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Y F Huang

Publications and source records attributed to Y F Huang.

At least 55 records · Page 3Linked to original sources
PubMed1998

Systemic and regional pharmacokinetics of levobupivacaine and bupivacaine enantiomers in sheep.

UNLABELLED: Commercially available bupivacaine is an equimolar mixture of R(+)- and S(-)-bupivacaine. S(-)-bupivacaine (levobupivacaine) is the subject of current clinical evaluation. We conducted partial cross-over systemic and regional pharmacokinetic studies of i.v. bupivacaine (12.5-200 mg) and levobupivacaine (6.25-200 mg) in ewes. Enantiospecific analysis of blood drug concentration-time data and of regional myocardial and brain drug mass balance data indicated that (a) there was a higher mean total body clearance of R(+)-bupivacaine than of S(-)-bupivacaine (as previously reported); (b) there were no differences in the systemic pharmacokinetics of S(-)-bupivacaine whether administered alone or as a component of bupivacaine; (c) there was no evidence of dose-dependent pharmacokinetics with either enantiomer; (d) for both enantiomers, mean calculated myocardial tissue concentrations of 1%-4% dose occurred between 3 and 5 min. Mean brain concentrations of 0.2%-1% dose occurred between 2 and 4 min after the administration of bupivacaine but between 4 and 5 min after the administration of levobupivacaine. There was no evidence that systemic toxicity induced by these local anesthetics significantly modified their pharmacokinetics, and there was no evidence of an enantiomer-enantiomer pharmacokinetic interaction for bupivacaine. IMPLICATIONS: Levobupivacaine comprises 50% of commercially available bupivacaine and is being considered for use in its own right. As a part of its preclinical evaluation, this study considered whether levobupivacaine behaved kinetically in the body in the same way as when administered as a component of bupivacaine.

Anesthetics, Local↗
PubMed1998

The enantiomer-specific kinetics and dynamics of verapamil after rapid intravenous administration to sheep: physiological analysis and modeling.

The lung, myocardial and systemic kinetics of the enantiomers of verapamil, and their myocardial effects, were measured after administration of 10 mg of racemic verapamil during 2 min to chronically instrumented sheep; the data were used to develop a physiological model of the process. Verapamil was characterized by relatively slow transit through the lungs and heart. The lung kinetic values were membrane limited, whereas the tissue/blood equilibrium half-life for the heart was approximately 8 min. There was little difference between the kinetic values of the enantiomers, with the exception of their extent of deep distribution into the lung. The time course of the increase in myocardial blood flow caused by verapamil was best related to the time course of the arterial verapamil concentrations, whereas the time course of increases in the interval between P and R waves of the electrocardiogram and decreases in the maximum rate of rise of left ventricular pressure were best related to the time course of its myocardial concentrations. Thus, the observed hysteresis for these effects compared with arterial blood was largely caused by the time required for the myocardial equilibration. The model predicted that the myocardial concentrations of verapamil were relatively insensitive to the duration of injection of a given bolus dose, but that rapid injection caused transient, high arterial concentrations. It also predicted that the bolus dose of verapamil should be modified over a 2-fold range to account for physiologically plausible variations in base-line cardiac output and myocardial blood flow.

Animals↗
PubMed1997

The effects of short intravenous infusions of thiopentone on myocardial function, blood flow and oxygen consumption in sheep.

The cardiovascular effects of slow (over two minutes) intravenous infusions of thiopentone 750 mg in conscious instrumented sheep breathing 100% oxygen were examined for 30 minutes following the start of the infusion. The maximum rate of rise of left ventricular pressure (an index of myocardial contractility) decreased significantly from 1 to 10 minutes, to a minimum of 45% of baseline. Heart rate increased by up to 33% above baseline from 0.5 min onwards. Both mean arterial pressure and cardiac output were decreased from between 1 and 7 min. Left ventricular minute work was transiently decreased, but left coronary blood flow and myocardial oxygen consumption showed little or no change from baseline. We conclude that in vivo, thiopentone administered at a relatively slow rate caused large reductions in myocardial contractility, and therefore cardiac reserve, in the absence of significant changes in myocardial blood flow or oxygen consumption.

Anesthetics, Intravenous↗
PubMed1997

Cockayne syndrome with tetralogy of Fallot: a case report.

Cockayne syndrome (CS) is a rare autosomal recessive disorder characterized by growth retardation, senile-like appearance, loss of subcutaneous adipose tissue, photosensitive dermatitis, microcephaly, deafness, pigmentary degeneration of retina, disproportionately long limbs, skeletal malformations with knee contractures and neurologic abnormalities. This is a description of a three-year-old boy with typical features of Cockayne syndrome complicated with tetralogy of Fallot, pneumonia and hepato-splenomegaly. He had been suffering from frequent attacks of pneumonia and had been hospitalized for several times since birth. Tetralogy of Fallot was diagnosed under echocardiography study and he died suddenly in hospital during a mydriatic procedure in the Ophthalmologic Clinic.

