous electrical stimulation of the infraorbital and middle mental nerves produced reflex contractions of the rostral belly of the digastricus muscle.     

Assessment of motor pathways by magnetic stimulation in human and veterinary medicine

Magnetic stimulation is a non-invasive and painless technique for studying the motor pathways in medical neurology. A time-varying magnetic field induces an electrical field in conducting objects, such as nervous tissue. The technique can be applied to nerve roots and peripheral nerves or to the motor cortex of the brain in human and veterinary medicine. In this review, the basic principles, applications and risk factors of peripheral nerve and motor cortex stimulation in human and veterinary medicine are discussed.     

Electrical stimulation of lumbar spinal nerve roots in dogs

The aim of this study was to test the applicability of electrical stimulation of lumbar spinal nerve roots and obtain normative electrical root stimulation (ERS) data for L7 nerve root and sciatic nerve in dogs. For that purpose ERS and sciatic nerve stimulations were performed consecutively, in totally 40 healthy dogs. ERS was applied in the L7/S1 intervertebral space via monopolar needle electrodes. Muscle responses were recorded from the gastrocnemius muscles on the left and right hind limbs. Sciatic nerve stimulation was performed at the greater trochanter level on the left hind limb, with records obtained from the left gastrocnemius muscle. Mean root latencies of the left and right side were 5.22?±?0.49 ms and 5.29?±?0.53 ms, respectively. There was no significant difference in root latency between the right and left sides. The mean terminal latency was 3.82?±?0.46 ms. The proximal motor nerve conduction velocity of the sciatic nerve was 63.15?±?3.43 m/s. The results of this study show that ERS provides objective data about the integrity of lumbar spinal nerve roots by evaluating the entire population of motor fibres and total length of the motor axon in dogs. ERS can be considered a useful diagnostic method for confirmation of diagnoses of lumbosacral diseases.     

Electrically induced blink reflex and facial motor nerve stimulation in beagles

Electrophysiologic assessment of the blink reflex test and the muscle-evoked potentials evoked by stimulation of the facial nerve were performed in 15 healthy adult Beagles before and after supraorbital (trigeminal) and facial anesthetic nerve blocks performed by lidocaine injections. Unilateral electrical stimulation of the supraorbital nerve elicited 2 ipsilateral (R1 and R2) and a contralateral (Rc) reflex muscle potential in orbicularis oculi muscles. Electrical stimulation of the facial nerve elicited 2 muscle potentials (a direct response [D] and a reflex faciofacial response [RF]) in the ipsilateral orbicularis oculi muscle. Anesthetic block of the left supraorbital nerve resulted in bilateral lack of responses upon left supraorbital nerve stimulation, but normal responses in right and left orbicularis oculi muscles upon right supraorbital stimulation. Right facial anesthetic block produced lack of responses in the right orbicularis oculi muscle regardless the side of supraorbital nerve stimulation. Results of this study demonstrate that the blink reflex can be electrically elicited and assessed in dogs. Reference values for the blink reflex responses and for the muscle potentials evoked by direct facial nerve stimulation in dogs are provided. The potential usefulness of the electrically elicited blink reflex test in the diagnosis of peripheral facial and trigeminal dysfunction in dogs was demonstrated.     

Use of needle enhancing software to improve injection technique amongst inexperienced anaesthetists performing ultrasound‐guided peripheral nerves blocks in dogs

ObjectiveTo determine if the use of needle enhancing software facilitate injection technique in ultrasound‐guided peripheral nerve blocks.Study designProspective, blinded, randomized controlled trial.AnimalsEight hind limbs from canine cadavers.MethodsThe limbs were randomly allocated to two groups; software on (group I) and software off (group II). Eight anaesthetists with no previous experience of ultrasound‐guided regional anaesthesia were recruited. Thirty‐six procedures were carried out (18 per group). After sciatic nerve visualisation via ultrasonography, the anaesthetist introduced a needle guided by ultrasonography. When the tip of the needle was considered by the anaesthetist to be as close as possible to the nerve without touching it, 0.05 mL of methylene blue dye was injected. Parameters evaluated included: number of attempts to visualise the needle with ultrasonography, time spent to perform the technique, subjective evaluation of ease of needle visualisation, proximity of the tip of the needle to the nerve, and, at dissection of the leg, inoculation site of the dye in relation to the nerve.ResultsSignificant differences between groups were identified in relation to the number of attempts (group I: median 1, IQR: 1 – 1 attempts versus group II: median 1, IQR: 1 – 4 attempts, p = 0.019), and the relationship between the dye and the nerve during hind limb dissection (72.2% of the nerves were stained in group I versus 16.6% in group II,p = 0.003). No significant difference between groups was observed with respect to the time taken to perform the procedure (group I: median 25.5, IQR: 18.4 – 44.3 seconds versus group II: median 35.7, IQR: 18.6–78.72 seconds, p = 0.31), subjective evaluation of the needle visualization (p = 0.45) or distance between the tip of the needle and the nerve as measured from the ultrasound screen (p = 0.23).Conclusions and clinical relevanceThis study identified greater success rate in nerve staining when the needle enhancing software was used. The results suggest that the use of this technique could improve injection technique amongst inexperienced anaesthetists performing ultrasound‐guided peripheral nerve blocks in dogs.     

Local anaesthetics for regional and intra-articular analgesia in the horse

During the course of a lameness examination, intra-articular or perineural administration of a local anaesthetic is often necessary to isolate the source of pain causing lameness. Local anaesthetics are useful for intraoperative and post-operative pain relief and may allow for elimination of, or a decrease in, general anaesthesia. Within recent years, new information has become available concerning the use of local anaesthetics for localisation of pain and for palliation of pain. New information indicates that

• Lidocaine is less efficacious than mepivacaine or ropivacaine in ameliorating lameness caused by pain.
• After administering a nerve block, loss of skin sensation may not correlate with loss of pain causing lameness.
• Local anaesthetic solution must be deposited within the sheath of the neurovascular bundle to be effective.
• The dose of a local anaesthetic, which is a factor of volume and concentration, affects potency and duration of a nerve block.
• Local anaesthetics are toxic to chondrocytes and synoviocytes. Lidocaine and bupivacaine appear to be more toxic than mepivacaine or ropivacaine. The clinical significance of the toxic effect of a single intra-articular injection of local anaesthetic is yet to be determined.
• Sodium bicarbonate can be added to a local anaesthetic solution to increase its potency and speed of onset.
• Epinephrine added to local anaesthetic solution prolongs and intensifies its analgesic effect.
• Mixing quick-acting, short-duration and slow-acting, long-duration local anaesthetics will not result in a quick-acting, long-duration drug combination.