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Biomedical subjects

U R Shettigar

Publications and source records attributed to U R Shettigar.

At least 19 recordsLinked to original sources
PubMed1998

Unpredictable response to vasodilator therapy in primary pulmonary hypertension.

A 49-year-old man with severe primary pulmonary hypertension unresponsive to multiple vasodilators showed beneficial response to intravenous (i.v.) isoproterenol with significant decrease in the pulmonary vascular resistance and increase in the cardiac output. However, the patient became dependent on i.v. isoproterenol and eventually died suddenly following an episode of bradyarrhythmia. Autopsy confirmed severe primary pulmonary hypertension. As the response to vasodilator therapy can be unpredictable in PPH, sequential hemodynamic evaluation of drugs is necessary for finding an optimal therapeutic agent.

Bradycardia↗
PubMed1995

Clinical rationale for the use of an ultra-short acting beta-blocker: esmolol.

Esmolol is a unique cardioselective, intravenous, ultra-short acting, beta-adrenergic blocking agent. A 9-minute half-life with rapid clinical onset and offset of action and the ability to titrate the drug to changing circumstances makes esmolol a useful addition to our treatment armamentarium. The efficacy and safety of esmolol have been shown in specific clinical settings, i.e. in patients with unstable angina, myocardial infarction, atrial fibrillation or flutter and supraventricular tachycardia. In the emergency management of hypertension, tachycardia or arrhythmia in critical care units, emergency room and surgery, esmolol is effective by attenuating hemodynamic responses from sympathetic activation or endogenous catecholamine release. With careful titration and monitoring of the patient, esmolol is relatively safe in the management of hypertension or tachyarrhythmias associated with congestive heart failure or chronic obstructive lung disease where beta-blockers are otherwise contraindicated. Different dosage schedules have been employed as per the clinical setting and the diagnosis. Generally, esmolol is infused intravenously in doses ranging from 25-300 micrograms/kg/min, along with a loading dose or bolus. The most frequently reported adverse effect associated with esmolol infusion was hypotension. Adverse effects due to beta-blockade can be corrected by down-titrating or discontinuing the infusion with complete disappearance of clinical effects in 20-30 minutes. Therefore, as an ultra-short acting beta-blocker, esmolol is an important therapeutic option in the acute clinical setting.

Adrenergic beta-Antagonists↗
PubMed1995

Echocardiographic diagnosis of pulmonary artery aneurysm.

A 72-year-old male referred for evaluation of a right hilar mass was asymptomatic with normal ECG, physical examination and laboratory tests. A 2-D echocardiogram with color Doppler revealed an aneurysm of the proximal right pulmonary artery.

Aged↗
PubMed1994

Management of rapid ventricular rate in acute atrial fibrillation.

Atrial fibrillation (AF) with rapid ventricular response is a common tachyarrhythmia requiring hospitalization. The increased morbidity and mortality due to the hemodynamic consequences of acute AF is well recognized. Management strategies may be formed based on the evaluation of the entire clinical context including cardiovascular status and the associated noncardiac clinical disorders. Intravenous (i.v.) beta blockers and calcium channel blockers are equally effective in rapidly controlling the ventricular rate in acute AF in selected individuals. The addition of digoxin to the regimen causes a favorable outcome. However, digoxin as a single agent is generally inefficacious in slowing the ventricular rate in acute AF. These standard pharmacotherapies however, are contraindicated in ventricular preexcitation syndrome associated with rapid ventricular rate due to AF. In this situation the drug of choice is i.v. procainamide. When clinical condition is unstable or hemodynamically compromised, cardioversion is the treatment of choice in all cases of AF with rapid ventricular rate. Radiofrequency ablation of the AV node or anomalous tract may be considered in refractory or high risk subjects as a last resort.

Anti-Arrhythmia Agents↗
PubMed1993

Combined use of esmolol and digoxin in the acute treatment of atrial fibrillation or flutter.

Safety and efficacy of simultaneous use of intravenous digoxin and esmolol in the control of rapid heart rate in 21 patients with atrial fibrillation or flutter was assessed. The mean age was 67 (range 40 to 90) years. Seven patients had class III congestive heart failure, with left ventricular ejection fraction between 18% and 61%. Baseline mean heart rate was 143 +/- 4. After 0.25 mg or 0.5 mg intravenous digoxin, esmolol was titrated with initial boluses from 2 mg/min to 16 mg/min in 25 minutes. A tolerated dose of esmolol infusion was adjusted for up to 48 hours. Rapid control of heart rate (29% decrease with heart rate 101 +/- 4) occurred at a mean interval of 21 minutes. Minimum heart rate was 87 +/- 4 at 90 minutes of treatment. Conversion to sinus rhythm occurred in five patients (25%), and one patient experienced mild transient congestive heart failure. No symptomatic hypotension or bronchospasm occurred. In conclusion, simultaneous use of digoxin and esmolol is effective in safely and rapidly controlling heart rate in atrial fibrillation or flutter.

