Pin-Tarng Chen

A New Technique to Assist Epidural Needle Placement Fiberoptic-guided Insertion Using Two Wavelengths

Background:Up to 10% of epidurals fail due to incorrect catheter placement. We describe a novel optical method to assist epidural catheter insertion in a porcine model. Methods:Optical emissions were tested on ex vivo tissues from porcine paravertebral tissues to identify optical reflective spectra. The wavelengths of 650 and 532 nm differentiated epidural space from the ligamentum flavum. We then used a hollow stylet that contained optical fibers to place epidural needles in anesthetized pigs. Real-time data were displayed on an oscilloscope and stored for analysis. A total of 50 punctures were done in four laboratory pigs. Data were expressed as mean ± SD. Results:Paired t test shows significant optical differences between the epidural space and the ligamentum flavum at both 650 nm (P < 0.001) and 532 nm (P = 0.014). Mean magnitudes for 650 nm, 532 nm, and their ratio were 3.565 ± 0.194, 2.542 ± 0.145, and 0.958 ± 0.172 at epidural space and 3.842 ± 0.191, 2.563 ± 0.131, and 1.228 ± 0.244 at ligamentum flavum, respectively. There were no differences in the optical characteristics of the ligamentum flavum and epidural space at different levels in the lumbar and thoracic region (two-way ANOVA P > 0.05). Conclusions:This is the first study to introduce a new optical method to localize epidural space in a porcine model. Epidural space could be identified by the changes in the reflective pattern of light emitted at 650 nm, which were specific for the ligamentum flavum and dural tissue. Real-time optical information successfully guided a modified Tuohy needle into the epidural space.

Discriminant analysis for anaesthetic decision-making: an intelligent recognition system for epidural needle insertion

BACKGROUND Incorrect placement of epidural catheters causes medical complications. We used linear discriminant analysis (LDA) to develop an intelligent recognition system (i-RS) in order to guide epidural placement and reduce physician error. METHODS We analysed real-time dual-wavelength fibreoptic data recorded from the end of an epidural needle in a live porcine model. Two categories of tissue layers were necessary for correct placement of catheter: epidural space and ligamentum flavum. The data were tested using linear, quadratic and logistic parametric analysis to identify which method could distinguish the two anatomical structures. RESULTS LDA was the best fit for our model. There was ∼80% sensitivity and specificity for correct anatomical identification. Error rates based on cross-validation were 17.0% for the epidural space and 18.6% for ligamentum flavum. Error rates were greater with the 532 nm compared with 650 nm wavelength. CONCLUSIONS The sensitivity and specificity of LDA for identifying the correct anatomical structure was similar to a physician who is an expert in epidural placement. Overall performance of an i-RS could be improved by expanding the database for decision-making and adding a category of uncertainty. This would reduce complications caused by incorrect epidural placement.

Instructor-based Real-time Multimedia Medical Simulation to Update Concepts of Difficult Airway Management for Experienced Airway Practitioners

Background: We integrated lecture, real‐time multimedia display and medical simulation into a new renewal airway management training protocol for experienced nurse anesthetists. Methods: Trainees of the Taiwan Association of Nurse Anesthetists from northern Taiwan and junior residents from our department were enrolled into the training program. A 4‐hour renewal curriculum in the management of airway emergen‐cies was developed, which consisted of a 2‐hour general lecture (including 4 divided sections) and a 2‐hour instructor‐based real‐time multimedia medical simulation of 4 specific techniques. After detailed explanation of each specific instrument at the beginning of each simulation, the instructors demonstrated accurate and successful management of 4 airway crises from clinical experience by using a standardized human patient simulator situated on the stage of the conference room. Meanwhile, real‐time display of instructors’ performance, responsive physical parameters and images from specific instruments were conducted by video camera and video processor, and projected on a 3‐frame screen. Brief summary and feedback were performed after each simulation. Trainees completed a questionnaire 6 months after they participated in the training program. Results: Two hundred and forty‐two nurse anesthetists and 13 young residents were trained with this protocol. The questionnaire revealed that the renewal training program was useful. Participants updated their knowledge of difficult airway management, gained more confidence, improved performance, and provided effective assistance in handling airway crises. Conclusion: Renewing practice guidelines and teaching airway management skills, especially for difficult airway crises and protection of personnel, continues to be an important issue. Instructor‐based real‐time multimedia simulation is a fast, useful and systematic renewal educational method for many participants with extensive experience of airway management to update their knowledge about difficult airway management, and acquire improved decision‐making and communication capabilities, skills of specific airway management. [J Chin Med Assoc 2008;71(4):174–179]

