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Biomedical subjects

T C Chan

Publications and source records attributed to T C Chan.

At least 19 recordsLinked to original sources
PubMed2001

Electrocardiographic manifestations: digitalis toxicity.

Toxicity from the digitalis family of cardiac glycoside medications remains common. Successful treatment depends on early recognition; however, the diagnosis of potentially life-threatening toxicity remains difficult because the clinical presentation is often nonspecific and subtle. The hallmark of cardiac toxicity is increased automaticity coupled with concomitant conduction delay. Though no single dysrhythmia is always present, certain aberrations such as frequent premature ventricular beats, bradydysrhythmias, paroxysmal atrial tachycardia with block, junctional tachycardia, and bidirectional ventricular tachycardia are common. Treatment depends on the clinical condition rather than serum drug level. Management varies from temporary withdrawal of the medication to administration of digoxin-specific Fab fragments for life-threatening cardiovascular compromise.

Aged↗
PubMed2001

Electrocardiographic manifestations: acute posterior wall myocardial infarction.

Posterior myocardial infarction (PMI) refers to infarction of the posterior wall of the left ventricle. Although often associated with inferior and lateral myocardial infarctions, detection of acute PMI is difficult because the standard 12-lead electrocardiogram does not adequately image the posterior wall of the left ventricle. We review the findings on 12-lead electrocardiogram with PMI, as well as discuss the utility of additional electrocardiographic leads in the diagnosis of PMI.

Electrocardiography↗
PubMed2001

The prehospital electrocardiogram.

Although widely used in Europe, the prehospital 12-lead electrocardiogram (EKG) has seen only limited use in this country. Reported benefits of the 12-lead EKG include shortening the door-to-needle time, accelerating the initiation of reperfusion therapy, and overall improving the prehospital and hospital management and outcome of patients with acute myocardial infarction. The field EKG also provides the basis for prehospital fibrinolysis. Concerns still exist, however, regarding the best means of providing real-time field interpretation of the prehospital EKG and the potential for inappropriate field time delay, triage, and treatment of patients. Moreover, questions remain about the overall clinical and cost benefit of expanding this resource universally. The following article reviews the role of prehospital EKG in caring for patients with acute coronary syndromes.

Electrocardiography↗
PubMed2000

A role for Xlim-1 in pronephros development in Xenopus laevis.

Xlim-1, a LIM class homeobox gene expressed in Xenopus laevis, is one of the earliest known marker genes of pronephros development and is expressed in pronephros rudiment. In this study, we examined the role of Xlim-1 in pronephros development. Temporal expression of Xlim-1 in explants was analyzed in a series of induction assays using RT-PCR analysis. Xlim-1 was expressed 9 to 15 h after activin/retinoic acid treatment, corresponding to pronephros differentiation in explants. We further examined the role of Xlim-1 using a series of microinjection experiments. Presumptive pronephric anlagen of embryos were injected with various Xlim-1 mutants, and effects of these Xlim-1 mutants on pronephrogenesis in embryos and in explants were analyzed by RT-PCR and immunohistochemistry. Dominant-negative Xlim-1 inhibited differentiation of pronephros in activin/retinoic acid-treated animal caps. In embryos injected with a dominant-negative form of Xlim-1, development of pronephric tubules was inhibited at the late tail-bud stage. Our results suggest that Xlim-1 may not initiate differentiation of the pronephros, but that it is necessary for growth and elongation in the development of pronephric tubules.

Activins↗
PubMed2000

Use of a complete neurological examination to screen for significant intracranial abnormalities in minor head injury.

Indications for head computed tomography (CT) scans are unclear in patients with nonpenetrating head injury and Glasgow Coma Scale (GCS) scores of 15. We performed a prospective study to determine if significant intracranial injury could be excluded in patients with GCS-15 and a normal complete neurological examination. A prospective trial of clinically sober adult patients with GCS = 15 on emergency department (ED) presentation after closed head injury with loss of consciousness or amnesia was conducted from May 1996 through April 1997. All subjects underwent a standardized neurological examination including mental status evaluation, and assessment of motor, sensory, cerebellar and reflex function before CT scan. During the study period, 58 patients met inclusion criteria. Fifty-five patients (95%) had normal CT scans and 23 (42%) had focal neurological abnormalities. Three patients (5%) had CT scan findings of acute intracranial injury, two of whom had normal neurological examinations. One patient had an acute subdural hematoma requiring emergent surgical decompression; the other had both an epidural hematoma and pneumocephalus that did not require surgery. Significant brain injury and need for CT scanning cannot be excluded in patients with minor head injury despite a GCS = 15 and normal complete neurological examination on presentation.

