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Biomedical subjects

R C Chan

Publications and source records attributed to R C Chan.

136 records · Page 8Linked to original sources
PubMedDate not supplied

Mucosal pharmacokinetics and pilot study of short course of parenteral imipenem in the eradication of Helicobacter pylori.

Eradication of Helicobacter pylori infection is known to reduce the incidence of duodenal ulcer recurrence. The most commonly used regimen for H. pylori infection is triple antimicrobial therapy for 1-2 weeks. This treatment is associated with frequent side effects and hence unsatisfactory compliance. As in vitro data showed that H. pylori is sensitive to imipenem, the pharmacokinetics of this drug in the gastric milieu, and the clinical efficacy of imipenem with omeprazole in eradicating H. pylori infection were studied. Imipenem/cilastatin levels in serum, gastric secretion and gastric mucosa were assayed in four patients after intravenous injection of a bolus dose of 500 mg. The serum and gastric secretion levels of imipenem achieved were more than 10 times the minimum inhibitory concentration of the drug for H. pylori. Gastric mucosal levels of imipenem vary considerably with time, which probably indicates rapid elimination of the drug into the gastric lumen. In the second part of this study, imipenem/cilastatin was given intravenously for the first 2 days after diagnosis of H. pylori infection in patients with endoscopically confirmed duodenal ulcers. The patients were also treated with 4 weeks of omeprazole. Clearance of H. pylori was initially achieved at the end of 2 days in 20 out of 22 (91%) patients. However, when the biopsies were repeated at 8 weeks, recurrence of H. pylori infection was evident in 19 cases (86.3%) indicating a failure of eradication. It was concluded that imipenem/cilastatin in combination with omeprazole failed to eradicate H. pylori infection.

Biopsy↗
PubMedDate not supplied

Comparison of oral ciprofloxacin and amoxycillin in treating infective exacerbations of bronchiectasis in Hong Kong.

A randomised double-blind controlled clinical trial was conducted to compare oral ciprofloxacin (500 mg b.d.) and amoxycillin (1 g t.d.s.) in the treatment of infective exacerbations of bronchiectasis. The commonest organism isolated from sputum was Pseudomonas aeruginosa, which accounted for 34% of all positive sputum cultures. Other Pseudomonas species and Haemophilus influenzae, accounted for 19%, respectively. Ciprofloxacin produced better clinical response, a higher sputum to serum antibiotic level (mean of 0.65 in the ciprofloxacin group vs. 0.18 in amoxycillin group, p = 0.0001), broader spectrum of antibacterial activity and less side-effect. It was also better tolerated by patients. The findings suggest that ciprofloxacin is an effective treatment of infective exacerbations of bronchiectasis.

Administration, Oral↗
PubMedDate not supplied

Effects of intracoronary radiation on thrombosis after balloon overstretch injury in the porcine model.

BACKGROUND: The main complications of PTCA remain thrombosis and restenosis. Recent studies have demonstrated reduction in the neointimal hyperplasia after intracoronary radiation (IR) with doses of 10 to 25 Gy of ionizing radiation delivered by either beta- or gamma-emitters to injured vessels. The purpose of this study was to examine the effect of ionizing radiation on the thrombosis rate (TR) of injured porcine coronary arteries. METHODS AND RESULTS: Thirty-four juvenile swine (63 coronary arteries) were subjected to overstretch balloon injury followed by IR with doses of 0 to 18 Gy of either beta- or gamma-radiation. Two weeks after treatment, tissue sections were perfusion-fixed, stained with hematoxylin-eosin and Verhoeff-van Gieson's stain, and analyzed for presence of a thrombus, thrombus morphology, and neointima formation by computer-assisted histomorphometry techniques. Although the overall TR increased dose-dependently from 0 to 18 Gy prescribed dose, luminal thrombi decreased. Thrombus area also decreased with increasing radiation dose, whether assessed at the prescription point or at the luminal surface, which corresponded to decreased intimal area. Furthermore, luminal thrombi present after IR tended to consist mostly of fibrin and thus were less organized than in controls. CONCLUSIONS: These results suggest that IR induces thrombosis but does not necessarily compromise the lumen. Strategies for reducing TR may further decrease intimal area as well as increasing the safety of this therapy.

Angioplasty, Balloon, Coronary↗
PubMedDate not supplied

Effects of thoraco-lumbar electric sensory stimulation on knee extensor spasticity of persons who survived cerebrovascular accident (CVA).

Spasticity is mostly due to an excess of impulses to alpha motor neurons partly resulting from a change of interneuron activity. Low threshold afferent has been reported to change the activity in interneuron. The purpose of this study is to investigate the effects of surface spinal paravertebral stimulation on knee extensor spasticity. Ten survivors of stroke, with knee extensor spasticity, received electric stimulation for five 45-minute periods through surface electrodes applied to the skin in the twelfth thoracic and first lumbar areas. The electric stimulations had an amplitude modulated alternating current (AC), with a carrier frequency of 2500 Hz, modulated to "beats" frequency of 20 Hz. Stimulation amplitude was raised to elicit sensory stimulation. The pre- and post-treatment evaluation included the modified Ashworth scale, active torque during controlled knee movements at various velocities, and electromyographic (EMG) activity during the torque measurements. Our results indicate that nine of ten subjects demonstrated a decrease in the modified Ashworth scale post-treatment. The EMG activity of the spastic quadriceps during active knee flexion was decreased post-treatment as compared with the value before treatment. The active torque value of knee flexion or extension at 30 degrees, 60 degrees, or 90 degrees/sec of angular velocity did not change significantly post-treatment. A trend of increasing spastic quadriceps EMG activity with respect to the angular velocity during an active knee flexion was established, with Ashworth scale considered. The level of EMG activity is higher when the Ashworth scale is higher. According to our results, the surface paravertebral sensory stimulation was effective in reducing quadriceps muscle spasticity of the subjects. Both the modified Ashworth scale and the EMG activity of spastic quadriceps during eccentric contraction are suggested as sensitive tools for measuring spasticity of persons who survived cerebrovascular accident (CVA).