Prevention of Dental Damage and Improvement of Difficult Intubation Using a Paraglossal Technique With a Straight Miller Blade

Patients with diseased teeth, or those who are difficult to intubate, have a higher risk of dental injury during laryngoscopy. We report 3 cases of smooth endotracheal intubation using a paraglossal technique with a straight Miller blade in patients with poor dentition. Three patients with poor dentition were scheduled to undergo surgery under general anesthesia. All patients presented with extremely loose upper central incisors and had lost the other right upper teeth, while micrognathia and prominent, loose upper incisors were noted in 1 case. We elected to use a straight Miller blade using a paraglossal approach. A nasopharyngeal airway was inserted after induction of general anesthesia to facilitate mask ventilation and prevent air leakage from the mask. The Miller blade was then inserted from the right corner of the mouth, avoiding contact with the vulnerable incisors, and advanced along the groove between the tongue and tonsil. The endotracheal tube was subsequently smoothly inserted after obtaining a grade 1 Cormack and Lehane view without dental trauma in all 3 cases. Direct laryngoscopy using the paraglossal straight blade technique avoids dental damage in patients with mobile upper incisors and no right maxillary molars. It is a practical alternative method that differs from the traditional Macintosh laryngoscope in patients with a high risk of dental injury during the procedure. This technique, which provides an improved view of the larynx, might also be helpful with patients in whom intubation is difficult.

Practical preprocedure measurement to estimate the required insertion depth and select the optimal size of tunneled dialysis catheter in uremic patients.

We evaluated two methods for preprocedure predicting the insertion depth of tunneled dialysis catheter (TDC) on chest radiograph (CXR). Patients undergoing TDC insertion via right internal jugular vein were enrolled. By Method 1, the insertion depth was calculated on preprocedure CXR as the distance from the anticipated venous tip (3.5 cm below the cavoatrial junction) to the prearranged skin puncture site (1.5 cm above the right clavicle). By Method 2, the insertion depth was derived by adding the length between the skin puncture site and the upper edge of the clavicle and the length of clavicle‐to‐tip. The TDC was placed at the estimated insertion depth. The distance of cavoatrial junction‐to‐arterial tip was then measured from postoperative supine CXR. One hundred and seventy and 121 TDCs were inserted by Method 1 and Method 2, respectively, while 127 and 92 preoperative supine CXR were used for preprocedure measurement. The mean distance of cavoatrial junction‐to‐arterial tip was 12.055 (8.5684) [mean (SD)], 11.27 (3.3261), 9.524 (5.1590), and 10.538 (2.6956) mm. Methods of determining the insertion depth by preprocedure measurement enable successful TDC tip placement. Method 2 and using preoperative supine CXR enabled more precise and flexible insertion.

Clinical Value of Application of Cerebral Oximetry in Total Replacement of the Aortic Arch and Concomitant Vessels

Cerebral ischemia or infarction caused by several equivocal mechanisms is a major complication after aortic arch replacement. Here, we report a 28-year-old male who underwent total replacement of the aortic arch and concomitant tributaries for hypoplasia of the transverse aortic arch and aortic branches. Continuous cerebral oxygen saturation (rSO2) monitoring was applied throughout the whole surgical course. According to the trend of rSO2, we could not only optimize the cerebral perfusion, but also confirm the patency of graft anastomosis. Therefore, monitoring rSO2 is very useful for determining cerebral perfusion during major surgery, especially in complicated repair of an aortic aneurysm, or replacement of the aortic arch and/or arch vessels.

