Fumio Nishihara

Alterations in autonomic nervous control of heart rate among tourists at 2700 and 3700 m above sea level.

OBJECTIVES Many travelers who are not specially trained for activities at high altitude are at risk of physical problems, including cardiovascular disorders, when exposed to high-altitude environments. In the present study, we investigated how actual acute exposure to altitudes of 2700 and 3700 m affected the autonomic nervous control of heart rate in untrained office workers. METHODS Physiological parameters (heart rate, respiratory rate, arterial blood oxygen saturation, and end-expiratory carbon dioxide tension) were measured at sea level, 2700 m, and 3700 m. The power of heart rate variability was quantified by determining the areas of the spectrum in 2 component widths: low frequency (LF; 0.04-0.15 Hz) and high frequency (HF; 0.15-0.5 Hz). The ratio of LF power to HF power (LF:HF), which is considered to be an index of cardiac sympathetic tone, was also assessed. RESULTS Both HF and LF heart rate variability decreased according to the elevation of altitude. High- and low-frequency powers at 3700 m were significantly lower than those at sea level (P < .01 for HF, P < .05 for LF). The LF:HF ratio at 2700 m was not significantly different from that at sea level. However, it was significantly increased at 3700 m (P < .01). CONCLUSIONS At 2700 and 3700 m, the activity of the autonomic nervous system measured by heart rate variability was decreased in untrained office workers. The sympathetic nervous system was dominant to the parasympathetic at 3700 m. These alterations in the autonomic nervous system might play some role in physical fitness at high altitudes.

The cerebral hemodynamic response to electrically induced seizures in man

The hemodynamic response to seizure has long been a topic for discussion in association with the neuronal damage resulting from convulsion. Electroconvulsive therapy (ECT) is an appropriate clinical model for the investigation of the cerebral physiology of seizure. In this study, we monitored the oxygenation state of brain tissue using near infrared (NIR) spectrophotometry, and flow velocity at the middle cerebral artery (MCA) using transcranial Doppler ultrasonography (tc-Doppler) in ninety cases where flow velocity at the middle cerebral artery (MCA) using transcranial Doppler ultrasonography (tc-Doppler) in ninety cases where ECT was prescribed to patients suffering from endogenous depression. Under general anesthesia with thiopental and succinyl choline, an electrical current was applied bilaterally at the minimal energy level. Throughout the therapy, end-tidal CO2 tension was maintained at 30-35 mmHg, and the SpO2 value was maintained above 98% by manual ventilation assistance. The total- and oxy-hemoglobin contents in the brain were reduced during the electrical shock, and then recovered to the pre-shock value (total-hemoglobin; 44.13 +/- 12.88 s after the shock, oxy-hemoglobin; 88.62 +/- 11.69 s after the shock). Subsequently, these values further increased beyond the preshock value. On the other hand, the deoxy-hemoglobin content increased for 90.73 +/- 15.88 s during and after the electrical shock, and decreased afterward. Reduction of cytochrome aa3 began 3.04 +/- 0.51 s after the electrical shock, and this was reoxygenated at 171.88 +/- 12.95 s after the shock.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Landiolol and esmolol prevent tachycardia without altering cerebral blood flow.

