Chien-Kun Ting

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.

Eyes in the needle: novel epidural needle with embedded high-frequency ultrasound transducer--epidural access in porcine model.

Background:Epidural needle insertion is usually a blind technique where the rate of adverse events depends on the experience of the operator. A novel ultrasound method to guide epidural catheter insertion is described. Methods:An ultrasound transducer (40 MHz, a −6 dB fractional bandwidth of 50%) was placed into the hollow chamber of an 18-gauge Tuohy needle. The single crystal was polished to a thickness of 50 &mgr;m, with a width of 0.5 mm. Tissue planes were identified from the reflected signals in an A-mode display. The device was inserted three times into both the lumbar and thoracic regions of five pigs (average weight, 20 kg) using a paramedian approach at an angle of 35–40°. The epidural space was identified using signals from the ligamentum flavum and dura mater. Epidural catheters were placed with each attempt and placement confirmed by contrast injection. Results:The ligamentum flavum was identified in 83.3% of insertions and the dura mater in all insertions. The dura mater signal was stronger than that of the ligamentum flavum and served as a landmark in all epidural catheter insertions. Contrast studies confirmed correct placement of the catheter in the epidural space of all study animals. Conclusions:This is the first study to introduce a new ultrasound probe embedded in a standard epidural needle. It is anticipated that this technique could reduce failed epidural blocks and complications caused by dural puncture.

Use of higher thromboelastogram transfusion values is not associated with greater blood loss in liver transplant surgery

Plasma‐containing products are given during the pre‐anhepatic stage of liver transplant surgery to correct abnormal thromboelastogram (TEG) values and prevent blood loss due to coagulation defects. However, evidence suggests that abnormal TEG results do not always predict bleeding. We questioned what effect using higher TEG values to initiate treatment would have on blood loss. A single transfusion protocol was used for all patients who underwent liver transplantation between 2007 and 2010. Thirty‐eight patients received coagulation products when standard TEG cutoff values were exceeded, whereas another 39 patients received coagulation products when the TEG values were 35% greater than normal. The results of postoperative coagulation tests for total blood loss and the use of blood products were compared for the 2 groups. When the critical TEG values for transfusion were higher, significantly fewer units of fresh frozen plasma (5.58 ± 6.49 versus 11.53 ± 6.66 U) and pheresis platelets (1.84 ± 1.33 versus 3.55 ± 1.43 U) were used. There were no differences in blood loss or postoperative blood product use. In conclusion, the use of higher critical TEG values to initiate the transfusion of plasma‐containing products is not associated with increased blood loss. Further testing is necessary to identify what TEG value predicts bleeding due to a deficit in coagulation factors. Liver Transpl 18:1254–1258, 2012.

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.

Clindamycin-induced Anaphylactic Shock During General Anesthesia

Clindamycin-related anaphylactic reaction is rarely reported. We report a male patient with buccal cancer who was undergoing radical neck dissection when life-threatening anaphylactic shock developed soon after intravenous infusion of clindamycin. Immediate cardiopulmonary resuscitation was performed, and the patient recovered uneventfully. Perioperative anaphylactic shock is a serious problem due to the difficulty of judgment and potentially disastrous outcome. Immediate diagnosis and halting of drug infusion should be the first actions taken.

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.

Response surface models in the field of anesthesia: A crash course.

Drug interaction is fundamental in performing anesthesia. A response surface model (RSM) is a very useful tool for investigating drug interactions. The methodology appeared many decades ago, but did not receive attention in the field of anesthesia until the 1990s. Drug investigations typically start with pharmacokinetics, but it is the effects on the body clinical anesthesiologists really care about. Typically, drug interactions are divided into additive, synergistic, or infra-additive. Traditional isobolographic analysis or concentration-effect curve shifts are limited to a single endpoint. Response surface holds the complete package of isobolograms and concentration effect curves in one equation for a given endpoint, e.g., loss of response to laryngoscopy. As a pharmacodynamic tool, RSM helps anesthesiologists guide their drug therapy by navigating the surface. We reviewed the most commonly used models: (1) the Greco model; (2) Reduced Greco model; (3) Minto model; and (4) the Hierarchy models. Each one has its unique concept and strengths. These models served as groundwork for researchers to modify the formula to fit their drug of interest. RSM usually work with two drugs, but three-drug models can be constructed at the expense of greatly increasing the complexity. A wide range of clinical applications are made possible with the help of pharmacokinetic simulation. Pharmacokinetic-pharmcodynamic modeling using the RSMs gives anesthesiologists the versatility to work with precision and safe drug interactions. Currently, RSMs have been used for predicting patient responses, estimating wake up time, pinpointing the optimal drug concentration, guide therapy with respect to patients well-being, and aid in procedures that require rapid patient arousal such as awake craniotomy or Stagnara wake-up test. There is no other model that is universally better than the others. Researches are encouraged to find the best fitting model for different occasions with an objective measure.

