Haruo Fukuyama

Relationship between aortic-to-radial arterial pressure gradient after cardiopulmonary bypass and changes in arterial elasticity.

Background An aortic-to-radial arterial pressure gradient may develop during and after cardiopulmonary bypass (CPB). The mechanisms of this pressure gradient remain controversial. To clarify the cause of the pressure gradient after CPB, the authors investigated the relationship between the pressure gradient and changes in the pulse wave velocity (PWV) before and after CPB. Methods The pressure gradient from the aorta to the radial artery and a change in PWV were measured with a wire (0.37 mm in diameter) tipped with a miniature pressure transducer in 12 patients undergoing cardiac surgery. The pressure distributions and waveforms were measured and recorded with electrocardiograph. The PWV was calculated by measuring the propagation time between the R wave of the electrocardiograph and the rising point of the arterial pressure waveform at 10-cm intervals. Results After CPB, 7 of 12 patients demonstrated a marked pressure gradient. In these patients, the pressure distribution showed a gradual decrease toward the periphery without a precipitous step-down in pressure at any one specific anatomic location. The PWV decreased as the intraarterial pressure decreased from the aorta to the radial artery, and the relative arterial elasticity decreased linearly toward the periphery. Conclusions The results showed that the decrease in PWV implies a decrease in arterial elasticity, and the decrease in the arterial elasticity correlated with the decrease in intraarterial pressure. These findings demonstrated that a radial artery pressure lower than the aortic pressure after CPB may be due to the decrease in arterial elasticity.

Development of a safe guidewire

As the result of a locking phenomenon that may occur in a guidewire inside a metal puncture needle when using the Seldinger technique to insert a central venous catheter, the guidewire can break and cause an embolism. To counter this possibility we devised a guidewire with a structure that made it difficult for locking to occur and compared it to conventional guidewires. Conventional guidewires are wound lengthways with a spring. The improved version has a special multi-ply structure. A series of 100 cases were divided into two groups: group A, the conventional guidewire group; and group B, the improved guidewire group. We punctured the internal jugular vein and attempted insertion of the guidewire through the side hole of a 22-gauge metal needle. We then compared the frequency of locking and the frequency of bending of the guidewire tips that have been withdrawn. In group A, locking occurred in 72% of the cases where the guidewire was unable to be inserted, but this figure was 0% in group B. The improved guidewire has the advantage of reducing the risk of locking and of guidewire breakage.

One-lung ventilation with the Univent tube in a pediatric patient undergoing video-assisted thoracoscopic surgery

required. In order to obtain a deflated lung for VATS, it was imperative to use an uncuffed Univent tube 8mm in external diameter, because the patient’s tracheal size was 10mm, as observed from the preoperative chest Xray (Fig. 1). No premedication was given. Anesthesia was induced by injecting 60mg of propofol, 25 μg of fentanyl, and 3mg of vecuronium intravenously. A small, uncuffed Univent tube, 3.5 mm in internal diameter was the placed in the trachea (Fig. 2). After induction of general anesthesia, a blocker tube was advanced into the right main bronchus under bronchoscopy, and a blocker balloon was positioned in place to deflate the right lung. A 22-gauge catheter was placed in the left radial artery. General anesthesia was maintained with 40%–100% oxygen and sevoflurane; occasionally, nitrous oxide and intravenous fentanyl (total, 200 μg) were administered. After pressure controlled ventilation (PCV) had been initiated, arterial blood gas analysis under bilateral ventilation showed a pH of 7.385, PaCO2 of 43.7mmHg, and PaO2 of 158mmHg, with a peak airway pressure of 15 cmH2O, FiO2 of 0.4, and ventilation frequency of 10 ·min21. By inflating the blocker cuff, we could block the right bronchus. However, a leak of anesthetic gas around the tracheal tube became obvious at an airway pressure of 18 cmH2O, causing difficulty in maintaining the static airway pressure of 20cmH2O. We expected that the proper levels of PaCO2 and PaO2 could be maintained during one lung anesthesia by increasing the frequency of ventilation. After the posture of the patient had been changed to the lateral position, one-lung anesthesia was initiated, and the fully deflated right lung was provided with a blocker cuff of 2.5ml. However, the leak increased beyond expectation, and the patient developed hypercapnia. The results of arterial blood analysis were pH 7.291, PCO2 66.3mmHg, and PO2 107 mmHg, with PCV peak airway pressure 20 cmH2O, ventilation frequency 15 ·min21, and 100% oxygen. Gauze was packed into the