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Biomedical subjects

J J Ross

Publications and source records attributed to J J Ross.

At least 37 records · Page 2Linked to original sources
PubMed1997

Self-learning fuzzy control of atracurium-induced neuromuscular block during surgery.

Self-learning fuzzy logic control has the important property of accommodating uncertain, non-linear and time-varying process characteristics. This intelligent control scheme starts with no fuzzy control rules and learns how to control each process presented to it in real time, without the need for detailed process modelling. A suitable medical application to investigate this control strategy is atracurium-induced neuromuscular block (NMB) of patients in the operating theatre. Here, the patient response exhibits high non-linearity, and individual patient dose requirements can vary five-fold during an operating procedure. A portable control system was developed to assess the clinical performance of a simplified self-learning fuzzy controller in this application. A Paragraph (Vital Signs) NMB device monitored T1, the height of the first twitch in a train-of-four nerve stimulation mode. Using a T1 setpoint = 10% of baseline in ten patients undergoing general surgery, a mean T1 error of 0.45% (SD = 0.44%) is found while a 0.13-0.70 mg k-1 h-1 range in the mean atracurium infusion rate is accommodated. The result compares favourably with more complex and computationally-intensive model-based control strategies for the infusion of atracurium.

Atracurium↗
PubMed1997

Pulmonary embolism from in situ right atrial thrombus after coronary artery bypass surgery.

Pulmonary embolism after cardiac surgery is attributed to embolization from thrombus within the deep venous system. We report two cases of pulmonary embolism after coronary artery bypass surgery in which transesophageal echocardiography detected in situ right atrial thrombus. The right atrium should be screened for thrombus in patients who have pulmonary embolism after cardiac surgery.

Aged↗
PubMed1997

Self-learning fuzzy logic control of neuromuscular block.

We have assessed the performance of a "self-learning" fuzzy logic controller to administer atracurium to a required depth of neuromuscular block. We studied 20 ASA I and II patients undergoing surgery anticipated to last longer than 90 min. A Datex Relaxograph was used to measure the degree of neuromuscular block, and control to a T1 twitch height set point of 10% of baseline neuromuscular function was selected. The controller commenced with a blank rule-base and instructed a Graseby 3400 infusion pump to administer an atracurium infusion to maintain this level of block. The system achieved stable control of neuromuscular block with a mean T1 error of -0.52% (SD 0.55%) accommodating a range in mean atracurium infusion rate of 0.25-0.44 mg kg-1 h-1. These results compare favourably with the more computationally intensive and unwieldy adaptive control strategies for atracurium infusion used previously. There was less variation in infusion rates than in our previously studied fixed rules fuzzy controller.

Adult↗
PubMed1997

Mendel's stem length gene (Le) encodes a gibberellin 3 beta-hydroxylase.

We describe the isolation of the Le gene of pea, which controls internode elongation and originally was described by Mendel. Heterologous screening of a pea cDNA library yielded a partial clone that was 61% identical to coding regions of the putative Arabidopsis gibberellin 3 beta-hydroxylase gene, GA4. DNA gel blot analysis with this cDNA revealed a HindIII restriction fragment length polymorphism between pea isolines differing at Mendel's Le locus. Genomic clones of the GA4-related gene were isolated from the Le and le isolines. Polymerase chain reaction combined with restriction fragment length polymorphism analysis were used to show that the gene mapped to the Le locus. A cDNA containing a complete open reading frame of the pea GA4-related gene was amplified by polymerase chain reaction from each isoline. Recombinant expression in Escherichia coli demonstrated that the product of the Le cDNA was a gibberellin 3 beta-hydroxylase that is able to convert GA20 to the bioactive GA1. Substantially reduced levels of gibberellin 3 beta-hydroxylase activity were measured, after expression of the le cDNA, by using identical methods. This reduced activity was associated with an alanine-to-threonine substitution in the predicted amino acid sequence of the enzyme near its proposed active site.

Amino Acid Sequence↗
PubMed1996

Risk of catheter-related emboli in patients with atherosclerotic debris in the thoracic aorta.

