Age and Ageing (1975) 4, 161
CONTROL OF WARFARIN THERAPY IN THE ELDERLY J. T. ECCLES Geriatric Department, Northwick Park Hospital, Harrow, Middlesex
Summary
INTRODUCTION
Drug therapy is more hazardous and prone to side-effects in old age—this is a generalization upheld by the clinical experience of doctors everywhere who treat the elderly, and was made the subject of a review by Wade (1972). It is well recognized that oral anticoagulants are no exception in presenting risks which increase with age (Pearson, 1953; Sise et al., 1958). Peuman (1956) found that the incidence of bleeding complications in the decade 70-80 was twice as great as in the 30-40 age-group. The many documented determinants of response to oral anticoagulants have been reviewed by O'Reilly & Aggeler (1970), but it appears that these determinants may change in the older age ranges. It was decided to study the elderly patients who had been on the anticoagulant Warfarin at Northwick Park Hospital, and try to determine the factors influencing the doses used in well controlled patients. It was hoped these factors could then be used as a guide to a suitable dose for individual old people. Patients and Methods All the patients in the series were over 65 and were anticoagulated with Warfarin at Northwick Park Hospital during the four-year period October 1970 to September 1974. The data noted from each patient's records were as follows: The name, hospital number, and age in years. The sex, and the weight in kg. The serum albumin and globulin levels in g/1 (normal range 35-50 for albumin, 15—35 for globulin). The blood urea level in mmol/1 (normal range 2.5-6.5) and the tri-iodothyromine (T3) uptake expressed as a percentage (normal range 94—119). All these values were the ones taken nearest to the time of commencement of Warfarin therapy. The sum of the Warfarin doses for the first ten days was noted, and the sum of the doses for days 11-17, and 1-17. If a patient's course of Warfarin did not last as long as 17 days that case was omitted. Since the aim of the study was to show the factors involved in well controlled cases (only then would the dose used be a meaningful parameter) all cases where the prothrombin ratio (patients one-stage prothrombin time divided by a control time) was outside the therapeutic range 1.6-3.0 were omitted; as were cases where there had been bleeding or other complications. Many drugs interact with oral anticoagulants and would interfere with their effects, so patients on interacting drugs (as listed in the comprehensive account of Stockley, 1973) were excluded from the series.
Downloaded from http://ageing.oxfordjournals.org/ at University of Sydney on June 7, 2016
Eighty patients over 65 years old with satisfactory coagulation control with Warfarin were selected and analysed to determine factors predictive of dose. Age followed by urea were the important predictors. Albumin, globulin, sex, weight and T3 uptake were not significant factors. It is concluded that care should be taken when Warfarin is given to older patients, particularly those with high blood-urea levels.
162
J. T. Eccles RESULTS
Eighty patients were available for study and Table I shows the means and standard deviations found for the studied parameters. Thirty-eight patients were male and 42 were female, but statistical examination revealed no significant sex differences for the other variables so all subsequent analyses were performed for the sexes combined. Table I. The means and standard deviations for the studied parameters Variable
Mean
80 76 75 75 80 59 80 80 80
73.2 64.0 37.2 30.7 0.8188 103.0 1.7000 1.4021 1.8843
Age
Weight Albumin Globulin Urea» T3 uptake Dose l-10 # Dose 11-17* Dose 1-17*
Standard deviation 6.6
11.9 4.5 4.4
0.1781 8.3
0.1599 0.2153 0.1605
• Log-normal distribution.
Each variable was tested against total Warfarin dose to see if there was a significant correlation. Significant correlations were found for age (r = 0.3515, P
CONTROL OF WARFARIN THERAPY IN THE ELDERLY J. T. ECCLES Geriatric Department, Northwick Park Hospital, Harrow, Middlesex
Summary
INTRODUCTION
Drug therapy is more hazardous and prone to side-effects in old age—this is a generalization upheld by the clinical experience of doctors everywhere who treat the elderly, and was made the subject of a review by Wade (1972). It is well recognized that oral anticoagulants are no exception in presenting risks which increase with age (Pearson, 1953; Sise et al., 1958). Peuman (1956) found that the incidence of bleeding complications in the decade 70-80 was twice as great as in the 30-40 age-group. The many documented determinants of response to oral anticoagulants have been reviewed by O'Reilly & Aggeler (1970), but it appears that these determinants may change in the older age ranges. It was decided to study the elderly patients who had been on the anticoagulant Warfarin at Northwick Park Hospital, and try to determine the factors influencing the doses used in well controlled patients. It was hoped these factors could then be used as a guide to a suitable dose for individual old people. Patients and Methods All the patients in the series were over 65 and were anticoagulated with Warfarin at Northwick Park Hospital during the four-year period October 1970 to September 1974. The data noted from each patient's records were as follows: The name, hospital number, and age in years. The sex, and the weight in kg. The serum albumin and globulin levels in g/1 (normal range 35-50 for albumin, 15—35 for globulin). The blood urea level in mmol/1 (normal range 2.5-6.5) and the tri-iodothyromine (T3) uptake expressed as a percentage (normal range 94—119). All these values were the ones taken nearest to the time of commencement of Warfarin therapy. The sum of the Warfarin doses for the first ten days was noted, and the sum of the doses for days 11-17, and 1-17. If a patient's course of Warfarin did not last as long as 17 days that case was omitted. Since the aim of the study was to show the factors involved in well controlled cases (only then would the dose used be a meaningful parameter) all cases where the prothrombin ratio (patients one-stage prothrombin time divided by a control time) was outside the therapeutic range 1.6-3.0 were omitted; as were cases where there had been bleeding or other complications. Many drugs interact with oral anticoagulants and would interfere with their effects, so patients on interacting drugs (as listed in the comprehensive account of Stockley, 1973) were excluded from the series.
Downloaded from http://ageing.oxfordjournals.org/ at University of Sydney on June 7, 2016
Eighty patients over 65 years old with satisfactory coagulation control with Warfarin were selected and analysed to determine factors predictive of dose. Age followed by urea were the important predictors. Albumin, globulin, sex, weight and T3 uptake were not significant factors. It is concluded that care should be taken when Warfarin is given to older patients, particularly those with high blood-urea levels.
162
J. T. Eccles RESULTS
Eighty patients were available for study and Table I shows the means and standard deviations found for the studied parameters. Thirty-eight patients were male and 42 were female, but statistical examination revealed no significant sex differences for the other variables so all subsequent analyses were performed for the sexes combined. Table I. The means and standard deviations for the studied parameters Variable
Mean
80 76 75 75 80 59 80 80 80
73.2 64.0 37.2 30.7 0.8188 103.0 1.7000 1.4021 1.8843
Age
Weight Albumin Globulin Urea» T3 uptake Dose l-10 # Dose 11-17* Dose 1-17*
Standard deviation 6.6
11.9 4.5 4.4
0.1781 8.3
0.1599 0.2153 0.1605
• Log-normal distribution.
Each variable was tested against total Warfarin dose to see if there was a significant correlation. Significant correlations were found for age (r = 0.3515, P
