Biomedical subjects

H Kitahata

Publications and source records attributed to H Kitahata.

At least 37 records · Page 2Linked to original sources

PubMed1998

Role of left atrial appendage in left atrial reservoir function as evaluated by left atrial appendage clamping during cardiac surgery.

We evaluated the role of left atrial appendage (LAA) in the left atrial (LA) reservoir function by assessing the changes in LA flow dynamics after LAA clamping during cardiac surgery. The subjects were 8 patients who had undergone coronary artery bypass grafting (CABG) and 7 who had undergone mitral valvular surgery due to mitral regurgitation. We recorded transmitral, pulmonary venous and LAA flow velocity patterns by intraoperative transesophageal pulsed Doppler echocardiography, monitoring LA pressure before and 5 minutes after LAA clamping. The maximal LAA area was significantly greater, and the peak late diastolic LAA emptying flow velocity was significantly lower before LAA clamping in the mitral regurgitation group than in the CABG group. In both groups, the peak early and late diastolic transmitral and pulmonary venous flow velocities significantly increased, and the peak second systolic pulmonary flow velocity significantly decreased during LAA clamping. There were no significant changes in heart rate and systemic systolic blood pressure during LAA clamping, whereas mean LA pressure and maximal LA dimension significantly increased in both the groups. The LA pressure-volume relation during ventricular systole shifted upward and to the left during LAA clamping, and the slope was steeper in the MR group than in the CABG group. We conclude that the LAA is more compliant than the LA main chamber, and plays an important role in LA reservoir function in the presence of LA pressure and/or volume overload.

Aged↗

PubMed1998

Anaesthetic management of a patient with Williams syndrome undergoing aortoplasty for supravalvular aortic stenosis.

PURPOSE: A case of a patient associated with Williams syndrome undergoing aortoplasty for supravalvular aortic stenosis is presented. CLINICAL FEATURES: Williams syndrome is a rare disease associated with a characteristic facies, supravalvular aortic stenosis, and mental retardation. A 15-yr-old girl with Williams syndrome underwent aortoplasty for supravalvular aortic stenosis. Anaesthesia was induced with fentanyl and thiamylal, and maintained with nitrous oxide, oxygen, sevoflurane, and continuous intravenous infusion of fentanyl. Supravalvular aortic stenosis was evaluated using a multiplane transesophageal echocardiography (TEE) probe before and after repair. CONCLUSION: Multiplane TEE was found to be very useful for anaesthetic management in a patient with Williams syndrome undergoing aortoplasty for supravalvular aortic stenosis.

Adolescent↗

PubMed1998

Effects of nicardipine on ventriculo-arterial coupling in humans.

The ratio of effective arterial elastance (Ea) to left ventricular elastance (Ees) is an indicator of the coupling between ventricular properties and arterial load properties. Another criterion for the coupling between an energy source and its load is the principle of economical fuel consumption, or mechanical efficiency, which is defined as the ratio of stroke work (SW) to myocardial oxygen consumption per beat (MVO2). It has been revealed that SW of ventricular contraction is maximized when Ea/Ees = 1, while mechanical efficiency is maximized when Ea/Ees = 0.5. The purpose of the present study was to investigate the ventriculo-arterial coupling during hypertension, and the effects of nicardipine on this relationship in surgical patients using Ea/Ees and SW/MVO2 as indicators. Anaesthesia was maintained with isoflurane, nitrous oxide, and fentanyl. Radial artery pressure was displayed on a polygraph, and left ventricular end-systolic and end-diastolic volumes were determined by use of transoesophageal echocardiography. Ees was calculated as MAP/(ESVI-4), where MAP is mean arterial pressure and ESVI is end-systolic volume index. Ea was calculated as the ratio of MAP to stroke volume index (SVI). Stroke work index (SWI) was calculated as the product of MAP and SVI. MVO2 was assessed by estimating the ventricular pressure-volume area index (PVAI), which is expressed as the sum of SWI and the end-systolic potential energy index. Before (baseline), and 3, 10, 20, and 30 min after i.v. nicardipine (30 micrograms kg-1), Ea/Ees and SWI/PVAI were determined in 14 surgical patients with intraoperative hypertension. Before nicardipine (during hypertension), Ea was almost equal to Ees, whereas Ea/Ees was significantly reduced to about 0.5-0.6 at 3, 10, and 20 min after nicardipine. SWI/PVAI was maximized and significantly greater than the baseline value at 3 min after nicardipine. These results suggest that, during hypertension, ventricular and arterial properties were so matched as to maximize SW at the expense of the work efficiency, whereas mechanical efficiency of ventricular contraction was maximized after nicardipine.

