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Biomedical subjects

K H Chan

Publications and source records attributed to K H Chan.

At least 181 records · Page 10Linked to original sources
PubMed1992

Interpleural administration of bupivacaine for postoperative analgesia after thoracotomy in patients with patent ductus arteriosus.

Interpleural analgesia for postoperative pain with bupivacaine 0.25%, 0.375% and 0.5% at dosage of 1.5 mg/kg was evaluated in three randomized groups (A, B and C) of 22 children having triple ligation for patent ductus arteriosus (PDA). Complete pain relief was obtained within 30 min irrespective of the concentration of bupivacaine. The duration of pain relief significantly varied with the concentrations of the drug used, respectively 5.02 +/- 0.4 h, 6.88 +/- 0.7 h and 8.24 +/- 1.08 h (mean +/- SD) for 0.25%, 0.375% and 0.5% bupivacaine (p less than 0.05). No side effects were observed and no other supplemented narcotics were given. We concluded that 0.5% bupivacaine at the dose of 1.5 mg/kg was effective in postoperative pain relief after thoracotomy in patients undergoing PDA ligation surgery.

Adolescent↗
PubMed1992

The significance of posttraumatic increase in cerebral blood flow velocity: a transcranial Doppler ultrasound study.

Using transcranial doppler ultrasonography, cerebral blood flow velocity was measured daily from both middle cerebral arteries in 121 patients who had suffered minor (n = 55), moderate (n = 16), or severe (n = 50) brain injury. Serial computed tomographic scans were performed to identify noncontusion-related infarction (NCI). Cerebral perfusion pressure was monitored continuously in 41 patients who had severe head injury; of these, 22 had continuous measurement of arterial and jugular bulb venous oxygen (SJO2) saturation. Abnormally high mean flow velocity (greater than 100 cm/s) was observed in 23 patients (minor injury, n = 3; moderate injury, n = 3; severe injury, n = 17), but was recorded only when cerebral perfusion pressure exceeded 60 mm Hg (P less than 0.0001). Fourteen patients who underwent SJO2 monitoring developed increased mean flow velocity (MFV). In 6, the arterial-jugular venous oxygen content difference (AVDO2) was below 4 ml/dl, indicating global cerebral hyperemia. All had bilateral elevation of MFV, and 6 of the 8 nonhyperemic patients (AVDO2, 4-9 ml/dl) had a unilateral increase of MFV (P = 0.018). Four of the 23 patients with increased MFV developed NCI, as compared with none of the patients without elevated MFV (P = 0.015). All patients with NCI had suffered severe brain injury, had unilateral elevation of MFV in the terriory of the relevant cerebral vessel, and had received therapy to correct reduced cerebral perfusion pressure (P = 0.008). NCI did not occur in any patient with increased MFV that was associated with global hyperemia.

Adolescent↗
PubMed1992

Control of intracranial pressure in patients with severe head injury.

Raised intracranial pressure (ICP) occurs at some time in 50-75% of severely head injured patients. Measurement of ICP alone is not sufficient. Arterial pressure must also be monitored: the important physiological variable is cerebral perfusion pressure. Detailed analysis of the ICP recording yields valuable information on the nature and cause of ICP, with implications for appropriate therapy. Additional measurements of importance include brain electrical activity, arterial and jugular venous oxygen saturation, and blood flow velocity in major intracranial arteries measured by transcranial Doppler sonography. These assessments not only add information about the cause of intracranial hypertension (vascular vs. nonvascular) but also help to regulate therapy, providing early warning that a treatment for reducing the ICP is actually producing global brain ischemia. In the management of raised ICP, all correctable factors must first of all be dealt with, then a choice made between hypnotic drugs and osmotic therapy according to whether the cause of raised ICP is, respectively, vascular or nonvascular.

Blood Volume↗
PubMed1991

Influence of controlled hypotension by adenosine triphosphate or nitroglycerin on the neuromuscular blocking effect of atracurium in dogs.