Child, Preschool↗
PubMed1997

Group A streptococcal septicemia with retropharyngeal abscess: a case report.

Group A streptococcal (GAS) septicemia is rare in occurrence but has a significant morbidity and mortality, whereas retropharyngeal abscess (RPA) is infrequent and it is most commonly found in children under the age of 6 years, with half of the cases occurring in children between 6 and 12 months old. This report concerns a case of GAS septicemia complicated with RPA. The patient, a five-year-old boy, was referred from a local medical department under the impression of meningitis. However, blood and throat cultures were both found to be positive for group A streptococci. Widening of the retropharyngeal space was noted in lateral neck roentgenography. RPA was confirmed by computed tomography (CT) of the neck. Ampicillin was prescribed for a period of four weeks. The patient was then discharged and oral form ampicillin was continued for four more weeks. No surgical incision and drainage was performed. Complete disappearance of the abscesses were noted via CT of the neck at an Outpatient Department follow-up.

Bacteremia↗
PubMed1997

Effects of sonication on articular cartilage in experimental osteoarthritis.

OBJECTIVE: To investigate the histological effect of therapeutic ultrasound on arthritic cartilage of rats with various severities of induced osteoarthritis. METHODS: Twenty-seven rats with 3 different stages (Grade I, II, III) of papain induced knee arthritis received 7 min pulse sonication treatment, 3 times/week for 4 weeks. Another 27 rats with the same severity of induced arthritis were studied as controls. The severity of arthritis and related histopathological changes of articular cartilage were evaluated by bone scan and histological findings with hematoxylin and eosin stain. RESULTS: "Severity indexes" based on bone scan decreased after sonication treatment in each study group. Histopathological findings indicated marked cartilage repair in the early stage of induced arthritis (Grade I). However, progressive cartilage damage present in untreated Grade II, III induced arthritis was significantly reduced after sonication. CONCLUSION: Therapeutic ultrasound enhances cartilage repair in the early stage, and has the effect of arresting further deteriorative damage in the later stage of induced arthritis.

Animals↗
PubMed1997

Peritoneoscintigraphy using Tc-99m MAA for diagnosis of diaphragmatic disruption in a peritoneal dialysis patient.

Massive hydrothorax is an infrequent but well-recognized complication of continuous ambulatory peritoneal dialysis (CAPD), and is often regarded as a contraindication to its use. We describe here a patient with massive hydrothorax that appeared during CAPD. Peritoneoscintigraphy was performed to demonstrate the clinical suspicion of a pleuroperitoneal communication and the pleurodesis using tetracycline was commenced and this allowed the successful continuance of CAPD.

Female↗
PubMed1996

Adverse haemodynamic effects of the rapid intravenous injection of hypotonic solutions in sheep.

The rapid intravenous administration of 10 ml of sterile water or hypotonic saline to five conscious sheep induced substantial adverse haemodynamic effects lasting 10 to 20 seconds. They included reductions in cardiac output (to 44 per cent of the baseline value measured in the 30 seconds before the injection), arterial blood pressure (67 per cent of baseline), left ventricular systolic pressure (60 per cent of baseline), myocardial contractility (60 per cent of baseline), and left coronary arterial blood flow (39 per cent of baseline), and increases in heart rate to 137 per cent of the baseline. The intensities of these effects were related directly to the rates of injection and inversely to the osmolalities of the solutions injected. Intravascular haemolysis was associated with the effects. These data are of potential importance to anyone administering drugs intravenously to sheep.

Animals↗
PubMed1996

A descriptive tool to characterize nonlinear kinetics, with applications to meperidine and lidocaine.

We describe an explorative data analysis tool which can detect and describe the presence of nonlinearities in multiple dose kinetics studies. The method is nonparametric (i.e. not dependent on modeling assumptions), uses regression to estimate the functions representing the kinetics, and makes the detection of nonlinearity a part of the model selection process. Flexible functions (splines) are used to describe the kinetics corresponding to the lowest given dose, and to describe the (possible) departure of the kinetics corresponding to higher doses from the reference kinetics. The estimated kinetics and departures can be examined to offer possible insight into the nature of the nonlinearity. The methodology is applied to the analysis of meperidine and lidocaine kinetics through the lungs and the heart. We find that the lung kinetics of lidocaine and meperidine are linear. However their myocardial kinetics are complex and nonlinear.

Animals↗
PubMed1996

Myocardial pharmacokinetics of thiopental in sheep after short-term administration: relationship to thiopental-induced reductions in myocardial contractility.

