Sensory blockade of S3 dermatome prevents pain during bladder catheterization.

PURPOSE: We often encounter patients who do not complain of pain on undergoing invasive urogenital or rectal procedures, despite incomplete epidural blockade of sacral cutaneous sensation. To clarify whether or not urethral pain is blocked faster than sacral cutaneous sensation during lumbar epidural anesthesia, we investigated the correlation between occurrence of urethral pain and loss of cold sensation in the S1-3 dermatomes. METHODS: In 46 gynecological patients, Group A (n=22) received 15 ml of 2% mepivacaine via an epidural catheter inserted cephaladly. Group B (n=24) received 5 ml of 2% mepivacaine directly in the epidural needle directed caudally and 10 ml of 2% mepivacaine via the epidural catheter inserted cephaladly. A Foley catheter was inserted into the urethra 30 min after the injection. RESULTS: Urethral pain, which was defined as a pained facial expression and/or complaint of pain, was observed in seven patients in Group A, and none in Group B. The caudad level of epidural blockade was significantly lower in patients without urethral pain (S3, median) than with urethral pain (L4) (P <0.05). In 39 patients without urethral pain, 19 (49%) experienced loss of cold sensation in the S1 dermatome, 27 (69%) in the S2 and 38 (97%) in the S3 25 min after the injection. CONCLUSION: Blockade of urethral visceral pain often occurs before complete sacral somatosensory blockade, and S3 somatosensory blockade is the important sacral level as an indicator of successful urethral sensory blockade.

Distribution of intrathecal catheter positions in rat.

BACKGROUND: Although drug administration through an intrathecal catheter is widely used in the study of spinal pharmacology, the catheter positions in transverse plane that may cause a limited spread of a solution remain unclear. In the first step to clarify this issue, the distribution of the intrathecal catheter position was investigated in rats. METHODS: A polyethylene catheter (PE-10) was inserted intrathecally 8.5 cm through the atlanto-occipital membrane, aiming the tip of the catheter to the dorsal surface of the spinal cord. Three or four weeks after the implantation of the catheter, 83 rats were transcardiacally perfused with fixative solution. The catheter positions were investigated longitudinally and transversely by cutting the spinal cord segmentally through the intervertebral disk at different spinal levels. RESULTS: Seventeen rats were excluded from further data analysis. Transversely, catheters were located in the left lateral subarachnoid space in 23 rats (35%), in the right lateral in 15 (23%), in the dorsal in 22 (33%), and in the ventral in 6 (9%). Longitudinally, catheter position was significantly higher in the ventral group (median, T9) than that in the dorsal group (T11/12) (P<0.01). CONCLUSION: Chronic intrathecal catheters were variously located in the rat spinal subarachnoid space in the transverse plane, and lateral subarachnoid placement of the catheter (58%) was frequently observed, whereas dorsal subarachnoid placement occurred in 33%.

Neurotoxicity of intrathecally administered tetracaine commences at the posterior roots near entry into the spinal cord.

BACKGROUND AND OBJECTIVES: Neurotoxicity of intrathecally administered local anesthetics is generating increased interest. This study was designed to examine the histopathologic effects of intrathecally administered tetracaine. METHODS: Sixty Wistar rats randomly received either 20%, 10%, 5%, 3%, 1%, 0.5%, or 0% tetracaine dissolved in 10% glucose solution or no solution via a chronically implanted intrathecal catheter. The spinal cord at L1, posterior and anterior roots and cauda equina were excised 5 days later, sectioned, processed, and prepared for light and electron microscopic examinations. RESULTS: Rats treated with tetracaine at 10% or 20% developed lesions in the posterior white matter and posterior roots. Rats injected with 3% or 5% tetracaine developed lesions, which began in the posterior roots close to the spinal cord and extended to the posterior white matter. The lesions were characterized by axonal degeneration. Injections of < or =1% of tetracaine did not cause any pathological changes. CONCLUSIONS: Our results suggest that the initial target of intrathecal tetracaine neurotoxicity may be the posterior roots at their entry into the spinal cord, where the axons are devoid of myelin sheath and thus representing a sensitive area for neurotoxic change.

Variation in rat sciatic nerve anatomy: implications for a rat model of neuropathic pain.

We discovered a variation of rat sciatic nerve anatomy as an incidental finding during the anatomical exploration of the nerve lesion site in a rat neuropathic pain model. To confirm the composition and distribution of rat sciatic nerve, macroscopic anatomical investigation was performed in both left and right sides in 24 adult Sprague-Dawley rats. In all rats, the L4 and L5 spinal nerves were fused tightly to form the sciatic nerve. However, the L6 spinal nerve did not fuse with this nerve completely as a part of the sciatic nerve, but rather sent a thin branch to it in 13 rats (54%), whereas in the remaining 11 rats (46%), L6 ran separately along with the sciatic nerve. Also, the L3 spinal nerve sent a thin branch to the L4 spinal nerve or sciatic nerve in 6 rats (25%). We conclude that the components of sciatic nerve in Sprague-Dawley rats vary from L3 to L6; however, the major components are L4 and L5 macroscopically. This finding is in contrast to the standard textbooks of rat anatomy which describe the sciatic nerve as having major contributions from L4, L5, and L6.

Radiographic findings of unilateral epidural block.

