Kaoru Hara

The interaction of antinociceptive effects of morphine and GABA receptor agonists within the rat spinal cord.

UNLABELLED Previous reports indicate that there may be an interaction between gamma-aminobutyric acid receptors and opioid receptors systems within the spinal cord, the antinociceptive effects of which have not been elucidated. We examined the effects of intrathecally coadministered morphine and muscimol or baclofen on somatic and visceral antinociception in rats. The tail flick (TF) test and colorectal distension (CD) test were used to assess somatic and visceral antinociceptive effects, respectively. Motor function was also assessed. The measurements were performed for 180 min after the intrathecal administration of morphine (0.1-10 micrograms), muscimol (0.2-10 micrograms), baclofen (0.03-1 microgram), combination of morphine and muscimol or baclofen, or saline. Morphine, muscimol, or baclofen increased both TF latency and CD threshold in a dose-dependent fashion. Although morphine 0.1 microgram, muscimol 0.2 microgram, or baclofen 0.03 microgram alone did not significantly increase TF latency and CD threshold, the combination of morphine 0.1 microgram and muscimol 0.2 microgram or baclofen 0.03 microgram significantly increased both TF latency and CD threshold. The coadministration of muscimol or baclofen increased the antinociceptive effects of morphine in intensity and duration. None of the rats showed motor dysfunction after the coadministration of morphine and muscimol 0.2 microgram, although muscimol produced motor paralysis of the lower limbs in a dose-dependent fashion. Those results suggest a clinical relevance of the coadministration of mu-opioids and GABA receptor agonists for pain control. IMPLICATIONS We examined the antinociceptive interaction between morphine and muscimol or baclofen at the spinal level in rats. Intrathecal muscimol or baclofen potentiated both somatic and visceral antinociceptive effects of morphine.

Ultrasound guided thoracic paravertebral block in breast surgery.

history of gradually worsening breathlessness and abdominal distension. She described dysphagia and a sensation of a mass at the back of her throat. Her symptoms were worse on lying flat. She had a history of hypothyroidism and Raynaud’s phenomenon, was taking thyroxine and was normally completely independent. Physical examination revealed a woman in obvious respiratory distress with marked inspiratory stridor, respiratory rate of 24 breaths. min and using her accessory muscles of respiration. Auscultation revealed no wheeze or crepitation. Arterial blood gases on 10 l.min oxygen revealed pH 7.38, PCO2 4.25 kPa, pO2 8.52 kPa. Abdominal examination revealed gross abdominal distension with normal bowel sounds. X-ray showed marked oesophageal and small bowel dilatation. Computerised Tomography of her chest and abdomen (Fig. 2) revealed oesophageal distension compressing the distal trachea. In the emergency department, she was treated with Heliox 28% and insertion of large-bore nasogastric tube with prompt resolution of symptoms. She made a good recovery and was followed up by the gastroenterology team. Oesphageal achalasia is an idiopathic motility disorder of the oesophagus, characterised by impaired relaxation of the lower oesophageal sphincter and oesophageal aperistalsis, with resultant dilatation of the oesophagus [1–3]. Respiratory complications can occur secondary to food regurgitation, with aspiration and respiratory tract infection as a result. Prompt recognition of this condition is critical to treatment, the mainstay of which is insertion of a nasogastric tube, although sublingual nitrates have been used with good effect. Definitive treatment includes endoscopic balloon dilatation of the lower oesophageal sphincter, surgical myotomy or botulinum toxin injection. Acute airway obstruction with stridor is a very rare presentation of achalasia. This case is highlighted to anaesthetists as they may be called upon to assess these patients in the accident and emergency department.

Incidence and Effects of Unintentional Intraneural Injection During Ultrasound-guided Subgluteal Sciatic Nerve Block

