Chizu Aso

Exercise-induced cerebral deoxygenation among untrained trekkers at moderate altitudes.

The pathophysiology of altitude-related disorders in untrained trekkers has not been clarified. In the present study, the effects of workload on cardiovascular parameters and regional cerebral oxygenation were studied in untrained trekkers at altitudes of 2700 m and 3700 m above sea level. We studied 6 males and 4 females at each altitude, and their average ages were 31.3+/-7.1 y at 2700 m and 31.2+/-6.8 y at 3700 m, respectively. The resting values of heart rate and mean blood pressure were not significantly different at 2700 m and 3700 m than at sea level. However, increases in these values after exercise were more prominent at high altitudes (heart rate increase = 51.6% at 2700 m and 70.4% at 3700 m; mean blood pressure increase: 19.0% at 2700 m and 17.2% at 3700 m). In addition, post-exercise blood lactate concentration was significantly higher at 3700 m than at sea level or at 2700 m (i.e., 7.6 mM at 3700 m, 3.8 mM at 2700 m, and 4.17 mM at 0 m, respectively). Exercise induced an acute reduction in the arterial oxygen saturation value (SpO2) at 2700 m and 3700 m (i.e., 11.2% reduction at 2700 m and 9.4% at 3700 m), whereas no changes were observed at sea level. The resting values of regional oxygen saturation (rSO2)--measured by a near infra-red spectrophotometer at sea level, 2700 m, and 3700 m-were nearly identical. Exercise at sea level did not reduce this value. In contrast, we observed a decrease in rSO2 after subjects exercised at 2700 m and 3700 m (i.e., 26.9% at 2700 m and 48.1% at 3700 m, respectively). The rSO2 measured 2 min and 3 min after exercise at 3700 m was significantly higher than the preexercise value. From these observations, we concluded that alterations in cardiovascular parameters were apparent only after an exercise load occurred at approximately 3000 m altitude. Acute reduction in cerebral regional oxygen saturation might be a primary cause of headache and acute mountain sickness among unacclimatized trekkers.

End-tidal carbon dioxide monitoring stabilized hemodynamic changes during ECT.

Accumulation of carbon dioxide (CO2) can disturb systemic and cerebral hemodynamics in patients receiving electroconvulsive therapy (ECT). The purpose of this study was to identify the effects of end-tidal CO2 monitoring on hemodynamic changes in patients who received ECT under propofol anesthesia. ECT was prescribed to 40 patients under propofol anesthesia. Ventilation was assisted using a face mask and 100% oxygen, with or without end-tidal CO2 monitoring. Heart rate was significantly increased in patients without end-tidal CO2 monitoring at 1 to 5 minutes after electrical stimulation (p < 0.01). Mean arterial blood pressure and middle cerebral artery blood flow velocity in the group without end-tidal CO2 monitoring were significantly larger than the values in the group with the monitor at 1 to 5 minutes after electrical stimulation. Arterial CO2 tension in the group without end-tidal CO2 monitoring was larger than the value in the group with the monitoring at 1 minute (45 ± 5 mm Hg with the monitor and 56 ± 8 without the monitor) and 5 minutes (37 ± 4 mm Hg with the monitor and 51 ± 8 without the monitor) after electrical stimulation (p < 0.01). Application of end-tidal CO2 monitoring is considered beneficial for safe and effective anesthesia management of patients undergoing ECT, especially patients with an intracranial disorder or ischemic heart disease.

Effects of cardiopulmonary resuscitation at high altitudes on the physical condition of untrained and unacclimatized rescuers.

OBJECTIVE The authors experienced a case of prolonged cardiopulmonary resuscitation (CPR) on Mount Fuji (3776 m) that demanded strenuous work by the rescuers. The objective of this study was to provide information regarding the physiologic effects on the rescuers of performing CPR at moderate altitude. METHODS The effects of CPR at 2700 m and 3700 m above sea level on the physical condition of the rescuers were studied in 8 male volunteers. RESULTS Cardiopulmonary resuscitation for 5 minutes at 3700 m significantly reduced arterial blood oxygen saturation and increased rate-pressure products (P < .05). Scores on the Borg scale, a subjective score of fatigue, after CPR action at 2700 m (P < .05) and 3700 m (P < .01) were higher than the scores at sea level. CONCLUSIONS Prolonged CPR at high altitude exerts a significant physical effect upon the condition of rescuers. A role for mechanical devices should be considered wherever possible.

Experimental use of a transportable hyperbaric chamber durable for 15 psi at 3700 meters above sea level

A transportable hyperbaric chamber durable for 15 psi of pressure was used to treat a patient suffering from moderate acute mountain sickness at 3700 m above sea level. The symptoms were ameliorated a few minutes after pressurization in the chamber. After a 20-minute stay in the chamber, the patient was completely free of symptoms. Since the chamber can be inflated by using compressed air from a cylinder, no strenuous work was required of the operators. This transportable chamber seems to be useful for the treatment of high-altitude disorders at around 3000 m above sea level.

