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Biomedical subjects

R B Smith

Publications and source records attributed to R B Smith.

At least 217 records · Page 12Linked to original sources
PubMed1986

The carotid sinus syndrome: a frequently overlooked cause of syncope in the elderly.

Exaggerated carotid sinus reflexes may account for alterations in consciousness responsible for significant disability and injury in elderly patients. Nonspecificity of symptoms and concomitant medical conditions frequently delay diagnosis and therapy. During a recent 9-year period, 82 patients were identified as having symptomatic carotid sinus hypersensitivity (CSH). Fifty-nine patients described complete syncope, 73 patients had multiple syncopal or near-syncopal episodes, and 40 patients related cervical pressure or motion as provocative events. Electrophysiologic testing demonstrated that 47% had cardioinhibitory CSH, 26% had vasodepressor CSH, and 27% had combined vasodepressor and cardioinhibitory CSH. The mean follow-up period of all patients was 36 months. Surgical therapy included ventricular demand pacemaker implantation in 33 patients and carotid sinus denervation in seven patients. Medical therapy was used in 32 patients, 11 mildly symptomatic patients were not treated, and 3 patients had carotid sinus irradiation. Pacemaker implantation relieved symptoms in 53%; however, 11 patients (33%) had significant postoperative complications. Carotid sinus denervation relieved symptoms in 86%, medical therapy in 54%, and carotid sinus irradiation in 33% of patients. Because of its demonstrated effectiveness in all variants of CSH and negligible perioperative morbidity, carotid sinus denervation should be offered to acceptable operative candidates when the diagnosis of CSH is confirmed.

Adult↗
PubMed1986

Alprazolam kinetics in patients with renal insufficiency.

Alprazolam kinetics following a single 1.0-mg oral dose of alprazolam were compared between seven dialysis-dependent patients with chronic renal failure and seven healthy controls matched for age, sex, and weight. There were no significant differences between patients and controls in alprazolam half-life (11.5 vs. 11.3 hours) or clearance of total drug (1.14 vs. 1.26 ml/min/kg). However, alprazolam free fraction was increased in renal failure patients (35.7% vs. 31.9% unbound, p less than 0.005). Free clearance of alprazolam averaged 23% lower in patients (3.2 vs. 4.1 ml/min/kg), but the difference was not significant. Renal insufficiency has a quantitatively small influence on alprazolam pharmacokinetics.

Adolescent↗
PubMed1986

A pharmacokinetic drug interaction between erythromycin and triazolam.

The effect of erythromycin on the pharmacokinetics of triazolam was studied in 16 normal male volunteers. Triazolam in 0.5-mg doses was administered alone and after 3 days of receiving erythromycin (333 mg tid) in a randomized complete crossover design. Plasma samples were collected for 24 hours post doses and analyzed for triazolam by electron-capture gas chromatography. Erythromycin administration resulted in a 52% decrease in triazolam clearance, significantly higher triazolam concentrations at the majority of sampling times, significantly longer triazolam half-lives of elimination (5.9 vs. 3.6 hours), and a 30% decrease in the triazolam apparent volume of distribution. No differences were observed in the times of peak triazolam concentration occurrence. In accordance with previously reported drug interactions involving macrolide antibiotics, erythromycin appears to significantly inhibit the metabolism of triazolam.

Adult↗
PubMed1985

Result of treatment of patients with stage D1 prostatic carcinoma.

Between 1972 and 1982, 59 patients who had documented pelvic lymph node metastases, proved by pelvic lymphadenectomy, were available for analysis. Radical retropubic prostatectomy was the primary treatment in 33 patients with or without other therapies, while 23 patients received external beam radiation therapy as their primary treatment. Three patients received hormonal therapy alone. Forty-two of 59 patients are alive for a crude survival of 71 per cent. Sixteen patients have died of metastases. Patients with low-grade tumors, small tumor burden, and limited lymph node metastases had excellent short-term survival after radical prostatectomy.

Carcinoma↗
PubMed1985

The management of superficial bladder tumors and carcinoma in situ with intravesical bacillus Calmette-Guerin.