PurposeSeveral ß-adrenergic-blocking drugs have been used during electroconvulsive therapy (ECT) to stabilize the hemo-dynamic alterations following electrical stimulation. The effects of two ultra-short acting ß-adrenergic-blocking drugs, esmolol and landiolol, on systemic and cerebral circulation were studied during ECT.MethodsIn the first study (n = 15), dose-dependent hemodynamic changes were studied when landiolol was administered immediately after induction of anesthesia. In the second study (n = 12), effects of esmolol and landiolol on systemic and cerebral circulation were compared. Patients in Study 1 received three doses of landiolol, and patients in Study 2 received two types of ß-adrenergic-blocking drugs, in a randomized crossover design in a series of ECT trials.ResultsIn the first study, 0.25 to 0.5 mg·kg-1 landiolol induced a lower heart rate after the electrical stimulation compared to vehicle (P < 0.01). Landiolol did not have significant effects on blood pressure. In the second study, heart rate was stabilized by 1.0 mg·kg-1 esmolol iv or 0.5 mg·kg-1 landiolol iv. Increase in mean blood pressure was ameliorated by esmolol (P < 0.01), but not by landiolol. Mean cerebral blood flow velocity in the middle cerebral artery increased at one to two minutes after the electrical stimulation regardless of the use of ß-adrenergic-blocking drugs (P < 0.01). Muscular and electroencephalo-graphic seizure durations were not significantly altered by the ß-adrenergic-blocking drugs.ConclusionLandiolol suppresses heart rate elevation during ECT without affecting blood pressure. Cerebral blood flow velocity in the middle cerebral artery is not affected by the use of either esmolol or landiolol.RésuméObjectifCertains ß-bloquants ont été utilisés pendant la sismothérapie pour stabiliser les changements hémodynamiques qui suivent la stimulation électrique. Les effets de deux ß-bloquants à action ultracourte sur la circulation générale et cérébrale, ľesmolol et le landiolol, ont été étudiés pendant la sismothérapie.MéthodeDans la 1e étude (n = 15), les changements hémodynamiques reliés à la dose ont été étudiés quand le landiolol est administré immédiatement après ľinduction de ľanesthésie. Dans la 2e étude (n = 12), les effets de ľesmolol et du landiolol sur la circulation générale et cérébrale ont été comparés. Les patients de la 1e étude ont reçu trois doses de landiolol et ceux de la 2e, deux types de ß-bloquants ďune façon randomisée et croisée dans une série ďépreuves de sismothérapie.RésultatsDans la 1e étude, de 0.25 à 0.5 mg·kg-1 de landiolol, comparé au véhicule, ont fait baisser la fréquence cardiaque après la stimulation électrique (P < 0.01). Le landiolol n’a pas eu ďeffet significatif sur la tension artérielle. Dans la 2e étude, la fréquence cardiaque a été stable avec 1.0 mg·kg-1 ďesmolol iv ou 0.5 mg·kg-1 de landiolol iv. La hausse de la tension artérielle moyenne a été corrigée par ľesmolol (P < 0.01), mais non par le landiolol. Le débit cérébral moyen dans ľartère cérébrale moyenne a augmenté de une à deux minutes après la stimulation électrique sans égard à ľusage de ß-bloquants (P < 0,01). La durée des convulsions musculaires et électroencéphalographiques n’a pas été significativement modifiée par les ß-bloquants.ConclusionLe landiolol supprime ľélévation de la fréquence cardiaque pendant la sismothérapie sans toucher la tension artérielle. Le débit cérébral dans ľartère cérébrale moyenne n’est pas modifiée par ľusage de ľesmolol ou du landiolol.

Pre-ictal bispectral index has a positive correlation with seizure duration during electroconvulsive therapy.

Propofol anesthesia increases the seizure threshold of patients receiving electroconvulsive therapy. Excessive neuronal suppression could result in an unacceptably short seizure. We sought to identify the correlation between the pre-ictal bispectral index (BIS) score and seizure duration in patients receiving electroconvulsive therapy under propofol anesthesia. BIS was monitored in 38 psychotically depressed patients. Anesthesia was induced by a bolus injection of 1 mg/kg of propofol. The duration of muscular and electroencephalographic seizure was measured during the therapy. The BIS immediately before the electrical shock was 54 ± 13. Both muscular and electroencephalographic seizure durations had a positive correlation with pre-ictal BIS (r = 0.68 and 0.73, respectively;P < 0.01). After the electrically induced seizure, BIS decreased to 30 ± 8, reflecting post-ictal suppression. BIS scores when the patients had awakened after the seizure had a wide variation (range, 29–81; mean, 45; sd, 13). In conclusion, seizure duration has a positive correlation with BIS immediately before electrical shock; however, BIS may not be an accurate predictor of awakening after electrical shock.