Adult↗

PubMed1996

[Isoflurane and sevoflurane impair left ventricular relaxation in dogs with fixed heart rate].

The effects of isoflurane (Iso) and sevoflurane (Sev) on left ventricular relaxation were evaluated in 22 open-chest dogs with fixed heart rate (130 beats.min-1) using atrial pacing. Fentanyl was injected intravenously to maintain anesthesia during the preliminary preparation. In both Iso and Sev groups (n = 11), left ventricular systolic pressure, mean aortic pressure and dp/dt max were significantly decreased at 0.5 MAC, but there was no significant change in left ventricular end-diastolic pressure. Left ventricular systolic function was depressed to the similar extent in both groups. In Sev group, -dp/dt max and time constant of isovolumic left ventricular pressure fall (T) increased significantly at 0.5 MAC but it increased at 1.5 MAC in Iso group. T at 0.5 MAC Sev was also significantly longer compared with T at equipotent Iso. These findings suggest that Sev may impair isovolumic left ventricular relaxation more strongly than Iso, and this may result from the difference of the effect of each agent on intracellular Ca2+ homeostasis in the myocardium.

Anesthetics, Inhalation↗

PubMed1996

[Blood coagulation-fibrinolysis system during transurethral resection evaluated by thrombelastography].

Intraoperative changes in blood coagulation-fibrinolysis system were evaluated in 21 patients under epidural anesthesia by thrombelastography. Ten patients received transurethral resection of prostate (TUR-P) and 11 patients received transurethral resection of bladder tumor (TUR-Bt). Thrombelastographic variables: reaction time (R), coagulation time (K), maximum amplitude (MA), and amplitude 60 min after MA (A 60) were measured. The coagulability was evaluated by R + K, the absolute strength of clot by MA, and fibrinolysis using MA-A60. There was no significant change of these indices in TUR-Bt group. On the other hand, in TUR-P group, R + K was significantly shortened and MA-A60 had a tendency to increase it, but MA caused no change. Resected prostatic weight correlated significantly with the decrease of MA, and had a tendency to correlate with the increase of MA-A60 in TUR-P group. Both coagulation and fibrinolysis were activated in TUR-P group. When the resected prostatic weight is large, the risk of coagulopathy may increase.

Anesthesia, Epidural↗

PubMed1995

[The effects of low dose clonidine on perioperative hemodynamics and anesthetic requirements in elderly patients].

The effects of clonidine, alpha 2-adrenergic receptor agonist, on perioperative hemodynamics and anesthetic requirements were studied in randomized 20 elderly patients without hypertension (ASA I-II) scheduled for elective abdominal surgery under general anesthesia. The control group (n = 10) was premedicated with oral diazepam 0.1 mg.kg-1 90 min prior to arrival in the operating room. The clonidine group (n = 10), in addition, received clonidine approximately 2.5 micrograms.kg-1 orally at the same time. Anesthesia was induced with fentanyl 2 micrograms.kg-1 and thiamylal 4 mg.kg-1. Vecuronium 0.15 mg.kg-1 following 0.01 mg.kg-1 priming dose was used to facilitate endotracheal intubation. Anesthesia was maintained with isoflurane in 50% nitrous oxide-oxygen and supplementary fentanyl. Clonidine effectively attenuated the cardiovascular response associated with laryngoscopy and tracheal intubation. Intraoperative variability of heart rate was significantly lower in patients receiving clonidine compared with controls. No significant differences in the requirements of either isoflurane or narcotic supplementation were observed between the two groups. We conclude that a low dose clonidine is a useful adjunct in the management of elderly patients without producing side effects.

Abdomen↗

PubMed1995

[Hypoxemia during cesarean section--evaluation of venous air embolism by transesophageal echocardiography].

We studied the incidence and cause of hypoxemia during Cesarean section under general anesthesia. Arterial oxygen desaturation (< or = 95%) occurred in 6 of 28 patients (21%). Venous air embolism (VAE) was detected in 7 of 28 subjects (25%), but the severity of which was mild and was not associated with oxygen desaturation. While, there were significant differences in obesity index, preoperative respiratory function, and PaO2 after the induction of anesthesia between the patients with and without oxygen desaturation. Our results suggest that hypoxemia may occur frequently during Cesarean section under general anesthesia, but is not caused by VAE, and is related with the physiological changes associated with pregnancy.

