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Biomedical subjects

K Amaha

Publications and source records attributed to K Amaha.

At least 91 records · Page 5Linked to original sources
PubMed1991

[Diaphragmatic fatigue and its recovery are influenced by markedly decreased cardiac output: possible involvement of neuromuscular junction].

Effects of highly decreased cardiac output on the development and recovery of diaphragmatic fatigue were studied in dogs. The fatigue was induced by supramaximal electrical stimulation (20 Hz) of phrenic nerves for 30 minutes. Cardiac output was reduced during this period to 30% of control value by mechanically obstructing inferior vena cava with a balloon in animals with lowered cardiac output group (lowered Qt group). Cardiac output was maintained at normal value throughout the experiment in animals of the other group (control group). The animals were observed for recovery for 60 minutes after induction of the fatigue. The standardized transdiaphragmatic pressure (Pdi/Pdi 100) and integrated electromyographic activity (Edi/Edi 100) elicited by electrical test stimuli (20, 100 Hz) were significantly lower in lowered Qt group (P less than 0.01) during entire fatigue and recovery period. The decrease of Pdi/Pdi 100 and Edi/Edi 100 at high frequency test stimuli (100 Hz) was observed only in lowered Qt group. These results suggest that when cardiac output is severely decreased the diaphragm is more susceptible to fatigue, and that this may be caused by a failure of neuromuscular junction as well as by an impaired excitation-contraction coupling.

Animals↗
PubMed1990

Serum diatrizoate level during intraoperative cholangiography in patients without choledochal obstructions.

To assess the degree of regurgitation of contrast media during intraoperative cholangiography, serum diatrizoate levels were measured in 15 patients without demonstrable bile duct obstructions. The maximum pressure achieved during the injection was measured in seven cases and ranged from 13 to 39 cm H2O (average 21.7 +/- 9.3 cm H2O). Only two of the 15 patients studied had detected serum diatrizoate (in one patient 7-14 micrograms I/ml and the other patient 119-200 micrograms I/ml) after completion of the injection. The data suggest that regurgitation of contrast media into the blood during intraoperative cholangiography does not depend solely on injection pressure. Moreover the data suggest that in order to prevent adverse reactions to accidental intravenous contrast administration nonionic contrast media should be used in most, if not all, radiographic studies as some contrast media reaches the bloodstream.

Cholangiography↗
PubMed1990

Tracheobronchial dilating effect of high frequency jet ventilation.

Effect of high frequency jet ventilation (HJFV) on tracheobronchial tone was examined in anesthetized dogs. Changes in intraluminal pressure of water-filled endotracheal cuff (Pcuff) were used as an indicator of tracheal smooth muscle tone. Animals were initially ventilated with conventional mechanical ventilation (CMV) to maintain normal Pa(CO)(2). HFJV (2.0 Hz.) was then applied to each animal in such a way to maintain the same mean airway pressure and Pa(CO)(2) as in CMV. Immediately after changing CMV to HFJV, Pcuff decreased significantly and remained decreased during the period of HFJV. After changing HFJV to CMV, Pcuff gradually returned to its previous level. Histamine-induced tracheobronchial constriction was partially released by HFJV as shown by a decrease in Pcuff and airway resistance (Raw) and by an increase in static lung-thorax compliance (Cst) measured immediately after the cessation of HFJV. These results suggest that HFJV has a tracheobronchial dilating action, presumably mediated by pulmonary stretch reflex, and this may be one of the mechanisms of an increase in mucous secretion and of other reported favorable effects of HFJV in some types of respiratory failure.

Journal Article↗
PubMed1990

[A study on the utility of flumazenil for patients in the ICU].

Flumazenil, a specific antagonist of benzodiazepines, was administered to adult patients receiving treatment at ICU, and its utility to hasten recovery from sedation was evaluated in 40 patients and its usefulness for differential diagnosis of sedated conditions was also evaluated in 5 patients. The efficacy rate for recovery from sedation induced by benzodiazepines was 85.0%. Moreover, flumazenil was considered to be useful for differentiation of sedated conditions when causes were unknown. Depression of respiration improved in association with improvement of consciousness level. In some patients an elevation in blood pressure was also observed with improved consciousness.

Adult↗
PubMed1990

[Impairment of neuromuscular transmission in fatigued canine diaphragm].

The role of impairment of neuromuscular transmission in fatigued canine diaphragm was investigated by comparing the function of fatigued diaphragm with that of neuromuscular junction (NMJ)-blocked diaphragm. Diaphragmatic fatigue was produced by intermittent supramaximal stimulation of bilateral phrenic nerves. Partial NMJ blockade was obtained by vecuronium bromide administered intravenously. During control study, no fade was observed either in integrated diaphragmatic electric activity (Edi) or transdiaphragmatic pressure (Pdi). In fatigued diaphragm, Edi generated by 100 Hz showed a remarkable fade. The fade was prominent in high frequency fatigue. In NMJ-blocked diaphragm, fade was observed in Pdi as well as in Edi produced by 100 Hz. The fade of Edi by 100 Hz was prominent. In low frequency fatigue, both Pdi and Edi produced by 20 Hz test stimulation were significantly lower than control values. These results show that in addition to impairment of excitation-contraction coupling, neuromuscular blockade is involved, at least in part, in low frequency diaphragmatic fatigue.

