Search PubMed⌕ Search

Biomedical subjects

P J Lin

Publications and source records attributed to P J Lin.

At least 109 records · Page 6Linked to original sources
PubMed1993

Thromboxane A2: an endothelium-derived vasoconstrictor in human internal mammary arteries.

The internal mammary artery (IMA) has become the conduct of choice for coronary artery bypass grafting. However, the IMA graft can exhibit vasoconstriction during the perioperative period. Experiments were designed to determine the role of cyclooxygenase products in human IMA during hypoxia. Rings of IMA, with and without endothelium, were suspended in organ baths containing physiologic salt solution. Rings were contracted with norepinephrine and then exposed to hypoxia for 15 minutes. In segments with endothelium, hypoxia induced a transient relaxation followed by contraction. This contraction was associated with a significantly increased production of thromboxane B2, the stable metabolite of thromboxane A2 (n = 10; from 120.7 +/- 3.5 pg/mg wet tissue before hypoxia to 175.8 +/- 5.2 pg/mg during hypoxia; p < 0.05). This hypoxic contraction could be attenuated by indomethacin. However, thromboxane B2 could not be detected in samples from organ baths containing IMA segments without endothelium before or during hypoxia. This study demonstrated that endothelium of human IMA grafts releases thromboxane A2 basally and that production is augmented by hypoxia, which acts to constrict the underlying vascular smooth muscle, increase vascular tone, and promote ischemic events such as vasospasm and thrombosis, particularly in hypoxemic patients.

Endothelins↗
PubMed1993

Surgical management of thrombotic disc valve.

Thrombotic obstruction, a rare but often fatal complication of cardiac valve prostheses, appears to occur more frequently in tilting-disc valves than in other valve designs. Its diagnosis and surgical treatment remain a challenge. Ten consecutive patients who had thrombosis of a tilting-disc valve prosthesis were treated in Chang Gung Memorial Hospital from November 1982 to August 1990. Preoperative clinical features, including exertional dyspnea, new murmur, and absence of a metallic click from the prosthetic valve, occurred in all of the patients. Symptoms were present for 1 week or more before reoperation in 70% of the patients; nevertheless, many patients were referred only after acute exacerbation of heart failure and development of pulmonary edema. Echocardiography confirmed prosthetic valve malfunction in 90% of the patients. One unconfirmed case was later documented by cardiac catheterization. Anticoagulant therapy was in the therapeutic range for only half of the patients at the time of admission. Prompt reoperation was performed for thrombectomy (8 patients, all survived) or valve replacement (2 patients, one death). Long-term outcome was satisfactory in all survivors with a mean follow-up of 31.6 months. These findings emphasize the importance of considering the diagnosis of thrombosis in patients with mechanical heart valve prostheses who are first seen with nonspecific symptoms and minor changes of their physical findings. The diagnosis could be easily made by echocardiography. Thrombectomy is an easy, fast, and safe procedure, especially for these critically ill patients.

Adult↗
PubMed1993

Endothelium-dependent response of human internal mammary artery to hypoxia.

To study the effect of hypoxia on vascular tone in human internal mammary artery (IMA), segments of IMA were suspended in organ chambers and contracted with norepinephrine (at a dose producing 30% of maximal contraction). Exposure of IMA segments with endothelium to hypoxia (partial pressure of oxygen, 38 +/- 4 mmHg) resulted in a transient relaxation (47 +/- 6%) followed by constriction (177 +/- 8%) (n = 14). IMA segments without endothelium exhibited a gradual decrease in tension that almost completely counteracted vasoconstriction. The initial transient endothelium-dependent relaxation could be blocked by indomethacin (10(-6)M) and was associated with a 51% increase in 6-ketoprostaglandin F1 alpha production (n = 22, P < 0.05). The endothelium-dependent contraction to hypoxia could be attenuated by indomethacin (n = 6, P < 0.05) or NG-monomethyl-L-arginine (10(-5)M; n = 9, P < 0.05) and was completely blocked by combination of these agonists (n = 6, P < 0.05). These experiments indicate that on exposure to hypoxia, the human IMA exhibits an initial prostacyclin-mediated relaxation followed by contraction due to the production of a constrictor prostanoid in addition to the inhibition of basal production of endothelium-derived relaxing factor.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

Prediction equations for single-breath carbon monoxide diffusing capacity from a Chinese population.