Adult↗

PubMed1995

[Effects of PGE1 on pulmonary arterial and venous flow in elderly patients--evaluation by transesophageal Doppler echocardiography].

Effects of PGE1 on pulmonary arterial and venous flow were evaluated noninvasively with transesophageal Doppler echocardiography in 13 elderly patients (70-79 years old), and the results were compared with those in control group of 13 patients (20-48 years old). In control group, infusion of PGE1 at a rate of 20 ng.kg-1.min-1 decreased pulmonary arterial pressure significantly, but not in elderly patients even at a rate of 50 ng.kg-1.min-1. In elderly patients, effects of PGE1 were more remarkable for afterload reduction than preload, so that cardiac output was maintained without change in stroke volume and heart rate, but with increase of heart rate in control patients. From our results, it is concluded that PGE1 may have less effect on pulmonary hemodynamics in elderly patients.

Adult↗

PubMed1995

[Bronchospasm during anesthesia in a patient with Prader-Willi syndrome].

A patient with Prader-Willi syndrome developed bronchospasm during anesthesia. The patient was a 9-year-old boy and was scheduled for orchiopexy. His psychomotor development was delayed, and at 12 months of age he was diagnosed as Prader-Willi syndrome by chromosomal examination. The patient weighed 17 kg, was 111 cm tall, and had no symptom of upper respiratory infection preoperatively. Preoperative examinations were normal except supraventricular extrasystole in electrocardiogram. Following administration of scopolamine 0.15 mg intramuscularly as preanesthetic medication, anesthesia was induced smoothly by slow induction using N2O-O2-sevoflurane. However, right after endotracheal intubation with vecuronium 2 mg, remarkable stridor was noticed. Despite hyperventilation, the patient exhibited hypercapnia, and the diagnosis of bronchospasm was made. Aminophylline and steroid were administered intravenously and halothane was inhaled instead of sevoflurane. The bronchospasm was improved gradually and surgery was finished. Prader-Willi syndrome is an uncommon disease first reported by Prader in 1956 and characterized by hypotonia, hypomentia, hypogonadism and obesity. In the perioperative management for a patient with Prader-Willi syndrome, special attention must be paid to the abnormalities in the upper and lower respiratory systems.

Adrenergic beta-Agonists↗

PubMed1994

[Effects of diltiazem hydrochloride on blood gases].

The effects of diltiazem, Ca ion channel blocker, on arterial blood gases were evaluated in 50 patients (G-I: 24 patients undergoing abdominal surgery, G-II: 26 patients undergoing non-abdominal surgery). Diltiazem hydrochloride was administered to prevent intraoperative hypertension as a bolus (5 mg) followed by a continuous infusion (5-10 micrograms.kg-1.min-1). Arterial blood gases were analyzed just before, as well as 5 and 15 min after the administration of diltiazem. In G-I, arterial blood oxygen tension decreased significantly (P < 0.001) from 210.8 +/- 42.4 to 197.7 +/- 50.2 mmHg 5 min after infusion, and to 193.2 +/- 53.4 mmHg 15 min after; while there was no significant difference in G-II. Diltiazem infusion may deteriorate oxygenation in patients undergoing abdominal surgery, and therefore oxygenation should be carefully monitored.

Abdomen↗

PubMed1994

[Severe hypoxemia during cesarean section].

We describe three cases in which severe hypoxemia occurred during cesarean section. The first and second patients showed low oxygen saturation (91, 90%, respectively) on their arrival at the operation room, and hypoxemia deteriorated rapidly after the induction of anesthesia. During surgery low oxygen saturation, ranging from 90 to 95%, persisted until the beginning of spontaneous respiration. In the third patient, oxygen saturation fell suddenly to 93% after the delivery of a neonate, and the arterial blood gas analysis revealed Pao2 68.5 mmHg with 38% oxygen. Hypoxemia was transient and resolved at the end of operation. Parturients have been reported to be likely to develop hypoxemia physiologically. Apnea for a short interval during tracheal intubation may cause severe hypoxemia in parturients compared with normal subjects. Ritodrine, a beta 2 stimulator, which was administered in the first and second patients just prior to operation, may be one of the factors leading to hypoxemia because of its inhibition of hypoxic pulmonary vasoconstriction. Venous air embolism (VAE) may occur frequently during cesarean section, especially during repair of the uterus. VAE may have caused hypoxemia in the third patient. In conclusion, parturients should be monitored carefully with pulse oximetry during cesarean section.