A phase II study was performed to assess the role of bacillus Calmette-Guerin as a prophylaxis against recurrent stages O and A bladder tumors, and in the treatment of existing superficial bladder tumors and carcinoma in situ. Tice strain bacillus Calmette-Guerin (1 vial, 2 to 8 times 10(8) organisms in 60 cc saline) was instilled intravesically without cutaneous inoculation. Instillations were given weekly for 6 weeks and then monthly or until recurrence in 22 patients with a history of recurrent tumors, while 22 with existing stages O and A transitional cell carcinoma, and 19 with carcinoma in situ were treated weekly for 8 weeks and then monthly for 12 months or until failure. Complications included cystitis in 88 per cent of the patients (severe in 20 per cent), fever in 15 per cent, a flu-like syndrome in 13 per cent, edema and pruritus in 1.5 per cent, and ureteral stenosis in 1.5 per cent. Twelve patients (19 per cent) did not complete the study owing to toxicity. Of the patients in the prophylaxis group 67 per cent have had no tumor recurrence 10 to 26 months (mean 15 months) after therapy. Of the patients with existing tumors 36 per cent had complete regression following bacillus Calmette-Guerin therapy and 23 per cent had a partial response. Among the patients with carcinoma in situ 13 (68 per cent) had reversal to normal urothelium and 3 (16 per cent) had marked improvement. None of the patients had recurrence at 11 to 20 months. Intravesical Tice strain bacillus Calmette-Guerin is effective as a prophylaxis against recurrent superficial bladder tumors and in the treatment of carcinoma in situ.

BCG Vaccine↗
PubMed1985

Pharmacodynamic evaluation of the benzodiazepine-oral contraceptive interaction.

The sedative, psychomotor, and memory effects of single oral doses of alprazolam (ALP), lorazepam (LOR), temazepam (TMP), and triazolam (TRZ) were evaluated in women taking oral contraceptives (OCs) and a comparable group of control women. Nine women taking OCs and 11 control women took doses of 1 mg ALP and 2 mg LOR and 10 OC users and 10 control women took 30 mg TMP and 0.5 mg TRZ on two occasions separated by 28 days. Minimal psychomotor impairment was noted after TMP. ALP, LOR, and TRZ produced greater performance impairment in the OC users. Correcting the maximum observed performance decrement for plasma concentration did not account for the differences between OC users and controls. After TMP, there was less sedation during the first 2 hours in OC users, who also had higher plasma TMP clearance. There were no differences in sedation between OC users and controls after ALP, LOR, and TRZ; however, there was less than 50% power to detect a 30% difference. Amnestic effects in OC users and controls did not differ after any of the four drugs. The observed patterns of anterograde amnesia were different, with the earliest and most pronounced recognition failure after TRZ (50% at 1.5 hours), while the LOR effect increased to a maximum (30%) 4 hours after dosing. Our data suggest that differences in benzodiazepine pharmacokinetics between OC users and control women do not account for observed differences in psychomotor impairment. Women taking OCs are more sensitive to the psychomotor effects of single oral doses of benzodiazepines.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Effects of end-stage renal disease and aluminum hydroxide on temazepam kinetics.

The kinetics of temazepam, 30 mg, were evaluated in 11 patients with end-stage renal disease. Age ranged from 18 to 65 years. On two occasions separated by 1 week, single oral 30 mg doses of temazepam were given once with water (TM) and once with 3600 mg aluminum hydroxide gel (TM + AHG). There were no significant differences in the maximum plasma concentration, the time to reach maximum concentration, or elimination rates between TM and TM + AHG dosing. In approximately half the subjects there were secondary temazepam peak concentrations. In the remaining subjects, temazepam elimination was biphasic, with the terminal t1/2 ranging from 11 to 77 hours. There was a lag time before absorption in all subjects. The percent free temazepam in plasma from dialysis subjects ranged from 4.4% to 8.8% (mean = 5.9%). Compared with literature reports of subjects with normal renal function, the maximum plasma concentration was lower and the percent free temazepam was higher in dialysis subjects. When sedation score was plotted against plasma temazepam concentration, there was clockwise hysteresis consistent with tolerance or adaptation to effects of the drug. Thus aluminum hydroxide gel does not affect temazepam absorption. The clinical significance of the low plasma concentrations and high free temazepam fraction in dialysis subjects is uncertain.

Absorption↗
PubMed1985

Concomitant renal revascularization in patients undergoing aortic surgery.

Sixty-three patients who underwent renal revascularization at the time of aortic surgery were retrospectively reviewed. These patients had significant renal artery stenosis in addition to either severe aortoiliac occlusive disease or aortic aneurysmal disease. Fifty-eight patients were hypertensive, whereas five patients were normotensive and these renal lesions were treated prophylactically. The operative mortality rate was 3%. Despite lack of selectivity in these patients with diffuse atherosclerosis, 60% (35 of 58) of the patients with hypertension could be classified as either "cured" or "improved." Patients with bilateral renal artery involvement and moderate azotemia were noted to improve with respect to renal function postoperatively. No patient has required chronic dialysis at a mean follow-up period of 22.6 months. Simultaneous aortic and renal artery surgery may be performed with low morbidity and mortality rates and produce a gratifying improvement in hypertension. Renal functional improvement and perhaps preservation of renal mass may be anticipated in selected patients.