Paradoxical Carbon Dioxide Embolism During Pneumoperitoneum in Laparoscopic Surgery for a Huge Renal Angiomyolipoma

We present a case of paradoxical gas embolism during CO2 insufflation in laparoscopic nephrectomy for a huge renal angiomyolipoma. Paradoxical CO2 embolism in the left heart chambers without demonstrable intracardiac right-to-left shunt was detected by transesophageal echocardiography (TEE). The surgical procedure was stopped immediately, but the patient recovered with mild neurologic deficit. We speculate that rapid pneumoperitoneum introduction pushed CO2 into the abnormal vasculature of the angiomyolipoma, which communicates with the systemic vascular system, causing pseudoaneurysm formation. Follow-up abdominal computed tomography showed a new pseudoaneurysm inside the tumor. If intracardiac right-to-left shunt is excluded for the reason of paradoxical gas existence, there remains extracardiac right-to-left shunt, with transpulmonary passage of the venous emboli being the most likely mechanism. In fact, the cause of paradoxical gas embolism in this case remains unknown. Therefore, laparoscopic surgery for huge angiomyolipoma should be performed with extreme caution; an open procedure may be considered as an alternative.

Fiber-needle swept-source optical coherence tomography system for the identification of the epidural space in piglets.

Background:Epidural needle insertion is traditionally a blind technique whose success depends on the experience of the operator. The authors describe a novel method using a fiber-needle–based swept-source optical coherence tomography (SSOCT) to identify epidural space. Methods:An optical fiber probe was placed into a hollow 18-gauge Tuohy needle. It was then inserted by an experienced anesthesiologist to continuously construct a series of two-dimensional SSOCT images by mechanically rotating the optical probe. To quantify this observation, both the average SSOCT signal intensities and their diagnostic potentials were assessed. The insertions were performed three times into both the lumbar and thoracic regions of five pigs using a paramedian approach. Results:A side-looking SSOCT is constructed to create a visual image of the underlying structures. The image criteria for the identification of the epidural space from the outside region were generated by the analysis of a training set (n = 100) of ex vivo data. The SSOCT image criteria for in vivo epidural space identification are high sensitivity (0.867 to 0.965) and high specificity (0.838 to 0.935). The mean value of the average signal intensities exhibits statistically significant differences (P < 0.01) and a high discriminatory capacity (area under curve = 0.88) between the epidural space and the outside tissues. Conclusions:This is the first study to introduce a SSOCT fiber probe embedded in a standard epidural needle. The authors anticipate that this technique will reduce the occurrence of failed epidural blocks and other complications such as dural punctures.

Fluid management guided by stroke volume variation failed to decrease the incidence of acute kidney injury, 30-day mortality, and 1-year survival in living donor liver transplant recipients.

Background: Low central venous pressure (CVP) produced by fluid restriction has been applied to liver transplant recipients in order to decrease blood loss. However, CVP is not reliable for monitoring intravascular volume and ventricular filling. In addition, doubts remain over the association between fluid restriction and acute kidney injury (AKI). We tested the utility of stroke volume variation (SVV), derived from the FloTrac/Vigileo system, as a decision‐making tool in fluid management. We examined the differences in fluid administration, urine output, postoperative AKI, and 30‐day and 1‐year survival rates between liver transplant recipients with fluid management guided by SVV and CVP. Methods: We retrospectively collected data on our liver transplant recipients with a Model for End‐stage Liver Disease score less than 30 and serum creatinine lower than 1.5 mg/dL from 2007 to 2010. Recipients in 2007 and 2008 who received CVP‐guided fluid management served as the control group. Recipients in 2009 and 2010 who received fluid administration triggered by SVV were recruited as the study group. The estimated blood loss, urine output, and fluid administered during the operation were recorded. Renal function was assessed using the RIFLE criteria on postoperative days 1 and 5. We also recorded the 30‐day and 1‐year survival. Results: Significantly more diuretic use and urine output were noted in the control group in spite of similar fluid administration. However, there was no significant difference in blood loss, AKI, or 30‐day and 1‐year survival rates. Conclusion: The outcomes of living donor liver transplant patients who had fluid therapy guided by an SVV less than 10% were similar to those of patients who were given fluids to reach a CVP of 10 mmHg. Our findings suggest that the two measures of vascular filling are similar in liver transplant recipients with demographic characteristics similar to those of our patients.