Benefits of the laryngeal mask for airway management during electroconvulsive therapy

Accumulation of carbon dioxide (CO2) can disturb systemic hemodynamics and increase the seizure threshold in patients receiving electroconvulsive therapy (ECT). The purpose of this study was to investigate the effects of the laryngeal mask on blood gas, hemodynamics, and seizure duration during ECT under propofol anesthesia. Ventilation was assisted using either a face mask (n = 23) or laryngeal mask (n = 23) and 100% oxygen. There was no significant difference in PaO2 between the two groups. PaCO2 was greater in the face mask group than the laryngeal mask group at 3 minutes (54 ± 11 mm Hg, 41 ± 8 mm Hg, respectively) and 5 minutes (52 ± 11 mm Hg, 43 ± 15 mm Hg, respectively) after electrical stimulation (p < 0.01). Mean blood pressure was higher than the corresponding preanesthesia value at 1 to 5 minutes after electrical stimulation in the face mask group and at 1 to 3 minutes after electrical stimulation in the laryngeal mask group. Mean seizure duration in the face mask group was significantly shorter than that in the laryngeal mask group (33 ± 11 seconds, 42 ± 10 seconds, respectively p < 0.01). The change in PaCO2 was minor in the laryngeal mask group compared with the face mask group and seizure duration was longer in the laryngeal mask group. Laryngeal mask may be suitable for airway management during ECT anesthesia, especially when fitting a face mask is difficult.

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.

Hemodynamic changes during electroconvulsive therapy under propofol anesthesia

Informed consent was obtained from each patient or, where necessary, the appropriate relative. The study protocol was approved by a local Clinical Study Committee, which considers the ethics and legal aspects of clinical investigations. ECT was prescribed to 30 patients suffering from endogenous depression. The patients ranged from 15 to 78 years of age and were in good physical heath. No patient had any known cardiovascular or cerebrovascular complication or drug allergy. All patients were treated more than six times (three times per week at 2-day intervals). The data were obtained in the second ECT trial in each case. To avoid an unfavorable parasympathetic reflex, atropine (0.01mg·kg 1) was given intramuscularly as premedication. Arterial blood pressure was measured continuously at the right radial artery by a tonometric BP monitor (CBM-7000; Colin, Komaki, Japan). General anesthesia was induced with propofol (1mg·kg 1). Propofol was administered over 15 s through an intravenous catheter. After loss of consciousness, succinylcholine chloride (1mg·kg 1) was administered and ventilation was assisted by a face mask with 100% oxygen. One minute after succinylcholine chloride injection, an electrical current was applied bilaterally for 5s at the minimal stimulus intensity, which had been determined in the first ECT trial by stepwise increasing electrical intensity. The electroshock stimulus was delivered by a trained psychiatrist using an ECT-stimulator (CS-1; Sakai Iryo, Tokyo, Japan). The efficacy of electrical stimulation was determined by the so-called tourniquet technique, which requires observation of convulsive movements of the distal leg, around which an inflated tourniquet was set to block the distribution of muscle relaxant. The end-expiratory CO2 partial pressure (endtidal CO2) at the nostrils and arterial blood oxygen saturation (SpO2) were monitored by a respiration monitor (Capnomac Ultima; Datex, Helsinki, Finland). The

Carbon dioxide exhalation temporarily increases during electroconvulsive therapy

Electroconvulsive therapy induces hypermetabolism and elevates oxygen and energy demands, while more carbon dioxide is produced than usual. The purpose of the present study was to determine the elevated carbon dioxide exhalation and the adequate ventilation volume during electroconvulsive threrapy. Carbon dioxide exhalation during an electrically induced seizure was continuously monitored by capnography and spirography in 15 patients with endogenous depression. A laryngeal mask airway was used to measure the airway gas flow. Data were collected during a total of 80 electroconvulsive therapy trials. The carbon dioxide exhalation at 1 min after electrical stimulation was higher than the control value (2.8 ± 0.4 versus 2.3 ± 0.3 ml·min−1·kg−1, mean ± SD; P < 0.05). The ventilation volume was increased for 3 min after the electrical stimulation to maintain the end-tidal carbon dioxide partial pressure at 35–40 mmHg. The results showed that increasing the ventilation volume by approximately 20% may be necessary to compensate for the increased carbon dioxide exhalation during electroconvulsive therapy.

