Masatomo Tezuka's research while affiliated with Dokkyo Medical University and other places

To perform spinal anesthesia, patients are usually placed in the lateral decubitus position with the knees drawn up to the stomach, the legs fully flexed, and the neck flexed to curve the back outward. Because the nerve roots of the cauda equina have considerable mobility in the subarachnoid space, the position of the cauda equina in the lateral decubitus position may be different from that in the supine position. However, the anatomic position of the cauda equina in the lateral decubitus position with fully flexed legs has not been carefully studied. In the present study, we geometrically measured the movement of the cauda equina in the subarachnoid space by changing positions, using magnetic resonance imaging (MRI). After obtaining the approval of the hospital ethics committee and written informed consent, 12 healthy volunteers (age, 34 years [SD, 10 years]; height, 169 cm [SD, 9 cm]; weight, 65 kg [SD, 10 kg]) were studied with MRI, and their positions were changed as follows: the supine position, lateral decubitus position without fully flexed legs, and lateral decubitus position with fully flexed legs. The movement of the central point of the spinal cord and cauda equina by changing position was evaluated. The spinal cord and cauda equina were observed in the gravity-dependent side of the subarachnoid space in each position. The movement to the gravity-dependent side by changing position from the supine to the lateral decubitus position was significant (mean [SD] in millimeters: T11/12, 0.7 [0.4]; T12/L1, 1.5 [0.9]; L1/L2, 3.0 [1.0]; L2/L3, 3.4 [1.0]; L3/L4, 2.7 [0.9]; L4/L5, 2.0 [0.9]; L5/S1, 1.2 [0.7]; S1/S2, 0.5 [0.2]). The most obvious shift was observed at the L2/3 intervertebral space. The fully flexed legs significantly moved the spinal cord and cauda equina to the ventral side of the subarachnoid space and created a free space in the dorsal side. The movement to the ventral side by the fully flexed legs was significant (mean [SD] in millimeters: T11/12, 2.2 [1.0]; T12/L1, 4.1 [1.5]; L1/L2, 6.1 [0.5]; L2/L3, 5.4 [0.9]; L3/L4, 5.1 [1.9]; L4/L5, 4.4 [1.1]; L5/S1, 5.0 [0.9]; and S1/S2, 2.6 [0.9]). The most obvious shift was observed at the L1/2 intervertebral space. The present study using MRI showed dynamical movement of the spinal cord and cauda equina due to changing position. The most obvious movements by changing from supine to lateral decubitus position and fully flexed legs were observed at the L2/3 and L1/2 levels, respectively.

The spinal cord and cauda equina move in the subarachnoid space by changing positions. The subarachnoid space is compressed from the dorsal side by epidural injection. At the end of gestation, the subarachnoid space is compressed from the ventral side by the engorged venous plexus. Idiopathic epidural lipomatosis is observed almost exclusively in the obese population. In the case of lipomatosis, the subarachnoid space is compressed by increased extradural fat around the thecal sac. We have had some severe cases of spinal canal stenosis in whom it is difficult to perform the spinal puncture. The authors showed some MR images and discussed morphological issues for spinal or epidural anesthesia.

Background: Stellate ganglion block (SGB) with lidocaine has been widely used in the treatment of pain or peripheral vascular diseases. However, there are no reports on the appropriate concentration of lidocaine for SGB using animals.Aims: The aim of this study is to examine the optimal effective concentration of lidocaine for SGB in pigs.Methods: We measured mean arterial pressure (MAP), heart rate (HR), and right and left brachial artery blood flow (BABF) before and after left SGB in pigs. The experimental protocol was designed as follows: (1) Left SGB with physiological saline solution 1.0 ml (Group PSS; n = 8); (2) Left SGB with 0.25% lidocaine 1.0 ml (Group 0.25L; n = 8); (3) Left SGB with 0.5% lidocaine 1.0 ml (Group 0.5L; n = 8); (4) Left SGB with 1.0% lidocaine 1.0 ml (Group 1.0L; n = 8); (5) Left SGB with 2.0% lidocaine 1.0 ml (Group 2.0L; n = 8).Results: MAP and HR did not change significantly throughout the study in all groups. There were no significant differences on left BABF throughout the study in the Group PSS. In the Groups 0.25L, 0.5L, 1.0L and 2.0L, left BABF increased significantly from 5 through 10, 20, 30 and 30 min after the block, respectively. The left BABF in the Group 1.0L was significantly higher than in the Group 0.5L 5 and 10 min after the block. No significant differences were observed between the Groups 1.0L and 2.0L throughout the study.Conclusions: We demonstrated that 1.0% lidocaine is the optimal effective concentration for SGB.