Background The present study was conducted to determine the incidence of unintentional intraneural injection during ultrasound-guided subgluteal sciatic nerve block using a low-frequency transducer. We also observed the effects of intraneural injection using ropivacaine and mepivacaine. Methods Enrolled in the study were 325 patients undergoing arthroscopic knee surgery, who each received a subgluteal sciatic nerve block under ultrasound guidance using 1.5% mepivacaine with 1:400,000 epinephrine or 0.5% ropivacaine. A block needle was inserted in-plane with the ultrasound transducer (5-2 MHz curved array) and advanced slowly under real-time ultrasound guidance until it was positioned immediately adjacent to the nerve. Twenty milliliters of either anesthetic was then injected to produce a circumferential spread. An ultrasound video was recorded and used to examine whether the local anesthetic was injected intraneurally. Sensory and motor blockade was evaluated for 30 mins after completion of the block. Duration of the block and any neurologic complications were also examined. Results Intraneural injection was detected in 46 patients (16.3%; 95% confidence interval, 12.3%–20.3%). Onset of sensory and motor blockade was significantly faster in patients with intraneural injection than those without either mepivacaine or ropivacaine. Duration of sensory blockade was similar between patients with and without intraneural injection. No patient developed postoperative neurologic complications. Conclusions Unintentional intraneural injection occurred at an incidence rate of 16.3% for the ultrasound-guided subgluteal approach to the sciatic nerve. Intraneural injection of mepivacaine or ropivacaine hastened the onset of blockade but did not affect block duration, and it did not result in clinical neural injury in our small sample of patients.

Ultrasound-guided anterior approach to sciatic nerve block: a comparison with the posterior approach.

BACKGROUND: Although the anterior approach to the sciatic nerve block has rarely been performed due to lack of reliable surface anatomical landmarks and technical difficulty, ultrasound guidance may make performance of this approach easier. In this study, we evaluated the clinical use of the ultrasound-guided anterior approach to sciatic nerve block and compared this approach with the posterior approach in adults. METHODS: One hundred patients undergoing minor knee surgery were randomly divided into two groups to receive anterior and posterior (subgluteal) approaches to sciatic nerve block, using 1.5% mepivacaine 20 mL with epinephrine combined with femoral and lateral femoral cutaneous nerve blocks. Both approaches to sciatic nerve block were performed using a low-frequency, 5 to 2 MHz, curved array transducer. Measurements included block execution time, depth and size of the nerve, needle depth, onset time of sensory and motor blockade, and duration of the block. RESULTS: The sciatic nerve was located significantly deeper and the needle depth was significantly greater in patients undergoing the anterior approach compared with the subgluteal approach. Both approaches were similar for execution time of sciatic nerve block, but the former took less time than the latter to perform all combinations of blocks. Although sensory block in the posterior femoral cutaneous nerve was achieved less often with the anterior approach compared with subgluteal approach (14.9% and 68.1%, respectively; P < 0.001), there were no differences in success rate, onset time or duration of blockade of the peroneal and tibial nerves between the two groups. CONCLUSION: The anterior approach to sciatic nerve block is performed as easily and successfully as the posterior approach using ultrasound guidance.

Epidural anesthesia and pulmonary function in a patient with amyotrophic lateral sclerosis

A myotrophic lateral sclerosis (ALS) is a degenerative disease of motor ganglia in the anterior horn of the spinal cord and spinal pyramidal tracts. Since the disease often involves atrophy and weakness of respiratory muscles resulting in respiratory failure and death, the anesthetic management of patients with ALS has been a controversial subject. General anesthesia may cause ventilatory depression due to abnormal responses to muscle relaxants (l-3). Regional anesthesia such as spinal and epidural anesthesia is also relatively contraindicated in patients with a motor neuron disease, including ALS, for the fear of exacerbating the disease (4,5). Although successful use of epidural anesthesia in the management of patients with this disease was reported recently (6), its effects on pulmonary function have not been discussed. We describe a case of ALS in which epidural anesthesia was successfully used for inguinal herniorrhaphy. Pulmonary function was examined, and no neurologic exacerbation was noted except for a temporal decrease in vital capacity (VC).

Spinal coadministration of ketamine reduces the development of tolerance to visceral as well as somatic antinociception during spinal morphine infusion.