Blood pressure control with glyceryl trinitrate during electroconvulsive therapy in a patient with cerebral aneurysm.

Electroconvulsive therapy (ECT) induces abrupt changes in systemic and cerebral haemodynamics that are problematical for patients with cardiovascular or cerebrovascular complications. Although there are no reports of ECT causing rupture of a cerebral aneurysm, excessive haemodynamic changes in such patients must be avoided. Short-acting -adrenoceptorblocking agents, e.g. esmolol, are suitable to attenuate hyperdynamic states after ECT. However, this type of drug is sometimes inapplicable for medical or social reasons. We describe a patient with a cerebral aneurysm who was successfully treated with glyceryl trinitrate before undergoing ECT. A 68-yr-old female diagnosed with endogenous depression and resistant to medication needed ECT. Preoperative evaluation with computed tomography revealed a cerebral aneurysm (6 mm in diameter) with a bleb in the middle section of the anterior communicating artery. Her family refused to have surgical clipping performed before the series of ECT. They understood the risks of both the procedure and cerebral aneurysm rupture, and written informed consent was obtained. Atropine 0.01 mg kg 1 intramuscularly (i.m.) was given as a vagolytic premedication. Arterial blood pressure was measured continuously at the right radial artery using a tonometric BP monitor (CBM-7000®; Colin Co Ltd, Komaki, Japan). The tc-Doppler probe (Sonos 5500®; Agilent Technology, Palo Alto, CA, USA) was adjusted to detect the middle cerebral artery flow (right temporal side) using a 2 MHz ultrasonic wave. The Doppler signals were obtained at a depth of 45–55 mm from the surface and the velocity was calculated automatically by tracing the waveforms. General anaesthesia was induced with propofol, 1 mg kg 1, over 15 s through an indwelling intravenous (i.v.) cannula. After consciousness had been lost, succinylcholine chloride (1 mg kg 1) was administered and the lungs inflated with 100% oxygen via a facemask. Glyceryl trinitrate (0.01–0.02 mg kg 1) was administered i.v. immediately after the succinylcholine to prevent excessive hypertension during the ECT. One minute later, an electrical current was applied bilaterally for 5 s at the minimal stimulus intensity, which had been determined in a first ECT trial by increasing the electrical intensity stepwise. The electroshock was delivered by a trained psychologist using an ECT stimulator (CS-1®; Sakai Iryo Co Ltd, Tokyo, Japan). The efficacy of electrical stimulation was determined using a tourniquet. The lungs were then gently inflated and PETCO2 at the nostrils was maintained at 4.0–4.7 kPa and SPO2 98%. The patient received ECT three times a week for a total of 20 treatments. Heart rate and blood pressure were largely unchanged after the ECT stimulus. Maximum changes of the averages (average of the 20 ECT sessions) were a 13.6% increase in heart rate (preanaesthesia 109 12 beats min 1, pre-electrical stimulus 107 10 beats min 1, maximum after the shock 122 10 beats min 1, respectively). The increase in mean blood pressure was 8.4% (preanaesthesia 81 12 mmHg, pre-electrical stimulus 71 11 mmHg, maximum after the shock 77 18 mmHg, respectively), 30 s after the electrical stimulus. The mean flow velocity in the middle cerebral artery was increased to a maximum of 12.7% at 30 s after the electrical stimulus (preanaesthesia 67 8 cm s 1, pre-electrical stimulus 65 7 cm s 1, maximum after the shock 73 10 cm s 1, respectively). The patient’s mental condition improved gradually, and she was discharged after the completion of the course of treatment without any physical problems. An intracranial aneurysm is listed as a contraindication of ECT, since the abrupt haemodynamic changes during therapy may cause aneurysmal rupture. However, there are several reports describing safe ECT management of patients with a cerebral aneurysm [1,2]. In all reports, some kind of antihypertensive drug was given to prevent excessive hypertension. Esmolol is the antihypertensive agent most used since short-acting -adrenoceptor-blocking European Journal of Anaesthesiology 2003; 20: 70–78