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Biomedical subjects

W T Sawyer

Publications and source records attributed to W T Sawyer.

18 recordsLinked to original sources
PubMed1992

Warfarin-induced intramural hematoma of the small intestine.

A case of warfarin-induced intramural hematoma and hemorrhagic infarction of the small intestine is described, and the literature on this adverse effect is reviewed. A 32-year-old white woman who had been receiving warfarin and carbamazepine came to a clinic complaining of lower back and stomach pain. She had a history of iliofemoral deep venous thromboses and seizures. A pelvic sonogram showed a large quantity of fluid present. Her prothrombin time (PT) was 29.2 sec. Her hemoglobin concentration and hematocrit were within the normal ranges. The patient was admitted to the hospital when her back pain increased and she vomited. The warfarin was discontinued. On day 5 the patient was still having abdominal pain and nausea. Her hemoglobin concentration and hematocrit had fallen to 6.6 g/dL and 20%, although her PT had decreased to 12.5 sec. On the same day, the patient underwent an exploratory laparotomy, and an indurated and ischemic area of jejunum was found and resected. The pathology report indicated the presence of hemorrhage and infarction consistent with an anticoagulant-related disorder. About 100 cases of intramural hematoma of the small intestine induced by anticoagulant therapy have been reported. Most patients are white males about 60 years of age. The sites most frequently involved are the duodenum and proximal jejunum. Symptoms include constipation, nausea, vomiting, and abdominal pain. Laboratory test and radiological findings are fairly nonspecific, but when found together in a patient receiving an anticoagulant, the diagnosis can be made with some confidence. Management may be complicated by the bleeding disorder, the intestinal obstruction if present, and the original indication for warfarin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Malabsorption of flucytosine in a pediatric patient with Shwachman syndrome.

The malabsorption of drugs from the gastrointestinal tract in patients with pancreatic insufficiency is not well documented in the literature. We describe a case of flucytosine malabsorption in a pediatric patient with Shwachman syndrome, a rare disease in the pediatric age group characterized by pancreatic insufficiency. A significant increase in serum concentrations of flucytosine was noted when the drug was administered in a lipophilic vehicle, possibly due to enhanced absorption.

Adult↗
PubMed1989

Effect of retrograde aminophylline administration on calcium and phosphate solubility in neonatal total parenteral nutrient solutions.

The effect of retrograde administration of aminophylline injection on calcium and phosphate solubility in neonatal total parenteral nutrient (TPN) solutions was studied. Neonatal TPN solutions containing two amino acids solutions in three concentrations (Travasol 1% and 2% and TrophAmine 2%) were formulated. Calcium and phosphate salts were added to achieve calcium concentrations of 10, 15, 20, 25, 30, or 40 meq/L and phosphorus concentrations of 10, 15, 20, 25, 30, or 40 mmol/L. Samples were inspected visually after 18-24 hours; solutions free of precipitation were then infused through two parallel syringe-pump systems designed to simulate clinical conditions for TPN solution administration to a 1-kg neonate. To one system, a 7.5-mg aminophylline dose was added as a manual retrograde injection; sterile water for injection was added as a manual retrograde injection to the other system. The solutions were inspected throughout a one-hour infusion period for precipitate formation in the i.v. apparatus, and the pH of the effluents was determined. Concurrent aminophylline administration resulted in visible precipitate in all but a few of the solutions tested. The solution containing Travasol 2%, calcium 10 meq/L, and phosphorus 10 mmol/L remained clear, as did the solutions containing TrophAmine 2% and the following concentrations of calcium and phosphorus: calcium 10 meq/L and phosphorus 10, 15, or 20 mmol/L; calcium 15 meq/L and phosphorus 10 or 15 mmol/L; and calcium 20 meq/L and phosphorus 10 or 15 mmol/L. An average increase in pH of 0.63 unit was noted in all solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminophylline↗
PubMed1988

Extreme warfarin intoxication secondary to possible covert drug ingestion.

A young adult male patient presented with an excessively prolonged prothrombin time (greater than 90 sec) following approximately two weeks of therapy with oral warfarin sodium, in doses between 2.5 and 5 mg/d. Repeated administration of vitamin K and fresh frozen plasma was required to reverse the anticoagulation and maintain a normalized prothrombin time. Serial warfarin plasma concentration measurements were used to interpret the apparently unusual prothrombin time response profile and to detect the possibility of covert drug ingestion.

