Hisayoshi Tamai

Effect of Methylprednisolone on Neuropathic Pain and Spinal Glial Activation in Rats

Background: Basic data are lacking regarding the efficacy and mechanisms of action of corticosteroids in neuropathic pain. Because recent studies indicate that spinal glial activation mediates the pathologic pain states, the authors sought to determine the effects of systemic and intrathecal methylprednisolone on the development and maintenance of neuropathic pain and spinal glial activation in a rat model. Methods: Rats were anesthetized, and L5 and L6 spinal nerves were tightly ligated. Then, continuous infusion of systemic (4 mg · kg−1 · day−1) or intrathecal (80 μg · kg−1 · day−1) methylprednisolone or saline was started. Mechanical allodynia and thermal hyperalgesia were evaluated on days 4 and 7 postoperatively with von Frey and Hargreaves tests, respectively. Spinal astrocytic activation was evaluated with glial fibrillary acidic protein immunoreactivity on day 7. In other groups of rats, continuous 3-day treatment with intrathecal methylprednisolone or saline was started 7 days after spinal nerve ligation, when neuropathic pain had already developed. Behavioral tests and immunostaining were performed up to 3 weeks after the treatment. Results: Spinal nerve ligation induced mechanical allodynia and thermal hyperalgesia on days 4 and 7 postoperatively. Glial fibrillary acidic protein immunoreactivity was remarkably enhanced on day 7. Both systemic and intrathecal methylprednisolone inhibited the development of neuropathic pain states and glial activation. Three-day treatment with intrathecal methylprednisolone reversed existing neuropathic pain state and glial activation up to 3 weeks after the treatment. Conclusion: Systemic and intrathecal methylprednisolone inhibited spinal glial activation and the development and maintenance of a neuropathic pain state in a rat model of spinal nerve ligation.

Role for cyclooxygenase 2 in the development and maintenance of neuropathic pain and spinal glial activation

Background: Lines of evidence have indicated that cyclooxygenase 2 plays a role in the pathophysiology of neuropathic pain. However, the site and mechanism of its action are still unclear. Spinal glia has also been reported to mediate pathologic pain states. The authors evaluated the effect of continuous intrathecal or systemic cyclooxygenase-2 inhibitor on the development and maintenance of neuropathic pain and glial activation in a spinal nerve ligation model of rats. Methods: Continuous intrathecal infusion of meloxicam (32 or 320 &mgr;g · kg−1 · day−1) or saline was started immediately after L5–L6 spinal nerve ligation. Mechanical allodynia and thermal hyperalgesia were evaluated on days 4 and 7 postoperatively. Spinal astrocytic activation was evaluated with glial fibrially acidic protein immunoreactivity on day 7. In other groups of rats, continuous intrathecal meloxicam was started 7 days after spinal nerve ligation, and effects on established neuropathic pain and glial activation were evaluated. Last, effects of continuous systemic meloxicam (16 mg · kg−1 · day−1) on existing neuropathic pain and glial activation were examined. Results: Intrathecal meloxicam prevented the development of mechanical allodynia and thermal hyperalgesia induced by spinal nerve ligation. It also inhibited spinal glial activation responses. In contrast, when started 7 days after the nerve ligation, intrathecal meloxicam did not reverse established neuropathic pain and glial activation. Systemic meloxicam started 7 days after ligation partially reversed neuropathic behaviors but not glial activation. Conclusions: Spinal cyclooxygenase 2 mediates the development but not the maintenance of neuropathic pain and glial activation in rats. Peripheral cyclooxygenase 2 plays a part in the maintenance of neuropathic pain.

Thoracic epidural catheter insertion using the caudal approach assisted with an electrical nerve stimulator in young children

Objectives We evaluated whether thoracic epidural catheter placement using the caudal approach and assisted with an electrical stimulator could be performed in young children. Methods Ten young children (1-4 years) who underwent abdominal surgeries were studied. Under general anesthesia without muscle relaxants, caudal catheter placement was performed using an 18-gauge Crawford-type needle and a 20-gauge radiopaque epidural catheter with a stainless-steel stylet. A metal adapter and a 3-way stopcock were attached to the catheter to connect to an electrical stimulator and to inject physiological saline. Electrical stimulation was performed intermittently while advancing the catheter until it reached the target length. The catheter position was confirmed on postoperative roentgenogram. Results The mean age of the subjects was 32.2 ± 10.1 months (13-48 months), and the height was 85.3 ± 6.1 cm (72-93 cm). In 9 of 10 patients, an epidural catheter could be placed at the first insertion. In 1 patient, the catheter could be placed successfully at the second insertion. The electrical current required for muscle contraction at the target length was 5.8 ± 1.5 mA. Conclusion Electrical stimulation reliably indicated the location of the catheter tip. This technique for thoracic epidural catheter insertion was easy to perform and could be used in young children.

Serum and cerebrospinal fluid concentrations of midazolam after epidural administration in dogs.