This study was designed to investigate the effects of ketamine, an N-methyl-D-aspartate receptor antagonist, on the development of tolerance to morphine and morphine antinociception during intrathecal infusion. Two intrathecal catheters were implanted in the subarachnoid space in male rats under pentobarbital anesthesia. One catheter was used for the intrathecal infusion with the following solutions: morphine 1 &mgr;g · kg−1 · hr−1 (M1) and 5 &mgr;g · kg−1 · hr−1 (M5); ketamine 250 &mgr;g · kg−1 · hr−1 (K250); morphine plus ketamine, 1 &mgr;g · kg−1 · hr−1 plus 250 &mgr;g · kg−1 · hr−1 (M1 + K250) and 5 &mgr;g · kg−1 · hr−1 + 250 &mgr;g · kg−1 · hr−1 (M5 + K250); or saline. The other catheter was used for morphine challenge tests. The responses to noxious somatic and visceral stimuli were measured by tail flick (TF) and colorectal distension (CD) tests, respectively. Measurements were performed once a day for 7 days. Challenge tests with intrathecal morphine were performed to assess the magnitude of tolerance on Day 5 and Day 7. The antinociceptive effect was evaluated by using the percent of maximal possible effect (%MPE). Morphine infusion produced significant increases in %MPEs in TF and CD tests, while the saline and K250 infusions did not show any changes. The M1 + K250 infusion significantly increased the %MPEs in TF and CD tests, although the M1 and K250 infusions alone showed no changes. M5 + K250 enhanced the increases of %MPEs in TF and CD tests compared with the M5 infusion alone. In the challenge tests, the M1 + K250 infusion showed no significant decrease in %MPEs and TF and CD tests. The M5 + K250 infusion significantly inhibited those decreases in %MPEs, although the M5 infusion showed significant decreases in TF and CD tests. We concluded that ketamine attenuated the development of morphine tolerance to antinociceptive effects and increased the somatic and visceral antinociception of morphine. Implications Intrathecally co-infused ketamine attenuated morphine tolerance to somatic and visceral antinociception and increased morphine antinociception at the spinal level. These results suggest that a combination of morphine with ketamine may have an advantage in long-term use of opioids for controlling visceral as well as somatic pain.

The interaction between gamma-aminobutyric acid agonists and diltiazem in visceral antinociception in rats.

To examine whether the γ-aminobutyric acid (GABA) receptor agonists and L-type voltage-dependent calcium channel blockers potentiate each other on the visceral antinociceptive effects at the spinal cord, we assessed visceral nociception with colorectal distension (CD) test in rats with an intrathecal catheter. The measurements were performed after intrathecal administration of a GABA agonist (muscimol or baclofen), a calcium channel blocker (diltiazem), or the combination of the two. CD threshold did not change after muscimol 0.1 μg, baclofen 0.01 μg, or diltiazem 100 μg, but increased slightly after muscimol 1 μg and baclofen 0.1 μg. When muscimol 0.1 μg or 1 μg was administered with diltiazem, the increase in CD threshold was significantly larger than muscimol alone(at 5 min, 26.2% versus 0.6% MPE (maximum possible effect) or 84.5% versus 19.5%MPE, respectively; P < 0.01). The CD threshold after the combination of baclofen 0.1 μg and diltiazem also showed a significantly larger increase than that seen after baclofen alone (at 5 min, 48.0% versus 14.3% MPE; P < 0.01). Motor paralysis observed with muscimol 1 μg did not increase when muscimol was co-administered with diltiazem. In conclusion, intrathecal diltiazemin combination with a GABA agonist, muscimol or baclofen, potentiated the GABA agonists-induced visceral antinociception without increasing motor paralysis.

The non-NMDA glutamate receptor antagonist CNQX augments lidocaine antinociception through a spinal action in rats.

UNLABELLED Non-NMDA glutamate receptor antagonists produce antinociceptive effects, but the antinociceptive interaction between non-NMDA glutamate receptor antagonists and local anesthetics has not been demonstrated. We designed this study to evaluate the antinociceptive effects of a non-NMDA glutamate receptor antagonist and its interaction with lidocaine in rats. Intrathecal catheters were implanted at the L4-5 level in rats. The tail flick (TF) and colorectal distension (CD) tests were used to assess somatic and visceral antinociceptive effects, respectively. The TF latency and CD threshold were measured before and for 180 min after the intrathecal administration of lidocaine (20-100 micrograms), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (0.4-4.0 micrograms), a combination of CNQX (0.2-0.6 microgram) and lidocaine (10-30 micrograms), or isotonic sodium chloride solution. The TF latency and CD threshold were converted to the percent maximal possible effect (%MPE). To determine synergistic interaction, isobolographic analysis was used. Lidocaine or CNQX increased %MPEs in both the TF and CD tests. The coadministration of CNQX 0.4 microgram and lidocaine 20 micrograms, which had no effect by alone, significantly increased %MPEs in the TF and CD tests for 30 min and 10 min, respectively. Isobolographic analysis revealed the synergistic antinociception of CNQX and lidocaine in the TF test. Motor impairment was not observed after that combination. We conclude that CNQX and lidocaine produce synergistic analgesia on somatic and visceral pain at the spinal level. IMPLICATIONS We investigated the antinociceptive effects of 6-cyano-7-nitroquinoxaline-2,3-dione and its interaction with lidocaine at the spinal level in rats. Intrathecal 6-cyano-7-nitroquinoxaline-2,3-dione produced both somatic and visceral antinociception, and its coadministration with lidocaine showed synergistic antinociceptive effects.