Adult↗
PubMed1985

The Emory prospective randomized trial: selective versus nonselective shunt to control variceal bleeding. Ten year follow-up.

From 1971 to 1975, 55 patients with variceal bleeding secondary to cirrhosis were entered into a prospective randomized trial comparing distal splenorenal (selective) and H-graft interposition (nonselective) shunt. This 10-year follow-up documents that selective shunt is better (p less than 0.05) in four of the five variables monitored. Control of bleeding: selective shunt prevented variceal bleeding better than interposition shunt due to the higher (0.05 less than p less than 0.1) occlusion rate (30%) of interposition shunt. Selective shunt maintained postoperative portal perfusion better (p less than 0.01) than patent interposition shunt. Seventy-five per cent of selective shunt survivors have portal perfusion at 10 years: no patient with a patent nonselective shunt perfuses the liver. Quantitative liver function was better preserved (p less than 0.01) 10 years after selective shunt than nonselective shunt. Postoperative encephalopathy occurred in fewer (p less than 0.01) selective (27%) than nonselective (75%) shunt patients over the 10 years. Survival: in the randomized population, the improved survival in the selective shunt subgroup did not reach statistical significance. However, improved survival was confirmed in nonalcoholics. Five of eight nonalcoholics operated with selective shunt are alive at 10 years with patent shunts. No nonalcoholic, of seven total, operated with nonselective shunt survived 10 years with a patent shunt. These data show that selective shunt was superior to nonselective shunt. There was less rebleeding and encephalopathy after distal splenorenal shunt; postoperative portal perfusion and hepatic function were maintained.

Clinical Trials as Topic↗
PubMed1985

Conventional and high-frequency ventilation in dogs with bronchopleural fistula.

Seven anesthetized dogs with bronchopleural fistulas were subjected to a sequence of continuous positive-pressure ventilation (CPPV), volume-controlled high-frequency positive-pressure ventilation (HFPPV), and high-frequency vibratory ventilation (HFVV). Adequate short-term ventilation and oxygenation were possible with all three ventilatory modes. During HFPPV and HFVV, PaCO2 was unchanged, but hypercarbia developed during CPPV. PaO2 decreased during each mode of ventilation, but HFPPV maintained PaO2 at a sufficient and constant level during the 30-min test period. HFPPV was the most efficient technique with respect to delivery of minute ventilation, the relation between fistula flow and delivered ventilation, and maintenance of both ventilation and oxygenation.

Animals↗
PubMed1985

Volume-controlled high frequency positive pressure ventilation for upper abdominal surgery. A clinical report.

Volume-controlled high-frequency positive pressure ventilation was evaluated and compared to intermittent positive pressure ventilation during anesthesia in 74 patients undergoing biliary tract surgery. There were no statistically significant differences in oxygenation or ventilation. Significantly lower airway pressures and lower tidal volumes were recorded during high frequency positive pressure ventilation. This technique was also used in eight morbidly obese patients during gastric stapling surgery, and provided adequate oxygenation and ventilation. Used intra-operatively, it also produced a quiet operative field, which the surgeons appreciated during cannulation of the biliary duct and stapling of the stomach. At the end of the anaesthesia, high frequency positive pressure ventilation was superimposed on spontaneous breathing and operated as a new mode of intermittent mandatory ventilation. This reduced the risk of hypoxia at the time of emergence from anaesthesia and at tracheal suctioning.

Anesthesia, General↗
PubMed1985

Effects of end stage renal disease and aluminium hydroxide on triazolam pharmacokinetics.

Triazolam 0.5 mg was administered to 11 dialysis patients and 11 age, weight and sex matched controls. Peak plasma concentrations (Cmax) were higher in control subjects, but there were no other differences between the groups. When dialysis patients took triazolam with 3600 mg aluminum hydroxide suspension, Cmax and AUC were increased into the range observed in control subjects. It appears that triazolam can be used at normal doses in patients with renal dysfunction, without regard to interaction with aluminum hydroxide gel, or to alterations in elimination.

Adolescent↗
PubMed1985

Apneic diffusion oxygenation and continuous flow apneic ventilation. A review.

