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Biomedical subjects

M Kuro

Publications and source records attributed to M Kuro.

At least 73 records · Page 4Linked to original sources
PubMed1993

Effects of flumazenil during administration of midazolam on pial vessel diameter and regional cerebral blood flow in cats.

We implanted closed cranial windows in ten cats in order to observe the response of pial vessel diameter by microscopy using fluorescein isothiocyanate-labeled dextran and regional cerebral blood flow (rCBF) by laser Doppler flowmetry during administration of midazolam and reversal with flumazenil. Midazolam was given at 0.8 mg.kg-1 x min-1 for 10 min and maintained at 0.04 mg.kg-1 x min-1 for 50 min (total 10 mg.kg-1). The diameter of arterioles and venules and rCBF showed no significant change. During the last 10 min of midazolam administration, flumazenil, given at 0.1 mg.kg-1 x min-1 for 10 min (total 1 mg.kg-1), caused an increase of MAP and rCBF (P < 0.01) at 5 min after infusion and diameter of larger arterioles (> 50 microns) and venules (50-100 microns) were dilated (P < 0.05). These results indicate that midazolam does not affect the diameter of cerebral arterioles and venules; however, the reversal effects of flumazenil against midazolam are transient vasodilation of larger arterioles accompanied by an elevation of MAP, and an increase in CBF.

Animals↗
PubMed1993

Adrenoceptor mechanism involved in thiopental-epinephrine-induced arrhythmias in dogs.

The authors investigated the role of alpha 1- and beta-adrenoceptors on induction of ventricular arrhythmias during thiopental anesthesia in dogs and compared with that during halothane anesthesia. Throughout this study, arrhythmogenic threshold of epinephrine during thiopental anesthesia was designed to be comparable with that during halothane anesthesia. Phenylephrine, an alpha 1-agonist, and isoproterenol, a beta-agonist, consistently failed to provoke arrhythmias during thiopental or halothane anesthesia. The interaction between phenylephrine and isoproterenol in inducing arrhythmias was synergistic and additive during halothane and thiopental anesthesia, respectively, indicating that adrenoceptor mechanism in thiopental-epinephrine arrhythmias is different from that in halothane-epinephrine arrhythmias. During thiopental anesthesia, incidence of arrhythmias with blood pressure elevation by epinephrine, phenylephrine, or angiotensin II was not different, and increasing heart rate by electrical pacing did not replace isoproterenol in the arrhythmogenic interaction between isoproterenol and phenylephrine. The results indicate that blood pressure elevation due to the combined inotropic action of alpha 1- and beta-adrenoceptor agonists is a critical factor in the genesis of thiopental-epinephrine arrhythmias.

Adrenergic alpha-Agonists↗
PubMed1993

Quantitative analysis of pulmonary clearance of exogenous dopamine after cardiopulmonary bypass in humans.

The contribution of the lung to the clearance of exogenous dopamine after cardiopulmonary bypass (CPB) was analyzed quantitatively in humans and compared with the contribution of the lung before CPB. The pulmonary and arterial plasma concentration of dopamine and the pulmonary plasma flow were measured simultaneously during infusion of dopamine. Contribution of the pulmonary circulation was defined as the ratio between clearance through the pulmonary circulation and the total plasma clearance of dopamine. The calculated contribution values after CPB were 12.0, 10.7, 11.4, 16.2, and 16.7% at the doses of 3.0, 4.0, 5.0, 6.0, and 7.0 micrograms.kg-1.min-1, respectively. Those values before CPB were 15.6% and 17.4% at the doses of 1.0 and 2.0 micrograms.kg-1.min-1, respectively. The comparison of the values before and after CPB did not achieve statistical significance. Furthermore, there were no significant correlations between the pulmonary clearance after CPB and mean pulmonary arterial pressure, pulmonary vascular resistance, or CPB time. The results suggest that the pulmonary clearance mechanism for dopamine after CPB is maintained as effectively as that before CPB and is not influenced by pulmonary hypertension or CPB time.

Adult↗
PubMed1993

Accuracy of continuous jugular bulb venous oximetry during cardiopulmonary bypass.

We evaluated the accuracy of fiberoptic catheter oximetry in the jugular bulb during conditions of normothermia, hemodilution, and hypothermia in 11 patients who underwent cardiac surgery with cardiopulmonary bypass (CPB). An oximetry catheter was inserted into the right jugular bulb under general anesthesia, calibrated by the in vitro (n = 7) or in vivo (n = 4) mode. Jugular bulb oxygen saturation (SjO2) with the catheter oximeter was compared with a concurrent laboratory CO-oximeter value from a blood sample during surgery. Nasopharyngeal temperature (NPT) and hemoglobin concentration (Hb) were also measured. The oximetric catheter SjO2 correlated closely with the CO-oximeter determinations in both calibration modes (in vitro, r2 = 0.88; in vivo; r2 = 0.96). Data in the in vitro calibrated group were grouped into three conditions; 1) normothermia and no hemodilution, 2) normothermia and hemodilution, and 3) hypothermia and hemodilution, and showed good correlations between SjO2 values measured by the two methods (r2 = 0.90, r2 = 0.81, r2 = 0.79, respectively). The difference in SjO2 values by the two methods was not significantly affected by changes in NPT and Hb during CPB. In conclusion, the continuous SjO2 monitoring with catheter oximetry during CPB would be accurate and reliable under either calibration mode. Moderate hypothermia and hemodilution during CPB did not significantly influence the accuracy.