Animals↗
PubMed1990

[A benzodiazepine antagonist flumazenil in clinical use--a dose finding study].

The effective dose, usefulness and side effects of flumazenil, a specific benzodiazepine antagonist, have been investigated in 72 sleeping patients after the end of the surgical operation who had received flunitrazepam 0.03 mg.kg-1, a long acting benzodiazepine. The patients received intravenous injections of flumazenil 0.1 mg, 0.2 mg, 0.4 mg and 0.8 mg per person as initial doses. Four minutes after the injection of flumazenil, the percentages of the patients who were awake, were 47.4% in 0.1 mg group, 82.4% in 0.2 mg group, 82.4% in 0.4 mg group and 88.2% in 0.8 mg group respectively. There were several side effects observed in all the groups except 0.2 mg group. However, they presented no clinical problems. Therefore, flumazenil 0.2 mg as the initial dose, is considered appropriate.

Adolescent↗
PubMed1989

Two-dimensional echocardiographic evaluation of inferior vena cava, right ventricle, and left ventricle during positive-pressure ventilation with varying levels of positive end-expiratory pressure.

The effects of intermittent positive-pressure ventilation (IPPV) with 0, 10, and 15 cm H2O of PEEP on inferior vena cava (IVC), right and left ventricular length and septal-lateral dimensions, and cardiac output were examined in 19 patients with respiratory failure using two-dimensional echocardiography. In five patients, cardiac output was also obtained by the thermodilution technique. As PEEP was increased, IVC dimensions increased during both inspiration and expiration, and the IVC collapsibility index decreased. This indicated an increase in venous stasis and decrease in venous return to the right atrium. Increasing PEEP was associated with progressive decreases in cardiac output, and length and septal-lateral dimensions of both ventricles. The decreased cardiac output during IPPV with 10 and 15 cm H2O PEEP may be due to the decreased venous return and ventricular filling. Cardiac output determined by echocardiography was correlated closely to that by the thermodilution technique.

Adult↗
PubMed1989

[Laryngeal mask--a newly designed oral airway].

A newly developed oral airway, laryngeal mask (LM), was used in 40 patients by anesthesiologists of varied clinical experiences. Clear airway was obtained in 37 patients (92.5%). There were 3 patients in whom it was difficult to establish clear airway, probably because of inappropriate fitting of mask to larynx or of folding of epiglottis. Controlled or assisted ventilation was performed adequately in most of the patients, but there was recognizable gas leak in 13 patients when the airway pressure was above 15 cmH2O. The LM has many attractive features compared with a traditional face mask, and some of the promising clinical applications of LM are discussed.

Adolescent↗
PubMed1989

[Clinical application of laryngeal mask airway].

The laryngeal mask is a unique alternative to the face mask and endotracheal tube offering significant benefits to both anesthesiologist and patient. We have applied laryngeal mask, 1) to create an adequate airway in cases of difficult or impossible intubation, 2) to establish a pathway for the fiberoptic bronchoscope, 3) to clear the airway for eye operation, and 4) to maintain the airway in patients in the lateral position. Further study, however, is necessary to establish definite indication for its application.

Adult↗
PubMed1989

[Mass flow anesthesia delivery system and its application].

Microcomputer-based anesthesia delivery system using mass flow control devices has been developed. System is superior in computer control to conventional anesthesia machine because there is no mechanical setting. System consists of three thermal mass flow controllers (TMFC), one vapor source controller (VSC), personal computer system, and air circuits. Personal computer system has facilities of digital output, analogue input and analogue output interfaces. TMFCs and VSC are devices which operational principle is based on the thermal conductance and they are controlled by electrical signals from computer in the system. TMFCs control the mass flow of nitrous oxide, oxygen and carbon oxide according to each input voltage signal. VSC regulates mass vapor of halothane in order to keep set value up by means of alteration of oxygen carrier gas flow. Computer always monitors the gas flow of the TMFCs and VSC so that computer compensates the change of the carrier gas flow of VSC by regulating the TMFC for oxygen. Mixed gas from TMFCs and VSC is supplied through the air circuit to subject. Characteristics of the system was measured by mass spectrometer and flowmeter. Stability was 0.05% change after 30 minutes at the initial set of 3%. Experiment on animals using mongrel dogs has been performed to verify the system functions.

Anesthesia, Inhalation↗
PubMed1989

[Anesthetic management of a patient with perforated necrotic trachea after radical esophageal cancer surgery].