The myocardial kinetics and dynamics of thiopental (750 mg over 2 min) were examined in chronically instrumented sheep (five studies in four sheep). The myocardial kinetics were studied by simultaneous rapid sampling of arterial and coronary sinus blood for 30 min. The myocardial kinetics for four of the five studies were best described by a single flow-limited compartment with apparent volumes of between 42 and 113 mL. These volumes equated to half-lives of equilibration between blood and myocardium of between 0.49 and 1.00 min when baseline blood flow was taken into account. The remaining study was better described by a model with a slight membrane limitation (permeability/flow ratio of approximately 2). Myocardial contractility was studied as a measure of myocardial pharmacodynamics and was reduced to 53% of baseline at approximately 2.5 min after the start of the dose. Effect compartment analysis showed that there was hysteresis between the time course of these contractility changes and the time course of the arterial concentrations, with effect compartment half-lives between 0.08 and 0.87 min. There was significantly less hysteresis for the coronary sinus concentrations. It is concluded that thiopental equilibrated rapidly with a component of the myocardium, and that consequently its effects on myocardial contractillity also rapidly equilibrated with both afferent and effluent myocardial blood.

Animals↗
PubMed1995

Comparison of myocardial ischaemia in post-infarction patients with and without angina: assessment by dipyridamole 201T1 imaging.

Ninety patients with old myocardial infarction were studied to evaluate the efficacy of intravenous dipyridamole 201Tl imaging for the detection of myocardial ischaemia in post-infarction patients, and to compare the prevalence of ischaemia in 63 patients with post-infarction angina (group I) and 27 patients without angina (group II). Thirty-four of the patients in group I and 15 of the patients in group II received coronary arteriography (CAG) for comparison; these were labelled groups IA and IIA, respectively. On 201Tl imaging, the incidence of scar with ischaemia in the infarct zone and scar with ischaemia at a distance were 72% and 42% in all patients, 89% and 52% in group I vs 33% and 19% in group II (P < 0.001 and P < 0.01, respectively). On CAG testing, the rates of infarct-related recanalization vessel and multi-vessel disease were 76% and 68% in group IA vs 40% and 40% in group IIA (P < 0.05 and P > 0.05, respectively). Thus, dipyridamole 201Tl imaging is a useful modality and post-infarction angina a proper indicator in the detection of myocardial ischaemia in post-infarction patients

Adult↗
PubMed1995

Technetium-99m albumin scintigraphy in the diagnosis of protein-losing enteropathy: a case report.

A 34-year-old female presenting with bilateral lower leg edema and distended abdomen was admitted to our hospital. The serum albumin was 1.42g/dl. Renal function and hepatic function were normal. Urinalysis did not show proteinuria. Tc-99m albumin scintigraphy was arranged for this patient to rule out protein-losing enteropathy. The results demonstrated loss of albumin into the intestines. We conclude that Tc-99m albumin scintigraphy of the abdomen is a valuable adjunct in the diagnosis of protein-losing enteropathy.

Adult↗
PubMed1994

The hemodynamic effects of intravenous bolus doses of meperidine in conscious sheep.

The hemodynamic effects of 100, 200, and 300 mg of meperidine injected intravenously were studied in five chronically instrumented adult ewes. The maximum rate of increase of left ventricular pressure was decreased, respectively, by 27.4% +/- 3.9%, 37.5% +/- 5.6%, and 31.9% +/- 13.0%, and recovery occurred by 5, 8, and 0.5 min, respectively. Mild central nervous system stimulatory effects (agitation) were observed in three of five sheep at 200 mg and moderate effects (rigor and jumping movements) were observed in four of five sheep at 300 mg. These doses also produced increases in heart rate (43%-64%) and mean arterial blood pressure (17%-27%). At these doses, cardiac output was increased for 0.5 min by approximately 25% without changes in stroke volume and left ventricular stroke work. Coronary blood flow was increased by 44%-81% for 0.5 min. We conclude that, in unpremedicated sheep, meperidine has a brief direct negative inotropic effect on the myocardium, but that at larger doses this is overridden by stimulatory central nervous system (CNS) and indirect hemodynamic effects.

Animals↗
PubMed1994

The pharmacokinetics of meperidine in the myocardium of conscious sheep.