The aim of this study is to compare 0.2% ropivacaine with 0.125% bupivacaine or 0.25% bupivacaine for the duration and magnitude of the vasodilation effect induced by sympathetic block. We measured mean arterial pressure, heart rate, and right and left brachial artery blood flow (BABF) before and after cervicothoracic sympathetic block in 24 dogs. The experimental protocol was designed as follows: (1) left cervicothoracic sympathetic block with 1.0 mL 0.2% ropivacaine (n =8), (2) left cervicothoracic sympathetic block with 1.0 mL 0.125% bupivacaine (n=8), and (3) left cervicothoracic sympathetic block with 1.0 mL 0.25% bupivacaine (n=8). Mean arterial pressure and heart rate did not change significantly throughout the study in either group. Left cervicothoracic sympathetic block with 0.2% ropivacaine increased left BABF significantly from 5 to 100 minutes after the block (baseline, 100%; peak at 10 minutes after the block, 254 +/- 38%; P <.01). Left cervicothoracic sympathetic block with 0.125% bupivacaine increased left BABF significantly from 5 to 80 minutes after the block (baseline, 100%; peak at 10 minutes after the block, 144 +/- 9%; P <.01). Left cervicothoracic sympathetic block with 0.25% bupivacaine increased left BABF significantly from 5 to 100 minutes after the block (baseline, 100%; peak at 10 minutes after the block, 235 +/- 61%; P <.01). Ropivacaine may be equally potent to bupivacaine at equal concentrations in sympathetic block in dogs.

The aim of this study was to examine the duration of vasodilation induced by sympathetic block with the addition of dexmedetomidine to mepivacaine. We measured right and left brachial artery blood flow (BABF) before and after stellate ganglion block used as a sympathetic block in dogs. The experimental protocol was designed as follows: (1) left stellate ganglion block using 1.0 mL 0.5% mepivacaine (n = 8), (2) left stellate ganglion block using the addition of dexmedetomidine 0.5 microg to 1.0 mL 0.5% mepivacaine (n = 8), and (3) left stellate ganglion block using the addition of dexmedetomidine 0.5 microg to 1.0 mL physiological saline solution (n = 8). Left stellate ganglion block with mepivacaine alone increased left BABF significantly from 5 minutes through 50 minutes after the block (baseline, 100%; peak at 10 minutes after SGB, 181 +/- 27%; P <.01). Left stellate ganglion block with the addition of dexmedetomidine to mepivacaine induced a significant increase of left BABF from 5 minutes through 90 minutes after the block (baseline, 100%; peak at 10 minutes after SGB, 174 +/- 36%; P <.01). Left and right BABF did not change significantly after stellate ganglion block with dexmedetomidine only. Right BABF decreased significantly after left stellate ganglion block with mepivacaine alone or the addition of dexmedetomidine to mepivacaine throughout the study. The addition of dexmedetomidine prolongs the duration of vasodilation induced by stellate ganglion block with mepivacaine used for sympathetic block in dogs.

A 68-year-old male with primary aldosteronism who was scheduled for electroconvulsive therapy (ECT). We used propofol and suxamethonium to induce anesthesia, and measured plasma levels of aldosterone to evaluate the influence of ECT during anesthesia. Although plasma levels of aldosterone increased gradually after ECT, there were no complications including severe hypertension or arrhythmia perioperatively.