Adult↗
PubMed1993

[Maintenance doses of vecuronium and pancuronium during hypothermic cardiopulmonary bypass].

In 31 patients undergoing coronary artery bypass grafting, we investigated the maintenance doses of pancuronium and vecuronium during hypothermic cardiopulmonary bypass. For all patients, the height of the first twitch of the train-of-four (T1) was measured with evoked electromyogram. During operation, T1 was kept from 5 to 15 per cent of control. Infusion doses of both muscle relaxants were controlled with a personal computer. During hypothermic cardiopulmonary bypass (body temperature 28 degrees C), requirement of both muscle relaxants decreased for about 90 per cent compared with pre bypass values. We consider that the prolongation of neuromuscular blockade is attributable to hypothermia rather than to other factors of cardiopulmonary bypass. After rewarming, maintenance dose of vecuronium remained about a half of the dose required in pre-bypass period. It suggests that elimination of vecuronium from liver and kidney is hindered not only during hypothermia but also after rewarming.

Cardiopulmonary Bypass↗
PubMed1993

Cerebral vascular reactivity to carbon dioxide before and after cardiopulmonary bypass in children with congenital heart disease.

We examined cerebral vascular reactivity to carbon dioxide before and after cardiopulmonary bypass in 15 pediatric patients aged 2 to 9 years undergoing cardiac operations. Cerebral vascular reactivity was noninvasively assessed by transcranial Doppler ultrasonography. The cerebral blood flow velocity was plotted as a function of arterial carbon dioxide partial pressure. An exponential function was fitted for these plots and an exponent of curve was defined as the cerebral vascular reactivity to carbon dioxide. There was no significant change in this reactivity after cardiopulmonary bypass as compared with before bypass (before 0.028 +/- 0.003; after 0.030 +/- 0.016). For the entire series, we obtained best-fit curves of y = 2.8e0.046x (r = 0.91) and y = 3.4e0.031x (r = 0.89) (x; arterial carbon dioxide partial pressure, y; percent changes of cerebral blood flow velocity) before and after cardiopulmonary bypass. We conclude that the cerebral vascular reactivity to carbon dioxide was preserved before and after cardiopulmonary bypass in children undergoing cardiac operations. These results suggest that cerebral perfusion before and after cardiopulmonary bypass is not critically compromised.

Blood Flow Velocity↗
PubMed1993

[Does rate of urine flow influence the difference between bladder temperature and nasopharyngeal temperature during cardiac surgery with cardiopulmonary bypass?].

Recently, bladder temperature (BT) monitoring is employed instead of rectal temperature because it is possible to keep the probe clean. The relationship between BT and core temperature is different in patients with steady state compared with those with rapid changes in temperatures. This study evaluated BT compared with nasopharyngeal temperature (NPT) reflecting brain temperature during cardiac surgery with induced hypothermia using cardiopulmonary bypass. During the steady state, after induction of anesthesia and immediately before cooling or rewarming, BT was equivalent to NPT independent of urine flow rate. In rapid cooling or rewarming phase of cardiopulmonary bypass, BT was not equivalent to NPT. BT preceded NPT in case of a very high urine flow rate, and with a lower urine flow rate delayed BT lagged behind NPT. During rapid changes in core temperature during cardiopulmonary bypass, the difference of BT to NPT depends on urine flow rate.

Adult↗
PubMed1993

[Monitoring of peripheral tissue oxygenation with near infrared spectrophotometry during abdominal or iliac aortic cross-clamping surgery].

Peripheral tissue oxygenation was monitored with near infrared spectrophotometry during abdominal or common iliac aortic cross-clamping surgery. Six patients who had abdominal aortic aneurysm (AAA) and eight patients who had aortic sclerotic occlusive disease (ASO) were studied. At the beginning of cross-clamping, oxyhemoglobin was decreasing and deoxyhemoglobin was increasing in all AAA patients. Average of 37 minutes following cross-clamping of abdominal aorta, both hemoglobin values were stabilized. On the other hand, changes in both hemoglobin values were delayed or missing in ASO patients. The results suggest that the duration from cross-clamping to stabilization is related to co-lateral blood flow. During operation, monitoring of peripheral blood flow with near infrared spectrophotometry is useful for detection of peripheral ischemia and for the estimation of postoperative local blood flow.