The neuromuscular blocking effect of atracurium under the influence of controlled hypotension by adenosine triphosphate (ATP) or nitroglycerin (NTG) was studied in mongrel dogs under halothane anesthesia. Under hypotensive state (60 +/- 5 mmHg) elicited by ATP (0.5 mg/kg/min) or NTG (1 microgram/kg/min), the neuromuscular blockade produced by atracurium (30 micrograms/kg, i.v.) was significantly potentiated and prolonged. The maximal depression of twitch contraction of the gastrocnemius-soleus muscle increased from 10 +/- 3% to 36 +/- 10% (ATP group) and 56.0 +/- 2.4% (NTG group), while the duration of neuromuscular blockade was prolonged from 663 +/- 96 s to 1060 +/- 277 s (ATP group), and 1375 +/- 441 s (NTG group). The potentiation and prolongation of neuromuscular blockade by atracurium was still apparent upon reversal of the hypotensive effect of ATP, but not of NTG, by dopamine infusion. We suggest that ATP may prolong and augment the effect of atracurium by reducing the presynaptic release of acetylcholine at the neuromuscular junction.

Adenosine Triphosphate↗
PubMed1991

Assessment of middle-ear status during experimental otitis media using magnetic resonance imaging.

Magnetic resonance imaging has proved to be a useful tool for in vivo imaging of a variety of tissues. In this study, magnetic resonance imaging was applied to the middle ear of experimental animals with otitis media. Results showed that the presence and distribution of effusion within the middle-ear space could be readily determined. Moreover, following injection of gadolinium-diethylenetriaminepentaacetic acid, a contrast agent, the inflamed middle-ear mucosa could be resolved. A comparison between magnetic resonance imaging and tympanometry with respect to the diagnosis of effusion showed that negative pressure tympanograms were equivocal (50% effusion) and that flat or normal tympanograms were in error in approximately 20% of the observations. These data document a role for magnetic resonance imaging in in vivo studies of the pathogenesis of otitis media with effusion.

Acoustic Impedance Tests↗
PubMed1991

Focal myositis. A new cause for the pediatric neck mass.

Focal myositis is an inflammatory pseudotumor of skeletal muscle that may involve the head and neck. It can closely mimic either a neoplastic or infectious process. We present the case of a 7-year-old boy with a 2-week history of a painful, unilateral neck swelling, fever, and torticollis. He failed to respond to antibiotic therapy and required an open neck exploration. An incisional biopsy of the indurated, inflammatory tissue adherent to his sternocleidomastoid muscle showed focal myositis. Focal myositis is an unusual, but important possibility in the differential diagnosis of any neck mass and especially one in a child. Although its cause is unknown, it is a self-limited disease and neither excisional biopsy nor radical resection is justified.

Abscess↗
PubMed1991

Antral choanal polyp presenting as obstructive sleep apnea syndrome.

Obstructive sleep apnea syndrome (OSAS) in children is commonly caused by adenotonsillar hypertrophy. The diagnostic criteria of OSAS in children are not so well delineated as in adults. We report the first case of antral choanal polyp presenting as OSAS in a 10-year-old boy that initially presented to the child psychiatry service for behavior disturbance, enuresis, and daytime somnolence. Overnight electroencephalogram sleep study revealed events consistent with OSAS. Multiple inhalant allergies, chronic maxillary sinusitis, and obstructive adenoid hypertrophy were diagnosed by the allergy and otolaryngology services. The child was scheduled for adenoidectomy when his sleep apnea symptoms persisted following antimicrobial therapy. Examination under anesthesia revealed a normal adenoid bed and a large left antral choanal polyp. Polypectomy was performed as dictated by parental consent. Postoperatively treatment with an intranasal steroid was begun. However, polypoid nasal mucosa recurred in 2 months and a Caldwell-Luc procedure was performed. Subjective reports following surgery indicated improvement in daytime irritability, attention, and mood. A follow-up overnight electroencephalogram sleep study confirmed resolution of OSAS.

Child↗
PubMed1991

Concentrations of azithromycin in human tonsillar tissue.

Patients scheduled to undergo tonsillectomy were administered 500 mg oral azithromycin as two 250 mg capsules given 12 h apart. Between 9 h and one week after the second dose, tonsil samples were taken during surgery and assayed for azithromycin. Mean concentrations in tonsillar tissue, 12 and 24 h after the second of the two 250 mg doses given 12 h apart, were 4.5 and 3.9 micrograms/g, respectively. Concurrent mean serum concentrations were approximately 0.03 and 0.01 micrograms/g, respectively. The mean concentration in tonsillar tissue 7.5 days after the last dose was 0.93 micrograms/g. The apparent half-life of drug in the tissue was 76 h. The ratio of mean concentration in tissue to that in serum was greater than 150-fold for all time intervals. The presence of high azithromycin concentrations in tonsillar tissue suggests that a once-daily regimen over five days or less may be effective in treating tonsillo-pharyngitis.

