Biomedical subjects
Publications and source records attributed to V S Murthy.
Gartner's duct cyst associated with ipsilateral renal aplasia is a rare anomaly and fewer than 40 cases have been reported in the literature. A case of Gartner's duct cyst presenting like an ureterocele on sonography, intravenous pyelography and CT are described.
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The use of trivalent influenza vaccination has been shown to reduce hospitalizations and mortality in high risk persons receiving the vaccine prior to endemic periods. Despite the generally accepted benefit of this vaccine, its use remains relatively low, with less than 40% of high risk persons actually receiving the vaccination. Increasing the vaccination rate is particularly difficult for physicians in small groups, practicing without sophisticated information systems, and for those practices in which small percentages of the patients are in HMO's or capitated plans. The setting for our study was eight primary care clinics, in a predominantly fee for service environment. We used several interventions to achieve the Healthy People 2000 goal of vaccinating 60% of the high risk of population. Those interventions included: mailings to patients recommending they get vaccinated, empowering non physician clinic personnel to administer vaccines without specific physician orders, and distributing comparative data of the vaccination rates at all participating clinic sites. We found that by using these interventions at eight different primary care clinic sites, we were able to achieve an influenza vaccination rate of 66.4% for our high risk population. We concluded that through collaboration eight primary care clinics can exceed the Healthy people 2000 goal of 60% compliance with influenza vaccination.
To study the detrimental effects of operating room noise, noise levels in operating rooms were first measured and the average noise level was calculated in Decibels, which was 77.32 dB(A). An audiocassette of 90 min duration was prepared recording the operating room noise. The same audiocassette was used later to expose the 20 anaesthesia residents to the operating room noise in the acoustically treated rooms of audiology department. The noise level during exposure was maintained at 77.32 dB(A). Two cognitive functions, mental efficiency and short-term memory were studied. The tests used were the Trail Making Test and Digit Symbol Test for mental efficiency and the Benton Visual Retention Test for short-term memory. The mean pre-exposure scores for the Trail Making Test, Digit Symbol Test and Benton Visual Retention Test were 22.9 +/- 1.94, 83 +/- 2.62 and 9.55 +/- 0.51 respectively. The mean during-exposure scores were 16.35 +/- 1.39, 74.05 +/- 3.46 and 5.8 +/- 0.41 respectively (P < 0.05). In conclusion, we observed that operating room noise reduced the mental efficiency and short-term memory of anaesthesia residents.
Twenty anaesthesia residents were exposed to a pre-recorded audio cassette of operating room noise. The noise level during exposure was maintained at 77.32 +/- 1 dB (A), which was the calculated average operating room noise in our institute. Two auditory functions i.e., speech reception threshold and speech discrimination were studied before and during exposure to noise in a pre-fixed order. The right and left ears were tested separately. Speech reception threshold showed a mean increase of 23.75 +/- 6.86 dB (A) for the right ear and 26.25 +/- 6.90 dB(A) for the left ear during exposure to noise, suggesting that speech communication may be possible only by raising the voice. Speech discrimination showed a mean percentage decrease of 23.3 +/- 4.82 per cent for the right ear and 23.5 +/- 3.89 per cent for the left ear implying that there can be a steep decrease in the ability to discriminate spoken words.
Sympathetic nervous system activity as indicated by circulating norepinephrine has been demonstrated to increase with advancing chronological age both at rest and during submaximal exercise. Much of the earlier work investigating this aging phenomenon used a younger group that had a higher peak oxygen consumption (VO2) than did the older group, which made comparisons difficult. In the present study, young [n = 7, 36 +/- 1.0 (SE) yr] and old subjects (n = 8, 61 +/- 1.2 yr) were matched on peak VO2 and then exercised at approximately the same relative submaximal VO2 (75%) and power output on a cycle ergometer for 21 min. Blood samples were collected at rest and in the 7th, 14th, and last minute of a 21-min exercise bout via an indwelling catheter in an antecubital vein. The norepinephrine responses for the young and old groups, respectively, were as follows: rest, 486 +/- 111 vs. 673 +/- 108; 7 min, 1,258 +/- 255 vs. 1,185 +/- 172; 14 min, 1,639 +/- 316 vs. 1,528 +/- 288; and 21 min, 2,038 +/- 488 vs. 1,936 +/- 453 pg/ml. These responses were not significantly different between the groups at any time period. The epinephrine values for the age groups were not statistically different: rest, 115 +/- 60 vs 88 +/- 51; 7 min, 140 +/- 18 vs. 326 +/- 88; 14 min, 216 +/- 33 vs. 366 +/- 104; and 21 min, 324 +/- 100 vs. 447 +/- 113 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)
A rare case of splenic hemangiomatosis with bone involvement in the upper extremity is presented. The findings on ultrasonography and CT scan abdomen were suggestive of splenic hemangiomatosis. X-ray of left forearm showed findings characteristic of osseous hemangiomatosis, which was subsequently confirmed on histology.