Aorta, Abdominal↗
PubMed1993

Anesthetic management of patients undergoing bilateral unifocalization.

We report on the anesthetic management of eight patients undergoing unifocalization for pulmonary atresia and ventricular septal defect with major aortopulmonary collateral arteries. Unifocalization was performed separately on the right and left lungs in the lateral decubitus position. During unifocalization, pulmonary blood flow to the nondependent lung is interrupted and arterial oxygenation is dependent solely on the blood flow to the dependent lung. Thus, PaO2 and SaO2 decreased significantly and PaCO2 increased significantly during unifocalization, as compared with before and after unifocalization. When these values are compared between first and second stage of unifocalization, SaO2 during second stage was lower than during first stage. Although PaO2, PaCO2, and pH during second stage tended to be worse than during first stage, the differences did not reach statistical significance. During unifocalization, especially in second stage, to prevent deterioration of these arterial gas variables, pulmonary blood flow had to be increased by frequent administration of catecholamine. In addition, bicarbonate infusion was also used to prevent progressive metabolic acidosis due to hypoxia during unifocalization. Because anticoagulant therapy was required during unifocalization, airway bleeding was a common complication.

Adolescent↗
PubMed1992

Selective beta 1 and beta 2 adrenoceptor blockade on epinephrine-induced arrhythmias in halothane anaesthetized dogs.

Beta 2 as well as beta 1 adrenoceptors have been recognized in the heart of vertebrates. They mediate a positive chronotropic action of catecholamines. We compared the effect of selective beta 1 and beta 2 adrenoceptor antagonists on the genesis of halothane-epinephrine arrhythmias in dogs. The arrhythmogenic dose (AD) of epinephrine was increased in the presence of l-metoprolol, a selective beta 1 antagonist (8.40 +/- 1.13 micrograms.kg-1 x min-1; mean +/- SEM), compared with control value (2.62 +/- 0.56) (P < 0.05). In contrast, ICI-118,551, a selective beta 2 antagonist, did not change the AD (2.36 +/- 0.43). Adding ICI-118,551 to l-metoprolol did not affect the AD of epinephrine in the presence of l-metoprolol alone (6.34 +/- 0.74 vs 8.40 +/- 1.13). These results suggest that selective beta 1 blockade is effective in preventing halothane-epinephrine arrhythmias, but selective beta 2 blockade is not.

Adrenergic beta-Antagonists↗
PubMed1992

Clinical evaluation of cerebral oxygen balance during cardiopulmonary bypass: on-line continuous monitoring of jugular venous oxyhemoglobin saturation.

To prevent brain damage during cardiopulmonary bypass (CPB), adequate cerebral perfusion for cerebral oxygen demand should be maintained. We monitored jugular venous oxyhemoglobin saturation (SjO2), which reflects the overall balance of cerebral oxygen supply and demand, continuously in 12 patients undergoing cardiac surgery. We examined whether this balance is disrupted during CPB, and if so, analyzed critical factors that affect this phenomenon. At the initiation of CPB, in spite of a significant decrease in mean arterial pressure, SjO2 did not change, and it was stable during the hypothermic period of CPB. On the other hand, a significant reduction in SjO2 was observed during the rewarming period, and SjO2 had an inverse linear correlation with nasopharyngeal temperature. Furthermore, the percent decrease of SjO2 was significantly related to "rewarming speed" (an average increase in temperature per minute). Our results indicate that temperature change during the rewarming period is a critical factor affecting the balance of cerebral oxygen supply and demand during CPB.

Adult↗
PubMed1992

Internal jugular vein catheterization in infants undergoing cardiovascular surgery: an analysis of the factors influencing successful catheterization.

Central venous catheterization for pressure monitoring and drug administration is often important in the anesthetic management of infants undergoing cardiovascular surgery. We examined the effects of patient age, weight, and central venous pressure and the experience of the anesthesiologist on the rate of successful catheterization and catheterization time of the internal jugular vein (IJV) in a prospective study. We studied 106 infants undergoing IJV catheterization for cardiovascular surgery over a 7-mo period at our institution. We catheterized the IJV by the high approach. The direct venipuncture or the Seldinger method was used according to the patient's weight. Overall successful catheterization rate was 97.2%, and the average catheterization time was 353 +/- 21 s (mean +/- SEM). Complications included arterial puncture in 12 cases (11.3%), hematoma formation in four cases (3.8%), and catheter malposition in two cases (1.9%), but pneumothorax was not observed. When a patient was younger than 3 mo or weighed less than 4.0 kg, successful catheterization rate decreased significantly to 81.3% and 78.6%, respectively. Catheterization time was inversely correlated with both age and weight, whereas central venous pressure did not affect either successful catheterization rate or catheterization time. We were unable to demonstrate that the experience of the anesthesiologist plays a significant role in the success or complication of the catheterization procedure. Our results indicate that IJV catheterization by the high approach is a reliable and useful technique in infants, and that the weight and age of the patient significantly influence the rate of successful catheterization.

