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Biomedical subjects

R W Snyder

Publications and source records attributed to R W Snyder.

At least 73 records · Page 4Linked to original sources

Esophagoatrial fistula with previous pericarditis complicating esophageal ulceration. Report of two cases and a review of the literature.

Sixteen cases of nontraumatic left atrial-esophageal fistulas have been reported previously. These fistulas usually result from chronic peptic esophagitis or cancer. The diagnosis is suggested by the triad of chronic dysphagia, hematemesis, and acute neurologic signs. There may be cardiac manifestations such as pericarditis, atrial fibrillation, or shock. An unusual feature of these fistulas is systemic embolization of food, air, or septic necrotic debris which may result in sudden central nervous system symptoms. All reported cases resulted in death due to hemorrhage, although there was often a variable time interval between the onset of hematemesis and the patient's death. The authors report two additional cases in which an episode of pericarditis preceded fistula development. Based on these 18 cases, the spectrum of esophagoatrial fistulas is reviewed, as well as the signs which may herald fistula development.

Aged↗

Bronchogenic carcinoma in situ on the carina eradicated by endobronchial biopsy.

Squamous cell carcinoma in situ of the bronchus is a rare disorder in an isolated clinical setting. We present a case of carcinoma in situ located on the carina with excisional biopsy via a fiberoptic bronchoscope and no recurrence after five years. To our knowledge, this represents the only case of carcinoma in situ treated solely with excisional biopsy. This case further emphasizes the importance of securing biopsy specimens for all mucosal abnormalities and raises the possibility of limited excision as sole therapy for carcinoma in situ.

Aged↗

A hypertensive emergency following cataract extraction and cornea transplantation.

We report a hypertensive crisis resulting from an unsuspected pheochromocytoma following a routine anterior segment procedure. Although pheochromocytomas are rare, ophthalmologists should be aware of the signs and symptoms of this tumor as well as of the possible role that postoperative administration of timolol may have in pheochromocytoma-triggered hypertension.

Adrenal Gland Neoplasms↗

Treatment of postvitrectomy fibrin formation with intraocular tissue plasminogen activator.

Twenty-five micrograms of human recombinant tissue plasminogen activator (tPA) was injected intracamerally into the eyes of three aphakic patients who developed severe intraocular fibrin formation within 24 hours after vitrectomy surgery. Fluid obtained from gas-fluid exchange specimens taken 24 hours after tPA injection was analyzed for tPA by an enzyme-linked immunosorbent assay and a spectrophotometric solid-phase fibrin assay. In each of the three patients, complete fibrin resolution occurred within four hours after the tPA injection. There were no complications associated with the intraocular tPA injections. There was measurable tPA activity 24 hours after the initial injection ranging from 0.23 to 1.4 micrograms. In contrast, tPA was undetectable in gas-fluid exchange specimens obtained from seven patients who did not receive intraocular tPA injections. Intraocular tPA is an effective means of treating postvitrectomy fibrin formation in selected aphakic patients.

Adolescent↗

Respiratory distress after a Nadbath block.

Dysphagia and respiratory distress developed in three patients after administration of a Nadbath block. This complication may have resulted from inadvertent paralysis of the vagus, ipsilateral glossopharyngeal, and spinal accessory nerves causing pooling of oropharyngeal secretions and laryngospasm. Respiratory distress after a Nadbath block may be managed by properly positioning the patient. Short hypodermic needles (less than 12 mm), small volumes of anesthetic solution (less than 3 ml), and omission of hyaluronidase may reduce the incidence of this complication.

Aged↗

Treatment of experimental intravitreal fibrin with tissue plasminogen activator.

We produced experimental intravitreal fibrin clots in rabbits that had previous gas compression of the vitreous or intact vitreous. Twenty-four hours after production of fibrin, the eyes were injected with 25 micrograms of tissue plasminogen activator or physiologic irrigation solution. In the gas compression group (n = 11), all tissue plasminogen activator-treated eyes cleared within six hours of injection; complete clearing was not seen until six days in the physiologic irrigation solution-treated eyes (n = 9). A similar response was seen in the intact vitreous group. No evidence of toxicity was observed as measured by slit-lamp biomicroscopy, intraocular pressure, corneal thickness, electroretinography, or histopathologic examination.

Animals↗

Use of tissue plasminogen activator in experimental hyphema.

Tissue plasminogen activator (tPA) is a fibrin-specific fibrinolytic agent that has recently been shown to be effective in accelerating the clearance of fibrin clots from the rabbit anterior chamber. We studied the effect of intracameral tPA on the clearance of experimental hyphema in the rabbit. Fifteen eyes were treated with an intracameral injection of tPA (1800 IU), 11 eyes were treated with a physiologic saline solution (PS) injection, and 16 eyes received no injection. Total hyphemas treated with tPA showed 80% clearance within 24 hours, while eyes treated with PS and untreated eyes cleared in 14 days. Measurement of corneal thickness revealed the tPA-treated eyes to have less corneal edema than eyes treated with PS and untreated eyes. There was no difference in intraocular pressure. The results indicate that tPA is effective in accelerating the clearance of experimental hyphema.

Animals↗

Intraocular fibrinolysis with recombinant human tissue plasminogen activator. Experimental treatment in a rabbit model.