Adolescent↗
PubMed2000

Safety and efficacy of the Rapid Four-Step Technique for cricothyrotomy using a Bair Claw.

The Rapid Four-Step Technique (RFST) has been demonstrated to be faster than standard open crico thyrotomy technique, but may have a higher incidence of cricoid injury with tracheal hook traction applied caudad. The "Bair Claw" is a novel device that may help eliminate these complications. This randomized, experimental trial used a fresh-frozen cadaver model of cricothyrotomy to compare speed and safety between RFST using a Bair Claw and standard open technique. Outcome measures included time to definitive airway, size of largest endotracheal (ET) tube able to be passed, and incidence of complications. We observed that RFST using a Bair Claw was significantly faster than standard open technique. There was no significant difference with regard to size of ET tube able to be passed with RFST using a Bair Claw versus standard open technique, and there was no damage to trachea or larynx observed with either technique. We concluded that RFST using a Bair Claw is faster and appears to be equally safe when compared to standard open technique in a fresh-frozen cadaver model of cricothyrotomy. The two techniques were equal with regard to maximal ET tube size.

Cadaver↗
PubMed2000

Rapid sequence intubation in the field versus hospital in trauma patients.

We conducted a retrospective review of all adult trauma patients who underwent prehospital field rapid sequence intubation (RSI) by aeromedical crews from 1988 through 1995 and compared them to all trauma patients who arrived by ground transportation and underwent RSI in the trauma suite from 1992 through 1995 at a University hospital. Of the 47 field RSI patients, 46 (97.9%) were successfully intubated, whereas 263 of the 267 (98.5%) hospital RSI patients were successfully intubated. There were no statistical differences in success rates, number of attempts, or immediate intubation events in the procedure between the two groups. There were no differences in delayed events with the exception of pneumonia, which occurred more frequently in the field RSI group (28% vs. 6%, respectively). We performed a subgroup analysis on isolated head injury patients to evaluate outcome. There was no difference in total hospital days, length of ICU stay, mortality or final disposition in the two head injury groups. Though this study is limited by small sample size, we conclude that field RSI is equally successful and safe as hospital RSI.

Adult↗
PubMed2000

Electrocardiographic manifestations: aberrant ventricular conduction.

Aberrant ventricular conduction is a common electrocardiographic (EKG) manifestation that occurs when the supraventricular electrical impulse is conducted abnormally through the ventricular conducting system. This results in a wide QRS complex that may be confused with a ventricular ectopic beat. This differentiation is important because the treatment and prognosis is quite different. Hemodynamically unstable patients with a wide-complex tachycardia should be promptly cardioverted. Although up to 10% of cases will defy differentiation, ventricular tachycardia and aberrant conduction can be distinguished utilizing history, physical examination, and EKG criteria. The mechanisms of aberrant ventricular conduction are discussed.

Calcium Channel Blockers↗
PubMed2000

Emergency department patient knowledge of medications.

Therapeutic decisions made by Emergency Physicians are often influenced by which prescribed medications are being taken by patients. We sought to assess Emergency Department (ED) patients' knowledge of their medications by using a survey. A convenience sample of adult ED patients was surveyed verbally by a research assistant. Two-hundred patients were enrolled. Only 48% of patients could recall or produce a list or the actual bottles of all of their medications, 39% knew the times they take their medications, and only 24% knew all the dosages. Seventeen percent brought a list or the actual medication bottles with them to the ED. Patients who had a primary care physician knew all their medications 51% of the time, compared to 43% who did not have a physician. Fifty-one percent of insured patients compared to 38% of non-insured patients could identify all of their medications. Although knowledge of medications is often critical for decision making in the ED, a significant number of patients are unable to provide this information.