The assessment of dermatomal level of surgical anesthesia after spinal tetracaine.

Transcutaneous electrical stimulation (TES), a 60-mA, 50-Hz continuous square wave, has been considered equivalent to surgical incision. We examined whether TES at a smaller current (10 mA) can be used to predict surgical anesthesia and compare the results with sensory block to cold, pinprick, and touch after the administration of spinal tetracaine. Two groups of 40 consecutive patients, 17–69 yr old and 70 yr old or older received a subarachnoid injection of 0.5% tetracaine in 10% glucose or saline according to the type of surgery. Patients undergoing abdominal surgery received glucose solution, and those scheduled for lower extremities surgery received saline solution, and thus, the resultant four groups of patients were studied. Neural block was assessed by the loss of sensation to cold, pinprick, touch, and TES at 10 mA (T10s), and tolerance (i.e., the loss of pain or discomfort) to TES at 10 (T10p) and 60 (T60) mA. Dermatomal levels of sensory block to cold, pinprick, and touch that were cephalad to T60 varied widely. In contrast, dermatomal levels of T10s and T10p cephalad to T60 were less variable, and the difference between T10s and T60 was the smallest among all the differences in any groups. Our results demonstrate that, regardless of patient age and baricity of a local anesthetic solution, T10s is a good predictor of T60 equivalent to the dermatomal level of surgical anesthesia. Implications Our results show that the loss of sensation to transcutaneous electrical stimulation at 10 mA, but not cold, pinprick, or touch, is a good predictor of the dermatomal level of block to transcutaneous electrical stimulation at 60 mA, which is considered equivalent to the dermatomal level of surgical anesthesia after the administration of spinal anesthesia.

Anaesthetic management of Caesarean section in a patient with Myelodysplastic Syndrome

PurposeThis case report describes the anaesthetic management for Caesarean section in a patient with myelodysplastic syndrome.Clinical featuresA woman with myelodysplastic syndrome underwent Caesarean section on two occasions. The first Caesarean section was performed at age 20 yr using general anaesthesia with nitrous oxide-oxygen and fentanyl. In her second pregnancy at 25 yr, there was severe pancytopenia at 28-wk gestation with a leukocyte count 3.6 × 109·L−1, erythrocyte count 1.2 × 1012·L−1, haemoglobin 50 g·L−1, haematocrit 14.7% and platelet count 5l × 109·L−1, Following leukocyte poor red celts and platelet transfusion, general anaesthesia was maintained with nitrous oxide-oxygen-sevoflurane and fentanyl. Both operations were uneventful and healthy infants were delivered.ConclusionIt is important to have a team approach (anaesthetist, obstetrician and haematologist) for the perianaesthetic management of patients with myelodysplastic syndrome. An exact assessment of the haematological condition, the need for prophylactic treatment and anaesthetic management should be determined for each individual patient.RésuméObjectifRapporter la prise en charge anesthésique pour césarienne d’une patiente présentant un syndrome myélodysplasique.Eléments cliniquesUne patiente présentant un syndrome myélodysplasique a subi deux césariennes. La première, à l’âge de 20 ans, fut réalisée sous anesthésie générale avec N2O —oxygène et fentanyl. La seconde grossesse, à l’âge de 25 ans, s’est compliquée d’une pancytopénie sévère à 28 semaines de gestation : les leucocytes étaient à 3,6 × 109·L−1, les érythrocytes à 1,2 × 1012·L−1, le taux d’hémoglobine à 50 g·L−1, l’hématocrite à 14,7% et les plaquettes à 51 × 109·L−1. Suite à des transfusions d’érythrocytes déleucocytés et de plaquettes, une césarienne fut réalisée sous anesthésie générale avec N2O — oxygène, sevoflurane et fentanyl. Les deux interventions se sont déroulées sans problème et des nouveaux-nés en bonne santé sont nés.ConclusionIl est important d’avoir une approche d’équipe multidisciplinaire (anesthésiste, obstétricien, hématologiste) pour la prise en charge périanesthésique de patients avec syndrome myélodysplasique. Une évaluation précise de la condition hématologique, la nécessité de traitements prophylactiques et le choix de la technique anesthésique doivent être adaptés à chaque patient.