We anesthetized a 69-year-old man with perforated necrotic trachea after radical esophageal cancer surgery. We recognized during the reoperation that necrotizing part of the trachea was perforated from the cricoid cartilage to 2cm above the carina. We ventilated the both lungs successfully without leaks by inserting a double-lumen tube into the trachea after tracheostomy. Postoperatively, the carina and the main bronchi were also necrotized and perforated. We ventilated the both lungs without leaks by inserting two single-lumen tubes into the left and right bronchi separately. But, eventually the distal part of the both bronchi was also necrotized and perforated. Finally, the patient died of respiratory failure due to hypoventilation on the 7th day after the re-operation. We should remember this type of emergency complication after radical esophageal cancer surgery.

Aged↗
PubMed1988

Inadvertent intrathecal administration of amidetrizoate.

Two cases are presented in which amidetrizoate (Urografin) was accidentally introduced into the intrathecal cavity. Intrathecal lavage and continuous administration of thiopentone were very successful in preventing further systemic deterioration.

Adult↗
PubMed1988

Effect of nicardipine hydrochloride on regional hypoxic pulmonary vasoconstriction.

The effects of nicardipine hydrochloride on regional hypoxic pulmonary vasoconstriction (HPV) were investigated in 14 open-chest mongrel dogs. In a second group of seven dogs, HPV responses with nicardipine were assessed during constant cardiac output controlled by inflation of a balloon placed in the inferior vena cava, as higher doses of nicardipine significantly increased cardiac output. In the group with uncontrolled cardiac output, selective ventilation of the left lower lobe lung (LLL) with 100% nitrogen caused a significant decrease in blood flow to the lobe (QLLL/Qt) to 47.8 +/- 5.5% and an increase in vascular resistance of the LLL (PVRLLL) from 6018 +/- 884 to 13807 +/- 1162 dyn s cm-5. Testing hypoxic responses during infusion of nicardipine 1, 3 and 6 micrograms kg-1 min-1 showed a dose-dependent depression of HPV response. Infusions of nicardipine 3 and 6 micrograms kg-1 min-1 with LLL hypoxia resulted in a slight decrease in lobar blood flow, and a hypoxia-induced increase in PVRLLL was not statistically significant. In the controlled cardiac output group, attenuation of HPV responses by nicardipine was similar to that in the uncontrolled cardiac output group.

Animals↗
PubMed1988

Changes in arterial norepinephrine concentration following intravenous administration in dogs with lung edema.

Arterial concentrations of given norepinephrine (NE) were measured after bolus administration in dogs with normal lungs and in those with oleic acid-induced lung edema. In both groups, the peak NE concentration was given by blood samples taken 30 sec after injection and the concentration showed a decreasing tendency thereafter. NE concentrations were always greater in the lung edema group than in the control group and a longer period was needed for NE concentrations to return to the baseline level. This delay in the clearance of NE from the circulation might reflect a diminished uptake by the pulmonary endothelium. This phenomenon may be used for the diagnosis of pulmonary endothelial injury.

Animals↗
PubMed1987

CO2 rebreathing of T-piece system in patients during recovery phase from acute respiratory failure.

Eight respiratory parameters which might affect the amount of carbon dioxide rebreathing were assessed in seven patients who were breathing spontaneously from large-bore T tube system during the recovery phase from acute respiratory failure. With multivariate regression analysis, the absolute amount of rebreathed CO2 at the connector of endotracheal tube (VINSPCO2) were approximately estimated by using relatively small number of parameters, including minute volume (VEXP), fresh gas inflow to T piece system (VFGI) and preferably by additional parameters concerning CO2 output of the patients.CO2 rebreathing ratio, VINSPCO2 divided by gross outward flux of CO2 at the connector (VEXPCO2), was predicted with simple regression equation by using (VEXP/VFGI) as follows,(VINSPCO2)/(VEXPCO2) = 0.405 + 0.33 x ln (VEXP/VFGI)The maximum (VEXP/VFGI) ratio to prevent rebreathing of CO2 at the connector was 0.30, whereas the ratio to prevent CO2 accumulation due to rebreathing was 0.45.

Journal Article↗
PubMed1987

Prevention of postischemic hypoperfusion after canine cardiac arrest by nicardipine.

We studied the effect of nicardipine (NC) on canine cerebral blood flow (CBF) after cerebral ischemia induced by cardiac arrest. Cerebral ischemia was produced by 10 min of electrically mediated ventricular fibrillation. An iv injection of NC (10 micrograms/kg) bolus was followed by continuous NC infusion (0.33 micrograms/kg X min) immediately after the circulation re-established itself. Local CBF was measured using the hydrogen-gas clearance method. The administration of NC maintained CBF at the pre-arrest level during postischemia, thus preventing the hypoperfusion observed in the control group with no NC. However, in the controls, CBF, reduced at 180 min after re-circulation, was not improved by NC infusion. Consequently, administering NC immediately after re-establishment of circulation may help maintain CBF during the postresuscitation period.

Animals↗