Adrenergic beta-Antagonists↗
PubMed1989

Inadvertent permanent ventricular pacing from the coronary vein: an electrocardiographic, roentgenographic, and echocardiographic assessment.

The incidence of inadvertent permanent ventricular pacing from the coronary vein is not known. In a retrospective analysis of 69 patients in whom transvenous pacemakers were implanted between 1979 and 1986, 12 patients were discovered to have right bundle-branch block pattern to the paced complexes on electrocardiogram. In this group, three patients were considered to have inadvertent placement of pacing lead in the coronary vein by two-dimensional echocardiographic criteria. No complications were noted in follow-up of 2-79 months. Monitoring of surface electrocardiogram, frontal and lateral fluoroscopy, and pacing threshold and sensing parameters (during implantation of pacemaker) were found to offer no absolute protection against malplacement of the lead. Placement of the lead into the lung field via the main pulmonary artery and then withdrawing with eventual positioning into the right ventricular apex will avoid malposition into the coronary vein. Two-dimensional echocardiography is useful for the diagnosis of pacing lead malplacement and should be performed in any patient with right bundle-branch block pattern in the surface electrocardiogram following pacemaker implantation.

Aged↗
PubMed1987

Plasma sialidase activity in acute myocardial infarction.

Increased plasma sialidase activity was demonstrated in 25 patients with acute myocardial infarction. The mean plasma sialic acid level after incubation with substrate neuramin lactose was 0.060 +/- 0.003 (SEM) mumol/sample compared with 0.017 +/- 0.003 mumol/sample in 24 patients without infarction (p less than 0.001). The erythrocyte endothelial cell adhesion index was highest when both cell types were sialidase treated (0.35 vs control 0.00 [p less than 0.05]). When sialidase (50 U/ml) was added to whole blood in plastic tubes, the mean clotting time was 7.17 +/- 1.0 (SD) minutes (n = 8) compared with a mean control of 15.45 +/- 3.9 minutes (p less than 0.01). Sialidase had no effect on prothrombin or partial thromboplastin times. The above studies suggest that increased plasma sialidase activity in patients with acute myocardial infarction may be associated with clumps of desialylated erythrocytes that may alter flow in the microcirculation.

Blood Coagulation↗
PubMed1987

Predilution hemofiltration for the removal of protein bound antigens.

In cancer, tumor antigen (Ag) and the antigen-antibody immune complexes (IC) have been implicated with the inhibition of macrophage or lymphocyte function, interleukin generation and induction of suppressor cells and immunosuppressants. Plasma exchange depletes both Ag and antibodies (Ab) from the circulation. However, the Abs might be cytotoxic to cancer cells. Hence, a better treatment would be to remove the Ag without depleting the Abs. Such a procedure involves dissociation of Ag from Ab either by a change in pH of the plasma or by a hemodilution of the blood followed by removal of both the free and the dissociated Ag by ultrafiltration. The present work presents a theoretical analysis of the predilution hemofiltration system designed to remove the antigens which are weakly bound to proteins. A single pool model for the patient was assumed. The variables which effect the clearance of Ag are the protein binding constant (K), the extent of dilution of blood, the initial ratio between Ag and Ab concentrations. A computer simulation of the derived mass balance equations shows that the clearance of total Ag from the plasma pool decreases with (i) increase in the value of K, but it can be off set by increasing the extent of hemodilution, and (ii) decrease in initial Ag/Ab ratio, but this effect can be minimized by increasing the hemodilution fluid flow rate.

Antigens, Neoplasm↗
PubMed1986

Theoretical studies on self-regulating insulin delivery system.

A theoretical analysis of a self-regulating insulin delivery (SRID) system was made using published in vitro results. The SRID system consists of an encapsulated glycosylated insulin bound to concanavalin A (conA) that exchanges insulin with glucose through a reversible chemical reaction between glucose and conA-insulin (C-I). The mathematical analysis of the in vitro results gave the values of the forward and reverse reaction rate constants. Using these calculated reaction rate constants, the insulin release rate was predicted from a SRID cylindrical pouch in response to a change in glucose concentration. The insulin release rate was found to be strongly affected by the diffusivity coefficients of insulin and glucose within the pouch, the radius of the pouch, membrane permeability, C-I concentration, and the kinetic rate constants. This mathematical analysis provides useful guidelines for the rational design of the SRID system.

Cell Membrane Permeability↗
PubMed1984

Noninvasive evaluation of the severity of aortic stenosis in adult patients.