UNLABELLED The epidural administration of midazolam has analgesic effects that might be mediated by gamma-aminobutyric acid type A receptors in the spinal cord. In this study, we examined both serum and cerebrospinal fluid (CSF) concentrations of midazolam after epidural administration to investigate the possibility of midazolam entering CSF directly from the epidural space. Five male mongrel dogs had catheters inserted in a femoral artery, the epidural space at L3-4, and the intrathecal space at the atlanto-occipital region under general anesthesia. Midazolam 1 mg/kg was epidurally administered, and arterial blood and CSF samples were collected until 240 min after the midazolam administration to measure midazolam concentration. Serum midazolam concentration increased and reached a peak at 30 min after the administration (224.8 +/- 30.5 ng/mL) and then decreased to 25.8 +/- 6.0 ng/mL at 240 min. Midazolam concentration in the CSF was less than the detection limit at 5 min, reached a peak at 30 min after the administration (7.2 +/- 4.7 ng/mL), and decreased to 3.6 +/- 3.3 ng/mL at 240 min. In conclusion, epidurally administered midazolam enters CSF, but CSF concentrations are only 3% of those in the systemic circulation. IMPLICATIONS Midazolam, which has spinally mediated analgesic potency, was epidurally administered in dogs, and serum and cerebrospinal fluid concentrations were measured. Epidurally administered midazolam enters the cerebrospinal fluid, but concentrations are only 3% of those in the systemic circulation.

The electrical properties of epidural catheters: what are the requirements for nerve stimulation guidance?

We designed the present study to investigate the electrical resistance of commercially available epidural catheters and to search for products and procedures suitable for nerve stimulation-guided insertion. Four types of epidural catheters were evaluated: 2 nonwire-reinforced catheters (19-gauge and 20-gauge nylon) and 2 wire-reinforced catheters (19-gauge without stylet and 20-gauge with stylet). The resistance of a catheter was calculated from the voltage level proportional to the fixed resistance in series circuit. In case of physiologic saline, the resistance of nonreinforced catheters was more than 700 k&OHgr;, whereas the wire-reinforced catheter was 14.4 ± 0.20 k&OHgr; without stylet and 10.1 ± 0.42 k&OHgr; with stylet. When the stylet was passed through a 20-gauge nylon catheter, the resistance decreased to 49.2 ± 1.96 k&OHgr;. When catheters were primed with 10% hypertonic saline, the resistance of both nonreinforced catheters decreased by one third compared with physiologic saline. The electrical resistance of the saline-filled epidural catheters significantly differed among products tested. We conclude that epidural catheterization that is guided by electrical stimulation should be performed only with catheters equipped with spiral stainless steel wire reinforcement or with a stainless steel stylet.

Reversible Tricuspid Valve Obstruction During Removal of Renal Cell Carcinoma with Intracardiac Tumor Extension

We report a case of reversible tricuspid valve (TV) obstruction during resection of renal cell carcinoma (RCC) with intracardiac tumor extension. Intraoperative transesophageal echocardiography (TEE) was useful in diagnosing this rare cause of hypotension and guiding surgical manipulation.

Optimal administration time of intramuscular midazolam premedication

The optimal administration time for intramuscular injection of midazolam as premedication was studied. Sixty patients ranging in age from 40 to 65 were included. A combination of atropine 0.3–0.5 mg and midazolam 0.08 mg·kg−1 was given to four groups of 15 subjects each in intramuscular injections 45, 30, 15 min, and immediately before entering the operating room. Blood pressure, heart rate, respiratory rate, depression of the root of the tongue, eyelash reflex, degree of sedation, and amnestic effect at the time of arriving the operating room were compared among the groups. There was no difference among the groups in blood pressure, heart rate, and respiratory rate. The depression of the root of the tongue, disappearance of verbal response, and eyelash reflex were found in the 30- and 45-min groups. The degree of sedation and amnestic effect were good except for the group who received midazolam immediately before entering the operating room. From the above results, intramuscular injection of midazolam 0.08 mg·kg−1 with atropine 0.3–0.5 mg is considered best when administered 15 min before entering the operating room.

Rapid induction with 7% sevoflurane inhalation-not the single-breath method.

The usefulness of the rapid anesthesia induction method with 7% sevoflurane, not the single-breath method, was investigated in 88 patients with ASA physical status 1. Anesthesia was induced with 3 l·min−1 nitrous oxide in 3 l·min−1 oxygen and sevoflurane 7% for 3 min (group A), 7% for 5 min (group B), 7% for 7 min (group C), and 5% for 7 min in conventional induction (group D). There were 22 patients in each group. Each sevoflurane concentration was given at the same time as the start of nitrous oxide inhalation except for group D. The changes in blood pressure and heart rate were the smallest in group A. The time for the loss of consciousness was shorter in groups A (47.2 s), B (44.9 s), and C (49.8 s) than in group D (73.4 s). During induction, body movements were seen in 18.2% in group A and 13.6% in the other 3 groups, but no other complications such as coughing, breath holding, or laryngospasm were seen in any group. In conclusion, the anesthesia induction method with 3 min of 7% sevoflurane inhalation was useful for rapid induction.

Sinus node dysfunction with interatrial conduction delay observed after left atrial myxoma resection through the superior septal approach

We report on a 64‐year‐old female patient who underwent cardiac surgery for left atrial myxoma, using the superior septal approach with large atrial septal wall resection and patch closure. The superior septal approach is reported to be a relatively safe method for preventing the development of sinus node dysfunction after cardiac surgery. However, this patient developed sinus node dysfunction after surgery and required the implantation of a permanent pacemaker. Moreover, in this case, determining the appropriate positions of the pacemaker leads was difficult because of the presence of a large conduction delay in the interatrium. Selecting the appropriate atrioventricular delay settings was important in order to achieve proper sequential contractions between the left atrium and the left ventricle.