Toshihiro Wagatsuma

Cesarean section and primary pulmonary hypertension: the role of intravenous dexmedetomidine

Primary pulmonary hypertension is a fatal disease that frequently becomes evident in pregnancy. The management of pregnant women with primary pulmonary hypertension poses a number of difficult problems, especially where regional anesthesia is considered to be contraindicated. A 30-year-old woman who developed primary pulmonary hypertension at 23 weeks of pregnancy was transferred to our hospital. Systolic pulmonary artery pressure and plasma brain natriuretic peptide levels were markedly elevated. Nitric oxide inhalation and prostacyclin prevented the progression of cardiac failure and reduced both plasma brain natriuretic peptide and pulmonary artery pressure. Cesarean section was performed at 32 weeks under general anesthesia. A combination of nitric oxide, prostacyclin, nitroglycerin, and dobutamine were administered during surgery. Intravenous dexmedetomidine was specifically used during emergence and recovery from anesthesia. This provided effective pain relief and hemodynamic stability. Throughout the clinical course, brain natriuretic peptide levels was monitored and used as an indicator of cardiac failure.

Effect of tube guide assembly of closed suction system on airway pressure gradient

We connected a Dual Adult TTL model 1600 test lung (Michigan Instruments, Grand Rapids, MI, USA), a pressure and flow sensor (OMR; Nihon Kohden, Tokyo, Japan), a TT (Mallinckrodt, St. Louis, MO, USA), another sensor, and an Evita 4 ventilator (Drägerwerk, Lubeck, Germany) in series (Fig. 2). Two kinds of TT (with IDs of 6.5 and 8.5mm) were used for this experiment. The distal side of each TT was set inside a plastic tube, which was connected to the test lung. The cuff was inflated with air to prevent leakage, and the proximal side of each TT was connected to the respiratory circuit of the Evita 4. We used the original Ballard Trach Care Directional Tip Closed Suction System for 12-Fr catheter (Ballard Medical Products, Midvale, UT, USA), and a modified closed suction system, in which the tube guide assembly in the L-connector was removed (Fig. 1). The settings of the Evita 4 ventilator were: tidal volume, 600ml; respiratory frequency, 12 breaths·min 1, inspiratory time, 1 s (with attenuation wave); FIO2, 0.21, inspiratory pause, 0%, and positive end-expiratory pressure (PEEP), 0cmH2O. The resistance and compliance of the test lung were set at 20cmH2O·l 1·s 1 and 0.05 l·cmH2O 1, respectively. The airway pressures were measured simultaneously at the proximal side of the closed suction system (P2) and the distal site of the TT (P1), and the flow was measured at the proximal site. Three signals (two pressures and one flow) were recorded simultaneously with a Power Book G3 (Apple Computer, Cupertino, CA, USA) via a MacLab AD converter (AD Instruments) at a sample rate of 100Hz. We calculated and analyzed the relationship between the airway pressure and the flow using Chart v3.6.4B5/s (AD Instruments) and Microsoft Excel (Microsoft, Redmond, WA, USA) for every breath. It has been reported that the pressure gradient across the TT (PTT) has a nonlinear dependence on the flow generated by the ventilator [2]. This relationship is

Influences of environmental noise level and respiration rate on the accuracy of acoustic respiration rate monitoring

We tested the hypothesis that the environmental noise generated by a forced-air warming system reduces the monitoring accuracy of acoustic respiration rate (RRa). Noise levels were adjusted to 45–55, 56–65, 66–75, and 76–85 dB. Healthy participants breathed at set respiration rates (RRset) of 6, 12, and 30/min. Under each noise level at each RRset, the respiration rates by manual counting (RRm) and RRa were recorded. Any appearance of the alarm display on the RRa monitor was also recorded. Each RRm of all participants agreed with each RRset at each noise level. At 45–55 dB noise, the RRa of 13, 17, and 17 participants agreed with RRset of 6, 12, and 30/min, respectively. The RRa of 14, 17, and 16 participants at 56–65 dB noise, agreed with RRset of 6, 12, and 30/min, respectively. At 66–75 dB noise, the RRa of 9, 15, and 16 participants agreed with RRset of 6, 12, and 30/min, respectively. The RRa of one, nine, and nine participants at 76–85 dB noise agreed with RRset of 6, 12, and 30/min, respectively, which was significantly less than the other noise levels (P < 0.05). Overall, 72.9% of alarm displays highlighted incorrect values of RRa. In a noisy situation involving the operation of a forced-air warming system, the acoustic respiration monitoring should be used carefully especially in patients with a low respiration rate.