Adult↗
PubMed2000

Electrocardiographic manifestations: patterns that confound the EKG diagnosis of acute myocardial infarction-left bundle branch block, ventricular paced rhythm, and left ventricular hypertrophy.

The 12-lead electrocardiogram (EKG), a powerful tool used in evaluating the chest pain patient, has its shortcomings. One such failing is encountered in a patient with one of the following electrocardiographic patterns: left bundle branch block (LBBB), ventricular paced rhythm (VPR), and left ventricular hypertrophy (LVH). These patterns reduce the ability of the EKG to detect acute coronary ischemic change and acute myocardial infarction (AMI). Several strategies are available to assist in the correct interpretation of these complicated electrocardiographic patterns, including a knowledge of the ST segment-T wave changes associated with these confounding patterns, performance of serial EKGs, and comparison with previous EKGs if available. This article suggests guidelines and interpretive tools for diagnosing AMI on EKG in patients with these confounding patterns.

Aged↗
PubMed2000

Longitudinal colour doppler study of superficial lymph nodes in non-Hodgkin's lymphoma patients on chemotherapy.

AIMS/METHODS: A longitudinal study of 22 malignant lymph nodes by colour Doppler (CD) and/or colour power (CP) ultrasonography was undertaken in 12 non-Hodgkin's lymphoma patients to delineate changes in vascularity, and correlate this response with clinical outcome. RESULTS: Reduced vascularity in response to chemotherapy was shown to be a positive prognostic sign. CONCLUSIONS: More persistent nodal vascularity may signify a less favourable prognosis.

Adult↗
PubMed2000

Spirometry in normal subjects in sitting, prone, and supine positions.

OBJECTIVE: Determine whether pulmonary function testing is affected by patient positioning. METHODS: In a descriptive study with measurements made in a sequential but randomized order at a university-based pulmonary function laboratory, 20 healthy men, ages 18-50 years, were evaluated with spirometric assessment of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and maximum voluntary ventilation (MVV) in the sitting, supine, and prone positions. Subjects were excluded for body mass index (BMI) > 30 kg/m2 or abnormal baseline spirometry. RESULTS: Comparing sitting to supine and prone positions, there was a statistically significant decline in the spirometry values (reported as percent of predicted normal +/- standard error of the mean). FVC was 102% +/- 4% while sitting, 95% +/- 4% while supine, and 94% +/- 4% while prone. FEV1 was 104% +/- 3% while sitting, 96% +/- 3% while supine, and 94% +/- 3% while prone. MVV was 115% +/- 4% while sitting, 102% +/- 4% while supine, and 97% +/- 3% prone. CONCLUSION: In healthy men with BMI < 30 kg/m2, changing from the sitting to supine or prone position results in statistically significant change in respiratory pattern. However, all spirometry values in each position were normal by American Thoracic Society definitions.

Adolescent↗
PubMed1998

Intracisternal osteogenic protein-1 enhances functional recovery following focal stroke.

Osteogenic protein-1 (OP-1, BMP-7) is a member of the transforming growth factor-beta (TGF-beta) superfamily that selectively induces dendritic outgrowth from cultured neurons. We injected human recombinant OP-1 (1 or 10 micrograms) or vehicle into the cisterna magna of mature male Sprague-Dawley rats 1 and 4 days after focal cerebral infarction induced by middle cerebral artery (MCA) occlusion. OP-1 treatment was associated with a marked enhancement of recovery of sensorimotor function of the impaired forelimb and hindlimb (contralateral to infarcts) as assessed by limb placing tests. This effect appeared to be dose dependent. There was no difference in infarct volume between OP-1 and vehicle-treated rats. The mechanisms of enhanced recovery by intracisternal OP-1 may include promotion of dendritic sprouting in the intact uninjured brain.

Analysis of Variance↗
PubMed1998

Postpartum coronary artery dissection.

A 34-year-old woman presented to the emergency department 12 weeks postpartum with chest pain. An ECG indicated an acute myocardial infarction. The patient underwent cardiac catheterization with findings suggestive of coronary artery dissection later confirmed on intravascular ultrasonography. She underwent emergency coronary artery bypass grafting and has subsequently done well.

Adult↗