The usefulness of esmolol in predicting the efficacy of treatment with an oral beta-adrenergic blocking agent was evaluated in 27 consecutive patients with neurocardiogenic syncope. Seventeen patients had a positive head-up tilt test response at baseline and 10 patients required intravenous isoproterenol for provocation of hypotension. All patients were then given a continuous esmolol infusion (500 micrograms/kg per min loading dose for 3 min followed by 300 micrograms/kg per min maintenance dose) and rechallenged with a head-up tilt test at baseline or with isoproterenol. Of the 17 patients with a positive baseline tilt test response, 11 continued to have a positive response to esmolol challenge. Sixteen patients (including all 10 patients with a positive tilt test response with isoproterenol) exhibited a negative response to upright tilt during esmolol infusion. Irrespective of their response to esmolol infusion, all patients had a follow-up tilt test with oral metoprolol after an interval of greater than or equal to 5 half-lives of the drug. All 16 patients (100%) with a negative tilt test response during esmolol infusion had a negative tilt test response with oral metoprolol. Of the 11 patients with a positive tilt test response during esmolol infusion, 10 (90%) continued to have a positive response with oral metoprolol. It is concluded that in the electrophysiology laboratory, esmolol can accurately predict the outcome of a head-up tilt response to oral metoprolol. This information may be helpful in formulating a therapeutic strategy at the initial head-up tilt test in patients with neurocardiogenic syncope.
Chronically administered verapamil can accumulate in cardiac tissues and may depress cardiac function despite low plasma concentration. To examine this, two groups of rabbits were injected intraperitoneally twice a day with either 1 mg/kg verapamil or saline for 28 days. Fourteen hours after the last dose, right atrial tissue and right ventricular papillary muscle were isolated. Plasma and myocardial tissue concentrations of verapamil were determined. Plasma samples contained no detectable amounts of verapamil, but the myocardium contained 2.1 +/- 0.6 (mean +/- SE) ng of verapamil per gram of wet tissue. Spontaneous action potentials recorded from the sinoatrial node in the verapamil-treated group showed decreases in the phase 0 and phase 4 depolarization rates, a slower pacemaker rate, and an attenuated response to epinephrine compared with the saline-treated group. Papillary muscle in the verapamil-treated group exhibited a significantly lower force of contraction and a depressed contractile response to epinephrine compared with the control group. There were no differences in rate or contractile responses the day after single injection with 2 mg/kg verapamil or saline twice a day. Myocardial verapamil concentration increased with the duration of treatment and with the doses given; myocardial verapamil concentration was 3.0 +/- 0.6 ng/g wet tissue in the group treated for 28 days with 2 mg/kg verapamil. Our study shows that chronic treatment of rabbits with verapamil decreases cardiac chronotropic and inotropic responses to adrenergic stimuli despite no detectable verapamil in plasma, and that accumulation of verapamil in the myocardium is probably associated with these effects.
The prescribing and usage patterns of two antihypertensive agents, terazosin (Hytrin) and enalapril maleate (Vasotec) were analyzed and compared over a 6-month study period, using data from the PDS Alpha Data Base. The study analyzed several variables for both physician prescribing patterns and patient responses. Overall, the two agents performed equally well during the study period, with 6-month retention rates (% of patients who continued to take the same medication) of approximately 60%. Although both drugs are judged to be good candidates for first-line antihypertensive therapy, it was observed during the study that family practitioners write considerably more prescriptions for terazosin than enalapril, while internists write more enalapril prescriptions. We concluded that these differences in prescribing and usage patterns were largely attributable to the manufacturers' marketing strategies and to how various physicians perceive the two agents, rather than to actual clinical differences between them.
