[Skin lesions on the back along the epidural Catheter].

We report a patient with anemia and hypoalbuminemia who developed decubitus ulcer along the epidural catheter. A 35-year-old woman underwent cesarean section under combined spinal-epidural anesthesia. Erosive and erythematous skin lesions along the epidural catheter were noted 48 hours after insertion of the epidural catheter. The skin lesions were thought to be decubitus ulcer along the epidural catheter due to mechanical pressure caused by fixation of the catheter with an adhesive tape after prolonged supine position.

A proposed mechanism for amitriptyline neurotoxicity based on its detergent nature.

Although amitriptyline has gained attention as a potent local anesthetic, recent animal studies showed that it can cause irreversible neural impairment. We hypothesized that nerve membrane disruption caused by solubilization, a common detergent property, accounted for amitriptyline neurotoxicity. We used a two-phase approach to test our hypothesis. Firstly, we determined (1) the molecular aggregation concentration of amitriptyline, (2) the concentration of amitriptyline that disrupts artificial lipid membranes and (3) the concentration of amitriptyline that causes hemolysis. Secondly, we compared these levels with neurotoxic concentrations determined from assessment in a rat model of spinal anesthesia using changes in cutaneous stimulus threshold (CST). Amitriptyline concentrations that caused molecular aggregation, model membrane disruption and hemolysis were 0.46%, 0.35% and 0.3%, respectively. Animal study showed a significant increase in CST at >or=0.3% of amitriptyline, indicating neurological impairment. Since amitriptyline caused model membrane disruption and hemolysis at the molecular aggregation concentration, solubilization plays a role in the destruction of artificial membranes and erythrocytes. Furthermore, these concentrations are also in good agreement with the minimum concentration causing neurological injury. Therefore, while additional studies, including histopathology, are necessary to clarify this observation, amitriptyline neurotoxicity appears to be associated with its detergent nature.

Quantitative and fiber-selective evaluation of dose-dependent nerve blockade by intrathecal lidocaine in rats.

We investigated whether cutaneous stimulus threshold (CST), as determined using a Neurometer, could be used for quantitative and differential nerve evaluation of reversible and irreversible nerve block following intrathecal lidocaine administration in rats. Rats with intrathecal catheters were randomly assigned to one of five groups (saline or 2, 5, 10, or 20% lidocaine). Prior to and 4 days after drug administration, CST was determined at 5, 250, and 2000 Hz. In the 2% lidocaine group, CST from end of lidocaine infusion to recovery from anesthesia was also monitored. Skin-clamp testing and gait observation were performed for comparison with CST findings. Behavioral examinations revealed persistent sensory or motor impairment lasting 4 days in groups receiving >/=5% lidocaine but not in the saline and 2% lidocaine groups. With 2% lidocaine, return to baseline CSTs at 5 and 250 Hz was delayed compared with thresholds at 2000 Hz. Although CSTs in the 5% group at 5 and 250 Hz increased significantly, thresholds at 2000 Hz did not differ from those in rats administered saline. CSTs with >/=10% lidocaine displayed no differences between frequencies. At each frequency, CSTs for rats with >/=5% lidocaine increased in a clearly concentration-dependent manner. These results suggest that CST testing enables evaluation of the different nerve functions for Abeta, Adelta, and C fibers in rats for lidocaine concentrations

Proper shoulder position for subclavian venipuncture: a prospective randomized clinical trial and anatomical perspectives using multislice computed tomography.