In 236 consecutive lumbar epidural anesthesia patients, epidurography was performed in seven patients who developed unilateral loss of cold sensation to clarify the cause of unilateral block. Epidurography demonstrated the epidural catheter tip location in the anterior epidural space in four patients (57%) and in the transforaminal passage in three patients (43%). In all seven patients, successful bilateral epidural anesthesia was obtained by a second puncture using another catheter. Our results showed that the most frequent cause of unilateral epidural blockade was the misplacement of the catheter into the anterior epidural space.

Treatment of postoperative pain with thoracic epidural morphine in oral malignant tumor patients.

CASE REPORT: Thoracic epidural morphine was administered to five patients who underwent radical resection and reconstructive surgery for oral malignant tumors. METHODS AND RESULTS: In case 1, an epidural catheter was inserted at the T3-T4 interspace, and 4 mg morphine was administered through the catheter approximately 5 h before the end of surgery. Forty-five minutes after the end of surgery, a total of 10 mg morphine was continuously infused over a 2-day period using a balloon infusion system. The patient did not complain of pain, and no other analgesics were necessary. There were no serious side effects throughout the treatment of postoperative pain. Good control of pain was obtained by this method in four similar cases. CONCLUSION: Thoracic epidural morphine was effective in the relief of postoperative pain following oral surgery in five cases.

[Resistance to anticoagulant activity of heparin in a patient for cardiac surgery].

Resistance to anticoagulant activity of heparin was observed in a patient for cardiac surgery. The activated coagulation time (ACT) was maintained over 300 seconds with additional doses of heparin which mounted to the total of 29 ml in 3 hours during cardiopulmonary bypass. Although antithrombin-III activity was not measured in this case, the heparin resistance might have been caused by the decrease in the activity of antithrombin-III which might have resulted from the preoperative malnutrition, infection of urinary tract and/or institution of intraaortic balloon pumping (IABP).

Development of a subdural motor blockade.

We report an unusual development of motor blockade following the subdural injection of local anaesthetic during attempted continuous lumbar epidural anaesthesia. Four characteristic features of subdural block, extensive spread, segmental distribution, delayed onset, and short duration of motor blockade were all features of the case. The patient had gradual development of complete motor blockade in the left upper extremity, incomplete in the right upper extremity, but absence of motor blockade in the lower extremities. The duration of complete motor blockade was 10 min in the hand and 35 min in the arm. The spread of contrast medium in the subdural space revealed the extent and degree of motor blockade.

Responses of neurons in nucleus ventralis posterolateralis of the cat thalamus' to hypogastric inputs.

Recordings were made from 68 units in the nucleus ventralis posterolateralis (VPL) of the cat thalamus, which responded to stimulation of hypogastric afferents. These units also received nociceptive inputs from the contralateral integument. Units which responded exclusively to hypogastric afferent inputs were not found. Thirty seven of the units were nociceptive specific (NS), and the remaining 31 were wide dynamic range (WDR) units. All of these units were located in the shell region of the lateral subdivision of the caudal VPL. NS units responding to hypogastric afferent inputs had a circumscribed cutaneous receptive field on the contralateral abdomen, gluteal region, tail or hind limb. These areas corresponded to tactile dermatomes T13-S2. Similarly, the cutaneous receptive fields of WDR units receiving hypogastric afferent inputs were distributed in the contralateral abdomen, gluteal region, tail and hind limb, with the sole exception of one unit, whose receptive field also included a part of the lower thorax. These findings extend the previous findings that the shell region of the caudal VPL of the cat thalamus constitutes a thalamic link in a visceral pain pathway, and that the visceral and cutaneous pathways share a common projection locus in the VPL.

Nociceptive body representation in nucleus ventralis posterolateralis of cat thalamus.

1. The somatotopic organization of nociceptive-specific (NS) and wide dynamic range (WDR) units in the nucleus ventralis posterolateralis (VPL) of the ventrobasal (VB) complex was studied. Experiments were carried out on adult cats anesthetized with urethane-chloralose. The recording sites of nociceptive units were marked by the electrophoretic deposition of pontamine sky blue from the recording microelectrode, and subsequently identified histologically in cresyl-violet stained sections. 2. It was found that NS units were located in the dorsal and ventral shell regions of the caudal VPL, whereas WDR units were located in a narrow zone of the shell region, just rostral to the NS zone. 3. NS units in the dorsal shell region had receptive fields on the contralateral dorsal surface of the body, whereas NS units in the ventral shell region had their receptive fields on the ventral aspect of the contralateral integument. 4. In the dorsal shell region, the contralateral body surface was represented in an orderly sequence. Units responding to noxious stimulation of the upper-most cervical dermatome were found in the most medial part of the shell region of the VPL, whereas those responding to stimulation of successively more caudal dermatomes were located more laterally, and in serial order. Units responding to noxious stimulation of the sacral dermatomes were thus found in the most lateral part. 5. In the ventral NS zone, the pattern was distorted by disproportionately large areas devoted to the fore- and hindpaw pads. In this region, therefore, NS units with receptive fields on the fore- and hindpaw pads were intermingled with other NS units that could have receptive fields located anywhere on the ventral body surface. It should be noted, however, that the remainder of the body surface was still represented in an orderly sequence; cervical dermatomes being represented medially, with successively more caudal dermatomes being represented progressively more laterally. 6. A similar somatotopic pattern was recognized in the distribution of the low-threshold centers of the receptive fields of WDR units.