Protein purification and cloning of diacylglycerol lipase from rat brain.

Diacylglycerol (DG) lipase, which hydrolyses 1-stearoyl-2-arachidonyl-sn-glycerol to produce an endocannabinoid, 2-arachidonoylglycerol, was purified from the soluble fraction of rat brain lysates. DG lipase was purified about 1,200-fold by a sequential column chromatographic procedure. Among proteins identified by mass spectrometry analysis in the partially purified DG lipase sample, only DDHD domain containing two (DDHD2), which was formerly regarded as a phospholipase A1, exhibited significant DG lipase activity. Rat DDHD2 expressed in Chinese hamster ovary cells showed similar enzymatic properties to partially purified DG lipase from rat brain. The source of DG lipase activity in rat brain was immunoprecipitated using anti-DDHD2 antibody. Thus, we concluded that the DG lipase activity in the soluble fraction of rat brain is derived from DDHD2. DDHD2 is distributed widely in the rat brain. Immunohistochemical analysis revealed that DDHD2 is expressed in hippocampal neurons, but not in glia.

Balance of older trekkers: data on alpine accidents and performance as assessed using a video game machine

The number of alpine accidents involving older trekkers has increased markedly in developed countries in recent years. More than 76.8% of the trekkers involved in alpine accidents in Japan were older than 40 years, with some experiencing a stroke or myocardial infarction while trekking at altitude. In the present study, we surveyed social trends in trekkers by interview at a popular mountain site, Mt Tanigawa (1963 m in altitude). The total number of trekkers interviewed was 511, and more than 60% of these were older than 40 years. Of trekkers older than 60 years, 42% complained of conditions such as hypertension or diabetes. In 2 volunteer groups (10 younger subjects and 10 older subjects), physical condition was assessed before and after trekking. Significant body weight loss induced by dehydration was observed more often in older subjects than in younger subjects (P < .05). Balance, as measured using the Nintendo WiiFit (Nintendo, Kyoto, Japan), worsened in the older group (P < .05). Local police records for 2009 showed that the total number of alpine accidents was 65. Injuries provoked by stumbling, slipping, and falling accounted for 51% of these, and 82% of casualties were older than 40 years, with 35% being older than 60 years. In conclusion, many older people involved in nonchallenging middle-altitude trekking have problems with regard to overall health and balance. Alpine accidents caused by myocardial infarction, stroke, or hypoglycemia tend to be more common in this population. Alpine rescue teams should be well prepared for this, and older trekkers should be made aware of their increased risk of injury in alpine settings.

Oxygen inhalation using an oxygen concentrator in a low-pressure environment outside of a hospital ☆

Supplementation with oxygen is fundamental in rescue and emergency medicine. However, transportation of oxygen cylinders or a rigid hyperbaric chamber requires large work forces. Also, oxygen in a cylinder may be completely consumed during a rescue action. The oxygen concentrators, which enrich the oxygen percentage of ambient air, may free rescuers from carrying heavy oxygen cylinders. In the present study, 2 types of oxygen concentrators were tested in a mountain hut located at an altitude of 3776 m. Oxygen concentration of the generated gas was 28.6% +/- 0.8% with the first machine, which was powered by an internal battery. Arterial oxygen saturation of the volunteers inhaling through the machine increased from the original 79% +/- 6% to 82% +/- 6%. When the machine was used with a semi-closed circuit, the value increased further to 90% +/- 3%. The second concentrator, which was powered by an external electric generator, outputted 90% +/- 2% oxygen. Arterial oxygen saturation of the volunteers increased to 95% +/- 1%. It is concluded that both types of oxygen concentrators were efficient at high altitude.

Transesophageal echocardiography is useful for an intraoperative diagnosis of pulmonary artery catheter entrapment.

