Assessment of the tissue diffusion of anesthetic agent following administration of a low palmar nerve block in horses.

OBJECTIVE: To investigate tissue diffusion of anesthetic agent following administration of low palmar nerve blocks (LPBs) in horses. DESIGN: Randomized clinical trial. ANIMALS: 12 adult horses. PROCEDURES: In 9 horses, mepivacaine hydrochloride-iohexol (50:50 dilution) injections were administered bilaterally (2 or 4 mL/site) to affect the medial and lateral palmar and palmar metacarpal nerves (4 sites). Lateral radiographic views of both metacarpal regions were obtained before and at 5, 15, 30, 60, 90, and 120 minutes after block administration; proximal and distal extents of contrast medium (and presumably anesthetic agent) diffusion from palmar and palmar metacarpal injection sites were measured and summed to determine total diffusion. Methylene blue solution was injected in forelimbs of 3 other horses that were subsequently euthanized to determine the potential route of anesthetic agent diffusion to the proximal suspensory ligament region. RESULTS: Mean extents of proximal and total contrast medium diffusion were 4.0 and 6.6 cm, respectively, for the palmar metacarpal nerves and 4.3 and 7.1 cm, respectively, for the palmar nerves. Subtle proximal diffusion secondary to lymphatic drainage was evident in 17 of the 18 limbs. Contrast medium was detected in the metacarpophalangeal joint or within the digital flexor tendon sheath in 8 and 7 limbs, respectively. In the cadaver limbs, methylene blue solution did not extend to the proximal suspensory ligament region. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, LPBs resulted in minimal proximal diffusion of anesthetic agent from the injection sites. Limbs should be aseptically prepared prior to LPB administration because inadvertent intrasynovial injection may occur.

Clinical evaluation of the use of three anesthetics in endodontics.

This study compared three anesthetics widely used in endodontics and analyzed the following variables: amount necessary to achieve adequate anesthesia; anesthetic efficacy, defined as no sensation during endodontic treatment; anesthetic duration; and cost-benefit. Sixty patients diagnosed with irreversible pulpitis of a mandibular molar were selected at the Dental Emergency Center of Universidade de Fortaleza, Brazil. Patients were randomly divided into three groups of 20 and were administered one of three anesthetic solutions for conventional regional block: 2% lidocaine with 1:2500 phenylephrine; 2% mepivacaine with 1:100,000 adrenaline and 4% articaine with 1:100,000 epinephrine. The following variables were studied: number of cartridges necessary to obtain anesthetic success; anesthetic efficacy, defined as no sensation during endodontic procedures; anesthetic duration; cost-benefit ratio for each anesthetic. Mean number of cartridges necessary to obtain anesthetic success was 2.76, and there was no statistically significant difference between the anesthetics used. Lidocaine had the best cost-benefit ratio. All anesthetics used were clinically efficient and had equivalent results for endodontic treatment.

MR lymphangiography for the assessment of the lymphatic system in patients undergoing microsurgical reconstructions of lymphatic vessels.

OBJECTIVE: To assess the morphology of the lymphatic system pre- and postoperatively in patients undergoing microsurgical reconstructions of the lymphatic vessels. MATERIALS AND METHODS: 8 lower extremities in 4 consecutive patients with secondary unilateral lymphedema of the lower extremities were examined by MR lymphangiography. 18 mL of gadoteridol and 1 mL of mepivacainhydrochloride 1% were subdivided into 10 portions and injected intracutaneously into the dorsal aspect of each foot at the region of the four interdigital webs and medial to the first proximal phalanx. MR imaging was performed with a 1.5-T system equipped with high-performance gradients. For MR lymphangiography a 3D-spoiled gradient-echo sequence was used. For evaluation of the lymphedema a heavily T2-weighted 3D-TSE sequence was performed. RESULTS: In 2 patients the 3D-TSE sequence demonstrated a decrease of the epifascial lymphedema in the postoperative acquisitions, whereby MR lymphangiography displayed an improvement of dermal-back areas and collateral lymphatic vessels. In one patient the epifascial lymphedema of the lower extremity decreased, whereas the diameter of the lymphatic vessels showed a constant diameter of 2 mm. In one patient with a lymphocutaneous fistula at the level of the right groin, the feeding lymphatic vessels and contrast media extravasation could clearly be visualized. The 3D-TSE sequence demonstrated an epi- as well as subfascial lymphedema of the right leg. CONCLUSION: MR lymphangiography is a safe and accurate diagnostic imaging method for the pre- and postoperative evaluation of the lymphatic circulation in patients undergoing microlymphatic surgery. Due to the minimal-invasiveness and lack of radiation, diagnostic follow-up MR lymphangiography examinations can be performed routinely and with no risk for the patient.

Hemodynamic assessment of local anesthetic administration by laser Doppler flowmetry.

OBJECTIVE: The hemodynamic effects of local anesthetic administration with and without a vasoconstrictor were compared by using laser Doppler flowmetry. STUDY DESIGN: Seventeen people participated in a single study session in which they were given 2 intraoral injections. The injections, which were administered in random order, consisted of 1.8 mL lidocaine (2%) with epinephrine (1:100,000) and mepivacaine (3%). Hemodynamic parameters consisting of blood pressure, heart rate, and laser Doppler flowmetry were reordered at regular intervals. RESULTS: The laser Doppler flowmeter detected changes in the peripheral perfusion of the finger that were not detected by changes in blood pressure and heart rate. The greatest change was associated with anxiety and occurred just before the injection. The inclusion of epinephrine in the local anesthetic resulted in a persistence of these changes. CONCLUSION: This investigation has confirmed the sensitivity of laser Doppler flowmetry as an investigational tool for assessing hemodynamic changes associated with anxiety and the administration of local anesthesia.

Assessment of sensory block in epidural anaesthesia by electric stimulation.

The onset of sensory block in lumbar epidural anesthesia was investigated in 26 patients, aged 18 to 84 years, employing the loss of discrimination to cold and pinprick, as well as by determining threshold electric stimulation (threshold intensities). A standard dose of 2% mepivacaine with adrenaline, 5 micrograms.ml-1, (0.1 ml per cm body height) was given and the patients' ability to discriminate stimuli within dermatomes T8, T10, T12, L2, L4 and S1 was investigated at five min intervals for 30 min after injection. From the results of the study it is concluded that i) The interval to peak analgesic efficacy of the anaesthetic solution used is < 30 min when assessments are based on the patients' ability to discriminate cold or pinprick but > 30 min when determinations of threshold intensities are employed. ii) Cold discrimination is lost earlier than discrimination to pinprick and at lower threshold intensities. iii) Threshold intensities describe the time course of onset of sensory block more precisely than results of testing by cold or pinprick. iv) The onset of sensory block was found to be positively correlated to the age of patients in the following respects: a) Threshold intensities during early onset in all investigated dermatomes except L2. b) Intensity of block in T8, T10, and S1 at the end of the study period. c) Time to loss of discrimination to cold and pinprick in T12, L2 and S1, and d) Threshold intensities at loss of discrimination to cold and pinprick. We propose that determinations of threshold intensities offer distinct advantages over conventional testing by cold and pinprick discrimination, especially when detailed analyses of the sensory blocking effects of local anaesthetic drugs are being investigated.