Adult↗
PubMed1988

Accuracy of tobramycin delivery by four i.v. infusion methods.

The accuracy of tobramycin delivery by four methods of intermittent intravenous infusion was studied in 11 healthy male volunteers. Subjects received intravenous tobramycin (as the sulfate salt) 1.5 mg/kg by each of four infusion methods in a nonblinded, randomized, four-way crossover design. The methods used for intravenous infusion were (1) minibag via gravity flow (MG), (2) minibag with the secondary infusion tubing inserted below a volumetric infusion pump (MP), (3) metered chamber via volumetric infusion pump (MC), and (4) syringe pump (SP). Doses were diluted to a volume of 50 mL, except for the two minibag methods, for which the dilution was necessarily greater because of manufacturer overfill. Intravenous flow rates for both primary fluid and drug administration were set at 100 mL/hr, and the duration of drug infusion was documented by observation for each administered dose. The fluid volume of 12 minibags was measured to assess manufacturer overfill. Fluid remaining in the secondary i.v. tubing for the minibag methods was collected after the infusion. Seventeen blood samples were obtained before and at various time intervals after each dose and analyzed in duplicate for tobramycin content by fluorescence polarization immunoassay. A mean of 10% of each dose remained in the secondary i.v. tubing at the completion of the infusion for the minibag methods, whereas less than 1% of each dose remained in the secondary tubing for the SP method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Effect of four intravenous infusion methods on tobramycin pharmacokinetics.

The influence of four intermittent intravenous infusion methods on the determination of tobramycin pharmacokinetic values and predicted doses was evaluated in 11 healthy adult volunteers. Each subject received tobramycin (as the sulfate salt) 1.5 mg/kg by each of four i.v. infusion methods: (1) minibag via gravity flow (MG), (2) minibag with the secondary infusion tubing inserted below a volumetric pump (MP), (3) metered chamber via volumetric pump (MC), and (4) syringe pump (SP). Infusion rates were initially set to administer each dose over a 30-minute period. Sixteen blood samples were obtained over an eight-hour period before and at various time intervals after each dose and were analyzed for tobramycin content by fluorescence polarization immunoassay. Area under the serum concentration-time curve from time zero to infinity (AUC0-infinity) was calculated by the trapezoidal rule. Serum tobramycin concentration data for each subject were fitted to a biexponential decay model with zero-order input. beta and V beta were calculated from fitted data. One-compartment pharmacokinetic values, elimination rate constant (kappa), apparent volume of distribution (V), and predicted doses to achieve steady-state peak concentrations of 6 micrograms/mL were calculated by the method of Sawchuk and Zaske. There were no significant differences in either beta or kappa among the infusion methods. V beta values (mean +/- S.D.) for the methods were 0.240 +/- 0.025 (MG), 0.257 +/- 0.025 (MP), 0.221 +/- 0.027 (MC), and 0.231 +/- 0.032 (SP) L/kg.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1986

Interference of digoxin-like immunoreactive substances with three digoxin immunoassays in patients with various degrees of renal function.

The effect of renal function and digoxin use in adult patients on interference from digoxin-like immunoreactive substances (DLIS) with three digoxin immunoassays was studied. Hospital patients entered into the study were categorized into the following groups according to renal function: group I (serum creatinine less than 1.5 mg/dL), group II (serum creatinine 1.5-2.5 mg/dL), group III (serum creatinine greater than 2.5 mg/dL, not on hemodialysis), and group IV (serum creatinine greater than 2.5 mg/dL, on maintenance hemodialysis). Medical records were reviewed to determine whether or not patients were receiving digoxin. Excess sera for analysis of serum digoxin concentrations (SDCs) was collected from routine laboratory tests. Serum samples were assayed singly by fluorescence polarization immunoassay (FPIA, Digoxin I, Abbott), radioimmunoassay (RIA, Micromedic), and affinity-column-mediated immunoassay (ACMIA, aca, E.I. du Pont). Correlation of SDCs obtained by RIA and ACMIA with FPIA results was determined using linear-regression analysis. A total of 177 patients met the study criteria; 98 were receiving digoxin. In patients on digoxin, SDCs by RIA were significantly higher than those obtained by FPIA in group II and III patients. SDCs obtained by ACMIA correlated well with and were not significantly different from those obtained by FPIA in any of the patient groups. Maximum differences and mean absolute differences in SDCs obtained by RIA were greater than those for ACMIA when compared with FPIA values in all patient groups. Over 40% of patients with renal dysfunction not on digoxin had false-positive SDCs by RIA; the highest of these values was seen in groups II and III.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Hypokalemia, hyperglycemia, and acidosis after intentional theophylline overdose.