A 57-yr-old man (weight, 61 kg; height, 158 cm) with a history of hypertension and smoking was scheduled for aortic valve replacement to treat severe aortic stenosis. Echocardiography revealed an aortic valve area of 0.6 cm and a mean pressure gradient of 66 mm Hg across the stenotic aortic valve. Left ventricular hypertrophy was evident with normal systolic function and impaired diastolic function indicated by an abnormal relaxation pattern. After anesthetic induction and tracheal intubation, a 5-MHz multiplane transesophageal echocardiography (TEE) probe (Agilent Technologies, Andover, MA) was inserted into the esophagus. A 7.5F pulmonary artery catheter (PAC) (Edward Lifesciences LLC, Irvine, CA) was then inserted through an 8.5F percutaneous sheath introducer (Argon Medical Devices, Athens, TX) positioned in the right internal jugular vein. A normal pulmonary artery wedge pressure tracing was obtained at a depth of 50 cm, and the position of the catheter tip in the right main pulmonary artery was confirmed by TEE. No difficulties or immediate complications were associated with PAC insertion, and TEE of the right atrium, right ventricle, and pulmonary artery revealed no obvious abnormalities. Two vena cava cannulae (DLP69328, 28F cannula for inferior vena cava [IVC]; Medtronic, Minneapolis, MN) were inserted into the right atrium for cardiopulmonary bypass (CPB). After aortic valve replacement, the patient was uneventfully separated from CPB, and the 2 vena cava cannulae were easily removed. About 1 h after separation from CPB, there was a change in the waveform of the PAC suggestive of catheter wedging. The PAC tip was thought to be located too deeply; the anesthesiologist encountered resistance while attempting to gently withdraw the PAC by pulling with mild force and the catheter did not move. Therefore, TEE was interrogated to determine the cause of the resistance. A midesophageal bicaval view, with the multiplane angle at 85° and a field depth of 12 cm, revealed an area of relatively high brightness resembling an echogenic spot on the PAC, which was accompanied by acoustic shadowing and was fixed in the IVC cannulation site (Fig. 1). Gentle traction on the PAC produced invagination of the IVC cannulation site (Fig. 1) (Video 1; see Supplemental Digital Content 1, http://links.lww.com/AA/A37, transesophageal echocardiography showing entrapment of a pulmonary artery catheter [PAC]. Midesophageal bicaval view shows PAC entrapment. An area of relatively high brightness, resembling an echogenic spot, is visible on the PAC [circle], accompanied by acoustic shadowing [triangles]. Traction on the PAC produced invagination of the right atrial wall [arrow] with the echogenic spot and acoustic shadowing. The right atrial wall resembles “tenting” following the manual traction. RA, right atrium; LA, left From the *Department of Anesthesiology, Gunma University Graduate School of Medicine, Gunma; and †Saitama Cardiovascular and Respiratory Center, Saitama, Japan. Accepted for publication July 14, 2009. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.anesthesia-analgesia.org). Address correspondence and reprint requests to Masataka Kuroda, MD, PhD, 3-39-22 Showa-machi, Maebashi City 3718511, Japan. Address e-mail to mkuroda@med.gunma-u.ac.jp. Copyright

The effect of gynecologic laparoscopy on propofol concentrations administered by the target-controlled infusion system

The purpose of this study was to assess the effect of gynecologic laparoscopy on propofol concentrations administered by the target-controlled infusion (TCI) system. Thirteen patients undergoing gynecologic laparoscopy (intraabdominal pressure of 10 mmHg) were enrolled in this study. Anesthesia was induced with vecuronium 0.1 mg·kg−1 and propofol, then maintained by 60% nitrous oxide and sevoflurane in oxygen and a constant infusion of propofol. Propofol was administered to all subjects by means of a target-controlled infusion to achieve propofol plasma concentration at 6.0 µg·ml−1 at intubation and 2.0 µg·ml−1 after intubation. Before and during laparoscopy, plasma propofol concentration was determined using high-performance liquid chromatograhy. Cardiac output (CO) and effective liver blood flow (LBF) were also measured using indocyanine green as an indicator. Before and during pneumoperitoneum, there were no significant differences in propofol concentations between each point. Propofol concentrations were well achieved to predicted concentrations administered by the TCI system during gynecologic laparoscopy under propofol and sevoflurane anesthesia.

Changes in Cerebral Oxygenation Assessed by Near-infrared Spectroscopy during Shoulder Arthroscopy in the Beach Chair Position after Brachial Plexus Block

Background: It is well known that patients undergoing shoulder surgery in the Beach Chair Position (BCP) have a potential risk for cerebral ischemia. Using Near-Infrared Spectroscopy (NIRS), this study aimed to test whether cerebral oxygenation in these patients was impaired by brachial plexus block accompanied with general anesthesia. Methods: Ultrasound-guided interscalene brachial plexus block was performed in 26 patients undergoing elective arthroscopic shoulder surgery under general anesthesia. In all subjects, cerebral oxygenation during anesthesia was evaluated by measuring the Tissue Oxygenation Index (TOI) with NIRS. Results: No differences were seen in TOI values between Pre-BCP and Post-BCP periods in both block and non-block sides, despite a decrease in mean blood pressure (P<0.05, repeated measures one-way ANOVA by the Bonferroni post hoc test). Additionally, no differences were seen in TOI values between block and non-block sides at any time point. Conclusion: Changing from the supine position to the BCP did not appear to impair cerebral oxygenation, regardless of brachial plexus block, in patients undergoing shoulder arthroscopy under general anesthesia.