Age Factors↗
PubMed1992

[Effects of hypothermia with cardiopulmonary bypass on posterior tibial nerve somatosensory evoked potentials in man].

Somatosensory evoked potential after posterior tibial nerve stimulation (PTN-SEP), as well as nasopharyngeal, bladder and plantar temperature were recorded in ten patients during cardiac surgery with hypothermic cardiopulmonary bypass. There was a best negative correlation between latencies (P27, P40 and the interpeak latency between P40 and P27 (P40-P27)) and nasopharyngeal temperature, but no correlation was found between latencies and plantar temperature during cooling and rewarming (27-37 degrees C) with cardiopulmonary bypass. No correlation was found between changes in amplitude and temperature. The slope of linear regression line of latencies versus nasopharyngeal temperature was -1.05 msec.degrees C-1 for P27 (r = -0.93), -1.47 msec.degrees C-1 for P40 (r = -0.95) and -0.43 msec.degrees C-1 for P40-P27 (r = -0.78). This study suggests that nasopharyngeal temperature measurement is required to aid the interpretation of PTN-SEP changes during hypothermia.

Adult↗
PubMed1992

[Effective high frequency jet ventilation setting for the preparation of internal thoracic artery for coronary artery bypass graft surgery].

Effective high frequency jet ventilation (HFJV) setting during the preparation of internal thoracic artery (ITA) was estimated in 35 patients who underwent coronary artery bypass graft (CABG) surgery. During ITA preparation, ventilation with the minimum lung movement without circulatory deterioration is necessary. Therefore, appropriate frequency, inspiratory time interval (Ti%) and working pressure (WP) for HFJV were investigated. Rising WP and prolonged Ti% provoked increasing tidal volume and decreasing PaCO2, whereas the lung extension disturbed the ITA preparation. By modifying the settings of frequency, Ti% and WP, we determined the frequency of 3Hz and Ti% of 50%. The correlation between WP at normocapnia and bodyweight (BW) is expressed in the following formula: WP = 0.16 x BW - 0.0003 (r = 0.72) Moreover satisfactory recording of end-tidal CO2 could not be obtained during HFJV. Therefore, we used transcutaneous CO2 (tc-CO2) analyzer. The coefficient between tc-CO2 and PaCO2 was 0.95, and tc-CO2 was useful as a non-invasive monitoring of PaCO2. There was little change in blood pressure, heart rate and cardiac output during HFJV. However mean pulmonary artery pressure (mPAP) increased significantly during hypercapnia especially when PaCO2 was over 50 mmHg. This suggests that mPAP may be more sensitive to PaCO2 compared with other circulatory parameters. HFJV with these settings produced good outcome for ventilation and circulation during the preparation of ITA.

Adolescent↗
PubMed1992

[A computerized anesthesia record system: four years' experience].

A computerized anesthesia record system is in routine use for cardiovascular procedures in our operating rooms. This system is implemented on an NEC PC-9801 personal computer and automatically collects hemodynamic variables from a polygraph as well as from intraoperative laboratory reports via RS-232C ports. Events such as intubation can be entered manually using a standard keyboard. Since the introduction of the system in 1987, the system has been used in 90 percent of the total cases performed and 2941 electronic data files were recorded in a four-year period. Excluding some short procedures for which the system was not used, failure to store records on disks resulted from system errors due to power-line troubles in the operating rooms as well as users' omission to command the system. User-acceptance of event entry was poor. In 74 percent of the cases, not a single event was entered. Advantage of an automated anesthesia record system over a hand-written record is being recognized. Wide-spread use of such a system will require ergonomic design of the system and man-machine interfaces suitable for use in an operating room.

Anesthesiology↗
PubMed1992

[The change in cerebral blood flow during hypotensive anesthesia induced by prostaglandin E1].

We investigated the effect of prostaglandin E1 (PGE1)--induced hypotension during sevoflurane anesthesia on the cerebral blood flow (CBF), autoregulation and internal jugular venous O2 tension (PjO2) in 8 patients undergoing neurosurgery. Although the mean arterial pressure decreased from 95.3 +/- 3.8 mmHg (mean +/- SD) to 63.6 +/- 8.0 mmHg by continuous intravenous infusion of PGE1, CBF did not change significantly (97.2 +/- 10.6% of control value). During hypotensive anesthesia, autoregulation was well maintained in all patients, and the values of PjO2 did not suggest brain hypoxia at all. The results indicate that hypotensive anesthesia induced by PGE1 and sevoflurane is a safe and a reliable method for neuroanesthesia.

Adult↗