Previous research established a relationship between circulating sulfoconjugated norepinephrine (NE-SO4) and oxygen consumption at various exercise intensities. In this study, the stability of the NE-SO4 response was examined during sustained exercise at a constant relative intensity. Seven trained men bicycled at 78 +/- 3% of their maximal O2 consumption for 28 min and then rested on the ergometer for a comparable duration. After a 30-min rest, plasma samples were collected through an indwelling catheter at 7-min intervals during the exercise and recovery periods. Free NE and epinephrine increased sixfold during exercise. These changes were accompanied by increases in sulfoconjugated catecholamines, but only NE-SO4 achieved statistical significance (rest, 712 +/- 602; exercise, 1,329 +/- 1,163 pg/ml). This occurred at three collection periods (14, 21, and 28 min). Approximately 35, 52, and 95% of NE, epinephrine, and dopamine, respectively, existed as sulfoconjugated during exercise. Subject variation was present in the sulfoconjugated catecholamine response that could not be attributed to corresponding differences in circulating free catecholamine release. These findings implicate blood flow as a factor in the sulfoconjugation of NE, but not epinephrine or dopamine.
ACC-9653, a prodrug of phenytoin synthesized to be water soluble, is converted to phenytoin by phosphatases. In this study, 43 patients received ACC-9653 IV or IM. Side effects were transient and minor. The conversion half-lives of ACC-9653 after intravenous and intramuscular administration averaged 8.4 and 32.7 minutes, respectively. Peak phenytoin concentrations occurred 42 minutes after IV and 151 minutes after IM administration.
The currently available phenytoin (PHT) solution has many disadvantages stemming from poor aqueous solubility of PHT. A novel approach to solve the problem has been the synthesis of a phosphate ester of PHT (PHT prodrug ACC-9653). This water-soluble compound is metabolized rapidly into PO4 and PHT. A four center open-label, baseline-controlled study of 43 patients with epilepsy maintained on oral twice-daily PHT monotherapy was performed to evaluate the safety and pharmacokinetic profile of the prodrug. Patients received an i.v. or i.m. dose of ACC-9653 at a dose equivalent to the patients' morning dose of PHT. Intravenous dosages were infused at a rate of 75 mg/min, and i.m. dosages were given as one or two injections. After a period of 6 days, during which patients were again maintained with oral PHT, they were given a dose of ACC-9653 via whichever route they had not yet received. The Tmax of the prodrug averaged 5.7 and 36 min (0.095 and 0.606 h) after i.v. and i.m. administrations, respectively. The elimination half-life of ACC-9653 (conversion from prodrug to PHT) after i.v. and i.m. administration was 8.4 and 32.7 min (0.140 and 0.545 h), respectively, and both were independent of the dose. The plasma clearance of ACC-9653 was not dependent on dose or route of administration and averaged 19.8 +/- 1.16 and 17.8 +/- 0.83 L/h after i.v. and i.m. administrations, respectively. The area under curve ratio of PHT after i.m. and i.v. ACC-9653 was 1.17 +/- 0.13 which was not significantly different from 1.(ABSTRACT TRUNCATED AT 250 WORDS)
In clinical practice, serum level monitoring of anticonvulsant drugs is usually adequate. When there is an alteration in the binding of the anticonvulsant drug to the plasma proteins, however, the relationship between the serum concentration and therapeutic efficacy or toxicity becomes difficult to interpret. This can occur with combinations such as non-steroidal anti-inflammatory drugs (NSAIDs), phenytoin (Dilantin), carbamazepine (Tegretol), and valproic acid (Depakene) or when the albumin level is low. A failure to rely on serum free levels of the anti-convulsant under these circumstances can easily result in poor clinical decisions. The technique of serum free level measurement and illustrative examples of specific cases are provided to document the usefulness of this invaluable laboratory test.