Most available prediction equations for the single breath carbon monoxide diffusing capacity, or DLCO, are based on white populations and do not account for racial differences. We performed this test on 436 Chinese adults. The method of measurement essentially followed the American Thoracic Society recommendations. Data on 306 subjects who had two technically acceptable test results provided prediction equations and upper and lower 95% confidence limits for healthy nonsmokers. Simple linear equations using age, height, and body weight as independent variables were generated and compared with nonlinear models. The use of nonlinear models did not add to the predictability of standard linear regressions. The distribution of residuals (predicted-measured values) was Gaussian with simple linear regressions. A comparison of predicted values for DLCO, calculated from different equations in an independent group of healthy subjects, revealed that the present set of equations had the smallest residual mean and standard deviation rankings compared with other equations for white subjects. These are the first DLCO equations proposed for Chinese men and women aged 20 to 70 yr. The predicted values from this study for DLCO and alveolar volume (VA), were significantly lower than those of most equations for white subjects, but were not for DLCO/VA. Although a portion of the differences may be explained by the additive effects of technical factors, the discrepancies can also be attributed to the smaller body size in this ethnic group, and consequently to the smaller lung volumes. Equations derived from whites, with inclusion of smokers, provided predicted values comparable to, or even lower than, those from this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Video-assisted thoracic surgery. Manipulation without trocar in 112 consecutive procedures.

Since learning of the video-assisted thoracoscopic techniques in the treatment of thoracic diseases, we have encountered many problems and difficulties because of the limited trocar space and lack of suitable instrumentations. Since March 1992, we have found a simple and easier way to perform this procedure, that is, manipulating through the extended incisional wound without using a trocar. Endoscopic and conventional thoracic instruments are able to pass through the incisional channel freely and manipulate similarly to the technique used in open thoracotomy. All the patients had less postoperative pain, reduced operative time, and prompt return to employment. The technique is effective and is herein described.

Humans↗
PubMed1993

Modified Fontan procedure for complex congenital heart disease.

The Fontan procedure is frequently used for correction of complex congenital heart disease, but the postoperative morbidity and mortality rates are still high. The results in 35 consecutive patients who underwent the Fontan procedure from January 1980 to June 1991 are reviewed. The patients comprised 26 boys and nine girls aged from 1.7 to 14.8 (mean 6.8) years. The underlying diseases were univentricular heart (19 patients), tricuspid atresia (eight), complete atrioventricular canal (three patients, two of whom had straddling atrioventricular valve) and other conditions (five). Valved conduits were implanted in four patients and non-valved in 15. Direct right atrium-pulmonary artery anastomosis was performed in 16 patients. The overall hospital mortality rate was 23% (eight patients); in the final year of the review it was 11%. Follow-up of the survivors ranged from 1 to 120 (mean 25) months. All except two patients attained New York Heart Association functional class I or II. Three patients underwent reoperation for atrioventricular valve regurgitation and conduit stenosis with good results. It is concluded that the Fontan procedure is a good palliative operation for complex congenital heart disease.

Adolescent↗
PubMed1993

Endothelium-derived relaxing factors.

The endothelium modulates vascular tone by liberating both dilator [endothelium-derived relaxing factors; EDRFs]and constrictor substances [endothelium-derived contracting factors; EDCFs]. This review focused on endothelium-derived relaxing factor, its discovery, characteristics, synthesis and interaction with vascular smooth muscle. The major endothelium-derived relaxing factor is nitric oxide formed from L-arginine, which activates guanylate cyclase in the smooth muscle, leading to accumulation of cyclic-GMP. Endothelial cells can also release endothelium-derived hyperpolarizing factor EDHF which also cause endothelium-dependent relaxation.

Animals↗
PubMed1993

Acute renal failure after open heart surgery: clinical experience with continuous arteriovenous hemodialysis.