Administration, Oral↗
PubMed1991

Lack of the alpha-1,2-linked N-acetyl-D-glucosamine epitope in the outer core structures of lipopolysaccharides from certain O serogroups and subspecies of Salmonella enterica.

A total of 176 strains of Salmonella enterica representing 116 serotypes were tested for the presence of the T6 epitope of the alpha-1,2-linked N-acetyl-D-glucosamine residue by reaction with a murine monoclonal antibody T6 specific for this structure in the Salmonella Ra core lipopolysaccharide (LPS). All 20 serotypes (70 strains) belonging to serogroups A to E were positive for the T6 epitope while 29% of the 96 serotypes (106 strains) belonging to O serogroups F to 67 were negative; 12 serotypes (12 strains) of subspecies IIIb Salmonella were positive for the T6 epitope, but 10 serotypes (11 strains) of subspecies IIIa Salmonella were found to lack this epitope. In T6-positive strains, the epitope was accessible to antibody binding in both the unsubstituted free rough core LPS and in the rough core LPS substituted with a few repeating units of O side chains. The presence or absence of the T6 epitope in Salmonella strains was not affected by culture conditions, the source of the isolate, the age of the culture or the presence of fimbriae antigens.

Acetylglucosamine↗
PubMed1991

Infection of a shunt by Mycobacterium fortuitum: case report.

Mycobacterium fortuitum is a rare cause of central nervous system infection; however, shunt infection caused by this organism has not been reported. We report a case of shunt infection subsequent to insertion of a ventriculoatrial shunt for obstructive hydrocephalus caused by a cerebellar hematoma. The shunt infection was controlled by removal of the shunt and a combination of systemic and intraventricular administration of amikacin, and oral administration of ofloxacin. The case is discussed and the pertinent literature reviewed.

Anti-Bacterial Agents↗
PubMed1991

Characterization of murine monoclonal antibodies against serogroup B salmonellae and application as serotyping reagents.

Six murine hybridoma monoclonal antibodies reactive with lipopolysaccharide antigens of Salmonella typhimurium were obtained from a fusion of immune spleen cells from mice immunized with S. typhimurium and NS1 myeloma cells. Four antibodies appeared to be specific for serogroup B salmonellae, while the remaining two antibodies were found to be cross-reactive with Salmonella paratyphi A. The exquisite specificities of the Salmonella serogroup B monoclonal antibodies were demonstrated by their unique reactivities with different serotypes of group B salmonellae but with neither other O serogroups of salmonellae nor a wide spectrum of standard strains of other bacterial species. Serotyping of salmonella strains by the slide agglutination method with two of the serogroup B-specific monoclonal antibodies demonstrated their usefulness as serotyping reagents for the identification of serogroup B salmonellae in a routine diagnostic bacteriology laboratory.

Agglutination Tests↗
PubMed1991

Nasopharyngeal carcinoma and lymphoinfiltration.

Originally referred to as 'lymphoepithelioma', undifferentiated and poorly differentiated nasopharyngeal carcinoma (NPC) tissues showed intense lymphoinfiltration. In a study of cryosections from 15 NPC tissues, we found that infiltrating lymphoid elements were comprised predominantly of lymphocytes, but plasma cells, follicular dendritic cells, and eosinophils were also commonly seen. Subpopulations of lymphocytes having the same phenotypes tend to aggregate, forming clusters or secondary follicles in stromatous tissues. The tumor areas were mainly infiltrated by T cells. Tumor cells and/or apparently normal epithelium in the paratumorous areas frequently expressed CD21, CD23, CD40 and a B lymphocytes carcinoma cross-reacting antigen (BLCa), all of which are involved in B cell activation and proliferation. CD21 and BLCa were strongly expressed near the surface of both squamous and columnar epithelium by those epithelial cells which are at advanced stage of differentiation, while CD40 was expressed by epithelial cells at earlier stages of differentiation located at or near the basement membrane. CD23 was mainly expressed by columnar cells and basal cells underlying squamous epithelium, but not, or weakly so, by flattened squamous cells or reserve cells underlying columnar epithelium. The large majority of tumor cells expressed CD40 and BLCa. A substantial proportion of them also expressed CD23, but the tumor cells were not reactive for CD21. Despite eosinophilic infiltration, IL-6 was not detected in tumor tissues. IL-1 was, however, detected in abundance in the cytoplasm of follicular dendritic-like cells and in the intercellular spaces in tumor areas and surrounding stromatous tissues. The immunobiology of NPC is discussed in the light of these observations.