To determine if a combination of noninvasive variables would be useful in the prediction of the severity of isolated aortic stenosis (AS), 53 patients (mean age 63.4 = 11 years) were evaluated by the following criteria: (1) aortic valve calcification in the plain chest x-ray film; (2) left ventricular hypertrophy by ECG and M-mode echocardiography; (3) faint or absent aortic closure sound; (4) timing of the peak of the systolic murmur; (5) half rise time (T time) of the carotid pulse; and (6) ejection time index. A numeric scoring system and a logistic regression model employing these variables were developed. The total maximum score was 16 points. Sensitivity and specificity for each variable were determined. Patients with clinically evident coronary artery disease (CAD) and significant aortic regurgitation were excluded. All patients underwent hemodynamic studies and coronary arteriography. Thirty-two patients had severe AS (aortic valve area less than 0.75 cm2) and 21 had mild to moderate AS (aortic valve area greater than 0.75 cm2). Significant CAD (greater than or equal to 50% reduction in luminal diameter) was present in 55% of patients. A total score of greater than or equal to 5 occurred in 59% (19 of 32) of patients with severe AS compared to 5% (1 of 21) of patients with mild AS. The presence of subclinical CAD moderately reduced the accuracy of the scoring system principally by its effect upon the timing of the systolic murmur and the ejection time. Combining the scoring system with the presence or absence of symptoms improved the identification of severe AS in patients with a low score.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Membrane cascade plasmapheresis: theoretical analysis and in vitro studies.

As the donor plasma required in plasmapheresis therapy is not only expensive but may also cause side effects and transfer of infections, attempt was made in the present work to generate continuously autologous purified plasma. A membrane cascade plasmapheresis (MCP) system was developed which: 1. Separates plasma from blood using a membrane plasma separator 2. Fractionates this plasma into two fractions using a secondary filter, one fraction rich in albumin and the other rich in immunoglobulins 3. Returns to the patient filtered blood combined with albumin-rich plasma fraction Ringer solution was used to compensate for the loss of plasma volume rejected as immunoglobulins. The main problem is to maximize the clearance of IgG and recovery of albumin. Theoretical analysis of the system shows that the clearance of IgG increases with the increase in Ringer solution flow rate. However, this increase in clearance of IgG is accompanied by a decrease in albumin recovery. Theoretical analysis presents a relationship between the clearance of protein as a function of their sieving coefficients of the secondary filter, plasma separation rate, and the priming volume. In vitro evaluation of the system using patient's plasma and a Kuraray 2A filter (secondary filter) show that the relative clearances of IgG and albumin lie in the range of 65-70% and 40-45%, respectively. Further improvement in the selectivity of the secondary filter is necessary to minimize the clearance of albumin and to increase the clearance of IgG.

Humans↗
PubMed1982

Collagen film for burn wound dressings reconstituted from animal intestines.

Collagen was isolated and purified from sheep intestines and cast into a film. The collagen film was cross-linked with ultraviolet light and reinforced by imbedding a nylon mesh. The collagen membrane was evaluated as a wound dressing for second- and third-degree burns in rats. Histopathological studies of the burns with and without the collagen dressings were made. The study showed the burn wounds dressed with collagen membrane exhibited rapid epithelialization with little inflammatory change and dense fibrous tissue ingrowth in the subdermal layers.

Amino Acids↗
PubMed1982

Portable artificial kidney with advantages of hemodialysis, hemofiltration, and hemoperfusion.

The FDA (filtration, dialysis, absorption) system developed in the present study operates on the principle of simultaneous filtration of blood and dialysis against its purified filtrate, the filtrate being purified by a multi-adsorption system. The filtration of blood is done using a hemofilter which permits clearance of solutes up to 50,000 daltons and easy removal of excess fluid overload under minimal osmotic imbalance conditions. The clearance of small solutes in the above pure-convective filtration process is enhanced by returning the purified filtrate to the hemofilter which introduces an additional diffusive mass transport to the otherwise pure-convective process. The purification of the filtrate is done by 3 kg charcoal and 450 gm of cation exchanger in the Ca++ and Na+ form. Sufficient urea binding is achieved by raising the post-treatment urea level from 50 mg% to 150 mg% which may be justified as the blood urea level below 300 mg% was found to be nontoxic by others. By this procedure, about 40 gm urea is removed per treatment by 3 kg charcoal and 3 to 4 liters of excess fluid discarded. Three kg of charcoal is found to bind an adequate amount of phosphate, thus eliminating the use of phosphate binders, such as alumina, which is a toxic material. The ion exchangers in the Ca++ and Na+ form bind an adequate amount of K+ without altering Na+ and Ca++ levels. The filtrate purification cartridge can be easily regenerated and sterilized, if necessary, thus making it inexpensive. A comparison of the FDA system with other systems clearly showed that it has the advantages of HD, HF, and HP while the major disadvantages of HD, HF, and HP are eliminated in the FDA system.

Anion Exchange Resins↗