Continuous arteriovenous hemodialysis (CAVHD) was employed in five patients who suffered from acute renal failure (ARF) after open heart surgery during the period from July 1991 to February 1992. All patients had a urine output of less than 400 mL/24h and clinical evidence of fluid overload. Most of the patients needed respiratory support for respiratory insufficiency and required vasopressor infusions. They could not tolerate conventional hemodialysis due to severe hemodynamic instability, and the concurrent thoracic surgery precluded the application of peritoneal dialysis. All patients tolerated the CAVHD well, despite persistent hypotension. The mean age of the five patients was 53.6 +/- 15.3 years. The duration of CAVHD treatment ranged from 1.5 to 22 days. Whole blood clearances for urea, creatinine and phosphate were 13.27 +/- 1.86 mL/min, 13.05 +/- 3.12 mL/min, and 13.99 +/- 2.61 mL/min, respectively. According to the clinical condition, ultrafiltration averaged 100-200 mL/h; up to 1 L/h could be obtained without difficulty. In these situations, large concurrent amounts of vasopressors and nutritional fluids could be easily prescribed without fear of fluid overload. The introduction of CAVHD allowed a more stabilized environment for gradual recovery of the temporarily compromised ventricular function after open heart surgery. Later, the hemodynamic status was stabilized without or with only minimal infusions of vasopressors in all five patients. Renal function recovered in four patients and one was shifted to conventional hemodialysis. All five patients survived under CAVHD treatment. There were no significant complications related to the application of CAVHD.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1993

Endothelium-derived contracting factors.

In the past decade, the importance of endothelium in modulating vascular tone has become apparent. Endothelium can produce different vasodilators, such as prostacyclin, endothelium-derived relaxing factor (most likely nitric oxide), and endothelium-derived hyperpolarizing factor. Endothelium can also produce endothelium-derived contracting factors (EDCF) which can induce constriction of the underlying vascular smooth muscle. Constriction may be mediated by a variety of products released by the endothelium. Thus, by responding to various stimuli and releasing either relaxing or contracting factors, the endothelium can set and modulate vascular tone.

Animals↗
PubMed1993

Radiation pneumonitis in rats and its modification by the angiotensin-converting enzyme inhibitor captopril evaluated by high-resolution computed tomography.

Adult male Sprague-Dawley rats were irradiated to the right hemithorax with a range of total doses delivered in 10 equal daily fractions of 4 MeV X rays. Half of each dose group consumed control feed, and half consumed feed containing the angiotensin-converting enzyme inhibitor captopril (50 mg/kg/day) continuously after the last irradiation. High-resolution computed tomography (CT) of the entire thorax was performed at 4 and 8 weeks after the last irradiation, and the findings with CT were correlated with hemodynamic data, heart weight, and pulmonary histopathology. Rats exposed to 20 or 40 Gy in 10 fractions exhibited no acute changes in right lung density. After 60 Gy in 10 fractions, however, right lung density in rats on the control diet increased significantly at 4 weeks, and then returned to normal at 8 weeks. Captopril-treated rats exposed to 60 Gy/10 fractions did not exhibit this transient increase in right lung density. After 80 Gy/10 fractions, right lung density increased to 0.60-0.65 g/cm3 at 4 weeks regardless of diet. At 8 weeks after 80 Gy/10 fractions, right lung density increased further in rats given the control diet, but decreased to near normal levels in captopril-treated animals. The density of the shielded left lung based on the CT was independent of both contralateral radiation dose and diet. Histological examination of the irradiated lungs indicated that these acute changes detected by CT were associated with the exudative and edematous phases of radiation pneumonitis, and that captopril reduced the severity of these changes. Irradiated (40-80 Gy/10 fractions) animals fed the control diet exhibited a significant increase in central venous and pulmonary artery pressure, and cardiac right ventricular hypertrophy. Captopril prevented or attenuated these hypertensive reactions. These data demonstrate that high-resolution CT can detect radiation reactions in rat lung within 4 weeks after 60 Gy/10 fractions, and that captopril spares these acute changes detected by CT. The mechanism of captopril action is not clear, but may be due in part to a reduction in pulmonary arterial pressure, resulting in less severe edema in the irradiated lung.