The pharmacokinetics of meperidine in blood and myocardium were studied in five conscious sheep. After an intravenous (i.v.) bolus of 100, 200, or 300 mg meperidine HCl, the maximum arterial blood concentrations (mean +/- SD) were 27.8 +/- 4.6, 66.8 +/- 13.3, and 114.5 +/- 23.1 micrograms/mL, respectively, and coronary sinus blood concentrations were 2.7 +/- 1.0, 7 +/- 1.5, and 13.7 +/- 2.5 micrograms/mL, respectively. These were linearly related to dose. Net uptake of meperidine into the myocardium occurred during the first minute and the maximum rates of uptake (influxes) were 5.1 +/- 2.6, 15.1 +/- 4.6, and 27.5 +/- 8.7 mg/min. Myocardial meperidine concentrations, calculated using mass balance principles for the 100-, 200-, and 300-mg doses, respectively, were 9.0 +/- 1.8, 20.5 +/- 8.6, and 34.1 +/- 7.4 micrograms/g at peak and had decreased to 57% +/- 11% of peak 5 min after injection. No pseudoequilibrium between blood and myocardial meperidine concentrations had been reached within the 15-min study period. Myocardial perfusion and blood-myocardial concentration gradients were both important determinants of meperidine myocardial pharmacokinetics. The fast uptake and brief sojourn of meperidine in the myocardium agreed with its rapid but transient negative inotropic effect reported previously.

Animals↗
PubMed1993

An estimate of the rate of direct drug diffusion from the surface of heart and kidney--implications for their representation as compartments.

In many regional pharmacokinetic experiments and models, the anatomical boundaries of the heart and kidney are intrinsically assumed to be barriers for drug diffusion such that these organs can be represented as one or more compartments. To test this, an experimental preparation was developed in which the heart and kidney of anaesthetized sheep were surrounded with 0.9% saline. The rate of drug diffusion from the surface of the organs into the saline was examined during constant-rate i.v. drug infusions. It was found that the maximum clearances of lidocaine and procainamide into the pericardial saline were 10.3-11.6 and 0.6-2.1 ml min-1 respectively, and the values for the kidney were 0.3-0.6, 0.1-1.0 and 0.4-1.3 ml min-1, for lidocaine, procainamide, and meperidine respectively. These corresponded to calculated times of 4-481 min to reach the steady-state saline concentration depending on the drug and the organ. The steady-state ratio of the saline concentrations over the arterial blood drug concentrations usually ranged from 0.5-1.0. It is concluded that drugs can rapidly enter regions of low or no perfusion surrounding these organs, and that the concept of treating the heart and kidney as compartments may not be valid in certain 'worst-case' situations.

Animals↗
PubMed1993

IV bolus administration of subconvulsive doses of lignocaine to conscious sheep: myocardial pharmacokinetics.

Mass balance principles were used to study the myocardial pharmacokinetics of lignocaine in conscious sheep. After i.v. bolus doses of lignocaine 50, 75 or 100 mg, arterial lignocaine concentrations reached a peak in approximately 16 s and these increased linearly with dose. Coronary sinus concentrations reached a peak between 83 and 129 s and the values showed poor relationships with dose. Net myocardial lignocaine uptake lasted for approximately 60 s--this was much shorter than the reported initial distribution half-life of lignocaine. The maximum rate of uptake was proportional to both the dose and the peak arterial lignocaine concentrations. At 15 min, the myocardial lignocaine concentrations were 46 (SD 22)% of their peak values. Pseudo-equilibrium between blood and myocardial lignocaine concentrations was not observed. It is concluded that, despite the myocardium being very well perfused, lignocaine myocardial concentrations were not well represented by blood lignocaine concentrations for at least 15 min. A greater understanding of the determinants of myocardial drug concentrations is required.

Animals↗
PubMed1993

Influence of cardiac output, injection time and injection volume on the initial mixing of drugs with venous blood after i.v. bolus administration to sheep.

The aim of this study was to quantitate factors affecting the initial "peak" of the pulmonary artery (PA) drug concentrations after i.v. bolus drug administration, which is a determinant of the subsequent drug uptake into both the lungs and other well-perfused organs. Indocyanine green (ICG) was used as a marker drug in anaesthetized (1.5% halothane) sheep prepared with an inferior vena cava injection catheter and a large-gauge pulmonary artery blood sampling catheter. For three ranges of cardiac output, 2.5-mg doses of ICG were injected in the following combinations: 10 ml injected over 1, 5 or 10 s; 5 or 25 ml injected over 1 s. On-line PA ICG concentrations were recorded for approximately 60 s using a densitometer. The mean maximum PA ICG concentrations (2-8 mg litre-1), the mean times at which they occurred (7-18 s after injection) and the time lags before ICG was detected in the PA (4-9 s), were inversely related to cardiac output, but linearly related to the time over which the injection was made. The area under the curve of the peak was related inversely to cardiac output only, while the aspect ratio of the peak was related inversely to the time over which the injection was made only. The injectate volume had no effect on any of the measured values. We conclude that, in some circumstances, the rate of injection of drugs with narrow margins of safety should be tailored to the cardiac output of an individual.

Animals↗