In the first part of the study performed at Stanford University, 30 Asian born and 163 non-Asian born patients matched by height and weight had left-sided double-lumen tubes selected on the basis of the width of each patient s trachea. In the second part of the study performed at the Philippines Lung Center and Santo Tomas University Hospital, left-sided double-lumen tubes were selected on the basis of the anesthesiologists clinical experience for 22 patients and by tracheal width guidelines for 35 patients. When tubes were selected by tracheal width, there was no difference between those used for Asian and non-Asian patients of similar size. We concluded that measurement of tracheal width can be used to select the appropriate size of left-sided double-lumen tubes for all patients.

STUDY OBJECTIVE: To investigate if the use of a new double lumen i.v. set (DLIS) decreases the incidence of propofol injection pain compared with single lumen i.v. set (SLIS) administration. DESIGN: Prospective, randomized, double-blinded study. SETTING: Operating rooms in a university hospital. PATIENTS: 50 adult ASA physical status I and II patients of both genders undergoing general anesthesia for elective surgery. INTERVENTIONS: Patients were injected with propofol either through a DLIS or a SLIS. MEASUREMENTS AND MAIN RESULTS: Three different pain indices were recorded to be present or absent: (1) verbal report of pain during propofol injection (2) grimacing during propofol injection, and (3) recall of injection pain in the recovery room. When the DLIS was used, the incidence of verbal pain, grimacing during propofol injection, and recall of pain during recovery were lowered significantly by 53%, 46%, and 52%, respectively (chi square analysis of contingency table with Yates correction, p \textless 0.05). CONCLUSIONS: The DLIS significantly reduced the incidence of propofol injection pain compared with SLIS. Further studies are indicated to evaluate the cost-effectiveness of this device.

Delivery of radiofrequency (RF) energy from the distal tip of electrophysiology catheters produces lesions that may be too small to ablate arrhythmogenic sites during a single application of RF energy. To produce larger lesions, we delivered RF energy via a quadripolar catheter in which all four electrodes were connected in unipolar fashion. The catheter (Webster Labs) had a 4-mm tip, 2-mm ring electrodes, and 2-mm interelectrode distance. Lesion size was compared using RF energy delivered in a multipolar configuration with that delivered only to the distal tip using fresh bovine ventricular tissue. In vivo, RF lesions were made in dogs using the distal tip as well as all four poles of the same catheter inserted percutaneously. RF energy was delivered using a constant voltage at a frequency of 400 kHz. Preliminary experiments were conducted to determine the maximum power deliverable without coagulation using each electrode configuration. The use of simultaneous multipolar RF ablation produced significantly larger lesions both in vitro and in vivo. The length of the lesion was increased by a factor of approximately 2 in both the in vitro and in vivo experiments. There was a trend toward an increasing depth of the lesion by simultaneously applying RF energy to all four electrodes. Lesion width was significantly increased in the in vivo studies. We concluded that simultaneous multipolar delivery of RF energy produces larger lesions than can be obtained with delivery of RF energy to the distal tip alone. This technique may offer a means of increasing lesion size, leading to a decrease in the number of applications of RF energy necessary for ablation of arrhythmias.

During radiofrequency (RF) catheter ablation of arrhythmias, temperatures that approach 100 degrees C cause a coagulum to form on the ablation electrode that results in an increase in electrical impedance and prevents further energy delivery. Since gold has nearly four times the thermal conductivity as platinum, the metal commonly used, it was postulated that gold tip electrodes could deliver more power and produce deeper lesions because of its greater heat dissipation from the electrode-tissue interface to the circulating blood. To test this hypothesis, RF energy was applied to fresh bovine ventricular myocardium using 6 French catheters with 2-mm long distal electrodes made from gold or platinum. Similar studies were also conducted using 7 French catheters with 4-mm long distal electrodes. Maximum lesion depth was defined as that produced with the level of energy just below that causing an impedance rise. A maximum lesion depth of 6.2 +/- 0.7 mm (mean +/- SD) was obtained with the gold 2-mm electrode and 4.7 +/- 0.5 mm with the platinum electrode (P = 0.003). The 4-mm gold electrode produced a maximum lesion depth of 7.2 +/- 1.4 mm, while a catheter with a 4-mm platinum electrode caused a maximum lesion depth of 5.8 +/- 0.7 mm (P = 0.05). We conclude that deeper lesions should be able to be made when RF energy is delivered to a gold rather than platinum tip electrode.