Adult↗

PubMed1993

[Is thoracic epidural anesthesia beneficial to myocardial ischemia?--Influence of hemodynamics].

The effects of thoracic epidural anesthesia (TEA) on regional myocardial blood flow (RMBF) and hemodynamics were evaluated in open-chest dogs with coronary artery stenosis. In the 6 dogs with pressure-rate quotients (PRQ) of greater than 0.8, TEA caused a significant increase of the ratio of endocardial to epicardial RMBF in the ischemic region and tended to increase the ratio of RMBF in the ischemic to normal area, resulting in improved myocardial ischemia. There was no reduction of myocardial ischemia in the 11 dogs with PRQ of less than 0.8. The hemodynamic effects determine whether TEA is favorable for the ischemic heart or not. It appears that PRQ is useful as an indicator of myocardial oxygen balance during TEA.

Anesthesia, Epidural↗

PubMed1993

[Left ventricular function during hypoxia--II: Effects of intramyocardial pH].

We investigated the effects of intramyocardial acidosis on cardiac function during hypoxia in mongrel dogs (n = 50). Intramyocardial pH in subendocardium of left ventricle was measured continuously using a pH electrode. During hypoxia (PaO2 = 20 mmHg) caused by inhalation of low oxygen fraction, intramyocardial pH decreased significantly following initial enhancement. Intramyocardial pH correlated significantly with arterial pH, base excess, lactic acid (LA) levels, coronary venous PcO2, and coronary venous-arterial PcO2 difference. There were significant correlations between intramyocardial pH with maximum rate of rise of left ventricular pressure (LV dp/dt max), left ventricular end-diastolic pressure (LVEDP), LVEDP/LVP and the time constant of exponential isovolumic left ventricular pressure fall. High arterial LA levels tended to cease myocardial LA uptake and production, turning LA balance into zero. LV dp/dt max was low in such a condition. Myocardial LA production decreased intramyocardial pH, but LV dp/dt max was maintained at high levels of LA production. These observations suggest that myocardial LA production maintains left ventricular function with the increase of ATP by acceleration of anaerobic glycolysis. In conclusion, during hypoxia, intramyocardial acidosis was caused by the increase of arterial LA level, myocardial anaerobic glycolysis and ATP breakdown, and it worsened left ventricular contractile function and relaxation. Arterial LA levels can play a major part in intramyocardial acidosis, but the increase in myocardial LA production might be beneficial to left ventricular contractile function.

Animals↗

PubMed1993

[Effects of sevoflurane on left ventricular diastolic function using transesophageal echocardiography].

The effects of sevoflurane on left ventricular diastolic filling were evaluated using transesophageal Doppler echocardiography in 10 normal subjects. The time-velocity integral of early filling decreased significantly with sevoflurane 1 MAC (7.73 +/- 2.05 to 6.82 +/- 1.90 cm), suggesting impaired left ventricular relaxation. Abnormal left ventricular relaxation results in compensatory increment of peak velocity and time-velocity integral during atrial filling, both of which were significantly decreased by sevoflurane in this study (35.5 +/- 6.6 to 29.1 +/- 4.8 cm.sec-1, 3.22 +/- 0.65 to 2.73 +/- 0.67 cm, respectively). Although the ratio of early peak velocity to late filling velocity was unchanged, it appears that left ventricular diastolic function including active relaxation, passive compliance, atrial contraction, and elastic recoil was impaired by sevoflurane 1 MAC.

Adult↗

PubMed1993

[Left ventricular function during hypoxia. 1: Effect of blood glucose level].

We investigated the effects of blood glucose levels and myocardial glucose uptake on cardiac function during hypoxia in mongrel dogs (N = 50). During hypoxia (PaO2 = 20 mmHg) caused by inhalation of low concentration of oxygen for 2 hours, left ventricular (LV) function including LV pressure, maximum rate of rise of LV pressure, and cardiac index decreased significantly following initial enhancement. There were significant correlations between these hemodynamic parameters and blood glucose levels. The blood glucose levels correlated significantly with myocardial glucose uptake and blood lactic acid levels (r = 0.660: P = 0.000, r = 0.380: P = 0.000, respectively). Eight of nine dogs which died within 90 minutes during hypoxia showed low blood glucose levels and high lactic acid levels. During hypoxia, myocardial glucose uptake increased to more than five times of control value. On the other hand myocardial lactic acid uptake decreased and turned to production. At the same degree of blood lactic acid levels, LV function was maintained better with high blood glucose levels than with low levels. With low blood glucose levels, myocardial lactic acid uptake and production tended to cease. The pronounced change in LV function during hypoxia could be partially explained by decreased production of ATP due to decrease in myocardial glucose uptake and high lactic acid levels. It seems that high blood glucose levels are preferable to maintain cardiac performance under such a condition.