The aim of this study was to evaluate the risk of performing cardiac catheterization or intraaortic balloon pump placement in patients with transesophageal echocardiographically detected atherosclerotic aortic debris. Cardiac catheterization was performed in 70 patients with atherosclerotic aortic debris (in 11 via the brachial approach and in 59 via the femoral approach) and in 71 control patients. An embolic event occurred in 10 (17%) of 59 patients with atherosclerotic aortic debris after femoral catheterization compared to 2 (3%) of 71 control patients without atherosclerotic aortic debris (p = 0.01). None of the 11 patients with atherosclerotic aortic debris who underwent brachial catheterization had an embolic event. An intraaortic balloon pump was placed in 10 patients with atherosclerotic aortic debris and in 12 control patients. An embolic event related to placement of the intraaortic balloon pump occurred in 5 (50%) of 10 patients with atherosclerotic aortic debris; no control patient had an embolic event (p = 0.02). Patients with mobile atherosclerotic aortic debris were at the highest risk for catheter-related embolism. The strongest clinical predictors of atherosclerotic aortic debris were advanced age and peripheral vascular disease. Transesophageal echocardiographic recognition of atherosclerotic aortic debris identifies patients at high risk of stroke or peripheral embolism after cardiac catheterization or intraaortic balloon pump placement. If the aortic debris is mobile, the risk is particularly high. When atherosclerotic aortic debris is detected, especially if the debris is mobile, substituting brachial for femoral catheterization and avoiding placement of an intraaortic balloon pump may reduce the risk of embolism.

Age Factors↗
PubMed1994

Spontaneous arterial embolization after thrombolytic therapy for acute myocardial infarction: the role of transesophageal echocardiography.

Arterial embolization from thrombolytic therapy for acute myocardial infarction is rare. We report two cases of spontaneous arterial embolization following the use of tissue plasminogen activator for acute myocardial infarction. Transesophageal echocardiography was able to identify the source of embolism as mobile atherosclerotic debris within the thoracic aorta. This information was of value in the management of these patients, in that femoral catheterization which could have precipitated further embolization was avoided.

Aged↗
PubMed1994

The role of echocardiography in blunt chest trauma: a transthoracic and transesophageal echocardiographic study.

Previous studies assessing the value of transthoracic echocardiography (TTE) in blunt chest trauma are limited because patients with severe chest wall injury often have suboptimal echocardiographic findings. Transesophageal echocardiography (TEE) can provide high quality images when the transthoracic image quality is poor. To provide complete echocardiographic assessment of cardiac structure and function we prospectively performed TTE in 105 patients with severe blunt chest trauma and TEE in 20 of the 105 patients (19%) whose TTE examination results were suboptimal. Myocardial contusion was diagnosed in 31 patients (30%), 22 by TTE and nine by TEE. Cardiac complications developed in 8 of 31 patients (26%) with myocardial contusion compared with 2 of 74 patients (3%) with normal echocardiographic findings (p = 0.001). Cardiac complications required treatment in only four patients. Echocardiography was of value in detecting severe right ventricular dysfunction as the cause of hypotension in two patients with suspected cardiac tamponade. Four patients with myocardial contusion died compared with two patients with normal echocardiographic findings (p = NS). No death was related to the cardiac status. In addition, TEE detected aortic injury in five patients, four with focal intimal tears and one with an aortic transection. We conclude that myocardial contusion is common following blunt chest trauma, rarely requires treatment, and is associated with a favorable prognosis. Only patients who develop cardiac complications benefit from echocardiography. Transesophageal echocardiography is of value when the TTE examination results are suboptimal and when aortic injury is suspected.

Abbreviated Injury Scale↗
PubMed1994

Impact of the incidental diagnosis of clinically unsuspected central pulmonary artery thromboembolism in treatment of critically ill patients.