Three cases of intentional theophylline overdose in adult patients are described. Among these, hypokalemia, hyperglycemia, and acidosis were found, and markedly elevated initial serum theophylline concentrations (106, 76.2, and 41.4 micrograms/ml) were measured. All patients recovered completely with conservative management. The observed biochemical abnormalities rapidly resolved during maintenance fluid therapy and modest potassium supplementation. In addition, seizures, ventricular arrhythmias, and other serious toxic effects were notably absent.

Acidosis↗
PubMed1979

Predictability of warfarin dose requirements: theoretical considerations.

The theoretical basis of the predictability of warfarin maintenance dose requirements was evaluated using computer-generated hypothetical patient responses to a 10-mg/day "loading" dose regimen. Correlations between these responses and projected maintenance dose requirements were evaluated statistically, and a significant relationship was identified.

Drug Administration Schedule↗
PubMed1979

Comparison of natriuretic and diuretic effects of single and divided doses of furosemide.

The natriuretic and diuretic effectiveness of once-daily and twice-daily furosemide administration schedules was compared in a two-way crossover study using six normal subjects. Urine was collected for 24hours before and after administration of the first dose of furosemide. Patients received one 40-mg dose or two 20-mg doses of the drug administered six hours apart. Sodium and potassium urine concentrations were measured through flame emission photometry using lithium as an internal standard. Chloride urine concentrations were determined using colorimetric measurement with mercuric thiocyanate. Results were statistically evaluated by a one-way analysis of variance. Results showed no statistically significant differences (p greater than 0.7) between the two regimens in the cumulative 24-hour excretion of sodium, potassium, chloride or water. The average 24-hour sodium excretion following a single 40-mg furosemide dose was 268.9 mEq, while that following administration of the two 20-mg doses was 294.2 mEq. Differences during various intervals within the 24-hour collection period were consistent with the relative sizes of doses administered. It would appear that single daily dose administration regimens would be a logical beginning for furosemide therapy, particularly when lower doses are being considered.

Adult↗
PubMedDate not supplied

Multicenter evaluation of six methods for predicting warfarin maintenance-dose requirements from initial response.

Warfarin maintenance-dose requirements predicted by six mathematical methods based on initial response to therapy were compared with patients' actual dose requirements in a multicenter trial. Data were collected for patients who had received an initial regimen of warfarin sodium 10 mg orally every 24 hours for three days and for whom a prothrombin time (PT) had been determined 16-20 hours after the third dose. Patients' individual dose requirements and PT values were recorded during one to three follow-up visits after discharge from one of seven medical centers. Prothrombin ratios (patient PT divided by control PT) calculated on day 4 were used for maintenance-dose prediction by five methods; a sixth method was based on the cumulative warfarin dose-PT response curve up to a PT value of 20 seconds. For 54 men and 30 women who qualified for the study, 197 maintenance-dose-PT response measurements were recorded; 95 in the first four weeks of therapy, 76 during weeks 5-12, and 26 at 6-12 months after initial treatment. Prothrombin ratios were within the therapeutic range (PT 1.5-2.5 times the control value) in 154 observations, and the mean actual warfarin sodium maintenance dose associated with therapeutic response was 7.6 mg/day. For patients with therapeutic prothrombin ratios, dose predictions by the five methods using prothrombin ratios (PRs) correlated significantly with actual dose requirements. The formula that predicted doses numerically closest to the actual dose is as follows: Dose = 11.17 - 21.08 (log PR). Only 45 observations were obtained for the sixth prediction method, and the correlation between actual and predicted doses was not significant. Initial warfarin maintenance-dose requirements can be predicted effectively based on one PT determination after administration of three daily 10-mg doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