Animals↗

PubMed1992

[Effects of sevoflurane on regional myocardial oxygen balance in the canine heart with coronary artery stenosis].

The effects of increasing inspired sevoflurane (Sev) concentrations (0.5, 1.0, 1.5, 2.0 MAC) on regional myocardial oxygen balance and metabolism were studied in 10 open-chest dogs with coronary artery stenosis. Regional myocardial oxygen balance was assessed by continuous recording of subendocardial and subepicardial oxygen tensions. After the basal measurement, the left circumflex coronary artery blood flow (CBFLCX) was reduced by 20% with a screw flow regulator. The institution of stenosis caused a slight but significant decline in subendocardial oxygen tension. Otherwise, there were no significant differences between basal values and those after the stenosis. During the subsequent inhalation of Sev at 0.5, 1.0 and 1.5 MAC, endocardial oxygen tension was maintained at the level of control value. Sev 2.0 MAC caused a severe reduction in systemic arterial pressure and resulted in a marked and significant decline of endocardial oxygen tension compared with control value. On the other hand, subepicardial oxygen tension remained unchanged during each Sev inhalation. The ratio of epicardial/endocardial oxygen tension did not show a significant decline with increasing Sev concentration. It seems that Sev may not possess sufficient potency to cause myocardial ischemia by redistribution of coronary blood flow.

Anesthesia, Inhalation↗

PubMed1991

[Effects of sevoflurane, isoflurane, and halothane on regional myocardial blood flow in the ischemic canine heart].

The effects of sevoflurane (Sev), isoflurane (Iso), and halothane (Hal) on coronary circulation were studied in 30 dogs with acute coronary arterial stenosis. Regional myocardial blood flow (rMBF) was measured by hydrogen clearance method. There was no significant difference between each anesthetic agent in heart rate, mean arterial pressure, and cardiac output under any anesthesia level. As the inspired concentration of each anesthetic is increased, rMBF decreased significantly and rMBF/rate-pressure-product (RPP) ratio increased in normal area. In Sev and Iso groups, rMBF/RPP ratios were higher than that in Hal group, suggesting luxury perfusion caused by Sev and Iso. In the ischemic area, rMBF was reduced depending on the inspired concentration of each anesthetic agent and transmural maldistribution of blood flow was not observed with any anesthetic agent. Nevertheless the ratio of rMBF in ischemic area to that of normal area was decreased in Sev and Iso groups, but not in Hal group. In this study, neither Sev nor Iso worsened regional myocardial ischemia. However, Sev-induced coronary vasodilation may cause regional myocardial ischemia by redistribution of flow under steal prone condition.

Anesthetics↗

PubMed1990

Hemodynamic effects of high-frequency jet ventilation in dogs with acute right coronary arterial ligation and pulmonary arterial banding.

The hemodynamic effects of high-frequency jet ventilation (HFJV), synchronized with diastole, and intermittent positive-pressure ventilation (IPPV) were studied in 10 dogs with acute right-sided myocardial ischemia and elevated right ventricular pressure. Myocardial ischemia was produced by ligation of the proximal right coronary artery (RCA), then the right ventricular pressure was elevated to facilitate the ischemia by banding the main pulmonary artery. Before and 1, 2, 3, and 5 hr after the RCA ligation, cardiorespiratory variables for each ventilatory mode and creatine phosphokinase MB isoenzyme (CPK-MB) were measured. During HFJV compared with IPPV: there were significant increases in stroke index and left ventricular stroke work index at all ischemic periods, and decreases in peak and mean airway pressures and pulmonary vascular resistance at all ischemic periods, and in the product of systolic right ventricular pressure and heart rate at 2 hr, 3 hr, and 5 hr. The difference in mean airway pressure between IPPV and HFJV correlated significantly with those in cardiac index and stroke index (r = 0.575 and 0.779, respectively). CPK-MB was significantly greater at 3 hr and 5 hr than that before RCA ligation. These findings suggest that HFJV synchronized with diastole offers hemodynamic advantages over IPPV to ischemic right ventricle with constricted pulmonary artery, mainly due to lowering the mean airway pressure.

Journal Article↗