Adult↗
PubMedDate not supplied

Yttrium-90 delivered via a centering catheter and afterloader, given both before and after stent implantation, inhibits neointima formation in porcine coronary arteries.

BACKGROUND: Intracoronary radiation (IR) studies have shown reduction of neointima formation (NF). Extrapolation of animal studies with beta-radiation to clinical trials have shown variable results, which may be related to dosimetry, centering issues, and/or shielding of beta-rays by the stent metal. We examined the effect of yttrium-90 (90Y), a pure beta-emitter delivered via an automatic afterloader to a centering catheter, on the inhibition of NF in balloon-injured (BI) porcine coronary arteries as well as in arteries receiving 90Y either prior to or following stent implantation (SI). METHODS: Twenty-three swine (44 coronary arteries) were studied. In the first study, IR (18 Gy at 1.2 mm from the balloon surface) was administered in 17 arteries following BI, while eight control arteries were subjected to BI only. In the second study, 10 swine (19 coronary arteries) underwent SI. IR (18 Gy) was administered in six arteries before and in eight arteries after SI, while five control arteries received SI only. The animals were sacrificed 2 weeks after BI and 4 weeks after SI. Their coronaries were perfusion fixed and stained, and vessel parameters (intimal area [IA] and medial fracture length [FL]) were analyzed by computer-aided histomorphometry. RESULTS: Arteries subjected to IR following BI had less NF compared to controls (IA/FL = 0.14 +/- 0.2 mm vs. 0.49 +/- 0.2 mm; P = 0.003). IA was reduced significantly in the arteries receiving radiation before and after SI compared to controls (0.92 +/- 0.98 and 0.00 +/- 0/00 vs. 2.72 +/- 1.2 mm2; P = 0.014), despite similar SI in all groups. CONCLUSIONS: IR with 90Y delivered via a centering catheter is safe and effective with complete and homogenous inhibition of NF in the context of BI or SI in the porcine coronary model.

Animals↗
PubMedDate not supplied

Antibiotics, biliary sepsis, and bile duct stones.

Bacteriologic studies of bile and blood cultures of 579 patients with ductal stones and infected bile revealed that 121 patients (21%) had associated bacteremia. Analysis of bile and stone cultures showed that Escherichia coli, Klebsiella sp, Enterobacter sp, Enterococcus sp, and Streptococcus sp were the most commonly isolated bacteria. Two-thirds of the patients with bacteremia had similar organisms isolated from blood and bile. Pharmacokinetic studies of the hepatic/biliary excretion profiles of ceftazidime, cefoperazone, imipenem, netilmicin, and ciprofloxacin were performed by ERCP and nasobiliary catheter drainage. The bile samples obtained immediately after cannulation from patients with complete biliary obstruction contained low or undetectable levels of the antibiotics administered--the exception being ciprofloxacin, which was present at a concentration of 20% of the serum level. In vitro determination of minimum inhibitory concentration of the aforementioned antibiotics against 199 isolates of biliary pathogens revealed imipenem and ciprofloxacin to have the highest antimicrobial activity. Based on pharmacokinetic studies and in vitro susceptibility findings, we conclude that ciprofloxacin is superior to the other tested antibiotics in prophylaxis and treatment of biliary sepsis.

Adolescent↗
PubMedDate not supplied

Compound muscle action potential amplitude and area changes in normal subjects and patients with carpal tunnel syndrome.

Lesions of mixed peripheral nerves are often diagnosed by means of electrodiagnostic tests, especially by motor and sensory conduction studies. In order to clarify the varying degrees of motor nerve involvement in patients with carpal tunnel syndrome (CTS), we designed this study for comparing the results of compound muscle action potential (CMAP) amplitude and area under the negative phase between normal persons (n = 662) and patients having CTS (n = 250). The CTS cases were categorized into two distinct groups, i.e., CTS-D (n = 120) having prolonged median sensory latency and normal needle examination, CTS-AD having prolonged median sensory latency and abnormal needle findings (n = 130). Subjects in the CTS-AD group showed significant reduction, both in CMAP amplitude and area from 3rd to 7th decades; however, in the CTS-D group there were significantly smaller CMAP amplitude from 5th to 7th decades but CMAP area demonstrated wide variations. These data indicate that CMAP amplitude and area are helpful in documenting motor nerve axonal loss, but care must be exercised when attempt is made to define axonal loss based either on area or amplitude because of the temporal dispersive effects.

Action Potentials↗