Mortality is high in unrecognized pulmonary embolism (PE), but the diagnosis is difficult to establish, especially in patients with coexisting cardiopulmonary disorders. We describe a group of 14 patients with pulmonary thromboemboli in whom transesophageal echocardiography (TEE) performed for coexisting cardiopulmonary conditions established the clinical diagnosis of PE not suspected prior to TEE. The patients had initial clinical diagnoses of heart failure (eight patients), cardiogenic shock (two patients), atrial septal defect (two patients), aortic dissection (one patient), and pneumonia (one patient). Thirteen patients had risk factors for PE. Transthoracic echocardiography (TTE) demonstrated right heart strain in eight patients but did not visualize PE in any of the patients. The TEE diagnosis of occult central pulmonary artery thromboembolism changed treatment in all 14 patients. Ten of the 14 patients were successfully discharged from the hospital. We conclude that occult central pulmonary artery thromboemboli are not uncommon in patients presenting with acute cardiopulmonary disorders and the presence of risk factors for PE and right heart strain on TTE should alert the physician to suspect PE. If and when TEE is performed in patients with acute cardiopulmonary disorders with risk factors for PE and right heart strain, the physician should evaluate the main pulmonary artery and its branches for central pulmonary artery thromboemboli.

Adult↗
PubMed1994

Transesophageal echocardiographic diagnosis of pulmonary arteriovenous malformation. Role of contrast and pulsed Doppler echocardiography.

Contrast echocardiography produced by peripheral injection of agitated saline solution is widely used for detecting intracardiac and intrathoracic extracardiac shunts, like pulmonary arteriovenous malformation (PAVM). Currently, localization of PAVM requires pulmonary angiography even after detection by computed tomography of the chest. Pulsed Doppler along with contrast echocardiography of the pulmonary veins performed during transesophageal echocardiography may aid in the localization of PAVM and in its diagnosis.

Aged↗
PubMed1993

Severe right ventricular contusion mimicking cardiac tamponade: the value of transesophageal echocardiography in blunt chest trauma.

Clinically, severe right ventricular contusion may mimic cardiac tamponade. We report two cases of suspected cardiac tamponade after blunt chest trauma in which the diagnosis of severe right ventricular contusion was made only by transesophageal echocardiography, avoiding unnecessary and hazardous pericardiocentesis. These cases illustrate the value of transesophageal echocardiography in diagnosing blunt chest trauma.

Adult↗
PubMed1992

Single-plane transesophageal echocardiography for assessing function of mechanical or bioprosthetic valves in the aortic valve position.

To assess the value and limitations of single-plane transesophageal echocardiography in the evaluation of prosthetic aortic valve function, 89 patients (69 mechanical and 20 bioprosthetic aortic valves) were studied by combined transthoracic and transesophageal 2-dimensional and color flow Doppler echocardiography. In the assessment of aortic regurgitation, the transthoracic and transesophageal echocardiographic findings were concordant in 71 of 89 patients (80%). In 8 patients, the degree of aortic regurgitation was underestimated by the transthoracic approach; in each case the quality of the transthoracic echocardiogram was poor. In 10 patients, transesophageal echocardiography failed to detect trivial aortic regurgitation due to acoustic shadowing of the left ventricular outflow tract from a mechanical valve in the mitral valve position. Transesophageal echocardiography was superior to transthoracic echocardiography in diagnosing perivalvular abscess, subaortic perforation, valvular dehiscence, torn or thickened bioprosthetic aortic valve cusps, and in clearly distinguishing perivalvular from valvular aortic regurgitation. Transesophageal echocardiography correctly diagnosed bioprosthetic valve obstruction in 1 patient, but failed to diagnose mechanical valve obstruction in another. In conclusion, transesophageal echocardiography offers no advantage over the transthoracic approach in the detection and quantification of prosthetic aortic regurgitation unless the transthoracic image quality is poor. Transesophageal echocardiography is limited in detecting mechanical valve obstruction and in detecting aortic regurgitation in the presence of a mechanical prosthesis in the mitral valve position. However, it is superior to transthoracic echocardiography in identifying perivalvular pathology, differentiating perivalvular from valvular regurgitation and in defining the anatomic abnormality responsible for the prosthetic valve dysfunction. Combined transthoracic and transesophageal examination provides complete anatomic and hemodynamic assessment of prosthetic aortic valve function.

Adolescent↗
PubMed1992

Closure of eyelid defects.

BACKGROUND: Repair of eyelid defects can be achieved by an array of procedures. OBJECTIVE: To provide a basic approach to repairing eyelid defects. METHODS: Defects are categorized by size. The method of repair for each defect is described. CONCLUSION: By selecting the proper method of closure, with due consideration of the size, location, and configuration of the defect, the cutaneous surgeon can repair eyelid defects whilst maintaining the best possible function and cosmetic appearance.

Eyelid Diseases↗