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Biomedical subjects

B R Canaday

Publications and source records attributed to B R Canaday.

3 recordsLinked to original sources

Interpreting digoxin concentrations.

In all cases, clinical assessment of the patient is the most critical factor in determining dose and interpreting concentrations. When done accurately, laboratory assessment of drug concentrations represents only one source of information. Serum concentrations must be taken into account along with all other relevant clinical data before one can arrive at appropriate management decisions. They must not be considered in isolation and out of context. If the laboratory report is at variance with your clinical judgment, "it will often be the better part of wisdom to question (or reject) the report."

Arrhythmias, Cardiac

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

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