Animals↗
PubMed1993

Gastro-pleural fistula related with penetrating stab injuries of the chest and abdomen: laparotomy or thoracotomy.

A 30-year-old male presented with left side empyema due to gastro-pleural fistula following repair of penetrating stab injuries of left lower chest and abdomen. Exploratory thoracotomy was done due to persistent moderate amount of purulent discharge. However, fistula tract was not detected through this approach. The small fistula tract was repaired finally through laparotomy. We recommended the abdominal approach if the disease is not combined with diaphragmatic hernia. Transabdominal approach showed superiority in this rare entity.

Abdominal Injuries↗
PubMed1992

One-stage operation for treatment after delayed diagnosis of thoracic esophageal perforation.

Perforation of the thoracic esophagus can be fatal unless diagnosed promptly and treated effectively. The high mortality with delayed treatment is due principally to an inability to effectively close the perforation and prevent leakage. From 1982 to 1988, 7 consecutive patients (aged 16 to 73 years) were treated after a delayed diagnosis (26 hours to 25 days) of thoracic esophageal perforation. In all patients, the perforation was closed after debridement with total exclusion of the esophagus (T-tube cervical esophagostomy plus absorbable ligatures applied to the esophagogastric junction and the cervical esophagus distal to the esophagostomy). Radical decortication and wide mediastinal and pleural drainage were also done. Nutritional supply was given through a feeding gastrostomy. Antibiotics were administered according to the results of cultures. All patients survived. Continuity of the esophagus was established by removal of the T tube and spontaneous absorption of the ligatures. Endoscopy and esophagography performed 4 weeks after the initial operation showed a well-healed esophagus without stenosis or leakage in all patients. No secondary thoracotomy or esophageal reconstruction was necessary. No dysphagia was noted during follow-up (range, 12 to 50 months; mean follow-up, 23 months). We conclude that primary closure of the perforation and total esophageal exclusion with the use of absorbable ligatures and T-tube esophagostomy can provide a one-stage operation with good results for repair of thoracic esophageal perforation diagnosed late.

Adolescent↗
PubMed1992

Bilateral bipartite medial cuneiform. A case report.

A fracture to the intermediate cuneiform that was not definitively detected on routine radiographs because of the overlap of the cuneiform was presented. Weightbearing x-rays did not provide additional information. The anatomical location of the fracture was identified only after a computed tomography scan was performed. An incidental finding, bilateral bipartite medial cuneiforms, was also observed on the computed tomography scan, which contributed to the overlap on routine radiographs. The anatomy of the bipartite medial cuneiforms seen on computed tomography was similar to that described by Barlow in 1942. Retrospective comparison to the initial radiographs with the computed tomography scan sections did reveal bipartite medial cuneiforms on these films as well. The podiatric physician should keep bipartition in mind when evaluating x-rays for any osseous pathology, especially fractures.

Adult↗
PubMed1992

[Valve replacement for aortic stenosis].

We retrospectively reviewed 122 consecutive patients with aortic stenosis from January 1977 to December 1990. There were 68 male and 54 female patients. Their age ranged from 5 to 73 years old (47 +/- 16, mean +/- SD). Sixty eight patients also had associated mitral valve lesion, 13 patients had tricuspid valve lesion, and 3 patients had coronary artery disease. Aortic valve replacement was performed on all patients. Mechanical valves were implanted in 86 cases and tissue valves in 36 cases. Associated procedures were performed in 54 cases: mitral valve replacement in 34 cases, mitral valve repair in 18 cases and coronary artery bypass grafting in 2 cases. A bicuspid aortic valve was found in 20 cases (16.4%). Hospital mortality was 4.9% (6 cases). Follow-up was completed in 95% of the surviving cases (110 cases). The survival rate was 82 +/- 3% at 13 years and redo-free rate was 73 +/- 8% at 13 years. Seven cases required redo operation, due to tissue valve degeneration in 5 and thrombosis of the mechanical valve in 2. All 7 patients survived. Late death occurred in 6 cases: 3 from malignancy, 2 from stroke and 1 from ventricular arrhythmia. We concluded that valve replacement for aortic stenosis is a safe and satisfactory procedure with good long-term results.