Antibodies, Monoclonal↗
PubMed1991

Familial sensorineural hearing loss: a correlative study of audiologic, radiographic, and vestibular findings.

A multidisciplinary approach to the study of a family with autosomal dominant sensorineural hearing loss is presented. The affected family members underwent extensive clinical and laboratory evaluation. They were found to have various degrees of bilateral congenital inner ear anomalies as imaged by computed tomography. The degree of structural abnormalities in the inner ears correlated with the severity of hearing impairment. Vestibular testing revealed nonspecific abnormalities generally correlating with audiologic and radiographic findings. This report presents a unique form of sensorineural hearing loss not previously described and is the first in-depth clinical study of nonsyndromal "Mondini dysplasia" occurring in a family.

Adult↗
PubMed1991

Clinical trial in adults of an antimicrobial varnish for reducing mutans streptococci.

An abbreviated treatment with a chlorhexidine-containing varnish was compared with a similar treatment with a placebo varnish and with a prophylaxis alone for its effects on the numbers of detectable salivary mutants streptococci in 51 adults. The varnishes, applied once weekly for four weeks, were held in place with a covering layer of either of two polyurethane sealants (FluorProtector or Adhesit). On the first appointment, the varnish-sealant combination was applied to all tooth surfaces, but on succeeding appointments only the occlusal and approximal surfaces were covered. The chlorhexidine varnish, covered with either sealant, reduced the salivary mutans streptococci by an average of 3 logs (99.9%) in all of the 20 subjects treated, and below detectable levels for at least four weeks in nine of them. In the groups receiving placebo varnish-sealant combinations, the mean log number of mutans streptococci of the subjects was reduced only by approximately 0.5 log (32%), and none of the subjects experienced loss of their detectable mutans streptococci for four weeks, although one subject did so for three weeks. No significant difference between the effects of the two polyurethane sealants was observed. Treatment with a single prophylaxis had no effect on mutans streptococcus levels. Subjects treated with chlorhexidine varnish also experienced an increase in S. sanguis and a small decrease in yeasts. Loss of detectable mutans streptococci did not cause changes in the numbers of other micro-organisms examined, beyond those observed with chlorhexidine varnish treatment alone.

Acrylic Resins↗
PubMed1991

Acute normovolemic hemodilution in coronary artery bypass graft surgery.

Twenty patients undergoing coronary artery bypass graft (CABG) surgery in April through May, 1990 in our hospital were included in this study to evaluate the merits and practicability of autologous blood transfusion. About 1,000 ml of arterial blood were collected via a radial arterial line and stored in a plastic bag containing CPD solution immediately after induction of anesthesia. Colloid or crystalloid solution was used to replace the volume deficit after the blood sampling. At the end of cardiopulmonary bypass and after adequate reversal of heparinization by protamine, the blood previously sampled was re-transfused to the patient via a peripheral venous line. Thirty patients undergoing CABG surgery, who did not receive autologous blood transfusion from February to June, 1990 save April and May were assigned as control. Comparison of the data between the two groups was made using the Student's t-test. It was found that the intraoperative acute normovolemic hemodilution could lower the hematocrit by approximately 12%. Packed red blood cells (PRBC) given intraoperatively in the autologous group was only 2.0 +/- 0.4 units whereas it was 5.3 +/- 0.7 units in the control group (p less than 0.001). Fresh frozen plasma (FFP) given intraoperatively in the autologous group was only 1.8 +/- 0.5 units whereas it was 6.6 +/- 0.7 units in the control group (p less than 0.001). The amount of platelets given intraoperatively in the autologous group was 1.9 +/- 1.0 units against 9.3 +/- 1.4 units in the control group (p less than 0.001). Thus, acute normovolemic hemodilution in CABG surgery decreased intraoperative requirement of bank blood components including PRBC, FFP and platelets.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