Intraocular fibrin formation following ocular surgery is a potentially binding problem. Current therapy for this postoperative fibrin response is often ineffective. In the rabbit, we developed a quantitative reproducible model for intraocular fibrin deposition. Using this model, we have tested the efficacy of human tissue plasminogen activator (tPA) in promoting intraocular fibrinolysis. Citrated rabbit plasma (0.2 mL) was injected intracamerally following paracentesis, resulting in fibrin clot formation within three hours. The fibrin clots were stable for four days, and then slowly lysed over the next four days. Approximately 24 hours after clot formation, various concentrations of human tPA were injected intracamerally. The time taken for clot lysis was dose dependent, with 1800 IU of tPA producing clot lysis in three hours. Toxicity, as measured by intraocular pressure, corneal thickness, inflammation, or cataract formation, was minimal.

Animals↗

Cardiovascular and renal effects of buspirone in several animal models.

Intravenous administration (0.3 or 3 mg/kg) of buspirone to anesthetized rats elicited a transient pressor response (14 +/- 2 mmHg) and sustained bradycardia. However, oral administration (30 mg/kg) reduced the blood pressure and heart rate of conscious normotensive (-14 +/- 4 mmHg) and DOCA-salt hypertensive rats (-22 +/- 5 mmHg). Buspirone (3-100 mg/kg, p.o.) elicited increases in urinary volume and electrolyte excretion of conscious normotensive rats and decreased these parameters in conscious mice. Buspirone was observed to possess alpha 1-adrenoceptor agonist activity in ganglion-blocked anesthetized rats. Buspirone (0.3-3 mg/kg, i.v.) elicited transient elevations in the blood pressure of open-chest anesthetized dogs. There was a sustained increase in total peripheral resistance and a decrease in aortic blood flow, heart rate, right ventricular contractile force and left ventricular dp/dt max. Intravenous and oral administration to anesthetized and conscious dogs elevated urinary volume and electrolyte excretion. However, the doses used to elicit the observed alterations in hemodynamic/renal function are considerably greater than those which produce anxiolytic effects. Thus, it is doubtful that anxiolytic doses of buspirone will produce cardiovascular alterations in patients.

Anesthesia↗

Differential cardioprotective properties of the l- and d- enantiomers of bucindolol in a canine model of heart failure.

In previous studies racemic bucindolol was found to reverse the effects of pentobarbital-induced heart failure in anesthetized dogs. Reductions of right ventricular contractile force (RVCF), left ventricular (LV) dp/dt, and aortic blood flow (ABF) serve as indicators of depressed cardiac function in this model. In this study, racemic bucindolol (0.25 mumol/kg +0.25 mumol/kg/hr) again evoked pronounced and sustained stimulant effects on these depressed parameters. l-Bucindolol (0.125 mumol/kg +0.125 mumol/kg/hr) was a more effective stimulator of cardiac function than d-bucindolol in this model. l-Bucindolol elicited maximal increases in RVCF, ABF, LV dp/dt and heart rate of 66, 19, 30 and 11%, respectively. In comparison, d-bucindolol maximally increased these parameters only 20, 14, 12 and 4%, respectively. Total peripheral resistance was reduced 29% by l-bucindolol and 19% by d-bucindolol. The responses to l-bucindolol and racemic bucindolol were essentially the same. The myocardial stimulation and vasodilation profile derived from l-bucindolol (at one-half the molar dose of bucindolol) suggests the possible preference for its use in clinical management of congestive heart failure over bucindolol, the racemic compound. The results further suggest that l-bucindolol could also be used to treat hypertensive patients with depressed cardiac function.

Adrenergic beta-Antagonists↗

Beneficial effects of bucindolol in a canine model of pentobarbital-induced heart failure.

Heart failure was induced in barbital-anesthetized dogs by administering high doses of pentobarbital. This procedure depresses cardiac function as indicated by a reduction in right ventricular contractile force (RVCF), left ventricular dp/dt and aortic blood flow. Bucindolol (0.1 mg/kg and 0.1 mg/kg/hr) elicited a pronounced and prolonged stimulant effect on these depressed indicators of cardiac function. Both RVCF and aortic blood flow returned to pre-failure levels, left ventricular dp/dt increased 43% but heart rate was elevated only slightly (14%). Total peripheral resistance was lowered 36% by bucindolol. The combination of myocardial stimulation and vasodilatation which contributed to the positive results in this acute model of pump failure suggests a possible role for bucindolol in the clinical management of congestive heart failure. Further these results suggest that bucindolol, in contrast to propranolol, could also be used in a sub-group of hypertensive patients with depressed cardiac function.

Animals↗

Cardiovascular effects of bucindolol (MJ 13105) in conscious dogs.

Bucindolol (MJ 13105), administered to conscious, normotensive dogs (a) attenuated the positive chronotropic and diastolic depressor response elicited by isoproterenol, (b) increased heart rate and (c) elevated plasma renin activity (PRA). Repeated daily administration of bucindolol caused a cumulative reduction in isoproterenol-elicited cardiac and vascular responses. The increase in heart rate was not blocked by atropine and only partially attenuated by propranolol. To study the effect of bucindolol on erect blood pressure, dogs were tilted rapidly through 90 degrees from the supine to a head-up erect position, a maneuver that reflexly increases blood pressure. Following the administration of bucindolol, blood pressure in the erect position was lower than before drug but was still higher than blood pressure in the supine position suggesting the compensatory reflex response to this postural change is still functional. Bucindolol had no significant effect on P wave and QRS durations or P-R and corrected Q-T intervals of the EKG.

Administration, Oral↗