ICI 147,798 has been shown to exhibit both diuretic and beta-antagonist properties in vivo. The present study investigated the nature and selectivity of the beta-antagonism in a variety of isolated tissues. ICI 147,798 produced a concentration-dependent suppression of the maximum chronotropic response of norepinephrine in guinea pig right atria (beta-1 adrenoceptor). ICI 147,798 caused a concentration-dependent shift to the right of the salbutamol concentration-response curve in the guinea pig trachea (beta-2 adrenoceptor), and Schild analysis suggested competitive inhibition. Propranolol produced parallel shifts to the right of the norepinephrine concentration-response curve in guinea pig right atria, except at relatively high concentrations. The inhibitory effects of propranolol in guinea pig right atria were reversed by greater than 95%, whereas the effects of ICI 147,798 were only slightly reversed after a 6-hr washout period. Preincubation of propranolol with ICI 147,798 in guinea pig right atria prevented completely the suppression of the norepinephrine maximum chronotropic response. Postincubation of propranolol with ICI 147,798 partially reversed the suppression of the maximum chronotropic response. ICI 147,798 had no effect on the maximum chronotropic responses of either histamine (H2-receptor) or forskolin (adenylate cyclase activation) in guinea pig right atria and had no effect on agonist responses in a variety of other receptor systems. The insurmountable beta-1 adrenoceptor antagonism was evaluated based on the assumptions of irreversible competitive antagonism, mixed competitive and noncompetitive antagonism and slowly dissociating competitive antagonism ("hemi-equilibrium" conditions). Concentration-dependent changes in norepinephrine KA values suggested the first three possibilities were unlikely.(ABSTRACT TRUNCATED AT 250 WORDS)
In rabbits, the characteristics of cardiac beta-1 receptor blockade produced by ICI 147,798, a novel beta receptor blocking agent with diuretic properties, were evaluated and compared with those of propranolol. In conscious rabbits, i.v. injections of 0.31, 1.0 and 3.1 mg/kg of ICI 147,798 and 1.0 mg/kg of propranolol caused significant bradycardia. ICI 147,798 produced a dose-dependent shift to the right of the dose-response (chronotropic) curve of isoproterenol with suppression of the maximal tachycardia, an effect characteristic of insurmountable beta receptor blockade. Propranolol also produced a shift to the right of the dose-response curve of isoproterenol without affecting the maximal tachycardia. ICI 147,798-induced antagonism was specific for beta adrenoceptors as it failed to modify the effects of acetylcholine, angiotensin II, phenylephrine, adenosine, histamine and prostaglandin E2 on mean arterial pressure and heart rate. In rabbits with prior autonomic blockade, ICI 147,798, like propranolol, failed to inhibit the positive chronotropic effects of theophylline which are mediated by postreceptor mechanisms. In reserpinized rabbits, ICI 147,798 was found to have no intrinsic sympathomimetic activity. Unlike the effects of propranolol, which were attenuated by first-pass through the hepatic vascular bed, the effects of ICI 147,798 were unaffected suggesting an absence of first-pass metabolism. The effects of propranolol (1.0 mg/kg i.v.) were not detectable at 24 hr after injection, whereas significant beta receptor blocking activity was still present at 24 hr after ICI 147,798 (1.0 mg/kg i.v.). The results suggest that ICI 147,798 is a specific, long-acting, insurmountable beta-1 receptor blocking agent without intrinsic sympathomimetic activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Beta-receptor-blocking agents are commonly used in the management of various cardiovascular diseases. Recently, esmolol, a pharmacokinetically novel cardioselective beta-receptor-blocking agent, has been introduced for use in the treatment of critically ill patients. It is devoid of intrinsic sympathomimetic activity and in doses used clinically, it has no direct depressant effect on the heart. Esmolol is an ester and is metabolized by choline-esterase to ASL 8123, an inactive molecule. Esmolol has an elimination half-life of nine minutes which accounts for its ultrashort duration of action. This unique pharmacokinetic property provides two advantages over other longer-acting beta-receptor-blocking agents. First, the magnitude of beta-receptor blockade can be titrated to a desired level. Second, if adverse effects are experienced, reducing the dosage or terminating the infusion results in rapid reversal of its pharmacological effects. Another ultrashort-acting, non-cardioselective beta-receptor blocking agent, flestolol is undergoing clinical evaluation. Esmolol has been approved for the management of supraventricular tachycardia. The clinical safety of these novel drugs will expand the use of beta-receptor-blocking agents in the management of cardiovascular diseases in critically ill patients.