Evolution of life coincides with the most rapid rate of rise in atmospheric oxygen concentration during Devonian time. Oxygen is essential for life, but at the same time is a cellular poison if present in tensions considerably higher than those the particular cellular milieu has become adapted to. Animals exposed to low oxygen tensions breathe continuously, e.g. most species of fish obtain their oxygen from a continuous flow of water at low oxygen tensions. Evolution from water to land breathing generally is associated with intermittent breathing, mass movement of gas in one direction, i.e. inhalation and exhalation. Intermittent breathing is part of this evolutionary process and reduces the inspired oxygen tension from 150 mmHg (19.95 kPa) to approximately 100 mmHg (13.3 kPa) at the alveolar blood interface. Perhaps evolution from continuous ventilation to intermittent breathing may be protecting the body against the high atmospheric oxygen tension. Therefore, it is not surprising that mammals can have adequate oxygen uptake with apneic diffusion oxygenation (ADO) and continuous flow apneic ventilation (CFAV). Mechanical ventilation classic techniques, i.e. intermittent positive-pressure ventilation and continuous positive-pressure ventilation, employ ventilatory frequencies close to the resting breathing rate of the adult. Utilizing low-compression patient circuits has made mechanical ventilation with higher frequencies possible. 60 to 400 breaths per min is used for high-frequency positive-pressure ventilation and high-frequency jet ventilation, and up to 40 Hz is used for high-frequency oscillation (HFO). The two extremes of artificial ventilation - ADO, i.e. supply of O2 by continuous flow, and HFO, i.e. supply of O2 by oscillatory changes - both primarily involve diffusion, even though convection (also secondary to cardiac oscillations) obviously is important in the process of gas exchange. Some recent experimental findings favor continued development and evaluation of CFAV as an additional alternative to artificial ventilation.

Animals↗
PubMed1985

Clinical application of continuous flow apneic ventilation.

Continuous flow apneic ventilation (CFAV) was studied in five adult female patients. After induction of anesthesia with thiopental sodium (5 mg/kg) and fentanyl (5 micrograms/kg), and paralysis with pancuronium bromide (0.12 mg/kg), the patients were ventilated with oxygen at an FIO2 of 1.0 by face mask. Two polyethylene catheters (outside diameter [OD] 2.5 mm) were each inserted into the right and left mainstem bronchi. Each catheter had a curved tip measuring 2 cm in length. The angulation of the catheter tip from the axis was 20 degrees for the right side and 30 degrees for the left side. The endobronchial position was checked by fiberoptic bronchoscopy. Subsequently, tracheal intubation was performed using a 7.5 mm OD tracheal tube. CFAV was started when both catheters were connected to the gas delivery system. Humidified oxygen was delivered at total flows between 0.6 and 0.7 1/min. Arterial blood gases were analyzed every 5 min for 30 min. Monitoring included electrocardiogram, indirect blood pressure, heart rate, temperature, and peripheral nerve stimulation. Adequate oxygenation was maintained in all patients, 39.76 +/- 4.32 kPa (299 +/- 37 mmHg) at 30 min. There was a significant rise in Paco2 (P less than 0.05) at 30 min compared to the control, 4.92 +/- 0.25 kPa compared to 7.30 +/- 0.53 kPa (37.0 +/- 1.9 mmHg compared to 54.9 +/- 4.0 mmHg). There was a mean rise in Paco2 of 0.03 kPa/min (0.6 mmHg/min) compared to 0.5 kPa/min (3.8 mmHg/min) with apneic diffusion ventilation. In one patient there was no increase in Paco2 during the 30 min of CFAV.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Pharmacokinetic consequences of long term coadministration of cimetidine and triazolobenzodiazepines, alprazolam and triazolam, in healthy subjects.

The influence of administration of cimetidine (1 g daily for 2 weeks) on the pharmacokinetics of alprazolam (0.5 mg t.i.d. for 1 week) and triazolam (0.5 mg nightly for 1 week) was investigated in two groups of 8 healthy subjects. The plasma AUC of these triazolobenzodiazepines were significantly increased. Moreover, for triazolam, the C max was increased and the plasma elimination half-life was prolonged; oral clearance of the two triazolobenzodiazepines was markedly reduced. It is suggested that the combined treatment cimetidine-alprazolam requires a reduced daily dosage (one third) of alprazolam or increased dosage intervals (b.i.d. instead of t.i.d.). For triazolam, used as a hypnotic drug, such dosage reduction appears unsuitable if administered on a once-nightly basis.

Adult↗
PubMed1985

Renovascular hypertension complicating neurofibromatosis.

Three patients, ages 13 months, 13 years, and 16 years, with renovascular hypertension complicating neurofibromatosis underwent vascular reconstruction with good results. A review of these patients, plus 47 additional patients from the literature, constitutes the basis of this report. The standard intravenous pyelogram revealed abnormalities in only 46 per cent of the patients. Definitive diagnosis required angiography and selective renal vein renin determinations. Unilateral and bilateral lesions were seen with equal frequency. Associated arterial abnormalities were common. Medical treatment and balloon angioplasty failed to control the blood pressure in all patients. Surgical therapy, either nephrectomy or vascular reconstruction, cured or significantly improved 95 per cent of the patients. Although one primary goal of operation is renal salvage, 40 per cent of the patients in this review underwent nephrectomy to control their hypertension.

Adolescent↗