Adolescent↗
PubMed1992

[Migration of Kirschner wire from the right sternoclavicular joint into the main pulmonary artery. A case report].

The use of Kirschner wires (K-wires) for bone and joint fixation carries the risk of migration of the wire from the fixation site over time. However, review of the literatures disclosed rather few reports on this issue. We describe such a case in order to emphasize the potential complication and serious hazard that migration of such metallic devices can result in, especially when the fixation site is close to the thoracic cavity.

Adult↗
PubMed1992

Global myocardial ischemia and reperfusion impair endothelium-dependent relaxations to aggregating platelets in the canine coronary artery. A possible cause of vasospasm after cardiopulmonary bypass.

Experiments were designed to determine whether endothelial cell injury contributes to increased coronary vascular tone after global cardiac ischemia and reperfusion. Canine hearts were exposed to global ischemia for 45 minutes and were reperfused for 60 minutes. Rings (5 to 6 mm long) of the left anterior descending coronary artery from reperfused hearts and from normal (control) hearts were suspended for isometric force measurement in organ chambers containing physiologic salt solution (37 degrees C, and 95% oxygen and 5% carbon dioxide). After contraction with prostaglandin F2 alpha, reperfused coronary arteries had significant impairment of endothelium-dependent relaxations to aggregating platelets (52% +/- 12% relaxation versus 102% +/- 11% for control segments; p less than 0.05). Reperfused arterial rings also exhibited impaired endothelium-dependent relaxations to the receptor-dependent agonist acetylcholine and the platelet-derived compounds adenosine diphosphate and serotonin. Importantly, endothelium-dependent relaxations to the non-receptor-dependent agonist A23187 were normal after ischemia and reperfusion. Quiescent (noncontracted) reperfused arterial rings lost the ability to counteract the constrictive effect of aggregating platelets on the coronary vascular smooth muscle (24% +/- 7% contraction versus 5% +/- 2% relaxation for control segments; p less than 0.05). Endothelium-independent contractions to potassium chloride and prostaglandin F2 alpha were similar in reperfused and normal arteries. Also, endothelium-independent relaxations to nitric oxide and isoproterenol were comparable in reperfused arteries and normal vessels. Thus global cardiac ischemia and reperfusion impair the normal endothelium-dependent relaxations to aggregating platelets and other receptor-dependent vasoactive drugs. This impairment of platelet-mediated coronary vasodilation may explain increased coronary vascular tone after cardiopulmonary bypass and could be an important pathophysiologic mechanism of postoperative coronary vasospasm.

Animals↗
PubMed1991

Production of endothelium-derived contracting factor is enhanced after coronary reperfusion.

To determine whether coronary reperfusion enhances the production of endothelium-derived contracting factor, we investigated dogs subjected to global cardiac ischemia (45 minutes) followed by reperfusion (60 minutes). Segments of reperfused and control coronary arteries were suspended in organ chambers to measure isometric force. Perfusate hypoxia caused endothelium-dependent contraction in the control and reperfused arteries. However, reperfused arteries exhibited hypoxic contraction that was significantly greater than control segments. The hypoxic contractions in both the control and reperfused arteries could be inhibited by NG-monomethyl-L-arginine (L-NMMA), the blocker of endothelial cell synthesis of nitric oxide from L-arginine. The action of L-NMMA could be reversed by L-arginine but not D-arginine. Thus, after reperfusion, augmented production of endothelium-derived contracting factor occurs by an L-arginine-dependent pathway. We hypothesize that nitric oxide produced by L-arginine metabolism combines with superoxide anion to produce the peroxynitrite anion (ONOO-), which is metabolized to endothelium-derived contracting factor or induces its synthesis. Augmented production of endothelium-derived contracting factor would favor vasospasm after reperfusion.

Animals↗