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Biomedical subjects

J L Chang

Publications and source records attributed to J L Chang.

At least 55 records · Page 3Linked to original sources
PubMed1982

Jet ventilation for operative laryngoscopy.

High pressure oxygen jet ventilation via a small bore endotracheal tube has been found to be a very effective method for operative laryngoscopy and bronchoscopy under general anesthesia. Advantages of this technique include easily visualization of the larynx and good access for surgical manipulations and bronchoscopic procedures while maintaining excellent patient oxygenation and ventilation. There are few contra-indications for this procedure. Over the past 7 years we have done several thousand operative laryngoscopies using high pressure oxygen jet ventilation with few complications and excellent anesthetic and surgical results.

Anesthesia↗
PubMed1981

Postoperative venous air embolism after removal of neck drains.

Venous air embolism has been known to be a major hazard during diagnostic, therapeutic, and surgical procedures. An acute massive venous air embolism can cause obstruction of the pulmonary outflow tract and subsequently result in cardiac standstill. Sudden cardiopulmonary instability occurred in a patient after removal of neck drains. Various methods of diagnosis and treatment can be used to manage this complication. An awareness of this potential complication and early diagnosis with prompt management are critical.

Drainage↗
PubMed1981

Stress-strain relationship and neurological sequelae of uniaxial elongation of the spinal cord of cats.

An in vivo experimental method was developed to measure the mechanical or rheological properties of the spinal cord of anesthetized cats. This novel approach resulted in measurements of the tensile force in the cord and the modulus of the spinal cord tissue under longitudinal elongation. Both sensory and motor function of the cats recovered within a week after a spinal cord segment had been stretched by a 50% elongation.

Animals↗
PubMed1981

Polyclonal B cell activator associated with alpha-2-macroglobulin in the serum of patients with rheumatoid arthritis.

We investigated whether patients with rheumatoid arthritis have a polyclonal B cell activator (PBA) in their serum by using three methods: (1) the ability of any PBA to maintain the surface Ig of rabbit or human B cells in vitro; (2) the induction of blast transformation in human B lymphocyte cultures, and (3) stimulation of nude mouse spleen cells in vitro. All three methods indicated that a PBA is present in the serum of patients with rheumatoid arthritis but not in normal individuals or in patients with arthritis in which autoimmune phenomena have not been demonstrated. The entire PBA activity in rheumatoid arthritis patient serum was found associated with the macroglobulin fraction obtained by Sephadex G-200 chromatography and was precipitated by rabbit anti-human alpha 2-macroglobulin, but not by rabbit anti-Ig antibody. When alpha 2-macroglobulin was purified from patient serum the entire PBA activity was recovered in this fraction. Normal alpha 2-macroglobulin prepared by the same procedure had no PBA activity. Thus, the existence of a PBA associated with alpha 2-macroglobulin was demonstrated in serum of patients with rheumatoid arthritis.

Animals↗
PubMed1981

An alpha2-macroglobulin associated factor produced by T lymphocytes which provides polyclonal stimulation of B lymphocytes to maintain the turnover of their surface Ig.

The supernatant of 'crowded' but not 'spread' rabbit spleen cell cultures contains a macroglobulin factor which behaves in an Ig-turnover assay as any T-independent antigen or polyclonal B-cell activator (PBA). In the supernatants of crowded rabbit lymphoid cell cultures prepared in serum free medium, the factor was found to be associated entirely with the alpha-macroglobulin (alpha M) fraction (alpha 1 + alpha 2). This alpha M was most probably actively secreted by the lymphocytes because: (i) sequential supernatants obtained in serum free medium of crowded cultures contained equal amounts of alpha M as well as equal PBA activity; (ii) the alpha M became labelled when the cells were grown in medium containing a radioactive amino acid. Macrophages were not required for the production of PBA. PBA was not produced when either crowded B or T cells were cultured alone but only when they were cultured together. Purified T cells were not triggered by any plant lectin to produce PBA. By use of anti-alpha 2M allotype antibodies and B and T cells from different rabbits, the PBA was shown to have the allotype of the T-cell donor. The PBA was associated with rabbit alpha 2M but not alpha 1M. We concluded that upon close contact, B cells stimulate T cells to produce a PBA associated with alpha 2M.

