The amount of blood withdrawn for diagnostic tests in critically ill patients.

This study involved the measurement of blood withdrawn from critically ill patients for diagnostic tests during their first 3 days in eight intensive-care units. The study was conducted over a 2 to 3 week period. Data were collected on the number of draws performed per day, the total volume of blood withdrawn per day, and the volume of blood per draw on 253 patients. The subject population was divided into four general diagnostic categories: Post-open-heart surgical, surgical, medical, and cardiac. Approximately 85 per cent of the blood samples were drawn via venipuncture with arterial and capillary samples performed less frequently. The results demonstrate that the total volume of blood withdrawn differed among the diagnostic categories and hospitals. The average amount ranged from 20 ml. per day in surgical patients to 50 ml. per day in post-open-heart surgical patients. The volumes withdrawn daily from the subjects were generally lower than the authors had anticipated.