BACKGROUND: Although the Trendelenburg position and shoulder bracing are recommended for safe subclavian venipuncture, the optimal shoulder position remains unclear. The current study observed spatial relations between the subclavian vein and surrounding structures using multislice computed tomography to determine optimal shoulder position for safe subclavian venipuncture and then conducted a small follow-up clinical trial to confirm these findings. METHODS: Thoracic multislice computed tomography was performed for seven adult volunteers at three shoulder positions: elevated (up); neutral; and lowered caudally (down). Overlap and distance between the clavicle and the subclavian vein and the diameter of the subclavian vein were measured. Anatomical relations between the subclavian artery and vein were also observed. The success rate for subclavian venipuncture was then compared between the up and down shoulder positions in 30 patients. RESULTS: In the multislice computed tomography study, the mean overlap ratios between clavicle and subclavian vein in the up, neutral, and down positions were 33.5, 36.9, and 40.0%, respectively. Overlap increased with lower shoulder position (up < neutral < down; P < 0.05). The mean distances between the clavicle and the subclavian vein in the up, neutral, and down positions were 6.8, 5.0, and 3.6 mm, respectively. Again, distance decreased with lower shoulder position (up < neutral < down; P < 0.05). The diameter of the subclavian vein did not differ among the three shoulder positions. The success rate for subclavian venipuncture was significantly higher in the down position compared with the up position (P = 0.003). CONCLUSIONS: Lowered shoulder position increases both overlap and proximity between the clavicle and the subclavian vein, producing a more constant relation between the clavicle and the subclavian vein, without affecting vein diameter. Proper use of a lowered shoulder position should thus increase the safety and reliability of subclavian venipuncture compared with other shoulder positions.

Neurological evaluation by intraoperative wake-up during carotid endarterectomy under general anesthesia.

Although general anesthesia allows relief from stressors such as pain, discomfort, or anxiety for patients undergoing carotid endarterectomy, neurologic assessment is less reliable than under local anesthesia. We describe a unique anesthetic management strategy for carotid endarterectomy patients incorporating the advantages of both general and local anesthesia. The technique allows thorough assessment of neurologic function during carotid cross-clamping by intraoperative wake-up, and guarantees airway management by tracheal intubation.

Possible mechanism of irreversible nerve injury caused by local anesthetics: detergent properties of local anesthetics and membrane disruption.

BACKGROUND: Irreversible nerve injury may result from neural membrane lysis due to the detergent properties of local anesthetics. This study aimed to investigate whether local anesthetics display the same properties as detergents and whether they disrupt the model membrane at high concentrations. METHODS: Concentrations at which dodecyltrimethylammonium chloride and four local anesthetic (dibucaine, tetracaine, lidocaine, and procaine) molecules exhibit self-aggregation in aqueous solutions were measured using an anesthetic cation-sensitive electrode. Light-scattering measurements in a model membrane solution were also performed at increasing drug concentrations. The concentration at which drugs caused membrane disruption was determined as the point at which scattering intensity decreased. Osmotic pressures of anesthetic agents at these concentrations were also determined. RESULTS: Concentrations of dodecyltrimethylammonium chloride, dibucaine, tetracaine, lidocaine, and procaine at which aggregation occurred were 0.15, 0.6, 1.1, 5.3, and 7.6%, respectively. Drug concentrations causing membrane disruption were 0.09% (dodecyltrimethylammonium chloride), 0.5% (dibucaine), 1.0% (tetracaine), 5.0% (lidocaine), 10.2% (procaine), and 20% (glucose), and osmotic pressures at these concentrations were 278, 293, 329, 581, 728, and 1,868 mOsm/kg H2O, respectively. CONCLUSIONS: These results show that all four local anesthetics form molecular aggregations in the same manner as dodecyltrimethylammonium chloride, a common surfactant. At osmotic pressures insufficient to affect the membrane, local anesthetics caused membrane disruption at the same concentrations at which molecular aggregation occurred. This shows that disruption of the model membrane results from the detergent nature of local anesthetics. Nerve membrane solubilization by highly concentrated local anesthetics may cause irreversible neural injury.

Lidocaine spray used to capture a live Clinostomum parasite causing human laryngitis.

This case report describes a patient who developed Clinostomum laryngitis after eating raw fresh-water fish. Parasite removal was performed under general anesthesia using a laryngomicroscopic method. Because it was difficult to capture the worm intact using forceps, it was sprayed with 8% lidocaine solution. This immediately inhibited peristaltic movement of the parasite allowing easy retrieval without tearing any part of the organism, thus facilitating parasite identification.