Animals↗
PubMed1980

Analysis and comparison of venous air embolism detection methods.

Changes in precordial ultrasonic Doppler patterns in dogs were compared with changes of end-tidal carbon dioxide (EtCO2) and pulmonary arterial pressure (PAP). Possible mechanisms of pulmonary arterial hypertension after air embolism in dogs are discussed. After the injection of air, an immediate change in the Doppler ultrasonic pattern was detected, including a shift of the base line. The duration of change of Doppler patterns varied depending upon the length of time that trapped air remained in the right heart. There was a delay of 15 to 30 seconds before the EtCO2 and PAP responded. In a group of dogs pretreated with 0.3 mg of propranolol per kg, there was a significant decrease in the PAP response due to induced air embolism compared to the control group (P < 0.05). We found that the Doppler ultrasonic device was the most sensitive for detecting venous air embolism at a level as low as 0.05 ml of air per kg compared to 0.25 ml/kg for the PAP and EtCO2 responses.

Animals↗
PubMed1980

Anesthetic considerations for the oral surgery patient with hemophilia.

Hemophiliac patients undergoing oral surgical procedures can be a challenge for both dental and medical personnel involved in their care and treatment. Anesthetic management of hemophiliac patients may be safely attained by various pain control techniques including local anesthesia. Possible complications resulting from administration of anesthesia must be kept in mind at all times. Preparation, caution, and gentleness are necessities for administration of safe and effective anesthesia to the hemophiliac patient.

Analgesics↗
PubMed1980

[Randomized controlled clinical trials with barbiturate treatment after cardiac arrest in the United States. Ethical and medicolegal aspects (author's transl)].

Brain protection during ischemia by barbiturates has been clearly demonstrated in many different experiments. Only recently the therapeutic value of large doses of thiopental administered early after cerebral circulatory arrest has been demonstrated experimentally in monkey. Noncontrolled studies in humans also indicate beneficial effect, however the treatment is not without potential complication. Controlled randomized studies in humans are needed to document its beneficial effect. Such studies have several unique medico-legal and ethical implications since the treatment has to be started in an unconscious patient and as early as possible after a totally unexpected cardiac arrest. Informed consent, ethical and medicolegal consideration of randomized controlled clinical trials is discussed and a modified approach to clinical trials in humans is suggested. The modification would not alter the scientific value of the studies, but resolve the ethical and medico-legal problems.

Barbiturates↗
PubMed1980

[Pathogenesis and treatment of anoxic encephalopathy. Definition and importance of experimental animal models (author's transl)].

A reproducible noninvasive monkey model for global brain ischemia with exact insult (no flow x 16 min) to the brain, with survival and with standardized preischemic, ischemic and postischemic variables is described. This model allowed us to demonstrate for the first time: 1) that a substantial part of brain damage early postischemia is reversible and amenable especially to barbiturate treatment; 2) that the postischemic brain shows increased vulnerability for additional insults. Optimal postischemic intensive monitoring and immobilization for 24-48 hours is important for improved outcome; 3) that immediate postischemic reperfusion pressure (MAP 110-150 mm Hg) significantly improves the outcome; 4) that heparinisation during ischemia has no protective effect and 5) that postischemic heparinisation and intravenous hemodilution does not ameliorate the outcome. The protective effect of trimetaphan against neurogenic pulmonary edema can be explained by the prevention of pulmonary hypertension but its protective effect on the development of secondary cerebral edema has to be elucidated.

Animals↗
PubMed1977

Air embolism.

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Embolism, Air↗