A Modified Supraclavicular Approach for Central Venous Catheterization by Manipulation of Ventilation in Ventilated Patients

Background:  Because of overuse and multiple implantations of hemodialysis catheters through internal jugular or subclavian vein (SCV) in patients with chronic hemodialysis, these veins often become stenotic or occlude, therefore necessitating alternative access. We introduce a new technique in ventilated patients for placement of tunneled cuffed chronic hemodialysis catheter: modified supraclavicular approach by cease of ventilation.

No enlargement of the right internal jugular vein of the dialysis patients in the Trendelenburg position

Background: The Trendelenburg position has been suggested for right internal jugular vein (RIJV) catheterization. However, this position can sometimes be functionally intolerable for chronic kidney disease patients. We conducted an ultrasound study to further investigate the efficacy of the use of the Trendelenburg position during tunneled dialysis catheter insertion via the RIJV in chronic kidney disease patients. Methods: We recruited into our study patients without a history of prior tunneled dialysis catheter insertion or neck surgery. Those patients with stenosis or thrombus in the RIJV were excluded. Serial ultrasound images were acquired with patients in the supine position, with the head rotated 30° to the left: Stage 0, table flat; Stage T, Trendelenburg tilt. Then, measurements of patient RIJV transverse diameter, anteroposterior (AP) diameter, and cross‐sectional area (CSA) were obtained. Results: Fifty dialysis patients and 40 healthy volunteers completed the study. There were no significant differences in the lateral diameter, AP diameter, or AP/lateral diameter ratio between the dialysis patients and healthy volunteers, whether in the supine or the Trendelenburg position. However, the CSA of the RIJV of the healthy volunteers in the Trendelenburg position was significantly larger than that in dialysis patients. The change in CSA from the supine to the Trendelenburg position was also significantly different between the two groups. Conclusion: In contrast to healthy volunteers, there was no enlargement of the RIJV when dialysis patients were in the Trendelenburg position. The reason for this phenomenon may be multifactorial, with diastolic dysfunction being the most likely cause, and further investigation is required to clarify the cause. Our investigation suggests that the supine position for central venous catheterization in dialysis patients is superior to the Trendelenburg position.

Innominate artery dissection with presentation of sudden right frontal desaturation detected by cerebral oximetry in complicated thoracic aortic aneurysm repair surgery: a case report

Cerebral oximetry is a noninvasive bedside monitor for cerebral oxygen saturation (rSO(2)). A patient with a thoracic aneurysm underwent combined surgical and endovascular repair. A sudden decrease in right rSO(2) led to the finding of acute innominate artery dissection. Immediate repair was instituted. Sudden asymmetry of rSO(2) may be a warning sign of underlying pathology.

Catheter-related right internal jugular vein thrombosis after chest surgery

Background Central venous catheters (CVCs) are frequently used for monitoring haemodynamic status and rapidly delivering fluid therapy during the peri- and postoperative periods. Indwelling CVCs are typically used 7-14 days postoperatively for additional monitoring and treatment, but patients may develop asymptomatic catheter-related thrombosis, leading to life-threatening pulmonary embolism and death. Early detection helps to avoid such complications. Methods This prospective observational study investigated the risk factors associated with catheter-related right internal jugular vein thrombosis in patients undergoing chest surgery. The study enrolled 24 patients who were scheduled to receive chest surgeries during which catheters were needed. To detect thrombus formation, Doppler ultrasound examinations from the thyroid cartilage level to the supraclavicular region were used after CVC placement and on each of the following days until the catheter was removed. Results No thrombosis was found in patients before surgery, but it appeared in 75% (18/24) after surgery. The risks of thrombosis increased with a longer duration of anaesthesia, greater amounts of bleeding, and use of postoperative ventilator support. Conclusions Earlier catheter removal may reduce the risk of catheter-related thrombosis and avoid possibly fatal complications after catheter-related thrombosis.